JP2000186232A - Re-releasable adhesive composition and re-releasable adhesive body using this - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a re-releasable adhesive composition which has a high adhesion property, is suitably used in tapes, labels, sheet, surface-protection films, etc., and stably exerts a sufficient sticking ability and releasability against an adherend, even when sticking and releasing are repeated under various environments. SOLUTION: A re-releasable adhesive composition comprises as a main agent a synthetic resin emulsion containing an adhesive acrylic polymer particle wherein the surface part (shell) and the inner part (core) are crosslinked. Preferably, the synthetic resin emulsion is in a state achieved by using a hydrophilic crosslinking agent in combination with a lipophilic crosslinking agent, a state wherein the hydrophilic crosslinking agent is a monomer having a silyl group and the lipophilic crosslinking agent is a monomer having two or more radical polymerizable unsaturated bonds, a state wherein the hydrophilic crosslinking agent is a polymerizable surfactant having two or more radical polymerizable unsaturated bonds and the lipophilic crosslinking agent is a monomer having a silyl group, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a removable pressure-sensitive adhesive composition and a removable pressure-sensitive adhesive, and more particularly, has excellent adhesiveness and can be suitably used for tapes, labels, sheets, surface protective films and the like. Removable pressure-sensitive adhesive composition which stably exhibits sufficient adhesiveness / peelability to an adherend even after repeated bonding / peeling under various environments, and the removable pressure-sensitive adhesive composition The present invention relates to a re-peelable pressure-sensitive adhesive body which is excellent in repeated sticking property and releasability by using.

[0002]

2. Description of the Related Art Conventionally, pressure-sensitive adhesive sheets have been processed into labels, seals, stickers, patches, and the like, and have been used in a very wide range of applications such as commercial use, office use, and home use. The pressure-sensitive adhesive sheet usually has a base material having a pressure-sensitive adhesive layer and a release sheet that is peelably adhered to the pressure-sensitive adhesive layer. In addition, paper, a film, a metal foil, or the like is used for the base material, and a high density base paper such as glassine paper, a clay-coated paper, a polyethylene laminate base paper, or the like is used for the release of a silicone compound or a fluorine compound. A coating agent is used, and in the pressure-sensitive adhesive layer, various types of pressure-sensitive adhesives such as rubber-based, acrylic-based, and vinyl ether-based, solvent-based, or solvent-free adhesives are used.

[0003] The pressure-sensitive adhesive sheet is an important factor that characterizes the pressure-sensitive adhesive sheet, because its properties, uses, and the like differ depending on the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer.

[0004] Among the above-mentioned pressure-sensitive adhesives, solvent-type pressure-sensitive adhesives have been widely used in the past. However, from the viewpoint of improving the global environment and working environment, recently, aqueous emulsion-type pressure-sensitive adhesives having little influence on the environment have been used. Adhesives have now come to be widely used. As this aqueous emulsion type pressure-sensitive adhesive, for example, mainly produced by an emulsion polymerization method,
Emulsions containing a (meth) acrylate ester having an alkyl group having 8 or less carbon atoms as a main component are used for general-purpose label applications.

[0005] The pressure-sensitive adhesive sheet is a permanent pressure-sensitive adhesive sheet (permanent pressure-sensitive adhesive sheet) which is used while being permanently adhered to an adherend such as a product, and the pressure-sensitive adhesive sheet is adhered to an adherend such as a product. After that, there is a removable adhesive sheet (removable adhesive sheet) which is peeled off and discarded from the adherend after the predetermined purpose is achieved, and a removable adhesive sheet using the aqueous emulsion type adhesive, It is mainly classified into adhesive sheets.

[0006] The re-peelable pressure-sensitive adhesive sheet has recently attracted attention among the pressure-sensitive adhesive sheets from the viewpoint of effective use of resources. For example, the pressure-sensitive adhesive sheet currently used for packing cardboard is difficult to peel off, which is one of the factors that hinders efficient recycling of cardboard, and there is a problem from the viewpoint of effective use of resources.

