JPH115959A - Heat-sensitive self-adhesive composition and heat-sensitive self-adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive self-adhesive compsn. having good water resistance and alkali peelability by selecting a heat-sensitive self-adhesive compsn. which forms a self-adhesive layer which, when dried at a temperature lower than a specified temp., exhibits a sea-island structure comprising a water-soluble resin component (A) as the sea and a polymer component (B) as the islands and which, when subjected to a heat treatment at a specified temp. or higher, exhibits a sea-island structure comprising component A as the islands and component B as the sea. SOLUTION: This compsn. contains component A and component B in a wt. ratio of (10/90)-(50/50) and forms a self-adhesive layer which, when dried at a temp. lower than 60 deg.C, exhibits a sea-island structure comprising component A as the sea and component B as the islands and which. when subjected to a heat treatment at 60 deg.C or higher, undergoes the inversion of the sea and islands, i.e., exhibits a sea-island structure comprising component A as the islands and component B as the sea. Component A is a water-soluble resin which is prepd. by neutralizing a copolymer comprising α,β-ethylenically unsatd. carboxylic acid units and hydrophobic freeradical polymerizable monomer units and has an acid value of 1 meq/g or higher. Component B is a polymer which is prepd. by the emulsion polymn. of a free-radical polymerizable monomer and has a glass transition point of -20 deg.C or lower and an acid value of 0.6 meq/g or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive adhesive composition and a heat-sensitive adhesive sheet, and more particularly, to a non-adhesive or extremely low-adhesive state in an initial state, while exhibiting adhesiveness by heat treatment. And a heat-sensitive adhesive sheet having the adhesive layer on a substrate.

[0002]

2. Description of the Related Art Generally, pressure-sensitive adhesive sheets are stored, distributed, sold, and the like, with a pressure-sensitive adhesive surface coated with release paper (release paper). In a roll-up type product such as an adhesive tape, a base material having a back surface subjected to a release treatment is used so that the product can be rewound during use. The release paper becomes unnecessary after the pressure-sensitive adhesive sheet is attached to the article, and a pressure-sensitive adhesive sheet that does not require a release paper is required from the viewpoint of resource saving and cost reduction. Furthermore, if the backing of the pressure-sensitive adhesive tape is not subjected to a release treatment, the manufacturing process of the pressure-sensitive adhesive tape substrate can be simplified, and the cost can be reduced.

As a pressure-sensitive adhesive sheet which does not require a release paper, a heat-sensitive pressure-sensitive adhesive sheet coated with a delayed tack-type pressure-sensitive adhesive (JP-B-62-21835 and JP-A-6-10084, etc.) is known. Discloses, as a delayed tack type adhesive, an adhesive obtained by mixing a solid plasticizer such as dicyclohexyl phthalate or the like with its surface coated with a colloid, and a thermoplastic resin such as an ethylene-vinyl acetate copolymer. I have. And in these prior documents, the adhesive is non-adhesive at room temperature,
It is described that the plasticizer is melted by heating to develop an adhesive force.

However, the conventional delayed tack-type pressure-sensitive adhesive containing a solid plasticizer has various problems as described in the following (a) to (d), and is limited to limited special uses. Currently, it cannot be used. (A) After the crystallization of the solid plasticizer has progressed, the adhesive strength is lost, so once it is peeled off from the adherend, it cannot be adhered to the adherend again; The heating temperature cannot be set freely because it depends on the melting point of the solid plasticizer; (c) After the crystallization has progressed, the pressure-sensitive adhesive becomes hard and loses its flexibility. If the adherend is bent or the adherend is vibrated, the adhesive layer may not follow the adherend and may be separated; and (d) the base material used for the adhesive sheet is a high-quality paper or the like. In this case, the plasticizer easily oozes out on the sheet surface when the pressure-sensitive adhesive sheet is heated.

On the other hand, Japanese Patent Application Laid-Open No. 8-269420 discloses a non-adhesive resin [component (A)] which suppresses the development of tackiness during storage of a pressure-sensitive adhesive sheet and the like. A pressure-sensitive adhesive composition comprising an acrylic resin emulsion [component (B)] for exhibiting properties is disclosed. The above-mentioned publication describes that a non-tacky pressure-sensitive adhesive layer is obtained by drying this pressure-sensitive adhesive composition at a relatively low temperature, and that the heat-treated pressure-sensitive adhesive layer develops tackiness. However, the pressure-sensitive adhesive layer formed from the heat-sensitive pressure-sensitive adhesive composition as described in the above-mentioned publication, what kind of structural change is caused by heat treatment to exhibit tackiness has not been known so far. . For this reason, it was difficult to design the heat-sensitive adhesive composition by estimating the properties of the adhesive layer after the heat treatment, for example, adhesive strength, water resistance, alkali releasability, and the like.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a substantially non-adhesive prior to heat treatment, which allows the release treatment of the pressure-sensitive adhesive layer such as a release paper or a backside of the substrate. It is another object of the present invention to provide a heat-sensitive adhesive composition which can be used without performing the heat treatment and can form an adhesive layer exhibiting an adhesive strength of a specific value or more after heat treatment. Another object of the present invention is to provide a heat-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the above-mentioned pressure-sensitive adhesive composition on a substrate.

[0007]

The present inventors have a sea-island structure in which component A is a sea (continuous layer) and component B is an island (discontinuous layer) before the heat treatment. According to a pressure-sensitive adhesive composition that forms a pressure-sensitive adhesive layer in which the sea and islands are reversed to change into a sea-island structure in which component A is an island and component B is a sea, and the heat-sensitive adhesive sheet including the pressure-sensitive adhesive layer The inventors have found that the above problems can be solved and completed the present invention.

That is, the heat-sensitive adhesive composition of the first invention in the present invention is an aqueous emulsion-type adhesive composition comprising the following components A and B, and the following component A is dried by drying at less than 60 ° C. The pressure-sensitive adhesive layer having a sea-island structure in which the sea and the following component B are islands is formed, and the pressure-sensitive adhesive layer is formed of 6
By heat treatment at 0 ° C. or more, the sea and the island are reversed to form a sea-island structure in which the following component A is an island and the following component B is a sea. Component A: a water-soluble resin in which a resin having an acid value of 1 meq / g or more is neutralized with a base. Component B: a polymer having a glass transition temperature of −20 ° C. or lower, obtained by emulsion polymerization of a radical polymerizable monomer.

The pressure-sensitive adhesive layer formed from the heat-sensitive pressure-sensitive adhesive composition of the present invention has the above-mentioned structure before and after the heat treatment, respectively. The use of a material can prevent unnecessary tackiness from being exhibited before the heat treatment. Further, the pressure-sensitive adhesive layer after the heat treatment (hereinafter, referred to as “pressure-sensitive adhesive layer after heating”) forms a sea-island structure in which component A is an island and component B is a sea, as described above. Therefore, component B
When a material having excellent adhesiveness is used, the adhesive strength after the heat treatment becomes better than when the adhesive layer after heating has a structure in which the components A and B are uniformly mixed.

Further, since the component A is discontinuously dispersed in the component B in the pressure-sensitive adhesive layer after heating, if a hydrophobic material is used as the component B, even if the component A is hydrophilic, It is possible to make the post-pressure-sensitive adhesive layer excellent in water resistance. Furthermore, if the component A which becomes an island portion after the heat treatment has high alkali solubility or alkali swelling property, it is possible to achieve both good water resistance and excellent alkali releasability in the pressure-sensitive adhesive layer after heating. In addition, in this specification, "alkaline peeling property" means the property of being peeled from an adherend in a short time by alkaline water.

Since the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention forms the above-mentioned sea-island structure by heat treatment, the components A and B are uniformly mixed in the pressure-sensitive adhesive layer after heating. Unlike the above case, the properties of the component B are mainly reflected in the adhesive performance of the adhesive layer after heating. That is, in the pressure-sensitive adhesive composition of the present invention, the performance of the pressure-sensitive adhesive layer after heating can be predicted to some extent from the performance of the pressure-sensitive adhesive layer formed from component B alone.

The heat-sensitive adhesive composition comprises a component A and a component B, as in the second invention, wherein the component A is a high molecular emulsifier and used for the emulsion polymerization of the component B. B is preferably a polymer obtained by emulsion polymerization of a radical polymerizable monomer in the presence of component A.

The preferred weight ratio of component A to component B is in the range of 10/90 to 50/50 as described in the third invention.

The component A is, as described in the fourth invention, a copolymer of an α, β-ethylenically unsaturated carboxylic acid unit and a hydrophobic radically polymerizable monomer unit as main constituent units. It is preferably a neutralized product.

