JP4707982B2 - Re-peelable water-based adhesive composition - Google Patents

Description

  The present invention can be used for applications such as pressure-sensitive adhesive tapes, pressure-sensitive adhesive sheets, pressure-sensitive adhesive labels, and surface protective films, and is excellent in adhesiveness, holding power, water resistance, and heat-resistant coloring property to various adherends, and after re-peeling. One-pack type re-peelable water-based pressure-sensitive adhesive composition that has excellent anti-staining properties such as no adhesive residue, and has little deterioration in initial adhesive strength over time even when used on a vinyl chloride resin substrate containing a plasticizer It is about.

Conventionally, re-peelable pressure-sensitive adhesive compositions have been widely used for applications such as pressure-sensitive adhesive tapes, pressure-sensitive adhesive sheets, pressure-sensitive adhesive labels, and surface protective films.
In recent years, from the viewpoint of environmental hygiene, various studies have been conducted on water-dispersed pressure-sensitive adhesives that do not use a solvent even in a re-peelable pressure-sensitive adhesive composition. For example, improvement of re-peelability and contamination resistance during re-peeling A) 50 to 99.9% by weight of an acrylate monomer having an alkyl group having 2 to 14 carbon atoms, b) 0.1 to 5% by weight of a carboxyl group-containing monomer, c) A water-soluble crosslinking agent containing an oxazoline group is added to a water-dispersed copolymer of a monomer mixture composed of 0 to 49.9% by weight of a monomer copolymerizable with the components a and b. The oxazoline group is added in an amount of 0.1 to 5 equivalents per equivalent of the carboxyl group contained in the solvent, the solvent-soluble component is 40% by weight or less, and the elastic modulus is ² to 50 kg / cm ² . Re-peeling pressure-sensitive contact with a peeling force of 500 g / 20 mm width or less An adhesive (for example, see Patent Document 1), a) 50 to 99.9% by weight of an acrylate monomer having an alkyl group having 2 to 14 carbon atoms, and b) a carboxyl group-containing monomer 0.1. A water-dispersed acrylate copolymer of a monomer mixture consisting of 0 to 49.9% by weight of the monomer a copolymerizable with the components a and b, containing carbodiimide groups. The crosslinking agent is blended so that the ratio of the carbodiimide group to the carboxyl group of the copolymer (carbodiimide group / carboxyl group) is 0.1 to 5.0, and the removability is 500 g / 20 mm width or less. A certain water dispersion type pressure sensitive adhesive for re-peeling (for example, refer to Patent Document 2) has been proposed.
Japanese Patent Laid-Open No. 10-114887 JP 2001-131512 A

However, in the disclosed technologies of Patent Documents 1 and 2, regarding removability, Patent Document 1 has an elapsed time of about 20 minutes at 23 ° C. after pasting, and Patent Document 2 also has a time of 24 hours at 23 ° C. and 65% RH after pasting. However, it does not satisfy the recent required performance, and the re-peelability over a longer time is required.
In addition, the above disclosed technology only considers removability only on a specific adherend such as a melamine coated plate and a stainless steel plate, and also does not consider water resistance and heat resistance coloration, and further improvements are made. There is also a need for a re-peelable water-based pressure-sensitive adhesive composition that is less likely to reduce initial adhesive strength over time even when used with a vinyl chloride resin substrate containing a plasticizer.

  Therefore, in the present invention, under such a background, excellent adhesion to various adherends, holding power, water resistance, heat-resistant coloring, and excellent stain resistance such as no adhesive residue after re-peeling, Furthermore, it is an object of the present invention to provide a one-component re-peelable water-based pressure-sensitive adhesive composition that causes little decrease in initial adhesive strength over time even when used with a vinyl chloride resin substrate containing a plasticizer. .

However, as a result of intensive studies in view of such circumstances, the present inventor has found that (meth) acrylic acid alkyl ester (a1) containing an alkyl group having 4 to 12 carbon atoms is contained in an amount of 50 to 99.9% by weight and containing no carboxyl group. A monomer mixture containing 0.1 to 20% by weight of a saturated monomer (a2) and 0 to 49.9% by weight of another unsaturated monomer (a3), an anionic reactive emulsifier , and a chain transfer agent A re-peelable aqueous pressure-sensitive adhesive composition comprising an emulsion [A] having a gel fraction of less than 70% by weight and a crosslinking agent [B] obtained by emulsion polymerization in the presence of The present invention was completed.

  In the present invention, in particular, the cross-linking agent [B] is at least one selected from the oxazoline-based compound (b1), the carbodiimide-based compound (b2), and the metal-based compound (b3), so that the adhesive force change with time is small. It is preferable in that it is excellent in removability and can be used as a one-component pressure-sensitive adhesive composition containing a crosslinking agent.

The re-peelable water-based pressure-sensitive adhesive composition of the present invention comprises (meth) acrylic acid alkyl ester (a1) 50 to 99.9% by weight, carboxyl group-containing unsaturated monomer containing an alkyl group having 4 to 12 carbon atoms. A monomer mixture containing (a2) 0.1 to 20% by weight and other unsaturated monomer (a3) 0 to 49.9% by weight in the presence of an anionic reactive emulsifier and a chain transfer agent Since it contains an emulsion [A] obtained by emulsion polymerization and having a gel fraction of less than 70% by weight and a crosslinking agent [B], it is excellent in adhesiveness, holding power, water resistance, and heat-resistant colorability. Excellent anti-contamination property that there is no adhesive residue after re-peeling. In addition, it has the effect that there is little decrease in initial adhesive strength over time even when used with a vinyl chloride resin base material containing a plasticizer. It is.

The present invention is described in detail below.
The emulsion [A] of the present invention is a (meth) acrylic acid alkyl ester (a1) containing a C 4-12 alkyl group, a carboxyl group-containing unsaturated monomer (a2), or other unsaturated monomer. It is obtained by emulsion polymerization of a monomer mixture containing (a3).

