JP7798424B2 - Adhesive composition for organic fibers, and organic fiber materials, rubber articles, organic fiber-rubber composites, and tires using the same - Google Patents

Description

The present invention relates to an adhesive composition for organic fibers (hereinafter also simply referred to as "adhesive composition"), as well as organic fiber materials, rubber articles, organic fiber-rubber composites, and tires that use the same.

Conventionally, for the purpose of reinforcing rubber articles such as tires, organic fibers such as tire cords made of nylon fibers or polyester fibers have been bonded to rubber compositions such as rubber compositions for tires to form organic fiber-rubber composites. A commonly used method for this bonding is to coat the organic fibers with an adhesive composition, embed them in the rubber composition, and co-vulcanize them with the rubber composition.

In addition, in the process of coating the organic fibers with the adhesive composition, a solvent is generally used to adjust the viscosity of the adhesive composition. However, since the solvent evaporates during this process, it is preferable to use water, which has a low environmental impact, as the solvent. Furthermore, when coating the organic fibers with the adhesive composition by immersion, it is necessary to make the adhesive composition have a low viscosity that allows it to be applied by immersion.

Generally, the components contained in aqueous adhesive compositions, i.e., those that are soluble or dispersible in water, must have a polar molecular structure. However, polymeric materials such as rubber and organic fiber substrates that serve as adherends have low polarity, and adhesion becomes difficult when there is a large difference in polarity between the surface of the rubber or organic fiber substrate and the components contained in the adhesive composition. Therefore, in order to use the above-mentioned aqueous adhesive composition as an adhesive composition for rubber articles, the components contained in the above-mentioned aqueous adhesive composition must have polarity because they are aqueous. However, this polarity must be controlled so that a difference in polarity with the adherend does not arise, resulting in a decrease in adhesion. Therefore, aqueous adhesive compositions that can meet these contradictory requirements are preferably used.

Here, with regard to the process of coating the organic fiber with the adhesive composition, an example of a process in which an organic fiber cord such as a tire cord is immersed in the adhesive composition will be described using Figure 1.

An organic fiber cord 1 is unwound from a winding roll and transported by a roll. It is then immersed in adhesive composition 2 in a dipping bath 3 containing the adhesive composition 2. The organic fiber cord 4 coated with adhesive composition 2 is then lifted out of the dipping bath 3, and excess adhesive composition 2 is removed by a squeeze roll 5. The organic fiber cord 4 coated with adhesive composition 2 is then transported further by a roll, dried in a drying zone 6, stretched by tension in a hot zone 7, where the resin is thermally cured, and then thermally cured in a normalization zone 8, where the tension is precisely adjusted to achieve the desired strength and elongation properties (normalization). The cord is then air-cooled outside the zone and wound onto a take-up roll. In this way, the organic fiber is coated with the adhesive composition.

The adhesive composition used so far has been an RFL (resorcinol-formaldehyde-latex) adhesive composition obtained by maturing a mixed liquid containing resorcinol, formaldehyde, and rubber latex, or an adhesive composition obtained by mixing this RFL adhesive composition with a specific adhesion promoter (see Patent Documents 1 to 4).

As is well known, in the rubber industry, an adhesive composition (Patent Document 1) consisting of a water-dispersible rubber latex component and an aqueous phenolic resin obtained by mixing and maturing water-soluble resorcinol and formaldehyde has been found to have the ability to bond to both the rubber substrate and the surface of less polar substrates such as organic fibers, and is therefore widely used worldwide. In bonding with the RFL adhesive composition, the rubber latex component provides co-vulcanization with the rubber substrate, while the phenolic resin component, a condensate of resorcinol and formaldehyde that has adhesive properties with organic fiber substrates, provides adhesion to the substrate.

Resorcinol is preferably used here because it provides a phenolic condensation resin, a type of resin that has high adhesion to the substrate, and because the polar functional group introduced into the phenol ring to achieve water solubility is a hydroxyl group, which has relatively little polarity and is less likely to cause steric hindrance, and therefore provides a resin component that has high adhesion to the organic fiber substrate.

The RFL adhesive composition is obtained by mixing and maturing resorcinol, formaldehyde, and a rubber latex that uses rosin acid or the like as an emulsifier during polymerization in the presence of a basic composition. It is believed that this causes the water-dissolved resorcinol and formaldehyde to condense in a resol-type condensation reaction in the presence of a base (see Patent Document 2), and that the rosin acid on the surface of the latex undergoes addition condensation with the terminal methylol groups of a resol-type phenol-formaldehyde addition condensate (see Non-Patent Document 1).

This aging process causes the latex to crosslink with the resol-type resorcinol-formaldehyde condensate via rosin acid, etc., strengthening adhesion, and the latex combines with the aqueous resin to form an encapsulated protective colloid. This suppresses the rubbery tackiness of the latex when processing the adhesive composition in equipment such as that shown in Figure 1, reducing staining of the equipment caused by the adhesive composition sticking to it.

The adhesion promoter added to the RFL adhesive composition is water-based, i.e., an adhesion promoter that can be dissolved or dispersed in water, in order to improve adhesion of the water-based adhesive composition to the surface of a substrate with low polarity, such as an organic fiber cord material.

Examples of the water-dispersible adhesion promoter include (blocked) isocyanates such as methylene diphenyl diisocyanate with a particle size of 0.01 to 0.50 μm (see Patent Document 3), and water-dispersed particles of water-insoluble phenolic novolac resins such as cresol novolac polyfunctional epoxy resins (see Patent Document 4).

Furthermore, examples of the above-mentioned adhesion promoters containing water-soluble groups that have been used in conjunction with RFL adhesive compositions include sodium hydroxide solutions of novolac condensates obtained by the novolac reaction of resorcinol and formaldehyde (see Patent Document 5), phenolic resins that dissolve in water in the presence of a basic substance, such as ammonium solutions of novolac condensates of chlorophenols and formaldehyde, and aqueous urethane compounds having (thermally dissociable blocked) isocyanate groups and groups that are self-water-soluble (see Patent Document 6).

However, in recent years, there has been a growing demand to reduce the amount of resorcinol used as a water-soluble component in RFL adhesive compositions in order to reduce the environmental impact.

To address this issue, various adhesive compositions using water as a solvent, which use polyphenols that do not contain resorcinol, have been studied and proposed.

For example, adhesive compositions that do not contain resorcinol or formaldehyde include an adhesive composition for organic fibers composed of rubber latex and lignin resin (see Patent Document 7) and an aqueous adhesive composition based on rubber latex, a polyphenol such as a flavonoid, and an aromatic polyaldehyde (see Patent Documents 8 and 9).

U.S. Pat. No. 2,128,229 Japanese Patent Application Laid-Open No. 2005-263887 Japanese Patent Application Laid-Open No. 2006-37251 Japanese Patent Application Publication No. 9-12997 WO 97/013818 JP 2011-241402 A International Publication No. 2018/003572 International Publication No. 2013/017421 Special Publication No. 2016-528337

Koichi Hakata, Network Polymer Vol. 31, No. 5, p. 252 (2010)

However, if an adhesive composition that does not contain resorcinol, such as that described in Patent Document 7, is simply a mixture of rubber latex and lignin resin, the high tack of the rubber latex reduces the mechanical stability of the adhesive liquid under shear strain. As a result, for example, in the process shown in Figure 1, in which the organic fiber cord 1 is coated with the adhesive composition 2 and then dried and thermally cured, the adhesive composition 2 adheres more to the squeeze roll 5 and the rolls in the drying zone 6, creating a new problem of poor workability in the process.

In addition, adhesive compositions that do not contain resorcinol tend to have reduced adhesion because the surface of the adhesive coating becomes rough when they adhere to the above-mentioned equipment. Furthermore, because crosslinking between the latex component and the resorcinol-formaldehyde condensate is not achieved, there is also the problem that the adhesion between the organic fiber and the coating rubber composition is reduced compared to conventional RFL adhesive compositions.

Furthermore, as in Patent Document 8, when an aqueous adhesive composition is produced by mixing an aromatic dialdehyde, such as terephthalaldehyde or 2,5-furandicarboxaldehyde, which has low solubility in water, with polyphenol mixed with rubber latex, the aromatic dialdehyde is difficult to dissolve in water during production, resulting in insufficient workability.

Furthermore, adhesive compositions that do not contain resorcinol, such as those described above, have the problem of reducing the cord strength of organic fiber cords coated with the adhesive composition.

The object of the present invention is to provide an adhesive composition for organic fibers that can ensure the desired adhesive properties without using resorcinol and that does not impair workability during use, as well as organic fiber materials, rubber articles, organic fiber-rubber composites, and tires that use the same.

In order to solve the above-mentioned problems, the present inventors conducted extensive research into the composition of adhesive compositions for organic fibers. As a result, they discovered that by blending an acetoacetyl group-modified polyvinyl alcohol with a specific rubber latex, and preferably further blending one or more of an aqueous compound having a (thermally dissociable blocked) isocyanate group, an amine compound, and a polyphenol, it is possible to obtain an adhesive composition for organic fibers that ensures the desired adhesive properties without using resorcinol and that does not impair workability during use, thereby completing the present invention.

That is, the adhesive composition for organic fibers of the present invention is characterized by containing (A) a rubber latex having an unsaturated diene, (B) an acetoacetyl group-modified polyvinyl alcohol, and (C) an aqueous compound having a (thermally dissociable blocked) isocyanate group.

The adhesive composition for organic fibers of the present invention further comprises the following (D) and (E):
(D) an amine compound, and
It is preferable that the adhesive composition for organic fibers of the present invention contains one or more compounds selected from the group consisting of polyphenols (E). In the adhesive composition for organic fibers of the present invention, it is preferable that the saponification degree of the acetoacetyl group-modified polyvinyl alcohol (B) is 80 mol % or more.

In the adhesive composition for organic fibers of the present invention, the (C) aqueous compound having a (thermally dissociable, blocked) isocyanate group is preferably (C-1) a water-dispersible (thermally dissociable, blocked) isocyanate compound composed of an addition product of a polyisocyanate having an aromatic ring and a blocking agent having one or more active hydrogen groups.

Here, a blocked methylene diphenyl diisocyanate can be suitably used as the water-dispersible (thermally dissociable blocked) isocyanate compound (C-1) formed by the addition product of a polyisocyanate having an aromatic ring and a blocking agent having one or more active hydrogen groups.

In addition, in the adhesive composition for organic fibers of the present invention, it is also preferable that the (C) aqueous compound having a (thermally dissociable blocked) isocyanate group be (C-2) an aqueous urethane compound having a (thermally dissociable blocked) isocyanate group.

Here, the (C-2) aqueous urethane compound having a (thermally dissociable blocked) isocyanate group includes:
(α) an organic polyisocyanate compound having 3 or more and 5 or less functional groups and a number average molecular weight of 2,000 or less;
(β) a compound having 2 or more and 4 or less active hydrogen groups and a number average molecular weight of 5,000 or less;
(γ) a thermally dissociable blocking agent, and
(δ) a compound having at least one active hydrogen group and at least one hydrophilic group which is anionic, cationic or nonionic;
The mixing ratio of each of (α), (β), (γ) and (δ) to the total amount is
(α) is 40% by mass or more and 85% by mass or less,
(β) is 5% by mass or more and 35% by mass or less,
(γ) is 5% by mass or more and 35% by mass or less, and
(δ) is 5% by mass or more and 35% by mass or less,
and reacting the mixture to give a reaction product,
When the molecular weight of the isocyanate group (—NCO) is 42, the composition ratio of the (thermally dissociable blocked) isocyanate group in the reaction product is preferably 0.5% by mass or more and 11% by mass or less.

Furthermore, the (C-2) aqueous urethane compound having a (thermally dissociable blocked) isocyanate group is a compound represented by the following general formula (1):
[In formula (1),
A is a residue of an organic polyisocyanate compound from which an active hydrogen group has been eliminated,
X is a residue of a polyol compound having 2 or more and 4 or less hydroxyl groups and a number average molecular weight of 5,000 or less, from which an active hydrogen group has been eliminated;
Y is a residue of the thermally dissociable blocking agent from which the active hydrogen group has been eliminated;
Z is a residue of a compound having at least one active hydrogen group and at least one salt-forming group or a hydrophilic polyether chain, from which the active hydrogen group has been eliminated;
n is an integer between 2 and 4,
p + m is an integer between 2 and 4 (m≧0.25)
can also be suitably used.

Furthermore, in the adhesive composition for organic fibers of the present invention, the (D) amine compound is preferably a polyfunctional amine compound having two or more primary to tertiary amino groups.

Furthermore, in the adhesive composition for organic fibers of the present invention, the (E) polyphenol is preferably a plant-derived compound having multiple phenolic hydroxy groups in the molecule, and is also preferably lignin, tannin, tannic acid, a flavonoid, or a derivative thereof.

The adhesive composition for organic fibers of the present invention may be free of resorcinol.

The organic fiber material of the present invention is characterized in that the surface of the organic fiber is coated with an adhesive layer made of the above-mentioned organic fiber adhesive composition. Furthermore, the organic fiber adhesive composition of the present invention can be particularly preferably used as a rubber-resin adhesive composition.

