JP5593093B2 - Acrylic emulsion-type pressure-sensitive adhesive composition, method for producing the same, and pressure-sensitive adhesive sheet - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet. Specifically, while maintaining the desired tack, the film has excellent mechanical strength and can reduce the pressure-sensitive adhesive remaining on the release sheet during labeling. In addition, the present invention relates to an acrylic emulsion-type pressure-sensitive adhesive composition excellent in removability, a method for producing the same, and a pressure-sensitive adhesive sheet.

Printing labels have a wide variety of uses. Among them, labeling of roll-to-roll using a labeling machine is used in many fields because it has better production efficiency than manual pasting. For example, a label for a campaign used as an application ticket such as a prize or a lottery for promoting sales of a product on an adherend such as a beverage container or a food container has a label feeding speed of 50 to 120 m / min. Pasting with a high-speed labeling machine is performed.
As an adhesive used for such a label, from the viewpoint of improving the global environment and working environment, as an alternative to an organic solvent-type adhesive, it is rapidly changing to an aqueous emulsion-type adhesive. A pressure-sensitive adhesive has a problem in that the mechanical strength of the film is lower than that of a solvent-type pressure-sensitive adhesive because the formed film is discontinuous.
In addition, when the label is peeled from the release sheet during labeling, if there is a release treatment defect such as a pinhole on the release sheet, the adhesive layer is stretched and deformed between the base material and breaks. Therefore, a very small amount may remain on the release sheet. The release sheet after the label is peeled is collected and wound while passing between the guide rolls. At this time, the release sheet comes into contact with a plurality of guide rolls, but there is a problem that the guide roll that comes into contact with the release treatment surface of the release sheet is contaminated by a very small amount of adhesive remaining on the release treatment surface. Furthermore, in the above-mentioned campaign label application, when being peeled off from the adherend after a certain period of time after being attached to the adherend, a performance (removability) is required in which the adhesive does not remain on the adherend. The
On the other hand, for example, in Patent Document 1, a room temperature adhesive copolymer mainly composed of an acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms is used as a main chain, and the glass transition point is A re-peelable pressure-sensitive adhesive made of an aqueous dispersion containing a graft polymer having a polymer at 70 to 150 ° C. as a side chain is disclosed. By increasing the glass transition point (Tg) of an acrylic copolymer, It is disclosed that releasability and low-temperature adhesiveness can be compatible. However, when the glass transition point is increased, the tack is significantly reduced, and thus there is a problem that the target performance as a pressure-sensitive adhesive cannot be expressed, and the pressure-sensitive adhesive label is accompanied by a labeling process using a high-speed labeling machine. Not suitable for use.

JP 2008-231436 A

  The present invention provides an acrylic emulsion-type pressure-sensitive adhesive that can shorten the aging period, has excellent mechanical strength of the film while maintaining tackiness, can reduce the pressure-sensitive adhesive remaining on the release sheet during labeling, and has excellent removability It aims at providing a composition, its manufacturing method, and an adhesive sheet.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have carried out an emulsion polymerization of an acrylic monomer mixture, and an alkali metal hydroxide and / or an alkaline earth metal water is contained in the mixture. The inventors have found that the object can be achieved by including an oxide, and have completed the present invention.

That is, the present invention provides the following (1) to (11).
(1) (A) (a1) (meth) acrylic acid alkyl ester and (a2) an acrylic emulsion copolymer obtained by emulsion polymerization of a monomer mixture containing a carboxyl group-containing unsaturated monomer, and (B) An acrylic emulsion-type pressure-sensitive adhesive composition containing a crosslinking agent, and (C) an alkali metal hydroxide and / or an alkaline earth before and / or during the emulsion polymerization of the monomer mixture. An acrylic emulsion-type pressure-sensitive adhesive composition containing a metal hydroxide.
(2) (C) Alkali metal hydroxide and / or alkaline earth metal hydroxide is contained 0.001 to 0.5 times equivalent to the carboxyl group in (A) acrylic emulsion copolymer. The acrylic emulsion-type pressure-sensitive adhesive composition according to (1) above.
(3) The above (1) or (2), wherein (C) the alkali metal hydroxide and / or alkaline earth metal hydroxide is at least one selected from potassium hydroxide, sodium hydroxide and lithium hydroxide. 2. An acrylic emulsion-type pressure-sensitive adhesive composition according to 1.
(4) The above (1) to (3), in which (A) 0.1 to 10.0% by mass of the structural unit derived from the carboxyl group-containing unsaturated monomer is contained in the acrylic emulsion copolymer (a2). The acrylic emulsion-type pressure-sensitive adhesive composition according to any one of the above.
(5) The acrylic emulsion-type pressure-sensitive adhesive composition according to any one of (1) to (4), wherein (B) the crosslinking agent is at least one selected from an epoxy compound, a carbodiimide compound, and an oxazoline compound. .
(6) The acrylic emulsion-type pressure-sensitive adhesive composition according to any one of the above (1) to (5), wherein the gel fraction of the dry film of the acrylic emulsion-type pressure-sensitive adhesive composition is 30% or more.
(7) The acrylic emulsion-type pressure-sensitive adhesive composition according to any one of (1) to (6), wherein the tensile stress at break is 0.5 MPa or more.
(8) The acrylic emulsion-type pressure-sensitive adhesive composition according to any one of the above (1) to (7), wherein the dry film of the acrylic emulsion-type pressure-sensitive adhesive composition has a Tg of −70 ° C. or more and −25 ° C. or less.
(9) A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed on at least one surface of the base sheet using the acrylic emulsion-type pressure-sensitive adhesive composition according to any one of (1) to (8).
(10) A method for producing an acrylic emulsion-type pressure-sensitive adhesive composition according to any one of the above (1) to (8), comprising (A) an acrylic emulsion-type copolymer and (B) a crosslinking agent, (A) An acrylic emulsion-type copolymer is a monomer mixture containing (a1) (meth) acrylic acid alkyl ester and (a2) carboxyl group-containing unsaturated monomer (C) an alkali metal hydroxide and A method for producing an acrylic emulsion-type pressure-sensitive adhesive composition obtained by emulsion polymerization in the presence of an alkaline earth metal hydroxide.
(11) The acrylic emulsion-type pressure-sensitive adhesive according to the above (10), wherein the acrylic emulsion-type pressure-sensitive adhesive composition is aged so that the gel fraction of the dry film of the acrylic emulsion-type pressure-sensitive adhesive composition is 30% or more. A method for producing the composition.

  According to the present invention, an acrylic system that can shorten the aging period, is excellent in the mechanical strength of the film while maintaining the target tack, can reduce the adhesive remaining on the release sheet during labeling, and is excellent in removability An emulsion-type pressure-sensitive adhesive composition, a method for producing the same, and a pressure-sensitive adhesive sheet can be provided.

The acrylic emulsion-type pressure-sensitive adhesive composition of the present invention contains an acrylic emulsion-type copolymer (A) and a crosslinking agent (B).
The acrylic emulsion copolymer (A) used in the present invention is obtained by emulsion polymerization of a monomer mixture containing (a1) (meth) acrylic acid alkyl ester and (a2) carboxyl group-containing unsaturated monomer. It is done.
First, the component (a1) in the acrylic emulsion copolymer (A) will be described.
The component (a1) used in the present invention is a (meth) acrylic acid alkyl ester, and a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms is preferably exemplified.
As component (a1), methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, (meth) acrylic Isobutyl acid, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, isooctyl (meth) acrylate, n-octyl (meth) acrylate, nonyl (meth) acrylate , Isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, isoundecyl (meth) acrylate, dodecyl (meth) acrylate, isododecyl (meth) acrylate ( Examples include tridecyl (meth) acrylate, isotridecyl (meth) acrylate, and tetradecyl (meth) acrylate.
Among these, from the viewpoint of balance of performance, methyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and hexyl (meth) acrylate are preferable, methyl methacrylate, n-acrylate. Butyl and 2-ethylhexyl acrylate are more preferable.
The component (a1) may be used alone or in combination of two or more.

