JPS62149777A - Hot pressure-sensitive adhesive - Google Patents

Abstract

PURPOSE:To obtain a hot pressure-sensitive adhesive which has small adhesive power at room temperature and reveals its power by heating at a low temperature for a short time, by incorporating a hot-melt resin into an acrylic graft polymer having a polymer of a high glass transition point on its side chain. CONSTITUTION:A graft polymer is prepared, which consists of a principal chain comprising a room-temperature self-adhesive copolymer composed of an acrylic ester having a 1-12C alkyl group (e.g., butyl acrylate) and an unsaturated carboxylic acid (e.g., acrylic acid), and a side chain comprising a polymer having a glass transition point of 70-150 deg.C (e.g., polymethyl methacrylate or polysty rene). A hot-melt resin is incorporated into this graft polymer to give an objec tive hot pressure-sensitive adhesive. The hot-melt resin preferably has a melting point of 70-200 deg.C, and the examples thereof include a phenolic resin, an epoxy resin, and a polyterpene resin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention comprises an acrylic graft polymer having 11 chains of a polymer with a high glass transition point, and
The present invention relates to a novel heat-sensitive adhesive that develops adhesive strength by short-time low-temperature heating.

Prior Art and Problems The large creep of pressure-sensitive adhesives is a major constraint on the expansion of applications, and its improvement is an important issue.

Hitherto, as a pressure-sensitive adhesive with improved creep properties, there has been known a pressure-sensitive adhesive prepared by adding a hot-melt resin to a common pressure-sensitive 11 adhesive (Japanese Patent Publication No. 13040/1982). Compared to thermosetting types that require heat treatment at 100°C or higher, this heat-melting resin-added type does not require expensive heating equipment, is easy to process, and has a heat-resistant adherend. It has the advantage that it can be applied even to those that do not have it.

However, conventionally known hot-melt resin additive types use a common pressure-sensitive adhesive and add a predetermined amount of a hot-melt resin having a predetermined melting point to it to achieve the desired pressure sensitivity. Since it is a system that balances the adhesion and heat resistance of the adhesive, it has had the problem of not being able to obtain an adhesive with satisfactory characteristics.
When a composition with excellent heat resistance is used, the melt viscosity becomes too high when activated by heating, resulting in poor wettability for adherends, especially adherends with rough surfaces, and sufficient adhesive strength cannot be obtained. On the other hand, if this point is improved and a low-temperature active type composition is created, the melt viscosity at high temperatures will be lower, but the original objective of creep resistance, especially creep resistance in the high l crystal region, will be lowered. There was a problem in that the problem was not improved satisfactorily.

Means for Solving the Problems The present inventors have overcome the above problems and developed a method that can be activated at a relatively low temperature of about 40 to 80°C and can also be applied to adherends with rough surfaces. Sufficient adhesive strength can be obtained,
Moreover, as a result of intensive research to develop a heat-sensitive adhesive that maintains sufficient adhesive strength even when placed at high temperatures higher than the heating temperature for bonding, we found that the base polymer has a high glass transition point. It was discovered that the object could be achieved by using a special acrylic raft polymer having a polymer in the side chain, and the present invention was completed.

That is, the present invention has a room temperature adhesive copolymer consisting of an acrylic ester having an alkyl group having 1 to 12 carbon atoms and an unsaturated carboxylic acid as its main chain, and has a glass transition point of 7.
The present invention provides a heat-sensitive adhesive comprising a graft polymer having a side chain of a polymer having a temperature of 0 to 150°C and a heat-melting resin mixed therein.

The graft polymer used in the present invention is a copolymer of an acrylic ester having an alkyl group having 1 to 12 carbon atoms and an unsaturated carboxylic acid, or a copolymer of a tertiary carboxylic acid in addition to these.
The main chain is a room temperature adhesive copolymer made of a copolymer containing a copolymerizable monomer as a component, and the glass transition point is 70 to 1.
The side chain is a 50°C polymer. By using this graft polymer, it is possible to obtain excellent heat resistance. If the glass transition point of the polymer as a side chain component is less than 70°C, the heat resistance will not be sufficiently improved;
If the temperature exceeds 50°C, adhesive properties such as wettability will deteriorate, which is not preferable.