[0015] The fifth invention of the present invention is the first invention.
The present invention relates to a heat-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the heat-sensitive adhesive composition according to any one of the inventions to the fourth invention on a substrate. That is,
The heat-sensitive adhesive sheet of the fifth invention has a pressure-sensitive adhesive layer having a sea-island structure in which the component A is the sea and the component B is an island on the base material, and the 180-degree peeling method specified in JIS Z 0237. Is 10g / 2 at 25 ° C
A pressure-sensitive adhesive sheet having a size of 5 mm or less, wherein a sea-island structure in which the component A is an island and the component B is a sea by the heat treatment at 60 ° C. or more, wherein the sea and the island of the pressure-sensitive adhesive layer are reversed. , The adhesive force changes to 100 g / 25 mm or more.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
In the following, acryl and / or methacryl are referred to as “(meth) acryl”, and acrylate and / or methacrylate are referred to as “(meth) acrylate”.

In the present specification, the “glass transition temperature” (hereinafter, referred to as “Tg”) of a polymer refers to a value obtained from the following formula. It should be noted that only Tg used in this formula is expressed in absolute temperature (K), and Tg used in other parts of the specification is Celsius temperature (° C.).
Expressed by

[0018]

1 / Tg = {W (a) / Tg (a)} + {W (b) / Tg (b)} + {W (c) / Tg (c)} +... In the formula: Tg = Tg (K) of the polymer W (a) = weight fraction of the structural unit composed of the monomer (a) in the polymer W (b) = consisting of the monomer (b) in the polymer Weight fraction of structural unit W (c) = weight fraction of structural unit composed of monomer (c) in polymer Tg (a) = glass transition temperature (K) of homopolymer of monomer (a) Tg (b) = glass transition temperature of homopolymer of monomer (b) (K) Tg (c) = glass transition temperature (K) of homopolymer of monomer (c)

The "sea-island structure" described in the present specification is a well-known concept, and is described in, for example, "New Edition Polymer Dictionary (edited by the Society of Polymer Science, Polymer Dictionary Editing Committee, published by Asakura Shoten)", No. 31
It is described in detail in the section "Sea-island structure" on the page. In this specification, “having a sea-island structure” is not limited to a structure in which the sea (continuous layer) is completely continuous and all of the islands (discontinuous layers) are independently dispersed in the sea. The meaning includes a state in which the island is partially interrupted and a state in which a part of the island is fused with each other.

(1) Component A Component A in the present invention is a water-soluble resin and has an acid value of 1
A resin in which meq / g or more is neutralized with a base.

(1-1) Acid Value First, in this specification, the “acid value” refers to an acid value per solid content of a resin or a polymer, and refers to a theoretical acid value calculated by an ordinary method. When the polymer or resin is neutralized with a base, it indicates the acid value before neutralization. “Meq / g” used as a unit of the acid value represents a milligram equivalent number of an acid in 1 g of a solid content of a resin or a polymer.

The acid value of the component A must be 1 meq / g or more, and is preferably 1 meq / g to 5 meq / g. When the acid value is less than 1 meq / g, the solubility of the component A in water is insufficient, so that the liquid stability of the pressure-sensitive adhesive composition containing the component A becomes insufficient or the presence of the component A When the emulsion polymerization of the component B is performed below, the polymerization becomes unstable. When the component A is used for an alkali-peelable pressure-sensitive adhesive composition, if the acid value is less than 1 meq / g, the alkali solubility or swellability of the component A is insufficient, so that the component A is formed from the composition. A sufficient alkali release property cannot be imparted to the pressure-sensitive adhesive layer. On the other hand, when the acid value of component A exceeds 5 meq / g, the water resistance of the pressure-sensitive adhesive layer may be insufficient.

(1-2) Composition The component A having the acid value includes a radical polymerizable monomer unit having a carboxyl group or a sulfonic acid group having the acid value and another radical polymerizable monomer unit. And rosin derivatives.

As the rosin derivative, a resin obtained by modifying rosin or hydrogenated rosin with an organic acid, specifically, a dibasic anhydride such as maleic anhydride or phthalic anhydride (hereinafter referred to as a resin)
It is called “organic acid-modified rosin”. )), A neutralized product with a base and the like can be used. Specific examples of the organic acid-modified rosin include Harima Chemical Co., Ltd., trade name Harimac T-8.
0; Rental Hercules Co., Ltd. product name pentalin 2
55 and 261; trade names Marquid NO31, NO32, NO33 and KE-60 manufactured by Arakawa Chemical Co., Ltd.
4; and the like.

In the present invention, α,
A copolymer having a β-ethylenically unsaturated carboxylic acid unit and a hydrophobic radically polymerizable monomer unit as main constituent units is preferably used, and among the above copolymers, those having a glass transition temperature of 20 ° C or higher are preferred. More preferably used. The above α,
Examples of the β-ethylenically unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, maleic anhydride and the like. Alternatively, two or more kinds can be used. The amount of the α, β-ethylenically unsaturated carboxylic acid that gives the acid value varies depending on the kind of the unsaturated carboxylic acid used, but is usually based on the total weight of all the monomers used for the synthesis of the component A. 3-40% by weight
It is preferred that it is about.

The radical polymerizable monomer used together with the α, β-ethylenically unsaturated carboxylic acid is water 100
Hydrophobic radically polymerizable monomers having a solubility in g of 2 g or less are preferable, for example, methyl methacrylate,
Ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate,
Hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,
Alkyl (meth) acrylates such as n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate and isononyl (meth) acrylate; styrene, α-methylstyrene, vinyltoluene, etc. And the like. The amount of these monomers to be used is preferably 30 to 80% by weight based on the total amount of all the monomers used for the synthesis of the component A.

In order to synthesize the component A, the above α,
A hydrophilic radically polymerizable monomer other than β-ethylenically unsaturated carboxylic acid may be used if necessary. Examples of such a hydrophilic radical polymerizable monomer include methyl acrylate, vinyl acetate, acrylonitrile, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and polyethylene glycol mono (meth) acrylate. ) Acrylate, polypropylene glycol mono (meth) acrylate, (meth) acrylamide, N-methylolacrylamide, glycidyl methacrylate, styrenesulfonic acid and its sodium salt, and 2-acrylamide-2-methylpropanesulfonic acid and its sodium salt Is mentioned.

The component A may be a base neutralized product of the graft copolymer. As the graft copolymer, a graft copolymer having a hydrophilic main chain and a hydrophobic side chain, or a graft copolymer having a hydrophobic main chain and a hydrophilic side chain is preferably used. In this case, since the affinity between the hydrophobic part of the component A and the component B is high, the liquid stability of the composition is excellent, and the hydrophilic part of the component A in the pressure-sensitive adhesive layer has a hydrophobic portion inside the island after heating. Since the adhesive portion is oriented to the outside of the island, the water resistance of the pressure-sensitive adhesive layer is improved. Component A
Has a high affinity between the hydrophobic portion of component (A) and the component B, so that the liquid stability of the pressure-sensitive adhesive composition is improved.

Further, the T of the hydrophilic portion of the graft copolymer
g is preferably higher than the hydrophobic portion of the graft copolymer. In this case, in the pressure-sensitive adhesive layer before heating, a hydrophobic portion having a low Tg is oriented inside the island composed of the component B, and a hydrophilic portion having a high Tg is oriented outside the island. Even if it is low, the pressure-sensitive adhesive layer before heating can be made non-tacky. Thereby, it is possible to prevent the development of adhesiveness before heating and to develop the adhesiveness by a heat treatment at a lower temperature than before in use.

(1-3) Glass Transition Temperature Component A preferably has a glass transition temperature of 20 ° C. or higher, more preferably 30 to 130 ° C., and even more preferably 40 to 120 ° C. . However,
This is not the case when component A is a graft copolymer as described above, and the glass transition temperature of the entire graft copolymer is -30 to 100 ° C (more preferably -20 to 100 ° C).
60 ° C., more preferably 0 ° C. or more and less than 20 ° C.). Further, the glass transition temperature of the hydrophilic portion of the graft copolymer is 20 ° C. or more (more preferably 30 ° C.).
To 130 ° C., more preferably 40 to 120 ° C.)
The glass transition temperature of the hydrophobic portion is preferably -20 ° C or lower (more preferably -30 ° C or lower, further preferably -40 ° C or lower).