The content of the structural unit derived from the component (a1) in the acrylic emulsion copolymer (A) is preferably 50 to 99.9% by mass, and more preferably 70 to 99.5% by mass. 80 to 99.0% by mass is more preferable.
By including 50% by mass or more of component (a1), sufficient adhesive strength and tack can be obtained, and by including 99.9% by mass or less of component (a2) and other unsaturated monomers as necessary. By containing, sufficient cohesive force can be obtained.

Next, the component (a2) in the acrylic emulsion copolymer (A) will be described.
(A2) As the carboxyl group-containing unsaturated monomer, an ethylenically unsaturated carboxylic acid such as acrylic acid, acrylic acid dimer, methacrylic acid, maleic acid, and itaconic acid is preferably used. Among these, acrylic acid and methacrylic acid are preferable from the viewpoints of price and availability. The component (a2) may be used alone or in combination of two or more.

The content of the structural unit derived from the component (a2) in the acrylic emulsion copolymer (A) is preferably 0.1 to 10.0% by mass, and 0.5 to 8.0% by mass. More preferably, it is more preferably 1.0 to 6.0% by mass.
By containing 0.1 to 10.0% by mass of the component (a2), the stability in the aqueous dispersion coating liquid state such as polymerization stability, dispersion stability, and mechanical stability, and the pressure-sensitive adhesive composition in the pressure-sensitive adhesive sheet The mechanical strength of the dry film can be made compatible. When the content is 0.1% by mass or more, the stability in a water-dispersed coating liquid state is improved, and when the content is 10% by mass or less, sufficient tack and water resistance are maintained, while the dry film of the pressure-sensitive adhesive composition is maintained. An appropriate degree of crosslinking is obtained, the mechanical strength of the dried film is improved, and good labeling suitability is obtained.

  In the acrylic emulsion copolymer (A), monomers other than the component (a1) and the component (a2) can be used as necessary. For example, sulfonic acid group-containing unsaturation such as vinyl sulfonic acid, styrene sulfonic acid, sulfoethyl (meth) acrylate, sulfopropyl (meth) acrylate, (meth) allyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid Monomers, phosphoric acid group-containing unsaturated monomers such as acid phosphooxyethyl (meth) acrylate, acid phosphooxypropyl (meth) acrylate, acid phosphooxypolyethylene glycol (meth) acrylate, (meth) acrylic acid 2- Hydroxyethyl, hydroxyl-containing unsaturated monomers such as (meth) acrylic acid hydroxyalkyl esters such as hydroxypropyl (meth) acrylate, aminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, ( Dimethacrylic acid (meth) acrylate Examples include amino group-containing unsaturated monomers such as Noethyl. Besides these, acrylamide, methacrylamide, diacetone acrylamide, acetoacetoxymethyl acrylate, acetoacetoxymethyl methacrylate, methylol acrylamide, butoxy N-methylol acrylamide, 2-methoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, methoxytriethylene glycol (meth) acrylate, 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3-tetrafluoropropyl (Meth) acrylate, β- (perfluorooctyl) ethyl (meth) acrylate, N-vinylpyrrolidone, N-vinyl-ε-caprolactam, cyclohexylmaleimide, methyl vinyl ether, butyl vinyl Vinyl ethers such as ruether and hexyl vinyl ether, vinyl acetate, vinyl propionate, vinyl chloride, chloroprene, styrene, t-butylstyrene, (meth) acrylonitrile, chloroacrylonitrile, glycidyl (meth) acrylate, allyl glycidyl ether, γ- ( (Meth) acryloxypropyltrimethoxysilane, (meth) acryloxybutyltrimethoxysilane, vinyltrimethoxysilane, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,6 hexanediol di (meth) acrylate And the like, and the like.

Next, the component (C) will be described.
In the monomer mixture containing (a1) (meth) acrylic acid alkyl ester and (a2) carboxyl group-containing unsaturated monomer, (C) alkali metal hydroxide and / or alkaline earth It contains a metal hydroxide. By including the component (C) in the monomer mixture, the mechanical strength of the dry film formed from the resulting acrylic emulsion-type resin composition is improved, and the removability of the pressure-sensitive adhesive sheet is improved.
Examples of the component (C) include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, and alkaline earth metal hydroxides such as magnesium hydroxide, calcium hydroxide and barium hydroxide. Among these, sodium hydroxide, potassium hydroxide, and lithium hydroxide are preferable, and sodium hydroxide and potassium hydroxide are more preferable from the viewpoint of easy balance of adhesive properties.
The said component (C) may be used individually or in mixture of 2 or more types.

The ratio of the alkali metal hydroxide and / or alkaline earth metal hydroxide to the carboxyl group in the acrylic emulsion copolymer is preferably 0.001 to 0.5 times equivalent, more preferably 0.03 to 0. .45 times equivalent, more preferably 0.05 to 0.4 times equivalent.
The pressure-sensitive adhesive sheet formed using the acrylic emulsion-type pressure-sensitive adhesive composition containing the component (C) in the above range has a mechanical strength and re-peeling while maintaining the target tack without lowering water resistance. It is possible to improve the property, and it is possible to reduce the residue of the pressure-sensitive adhesive on the release sheet in the labeling step, thereby preventing the problem of guide roll contamination.

Next, the manufacturing method of an acrylic emulsion type copolymer (A) is demonstrated.
The acrylic emulsion-type copolymer (A) uses an emulsifier to prepare a monomer mixture containing the component (a1), the component (a2), and other monomers used as necessary, and (C) an alkali. It can be obtained by emulsion polymerization in the presence of a metal hydroxide and / or an alkaline earth metal hydroxide.
(C) Although there is no restriction | limiting in particular as an addition method of an alkali metal hydroxide and / or an alkaline-earth metal hydroxide, Before the emulsion polymerization and / or during emulsion polymerization, the aqueous solution adjusted beforehand to the desired density | concentration It is preferable to add to the reaction system in the form.

As the emulsifier, an anionic or nonionic reactive emulsifier or a non-reactive emulsifier is used.
Examples of the anionic reactive emulsifier include “Adekalia Soap SE-20N”, “Adekalia Soap SE-10N”, “Adekalia Soap PP-70”, “Adekalia Soap PP-710”, “Adekalia Soap SR-”. 10 ”,“ Adekaria Soap SR-20 ”[above, manufactured by ADEKA Corporation],“ Eleminol JS-2 ”,“ Eleminol RS-30 ”[above, manufactured by Sanyo Chemical Industries, Ltd.],“ Latemuru E-118B ” "Latemul S-180A", "Latemul S-180", "Latemul PD-104" (manufactured by Kao Corporation), "Aqualon BC-05", "Aqualon BC-10", "Aquaron BC-20" , "Aqualon HS-05", "Aquaron HS-10", "Aquaron HS-20", "New Frontier S-510", "A “Aron KH-05”, “Aqualon KH-10” (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), “Phosfinol TX” (manufactured by Toho Chemical Co., Ltd.), polyoxyethylene lauryl ether reactive emulsifier [“ Emulgen 103 ", manufactured by Kao Corporation] and the like.
Nonionic reactive emulsifiers include “ADEKA rear soap NE-10”, “ADEKA rear soap NE-20”, “ADEKA rear soap NE-30”, “ADEKA rear soap NE-40”, and “ADEKA rear soap ER-”. 10 ”,“ Adekaria soap ER-20 ”,“ Adekaria soap ER-30 ”,“ Adekaria soap ER-40 ”(manufactured by ADEKA Corporation),“ Aquaron RN-10 ”,“ Aquaron RN-20 ” ”,“ AQUALON RN-30 ”,“ AQUALON RN-50 ”[above, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.], and the like, but it is only necessary to have reactivity, and it is not particularly limited thereto. .

