JP2004277711A - Repeelable aqueous pressure-sensitive adhesive composition and pressure-sensitive adhesive product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a repeelable aqueous pressure-sensitive adhesive composition having excellent pressure-sensitive adhesive properties, capable of being easily peeled from a surface of an adherend, even when allowed to stand for a long time after completion of adhering to the adherend, and capable of exhibiting excellent resistance to whitening by water, even when used in a field in which the resistance to whitening by water is required, and to provide a pressure-sensitive adhesive product. <P>SOLUTION: The repeelable aqueous pressure-sensitive adhesive composition contains polymer particles [X] which comprise a polymer containing carbonyl and carboxyl groups and having an acid value of 3-30 and have an average particle diameter of ≤300 nm and a hydrazine derivative [Y] which has at least two hydrazino groups in its molecule, wherein a film formed out of the repeelable aqueous pressure-sensitive adhesive composition has a glass transition temperature of ≤-25°C and a gel fraction of ≥80 wt%, and contains a water extract in an amount of ≤2 wt%. The pressure-sensitive adhesive product is composed of the composition and a layer of a base material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a removable aqueous pressure-sensitive adhesive composition having excellent adhesive properties and removability and excellent water whitening resistance, and an adhesive product obtained by applying the same to a substrate.

  BACKGROUND ART Adhesive labels are used in various fields, but there are applications in which an adhesive label is peeled off from an adherend after a certain period of time has elapsed after being attached to the adherend. At this time, a part of the adhesive often remains on the adherend. In addition, when the base material is paper, the strength of the paper is low, so that it is often difficult to remove the paper from the adherend due to paper breakage. A removable pressure-sensitive adhesive that can be easily peeled from an adherend without such a problem has been proposed.

  In recent years, the shift from a solvent-type resin to an aqueous resin has been progressing in view of environmental issues. In the field of pressure-sensitive adhesives, it is desired to replace the solvent-type pressure-sensitive adhesive with a water-based pressure-sensitive adhesive. A typical example of the water-based pressure-sensitive adhesive is an emulsion-type water-based pressure-sensitive adhesive obtained by polymerizing various ethylenically unsaturated monomers.

  However, the emulsion-type aqueous pressure-sensitive adhesive is easily whitened when it comes into contact with water, that is, has low water-whitening resistance, and thus has become a major problem in replacing the solvent-type pressure-sensitive adhesive. In particular, when replacing a solvent-based pressure-sensitive adhesive conventionally used for transparent film labeling with an emulsion-type water-based pressure-sensitive adhesive, improvement of water-whitening resistance is the biggest problem.

  In order to improve water whitening resistance, polymer particles having a two-layer structure having different functional group monomer contents in the monomer composition are produced, or an alkyl having an alkyl group having 4 to 12 carbon atoms ( An aqueous dispersion obtained by producing and blending two types of polymer particles having different functional group monomer contents in a monomer composition mainly composed of (meth) acrylate has two hydrazino groups. A water-removable pressure-sensitive adhesive for re-peeling containing a hydrazine derivative is disclosed (for example, see Patent Document 1). However, in this method, not only sufficient performance is not obtained in the removability, but also the water-whitening resistance, which is the biggest problem of the emulsion-type aqueous pressure-sensitive adhesive, is notable.

JP-A-2002-105422

  The object of the present invention is excellent in adhesiveness, and can be easily peeled off from the surface of the adherend even after being left for a long time after pasting to the adherend, and further used in the field where water whitening resistance is required. The present invention also provides a removable water-based pressure-sensitive adhesive composition and a pressure-sensitive adhesive product exhibiting excellent water whitening resistance.

As a result of intensive studies to solve the problems, the following findings were obtained.
(1) A water-extractable amount of a film formed from the aqueous pressure-sensitive adhesive composition is 2% by weight or less, and the polymer comprises a polymer having an acid value of 3 to 30 and containing a carbonyl group and a carboxyl group dispersed in an aqueous medium. When the polymer particles [X] have an average particle diameter of 300 nm or less, the water whitening resistance is improved.
(2) The aqueous pressure-sensitive adhesive composition contains a compound [Y] having at least two hydrazino groups, and the gel fraction of a film formed from the aqueous pressure-sensitive adhesive composition is 80% by weight. Above, the removability is improved.
(3) When the glass transition temperature of the film is −25 ° C. or lower, the balance between the removability of the pressure-sensitive adhesive film and the adhesive strength is good.

  The present invention is based on such findings. That is, the present invention relates to a polymer particle [X] having an average particle diameter of 300 nm or less comprising a polymer having a carbonyl group and a carboxyl group and having an acid value of 3 to 30, and at least two hydrazino groups in the molecule. A water-soluble pressure-sensitive adhesive composition comprising the hydrazine derivative [Y] having a glass transition temperature of -25 ° C or lower and a gel component. Provided is a removable aqueous pressure-sensitive adhesive composition, characterized in that the ratio is 80% by weight or more and the amount of a water extract is 2% by weight or less.

  The present invention also provides an adhesive product comprising a substrate and a layer of the removable aqueous adhesive composition.

  According to the present invention, it is possible to provide a removable water-based pressure-sensitive adhesive composition having excellent water whitening resistance, adhesive strength, and removability. Further, the pressure-sensitive adhesive product of the present invention is excellent in water whitening resistance, adhesive strength, and removability, and is suitable as a pressure-sensitive adhesive label, a pressure-sensitive adhesive tape, a special pressure-sensitive adhesive sheet and the like.

  It is necessary that the content of the carboxyl group in the polymer particles [X] is an amount having an acid value in a range of 3 to 30, and if the acid value is in such a range, the polymer particles [X] The dispersion stability in aqueous media, the removability of the pressure-sensitive adhesive film and the adhesive strength can be imparted in a well-balanced manner, and the water whitening resistance is also improved. When the acid value is less than 3, the adhesive strength decreases, and when the acid value exceeds 30, the adhesive force increases with time, and the removability decreases.

  Further, the average particle size of the polymer particles [X] used in the present invention needs to be 300 nm or less in order to obtain a removable aqueous pressure-sensitive adhesive exhibiting good water whitening resistance. If the average particle size exceeds 300 nm, the water whitening resistance is undesirably reduced. Among these, 10 to 300 nm is particularly preferable. Here, the average particle diameter of the particles refers to a 50% median diameter on a volume basis of the emulsion particles, and the numerical values are based on values obtained by measurement by a dynamic light scattering method described in Examples described later.

