JPH0147510B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to hot-melt pressure-sensitive adhesives, and more particularly to novel hot-melt pressure-sensitive adhesives containing a block copolymer, a tackifying resin, and a specific softener. As is well known, hot-melt pressure-sensitive adhesives are faster to apply than solvent-based adhesives when producing adhesive paper and tape, do not require solvent drying or recovery equipment, and are free from fire hazards. thing,
It has the advantage of not polluting the atmosphere or working environment, and is superior to solvent-based pressure-sensitive adhesives in all aspects of economy, pollution prevention, and safety, and its use is rapidly becoming widespread in the pressure-sensitive adhesive paper industry. It's coming. Hot-melt pressure-sensitive adhesives are generally composed of an elastomer and a tackifying resin, but these components can be uniformly mixed in the absence of a volatile medium such as an organic solvent. In addition, the resulting adhesive has workability (melt viscosity) that allows it to be easily applied to substrates such as paper, cellophane, and woven fabric, and has the adhesive strength, adhesion strength, and cohesive strength (hereinafter referred to as These are called the "three adhesive properties"), so they usually use plasticizers such as phthalate esters, liquid terpene resins, liquid petroleum resins, liquid xylene-formaldehyde resins, liquid coumaron-indene resins, and partial hydrogen. A liquid resin such as rosin methyl ester is further blended as a softening agent. However, these known softeners have insufficient compatibility with the block copolymer used as the elastomer, reducing the adhesive strength of the resulting adhesive, and the volatilization of volatile substances and coloring during melting significantly reduce the commercial value. It has various drawbacks, such as reduced capacity. In addition, various petroleum-based extender oils are known as softeners that can improve tackiness to some extent, but when blending these oils, it is important to use block copolymers that have excellent cohesive and adhesive strength. The fatal drawback is that it inhibits As mentioned above, a hot-melt pressure-sensitive adhesive that has the three adhesive properties and other properties that are fully satisfactory has not yet been developed. In particular, it has poor adhesion at low temperatures, making it difficult to put it to practical use in packaging and labeling frozen foods, and for use in cold regions. The present invention has discovered a new softening agent that can eliminate all of the various drawbacks observed in various conventionally known softeners, and can also completely eliminate the drawback of poor tackiness at low temperatures found in this type of adhesive. It was completed by this. That is, the present invention comprises a block copolymer (hereinafter referred to as component (a)) consisting of 50 to 90% by weight of elastomer blocks and 50 to 10% by weight of non-elastomeric blocks, and a tackifier with a softening point of 50 to 150°C (hereinafter referred to as component (a)). that
(b) component) and a softener, characterized in that the softener is an ester of higher monohydric alcohols and rosins (hereinafter referred to as component (c)). Related to hot melt pressure sensitive adhesives. The hot-melt pressure-sensitive adhesive of the present invention exhibits three outstanding adhesive properties when applied to a base material such as polyester film, paper, woven fabric, or plywood and made into an adhesive tape or sheet. There is no volatilization of substances, and the melt viscosity is low and constant, and there is very little increase in viscosity or coloring during heating and melting. In particular, the adhesive of the present invention is significantly different from conventionally known adhesives of this type containing various softeners, in that it has (a)
It is characterized by its ability to significantly improve tackiness, particularly at low temperatures, without impairing the excellent cohesive force and adhesive strength inherent to the block copolymer as a component. As the block copolymer used as component (a) in the adhesive of the present invention, any of various known block copolymers can be used. Representative examples include copolymers represented by the following formulas [] to []. (A) - _l B [] (A-B) - _n A [] B (-A-B) _o [] [In each formula, A is a non-elastomer block, B is an elastomer block, l, m and n are 1 In each formula, the total A block is 10 to 50% by weight. ] Specific examples of monomers constituting block A in each of the above formulas include styrene, methylstyrene, chlorostyrene, vinyltoluene, vinylxylene, acrylonitrile, methyl methacrylate, etc. It is preferable to have a glass transition point of . Specific examples of monomers constituting block B include butadiene, isoprene, methyl isoprene, etc. Block B may also be hydrogenated, and its glass transition point is different from that of block A. The temperature is preferably 50°C or higher, particularly 100°C or higher. In the present invention, the tackifying resin used as component (b) is 50 to
It has a softening point of 150℃, and if it has a softening point exceeding 150℃, it will have poor compatibility with component (a), or even if it is compatible, the adhesive strength will decrease when used as an adhesive. Otherwise, the melt viscosity tends to increase, which is undesirable. On the other hand, if it is lower than 50°C, the cohesive force decreases, which is also not preferable. As this component (b), various known tackifying resins can be used as long as they have the above-mentioned softening point. Specifically, rosins such as gum rosin and utudrosin, modified rosins such as disproportionated rosin and dimerized rosin, glycol, glycerin,
Examples include esterified products of pentaerythritol etc. and the above rosin or modified rosin, terpene resins, terpene phenol resins, aliphatic, aromatic or alicyclic petroleum resins, and coumaron indene resins. Furthermore, each of the above resins can be advantageously reduced in its unsaturated bond content by hydrogenation,
Properties such as heat resistance and weather resistance can be further improved. In the present invention, it is essential to further mix component (c) with the above-mentioned components (a) and (b), and by adding this component (c), the hot melt type has extremely excellent properties that have never been seen before. A pressure sensitive adhesive having the following properties is obtained. Specifically, the higher monohydric alcohols constituting the ester as component (c) include hexyl alcohol, heptyl alcohol, octyl alcohol, 2-ethylhexyl alcohol,
Examples include nonyl alcohol, decyl alcohol, lauryl alcohol, dodecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol, etc. Among these, those having 8 to 16 carbon atoms can be obtained from these. When used as a softening agent, it is preferable to use the ester as a softener because it can provide an adhesive with a well-balanced adhesive force and cohesive force. When using an alcohol with a carbon number of 7 or less, the resulting pressure-sensitive adhesive containing rosin ester tends to have insufficient adhesive strength, especially at low temperatures; When using adhesives, the three adhesive properties of the adhesive generally tend to decrease. In addition, the above-mentioned higher monohydric alcohols are roughly divided into natural alcohols obtained from natural products such as coconut oil and pine oil, and synthetic alcohols obtained from the petrochemical industry according to their acquisition route (raw material). Although any of these can be used in the same way, the above synthetic alcohols include, for example, ethylene,
It is advantageous because it can be produced at low cost and in large quantities by oxo reaction of a low polymer of α-olefin such as propylene. Examples of the synthetic alcohol include "Diadol 115H or 135" (manufactured by Mitsubishi Chemical Corporation, a mixed alcohol with carbon numbers of 11, 13 and 15), "Oxocol 1215" which is commercially available as a mixture of two or more alcohols with different carbon numbers. (manufactured by Nissan Petrochemical Co., Ltd., mixed alcohol with 12 to 15 carbon atoms). As the rosin to be esterified with the above-mentioned higher monohydric alcohols, any of gum rosin, oil rosin, tall oil rosin, hydrogenated rosin, disproportionated rosin, etc. can be used, but hydrogenated rosin, disproportionated rosin, etc. A stabilized rosin is preferred. Such stabilization treatment can be carried out according to a conventional method. In particular, in the present invention, the rosin after treatment contains about 5% by weight or less, preferably about 1% by weight or less, of an abietic acid type resin acid having a conjugated double bond. It is preferable to use one that has been treated as such. The esterification reaction between the higher monohydric alcohol and rosin can be carried out according to various known methods, for example, by heating the two to react at a temperature of about 180 to 300°C for about 2 to 10 hours. obtain. The ester thus obtained [component (c)]
usually has a yellow to brown transparent liquid to balsamic appearance and an acid value of about 15 or less, preferably 10 or less. The hot melt type pressure sensitive adhesive of the present invention has the above-mentioned properties.
It is manufactured by blending component (a), component (b), and component (c) as main components. The blending ratio of these three components can vary over a wide range, but generally 30 to 300 parts by weight of component (b) to 100 parts by weight of component (a), preferably 50 to 200 parts by weight, and component (c). 5 to 100 parts by weight, preferably 10 to 50 parts by weight. These three components can be easily made into a hot-melt pressure-sensitive adhesive tape or sheet by heating and mixing the mixture and applying it directly to a base material using a roll coater or the like. As the base material, polyester film, cellophane, paper, woven fabric, plywood, etc. can be used. Further, in the above, in addition to elastomers such as natural rubber and synthetic rubber, ordinary plasticizers, antioxidants, fillers, etc. may be further added as necessary. Hereinafter, production examples of specific esters serving as component (c) will be listed as reference examples, and then production examples of the adhesive of the present invention will be listed as examples. In addition, the middle part and percentage in each example are based on weight. Reference example 1 500 parts of disproportionated rosin (abietic acid content 0%) with an acid value of 160 and a softening point of 80°C, synthetic alcohol (tridecyl alcohol 58%, pentadecyl alcohol)
389 parts of 42% mixture) and 1 part of methanesulfonic acid were charged in a Kolben, and 260 to 270
After heating and reacting at ℃ for 4 hours, keep warm under reduced pressure for 30 minutes and take out. The product had an acid number of 5.9, a color (Gardner color) of 8, and a viscosity (25°C) of 680 cps. This is called ester A. Reference Examples 2 to 5 Esters are obtained in the same manner as in Reference Example 1 using various alcohols and rosins. The properties of the obtained ester are shown in Table 1. Comparative Reference Examples 1 to 3 Esters are obtained in the same manner as in Reference Example 1 using alcohols other than higher monohydric alcohols (methyl alcohol, butyl alcohol, or triethylene glycol). The properties of the obtained ester are shown in Table 1 below.