  The (meth) acrylic acid alkyl ester (a1) containing an alkyl group having 4 to 12 carbon atoms is not particularly limited. For example, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-hexyl (meth) Acrylate, 2-ethylhexyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, isooctyl (meth) acrylate, n-octyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl ( (Meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, isoundecyl (meth) acrylate, dodecyl (meth) acrylate, isododecyl (meth) acrylate, and the like. ) Acrylate, 2-ethylhexyl acrylate are preferably used. These may be used alone or in combination of two or more.

  The carboxyl group-containing unsaturated monomer (a2) is not particularly limited, and examples thereof include acrylic acid, acrylic acid dimer, methacrylic acid, crotonic acid, itaconic acid, maleic acid and the like, among which acrylic acid, methacrylic acid and the like. Is preferably used. These may be used alone or in combination of two or more.

  Furthermore, as other unsaturated monomer (a3), it is not specifically limited, For example, carbon number, such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, etc. (Meth) acrylic acid alkyl ester having 1 to 3 alkyl groups, (meth) acrylic acid having an alkyl group having 13 or more carbon atoms such as tridecyl (meth) acrylate, isotridecyl (meth) acrylate, tetradecyl (meth) acrylate, etc. Alkyl ester, dimethylaminoethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, methoxytriethylene glycol (meth) acrylate, acrylonitrile, methacrylonitrile, styrene, α-methyls Ren, vinyl acetate, vinyl propionate, vinyl chloride, alkyl vinyl ether.

  Further, as the unsaturated monomer (a3), in addition to the above, a functional group-containing unsaturated monomer, such as a hydroxyl group-containing unsaturated monomer, an epoxy group-containing unsaturated monomer, or an alkoxysilyl group-containing unsaturated monomer A monomer, an amide group, a methylol group, an unsaturated monomer containing a carbonyl group, a polyfunctional unsaturated monomer, or the like may be used.

Examples of the hydroxyl group-containing unsaturated monomer include 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate.
Examples of the epoxy group-containing monomer include glycidyl (meth) acrylate and allyl glycidyl ether.

  Examples of the alkoxysilyl group-containing unsaturated monomer include (meth) acryloxyethyltrimethoxysilane, (meth) acryloxyethyltriethoxysilane, γ- (meth) acryloxypropyltrimethoxysilane, and γ- (meth). Acryloxypropyltriethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropyldimethylmethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryl Roxypropyldimethylethoxysilane, γ- (meth) acryloxypropyltrichlorosilane, γ- (meth) acryloxypropylmethyldichlorosilane, γ- (meth) acryloxypropyldimethylchlorosilane, γ- (meth) acryloxypropyltripropio Sisilane, γ- (meth) acryloxypropylmethyldipropoxysilane, γ- (meth) acryloxypropyltributoxysilane, (meth) acryloxybutyltrimethoxysilane, (meth) acryloxypentyltrimethoxysilane, (meta ) Acryloxyhexyltrimethoxysilane, (meth) acryloxyhexyltriethoxysilane, (meth) acryloxyoctyltrimethoxysilane, (meth) acryloxydecyltrimethoxysilane, (meth) acryloxydecyltrimethoxysilane, (meth) ) Acryloxyoctadecyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripolopoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, vinylmethyldipropo Shishiran, and the like.

  Examples of unsaturated monomers containing an amide group, a methylol group, or a carbonyl group include acrylamide, methacrylamide, N-methylol acrylamide, butoxy N-methylol acrylamide, diacetone acrylamide, and 2- (acetoacetoxy) ethyl (meth). Examples thereof include acrylate and allyl acetoacetate.

  Examples of the polyfunctional unsaturated monomer include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and propylene glycol di (meth). Acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butanediol di (meth) Acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) ) Acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethanetetra (meth) acrylate, glycerin methacrylate acrylate, tris (meth) acryloyloxyphosphate, glycerin di (meth) acrylate, diallyl terephthalate, tetraallyloxyethane, divinyl Examples thereof include benzene and tri (meth) allyl isocyanurate. These may be used alone or in combination of two or more.

  In the present invention, the content ratio of the (meth) acrylic acid alkyl ester (a1), the carboxyl group-containing unsaturated monomer (a2), and the other unsaturated monomer (a3) is an alkyl (meth) acrylate. The ester (a1) is 50 to 99.9% by weight, the carboxyl group-containing unsaturated monomer (a2) is 0.1 to 20% by weight, and the other unsaturated monomer (a3) is 0 to 49.9% by weight. Preferably, (meth) acrylic acid alkyl ester (a1) is 55 to 99.5% by weight, carboxyl group-containing unsaturated monomer (a2) is 0.5 to 15% by weight, and other unsaturated monomers The monomer (a3) is 0 to 44.5% by weight, more preferably (meth) acrylic acid alkyl ester (a1) is 60 to 99% by weight, and the carboxyl group-containing unsaturated monomer (a2) is 1 to 1. 10% by weight, other Unsaturated monomer (a3) is 0 to 39 wt%.

  If the (meth) acrylic acid alkyl ester (a1) is less than 50% by weight, sufficient adhesive strength and tack cannot be obtained. If it exceeds 99.9% by weight, the carboxyl group-containing unsaturated monomer (a2) is small and sufficient. Re-peelability cannot be obtained. When the carboxyl group-containing unsaturated monomer (a2) is less than 0.1% by weight, the polymerization stability and mechanical stability are lowered and the removability is insufficient, and when it exceeds 20% by weight, the viscosity of the emulsion is increased. Handling becomes worse, and adhesive strength and tack are also lowered. If the other unsaturated monomer (a3) exceeds 49.9% by weight, the adhesive strength and tack are lowered, which is not preferable.

