JPH08302321A - Acrylic pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE: To obtain an acrylic pressure-sensitive adhesive compsn. well balanced between tackiness and holding performance. CONSTITUTION: An acrylic copolymer obtd. by the copolymn. of an alkyl (meth) acrylate, a vinyl monomer contg. a hydroxyl group, and a vinyl monomer contg. a carboxyl group is blended with a naphthalene compd. contg. at least one hydroxyl group, and a crosslinking agent to obtain the objective compsn.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an acrylic pressure-sensitive adhesive composition.

[0002]

2. Description of the Related Art An acrylic pressure-sensitive adhesive composition has a tackiness on its own and can be a pressure-sensitive adhesive without the addition of a tackifying resin. The adhesive strength in is weak. Therefore, usually, a tackifying resin is added as in the case of other pressure-sensitive adhesives to improve the adhesive performance (for example, JP-A-3-281).
587).

However, although the peeling force and tack have been improved, the holding power at high temperature is still insufficient, and there remains a problem that it is difficult to balance the adhesive physical properties.

[0004]

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide an acrylic pressure-sensitive adhesive composition having a well-balanced adhesive force and holding performance.

[0005]

The gist of the present invention is to provide an acrylic pressure-sensitive adhesive composition obtained by copolymerizing an acrylic (meth) acrylate with a vinyl monomer having a hydroxyl group or a vinyl monomer having a carboxyl group. The system copolymer (A), the naphthalene compound (B) containing at least one or more hydroxyl groups, and the cross-linking agent (C) are mixed.

The acrylic copolymer used in the present invention is obtained by copolymerizing an alkyl (meth) acrylate with a vinyl monomer having a hydroxyl group or a vinyl monomer having a carboxyl group, and the alkyl (meth) acrylate alone is used. Alternatively, it can be obtained by polymerization or copolymerization in combination with a monomer copolymerizable therewith.

The above alkyl (meth) acrylate preferably has an alkyl group having 2 to 14 carbon atoms. If it is less than 2 or more than 14, the properties as an adhesive are impaired. More preferably, it is 4-9. The alkyl (meth) acrylate is not particularly limited, and examples thereof include ethyl acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, t-. Butyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl acrylate,
2-Ethylhexyl (meth) acrylate, isononyl acrylate, lauryl (meth) acrylate, etc. are mentioned. These may be used alone or in combination of two or more.

The vinyl monomer having a hydroxyl group used in the present invention is not particularly limited, and examples thereof include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate and 4-hydroxy (meth).
Examples thereof include butyl acrylate, caprolactone-modified (meth) acrylate, polyoxyethylene oxide-modified (meth) acrylate and the like.

The blending amount of the vinyl monomer having a hydroxyl group is preferably 0.05 to 1.0% by weight in the copolymer. If it is less than 0.05% by weight, the degree of crosslinking of the pressure-sensitive adhesive does not increase and sufficient creep properties cannot be obtained. If it exceeds 1.0% by weight, the initial adhesive strength is lowered.

The vinyl monomer containing a carboxyl group used in the present invention is not particularly limited.
(Meth) acrylic acid, itaconic acid, (anhydrous) maleic acid, (anhydrous) fumaric acid, etc. are mentioned. The amount of the vinyl monomer containing a carboxyl group is preferably 0.5 to 10% by weight in the copolymer. If it is less than 0.5% by weight, the degree of crosslinking of the pressure-sensitive adhesive does not increase, so that sufficient creep properties cannot be obtained, and if it exceeds 10% by weight, the initial adhesive strength is lowered. More preferably, it is 1 to 5% by weight.

The vinyl monomer containing a hydroxyl group or the vinyl monomer containing a carboxyl group is appropriately selected depending on the kind of the cross-linking agent to be used, but both can be used together regardless of the cross-linking agent.

The monomer copolymerizable with the alkyl (meth) acrylate used in the present invention is not particularly limited, and examples thereof include (meth) acrylonitrile, n-vinylpyrrolidone, n-vinylcaprolactam, acryloylmorpholine, ( Vinyl polar mer having high polarity such as (meth) acrylamide, dimethylaminoethyl (meth) acrylate, diethylaminomethyl (meth) acrylate, dimethylaminopropylacrylamide; vinyl monomer capable of copolymerization such as methyl (meth) acrylate, styrene and vinyl acetate Etc. The blending amount of the monomer copolymerizable with the alkyl (meth) acrylate is preferably 0.5 to 30% by weight in the copolymer.

The above-mentioned polymerization method is not particularly limited, and examples thereof include bulk polymerization, solution polymerization, dispersion polymerization and emulsion polymerization. The polymerization initiation method includes, for example, a method using a thermal polymerization initiator such as benzoyl peroxide, lauroyl peroxide, and azoisobutyroyl nitrile; a photopolymerization initiator such as benzoin, benzoin methyl ether, and benzophenone, and ultraviolet irradiation and electron beam irradiation. Methods and the like.

