JPH01272679A - Tacky agent for removing - Google Patents

Abstract

PURPOSE:To obtain a removable tacky agent, consisting of a graft polymer consisting of a backbone chain polymer, consisting of a specific alkyl acrylate and side chain polymer respectively having a specific glass transition point and excellent in initial adhesive, cohesive force and removability. CONSTITUTION:A removable tacky agent consisting essentially of a graft polymer, having the backbone chain formed from a polymer consisting of an alkyl acrylate having a >=4C, preferably 4-15C alkyl group and <=-40 deg.C glass transition point and side chains formed from a polymer with >=50 deg.C glass transition point preferably consisting of acrylonitrile, etc., and having preferably 50000-5000000 weight-average molecular weight preferably by a method using a macromonomer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a removable pressure-sensitive adhesive which has excellent initial adhesion and removability and is suitable for surface protection sheets and the like.

BACKGROUND ART AND PROBLEMS There are fields in which pressure-sensitive adhesives are required to be easily removable. A typical example is a surface protection sheet.

The performance required of this removable adhesive is that it will not peel off from the adherend until the purpose is achieved and it is peeled off, and that it can be peeled off smoothly without leaving any adhesive residue when re-peelable. . That is, it has excellent initial adhesive strength, is resistant to increase in adhesive strength over time, and has excellent cohesive strength. Furthermore, surface protection sheets for metal plates etc. will tear,
There are also cases where performance is required to follow processing such as deep drawing and bending without causing wrinkles, protrusion, or lifting.

Conventionally, removable adhesives 7 have been linear-type adhesives copolymerized with carboxyl group-containing monomers such as acrylic acid and methacrylic acid, or hydroxyl group-containing monomers such as 2-hydroxyethylester of acrylic acid and methacrylic acid. Acrylic copolymers have been proposed.

However, products copolymerized with carboxyl group-containing monomers have a large increase in adhesive strength and are poor in removability.
Products copolymerized with hydroxyl group-containing monomers have a problem in that they have poor initial adhesive strength and tend to peel off before being re-peeled.

Attempts have been made to add acrylonitrile, methyl methacrylate, etc. to the copolymerization components, but these are not satisfactory solutions due to poor adhesion at low 1'A (below about 0°C).
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Solve the problem? In order to develop an adhesive for peeling, the present inventors have developed an adhesive with excellent adhesion and cohesive force, and a small adhesive force for re-peeling. I earnestly researched 4-・Achieved the goal by using a special graft polymer.
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That is, the present invention provides the following features: )':) The present invention provides a 5-4 female pressure-sensitive adhesive in which the side chain-forming polymer is composed of a graft polymer with a temperature of 50° C. or higher.

Made by j4'! By forming the main term in the graft polymer with a polymer having a glass transition point of 140°C or less using an acrylic acid alkyl ester Jl whose alkyl group has 4 or more carbon atoms,
It is possible to have an excellent initial adhesion force and a small increase in adhesion force over time. In addition, by forming the side chains in the graft polymer with a polymer with a glass transition point of 50°C or higher, it has excellent cohesive strength and does not easily leave adhesive residue.
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Examples of Constituent Elements of the Invention The removable pressure-sensitive adhesive of the present invention is made of a graft polymer, and the graft polymer has a glass transition point of 140°C or less.
Complex formation poly 1. "2. 59℃ or higher": Formation of side chains 71
': From Lima "A 6 o, molecular weight is based on weighted average molecular weight - 'Ll" jg 5000 or more'' 0, especially 5.
Approximately 5 million yen is appropriate.

Main chain form, d; l-li, /iJ, Oj, 7, below the galactic transition point ~ 40X゛, forming a ) and phosphorus, acrylic acid lobes, acrylic acid 2- J-tyl to 4-syl, isonol acrylate, octyl acrylate, amyl acrylate, etc. where the number of carbon atoms in the alkyl group is .1- or less
-1 acrylic acid alkyl ester of i to 15 in 1
It is composed of one species or two or more species. Within a range that satisfies the glass transition point conditions, other monomers, for example, known modifying monomers may be copolymerized with the acrylic pressure-sensitive adhesive such as 2-hydroxyethyl acrylate.

