JP2010150515A - Exfoliation-type aqueous adhesive composition, exfoliation-type aqueous adhesive, and exfoliation-type aqueous adhesive member obtained by using the adhesive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exfoliation-type aqueous adhesive composition the adhesive power of which is hardly increased with time and which is so excellent in contamination resistance that the leftover adhesive composition or traces of the adhesive composition are hardly left on an adherend when the adhesive composition is exfoliated. <P>SOLUTION: The exfoliation-type aqueous adhesive composition includes an acrylic emulsion [A] and crosslinking agents [B]. The crosslinking agents [B] comprise a crosslinking agent (b1) having an oxazoline group and another crosslinking agent (B2) having a carbodiimide group. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an adhesive tape or sheet for temporary surface protection or temporary adhesion for preventing scratches or preventing contamination during transportation, processing, cutting, etc. of metal plates, glass plates, plastic plates, etc. The present invention relates to a release-type aqueous pressure-sensitive adhesive composition useful as an agent. More specifically, a peelable water-based pressure-sensitive adhesive that can be used as a one-component curable water-based pressure-sensitive adhesive that exhibits little increase in adhesive strength over time and exhibits excellent peelability even when a synthetic paper or film-based substrate is used. It relates to a composition.

Conventionally, peelable pressure-sensitive adhesive compositions have been widely used for surface protective films, coating masking tapes, adhesive seals, and the like. For example, surface protection films temporarily protect the surface of these products to prevent scratches, contamination, corrosion, etc. during transportation, processing, cutting, storage, etc. of metal products, plastic products, glass products, etc. After the purpose is reached, it is peeled off from the product surface.
Such a surface protective film adheres to the adherend during transport, processing, cutting, storage, etc. of metal products, plastic products, glass products, etc. After reaching this, the peelability is required such that it can be easily peeled off from the adherend.

  However, the pressure-sensitive adhesive tape or sheet is likely to have an increase in adhesive force due to a change over time after being attached, and as a result, it is difficult to peel off when the surface protective film is peeled off from the adherend, and the peeling work takes time. There may be problems such as adhesiveness at the time of peeling and peelability such as stain resistance after peeling, such as contamination of adhesive residue and sticking marks of the adhesive.

In recent years, from the viewpoint of environmental hygiene, various studies have been made on water-dispersed pressure-sensitive adhesives that do not use a solvent even in a peelable pressure-sensitive adhesive composition. For example, improvement in peelability and improvement in stain resistance during 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) An aqueous dispersion copolymer of a monomer mixture consisting of 0 to 49.9% by weight of a monomer copolymerizable with component b contains a water-soluble crosslinking agent containing an oxazoline group in the copolymer. It has a layer obtained by cross-linking a peelable pressure-sensitive adhesive prepared by blending 0.1 to 5 equivalents of oxazoline group per equivalent of carboxyl group, and the solvent-soluble content of this layer is 40% by weight. hereinafter, the elastic modulus was to 50 kg / cm ^2, melamine coated And then left at 23 ° C. for 20 minutes, and then an adhesive sheet having a peel force of 500 g / 20 mm width or less when peeled 180 ° at a tensile speed of 30 m / min (in an atmosphere of 23 ° C. and 65% RH) (for example, , See Patent Document 1).

  Further, 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, and c) the above a, A cross-linking agent containing a carbodiimide group is added to the water-dispersed acrylate copolymer of a monomer mixture consisting of 0 to 49.9% by weight of a monomer copolymerizable with the component b, and the carboxyl group of the copolymer. Water-dispersible pressure-sensitive adhesive for re-peeling having a re-peelability of 500 g / 20 mm width or less, wherein the ratio of carbodiimide group to carbodiimide group (carbodiimide group / carboxyl group) is 0.1 to 5.0 (For example, see Patent Document 2) has also been proposed.

  In addition, (meth) acrylic acid alkyl ester (a1) containing 50 to 99.9% by weight of an alkyl group having 4 to 12 carbon atoms, carboxyl group-containing unsaturated monomer (a2) 0.1 to 20% by weight The gel fraction obtained by emulsion polymerization of a monomer mixture containing 0 to 49.9% by weight of other unsaturated monomers (a3) in the presence of an anionic reactive emulsifier is 70% by weight. A re-peelable water-based pressure-sensitive adhesive composition (for example, see Patent Document 3) or an alkyl group having 4 to 12 carbon atoms, which comprises an emulsion [A] less than the above and a crosslinking agent [B]. Containing (meth) acrylic acid alkyl ester (a1) 50-99.9% by weight, carboxyl group-containing unsaturated monomer (a2) 0.1-10% by weight, other unsaturated monomer (a3) 0 A monomer mixture containing ˜49.9% by weight A re-peelable aqueous solution comprising an emulsion [A] obtained by emulsion polymerization in the presence of an on-type reactive emulsifier, a crosslinking agent [B], and a phosphate ester compound [C]. An adhesive composition (see, for example, Patent Document 4) has also been proposed.

Japanese Patent Laid-Open No. 10-114887 JP 2001-131512 A JP 2006-45410 A JP 2006-45411 A

However, in the disclosed techniques of Patent Documents 1 and 2, the peelability is not yet satisfactory with respect to the recent required performance, and a further long-term peelability is required.
In addition, in the disclosure techniques of Patent Documents 3 and 4, the aqueous pressure-sensitive adhesive composition tends to decrease the holding power and peelability when left in an emulsion state for a long time, and is still not satisfactory. There is no need for further improvement.

  Furthermore, the adhesion in various base materials and the resulting contamination are not taken into consideration, and further improvements are required. Further, there is little increase in adhesive strength over time, good contamination resistance, and calcium carbonate. There is a need for a peelable water-based pressure-sensitive adhesive composition suitable for both cases, such as when using a paper substrate such as neutral paper or glossy paper, which contains a large amount, or when using a substrate such as synthetic paper or synthetic resin film. Yes.

  Therefore, in the present invention, under such a background, the adhesiveness to various adherends is excellent, the adhesive force change with time is small, and there is no adhesive residue after peeling. , Peelable water-based pressure-sensitive adhesive composition, Peelable water-based pressure-sensitive adhesive composition suitable for both paper and film substrates It aims at providing a type adhesion member.

