JPH04154882A - Tacky agent - Google Patents

Abstract

PURPOSE:To obtain a tacky agent constituting a tacky tape or tacky sheet, etc., free from reduction in tackiness by a plasticizer, comprising an acrylic copolymer containing a specific alkyl (meth) acrylate and N-vinylpyrrolidone. CONSTITUTION:The objective tacky agent comprising an acrylic copolymer containing (A) >=50wt.%, preferably >=70wt.% alkyl (meth)acrylate containing 4-14C alkyl and (B) 3-30wt.%, preferably 5-20wt.% N-vinylpyrrolidone. The tacky agent preferably contains further 0-30wt.% copolymerizable unsaturated monomer.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an adhesive constituting an adhesive layer of an adhesive tape, an adhesive sheet, etc. The present invention relates to an acrylic pressure-sensitive adhesive that does not suffer from a decrease in adhesive strength due to the plasticizer when the adherend to be pasted is made of a soft vinyl chloride resin containing a plasticizer.

(Prior Art) Rubber adhesives and acrylic adhesives are usually used as this type of adhesive. Rubber adhesives include natural rubber, NBR (acrylonitrile-butadiene rubber), 5
The main components are synthetic rubber such as BR (styrene-butadiene rubber) and a tackifying resin, and the acrylic adhesive is mainly composed of an acrylic acid ester copolymer. In addition to being used by themselves to bond adherends, these adhesives can also be used in the form of adhesive tapes or adhesive sheets by holding them in layers on a base material, or double-sided adhesive tapes with both sides covered with release paper. It is used in the form of

By the way, when a soft vinyl chloride resin product containing a plasticizer is used as an adherend and the adhesive itself is applied or an adhesive tape or adhesive sheet is attached to the adherend, a soft vinyl chloride resin plate containing a plasticizer - When bonding two pieces with double-sided adhesive tape, the plasticizer in the resin migrates over time to the adhesive itself or to the adhesive layer of the adhesive tape, adhesive sheet, or double-sided adhesive tape, which reduces the adhesiveness of the adhesive. There is a problem that performance is significantly degraded.

Even when a tape or sheet made of a soft vinyl chloride resin containing a plasticizer is used as a base material for an adhesive tape or adhesive sheet, the same problem caused by plasticizer migration as described above occurs.

As a countermeasure against this, for acrylic adhesives, for example, a resol type phenolic resin may be mixed with the adhesive as described in JP-A-53-94519;
As described in Japanese Patent Application No. 972, an adhesion imparting resin is used in combination with the adhesive, or as described in JP-A-1-101384, a crosslinkable monomer and a metal complex are used in combination in the adhesive. As described in Japanese Patent Application Laid-open No. 63-230783, many studies have been conducted to improve adhesives, such as mixing nitrified cotton with adhesives.

However, in recent years, with the expansion of applications such as adhesive tape,
The performance required for this has also increased, and it has been difficult to solve the above-mentioned problems caused by plasticizer migration only by improving the adhesive as described above.

Therefore, Japanese Patent Application Publication No. 56-136871 and Japanese Patent Publication No. 64
As described in Publication No. 9352, a primer is first applied to the surface of a soft vinyl chloride resin product to be an adherend,
A method of applying adhesive or pasting adhesive tape on top of the primer has been proposed and put into practical use. However, in other words, this method is not practical unless the adhesive is used in combination with a primer, and therefore an extra step of applying the primer is required. Furthermore, for example, during outdoor on-site construction, it is extremely difficult to evenly apply a primer to the surface of a large-area soft vinyl chloride resin adherend.

(Problems to be Solved by the Invention) From the above points, there has been a strong desire for an adhesive that can prevent a decrease in adhesive strength caused by plasticizer migration without using a primer.

The purpose of the present invention is to meet this demand, and when the base material of an adhesive tape or adhesive sheet or the adherend to which it is attached is made of a soft vinyl chloride resin containing a plasticizer, It is an object of the present invention to provide an acrylic pressure-sensitive adhesive that can effectively suppress a decrease in adhesive strength and holding power due to transfer of a plasticizer from a resin to a pressure-sensitive adhesive.

(Means for Solving the Problems) The present inventors synthesized copolymers consisting of various monomers and measured their adhesion to soft vinyl chloride resins. After further investigation, we discovered that the lower the content of active hydrogen-containing monomers such as acrylic acid, the lower the adhesive strength after plasticizer transfer. We obtained the knowledge that this can be suppressed. The present invention was completed based on such knowledge.