  The gel fraction of the coating formed from the removable aqueous pressure-sensitive adhesive composition of the present invention is required to be 80% by weight or more in order to balance the adhesive strength of the pressure-sensitive adhesive and the removability. If the gel fraction is less than 80% by weight, the removability is undesirably reduced. Among these, it is usually preferable to control at 85 to 98%. The gel fraction means a ratio of an insoluble portion of the coating film of the aqueous pressure-sensitive adhesive composition to toluene. The gel fraction is based on a numerical value obtained by a measurement method and a formula described in Examples described later.

  Therefore, in order to achieve a good balance between the adhesive force and the removability of the pressure-sensitive adhesive, the acid value of the polymer particles [X] is 3 to 30 mg-KOH / g, and the removable aqueous pressure-sensitive adhesive composition has It is necessary that the film containing the hydrazine derivative [Y] having at least two hydrazino groups in the molecule and the glass transition temperature of the film formed from the removable aqueous pressure-sensitive adhesive composition be -25 ° C. .

  Further, the amount of the water extract formed from the removable aqueous pressure-sensitive adhesive composition of the present invention needs to be 2% by weight or less. It is preferable that the amount of the water extract is as small as possible. If the amount of the water extract exceeds 2% by weight, the water-whitening resistance of the removable aqueous pressure-sensitive adhesive film is undesirably reduced.

  Therefore, in order to obtain good water whitening resistance, the average particle diameter of the polymer particles [X] is 300 nm or less, and the amount of the water extract formed from the removable aqueous pressure-sensitive adhesive composition is 2% by weight or less. It is necessary to be.

  Next, the film formed from the removable aqueous pressure-sensitive adhesive composition of the present invention must have a glass transition temperature (hereinafter, referred to as Tg) of −25 ° C. or lower. When the Tg is in this range, the physical properties of the pressure-sensitive adhesive, that is, the balance of physical properties such as adhesive strength and holding power are excellent. If the Tg exceeds -25 ° C, the adhesive strength required as a removable aqueous pressure-sensitive adhesive cannot be obtained, which is not preferable. Further, the temperature is preferably from -25 to -60 ° C. Here, Tg in the present invention is based on a numerical value obtained by a measurement method described in Examples below.

  Next, the removable aqueous pressure-sensitive adhesive composition of the present invention is obtained, for example, by emulsion copolymerization of a monomer component described below. Specifically, the polymer of the polymer particles [X] comprises (a) at least one carbonyl group-containing ethylenically unsaturated monomer in the molecule, and 0.1 to 2 weight per monomer. %, (B) a carboxyl group-containing ethylenically unsaturated monomer, 0.5 to 4% by weight, and (c) an alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms. Copolymers obtained by copolymerizing a polymerizable monomer mixture containing 4% by weight as an essential component are exemplified. At this time, if necessary, an unsaturated monomer (d) other than the above (a) to (c) may be used in the range of 0.001 to 55% by weight.

  The carbonyl group-containing ethylenically unsaturated monomer (a) is not particularly limited, and has a functional group reactive with the hydrazino group of the above-mentioned hydrazine derivative [Y], for example, acrolein, diacetone Acrylamide, formylstyrene, vinyl ethyl ketone, acetoacetoxyethyl (meth) acrylate, diacetone (meth) acrylate, acetonyl acrylate, 2-hydroxypropyl acrylate-acetyl acetate, butanediol-1,4-acrylate-acetyl acetate, and the like. Can be In particular, it is preferable to use diacetone acrylamide because the adhesive strength and removability of the adhesive can be imparted in a well-balanced manner. The amount of the carbonyl group-containing ethylenically unsaturated monomer used is in the range of 0.1 to 2% by weight, particularly preferably 0.2 to 2% by weight. When it is in this range, good removability can be imparted.

  Next, the ethylenically unsaturated monomer (b) having a carboxyl group is not particularly limited as long as it has a carboxyl group and an ethylenically unsaturated group in the molecule. Examples of such ethylenically unsaturated monomers include, for example, acrylic acid, methacrylic acid, β-carboxyethyl (meth) acrylate, 2- (meth) acryloylpropionic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, itacone Acid half ester, maleic acid half ester, maleic anhydride, itaconic anhydride, ω-carboxy-polycaprolactone (meth) acrylate, β- (meth) acryloyloxyethyl hydrogen succinate, β- (meth) hydroxyethyl hydrogen phthalate, And a salt thereof, and the like, and one or a mixture of two or more thereof can be used. Among these, it is particularly preferable to use methacrylic acid in terms of excellent stability during polymerization of the monomer component and water whitening resistance. The amount of the ethylenically unsaturated monomer having a carboxyl group to be used is preferably 0.5 to 4% by weight, particularly preferably 0.5 to 3% by weight. In this range, the adhesive strength and the removability can be imparted in a well-balanced manner.

  Examples of the alkyl (meth) acrylate (c) having an alkyl group having 4 to 12 carbon atoms include n-butyl (meth) acrylate, i-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, i-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, i-nonyl (meth) acrylate, n-decyl (meth) acrylate, n- Lauryl (meth) acrylate and the like can be mentioned, and one kind or a mixture of two or more kinds thereof can be used. Among these, an alkyl (meth) acrylate having an alkyl group having 4 to 9 carbon atoms is preferable because of good polymerizability. The amount of the alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms is preferably 45 to 99.4% by weight, particularly preferably 64 to 95% by weight. . When it is in this range, the Tg of the pressure-sensitive adhesive film described above can be adjusted to a desired range, and the pressure-sensitive adhesive properties can be imparted in a well-balanced manner.

  Examples of the unsaturated monomer (d) other than the above (a) to (c) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, t-butyl (meth) acrylate, stearyl (meth) acrylate (Meth) acrylates such as phenyl (meth) acrylate and benzyl (meth) acrylate; 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3-pentafluoropropyl (meth) Fluorine-containing ethylenically unsaturated monomers such as acrylate, perfluorocyclohexyl (meth) acrylate, 2,2,3,3-tetrafluoropropyl (meth) acrylate, and β- (perfluorooctyl) ethyl (meth) acrylate Such as vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl versatate; Nyl esters; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, amyl vinyl ether, and hexyl vinyl ether; nitrile group-containing ethylenically unsaturated monomers such as (meth) acrylonitrile; styrene, α-methylstyrene, vinyl Vinyl compounds having an aromatic ring such as toluene, vinylanisole, α-halostyrene, vinylnaphthalene and divinylstyrene; and isoprene, chloroprene, butadiene, ethylene, tetrafluoroethylene, vinylidene fluoride, N-vinylpyrrolidone and the like. The amount of these substances to be used is preferably 0.1 to 55% by weight, particularly preferably 5 to 55% by weight.