For example, the side chain forming borine has a glass transition point of 50°C or higher,
It is composed of one or more monomers such as acrylic nitrile, acrylamide, methyl methacrylate, 2-hydro-dipropyl methacrylate, acrylic acid, and methacrylic acid to form a polymer. Acrylonitrile and methyl methacrylate are preferably used. Other monomers, such as the above-mentioned acrylic acid alkyl esters and modifying monomers, may be copolymerized within a range that satisfies the glass transition point conditions.

The above-mentioned graft polymer can be obtained, for example, by a method using a conventional graft polymer or a macromonomer. A macromonomer is a relatively high molecular weight monomer that has a polymerizable unsaturated group at the end, and is introduced into the main chain via the polymerizable unsaturated group by copolymerizing with a monomer for forming a raw daughter, and the remaining part forms a side chain. Therefore, the method using a macromonomer is preferred from the viewpoint of efficient preparation of the graft polymer, easy homogenization of the side chain-forming polymer, and controllability of the molecular weight of the side chain-forming polymer.

The macromonomer can be synthesized, for example, by reacting a living polymerized polymer with a polymerizable unsaturated compound containing a functional group such as glycidyl acrylate. In the present invention, macromonomers synthesized using the monomers for forming side chains and having a heavy state average molecular weight of 2000 or more, particularly 2000=50000 are preferably used (
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Graft polymerization using a macromonomer and a main chain-forming monomer can be performed, for example, by a solution polymerization method, a bulk polymerization method, or the like. Solubility f due to easy copolymerization operation
&Polymerization method is preferred. Solution polymerization can be carried out by applying a conventional method using a polymerization initiator typified by a peroxide such as benzoyl peroxide or potassium persulfate, or an azo compound such as azobisisobutyronitrile. .

Examples of organic solvents include n-hebutane, toluene, benzene, n-hexane, dioxane, methyl, 1-methyl ketone,
Methyl isobutyl ketone, ethyl acetate and the like are preferably used, and alcohols such as methanol, ethanol and isopropanol can also be used.

1) Release adhesive of the present invention i:j: It can be preferably used for things that require release properties, for example, surface protection sheets.Surface protection The sheet is a thin base material with an adhesive layer.The amount of adhesive applied is determined as appropriate depending on the purpose of use, but is generally 2 to 20.
00 g/d (solid content). Thin substrates include thin substrates typically made of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyester, paper, metal, etc., with a thickness of ~500 us, and IC substrates with a thickness of typically 500 μs. ! A foam sheet having a diameter of 11 or less is generally used.

The adhesive layer is crosslinked as necessary to adjust adhesive properties such as cohesive force. The crosslinking treatment can be carried out by conventional methods such as adding a crosslinking agent to the adhesive or irradiating with ultraviolet rays or electron beams. As a crosslinking agent, aliphatic diisocyanate-1, aromatic poly(di,tri)isocyanate
- Multifunctional isocyanate compounds such as butyl etherified melamine, trimethylol, trimethylol, melamine, (and other known compounds such as epoxy compounds) may be used. When performing crosslinking treatment by irradiation such as irradiation, a photopolymerizable polyfunctional unsaturated compound or a photopolymerization initiator is added to the adhesive as necessary). 21. The photopolymerizable polyfunctional unsaturated compounds used include 7.1,4,-butanediol di(meth)acrylate, ■,6-hexanediol di(meth)acrylate, 1, and diethyl. ethylene glycol di(meth)acrylate, poly(3-14)-T, ethylene glycol di(meth)acrylate (
Meta) acrylate, neopentyl glycolate (
Meta) acrylate, jib [1 strand/glycol di(
methacrylate, trimethylolpropane tri(meth)acrylate, pentachloride salt (
meth)acrylic-1, pentaerythritol tetra(
meth)acrylate 1/-, oligoester (meth)acrylate 1-, epoxy (meth)acrylate, urethane (
Examples include meth)acrylay-1-. In addition, as the photopolymerization initiator 8'-, beni/zoin, benzoin methyl apur, penzoin isozolobil ethyl, benzoin isobutyl L-thyl, benzyl dimethyl ketal benzophenone, anthraquinone , 2-, Metino! r-anthraquinone, 2-t-butylanthraquinone, 9
, 10-phenanthyl, quinone, diacetyl, dibenzoyl, 2,2-jethoxyacetophenone, 2,4
Examples include carbonyl compounds such as -diethylthioxanthone, 2-chlorothioxanthone, and 2-methylthioxanthone. Sensitization may also be carried out by using an amine in combination.

