JP4507610B2 - Re-peelable water-based pressure-sensitive adhesive composition and pressure-sensitive adhesive product - Google Patents

Description

  The present invention relates to a re-peelable water-based pressure-sensitive adhesive composition having excellent pressure-sensitive adhesive properties and re-peelability, and excellent in water whitening resistance, and a pressure-sensitive adhesive product coated with the same.

  Adhesive labels are used in various fields, and some of them are used to be peeled off from an adherend after a predetermined time has elapsed since being attached to the adherend. At this time, a part of the pressure-sensitive adhesive often remains on the adherend. In addition, when the base material is paper, the strength of the paper is weak, so it is often difficult to tear the paper and remove it from the adherend. There has been proposed a re-peelable pressure-sensitive adhesive that can be easily peeled off from an adherend without such a situation.

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

  However, emulsion-type water-based pressure-sensitive adhesives are easily whitened when they come into contact with water, that is, they have a low water whitening resistance, and are therefore a big problem in replacing solvent-type pressure-sensitive adhesives. In particular, when replacing a solvent-type pressure-sensitive adhesive conventionally used for transparent film label applications with an emulsion-type water-based pressure-sensitive adhesive, improvement of water whitening resistance is the greatest 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 alkyl having an alkyl group having 4 to 12 carbon atoms ( The aqueous dispersion obtained by producing and blending two kinds of polymer particles having different functional group monomer contents in the monomer composition mainly composed of (meth) acrylate has two hydrazino groups. A re-peeling water-dispersed pressure-sensitive adhesive containing a hydrazine derivative is disclosed (for example, see Patent Document 1). However, in this method, not only the removability and sufficient performance cannot be obtained, but also the water whitening resistance, which is the biggest problem of the emulsion-type aqueous pressure-sensitive adhesive, is remarkable.

JP 2002-105422 A

  The object of the present invention is excellent in adhesiveness, can be easily peeled off from the adherend surface even after being left for a long time after being attached to the adherend, and is further used in fields where water whitening resistance is required. In such a case, the present invention also provides a re-peelable water-based pressure-sensitive adhesive composition and a pressure-sensitive adhesive product that exhibit excellent water whitening resistance.

As a result of earnest examination to solve the problem, the following knowledge was obtained.
(1) The aqueous extract amount of the film formed from the aqueous pressure-sensitive adhesive composition is 2% by weight or less, and consists of a polymer having a carbonyl group and a carboxyl group dispersed in an aqueous medium and having an acid value of 3 to 30. Water-whitening resistance is improved when the average particle diameter is polymer particles [X] of 300 nm or less.
(2) The aqueous pressure-sensitive adhesive composition contains at least two compounds [Y] having a hydrazino group, and the gel fraction of a film formed from the aqueous pressure-sensitive adhesive composition is 80% by weight. When it is 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 force is good.

The present invention is based on such knowledge. That is, the present invention relates to (a) 0.1 to 2% by weight of at least one carbonyl group-containing ethylenically unsaturated monomer in the molecule per all monomers , and (b) carboxyl group-containing ethylenically unsaturated monomer. A polymerizable monomer mixture comprising, as essential components, 0.5 to 4% by weight of monomer and (c) 45 to 99.4% by weight of alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms. Polymer particles [X] consisting of a polymer having a carbonyl group and a carboxyl group obtained by emulsion copolymerization and having an acid value of 3 to 30 and having an average particle size of 300 nm or less, and carbodihydrazide or adipic acid dihydrazide An aqueous pressure-sensitive adhesive composition comprising a hydrazine derivative [Y] having at least two hydrazino groups in the molecule, and an acetylenic diol surfactant [Z], wherein the detachable water A film formed from the adhesive composition has a glass transition temperature of −25 ° C. or less, a gel fraction of 80% by weight or more, and a water extract amount of 2% by weight or less. An adhesive composition is provided.

  Moreover, this invention also provides the adhesive product comprised from a base material and the layer of said re-peelable water-based adhesive composition.

  According to the present invention, a re-peelable water-based pressure-sensitive adhesive composition having excellent water whitening resistance, adhesive strength, and re-peelability can be provided. 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, pressure-sensitive adhesive tape, special pressure-sensitive adhesive sheet, and the like.

  The content of the carboxyl group in the polymer particle [X] needs to be an amount in the range of 3 to 30 as the acid value. If the acid value is in the range, the polymer particle [X] It is possible to impart dispersion stability in an aqueous medium, re-peelability of the pressure-sensitive adhesive film and adhesive force in a well-balanced manner, and improve water whitening resistance. 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 is required to be 300 nm or less in order to obtain a re-peelable water-based pressure-sensitive adhesive exhibiting good water whitening resistance. When the average particle diameter exceeds 300 nm, the water whitening resistance is lowered, which is not preferable. Among these, 10 to 300 nm is particularly preferable. Here, the average particle diameter of the particles refers to the 50% median diameter of the emulsion particles on the volume basis, and the numerical values are based on values obtained by measurement by the dynamic light scattering method described in Examples below.