  However, the present inventor has made extensive studies in view of such circumstances, and as a result, in a pressure-sensitive adhesive composition containing an acrylic emulsion and a cross-linking agent, a peelable aqueous pressure-sensitive adhesive using a combination of at least two specific cross-linking agents. The agent composition was found to be excellent in stain resistance such that the change in adhesive force was small even when it was changed over time under high temperature and high humidity conditions, and there was no adhesive residue after peeling, and the present invention was completed.

That is, the gist of the present invention is a peelable aqueous pressure-sensitive adhesive composition containing an acrylic emulsion [A] and a crosslinking agent [B], and the crosslinking agent [B] contains a cross-linking agent (b1) containing an oxazoline group. ) And a carbodiimide group-containing crosslinking agent (b2).
The present invention also provides a peelable water-based pressure-sensitive adhesive comprising the peelable water-based pressure-sensitive adhesive composition, and further a peelable pressure-sensitive adhesive member in which the peelable water-based pressure-sensitive adhesive is laminated on at least one surface of a substrate. Is.

  In the present invention, the term “peeling” refers to removing once applied, and includes the meaning of re-peeling that is once applied again and then removed. Moreover, an adhesive member is a meaning including an adhesive sheet, an adhesive tape, an adhesive film, etc.

  The peelable water-based pressure-sensitive adhesive composition of the present invention is a peelable water-based pressure-sensitive adhesive composition containing an acrylic emulsion [A] and a cross-linking agent [B], and the cross-linking agent [B] contains an oxazoline group. Since it contains the cross-linking agent (b1) and the cross-linking agent (b2) containing a carbodiimide group, there is little increase in adhesion over time, and contamination such as adhesive residue or sticking marks on the adherend during peeling It shows an excellent effect of anti-contamination property such as a small amount.

Hereinafter, the present invention will be specifically described.
The peelable pressure-sensitive adhesive composition of the present invention comprises an acrylic emulsion [A] and a crosslinking agent [B].
The acrylic emulsion [A] is obtained by dispersing and stabilizing an acrylic resin obtained by copolymerizing an acrylic monomer as a main component with an emulsifier, and the main component refers to the entire copolymer component. On the other hand, it means 50% by weight or more.
Among them, (meth) acrylic acid alkyl ester (a1), carboxyl group-containing unsaturated monomer (a2) and other unsaturated monomer (a3) containing an alkyl group having 4 to 12 carbon atoms are copolymerized components. It is preferable that the acrylic resin (a) is an acrylic emulsion that is dispersed and stabilized by an emulsifier from the viewpoint that both high adhesive force and good peelability can be achieved.

  Such an acrylic emulsion [A] is, for example, a (meth) acrylic acid alkyl ester (a1) containing a C 4-12 alkyl group, a carboxyl group-containing unsaturated monomer (a2), and other non-reactive monomers. The copolymer component containing the saturated monomer (a3) can be obtained by emulsion polymerization in the presence of an emulsifier.

  In the present invention, (meth) acryl means acryl or methacryl, (meth) acryloyl means acryloyl or methacryloyl, and (meth) acrylate means acrylate or methacrylate.

  Examples of the (meth) acrylic acid alkyl ester (a1) containing an alkyl group having 4 to 12 carbon atoms include n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-hexyl (meth) acrylate, 2 -Ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, isooctyl (meth) acrylate, n-octyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate , Aliphatic (meth) acrylates such as undecyl (meth) acrylate, isoundecyl (meth) acrylate, dodecyl (meth) acrylate, isododecyl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth ) Aromatic (meth) acrylates such as acrylate, and the like. Among them, (meth) acrylic acid alkyl esters containing an alkyl group having 4 to 10 carbon atoms and more preferably 4 to 8 carbon atoms are preferable, and specifically n-butyl. (Meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like are preferably used, and 2-ethylhexyl acrylate is particularly preferably used. These may be used alone or in combination of two or more.

  Examples of the carboxyl group-containing unsaturated monomer (a2) 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 are preferably used. It is done. These may be used alone or in combination of two or more.

  Furthermore, as other unsaturated monomer (a3), C1-C3, such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, etc., for example. (Meth) acrylic acid alkyl ester having an alkyl group, (meth) acrylic acid alkyl ester having 13 or more alkyl groups such as tridecyl (meth) acrylate, isotridecyl (meth) acrylate, tetradecyl (meth) acrylate, dimethyl Aminoethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, methoxytriethylene glycol (meth) acrylate, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, vinyl acetate Le, vinyl propionate, vinyl chloride, alkyl vinyl ether.

  In addition to the above, as the unsaturated monomer (a3), a monomer that reacts with the carboxyl group-containing unsaturated monomer (a2), a monomer that can react with each other, and a self-crosslinkable functional group. Unsaturated monomer containing a hydroxyl group-containing unsaturated monomer, an epoxy group-containing unsaturated monomer, an alkoxysilyl group-containing unsaturated monomer, an amide group, a methylol group, or a carbonyl group A body or the like may be used.

Examples of the hydroxyl group-containing 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 monomer include (meth) acryloxyethyltrimethoxysilane, (meth) acryloxyethyltriethoxysilane, γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acrylic. Roxypropyltriethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropyldimethylmethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxy Propyldimethylethoxysilane, γ- (meth) acryloxypropyltrichlorosilane, γ- (meth) acryloxypropylmethyldichlorosilane, γ- (meth) acryloxypropyldimethylchlorosilane, γ- (meth) acryloxypropyltripropoxy Run, γ- (meth) acryloxypropylmethyldipropoxysilane, γ- (meth) acryloxypropyltributoxysilane, (meth) acryloxybutyltrimethoxysilane, (meth) acryloxypentyltrimethoxysilane, (meta ) Acryloxyhexyltrimethoxysilane, (meth) acryloxyhexyltriethoxysilane, (meth) acryloxyoctyltrimethoxysilane, (meth) acryloxydecyltrimethoxysilane, (meth) acryloxydecyltrimethoxysilane, (meth) ) Acryloxyoctadecyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, vinylmethyldipropoxy Run, and the like.

  Examples of 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) acrylate. And allyl acetoacetate.