The graft polymer can be prepared by, for example, a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a suspension polymerization method, or the like.

In the present invention, the copolymer is composed of a reaction product of 50 to 99 parts by weight of an acrylic ester, 1 to 15 parts by weight of an unsaturated carboxylic acid, and 0 to 49 parts by weight of a copolymerizable monomer. Preferably used.

If the amount of acrylic ester used is less than 50 parts by weight, the resulting hot pressure-sensitive adhesive may not have satisfactory adhesive properties. On the other hand, if the amount of the unsaturated carboxylic acid used is less than 1 part by weight, the resulting hot pressure-sensitive adhesive will have poor adhesive strength, and if it exceeds 15 parts by weight, the adhesive properties may be poor. In addition, if the amount of the copolymerizable monomer, which is incorporated into the main chain as necessary to adjust the balance between adhesiveness and adhesive strength, exceeds 49 parts by weight, the adhesiveness of the resulting hot pressure-sensitive adhesive will decrease. may decrease.

As the graft polymer in the present invention, one consisting of a reaction product of 100 parts by weight of the above-mentioned copolymer and 3 to 30 parts by weight of a polymer having a predetermined glass transition point is preferably used. If the amount of the polymer used is less than 3 parts by weight, the resulting hot pressure-sensitive adhesive will not have sufficient heat resistance;
If it exceeds 0 parts by weight, adhesiveness may decrease.

Preferred examples of acrylic esters having an alkyl group having 1 to 12 carbon atoms for preparing the above copolymer include ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, Examples include esters of acrylic acid or methacrylic acid such as isononyl acrylate, butyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, and isononyl methacrylate.

In addition, preferred examples of unsaturated carboxylic acids include:
Examples include α, β-unsaturated carboxylic acids represented by acrylic acid, methacrylic acid, and itaconic acid.

On the other hand, examples of preferable copolymerizable monomers used as necessary include esters of acrylic acid or methacrylic acid having a 2-hydroxyethyl group, 2-hydroxypropyl group, 2-methoxyethyl group, or glycidyl group;
Vinyl acetate, vinyl propionate, acrylonitrile,
Examples include compounds having one ethylenic double bond, such as styrene and vinyltoluene.

On the other hand, preferred examples of polymers as side chain components in the graft polymer include polymers of methyl methacrylate, styrene, hinyltoluene, acrylic acid, and methacrylic acid.

Incidentally, none of the constituent components is limited to those mentioned above, and only one kind may be used for convenience, or two or more kinds may be used in combination.

The hot pressure-sensitive adhesive of the present invention is obtained by blending the above-mentioned graft polymer with a hot-melt resin. Due to the formulation of this hot-melt resin, the tack is low at room temperature before heat bonding treatment (at room temperature, it exhibits virtually no adhesive force or has weak tack, but is activated in a short time by heat treatment and has sufficient adhesive strength). The amount of the heat-melting resin in the hot pressure-sensitive adhesive of the present invention is suitably 50 to 200 parts by weight per 100 parts by weight of the graft polymer. If the amount is less than 200 parts by weight, the time from heating and melting to reassimilation of the obtained adhesive will be longer and the shear adhesive strength will be weaker, while if it exceeds 200 parts by weight, the wettability of the obtained adhesive to the adherend will be reduced. is less desirable.

In the present invention, a thermofusible resin having a melting point of 70 to 200°C is preferably used. If the melting point is less than 70°C, the resulting adhesive will have poor heat resistance, and if it exceeds 200°C, a large amount of heat will be required to activate the resulting adhesive, which is undesirable.

Examples of heat-melting resins that can be preferably used include, but are not limited to, phenolic resins, xylene resins, polyterpene resins, coumaron indene resins, and epoxy resins. Only one type of heat-melting resin may be used, or two or more types may be used in combination.

Effects of the Invention The heat-sensitive pressure-sensitive adhesive of the present invention uses a special graft polymer for the Heasborima, so its adhesive strength at room temperature before heat bonding treatment is small, making it difficult to handle. It can be activated with a short heat treatment, making the adhesive process easy, and has excellent adhesive strength. It also maintains satisfactory adhesive strength even in an atmosphere at a temperature higher than the heat treatment temperature, and has creep resistance. It is also excellent.

