JP2734607B2 - Resin composition for adhesive - Google Patents

Description

TECHNICAL FIELD The present invention relates to a solvent-type resin composition for acrylic pressure-sensitive adhesives. In particular, the present invention relates to a resin composition for pressure-sensitive adhesive having good adhesion and heat resistance to metals such as iron, stainless steel and aluminum, molded products such as polystyrene, ABS and PVC and plastic substrates such as sheets and films.

(Prior Art) Conventionally, acrylic adhesives have been widely used for various tapes, labels, stickers, seals and the like. Especially in recent years, with the rationalization of the assembly of automobiles, electric equipment, office automation equipment, etc., the usage of non-structural adhesive parts has increased.

Generally, the properties required for acrylic adhesives are adhesion, heat-resistant creep resistance and coating workability, but automobiles, electrical equipment, and OA equipment may be used in places with high temperatures, and are particularly resistant to heat. Sex is required.

Adhesives include acrylic resin, phenol resin, rosin, petroleum resin, xylene resin and their modified resins, addition of adhesive adhesives of derivatives, ethylene-vinyl ester copolymer, natural rubber, synthetic rubber, etc. The performance balance is adjusted by using a resin together.

Acrylic resins used for adhesives are generally high in molecular weight and low in glass transition temperature (Tg). To balance the performance, the composition of the monomers to be copolymerized, the molecular weight of the polymer, and the molecular weight distribution are adjusted. In order to introduce a crosslinked structure into the adhesive coating film after coating, a hydroxyl group-containing monomer is copolymerized during the acrylic resin synthesis, and an isocyanate compound and/or an amino resin is added when the adhesive is compounded. ing.

(Problems to be Solved by the Invention) However, it has been difficult to improve the heat resistance of the acrylic resin used for the conventional pressure-sensitive adhesive while maintaining the adhesiveness and coating workability. For example, if the molecular weight of the acrylic resin is increased, the heat resistance is improved, but the viscosity of the adhesive increases and the coating workability deteriorates.

If the crosslink density is increased by increasing the hydroxyl group concentration of the resin or increasing the amount of the curing agent, the heat creep resistance is improved but the adhesion is deteriorated.

Further, there is a problem that when the addition amount of the tackifier is increased to compensate for the deterioration of the adhesiveness, the heat resistance is deteriorated.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a resin composition for pressure-sensitive adhesive, which has good heat resistance while maintaining adhesiveness and coatability. is there.

(Means for Solving the Problems) The present invention is directed to 0.1 to 5% by weight of a monoethylenically unsaturated monomer having a hydroxyl group selected from hydroxyalkyl methacrylate and hydroxyalkyl acrylate and other ethylenically unsaturated monomer. A compound containing 95 to 99.9% by weight of a monomer is copolymerized with an organic peroxide having 3 or more branched peroxide groups in one molecule to obtain a weight average molecular weight of 100,000 or more. The present invention relates to a resin composition for pressure-sensitive adhesive, which contains the polymer (A).

Examples of the monoethylenically unsaturated monomer having a hydroxyl group, which is a constituent component of the polymer (A), include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate and 2 methacrylate. -Hydroxyalkyl methacrylate such as hydroxypentyl, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, hydroxyalkyl acrylate such as 2-hydroxypentyl acrylate.

These monoethylenically unsaturated monomers having a hydroxyl group are blended in an amount of 0.1 to 5% by weight of one kind or two or more kinds. It is preferable to add 0.1 to 1% by weight. If the content of this unsaturated monomer is less than 0.1% by weight, the crosslink density of the resin composition for pressure-sensitive adhesives will be low and the performance will not be fully exhibited. Also, the viscosity becomes high and the workability is reduced.

Other ethylenically unsaturated monomers include, for example, unsaturated acids containing a carboxyl group such as acrylic acid, methacrylic acid, maleic acid and itaconic acid, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-acrylic acid.
Butyl, acrylic acid alkyl ester such as 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, methacrylic acid n-
Butyl, isobutyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, alkyl methacrylates, styrene, vinyltoluene, styrene monomers such as α-methylstyrene, glycidyl acrylate, methacrylic acid Examples thereof include glycidyl, vinyl acetate, acrylonitrile, methacrylonitrile and the like.

In order to increase the molecular weight, other ethylenically unsaturated monomers such as divinylbenzene and ethylene glycol dimethacrylate are copolymerized with a monomer having two or more ethylenically unsaturated double bonds in one molecule. Good. Since the gelation may occur during the polymerization reaction, the ratio of copolymerization is 0.
It is preferably 5% by weight or less.