When the glass transition temperature of the component A or the glass transition temperature of the hydrophilic portion or the hydrophobic portion thereof is less than the above range, the adhesive strength of the pressure-sensitive adhesive layer before the heat treatment becomes too high, and the "release paper" To provide a pressure-sensitive adhesive sheet that can be used without performing a peeling treatment on the pressure-sensitive adhesive layer such as a peeling treatment of the base material or the back surface of the base material ”in some cases. On the other hand, if the glass transition temperature exceeds the above range, the heating temperature required to develop the adhesiveness becomes high, and the energy cost increases, which is not preferable.

(1-4) Production Method When the component A is a polymer of a radical polymerizable monomer, various polymerization methods can be adopted as a polymerization method for obtaining the component A. Known methods such as a polymerization method and a method using a radical polymerization initiator can be used. Among them, a polymerization method using a radical polymerization initiator is preferable from the viewpoint of easiness of polymerization operation, easiness of controlling the molecular weight of the obtained copolymer before neutralization, and the like. As the polymerization method, a solution polymerization method, a bulk polymerization method, a suspension polymerization method,
Examples thereof include an emulsion polymerization method and a precipitation polymerization method, and it is preferable to use a solution polymerization method or an emulsion polymerization method.

In this solution polymerization method, the component A can be obtained smoothly by dissolving the above-mentioned radically polymerizable monomer in an organic solvent and conducting polymerization using an appropriate radically polymerizable initiator. As the organic solvent, one or more organic solvents selected from ketones, acetates, aromatic hydrocarbons, aliphatic hydrocarbons, alcohols and the like can be used, and among them, methyl ethyl ketone And / or isopropyl alcohol is preferably used. As the radical polymerization initiator used in the solution polymerization, any of those used in general radical polymerization can be used. For example, a persulfate-based polymerization initiator, an azo-based polymerization initiator, a redox-based polymerization initiator can be used. Initiators and the like can be mentioned. The preferred amount of the polymerization initiator to be used is 0.1 to 5% by weight based on the total amount of the monomers.

When the component A is produced by an emulsion polymerization method, the radical polymerizable monomer is mixed and dispersed in water together with an emulsifier as disclosed in, for example, JP-A-6-271779. The above component A can be smoothly obtained by preparing a monomer emulsion by means of a continuous polymerization method using a suitable radically polymerizable initiator and continuously adding it to a reactor.

The polymerization temperature for obtaining the component A is 10 to 1
The temperature is preferably about 50 ° C, more preferably 60 to 100 ° C. The polymerization time is suitably from 1 to 100 hours, and more preferably from 3 to 10 hours.

The number average molecular weight of the component A is 1,000
Preferably it is ~ 50,000. Number average molecular weight is
If it is less than 1,000, the water resistance of the pressure-sensitive adhesive layer tends to be insufficient. On the other hand, when the number average molecular weight exceeds 50,000, the viscosity becomes high and the production of the component A becomes difficult, and the solubility of the component A in water becomes insufficient and the liquid stability of the composition is reduced. When the emulsion polymerization of the component B is performed in the presence of the component A, the polymerization becomes unstable. Further, it may be difficult to reverse the sea and the island by heating the pressure-sensitive adhesive layer, or it may be difficult to form a sea-island structure before and / or after heating the pressure-sensitive adhesive layer.
In order to adjust the number average molecular weight, a chain transfer agent may be appropriately added to the polymerization system.

Component A is obtained by neutralizing some or all of the acidic groups, such as carboxyl groups and sulfonic acid groups, of component A synthesized as described above with a base. Examples of the base used for neutralization include ammonia; amines such as alkylamine, allylamine and alkanolamine; alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkaline earth metal salts such as magnesium and calcium; Can be used. Among them, it is preferable to use a base having a boiling point of 110 ° C. or lower, such as ammonia, methylamine, ethylamine, propylamine, and isopropylamine, and it is particularly preferable to use ammonia. In this case, since the base is easily removed from the pressure-sensitive adhesive layer in the drying step after coating, a pressure-sensitive adhesive layer having excellent water resistance can be obtained.

The component A in the present invention may not necessarily be completely neutralized, but must be neutralized to the extent that the component A becomes water-soluble. Specifically, it is preferable that 30 mol% or more of the acidic group of the component A is neutralized, and it is more preferable that 50 mol% or more is neutralized. When the neutralization amount of the acidic group is less than 50 mol%, if the solubility of the component A in water is insufficient, the pressure-sensitive adhesive composition tends to be unstable, such as separation of the liquid over time. In addition, since the surface activity of component A is low, this component A
When component B is emulsion-polymerized in the presence of, the polymerization tends to be unstable.

The component A is preferably a resin having a low crosslinking density or a substantially non-crosslinked resin. If the component A is excessively crosslinked, the solubility of the component A in water tends to be insufficient. Further, if the crosslink density of the component A forming the sea-island structure sea in the pressure-sensitive adhesive layer before heating is too high,
In some cases, the movement of the molecular chain constituting the component A is limited, and the sea-island is difficult to reverse even when the heat treatment is performed.

(2) Component B Component B in the present invention is a polymer having a Tg of -20 ° C. or lower, obtained by emulsion polymerization of a radical polymerizable monomer.

(2-1) Acid Value The acid value of the component B is preferably 0.6 meq / g or less, more preferably 0.2 meq / g or less. When the acid value of component B exceeds 0.6 meq / g,
The water resistance of the pressure-sensitive adhesive layer may be insufficient. As the component B of the present invention, a polymer having an acid value of 0 meq / g is particularly preferably used.

The acid value of the component B is preferably lower than the acid value of the component A by 0.5 meq / g or more, more preferably 1 meq / g or more. Component A
Is less than 0.5 meq / g, component A and component B are mixed in the pressure-sensitive adhesive layer after heating, so that component A is an island and component B is a sea. May not be formed.

(2-2) Glass transition temperature The Tg of the above component B must be -20 ° C or less;
The temperature is preferably -50 ° C or lower. Component B has a Tg of-
If the temperature exceeds 20 ° C., sufficient adhesive performance cannot be obtained in the adhesive layer after heating.

(2-3) Composition As the component B, various polymers obtained by emulsion polymerization of a radical polymerizable monomer and having a Tg satisfying the above range can be used. For example, an emulsion polymer of a radical polymerizable monomer having a (meth) acrylic acid ester as a main component (hereinafter, referred to as an “acrylic monomer”), a radical polymerizable monomer having ethylene and a vinyl ester as a main component. Polymer (hereinafter, referred to as “ethylene-vinyl ester monomer”), a conjugated diene monomer, and a monomer copolymerizable with the conjugated diene monomer (hereinafter, referred to as “conjugated diene monomer”). An emulsion polymer of a radical polymerizable monomer having a main component of “monomer”) can be used. When the component B is an emulsion polymer of an ethylene-vinyl ester monomer or a conjugated diene monomer, the pressure-sensitive adhesive layer after heating shows a good pressure-sensitive adhesive strength to a polyolefin-based resin. There is an advantage that a composition is easily obtained. On the other hand, when the component B is an emulsion polymer of an acrylic monomer,
There is an advantage that a pressure-sensitive adhesive layer excellent in weather resistance and transparency is easily obtained.

Examples of the "vinyl ester monomer" in the above "ethylene-vinyl ester monomer" include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl laurate, vinyl versatate and the like. . Examples of the “conjugated vinyl monomer” in the “conjugated vinyl monomer” include butadiene, isoprene, chloroprene, and isobutylene.

The above-mentioned “acrylic monomer” includes, as a main component, an alkyl (meth) acrylate and, if necessary, another radical polymerizable monomer copolymerizable therewith (hereinafter referred to as “acrylic monomer”). Is sometimes referred to as a "copolymerizable monomer.") Is preferably used in a small amount, preferably 40% by weight or less. As the “alkyl (meth) acrylate”, the alkyl group has 1 carbon atom.
And (12) alkyl (meth) acrylate are preferably used. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate Hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate and ( Examples thereof include isononyl (meth) acrylate, decyl (meth) acrylate, and lauryl (meth) acrylate, and one or more of these alkyl (meth) acrylates can be used. In particular, in the present invention, as the radical polymerizable monomer used for the production of the component B, one or more alkyl (meth) acrylates having 4 to 9 carbon atoms in the alkyl group are used as the main component. Is preferred.