  Among these, it is particularly preferable to use (meth) acrylic acid esters from the viewpoint of excellent stability during polymerization of the monomer component.

  Further, as unsaturated monomers (d) other than the above (a) to (c), in order to improve the gel fraction of the removable aqueous pressure-sensitive adhesive to a desired range, other than carbonyl groups and carboxyl groups. It is also possible to use an ethylenically unsaturated monomer containing a crosslinkable reactive group. Examples thereof include glycidyl group-containing polymerizable monomers such as glycidyl (meth) acrylate and allyl glycidyl ether; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and polyethylene glycol mono (meth). Hydroxyl-containing polymerizable monomers such as acrylate and glycerol mono (meth) acrylate; aminos such as aminoethyl (meth) acrylate, N-monoalkylaminoalkyl (meth) acrylate, and N, N-dialkylaminoalkyl (meth) acrylate Group-containing polymerizable monomers; methylolamido such as N-methylol (meth) acrylamide, N-isopropoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-isobutoxymethyl (meth) acrylamide A polymerizable monomer containing a group or an alkoxylated compound thereof; vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ- (meth) acryloxypropyltrimethoxysilane, γ- ( (Meth) acryloxypropyltriethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxypropyltriisopropoxysilane, N-β A silyl group-containing polymerizable monomer such as-(N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane and its hydrochloride; an aziridinyl group-containing polymerizable monomer such as 2-aziridinylethyl (meth) acrylate (Meth) acryloyl isocyana Isocyanate group and / or blocked isocyanate group-containing polymerizable monomer such as phenol or methylethylketoxime adduct of (meth) acryloyl isocyanatoethyl; 2-isopropenyl-2-oxazoline, 2-vinyl-2 Oxazoline group-containing polymerizable monomers such as -oxazoline; amide group-containing polymerizable monomers such as (meth) acrylamide, N-monoalkyl (meth) acrylamide, N, N-dialkyl (meth) acrylamide; dicyclopentenyl Cyclopentenyl group-containing polymerizable monomers such as (meth) acrylate; allyl group-containing polymerizable monomers such as allyl (meth) acrylate. The amount of these substances used is preferably 0.001 to 20% by weight, particularly preferably 0.01 to 10% by weight.

  In addition, the crosslinkable reactive group of the polymer composed of these monomer components causes the polymers to crosslink with each other, so that the gel fraction of the coating formed from the removable aqueous pressure-sensitive adhesive composition described later is 80% by weight. % Or more can be adjusted.

  As the unsaturated monomer (d) other than the above (a) to (c), in order to improve the gel fraction of the removable aqueous pressure-sensitive adhesive to a desired range, two unsaturated monomers in the molecule are used. Polyfunctional ethylenically unsaturated monomers containing the above ethylenically unsaturated groups can also be used. For example, ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol Examples thereof include di (meth) acrylate, diallyl phthalate, divinylbenzene, and allyl (meth) acrylate. The use amount of these substances is preferably 0.001 to 10% by weight, particularly preferably 0.001 to 5% by weight.

  When these polyfunctional ethylenically unsaturated monomers are used, the cohesive force of the pressure-sensitive adhesive is improved, and the holding power becomes good.However, in order to make the balance between the adhesive strength and the holding power good, As described above, the amount of the polyfunctional ethylenically unsaturated monomer used is preferably such that the gel fraction of the pressure-sensitive adhesive film is 80% by weight or more. The amount of these substances used is preferably 0.001 to 10% by weight, particularly preferably 0.5 to 5% by weight.

  Further, as the unsaturated monomer (d) other than the above (a) to (c), the obtained removable aqueous pressure-sensitive adhesive is used for the purpose of improving the stability during emulsion polymerization and the storage stability of the emulsion. An ethylenically unsaturated group containing a sulfonic acid group and / or a sulfate group (and / or a salt thereof), a phosphoric acid group and / or a phosphoric ester group (and / or a salt thereof) within a range that does not lower the water whitening resistance of Monomers can be used in combination. Examples of such unsaturated monomers (d) include vinylsulfonic acids such as vinylsulfonic acid and styrenesulfonic acid or salts thereof, allyl group-containing sulfonic acids such as allylsulfonic acid and 2-methylallylsulfonic acid, and Salts thereof, (meth) acrylate group-containing sulfonic acids such as 2-sulfoethyl (meth) acrylate and 2-sulfopropyl (meth) acrylate or salts thereof, and (meth) acrylates such as (meth) acrylamide-t-butylsulfonic acid Acrylamide group-containing sulfonic acids or salts thereof, and "Adecaria Soap PP-70, PPE-710" (manufactured by Asahi Denka Kogyo Co., Ltd.) having a phosphate group, and the like, and one or a mixture of two or more thereof Can be used. The amount of these substances used is preferably 0.1 to 2% by weight, particularly preferably 0.1 to 1% by weight.

  The removable aqueous pressure-sensitive adhesive composition of the present invention comprises, for example, the carbonyl group-containing ethylenically unsaturated monomer (a), the carboxyl group-containing ethylenically unsaturated monomer (b) and a carbon atom It is obtained by emulsion-copolymerizing an alkyl (meth) acrylate (c) having an alkyl group of 4 to 12 and another ethylenically unsaturated monomer (d).

  As the polymerization initiator used in the polymerization of the polymer, a radical polymerization initiator is used. Examples of the radical polymerization initiator include persulfates, organic peroxides, and hydrogen peroxide.

  The polymer can be obtained by radical polymerization using only these peroxides, or also by a redox polymerization initiator system using the above peroxide in combination with a reducing agent.

  Further, azo initiators such as 4,4'-azobis (4-cyanovaleric acid) and 2,2'-azobis (2-amidinopropane) dihydrochloride can also be used as the polymerization initiator.

  Among the above polymerization initiators, it is particularly preferable to use an organic peroxide-based polymerization initiator since the water-whitening resistance of the pressure-sensitive adhesive film is significantly improved.