When polymerizing a compound containing a monoethylenically unsaturated monomer having a hydroxyl group and another ethylenically unsaturated monomer, an organic compound having three or more peroxide groups in a molecule in a branched form is used. Peroxides are used as polymerization initiators.
An example of such an organic peroxide is 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane having the following structural formula.

The polymer synthesized by using this compound as a polymerization initiator has a structure in which polymer chains are radially extended around the compound (hereinafter referred to as "star polymer" due to its shape). Star-shaped polymers have a three-dimensional network structure even with extremely small cross-links, compared to polymers with straight-chain polymer chains composed of compounds with two or less peroxide groups in one molecule as polymerization initiators. Heat resistance is improved.

Further, as a polymerization initiator, a peroxide having one peroxide group in one molecule such as benzoyl peroxide, dicumyl peroxide, and dibutyl peroxide, 1,1-di-t-butylperoxy-3, It is also possible to use a peroxide having two peroxide groups in one molecule such as 3,5-trimethylcyclohexane and an azobis compound such as azobisisobutyronitrile. However, it is preferable that the amount of the polymerization initiator used in combination is 50% by weight or less of the organic peroxide having 3 or more peroxide groups in one molecule so that the amount of the star-shaped polymer formed does not decrease. ..

Examples of the solvent used for the polymerization include aromatic organic solvents such as toluene and xylene, ketone organic solvents such as methyl ethyl ketone and methyl isobutyl ketone, ester organic solvents such as ethyl acetate and butyl acetate.

The weight average molecular weight of the polymer (A) is 100,000 or more. 30
It is preferably in the range of 10,000 to 600,000. If it is less than 100,000, the heat resistance of the pressure-sensitive adhesive, which is the object of the present invention, will not be exhibited. On the other hand, if the weight average molecular weight is too high, the viscosity will be high and the coating workability will be reduced. The weight average molecular weight in the present invention is a polystyrene-equivalent molecular weight measured by gel permeation chromatography (hereinafter abbreviated as "GPC").

The resin composition for pressure-sensitive adhesives of the present invention further comprises an isocyanate compound (B) as a curing agent in addition to the polymer (A).
And preferably containing an amino resin (C).

Examples of the isocyanate compound (B) include tolylene diisocyanate, xylylene diisocyanate,
Tetramethylene diisocyanate, hexamethylene diisocyanate, trimethyl hexamethylene diisocyanate, tolidine diisocyanate, 4,4'-diphenylmethane diisocyanate, isophorone diisocyanate,
Polyfunctional isocyanate compounds such as 1,5-naphthalene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, transvinylylene diisocyanate, triphenylmethane diisocyanate and polyphenylmethane diisocyanate, these isocyanate compounds and dipropyglycol, diethylene glycol, 1 Isocyanate terminal adducts obtained by reacting polyhydric alcohols such as 6,6-hexanediol and trimethylolpropane, trimers such as hexamethylene diisocyanate, isophorone diisocyanate and tolylene diisocyanate,
Tris-(isocyanate-hexyl)-biuret polyisocyanate, methylene-bridged polyphenyl polyisocyanate, all or some of the isocyanate groups of these compounds are active methylene compounds such as ethyl acetoacetate and acetylacetone, alcohols such as ethanol and propanol. , Phenols such as phenol and cresol, acid amides or acid imides such as acetamide and succinimide, and block isocyanate compounds protected with a blocking agent such as ketone or aldehyde oximes such as cyclohexaneoxime and acetoxime. Be done.

In the present invention, these 1 type(s) or 2 or more types can be used. These isocyanate compounds are preferably blended in an amount of 0.7 to 1.5 equivalents based on 1 equivalent of hydroxyl groups in the polymer (A). If the compounding amount of the isocyanate compound is less than 0.7 equivalent, the crosslinking is insufficient, so that the heat resistance is lowered, and if the compounding amount of the isocyanate compound exceeds 1.5 equivalent, the adhesion tends to be lowered.

Examples of the amino resin (C) include urea resin,
Examples include melamine resin, acetoguanamine resin, benzoguanamine resin, and their alkyl ether compounds. These amino resins are 0.5 to
It is preferable to mix 1.5 times the amount. If the amount of the amino resin compounded is less than 0.5 times, the crosslinking will be insufficient and the heat resistance will decrease. If the amount of the amino resin compounded exceeds 1.5 times, the adhesion will tend to decrease.

The pressure-sensitive adhesive resin composition of the present invention preferably further contains a tackifier in addition to the polymer (A), the isocyanate compound (B) and the amino resin (C).

Examples of the tackifier (D) include rosin resin, terpene resin, aliphatic petroleum resin, aromatic petroleum oil, coumarone resin, alkylphenol resin, xylene resin and the like. These are preferably used in an amount of 30% by weight or less in the solid content of the adhesive resin composition.