  In the present invention, emulsion polymerization is carried out using a monomer mixture of the above (meth) acrylic acid alkyl ester (a1), carboxyl group-containing unsaturated monomer (a2), and other unsaturated monomer (a3). Thus, the emulsion [A] is obtained. In such emulsion polymerization, it is necessary to carry out in the presence of an anionic reactive emulsifier. By using such an anionic reactive emulsifier, adhesion to a substrate and water resistance can be obtained. And removability are improved, and the effects of the present invention are remarkably exhibited.

  Such an anionic reactive emulsifier is not particularly limited as long as it is an anionic emulsifier and has a reactivity, and examples thereof include those having the structures of the following general formulas (1) to (11). It is done.

[In the general formulas (1) to (11), R ₁ is an alkyl group, R ₂ is hydrogen or a methyl group, R ₃ is an alkylene group, n is an integer of 1 or more, and m and l are integers of 1 or more. (M + 1 = 3), X is either SO ₃ NH ₄ or SO ₃ Na. ]

  Specific examples of the emulsifier include “Adekaria soap SE-20N”, “Adekaria soap SE-10N”, “Adekaria soap PP-70”, “Adekaria soap PP-710”, and “Adekaria soap SR-”. "10", "Adekaria soap SR-20" (manufactured by Asahi Denka Kogyo Co., Ltd.), "Eleminol JS-2", "Eleminol RS-30" (manufactured by Sanyo Kasei Kogyo Co., Ltd.), "Latemul S-180A" “Latemul S-180”, “Latemul PD-104” (manufactured by Kao Corporation), “Aqualon BC-05”, “Aqualon BC-10”, “Aqualon BC-20”, “Aqualon HS-05”, “Aqualon HS-10”, “Aquaron HS-20”, “New Frontier S-510”, “Aquaron KH-05”, “Aquaron KH-10” [ On, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.], "phosphino - Le TX" [manufactured by Toho Chemical Industry Co., Ltd.]) commercially available products, and the like.

  Among the above-mentioned emulsifiers, those that are neutralized with a monovalent metal salt (for example, sodium salt, potassium salt, etc.) and do not contain an ethylene oxide chain in the structure, specifically, “ELEMINOL JS-2” "Latemul S-180" and the like are most preferable from the viewpoint that heat resistance colorability and initial adhesive strength decrease with time in use with a vinyl chloride resin base material containing a plasticizer are small.

The amount of the anionic reactive emulsifier used is preferably 0.5 to 10 parts by weight, more preferably 0.8 to 100 parts by weight with respect to 100 parts by weight of the monomer mixture (a1) to (a3). 7 parts by weight, particularly preferably 1 to 5 parts by weight. If the emulsifier is less than 0.5 parts by weight, the emulsion polymerization becomes unstable, and if it exceeds 10 parts by weight, the amount of unreacted emulsifier increases, which is not preferable because it causes substrate adhesion and adherend contamination.
The emulsifier may be added to an emulsified monomer solution composed of a monomer mixture, may be added in advance to the polymerization can, or both may be used in combination.

If necessary, an anionic emulsifier having no reactivity, a nonionic emulsifier having no reactivity, or a nonionic reactive emulsifier can be used in combination.
Examples of the anionic emulsifier having no reactivity include alkyl sulfates, alkylbenzene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ether disulfonates, polyoxyethylene alkyl sulfates, polyoxyethylene alkyl phosphates, and the like. .

  Examples of the nonionic emulsifier having no reactivity include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, oxyethylene-oxypropylene block polymer, sorbitan fatty acid ester, polyoxyethylene fatty acid and the like.

  Nonionic reactive emulsifiers include, for example, those in the above general formulas (1) to (11) in which X is changed to hydrogen. Specifically, “Adekalia soap NE-10”, “Adekalia” "SOPE NE-20", "ADEKA rear soap NE-30", "ADEKA rear soap NE-40", "ADEKA rear soap ER-10", "ADEKA rear soap ER-20", "ADEKA rear soap ER-30" , "Adekaria soap ER-40" [manufactured by Asahi Denka Kogyo Co., Ltd.], "AQUALON RN-10", "AQUALON RN-20", "AQUALON RN-30", "AQUALON RN-50" [above, Commercial products such as “Daiichi Kogyo Seiyaku Co., Ltd.”.

  In performing the emulsion polymerization, a polymerization initiator is used. However, the polymerization initiator is not particularly limited, and any water-soluble or oil-soluble one can be used. Specifically, an alkyl peroxide, t-Butyl hydroperoxide, cumene hydroperoxide, p-methane hydroperoxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, t-butylcumyl peroxide, benzoyl peroxide , Dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 3,3,5-trimethylcyclohexanone Peroxide, methylcyclohexa Organic peroxides such as N-peroxide, di-isobutylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, t-butylperoxyisobutyrate, 2,2′-azobisisobutyronitrile, dimethyl- 2,2′-azobisisobutyrate, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-methylbutyronitrile), potassium persulfate, sodium persulfate, Ammonium persulfate, hydrogen peroxide, ammonium (amine) salt of 4,4′-azobis-4-cyanovaleric acid, 2,2′-azobis (2-methylamidooxime) dihydrochloride, 2,2′-azobis ( 2-methylbutanamidooxime) dihydrochloride tetrahydrate, 2,2′-azobis {2-mes Ru-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] -propionamide}, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], various Redox catalyst (in this case, as the oxidizing agent, ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide, p-methane hydroperoxide, etc. As the reducing agent, sodium sulfite, acidic sodium sulfite, Rongalite, ascorbic acid, etc. are used.) Among these, potassium persulfate, persulfate, and Sodium sulfate, redox catalyst (oxidizer: potassium persulfate, persulfate Sodium acid, reducing agent: sodium sulfite, acidic sodium sulfite) and the like are preferable.

  The amount of the polymerization initiator used is preferably 0.01 to 5 parts by weight, more preferably 0.03 to 3 parts by weight, with respect to 100 parts by weight of the monomer mixture (a1) to (a3). If it is less than 0.01 parts by weight, the polymerization rate is slow, and if it exceeds 5 parts by weight, the removability is lowered, which is not preferable.