The weight average molecular weight of the acrylic copolymer is preferably 200,000 to 1,500,000. When it is less than 200,000, it becomes difficult to obtain the necessary cohesive force, and when it exceeds 1.5 million, the viscosity becomes high and the productivity in the mixing step and the coating step of the tackifying resin deteriorates. More preferably 35
It is 10,000 to 750,000.

The naphthalene compound (B) having at least one hydroxyl group used in the present invention is not particularly limited, and examples thereof include 1-naphthol, 2-naphthol, 4-chloro-1-naphthol, 1, Examples thereof include 2-dihydroxynaphthalene and 2,7-dihydroxynaphthalene. Of these, 2-naphthol is preferable. These may be used alone or in combination of two or more.

The content of the naphthalene compound (B) having one or more hydroxyl groups is 100% by weight of the acrylic copolymer 100.
5 to 50 parts by weight is preferable with respect to parts by weight. If it is less than 5 parts by weight, the effect of the addition of the naphthalene compound containing one or more hydroxyl groups cannot be obtained, and if it exceeds 50 parts by weight, the initial adhesive strength of the resulting acrylic pressure-sensitive adhesive composition decreases.

In order to improve the adhesive strength of the acrylic pressure-sensitive adhesive composition, by using the naphthalene compound (B) having at least one or more hydroxyl groups, the acrylic pressure-sensitive adhesive composition having a well-balanced pressure-sensitive adhesive strength and holding performance. The thing is obtained.

The crosslinking agent (C) used in the present invention is a compound capable of reacting with at least one selected from a hydroxyl group and a carboxyl group. The cross-linking agent capable of reacting with the hydroxyl group is not particularly limited, and examples thereof include alkoxysilane compounds such as trimethoxysilane, triethoxysilane, and tributoxysilane.

The cross-linking agent capable of reacting with the above-mentioned carboxyl group is not particularly limited, and examples thereof include N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide) and methylolpropane-tri-β-. Aziridinyl propionate, bisisofuroyl-1- (2-methylaziridine), N, N'-diphenylmethane-4,4 '
-Bis (1-aziridinecarboxamide), trimethylolpropane-tri-β- (2-methylaziridine)
Examples thereof include aziridine compounds such as propionate.

The cross-linking agent capable of reacting with the above hydroxyl group and carboxyl group is not particularly limited, and examples thereof include aromatic compounds such as tolylene diisocyanate (TDI), tolidine diisocyanate (TODI), xylylene diisocyanate and diphenylmethane diisocyanate (MDI). Diisocyanate compound; hexamethylene diisocyanate (HMDI), isophorone diisocyanate (ID
I) or other aliphatic or alicyclic diisocyanate compound; trimethylolpropane tolylene diisocyanate trimer adduct; triphenylmethane triisocyanate, methylenebis (4-phenylmethane) triisocyanate compound or the like; ethylene glycol di Glycidyl ether, triglycidyl ether, 1,6
-Hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diglycidyl amine, N, N, N ', N'-tetraglycidyl-m-xylene diamine, 1,3-bis (N, N'- Examples thereof include epoxy compounds such as diglycidylaminomethyl) cyclohexane.

The amount of the above crosslinking agent added is preferably such that the gel fraction after crosslinking is 20 to 50% by weight. When the gel fraction is less than 20% by weight, sufficient creep properties cannot be obtained, and when it exceeds 50% by weight, the initial adhesive strength is lowered. The gel fraction is determined by immersing the crosslinked acrylic pressure-sensitive adhesive composition in tetrahydrofuran and allowing it to stand for 24 hours, after which the weight of the insoluble matter (after drying) and the weight ratio of the blended pressure-sensitive adhesive composition (% by weight). Is obtained by measuring.

In the present invention, a generally used tackifying resin may be added to the acrylic pressure-sensitive adhesive composition in an amount of 15 parts by weight or less based on 100 parts by weight of the acrylic copolymer. The tackifying resin is not particularly limited, and examples thereof include partially disproportionated rosin, disproportionated rosin, hydrogenated rosin, polymerized rosin, and rosin derivatives such as esterified products of a mixture of these and polyhydric alcohols; and C5 series. , C9-based petroleum resins; styrene-based; pinene-based terpene resins and the like.

In the acrylic pressure-sensitive adhesive composition of the present invention, known pressure-sensitive adhesive additives such as fillers, pigments and dyes may be used, if necessary.

A pressure-sensitive adhesive tape is obtained by applying the acrylic pressure-sensitive adhesive composition of the present invention to one side or both sides of a substrate to form a pressure-sensitive adhesive layer. The base material is not particularly limited, and examples thereof include paper; nonwoven fabric; synthetic resin film such as polyester resin and polyolefin resin; synthetic resin foam such as polyolefin resin, polyurethane resin, polychloroprene resin, and acrylic resin. . Furthermore,
By molding only the acrylic pressure-sensitive adhesive composition into a sheet, a non-support type double-sided pressure-sensitive adhesive tape having no substrate layer can be obtained.

