JPH0734052A - Pressure-sensitive adhesive and adhesive sheet using the same - Google Patents

Abstract

PURPOSE:To obtain the subject adhesive containing an acrylic polymer obtained by copolymerization of an acrylic monomer and a specific monomer as a main component, having good adhesiveness to various adherends, excellent in moisture proof characteristics and having high reliability. CONSTITUTION:This adhesive is obtained by copolymerizing a monomer mixture of (A) 60-97wt.% of an acrylic monomer expressed by formula I (R<1> is H or methyl; R<2> is a 2-4C alkyl), (B) 3-30wt.% of a maleimide compound expressed by formula II (R<3> is H or a monovalent organic group) and (C) 3-30wt.% of other monomer [e.g. (meth)acrylic acid or carboxyethyl acrylate] copolymerizable with the components A and B.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive containing an acrylic polymer as a main component and having excellent adhesive performance and moisture resistance, and a sheet-shaped or tape-shaped adhesive. It is related to adhesive sheets.

[0002]

2. Description of the Related Art A pressure sensitive adhesive containing an acrylic polymer as a main component has an advantage that it is excellent in light resistance, weather resistance and oil resistance due to the above polymer. In addition, acrylic pressure-sensitive adhesive tape with plastic or paper as the surface substrate has excellent adhesive performance such as adhesive strength and cohesive strength, and aging resistance such as heat resistance and weather resistance. ,
Widely used in various fields.

Recently, for the purpose of simplifying the work and improving the working environment, a pressure-sensitive adhesive in the form of a sheet or tape is used instead of the liquid type adhesive. The treatment has become established, and further improvements in various properties such as adhesive force and cohesive force are desired in these treatments.

In order to meet such demands, in particular, in order to improve the adhesive performance such as adhesive force and cohesive force, various polar group-containing monomers are used together with the acrylic monomer during the synthesis of the acrylic polymer. It is often done.

[0005]

However, the use of a polar group-containing monomer tends to impair the moisture resistance of the pressure-sensitive adhesive, that is, the adhesive strength tends to decrease with time in a humid environment, which is a problem in reliability. Inferior in sex. Therefore, there is a limit to the improvement of the adhesive performance by using the above monomer.

In view of the above-mentioned conventional circumstances, the present invention provides a highly reliable pressure-sensitive adhesive having excellent adhesive performance and improved moisture resistance, and a sheet-like or tape-like adhesive. The purpose is to provide adhesive sheets in the form of.

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the inventors of the present invention have found that an acrylic polymer composed of a copolymer of an acrylic monomer and a specific monomer is used. The inventors have found that a highly reliable pressure-sensitive adhesive having excellent adhesiveness and moisture resistance can be obtained by using the combined material, and have completed the present invention.

That is, the present invention provides, as an acrylic polymer, the following components a to c; a) the following formula (I); CH ₂ ═C (R ¹ ) COOR ² ... (I) (wherein R ¹ is hydrogen or a methyl group, and R ² is an alkyl group having 2 to 14 carbon atoms) 50 to 98% by weight of an acrylic monomer b) The following formula (II); (In the formula, R ³ is hydrogen or a monovalent organic group) 2 to 50 wt% of maleimide compound c) Other monomers 0 to 3 copolymerizable with the above-mentioned a and b components
A pressure-sensitive adhesive containing a copolymer of a monomer mixture of 0% by weight as a main component, and a sheet-like or tape-like having a layer of this pressure-sensitive adhesive on one or both sides of a support. The present invention relates to adhesive sheets in the form of the above.

[0009]

In the acrylic monomer as the component a in the present invention, R ² in the above formula (I) is, for example, butyl group, isobutyl group, isoamyl group, hexyl group, heptyl group, It is an ester of acrylic acid or methacrylic acid composed of an alkyl group such as a 2-ethylhexyl group, an isooctyl group, an isononyl group, and an isodecyl group.
When the carbon number of R ² is less than 2, it becomes a material having a high glass transition temperature, so-called Tg, and the wettability as a pressure-sensitive adhesive decreases, the initial adhesiveness (tack) deteriorates, and it exceeds 14 Then, there is a problem of poor adhesion.

The acrylic monomer as the component a is used in the range of 50 to 98% by weight, preferably 60 to 97% by weight, based on the total amount of the monomers, and one or more of them are used. 5
When it is less than 0% by weight, as in the case where the number of carbon atoms of the alkyl group is less than 2, the component having a low Tg becomes too small to exhibit the performance as a pressure-sensitive adhesive, and the amount of 98% by weight is reduced. If it exceeds, the absolute amount of the component b, which will be described later, is insufficient, and it becomes difficult to achieve both adhesive performance and moisture resistance.