  Examples of the organic peroxides include, for example, diacyl peroxides such as benzoyl peroxide, lauroyl peroxide, and decanoyl peroxide; dialkyl peroxides such as t-butylcumyl peroxide and dicumyl peroxide; and t-butylperoxide. Examples include peroxyesters such as oxylaurate and t-butylperoxybenzoate, and hydroperoxides such as cumene hydroperoxide, paramenthane hydroperoxide, and t-butyl hydroperoxide.

  Examples of the reducing agent used in the redox polymerization initiator include ascorbic acid and its salts, erythorbic acid and its salts, tartaric acid and its salts, citric acid and its salts, and metal salts of formaldehyde sulfoxylate. Is mentioned.

  Further, in order to adjust the molecular weight of the polymer, it is preferable to use a compound having a chain transfer ability as a molecular weight modifier. Examples of the compound include lauryl mercaptan, octyl mercaptan, dodecyl mercaptan, 2-mercaptoethanol, octyl thioglycolate, 3-mercaptopropionic acid, mercaptans such as thioglycerin, and α-methylstyrene dimer. .

  When producing a polymer in an aqueous medium, an emulsifier and other dispersion stabilizers can be used, if necessary, as long as the water resistance of the pressure-sensitive adhesive film is not reduced. As the emulsifier, an anionic emulsifier, a cationic emulsifier, a nonionic emulsifier and the like can be used, but an anionic emulsifier and a nonionic emulsifier are preferable.

  Examples of the anionic emulsifier include, for example, sulfates of higher alcohols and salts thereof, alkylbenzene sulfonates, polyoxyethylene alkylphenyl sulfonates, polyoxyethylene alkyl diphenyl ether sulfonates, alkyl diphenyl ether disulfonates, dialkyl succinates. Ester sulfonates and the like. Examples of the nonionic emulsifier include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene diphenyl ether, polyoxyethylene-polyoxypropylene block copolymer, and the like.

  Further, an emulsifier having a polymerizable unsaturated double bond in a molecule, which is generally called a “reactive emulsifier”, can also be used. Commercial products of such reactive emulsifiers include, for example, “Latemul S-180” having a sulfonic acid group and a salt thereof (manufactured by Kao Corporation), “Eleminol JS-2, RS-30” [Sanyo Chemical Industries, Ltd. "Aqualon HS-10, HS-20" having a sulfate group and a salt thereof [manufactured by Daiichi Kogyo Seiyaku Co., Ltd.], "Adecaria Soap SE-10, SE-20" [Asahi Denka Kogyo Co., Ltd.] "New Frontier A-229E" having a phosphate group [Daiichi Kogyo Seiyaku Co., Ltd.] and the like; "Aqualon RN-10, RN-20, RN- having a nonionic hydrophilic group" 30, RN-50 "[manufactured by Daiichi Kogyo Seiyaku Co., Ltd.] and the like.

  In addition, other dispersion stabilizers other than the emulsifier can be used. Examples of such dispersion stabilizers include polyvinyl alcohol, cellulose ether, starch, maleated polybutadiene, maleated alkyd resin, polyacrylic acid (salt), polyacrylamide, aqueous acrylic resin, aqueous polyester resin, and aqueous polyamide resin. And a synthetic or natural water-soluble polymer such as an aqueous polyurethane resin.

  The amount of the emulsifier and the dispersion stabilizer is preferably as small as possible from the viewpoint of water resistance and adhesive strength of the obtained pressure-sensitive adhesive film. % By weight or less.

  In addition, at the time of polymerization, it is also possible to add a hydrophilic solvent, a hydrophobic solvent, and various additives, but it is preferable that the amount used is controlled within a range that does not adversely affect the obtained adhesive film. . The temperature at which the polymer is polymerized varies depending on the type of monomer used, the type of polymerization initiator, etc., but when polymerizing in an aqueous medium, it is usually preferable to perform the polymerization in a temperature range of 30 to 90 ° C. .

  Specific methods for producing the polymer include (1) water, a carbonyl group-containing ethylenically unsaturated monomer, a carboxyl group-containing ethylenically unsaturated monomer, and an alkyl group having 4 to 12 carbon atoms. A method in which a polymerizable monomer having an alkyl (meth) acrylate as an essential component, other ethylenically unsaturated monomers, a polymerization initiator, and if necessary, an emulsifier and a dispersion stabilizer, are mixed together and polymerized. 2) A method in which water, an ethylenically unsaturated monomer, and an emulsifier are preliminarily mixed and dropped, so-called a pre-emulsion method, and (3) a method of dropping a monomer. Among these, in particular, from the viewpoint of stability during polymerization, production by the pre-emulsion method of (2) is preferable because of containing a carboxyl group, having an acid value of 3 to 30 and an average particle diameter of 300 nm or less. It is preferable because an aqueous dispersion in which the united particles [X] are dispersed can be easily obtained.

  As a specific method of the above (2), for example, an aqueous medium, a polymerization initiator, and a polymer are placed in a stirred reactor equipped with a dropping funnel, and then the temperature of the reactor is raised to the polymerization temperature, A method of dropping a monomer component from a funnel may be used. At this time, the inside of the reactor may be an open system, but is preferably replaced with an inert gas such as nitrogen. Further, the polymerization temperature varies depending on the type of the monomer to be used, the type of the polymerization initiator, and the like, but usually, a temperature range of 30 to 90 ° C is appropriate, and more preferably, a range of 40 ° C to 85 ° C. . The dropping rate of the monomer component is preferably adjusted as appropriate according to the ratio of the polymer to the monomer component and the solid concentration of the obtained aqueous polymer dispersion, and is not particularly limited.

  During the emulsion polymerization, a hydrophilic solvent, a hydrophobic solvent and various additives can be added as long as the effects of the present invention are not impaired.

  In addition, the removable water-based pressure-sensitive adhesive composition of the present invention includes a filler, a pigment, a pH adjuster, a film-forming auxiliary, and a leveling agent described below, as long as the desired effect of the present invention is not impaired. Well-known substances such as a thickener, a water repellent, a tackifier, and an antifoaming agent can be appropriately added and used.

  The removable water-based pressure-sensitive adhesive composition of the present invention can be applied to various pressure-sensitive adhesive products, particularly products requiring water whitening resistance and removability.