[Table] In Table 1, the synthetic alcohol ^* is a mixture of 58% alcohol with 13 carbon atoms and 42% alcohol with 15 carbon atoms, and the synthetic alcohol ^** is 100% alcohol with 11 carbon atoms. Examples 1 to 5 Thirty parts of each of the esters A to E obtained in Reference Examples 1 to 5 above were used as a softening agent to prepare a commercially available polystyrene-polyisoprene-polystyrene type block copolymer (manufactured by Shell Chemical Co., Ltd.). clayton
TR1107”, polyisoprene block content 86%)
An adhesive composition sample is obtained by melt-mixing at 170°C with 100 parts of a commercially available aliphatic petroleum resin ("Wingtak 95" manufactured by Gutdeyer, softening point 95°C). Each sample was applied onto a polyester film using an applicator at a temperature of 180°C.
Apply to a thickness of 30 μm to obtain an adhesive tape. The results of measuring the tackiness, adhesive force, and cohesive force of the obtained adhesive tapes are shown in Table 2, along with the melt viscosity (by Epprecht viscometer) of each adhesive sample. The characteristics of the adhesive tape shall be measured using the following test method. <Adhesion> At 0°C or 20°C, J. Dow method (J.
Dow method). <Adhesive strength> A 25 mm wide polyester film was coated with each adhesive sample, and this was coated with a K-liner (basis weight
240g/m ² ) and an Instron type testing machine (“Tensilon UTM-” manufactured by Toyo Sokki Co., Ltd.)
Peel it 180 degrees at a speed of 300 mm/min and measure the load required for peeling. <Cohesive force> A 25 mm wide polyester film was coated with each adhesive sample, and this test piece was pasted onto the same K liner as above in an area of 25 mm x 25 mm.
The distance of deviation (mm) is measured by a creep test using PSTC-7. Comparative Examples 1 to 4 Same as Example except that 30 parts each of the esters obtained in Comparative Reference Examples 1 to 3 and commercially available extender oil ("Cielflex 371" manufactured by Shell Chemical Co., Ltd.) were used as softeners. to obtain an adhesive composition sample. Each of the obtained samples was tested in the same manner as in the Examples, and the results are shown in Table 2 below.