  Further, the gel fraction of the film formed from the re-peelable water-based pressure-sensitive adhesive composition of the present invention is required to be 80% by weight or more from the balance between the adhesive strength of the pressure-sensitive adhesive and the re-peelability. When the gel fraction is less than 80% by weight, the removability is lowered, which is not preferable. Among these, it is usually preferable to control at 85 to 98%. The said gel fraction means the ratio of the insoluble part with respect to the toluene of the film | membrane of an aqueous adhesive composition. A gel fraction is based on the numerical value calculated | required by the measuring method and formula described in the postscript Example.

  Therefore, in order to achieve a good balance between the adhesive strength 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 re-peelable water-based pressure-sensitive adhesive composition is It is necessary that the film formed of the detachable aqueous pressure-sensitive adhesive composition contains a hydrazine derivative [Y] having at least two hydrazino groups in the molecule and has a glass transition temperature of −25 ° C. .

  Moreover, the amount of the water extract formed from the re-peelable aqueous pressure-sensitive adhesive composition of the present invention needs to be 2% by weight or less. The smaller the amount of water extract, the better, and it is usually preferable to control the amount to 0.1 to 1.8% by weight. When the amount of the water extract exceeds 2% by weight, the water whitening resistance of the re-peelable water-based pressure-sensitive adhesive film is lowered, which is not preferable.

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

  Next, the film formed from the re-peelable aqueous pressure-sensitive adhesive composition of the present invention needs to have a glass transition temperature (hereinafter referred to as Tg) of −25 ° C. or lower. When the Tg is within 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. When Tg exceeds −25 ° C., the adhesive force necessary for the re-peelable aqueous pressure-sensitive adhesive cannot be obtained, which is not preferable. Furthermore, it is especially preferable that it is -25--60 degreeC. Here, Tg in this invention is based on the numerical value obtained by the measuring method described in the postscript Example.

  Next, the re-peelable aqueous pressure-sensitive adhesive composition of the present invention can be obtained, for example, by emulsion copolymerization of monomer components described later. Specifically, the polymer of the polymer particles [X] is (a) at least one carbonyl group-containing ethylenically unsaturated monomer in the molecule, 0.1 to 2 wt. %, (B) carboxyl group-containing ethylenically unsaturated monomer, 0.5 to 4% by weight, and (c) alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms, 45 to 99. Examples thereof include a copolymer obtained by copolymerizing a polymerizable monomer mixture containing 4% by weight as an essential component. Under the present circumstances, you may use together unsaturated monomer (d) other than said (a)-(c) as needed in 0.001-55 weight%.

  The carbonyl group-containing ethylenically unsaturated monomer (a) is not particularly limited, and has a functional group having reactivity with the hydrazino group of the hydrazine derivative [Y] described above. For example, acrolein, diacetone Examples include 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. It is done. In particular, it is preferable to use diacetone acrylamide because the adhesive strength and removability of the pressure-sensitive adhesive can be imparted with a good balance. The amount of the carbonyl group-containing ethylenically unsaturated monomer used is preferably in the range of 0.1 to 2% by weight, particularly preferably 0.2 to 2% by weight. When in this range, good removability can be imparted.

  Next, as an ethylenically unsaturated monomer (b) which has a carboxyl group, if it has a carboxyl group and an ethylenically unsaturated group in a molecule | numerator, it will not be specifically limited, It can use. Examples of the ethylenically unsaturated monomer include acrylic acid, methacrylic acid, β-carboxyethyl (meth) acrylate, 2- (meth) acryloylpropionic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, and 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 salts thereof and the like, and one or a mixture of two or more thereof can be used. Among these, methacrylic acid is preferably used in terms of excellent stability during polymerization of the monomer component and excellent water whitening resistance. The amount of the ethylenically unsaturated monomer having a carboxyl group used is preferably 0.5 to 4% by weight, particularly preferably 0.5 to 3% by weight. When it exists in this range, adhesive force and removability can be provided with good balance.

  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- A lauryl (meth) acrylate etc. can be mentioned, The 1 type (s) or 2 or more types of mixture 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 used is preferably 45 to 99.4% by weight, particularly preferably 64 to 95% by weight. . When it exists in this range, since Tg of the adhesive film mentioned above can be adjusted to a desired range and an adhesive physical property can be provided with sufficient balance, it is preferable.