  As the content ratio of the (meth) acrylic acid alkyl ester (a1), carboxyl group-containing unsaturated monomer (a2) and other unsaturated monomer (a3) containing the alkyl group having 4 to 12 carbon atoms. Are preferably 80 to 99.9% by weight of (meth) acrylic acid alkyl ester (a1), 0.1 to 2% by weight of carboxyl group-containing unsaturated monomer (a2), and other unsaturated monomers (A3) is 0 to 19.9% by weight, particularly preferably (meth) acrylic acid alkyl ester (a1) is 85 to 99.8% by weight, and carboxyl group-containing unsaturated monomer (a2) is 0.8. 2 to 1.5% by weight, other unsaturated monomer (a3) is 0 to 13.5% by weight, more preferably (meth) acrylic acid alkyl ester (a1) is 90 to 99.7% by weight. Carboxyl group-containing Monomer (a2) is 0.3 to 1.2 wt%, other unsaturated monomer (a3) is from 0 to 8.8 wt%.

  If the amount of the (meth) acrylic acid alkyl ester (a1) is too small, sufficient adhesion and tack tend not to be obtained. If the amount is too large, the amount of the carboxyl group-containing unsaturated monomer (a2) becomes small, and sufficient peelability is obtained. There is a tendency not to be obtained. If the amount of the carboxyl group-containing unsaturated monomer (a2) is too small, the stability tends to decrease and the peelability tends to be insufficient. If the amount is too large, the viscosity of the emulsion rises and handling becomes poor, and the adhesive strength, Tack also tends to decrease. Moreover, when there are too many other unsaturated monomers (a3), there exists a tendency for adhesive force and a tack to fall.

The acrylic emulsion [A] used in the present invention comprises the above (meth) acrylic acid alkyl ester (a1), carboxyl group-containing unsaturated monomer (a2), and other unsaturated monomer (a3). Although it manufactures, it is preferable at the point which can manufacture stably the monomer mixture of the copolymerization component containing (a1)-(a3) in presence of an emulsifier in this invention in the presence of an emulsifier.
In such emulsion polymerization, the use of only an anionic reactive emulsifier or the use of only an anionic non-reactive emulsifier can be used without any problem, but in particular, an anionic reactive emulsifier and an anionic non-reactive emulsifier should be used in combination. It is preferable to use the anionic reactive emulsifier and the anionic nonreactive emulsifier in combination, so that the polymerization can be performed more stably, and the substrate adhesion and peelability are improved, and the effects of the present invention are remarkable. Demonstrate.

  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.

[Wherein, in 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 anionic reactive emulsifier include “ADEKA rear soap SE-20N”, “ADEKA rear soap SE-10N”, “ADEKA rear soap PP-70”, “ADEKA rear soap PP-710”, “ADEKA "Rear Soap SR-10", "Adekaria Soap SR-20" (above, manufactured by Asahi Denka Kogyo Co., Ltd.), "Eleminol JS-2", "Eleminol RS-30" (above, Sanyo Kasei Kogyo Co., Ltd.), "Latemuru "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, Aqualon HS-20, New Frontier S-510, Aqualon KH-05, Aquaro KH-10 "[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 anionic reactive emulsifiers, the above general formulas (3), (4), (5), (5), (5), (5) 9), an emulsifier having the structure represented by (10), that is, an anionic reactive emulsifier having no alkylphenol structure, specifically, “ADEKA rear soap SR-10”, “ADEKA rear soap SR-20”, “ “Eleminol JS-2”, “Eleminol RS-30”, “Latemul S-180A”, “Latemul S-180”, “Latemul PD-104”, “Aqualon KH-05”, “Aqualon KH-10”, etc. are suitable It is. Among these, “AQUALON KH-10” and “Latemul PD-104” are more preferable since they have good peelability.

  Examples of the anionic non-reactive emulsifier include alkyl sulfates, alkylbenzene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ether disulfonates, polyoxyethylene alkyl sulfates, polyoxyethylene alkyl phosphates, and the like. . Among them, it is preferable that the emulsifier does not have an alkylene oxide chain, and further it has no alkylene oxide chain and has one or more, preferably two or more benzene ring skeleton structures. It is preferable from the viewpoint of good adhesion to the substrate, and usually it is preferably 5 or less benzene ring skeleton structures. Specific examples include alkyl benzene sulfonate and alkyl diphenyl ether disulfonate.

  About the usage-amount of the said anionic reactive emulsifier and an anionic non-reactive emulsifier, it is 0.5-10 weight part as a total amount with respect to 100 weight part of monomer mixtures of (a1)-(a3). It is preferably 0.8 to 7 parts by weight. If the amount of the emulsifier is too small, the emulsion polymerization tends to become unstable. If the amount is too large, the water resistance is lowered, and the adhesion of the substrate and the contamination of the adherend when exposed to high humidity conditions are caused. Tend to be.

  When an anionic reactive emulsifier and an anionic nonreactive emulsifier are used in combination, the mixing ratio of the anionic reactive emulsifier and the anionic nonreactive emulsifier is as follows: anionic reactive emulsifier / anionic nonreactive The emulsifying emulsifier is preferably 0.2 to 5 (weight ratio), and particularly preferably 0.3 to 3 (weight ratio).

  If necessary, a nonionic non-reactive emulsifier or a nonionic reactive emulsifier can be used in combination.

  Examples of nonionic non-reactive emulsifiers 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 addition, an emulsifier may be added to the emulsion monomer liquid which consists of a monomer mixture, may be previously added to the superposition | polymerization can, and may use both together.

  In carrying out the emulsion polymerization, it is preferable to use a polymerization initiator, and the polymerization initiator is not particularly limited, and any of water-soluble and oil-soluble can be used. Oxide, 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, methyl Organic peroxides such as clohexanone peroxide, di-isobutyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butylperoxyisobutyrate, 2,2′-azobisisobutyronitrile, Dimethyl-2,2′-azobisisobutyrate, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-methylbutyronitrile), potassium persulfate, persulfate Sodium, ammonium persulfate, hydrogen peroxide, 4,4′-azobis-4-cyanovaleric acid ammonium (amine) salt, 2,2′-azobis (2-methylamidooxime) dihydrochloride, 2,2′- Azobis (2-methylbutanamide oxime) dihydrochloride tetrahydrate, 2,2'-azo {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] -propionamide}, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propion Amide], various redox catalysts (in this case, as the oxidizing agent, ammonium persulfate, potassium persulfate, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide, p-menthane hydroperoxide, etc. As the reducing agent, sodium sulfite, acidic sodium sulfite, Rongalite, ascorbic acid, etc. are used.) Among these, potassium persulfate, ammonium persulfate, 2,2′-azobisisobutyronitrile, 2 , 2'-azobis (2-methylbutyronitrile), 2,2 ' -Azobis (2,4-dimethylvaleronitrile), dimethyl-2,2'-azobisisobutyrate, various redox catalysts and the like are suitable.