However, the aqueous emulsion-type pressure-sensitive adhesive used in the conventional re-peelable pressure-sensitive adhesive sheet has a sufficient re-peelability, but is insufficient in adhesiveness and cannot be put to practical use. Even if it has adhesiveness and removability, there is a problem that when it is exposed to a high temperature, the adhesive force increases with time and the removability becomes poor. Specifically, Japanese Patent Application Laid-Open Nos. 10-183083 and 10-4
In the case of an aqueous emulsion-type pressure-sensitive adhesive described in JP-A-6118, JP-A-62-129374, etc., an alkoxysilyl group-containing monomer and a radical polymerizable surfactant are used. There is a problem that the re-peelable pressure-sensitive adhesive sheet using is difficult to peel off when left at a high temperature for a long time.

In recent years, the re-peelable pressure-sensitive adhesive sheet has been frequently used as a price tag or a label for process control which is frequently replaced. The re-peelable pressure-sensitive adhesive sheet does not contaminate the adherend when it is finally peeled off, in other words, the pressure-sensitive adhesive can be easily removed without remaining on the adherend which is a product (no adhesive residue). It can be peeled, and further, regardless of the material of the adherend, it is required as a basic performance that it can be peeled not only in the initial stage of use but also in a state where no adhesive remains even after repeated use, and has excellent re-peelability, At present, there is no device that has sufficient basic performance.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, the present invention has excellent adhesiveness, and can be suitably used for tapes, labels, sheets, surface protective films, and the like,
A re-peelable pressure-sensitive adhesive composition that stably exhibits sufficient adhesiveness and releasability even on an adherend even when repetition of re-peeling and peeling under various environments, and the re-peelable pressure-sensitive adhesive composition An object of the present invention is to provide a re-peelable pressure-sensitive adhesive body which is excellent in repeated sticking property and releasability by being used.

[0010]

Means for solving the above problems are as follows. That is, <1> a removable adhesive composition containing a synthetic resin emulsion containing an adhesive acrylic polymer particle having a crosslinked surface layer (shell) and internal (core) as a main component. . <2> The removable pressure-sensitive adhesive composition according to <1>, wherein the synthetic resin emulsion is obtained by using a hydrophilic crosslinking agent and a lipophilic crosslinking agent in combination. <3> Removability according to <2>, wherein the hydrophilic crosslinking agent is a monomer having a silyl group, and the lipophilic crosslinking agent is a monomer having two or more radically polymerizable unsaturated bonds. It is an adhesive composition. <4> The method according to <2>, wherein the hydrophilic crosslinking agent is a polymerizable surfactant having two or more radically polymerizable unsaturated bonds, and the lipophilic crosslinking agent is a monomer having a silyl group. It is a peelable pressure-sensitive adhesive composition. <5> A removable adhesive having the removable adhesive composition according to any one of <1> to <4> on a substrate.

In the removable pressure-sensitive adhesive composition according to the above <1>, the main component is a synthetic resin emulsion containing adhesive acrylic polymer particles having a crosslinked surface layer (shell) and internal (core). Therefore, the removability does not decrease even when exposed to a high temperature condition for a long time. That is, the acrylic polymer particles are easily moved by heat,
Since both the inside and the surface layer are cross-linked, thermal motion is effectively suppressed. When the acrylic polymer particles are not crosslinked, under long-term high-temperature conditions, the thermal motion is not suppressed, and the particles are fluidized and the wettability with the adherend is improved, so that the concave portion on the surface of the adherend is improved. And exerts an anchor effect, so that the adhesiveness increases and the releasability decreases. However, in the case of the acrylic polymer particles, the inside is cross-linked, and the surface layer portion is also cross-linked within a range that does not adversely affect the adhesiveness, so that the thermal motion of the entire particle is effectively suppressed, The peelability does not decrease even under long-term high temperature conditions.

In the removable pressure-sensitive adhesive composition according to the item <2>, since the synthetic resin emulsion is obtained by using a hydrophilic cross-linking agent and a lipophilic cross-linking agent in combination, the inside and the surface layer of the acrylic polymer particles can be obtained. The part is crosslinked. During the polymerization of the acrylic polymer particles, the hydrophilic cross-linking agent is easily present in the vicinity of the surface of the particle, and conversely, the lipophilic cross-linking agent is easily present inside the particle, and the inside of the particle and the surface Acrylic polymer particles whose parts are crosslinked are obtained. As a result, the thermal motion of the whole particles is effectively suppressed, so that the releasability does not decrease even under a long-term high-temperature condition.