In the organic fiber material of the present invention, the organic fiber is preferably a cord formed by twisting together multiple filaments. In this case, it is more preferable that the cord has a first twist and a second twist, and that the twist coefficient of the first twist is 1,300 or more and 2,500 or less, and that of the first twist is 900 or more and 1,800 or less.

Furthermore, in the organic fiber material of the present invention, it is preferable that the adhesive layer has a dry mass of 0.5 to 6.0% by mass of the cord.

Furthermore, in the organic fiber material of the present invention, it is preferable that the organic fiber is made of polyester resin.

The rubber article of the present invention is characterized by being reinforced with the above-mentioned organic fiber material.

The organic fiber-rubber composite of the present invention is a composite of organic fiber and rubber, characterized in that the organic fiber is coated with the above-mentioned organic fiber adhesive composition.

The tire of the present invention is characterized by using the above-mentioned organic fiber-rubber composite, particularly an organic fiber cord-rubber composite.

The present invention provides an adhesive composition for organic fibers that can ensure the desired adhesive properties without using resorcinol and does not impair workability during use, as well as organic fiber materials, rubber articles, organic fiber-rubber composites, and tires that use the same.

FIG. 2 is a schematic diagram showing an example of a process for coating an organic fiber cord with an adhesive composition by dipping. 1 is a schematic cross-sectional view showing an example of an organic fiber-rubber composite of the present invention.

The adhesive composition for organic fibers, organic fiber materials, rubber articles, organic fiber-rubber composites, and tires of the present invention are described in detail below based on their embodiments. These descriptions are intended to exemplify the present invention and are not intended to limit the present invention in any way.

When ranges are expressed in this specification, unless otherwise specified, the ends of the ranges are included within the range.

[Adhesive composition for organic fibers]
The adhesive composition for organic fibers of the present invention essentially contains (A) a rubber latex having an unsaturated diene and (B) an acetoacetyl group-modified polyvinyl alcohol, and preferably further contains the following (C) to (E):
(C) an aqueous compound having a (thermally dissociable blocked) isocyanate group,
(D) an amine compound, and
(E) Contains one or more compounds selected from the group consisting of polyphenols.

The adhesive composition for organic fibers of the present invention, with its above-described structure, can achieve good adhesion without the use of resorcinol, and can particularly ensure good adhesion between organic fibers and a coating rubber composition. In the adhesive composition for organic fibers of the present invention, (A) a rubber latex having an unsaturated diene, and preferably further one or more compounds selected from the group consisting of (C) an aqueous compound having a (thermally dissociable blocked) isocyanate group, (D) an amine compound, and (E) a polyphenol, contribute to improved adhesion. Furthermore, the adhesive composition for organic fibers of the present invention uses (B) an acetoacetyl-modified polyvinyl alcohol, which suppresses the tack of the rubber latex, measured as the mechanical stability of the adhesive liquid under shear strain. This suppresses adhesion of the adhesive composition to rolls and other devices, particularly during the process of coating organic fibers with the adhesive composition and drying and thermal curing, thereby improving workability. Therefore, the adhesive composition for organic fibers of the present invention can achieve the desired adhesion without the use of resorcinol, while also ensuring good workability during use. Furthermore, the adhesive composition for organic fibers of the present invention does not require the use of resorcinol, thereby reducing the environmental impact.

Therefore, the adhesive composition for organic fibers of the present invention can be free of resorcinol. Furthermore, it is preferable that the adhesive composition for organic fibers of the present invention further does not contain formaldehyde.

The adhesive composition for organic fibers of the present invention is particularly useful when applied to organic fiber cords, as described below.

<(A) Rubber Latex Having Unsaturated Diene>
In the adhesive composition for organic fibers of the present invention, examples of the (A) rubber latex having an unsaturated diene include (A-1) a synthetic rubber latex having an unsaturated diene and (A-2) a natural rubber latex.

In the adhesive composition for organic fibers of the present invention, the (A-1) synthetic rubber latex having an unsaturated diene refers to a synthetic rubber latex containing an unsaturated diene that is vulcanizable by sulfur.

In one embodiment of the present invention, the synthetic rubber latex having an unsaturated diene (A-1) contained in the adhesive composition for organic fibers is a component for bonding the adhesive layer of the adhesive composition for organic fibers to the coating rubber composition that serves as the adherend. The synthetic rubber latex having an unsaturated diene is compatible with the rubber polymer contained in the coating rubber composition that serves as the adherend, and further, the unsaturated diene moieties co-vulcanize to form a rubber co-vulcanization bond. As a result, the adhesive composition for organic fibers of the present invention, which contains the synthetic rubber latex having an unsaturated diene (A-1), can provide good adhesion between, for example, organic fiber cords and the coating rubber composition.

Examples of the (A-1) synthetic rubber latex containing an unsaturated diene include, but are not limited to, styrene-butadiene copolymer rubber latex, vinylpyridine-styrene-butadiene copolymer rubber latex, carboxyl group-modified styrene-butadiene copolymer rubber latex, nitrile rubber latex, and chloroprene rubber latex. These may be used alone or in combination of two or more.

Of the above, vinylpyridine-styrene-butadiene copolymer rubber latex is preferred. Vinylpyridine-styrene-butadiene copolymer rubber latex is a rubber latex that has traditionally been widely used in adhesive compositions and in articles such as tires. In the adhesive composition for organic fibers of the present invention, it also provides good bonding between the adhesive layer and the rubber substrate, and its advantages of being relatively soft and flexible allow for deformation of the organic fiber cord without causing the adhesive layer to split.

Furthermore, the content (solids content) of the synthetic rubber latex having an unsaturated diene (A-1) relative to the total solids content in the adhesive composition for organic fibers of the present invention is not particularly limited, but is preferably 25% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more. Furthermore, the content of the synthetic rubber latex having an unsaturated diene (A-1) is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less. When the content of the synthetic rubber latex having an unsaturated diene (A-1) is 25% by mass or more, the compatibility of the rubber polymers in the adherend rubber composition and the rubber latex contained in the adhesive composition becomes more appropriate, resulting in better adhesion of the coating rubber in the organic fiber-rubber composite. On the other hand, if the content of the (A-1) unsaturated diene-containing synthetic rubber latex is 95% by mass or less, the amount of resin components contained as other components in the adhesive composition can be ensured to be relatively constant or above. As a result, the cohesive failure resistance of the adhesive layer is sufficiently ensured, and failure within the adhesive layer is less likely to occur, resulting in sufficient adhesion.

The above-mentioned (A-1) synthetic rubber latex containing an unsaturated diene can be obtained, for example, by dissolving an emulsifier such as potassium rosinate in water, adding a mixture of monomers to the mixture, and then adding an electrolyte such as sodium phosphate and peroxides as a polymerization initiator to carry out polymerization. After reaching a predetermined conversion rate, a charge transfer agent is added to terminate the polymerization, and the remaining monomers are then removed. It is also preferable to use a chain transfer agent during polymerization.

The emulsifier may be one or more of the following: anionic surfactants such as alkali metal salts of fatty acids, alkali metal salts of rosin acid, formaldehyde-condensed sodium naphthalenesulfonate, sulfate esters of higher alcohols, alkylbenzenesulfonates, and aliphatic sulfonates; or nonionic surfactants such as alkyl esters, alkyl ethers, and alkylphenyl ethers of polyethylene glycol.

Among these emulsifiers, metal salts of rosin acid, especially alkali metal salts of rosin acid, are preferred. These can be used alone, i.e., by themselves, or in combination with two or more other emulsifiers. Rosin acid is a mixture of resin acids with similar chemical structures, primarily consisting of tricyclic diterpenes obtained from pine resin and other materials. These resin acids have three ring structures, two double bonds, and one carboxyl group, and the double bond portion contains a highly reactive functional group that can esterify with the methylol end of unsaturated carboxylic acids or resole-type phenolic resins at the carboxyl group portion.

The amount of such emulsifier used is typically 0.1 to 8 parts by mass, and preferably 1 to 5 parts by mass, per 100 parts by mass of all monomers used in latex polymerization.

The polymerization initiator may be, for example, a water-soluble initiator such as potassium persulfate, sodium persulfate, or ammonium persulfate, a redox initiator, or an oil-soluble initiator such as benzoyl peroxide. Among these, potassium persulfate is preferred.

Examples of the chain transfer agent include monofunctional alkyl mercaptans such as n-hexyl mercaptan, t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, n-tetradecyl mercaptan, and t-hexyl mercaptan; bifunctional mercaptans such as 1,10-decanedithiol and ethylene glycol dithioglycolate; trifunctional mercaptans such as 1,5,10-caneditrithiol and trimethylolpropane tristhioglycolate; tetrafunctional mercaptans such as pentaerythritol tetrakisthioglycolate; disulfides; halogen compounds such as carbon tetrachloride, carbon tetrabromide, and ethylene bromide; α-methylstyrene dimer, terpinolene, α-terpinene, dipentene, and allyl alcohol. These may be used alone or in combination of two or more.

Of these chain transfer agents, alkyl mercaptans are preferred, and n-octyl mercaptan and t-dodecyl mercaptan are more preferred. Of these, t-dodecyl mercaptan is most preferred.

The amount of such chain transfer agents used is typically 0.01 to 5 parts by mass, and preferably 0.1 to 3 parts by mass, per 100 parts by mass of all monomers used in latex polymerization.

In addition to the above components, the latex may contain general-purpose additives such as anti-aging agents such as hindered phenols, silicone-based, higher alcohol-based, and mineral oil-based defoamers, reaction terminators, and antifreeze agents, as needed.

<<Vinylpyridine-styrene-butadiene copolymer rubber latex>>
The vinylpyridine-styrene-butadiene copolymer rubber latex is a terpolymer of a vinylpyridine-based monomer, a styrene-based monomer, and a conjugated diene-based butadiene monomer, and may further contain other monomers copolymerizable with these monomers.

Here, the vinylpyridine-based monomer includes vinylpyridine and substituted vinylpyridines in which hydrogen atoms in the vinylpyridine have been substituted with substituents. Examples of such vinylpyridine-based monomers include 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyridine, and 5-ethyl-2-vinylpyridine, with 2-vinylpyridine being preferred. These vinylpyridine-based monomers may be used alone or in combination of two or more.

The above-mentioned styrene-based monomers include styrene and substituted styrenes in which the hydrogen atoms in the styrene have been replaced with substituents. Examples of the above-mentioned styrene-based monomers include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-diynopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, and hydroxymethylstyrene. Of these, styrene is preferred. These styrene-based monomers may be used alone or in combination of two or more.

The above-mentioned conjugated diene butadiene monomers include aliphatic conjugated butadiene compounds such as 1,3-butadiene and 2-methyl-1,3-butadiene, with 1,3-butadiene being preferred. These conjugated diene butadiene monomers may be used alone or in combination of two or more.

The vinylpyridine-styrene-butadiene copolymer rubber latex can be synthesized using known methods, specifically, for example, the method described in Japanese Patent Application Laid-Open No. 9-78045, which was developed by the inventors of the present invention. Using these methods, it is possible to create various compositions and intra-particle structures, such as copolymers with uniform or varying composition ratios, within the same particle of vinylpyridine-styrene-butadiene copolymer rubber latex.

With regard to the above-mentioned vinylpyridine-styrene-butadiene copolymer rubber latex, commercially available copolymers having a uniform monomer mixture ratio within the same particle include Nipol 2518 manufactured by Nippon Zeon Co., Ltd. and Piratex manufactured by Nippon A&L Co., Ltd. Commercially available copolymers having different monomer mixture ratios within the same particle include V0658 manufactured by JSR Corporation. All of these can be used as the unsaturated diene-containing synthetic rubber latex (A-1) in the adhesive composition for organic fibers of the present invention.

While the vinylpyridine-styrene-butadiene copolymer rubber latex does not have any particular limitations on the vinylpyridine:styrene:butadiene monomer ratio, it is preferable for the copolymer constituting the vinylpyridine-styrene-butadiene copolymer particles to contain a copolymer obtained by polymerizing a monomer mixture consisting of 5-20% by mass of vinylpyridine, 10-40% by mass of styrene, and 45-75% by mass of butadiene. A vinylpyridine content of 5% by mass or greater provides an appropriate amount of pyridine moieties with a vulcanization-accelerating effect within the rubber component, increasing the degree of crosslinking by sulfur and further improving the adhesive strength of the entire adhesive layer. A vinylpyridine content of 20% by mass or less prevents the degree of crosslinking of the rubber from becoming over-vulcanized, resulting in a hard adhesive. Furthermore, a styrene content of 10% by mass or greater ensures sufficient strength of the latex particles and adhesive layer, further improving adhesive strength. A styrene content of 40% by mass or less leads to adequate co-vulcanization between the adhesive layer and the adhered rubber, while still ensuring sufficient adhesive strength. Furthermore, if the butadiene content is 45% by mass or more, more sufficient cross-linking can be formed, while if it is 75% by mass or less, the cross-linking is moderate, ensuring good durability against changes in volume and modulus. The composition ratio of the vinylpyridine:styrene:butadiene monomer mixture can preferably be, for example, 15:15:70.