[0025]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Preparation of Acrylic Copolymers 1 to 3 According to the blending composition shown in Table 1, n-butyl acrylate, 2-ethylhexyl acrylate, acrylic acid, 2
-Hydroxyethyl acrylate and 0.05 parts by weight of lauroyl mercaptan together with 80 parts by weight of ethyl acetate were placed in a five-necked flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel and a nitrogen gas inlet, and dissolved by stirring. The resulting mixture was homogenized, and then purged with nitrogen gas for about 30 minutes to remove oxygen existing in the monomer solution. Then, the air in the flask was replaced with nitrogen gas, the temperature was raised with stirring, the temperature was maintained at 70 ° C., and a solution prepared by dissolving 0.03 part by weight of benzoyl peroxide in 1 part by weight of ethyl acetate was added, After dropping with a dropping funnel, a polymerization reaction was performed at the same temperature for 10 hours to obtain a solution of an acrylic copolymer. The molecular weights shown in Table 1 were determined by gel permeation chromatography based on standard polystyrene and tetrahydrofuran as the eluent.
The detection was performed using a refractometer.

[0027]

[Table 1]

Acrylic adhesive composition and adhesive tape
According to the composition (A to I, a to g) shown in Preparation Tables 2 and 3, acrylic copolymers 1 to 3 and naphthol were uniformly mixed while being diluted with toluene, and 45% by weight of an adhesive composition. After adding the crosslinking agent to the solution of each pressure-sensitive adhesive composition and mixing them uniformly, the solution is coated on a release sheet with a baker-type applicator and dried by a gear oven at 100 ° C. for 5 minutes to give a pressure-sensitive adhesive of 60 μm. Layers were formed. The laminate was transferred by laminating it on both sides of a nonwoven fabric weighing 14 g / m ² , and then cured at 40 ° C. for 3 days to obtain a double-sided tape. The details of each component in Tables 2 and 3 are as follows. Tackifying resin 1: Alkylphenol-modified xylene resin, manufactured by Mitsubishi Gas Chemical Co., Inc., trade name "Nikanol HP12
0 "Crosslinking agent No. 1: Ethyl acetate solution of tolylene diisocyanate adduct of trimethylolpropane, manufactured by Nippon Polyurethane Industry Co., Ltd., solid content 55% by weight, trade name “Coronate L55E” Crosslinking agent No. 2: N, N'-hexamethylene-1,6-
Bis (1-aziridine carboxide) (HDU)

[0029]

[Table 2]

[0030]

[Table 3]

Evaluation method of adhesive tape ( evaluation of SP adhesive strength)
2kg on SUS304 plate with 20mm width according to 0237
Rubber roller pasted with one round trip load, 23 ℃, 2
After leaving for 0 minutes, 180 degree direction, pulling speed 300m
The peel strength was measured under the condition of m / min. (Evaluation of tacking force) The above adhesive tape was compliant with JIS Z 0
The initial tack force was measured based on the 237 tack test method (rolling ball method). (Evaluation of holding power against SUS) According to JIS Z 0237, a double-sided adhesive tape cut into a width of 20 mm and a length of 100 mm is adhered to a SUS304 plate having a thickness of 1.5 mm, a width of 25 mm, and a length of 100 mm, and a length of 20 mm is 2 kg. A rubber roller is pasted under a load of one reciprocation, left in an atmosphere of 23 ° C-65% RH for 20 minutes, and then left in an atmosphere of 80 ° C for 20 minutes, with a double-sided tape on the lower side in a constant temperature dryer of 80 ° C. Was vertically suspended, a load of 1 kg was applied vertically to the lower end of the double-sided tape, and it was left vertically, and the dropping time (minute) within 1 hour or the deviation distance (mm) after 1 hour was measured.

[0032]

[Table 4]

[0033]

[Table 5]

[0034]

EFFECTS OF THE INVENTION Since the acrylic pressure-sensitive adhesive composition of the present invention has the above-mentioned constitution, an acrylic pressure-sensitive adhesive composition having a well-balanced pressure-sensitive adhesive force and holding performance can be obtained. In addition, an acrylic pressure-sensitive adhesive composition which does not vary among lots of products can be obtained.

Claims (2)

[Claims] 1. An acrylic copolymer (A) obtained by copolymerizing an alkyl (meth) acrylate with a vinyl monomer having a hydroxyl group or a vinyl monomer having a carboxyl group, and naphthalene having at least one hydroxyl group. An acrylic pressure-sensitive adhesive composition comprising a compound (B) and a crosslinking agent (C). 2. The acrylic pressure-sensitive adhesive composition according to claim 1, wherein the naphthalene compound is 2-naphthol.