Examples Reference Example 1 100 parts of styrene was added to 70 parts of styrene in ethyl acetate containing 2 parts (by weight, same hereinafter) of 4,4'-azobis-4-cyanovaleric acid as an initiator and 5 parts of iodoacetic acid as a chain transfer agent. The reaction was carried out at .degree. C. for 24 hours to obtain terminally carboxylated polystyrene (weight average molecular weight of about 10.000).

Next, the obtained terminal carboxylated polystyrene 100
and 4 parts of glycidyl methacrylate were reacted in xylene in the presence of hydroquinone using tri-n-butylamine as a catalyst to obtain polystyryl methacrylate.

Reference Example 2 80 parts of isononyl acrylate, 14 parts of ethyl acrylate, 5 parts of acrylic acid, and 1 part of 2-hydroxyethyl acrylate in ethyl acetate were started with 0.1 part of 2.2°-azobisisobutyronitrile. The reaction was carried out as an agent at 65° C. for 6 hours to give one solution of a polymer having an fffffi average molecular weight of about 800,000.

Example 1 70 parts of 2-ethylhexyl acrylate, 20 parts of vinyl acetate
1 part, 10 parts of acrylic acid and 5 parts of polystyryl methacrylate of Reference Example 1 were mixed in acetone with 0.2 part of 2.2'-azobisisobutyronitrile as initiator 1 at 55°C.
Weight average molecular weight of about 700,00 obtained by reacting for 0 hours
Add 100% of this polymer to a solution of 0% graft polymer (A).
120 parts of terpene-modified phenolic resin (melting point 100°C) and 0.5 parts of polyisocyanate were added and mixed per part, and this was coated on release paper to a dry thickness of 5011 m, and heated at 80°C. The adhesive was dried for 5 minutes to obtain an adhesive comprising the hot pressure sensitive adhesive of the present invention.

Example 2 97 parts of butyl acrylate, 3 parts of methacrylic acid, and 10 parts of the polystyryl methacrylate of Reference Example 1 were reacted in toluene with benzoyl peroxide as an initiator at 65°C for 8 hours, and the weight average molecular weight was about 400. ,000 of graft polymer (B) per 100 parts of this polymer.
coumaron indene resin (1!Ii point 130℃) and 1
of polyisocyanate and mix it.
I Apply on the release paper so that the thickness after drying is 5 parts m,
The adhesive was dried at 100° C. for 3 minutes to obtain an adhesive comprising the heat-sensitive adhesive of the present invention.

Example 3 To the solution of Reference Example 2, 0.5 part of benzoyl peroxide was added per 100 parts of the polymer, and to this 25 parts of methyl methacrylate was added.
of the solution was added dropwise at 70°C over 3 hours, and then reacted at 75°C for another 2 hours to obtain a weight average molecular weight of about soo, o.
Add this polymer 10 to the solution of graft polymer (C) of oo.
Add and mix 180 parts of phenol-modified xylene resin (melting point 80°C) and 0.3 parts of polyisocyanate per 0 parts, and apply this onto release paper so that the thickness after drying is 5 parts m. , and was dried at 70° C. for 5 minutes to obtain an adhesive comprising the heat-sensitive adhesive of the present invention.

Example 4 60 parts of isooctyl acrylate, 38 parts of 2-methoxyethyl acrylate, 2 parts of methacrylic acid, and 15 parts of polystyryl methacrylate of Reference Example 1 were mixed at 2°2° in a mixed solvent of toluene/cyclohexane (1/1). - To a solution of a graft polymer (D) having a weight average molecular weight of about soo, ooo obtained by reacting at 60°C for 16 hours using 0.3 parts of azobisisobutyronitrile as an initiator, 60 parts per 100 parts of this polymer is added. Terpene-modified phenolic resin (melting point 100
<60 parts of the same phenol-modified xylene resin (melting point 80 °C) as in (°C) and 1 part of polyisocyanate were added and mixed, and this was coated on release paper so that the thickness after drying was 5 parts m. The adhesive was then dried at 900C for 4 minutes to obtain an adhesive comprising the heat-sensitive adhesive of the present invention.