The polymer composition (A), the isocyanate compound (B), the amino resin (C), the tackifier (D) and the like are blended to obtain the resin composition for pressure-sensitive adhesive of the present invention. When dissolved in another solvent, a solution-form resin composition for pressure-sensitive adhesive is obtained. As the organic solvent, those exemplified as the solvent used when producing the polymer (A) can be used. The obtained resin composition for pressure-sensitive adhesive is a pressure-sensitive adhesive film,
Used as an adhesive component such as adhesive tape.

(Examples) Hereinafter, examples of the present invention will be specifically described.
The present invention is not limited to this specific example. In addition,
Hereinafter, "parts" and "%" indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Examples 1 to 5 The composition (I) shown in Table 1 was placed in a reactor equipped with a mixer and a condenser and heated to 80° C. to prepare the composition (II) shown in Table 1.
Was added dropwise over 15 minutes and the temperature was kept for 7 hours for reaction. After cooling, toluene was added so that the solid content was about 40%.

The weight average molecular weight, number average molecular weight, non-volatile content and viscosity of this polymer were measured by the following methods. The measurement results are shown in Table 1. Table 1 also shows the molecular weight dispersity and acid value.
Shown in.

* ₁ Weight average molecular weight and number average molecular weight; measured by gel permeation chromatography (GPC) with standard polystyrene using a calibration curve.

* ₂ Viscosity: Measured at 25°C using a Gardner viscometer.

* ₃ Nonvolatile matter: About 1.5 g of the polymer (A) was transferred to a shearer, precisely weighed, dried at 108° C. for 3 hours, and then precisely weighed again to obtain the value.

<GPC conditions> Equipment used: Hitachi 635 type HLC, Column: Gelpack R440, R4
50 and R400M (trade name of Hitachi Chemical Co., Ltd.), eluent: tetrahydrofuran, column temperature: 25°C, flow rate: 2m
l/min, detector: differential refractometer To 100 parts of the obtained polymer (A), the isocyanate compound (B) and ami resin (C) shown in Table 2 were added to obtain a resin composition for pressure-sensitive adhesive. ..

The resulting adhesive resin composition was applied to a polyester film (25 μm) using a roll coaster, and then at 100° C.
It was cured by heating for 20 minutes and dried to obtain a tape having an adhesive layer thickness of about 50 μm.

The obtained tape was used to test adhesion and heat resistance.
The test method is as follows.

(1) Adhesion test: A tape 20 cm wide and 50 mm long was attached to a stainless steel plate that had been longitudinally polished with water resistant abrasive paper, and then
The 0°C peel peel strength is measured. Measurement temperature 23±2℃, 80±
2℃, pulling speed 200mm/min.

[Measuring device: Autograph (manufactured by Shimadzu Corp.)] (2) Heat resistance test: Attach one end of a tape cut to a width of 20 mm and a length of 40 mm to a stainless steel plate that has been vertically polished with water resistant abrasive paper (tape) 20mm x 20mm which is half of the above) is applied), a load of 500g is applied to the other end that is not affixed (shearing direction), left in the atmosphere of 80℃, 100℃, until it slips off. Measure the time or the length shifted from the original position after 1 hour.

[Measuring device: heat-resistant creep tester (manufactured by Toyo Seiki Co., Ltd.)]

The test results are shown in Table 4.

Comparative Examples 1 to 4 The composition (I) shown in Table 3 was placed in a reactor equipped with a mixer and a condenser, heated to 90°C (however, 80°C in Example 4), and the composition shown in Table 3 ( II) was added dropwise in about 15 minutes and kept warm for 7 hours to react. After cooling, the non-volatile content was adjusted in the same manner as in Example, and the properties of the polymer were measured and shown in Table 3. Adjustment of the resin composition for pressure-sensitive adhesives and preparation of tapes were performed in the same manner as in the examples, and the same tests were conducted. The test results are shown in Table 4.

(Effects of the Invention) The resin composition for pressure-sensitive adhesives according to the present invention can have excellent heat resistance while maintaining the adhesiveness and coatability.

Claims (2)

(57) [Claims] 1. 0.1 to 5% by weight of a monoethylenically unsaturated monomer having a hydroxyl group selected from hydroxyalkyl methacrylate and hydroxyalkyl acrylate and 95 to 99.9% by weight of another ethylenically unsaturated monomer. Containing a polymer (A) having a weight average molecular weight of 100,000 or more obtained by copolymerizing a compound containing the same with an organic peroxide having 3 or more branched peroxide groups in one molecule. A resin composition for a pressure-sensitive adhesive. 2. The resin composition for pressure-sensitive adhesives according to claim 1, which further contains an isocyanate compound (B) and an amino resin (C) as a curing agent.