JP2001335766A - Blister-resistant self-adhesive composition and self- adhesive sheet obtained by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellently blister-resistant self-adhesive composition obtained by a stable polymerization reaction, having a low viscosity enough to be applied and causing no blister such as a swelling or a scab with the lapse of time at ordinary temperature or under a high temperature and high humidity condition after pasted on the surfaces of various plastic molded articles and to prepare a self-adhesive sheet obtained by using the same. SOLUTION: The blister-resistant self-adhesive composition comprises a copolymer (A) having a weight-average mol.wt. of 10,000-2010,000 and comprising (a) a (meth)acrylate bearing a 1-12C alkyl group as a main component, (b) 1-30 wt.% of a styrenic monomer, (c) 0.1-7 wt.% of a carboxyl group-containing unsaturated monomer and (d) 0.1-15 wt.% of an amino group-containing unsaturated monomer, which is a tertiary amine, (provided that the total of (a), (b), (c) and (d) is 100 wt.%), and, added thereto, 0.05-5 wt.%, based on 100 pts.wt. of the copolymer (A), of a crosslinking agent (B) bearing a glycidyl group. The self-adhesive sheet is obtained by using the composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a blister-resistant pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet using the same. More specifically, the present invention relates to an excellent blister-resistant pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet which do not generate blisters such as blisters or floating at room temperature or high temperature over time after being attached to the surface of various plastic molded products. .

[0002]

2. Description of the Prior Art Conventionally, pressure-sensitive adhesive sheets coated with a pressure-sensitive adhesive can be easily attached by simply pressing, and unlike the adhesives generally used, no solvent or pollution is required. Are preferred and are widely used in many fields. In recent years, as the number of plastic products has increased in response to the demand for lighter products, the use of pressure-sensitive adhesive sheets as labels on plastic molded products and plastic packaging materials has been increasing. Adhesive sheets are often affixed to a transparent plastic, for example, a resin plate of polycarbonate, polymethyl methacrylate, polystyrene, or the like, for protecting the surface from scratches and for decoration. However, when a conventional pressure-sensitive adhesive sheet or label using a film with a gas barrier property such as polyester as a base sheet is affixed to a resin plate such as polycarbonate, acrylic or styrene, the gap between the pressure-sensitive adhesive sheet or label and the resin adherend can be reduced. Air bubbles are generated in the air, and so-called blisters such as blisters and floating are often generated.
In particular, this phenomenon is remarkable under high temperature or high temperature and high humidity. The occurrence of such blisters impairs the beauty of the product and also causes the labels to fall off. In particular, in the case of a transparent label, the pressure-sensitive adhesive surface is seen through in an avatar-like or cloudy state, and the actual situation is that the appearance is inevitably impaired. This blister is caused by the plastic film used as the adhesive base sheet, which becomes a barrier layer for trace gas generated from plastic molded products such as polycarbonate, so there is no place for gas to escape, and blisters and floating It is considered that blisters occur.

Various studies have been made to prevent these problems. For the adhesive sheet, a method in which a gas-permeable layer such as a porous material is present between the sheet and the adhesive layer, or a method in which the base sheet itself is made air-permeable, and furthermore, the release paper is made to have scattered spots. A method of eliminating the blister state by, for example, processing the adhesive so that the surface of the pressure-sensitive adhesive is not flat but embossed in a dotted manner has been considered. However, in these methods, there are problems that the thickness of the pressure-sensitive adhesive sheet is increased and that the transparency is impaired so that the pressure-sensitive adhesive sheet cannot be used as a transparent label.