  In consideration of emulsion polymerization stability and mechanical stability of the emulsion, a non-reactive emulsifier may be used, or it may be used in combination with the aforementioned reactive emulsifier. Such a non-reactive emulsifier is not particularly limited, and a known emulsifier usually used for emulsion polymerization is used. For example, sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene lauryl sulfate, sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene Anionic emulsifiers such as sodium alkylsulfosuccinate, for example, nonionic emulsifiers such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene polyoxypropylene block polymer and the like.

  The amount of these emulsifiers used is preferably 0.1 to 8.0 parts by weight, and 0.5 to 5.0 parts by weight, based on 100 parts by weight of the monomer mixture, as active ingredients (components excluding solvents and various additives). Part is more preferred. By making the used amount of the emulsifier 0.1 parts by mass or more, emulsion polymerization stability, storage stability of the resulting emulsion, and mechanical stability are ensured, and by making the use amount 8.0 parts by mass or less, hydrophilicity is obtained. It is possible to prevent the water resistance from being lowered due to the excessive increase in the water resistance.

(A) The conditions for emulsion polymerization for preparing the acrylic emulsion-type copolymer are not particularly limited, and the conditions applied in ordinary emulsion polymerization can be applied as they are. In general, after replacing the inside of the reactor with an inert gas, the temperature is increased while stirring under reflux, and the polymerization is carried out for about 1 to 8 hours after starting the temperature increase in a temperature range of about 40 to 100 ° C.
When preparing the composition by an emulsion polymerization method, a polymerization initiator is usually used. As polymerization initiators, azo compounds such as 2,2′-azobis (2-methylpropionamidine) dihydrochloride, persulfates such as ammonium persulfate and potassium persulfate, and peroxides such as benzoyl peroxide should be used. Can do.
The amount of the polymerization initiator used is preferably 0.01 to 5 parts by mass and preferably 0.01 to 3 parts by mass with respect to a total of 100 parts by mass of the monomer mixture used for emulsion polymerization. More preferred. When the amount of the polymerization initiator used is 5 parts by mass or less, deterioration of water resistance and heat resistance due to a decrease in molecular weight is prevented, and when it is 0.01 parts by mass or more, a problem of poor adhesion occurs. Can be prevented.

When the monomer mixture is emulsion-polymerized using a reactive emulsifier, a chain transfer agent can be used. As the chain transfer agent, for example, terpene compounds such as α-pinene, β-pinene, limonene, and terpinolene can be preferably used. Also, compounds having a thiol group or a hydroxyl group are generally known.
Examples of the compound having a thiol group include mercaptans such as lauryl mercaptan, 2-mercaptoethyl alcohol, dodecyl mercaptan (1-dodecanethiol), mercaptosuccinic acid, n-butyl mercaptopropionate and octyl mercaptopropionate. Examples include alkyl mercaptopropionate and alkoxyalkyl mercaptopropionate such as methoxybutyl mercaptopropionate. Examples of the compound having a hydroxyl group include alcohols such as methyl alcohol, n-propyl alcohol, isopropyl alcohol (IPA), t-butyl alcohol, and benzyl alcohol.

  The amount of the chain transfer agent used is preferably 0.01 to 1 part by mass with respect to 100 parts by mass in total of the monomer mixture used for emulsion polymerization. By making the amount of chain transfer agent used within the above range, it is possible to prevent deterioration of water resistance, heat resistance, etc. due to a decrease in molecular weight, to prevent deterioration of adhesive properties, and to cause a problem of guide roll contamination. Can be prevented.

When emulsion polymerization is performed on the monomer mixture using a reactive emulsifier, pH adjustment may be performed, and a pH buffering agent may be used in combination as necessary. The pH buffering agent is not particularly limited as long as it has a pH buffering action. For example, sodium bicarbonate, potassium bicarbonate, monosodium phosphate, monopotassium phosphate, disodium phosphate, trisodium phosphate, Examples thereof include sodium acetate, ammonium acetate, sodium formate, and ammonium formate.
The amount of the pH buffering agent is not particularly limited. These pH buffering agents may be added before polymerization or during polymerization.

(A) The average particle diameter of the emulsion particles in the acrylic emulsion-type copolymer is about 100 to 500 nm, preferably 100 to 300 nm. When the average particle size is within the above range, emulsion polymerization stability, storage stability of the resulting emulsion, mechanical stability, and physical property balance of the adhesive composition film after drying, that is, adhesion to the substrate, An adhesive having an excellent balance of wettability to the adherend, water resistance, cohesion, transparency, and mechanical strength can be obtained.
When the average particle size is 100 nm or more, stable emulsion particles can be obtained, and an increase in the amount of emulsifier used can be prevented. When the average particle size is 500 nm or less, adhesion to the substrate, transparency of the resulting pressure-sensitive adhesive layer, and water resistance are ensured. The average particle size of the emulsion particles can be controlled by the type and concentration of the emulsifier added during polymerization, the concentration of the polymerization initiator, and the like. Here, the average particle diameter of the emulsion particles is based on a volume-based median diameter value obtained by measurement with a laser diffraction / scattering particle size distribution measuring apparatus.

Next, the crosslinking agent (B) will be described in detail.
The crosslinking agent (B) is not particularly limited, and examples thereof include an epoxy compound, a carbodiimide compound, an oxazoline compound, a hydrazide compound, an isocyanate compound, an alkoxysilane compound, and an amine compound. Of these, epoxy compounds, carbodiimide compounds, and oxazoline compounds are preferably used from the viewpoints of reactivity with the carboxyl group in the component (a2), adhesion to the base material, adhesive strength, cohesive strength, and excellent availability. An epoxy compound is more preferably used.

The epoxy compound may be any compound having two or more epoxy groups or glycidyl groups in the molecule, such as bisphenol A / epichlorohydrin type epoxy resin, sorbitol polyglycidyl ether (for example, manufactured by Nagase ChemteX Corporation). , “Denacol EX-611”, “Denacol EX-612”, “Denacol EX-614”, “Denacol EX-614B”, “Denacol EX-622”, etc.), polyglycerol polyglycidyl ether (for example, Nagase ChemteX Corporation) “Denacol EX-512”, “Denacol EX-521”, etc.), pentaerythritol polyglycidyl ether (for example, “Denacol EX-411” manufactured by Nagase ChemteX Corporation), diglycerol polyglycidyl ether For example, “Denacol EX-421” manufactured by Nagase ChemteX Corporation), glycerol polyglycidyl ether (for example, “Denacol EX-313”, “Denacol EX-314” manufactured by Nagase ChemteX Corporation), trimethylol, etc. Propane polyglycidyl ether (for example, “Denacol EX-321” manufactured by Nagase ChemteX Corporation), neopentylglycol diglycidyl ether (for example, “Denacol EX-211” manufactured by Nagase ChemteX Corporation), 6-hexanediol diglycidyl ether (for example, “Denacol EX-212” manufactured by Nagase ChemteX Corporation), ethylene glycol diglycidyl ether (for example, “Denacol EX-810” manufactured by Nagase ChemteX Corporation, “Denaco” EX-811 ", etc.), diethylene glycol diglycidyl ether (eg," Denacol EX-850 "," Denacol EX-851 ", etc., manufactured by Nagase ChemteX Corporation), polyethylene glycol diglycidyl ether (eg, Nagase ChemteX Corporation) “Denacol EX-821”, “Denacol EX-830”, “Denacol EX-832”, “Denacol EX-841”, “Denacol EX-861”, etc.), propylene glycol diglycidyl ether (for example, Nagase Chem) "Denacol EX-911" manufactured by Tex Co., Ltd.), polypropylene glycol diglycidyl ether (for example, "Denacol EX-941", "Denacoll EX-920", "Denacol EX-931" manufactured by Nagase ChemteX Corporation) Etc.), diglycidylaniline, N, N, N ′, N′-tetraglycidyl-m-xylenediamine, 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane and the like.
Among these, the aqueous type is preferable.