In the maleimide compound as the component b in the present invention, R ³ in the above formula (II) is hydrogen (maleimide itself), or an alkyl group, a cycloalkyl group, an allyl group, an aralkyl group or these A monovalent organic group in which a functional group is further introduced into, for example, methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group, lauryl group, cyclohexyl group, phenyl group, methylphenyl group, methoxyphenyl group. Examples thereof include an enyl group, a chlorophenyl group, a nitrophenyl group and a carboxyphenyl group.

The maleimide compound as the component b is used in the range of 2 to 50% by weight, preferably 3 to 30% by weight, based on the total amount of the monomers, and one or more types thereof are used. If it is less than 2% by weight, the desired effect of improving the moisture resistance of the present invention cannot be obtained, and if it exceeds 50% by weight, it is difficult to maintain the low Tg desired as a pressure-sensitive adhesive, and the initial adhesive strength is insufficient. Will be done.

The monomer of the component c in the present invention may be any monomer which can be copolymerized with the above-mentioned components a and b, and examples thereof include (meth) acrylic acid and carboxyethyl acrylate.
Carboxyl group-containing monomers such as glutamine, itaconic acid, maleic acid, and crotonic acid; Phosphoric acid group-containing monomers such as 2-hydroxyethyl (meth) acryloyl phosphate;
Amide-based monomers such as (meth) acrylamide and N-substituted (meth) acrylamide; vinyl-based monomers such as vinyl acetate, N-vinylpyrrolidone, N-vinylcarboxylic acid amides, and styrene.

Further, glycidyl (meth) acrylate,
2-Hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate
(Meth) acryl other than a-component such as polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, fluorine (meth) acrylate, silicone (meth) acrylate, etc. Acid ester type monomers and the like can also be used.

Further, a polyfunctional (meth) acrylate or the like can also be used, if necessary, when post-crosslinking with an electron beam or the like under a non-crosslinking agent is desired. Specifically, hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) ) Acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate And other epoxy (meth) acrylates, polyester (meth) acrylates, urethane (meth) acrylates and the like.

If necessary, one or more monomers of the component c may be used in an amount of 30% by weight or less, preferably 25% by weight or less, based on the total amount of the monomers. If it exceeds 30% by weight, the performance as an acrylic resin is difficult to be expressed, and the properties as a pressure-sensitive adhesive cannot be balanced.

The acrylic polymer of the present invention has the above-mentioned a,
A copolymer of a monomer mixture consisting of two components b or three components a to c, which is obtained by subjecting the above-mentioned monomer mixture to a solution polymerization method, an emulsion polymerization method, or a block method by a conventional method. It can be obtained by copolymerization by a method such as a polymerization method or a kendaku polymerization method. Among the above-mentioned polymerization methods, in the bulk polymerization method, a polymerization method by ultraviolet irradiation is preferably adopted.

In the above copolymerization, a thermal polymerization initiator or a photopolymerization initiator can be used, if necessary, in the range of 0.001 to 5% by weight based on the whole polymerization raw material (solid content). Examples of the thermal polymerization initiator include benzoyl peroxide, azobisisobutyronitrile, tert-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxy dicarbonate, di-n-propyl peroxy dicarbonate.
G, di (2-ethoxyethyl) peroxydicarbone
Tert-butyl peroxyneodecanoate, t
ert-butyl peroxypivalate, di (3,5,5
-Trimethylhexanoyl) peroxide, dilauroylperoxide, dipropionylperoxide,
Examples thereof include diacetyl peroxide.

As the photopolymerization initiator, 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone, α-hydroxy-α, α'-dimethylacetophenone, methoxyacetophenone, 2 , 2-Dimethoxy-2-phenylacetophenone and other acetophenone type initiators; benzoin ethyl ether, benzoin isopropyl ether and other benzoin ether type initiators; benzyl dimethyl ketal and other ketal type initiators Initiators: Other examples include halogenated ketones, acyl phosphinoxides, acyl phosphonates and the like. Since the maleimide compound has absorption up to a relatively long wavelength side in the ultraviolet region, it is preferable to use an initiator which is activated particularly on the long wavelength side among the above initiators.

The pressure-sensitive adhesive of the present invention contains the acrylic polymer thus obtained as a main component, and if necessary, natural or synthetic resins, glass fibers, glass beads, metal powder, inorganic powder, etc. Additives such as fillers, pigments and colorants can be included as optional components.

Further, the pressure-sensitive adhesive may be one which has been appropriately crosslinked. The cross-linking treatment is carried out by adding the above-mentioned polyfunctional (meth) acrylate as an internal cross-linking agent at the time of obtaining an acrylic polymer, or after obtaining an acrylic polymer, it is added as an external cross-linking agent. It can be carried out by adding a functional isocyanate compound or an epoxy compound. In addition, you may make it perform a bridge | crosslinking process by active rays, such as electron beam irradiation.

The adhesive sheet of the present invention is provided with a layer made of such a pressure-sensitive adhesive on one side or both sides of the support so as to have a desired thickness. It is in the form of. As the above-mentioned support, plastic film, paper, non-woven fabric, foam, metal foil and the like can be used, and one having one surface or both surfaces subjected to a peeling treatment or an adhesive treatment may be used.