In the present invention, in addition to the above-mentioned (A-1) synthetic rubber latex having an unsaturated diene, (A-2) natural rubber latex can be used as the (A) rubber latex having an unsaturated diene. The natural rubber latex is not particularly limited, and examples that can be used include field latex, ammonia-treated latex, centrifugal concentrated latex, deproteinized latex treated with a surfactant or enzyme, and combinations of these. Of these, it is preferable to use field latex.

The amount of (A-2) natural rubber latex (solids content) relative to the total solids in the adhesive composition of the present invention is not particularly limited, but is preferably 25% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more. Furthermore, the amount of (A-2) natural rubber latex is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less.

<(B) Acetoacetyl Group-Modified Polyvinyl Alcohol>
The acetoacetyl group-modified polyvinyl alcohol (B) can be obtained by reacting a polyvinyl alcohol resin with diketene by a known method, etc. For example, although the production method is not particularly limited, it can be obtained by a method of dispersing a polyvinyl alcohol resin in a solvent such as acetic acid and then adding diketene, a method of dissolving a polyvinyl alcohol resin in a solvent such as dimethylformamide or dioxane in advance and then adding diketene, or a method of contacting a polyvinyl alcohol resin with diketene gas or liquid diketene.

In the present invention, the (B) acetoacetyl group-modified polyvinyl alcohol can typically have an acetoacetyl group modification degree of 0.05 mol% or more. The acetoacetyl group modification degree of the (B) acetoacetyl group-modified polyvinyl alcohol is preferably 0.1 to 40 mol%, more preferably 1 to 20 mol%, and most preferably 2 to 15 mol%. When the acetoacetyl group modification degree is 0.05 mol% or more, the adhesive layer can have sufficient water resistance.

The polyvinyl alcohol resin used in (B) acetoacetyl group-modified polyvinyl alcohol is obtained by saponifying a polyvinyl acetate resin. Examples of polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate with other monomers copolymerizable with it. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, vinyl ethers, and acrylamides containing ammonium groups. This polyvinyl alcohol resin may also be further modified; for example, polyvinyl polymers or polyvinyl acetals modified with aldehydes can also be used.

The degree of saponification of (B) acetoacetyl group-modified polyvinyl alcohol is not particularly limited as long as (B) acetoacetyl group-modified polyvinyl alcohol is water-soluble, but is preferably 80 mol% or more, more preferably 85 to 100 mol%, and particularly preferably 98 mol% or more, depending on the degree of saponification of the polyvinyl alcohol-based resin contained. When (B) acetoacetyl group-modified polyvinyl alcohol has a degree of saponification of 80 mol% or more, sufficient water solubility is exhibited, preventing the occurrence of problems such as reduced workability of the adhesive composition liquid.

The degree of polymerization of (B) acetoacetyl group-modified polyvinyl alcohol is not particularly limited as long as the acetoacetyl group-modified polyvinyl alcohol is soluble in water, but it is preferably in the range of 100 to 10,000, and more preferably 200 to 5,000. If the molecular weight of (B) acetoacetyl group-modified polyvinyl alcohol is 10,000 or less, the occurrence of problems such as increased viscosity of the adhesive composition liquid and reduced workability can be suppressed.

(B) Commercially available acetoacetyl group-modified polyvinyl alcohols include, but are not limited to, the Gohsenex Z series manufactured by Mitsubishi Chemical Corporation, including Z-100, Z-200, Z-210, Z-220, Z-300, Z-320, and Z-410.

(B) Acetoacetyl group-modified polyvinyl alcohol has long been known as a condensation agent with various materials such as amines, hydrazides, aldehydes, and metal salts in aqueous solution, and as a self-crosslinking agent when subjected to heat treatment. It has also been widely used as an emulsifier for vinyl acetate emulsions, as a condensation agent for coatings on coated and uncoated paper that require water resistance, and for imparting water resistance to adhesives and binders. While there have been some studies to date in which (B) acetoacetyl group-modified polyvinyl alcohol has been used in adhesive compositions to crosslink resins, there have been few known examples of its use as an adhesive composition for bonding rubber and resin by mixing with a rubber component such as rubber latex.

Conventionally, in adhesive compositions containing resorcinol and formaldehyde, the resorcinol and formaldehyde form a resol-type resorcinol-formaldehyde condensate between rubber latex particles dispersed in an aqueous solvent. At the same time, the methylol groups of the resorcinol-formaldehyde condensate add to and co-condense with rosinate salts, etc., used as emulsifiers, on the surface of the rubber latex in the adhesive composition. This chemically crosslinked coating of the phenolic resin formed suppresses the tackiness of the rubber latex.

On the other hand, in the adhesive composition for organic fibers of the present invention, (B) acetoacetyl group-modified polyvinyl alcohol functions as an emulsifier, coating the surface of the synthetic rubber latex containing an unsaturated diene and forming a complex with the rubber latex containing an unsaturated diene, and this coating has the effect of suppressing the tackiness of the rubber latex containing an unsaturated diene.

As a result, the organic fiber adhesive composition of the present invention, which contains (B) acetoacetyl group-modified polyvinyl alcohol, suppresses the tackiness of the rubber latex, which is measured as the mechanical stability of the adhesive liquid under shear strain. This makes it possible to suppress adhesion of the organic fiber adhesive composition to rolls and the like during the process of coating an organic fiber cord with the organic fiber adhesive composition and drying and thermal curing it, thereby improving workability.

Furthermore, in the process of coating the surface of an organic fiber cord with the organic fiber adhesive composition of the present invention and drying and heat-curing the composition, (B) acetoacetyl group-modified polyvinyl alcohol not only chemically crosslinks with the self-crosslinking agent during heat treatment, but also, if the organic fiber adhesive composition of the present invention contains other components, chemically crosslinks with those components, thereby improving the adhesion between the organic fiber and the coating rubber composition.

For example, when the adhesive composition for organic fibers of the present invention contains (C) an aqueous compound having a (thermally dissociable blocked) isocyanate group, the hydroxyl groups derived from the polyvinyl alcohol in (B) acetoacetyl group-modified polyvinyl alcohol chemically crosslink with the isocyanate group (NCO group) component dissociated by the blocking agent for the (thermally dissociable blocked) isocyanate group in component (C), thereby improving the adhesion between the organic fiber and the coating rubber composition.

Furthermore, for example, the acetoacetyl groups of (B) acetoacetyl group-modified polyvinyl alcohol can be chemically crosslinked with (D) the amine compound component to further improve the adhesion between the organic fiber and the coating rubber composition.

The acetoacetyl group-modified polyvinyl alcohol (B) used in the present invention is available in the form of a powder or an aqueous solution, but when used in the adhesive composition for organic fibers of the present invention, it is preferably used as an aqueous solution.

The content (solids content) of the (B) acetoacetyl group-modified polyvinyl alcohol relative to the total solids content of the adhesive composition for organic fibers of the present invention is not particularly limited, but is preferably 0.05% by mass or more and 25% by mass or less. The content of the (B) acetoacetyl group-modified polyvinyl alcohol is more preferably 0.2% by mass or more and 15% by mass or less, and even more preferably 0.4% by mass or more and 12% by mass or less.

When the content of the (B) acetoacetyl group-modified polyvinyl alcohol is 0.05% by mass or more, its function as an emulsifier can suppress the tackiness of the rubber latex by coating the synthetic rubber latex containing an unsaturated diene. Furthermore, when the content of the (B) acetoacetyl group-modified polyvinyl alcohol is 0.2% by mass or more, crosslinking of the adhesive composition for organic fibers of the present invention increases the fracture resistance of the adhesive layer, thereby advantageously improving the adhesion between the organic fiber and the coating rubber composition. Furthermore, when the content of the (B) acetoacetyl group-modified polyvinyl alcohol is 25% by mass or less, the amount of (B) acetoacetyl group-modified polyvinyl alcohol contained in the liquid adhesive composition for organic fibers of the present invention is not too high, thereby suppressing a decrease in workability caused by an increase in the liquid viscosity of the adhesive composition.

<(C), (D), and (E)>
The adhesive composition for organic fibers of the present invention preferably further contains one or more compounds selected from the group consisting of (C) an aqueous compound having a (thermally dissociable blocked) isocyanate group, (D) an amine compound, and (E) a polyphenol.

In the adhesive composition for organic fibers of the present invention, the aqueous compound (C) having a (thermally dissociable blocked) isocyanate group functions as a crosslinking agent, contributing to, for example, improving the adhesion between the organic fiber and the coating rubber composition.

In addition, the (D) amine compound can improve the adhesion between the organic fiber and the coating rubber composition by, for example, chemically crosslinking with the acetoacetyl group of the (B) acetoacetyl group-modified polyvinyl alcohol contained in the adhesive composition for organic fibers of the present invention.

Furthermore, (E) polyphenol has the function of improving the affinity between the organic fiber adhesive composition and the surface of the organic fiber, thereby improving the adhesion between the organic fiber and the coating rubber composition.

Therefore, (C) the aqueous compound having a (thermally dissociable blocked) isocyanate group, (D) the amine compound, and (E) the polyphenol all contribute to improving adhesion, for example, improving adhesion between the organic fiber and the coating rubber composition.

<(C) Aqueous Compound Having a (Thermally Dissociable Blocked) Isocyanate Group>
The (thermally dissociable blocked) isocyanate group of the aqueous compound (C) having a (thermally dissociable blocked) isocyanate group means a thermally dissociable blocked isocyanate group or an isocyanate group.

Specifically, the above-mentioned (thermally dissociable blocked) isocyanate group includes (a) a thermally dissociable blocked isocyanate group formed when an isocyanate group reacts with a thermally dissociable blocking agent for the isocyanate group, (b) an isocyanate group that has not reacted with the thermally dissociable blocking agent for the isocyanate group, (c) an isocyanate group formed when a thermally dissociable blocking agent dissociates from a thermally dissociable blocked isocyanate group, and (d) an isocyanate group.

The term "aqueous" in the above (C) aqueous compound having a (thermally dissociable blocked) isocyanate group refers to water-soluble or water-dispersible. Furthermore, the term "water-soluble" does not necessarily mean complete water-solubility, but rather partial water-solubility or the absence of phase separation in the aqueous solution of the adhesive composition.

The above-mentioned (C) aqueous compound having a (thermally dissociable, blocked) isocyanate group is preferably (C-1) a water-dispersible (thermally dissociable, blocked) isocyanate compound (hereinafter also referred to simply as "component (C-1)") consisting of an addition product of a polyisocyanate having an aromatic ring and a blocking agent having one or more active hydrogen groups. In this case, when the adhesive composition for organic fibers is used with organic fibers, the adhesion between the organic fibers and the coating rubber composition is improved.

Here, with regard to the above component (C-1), the term "active hydrogen group" refers to a group containing hydrogen that becomes active hydrogen (atomic hydrogen (hydrogen radical) and hydride ion (hydride)) when placed under suitable conditions. Examples of such active hydrogen groups include amino groups and hydroxyl groups.

The thermally dissociable blocking agent is not particularly limited, as long as it is a blocking compound that protects the isocyanate groups from any chemical reaction while, if necessary, dissociating the blocking agent through heat treatment to restore the isocyanate groups. Specifically, in the process shown in Figure 1, the heat treatment temperature for thermal curing after the adhesive treatment liquid is applied and dried is preferably a thermal dissociation temperature at which the crosslinking reactivity of the isocyanate groups that have been blocked with the thermally dissociable blocking agent and whose reactivity has been suppressed can be restored.

Blocking agents include, but are not limited to, alcohols, phenols, active methylenes, oximes, lactams, amines, etc., and specific examples include lactams such as ε-caprolactam, δ-valerolactam, and γ-butyrolactam; phenols such as phenol, cresol, ethylphenol, butylphenol, octylphenol, nonylphenol, dinonylphenol, thiophenol, chlorophenol, and amylphenol; oximes such as methyl ethyl ketoxime, acetoxime, acetophenone oxime, benzophenone oxime, and cyclohexanone oxime; alcohols such as methanol, ethanol, butanol, isopropyl alcohol, butyl alcohol, and cyclohexanol; malonic acid dialkyl esters such as dimethyl malonate and diethyl malonate; active methylenes such as methyl acetoacetate, ethyl acetoacetate, and acetylacetone; and mercaptans such as butyl mercaptan and dodecyl mercaptan. Examples of suitable amines include captans; amides such as acetanilide and acetic acid amide; imides such as succinimide, phthalimide, and maleimide; sulfites such as sodium bisulfite; cellosolves such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve; pyrazoles such as pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 3-methyl-5-phenylpyrazole; amines such as dimethylamine, diethylamine, di-n-propylamine, diisopropylamine, dicyclohexylamine, diphenylamine, xylidine, N,N-diethylhydroxyamine, N,N'-diphenylformamidine, 2-hydroxypyridine, 3-hydroxypyridine, and 2-mercaptopyridine; and triazoles such as 1,2,4-triazole. Mixtures of two or more of these may also be used.