As described above, in the production of the component B, together with the alkyl (meth) acrylate,
Other copolymerizable monomers may be used as the minor component. Examples of such “other copolymerizable monomers” include, for example, vinyl aromatic monomers such as styrene, α-methylstyrene, and vinyl toluene; (meth) acrylic acid, crotonic acid,
Unsaturated carboxylic acids such as cinnamic acid, itaconic acid, fumaric acid and maleic acid; monoalkyl esters of unsaturated dicarboxylic acids such as monoethyl itaconate, monobutyl fumarate and monobutyl maleate; (meth) Hydroxyl-containing vinyl monomers such as 2-hydroxyethyl acrylate, 2-hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, and polypropylene glycol mono (meth) acrylate; (meth) acrylonitrile, vinyl acetate, ( Meta)
Examples thereof include acrylamide, N-methylolacrylamide, glycidyl methacrylate, vinyl acetate, vinyl chloride, and vinylidene chloride. One or more of these copolymerizable monomers can be used.

When the above-mentioned "other copolymerizable monomer" is used, its use ratio is 40% by weight or less as described above, based on the total weight of the radical polymerizable monomer used for producing the component B. It is preferred that 40% by weight
This is because, if it exceeds, the adhesive performance of the adhesive layer after heating tends to be insufficient.

(2-4) Production Method As an example of the method for obtaining the above component B, there can be mentioned a conventional emulsion polymerization method using a conventionally known surfactant as an emulsifier. Examples of the surfactant used herein include anionic surfactants such as higher alcohol sulfate sodium salt, alkylbenzene sulfonate sodium salt, dialkyl succinate sodium sulfonate, and alkyl diphenyl ether disulfone sodium acid; and polyoxyethylene alkylallyl. Nonionic surfactants such as ether and polyoxyethylene polyoxypropylene block copolymers can be mentioned. Further, a reactive anionic surfactant such as sodium allyl alkyl sulfonate, alkyl allyl sulfosuccinate and polyoxyethylene alkyl allyl glycerin ether sulfate may be used.

As another method for obtaining the component B, a method in which the radical polymerizable monomer used for the production of the component B is emulsion-polymerized in the presence of the component A as in the second invention. In this emulsion polymerization method, since the component A functions as a surfactant (emulsifier), the amount of an emulsifier such as a protective colloid or another surfactant used during the emulsion polymerization can be made smaller than in the case of ordinary emulsion polymerization. . Further, if desired, no other emulsifier can be used. As a result, the water resistance of the pressure-sensitive adhesive layer can be improved as compared with the case where the component B is produced by ordinary emulsion polymerization. Incidentally, when the radical polymerizable monomer used for producing the component B is emulsion-polymerized in the presence of the component A,
An emulsion containing both components A and B is obtained. Therefore, in this case, the pressure-sensitive adhesive composition or pressure-sensitive adhesive layer of the present invention can be formed from this emulsion without separately adding the component A, and the production method is most preferable from the viewpoint of water resistance. Alternatively, component A may be further added to the emulsion thus obtained.

As the polymerization initiator that can be used for the emulsion polymerization for obtaining the component B, any polymerization initiator generally used for the emulsion polymerization can be used.
Examples of the radical polymerization initiator for obtaining the same include the same organic peroxides, inorganic peroxides, and azo compounds as described above. The preferred amount of the polymerization initiator to be used is 0.1 to 5% by weight based on the total amount of the monomers.

This component B preferably does not have an acidic group, but may have an acidic group within the range of the acid value or less. In order to prevent the inside of the system from becoming unstable when component A is added, component B is neutralized with a base or the like used for neutralizing component A to bring its pH closer to the pH of component A. It is preferable to keep it.

(3) Pressure-sensitive adhesive composition The pressure-sensitive adhesive composition of the present invention may be a mixture of the above-mentioned component A and the above-mentioned component B, and may be a radical polymerization used in the production of the above-mentioned component B. It may be a reaction product obtained by emulsion-polymerizing a water-soluble monomer in the presence of the component A. In the above case, there is an advantage that the production of the pressure-sensitive adhesive composition is simple and a composition having a high solid content is easily obtained. On the other hand, in the above case, the component B
Since the component A is used as an emulsifier in the emulsion polymerization of the above, there is an advantage that the water resistance of the pressure-sensitive adhesive layer can be improved as described above, and the composition has excellent storage stability. That is, when the component A and the component B are blended, a part or all of the surfactant adsorbed on the polymer particle surface of the emulsion composed of the component B is desorbed and replaced by the component A. In some cases, the storage stability is impaired. In a remarkable case, the mixture may be gelled to make application impossible. In the above case, such a problem is prevented. Furthermore, the pressure-sensitive adhesive composition of the present invention further blended the above component A with a polymer obtained by emulsion polymerization of the radical polymerizable monomer used for the production of the above component B in the presence of the above component A. It may be something.

(3-1) Weight ratio of component A to component B In the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention and the pressure-sensitive adhesive composition of the present invention, the weight ratio of component A to component B is /
Component B is preferably 10/90 to 50/50, and more preferably component A / component B is 15/85 to 40/60. If the weight ratio of component A to the total weight of component A and component B is less than 10%, it is difficult for the pressure-sensitive adhesive layer before the heat treatment to have a sea-island structure in which component A is the sea and component B is the island. As a result, the pressure-sensitive adhesive layer before the heat treatment may unnecessarily exhibit an adhesive force. On the other hand, component A
If the weight ratio exceeds 50%, the water resistance of the pressure-sensitive adhesive layer is reduced, and the adhesive strength is apt to be insufficient. If the weight ratio of the component A is too high, it is difficult to form a sea-island structure in which the component A is an island and the component B is a sea in the pressure-sensitive adhesive layer after the heat treatment.

(3-2) Liquid Properties The pressure-sensitive adhesive composition of the present invention has a solid content concentration of 30 to 70.
%, More preferably 35 to 65% by weight. If the solid content is less than 30% by weight, the drying property of the composition is insufficient, while if it exceeds 70% by weight, the production becomes difficult and the viscosity of the composition tends to be excessively high.

The composition of the present invention usually comprises particles in which component A, which is a water-soluble resin, is located on the outside and component B is located on the inside. Therefore, the dispersion state of the component B in water is stabilized by the presence of the component A, so that the amount of other emulsifiers added to supplement the liquid stability of the composition can be reduced, whereby the adhesiveness can be reduced. The water resistance of the agent layer is further improved. In addition, since the component A of the present invention is water-soluble, unlike the case where the component A is insoluble in water, the liquid stability of the composition is good because no sedimentation or aggregation of the component A occurs in the composition. is there.

(3-3) Other Ingredients The pressure-sensitive adhesive composition of the pressure-sensitive adhesive sheet of the present invention and the pressure-sensitive adhesive layer of the present invention can be used as antifoaming agents commonly used in general pressure-sensitive adhesives, depending on the application. , Surfactants, fungicides, fragrances, neutralizers,
Tackifier, thickener, leveling regulator, antifreeze,
Foaming agents, antioxidants, ultraviolet absorbers, reinforcing agents, fillers, pigments, optical brighteners, antistatic agents, antiblocking agents, flame retardants, crosslinkers, plasticizers, lubricants, organic solvents or colorants, etc. One or more kinds may be contained.

(4) Pressure-sensitive adhesive sheet The heat-sensitive pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the first to fourth inventions on a substrate, and has a pressure-sensitive adhesive strength before heat treatment. Is extremely low at 10 g / 25 mm or less. Therefore, in this state, the product can be handled as it is without performing a release treatment on the adhesive layer such as a release paper or a release treatment on the back surface of the substrate. This pressure-sensitive adhesive sheet expresses a pressure-sensitive adhesive strength of 100 g / 25 mm or more only after a heat treatment at 60 ° C. or higher.

(4-1) Substrate The type of the substrate in the pressure-sensitive adhesive sheet of the present invention is not particularly limited as long as the material can withstand the heat treatment temperature of the pressure-sensitive adhesive sheet. Can be used, such as cloth, paper, leather, wood, metal, glass, films and sheets made of various plastics,
Plates, foamed plastic sheets and the like can be mentioned. Examples of the substrate made of the plastic include substrates made of polyester, polyamide, vinyl chloride polymer, polyethylene, polypropylene, polyurethane, and the like. Further, the shape of the base material is a long body, one cut into a predetermined size (for example, square, circular, elliptical,
(Pre-cut into other shapes).

(4-2) Pressure-Sensitive Adhesive Layer In the heat-sensitive pressure-sensitive adhesive sheet of the present invention, the thickness of the pressure-sensitive adhesive layer can be appropriately adjusted depending on the use and the like, but is generally about 1 μm to 1 mm. Is preferred. Thereby, it is possible to make the adhesive layer exhibit good adhesiveness after the heat treatment.