  The amount of the polymerization initiator used is 100 parts by weight of the monomer mixture of (meth) acrylic acid alkyl ester (a1), carboxyl group-containing unsaturated monomer (a2), and other unsaturated monomer (a3). On the other hand, the amount is preferably 0.03 to 5 parts by weight, more preferably 0.05 to 3 parts by weight. If the amount is too small, the polymerization rate tends to be slow, and if the amount is too large, the peelability tends to decrease.

  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.

Further, if necessary, a pH buffer may be used at the time of polymerization to adjust the pH at the time of polymerization. The amount of the pH buffer used is the monomer mixture 100 of (a1) to (a3). It is preferable that it is 0.01-10 weight part with respect to a weight part, especially 0.1-3 weight part.
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 based on 100 parts by weight of the monomer mixture of (meth) acrylic acid alkyl ester (a1), carboxyl group-containing unsaturated monomer (a2), and other unsaturated monomer (a3). The amount is preferably 25 to 200 parts by weight, more preferably 30 to 150 parts by weight, and particularly preferably 35 to 120 parts by weight. If the amount of water used is too small, the resulting resin composition will have a high viscosity, and the polymerization stability will tend to decrease. If it is too much, the concentration of the resulting resin composition will be low, and drying will occur when forming a film. Tend to decrease.

In the presence of an emulsifier, the polymerization initiator is prepared by mixing a monomer mixture of the (meth) acrylic acid alkyl ester (a1), the carboxyl group-containing unsaturated monomer (a2), and the other unsaturated monomer (a3). As a method for the polymerization,
(1) After water is charged in a reaction can and heated, an emulsion obtained by mixing and emulsifying water, an emulsifier and a monomer mixture in advance is dropped or divided to polymerize.
(2) After charging water in the reaction can and raising the temperature, a part of the emulsion prepared by mixing and emulsifying water, emulsifier and monomer mixture in advance is charged and polymerized, and the remaining emulsion is added dropwise or dividedly. To continue the polymerization.
(3) Water, an emulsifier and the like are charged in a reaction can and heated, and then the whole amount of an emulsion obtained by mixing and emulsifying water, an emulsifier and a monomer mixture in advance is dropped or divided and polymerized.
Etc.

The polymerization conditions in the above polymerization method are not particularly limited. For example, in the methods (1) and (3), a temperature range of about 40 to 90 ° C. is usually appropriate, and dropping or divided addition is performed for 1 to 8 hours. The reaction is carried out at about the same temperature, followed by aging at the same temperature for about 1 to 5 hours.
In the method (2), 1 to 50% by weight of the monomer mixture is polymerized at 40 to 90 ° C. for 0.1 to 1 hour, and then the remaining monomer mixture is dropped or divided over about 1 to 8 hours. After that, it is aged for about 1 to 5 hours at the same temperature.

In the above polymerization method, the monomer mixture may be used by dissolving an emulsifier (or a part of the emulsifier) in the monomer mixture. However, as described above, the state of the O / W type emulsion is previously determined. Is preferable from the viewpoint of polymerization stability.
The method for preparing the emulsion is not particularly limited, but after dissolving the emulsifier in water, the (meth) acrylic acid alkyl ester (a1), the carboxyl group-containing unsaturated monomer (a2), and other unsaturated monomers. Examples include a method of preparing the body (a3) and stirring and emulsifying the mixed solution, or a method of preparing the above (a1) to (a3) with stirring after dissolving the emulsifier in water.

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.

  Thus, an acrylic emulsion [A] is obtained. In the present invention, the acrylic emulsion [A] preferably has a gel fraction of 40 to 90% by weight, more preferably 45 to 85% by weight, particularly 50%. ~ 80 wt% is preferred. If the gel fraction is too small, even if the amount of the cross-linking agent [B] is increased, the amount of adhesive residue tends to be large and the stain resistance tends to be poor, and the increase in adhesive strength over time tends to increase. . On the other hand, if it is too large, the adhesive force tends to be small or the adhesion to the substrate tends to be reduced.

  Examples of a method for adjusting the gel fraction of the acrylic emulsion [A] to 40 to 90% by weight or more include blending of a chain transfer agent and polyfunctional unsaturated monomer (at least two in the molecule). A monomer having an unsaturated group) or an unsaturated monomer having a self-crosslinkable functional group (such as a hydrolyzable silyl group-containing monomer or a methylol group-containing monomer) as a copolymerization component. And a method of copolymerizing unsaturated monomers having functional groups capable of reacting with each other.

  The gel fraction of the acrylic emulsion [A] is the ratio of the solvent-insoluble component of the resin composition. In the 10 μm coating film of the acrylic emulsion [A] dried at 40 ° C. for 24 hours. It is determined as a ratio (%) of the remaining coating film weight after immersion to the coating film weight before immersion when dipped in toluene at 23 ° C. for 24 hours and dried.

The average particle size of the resulting acrylic emulsion [A] is 2 μm or less, particularly 1 μm or less, and it is possible to adjust the high concentration and low viscosity required for high-speed coating. It is preferable in a certain point.
Further, the resin concentration of the acrylic emulsion [A] is preferably 40 to 68% by weight, particularly 50 to 65% by weight, from the viewpoint of drying property and coating property.

  Next, the crosslinking agent [B] used in the present invention comprises a crosslinking agent (b1) containing an oxazoline group and a crosslinking agent (b2) containing a carbodiimide group.