[Table] Examples 6 and 7 Commercially available polystyrene-polybutadiene-polystyrene block copolymer (“Krayton 1102” manufactured by Shell Chemical Co., Ltd., polybutadiene block content
72%) 100 parts, commercially available hydrogenated aromatic petroleum resin (“Alcon M90” manufactured by Arakawa Chemical Co., Ltd.),
Softening point: 90°C) 100 parts and ester A obtained in Reference Example
Alternatively, a predetermined amount of B was melt-mixed at 180°C, and samples were prepared in the same manner as in Examples 1 to 5 and then subjected to the same test. The results are shown in Table 3. Comparative Example 5 The same procedure as in Example 6 was repeated except that Ester A used as a softener was replaced with Ester α obtained in Comparative Reference Example. The results are shown in Table 3.

【table】

Claims (1)

[Scope of Claims] 1. A hot-melt pressure-sensitive material comprising a block copolymer consisting of 50-90% by weight of elastomeric blocks and 50-10% by weight of non-elastomeric blocks, a tackifier and a softener with a softening point of 50-150°C. A hot-melt pressure-sensitive adhesive characterized in that the softening agent is an ester of higher monohydric alcohol and rosin. 2. The hot-melt pressure-sensitive adhesive according to claim 1, wherein the higher monohydric alcohol has 8 to 16 carbon atoms. 3. The hot-melt pressure-sensitive adhesive according to claim 1 or 2, which contains 30 to 300 parts by weight of a tackifying resin and 5 to 100 parts by weight of a softener per 100 parts by weight of the block copolymer. .