  The carbodiimide compound may be any compound containing at least two carbodiimide groups in the molecule. For example, “Carbodilite SV-02”, “Carbodilite V-02”, “Carbodilite V-02” manufactured by Nisshinbo Industries, Ltd. L2 "," Carbodilite V-04 "," Carbodilite V-06 "," Carbodilite E-01 "," Carbodilite E-02 "," Carbodilite E-04 "and the like.

  Any oxazoline-based compound may be used as long as it contains at least two oxazoline groups in the molecule, and an addition-polymerizable 2-oxazoline having a substituent having an unsaturated carbon-carbon bond at the 2-position carbon position (for example, 2-isopropenyl-2-oxazoline) and other unsaturated monomers, etc., and commercially available products such as “Epocross WS-300” and “Epocross WS-500” manufactured by Nippon Shokubai Co., Ltd. “Epocross WS-700”, “Epocross K-2010E”, “Epocross K-2020E”, “Epocross K-2030E” and the like.

  The hydrazide compound may be any compound having at least two or more hydrazide groups in the molecule, such as oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, Examples thereof include maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide and the like.

  The isocyanate compound may be any compound containing at least two isocyanate groups in the molecule, such as toluylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, metaxylylene diisocyanate. , 1,5-naphthalene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated toluylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, tetramethylxylene diisocyanate, etc., "Sumijour N" (manufactured by Sumitomo Bayer Urethane Co., Ltd.) Bullet polyisocyanate compounds such as “Desmodur IL”, “Desmodur HL” (Bayer A.). ), "Coronate EH" (manufactured by Nippon Urethane Industry Co., Ltd.), polyisocyanate compounds having an isocyanurate ring, "Sumijoule L" (manufactured by Sumitomo Bayer Urethane Co., Ltd.), "Coronate HL" (Nihon Polyurethane) Manufactured by Kogyo Co., Ltd.), adduct-type polyisocyanate compounds such as “Takenate WD-725”, “Takenate WD-720”, “Takenate WD-730” and “Takenate WB-700” (manufactured by Mitsui Chemicals Polyurethane Co., Ltd.) Examples thereof include self-emulsifying water-dispersed polyisocyanate compounds such as “Aquanate 100”, “Aquanate 110”, “Aquanate 200”, and “Aquanate 210” (manufactured by Nippon Polyurethane Industry Co., Ltd.). Among these, the aqueous type is preferable. Moreover, you may use block isocyanate.

  Examples of alkoxysilane compounds include alkoxysilyl group-containing unsaturated monomers such as γ- (meth) acryloxypropyltrimethoxysilane, (meth) acryloxybutyltrimethoxysilane, vinyltrimethoxysilane, methyltrimethoxysilane, Methyltriethoxysilane, methyltriisopropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, phenylmethyldimethoxysilane, tetramethoxysilane, tetraethoxy Silane, tetraisopropoxysilane, tetrabutoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, 3 Glycidoxypropyltrimethoxysilane, 3-glycidoxypropyl triethoxysilane, and the like.

  Any amine compound may be used as long as it contains at least two amino groups in the molecule. For example, “Epomin SP-003”, “Epomin SP-006”, “Epomin SP-012”, “Epomin SP”. -018 "," Epomin SP-200 "," Epomin P-1000 "(manufactured by Nippon Shokubai Co., Ltd.)," Polyment SK-1000 "," Polyment NK-100PM "," Polyment NK-200PM "( As described above, aminoethylated acrylic polymers such as Nippon Shokubai Co., Ltd. are listed.

The crosslinking agent (B) is preferably blended so that the crosslinking agent is in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of the acrylic emulsion copolymer of the component (A). The range of 0.05-15 mass parts is more preferable, and the range of 0.1-10 mass parts is further more preferable.
By mix | blending a crosslinking agent (B) so that it may become 0.01-20 mass parts, the tack required for labeling suitability (sticking property to a to-be-adhered body) and an elasticity modulus can be made compatible. If it is 0.01 parts by mass or more, the elastic modulus will not be too low, so that the adhesive can be prevented from remaining on the release sheet, and the cohesive force necessary for maintaining removability. This improves the storage stability of the pressure-sensitive adhesive sheet after long-term storage in a high-temperature environment. Moreover, if it is 20 mass parts or less, since a moderate crosslinking degree is obtained in the dry film | membrane of an adhesive composition, and an elasticity modulus does not become high too much, sufficient tack can be maintained and labeling suitability is obtained.

In the acrylic emulsion-type pressure-sensitive adhesive composition of the present invention, in addition to the components (A) to (C), components such as a thickener, a tackifier, and a plasticizer are blended as necessary. Also good.
As the thickener, those selected from the group consisting of cellulose thickeners, polyacrylic acid thickeners, urethane thickeners, and mixtures thereof are used. Examples of the cellulose thickener include hydroxypropylcellulose, hydroxypropylmethylcellulose acetate succinate, hydroxypropylmethylcellulose, polyvinylpyrrolidone and polyacrylic acid. Of these, polyacrylic acid thickeners, urethane thickeners, hydroxypropylcellulose and / or hydroxypropylmethylcellulose acetate succinate are preferred, and polyacrylic thickeners or urethane thickeners are added. Is more preferable.
Although the compounding quantity of a thickener is suitably adjusted according to desired viscosity, it shall be 1-10 mass parts with respect to 100 mass parts of acrylic emulsion-type adhesive compositions (solid content conversion) of this invention. Is preferred.

Examples of the tackifier include synthetic resin systems such as rosin-based, terpene-based natural resin-based, and petroleum resin-based. Specifically, "Harry Star SK-508", "Harry Star SK-508H", "Harry Star SK-532D", Harrier Star SK-816E, "Harri Star SK-822E", "Harri Star" are commercially available products. "SK-218NS", "Harry Star SK-70D", "Harry Star SK-501", "Harry Star SK-501NS", "Harry Star SK-385NS", "Harry Star SK-370N" [End Manufactured, trade name], "Superester E-720", "Superester E-730-55", "Superester E-650", "Superester E-865", "Tamanol E-100", "Tamanol E" -200 "," Emulsion AM-1002 "," Superester NS-100H "," Super "Ester NS-125A", "Superester NS-100A", "Superester NS-120B", "Superester E-625-NT", "Superester E-865-NT", "Tamanol E-200-NT" [Arakawa Chemical Industries, Ltd., trade name], “YS Resin TO125”, “YS Resin TO115”, “YS Resin TO105”, “YS Resin TR105”, “YS Polystar U115”, “YS Polystar 2130”, “YS Polystar 2115”, “YS Polystar 2100”, “YS Polystar T145”, “YS Polystar T130”, “YS Polystar T115”, “YS Polystar T100”, “YS Polystar S145”, “Mighty Ace G150”, “Mighty” Ace G125 "," YS "Polystar TH130", "Nanolet R-1050", "Nanolet G-1250", "YS Resin TO85", "YS Polystar T80", "YS Polystar T50", "YS Polystar T30" [above, manufactured by Yashara Chemical Co., Ltd. Name].
These tackifiers may be added to a mixture containing an ethylenically unsaturated monomer at the time of polymerization, or the tackifier itself may be emulsified by a known method and added to the emulsion of the acrylic copolymer (A). it can. About what is already marketed as an aqueous dispersion, it can add to an aqueous dispersion-type acrylic adhesive composition as it is.
It is preferable that the compounding quantity of a tackifier is 0.1-20 mass parts with respect to 100 mass parts of acrylic emulsion type copolymers (A) (solid content conversion), and 0.5-16 mass parts It is more preferable that If the compounding quantity of a tackifier is 0.1 mass part or more, a substantial effect will be acquired and it will be excellent in adhesive force and base-material adhesiveness. When the amount is 20 parts by mass or less, the apparent Tg of the pressure-sensitive adhesive layer is increased, thereby preventing the adhesive force and the substrate adhesion from being difficult to obtain. These tackifiers may be used in combination of two or more as required.