  Examples of the unsaturated monomer (d) other than (a) to (c) include methyl (meth) acrylate, ethyl (meth) acrylate, t-butyl (meth) acrylate, and stearyl (meth) acrylate. , (Meth) acrylic esters 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, β- (perfluorooctyl) ethyl (meth) acrylate Vinyl acetate, vinyl propionate, vinyl butyrate, vinyl versatate, etc. Nyl esters; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, amyl vinyl ether, 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, divinylstyrene; isoprene, chloroprene, butadiene, ethylene, tetrafluoroethylene, vinylidene fluoride, N-vinylpyrrolidone and the like. The amount of these substances used is preferably 0.1 to 55% by weight, particularly preferably 5 to 55% by weight.

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

  Moreover, as unsaturated monomers (d) other than the above (a) to (c), for the purpose of improving the gel fraction of the releasable aqueous pressure-sensitive adhesive to a desired range, other than carbonyl group and carboxyl group It is also possible to use an ethylenically unsaturated monomer containing a crosslinkable reactive group. Examples of these include glycidyl group-containing polymerizable monomers such as glycidyl (meth) acrylate and allyl glycidyl ether; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) Hydroxyl group-containing polymerizable monomers such as acrylate and glycerol mono (meth) acrylate; amino such as aminoethyl (meth) acrylate, N-monoalkylaminoalkyl (meth) acrylate, and N, N-dialkylaminoalkyl (meth) acrylate Group-containing polymerizable monomer: methylol amide such as N-methylol (meth) acrylamide, N-isopropoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-isobutoxymethyl (meth) acrylamide Group or an alkoxylate-containing polymerizable monomer; vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ- (meth) acryloxypropyltrimethoxysilane, γ- ( (Meth) acryloxypropyltriethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxypropyltriisopropoxysilane, N-β Silyl group-containing polymerizable monomers such as-(N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane and its hydrochloride; aziridinyl group-containing polymerizable monomers such as 2-aziridinylethyl (meth) acrylate Mer; (meth) acryloyl isocyana Isocyanate- and / or blocked isocyanate group-containing polymerizable monomers such as phenol or methyl ethyl ketoxime adduct of (meth) acryloyl isocyanate ethyl; 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 Examples include 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.

  Further, the crosslinkable reactive group of the polymer composed of these monomer components is used to crosslink between the polymers, so that the gel fraction of the film formed from the re-peelable aqueous pressure-sensitive adhesive composition described later can be 80 wt. % Or more can be adjusted.

  Moreover, as unsaturated monomer (d) other than said (a)-(c), in order to improve the gel fraction of a releasable water-based adhesive to a desired range, two in a molecule | numerator 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 include di (meth) acrylate, diallyl phthalate, divinylbenzene, allyl (meth) acrylate, and the like. The amount of these substances to be used 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 is good, but in order to make the balance between the adhesive force and the holding power good, As described above, the polyfunctional ethylenically unsaturated monomer is preferably used in such an amount 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 releasable aqueous pressure-sensitive adhesive obtained for the purpose of improving the stability during emulsion polymerization and the storage stability of the emulsion. Ethylenic unsaturation containing sulfonic acid groups and / or sulfate groups (and / or salts thereof), phosphoric acid groups and / or phosphate ester groups (and / or salts thereof) within a range not deteriorating the water whitening resistance of A monomer can be used in combination. Examples of the unsaturated monomer (d) include vinyl sulfonic acids such as vinyl sulfonic acid and styrene sulfonic acid or salts thereof, allyl group-containing sulfonic acids such as allyl sulfonic acid and 2-methylallyl sulfonic acid, or the like. Its salts, (meth) acrylate group-containing sulfonic acids such as 2-sulfoethyl (meth) acrylate, 2-sulfopropyl (meth) acrylate or salts thereof, (meth) such as (meth) acrylamide-t-butylsulfonic acid Examples thereof include acrylamide group-containing sulfonic acids or salts thereof, “Adekaria Soap PP-70, PPE-710” (manufactured by Asahi Denka Kogyo Co., Ltd.) having a phosphate group, and one or a mixture of these. 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 re-peelable aqueous pressure-sensitive adhesive composition of the present invention includes, for example, the aforementioned carbonyl group-containing ethylenically unsaturated monomer (a), an ethylenically unsaturated monomer (b) containing a carboxyl group, and a carbon atom. It is obtained by emulsion copolymerization of an alkyl (meth) acrylate (c) having an alkyl group having 4 to 12 numbers and other ethylenically unsaturated monomer (d).