[0013] In the removable pressure-sensitive adhesive composition according to the above <3>, the hydrophilic crosslinking agent is a monomer having a silyl group, and the lipophilic crosslinking agent has two radical polymerizable unsaturated bonds. Since it is a monomer having the above, the cross-linking of the inside of the particles and the surface layer portion is stronger, and the thermal motion of the obtained acrylic polymer particles as a whole is more effectively suppressed. Does not drop.

[0014] In the removable pressure-sensitive adhesive composition according to <4>, the hydrophilic crosslinking agent is a polymerizable surfactant having two or more radically polymerizable unsaturated bonds, and the lipophilic crosslinking agent is Since it is a monomer having a silyl group, the inside and the surface layer of the particles are more strongly crosslinked, and the thermal motion of the entire acrylic polymer particles obtained is more effectively suppressed. The peelability does not decrease. Moreover, since the emulsifier is bonded to the polymer by radical polymerization, contamination of the adherend and adhesive residue at the time of re-peeling are effectively suppressed.

The removable pressure-sensitive adhesive body according to the above <5> has the removable pressure-sensitive adhesive composition according to any one of the above <1> to <4> on a substrate, so that it can be used under long-term high-temperature conditions. However, the releasability does not decrease, and the repetitive adhesion and removability are excellent.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The removable pressure-sensitive adhesive composition of the present invention comprises a synthetic resin emulsion containing substantially tacky acrylic polymer particles having a surface layer (shell) and an internal (core) crosslinked. As a main ingredient, it contains other components selected as necessary. Further, the removable adhesive of the present invention has the removable adhesive composition of the present invention on a substrate. Hereinafter, the removable pressure-sensitive adhesive composition and the removable pressure-sensitive adhesive body of the present invention will be described.

(Synthetic Resin Emulsion) The synthetic resin emulsion contains adhesive acrylic polymer particles. The synthetic resin emulsion, a monomer composition,
It is obtained by emulsion polymerization using a polymerizable surfactant as an emulsifier.

-Monomer composition- The monomer composition contains a crosslinkable monomer, a main monomer, and other components.

--Crosslinkable monomer-- The crosslinkable monomer can be appropriately selected from known ones. For example, a monomer having two or more radically polymerizable unsaturated bonds, a silyl group And a monomer having the formula:

Examples of the monomer having two or more radically polymerizable unsaturated bonds include divinyl compounds, di (meth) acrylate compounds, tri (meth) acrylate compounds, tetra (meth) acrylate compounds, diallyl compounds, triallyl compounds And a tetraallyl compound. Specifically, divinylbenzene, divinyl adipate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate , Neopentyl glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,3-butyl di (meth) acrylate, trimethylolethanetri (meth) acrylate, trimethylolpropanetri (meth) acrylate, Dipentaerythritol (meta)
Acrylate, diallyl phthalate, triallyl dicyanurate, tetraallyloxyethane and the like can be mentioned. Among these, tetraallyloxyethane, divinylbenzene, ethylene glycol di (meth) acrylate, and the like are preferable in terms of easy copolymerization, polymerization stability, and uniform crosslinking.

As the monomer having a silyl group, for example, an organoalkoxysilyl group-containing monomer is preferably exemplified. For example, vinyltrimethoxysilane,
Vinyl methyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxysilane, vinyl (2-methoxyethoxy) silane, vinylalkoxysilane such as vinyltriacetoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyl Epoxyalkoxysilanes such as methyldimethoxysilane, 3,4-epoxycyclohexylethyltrimethoxysilane, 3,4-epoxycyclohexylethyldimethoxysilane, mercaptoalkoxysilanes such as γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethylsilane Methoxysilane, γ-methacryloxypropyltriethoxysilane, and the like.