Among these blocking agents, phenol, ε-caprolactam, and ketoxime are preferred, as they tend to thermally dissociate when heated, resulting in stable thermal curing of the organic fiber adhesive composition.

The above-mentioned component (C-1) specifically includes aromatic polyisocyanates or araliphatic polyisocyanates. Examples of aromatic isocyanates include phenylene diisocyanates such as m-phenylene diisocyanate and p-phenylene diisocyanate; tolylene diisocyanates such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate (TDI); 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI); dialkyl Examples of the aromatic polyisocyanates include diphenylmethane diisocyanates such as diphenylmethane diisocyanate and tetraalkyldiphenylmethane diisocyanate; polymethylene polyphenyl polyisocyanate (polymeric MDI); m- or p-isocyanatophenylsulfonyl isocyanates; diisocyanatobiphenyls such as 4,4'-diisocyanatobiphenyl and 3,3'-dimethyl-4,4'-diisocyanatobiphenyl; naphthalene diisocyanates such as 1,5-naphthylene diisocyanate; etc. Examples of the aromatic aliphatic polyisocyanates include xylylene diisocyanates such as m-xylylene diisocyanate, p-xylylene diisocyanate (XDI), and tetramethylxylylene diisocyanate; diethylbenzene diisocyanate; and α,α,α,α-tetramethylxylylene diisocyanate (TMXDI). Other examples include modified products of the above polyisocyanates, such as carbodiimides, polyols, and allophanates.

Of these polyisocyanates containing an aromatic ring in the molecule, aromatic isocyanates are preferred from the viewpoint of the cord bundling properties of the organic fiber adhesive composition, more preferably tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), or polymethylene polyphenyl polyisocyanate (polymeric MDI), and particularly preferably diphenylmethane diisocyanates (MDIs). Using a blocked methylene diphenyl isocyanate, particularly a blocked methylene diphenyl diisocyanate (diphenylmethane diisocyanate), as component (C-1) improves the adhesion between the organic fiber and the coating rubber composition when the organic fiber adhesive composition is used with the organic fiber.

More preferably, the aqueous compound having a (thermally dissociable blocked) isocyanate group (C) is an aqueous urethane compound having a (thermally dissociable blocked) isocyanate group (C-2) (hereinafter simply referred to as "component (C-2)"). In this case, too, when the adhesive composition for organic fibers is used with organic fibers, the adhesion between the organic fibers and the coating rubber composition is improved. For ease of explanation, details of component (C-2) are provided below.

The content (solids content) of the aqueous compound having (C) a (thermally dissociable blocked) isocyanate group relative to the total solids content of the organic fiber adhesive composition of the present invention is not particularly limited, but is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more. Furthermore, the content of the aqueous compound having (C) a (thermally dissociable blocked) isocyanate group is preferably 75% by mass or less, more preferably 60% by mass or less, and even more preferably 45% by mass or less. A content of the aqueous compound having (C) a (thermally dissociable blocked) isocyanate group of 5% by mass or more improves the adhesion between the organic fiber and the coating rubber composition. Furthermore, a content of the aqueous compound having (C) a (thermally dissociable blocked) isocyanate group of 75% by mass or less makes it possible to ensure a certain relative amount of other components, such as rubber latex, incorporated into the organic fiber adhesive composition, thereby improving adhesion to the rubber substrate.

Here, conventional adhesive compositions for organic fibers containing resorcinol and formaldehyde form a sea-island structure in which rubber latex particles (likened to islands) are dispersed in a phenolic resin (likened to the sea) formed by co-condensation of resorcinol and formaldehyde, resulting in good adhesion between the phenolic resin that coats the surface of the organic fibers and the organic fibers.

On the other hand, in one preferred embodiment of the adhesive composition for organic fibers of the present invention, the aqueous compound having (C) a (thermally dissociable blocked) isocyanate group acts as an adhesion promoter, instead of the phenolic resin obtained by co-condensation of resorcinol and formaldehyde, due to the following two functional effects (a) and (b). As a result, in the adhesive composition for organic fibers, the aqueous compound having (C) a (thermally dissociable blocked) isocyanate group contributes to the characteristic of good adhesion between the organic fiber and the coating rubber composition.

(a) The functional effect of distributing the aqueous compound near the interface between the organic fiber and the adhesive layer formed by the adhesive composition for organic fibers, thereby promoting adhesion between the organic fiber and the adhesive layer.
(b) Within the adhesive layer of the adhesive composition for organic fibers, a three-dimensional network structure is formed by crosslinking with the isocyanate groups of the compound having the (thermally dissociable blocked) isocyanate group, thereby providing a functional effect of reinforcing the adhesive layer.

In one embodiment of the adhesive composition for organic fibers of the present invention, an example of the principles behind the functional effects (a) and (b) of the aqueous compound (C) having a (thermally dissociable blocked) isocyanate group as an adhesion promoter is described in detail below.

<<Functional Effect of (a) as Adhesion Promoter>>
Polyester synthetic resin materials, such as polyethylene terephthalate, which are widely used as organic fibers, consist of flat, linear polymer chains. The surfaces of the polymer chains or the gaps between the polymer chains have a π-electron atmosphere derived from aromatic compounds contained in the polymer chains. Furthermore, polyester has particularly few hydroxyl groups on its surface compared to 6,6-nylon.

Therefore, organic fiber adhesive compositions used for polyester organic fibers have traditionally contained molecules with a planar structure (a portion that easily diffuses into organic fibers) having aromatic rings with aromatic π electrons on their sides as an adhesion promoter, with the aim of ensuring that the organic fiber adhesive composition disperses into the gaps between the polymer chains of the organic fibers and that the adhesive layer formed by the organic fiber adhesive composition adheres closely to the surface of the polymer chains of the organic fibers in order to obtain sufficient adhesive strength.

<<Functional Effect of (b) as Adhesion Promoter>>
In the adhesive layer containing the component (C-1), as described above, a covalent bond is formed by isocyanate crosslinking between the hydroxyl group of the acetoacetyl group-modified polyvinyl alcohol (B) contained in the adhesive composition for organic fibers and the isocyanate resulting from the dissociation of the blocking agent by heat treatment, thereby strengthening the adhesion achieved by the adhesive composition for organic fibers.

The particle size of the above component (C-1) is preferably 0.01 to 0.50 μm. When the particle size of the above component (C-1) is 0.50 μm or less, the smaller the particle size, the less likely the component (C-1) will settle in the liquid, and the less likely it will be dispersed non-uniformly in the adhesive layer.

On the other hand, (C-2) an aqueous urethane compound having a (thermally dissociable blocked) isocyanate group is highly water-soluble, making it less likely for components to settle in the adhesive composition liquid, and less likely for the components to become uneven even when stored stationary, resulting in stable adhesion over time and making it preferable.

<<Thermal dissociation blocking agent, water-based urethane compound>>
The thermally dissociable blocking agent of component (C-2) is not particularly limited as long as it is a blocking agent compound that can protect the isocyanate group from any chemical reaction while dissociating the blocking agent by heat treatment as necessary to restore the isocyanate group. Specific examples of the thermally dissociable blocking agent include the same compounds as the blocking agents described above for component (C-1). Preferred examples include phenols such as phenol, thiophenol, chlorophenol, cresol, resorcinol, p-sec-butylphenol, p-tert-butylphenol, p-sec-amylphenol, p-octylphenol, and p-nonylphenol; secondary or tertiary alcohols such as isopropyl alcohol and tert-butyl alcohol; aromatic secondary amines such as diphenylamine and xylidine; and phthalic acid imide. caprolactams such as ε-caprolactam; active methylene compounds such as dialkyl malonate, dimethyl malonate, and other malonic acid esters, acetylacetone, and alkyl acetoacetate; oximes such as acetoxime, methyl ethyl ketoxime, and cyclohexanone oxime; basic nitrogen compounds such as 3-hydroxypyridine, 1,2-pyrazole, 3,5-dimethylpyrazole, 1,2,4-triazole, diisopropylamine, and N,N'-diphenylformamidine; and acidic sodium sulfite.

Among these blocking agents, phenol, ε-caprolactam, and ketoxime are preferred, as they are easily thermally dissociated by heating to achieve stable thermal curing of the organic fiber adhesive composition.

Here, the term "aqueous" in reference to the aqueous urethane compound means that it is water-soluble or water-dispersible. Furthermore, the term "water-soluble" does not necessarily mean that it is completely water-soluble, but rather that it is partially water-soluble or that it does not undergo phase separation in the aqueous solution of the organic fiber adhesive composition.

The urethane compound of the aqueous urethane compound is a compound having a covalent bond formed between the nitrogen of an amine and the carbon of a carbonyl group, and means a compound represented by the following general formula (2).
In the above formula (2), R and R' represent hydrocarbon groups.

The molecular weight of the aqueous urethane compound (C-2) having a (thermally dissociable blocked) isocyanate group is not particularly limited as long as it remains aqueous, but a number average molecular weight of 1,500 to 100,000 is preferred, and a number average molecular weight of 9,000 or less is particularly preferred.

As mentioned above, the method for synthesizing the above component (C-2) is not particularly limited, and can be a known method, such as the method described in JP-A-63-51474.

<<(C-2) Preferred Embodiments of Aqueous Urethane Compound Having a (Thermally Dissociable Blocked) Isocyanate Group>>
A preferred embodiment of the component (C-2) is a reaction product obtained by mixing and reacting (α) an organic polyisocyanate compound having 3 to 5 functional groups and a number average molecular weight of 2,000 or less, (β) a compound having 2 to 4 active hydrogen groups and a number average molecular weight of 5,000 or less, (γ) a thermally dissociable blocking agent, and (δ) a compound having at least one active hydrogen group and at least one hydrophilic group that is anionic, cationic, or nonionic, in a predetermined mixing ratio, wherein the proportion of (thermally dissociable blocked) isocyanate groups in the reaction product is 0.5 to 11 mass % when the molecular weight of the isocyanate group (—NCO) is 42. In this case, when the adhesive composition is used on organic fibers, the adhesion between the organic fibers and the coating rubber composition is improved. This is because such a component (C-2) has both a moiety consisting of a (thermally dissociable blocked) isocyanate group and a hydrophilic moiety having a hydrophilic group, and therefore has the advantage of increasing the self-water solubility of the urethane compound.

The mixing ratio of each of the total amounts of (α), (β), (γ), and (δ) is 40% by mass or more and 85% by mass or less for (α), 5% by mass or more and 35% by mass or less for (β), 5% by mass or more and 35% by mass or less for (γ), and 5% by mass or more and 35% by mass or less for (δ).

The above-mentioned (α) organic polyisocyanate compound having 3 to 5 functional groups and a number-average molecular weight of 2,000 or less is not particularly limited, but is preferably an aromatic polyisocyanate compound and its oligomers, and may also be other aliphatic, alicyclic, or heterocyclic polyisocyanate compounds and their oligomers. This is because the reaction product (C-2), obtained by reacting such (α) organic polyisocyanate compound having 3 to 5 functional groups and a number-average molecular weight of 2,000 or less, is more easily dispersed in the gaps between the polymer chains of the organic fibers.

Specific examples of aliphatic polyisocyanate compounds include ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecane diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, dimer acid diisocyanate, and lysine diisocyanate. Specific examples of alicyclic polyisocyanate compounds include cyclobutane diisocyanate, Examples of the heterocyclic polyisocyanate compounds include 1,3,5-tris(2'-isocyanatomethyl)cyclohexane, ... Examples of aromatic polyisocyanate compounds include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, m-tetramethylxylylene diisocyanate, p-tetramethylxylylene diisocyanate, methine tris(4-phenylisocyanate), tris(4-isocyanatophenyl)methane, thiophosphate tris(4-isocyanatophenyl ester), 3-isopropenyl-α',α'-dimethylbenzyl isocyanate, and oligomer mixtures thereof, as well as modified products of these polyisocyanate compounds such as carbodiimides, polyols, and allophanates.

Among these, aromatic polyisocyanate compounds are preferred, with methylene diphenyl polyisocyanate and polyphenylene polymethylene polyisocyanate being particularly preferred. Polyphenylene polymethylene polyisocyanate having a number average molecular weight of 2,000 or less is particularly preferred, with polyphenylene polymethylene polyisocyanate having a number average molecular weight of 1,000 or less being particularly preferred. This is because component (C-2), which is the reaction product obtained after reacting such organic polyisocyanate compounds (α) having 3 to 5 functional groups and a number average molecular weight of 2,000 or less, is more easily dispersed in the gaps between the polymer chains of organic fibers.