  A radical polymerization initiator is used as the polymerization initiator used for polymerizing the polymer. Examples of the radical polymerization initiator include persulfates, organic peroxides, hydrogen peroxide, and the like.

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

  Furthermore, 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 polymerization initiator because the water whitening resistance of the pressure-sensitive adhesive film is remarkably improved.

  Examples of organic peroxides include diacyl peroxides such as benzoyl peroxide, lauroyl peroxide, and decanoyl peroxide, dialkyl peroxides such as t-butylcumyl peroxide, dicumyl peroxide, and t-butyl peroxide. Examples include peroxyesters such as oxylaurate and t-butylperoxybenzoate, hydroperoxides such as cumene hydroperoxide, paramentane hydroperoxide, and t-butyl hydroperoxide.

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

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

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

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

  Furthermore, an emulsifier having a polymerizable unsaturated double bond in the molecule generally called “reactive emulsifier” can also be used. Examples of such commercially available reactive emulsifiers include “Latemul S-180” (manufactured by Kao Corporation), “Eleminol JS-2, RS-30” [Sanyo Chemical Industries, Ltd. "Aqualon HS-10, HS-20" [Daiichi Kogyo Seiyaku Co., Ltd.], "Adekaria soap SE-10, SE-20" [Asahi Denka Kogyo Co., Ltd.] having sulfate groups and salts thereof "New Frontier A-229E" [manufactured by Daiichi Kogyo Seiyaku Co., Ltd.] etc. having a phosphate group; "Aqualon RN-10, RN-20, RN-" having a nonionic hydrophilic group 30, RN-50 "[Daiichi Kogyo Seiyaku Co., Ltd.] and the like.

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

  The amount of the emulsifier and the dispersion stabilizer is preferably as small as possible from the viewpoint of the water resistance and adhesive strength of the resulting pressure-sensitive adhesive film, and the amount used is 2 with respect to the solid content of the polymer. It is preferable to set the weight% or less.

  Also, during the polymerization, it is possible to add a hydrophilic solvent, a hydrophobic solvent, and various additives, but the amount used is preferably limited to a range that does not adversely affect the resulting adhesive film. . The temperature at which the polymer is polymerized varies depending on the type of monomer to be used, the type of polymerization initiator, etc., but when polymerizing in an aqueous medium, it is usually preferably carried out in the temperature range of 30 to 90 ° C. .

  Specific production methods of 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 an emulsifier and a dispersion stabilizer as needed are mixed and polymerized, ( 2) Methods such as a so-called pre-emulsion method in which water, an ethylenically unsaturated monomer, and an emulsifier previously mixed are dropped, and (3) a monomer dropping method, and the like. Among these, the production by the pre-emulsion method (2) particularly from the viewpoint of stability at the time of polymerization contains a carboxyl group, an acid value of 3 to 30, and an average particle size of 300 nm or less. This is preferable because an aqueous dispersion in which the coalesced 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 put into a stirring reactor equipped with a dropping funnel, and then the temperature of the reactor is increased to the polymerization temperature, and dropping is performed. The method of dripping a monomer component from a funnel is mentioned. At this time, the inside of the reactor may be an open system, but is preferably replaced with an inert gas such as nitrogen. The polymerization temperature varies depending on the type of monomer used, the type of polymerization initiator, and the like, but usually a temperature range of 30 to 90 ° C is appropriate, and a range of 40 ° C to 85 ° C is more preferable. . 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 content concentration of the resulting aqueous polymer dispersion, and is not particularly limited.

  In the emulsion polymerization, it is also possible to add a hydrophilic solvent, a hydrophobic solvent and various additives as long as the effects of the present invention are not impaired.

  Further, the re-peelable water-based pressure-sensitive adhesive composition of the present invention includes a filler, a pigment, a pH adjuster, a film forming aid, and a leveling agent described later, as long as the desired effect of the present invention is not impaired as necessary. Well-known ones such as thickeners, water repellents, tackifiers and antifoaming agents can be appropriately added and used.

  The re-peelable 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 re-peelability.

  When manufacturing an adhesive product (adhesive tape, adhesive label, etc.), a method of directly applying to a base material used for a tape or a label and then bonding to a release paper, and a base material after applying to a release paper and drying In particular, in the latter method, the releasable water-based adhesive is applied to the release paper, and the surface energy of the release paper is low. However, the re-peelable water-based pressure-sensitive adhesive has a problem that repelling and squeaking are likely to occur during coating. In order to suppress these phenomena, it is necessary to improve the wettability of the re-peelable water-based pressure-sensitive adhesive with respect to the release paper to obtain a smooth coated surface. Conventionally, an interface as a wettability improver (hereinafter referred to as a leveling agent) An activator is added to solve the problem. However, when a leveling agent is added, there is a drawback that the water whitening resistance of the pressure-sensitive adhesive film is deteriorated.