These crosslinkable monomers may be used alone or in combination of two or more. In the present invention, among these crosslinking monomers, various types of monomers having two or more radically polymerizable unsaturated bonds, γ-
Mercaptoalkoxysilanes such as mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropyltriethoxysilane can be used as the lipophilic crosslinking agent. The use of the lipophilic crosslinking agent is preferable in that the inside of the acrylic polymer particles can be crosslinked.
Further, among these crosslinking monomers, vinyltriethoxysilane, vinylmethoxyethoxysilane and the like can be used as a hydrophilic crosslinking agent. These are preferred in that they can crosslink the surface layer of the acrylic polymer particles.

The amount of the crosslinkable monomer used is preferably from 0.01 to 5% by weight based on all monomers. When the amount is less than 0.01 part by weight, the change with time in the adhesive force at high temperature becomes large, and the removability may be impaired. When the amount exceeds 5% by weight, the adhesiveness decreases. (Especially, the initial adhesive strength is reduced.) A good removable adhesive may not be obtained.

--Main monomer-- The main monomer is a monomer component that forms the skeleton of the adhesive acrylic polymer particles.
Preferable examples include alkyl (meth) acrylate having an alkyl group having 2 to 14 carbon atoms. Specific examples include ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl. Examples include methacrylate, n-, t-, and iso-butyl methacrylates, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, and cyclohexyl acrylate. These may be used alone or in combination of two or more.

Examples of the copolymerizable monomer include aromatic vinyl compounds such as ethylene, vinyl chloride, vinylidene chloride, styrene and methyl styrene, vinyl acetate, vinyl propionate, and vinyl esters of branched carboxylic acids. Ethyl esters of vinyl esters, vinyl phosphate, acrylonitrile, N-methylolacrylamide, glycidyl methacrylate, 2-hydroxyalkyl acrylate, alkoxyethyl acrylate, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, etc. Carboxylic acid, and the like. These may be used alone or in combination of two or more. Among these, butyl acrylate, 2 butyl acrylate, and butyl acrylate are required in order for the obtained acrylic polymer particles to exhibit tackiness, in other words, in order for the glass transition temperature (Tg) to be −20 ° C. to −60 ° C. -Ethylhexyl acrylate is preferably used, and in addition, methacrylic acid and acrylic acid are preferably used in view of the dispersion stability of the acrylic polymer particles in the synthetic resin emulsion. The use amount of methacrylic acid and acrylic acid is preferably 0.2 to 10% by weight based on all monomers. The used amount of the methacrylic acid and acrylic acid is 0.2
If the amount is less than 10 parts by weight, the change with time of the adhesive strength at high temperature becomes large, and the removability may be impaired. If the amount exceeds 10% by weight, the adhesiveness is reduced (particularly, the initial adhesive strength is reduced. ) A good removable adhesive may not be obtained.

--Other components-- The other components are not particularly limited and may be appropriately selected depending on the intended purpose within a range not to impair the effects of the present invention. Such as monomers, polymerization initiators, aqueous media, reaction buffers, chain transfer agents, thickeners, wetting agents, preservatives, tackifiers, defoamers, colorants, pigments, etc. No particular limitation is imposed as long as it is used and when it is used for producing a pressure-sensitive adhesive composition.

The polymerization initiator can be used without any particular limitation as long as it can be used for ordinary emulsion polymerization. For example, persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate, hydrogen peroxide, butyl Examples include organic peroxides such as peroxides, and redox-based polymerization initiators obtained by combining these with a reducing agent. These may be used alone or in combination of two or more. Among these, Redox-based polymerization initiators are preferred in that they can increase the degree of polymerization of the polymer and suppress changes over time in adhesive strength.

The aqueous medium is not particularly limited.
It can be appropriately selected according to the purpose, and examples thereof include water, a mixed solution of water and a water-soluble solvent such as alcohol.

Examples of the reaction buffer include sodium acetate, ammonium acetate, sodium diphosphate and the like. These may be used alone or in combination of two or more.