The pressure-sensitive adhesive layer has a sea-island structure in which the component A is a sea and the component B is an island before the heat treatment. The structure changes to an island and the component B is a sea. This situation is schematically shown in FIGS. 1A and 1B.

FIG. 1A shows the state of the pressure-sensitive adhesive layer before heating, in which a sea-island structure is formed in which component A is the sea and component B is the island. Therefore, if a substantially non-tacky material at room temperature is used as the component A, the pressure-sensitive adhesive layer before the heat treatment can be made non-tacky. Thereby, the pressure-sensitive adhesive sheet before heating can be used without using a release paper or performing a release treatment such as a release treatment on the back surface of the base material.

FIG. 1B shows the pressure-sensitive adhesive layer after a heat treatment at 60 ° C. or higher for the pressure-sensitive adhesive layer before heating. By this heat treatment, the sea and the island are reversed, and a sea-island structure is formed in which component A becomes an island and component B becomes a sea. As described above, the post-heating pressure-sensitive adhesive layer of the present invention has a structure in which the low-viscosity or non-tacky component A is dispersed in the component B, so that when the component A and the component B are uniformly mixed, In comparison, the adhesive strength of the adhesive layer after heating is better. Further, if a hydrophobic material is used as the component B, the continuous layer in the adhesive layer after heating becomes hydrophobic. Therefore, even if the component A which is a discontinuous layer is hydrophilic, the adhesive layer after heating can be made water-resistant. It is possible to make it excellent. Furthermore, if the component A has high alkali solubility or alkali swellability,
It is possible to achieve both good water resistance and excellent alkali peelability in the pressure-sensitive adhesive layer after heating.

Incidentally, a non-adhesive resin [component (A)] and an adhesive acrylic resin emulsion [component (B)] as described in the above-mentioned JP-A-8-269420.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition comprising, after the heat treatment, the component A and the component B are not uniformly mixed, but the “sea-island structure in which the component A becomes an island and the component B becomes the sea” Is found for the first time by the present inventors.

(4-3) Production Method The heat-sensitive adhesive sheet of the present invention is prepared by applying the pressure-sensitive adhesive composition of the first to fourth inventions to one or both surfaces of the above-mentioned substrate, and applying it by an appropriate method. It can be manufactured by a method such as drying. At this time, the method of applying the pressure-sensitive adhesive composition to the substrate is not particularly limited, and may be performed using any method such as roll coater coating, spray coating, casting coating, doctor blade coating, brush coating, and the like. it can. In drying the pressure-sensitive adhesive composition applied on the base material, the temperature of the pressure-sensitive adhesive layer in the finally obtained pressure-sensitive adhesive sheet is such that the pressure-sensitive adhesive layer does not exhibit tackiness at room temperature, or the pressure-sensitive adhesive layer is such that the component A becomes sea. It is necessary to heat at a temperature at which the pressure-sensitive adhesive layer having a sea-island structure in which the component B is an island can be formed.

(4-4) Method of Use The heat-sensitive adhesive sheet of the present invention has an adhesive strength at a temperature of 25 ° C. of not more than 10 g / 25 mm according to JIS Z 0237 at a temperature of 25 ° C. Does not show, or the adhesion at room temperature is extremely small,
Unlike conventional general-purpose pressure-sensitive adhesive sheets, they can be stored, distributed, and sold without any release treatment of the pressure-sensitive adhesive layer. can do. At this time, the term "not subjected to release treatment" in the present invention means that the pressure-sensitive adhesive sheet of the heat-sensitive adhesive sheet is not covered with a release paper. Means not to apply. Of course, if necessary, for example, 25
When the pressure-sensitive adhesive strength at 3 ° C. is 3 to 10 g / 25 mm, the pressure-sensitive adhesive sheet may be subjected to a release treatment depending on its use.

When the heat-sensitive adhesive sheet of the present invention is adhered to an adherend, the adhesive layer of the heat-sensitive adhesive sheet is heated, the adherend side is heated, or the heat-sensitive adhesive sheet is adhered to the adhesive layer. The heat-sensitive adhesive sheet can be adhered to the adherend by heating both of the adherends. The heating temperature for causing the pressure-sensitive adhesive layer to exhibit tackiness depends on the Tg of the entire component A contained in the pressure-sensitive adhesive composition, and usually the Tg
A temperature higher than 10 ° C., preferably higher than 30 ° C. is suitable. Here, if the heating temperature is too high, there is a possibility that the workability of attaching the pressure-sensitive adhesive sheet and the thermal efficiency may be reduced, or the base material may be deteriorated or deformed. For this reason, the heating temperature is preferably set to 60 to 180 ° C.,
More preferably, the temperature is set to 40 ° C.

The pressure-sensitive adhesive sheet of the present invention once adhered to the adherend does not peel off spontaneously when the temperature returns to room temperature, and is favorably adhered to the adherend without losing its adhesiveness. I'm wearing Then, when it is desired to peel the heat-sensitive adhesive sheet of the present invention from the adherend, it can be easily peeled off from the adherend by pulling with a hand or the like, similarly to a general-purpose pressure-sensitive adhesive sheet, and the peeled material is an adhesive. Since the layer remains tacky, it can be re-applied to the same or another adherend.

The material and type of the adherend to which the heat-sensitive adhesive sheet of the present invention can be adhered are not particularly limited, and examples thereof include cloth, paper, leather, wood, metal, glass, concrete, ceramic, and the like.
It can be satisfactorily adhered to any of polyester, polyethylene, polypropylene, polyvinyl chloride, polyurethane, polycarbonate, polyamide, polyimide, styrene-based polymer, rubbers and the like.

The heat-sensitive adhesive sheet of the present invention, for example, when the acid value of the component B is 0.6 meq / g or less, is an alkaline peeling agent for a label to be attached to a bottle for filling beverages such as a beer bottle. It can be suitably used as a pressure-sensitive adhesive sheet.
Such an alkali-peelable pressure-sensitive adhesive sheet has a high adhesive strength to a bottle as an adherend, and has good water resistance at the time of immersion in cold water. Peeling property (alkali peeling property)
Is required. In the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive layer after heat treatment has a hydrophilic portion with a high acid value in a continuous layer (sea) composed of Component B having a low acid value and good water resistance, and has an alkali-soluble property. Alternatively, since it has a sea-island structure in which a discontinuous layer (island) composed of the component A having a high alkali swelling property is dispersed, it is possible to achieve both good water resistance and adhesiveness, and excellent alkali releasability.

[0071]

The present invention will be described more specifically with reference to the following examples and comparative examples. In the following examples, “parts” and “%” are “parts by weight” unless otherwise specified.
And "% by weight". The abbreviations used below and their contents are shown in Table 1 below. Furthermore, the Tg value of the homopolymer of each monomer used for calculating the Tg of the polymer in this specification is also shown.

[0072]

[Table 1] Abbreviation: Contents Tg (° C) MMA: methyl methacrylate 105 HEMA: 2-hydroxyethyl methacrylate 55 MAA: methacrylic acid 130 IBX: isobornyl methacrylate 180 AMA: allyl methacrylate 52 AA: acrylic acid 105 AEH: 2-ethylhexyl acrylate-85 BA: acrylic acid Butyl-54 ST: Styrene 100 EL: Ethylene-125 BD: Butadiene-83 VAC: Vinyl acetate 30 HEA: 2-hydroxyethyl acrylate-15 AIBN: 2,2'-azobisisobutyronitrile APS: Ammonium persulfate

[1] Preparation of Pressure-Sensitive Adhesive Composition [1-1] Synthesis or Preparation of Component A (a) Synthesis by Solution Polymerization The following Synthesis Examples 1 to 5 correspond to Component A corresponding to Component A of the present invention.
This is an example in which Nos. 1 to 5 are synthesized by a solution polymerization method.

(Synthesis Example 1) (1) A polymerization initiator was added to a mixture comprising 90 parts of MMA and 10 parts of AA as monomers, 1.5 parts of dodecyl mercaptan as a chain transfer agent, and 100 parts of methyl ethyl ketone as an organic solvent. Was dissolved in a flask equipped with a stirrer, a condenser, a thermometer and a nitrogen inlet tube at 80 ° C. under a nitrogen atmosphere.
For 4 hours to polymerize. Thereafter, 0.5 parts of AIBN was further added, and the mixture was heated to the same temperature for 5 hours to obtain a methyl ethyl ketone solution of a copolymer (acid value: 1.4 meq / g) having a solid content of 50%. This copolymer corresponds to Component A described above. (2) Aqueous ammonia is gradually added to 200 parts of the methyl ethyl ketone solution of the copolymer obtained in the above (1) under stirring to neutralize the carboxyl groups in the copolymer and to adjust the pH of the reaction solution. Was set to about 7 to 8. Thereafter, methyl ethyl ketone was removed under reduced pressure at a temperature of 50 ° C. to obtain an aqueous solution A1 _aq of the component A1 in which a carboxyl group was neutralized. The solid content of this aqueous solution A1 _aq is 50
% And its pH was 7.7.