  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, alkyls. Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene diphenyl ether, polyoxyethylene- Examples thereof include polyoxypropylene block copolymers and acetylenic diol surfactants. Examples of cationic surfactants include alkyl (amido) betaines and alkyldimethyls. Min'okishido, and the like.

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

  Among these, the re-peelable water-based pressure-sensitive adhesive composition of the present invention includes an anionic surfactant, a succinic acid dialkyl ester sulfonate surfactant, and a nonionic surfactant. Examples of acetylenediol surfactants and fluorosurfactants include megafac F-142D, megafac F-1405 (manufactured by Dainippon Ink and Chemicals), and ZONYL FSN (manufactured by DuPont). Examples of the fluoroalkylethylene oxide adduct and silicone surfactant include polyether-modified dimethylsiloxanes such as SILWET FZ-2166 (manufactured by Nihon Unicar Co., Ltd.), BYK 348 (manufactured by Big Chemie Japan Co., Ltd.), It is preferable to use one or a mixture of two or more of these from the viewpoint of excellent coating properties. Arbitrariness.

  Furthermore, it is more preferable to use an acetylenic diol surfactant [Z] from the viewpoint that the 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, Surfinol PSA216. , Surfinol PSA 336, Dinol 604 (manufactured by Air Products Japan Co., Ltd.) can be used, and one or a mixture of two or more of these can be used. The addition amount of the acetylenic diol surfactant [Z] is not particularly limited, but is 0.1% per 100 parts by weight of the polymer particles [X] from the viewpoint of not impairing the good water whitening resistance of the pressure-sensitive adhesive film. -3.0 weight part is preferable.

  The amount of the leveling agent used is not particularly limited as long as repelling and squeezing at the time of coating are sufficiently suppressed and a smooth coating surface can be obtained, but it is 0.1% relative to the solid content of the re-peelable aqueous pressure-sensitive adhesive. Use in the range of ˜2 parts by weight is preferable because it does not adversely affect the adhesive physical properties such as adhesive strength of the adhesive.

  The leveling agent may be used in addition to the method of adding the polymer particles [X] to the aqueous dispersion in which the polymer particles [X] are dispersed. The method of using as a surfactant for emulsion polymerization at the time of manufacture is also mentioned.

  In general, in order to impart polymerization stability during emulsion polymerization, as described above, surfactants such as an anionic emulsifier, a cationic emulsifier, a nonionic emulsifier, and a reactive emulsifier, and other A dispersion stabilizer is used. However, the polymerization stability improves as the amount of use increases, but the water whitening resistance of the resulting re-peelable aqueous pressure-sensitive adhesive film decreases.

  On the other hand, when the acetylenic diol surfactant [Z] is used during emulsion polymerization among the leveling agents, polymerization stability can be imparted in addition to the effect as the leveling agent. Furthermore, since the water-whitening resistance of the obtained re-peelable water-based pressure-sensitive adhesive film is not impaired, it is particularly preferable.

  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 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, ethylene-1,2-dihydrazine, propylene-1,3-dihydrazine, butylene-1,4-dihydrazine, etc. Among them, carbodihydrazide and adipic acid dihydrazide are particularly preferable because they can give good removability.

  Since the blending ratio of the hydrazine derivative [Y] having at least two hydrazino groups in the molecule is good in adhesive strength and removability, hydrazino groups per equivalent of carbonyl groups in the polymer particles (X). However, it is preferable that it is 0.05-5 equivalent, and 0.2-3 equivalent is especially preferable.

  Next, the pressure-sensitive 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 above-described re-peelable water-based pressure-sensitive adhesive composition. Examples of the substrate include paper, plastic film, and nonwoven fabric.

  In particular, since the re-peelable water-based pressure-sensitive adhesive composition of the present invention is excellent in water whitening resistance, it can be suitably used for the production of pressure-sensitive adhesive products 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 of forming a layer of the pressure-sensitive adhesive composition using the re-peelable water-based pressure-sensitive adhesive composition of the present invention, the re-peelable water-based pressure-sensitive adhesive composition is directly coated on the substrate and dried. The water-based pressure-sensitive adhesive composition is coated on a release material such as a paper or a plastic film that has been subjected to a release treatment with silicone or the like, and dried to form a pressure-sensitive adhesive layer. There is a transfer method in which a base material is stacked on the agent layer and pressed to transfer the pressure-sensitive adhesive layer 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 re-peelable aqueous pressure-sensitive adhesive composition of the present invention generally has a solid content concentration 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. Nine. In the case of coating by the above direct method, although it depends on the type of coating method, in general, a low viscosity is often required for coating at a higher speed. Moreover, when applying by a transfer method, the thing whose viscosity is 300-10,000 mPa * s (BM type | mold viscosity meter, 60 rotations, 25 degreeC) is preferable.