  As the crosslinking agent (b1) containing such an oxazoline group, an addition-polymerizable 2-oxazoline (for example, 2-isopropenyl) having a substituent having an unsaturated carbon-carbon bond at the 2-position carbon position, which is an oxazoline-based compound. -2-oxazoline) and other unsaturated monomers, and water-soluble “Epocross WS-300”, “Epocross WS-500” manufactured by Nippon Shokubai Co., Ltd., “ Epocross WS-700 ”and emulsion type“ Epocross K-2010E ”,“ Epocross K-2020E ”,“ Epocross K-2030 ”and the like, among which water-soluble“ Epocross WS-500 ”,“ Epocross WS- ” 700 "is preferred in that it is excellent in stain resistance and the effect of suppressing the increase in adhesive strength over time.

  The crosslinking agent (b2) containing such a carbodiimide group may be any one containing at least two carbodiimide groups. For example, water-soluble “carbodilite V-02” and “carbodilite V-02-” manufactured by Nisshinbo Co., Ltd. L2 ”,“ Carbodilite V-04 ”,“ Carbodilite V-06 ”, emulsion type“ Carbodilite E-01 ”,“ Carbodilite E-02 ”,“ Carbodilite E-04 ”, etc. “Carbodilite V-04” is preferable in that it is excellent in stain resistance and the effect of suppressing an increase in adhesive strength over time.

  In the cross-linking agent [B], the content of the cross-linking agent (b1) containing an oxazoline group is such that the oxazoline group per equivalent of the carboxyl group contained in the acrylic resin (a) in the acrylic emulsion [A]. Is preferably 0.01 to 1 equivalent, more preferably 0.02 to 0.5 equivalent, particularly 0.03 to 0.3 equivalent of adhesive strength and peelability. It is preferable in terms of good balance. If the content is too small, the increase in adhesive strength with time under heat-promoting conditions when using a paper substrate such as neutral paper tends to increase, or the cohesive force decreases and the stringing during peeling tends to increase. If the amount is too large, there is a tendency that sufficient adhesive strength cannot be obtained.

  Furthermore, the content of the crosslinking agent (b2) containing a carbodiimide group is 0.01 to 1 equivalent of carbodiimide group per equivalent of carboxyl group contained in the acrylic resin (a) in the acrylic emulsion [A]. The amount is preferably 0.02 to 0.5 equivalent, and particularly preferably 0.03 to 0.3 equivalent in terms of a good balance between adhesion and peelability. When the content is too small, the peelability under the heat resistance promotion condition and the moisture resistance promotion condition when using a substrate such as a synthetic paper or a film tends to be lowered. When the content is too large, sufficient adhesive strength cannot be obtained. Tend.

  Moreover, as a mixture ratio of the crosslinking agent (b1) containing an oxazoline group and the crosslinking agent (b2) containing a carbodiimide group, (b1) / (b2) is 0.05 to 20 (functional group equivalent ratio). It is preferably 0.1 to 15 (functional group equivalent ratio), more preferably 0.5 to 10 (functional group equivalent ratio). If the blending ratio is out of the above range, that is, if (b1) / (b2) is too small, an increase in adhesive strength with time under heat-promoting conditions when using a paper substrate such as neutral paper becomes large, or cohesive strength Tends to be small, and the stringing at the time of peeling tends to increase. If it is too large, the peelability tends to decrease under the conditions for promoting heat resistance and humidity when using a substrate such as synthetic paper or film. Furthermore, it is preferable that the crosslinking agent (b1) containing an oxazoline group is larger in functional group equivalent than the crosslinking agent (b2) containing a carbodiimide group, and (b1) / (b2) is 1.1 to 10 (functional Group equivalent ratio), particularly 1.5 to 6 (functional group equivalent ratio).

  As the crosslinking agent [B] used in the present invention, in addition to the crosslinking agents (b1) and (b2), a conventionally known crosslinking agent can be used as necessary. For example, the metal compound (b3) An epoxy compound (b4), an aziridine compound (b5), an isocyanate compound (b6), a melamine compound (b7), a hydrazine compound (b8), an amine compound (b9), and the like can be used.

  Examples of the metal compound (b3) include metal alkoxides such as tetraethyl titanate, tetraethyl zirconate, and aluminum isopropionate, and aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, and chromium. And 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.

Examples of the epoxy compound (b4) include bisphenol A / epichlorohydrin type epoxy resin, sorbitol polyglycidyl ether (for example, “Denacol EX-611”, “Denacol EX-612”, “Denacol” manufactured by Nagase ChemteX Corporation). EX-614 "," Denacol EX-614B "," Denacol EX-622 ", etc.), polyglycerol polyglycidyl ether (for example," Denacol EX-512 "," Denacol EX-521 "manufactured by Nagase ChemteX) , Pentaerythritol polyglycidyl ether (for example, “Denacol EX-411” manufactured by Nagase ChemteX Corporation), diglycerol polyglycidyl ether (for example, “Denacol E manufactured by Nagase ChemteX Corporation)
X-421 ", etc.), glycerol polyglycidyl ether (for example," Denacol EX-313 "," Denacol EX-314 "manufactured by Nagase ChemteX), etc.), trimethylolpropane polyglycidyl ether (eg, manufactured by Nagase ChemteX) "Denacol EX-321"), resorcinol diglycidyl ether (for example, "Denacol EX-201" manufactured by Nagase ChemteX Corporation), neopentyl glycol diglycidyl ether (for example, "Denacol EX manufactured by Nagase ChemteX Corporation"). -211 ", etc.), 1,6-hexanediol diglycidyl ether (for example," Denacol EX-212 "manufactured by Nagase ChemteX), hydrogenated bisphenol A diglycidyl ether (for example, Nagase ChemteX) Made by Nacol EX-252 ”, etc.), ethylene glycol diglycidyl ether (eg,“ Denacol EX-810 ”,“ Denacol EX-811 ”, etc., manufactured by Nagase ChemteX), diethylene glycol diglycidyl ether (eg, manufactured by Nagase ChemteX) "Denacol EX-850", "Denacol EX-851", etc.), polyethylene glycol diglycidyl ether (for example, "Denacol EX-821", "Denacol EX-830", "Denacol EX-832" manufactured by Nagase ChemteX Corporation) ”,“ Denacol EX-841 ”,“ Denacol EX-861 ”, etc.), propylene glycol diglycidyl ether (eg“ Denacol EX-911 ”manufactured by Nagase ChemteX Corporation), polypropylene glycol diglycidyl ether For example, Nagase ChemteX Corp., "Denacol EX-941", "Denacol EX-920", and "Denacol EX-931" and the like.