The (β) compound having two or more and four or less active hydrogen groups and a number average molecular weight of 5,000 or less is not particularly limited, but specific examples thereof include compounds selected from the group consisting of the following (i) to (vii):
(i) polyhydric alcohols having 2 to 4 hydroxyl groups and a number average molecular weight of 5,000 or less;
(ii) polyamines having 2 to 4 primary and/or secondary amino groups and a number average molecular weight of 5,000 or less;
(iii) amino alcohols having two to four primary and/or secondary amino groups and a hydroxyl group and having a number average molecular weight of 5,000 or less;
(iv) polyester polyols having 2 to 4 hydroxyl groups and a number average molecular weight of 5,000 or less;
(v) polybutadiene polyols having 2 to 4 hydroxyl groups and a number average molecular weight of 5,000 or less, and copolymers thereof with other vinyl monomers;
(vi) polychloroprene polyols having 2 to 4 hydroxyl groups and a number average molecular weight of 5,000 or less, and copolymers thereof with other vinyl monomers;
(vii) Polyether polyols having 2 to 4 hydroxyl groups and a number average molecular weight of 5,000 or less,
C2-C4 alkylene oxide polyadducts of polyamines, polyhydric phenols and amino alcohols, C2-C4 alkylene oxide polyadducts of C3 or higher polyhydric alcohols, C2-C4 alkylene oxide copolymers, or C3-C4 alkylene oxide polymers.

Here, with regard to the above component (C-2), the term "active hydrogen group" refers to a group containing hydrogen that becomes active hydrogen (atomic hydrogen (hydrogen radical) and hydride ion (hydride)) when placed under suitable conditions. Examples of such active hydrogen groups include amino groups and hydroxyl groups.

The compound (δ) having at least one active hydrogen group and at least one anionic, cationic, or nonionic hydrophilic group includes, but is not limited to, taurine, N-methyltaurine, N-butyltaurine, aminosulfonic acids such as sulfanilic acid, and aminocarboxylic acids such as glycine and alanine.

The method for synthesizing component (C-2) by mixing and reacting the above (α), (β), (γ), and (δ) is not particularly limited, but can be a known method such as the method described in JP-A-63-51474.

<<(C-2) Another Preferred Embodiment of Aqueous Urethane Compound Having a (Thermally Dissociable Blocked) Isocyanate Group>>
Another preferred embodiment of the component (C-2) is a reaction product obtained by mixing and reacting (α) an organic polyisocyanate compound having 3 to 5 functional groups and a number-average molecular weight of 2,000 or less, (β) a compound having 2 to 4 active hydrogen groups and a number-average molecular weight of 5,000 or less, (γ) a thermally dissociable blocking agent, (δ) a compound having at least one active hydrogen group and at least one anionic, cationic, or nonionic hydrophilic group, and (ε) a compound other than (α), (β), (γ), and (δ) that contains an active hydrogen group, in a predetermined mixing ratio, wherein the proportion of (thermally dissociable blocked) isocyanate groups in the reaction product is 0.5 to 11 mass % when the molecular weight of the isocyanate group (—NCO) is 42. This is because such a component (C-2) has both a moiety consisting of a (thermally dissociable blocked) isocyanate group and a hydrophilic moiety having a hydrophilic group, and therefore has the advantage of increasing the self-water solubility of the urethane compound.

The mixing ratio of each of the total amounts of (α), (β), (γ), (δ), and (ε) is 40% by mass or more and less than 85% by mass for (α), 5% by mass or more and less than 35% by mass for (β), 5% by mass or more and less than 35% by mass for (γ), 5% by mass or more and less than 35% by mass for (δ), and more than 0% by mass and less than 45% by mass for (ε).

Here, the (α) organic polyisocyanate compound having 3 to 5 functional groups and a number-average molecular weight of 2,000 or less, (β) compound having 2 to 4 active hydrogen groups and a number-average molecular weight of 5,000 or less, (γ) thermally dissociable blocking agent, and (δ) compound having at least one active hydrogen group and at least one anionic, cationic, or nonionic hydrophilic group are as described above in <<(C-2) Preferred Embodiments of Aqueous Urethane Compound Having (Thermally Dissociable Blocked) Isocyanate Groups>>>, except for the mixing ratio.

The method for synthesizing component (C-2) by mixing and reacting the above (α), (β), (γ), (δ), and (ε) is not particularly limited, but can be a known method such as the method described in JP-A-63-51474.

<<(C-2) Yet Another Preferred Embodiment of Aqueous Urethane Compound Having a (Thermally Dissociable Blocked) Isocyanate Group>>
Yet another preferred embodiment of the component (C-2) is a compound represented by the following general formula (1):
[In formula (1),
A is a residue of an organic polyisocyanate compound from which an active hydrogen group has been eliminated,
X is a residue of a polyol compound having 2 or more and 4 or less hydroxyl groups and a number average molecular weight of 5,000 or less, from which an active hydrogen group has been eliminated;
Y is a residue of the thermally dissociable blocking agent from which the active hydrogen group has been eliminated;
Z is a residue of a compound having at least one active hydrogen group and at least one salt-forming group or hydrophilic polyether chain, from which the active hydrogen group has been eliminated;
n is an integer between 2 and 4,
p + m is an integer between 2 and 4 (m≧0.25)
[0039] In this case as well, when the adhesive composition is used on organic fibers, the adhesion between the organic fibers and the coating rubber composition is improved. This is because the component (C-2) has both a moiety consisting of a (thermally dissociable blocked) isocyanate group and a hydrophilic moiety having a hydrophilic group, thereby providing the advantage of increasing the self-water solubility of the urethane compound.

Here, it is preferable that the organic polyisocyanate compound A in general formula (1), which is the residue of the organic polyisocyanate compound from which the active hydrogen group has been eliminated, contains an aromatic ring. This is because this makes it easier for component (C-2) to disperse in the gaps between the polymer chains of the organic fiber.

Although not particularly limited, specific examples include methylene diphenyl polyisocyanate and polyphenylene polymethylene polyisocyanate. Polyphenylene polymethylene polyisocyanate with a number average molecular weight of 6,000 or less is preferred, and polyphenylene polymethylene polyisocyanate with a number average molecular weight of 4,000 or less is particularly preferred.

The polyol compound having two or more and four or less hydroxyl groups and a number average molecular weight of 5,000 or less, which is the residue obtained by eliminating the active hydrogen group from a polyol compound having two or more and four or less hydroxyl groups and a number average molecular weight of 5,000 or less, represented by X in general formula (1), is not particularly limited, but specific examples thereof include compounds selected from the group consisting of the following (i) to (vi):
(i) polyhydric alcohols having 2 to 4 hydroxyl groups and a number average molecular weight of 5,000 or less;
(ii) amino alcohols having two to four primary and/or secondary amino groups and a hydroxyl group and having a number average molecular weight of 5,000 or less;
(iii) polyester polyols having 2 to 4 hydroxyl groups and a number average molecular weight of 5,000 or less;
(iv) polybutadiene polyols having 2 to 4 hydroxyl groups and a number average molecular weight of 5,000 or less, and copolymers thereof with other vinyl monomers;
(v) polychloroprene polyols having 2 to 4 hydroxyl groups and a number average molecular weight of 5,000 or less, and copolymers of these with other vinyl monomers;
(vi) Polyether polyols having 2 to 4 hydroxyl groups and a number average molecular weight of 5,000 or less;
C2-C4 alkylene oxide polyadducts of polyamines, polyhydric phenols and amino alcohols, C2-C4 alkylene oxide polyadducts of C3 or higher polyhydric alcohols, C2-C4 alkylene oxide copolymers, or C3-C4 alkylene oxide polymers.

The above component (C-2) is not particularly limited, but commercially available products such as Elastron BN27, BN77, and BN11 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. can also be used. Of these, Elastron BN77 is preferred.

<(D) Amine Compound>
One preferred embodiment of the adhesive composition for organic fibers of the present invention comprises (A) a rubber latex having an unsaturated diene, (B) an acetoacetyl group-modified polyvinyl alcohol, and (D) an amine compound.

As the (D) amine compound, a polyfunctional amine compound having two or more primary, secondary, or tertiary amino groups is preferably used. Specific examples of the (D) amine compound include ethylenediamine, propylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, phenylenediamine, metaxylenediamine, diethylenetriamine, triethylenetetramine, triaminopropane, and amino group-containing resins such as polyvinylamine, polyethyleneimine, polyallylamine, and polylysine.

The number average molecular weight of the amino group-containing resin is, for example, 100 to 1,000,000, preferably 200 to 10,000, and more preferably 300 to 5,000. The number average molecular weight of the amino group-containing resin can be determined, for example, by a known viscosity method. If the molecular weight of the amino group-containing resin is too large, gel crosslinking may occur in the adhesive composition liquid, causing the viscosity to become too high, which may result in problems with workability.

Among these, in the present invention, polyethyleneimine, which is an amino group-containing resin, can be suitably used as the amine compound (D). Polyethyleneimine is a water-soluble polymer obtained by polymerizing ethyleneimine, and is a polymer consisting of repeating units of amine and ethylene (CH ₂ CH ₂ ). Polyethyleneimine generally contains primary, secondary, and tertiary amino groups, and for example, polyethyleneimine, which is not a completely linear molecule but has a branched structure and has an average molecular weight of about 600 as a commercially available reagent, can be used.

In the adhesive composition for organic fibers of the present invention, the (D) amine compound polyethyleneimine interacts with the acetoacetyl groups of the (B) acetoacetyl-modified polyvinyl alcohol, which is emulsified by the action of an emulsifier, on the surface of rubber latex dispersed in an aqueous solvent, through chemical crosslinking and other interactions, thereby strengthening the protective film on the latex surface and suppressing the tackiness of the rubber latex. This makes it possible to suppress adhesion of the adhesive composition to rolls and the like during the process of coating an organic fiber cord with the adhesive composition and drying and thermal curing it, thereby improving workability.

The polyethyleneimine used in the present invention is available in liquid form, but when used in the adhesive composition of the present invention, it is preferably used as an aqueous solution.

The content (solids content) of the (D) amine compound relative to the total solids content of the adhesive composition for organic fibers of the present invention is not particularly limited, but is preferably 0.3% by mass or more, and more preferably 1.0% by mass or more. Furthermore, the content (solids content) of the (D) amine compound is preferably 35% by mass or less, and more preferably 25% by mass or less.

<(E) Polyphenols>
One preferred embodiment of the adhesive composition for organic fibers of the present invention contains (A) a rubber latex having an unsaturated diene, (B) an acetoacetyl group-modified polyvinyl alcohol, and (E) a polyphenol.

The (E) polyphenol is preferably a plant-derived compound having multiple phenolic hydroxy groups within the molecule. In this case, when the adhesive composition is used with organic fibers, the adhesion between the organic fibers and the coating rubber composition is improved. Specific examples of (E) polyphenols include lignin, tannin, tannic acid, flavonoids, and derivatives thereof. In this case, too, when the adhesive composition is used with organic fibers, the adhesion between the organic fibers and the coating rubber composition is improved.

Research has long been conducted into isolating polyphenols such as lignin and tannin, which are components of wood and bark, and reacting them with formaldehyde to produce adhesives (see, for example, JP 07-53858 A), but there is little knowledge about producing aqueous adhesive compositions that do not contain resorcinol.

The polyphenol (E) is preferably lignin or a derivative thereof. Lignin, along with polysaccharides such as cellulose, is a major component of plant cell walls. Lignin contains functional groups such as hydroxyl groups, methoxy groups, carbonyl groups, and carboxyl groups, and phenolic hydroxyl groups in particular are highly reactive and can interact with cationic polymers such as polyethyleneimine.

Lignin is a polymer with a structure based on phenylpropane, but the molecular structure of lignin varies widely, and because it is a large biopolymer that forms a three-dimensional network structure, its molecular structure has not yet been fully elucidated.

Because natural lignin forms a strong composite material with polysaccharides such as cellulose in plant cell walls, isolating natural lignin without denaturing its chemical structure is considered extremely difficult. Various industrial separation methods are used to extract lignin from materials such as wood. Lignins obtained after separation include sulfonate lignin, kraft lignin, soda lignin, and steam-exploded lignin. Among these industrially handled lignins, lignosulfonates or kraft lignins, which are obtained on a large scale from the pulp waste liquor of chemical pulping in paper pulp manufacturing processes, are well-known materials from the standpoints of availability and economy.

Other examples of lignins include lignins modified by hydroxymethylation, epoxidation, denitrification, acylation, or hydroxylation, diethanolamine-modified lignin, enzyme-modified lignin, laccase-modified lignin, urea-modified lignin, lignosulfonates, Alcel process lignin, alkaline granite process lignin, and polyethylene glycol-added lignin.

The kraft lignin is derived from a chemical pulping process (high-temperature, high-pressure reaction) known as the kraft cooking process, which involves adding wood chips, such as hardwood, softwood, miscellaneous wood, bamboo, kenaf, and bagasse, to a digester along with a cooking liquor containing sodium hydroxide and sodium sulfide. Acid and/or carbon dioxide are added to the kraft waste liquor obtained after kraft cooking to precipitate the dissolved modified lignin, and the resulting precipitate is then dehydrated and washed to obtain the product. Furthermore, the precipitate after dehydration and washing can be dissolved by adding an organic solvent such as alcohol or acetone, and the insoluble impurities can be separated and dried for purification, or modified by introducing various functional groups as needed. The kraft lignin can be obtained as a commercially available product. Among these, Sigma-Aldrich Co. The preferred reagent is "Lignin Alkali Kraft" (CAS Number: 8068-05-1) manufactured by L.P.L.C.