  When producing an adhesive product (adhesive tape, adhesive label, etc.), a method of directly applying to a substrate used for a tape or a label and then bonding it to a release paper, and a method of applying the release paper to the substrate after drying and applying Although there is a method of transferring to the release paper, especially in the latter method of applying a removable water-based adhesive to the release paper, since the surface energy of the release paper is low, there is no problem with the conventional solvent-based adhesive However, the re-peelable water-based pressure-sensitive adhesive has a problem that cissing and bleeding are easily generated at the time of coating. In order to suppress these phenomena, it is necessary to improve the wettability of the removable aqueous pressure-sensitive adhesive to the release paper to obtain a smooth coated surface. Conventionally, as a wettability improver (hereinafter referred to as a leveling agent), The problem is solved by adding an activator. However, the addition of a leveling agent has the disadvantage that the water-whitening resistance of the pressure-sensitive adhesive film deteriorates.

  Commonly used leveling agents include anionic surfactants, nonionic surfactants, cationic surfactants, and zwitterionic surfactants. More specifically, examples of the anionic surfactant include sulfates of higher alcohols and salts thereof, alkylbenzene sulfonates, polyoxyethylene alkylphenyl sulfonates, polyoxyethylene alkyl diphenyl ether sulfonates, and alkyl Diphenyl ether disulfonate, succinic acid dialkyl ester sulfonate and the like, and as the nonionic surfactant, for example, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene diphenyl ether, polyoxyethylene- Examples thereof include a polyoxypropylene block copolymer and an acetylenic diol-based surfactant. Examples of the cationic surfactant include alkyl (amide) betaine and alkyldimethyl. Min'okishido, and the like.

  In addition to the above-mentioned surfactants, fluorine-based surfactants and silicone-based surfactants can also be used as special surfactants.

  Among them, those used in the removable aqueous pressure-sensitive adhesive composition of the present invention include, as an anionic surfactant, a dialkyl succinate sulfonate surfactant, and a nonionic surfactant. Examples of the acetylene diol-based surfactant and the fluorine-based surfactant include Megafac F-142D, Megafac F-1405 (manufactured by Dainippon Ink and Chemicals, Inc.), and ZONYL FSN (manufactured by DuPont). Examples of fluoroalkylethylene oxide adducts and silicone surfactants include polyether-modified dimethylsiloxanes such as SILWET FZ-2166 (manufactured by Nippon Unicar Co., Ltd.) and BYK 348 (manufactured by BYK Japan KK). The use of one or a mixture of two or more of these is preferred from the viewpoint of excellent coatability. Arbitrariness.

  Further, it is more preferable to use an acetylenic diol-based surfactant [Z] from the viewpoint that good water-whitening resistance of the pressure-sensitive adhesive film is not impaired. Specific examples of the acetylenic diol surfactant [Z] include Surfinol 104PA, Surfinol 420, Surfinol 440, Surfinol 465, Surfinol 485, Surfinol 504, Surfinol 504, Surfinol PSA204 and Surfinol PSA216. And Surfynol PSA336 and Dynol 604 (manufactured by Air Products Japan Co., Ltd.), and one or a mixture of two or more of these can be used. The amount of the acetylene diol-based surfactant [Z] to be added is not particularly limited. However, from the viewpoint of not impairing the excellent water-whitening resistance of the pressure-sensitive adhesive film, 0.1 to 100 parts by weight of the polymer particles [X]. -3.0 parts by weight is preferred.

  The amount of the leveling agent used is not particularly limited as long as repelling and shrinkage at the time of coating can be sufficiently suppressed and a smooth coated surface can be obtained, but 0.1 to the solid content of the removable water-based adhesive. When used in an amount of from 2 to 2 parts by weight, the adhesive properties such as adhesive strength of the adhesive are not adversely affected, so that it is preferable.

  The method of using the leveling agent may be, after obtaining the polymer particles [X], adding to the aqueous dispersion in which the polymer particles [X] are dispersed. A method of using as a surfactant for emulsion polymerization at the time of production is also included.

  Generally, in order to impart polymerization stability at the time of emulsion polymerization, as described above, anionic emulsifier, cationic emulsifier, nonionic emulsifier, further surfactants such as reactive emulsifier, and other A dispersion stabilizer is used. However, although the polymerization stability is improved as the amount used increases, the water-whitening resistance of the removable water-based pressure-sensitive adhesive film obtained decreases.

  On the other hand, when the acetylene diol-based surfactant [Z] among the above-mentioned leveling agents is used at the time of emulsion polymerization, polymerization stability can be imparted in addition to the effect as the leveling agent. Furthermore, it is particularly preferable because the water-whitening resistance of the removable water-based pressure-sensitive adhesive film obtained is not impaired.

  Next, the hydrazine derivative [Y] having at least two hydrazino groups in the molecule used in the present invention is not particularly limited. For example, carbodihydrazide, oxalic dihydrazide, malonic dihydrazide, succinic dihydrazide, glutaric acid Dihydrazide, adipic dihydrazide, sebacic dihydrazide, maleic dihydrazide, fumaric dihydrazide, itaconic dihydrazide, ethylene-1,2-dihydrazine, propylene-1,3-dihydrazine, butylene-1,4-dihydrazine and the like. Among them, carbodihydrazide and adipic dihydrazide are particularly preferred in that good removability can be imparted.

  The compounding ratio of the hydrazine derivative [Y] having at least two hydrazino groups in the molecule is such that the hydrazino group per equivalent of the carbonyl group in the polymer particles (X) is good because the adhesive force and the removability are good. Is preferably 0.05 to 5 equivalents, and particularly preferably 0.2 to 3 equivalents.

  Next, the adhesive product of the present invention will be described.

  The pressure-sensitive adhesive product of the present invention is composed of a substrate and a layer of the removable aqueous pressure-sensitive adhesive composition. Examples of the substrate include paper, plastic film, and nonwoven fabric.

  In particular, since the removable aqueous pressure-sensitive adhesive composition of the present invention has excellent water whitening resistance, it can be suitably used for the production of a pressure-sensitive adhesive product using a transparent substrate. Specific examples of the transparent substrate include plastic films such as cellophane, polyethylene, polypropylene, polyester, polyethylene terephthalate, polystyrene, polyvinyl chloride, polyacetate, polycarbonate, and acrylic resin.