The pressure-sensitive adhesive of the present invention and the adhesive sheets thereof having the above-described structure realize a highly reliable adhesive treatment with excellent adhesive performance and moisture resistance. The reason for this is not clear, but the maleimide compound as the component b constituting the acrylic polymer is excellent in water resistance and has an appropriate polarity, which gives the pressure-sensitive adhesive an appropriate cohesive force. It is presumed that this is due to things such as bringing.

[0024]

As described above, according to the present invention, since the main component is the acrylic polymer which is a copolymer of the acrylic monomer and the specific monomer, various adherends can be obtained. On the other hand, it is possible to provide a highly reliable pressure-sensitive adhesive which exhibits excellent adhesiveness and also has excellent moisture resistance, and its adhesive sheet.

[0025]

EXAMPLES Next, examples of the present invention will be described to more specifically describe. In the following, "parts" means "parts by weight".

Example 1 150 parts of ethyl acetate, 80 parts of 2-ethylhexyl acrylate, 5 parts of acrylic acid, 10 parts of cyclohexylmaleimide, polymerization were placed in a reaction vessel equipped with a cooling tube, a nitrogen introducing tube, a thermometer and a stirrer. 0.5 parts of azobisisobutyronitrile was added as an initiator, and the mixture was heated at 60 ° C. for 4 hours and then 80
Polymerization was carried out at 0 ° C. for 2 hours to obtain a copolymer solution having a polymerization rate of 99% by weight.

To this solution, with respect to 100 parts of the copolymer,
A pressure sensitive adhesive solution was prepared by adding 3 parts of a trimethylolpropane-tolylene diisocyanate adduct as a crosslinking agent. This solution was coated on a polyester film having a thickness of 25 μm and dried to prepare an adhesive sheet having a layer of pressure-sensitive adhesive having a thickness of 50 μm.

Examples 2 to 7 The polymerization rate was 98.5 to 9 in the same manner as in Example 1 except that the composition of the monomer mixture was changed as shown in Tables 1 and 2.
6% copolymer solution of 9% was obtained, and the same cross-linking agent as in Example 1 was added thereto in the same amount as in Example 1 to prepare 6 pressure-sensitive adhesive solutions. Six kinds of adhesive sheets were produced in the same manner as in Example 1 using each solution.

Comparative Examples 1 to 3 In the same manner as in Example 1 except that the composition of the monomer mixture was changed as shown in Table 3, three types of copolymer solutions having a polymerization rate of 99% were obtained. The same cross-linking agent as in Example 1 was added thereto to prepare 3 kinds of pressure-sensitive adhesive solutions. Using each solution, three kinds of adhesive sheets were produced in the same manner as in Example 1.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

With respect to the adhesive sheets prepared in Examples 1 to 7 and Comparative Examples 1 to 3 above, the quality of the adhesive performance (particularly tack) as a pressure-sensitive adhesive was examined, and a moisture resistance test was conducted in the following manner. I went. The results are shown in Table 4 below.

<Moisture resistance test> A clean SUS plate, the surface of which was sanded with # 280 sandpaper and degreased with a solvent, was pasted with an adhesive sheet in a width of 20 mm and heated at 50 ° C. for 5 days. The adhesive force when the adhesive force is aged and the adhesive force is stable (initial adhesive force) and the adhesive force after immersing this in distilled water for 4 days (adhesive force after the test) are drawn at a pulling speed of 300 mm / min. At 1
It was measured by peeling at 80 degrees. In addition, the retention rate of the adhesive force after the test was calculated as (adhesive force after the test / initial adhesive force) × 100%.

[0035]

[Table 4]

From the results of Table 4 above, Example 1 of the present invention
The adhesive sheets of Nos. 7 to 7 have excellent adhesive performance as compared with the adhesive sheets of Comparative Examples 1 to 3 and have extremely excellent moisture resistance characteristics, and have extremely high reliability. I understand.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hozumi Tanaka 1-2-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Eiichiro Fukusaki 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation

Claims (2)

[Claims] 1. The following components a to c; a) the following formula (I); CH ₂ ═C (R ¹ ) COOR ² (I) (wherein R ¹ is hydrogen or a methyl group, and R ² is 50 to 98% by weight of an acrylic monomer represented by an alkyl group having 2 to 14 carbon atoms) b) the following formula (II); (In the formula, R ³ is hydrogen or a monovalent organic group) 2 to 50 wt% of maleimide compound c) Other monomers 0 to 3 copolymerizable with the above-mentioned a and b components
A pressure-sensitive adhesive whose main component is a copolymer of 0% by weight of a monomer mixture. 2. Adhesive sheets having a layer comprising the pressure-sensitive adhesive according to claim 1 on one side or both sides of a support.