  The polymerization initiator may be added in advance to the polymerization can, may be added immediately before the start of polymerization, or may be added during the polymerization as necessary. Moreover, you may add to the monomer mixture of (a1)-(a3) previously, or may add to the emulsion liquid which consists of this monomer mixture. In addition, the polymerization initiator may be separately dissolved in a solvent or the above monomer and added, or the dissolved polymerization initiator may be further added in an emulsified form.

If necessary, a pH buffering agent may be used in combination for pH adjustment during polymerization. The amount of the pH buffering agent used is 100 parts by weight of the monomer mixture (a1) to (a3). The amount is preferably 0.01 to 10 parts by weight, particularly 0.1 to 3 parts by weight.
The pH buffering agent is not particularly limited as long as it has a pH buffering action. Specifically, sodium bicarbonate, potassium bicarbonate, monosodium phosphate, monopotassium phosphate, disodium phosphate, phosphorus Examples thereof include trisodium acid, sodium acetate, ammonium acetate, sodium formate, and ammonium formate.

  The amount of water used is preferably 20 to 400 parts by weight, more preferably 25 to 200 parts by weight, particularly preferably 30 to 100 parts by weight based on 100 parts by weight of the monomer mixture of (a1) to (a3). 150 parts by weight. If the amount of water used is less than 20 parts by weight, the resulting resin composition will have a high viscosity, and the polymerization stability will also be reduced. If the amount exceeds 400 parts by weight, the concentration of the resulting resin composition will be low, resulting in film formation. This is not preferable because the drying property is reduced.

The monomer mixture of (a1) to (a3) is polymerized with the initiator in the presence of an anionic reactive emulsifier.
(1) Charge the whole amount of monomer mixture, emulsifier, water, etc., polymerize by heating.
(2) Charge water, an emulsifier, and a part of the monomer mixture into the reaction can, polymerize by heating, then continue the polymerization by dropping or dividing the remaining monomer mixture.
(3) Water, an emulsifier, etc. are charged into the reaction can and the temperature is raised, and then the entire amount of the monomer mixture is dropped or divided and polymerized.
However, the methods (2) and (3) are preferable because the polymerization temperature can be easily controlled.

The polymerization conditions in the polymerization method are not particularly limited.
In the method (1), a temperature range of about 40 to 100 ° C. is appropriate, and the reaction is carried out for about 1 to 8 hours after the start of temperature increase.
In the method (2), 1 to 50% by weight of the monomer mixture is polymerized at 40 to 90 ° C. for 0.1 to 4 hours, and then the remaining monomer mixture is dropped or divided over about 1 to 5 hours. After that, it is aged for about 1 to 3 hours at the same temperature.
In the method (3), water is charged into a polymerization can, heated to 40 to 90 ° C., and the monomer mixture is dropped or added over about 2 to 5 hours, and then at the same temperature for about 1 to 3 hours. Mature.

In the above polymerization method, the monomer mixture is preferably polymerized by dissolving the emulsifier (or part of the emulsifier) in the monomer mixture or by preliminarily setting it as an O / W type emulsion. This is preferable.
The method for adjusting the emulsified liquid is not particularly limited, but the above-described (a1) to (a3) are prepared after dissolving the emulsifier in water, and the mixed liquid is stirred and emulsified, or the emulsifier is dissolved in water and then stirred. However, the method etc. which prepare said (a1)-(a3) are mentioned.

Agitation at the time of emulsification of the emulsion can be carried out using a stirring device in which the components are mixed and a stirring blade such as a homodisper or paddle blade is attached.
There is no problem as long as the temperature during emulsification is such that the mixture does not react during emulsification, and usually about 5 to 60 ° C. is appropriate.

  Thus, an emulsion [A] is obtained. In the present invention, the emulsion [A] needs to have a gel fraction of less than 70% by weight, preferably 10 to 60% by weight, particularly preferably 20 to 55%. % By weight. If the gel fraction is 70% by weight or more, sufficient adhesion to the substrate cannot be obtained, which causes an adhesive residue after re-peeling and is inappropriate.

  A method for adjusting the gel fraction of the emulsion [A] to less than 70% is not particularly limited, but a chain transfer agent of alcohols such as methanol, ethanol and isopropyl alcohol and mercaptans such as dodecyl mercaptan and lauryl mercaptan at the time of polymerization. And a method of adjusting the amount of the polymerization initiator.

  The gel fraction of the emulsion [A] is the ratio of the solvent-insoluble component of the resin composition. In the 10 μm coating film of the emulsion [A] dried at 40 ° C. for 24 hours, It is calculated | required as a ratio (%) of the residual coating-film weight after immersion with respect to the coating-film weight before immersion when immersed at 24 degreeC for 24 hours.

The average particle diameter of the acrylic resin in the obtained emulsion [A] is 200 nm or less, particularly 100 to 180 nm, more preferably 120 to 170 nm, in terms of water resistance, particularly water whitening resistance. preferable.
Further, the solid content concentration of the emulsion [A] is preferably 10 to 65% by weight, particularly 20 to 55% by weight from the viewpoint of drying property and coating property, and the acrylic resin in the emulsion [A]. The glass transition temperature is preferably −60 to −25 ° C. from the viewpoint of suppressing a decrease in initial adhesive strength over time in use with a vinyl chloride resin substrate containing a plasticizer, and having high adhesive strength. Is preferably −55 to −30 ° C., more preferably −50 to −35 ° C.