(Synthesis Examples 2 to 5) The components were prepared in the same manner as in Synthesis Example 1 except that the monomer composition, the amount of the chain transfer agent, and the amount of the initiator dissolved in the mixed solution were as shown in Table 2 below. A
2-A5 were synthesized respectively. "AB-6" used in Synthesis Example 3 was a methacryloylated polybutyl acrylate macromonomer at one end (manufactured by Toagosei Co., Ltd., trade name "Macromonomer AB-6", number average molecular weight 6,000).
0). Further, the obtained component A3 was prepared by using MMA-AA
It is a graft copolymer having a hydrophilic main chain composed of a copolymer and a hydrophobic side chain composed of polybutyl acrylate.

[0076]

[Table 2]

(B) Synthesis by Emulsion Polymerization The following synthesis examples 6 and 7 are examples in which components A6 and 7 corresponding to the component A of the present invention were synthesized by an emulsion polymerization method.

(Synthesis Example 6) (1) To 90 parts of MMA and 10 parts of AA as monomers,
3 parts of octyl thioglycolate as a chain transfer agent was mixed to obtain a monomer mixture. To 100 parts of this monomer mixture was added sodium lauryl sulfate (0.1%) as an emulsifier for polymerization.
One part and 50 parts of deionized water were added and emulsified by stirring to prepare a monomer emulsion. (2) 30 parts of deionized water was charged into a flask equipped with a stirrer, a condenser, a thermometer, and a nitrogen inlet tube, and an APS aqueous solution (2 parts of APS and 6 parts of deionized water) was maintained under a nitrogen atmosphere while maintaining the inside of the reactor at 70 ° C. 8 parts) and 150 parts of the above monomer emulsion were added dropwise over 3 hours. After maintaining the same temperature for 2 hours after the completion of the dropwise addition, the reaction system was cooled to terminate the polymerization, thereby obtaining an aqueous polymer emulsion having a solid content of 50%. This is an emulsion composed of the polymer A6 corresponding to the component A described above. The above polymer A
The acid value of No. 6 was 1.4 meq / g. (3) By neutralizing the carboxyl group in the polymer A6 by gradually adding aqueous ammonia while stirring the emulsion, the pH of the reaction solution was adjusted to about 7 to 8, and an aqueous solution of the component A6 was obtained. The solids content of this aqueous solution was 45% and its pH was 7.7.

(Synthesis Example 7) Component A7 was synthesized in the same manner as in Synthesis Example 6 except that the monomer composition, the type and amount of the emulsifier for polymerization, and the amount of the chain transfer agent were as shown in Table 3 below. did.

[0080]

[Table 3]

(C) Preparation of Component A by Neutralization of Commercial Resin (Synthesis Example 8) Block copolymer of maleic anhydride and isobutylene [trade name “Isoban 60” manufactured by Kuraray Co., Ltd.]
0 ", molecular weight 6,000, acid value 6.5 meq / g] was neutralized with aqueous ammonia to obtain an aqueous solution of component A8. The solid content of this aqueous solution was 30%, and the pH was 9.0.

(Synthesis Example 9) Block copolymer of maleic anhydride and isobutylene [Kuraray Co., Ltd., trade name “Isoban 04”, molecular weight 60,000, acid value 6.5 meq.
/ G] was neutralized with aqueous ammonia to obtain an aqueous solution of Component A9. This aqueous solution has a solid content of 30% and a pH of 9.0.
Met.

(Synthesis Example 10) Maleic acid-modified rosin-based synthetic resin [trade name "Marquid 3" manufactured by Arakawa Chemical Industries, Ltd.
2 ", acid value 2.3 meq / g, Tg 109.2 ° C] was neutralized with aqueous ammonia to obtain an aqueous solution of component A10. The solid content of this aqueous solution was 50%, and the pH was 9.0.

[1-3] Synthesis of pressure-sensitive adhesive composition [1-3-1] Synthesis of pressure-sensitive adhesive composition by emulsion polymerization in the presence of component A In the presence of component A obtained by the above synthesis example, A pressure-sensitive adhesive composition comprising the following aqueous polymer emulsion was synthesized by emulsion polymerization of the radical polymerizable monomer used in the production of B.

Example 1 A monomer mixture was prepared by mixing 99 parts of BA and 1 part of HEMA. Stirrer, condenser,
In a flask equipped with a thermometer and a nitrogen inlet tube, 70 parts of deionized water and an aqueous solution A1 _aq 40 of the component A1 obtained in Synthesis Example 1 were added.
Parts (active ingredient 20 parts), 60 ° C under nitrogen atmosphere
After the temperature was raised to 1, the t-butyl hydroperoxide 1
5 parts of a 0% aqueous solution, 5 parts of a 10% aqueous solution of formaldehyde sodium sulfoxylate dihydrate (trade name "Rongalit C", manufactured by Iron and Steel Chemical Co., Ltd.), and the above monomer mixture 80 parts were added dropwise over 3 hours. After maintaining the same temperature for 2 hours after the completion of the dropwise addition, the reaction system was cooled to terminate the polymerization, neutralized with aqueous ammonia to a pH of 7 to 8, and a solid content of about 5%.
A 0% aqueous polymer emulsion was obtained.

(Example 2) 99 parts of AEH and HEMA1
Parts were mixed to obtain a monomer mixture. This monomer mixture 8
To 0 parts, 40 parts of the aqueous solution A2 _{aq of the} component A2 obtained in Synthesis Example 2 (20 parts of the active ingredient) and 40 parts of deionized water were mixed and emulsified by stirring to prepare a monomer emulsion. Stirrer,
40 parts of deionized water was charged into a flask equipped with a condenser, a thermometer and a nitrogen inlet tube, and the system was heated to 70% under a nitrogen atmosphere.
After the temperature was raised to 3 ° C., a 3% aqueous solution of APS 10
And 160 parts of the above-mentioned monomer emulsion were added dropwise over 3 hours. After maintaining the same temperature for 2 hours from the end of the dropwise addition, the reaction system was cooled to terminate the polymerization, neutralized with aqueous ammonia to pH 7 to 8, and an aqueous polymer emulsion having a solid content of about 50% was added. Obtained.

(Examples 3 to 5 and Comparative Examples 1 and 2) An aqueous solution was prepared in the same manner as in Example 1 except that the component A shown in Table 4 was used instead of the component A1 used in Example 1 above. A polymer emulsion was obtained.

[0088]

[Table 4]

[1-3-2] Preparation of pressure-sensitive adhesive composition by blending components A and B (a) Synthesis of component B by emulsion polymerization (Synthesis Examples 7 and 8) This is an example in which component B is synthesized by polymerizing an acrylic monomer by a normal emulsion polymerization method. That is, a method similar to that of Example 1 was adopted except that 0.2 parts of sodium lauryl sulfate was used in place of the component A1 used in Example 1 and the composition of the monomer mixture was as shown in Table 5 below. As a result, an aqueous polymer emulsion was obtained.

(Synthesis Example 9) Component B, which is an emulsion polymer of an ethylene-vinyl ester monomer, was synthesized by the following method. (1) The inside of a temperature-adjustable pressure reactor (autoclave) equipped with a stirrer is purged with nitrogen in advance, and deionized water 60
Parts, sodium lauryl sulfate 0.2 part, hydroxyethyl cellulose 0.5 part, sodium acetate 0.06 part and Rongalite 0.6 part. (2) After elevating the temperature of the reactor to 55 ° C. and adding EL, adjusting the pressure to 60 kg / cm ² , 20 parts of VAC and AE
A monomer mixture consisting of 60 parts of H and 40 parts of a 10% aqueous solution of APS were added dropwise over 5 hours. After maintaining the same temperature for 2 hours after the completion of the dropwise addition, the reaction system was cooled to terminate the polymerization, neutralized with aqueous ammonia to adjust the pH to 7 to 8, and an emulsion comprising the copolymer B3 was obtained. The solid content of this emulsion was 50%, and the composition of copolymer B3 calculated from the mass balance was EL / VAC / AEH = 20/20/60 as shown in Table 4 below.

