JPH0781121B2 - Sprayable adhesive composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an acrylate polymer-based aerosol adhesive composition.

2. Description of the Related Art There is a great demand for aerosol type adhesives used for materials such as papers, woods, cloths and plastics, and it is very convenient. However, there was nothing very satisfactory before the present invention. For example, in order to enable spraying, the solid content of the adhesive must be reduced, resulting in wasting solvent and propellant, and the solvent may seep through the adherend, and sometimes the solvent adheres to the adherend. In some cases, it was dissolved or the hue was changed, and the adhesive function was not achieved.

In an aerosol type adhesive having an appropriate solid content,
When an elastomer that gives cohesive force is used as an adhesive component, the sprayability is poor and a rubbery thread like a web is formed, which is not satisfactory. Even if the sprayability is improved, none of them have utility value because the spray port is easily clogged or the adhesive function is insufficient.

The cohesive force is an indispensable element for the adhesive to have an adhesive function, and a polymeric elastic body is required for the cohesive force. However, elastic bodies generally have spinnability, and therefore, when such a high-molecular-weight elastic body is applied to an aerosol-type adhesive, when the adhesive is sprayed, a web-like body like a spider web is generated. Cause. In other words, there is a relationship that if the adhesive function is satisfied, the sprayability is deteriorated, and if the sprayability is improved, the adhesive function is lacked. Therefore, a satisfactory aerosol type adhesive was not made available.

In a rubber-like elastic body, a patent has been filed for an invention using an elastic body having a cross-linking structure (crosslinked network structure) as a method of minimizing the spinnability while maintaining the original physical properties. For details, see JP-B-45-22239, and for acrylics, see JP-B-46-12640).

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention eliminates the formation of spider webs (spreadability) that occurs when an aerosol-type adhesive is sprayed, and more than the aerosol-type adhesive based on a cross-linked polymer. It is intended to provide an aerosol type adhesive having excellent adhesiveness.

Means for Solving the Problems The main point of the present invention is to use an uncrosslinked linear acrylate polymer synthesized by an emulsion polymerization method as an adhesive main component of an aerosol type adhesive.

The present inventors have completed the present invention by paying attention to the fact that it is very good to synthesize an acrylate polymer by an emulsion polymerization method in order to eliminate the spinnability of the acrylate polymer.

That is, the present invention is a sprayable adhesive composition containing a volatile organic solvent, a tackifier, and a propellant, wherein
It has a coercive force value of 3.0 mm and is about the same as an uncrosslinked linear acrylate polymer synthesized by the emulsion polymerization method.
A sprayable adhesive characterized in that it contains 2.5% to about 30% by weight.

The components of the present invention will be described in detail below.

(Acrylate Polymer) The acrylate polymer used in the present invention has elasticity or rubber-like properties and has tackiness, and can be generally used as a component of a pressure-sensitive adhesive.

Considering the case of using a linear acrylate polymer as a component of the adhesive and the case of using a cross-linked acrylate polymer, the linear polymer is naturally superior in the wetting to the adherend, In terms of the bonding force between the insoluble particles, the linear polymer that is not cross-bonded is physically superior, and the linear polymer that is not cross-bonded is the dominant base of the adhesive. Is obvious.

Acrylate polymers that can be used in the present invention include acrylic acid ester homopolymers, methacrylic acid ester homopolymers, acrylic acid ester copolymers and methacrylic acid ester copolymers.

As the alcohol component constituting the acrylic acid ester or the methacrylic acid ester, an alcohol having no third alkyl group as exemplified below can be used.

n-butanol, n-pentanol, isopentanol, 1-methylbutanol, 2-methylbutanol, 1-methylpentanol, 2-methylpentanol, 3-methylpentanol, 2-ethylbutanol, 3-pentanol , 3,5,5-trimethylhexanol, 3-heptanol, 2-ethylhexanol, isooctanol, n-nonanol isononanol, n-decanol, n-dodecanol, isododecanol.

The acrylate component should contain at least a major proportion of esters having an alkyl chain length of at least 4 carbon atoms (this portion being attached to the oxy atom of the R-COO- group). And the average number of all carbon atoms in the alcohol component should be in the range of about 4 to about 12.

Examples of suitable monomers for copolymerization with the above-mentioned acrylic acid ester or methacrylic acid ester include the followings.

Acrylic acid, methacrylic acid, itaconic acid, acrylamide, N-alkyl mono-substituted acrylamide, methacrylamide, methacrylonitrile, vinyl acetate.

The copolymerization ratio of these comonomers and acrylic acid ester is about 80% by weight to about 98% by weight of acrylic acid ester, preferably about 88% by weight to about 97% by weight, and about 2% by weight of other comonomer. % To about 20% by weight, preferably about 3% by weight
~ About 12% by weight.