Further, regarding the pressure-sensitive adhesive composition, JP-A No.
In JP-A-3481, (meth) acrylates,
An acrylic pressure-sensitive adhesive composition obtained by radically copolymerizing a copolymerizable carboxyl group-containing compound and a tertiary amine having a vinyl group has been disclosed. When a tertiary amine having a tertiary amine is used in combination, a cross-linking reaction occurs during polymerization, resulting in high viscosity or gelation, low reaction stability, and a problem in coatability. JP-A-2-292382 discloses a pressure-sensitive composition comprising an acrylic copolymer obtained by polymerizing an amino group-containing unsaturated monomer having a specific structural formula and an alkyl (meth) acrylate, and a crosslinking agent. Although an adhesive composition is disclosed, the degree of cross-linking advances with time, the adhesive strength decreases, and the effect of preventing blistering such as blisters and floating is low. JP-A-8-3521 discloses a (meth) acrylate having an alkyl group having 4 to 12 carbon atoms,
A blister-resistant pressure-sensitive adhesive for a pressure-sensitive adhesive sheet comprising a copolymer of an (meth) acrylic acid ester having an alkyl group and a polar monomer and an aziridine-based crosslinking agent is disclosed. Insufficient blister resistance. JP-A-10-310754 discloses a resin composition (1) having a specific molecular weight obtained by copolymerizing an alkyl (meth) acrylate having 1 to 12 carbon atoms and a carboxyl group-containing unsaturated monomer. ,
It is obtained by copolymerizing one or more monomers selected from alkyl methacrylate or cycloalkyl methacrylate having 1 to 20 carbon atoms, benzyl methacrylate or styrene with an amino group-containing unsaturated monomer. A pressure-sensitive adhesive composition containing a resin composition (2) having a specific Tg and a specific molecular weight is disclosed. This pressure-sensitive adhesive composition is of a two-liquid type in which carboxyl groups and amino groups are prevented from entering the same reaction system, but has insufficient blister resistance at high temperature and high humidity over time.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to stabilize the polymerization reaction, have a low viscosity suitable for coating, and after applying it to the surface of various plastic molded articles, at room temperature or at room temperature. An object of the present invention is to provide an excellent blister-resistant pressure-sensitive adhesive composition which does not generate blisters such as blisters and floating at high temperature and high humidity, and a pressure-sensitive adhesive sheet using the same.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies on the development of a pressure-sensitive adhesive for pressure-sensitive adhesive sheets having excellent blister resistance. Polymerization of an unsaturated monomer containing an amino group, which is a saturated monomer and a tertiary amine, with a styrene monomer which is not usually used due to low copolymerizability in solution polymerization of an adhesive, leads to polymerization stability. It has been found that even when a crosslinking agent is used, the adhesive strength after storage is small and the blister resistance is improved, and the present invention has been achieved.

That is, the present invention provides (a) an alkyl (meth) acrylate having an alkyl group having 1 to 12 carbon atoms as a main component, (b) 1 to 30% by weight of a styrene monomer,
(C) 0.1 to 7% by weight of a carboxyl group-containing unsaturated monomer and (d) 0.1 to 15% by weight of an amino group-containing unsaturated monomer which is a tertiary amine (provided that (a), (B),
(A) wherein the weight-average molecular weight of the copolymer (A) is 10,000 to 200,000.
An object of the present invention is to provide a blister-resistant pressure-sensitive adhesive composition obtained by adding 0.05 to 5% by weight of a crosslinking agent (B) having a glycidyl group to 100 parts by weight, and a pressure-sensitive adhesive sheet using the same.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail. The (a) alkyl group used in the present invention has 1 carbon atom.
Specific examples of the alkyl (meth) acrylates of Nos. To 12 include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, and 2-ethylhexyl ( Examples thereof include (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, and lauryl (meth) acrylate. At least one or more of these groups can be used. Preferably, it is an alkyl acrylate having 2 to 12 carbon atoms. Further, if necessary, other copolymerizable unsaturated monomers can be used. Examples of the copolymerizable unsaturated monomer include (meth) acrylonitrile, vinyl acetate, vinyl propionate, and vinyl versatate.

The styrene monomer (b) used in the present invention is a very important essential component in the present invention. Due to the low copolymerizability in the solvent polymerization reaction of pressure sensitive adhesives, carboxyl group-containing unsaturated monomers and amino group-containing unsaturated monomers are reacted in the same system by using styrene-based monomers that are not usually used in combination. Even when the reaction is performed, there is no occurrence of gelation or the like, and the stability during the reaction is good. The molecular weight of the copolymer is suppressed, and the adhesive sheet processed by adding a crosslinking agent has an effect of preventing a decrease in adhesiveness after storage and a blister property. Its usage is 1
３０30% by weight. If the amount used is less than 1% by weight, the effect of preventing blistering is small, and if it exceeds 30% by weight, the copolymerizability is impaired, the molecular weight of the obtained copolymer is reduced, and the cohesive strength is reduced. And the holding force does not reach the predetermined strength. The preferred amount is 5 to 20% by weight.
It is. Specific examples of the styrene monomer used include styrene, α-methylstyrene, chlorostyrene, and 4-styrene.
Examples include hydroxystyrene and vinyl toluene. Preferably it is styrene.