  Furthermore, in the emulsion [A] obtained above, at least a part of the carboxyl groups contained in the acrylic resin is preferably neutralized with a monovalent metal salt from the viewpoint of heat-resistant coloring, and such It does not specifically limit as a neutralizing agent for neutralization, Sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate etc. are mentioned. In such neutralization, 0.01 to 0.5 equivalents, particularly 0.05 to 0.2 equivalents per 1 equivalent of the carboxyl group contained in the acrylic resin may be neutralized for heat resistance and water resistance. In view of the fact that there is no decrease in initial adhesive strength over time in use with a vinyl chloride resin substrate containing a plasticizer.

  Next, the crosslinking agent [B] used in the present invention is not particularly limited as long as it crosslinks with the carboxyl group of the carboxyl group-containing unsaturated monomer (a2). For example, the oxazoline compound (b1) Carbodiimide compound (b2), metal compound (b3), epoxy compound, aziridine compound, isocyanate compound, melamine compound, amine compound, etc., among which aqueous type oxazoline compound (b1) ), The carbodiimide compound (b2), and the metal compound (b3) have small changes in adhesive strength over time, excellent re-peelability, and excellent stability of the mixed liquid after blending the crosslinking agent. It is preferable at the point which can be used as an adhesive composition.

Examples of the oxazoline-based compound (b1) include addition polymerizable 2-oxazolines (for example, 2-isopropenyl-2-oxazoline) having a substituent having an unsaturated carbon-carbon bond at the 2-position carbon position and other non-polymerizable compounds. Examples include commercially available products such as copolymers with saturated monomers, “Epocross WS-500”, “Epocross WS-700”, “Epocross K-2010E”, and “Epocross K-2020E” manufactured by Nippon Shokubai Co., Ltd. , “Epocross K-2030E” and the like.
The carbodiimide compound (b2) may be any compound containing at least two carbodiimide groups. For example, “Carbodilite V-02”, “Carbodilite V-02-L2”, “Carbodilite V-04” manufactured by Nisshinbo Co., Ltd. ”,“ Carbodilite V-06 ”,“ Carbodilite E-01 ”,“ Carbodilite E-02 ”, and the like.
Examples of the metal compound (b3) include metal alkoxides such as tetraethyl titanate, tetraethyl zirconate, and aluminum isopropionate, aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, Examples include acetylacetone and acetoacetate of polyvalent metals such as zirconium, metal chelate compounds of ethylenediaminetetraacetic acid coordination compounds, acetic acid-ammonium complex salts, ammonium-carbonate complex salts, and the like. Of these, the aqueous type is preferred.

  Examples of the epoxy compound include bisphenol A / epichlorohydrin type epoxy resin, sorbitol polyglycidyl ether (for example, “Denacol EX-611”, “Denacol EX-612”, “Denacol EX-614” manufactured by Nagase ChemteX Corporation). , “Denacol EX-614B”, “Denacol EX-622”, etc.), polyglycerol polyglycidyl ether (for example, “Denacol EX-512”, “Denacol EX-521”, etc., manufactured by Nagase ChemteX Corporation), pentaerythritol poly Glycidyl ether (for example, “Denacol EX-411” manufactured by Nagase ChemteX), diglycerol polyglycidyl ether (for example, “Denacol EX-421” manufactured by Nagase ChemteX), etc., glycerol polyglycy Ruether (for example, “Denacol EX-313”, “Denacol EX-314”, etc., manufactured by Nagase ChemteX), trimethylolpropane polyglycidyl ether (eg, “Denacol EX-321”, etc., manufactured by Nagase ChemteX), Resorcinol diglycidyl ether (for example, “Denacol EX-201” manufactured by Nagase ChemteX), neopentyl glycol diglycidyl ether (for example, “Denacol EX-211” manufactured by Nagase ChemteX), 1,6- Hexanediol diglycidyl ether (for example, “Denacol EX-212” manufactured by Nagase ChemteX Corporation), hydrogenated bisphenol A diglycidyl ether (for example, “Denacol EX-252” manufactured by Nagase ChemteX Corporation) , Ethylene Cole diglycidyl ether (for example, “Denacol EX-810”, “Denacol EX-811”, etc., manufactured by Nagase ChemteX Corporation), diethylene glycol diglycidyl ether (eg, “Denacol EX-850”, “ Denacol EX-851 "), polyethylene glycol diglycidyl ether (for example," Denacol EX-821 "," Denacol EX-830 "," Denacol EX-832 "," Denacol EX-841 "manufactured by Nagase ChemteX Corporation, “Denacol EX-861”, etc.), propylene glycol diglycidyl ether (eg, “Denacol EX-911” etc., manufactured by Nagase ChemteX), polypropylene glycol diglycidyl ether (eg, “Denaco” manufactured by Nagase ChemteX) EX-941 "," Denacol EX-920 "," Denacol EX-931 "and the like. Among these, an aqueous type is preferable.

Any aziridine compound may be used as long as it contains at least two aziridine groups. Examples thereof include “Chemite DZ-33” and “Chemite DZ-22E” (manufactured by Nippon Shokubai Co., Ltd.).
Examples of the isocyanate compound include toluylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, metaxylylene diisocyanate, 1,5-naphthalene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated toluylene diisocyanate. , Hydrogenated xylylene diisocyanate, isophorone diisocyanate, tetramethylxylene diisocyanate, and other isocyanate compounds, bullet polyisocyanate compounds such as “Sumijour N” (manufactured by Sumitomo Bayer Urethane Co., Ltd.), “Desmodur IL”, “Desmodur HL” (Made by Bayer AG), and has an isocyanurate ring such as “Coronate EH” (made by Nippon Urethane Co., Ltd.) Polyisocyanate compounds, adduct polyisocyanate compounds such as “Sumijour L” (manufactured by Sumitomo Bayer Urethane Co., Ltd.), adduct polyisocyanate compounds such as “Coronate HL” (manufactured by Nippon Polyurethane Co., Ltd.), “Aquanate 100”, “Aquanate” 110 ”,“ Aquanate 200 ”,“ Aquanate 210 ”(manufactured by Nippon Polyurethane Co., Ltd.), and the like. Among these, a water dispersion type is preferable. A blocked isocyanate may also be used.