In the present invention, when the molecular weight of the acrylate polymer is lower than several hundreds of thousands, the acrylate polymer is completely dissolved in the solvent and insoluble particles cannot be formed. Further, if the molecular weight of the acrylate polymer is higher than several tens of millions, the solubility is lost and it becomes difficult to form insoluble particles, and the tackiness becomes poor and the original adhesive function is not fulfilled.

An emulsion is a collection of particles. Once the particles are completely dissolved in the solvent, it becomes a uniform liquid and there are no particles. The particles here do not completely dissolve in a solvent, but have a nucleus in the center and the surroundings are dissolved in a solvent. When the molecular weight is excessively large, the solubility is lost and large particles can be obtained, but the desired fine particles cannot be obtained.

(Difference between cross-linking and linear) Since an adhesive to which a cross-linking acrylate polymer is applied as a component of an aerosol type adhesive is known, it may seem that the present invention was simply invented. , The present invention is essentially different from such known aerosol type adhesives. That is, since the cross-linked acrylate polymer has a network structure, it is easy to form insoluble particles (meaning sol or colloidal particles) that improve sprayability.

In contrast, since the acrylate polymer used in the present invention is a linear polymer, it is essentially soluble and it is difficult to form and stabilize insoluble particles. ,
The present inventors have found a method of forming insoluble particles of a acrylate polymer having a linear structure, found that the insoluble particles are stabilized by a combination of a tackifier and a solvent, and applied the present invention.

(Necessity of Emulsion Polymerization) The reason why the emulsion polymerization method is required for an acrylate polymer is that the molecular weight is high from the viewpoint of adhesiveness, the solution viscosity is low from the viewpoint of sprayability, and the spinnability is not required. Solution polymerization is difficult to achieve, and emulsion polymerization is the most suitable. Emulsion polymerization has a higher molecular weight than solution polymerization and has a low solution viscosity and no stringing phenomenon. This (that is, the solution viscosity of the polymer is low and there is no stringing phenomenon) is about 100 μm to about 0.01 μm, which is characteristic of emulsions.
This is because it is composed of aggregates of particles and has the property of thixotropy, and this property is optimal for aerosol.

Emulsifiers that can be used in the emulsion polymerization method are alkali soaps, organic amine soaps, sulfuric acid esters of higher alcohols, etc., and potassium persulfate, ammonium persulfate, hydrogen peroxide, etc. are used as polymerization catalysts.

(Formation of Insoluble Particles) The formation of insoluble particles is generally performed by dispersing the crosslinked polymer in a high speed and high shear mixer or by using a roll type pulverizer. That is, these methods are physical methods.

The present inventors have found that the constituent particles of the acrylate polymer emulsion are chemically insoluble particles in a volatile solvent. It is common knowledge that when a coagulant is added to an acrylate polymer emulsion, the acrylate polymer becomes a large mass and solidifies. Even if the solidified lump of the acrylate polymer is stirred in a solvent, it is not easily dispersed, and a known physical method is required, which makes it very difficult to form insoluble particles. Coagulants include acids, alkalis, salts and the like, and methanol and acetone are also known.

However, it is difficult to achieve the object of the present invention because these coagulants coagulate in a large mass.
Here, the inventors paid attention to a coagulant having a low coagulation effect. Taking alcohol as an example, when methanol or ethanol is used as a coagulant, it becomes a large lump and coagulates. However, when n-propyl alcohol is used as a coagulant, large lumps are not solidified but are solidified into particles. When the solidification state is still incomplete, methanol is gradually added to obtain completely solidified particles. If it is still not perfect, add salt etc. When filtered, a particulate solid is taken out, washed with methanol, and filtered to remove almost all water. It was discovered that the acrylate polymer forms insoluble particles when the tackifier and solvent are added to this solid and stirred.

It is generally known that the emulsion (water-based) is salted out to take out the contents (acrylic adhesive), but in the general salting-out method, the contents become a lump and it is impossible to make it into particles. . A big discovery was made here, and it was discovered that salting out with an alcohol having a small salting-out effect does not form a mass, but salting out in the form of particles. It took a great deal of effort until it was found that salting out with a substance having a small salting out effect would cause salting out in the form of particles.

(Retention) A retention test was found to grasp the sprayable physical properties necessary for this acrylate polymer, and an aerosol type adhesive agent based on an acrylate polymer having a retention value of 0.0 mm to about 3.0 mm. On the other hand, it was discovered that it gave good sprayability without generating spider webs and had a satisfactory adhesive function.