The aziridine compound (b5) may be any compound containing at least two aziridine groups. For example, “Chemite PZ-33”, “Chemite DZ-22E” (
Nippon Shokubai Co., Ltd.).

  Examples of the isocyanate compound (b6) include toluylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, metaxylylene diisocyanate, 1,5-naphthalene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogen. Isocyanate compounds such as hydrogenated toluylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, tetramethylxylene diisocyanate, burette polyisocyanate compounds such as “Sumijour N” (manufactured by Sumitomo Bayer Urethane Co., Ltd.), “Desmodur IL”, “ Isocyanurates such as "Death Module HL" (manufactured by Bayer AG), "Coronate EH" (manufactured by Nippon Urethane Co., Ltd.) A polyisocyanate compound having a carbonate ring, an adduct polyisocyanate compound such as “Sumijour L” (manufactured by Sumitomo Bayer Urethane Co., Ltd.), an adduct polyisocyanate compound such as “Coronate HL” (manufactured by Nippon Polyurethane Co., Ltd.), “Aquanate 100” Self-emulsifying water-dispersed polyisocyanate compounds such as “Aquanate 110”, “Aquanate 200”, and “Aquanate 210” (manufactured by Nippon Polyurethane Co., Ltd.).

  Examples of the melamine compound (b7) include hexamethoxymethylol melamine and methoxymethylol urea.

  The hydrazide compound (b8) may be any compound having at least two hydrazide groups in the molecule. For example, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, Sebacic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide, 1,3-bis (hydrazinocarbonoethyl) -5-isopropylhydantoin, 7,11-octadecadien-1,18 dicarbohydrazide, etc. Can be mentioned. When the hydrazide compound (b8) is used, it is preferable to use a carbonyl group-containing unsaturated monomer as the other unsaturated monomer (a3) as a constituent component of the acrylic emulsion [A].

  Examples of the amine compound (b9) include 1,3-diaminopropane, bis- (3-aminopropyl) ether, 1,2-bis- (3-aminopropoxy) ethane, 1,3-bis- (3- Aminopropoxy) -2,2-dimethylpropane, 1,4-diaminobutane and the like.

  The above-mentioned crosslinking agents (b3) to (b9) other than the crosslinking agents (b1) and (b2) depend on the kind of the crosslinking agent, but the peelable aqueous pressure-sensitive adhesive of the present invention is used as a one-component curable pressure-sensitive adhesive. In the case of using, the blending within a range not inhibiting the use is preferable.

  Further, if necessary, a tackifier (for example, rosin-based, rosin ester-based, polyterpene resin, chroman-indene resin, petroleum-based resin, terpene phenol-based resin, etc.) can be blended. As a method of blending such a tackifier, for example, a method of blending an emulsion-type tackifier during or after emulsion polymerization, or dissolving a solid-type tackifier in an unsaturated monomer mixture, The method of mix | blending by emulsion polymerization is mentioned. Other plasticizers (eg liquid polybutene, mineral oil, lanolin, liquid polyisoprene and liquid polyacrylate), antiseptic / antifungal agents, rust preventives, freeze-thaw stabilizers, plasticizers, high boiling point solvents, pigments, colorants, Add fillers (zinc white, titanium white, calcium carbonate, clay, etc.), metal powder, antifoaming agent, thickener, adhesion control agent, etc. as appropriate, or before or during polymerization of the above emulsion polymerization It can also be added.

Thus, the peelable water-based pressure-sensitive adhesive composition of the present invention can be obtained. Such a peelable water-based pressure-sensitive adhesive composition is usually formed by forming a pressure-sensitive adhesive that is applied to a substrate sheet and crosslinked with a cross-linking agent. Often used as a peelable pressure-sensitive adhesive member such as a sheet or a pressure-sensitive adhesive tape, and in order to produce a pressure-sensitive adhesive member such as a pressure-sensitive adhesive sheet or pressure-sensitive adhesive tape, the peelable water-based pressure-sensitive adhesive composition of the present invention is used as it is or Adjust to an appropriate concentration and apply to the treated surface of the base material that has been subjected to silicon treatment or the like, or apply directly to the base material, for example, by heat treatment at 80 to 105 ° C. for 5 seconds to 10 minutes. The adhesive layer can be formed by drying.
Alternatively, the release-type aqueous pressure-sensitive adhesive composition can be applied to a release film and dried, and then transferred onto a substrate.

Examples of the base material include, but are not limited to, paper, synthetic paper, plastic film, metal foil, and the like. Examples of the paper and synthetic paper base material include high-quality paper, cast-coated paper, and coating. Examples include paper materials such as paper, neutral paper, art paper, synthetic paper mainly made of polypropylene, and thermal paper. In the present invention, particularly when neutral paper or glossy paper containing calcium carbonate is used, a remarkable effect is exhibited. Examples of the plastic film substrate include polyvinyl chloride, polybutene, polybutadiene, polyurethane, ethylene-vinyl acetate copolymer, polyethylene terephthalate, polyethylene, polypyropylene, ethylene-propylene copolymer, polymethylpentene, polybutylene terephthalate. Etc. In addition, a porous material such as a nonwoven fabric can be used as the base material for the double-sided tape.
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.

The peelable water-based pressure-sensitive adhesive composition of the present invention is for temporary surface protection or temporary adhesion for preventing scratches or contamination during transport, processing, cutting, etc. of metal plates, glass plates, plastic plates, etc. It is used as a pressure-sensitive adhesive tape or sheet pressure-sensitive adhesive.
For example, it has sufficient adhesive force when protecting the surface of the adherend, and after the processing such as transportation, processing, cutting, etc., the adhesive member such as an adhesive sheet or adhesive tape is removed from the adherend. It can be easily peeled off.

  Thus, the peelable pressure-sensitive adhesive composition of the present invention comprises an acrylic emulsion [A], a crosslinking agent [B] containing a crosslinking agent (b1) containing an oxazoline group and a crosslinking agent (b2) containing a carbodiimide group. Because it contains, there is little increase in adhesive strength over time, and it has excellent stain resistance such as less adhesive residue and sticking marks on the adherend when peeled, and one-part curable aqueous It can also be used effectively as an adhesive composition.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to a following example, unless the summary is exceeded.
In the examples, “%” and “part” mean weight basis unless otherwise specified.