  Since the pressure-sensitive adhesive product of the present invention is excellent in adhesive strength and water whitening resistance, it is suitable for pressure-sensitive adhesive labels, pressure-sensitive adhesive tapes, special pressure-sensitive adhesive sheets and the like.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples. In the following, unless otherwise specified, “%” represents “% by weight”, and “part” represents “part by weight”.

The evaluation method used in the present invention will be described below.
[Measurement method of acid value]
A re-peelable water-based pressure-sensitive adhesive composition is applied onto a glass plate with a 3 mil applicator, dried at room temperature for 1 hour to form a semi-dry pressure-sensitive adhesive film (sample), and the obtained pressure-sensitive adhesive film is then applied to the glass plate. Then, 1 g of this pressure-sensitive adhesive film was precisely weighed and dissolved in 100 g of tetrahydrofuran (THF) as a measurement sample. The measuring method was a neutralization titration method using an aqueous potassium hydroxide solution. In addition, about the sample which did not melt | dissolve in tetrahydrofuran, since the measurement by this method is impossible, the calculated value calculated | required from the preparation amount of the carboxyl group-containing monomer used at the time of re-peeling type water-based adhesive composition manufacture Was determined as the acid value.
[Measurement method of average particle size]
The value of the average particle diameter (50% median diameter based on volume) measured with a Nikkiso Co., Ltd. Microtrac UPA type particle size distribution analyzer was determined.
[Method for measuring Tg]
The re-peelable aqueous pressure-sensitive adhesive composition was applied to a glass plate so that the film thickness after drying was 0.3 mm, dried at 25 ° C. for 24 hours, then peeled off from the glass plate, and further at 100 ° C. for 5 minutes. Using the dried sample as a sample, about 10 mg of a sample was weighed in an aluminum cylindrical cell having a diameter of 5 mm and a depth of 2 mm, and a DSC-2920 modulated differential scanning calorimeter manufactured by TA Instruments was used. It was determined by measuring an endothermic curve when the temperature was raised from −150 ° C. to 100 ° C. at a rate of temperature increase of 20 ° C./min.
[Measurement method of gel fraction]
The re-peelable water-based pressure-sensitive adhesive composition was applied onto a glass plate so that the film thickness after drying was 0.3 mm, dried at 25 ° C. for 24 hours, then peeled off from the glass plate, and further at 100 ° C. The dried material was cut into 50 mm squares and used as samples. Next, the weight (G1) of the sample before being immersed in toluene is measured in advance, and the toluene insoluble portion of the sample after being immersed in a toluene solution at room temperature for 24 hours is separated by filtering 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 formula.

Gel fraction (% by weight) = (G2 / G1) × 100
[Method for measuring the amount of water extract]
The re-peelable aqueous pressure-sensitive adhesive composition was applied to a glass plate so that the film thickness after drying was 0.3 mm, dried at 25 ° C. for 24 hours, then peeled off 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 20 mm squares, and the weight (W1) was measured to obtain a test film. After immersing the test film in 25 ° C. water for 7 days, pulling up and wiping off the moisture on the film surface, the film was dried at 110 ° C. for 1 hour, allowed to cool, and then the weight (W2) was measured. The water extract amount of the film was determined according to

Water extract amount (% by weight) = {(W1-W2) / W1} × 100
[Measurement method of water whitening resistance test]
A re-peelable water-based pressure-sensitive adhesive composition was applied to the surface of a polyethylene terephthalate film having a thickness of 25 μm 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 as a sample. . Soak the sample in water at 30 ° C for 24 hours so that the adhesive coated surface is exposed, measure the turbidity of the sample before and after water immersion with a turbidimeter, and measure the degree of change in turbidity by W The water whitening resistance was evaluated as a value.

Turbidity meter: Nippon Denka Kogyo Co., Ltd. turbidity meter NDH-300A
Measurement light source: Halogen lamp Light receiving element: Silicon photocell according to JIS K7105 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 (%)
The degree of change in turbidity: W value = H1 / H0 (H0: turbidity before water immersion, H1: turbidity after water immersion), and then the result was determined according to the following criteria.