The present inventors have found that an aerosol type adhesive agent based on an acrylate polymer having a coercive force value of 0.0 mm to about 3.0 mm fulfills an adhesive function without generating spider webs at the time of spraying. An acrylate polymer showing a coercive force value of about 3.0 mm or more has a low molecular weight, is completely dissolved in a solvent, insoluble particles are not formed, and when this acrylate polymer is sprayed, a cobweb is generated. Become. The holding force value cannot be measured (the interface breaks and falls within 1 hour)
Such acrylate polymers are not included in the present invention because not only do they have a high molecular weight, which makes them insoluble and difficult to form insoluble particles, but they no longer perform their adhesive function.

When the molecular weight is excessively large, the solubility is lost and large particles are obtained, but fine particles intended by the present invention cannot be obtained.

(Contents of Retention Test) Acrylate polymer emulsion is uniformly applied on 25 μm thick polyester. To dry after application
Put in oven at 120 ° C and take out after 3 minutes. The thickness of the dried acrylate polymer should be 20 μm. Since the coated surface is sticky, the release paper treated with silicone is pasted immediately after taking it out from the oven, and used as the data. Take 3 pieces with a width of 12 mm and a length of about 150 mm from the material to make a test piece. Twelve test pieces on one end of a clean glass plate
Peel off the release paper so that the area of mm × 20 mm is in contact, and attach the test piece, and fold the non-attached part with the inner surface inside. From the top of the test piece, use a rubber roller weighing 2 kg to make one round trip at a crimping speed of approximately 300 mm / min and perform crimping. 20
After more than a minute, stop one end of the glass plate with a stopper and allow the test piece to hang vertically.
Attach a 0g weight. Be careful not to apply a weight other than 500g to the test piece so that the weight does not shake gently. Further, the glass plate is positioned so that a peeling force is not applied to the attached test piece or a frictional resistance is not applied between the test piece and the glass plate. Apply a load of 500 g for 1 hour, divide the displaced distance by the unit of 0.1 mm, and calculate the average value to obtain the holding force value.

(Tackifier) The tackifier used in the present invention is mainly used for improving adhesiveness and stabilizing insoluble particles. Tackifiers include phenolic resins, terpene resins, petroleum resins, rosins,
It includes rosin esters, terpene phenol resins, styrene resins, aromatic resins and other hydrogenated products thereof, and modified resins such as those commonly used in the field of adhesives and adhesives. The tackifier is an acrylate polymer 10
10 to 250 parts by weight relative to 0 parts by weight, preferably about 50
Parts by weight to about 200 parts by weight are included.

(Volatile Organic Solvent) When an acrylate polymer emulsion is directly combined with a propellant, it becomes an aerosol type adhesive, but since the dispersion medium of the emulsion is a liquid containing water as a main component, such an aerosol type adhesive is It takes a long time from spraying to drying and is practically difficult to use.
Therefore, in the present invention, a volatile organic solvent is added.

It is necessary to consider the drying speed, the compatibility with the adhesive, and the fact that the adherend is not damaged.For example, volatile organic solvents such as pentane, hexane, methyl ethyl ketone (MEK), and lower alcohols. Can be used, with n-hexane being particularly preferred.

The content of the volatile organic solvent is preferably about 20-60% of the total amount of the adhesive of the present invention.

(Propellant) As the propellant used in the present invention, a liquefied gas or a compressed gas generally used for an aerosol can be used, and a liquefied propane gas (LPG) is particularly advantageous. Appropriate amount of propellant is about 70% to about 20% by volume of the total sprayable adhesive of the present invention.

(Additive) The adhesive of the present invention may optionally contain additives such as plasticizers and anti-aging agents, which are added in small amounts. As such additives, known additives used in the field of pressure-sensitive adhesives or adhesives can be used.

EXAMPLES Examples are shown below to make the present invention easier to understand, but the following examples are not intended to limit the present invention.

Example 1 Synthesis of an acrylate polymer emulsion is carried out according to the following composition (parts by weight).

2-Ethylhexyl acrylate 92 Vinyl acetate 3 Acrylic acid 5 Distilled water 100 t-Dodecyl mercaptan 0.15 Potassium persulfate 0.3 Fatty acid soap 3 Distilled water and fatty acid soap (emulsifier) were put into a stirring vessel and stirred. Stirring was continued until the polymerization was completed. 2-ethylhexyl acrylate, vinyl acetate, acrylic acid and t-
A mixture of dodecyl metacaptan (chain transfer agent) that was uniformly mixed was added to the kettle. The kettle was sealed and replaced with nitrogen while heating to about 38 ° C.

Potassium persulfate (polymerization catalyst) is added to the kettle to advance the polymerization reaction. About 10 after the reaction temperature reaches the maximum temperature
Cooled after ~ 20 minutes to give an acrylate polymer emulsion.