That is, the present invention provides alkyl (meth)acrylates in which the number of carbon atoms in the alkyl group is in the range of 4 to 14 (hereinafter abbreviated as C4-14 alkyl (meth)acrylate).
The adhesive is characterized by containing an acrylic copolymer comprising 50% by weight or more and 3 to 30% by weight of N-vinylpyrrolidone.

The 04-,4-alkyl (meth)acrylate serving as the main monomer is a (meth)acrylate in which the argyl group is butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, inoctyl, etc., and has a low polarity. and those with low Tg (glass transition temperature) are used.

For (meth)acrylates in which the number of carbon atoms in the alkyl group is less than 4, the resulting copolymer has low adhesive strength;
If it exceeds 4, the cohesive force decreases. Therefore, the number of carbon atoms in the alkyl group is limited to 4 to 14.

The content of 04-14 alkyl (meth)acrylate is 5
It is limited to 0% by weight or more. The reason is that if the content is less than 50% by weight, the adhesive becomes too hard and its adhesive strength decreases. A particularly preferred content of 04-14 alkyl (meth)acrylate is 70% by weight or more.

The 04-14 alkyl (meth)acrylate may contain O to 30% by weight of a copolymerizable unsaturated monomer such as vinyl acetate, ethyl acrylate, methyl (meth)acrylate, acrylonitrile. If the content of the unsaturated monomer exceeds 30% by weight, the adhesive becomes hard and the adhesive strength decreases, which is not preferable.

Typical acrylic adhesives have the above acrylic monomer as the main monomer, and a reactive highly polar α, β unsaturated carboxylic acid such as (meth)acrylic acid, itaconic acid and/or maleic acid for cohesive strength. It has a structure in which the main component is a copolymer contained as an imparting component, and the above-mentioned highly polar monomer is used as a reaction site, and is crosslinked with a required crosslinking agent. In particular, acrylic acid has good compatibility and reactivity with the above-mentioned acrylic monomers, makes it easy to balance the three basic physical properties of adhesives such as adhesive force, peeling force, holding power, and tack, and also has good reactivity with the above-mentioned crosslinking agents. It is a monomer often used in acrylic adhesives because it provides a suitable crosslinked adhesive and is inexpensive.

The feature of the present invention is that the cohesive force imparting component constituting the acrylic copolymer does not substantially use α,β unsaturated carboxylic acid having reactive active hydrogen as described above, and N-vinylpyrrolidone is used instead. The point is to use the required amount.

When the content of N-vinylpyrrolidone is less than 3% by weight, the cohesive force of the sticky agent decreases, resulting in a phenomenon in which the sticky agent remains on the adherend upon peeling. On the other hand, if the content is more than 30% by weight, the adhesive becomes hard and loses adhesive strength at low temperatures. Therefore, the content of N-vinylpyrrolidone is 3~
Limited to 30% by weight. A particularly preferred content of N-vinylpyrrolidone is 5 to 20 ffl96.

The acrylic copolymer of the present invention can be prepared in a suitable solvent with a
Dissolve the required amount of 4-alkyl (meth)acrylate and N-vinylpyrrolidone, add the required amount of copolymerizable unsaturated monomer as necessary, add a polymerization initiator, and make the mixture. It is prepared by raising the temperature and carrying out a polymerization reaction. The polymerization reaction is practically carried out by solution polymerization. In this case, the reaction solvent generally includes esters such as methyl acetate and ethyl acetate; aromatic hydrocarbons such as benzene, toluene, and xylene; alicyclic hydrocarbons such as cyclohexane; and ketones such as acetone and methyl ethyl ketone. , these may be used alone or in combination as appropriate. In addition to solution polymerization, any method such as emulsion polymerization and suspension polymerization can be used as the polymerization method. In addition, as the polymerization initiator, known polymerization initiators such as various peroxides such as benzoyl peroxide and lauryl peroxide, and azo compounds such as azobisisobutyronitrile may be used alone or in combination as appropriate. Ru. These are usually 9 Ells 100
It is used in a proportion of 0.01 to 1 part by weight.