Examples of the plasticizer include liquid polybutene, mineral oil, lanolin, liquid polyisoprene, liquid polyacrylate, dioctyl phthalate, propylene glycol fatty acid ester (used in Examples), triethanolamine, glycerin, diglycerin, amine alkylene oxide addition Thing etc. are mentioned.
The amount of the plasticizer is preferably 0.1 to 10 parts by mass, and 0.1 to 5 parts by mass with respect to 100 parts by mass of the acrylic emulsion copolymer (A) (in terms of solid content). Is preferred. If the compounding quantity of a plasticizer is 0.1 mass part or more, a substantial effect will be acquired and it will be excellent in adhesive force and base-material adhesiveness. If it is 10 mass parts or less, it can prevent that an adhesive layer becomes flexible too much. These plasticizers may be used in combination of two or more as required.

The acrylic emulsion-type pressure-sensitive adhesive composition of the present invention has a solid content (nonvolatile content) of usually about 30 to 65% by mass, preferably 40 to 60% by mass. The viscosity is usually about 50 to 20,000 mPa · s (BM type viscometer, 25 ° C.), preferably 100 to 15,000 mPa · s.
Furthermore, the pH is usually in the range of 6-9.
It is preferable that the solid content, viscosity, and pH are within the above ranges from the viewpoints of drying property, coating property, dispersion stability of the coating solution, and handling property.

  The gel fraction of the dry film formed from the acrylic emulsion-type pressure-sensitive adhesive composition of the present invention is not particularly limited, but is preferably 30% or more, more preferably 40% or more, and still more preferably 50% or more. When the gel fraction is 30% or more, the cohesive force and water resistance of the pressure-sensitive adhesive are improved. Furthermore, if the gel fraction is 40% or more, better removability of the pressure-sensitive adhesive sheet can be obtained. On the other hand, from the viewpoint of adhesion to the substrate and wettability to the adherend, the gel fraction is preferably 90% or less, and more preferably 85% or less. From the above viewpoint, the gel fraction is preferably 30 to 90%, preferably 40 to 90%, and more preferably 50 to 85%. The gel fraction of the pressure-sensitive adhesive layer is the ratio of the solvent-insoluble portion of the pressure-sensitive adhesive layer. When the pressure-sensitive adhesive layer dried at 90 ° C. for 1 minute is immersed in tetrahydrofuran at 23 ° C. for 72 hours and dried. It is calculated | required as a ratio (%) of the residual adhesive layer mass after immersion with respect to the adhesive layer mass before immersion.

The gel fraction of the dry film can be adjusted to the above range by aging the acrylic emulsion-type pressure-sensitive adhesive composition. Aging in the present invention refers to a step of aging the acrylic emulsion-type pressure-sensitive adhesive composition so that the crosslinking reaction with the crosslinking agent proceeds and the gel fraction is in the above range.
The aging conditions of the acrylic emulsion-type pressure-sensitive adhesive composition are not particularly limited, but are preferably in the range of 15-50 ° C, more preferably 18-40 ° C, preferably 1 day or more, more preferably 1-10 days, More preferably, aging is preferably performed for 2 to 8 days. Since the acrylic emulsion-type pressure-sensitive adhesive composition of the present invention can shorten the aging period, production efficiency can be improved.
The aging method of the acrylic emulsion-type pressure-sensitive adhesive composition is not particularly limited.For example, after the acrylic emulsion-type pressure-sensitive adhesive composition is applied to a release sheet or a substrate in the production process of the pressure-sensitive adhesive sheet described later, It is preferable to age the pressure-sensitive adhesive composition.

  The breaking stress in the tensile test at a tensile rate of 1000 mm / min of the dry film formed from the acrylic emulsion-type pressure-sensitive adhesive composition of the present invention is preferably 0.5 MPa or more, more preferably 0.5 to 2.5 MPa, More preferably, it is 0.5-2.0 MPa. By setting the breaking stress within the above range, the mechanical strength of the coating necessary for labeling suitability (adhesion suitability to adherends) can be obtained, and there is little adhesive remaining on the release sheet in the labeling process. An adhesive sheet excellent in peelability can be obtained.

  The glass transition point (Tg) of the dry film formed from the acrylic emulsion-type pressure-sensitive adhesive composition of the present invention is preferably -70 ° C to -25 ° C, more preferably -65 ° C to -30 ° C, particularly preferably. It is -60 degreeC--40 degreeC. By keeping Tg within the above range, the mechanical strength is obtained while maintaining the target tack, the adhesiveness to the adherend in the labeling step is excellent, and there is little residual adhesive on the release sheet, An adhesive sheet excellent in removability can be obtained.

The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer formed on at least one side of a substrate using the acrylic emulsion-type pressure-sensitive adhesive composition of the present invention, and the pressure-sensitive adhesive layer on one side of the substrate. It is preferable to have a release sheet on the pressure-sensitive adhesive layer. The acrylic emulsion-type pressure-sensitive adhesive composition of the present invention can be processed into the pressure-sensitive adhesive sheet of the present invention by applying to a substrate and drying.
The substrate is not particularly limited as long as it is a support for the pressure-sensitive adhesive layer, and is a known synthetic resin film, high-quality paper, coated paper, impregnated paper, or other synthetic paper having a cavity inside, Nonwoven fabrics can be used. Among these, a synthetic resin film is preferable in consideration of applications for which water resistance is expected.
The material of the synthetic resin film is not particularly limited, and is a polyolefin resin such as a polyethylene resin or a polypropylene resin, a polyester resin such as a polybutylene terephthalate resin or a polyethylene terephthalate resin, an acetate resin, an acrylonitrile / butadiene / styrene (ABS) resin, Examples thereof include synthetic resin films such as polystyrene resin, vinyl chloride resin, polyimide resin, polylactic acid resin, and polyamide resin, and those films subjected to metal vapor deposition such as aluminum.
The synthetic resin film used as the base material for the pressure-sensitive adhesive sheet may be unstretched, or may be stretched in a uniaxial direction or a biaxial direction such as longitudinal or lateral.

The method for producing the pressure-sensitive adhesive sheet of the present invention is not particularly limited. For example, the acrylic emulsion-type pressure-sensitive adhesive composition is usually applied to a release sheet and dried to form a pressure-sensitive adhesive layer. Transfer coating method for bonding to the surface of the adhesive sheet substrate, and then directly applying the adhesive to the surface of the adhesive sheet substrate and drying to form an adhesive layer and then directly bonding to the release sheet A coating method can also be employed.
The coating method of the pressure-sensitive adhesive composition is not particularly limited, and conventionally known coating methods can be used. For example, comma coater, knife coater, roll coater, roll knife coater, gravure coater, vario gravure coater, air knife Examples thereof include a method using a coating apparatus such as a coater, a bar coater, a die coater, or a curtain coater.