(Examples 2 to 6) Using the raw materials having the compositions (parts by weight) shown in Table 1, acrylate polymer emulsions used in the present invention were synthesized in the same manner as in the method of Example 1.

Various resins were added to the acrylic polymer of Comparative Example 1,
The molecular weight became excessively large and the adhesiveness was poor. Regarding the holding property, a piece of polyester adhesive tape for measurement (with a weight) was peeled and dropped from the glass plate for measuring the holding power.

Various resins were added to the acrylic polymer of Comparative Example 2,
Poor sprayability due to excessively strong solvent solubility. The retention was not good either.

(Example 7) Acrylate polymer emulsion 10 obtained in Example 1
To 0 g, 30 g of n-propyl alcohol was added to solidify the acrylate polymer into particles. Further, 70 g of methanol was gradually added to completely solidify the acrylate polymer into particles. The mixture thus obtained was filtered to take out a particulate solid body, further washed with 100 g of methanol and then filtered to take out a particulate solid body.

YS Polystar T-80 (trade name of terpene phenol resin manufactured by Yasuhara Yushi Kogyo Co., Ltd.) 100 g, YES Resin Px1000 (trade name of terpene resin manufactured by Yasuhara Yushi Kogyo Co., Ltd.) per 100 g of the obtained acrylate polymer. 50 g, Antage W-500 (trade name of bisphenol-based antioxidant manufactured by Kawaguchi Chemical Co., Ltd.) 1 g, and n-hexane 650 g were added and stirred. After pressure filtration with a cloth of about 150 mesh, an adhesive composition in which insoluble particles were formed was obtained.

Further, with respect to the acrylate polymer emulsions obtained in Examples 2 to 6, adhesives having insoluble particles formed were obtained by the same method as described above.

(Examples 8 to 18) Adhesives (adhesives of the present invention) were obtained in the same manner as in Example 7, according to the compositions shown in Table 2 below.

The following raw materials were used in Examples 8-18.

The following were used as the acrylate polymer.

In Examples 8 and 9, the acrylate polymer of Example 1 was used.

In Examples 10 and 11, the acrylate polymer of Example 2 was used.

In Examples 12 and 13, the acrylate polymer of Example 3 was used.

In Examples 14 and 15, the acrylate polymer of Example 4 was used.

In Examples 16 and 17, the acrylate polymer of Example 5 was used.

In Example 18, the acrylate polymer of Example 6 was used.

Tamanor 51 from Arakawa Chemical Industry Co., Ltd. as a phenolic resin
0, YS from Yasuhara Yushi Kogyo Co., Ltd. as a terpene phenol resin
Polystar T-80, YS resin Px10 from Yasuhara Yushi Kogyo Co., Ltd. as a terpene resin
00, Picolastic A-75 from Hercules Co., Ltd. as styrene resin, Quinton A100 from Nippon Zeon Co., Ltd. as petroleum-based resin, Ester gum H from Arakawa Chemical Industry Co., Ltd. as rosin ester resin.

All of them maintained good adhesiveness.

(Example 19) 240 cc of the liquid having the insoluble particles formed in Example 7 and 160 cc of propellant (LPG 5 kg / cm ² ) were filled in an aerosol container to obtain an aerosol-type adhesive.

The obtained aerosol-type adhesive has a good spraying state, does not generate spider webs, does not bleed through even when sprayed on corrugated cardboard, etc., and the applied adhesive can be applied neatly without dripping. It was

The cardboard was sprayed and naturally dried for about 10 minutes, the cardboards were stuck together, and the adhesive strength was examined several hours later. Even if it was peeled off by hand, it did not come off easily, and the cardboard was destroyed.

EFFECTS OF THE INVENTION The adhesive of the present invention has a strong adhesive function while maintaining cohesive force and without forming spider webs.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Satoru Nagao Satoru Nagao 2-4, 9dannami, Chiyoda-ku, Tokyo Nichiban Co., Ltd. (56) References JP-A-60-199086 (JP, A) JPB 46-12640 (JP, B1)

Claims (1)

[Claims] 1. A sprayable adhesive composition containing an adhesive main component, a volatile organic solvent, a tackifier and a propellant, which has a holding power value of 0.0 mm to 3.0 mm as the adhesive main component. , Containing 2.5% by weight to 30% by weight of a non-crosslinked linear acrylate polymer synthesized by the emulsion polymerization method, and the content of the tackifier is 10 parts by weight to 100 parts by weight of the acrylate polymer. 250 parts by weight, and the solid content in the adhesive composition is 10 parts by weight to 35 parts by weight with respect to 100 parts by weight of the adhesive composition, A sprayable adhesive composition.