The above-mentioned sulfonated lignins are lignin sulfonic acids and their salts obtained using waste liquor eluted from sulfite pulp as a raw material in the sulfite cooking chemical pulping process, in which wood chips are reacted with a cooking liquor containing sulfite and/or sulfite salts at high temperature and pressure. Particularly preferred examples include calcium lignin sulfonate, sodium lignin sulfonate, potassium lignin sulfonate, and magnesium lignin sulfonate. Of these, sodium lignin sulfonate is preferred. These sulfonated lignins are commercially available; for example, lignin sulfonates or modified lignin sulfonates such as the Sunex series from Nippon Paper Industries Co., Ltd. can be used.

High-value-added lignin sulfonates include, for example, high-purity products, as well as partially desulfonated (low-) lignin sulfonates, which have a reduced degree of sulfonation achieved by heating lignin sulfonates in an alkaline aqueous solution using sodium hydroxide or ammonia in the presence of an oxidizing agent such as oxygen (see, for example, JP 2016-135834 A). Examples of high-purity or modified lignin sulfonates include the Pearlex series, manufactured by Nippon Paper Industries Co., Ltd., and examples of partially desulfonated lignin sulfonates include the Vanilex series, manufactured by Nippon Paper Industries Co., Ltd. Among these, the reagent "Lignin (Alkali)" (CAS Number: 8061-51-6, solid powder), manufactured by Tokyo Chemical Industry Co., Ltd., is preferred, as it is a partially desulfonated (low-) sulfonated lignin sulfonate with a reduced degree of sulfonation.

Tannins are a group of polyphenolic compounds found in a wide range of plants, including woody trees, as well as fruits, leaves, and seeds, such as grapes, persimmons, berries, cloves, legumes, medicinal herbs, tea leaves, and cocoa beans. Tannin molecules generally contain numerous hydroxyl groups, and often carboxyl groups, and tend to form strong complexes and conjugates with a wide range of macromolecules.

The above-mentioned tannins include tannic acid, proanthocyanidins, flavonoids, gallic acid esters, catechins, etc., as well as their derivatives such as salts and modified forms. Furthermore, the above-mentioned flavonoids are ubiquitous in the leaves, stems, and bark of plants, and are generally called tannins, but they consist of hydrolyzable tannins and condensed tannins. These tannins can be distinguished by boiling them in dilute hydrochloric acid; condensed tannins form an insoluble precipitate, while hydrolyzable tannins hydrolyze to produce water-soluble substances.

Both hydrolyzable and condensed tannins are water-soluble and can be extracted from plant materials such as wood, bark, leaves, fruits, pods, and insect larvae using methods such as hot water extraction. Hydrolyzable tannins can be obtained, for example, from chestnut and nut wood, oak bark, tea leaves, and gallnut and gallnut insect larvae. Condensed tannins can be obtained from quebracho wood, mimosa bark, persimmons, and buckwheat seeds. Among these, preferred hydrolyzable tannins include tannic acid obtained from gallnut and other fruits, available from Nakarai Tesque, Inc. under the reagent name "Tannic Acid" (CAS Number: 1401-55-4-6, solid powder), and condensed tannins obtained from mimosa bark, available from Kawamura Tsusho Co., Ltd. under the trade name "Mimosa" (solid powder).

The content (solids content) of the (E) polyphenol relative to the total solids in the organic fiber adhesive composition of the present invention is not particularly limited, but is preferably 2% by mass or more, more preferably 5% by mass or more, and even more preferably 8% by mass or more. The content of the (E) polyphenol is preferably 75% by mass or less, more preferably 50% by mass or less, and even more preferably 35% by mass or less. A content of the (E) polyphenol of 2% by mass or more improves the adhesion between the organic fiber and the coating rubber composition. A content of the (E) polyphenol of 75% by mass or less makes it possible to ensure a certain relative amount of other components, such as rubber latex, blended into the organic fiber adhesive composition, resulting in better adhesion to the rubber substrate.

<Method of manufacturing adhesive composition for organic fibers>
The adhesive composition for organic fibers of the present invention contains, as essential components, (A) a rubber latex having an unsaturated diene and (B) an acetoacetyl group-modified polyvinyl alcohol, and more preferably contains one or more compounds selected from the group consisting of (C) an aqueous compound having a (thermally dissociable blocked) isocyanate group, (D) an amine compound, and (E) a polyphenol.

When producing the above-mentioned adhesive composition for organic fibers, (A) the rubber latex having an unsaturated diene and (B) the acetoacetyl group-modified polyvinyl alcohol are mixed, and then (C) the aqueous compound having a (thermally dissociable blocked) isocyanate group, (D) the amine compound, and (E) the polyphenol can be mixed in any order.

In the adhesive composition for organic fibers of the present invention, the mixing mass ratio [(A):(B)] (on a solids basis) of (A) the rubber latex having an unsaturated diene and (B) the acetoacetyl group-modified polyvinyl alcohol is not particularly limited, but is preferably in the range of 100:0.1 to 100:25, and more preferably in the range of 100:0.2 to 100:15.

When the mixing ratio by mass is 100:0.1 or more (a ratio of 1,000 or less), a coating of microcapsules of (B) acetoacetyl-modified polyvinyl alcohol can be formed around the (A) unsaturated diene-containing rubber latex as a core, and a sufficiently strong adhesive layer can be obtained. Furthermore, when the mixing ratio by mass is 100:25 or less (a ratio of 4 or more), the coating of microcapsules of (B) acetoacetyl-modified polyvinyl alcohol formed around the (A) unsaturated diene-containing rubber latex as a core does not become too thick. When the coated rubber composition and the adhesive composition for organic fibers are co-vulcanized to bond the coated rubber composition and the adhesive composition for organic fibers, the coated rubber composition and the adhesive composition for organic fibers are well compatible with each other. As a result, the initial process of adhesion between the coated rubber composition and the adhesive composition for organic fibers proceeds smoothly.

When mixing the (A) rubber latex containing an unsaturated diene with the (B) acetoacetyl-modified polyvinyl alcohol, a known water-soluble material capable of strengthening the film formed from the (B) acetoacetyl-modified polyvinyl alcohol can be used in combination with a conventional coacervate. Examples of such materials include gum arabic, carrageenan, CMCs, and electrolytes made from organic or inorganic salts, such as salts with cations like sodium chloride, potassium chloride, magnesium chloride, and ammonium chloride, and salts with anions like sulfates, phosphates, carbonates, and acetates. Furthermore, water-soluble liquids in which the film-forming material dissolves less than in water can also be used, such as alcohols like ethanol and propanol, or water-soluble polymers like isobutylene-maleic anhydride ring-opening copolymer salts.

In the adhesive composition for organic fibers of the present invention, the mixing mass ratio [(A):[(C) + (D) + (E)]] (solids equivalent) of (A) a rubber latex having an unsaturated diene to (C) an aqueous compound having a (thermally dissociable blocked) isocyanate group, (D) an amine compound, and (E) a compound selected from the group consisting of polyphenols is not particularly limited, but is preferably in the range of 100:5 to 100:300, more preferably in the range of 100:10 to 100:150, and even more preferably in the range of 100:15 to 100:60.

When the mixing mass ratio is 100:5 or more (20 or less), the proportion of the rubber latex having an unsaturated diene (A) in the organic fiber adhesive composition is not too high, allowing the adhesive layer formed by the organic fiber adhesive composition to maintain sufficient fracture resistance and prevent a decrease in adhesion under strain. Furthermore, when the mixing mass ratio is 100:300 or less (one-third or more), the proportion of the rubber latex having an unsaturated diene (A) in the organic fiber adhesive composition is not too low, allowing the coated rubber composition, which serves as an adherend for the organic fiber, and the adhesive composition for organic fiber to be co-vulcanized and bonded together, to achieve good compatibility between the coated rubber composition and the adhesive composition for organic fiber. As a result, the adhesion between the coated rubber composition and the adhesive composition for organic fiber is sufficiently high.

Furthermore, the above (A) rubber latex having an unsaturated diene, (B) acetoacetyl group-modified polyvinyl alcohol, (C) aqueous compound having a (thermally dissociable blocked) isocyanate group, (D) amine compound, and (E) polyphenol are preferably aqueous. This is because water, which causes less environmental pollution, can be used as a solvent.

[Organic fiber materials]
The adhesive composition for organic fibers constructed as described above is applied to the surface of organic fibers, for example, organic fibers made of polyester resin, aromatic polyamide resin, acrylic resin, or the like, and then subjected to an appropriate heat treatment, whereby an adhesive layer made of the adhesive composition for organic fibers is applied to the surface of the organic fibers, thereby producing an adhesive-treated organic fiber material.

The organic fiber material of the present invention is characterized in that the surface of the organic fiber is coated with an adhesive layer made of the organic fiber adhesive composition. This allows for an organic fiber material with excellent durability while ensuring environmental friendliness and workability. It is particularly preferred that the organic fiber be made of polyester resin, aromatic polyamide resin, or acrylic resin, and of these, it is preferable that the organic fiber be made of polyester resin. It is also preferable that the organic fiber be a cord made by twisting together multiple filaments.

Methods for coating the surface of organic fibers with the adhesive composition include immersing the organic fibers in the adhesive composition, applying the adhesive composition to the organic fibers with a brush, or spraying the adhesive composition onto the organic fibers. Any appropriate method can be selected as needed. There are no particular limitations on the method for coating the surface of organic fibers with the adhesive composition. However, when coating the surface of organic fibers with the adhesive composition, it is preferable to dissolve the adhesive composition in various solvents to reduce the viscosity, as this makes coating easier. Furthermore, it is environmentally preferable for the solvent used to reduce the viscosity of the adhesive composition to consist primarily of water.

The solution concentration of the adhesive composition with which the organic fibers are impregnated is not particularly limited, but is preferably 5.0% by mass or more and 25.0% by mass or less, and more preferably 7.5% by mass or more and 20.0% by mass or less, in terms of solid content relative to the mass of the organic fibers.

Here, the thickness of the adhesive layer made from the above adhesive composition is not particularly limited, but is preferably 50 μm or less, and more preferably 0.5 μm or more and 30 μm or less.

In particular, when the organic fiber material of the present invention is applied to tires, if the amount of adhesive composition applied by the adhesive treatment becomes thick, adhesion durability under tire rolling tends to decrease. This is because the adhesive composition at the interface of the adhered fiber material has high rigidity, so it bears the stress caused by strain and undergoes relatively little deformation, but the deformation caused by strain increases with distance from the interface. Because the adhesive composition contains a higher amount of thermosetting condensate than the adhered rubber material, it is hard and brittle, and is therefore prone to greater adhesive fatigue under repeated strain. For these reasons, the average thickness of the adhesive composition layer is preferably 50 μm or less, and more preferably 0.5 μm or more and 30 μm or less.

When the organic fiber is a cord, the adhesive layer preferably has a dry mass of 0.5 to 6.0% of the mass of the cord in the organic fiber material. By keeping the dry mass of the adhesive layer within this range, appropriate adhesiveness can be ensured.

The organic fiber material, whose surface is coated with the organic fiber adhesive composition, is then dried, for example, at a temperature of 100°C to 210°C, and then heat-treated. This heat treatment is preferably carried out at a temperature above the glass transition temperature of the polymer in the organic fiber, preferably at a temperature above the polymer's melting temperature minus 70°C and below the polymer's melting temperature minus 10°C. The reason for this is that below the polymer's glass transition temperature, the polymer's molecular mobility is poor, preventing sufficient interaction between the adhesion-promoting components of the organic fiber adhesive composition and the polymer, resulting in insufficient bonding strength between the organic fiber adhesive composition and the organic fiber. Such organic fibers may be pretreated using electron beams, microwaves, corona discharge, plasma treatment, etc.

[Rubber articles]
The adhesive composition for organic fibers of the present invention can be suitably used for reinforcing various rubber articles. The rubber article of the present invention is characterized by being reinforced with the above-mentioned organic fiber material. This allows the rubber article to be excellent in durability while ensuring environmental friendliness and workability. Examples of such rubber articles of the present invention include tires, as well as conveyor belts, belts, hoses, air springs, etc.

[Organic fiber-rubber composite]
The organic fiber-rubber composite of the present invention is a composite of organic fiber and rubber, characterized in that the organic fiber is coated with the above-mentioned adhesive composition for organic fibers. This makes it possible to obtain good adhesion without using resorcinol, and to obtain an organic fiber-rubber composite with good environmental friendliness and workability. The adhesive composition for organic fiber of the present invention is particularly excellent in adhesion between organic fibers such as organic fiber cords and the coated rubber composition.

The organic fiber-rubber composite of the present invention will be described in detail with reference to Figure 2.

Figure 2 is a schematic cross-sectional view showing an organic fiber cord-rubber composite, which is an example of an organic fiber-rubber composite of the present invention. In the organic fiber-rubber composite 31 shown in Figure 2, the outer radial surface of the organic fiber cord 1 is coated with an adhesive layer 32 made from the organic fiber adhesive composition 2 of the present invention. The organic fiber cord 1 is then bonded to a coating rubber composition 33 located further outward in the radial direction via the adhesive 32 made from the organic fiber adhesive composition 2, thereby forming the organic fiber-rubber composite 31 of the present invention.