Examples of the chain transfer agent include alcohols such as methanol, ethanol, propanol and butanol, acetone, methyl ethyl ketone, cyclohexane, acetophenone, acetaldehyde, propionaldehyde, n-butyraldehyde, furfural and benzaldehyde. And carboxylic acids of No. 8, dodecyl mercaptan, lauryl mercaptan, normal mercaptan, thioglycolic acid, octyl thioglycolate (TGO), mercaptans such as thioglycerol, and the like. These may be used alone or in combination of two or more.

Examples of the thickener include polyvinyl alcohol and its derivatives, hydroxyethyl cellulose, methyl cellulose, starch derivatives, polyvinyl pyrrolidone, water-soluble polyurethane resins, water-soluble acrylic resins,
Examples include a water-soluble polycarboxylic acid resin and an alkali-thickened acrylic resin emulsion. These may be used alone or in combination of two or more.

The wetting agent includes, for example, organic solvents such as alcohol having a surface tension lowering ability, and surfactants having a surface tension lowering ability. Surfactants having a reducing ability are preferred. Examples of the surfactant having the surface tension lowering ability include an anionic fluorinated surfactant (for example, perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl phosphate, etc.), cationic Fluorosurfactants (for example,
Perfluoroalkyltrimethylammonium salts, etc.) amphoteric fluorinated surfactants (eg, perfluoroalkylbetaine, etc.), nonionic fluorinated surfactants (eg, perfluoroalkylamine oxide, perfluoroalkylethylene oxide adducts, etc.), alkyl Sulfosuccinates (eg, dioctylsulfosuccinate, etc.), polyoxyalkylene alkyl ether phosphates (eg, polyoxyalkylene alkyl ether phosphonates, polyoxyalkylene alkyl ether phosphates, etc.), alkyl allyl sulfonates and Condensates, alkyl sulfates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl phenyl ether sulfates, polyoxyethylene alkyl ethers, polyoxyethylene Chi alkylphenyl ethers, polyoxyethylene sorbitan fatty acid esters, and the like. These may be used alone or in combination of two or more. Among these, anionic fluorine-based surfactants and nonionic fluorine-based surfactants are preferred.

-Emulsifier- The emulsifier is not particularly limited as long as it can be used in ordinary emulsion polymerization, and examples thereof include anionic surfactants, nonionic surfactants, cationic surfactants, Nonionic protective colloids, anionic protective colloids, cationic protective colloids and the like can be mentioned. These emulsifiers may be used alone,
Two or more kinds may be used in combination.

Among these emulsifiers, it is preferable to use at least one of the above-mentioned anionic surfactant and the above-mentioned nonionic surfactant for emulsion polymerization of the above-mentioned main monomer, that is, the alkyl (meth) acrylate. It is.

Examples of the anionic surfactant include alkyl or alkyl allyl sulfonates, such as sodium alkyl benzene sulfonate, sodium alkyl sulfonate, sodium polyoxyethylene alkyl ether sulfonate, alkyl or alkyl allyl sulfate, and dialkyl. Sulfosuccinate, and the like.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether type, polyoxyethylene alkyl phenyl ether type, polyoxyethylene carboxylic acid ester type, polyoxyethylene glycol or polyoxypropylene glycol type. No.

Also, a polymerizable surfactant having a radical polymerizable unsaturated bond can be suitably used, and specific examples thereof include the following compounds (1) to (5). These may be used alone or in combination of two or more.

Compound (1)

Embedded image

Compound (2)

Embedded image

Compound (3)

Embedded image

Compound (4)

Embedded image

Compound (5)

Embedded image

Among the above-mentioned polymerizable surfactants having a radical polymerizable unsaturated bond, polymerizable surfactants having two or more radical polymerizable unsaturated bonds are used as a crosslinking agent, in particular, a hydrophilic crosslinking agent in the present invention. It is preferably used because it does not contaminate the adherend and can reduce adhesive residue, and the polymerizable surfactant having two or more radical polymerizable unsaturated bonds is preferably used. When used as part of an emulsifier, the polymerizable surfactant having two or more radically polymerizable unsaturated bonds exhibits the same action as a hydrophilic crosslinking agent, and can crosslink the surface layer of the acrylic polymer particles, This is preferable in that a change with time in the adhesive force of the removable pressure-sensitive adhesive composition can be effectively suppressed, and the removable property can be improved.