In addition, the adhesive used in the present invention may contain other compounding agents that may be added to the acrylic adhesive, such as adhesion improvers, surfactants, softeners, plasticizers, antioxidants, etc., as necessary. may be included.

Effects of the Invention According to the removable pressure-sensitive adhesive of the present invention, it is made of a graft polymer with special glass transition temperature characteristics, has excellent initial adhesive strength and cohesive strength, has a small increase in adhesive strength at seams, and is easy to re-peel. A pressure-sensitive adhesive layer with excellent properties can be obtained. In addition, the adhesive layer does not easily leave adhesive residue and is excellent in non-contaminating the adherend after re-peeling.

Examples Example 1 80 parts of butyl acrylate (parts by weight, same hereinafter), 10 parts of 2-ethylhexyl acrylate, 1 part of methyl methacrylate
Weight average molecule consisting of 0 parts! 110,000 macro monomers 10
1 part and 1 part of acrylic acid were polymerized in ethyl acetate by a conventional method to obtain a solution containing a graft polymer having a weight average molecular weight of 660,000. Then, graft polymer 1 was added to this solution.
A removable adhesive was obtained by blending 1 part of an epoxy crosslinking agent per 00 parts.

A polymer having the same composition as the main chain-forming polymer in the graft polymer was separately prepared and its glass transition point was examined and found to be -54°C. In addition, the glass transition point of the side chain-forming polymer equivalent, which was investigated in the same manner, was 105°C.

Example 2 80 parts of 2-ethylhexyl acrylate, 20 parts of the macromonomer used in Example 1, and 2 parts of 2-hydroxyethyl acrylate were polymerized in ethyl acetate by a conventional method.
A solution containing a graft polymer having a weight average molecular weight of 480,000 was obtained. Next, 5 parts of an isocyanate-based Takarabridge agent per 100 parts of the graft polymer was added to this solution to obtain a removable adhesive.

The glass transition point of the main chain-forming polymer equivalent to the graft polymer i'j was -70°C.

Example 3 80 parts of butyl acrylate and 20 parts of the macromonomer used in Example 1 were polymerized in ethyl acetate by a conventional method.
A solution containing Gra7tovolima having a weight average molecular weight of 720,000 was obtained. Next, 100 parts of dioctyl phthalate, 5 parts of trimethylolpropane triacrylate, and 0.3 parts of 2-t-butylanthraquinone were added to this solution per 100 parts of the graft polymer to obtain a removable adhesive.

The glass transition point of the main chain-forming polymer equivalent in the graft polymer was -55°C.

Example 4 First, 80 parts of butyl acrylate and 1 part of 2-hydroxyethyl acrylate were polymerized in toluene to obtain a main chain-forming polymer, then an initiator was added, the reaction system was heated, and the reaction system was heated. By the usual graft polymerization method in which 20 parts of methyl methacrylate is added dropwise to form a side chain polymer, the weight average molecular weight is 57.
Tens of graft polymers were prepared, and 5 parts of incyanate crosslinking agent was added to this solution per 100 parts of graft polymer to obtain a removable pressure-sensitive adhesive.