Comparative Example 1 70 parts of 2-ethylhexyl acrylate, 20 parts of vinyl acetate
10 parts of acrylic acid and 5 parts of styrene in acetone using 0.2 parts of 2,2'-azobisisobutyronitrile as an initiator at 55 DEG C. for 10 hours, with a weight average molecular weight of about 600. 000 polymer (E), 120 parts of terpene-modified phenolic resin (melting point 100°C) and 0.5 parts of polyisocyanate were added and mixed per 100 parts of this polymer, and this was dried on release paper. Thickness is 5
It was coated to a thickness of 0 μm and dried at 80° C. for 5 minutes to obtain an adhesive.

Comparative Example 2 To a solution of the same graft polymer (A) as in Example 1, 250 parts of terpene-modified phenol resin (melting point 100°C) and 0.5 parts of polyisocyanate were added and mixed per 100 parts of this polymer. was applied onto a tlJ release paper so that the thickness after drying would be 50 μm, and dried at 80° C. for 5 minutes to obtain an adhesive.

Comparative Example 3 To a solution of the same graft polymer (A) as in Example 1, 120 parts of xylene resin (softening point 5
°C) and 0.5 part of polyisocyanate and mix, apply this on release paper to a dry thickness of 5011111, and dry at 80°C for 5 minutes to release the adhesive. Obtained.

Comparative Example 4 To the solution of Reference Example 2, 0.5 part of benzoyl peroxide was added per 100 parts of the solid content, and to this 25 parts of butyl methacrylate was added.
180 parts of phenol-modified xylene resin (with a high point of 80 °C) and 0.3 parts of polyisocyanate, mixed, coated on release paper to a dry thickness of 5 parts m, dried at 70 °C for 5 minutes, and adhesive I got it.

Evaluation Test Temperature Cycle Test The adhesive with a thickness of 50 μm obtained in the Examples and Comparative Examples is temporarily attached to an aluminum plate (thickness 0.7 mm), and this is attached to an aluminum plate (thickness 1,0 mm) at 100°C for 60 seconds (
0.1 kg/ant), a test piece was prepared, and the following temperature cycle test was repeated 10 times to examine the state of peeling at the bonded end.

The results are shown in Table 1.

Ni”LL 50um thick adhesive on aluminum plate (0,7+n+
n) Temporarily bonded between two sheets with an adhesive area of 1010 mm x 1 O, then at a temperature of 60°C, 80°C or 100°C, O, 1k
A test piece was prepared by heating and pressing at a pressure of g/c- for 60 seconds, and its tensile strength was measured using an Instron universal tensile tester (tensile speed 10/min, 20°C, 6
5%R1H8). The results are shown in Table 2.

Table 2 From Tables 1 and 2, it can be seen that the heat-sensitive pressure sensitive adhesive of the present invention as an example adhered to an aluminum plate without peeling even in a severe temperature cycle test, and that it showed a large adhesion. It can be seen that it has strength.

Claims (1)

[Claims] 1. The main chain is a room-temperature sticky copolymer consisting of an acrylic ester having an alkyl group having 1 to 12 carbon atoms and an unsaturated carboxylic acid, and has a glass transition point of 70 to 150°C. A heat-sensitive adhesive made by blending a thermofusible resin with a graft polymer that has a polymer as a side chain. 2. The adhesive according to claim 1, wherein the acrylic acid ester is an ester of acrylic acid or methacrylic acid, and the unsaturated carboxylic acid is an α,β-unsaturated carboxylic acid. 3. Room temperature adhesive copolymer is acrylic acid ester 50
The adhesive according to claim 1, which is a reaction product of ~99 parts by weight, 1 to 15 parts by weight of an unsaturated carboxylic acid, and 0 to 49 parts by weight of a copolymerizable monomer. 4. The adhesive according to claim 3, wherein the copolymerizable monomer has one ethylenic double bond. 5. The adhesive according to claim 1, wherein the graft polymer is a reaction product of 100 parts by weight of a room temperature adhesive copolymer and 3 to 30 parts by weight of the glass transition point polymer. 6. The adhesive according to claim 1, wherein the hot-melt resin has a melting point of 70 to 200°C. 7. Claim 1, wherein the blending amount of the hot-melt resin is 50 to 200 parts by weight per 100 parts by weight of the graft polymer.
Adhesives listed in section.