○: The degree of turbidity change W value is less than 5 Δ: The degree of turbidity change W value is 5 or more and less than 30 ×: The degree of turbidity change W value is 30 or more [Measurement method of adhesive strength]
The re-peelable water-based pressure-sensitive adhesive composition was applied to 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. A stainless steel plate was used as the pressure-sensitive adhesive sheet and the adherend, and the 180-degree peel strength was measured in an atmosphere of 23 ° C. and 50% RH in accordance with JIS Z-0237 to obtain adhesive strength.
[Measurement of holding power]
Create a pressure-sensitive adhesive sheet in the same way as when measuring the adhesive force, stick the pressure-sensitive adhesive sheet to the stainless steel plate so that the bonding area is 25 mm x 25 mm, and measure the time until it peels off under a load of 1 kg at 40 ° C. The holding time was defined as holding power. Moreover, when it was hold | maintained after 300 minutes, the holding | maintenance time was 300 minutes or more, the shift | offset | difference width from the initial sticking position was measured, and it described together.
[Removability]
An adhesive sheet was prepared in the same manner as when measuring the adhesive force, and the adhesive sheet was pasted on a stainless steel plate so that the adhesive area was 25 mm × 25 mm. After being left in an atmosphere of 23 ° C. and 65% RH for 30 days, it was placed in a tensile tester. Then, peeling was performed at a pulling speed of 300 mm / min, and the state of the adherend surface after peeling was visually determined.

  ○: It can be peeled cleanly without glue residue or paper tearing.

  Δ: Residue remaining or paper tears partially.

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

Example 1
A reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel was charged with Latemul E-118B (Kao Co., Ltd .: active ingredient 25%) 0.4 parts and deionized water 45 parts, 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, and then 87.5 parts of 2-ethylhexyl acrylate, 10 parts of methyl methacrylate, 2 parts of methacrylic acid, A monomer pre-emulsion prepared by adding 1.6 parts of Latemul E-118B and 15 parts of deionized water to a monomer mixture comprising 0.5 parts of acetone acrylamide and 1 part of lauryl mercaptan (with the monomer mixture and 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 in the reaction vessel at 75 ° C., the remaining monomer pre-emulsion (114.6 parts), an aqueous solution of t-butyl hydroperoxide (active ingredient 1%), an aqueous solution of L-ascorbic acid ( Using an additional dropping funnel, 15 parts of an active ingredient (0.5%) were dropped and polymerized over 240 minutes while maintaining the reaction vessel temperature at 75 ° C.

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

  As a leveling agent, 1.2 parts of Surfynol 420 [produced by Air Products Japan: active ingredient 100%] and 0.3 parts of adipic acid dihydrazide are added to the above aqueous dispersion of polymer particles [X]. Then, the mixture was filtered through a 100 mesh wire net to obtain a re-peelable water-based 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 adhesive sheet, adhesion of film obtained using re-peelable water-based pressure-sensitive adhesive composition of the present invention Table 1 shows the evaluation results of force, holding force, removability, and tack.

Example 2
A reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel was charged with 0.4 parts of Latemul E-118B, 0.3 parts of Surfynol 420, 45 parts of deionized water, and nitrogen was added. 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 added, followed by 88 parts of 2-ethylhexyl acrylate, 10 parts of methyl methacrylate, 1 part of methacrylic acid, diacetone acrylamide. 1 part of lauryl mercaptan and 1 part of lauryl mercaptan were emulsified by adding 1.2 parts of Aqualon KH-1025 [Daiichi Kogyo Seiyaku Co., Ltd .: active ingredient 25%] and 15 parts of deionized water. Add a part (3 parts) of a monomer pre-emulsion (referred to the monomer mixture, emulsifier and water emulsified with water) and polymerize in 60 minutes while maintaining the reaction vessel temperature at 75 ° C. It was. Subsequently, while maintaining the temperature in the reaction vessel at 75 ° C., the remaining monomer pre-emulsion (114.2 parts), an aqueous solution of t-butyl hydroperoxide (1% active ingredient), an aqueous solution of L-ascorbic acid ( Using an additional dropping funnel, 15 parts of an active ingredient (0.5%) were dropped and polymerized over 240 minutes while maintaining the reaction vessel temperature at 75 ° C.

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

  After adding 0.6 part of adipic acid dihydrazide to the aqueous dispersion of the above polymer particles [X], the mixture was filtered through a 100-mesh wire mesh to obtain a re-peelable 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 adhesive sheet, adhesion of film obtained using re-peelable water-based pressure-sensitive adhesive composition of the present invention Table 1 shows the evaluation results of force, holding force, removability, and tack.

Examples 3-5
A re-peelable water-based pressure-sensitive adhesive composition of the present invention was obtained in 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 concentration, and viscosity of the polymer particles contained in this re-peelable aqueous pressure-sensitive adhesive composition were as described in Table 1. Further, the glass transition temperature (actually measured Tg), gel fraction (toluene insoluble fraction), water extract amount, water whitening resistance and adhesive strength of the pressure-sensitive adhesive sheet obtained from this re-peelable water-based pressure-sensitive adhesive composition , Holding power, removability, and tack evaluation results are as described in Table 1.