Examples of melamine compounds include hexamethoxymethylol melamine and methoxymethylol urea.
Examples of amine compounds include 1,3-diaminopropane, bis- (3-aminopropyl) ether, 1,2-bis- (3-aminopropoxy) ethane, 1,3-bis- (3-aminopropoxy)- Examples include 2,2-dimethylpropane and 1,4-diaminobutane.

  The content of the crosslinking agent [B] is such that the reactive group contained in the crosslinking agent is 0.001 to 1.0 equivalent per equivalent of carboxyl group contained in the acrylic resin in the emulsion [A]. In particular, the ratio is preferably 0.005 to 0.1 equivalent, more preferably 0.01 to 0.08 equivalent. If the content is less than 0.001 equivalent, crosslinking between the particles is insufficient and re-peelability is poor. It is not preferable because the properties are lowered.

  Further, in the present invention, if necessary, an adhesive resin (modified rosin such as maleated rosin, fumarated rosin, acrylated rosin, stabilized rosin subjected to disproportionation, dimerization, hydrogenation, etc., Rosin resins such as those obtained by esterifying rosin with glycerin or pentaerythritol, xylene resin, terpene resin, terpene phenol resin, petroleum resin, coumarone indene resin, styrene resin, ethylene / vinyl acetate resin, etc.), plasticizer (For example, liquid polybutene, mineral oil, lanolin, liquid polyisoprene and liquid polyacrylate, etc.), antiseptic / antifungal agent, rust inhibitor, antifreezing agent, high boiling point solvent, pigment, colorant, filler (zinc white, titanium white) , Calcium carbonate, clay, etc.), metal powder, antifoaming agent, thickener, wetting agent, adhesion control agent, UV absorber and light ammonium Weather resistance imparting agents such as agents, or adding such an antioxidant as appropriate, it can also be or added during the polymerization or before the polymerization of the emulsion polymerization.

Thus, the re-peelable water-based pressure-sensitive adhesive composition of the present invention is obtained, but such a re-peelable water-based pressure-sensitive adhesive composition is usually provided as a pressure-sensitive adhesive layer on a substrate sheet or the like and is practically used as a pressure-sensitive adhesive sheet or pressure-sensitive adhesive tape In order to produce such a pressure-sensitive adhesive sheet or pressure-sensitive adhesive tape, the re-peelable water-based pressure-sensitive adhesive composition of the present invention was first adjusted as it was or to an appropriate concentration and subjected to silicon treatment or the like. The pressure-sensitive adhesive layer can be formed by coating on the treated surface of the base material, or directly on the base material and drying by, for example, heat treatment at 80 to 120 ° C. for 5 seconds to 10 minutes.
Alternatively, the re-peelable water-based pressure-sensitive adhesive composition can be applied to a release paper or a release film and dried, and then transferred onto a substrate.

Such a substrate is not particularly limited, and for example, polyvinyl chloride, polyvinylidene chloride, polybutene, polybutadiene, polyurethane, ethylene-vinyl acetate copolymer, polyethylene terephthalate, polyethylene, polypyropylene, ethylene-propylene copolymer, poly Examples thereof include films such as methylpentene and polybutylene terephthalate, metal foils, and porous materials such as paper and nonwoven fabric.
The thickness of the substrate is usually preferably 10 to 300 μm, particularly preferably 20 to 100 μm. On one side or both sides of the substrate, a layer made of the above-described re-peelable aqueous pressure-sensitive adhesive composition is 1 to 100 μm, and further 3 It is provided in a thickness of ˜50 μm, particularly 5-30 μm, and forms such as a sheet shape or a tape shape.
In the present invention, even when used on a vinyl chloride resin base material containing a plasticizer, the initial adhesive strength is not lowered with time, and is particularly effective.

  The re-peelable water-based pressure-sensitive adhesive composition of the present invention is used for temporary surface protection or temporary adhesion to prevent scratches or contamination during transport, processing, cutting, etc. of metal plates, glass plates, plastic plates, etc. It is very useful as a pressure-sensitive adhesive tape or sheet or adhesive for a re-peeling label, or as a pressure-sensitive adhesive for a marking film used in advertising stickers, decorative stickers, display stickers, and the like.

Thus, the re-peelable water-based pressure-sensitive adhesive composition of the present invention is a (meth) acrylic acid alkyl ester (a1) containing 50 to 99.9% by weight of an alkyl group having 4 to 12 carbon atoms and a carboxyl group-containing unsaturated monomer. A monomer mixture containing 0.1 to 20% by weight of the body (a2) and 0 to 49.9% by weight of the other unsaturated monomer (a3) in the presence of an anionic reactive emulsifier and a chain transfer agent . In addition, since the emulsion [A] obtained by emulsion polymerization and having a gel fraction of less than 70% by weight and a crosslinking agent [B] are contained, the adhesiveness to various adherends, the holding power, and the water resistance Excellent anti-fouling properties such as no color residue, no adhesive residue after re-peeling, and lower initial adhesive strength over time even when used with a vinyl chloride resin substrate containing a plasticizer It shows the effect that there is little.

Hereinafter, the present invention will be specifically described with reference to examples.
In the examples, “%” and “part” mean weight basis unless otherwise specified.