(Synthesis Example 10) Component B, which is an emulsion polymer of a conjugated diene monomer, was synthesized by the following method. The inside of a pressure-controllable reactor (autoclave) equipped with a stirrer is purged with nitrogen in advance, and 100 parts of deionized water, 0.2 part of sodium lauryl sulfate, 0.08 part of sodium ethylenediaminetetraacetate, 0.08 part of sodium persulfate 1.2
Parts, sodium hydroxide 0.3 parts, BD 50 parts, BA15
Parts, 30 parts of ST and 5 parts of HEA were charged and polymerized for 15 hours. After the completion of the polymerization, the pH of the reaction solution was adjusted to 7 with sodium hydroxide, and the remaining monomers were removed by steam stripping to obtain an emulsion composed of the copolymer B4.

[0092]

[Table 5]

(B) Preparation of pressure-sensitive adhesive composition (Examples 6 to 10 and Comparative Examples 3 to 5) The components A and B obtained in the above synthesis examples were mixed at a solid content ratio shown in Table 6 below. An aqueous emulsion-type pressure-sensitive adhesive composition was synthesized. Among them, Comparative Examples 4 and 5 are pressure-sensitive adhesive compositions containing no component A. The component B5 used in Example 10 was an ethylene-based aqueous emulsion (manufactured by Sumitomo Chemical Co., Ltd.
(Trade name: Sumikaflex EVA-921, solid content 60%, Tg-40 ° C).

[0094]

[Table 6]

[2] Evaluation of pressure-sensitive adhesive composition The pressure-sensitive adhesive layers or sheets formed from the pressure-sensitive adhesive compositions obtained in Examples 1 to 12 and Comparative Examples 1 to 5 were subjected to the following (1) to ( The measurement or evaluation of 4) was performed. The results are shown in Table 7 below.

(1) Structure of Pressure-Sensitive Adhesive Layer The pressure-sensitive adhesive composition of Example 2 was applied on a polyester film having a thickness of 50 μm so that the thickness of the coating film after drying was 20 to 30 μm. After drying for 5 minutes, an adhesive layer was formed. This pressure-sensitive adhesive layer (hereinafter, referred to as a “low-temperature-dried pressure-sensitive adhesive layer”) is subjected to vapor dyeing in the presence of an aqueous ruthenic acid solution, and furthermore, an epoxy resin-embedded one is subjected to transmission electron microscopy (TEM) by ultrathin sectioning. Observed using. On the other hand, the pressure-sensitive adhesive layer obtained by applying the pressure-sensitive adhesive composition of Example 2 in the same manner as described above and drying at 140 ° C. for 2 minutes (hereinafter, referred to as “high-temperature-dried pressure-sensitive adhesive layer”) is similarly obtained. Treated and observed with a transmission electron microscope. According to the above method of staining with ruthenic acid vapor, it is known that polystyrene and the like are strongly stained, while polymethyl methacrylate and the like are not stained much (Macromolecu
les, Vol. 16, No. 4, 1983, P. 589-598).

The obtained TEM photographs are shown in FIGS.
It is shown in (B). FIG. 2 (A) shows the low-temperature-dried pressure-sensitive adhesive layer observed at a magnification of 40,000, and the part that is easily dyed by ruthenic acid (component A; the easily dyeable St is copolymerized) becomes the sea and is dyed. It can be seen that a sea-island structure in which a portion (component B) that is difficult to be formed is an island is formed. FIG. 2 (B) shows that the high-temperature dried pressure-sensitive adhesive layer was magnified by 40,
In contrast to FIG. 2, a sea-island structure was formed in which the portion that was not easily dyed by ruthenic acid (component B) turned into a sea and the portion that was easily dyed (component A) turned into islands. That is, it can be seen that the sea-island of the component A and the component B was reversed by heating to form the pressure-sensitive adhesive layer of the present invention.

For Examples 1, 3 to 12 and Comparative Examples 1 to 5, TEM observations of the low-temperature-dried pressure-sensitive adhesive layer and the high-temperature-dried pressure-sensitive adhesive layer were carried out in the same manner as described above, and the presence or absence of a sea-island structure and formation of seas and islands were performed. The types of components were investigated.

(2) Adhesive force of pressure-sensitive adhesive sheet A pressure-sensitive adhesive composition is applied to a coated paper for label as a base material so that the thickness of the coating film after drying is 20 μm to 30 μm, and the coating composition is heated at 40 ° C. for 5 minutes. It dried and the adhesive sheet was created. A test piece obtained by cutting this adhesive sheet to a width of 25 mm and a length of about 250 mm (hereinafter, referred to as a “test piece before heat treatment”), and a test piece before heat treatment at 140 ° C.
After heating for 2 minutes at 23 ° C, 65% humidity
(Hereinafter referred to as “heat-treated test piece”) for 24 hours in an atmosphere of JIS Z 023
The adhesive strength was measured according to the 180 degree peeling method specified in 7. That is, under a condition of a temperature of 23 ° C. and a humidity of 65%, the test piece was attached to a polished stainless steel plate as a test plate, and a 2 Kg rubber roller was reciprocated once and pressed. 30 minutes after the crimping, at a pulling speed of 300 mm / min,
The 180 degree peeling adhesion to the test plate was measured.
The measurement results were shown in the following four stages. A: 500 g / 25 mm or more B: 100 g / 25 mm or more, less than 500 g / 25 mm C: More than 10 g / 25 mm and less than 100 g / 25 mm D: 10 g / 25 mm or less

Further, the adhesive strength of the component B alone prepared in Synthesis Examples 7 to 10 was measured in the same manner as in Examples 1 to 12 and Comparative Examples 1 to 5. The results are shown in Table 5 in the same notation as described above.

(3) Water Resistance A pressure-sensitive adhesive sheet prepared in the same manner as in the above-mentioned pressure-sensitive adhesive strength test was 80 m
The test piece (heat-treated test piece) was cut into a length of about 100 mm and heat-treated at 140 ° C. for 2 minutes.
And This test piece was attached to the side of a beer bottle, and a 2 kg rubber roller was pressed back and forth once. Two days after the pressure bonding, the test piece was immersed in water at 10 ° C., and the peeled state of the test piece was observed.
The measurement results were shown in the following three stages. In this test, “peeling” means a state where at least a part of the test piece has peeled off from the beer bottle. 〇: No peeling even after 60 hours △: Peeling occurred in 20 hours or more and less than 60 hours ×: Peeling occurred in less than 20 hours

(4) Alkali Peelability A test piece (heat-treated test piece) formed in the same shape by the same method as in the above-described water resistance test was attached to the side of a beer bottle.
A Kg rubber roller was pressed back and forth once. 2 from crimping
One day later, the test piece was immersed in a 3% by weight aqueous solution of sodium hydroxide at 70 ° C., and the peeled state of the test piece was observed. The measurement results were shown in the following three stages. 〇: Test piece peeled off in less than 2 minutes △: Test piece peeled off in 2 minutes or more and less than 6 minutes ×: Test piece did not peel off even after 6 minutes

[0103]

[Table 7]

As can be seen from Table 7, it was difficult to observe a composition having a small difference in the degree of ruthenic acid staining between the component A and the component B. Formed a substantially non-tacky pressure-sensitive adhesive layer having a sea-island structure in which component A was a sea and component B was an island.
After heating, it was observed that these pressure-sensitive adhesive layers changed to a sea-island structure in which component A was an island and component B was an ocean. The heat-treated test pieces of Examples 1 to 12 all had high adhesive strength, and were also excellent in water resistance and alkali peelability. Among them, the acid value is 6.5 meq / g.
In Example 11 using Component A8, which was slightly higher, the water resistance was slightly lower than in the other Examples.

A part of the obtained TEM photograph is shown in FIGS.
Shown in FIGS. 3 (A) and 3 (B) show TEs obtained by observing the low-temperature and pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive composition of Example 3 at a magnification of 100,000, respectively.
It is an M photograph. As in Example 2, the low-temperature-dried pressure-sensitive adhesive layer has a sea-island structure in which component A is sea and component B is an island. It is a sea-island structure. FIG. 4 (A) and FIG.
(B) shows that the low-temperature dried pressure-sensitive adhesive layer and the high-temperature dried pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of Example 5 were magnified by 4
It is a TEM photograph observed at 0,000. The low-temperature-drying pressure-sensitive adhesive layer shown in FIG. 4 (A) has a sea-island structure in which component A is a sea and component B is an island, although islands composed of component B are partially fused. Further, the high-temperature dried pressure-sensitive adhesive layer shown in FIG. 4B has a sea-island structure in which the sea-island is reversed and the component A is an island and the component B is a sea. In addition, the blank part seen in two places of the upper part of FIG. 4 (A) has a hole in a part of the section when creating an ultrathin section for observation.