The use amount of the emulsifier is preferably 0.5 to 5.0% by weight based on the main monomer. If the amount is less than 0.5% by weight, aggregates may be generated during the emulsion polymerization, and the polymerization stability may be poor. When peeling the removable adhesive using the removable adhesive composition, the adhesive may remain on the adherend.

-Emulsion Polymerization- The method of the emulsion polymerization is not particularly limited and can be appropriately determined according to the purpose. For example, the emulsifier, water, the crosslinkable monomer, The main monomer is charged, the temperature is increased, and a batch polymerization method in which the polymerization is allowed to proceed by adding the polymerization initiator or the like, or the emulsifier, water, and the crosslinkable monomer are charged in a polymerization vessel, and the temperature is increased. do it,
A monomer dropping method of dropping the main monomer, or
In the monomer dropping method, an emulsified monomer dropping method in which the main monomer to be dropped is emulsified in advance with the emulsifier and water and then dropped, may be mentioned. Among these, the method of dropping the emulsified monomer composition is preferable from the viewpoint of polymerization stability. In the present invention, it is preferable to use the lipophilic crosslinking agent and the hydrophilic crosslinking agent in combination during the emulsion polymerization. In this case, the acrylic polymer particles in which the inside (core) of the acrylic polymer particles are cross-linked by the lipophilic cross-linking agent, the surface layer (shell) is cross-linked by the hydrophilic cross-linking agent, and the inside and the surface layer are cross-linked, respectively. It is preferable in that polymer particles can be obtained. At the time of the emulsion polymerization, the amount of the lipophilic cross-linking agent and the hydrophilic cross-linking agent to be used is set to 0.1 to all monomers.
It is preferably from 01 to 3% by weight. The usage amount is
If the content is less than 0.01% by weight, adhesive residue may be left,
If it exceeds 3% by weight, the tackiness and anchoring properties may be reduced. By this emulsion polymerization, the synthetic resin emulsion is obtained.

-Adhesive Acrylic Polymer Particles- The synthetic resin emulsion thus obtained contains substantially adhesive acrylic polymer particles. The term “substantially tacky” as used herein means that, after applying and drying a synthetic resin emulsion containing acrylic polymer particles, the layer exhibits tackiness at normal temperature by finger tack, As a measure of the tackiness, the glass transition point (Tg) calculated by the Fox equation of the polymer is −
The temperature is preferably from 20C to -60C. If the glass transition temperature (Tg) is higher than -20 ° C, the adhesive strength may be insufficient, and if it is lower than -60 ° C, the change over time in the adhesive strength may increase.

In the acrylic polymer particles,
The surface layer (shell) and the inside (core) have a crosslinked structure. The presence or absence of the crosslinked structure can be verified, for example, as follows. That is, a film of the synthetic resin emulsion is prepared, toluene is applied to the film, an uncrosslinked polymer component is extracted, and a ratio (%) of a residue that cannot be extracted, that is, a toluene insoluble content (%) is calculated. The crosslinked structure of the surface layer (shell) and the interior (core) can be verified based on the state at the time of dissolving and dipping the film and the toluene insoluble content (%).

When the toluene insoluble content is less than 10% and the whole is in a swollen state, only the surface layer (shell) is in a crosslinked state, and when the toluene insoluble content is less than 90% is partially swollen, the inside ( Core) is in a cross-linked state and 90
In the case of １００100%, the film hardly dissolves and swells, and it is estimated that the surface layer (shell) and the inside (core) are in a crosslinked state.

The removable pressure-sensitive adhesive composition of the present invention comprises the above-mentioned synthetic resin emulsion as a main component, and the content of the synthetic resin emulsion in the removable pressure-sensitive adhesive composition is 7%.
It is preferably from 0 to 100% by weight, more preferably from 90 to 100% by weight. The removable pressure-sensitive adhesive composition of the present invention may contain other components selected as necessary within a range that does not impair the effects of the present invention. The same thing as the other component contained in a body composition is mentioned.