Example 1
n-butyl acrylate (a1) 85.0 parts, acrylic acid (a2) 1.5 parts, methacrylic acid (a2) 3.0 parts), methyl methacrylate (a3) 10.5 parts, lauryl mercaptan 0 as chain transfer agent .05 parts, anionic reactive emulsifier (manufactured by Sanyo Chemical Industries, “Eleminol JS-2”: active ingredient 38%, structure of the above general formula (3), R ₁ : alkyl group, X: SO ₃ Na) 3.13 parts, 0.5 parts of dibasic sodium phosphate as a pH buffering agent and 43.78 parts of water were mixed and stirred to obtain an emulsion composed of a monomer mixture.
Next, an anionic reactive emulsifier (manufactured by Sanyo Chemical Industries, “Eleminol JS-2”: active ingredient 38%, structure of the above general formula (3), R ₁ : Alkyl group, X: SO ₃ Na) 0.52 part and 39.3 parts of water were charged, and the temperature was raised to 75 ° C. with stirring, and then 5% (7.37 parts) of the above emulsion was added. Furthermore, after raising the temperature to 80 ° C., 1.0 part of 3% potassium persulfate aqueous solution was added to carry out emulsion polymerization, and then 15 minutes later, the remaining 95% (140.09 parts) of the above emulsion and 3% A mixed solution in which 3.0 parts of an aqueous potassium persulfate solution was mixed was dropped over 3.5 hours. After completion of the dropping, stirring was continued for 2 hours while maintaining the temperature at 80 ° C., followed by cooling to 60 ° C. and adding 4.5 parts of 5% aqueous ammonia solution to neutralize acid groups. Thereafter, it was cooled to 55 ° C., and 0.5 parts of 10% aqueous solution of tertiary butyl hydroperoxide (manufactured by NOF Corporation, “Perbutyl H-69”) and 1.0 part of 5% sodium sulfite aqueous solution were added, respectively. After reacting for 15 minutes, 0.5 parts of 10% aqueous solution of tertiary butyl hydroperoxide (manufactured by NOF Corporation "Perbutyl H-69") and 1.0 part of 5% aqueous sodium sulfite solution were added again. For 15 minutes. Then, after cooling to 30 ° C., 6.0 parts of a 2.5% aqueous sodium hydroxide solution was added, the pH was adjusted to 8.0, and the mixture was filtered through a 200-mesh wire mesh to obtain an emulsion [A]. (Gel fraction 51%, solid content 50.0%, viscosity 2200 mPa · s, average particle size 140 μm, glass transition temperature −38 ° C.).

Further, to the obtained emulsion [A], 0.7 parts (0.28 parts as an active ingredient) of “Epocross WS-500” manufactured by Nippon Shokubai Co., Ltd. as a crosslinking agent with respect to 100 parts of the solid content of the emulsion, “SN Deformer JK” (manufactured by San Nopco) 0.1 part as a foaming agent, “SN Wet 970” (manufactured by San Nopco) 0.5 part as a wetting agent, “Adecanol UH-541” (Asahi Denka Co., Ltd.) as a thickener (Manufactured) 0.3 part was added to obtain a re-peelable water-based pressure-sensitive adhesive composition of the present invention.
About the obtained re-peelable water-based pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet was prepared as follows and evaluated as follows.

[Preparation of adhesive sheet]
(Adhesive sheet [I])
The obtained re-peelable water-based pressure-sensitive adhesive composition was applied onto a release paper so that the thickness after drying was 20 μm, dried at 100 ° C. for 3 minutes, and then applied to a vinyl chloride resin film (thickness 50 μm). The pressure-sensitive adhesive sheet [I] was produced by transfer.
(Adhesive sheet [II])
The obtained re-peelable water-based pressure-sensitive adhesive composition was applied onto a release paper so that the thickness after drying was 20 μm, dried at 100 ° C. for 3 minutes, and then polyethylene terephthalate film (manufactured by Toray Industries, Inc., “Lumiler”). T-60 "and a thickness of 50 µm) to prepare an adhesive sheet [II].

(Initial adhesive strength)
30 minutes after adhering the obtained adhesive sheet [I] to a SUS304 polishing plate at 23 ° C. and 50% RH by reciprocating a 2 kg roller twice, in accordance with the method for measuring the adhesive strength of JIS Z 0237 180 degree peel strength (N / 25 mm) was measured.

(Initial adhesive strength after heat treatment of adhesive sheet)
The obtained pressure-sensitive adhesive sheet [I] was allowed to stand at 80 ° C. for 7 days, and then adhered to a SUS304 polishing plate at 23 ° C. and 50% RH by reciprocating a 2 kg roller twice, and 30 minutes later, JIS Z 0237 The 180 degree peel strength (N / 25 mm) was measured according to the method for measuring the adhesive strength.

(Heat resistant colorability)
The obtained adhesive sheet [II] was affixed to a melamine-coated board (white) (manufactured by Nippon Test Panel Co., Ltd.) and allowed to stand at 80 ° C. for 7 days, and the ΔE value was determined as “SZ OPTICAL SENSOR” Measured by Kogyo Co., Ltd. [reflection mode].

(Removability)
(1) Adhesive strength after aging The obtained adhesive sheet [II] was prepared by using (i) a SUS304 polishing plate, (ii) a hard vinyl chloride plate (manufactured by Nippon Test Panel), (iii) a melamine-coated plate (Japan test panel) Made by 2 reciprocating 2 kg rollers at 23 ° C. and 50% RH, respectively, and then (a) left at 70 ° C. for 7 days, and (b) 40 ° C., 90% RH, 7 days. About 180 degree peel strength (N / 25mm) was measured according to the measuring method of the adhesive force of JISZ0237 after leaving it to stand.

(2) Contamination resistance after elapse of time After (a) the above-mentioned (a) left at 70 ° C. for 7 days and (b) the adhesion strength after being left at 40 ° C., 90% RH for 7 days, the adherend was measured. The degree of contamination on the surface was visually observed, and the contamination resistance was evaluated as follows.
○ ··· Contamination was not observed △ ··· Attached marks were observed × 1 ······ Remaining adhesive was observed (peeling at the substrate interface)
× 2: Adhesive residue was observed (adhesive cohesive failure)

(Water whitening resistance)
The obtained pressure-sensitive adhesive sheet [II] was attached to an acrylic plate and observed for whitening after being immersed in warm water at 40 ° C. for 7 days, and evaluated as follows.
○ ・ ・ ・ No whitening △ ・ ・ ・ Slightly whitened × ・ ・ ・ Significantly whitened

(Holding power)
The obtained adhesive sheet [II] was attached to a stainless steel plate so that the area was 25 mm × 25 mm, and a 1 kg load was applied under the condition of 40 ° C., and the holding power measurement method of JIS Z 0237 was applied. Similarly, the deviation (mm) or drop time (min) after 24 hours was measured.