Although there is no restriction | limiting in particular in the thickness of the base material for adhesive sheets, Usually, it is the range of 10-200 micrometers, and from the surface of the ease of handling, Preferably it is 25-150 micrometers.
The base material for pressure-sensitive adhesive sheets may be colored or colorless and transparent. Moreover, you may give printing, printing, etc. to one side of the base material for adhesive sheets.
Accordingly, the surface for printing, printing, etc. of the base material for the pressure-sensitive adhesive sheet may be provided with a heat-sensitive recording layer, a print-receiving layer capable of performing thermal transfer, inkjet, laser printing, etc., a printability improving layer, etc. .
In addition, the surface for forming the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet base material is subjected to easy adhesion treatment such as primer treatment or corona treatment for the purpose of improving the adhesion (keying force) with the pressure-sensitive adhesive layer. May be.
Although there is no restriction | limiting in particular in the thickness of an adhesive layer, Usually, 10-50 micrometers, Preferably it is 15-35 micrometers. The thickness of the pressure-sensitive adhesive sheet obtained by laminating the pressure-sensitive adhesive sheet base material, the pressure-sensitive adhesive layer and the release sheet is preferably such that it can be introduced into a printer or the like, and is usually 50 to 300 μm, preferably 60 to 250 μm.

The release sheet is not particularly limited, and it is desirable that the release sheet layer is formed on the release sheet base material.
Examples of the base material for the release sheet include paper, synthetic paper, and synthetic resin film.
As the paper, for example, a paper base such as fine paper, glassine paper, coated paper, a paper base such as a laminated paper obtained by laminating a thermoplastic resin such as polyethylene or polypropylene to these paper bases, and high-quality paper, Glassine paper, coated paper, etc. include paper bases treated with cellulose, starch, polyvinyl alcohol, acrylic-styrene resin, etc., and synthetic resin films include, for example, polyethylene resins, polyolefin resins such as polypropylene resins, Examples thereof include films made of polyester resins such as polybutylene terephthalate resin and polyethylene terephthalate resin, and films obtained by subjecting these synthetic resin films to easy adhesion treatment.
The release agent layer can be formed using a known release agent. Examples of the release agent include silicone resins, fluorine resins, long chain alkyl-containing resins, alkyd resins, polyolefin resins, and isoprene. Preferably, at least one selected from rubber-based elastomers such as a base resin and a butadiene-based resin is used.
The thickness of the release agent layer is preferably 0.05 to 2.0 μm, more preferably 0.1 to 1.5 μm. There is no restriction | limiting in particular in the thickness of the base material for release sheets, Usually, it is 30-200 micrometers.

The pressure-sensitive adhesive sheet of the present invention may be a flat sheet or may be rolled up. The adherend to which the pressure-sensitive adhesive sheet of the present invention is affixed may be a flat plate, a cylindrical one, or a three-dimensional curved surface.
As a suitable application of the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive sheet printed on the substrate surface is a pressure-sensitive adhesive in which only the base material and the pressure-sensitive adhesive layer are continuously cut out to a predetermined shape and size without cutting out the release sheet. Campaign labels that are made on sheets (labels) and can be applied to high-speed labeling machines using beverage containers such as aluminum cans, steel cans, and plastic bottles as adherends. It can be widely used for high-speed labeling.
Thus, even if the label is peeled from the release sheet at a high speed, the pressure-sensitive adhesive does not remain on the release sheet side, and contamination of the guide roll can be prevented. Furthermore, the pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet of the present invention have high tack, are excellent in labeling at high speed, have good adhesion to the base material, and have a long period of time since there is little increase in adhesive strength after application. Can be easily peeled off again from the adherend.

EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these examples.
Measurement and evaluation of the physical or mechanical properties of the dried film of the acrylic emulsion-type pressure-sensitive adhesive composition obtained in the examples and comparative examples were performed as follows.
(1) Gel fraction Only the pressure-sensitive adhesive layer was peeled off from the substrate-less pressure-sensitive adhesive sheets produced in Examples and Comparative Examples, and immersed in tetrahydrofuran for 72 hours under a 23 ° C. environment, and undissolved components were dried at 120 ° C. for 3 hours. The mixture was allowed to stand for 3 hours under conditions of 23 ° C. and a relative humidity of 50%, and then the mass was measured. The gel fraction was calculated by the following equation. The gel fraction was measured after the acrylic emulsion-type pressure-sensitive adhesive composition was applied to a release sheet and dried, and then the pressure-sensitive adhesive composition was aged for 0 days, 3 days, and 7 days at 23 ° C., respectively. .
Gel fraction (% by mass) = (mass of undissolved component after immersion / drying / massage of adhesive layer before immersion) × 100
(2) Breaking stress The release sheet of the substrate-less pressure-sensitive adhesive sheet prepared in Examples and Comparative Examples was removed, and a plurality of sheets were stacked and laminated until the thickness of the pressure-sensitive adhesive layer became 200 μm, thereby preparing a test sample. A test sample stored at 23 ° C. and cut into a length of 50 mm, a width of 15 mm, and a thickness of 400 μm in an environment of 23 ° C. and 50% RH after one week of coating and drying is “Universal Material Testing Machine 5581” (Instron Japan) Tensile test was conducted at a pulling speed of 1000 mm / min using a company limited, and the breaking stress was measured.
(3) Measurement of glass transition point (Tg) About 20 mg of the pressure-sensitive adhesive was collected from the base-less pressure-sensitive adhesive sheets prepared in Examples and Comparative Examples, and “DSC Q2000” (manufactured by TA Instruments Japan Co., Ltd.) Tg was measured at a heating rate of 20 ° C./min.

The labeling, labeling characteristics, and re-peelability were evaluated as follows.
(4) Labeling suitability evaluation (patch suitability)
The pressure-sensitive adhesive roll obtained by winding the pressure-sensitive adhesive sheet was cut into 5 rolls having a width of 20 mm and a length of 500 m, and punching was performed so that the label size was 15 mm × 15 mm and the label interval was 3 mm. Using these 5 rolls of adhesive rolls, an intermittent labeling test was conducted using a labeling machine SRV150EV2 (manufactured by Lintec Corporation) with the adherend as an aluminum can at a feeding speed of 100 m / min. Whether the label can be attached to the adherend or whether it can be peeled off without being attached was visually determined and evaluated according to the following criteria based on the labeling ratio.
○: The rate of labeling is 80% or more. Δ: The rate of labeling is 50-80%.
X: Ratio of labeling is 50% or less

(5) Contamination evaluation of guide roll by transfer of adhesive remaining on release film The adhesive roll formed by winding the adhesive sheet is cut into 5 rolls with a width of 20 mm and a length of 500 m, label size 15 mm × 15 mm, between labels The punching process was carried out so that the thickness became 3 mm. Using these 5 rolls of adhesive rolls, an intermittent labeling test was conducted with a labeling machine SRV150EV2 (manufactured by Lintec Corporation) at a feeding speed of 100 m / min. After continuously testing 5 rolls of the adhesive roll, the stickiness of the guide roll contacting the release treatment surface was evaluated according to the following criteria.
○: No stickiness.
Δ: Slightly sticky.
X: There is stickiness.