[Production of acrylic emulsion [A]]
2-ethylhexyl acrylate (a1) 99.2 parts, acrylic acid (a2) 0.8 parts, 1-dodecanethiol 0.03 parts, anionic reactive emulsifier (Daily Kogyo Seiyaku Co., Ltd., “AQUALON KH-10” ) 1.2 parts, 1.2 parts of an anionic non-reactive emulsifier (manufactured by Kao Corporation, “Perex SS-L”) and 31.5 parts of water were mixed and stirred to obtain an emulsion comprising a monomer mixture. .
Next, 19.9 parts of water was added to a flask equipped with a condenser and a stirring blade, and the mixture was stirred and dissolved. After the temperature was raised to 75 ° C., 0.6 part of a 10% aqueous ammonium persulfate solution was added, and 5 After a minute, 1.9 parts of the above emulsion and 10% aqueous ammonium persulfate solution were added dropwise, and the entire amount was added dropwise over 4 hours to carry out emulsion polymerization. After completion of the dropwise addition, stirring was continued for 2 hours while maintaining at 80 ° C., and then the mixture was cooled to 60 ° C. and 2 parts of 10% aqueous ammonia solution was added to neutralize the acid groups. Then, it cools to 55 degreeC and adds 0.5 part of 10% aqueous solution of tertiary butyl hydroperoxide (Nippon Yushi Co., Ltd. "Perbutyl H-69") and 0.5 part of 10% sodium hydrogensulfite aqueous solution, 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 0.5 part of 10% aqueous sodium hydrogen sulfite solution are again added. Added and allowed to react for 15 minutes. Thereafter, the mixture was cooled to 30 ° C., filtered through a 150 mesh nylon mesh, and adjusted to pH 8.4 with 10% aqueous ammonia to obtain an acrylic emulsion [A] (gel fraction 66%, average particle size) System 403 μm, solid content 62.5%, viscosity 450 mPa · s). Moreover, the coarse particle amount of the obtained acrylic emulsion [A] was 1.0 mg.

In addition, the evaluation method of the coarse particle amount of acrylic emulsion [A] is as follows.
(Rough particle amount)
The coarse particles obtained by drying the filtration residue of the acrylic mesh [A] obtained by filtration through a 150 mesh nylon mesh at 105 ° C. for 1 hour when the acrylic emulsion [A] was obtained as described above were weighted relative to 100 g of the emulsion (mg ).

Example 1
To the acrylic emulsion [A] obtained above, “Epocross WS-700” (b1) manufactured by Nippon Shokubai Co., Ltd. as a cross-linking agent is 2.44 parts (0.2 part as an active ingredient) with respect to 100 parts solids of the emulsion. 61 parts: 0.25 equivalents relative to the carboxyl group) and “Carbodilite V-04” (b2) manufactured by Nisshinbo Co., Ltd., 0.85 parts (1004 parts as an active ingredient: 0.34 parts as an active ingredient): 0.09 equivalent) with respect to the carboxyl group, and 0.75 parts of “SN Wet 970” manufactured by San Nopco as a wetting agent and 100% of “No. 0.01 part of SN deformer 777 ", 0.12 part of" ES-N "manufactured by Kitahiro Chemical Co., Ltd. as a release modifier, and finally" Adekano "manufactured by ADEKA, a thickener. Le UH-541VF "and added to non-volatile content of 55% water, was adjusted to a viscosity 2000 mPa · s (BM type, 12 rpm, 23 ° C.), to obtain a releasable aqueous pressure-sensitive adhesive composition of the present invention [A].
The obtained peelable water-based pressure-sensitive adhesive composition [A] was evaluated as follows.

(Initial adhesive strength)
The obtained aqueous pressure-sensitive adhesive composition [A] was applied to a commercially available silicone release paper so that the dry weight was 18 g / m ^2, and dried in an electric oven at 100 ° C. for 2 minutes, and then the substrate As a main raw material, cast coated paper [I] containing commercial calcium carbonate (weighing 84.9 g / m ² , trade name “Mirror Coat Gold (73)”, manufactured by Oji Paper Co., Ltd.) and commercially available polypropylene Using the synthetic paper [II] (trade name “Yupotac SGS80”, manufactured by YUPO Corporation), the laminate was laminated with a laminating roll at a pressure of 25 N / cm ² to obtain an adhesive sheet.
The adhesive sheet was aged at 23 ° C. for 7 days, and then adhered to a SUS304 plate polished with sandpaper having a surface roughness of # 280 at 23 ° C. and 50% RH by reciprocating a 2 kg roller twice. After 180 hours, 180 degree peel strength (N / 25 mm) was measured according to the method of measuring the adhesive strength of JIS Z 0237.

(Peelability)
(1) Adhesive strength after elapse of time The obtained aqueous pressure-sensitive adhesive composition [A] was applied to a commercially available silicone release paper so that the dry weight was 18 g / m ^2, and was applied in an electric oven at 100 ° C. After drying for a minute, commercially available cast coated paper [I] containing calcium carbonate (weighing 84.9 g / m ² , trade name, “Mirror Coat Gold (73)”, manufactured by Oji Paper Co., Ltd.), and commercially available Using a synthetic paper [II] (trade name, “Yupotac Base Paper SGS80”, manufactured by YUPO Corporation) made of polypropylene as a main raw material, lamination was performed with a laminating roll at a pressure of 25 N / cm ² to obtain an adhesive sheet. . The pressure-sensitive adhesive sheet was aged at 23 ° C. for 7 days, and then adhered to a SUS304 plate polished with sandpaper having a surface roughness of # 280 by reciprocating two 2 kg rollers at 23 ° C. and 50% RH. The change (i) (after leaving at 70 ° C. for 7 days) and the change with time (ii) (after leaving at 40 ° C., 80% RH for 7 days) according to the measurement method of adhesive strength of JIS Z 0237 Degree peel strength (N / 25 mm) was measured.