The carboxyl group-containing unsaturated monomer (c) used in the present invention is required for improving the adhesion to various plastics. Specific examples of the carboxyl group-containing unsaturated monomer include (meth) acrylic acid, maleic acid,
Crotonic acid and the like. At least one or more of these groups can be used. Acrylic acid is preferred. The amount used is 0.1 to 7% by weight. If the amount is less than 0.1% by weight, sufficient blister resistance cannot be obtained, and if it exceeds 7% by weight, the adhesive strength may be undesirably reduced. A preferred amount is 1 to 5% by weight.

The amino group-containing unsaturated monomer (d) used in the present invention, which is a tertiary amine, is necessary for improving blister resistance to various plastics. As the amino group-containing unsaturated monomer, specifically, dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminoethyl (meth)
Acrylate, diethylaminopropyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N-dibutylaminoethyl (meth) acrylamide, N, N-dimethylamino Propyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide and the like. At least one or more of these groups can be used. The amount used is 0.1 to 15% by weight. If the amount is less than 0.1% by weight, sufficient blister resistance cannot be obtained. The preferred amount is
1 to 10% by weight. Comparing the amount of the (c) carboxyl group-containing unsaturated monomer with the amount of the (d) tertiary amine-containing amino group-containing unsaturated monomer, the tertiary amine amino group-containing unsaturated monomer It is preferable that the amount of the polymer is larger than the amount of the carboxyl group-containing unsaturated monomer in order to improve the blister resistance.

The weight average molecular weight of the pressure-sensitive adhesive composition of the present invention must be in the range of 10,000 to 200,000. If it is less than 10,000, the cohesive force is insufficient even if a crosslinking agent is used, and the blister resistance is insufficient. If it exceeds 200,000, the use of a cross-linking agent causes the adhesive strength to decrease over time, resulting in insufficient blister resistance. The preferred range of the weight average molecular weight is 30,000 to 100,000. The weight average molecular weight is a weight average molecular weight in terms of polystyrene.

As the crosslinking agent (B) having a glycidyl group used in the present invention, a compound having at least two or more glycidyl groups in one molecule can be used. Specifically, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether ,
Examples include polyfunctional glycidyl compounds such as tetraglycidyl xylene diamine, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, and sorbitol polyglycidyl ether. The amount used is 0.05 to 100 parts by weight of the copolymer (A) of the present invention.
5 parts by weight. When the amount is less than 0.05 part by weight, sufficient blister resistance cannot be obtained, and when it exceeds 5 parts by weight, the adhesive strength is reduced and the blister resistance cannot be obtained.

The copolymer (A) of the present invention can be usually produced by bulk polymerization, solution polymerization or the like, but is preferably solution polymerization. The solvent used is a common organic solvent such as ethyl acetate, toluene, hexane and acetone. The polymerization initiator used in the polymerization may be an oil-soluble polymerization initiator such as a peroxide such as benzoyl peroxide or lauryl peroxide, or an azobis compound such as azobisisobutyronitrile or azobisvaleronitrile. it can.

For the purpose of adjusting the tackiness of the copolymer (A) of the present invention, various copolymers may be blended as required. Specific examples used in the compounding include terpene-based, terpene-phenol-based, coumarone-indene-based, styrene-based, rosin-based, xylene-based, phenol-based, petroleum-based tackifying resins, melamine resins, antioxidants, Examples include an ultraviolet absorber, a filler, and a pigment.

The blister-resistant pressure-sensitive adhesive composition of the present invention is applied to various base sheets to obtain a blister-resistant pressure-sensitive adhesive sheet. The base material is polyethylene, polypropylene,
Sheets or films made of synthetic resins such as films of ethylene-vinyl acetate copolymer, polyester, polyvinyl chloride, polycarbonate, polyamide, polystyrene, and composite films thereof, and synthetic paper can be used. Prior to applying the pressure-sensitive adhesive, the surface of the plastic film may be subjected to a corona treatment or the like in order to improve the adhesiveness. Alternatively, a plastic film whose one surface is back-treated with a silicon release agent, a silicone acrylic resin, or the like can be used. Further, the plastic film adhesive layer coated with the adhesive can be protected by a general-purpose silicon release paper, a silicon release film, or the like.