(6) Removability evaluation The pressure-sensitive adhesive sheet was cut into a size of 30 mm × 50 mm, and the pressure-sensitive adhesive sheet test piece was attached to a stainless steel plate (SUS420) in an environment of 23 ° C. and 50% RH.
The pressure-sensitive adhesive sheet test piece was left on the stainless steel plate for 24 hours in the same environment, and then allowed to stand in a 70 ° C. environment for 7 days.
Thereafter, the test piece which was returned to the environment of 23 ° C. and 50% RH and allowed to stand for 24 hours was peeled off by hand at a speed of 0.3 m / min and 50 m / min, and the adhesive remaining on the stainless steel plate was observed. Evaluation was made according to the following criteria. The re-peelability test was evaluated after the acrylic emulsion-type pressure-sensitive adhesive composition was applied to a release sheet and dried, and then the pressure-sensitive adhesive composition was aged for 0 days, 3 days, and 7 days at 23 ° C. It was.
◎: No glue residue ○: Very little glue residue △: More than 10% glue residue ×: More than 50% glue residue

Example 1
In a container equipped with a stirrer, a thermometer, and a dropping funnel, 100 parts by mass of butyl acrylate (BA) as component (a1), 1.5 parts by mass of methacrylic acid (MAA) (molecular weight 86.09) as component (a2) And 1 part by weight of hydroxyethyl methacrylate (HEMA) (molecular weight 130.14) as other monomer components, and polyoxyethylene alkyl ether sulfate sodium salt [“Ramtel E-118B”, Kao Corporation as an emulsifier 1.5 parts by mass, allyl alkyl sulfosuccinate ester salt ["Eleminol JS-2", manufactured by Sanyo Chemical Co., Ltd.] 3 parts by mass, 17.4 parts by mass of 0.1 M aqueous potassium hydroxide (based on methacrylic acid) 0.1 times equivalent) and 40 parts by mass of ion-exchanged water, and stirred at room temperature to prepare an emulsion of the unsaturated monomer mixture in advance. Made.
Separately, 28 parts by mass of ion-exchanged water was charged into a reactor equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen introduction tube, and a dropping funnel, nitrogen was sealed, and the internal temperature was raised to 80 ° C. While maintaining, 2 parts by mass of a 10% by mass aqueous ammonium persulfate solution was charged as a polymerization initiator.
Next, the emulsion of the unsaturated monomer mixture prepared in advance was transferred to a dropping funnel and dropped over 4 hours. At the same time, 4 parts by mass of a 5% by mass ammonium persulfate aqueous solution was added dropwise to carry out emulsion polymerization at an internal temperature of 80 ° C.
After completion of dropping, the mixture was aged at 80 ° C. for 4 hours to obtain an acrylic emulsion copolymer having an average particle size of 200 nm. Then, after cooling to room temperature and neutralizing with aqueous ammonia, purified water was added to adjust the solid content to 50 mass% and pH to 8.0.

  Further, a thickener [“ASE-60”, manufactured by Rohm and Haas Japan Co., Ltd.] is added to the acrylic emulsion copolymer, and the viscosity is 10000 mPa · s (BM type viscometer). Was measured under the conditions of # 4 rotor, 12 rotations / minute, 25 ° C.]. Then, 16.0 parts by mass of a tackifier (trade name “Superester E-650” manufactured by Arakawa Chemical Industries, Ltd.) was added to 100 parts by mass of the solid content. Immediately before coating, 1.2 parts by mass of an epoxy crosslinking agent (trade name “Denacol EX-313” manufactured by Nagase ChemteX Corporation) was added to obtain an acrylic emulsion-type pressure-sensitive adhesive composition.

Acrylic emulsion obtained above using a roll knife coater on a release-treated surface of a light release film (trade name “SP-PET3801” manufactured by Lintec Corporation) so that the coating thickness after drying is 25 μm. The mold pressure-sensitive adhesive composition was applied and dried at 90 ° C. for 2 minutes to form a dry film of the pressure-sensitive adhesive composition.
Next, a substrate-less double-sided pressure-sensitive adhesive sheet was obtained by laminating with a heavy release film (trade name “SP-PET3811” manufactured by Lintec Corporation) to give a difference in peeling force.
Remove the release sheet of the baseless double-sided pressure-sensitive adhesive sheet obtained as described above, and stack multiple sheets until the pressure-sensitive adhesive layer has a thickness of 200 μm and store at 23 ° C. for one week of coating and drying Later, the breaking stress and the glass transition point were evaluated. The gel fraction was evaluated by applying and drying the acrylic emulsion-type pressure-sensitive adhesive composition on a light release film, and then drying the pressure-sensitive adhesive composition for 0 days, 3 days, and 7 days at 23 ° C. Was performed after aging.

Further, on the release-treated surface of the release sheet (made by Lintec Corporation, glassine paper released by silicone resin, trade name: SP-8K Ao), the acrylic emulsion-type pressure-sensitive adhesive composition obtained above is rolled knife Using a coater, coating was performed so that the coating thickness after drying was 20 μm, followed by drying at 90 ° C. for 2 minutes to form an adhesive layer. Next, the pressure-sensitive adhesive sheet obtained by bonding the above-obtained pressure-sensitive adhesive layer and polypropylene synthetic paper (trade name “YUPO SGS80” manufactured by YUPO CORPORATION) was wound up to obtain a pressure-sensitive adhesive roll.
The adhesive roll obtained as described above was stored at 23 ° C. for one week, and then evaluated for labeling suitability and contamination of the guide roll. The evaluation of the re-peelability test was carried out by coating and drying the acrylic emulsion-type pressure-sensitive adhesive composition on a release sheet and bonding it to synthetic paper, and then subjecting the pressure-sensitive adhesive composition to 0 ° C, 3 days and 7 days at 23 ° C. And after the aging of the pressure-sensitive adhesive composition.

Example 2
The same procedure as in Example 1 was carried out except that the potassium hydroxide aqueous solution concentration used was 0.2 M (0.2 times equivalent to methacrylic acid), and a baseless double-sided pressure-sensitive adhesive sheet and pressure-sensitive adhesive roll were prepared. Measurements and evaluations were made.

Example 3
The same procedure as in Example 1 was carried out except that the potassium hydroxide aqueous solution concentration used was 0.4 M (0.4 times equivalent to methacrylic acid), and a baseless double-sided pressure-sensitive adhesive sheet and pressure-sensitive adhesive roll were prepared. Measurements and evaluations were made.

Example 4
A substrate-less double-sided pressure-sensitive adhesive sheet and pressure-sensitive adhesive roll were prepared in the same manner as in Example 1 except that the alkali metal hydroxide used was sodium hydroxide (aqueous solution concentration 0.2M, 0.2 times equivalent to methacrylic acid). Then, the same measurement and evaluation were performed.

Example 5
(A1) 100 parts by mass of 2-ethylhexyl acrylate (2EHA) is used instead of BA as the component, and the concentration of the aqueous potassium hydroxide solution used is 0.2 M (0.2 times equivalent to methacrylic acid). Except having done, it carried out similarly to Example 1, produced the base material-less double-sided adhesive sheet and the adhesive roll, and performed the same measurement and evaluation.

Example 6
As component (a1), 50.0 parts by mass of butyl acrylate (BA) and 50.0 parts by mass of 2-ethylhexyl acrylate (2EHA) are used. As component (a2), MAA is acrylic acid (AA). The same procedure as in Example 1 was carried out except that the amount of 0.1M potassium hydroxide used was changed to 20.8 ml (0.1 times equivalent to acrylic acid) instead of 1.5 parts by mass, and no substrate was used. A double-sided pressure-sensitive adhesive sheet and a pressure-sensitive adhesive roll were prepared, and the same measurement and evaluation were performed.

Example 7
(A1) Component is 40.0 parts by mass of butyl acrylate (BA), 40.0 parts by mass of acrylate-2-ethylhexyl (2EHA), 20.0 parts by mass of methyl methacrylate (MMA), and the hydroxylation used. Except that the concentration of the aqueous potassium solution was 0.2M (0.2 times equivalent to methacrylic acid), the same procedure as in Example 1 was performed to prepare a substrate-less double-sided pressure-sensitive adhesive sheet and pressure-sensitive adhesive roll. I did it.

Example 8
The component (a1) is 100 parts by mass of butyl acrylate (BA), the component (a2) is 4.0 parts of methacrylic acid (MAA), and the concentration of aqueous potassium hydroxide used is 0.27 M (0 with respect to methacrylic acid). .1 times equivalent) except that the substrateless double-sided PSA sheet and PSA roll were prepared and subjected to the same measurements and evaluations.

Example 9
The component (a1) is 100 parts by mass of butyl acrylate (BA), the component (a2) is 8.0 parts of methacrylic acid (MAA), and the concentration of the aqueous potassium hydroxide solution used is 0.53M (0 with respect to methacrylic acid). .1 times equivalent) except that the substrateless double-sided PSA sheet and PSA roll were prepared and subjected to the same measurements and evaluations.