In addition to the organic fiber cord-rubber composite, reinforcing materials for rubber articles using the organic fiber adhesive composition of the present invention can also be in the form of short fibers, nonwoven fabrics, etc.

<Organic fiber cord>
An organic fiber cord, which is an example of the organic fiber, is used to supplement the strength of rubber articles such as tires. When using the organic fiber cord as a reinforcing material, first, spun organic fiber raw yarn is twisted to form an organic fiber cord. Then, the organic fiber cord is embedded in rubber that coats the organic fiber cord using an organic fiber adhesive composition, and the organic fiber cord is vulcanized and bonded to form an organic fiber-rubber composite. This organic fiber-rubber composite can be used as a reinforcing member for rubber articles such as tires.

The material of the organic fiber is not particularly limited, but examples include aliphatic polyamide fibers such as polyester, 6-nylon, 6,6-nylon, and 4,6-nylon; protein fibers such as artificial fibroin fibers; polyketone fibers; aromatic polyamide fibers such as polynonamethylene terephthalamide and paraphenylene terephthalamide; acrylic fibers; carbon fibers; and cellulose fibers such as rayon and lyocell. Of these, polyester, 6-nylon, and 6,6-nylon are preferred, with polyester being particularly preferred.

The polyester material is a polymer having ester bonds in its main chain; more specifically, 80% or more of the repeating units in the main chain are ester bonds. Examples of the polyester include, but are not limited to, those obtained by condensing glycols such as ethylene glycol, propylene glycol, butylene glycol, methoxypolyethylene glycol, and pentaerythritol with dicarboxylic acids such as terephthalic acid, isophthalic acid, and their dimethyl forms through an esterification or transesterification reaction. The most typical polyester is polyethylene terephthalate.

The organic fiber cord is preferably an organic fiber cord made by twisting together multiple monofilament filaments, particularly for the purpose of reinforcing rubber articles such as tires and conveyor belts. Furthermore, the organic fiber cord is preferably an organic fiber cord made by twisting together a top-twisted monofilament filament and a bottom-twisted monofilament filament. In this case, it is more preferable that the twist coefficient of the bottom twist be 1,300 or more and 2,500 or less, and/or the twist coefficient of the top twist be 900 or more and 1,800 or less.

In the present invention, the organic fiber is preferably a polyester (polyethylene terephthalate) tire cord with a twist structure of 1670 dtex/2, a top twist of 39 turns/10 cm, and a bottom twist of 39 turns/10 cm, and the adhesive composition is adhered to this tire cord to form an organic fiber-rubber composite.

<<Coating rubber composition for organic fiber-rubber composite>>
The coating rubber composition constituting the organic fiber-rubber composite of the present invention is preferably a rubber component blended with various compounding agents commonly used in the rubber industry. The rubber component is not particularly limited, and examples thereof include natural rubber, conjugated diene-based synthetic rubbers such as polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), and butyl rubber (IIR), as well as ethylene-propylene copolymer rubber (EPM), ethylene-propylene-diene copolymer rubber (EPDM), and polysiloxane rubber. Of these, natural rubber and conjugated diene-based synthetic rubber are preferred. These rubber components may be used alone or in combination of two or more.

<<Method of manufacturing organic fiber-rubber composite>>
The organic fiber-rubber composite of the present invention can be produced by coating organic fibers such as organic fiber cords with the adhesive composition for organic fibers of the present invention to form an adhesive layer, and then co-vulcanizing and bonding the rubber latex having an unsaturated diene (A) in the adhesive composition for organic fibers and the rubber component in the coating rubber composition that is the adherend of the organic fibers.

To co-vulcanize the rubber components in the above-mentioned coated rubber composition, organic vulcanizing agents such as sulfur, thiarium polysulfide compounds such as tetramethylthiarium disulfide and dipentamethylenethiarium tetrasulfide, 4,4-dithiomorpholine, p-quinone dioxime, p,p'-dibenzoquinone dioxime, and cyclic sulfur imides can be used. Among these, sulfur is preferred. Furthermore, the rubber components in the above-mentioned coated rubber composition can be appropriately blended with various additives commonly used in the rubber industry, such as fillers such as carbon black, silica, and aluminum hydroxide, as well as vulcanization accelerators, antioxidants, and softeners.

It goes without saying that the adhesive composition for organic fibers of the present invention also provides effective adhesion in an adhesion method in which a vulcanizing agent contained in an adherend made of a synthetic resin material such as organic fiber and/or an adherend made of a coated rubber composition migrates to the adhesive composition for organic fibers, and the migrated vulcanizing agent crosslinks the adhesive composition for organic fibers.

[tire]
The tire of the present invention uses the organic fiber-rubber composite of the present invention, which allows for good adhesion without using resorcinol, resulting in a tire with good environmental friendliness and workability.

In the tire of the present invention, the organic fiber-rubber composite can be used, for example, as a reinforcing layer around the belt, such as in the carcass, belt, belt reinforcing layer, or flipper.

Depending on the type of tire to be used, the tire of the present invention may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, or by molding a semi-vulcanized rubber that has undergone a pre-vulcanization process or the like and then further vulcanizing it. The tire of the present invention uses organic fiber cords, etc., treated with the organic fiber adhesive composition described above at some location on the tire, but other components are not particularly limited and known components can be used. The tire of the present invention is preferably a pneumatic tire, and the gas used to fill the pneumatic tire can be normal air or air with an adjusted oxygen partial pressure, as well as inert gases such as nitrogen, argon, and helium.

The adhesive composition for organic fibers of the present invention, as well as the organic fiber material and organic fiber-rubber composites using the same, can be applied to all kinds of rubber products, including conveyor belts, belts, hoses, air springs, and the like, in addition to the tires mentioned above.

The present invention will be explained in more detail below using examples, but the present invention is not limited to the following examples in any way.

<(A-1) Synthetic Rubber Latex Having Unsaturated Diene>
In the following Comparative Examples 1, 3 to 8, Examples 1 to 6, and Reference Examples 1 to 5, a vinylpyridine-styrene-butadiene copolymer latex was used as the synthetic rubber latex having an unsaturated diene (A-1), which was prepared as follows in accordance with Comparative Example 1 described in JP-A-9-78045.

130 parts by weight of deionized water and 4.0 parts by weight of potassium rosinate as an emulsifier were charged into a nitrogen-purged 5-liter autoclave and dissolved. A monomer mixture consisting of 15 parts by weight of vinylpyridine monomer, 15 parts by weight of styrene, and 70 parts by weight of butadiene, along with 0.60 parts by weight of t-dodecyl mercaptan as a chain transfer agent, was then charged and emulsified. The temperature was then raised to 50°C, and 0.5 parts by weight of potassium persulfate as a polymerization initiator was added to initiate polymerization. After the reaction rate of the monomer mixture reached 90%, 0.1 parts by weight of hydroquinone was added to terminate the polymerization. Next, unreacted monomer was removed under reduced pressure, yielding a vinylpyridine-styrene-butadiene copolymer latex with a solids concentration of 41% by weight.

<(A-2) Natural Rubber Latex>
In the following Comparative Example 2 and Example 7, a field latex having a solid content of 60% was used as the natural rubber latex (A-2) after adjusting the solid content to 41% with deionized water.

<(B) Acetoacetyl Group-Modified Polyvinyl Alcohol>
In the following Examples 1 to 7 and Reference Examples 1 to 5, the acetoacetyl group-modified polyvinyl alcohol (B) was (B-1) Mitsubishi Chemical Corporation's trade name "Gohsenex Z-200" (solids concentration 10%, saponification degree 99 mol% or more, aqueous solution), (B-2) Mitsubishi Chemical Corporation's trade name "Gohsenex Z-300" (solids concentration 10%, saponification degree 98 to 99 mol%, aqueous solution), or (B-3) Mitsubishi Chemical Corporation's trade name "Gohsenex Z-410" (solids concentration 10%, saponification degree 97.5 to 99.5%, aqueous solution), which was diluted with deionized water by the following method to obtain a 5% aqueous solution.

First, 50.0 g of the acetoacetyl-modified polyvinyl alcohols (B-1) to (B-3) described above was gradually added to 950.0 g of deionized water stirred at room temperature. After stirring this solution for 10 minutes at room temperature, it was heated to an internal temperature of 85 to 90°C and continued stirring at that temperature for 2 hours. After confirming dissolution of the acetoacetyl-modified polyvinyl alcohol, the aqueous solution of acetoacetyl-modified polyvinyl alcohol was cooled to room temperature. The dissolved aqueous solution of polyvinyl alcohol was then filtered through a 1 μm filter, and deionized water was added to replace the water that evaporated during heating and stirring, producing an aqueous solution of acetoacetyl-modified polyvinyl alcohol with a solids concentration of 5% by mass. This aqueous solution was used to prepare the adhesive composition.

<(C) Aqueous Compound Having a (Thermally Dissociable Blocked) Isocyanate Group>
In the following Comparative Example 3 and Example 6, Grillbond IL-6 (solid content concentration: 50% by mass), a product of EMS-CHEMIE HOLDIMG AG, which is a blocked compound of caprolactam with methylene diphenyl diisocyanate (C-1), was used as is as the aqueous compound having a (thermally dissociable blocked) isocyanate group (C).

In the following Comparative Example 4 and Examples 1 to 5 and 7, the aqueous compound having a (thermally dissociable blocked) isocyanate group (C) was used as is, as is, the product name "Elastron BN77" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. (an aqueous urethane compound having a (thermally dissociable blocked) isocyanate group (C-2), blocking agent thermal dissociation temperature: approximately 160°C, pH: 8.0, solids concentration: 31% by mass).

<(D) Amine Compound>
In the following Comparative Example 5 and Reference Example 2, the (D) amine compound was a reagent named "polyethyleneimine (average molecular weight: approximately 600)" (CAS number: 9002-98-6, liquid) manufactured by Wako Pure Chemical Industries, Ltd., diluted with deionized water to prepare an aqueous solution with a solids concentration of 10 mass %, and this aqueous solution was used in preparing the adhesive composition.

<(E) Polyphenols>
In the following Comparative Examples 6 to 8, Example 4, and Reference Examples 3 to 5, the following polyphenols were used as the (E) polyphenol: kraft lignin (E-1), lignin sulfonate (E-2), and condensed tannin (E-3). These powdered polyphenols were dissolved in deionized water to prepare aqueous solutions with a solids concentration of 5% by mass, and these aqueous solutions were used to prepare adhesive compositions.

(E-1) Kraft lignin, product name "Lignin, alkaline" (CAS Number: 8068-05-1), manufactured by Sigma-Aldrich Co. LLC. (E-2) Partially desulfonated lignin sulfonate, product name "Lignin (alkali)" (CAS Number: 8061-51-6), manufactured by Tokyo Chemical Industry Co., Ltd., with a reduced degree of sulfonation. (E-3) Tannin, product name "Mimosa" (solid powder), manufactured by Kawamura Tsusho Co., Ltd.

<<Preparation of Latex Adhesive Compositions (Comparative Examples 1 and 2)>>
The rubber latex (A) and water were blended (wet blended) as shown in Table 2, and the amounts were adjusted to give a solids concentration of 17% by mass. The mixture was then thoroughly stirred to obtain a latex adhesive composition. In the following Comparative Example 1, the synthetic rubber latex having an unsaturated diene (A-1) was used, and in Comparative Example 2, the natural rubber latex (A-2) was used.

<<Preparation of Latex-Waterborne Urethane Adhesive Compositions (Comparative Examples 3 and 4)>>
The synthetic rubber latex having an unsaturated diene (A-1) and the aqueous compound having a (thermally dissociable blocked) isocyanate group (C-1) were blended (wet blending) as shown in Table 2, and the amount of water was adjusted with water so that the solids concentration of the adhesive composition would be 17 mass %, followed by mixing and sufficient stirring to obtain a latex-aqueous urethane adhesive composition (Comparative Example 3).

Furthermore, the above-mentioned (A-1) synthetic rubber latex having an unsaturated diene and the above-mentioned (C-2) aqueous compound having a (thermally dissociable blocked) isocyanate group were blended (wet blending) as shown in Table 2, and the amount of water was adjusted to give a solids concentration of 17% by mass in the adhesive composition. The mixture was then thoroughly stirred to obtain a latex-waterborne urethane adhesive composition (Comparative Example 4).

<<Preparation of Latex-Amine Compound Adhesive Composition (Comparative Example 5)>>
The above (A-1) unsaturated diene-containing synthetic rubber latex and the above (D) amine compound were blended (wet blending) as shown in Table 2, and the amount of water was adjusted to give a solids concentration of the adhesive composition of 17 mass %, followed by mixing and sufficient stirring to obtain a latex-amine compound adhesive composition (Comparative Example 5).