On the other hand, in Comparative Examples 1 to 3, the pressure-sensitive adhesive layer before heating had a sea-island structure in which component A was the sea and component B was the island. The island did not reverse. For this reason, the heat-treated test piece remained substantially non-tacky, and the water resistance was poor due to the presence of a large amount of the hydrophilic component A on the surface of the pressure-sensitive adhesive layer. In Comparative Example 1, the component A in the sea in the pressure-sensitive adhesive layer before heating was a copolymer containing AMA, which is a crosslinkable monomer. It is probable that the movement of the coalescence was restricted and the sea-island did not reverse. The reason why the sea-island did not reverse in Comparative Example 2 is considered to be that the Tg of the component A was as extremely high as 171.5 ° C. The reason why the sea-island did not reverse in Comparative Example 3 is considered to be that the molecular chain of component A was as high as 60,000, so that the molecular chains were difficult to move.

Further, in Comparative Examples 4 and 5 containing no component A, the sea-island structure was not formed before and after heating, and the adhesive strength of the adhesive layer before heating was too high. It could not be used without subjecting the layer to a release treatment. Moreover, since it was composed only of the component B having high water resistance, the alkali releasability was insufficient.

TEM photographs of the pressure-sensitive adhesive layers formed from Comparative Examples 4 and 5 are shown in FIGS. 5 and 6. The black fine particles seen in the figure are presumed to be emulsifiers. FIG.
(A) and FIG. 5 (B) are TEM photographs of the low-temperature dried pressure-sensitive adhesive layer and the high-temperature dried pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of Comparative Example 4, respectively, at a magnification of 25,000.
Since Comparative Example 4 does not contain Component A, no sea-island structure was formed, and it was found that the structure of the pressure-sensitive adhesive layer was not changed by the heat treatment. FIG. 6 is a TEM photograph obtained by observing the low-temperature dried pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of Comparative Example 5 at a magnification of 20,000. As in Comparative Example 4, component A was not included. It turns out that it has not formed.

The present invention is not limited to the specific embodiments described above, but may be variously modified within the scope of the present invention in accordance with the purpose and application.

In the present invention, a water-soluble resin is used as the component A, but a water-dispersible resin composed of a resin having an acid value of 1 meq / g or more or a neutralized product of the resin with a base is used as the component A. In addition, it is possible to obtain a heat-sensitive adhesive composition that forms an adhesive layer exhibiting almost the same performance as the present invention, although the liquid stability is slightly lower than the composition of the present invention. is there. For example, when the polymer A2 was not neutralized in Synthesis Example 2, the obtained polymer A
Although 2 ′ was water-dispersible, when the pressure-sensitive adhesive composition adjusted in the same manner as in Example 6 using this polymer A2 ′ was evaluated, the pressure-sensitive adhesive strength before heating was low enough to be practically sufficient.
After heating, it showed practically sufficient adhesive strength, water resistance and alkali peelability.

[0111]

According to the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention or the heat-sensitive pressure-sensitive adhesive sheet of the present invention having this pressure-sensitive adhesive layer, the sea-island of the component A and the component B is reversed before and after the heat treatment. Thereby, while being substantially non-adhesive before heating, excellent adhesive strength can be exhibited after heating. At this time, since the pressure-sensitive adhesive layer after heating has a sea-island structure in which component A is an island and component B is a sea, the adhesive strength after heat treatment is lower than a structure in which component A and component B are uniformly mixed. Is good. In addition, since component A is discontinuously dispersed in component B,
If a material having a high alkali solubility or alkali swelling property is used as the component A, and a hydrophobic material is used as the component B, the pressure-sensitive adhesive composition or pressure-sensitive adhesive sheet of the present invention can have good water resistance and excellent alkali peelability. Can be used as an alkali-peelable heat-sensitive adhesive sheet having

Furthermore, since the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention has a sea-island structure in which component A is sea and component B is islands after heating, component A and component B are uniformly formed. The performance of the component B can be more strongly reflected on the pressure-sensitive adhesive layer after heating than in the case of mixing. Therefore, it is possible to efficiently design the pressure-sensitive adhesive composition.

[Brief description of the drawings]

FIG. 1A is a schematic diagram showing a state of a pressure-sensitive adhesive layer of the present invention before heat treatment, and FIG. 1B is a schematic diagram showing a state after heat treatment.

FIG. 2A is a TEM photograph showing the structure of an adhesive layer obtained by drying the adhesive composition of Example 2 at 40 ° C.
(B) is a TEM photograph showing the structure of the pressure-sensitive adhesive layer obtained by drying the pressure-sensitive adhesive composition of Example 2 at 140 ° C.

FIG. 3A is a TEM photograph showing the structure of a pressure-sensitive adhesive layer obtained by drying the pressure-sensitive adhesive composition of Example 3 at 40 ° C.
(B) is a TEM photograph showing the structure of the pressure-sensitive adhesive layer obtained by drying the pressure-sensitive adhesive composition of Example 3 at 140 ° C.

FIG. 4A is a TEM photograph showing the structure of a pressure-sensitive adhesive layer obtained by drying the pressure-sensitive adhesive composition of Example 5 at 40 ° C.
(B) is a TEM photograph showing the structure of the pressure-sensitive adhesive layer obtained by drying the pressure-sensitive adhesive composition of Example 5 at 140 ° C.

FIG. 5A is a TEM photograph showing the structure of a pressure-sensitive adhesive layer obtained by drying the pressure-sensitive adhesive composition of Comparative Example 4 at 40 ° C.
(B) is a TEM photograph showing the structure of the pressure-sensitive adhesive layer obtained by drying the pressure-sensitive adhesive composition of Comparative Example 4 at 140 ° C.

FIG. 6 is a TEM photograph showing the structure of a pressure-sensitive adhesive layer obtained by drying the pressure-sensitive adhesive composition of Comparative Example 5 at 40 ° C.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Iesako 1 at Funamicho, Minato-ku, Nagoya-shi, Aichi Prefecture Inside Nagoya Research Institute, Toagosei Co., Ltd. (72) Inventor Jin Kato Funami, Minato-ku, Nagoya-shi, Aichi No. 1 in the town, Nagoya R & D Co., Ltd.

Claims (5)

[Claims] An aqueous emulsion-type pressure-sensitive adhesive composition comprising the following component A and the following component B, which has a sea-island structure in which the following component A becomes a sea and the following component B becomes an island by drying at a temperature lower than 60 ° C. Form an adhesive layer, the adhesive layer,
A heat-sensitive adhesive composition comprising a sea-island structure in which the sea and islands are reversed by heat treatment at 60 ° C. or more, and the following component A is an island and the following component B is a sea. Component A: a water-soluble resin in which a resin having an acid value of 1 meq / g or more is neutralized with a base. Component B: a polymer having a glass transition temperature of −20 ° C. or lower, obtained by emulsion polymerization of a radical polymerizable monomer. 2. A composition comprising a component A and a component B, wherein the component A is a polymer emulsifier used in the emulsion polymerization of the component B, and the component B is a radical polymerizable monomer in the presence of the component A. The heat-sensitive adhesive composition according to claim 1, which is a polymer obtained by subjecting a polymer to emulsion polymerization. 3. The weight ratio of component A to component B is 10/90.
The heat-sensitive adhesive composition according to claim 1, wherein the ratio is from 50 to 50/50. 4. The component A is a neutralized product of a copolymer having α, β-ethylenically unsaturated carboxylic acid units and hydrophobic radically polymerizable monomer units as main constituent units. 2
Or the heat-sensitive adhesive composition according to 3. 5. A pressure-sensitive adhesive layer formed from the heat-sensitive pressure-sensitive adhesive composition according to any one of claims 1 to 4, having a sea-island structure in which component A is a sea and component B is an island. On a substrate, and has an adhesive strength of 10 g / 2 at a temperature of 25 ° C. by a 180 ° peeling method specified in JIS Z 0237.
A pressure-sensitive adhesive sheet having a size of 5 mm or less, wherein the heat treatment at 60 ° C. or higher causes the sea and islands of the pressure-sensitive adhesive layer to be reversed to form a sea-island structure in which component A is an island and component B is a sea, The adhesive strength is 100g / 25mm
A heat-sensitive adhesive sheet characterized by the above changes.