The molecular weight of the acrylic copolymer is particularly limited.
= Although it is not, the weight average molecular weight in terms of polystyrene determined by gel permeation chromatography is 100,000 to 1,000,000, preferably 300,000 to 700,000.

Acrylic copolymers are used for the purpose of maintaining the physical properties of adhesives even at high temperatures, increasing the adhesive strength and cohesive force for highly polar adherends such as vinyl chloride resin, and increasing the cohesive force of double-sided tapes. , preferably crosslinked. As the crosslinking agent, a crosslinking agent such as an isocyanate-1 compound, an epoxy compound, or an organometallic complex is used.

Crosslinking is performed by known methods such as electron beam irradiation, thermal crosslinking using a peroxide such as peroxide as a catalyst, and curing using an isocyanate crosslinking agent. When crosslinking with an isocyanate crosslinking agent, 2-
A monomer serving as a crosslinking starting point such as hydroxy (meth)acrylate is copolymerized with the main monomer in an amount of 0.1 to 1%.

When using α, β unsaturated carboxylic acid as a crosslinking starting point monomer, it is better to use as little amount as possible, and 0
．． It is 5% by weight or less, preferably 0.1% by weight or less.

In addition to the acrylic copolymer, the adhesive according to the present invention includes:
If necessary, a tackifying resin such as xylene resin, phenol-modified xylene resin, phenol resin, chroman resin, b-gin or rosin-modified resin may be added. The amount of tackifying resin added is 100% of the acrylic copolymer.
The amount is 0 to 30 parts by weight.

(Function) Since the adhesive according to the present invention includes an acrylic copolymer containing a required amount of N-vinylpyrrolidone, the plasticizer is transferred from the adherend or base material to the acrylic copolymer. However, the adhesion and holding power are hardly or never reduced by the plasticizer.

Although the reason for this is not clear, it is thought to be as follows.

With conventional adhesives that are mainly composed of copolymers containing α,β-unsaturated carboxylic acids containing active hydrogen as a cohesive force imparting component, plasticizers migrate into the adhesive and soft chloride When it accumulates at the interface with the vinyl resin, the adhesive force and holding power decrease, and the reason for this decrease in performance is the phenomenon in which functional groups such as carboxyl groups that have active hydrogen are denatured. it is conceivable that.

In contrast, in the present invention, as the cohesive force imparting component, the α,β unsaturated carboxylic acid having reactive active hydrogen as described above is not substantially used, and the required amount of N-vinylpyrrolidone is used. There is no room for such metamorphosis to occur,
Therefore, it is thought that even if the plasticizer migrates, the adhesive strength and holding power will not decrease.

(Examples) Next, examples of the present invention and some comparative examples to be compared with the examples of the present invention will be listed, and performance test results of each adhesive will be shown.

Example 1 In a reactor equipped with a thermometer, a stirrer, and a dropping funnel, 95 parts by weight of butyl acrylate and 5 parts by weight of N-vinylvinyl acrylate were dissolved in 100 parts of ethyl acetate, and benzoyl peroxide was added as a polymerization initiator to this solution. 0.2 part of oxide was added. This mixed solution was stirred at 80° C. for 8 hours under nitrogen reflux to carry out a polymerization reaction to obtain an adhesive solution.

This adhesive solution was applied to a polyester film with a thickness of 38μ so that the layer thickness after drying was 70μ, and the temperature was 100μ.
Dry at ℃ for 5 minutes. Next, the obtained layer was crosslinked by irradiating it with an electron beam to prepare an adhesive tape having a crosslinked adhesive layer.

Example 2 An adhesive tape was prepared in the same manner as in Example 1, except that 90 parts by weight of butyl acrylate and 10 parts by weight of N-vinylpyrrolidone were used as copolymerization monomers.

Example 3 Polymerization was carried out under the same conditions as in Example 1 except that 70 parts by weight of isononyl acrylate and 30 parts by weight of N-vinylpyrrolidone were used as monomers for copolymerization to obtain an adhesive solution. Ta. Add xylene resin (product name:
20i11f parts of ``Dicanol'' (manufactured by Mitsubishi Gas Chemical Co., Ltd.) were mixed, and an adhesive tape was obtained in the same manner as in Example 1.

Example 4 Butyl acrylate 79', 9 as a copolymerization monomer
parts by weight, 10 parts by weight of vinyl acetate, 10 parts by weight of N-vinylpyrrolidone, and 2-hydroxymethacrylate-1-0,
Polymerization was carried out using 1 part by weight under the same conditions as in Example 1 except for the above, to obtain an adhesive solution.