Example 10
Except not adding the tackifier, it carried out similarly to Example 1, the base-material-free double-sided adhesive sheet and the adhesive roll were produced, and the same measurement and evaluation were performed.

Example 11
The same procedure as in Example 1 was carried out except that the carbodiimide-based crosslinking agent (trade name “Carbodilite V-02”, manufactured by Nisshinbo Industries, Ltd.) was used as the crosslinking agent used, and the substrateless double-sided pressure-sensitive adhesive sheet and An adhesive roll was prepared, and the same measurement and evaluation were performed.

Example 12
The cross-linking agent used was the same as in Example 1 except that the oxazoline-based cross-linking agent (Nippon Shokubai Co., Ltd., trade name “Epocross WS-500”) was changed to 4.9 parts by mass. An adhesive roll was prepared, and the same measurement and evaluation were performed.

Example 13
The emulsifier used was polyoxyethylene alkyl ether sulfate sodium salt (product of Kao Corporation, product name: Ramter E-118B) 2.0 parts by mass, polyoxyethylene alkyl allyl ether sulfate ester salt (Daiichi Kogyo Seiyaku Co., Ltd.). , Trade name: Aqualon KH-05) 0.5 parts by mass, polyoxyethylene alkyl ether (product name: Emulgen 103) 0.5 parts by mass A material-less double-sided pressure-sensitive adhesive sheet and a pressure-sensitive adhesive roll were prepared, and the same measurement and evaluation were performed.

Example 14
The same as in Example 1 except that 0.5 parts by mass of propylene glycol fatty acid ester (manufactured by Riken Vitamin Co., Ltd., product name: Riquemar PL-100) was added as a plasticizer to the mixture of unsaturated monomers prepared in advance. The substrate-less double-sided pressure-sensitive adhesive sheet and the pressure-sensitive adhesive roll were prepared, and the same measurement and evaluation were performed.

Comparative Example 1
Except that potassium hydroxide was not added during the polymerization, the same procedure as in Example 1 was performed to prepare a baseless double-sided PSA sheet and PSA roll, and the same measurement and evaluation were performed.

Comparative Example 2
The same procedure as in Example 1 was conducted except that potassium hydroxide was not added during the polymerization and the component (a1) was changed to 100.0 parts by mass of 2-ethylhexyl acrylate (2EHA). Rolls were produced and subjected to the same measurement and evaluation.

Comparative Example 3
Potassium hydroxide was not added during the polymerization, the component (a1) was 50.0 parts by mass of butyl acrylate (BA), the acrylate-2-ethylhexyl (2EHA) was 50.0 parts by mass, and the component (a2) was methacrylic acid. (AA) Except for 1.5 parts, the same procedure as in Example 1 was carried out to prepare a substrate-less double-sided PSA sheet and PSA roll, and the same measurement and evaluation were performed.

Comparative Example 4
The same procedure as in Example 1 was conducted except that potassium hydroxide was not added during the polymerization, and the component (a1) was changed to 75.0 parts by mass of butyl acrylate (BA) and 25.0 parts by mass of methyl methacrylate (MMA). A base material-less double-sided pressure-sensitive adhesive sheet and a pressure-sensitive adhesive roll were prepared, and the same measurement and evaluation were performed.

Comparative Example 5
Except that the crosslinking agent was not added, the same procedure as in Example 1 was carried out to prepare a substrate-less double-sided PSA sheet and PSA roll, and the same measurements and evaluations were performed.

Comparative Example 6
Without adding potassium hydroxide aqueous solution during the polymerization, 17.4 parts by weight of 0.1M potassium hydroxide aqueous solution (0.1 times equivalent to methacrylic acid) is used together when neutralizing with aqueous ammonia after polymerization. Except having done, it carried out similarly to Example 1, produced the base material-less double-sided adhesive sheet and the adhesive roll, and performed the same measurement and evaluation.

  From Table 1 and Table 2, the adhesive sheet of Examples 1-14 can shorten an aging period compared with Comparative Examples 1-6, is excellent in the mechanical strength of the dry film of an adhesive composition, and labeling suitability, Adhesive does not remain on the release sheet side during labeling, can prevent contamination of the guide roll, and does not cause adhesive residue on the adherend even after a certain period of time at high temperature after labeling. It turns out that it can peel easily.

  The pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the acrylic emulsion-type pressure-sensitive adhesive composition of the present invention can shorten the aging period, and is particularly useful in fields requiring re-peelability in labeling.

Claims (10)

(A) an acrylic emulsion copolymer obtained by emulsion polymerization of a monomer mixture containing (a1) (meth) acrylic acid alkyl ester and (a2) a carboxyl group-containing unsaturated monomer, and (B) An acrylic emulsion-type pressure-sensitive adhesive composition containing a crosslinking agent that is at least one selected from an epoxy compound, a carbodiimide compound, and an oxazoline compound, and before emulsion polymerization of the monomer mixture and / or emulsion polymerization An acrylic emulsion-type pressure-sensitive adhesive composition containing (C) an alkali metal hydroxide and / or an alkaline earth metal hydroxide therein.   (C) Alkali metal hydroxide and / or alkaline earth metal hydroxide is contained 0.001-0.5 times equivalent to the carboxyl group in (A) acrylic emulsion-type copolymer. 2. An acrylic emulsion-type pressure-sensitive adhesive composition according to 1.   (C) The acrylic emulsion according to claim 1 or 2, wherein the alkali metal hydroxide and / or alkaline earth metal hydroxide is at least one selected from potassium hydroxide, sodium hydroxide and lithium hydroxide. Type pressure-sensitive adhesive composition.   (A) The acrylic emulsion type copolymer contains 0.1 to 10.0% by mass of a structural unit derived from (a2) a carboxyl group-containing unsaturated monomer. Acrylic emulsion-type pressure-sensitive adhesive composition. The acrylic emulsion-type pressure-sensitive adhesive composition according to any one of claims 1 to 4 , wherein the gel fraction of the dry film of the acrylic emulsion-type pressure-sensitive adhesive composition is 30% or more. The acrylic emulsion-type pressure-sensitive adhesive composition according to any one of claims 1 to 5 , wherein the dry film of the acrylic emulsion-type pressure-sensitive adhesive composition has a tensile stress at break of 0.5 MPa or more. The acrylic emulsion-type pressure-sensitive adhesive composition according to any one of claims 1 to 6 , wherein the dry film of the acrylic emulsion-type pressure-sensitive adhesive composition has a Tg of -70 ° C or higher and -25 ° C or lower. Pressure-sensitive adhesive sheet having on at least one surface of the substrate sheet, a pressure-sensitive adhesive layer formed is formed by using an acrylic emulsion type pressure-sensitive adhesive composition according to any one of claims 1-7. (A) an acrylic emulsion type copolymer and (B) an epoxy compound, acrylic according to any one of claims 1 to 7 including a cross-linking agent is at least one selected from a carbodiimide compound and an oxazoline compound A method for producing an emulsion-type pressure-sensitive adhesive composition comprising: (a1) a monomer mixture containing (meth) acrylic acid alkyl ester and (a2) a carboxyl group-containing unsaturated monomer; (C) an alkali metal hydroxide And / or emulsion polymerization in the presence of an alkaline earth metal hydroxide to obtain (A) an acrylic emulsion-type copolymer, and a method for producing an acrylic emulsion-type pressure-sensitive adhesive composition. The production of an acrylic emulsion-type pressure-sensitive adhesive composition according to claim 9 , wherein the acrylic emulsion-type pressure-sensitive adhesive composition is aged so that the gel fraction of the dry film of the acrylic emulsion-type pressure-sensitive adhesive composition is 30% or more. Method.