<<Preparation of Latex-Polyphenol Adhesive Compositions (Comparative Examples 6 to 8)>>
The above (A-1) synthetic rubber latex having an unsaturated diene and the above (E) polyphenol were blended (wet blending) as shown in Table 3, and the amount of water was adjusted to give a solids concentration of the adhesive composition of 17 mass %, followed by mixing and sufficient stirring to obtain latex-polyphenol adhesive compositions (Comparative Examples 6 to 8).

<<Preparation of Adhesive Compositions (Examples 1 to 7, Reference Examples 1 to 5) According to an Embodiment of the Invention>>
As shown in Tables 3 to 5, each of the predetermined (A) rubber latex having an unsaturated diene, (B) acetoacetyl group-modified polyvinyl alcohol, (C) aqueous compound having a (thermally dissociable blocked) isocyanate group (Examples 1 to 7), (D) amine compound (Reference Example 2), and (E) polyphenol (Example 4, Reference Examples 3 to 5) was blended in this order (wet blending), the amount of water was adjusted with water so that the solids concentration of the adhesive composition became 17% by mass, and the mixture was then thoroughly stirred to obtain adhesive compositions (Examples 1 to 7, Reference Examples 1 to 5) according to one embodiment of the present invention.

<Coating of tire cord with each adhesive composition>
As the organic fiber cord, a tire cord made of polyethylene terephthalate having a twist structure of 1670 dtex/2, a top twist number of 39 times/10 cm, and a bottom twist number of 39 times/10 cm was used.

The tire cord was immersed in each of the adhesive compositions of Comparative Examples 1 to 8, Examples 1 to 7, and Reference Examples 1 to 5 so that the concentration of the adhesive composition impregnated into the tire cord was 3.8% by mass relative to the mass of the organic fiber cord. The cord was then sequentially dried in the drying zone (150°C, 60 seconds), thermally cured in the hot zone while applying tension (0.8 kg/cord), and thermally cured in the normalization zone while releasing the tension (240°C, 60 seconds), yielding tire cords coated with each of the adhesive compositions of Comparative Examples 1 to 8, Examples 1 to 7, and Reference Examples 1 to 5.

<Preparation of tire cord-rubber composite>
Tire cords coated with the adhesive compositions of Comparative Examples 1 to 8, Examples 1 to 7, and Reference Examples 1 to 5 were embedded in unvulcanized rubber compositions and co-vulcanized at 155° C. for 20 minutes. The unvulcanized rubber composition used for coating was a rubber composition containing natural rubber, styrene-butadiene rubber, carbon black, vulcanization chemicals, etc.

<Evaluation of workability of adhesive composition>
The adhesive compositions of the comparative examples and examples were evaluated for workability as follows.

<<Evaluation of mechanical stability (solidification rate)>>
The mechanical stability (coagulation rate) of each adhesive composition was measured in accordance with the method specified in JIS K6392-1995 using a Maron mechanical stability tester for copolymer latex compositions (Maron Stability Tester No. 2312-II, manufactured by Kumagai Riki Kogyo Co., Ltd.).

In summary, each adhesive composition was subjected to shear strain for 10 minutes using the rotor of the Maron mechanical stability tester at a compression load of 10 kg and a rotation speed of 1,000 r/min, and then the solidification rate (%) was evaluated using the following formula from the amount of solidified material that was generated, and rounded off to one decimal place to obtain a value. A smaller value indicates better mechanical stability.
Coagulation rate (%) = [(dry mass of generated coagulation) / (mass of solid content of test adhesive liquid)] × 100

<<Evaluation of adhesion to squeeze rolls>>
The polyethylene terephthalate tire cord, which is an organic fiber cord, was continuously treated for 2000 m in a dipping treatment machine storing each adhesive composition, and the amount of each adhesive composition adhering to the squeeze roll was visually observed and evaluated on the following 5-point scale.
Extra large: Especially large.
Large: Many.
Medium: Moderate.
Small: Few.
Minor: Very little.

<Evaluation of Adhesion Properties of Adhesive Compositions>
The adhesive properties of the adhesive compositions of the comparative examples and examples were evaluated as follows.

<<Evaluation of Adhesion Strength>>
The tire cord-rubber composite obtained using each adhesive composition was pulled at a speed of 300 mm/min to peel the tire cord from the tire cord-rubber composite, and the peel resistance per tire cord was determined, which was taken as the adhesive strength (N/cord).

<<Evaluation of the adhesion state of the coated rubber>>
The tire cord peeled from the tire cord-rubber composite was visually inspected for adhesion of the coating rubber, and scored according to Table 1 below.

<Results of workability evaluation and adhesion evaluation of adhesive compositions>
The formulations of the adhesive compositions of the comparative examples and examples are shown in Tables 2 to 5 below, and the results of the workability evaluation and adhesiveness evaluation are shown in Table 6 below.

* A-1) Vinylpyridine latex: vinylpyridine-styrene-butadiene copolymer latex (solid content concentration 41% by mass) synthesized by the above method
*A-2) Natural rubber latex: Field latex (solid concentration 41%)
*B-1) Acetoacetyl group-modified polyvinyl alcohol: manufactured by Mitsubishi Chemical Corporation, trade name "Gohsenex Z-200" (purity 93.5% or more, powder), saponification degree 99% or more, viscosity of 4% aqueous solution at 20°C 11.5 to 14.0 mPa s (catalog value)
*B-2) Acetoacetyl group-modified polyvinyl alcohol: manufactured by Mitsubishi Chemical Corporation, trade name "Gohsenex Z-300" (purity 93.5% or more, powder), saponification degree 98-99%, viscosity of 4% aqueous solution at 20°C 24.0-30.0 mPa·s (catalog value)
*B-3) Acetoacetyl group-modified polyvinyl alcohol: manufactured by Mitsubishi Chemical Corporation, trade name "Gohsenex Z-410" (purity 93.5% or more, powder), saponification degree 97.5 to 99.5%, viscosity of 4% aqueous solution at 20°C 43.5 to 58.5 mPa s (catalog value)
*C-1) (Thermally dissociable blocked) aqueous compound having an isocyanate group: EMS-CHEMIE HOLDIMG AG, trade name "GRILLBOND IL-6" (solid content concentration 50% by mass), blocked compound of methylene diphenyl diisocyanate and caprolactam *C-2) (Thermally dissociable blocked) aqueous compound having an isocyanate group: Dai-ichi Kogyo Seiyaku Co., Ltd., trade name "ELASTRON BN77" (blocking agent thermal dissociation temperature: approximately 160°C, pH 8.0, solid content concentration 31% by mass), (thermally dissociable blocked) aqueous urethane compound having an isocyanate group *D) Polyethyleneimine: Wako Pure Chemical Industries, Ltd., reagent name "Polyethyleneimine, average molecular weight 600" (solid content concentration 100% by mass, liquid)
*E-1) Polyphenol: Sigma-Aldrich Co. LLC, product name "Lignin, alkaline" (CAS Number: 8068-05-1) Kraft lignin *E-2) Polyphenol: Tokyo Chemical Industry Co., Ltd., product name "Lignin (alkali)" (CAS Number: 8061-51-6) Partially desulfonated lignin sulfonate with reduced degree of sulfonation *E-3) Polyphenol: Kawamura Tsusho Co., Ltd., product name "Mimosa" (solid powder) tannin

Table 6 shows that adding (B) acetoacetyl-modified polyvinyl alcohol to (A) rubber latex containing an unsaturated diene extends the usable life of the adhesive composition due to its antibacterial effect.

Furthermore, Table 6 shows that in each of the Examples and Reference Examples, adhesive compositions were obtained that had good workability and good adhesion between the organic fiber and the coating rubber composition.

The present invention provides an adhesive composition for organic fibers that can ensure the desired adhesive properties without using resorcinol and does not impair workability during use, as well as organic fiber materials, rubber articles, organic fiber-rubber composites, and tires that use the same. Therefore, the present invention can be used in industrial fields that manufacture rubber articles such as tires.

1: Organic fiber cord 2: Adhesive composition 3: Dipping bath
4: Organic fiber cord coated with adhesive composition 5: Squeeze roll 6: Drying zone 7: Hot zone 8: Normalizing zone 31: Organic fiber-rubber composite 32: Adhesive layer made of adhesive composition 33: Coated rubber composition

Claims (20)

An adhesive composition for organic fibers, comprising: (A) a rubber latex having an unsaturated diene; ( B) an acetoacetyl group-modified polyvinyl alcohol ; and (C) an aqueous compound having a (thermally dissociable blocked) isocyanate group . Furthermore, the following (D) and (E) :
( D) an amine compound, and
2. The adhesive composition for organic fibers according to claim 1, further comprising (E) one or more compounds selected from the group consisting of polyphenols. The adhesive composition for organic fibers according to claim 1 or 2, wherein the degree of saponification of the (B) acetoacetyl group-modified polyvinyl alcohol is 80 mol% or more. 2. The adhesive composition for organic fibers according to claim 1, wherein the aqueous compound having a (thermally dissociable, blocked) isocyanate group (C) is a water-dispersible (thermally dissociable, blocked) isocyanate compound (C- 1 ) composed of an addition product of a polyisocyanate having an aromatic ring and a blocking agent having one or more active hydrogen groups. The adhesive composition for organic fibers according to claim 4, wherein the water-dispersible (thermally dissociable blocked) isocyanate compound (C-1) comprising an addition product of a polyisocyanate having an aromatic ring and a blocking agent having one or more active hydrogen groups is a blocked product of methylene diphenyl diisocyanate. The adhesive composition for organic fibers according to claim 1 , wherein the aqueous compound having a (thermally dissociable blocked) isocyanate group (C) is an aqueous urethane compound having a (thermally dissociable blocked) isocyanate group (C-2). The aqueous urethane compound (C-2) having a (thermally dissociable blocked) isocyanate group is
(α) an organic polyisocyanate compound having 3 or more and 5 or less functional groups and a number average molecular weight of 2,000 or less;
(β) a compound having 2 or more and 4 or less active hydrogen groups and a number average molecular weight of 5,000 or less;
(γ) a thermally dissociable blocking agent, and
(δ) a compound having at least one active hydrogen group and at least one hydrophilic group which is anionic, cationic or nonionic;
The mixing ratio of each of (α), (β), (γ) and (δ) to the total amount is
(α) is 40% by mass or more and 85% by mass or less,
(β) is 5% by mass or more and 35% by mass or less,
(γ) is 5% by mass or more and 35% by mass or less, and
(δ) is 5% by mass or more and 35% by mass or less,
and reacting the mixture to give a reaction product,
7. The adhesive composition for organic fibers according to claim 6, wherein the constituent ratio of the (thermally dissociable blocked) isocyanate group in the reaction product is 0.5% by mass or more and 11% by mass or less, when the molecular weight of the isocyanate group (—NCO) is 42. The aqueous urethane compound (C-2) having a (thermally dissociable blocked) isocyanate group is represented by the following general formula (1):
[In formula (1),
A is a residue of an organic polyisocyanate compound from which an active hydrogen group has been eliminated,
X is a residue of a polyol compound having 2 or more and 4 or less hydroxyl groups and a number average molecular weight of 5,000 or less, from which an active hydrogen group has been eliminated;
Y is a residue of the thermally dissociable blocking agent from which the active hydrogen group has been eliminated;
Z is a residue of a compound having at least one active hydrogen group and at least one salt-forming group or a hydrophilic polyether chain, from which the active hydrogen group has been eliminated;
n is an integer between 2 and 4,
p + m is an integer between 2 and 4 (m≧0.25)
The adhesive composition for organic fibers according to claim 6, wherein the organic fiber adhesive composition is The adhesive composition for organic fibers according to claim 2, wherein the (D) amine compound is a polyfunctional amine compound having two or more primary, secondary, or tertiary amino groups. The adhesive composition for organic fibers according to claim 2, wherein the (E) polyphenol is a plant-derived compound having multiple phenolic hydroxy groups in the molecule. The adhesive composition for organic fibers according to claim 2, wherein the (E) polyphenol is lignin, tannin, tannic acid, a flavonoid, or a derivative thereof. The adhesive composition for organic fibers according to any one of claims 1 to 11, which does not contain resorcinol. An organic fiber material characterized in that the surface of organic fibers is coated with an adhesive layer comprising the organic fiber adhesive composition according to any one of claims 1 to 12. The organic fiber material according to claim 13, wherein the organic fiber is a cord made by twisting together multiple filaments. The organic fiber material according to claim 14, wherein the cord has a first twist and a second twist, the twist coefficient of the first twist being 1,300 or more and 2,500 or less, and the twist coefficient of the second twist being 900 or more and 1,800 or less. The organic fiber material according to claim 14 or 15, wherein the adhesive layer has a dry weight of 0.5 to 6.0% by weight of the cord. The organic fiber material according to any one of claims 13 to 16, wherein the organic fibers are made of polyester resin. A rubber article reinforced with the organic fiber material described in any one of claims 13 to 17. An organic fiber-rubber composite comprising organic fibers and rubber, the organic fibers being coated with the organic fiber adhesive composition described in any one of claims 1 to 12. A tire characterized by using the organic fiber-rubber composite according to claim 19.