The removable pressure-sensitive adhesive composition of the present invention is applied on a substrate appropriately selected according to the purpose according to known methods and conditions, and dried to form a desired pressure-sensitive adhesive layer. Can be. The pressure-sensitive adhesive layer of the removable pressure-sensitive adhesive composition of the present invention has excellent adhesiveness, and has sufficient adhesiveness and peelability to an adherend even when repeatedly bonded and peeled in various environments. It can be easily peeled off even if left at a high temperature for a long time after sticking to an adherend, and can be stuck again once peeled.

The removable adhesive of the present invention has the removable adhesive composition on a substrate. The size, shape, structure, material, and the like of the substrate are not particularly limited and can be appropriately selected depending on the purpose. For example, when the material of the base material is paper, plastic film, or the like, the removable adhesive can be various tapes, labels, sheets, surface protective films, and the like. The re-peelable pressure-sensitive adhesive body is excellent in repeated sticking property and peeling property.

[0052]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1 Preparation of Emulsion Monomer Composition The following components were blended in a stainless steel reactor and emulsified while stirring with a mixer. 2-ethylhexyl acrylate 45 parts by weight Butyl acrylate 50 parts by weight Methyl methacrylate 5 parts by weight Acrylic acid 2 parts by weight 2-hydroxyethyl methacrylate・ ・ 1 part by weight γ-methacryloxypropyltrimethoxysilane ・ ・ ・ 0.05 parts by weight (lipophilic cross-linking agent) Water ・ ・ ・ ・ ・ ・ ・ ・ ・35 parts by weight Polyoxyethylene alkylpropenyl phenyl ether sulfate ammonium salt 2.0 parts by weight (di) methacrylic acid acid phosphate ester 0.5 parts by weight

-Emulsion polymerization- In a flask equipped with a stirrer, a thermometer, a condenser and a nitrogen inlet tube, 27 parts by weight of water and 1.0 part by weight of disodium hydrogen phosphate were charged, and the temperature was raised to 55 ° C under a nitrogen atmosphere. 5% and 10% of the emulsified monomer composition prepared in advance.
1.0 part by weight of a 5% ammonium persulfate solution and 1 part by weight of a 5% aqueous sodium sulfite solution were added, and the initial polymerization was carried out for 40 minutes. Subsequently, the remaining emulsified monomer composition and 10
2 parts by weight of a 5% aqueous ammonium persulfate solution and 4 parts of a 5% aqueous sodium acid sulfite solution were continuously dropped. After the completion of the dropwise addition, the reaction was continued at the same temperature for another 1.5 hours to complete the polymerization. Thereafter, 2.5% by weight of 10% aqueous ammonia was added for neutralization to obtain a synthetic resin emulsion.

-Production of Removable Adhesive Composition- An antifoaming agent, a wetting agent and a preservative are added to the obtained synthetic resin emulsion, and water is adjusted so as to have a non-volatile content of 55%. The viscosity was adjusted to 4000 to 6000 (BL viscometer, 12 rpm) to obtain a removable adhesive composition.

(Examples 2 to 5) The procedure of Example 1 was repeated, except that the emulsified monomer composition was changed as shown in Table 1.

(Comparative Examples 1 and 2) The procedure of Example 1 was repeated, except that the emulsified monomer composition was changed as shown in Table 2.

<Evaluation> The following evaluation was performed on the obtained removable pressure-sensitive adhesive composition, and the results are shown in Tables 3 and 4.

<Verification of Crosslinking Property> The removable pressure-sensitive adhesive composition obtained was dried and formed into a film, and its weight was measured.
This is extracted with toluene at room temperature for 24 hours, and the state and weight of the remaining film are measured. From this, the toluene insoluble content (%) was calculated by the following formula, and evaluated based on the following criteria. ×: poor crosslinking 10% ≦ toluene insoluble content <90% △: insufficient crosslinking 90% ≦ toluene insoluble % <100% .....: Good crosslinkability

[0060]

(Equation 1)