  As a method for forming a layer of the pressure-sensitive adhesive composition using the removable water-based pressure-sensitive adhesive composition of the present invention, the above-mentioned substrate is directly coated with the removable water-based pressure-sensitive adhesive composition and dried. The water-based pressure-sensitive adhesive composition is applied and dried on a release method such as a paper or a plastic film or the like, which has been subjected to a release treatment with silicone or the like, to form a pressure-sensitive adhesive layer. There is a transfer method in which a base material is superimposed on the agent layer, pressure is applied, and the pressure-sensitive adhesive layer is transferred onto the base material.

  Examples of the coating method include a method using a roll coater, a comma coater, a lip coater, a fountain die coater, a gravure coater, or the like as a coating machine.

  The removable pressure-sensitive adhesive composition of the present invention generally has a solid content of 50 to 70% by weight, a viscosity of 10 to 10,000 mPa · s (BM type viscometer, 60 rotations, 25 ° C), and a pH of 6 to 6. 9 When applying by the above-mentioned direct method, although it depends on the kind of application method, in general, low viscosity is often required in order to apply at a higher speed. In the case of coating by the transfer method, those having a viscosity of 300 to 10,000 mPa · s (BM viscometer, 60 rotations, 25 ° C.) are preferable.

  The pressure-sensitive adhesive product of the present invention is excellent in adhesive strength and water-whitening resistance, and thus is suitable for a pressure-sensitive adhesive label, a pressure-sensitive adhesive tape, a special pressure-sensitive adhesive sheet, and the like.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the scope of the present invention is not limited to these Examples. In the following, unless otherwise specified, “%” indicates% by weight and “parts” indicates “parts by weight”.

The evaluation method used in the present invention will be described below.
[Method of measuring acid value]
A re-peelable aqueous pressure-sensitive adhesive composition is applied on a glass plate with a 3 mil applicator, and dried at room temperature for 1 hour to form a semi-dry pressure-sensitive adhesive film (sample). Then, 1 g of the pressure-sensitive adhesive film was precisely weighed and dissolved in 100 g of tetrahydrofuran (THF) to obtain a measurement sample. The measurement was performed by a neutralization titration method using an aqueous potassium hydroxide solution. For samples not dissolved in tetrahydrofuran, measurement by this method is impossible, so the calculated value obtained from the charged amount of the carboxyl group-containing monomer used in the production of the removable aqueous pressure-sensitive adhesive composition Was determined as the acid value.
[Measurement method of average particle size]
The value of the average particle diameter (50% median diameter on a volume basis) measured by a Microtrac UPA type particle size distribution analyzer manufactured by Nikkiso Co., Ltd. was determined.
[Method of measuring Tg]
The re-peelable aqueous pressure-sensitive adhesive composition is applied to a glass plate so that the film thickness after drying becomes 0.3 mm, dried at 25 ° C. for 24 hours, peeled from the glass plate, and further at 100 ° C. for 5 minutes The dried sample was used as a sample, and about 10 mg of the sample was weighed into an aluminum cylindrical cell having a diameter of 5 mm and a depth of 2 mm, and nitrogen was measured using a DSC-2920 modulated differential scanning calorimeter manufactured by TA Instruments. An endothermic curve was measured when the temperature was raised from -150 ° C to 100 ° C at a rate of 20 ° C / min in an atmosphere.
[Method for measuring gel fraction]
A water-removable water-based pressure-sensitive adhesive composition was applied on a glass plate so as to have a thickness of 0.3 mm after drying, dried at 25 ° C. for 24 hours, peeled from the glass plate, and further dried at 100 ° C. for 5 hours. The sample dried for 50 minutes was cut into a square of 50 mm, and this was used as a sample. Next, the weight (G1) of the sample before immersion in toluene was measured in advance, and the toluene-insoluble portion of the sample after immersion in a toluene solution at room temperature for 24 hours was separated by filtration through a 300 mesh wire mesh. The weight (G2) of the residue after drying at 110 ° C. for 1 hour was measured, and the gel fraction was determined according to the following equation.

Gel fraction (% by weight) = (G2 / G1) × 100
[Method for measuring the amount of water extract]
The removable pressure-sensitive adhesive composition is applied to a glass plate so that the film thickness after drying is 0.3 mm, dried at 25 ° C. for 24 hours, peeled from the glass plate, and further at 120 ° C. for 5 minutes The remaining water was evaporated by heat treatment. The film was cut into a 20 mm square and the weight (W1) was measured to obtain a test film. The test film was immersed in water at 25 ° C. for 7 days, pulled up and lightly wiped the water on the film surface, dried at 110 ° C. for 1 hour, allowed to cool, and measured for weight (W2). The amount of water extract in the film was determined according to

Amount of water extract (% by weight) = {(W1-W2) / W1} × 100
[Measurement method of water whitening resistance test]
On the surface of a polyethylene terephthalate film having a thickness of 25 μm, a removable aqueous pressure-sensitive adhesive composition was applied so that the film thickness after drying was 25 μm, and dried at 100 ° C. for 2 minutes to prepare a pressure-sensitive adhesive sheet, which was used as a sample. . The sample was immersed in water at 30 ° C. for 24 hours so that the adhesive-coated surface was exposed, and the turbidity of the sample before and after immersion in water was measured with a turbidimeter, and the degree of change in the turbidity was measured using W And water whitening resistance was evaluated.

Turbidity meter: NDH-300A turbidity meter manufactured by Nippon Denshoku Industries Co., Ltd.
Measurement light source: Halogen lamp Light receiving element: Silicon photocell based on JIS K7105 The turbidity and the degree of change in turbidity before and after immersion in water were determined according to the following equations.

Turbidity H = (DF / TL) × 100
TL; total transmittance (%)
DF; diffuse transmittance (%)
After determining the degree of change in turbidity; W value = H1 / H0 (H0: turbidity before immersion in water, H1: turbidity after immersion in water), the results were determined according to the following criteria.