(2) Contamination resistance after aging Adhesive strength of the above-mentioned change with time (i) (after leaving at 70 ° C. for 7 days) and change with time (ii) (after leaving at 40 ° C., 80% RH for 7 days) After measuring, the degree of contamination of the adherend surface was visually observed, and the contamination resistance was evaluated as follows. Moreover, the adherend was changed to a melamine-coated plate (white) manufactured by Partec Co., Ltd., and the same contamination was evaluated.
○: No contamination was observed. △ ... Adhesive residue was slightly observed. × ... Adhesive residue was observed throughout.

Example 2
In the same manner as in Example 1, the aqueous pressure-sensitive adhesive composition [A] obtained above was transferred to a screw-mouth type reagent bottle (200 ml) and stored in a thermostatic device at 40 ° C. for 1 month. An adhesive sheet was obtained and evaluated in the same manner as in Example 1.

Examples 3-4, Comparative Examples 1-3
As shown in Table 1, the acrylic emulsion [A] obtained above was blended with a crosslinking agent to obtain a peelable aqueous pressure-sensitive adhesive composition. The resulting peelable aqueous pressure-sensitive adhesive composition was the same as in Example 1. Was evaluated. Further, a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1.
The evaluation results of Examples and Comparative Examples are shown in Tables 2 and 3.

note)
-The numerical value in a table | surface shows a compounding quantity (part). However, the numerical value in () indicates the amount of active ingredient (parts).
WS-700 (trade name “Epocross WS-700”, manufactured by Nippon Shokubai Co., Ltd., active ingredient 25%, oxazoline group equivalent: 220 (molecular weight per oxazoline group))
V-04 (trade name “Carbodilite V-04” manufactured by Nisshinbo Co., Ltd., active ingredient 40%, carbodiimide group equivalent: 334 (molecular weight per carbodiimide group))
-Number of oxazoline groups: oxazoline group (mole) in cross-linking agent / carboxyl group (mole) in emulsion [A]
-Number of carbodiimide groups: carbodiimide group (mole) in crosslinking agent / carboxyl group (mole) in emulsion [A]

note)
Base material I Cast coated paper: trade name “Mirror Coat Gold (73)”, manufactured by Oji Paper Co., Ltd., weighing 84.9 g / m ² ,
Symbols in the table (Break): Substrate destruction / Change over time (i) is an evaluation after being left at 70 ° C. for 7 days, Change over time (ii) is an evaluation after being left at 40 ° C. and 80% RH for 7 days It is.

note)
-Base material II Polypropylene synthetic paper: Trade name "Yupotac base paper SGS80", manufactured by YUPO CORPORATION-Symbols in the table (roll): Transfer of glue, (coagulation): Cohesive failure-Temporal change in the table (i ) Is an evaluation after being left at 70 ° C. for 7 days, and change with time (ii) is an evaluation after being left at 40 ° C. and 80% RH for 7 days.

  From the above results, since Comparative Examples 1 to 3 do not use the crosslinking agents (b1) and (b2) in combination, the adhesive strength under heat and moisture resistance increases greatly with time. Whereas the synthetic paper of the material is used as a base material, the stain resistance cannot be made compatible and the peelability is inferior, whereas in Examples 1-4, the crosslinking agents (b1) and (b2) Since it is used in combination, it can be seen that an adhesive member with little change over time and excellent stain resistance is obtained, and is useful as a peelable water-based pressure-sensitive adhesive composition. In particular, Example 2 shows that it is useful as a one-part curable peelable water-based pressure-sensitive adhesive.

  The peelable water-based pressure-sensitive adhesive composition of the present invention is useful for applications such as a surface protective film, a coating masking tape, a pressure-sensitive adhesive seal, and a pressure-sensitive adhesive label because it has little change with time in adhesive properties and is excellent in releasability.

Claims (10)

  A release-type aqueous pressure-sensitive adhesive composition comprising an acrylic emulsion [A] and a crosslinking agent [B], wherein the crosslinking agent [B] contains a crosslinking agent (b1) containing an oxazoline group and a crosslinking containing a carbodiimide group. A release-type aqueous pressure-sensitive adhesive composition comprising an agent (b2).   The acrylic emulsion [A] is a (meth) acrylic acid alkyl ester (a1) containing a C 4-12 alkyl group, a carboxyl group-containing unsaturated monomer (a2) and other unsaturated monomers ( The peelable water-based pressure-sensitive adhesive composition according to claim 1, wherein the acrylic resin (a) containing a3) as a copolymerization component is an acrylic emulsion that is dispersed and stabilized with an emulsifier.   The acrylic emulsion [A] is a (meth) acrylic acid alkyl ester (a1) containing a C 4-12 alkyl group, a carboxyl group-containing unsaturated monomer (a2) and other unsaturated monomers ( The release-type aqueous pressure-sensitive adhesive composition according to claim 1 or 2, wherein the copolymer component containing a3) is emulsion-polymerized in the presence of an emulsifier.   The peelable aqueous pressure-sensitive adhesive composition according to claim 2 or 3, wherein the emulsifier comprises an anionic reactive emulsifier and an anionic non-reactive emulsifier.   The peelable water-based pressure-sensitive adhesive composition according to claim 4, wherein the anionic non-reactive emulsifier is an emulsifier having no alkylene oxide chain.   6. The peelable aqueous pressure-sensitive adhesive composition according to claim 4 or 5, wherein the anionic nonreactive emulsifier is an anionic nonreactive emulsifier having one or more benzene ring skeleton structures.   The amount by which the content of the crosslinking agent (b1) containing an oxazoline group is 0.01 to 1 equivalent per 1 equivalent of carboxyl groups contained in the acrylic resin (a) in the acrylic emulsion [A]. The peelable water-based pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein   The amount by which the content of the crosslinking agent (b2) containing a carbodiimide group is 0.01 to 1 equivalent of carbodiimide group per equivalent of carboxyl group contained in the acrylic resin (a) in the acrylic emulsion [A]. The peelable water-based pressure-sensitive adhesive composition according to any one of claims 1 to 7, wherein   A peelable water-based pressure-sensitive adhesive comprising the peelable pressure-sensitive adhesive composition according to claim 1.   A peelable pressure-sensitive adhesive member, wherein the peelable aqueous pressure-sensitive adhesive according to claim 9 is laminated on at least one surface of a substrate.