The blister-resistant pressure-sensitive adhesive composition of the present invention comprises:
The coating can be performed by a commonly used coating device, for example, a roll coating device. The amount of application varies depending on the intended use, but the application thickness is usually 5 to 300 μm.

The blister-resistant pressure-sensitive adhesive sheet of the present invention is effectively used on the surface of a molded article made of a resin which easily generates gas, that is, a styrene resin, a polycarbonate resin, an unsaturated polyester resin, etc. to prevent blisters. can do.

[0019]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited by these examples.
In the Examples and Comparative Examples, “parts” or “%” means “parts by weight” or “% by weight” unless otherwise specified.

Production Example 1 (Copolymer A-1) Nitrogen gas was charged into a reactor equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, and then 100 parts of ethyl acetate, 89 parts of butyl acrylate, and styrene. 5 parts, acrylic acid 2
Parts, 4 parts of dimethylaminoethyl methacrylate and 0.2 part of azobisisobutyronitrile as a polymerization initiator. The reaction is carried out at a reflux temperature of ethyl acetate for 8 hours in a stream of nitrogen gas while stirring. After completion of the reaction, 85 parts of toluene is added and the mixture is cooled to room temperature. Viscosity 3,500 mPa · s, solid content 3
5%, copolymer A- having a weight average molecular weight of 80,000
1 was obtained.

Production Example 2 (Copolymer A-2) After nitrogen gas was sealed in a reactor equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet tube, 50 parts of ethyl acetate, 84 parts of butyl acrylate, styrene 10 parts, acrylic acid 2
Parts, 4 parts of dimethylaminoethyl methacrylate and 0.2 part of azobisisobutyronitrile as a polymerization initiator. The reaction is carried out at a reflux temperature of ethyl acetate for 8 hours in a stream of nitrogen gas while stirring. After the reaction is completed, 135 parts of toluene is added and the mixture is cooled to room temperature. Copolymer A having a viscosity of 3,000 mPa · s, a solid content of 35%, and a weight average molecular weight of 65,000
-2 was obtained.

Production Examples 3 to 6 (Copolymers A-3 to 6) In Production Examples 3 to 6, the types and amounts of the monomers are changed as shown in Table 1 in the same manner as in Production Example 2. Except for the above, copolymers A-2 to A-6 were similarly obtained.

Production Examples 7 to 9 (Copolymers A-7 to 9) Production Example 7 is an example in which the styrene monomer of Production Example 1 was not used, and Production Example 8 was a functional product of Production Example 2. The group-containing monomer is an example in which only acrylic acid is used. Production Example 9 is an example in which the functional group-containing monomer in Production Example 2 is only dimethylaminoethyl methacrylate, and reacts in the same manner as in Production Examples 1 and 2. As a result, copolymers A-7 to A-9 were obtained. It is shown in Table 2.

[0024]

[Table 1]

[0025]

[Table 2]

In Tables 1 and 2, the types of monomers are indicated by the following abbreviations. BA: butyl acrylate St: styrene AAC: acrylic acid DMAEMA: dimethylaminoethyl methacrylate DMAPA: dimethylaminopropyl acrylamide

Example 1 In Example 1, a bisphenol A type polyfunctional epoxy compound (Asahi Co., Ltd.), a crosslinking agent having a glycidyl group, was added to 100 parts of the solid content of the copolymer A-1 obtained in Production Example 1. Made by Denka Kogyo Co., Ltd. Adeka Resin EP-41000
E) 0.5 part was added and mixed well to obtain a blister-resistant pressure-sensitive adhesive. The adhesive is dried on a dryer at 100 ° C. for 60 seconds, coated on release paper so that the thickness becomes 25 μm (dry), transferred to an aluminum-evaporated polyester film having a thickness of 25 μm, and then applied to an adhesive sheet. Was prepared. As shown in Table 3, the results showed that the blister resistance at the initial stage and after the storage was good, and that both the adhesive strength and the holding power were good.