；: Turbidity change W value is less than 5 △: turbidity change W value is 5 or more and less than 30 ×: turbidity change W value is 30 or more [Method of measuring adhesive strength]
A removable water-based pressure-sensitive adhesive composition was applied on the surface of a 25 μm-thick polyethylene terephthalate film so that the film thickness after drying was 25 μm, and dried at 100 ° C. for 2 minutes to prepare a pressure-sensitive adhesive sheet. Using a pressure-sensitive adhesive sheet and a stainless steel plate as an adherend, a 180 ° peel strength was measured in an atmosphere of 23 ° C. and 50% RH according to JIS Z-0237, and the adhesive strength was determined.
[Measurement of holding force]
A pressure-sensitive adhesive sheet was prepared in the same manner as when measuring the adhesive force, the pressure-sensitive adhesive sheet was stuck on a stainless steel plate so that the bonding area was 25 mm × 25 mm, and the time required for peeling off at 40 ° C. with a load of 1 kg was measured. The holding time was defined as the holding force. In the case where the sheet was held even after 300 minutes, the holding time was set to 300 minutes or more, and the deviation width from the initial sticking position was measured and also described.
[Removability]
A pressure-sensitive adhesive sheet was prepared in the same manner as in the measurement of the adhesive force, the pressure-sensitive adhesive sheet was stuck on a stainless steel plate so that the bonding area was 25 mm × 25 mm, and left in an atmosphere of 23 ° C. and 65% RH for 30 days. And the state of the surface of the adherend after peeling was visually judged.

  ；: Clean peeling without adhesive residue or paper tear.

  Δ: Partially glue residue or paper tear.

×: Adhesive residue or paper tear on the entire surface.
[tack]
A pressure-sensitive adhesive sheet was prepared in the same manner as in the measurement of the adhesive force, and the pressure-sensitive adhesive sheet was measured in an atmosphere of 23 ° C. and 50% RH according to the ball rolling method of JIS Z-0237.

Example 1
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen introducing pipe, a thermometer, and a dropping funnel, 0.4 part of Latemul E-118B [manufactured by Kao Corporation: 25% active ingredient] and 45 parts of deionized water were put. The temperature was raised to 75 ° C. while blowing nitrogen. Under stirring, 0.02 part of t-butyl hydroperoxide and 0.01 part of L-ascorbic acid were added, followed by 87.5 parts of 2-ethylhexyl acrylate, 10 parts of methyl methacrylate, 2 parts of methacrylic acid, A monomer pre-emulsion was prepared by adding 1.6 parts of latemul E-118B and 15 parts of deionized water to a monomer mixture consisting of 0.5 parts of acetone acrylamide and 1 part of lauryl mercaptan and emulsifying the mixture. A portion (3 parts) of the monomer emulsified with an emulsifier and water) was added, and polymerization was carried out for 60 minutes while maintaining the temperature in the reaction vessel at 75 ° C. Subsequently, while maintaining the temperature inside the reaction vessel at 75 ° C., the remaining monomer pre-emulsion (114.6 parts), 15 parts of an aqueous solution of t-butyl hydroperoxide (1% of active ingredient), and an aqueous solution of L-ascorbic acid (1%) 15 parts of the active ingredient (0.5%) was dropped and polymerized using a separate dropping funnel over 240 minutes while maintaining the temperature in the reaction vessel at 75 ° C.

  After completion of the dropwise addition, the mixture was stirred at the same temperature for 120 minutes, the content was cooled, and adjusted to pH 8.0 with aqueous ammonia (active ingredient 10%). The aqueous dispersion of the polymer particles [X] obtained here had a solid concentration of 52.9%, a viscosity of 230 mPa · s, and an average particle diameter of 280 nm. The acid was determined from the charged amount of the carboxyl group-containing monomer. The value was 13.

  To the aqueous dispersion of the polymer particles [X], 1.2 parts of Surfynol 420 (manufactured by Air Products Japan K.K .: 100% active ingredient) and 0.3 part of adipic dihydrazide are added as leveling agents. After that, the mixture was filtered through a 100-mesh wire net to obtain a removable aqueous pressure-sensitive adhesive composition of the present invention.

  Glass transition temperature (actually measured Tg), gel fraction (toluene-insoluble fraction), water extract amount, water-whitening resistance of pressure-sensitive adhesive sheet, adhesion of coating film obtained using removable water-based pressure-sensitive adhesive composition of the present invention Table 1 shows the evaluation results of the force, the holding power, the removability, and the tack.

Example 2
0.4 parts of Latemul E-118B, 0.3 parts of Surfynol 420, and 45 parts of deionized water were put into a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet, a thermometer, and a dropping funnel. The temperature was raised to 75 ° C. while blowing. Under stirring, 0.02 part of t-butyl hydroperoxide and 0.01 part of L-ascorbic acid were subsequently added, followed by 88 parts of 2-ethylhexyl acrylate, 10 parts of methyl methacrylate, 1 part of methacrylic acid, and diacetone acrylamide. To a monomer mixture consisting of 1 part of lauryl mercaptan and 1 part of lauryl mercaptan, 1.2 parts of Aqualon KH-1025 [manufactured by Daiichi Kogyo Seiyaku Co., Ltd .: 25% of active ingredient] and 15 parts of deionized water were added and emulsified. A part (3 parts) of the monomer pre-emulsion (the monomer is emulsified with the above-mentioned monomer mixture, emulsifier and water) is added, and polymerization is carried out for 60 minutes while maintaining the temperature in the reaction vessel at 75 ° C. Was. Subsequently, while maintaining the temperature in the reaction vessel at 75 ° C., the remaining monomer pre-emulsion (114.2 parts), 15 parts of an aqueous solution of t-butyl hydroperoxide (1% of active ingredient), and an aqueous solution of L-ascorbic acid (1%) 15 parts of the active ingredient (0.5%) was dropped and polymerized using a separate dropping funnel over 240 minutes while maintaining the temperature in the reaction vessel at 75 ° C.

  After completion of the dropwise addition, the mixture was stirred at the same temperature for 120 minutes, the content was cooled, and adjusted to pH 8.0 with aqueous ammonia (active ingredient 10%). The aqueous dispersion of the polymer particles [X] obtained here had a solid content concentration of 53.5%, a viscosity of 360 mPa · s, and an average particle diameter of 210 nm, and was obtained from the charged amount of the carboxyl group-containing monomer. The value was 6.5.

  After adding 0.6 parts of adipic dihydrazide to the aqueous dispersion of the polymer particles [X], the mixture was filtered through a 100-mesh wire net to obtain a removable aqueous adhesive composition of the present invention.

  Glass transition temperature (actually measured Tg), gel fraction (toluene-insoluble fraction), water extract amount, water-whitening resistance of pressure-sensitive adhesive sheet, adhesion of coating film obtained using removable water-based pressure-sensitive adhesive composition of the present invention Table 1 shows the evaluation results of the force, the holding power, the removability, and the tack.