Comparative Examples 1-3
A re-peelable water-based pressure-sensitive adhesive composition was obtained in 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 diameter, solid content concentration, and viscosity of the polymer particles contained in this re-peelable aqueous pressure-sensitive adhesive composition were as described in Table 1. Further, the glass transition temperature (actually measured Tg), gel fraction (toluene insoluble fraction), water extract amount, water whitening resistance and adhesive strength of the pressure-sensitive adhesive sheet obtained from this re-peelable water-based pressure-sensitive adhesive composition , Holding power, removability, and tack evaluation results are as described in Table 1.

Comparative Example 4
Into a reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel, 0.4 parts of Rebenol WZ [manufactured by Kao Corporation: 25% active ingredient] and 28 parts of deionized water are added, and nitrogen is added. The temperature was raised to 75 ° C. while blowing. Under stirring, 0.02 part of potassium persulfate was added, and then, 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, 1. 6 parts and 20 parts of deionized water were added to emulsify the monomer pre-emulsion (referred to the monomer mixture, emulsifier and water in which the monomer was emulsified), and a reaction (3 parts) was added. Polymerization was performed for 60 minutes while maintaining the temperature in the container 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 (active ingredient 1%) were each added using a separate dropping funnel. 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, while keeping the temperature in the reaction vessel at 75 ° C., 1.6 parts of rebenol WZ was deionized to 1.6 parts of monomer mixture consisting of 47 parts of 2-ethylhexyl acrylate, 1 part of acrylic acid and 2 parts of diacetone acrylamide. A monomer mixture consisting of a monomer pre-emulsion emulsified with the addition of 20 parts of water and 10 parts of an aqueous solution of potassium persulfate (active ingredient 1%) were immediately put in the reaction vessel temperature using separate dropping funnels. Was polymerized dropwise over 120 minutes while maintaining at 75 ° C. After completion of the dropwise addition, the mixture was stirred at the same temperature for 120 minutes, the contents were cooled, and adjusted with ammonia water (active ingredient 10%) so that the pH was 8.0. The aqueous dispersion obtained here had a solid content concentration of 51.8%, a viscosity of 300 mPa · s, an average particle size of 290 nm, and an acid value determined from the charged amount of the carboxyl group-containing monomer was 15.6. It was.

  After adding 0.3 part of adipic acid dihydrazide to said aqueous dispersion, it filtered with a 100 mesh metal-mesh, and obtained the releasable water-based adhesive composition.

  Glass transition temperature (measured Tg), gel fraction (toluene insoluble fraction), amount of water extract, and water whitening resistance, adhesive strength, and retention of the adhesive sheet obtained using the re-peelable aqueous adhesive composition Tables 1 and 2 show the evaluation results of force, removability, and 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; EPOCROSS WS-500 manufactured by Nippon Shokubai Co., Ltd.
OT-75; AEROSIL OT-75 manufactured by Mitsui Cytec Co., Ltd.
The amounts of monomers, surfactants, polymerization initiators, crosslinking agents, and leveling agents used in Tables 1 and 2 are expressed in parts by weight of solid content.

Claims (4)

Total monomer acids per (a) at least one carbonyl group-containing ethylenically in the molecule an unsaturated monomer 0.1 to 2 wt%, (b) a carboxyl group-containing ethylenically unsaturated monomer 0.5 Obtained by emulsion copolymerization of a polymerizable monomer mixture containing ˜4 wt% and (c) 45 to 99.4 wt% of alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms as essential components Polymer particles [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 in a molecule that is carbodihydrazide or adipic acid dihydrazide A hydrazine derivative [Y] having a hydrazino group and an acetylenic diol surfactant [Z], which is an aqueous pressure-sensitive adhesive composition, The re-peelable aqueous pressure-sensitive adhesive composition is characterized in that the film formed has a glass transition temperature of −25 ° C. or less, a gel fraction of 80% by weight or more, and a water extract amount of 2% by weight or less. The polymer particles [X] is an organic peroxide-based polymerization initiator is one in which polymer underwent emulsion polymerization using claim 1 releasable aqueous pressure-sensitive adhesive composition. The re-peelable aqueous pressure-sensitive adhesive composition according to claim 1, wherein the polymer particles [X] are obtained by emulsion polymerization in the presence of an acetylenic diol surfactant [Z]. A pressure-sensitive adhesive product comprising a base material and a layer of the re-peelable water-based pressure-sensitive adhesive composition according to any one of claims 1 to 3 .