Examples 2 to 6 Examples 2 to 6 are exactly the same as Example 1 except that the copolymer A-1 of Example 1 is changed to copolymers A-2 to A-6 shown in Table 1. Thus, an adhesive sheet was prepared. The results were all good as shown in Table 3.

Examples 7 to 9 Examples 7 and 8 differ from Example 2 in that the amount of the glycidyl group-containing cross-linking agent is changed. A pressure-sensitive adhesive sheet was produced in exactly the same manner as in Example 2 except that 3-bis (N, N-diglycidylaminomethyl) cyclohexane (trade name C, manufactured by Mitsubishi Gas Chemical Co., Ltd.) was used. The results were all good as shown in Table 3.

Comparative Examples 1 to 3 Comparative Examples 1 to 3 were carried out in exactly the same manner as in Example 1 except that the copolymer A-1 of Example 1 was changed to copolymers A-7 to A-9 shown in Table 2. Thus, an adhesive sheet was prepared. As shown in Table 3, the results of Comparative Examples 1 and 2 were good in the initial blister resistance, but poor in the blister resistance after storage. Comparative Example 3 was poor in both initial and post-storage blister resistance.

Comparative Examples 4 and 5 Comparative Example 4 was different from Comparative Example 1 in that the amount of the glycidyl group-containing cross-linking agent was increased. A pressure-sensitive adhesive sheet was produced in exactly the same manner as in Example 1 except that triresin isocyanate (trade name: Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) was used instead of the crosslinking agent. As shown in Table 3, the blister resistance of Comparative Example 4 was good, but the blister resistance after storage was poor. In Comparative Example 5, both the initial and after storage blister resistances were poor.

[0032]

[Table 3]

Test Method Blister Resistance (A) Initial Blister Resistance The pressure-sensitive adhesive sheet obtained in the present invention was cut into a size of 55 × 75 mm to obtain a test piece. The test piece was placed on a transparent polycarbonate plate (Mitsubishi Gas Chemical Co., Ltd. Iupilon sheet 3m)
m thickness), left for 1 hour at 23 ° C. and 65% RH, and then left for 24 hours in an atmosphere of 80 ° C. 23
The temperature was returned to 65 ° C. and 65% RH, and the change in the surface of the pressure-sensitive adhesive sheet was observed. (B) Blister resistance after storage After the pressure-sensitive adhesive sheet obtained in the present invention is left in an atmosphere of 70 ° C. for one month, a change in the surface is observed in the same manner as the initial blister resistance. ：: No blister was generated. ：: Several blisters were generated on the surface. ×: Many blisters occurred. 2. Adhesive force (a) Initial adhesive force The adhesive sheet obtained in the present invention is peeled off at 180 ° according to JIS Z0237, and the adhesive force is measured 20 minutes after application. (B) Adhesive force after storage After leaving the adhesive sheet obtained in the present invention in an atmosphere of 70 ° C. for one month, it is measured in the same manner as the initial adhesive force. 3. Holding force According to JIS Z0237, the pressure-sensitive adhesive sheet obtained in the present invention is measured at 40 ° C. under a load of 1 kg, and the number of seconds until the adhesive sheet falls is measured. Here, the code NC is no deviation, and CF is
Represents cohesive failure.

[0034]

The pressure-sensitive adhesive sheet using the blister-resistant pressure-sensitive adhesive composition of the present invention can effectively prevent the occurrence of blisters and has sufficient adhesive strength and holding power.
It can be suitably used for an adherend such as a polycarbonate resin and a styrene resin.

Claims (2)

[Claims] Claims: 1. A (a) alkyl (meth) acrylate having an alkyl group having 1 to 12 carbon atoms as a main component,
(B) 1 to 30% by weight of a styrene monomer, (c) 0.1 to 7% by weight of a carboxyl group-containing unsaturated monomer, and (d)
Amino group-containing unsaturated monomer that is a tertiary amine 0.1 to 0.1
Copolymer (A) 100 having a weight average molecular weight of 10,000 to 200,000 comprising 15% by weight (the total of (a), (b), (c) and (d) is 100% by weight) Crosslinking agent (B) having a glycidyl group per part by weight of 0.05
A blister-resistant pressure-sensitive adhesive composition containing up to 5% by weight. 2. A blister-resistant pressure-sensitive adhesive sheet obtained by applying the blister-resistant pressure-sensitive adhesive composition according to claim 1 to a base sheet.