(Ball tack)
In the obtained pressure-sensitive adhesive sheet [II], J.P. Using a dow ball tack measuring machine, the ball number of the maximum diameter that stops on the test piece (adhesive surface) was measured at a test piece of 25 mm × 100 mm and an angle of 30 ° under the condition of 23 ° C. × 50% RH. .

Examples 2-10, Comparative Examples 1-3
Emulsion [A] was obtained in the same manner as in Example 1 except that the formulation was changed as shown in Tables 1 to 3. Furthermore, except that a crosslinking agent was added to the obtained emulsion [A] as shown in Tables 1 to 3, it was carried out in the same manner as in Example 1 to obtain a re-peelable aqueous pressure-sensitive adhesive composition, and the obtained re-peelable type Evaluation similar to Example 1 was performed about the water-based adhesive composition.
The evaluation results of Examples and Comparative Examples are shown in Tables 4 and 5.

In addition, the numerical value of a monomer mixture in the table | surface, a chain transfer agent, an emulsifier, a neutralizing agent, and a crosslinking agent shows a compounding quantity (part). However, the numerical value in () of a crosslinking agent shows the equivalent number of the crosslinking agent per 1 equivalent of carboxyl groups in acrylic resin.
(emulsifier)
・ JS-2 (manufactured by Sanyo Chemical Industries, “Eleminol JS-2”: active ingredient 38%)
RAA-11902 ("RAA-11902" manufactured by Nippon Emulsifier Co., Ltd .: 30% active ingredient non-reactive anionic emulsifier)
(Crosslinking agent)
WS-500 (“Epocross WS-500” manufactured by Nippon Shokubai Co., Ltd .: 40% active ingredient)
K-2010E (“Epocross K-2010E” manufactured by Nippon Shokubai Co., Ltd .: active ingredient 40%)
V-04 (Nisshinbo's “Carbodilite V-04”: 40% active ingredient)
A 10% aqueous solution of a metal compound (zinc ammonium acetate [Zn (NH ₃ ) ₄ (CH ₃ COO) ₂ ])

注）表中の（ａ）は７０℃、７日間放置した後の評価、（ｂ）は４０℃、９０％ＲＨ、７日間放置した後の評価である。

Note) (a) in the table is an evaluation after being left at 70 ° C. for 7 days, and (b) is an evaluation after being left at 40 ° C. and 90% RH for 7 days.

  The re-peelable water-based pressure-sensitive adhesive composition of the present invention comprises (meth) acrylic acid alkyl ester (a1) 50 to 99.9% by weight, carboxyl group-containing unsaturated monomer containing an alkyl group having 4 to 12 carbon atoms. (A2) A monomer mixture containing 0.1 to 20% by weight and other unsaturated monomer (a3) 0 to 49.9% by weight is subjected to emulsion polymerization in the presence of an anionic reactive emulsifier. Since the obtained emulsion [A] having a gel fraction of less than 70% by weight and the cross-linking agent [B] are contained, the adhesiveness, holding power, water resistance, and heat resistance coloring property to various adherends are improved. Excellent and excellent in anti-contamination property that there is no adhesive residue after re-peeling. Furthermore, even when used with a vinyl chloride resin base material containing a plasticizer, it shows an effect that there is little decrease in initial adhesive strength over time. Metal plate, glass plate, plastic Adhesive tape or sheet for temporary surface protection or temporary adhesion for prevention of scratches and contamination during transport, processing, cutting, etc. It is very useful as an adhesive for marking films used in decorative stickers, display stickers and the like.

Claims (8)

(Meth) acrylic acid alkyl ester containing 4 to 12 carbon atoms (meth) acrylic acid ester (a1) 50 to 99.9% by weight, carboxyl group-containing unsaturated monomer (a2) 0.1 to 20% by weight, other A gel fraction obtained by emulsion polymerization of a monomer mixture containing 0 to 49.9% by weight of an unsaturated monomer (a3) in the presence of an anionic reactive emulsifier and a chain transfer agent has a gel fraction of 70 A re-peelable water-based pressure-sensitive adhesive composition comprising an emulsion [A] of less than% by weight and a crosslinking agent [B].   The re-peelable aqueous pressure-sensitive adhesive composition according to claim 1, wherein the anionic reactive emulsifier uses a compound neutralized with a monovalent metal salt.   The re-peelable aqueous pressure-sensitive adhesive composition according to claim 1 or 2, wherein the anionic reactive emulsifier uses a compound that does not contain an ethylene oxide chain in the structure.   The detachable water-based pressure-sensitive adhesive according to any one of claims 1 to 3, wherein at least a part of the carboxyl groups contained in the acrylic resin in the emulsion [A] is neutralized with a monovalent metal salt. Agent composition.   The re-peelable water-based pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein an average particle diameter of the acrylic resin in the emulsion [A] is 200 nm or less.   The crosslinking agent [B] is at least one selected from the oxazoline-based compound (b1), the carbodiimide-based compound (b2), and the metal-based compound (b3). Peelable aqueous pressure-sensitive adhesive composition.   The crosslinking agent [B] is contained at a ratio of 0.001 to 1.0 equivalent of reactive groups contained in the crosslinking agent per equivalent of carboxyl groups contained in the acrylic resin in the emulsion [A]. The re-peelable water-based pressure-sensitive adhesive composition according to any one of claims 1 to 6. The re-peelable water-based pressure-sensitive adhesive composition according to any one of claims 1 to 7, which is used as a pressure-sensitive adhesive for a marking film.