The same procedure as in Example 1 was used except that 0.8 parts by weight of an isocyanate crosslinking agent (trade name [Coronet] HLJ (manufactured by Nippon Polyurethane Kogyo Co., Ltd.) was used as the crosslinking agent, and the crosslinking was carried out by the moisture curing method. I got the tape.

Comparative Example 1 As monomers for copolymerization, 89 parts by weight of butyl acrylate, 10 parts by weight of N-vinylpyrrolidone, and 1 part by weight of acrylic acid were used.
Adhesive tapes were prepared in the same manner as in Example 1 except that parts by weight were used.

Comparative Example 2 Isooctyl acrylate 93 as a copolymerization monomer
An adhesive tape was prepared in the same manner as in Example 1 except that 7 parts by weight and 7 parts by weight of acrylic acid were used.

Comparative Example 3 The same operation as in Example 1 was carried out except that 79 parts by weight of butyl acrylate, 20 parts by weight of ethyl acrylate (EA), and 1 part by weight of N-vinylpyrrolidone were used as the *i-form for copolymerization. An adhesive tape was prepared.

Comparative Example 4 An adhesive tape was prepared in the same manner as in Example 3, except that 65 parts by weight of 2-ethylhexyl acrylate and 35 parts by weight of N-vinylpyrrolidone were used as monomers for copolymerization. did.

Performance test 1) Adhesion (peel force) test Adherents: 100 parts by weight of polyvinyl chloride, 50 parts by weight (29.4% by weight) of dioctyl phthalate, 2 parts by weight of epoxidized Soyura, 3 parts by weight of metal stabilizer. and a soft vinyl chloride resin plate consisting of 15 layers of calcium bicarbonate (
30mm x 80mm x 5mm) was used. A 25 mm x 125 mm adhesive tape test piece was attached to this adherend by pressing it back and forth once with a 21 cg roller. Next, the adherend to which the adhesive tape was applied was aged in an atmosphere at a temperature of 90° C., and the plasticizer in the adherend was transferred to the adhesive layer of the adhesive tape. In this state, the adhesive tape was subjected to a 180° peel test according to JIS 20237, and changes in peel force were measured.

2) Holding power test After applying the adhesive tape test piece to the adherend in the same manner as above to accelerate aging, a holding power test was conducted using a weight of 11 c g at a temperature of 80 ° C according to JIS 20237, The time required for the adhesive tape to peel off from the adherend and fall was measured.

In this test, a 15 mm x 25 mm adhesive/tape test piece was used.

The results of each test are summarized in Table 1.

(Left below) Table 1 In Table 1, BA is butyl acrylate, vP is N-vinylpyrrolidone, INA is isononyl acrylate, XR is xylene resin, VAc is vinyl acetate, 2HMA is 2-hydroxymethacrylate-1, AAc represents acrylic acid, 10A represents isooctyl acrylate-1., EA represents ethyl acrylate, and 2EHA represents 2-ethylhexyl acrylate.

As is clear from Table 1, the adhesive according to the present invention is found to be superior in adhesive strength, holding power, and stability over time after heat aging compared to conventional adhesives.

(Effects of the Invention) Since the adhesive according to the present invention includes an acrylic copolymer containing a required amount of N-vinylpyrrolidone, it can be used as a base material for adhesive tapes, adhesive sheets, etc., or for pasting. When the target adherend is made of a soft vinyl chloride resin containing a plasticizer, it effectively prevents the decrease in adhesive strength and holding power due to the transfer of the plasticizer from the soft vinyl chloride resin to the adhesive. It is a useful adhesive that can be suppressed.

that's all Patent applicant Sekisui Chemical Co., Ltd. Representative Kaoru Hirota

Claims (3)

[Claims] (1) Includes an acrylic copolymer comprising 50% by weight or more of an alkyl (meth)acrylate whose alkyl group has a carbon number of 4 to 14 and 3 to 30% by weight of N-vinylpyrrolidone. Adhesive with special features. (2) The adhesive according to claim 1, wherein the acrylic copolymer contains 0 to 30% by weight of a copolymerizable unsaturated monomer. (3) The adhesive according to claim 1, wherein the acrylic copolymer is crosslinked.