The glass transition point of the main chain forming polymer in the graft polymer was -55°C, and the glass transition point of the side chain forming polymer equivalent was 105°C.

Comparative Example 1 100 parts of butyl acrylate and 2 parts of 2-hydroxyethyl acrylate were polymerized in ethyl acetate by a conventional method.
A solution containing an acrylic copolymer having an iut average molecular weight of 910,000 was obtained, and 5 parts of an isocyanate crosslinking agent per 100 parts of the acrylic copolymer was blended into this solution to obtain an adhesive.

Comparative Example 2 80 parts of butyl acrylate, 20 parts of methyl methacrylate and 2 parts of acrylic acid were polymerized in ethyl acetate by a conventional method to obtain a solution containing an acrylic copolymer having a weight average molecular weight of 50,000. An adhesive was obtained by adding 3 parts of incyanate crosslinking agent per 100 parts of the acrylic copolymer to the solution.

Comparative Example 3 100 parts of ethyl acrylate and 2 parts of 2-hydroxyethyl acrylate were polymerized in ethyl acetate by a conventional method,
A solution containing an acrylic copolymer having a weight average molecular JI of 1 million was obtained, and 5 parts of incyanate crosslinking agent per 100 parts of the acrylic copolymer was blended into this solution to obtain an adhesive.

The adhesives obtained in the evaluation test examples and comparative examples were applied to a 60μ-thick polyethylene film whose surface had been corona-treated, and then heated and dried to produce a surface protection sheet having a 10μm-thick adhesive layer. was obtained and subjected to the following test.

However, for the adhesive of Example 3, the thickness was 1
ion polyvinyl chloride sheet and then irradiated with ultraviolet rays for polymerization treatment to obtain a surface protection sheet having an adhesive layer with a thickness of lhm.

[Initial adhesive strength] At 23°C, the surface protection sheet was attached to a 0.4 m thick stainless steel plate (SOS 3048A finish), and the adhesive strength after 30 minutes (180 degrees beer, tensile speed 300 m)
/min) was measured.

[Adhesive strength increase property 1] According to the above, the surface protection sheet was adhered to a stainless steel plate and then left at 50°C for 7 days, and after cooling to 23°C, the adhesive strength was measured.

[Non-staining] A surface protection sheet was attached to a glass plate, left at 50°C for 24 hours, then taken out and the surface protection sheet was peeled off.
As shown in the figure, a drop of water 2 is dropped on the peeled surface of the glass plate 1, and the angle (θ) is measured using a contact angle meter, and the contact angle is 1.
The evaluation was made with L7 as ○ when the temperature was 0 degrees or less, and × when the temperature was 11 degrees or more.

[Workability] When the stainless steel plate 4 to which the surface protection sheet is attached in the same manner as described above is drawn using the punch 3 and die 5 as shown in FIG. 2, the surface protection sheet after processing is wrinkled, torn, or ○, if there are no problems such as lifting and a good adhesion condition is maintained.
△ if there are wrinkles, tears, lifting, etc.
If there are significant wrinkles or tears, or if the entire surface is floating
It was evaluated as

The above results are shown in the table.

From the table, it can be seen that the surface protection sheet using the removable adhesive of the present invention has only a small initial adhesive strength, a small oral increase in adhesive strength, excellent removability, and excellent non-staining properties. Recognize.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a contact angle measuring method, and FIG. 2 is an explanatory diagram of a drawing process. 1 Glass plate 2: Water drop 3: Bonchi 4o: Stainless steel plate with surface protection sheet 5: Mold patent applicant Nitto Electric Industry Co., Ltd.

Claims (1)

[Claims] 1. The glass transition point of the main chain-forming polymer consisting of an acrylic acid alkyl ester in which the alkyl group has 4 or more carbon atoms is -4.
A removable pressure-sensitive adhesive characterized by comprising a graft polymer having a temperature of 0°C or lower and a side chain forming polymer having a temperature of 50°C or higher.