<Adhesive Strength and Removability> The obtained removable pressure-sensitive adhesive composition was applied to a paper substrate by a bar coater using a bar coater.
g / m ² (dry) and dried at 100 ° C. for 1 minute to prepare a removable adhesive (removable adhesive sheet). This was adhered to a cardboard and crimped at ² kgf / m ² . After attaching the re-peelable pressure-sensitive adhesive sheet, after 24 hours at room temperature and 50 ° C. × 24 hours, the adhesive sheet is peeled off, and its adhesive force is measured by an autograph (manufactured by Shimadzu Corporation;
CS-2000). Here, those having an increase in adhesive strength after aging of less than 2.0 N / 25 mm were evaluated as having good re-peelability after thermal aging, with respect to re-peelability.

[0062]

[Table 1]

[0063]

[Table 2]

In Tables 1 and 2, the components of methyl methacrylate, acrylic acid, 2-hydroxyethyl methacrylate, water and emulsifier are omitted. In Tables 1 and 2, "BA" means butyl acrylate, "2EHA" means 2-ethylhexyl acrylate, and "crosslinking agent a" means vinyl triethoxysilane (hydrophilic). And "crosslinking agent b" means vinylmethoxyethoxysilane (hydrophilic), and "crosslinking agent c"
Means γ-methacryloxypropyltrimethoxysilane (lipophilic), “crosslinking agent d” means divinylbenzene (lipophilic), and “crosslinking agent e” means triallyl isocyanurate (lipophilic). Means “crosslinking agent f”
It means ethylene glycol dimethacrylate (lipophilic).

[0065]

[Table 3]

[0066]

[Table 4]

As is clear from the results in Tables 3 and 4, in the case of the removable adhesive composition of the present invention and the removable adhesive body using the same, the toluene-insoluble content was 10%.
0%, which indicates that the acrylic polymer particles are rich in crosslinkability and that the inside and the surface layer of the acrylic polymer particles are crosslinked. By including these particles, the initial adhesive strength (adhesive strength) is good, and even after aging under a different environment, the peel strength is not increased and the peeling becomes difficult. It was excellent in property and was rich in repeated sticking property and peeling property. On the other hand, in the case of the comparative example, the crosslinkability of the acrylic polymer particles was not sufficient, the peelability of the re-peelable pressure-sensitive adhesive composition was inferior, and the adhesive force significantly increased after a lapse of time in different environments. Was inferior in sticking property and adhesiveness.

[0068]

According to the present invention, the above-mentioned conventional problems can be solved. Further, according to the present invention, it is excellent in adhesiveness, and can be suitably used for tapes, labels, sheets, surface protective films, etc., and can be sufficiently adhered to an adherend even when repeatedly adhered and peeled in various environments. Provided is a re-peelable pressure-sensitive adhesive composition stably exhibiting adhesive property and releasability, and a re-peelable pressure-sensitive adhesive body having excellent repetitive adhesive property and releasability by using the re-peelable pressure-sensitive adhesive composition. be able to.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J004 AA10 AB01 CB02 CB03 CC02 FA04 4J038 CG142 EA011 KA03 KA09 MA02 MA08 MA10 NA10

Claims (5)

[Claims] 1. A removable pressure-sensitive adhesive composition comprising, as a main component, a synthetic resin emulsion containing pressure-sensitive acrylic polymer particles whose surface layer (shell) and inside (core) are crosslinked. 2. The removable pressure-sensitive adhesive composition according to claim 1, wherein the synthetic resin emulsion is obtained by using a hydrophilic crosslinking agent and a lipophilic crosslinking agent in combination. 3. The re-stripping according to claim 2, wherein the hydrophilic crosslinking agent is a monomer having a silyl group, and the lipophilic crosslinking agent is a monomer having two or more radically polymerizable unsaturated bonds. Adhesive composition. 4. The method according to claim 2, wherein the hydrophilic crosslinking agent is a polymerizable surfactant having two or more radically polymerizable unsaturated bonds, and the lipophilic crosslinking agent is a monomer having a silyl group. Removable pressure-sensitive adhesive composition. 5. A removable adhesive comprising the removable pressure-sensitive adhesive composition according to claim 1 on a substrate.