Examples 3 to 5
A removable water-based pressure-sensitive adhesive composition of the present invention was obtained in exactly the same manner as in Example 1 except that the monomer mixture shown in Table 1 was used. The acid value, average particle diameter (50% median diameter), solid content and viscosity of the polymer particles contained in the removable aqueous pressure-sensitive adhesive composition were as described in Table 1. Further, the glass transition temperature (measured Tg), gel fraction (toluene insoluble fraction), amount of water extract, water whitening resistance of the pressure-sensitive adhesive sheet, and adhesive strength of the film obtained from this removable aqueous pressure-sensitive adhesive composition The results of the evaluation of retention, holding power, removability and tack were as shown in Table 1.

Comparative Examples 1-3
A removable aqueous pressure-sensitive adhesive composition was obtained in exactly the same manner as in Example 1 except that the monomer mixture shown in Table 2 was used. The acid value, gel fraction, average particle size, solid content, and viscosity of the polymer particles contained in this removable aqueous pressure-sensitive adhesive composition were as described in Table 1. Further, the glass transition temperature (measured Tg), gel fraction (toluene insoluble fraction), amount of water extract, water whitening resistance of the pressure-sensitive adhesive sheet, and adhesive strength of the film obtained from this removable aqueous pressure-sensitive adhesive composition The results of the evaluation of retention, holding power, removability and tack were as shown in Table 1.

Comparative Example 4
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen introduction pipe, a thermometer, and a dropping funnel, 0.4 part of Levenol WZ [manufactured by Kao Corporation: 25% active ingredient] and 28 parts of deionized water are put, and nitrogen is added. The temperature was raised to 75 ° C. while blowing. Under stirring, 0.02 parts of potassium persulfate was added, and then 1: 1 part of Levenol WZ was added to a monomer mixture consisting of 48.5 parts of 2-ethylhexyl acrylate, 1 part of acrylic acid, and 0.5 part of diacetone acrylamide. 6 parts and 20 parts of deionized water were added to emulsify the monomer, and a part (3 parts) of a monomer pre-emulsion (which is obtained by emulsifying the monomer with the above-mentioned monomer mixture, emulsifier and water) was added, and the reaction was carried out. The polymerization was carried out for 60 minutes while maintaining the temperature in the vessel at 75 ° C. Subsequently, while maintaining the temperature in the reaction vessel at 75 ° C., the remaining monomer pre-emulsion (75.9 parts) and 10 parts of an aqueous solution of potassium persulfate (1% of active ingredient) were added using separate dropping funnels. The polymerization was carried out dropwise over 120 minutes while maintaining the temperature in the reaction vessel at 75 ° C.

  After completion of the dropwise addition, 1.6 parts of Levenol WZ was deionized to a monomer mixture consisting of 47 parts of 2-ethylhexyl acrylate, 1 part of acrylic acid, and 2 parts of diacetone acrylamide while maintaining the temperature in the reaction vessel at 75 ° C. A monomer mixture consisting of a monomer pre-emulsion emulsified by adding 20 parts of water, and 10 parts of an aqueous solution of potassium persulfate (1% of active ingredient) are immediately added to the reaction vessel using separate dropping funnels. Was maintained at 75 ° C. for 120 minutes to carry out polymerization. After completion of the dropwise addition, the mixture was stirred at the same temperature for 120 minutes, the content was cooled, and adjusted to pH 8.0 with aqueous ammonia (active ingredient 10%). The aqueous dispersion obtained here had a solid concentration of 51.8%, a viscosity of 300 mPa · s, an average particle size of 290 nm, and an acid value of 15.6 determined from the charged amount of the carboxyl group-containing monomer. Was.

  After 0.3 part of adipic dihydrazide was added to the aqueous dispersion, the mixture was filtered through a 100-mesh wire net to obtain a removable aqueous pressure-sensitive adhesive composition.

  Glass transition temperature (measured Tg), gel fraction (toluene-insoluble fraction), water extract amount, water-whitening resistance, adhesive strength, and retention of the pressure-sensitive adhesive sheet obtained by using the removable pressure-sensitive adhesive composition Tables 1 and 2 show the evaluation results of the force, the removability, and the tack.

The official names of the abbreviations in Tables 1 and 2 are shown below.
2-EHA; 2-ethylhexyl acrylate BA; n-butyl acrylate MMA; methyl methacrylate MAA; methacrylic acid AA; acrylic acid DAAM; diacetone acrylamide L-SH; lauryl mercaptan TBHP; t-butyl hydroperoxide KPS; ADH; adipic acid dihydrazide CDH; carbodihydrazide WS-500; Nippon Shokubai Co., Ltd. Epocross WS-500
OT-75: AEROSIL OT-75 manufactured by Mitsui Cytec Co., Ltd.
The amounts of the monomers, surfactants, polymerization initiators, cross-linking agents, and leveling agents used in Tables 1 and 2 are represented by parts by weight of the solid content.

Claims (6)

Polymer particles [X] containing a carbonyl group and a carboxyl group and having an acid value of 3 to 30 and having an average particle diameter of 300 nm or less, and a hydrazine derivative having at least two hydrazino groups in the molecule [ Y], wherein the film formed from the removable aqueous pressure-sensitive adhesive composition has a glass transition temperature of −25 ° C. or less and a gel fraction of 80% by weight or more. And a water-extractable amount of 2% by weight or less. (A) at least one carbonyl group-containing ethylenically unsaturated monomer per molecule, 0.1 to 2% by weight, (b) carboxyl group The essential components are an ethylenically unsaturated monomer, 0.5 to 4% by weight, and (c) an alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms, and 45 to 99.4% by weight. The removable aqueous pressure-sensitive adhesive composition according to claim 1, which is a copolymer obtained by copolymerizing the polymerizable monomer mixture thus obtained. The removable aqueous pressure-sensitive adhesive composition according to claim 1, wherein the polymer particles [X] are emulsion-polymerized using an organic peroxide-based polymerization initiator. The removable aqueous pressure-sensitive adhesive composition according to claim 1, further comprising an acetylenic diol-based surfactant [Z]. The removable aqueous pressure-sensitive adhesive composition according to claim 4, wherein the polymer particle [X] is obtained by emulsion polymerization in the presence of an acetylene diol-based surfactant [Z]. An adhesive product comprising a substrate and a layer of the removable aqueous adhesive composition according to any one of claims 1 to 5.