JP4748347B2 - Aqueous pressure-sensitive adhesive composition, method for producing the same, and pressure-sensitive adhesive product - Google Patents

Description

  The present invention relates to an aqueous pressure-sensitive adhesive composition that provides an aqueous pressure-sensitive adhesive having excellent adhesion and holding power, and a method for producing a water-dispersed pressure-sensitive adhesive composition that can be obtained with high productivity.

  In recent years, the shift from solvent-based resins to water-based resins has progressed in view of environmental problems, but 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 pressure-sensitive adhesive is an acrylic emulsion-type water-based pressure-sensitive adhesive obtained by polymerizing various ethylenically unsaturated monomers.

  Such an aqueous pressure-sensitive adhesive is generally obtained by emulsion polymerization. Emulsion polymerization carried out in an aqueous medium does not require an organic solvent, and therefore has no fire hazard or pollution problem, and is used for the production of various polymers. In the production of an acrylic polymer by emulsion polymerization, there are a method in which monomer components are charged all at once and emulsion polymerization is carried out, and a method in which monomer components are added dropwise to the polymerization system little by little to carry out emulsion polymerization.

  When an acrylic polymer obtained by emulsion polymerization by these methods is used as a pressure-sensitive adhesive, the cohesive force is often insufficient. If the cohesive force is insufficient, the resistance to the shearing force applied to the adhesive layer (displacement resistance) is insufficient, that is, the holding force is insufficient. Therefore, when such an acrylic polymer is used as a pressure-sensitive adhesive, as one means for improving the cohesive force, the polymer is crosslinked to increase the molecular weight, thereby improving the cohesive force of the pressure-sensitive adhesive layer and improving the holding power. There is a means. As the method, there is a method of adding a crosslinking agent to improve the holding power, and as the crosslinking agent, a melamine compound, an epoxy compound, a hydrazine compound, an oxazoline compound, a metal salt, or the like is used. However, when the polymer is cross-linked using a cross-linking agent or the like to increase the molecular weight and improve the holding power, there is a drawback that the adhesive strength to the adherend is reduced. Conversely, if the degree of cross-linking of the polymer is adjusted in order to prevent a decrease in adhesive strength, sufficient holding power cannot be obtained. That is, if one performance is improved, the performance of the other is lowered, and it is difficult to obtain a pressure-sensitive adhesive having both excellent adhesive strength and holding power.

  Therefore, reduce the low molecular weight component in the water-dispersed acrylic polymer as much as possible, improve the adhesion failure to the adherend due to the low molecular weight component at the time of adhesion for a long time, and when peeling again after adhering to the adherend In order to improve the contamination of the adherend, the relationship of log M> 3 log S-2 is satisfied, where S is the soluble fraction (%) in tetrahydrofuran and M is the weight average molecular weight (10,000) of the soluble portion. An aqueous pressure-sensitive adhesive composition is disclosed. (For example, refer to Patent Document 1.) However, a pressure-sensitive adhesive having such characteristics does not exhibit sufficient adhesive force.

  Adhesive strength and cohesive strength can be achieved by combining the means for emulsion polymerization of acrylic monomers with specific polymerization initiators and the means for emulsion polymerization while dropping emulsions of acrylic monomers. A method for producing an aqueous pressure-sensitive adhesive composition that can easily satisfy both of the above has been disclosed. (For example, refer to Patent Document 2) However, the pressure-sensitive adhesive obtained by this method has not yet solved the problem of achieving both sufficient adhesive force and holding force.

JP-A-7-228612 (page 2-4) JP 2002-60713 (page 2-4)

  Accordingly, an object of the present invention is to provide an acrylic water-based pressure-sensitive adhesive composition that is excellent in both adhesive force and holding power and a method for producing the same.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have obtained water obtained by emulsion polymerization of a polymerizable monomer obtained by adding (Va) acid vinyl ester (B) to (meth) acrylates. The present invention was completed by finding that the dispersion-type pressure-sensitive adhesive has excellent adhesion and holding power.

  In the present invention, as a production method for obtaining an aqueous pressure-sensitive adhesive composition having excellent adhesion and holding power, a polymerizable monomer (A) mainly composed of (meth) acrylates and vinyl versatate A production method in which a polymerizable monomer containing an ester (B) is charged all at once into a closed pressure reaction vessel in which an aqueous medium is present and emulsion polymerization is performed. In particular, the polymerization conversion rate of the monomer component is 95%. It has also been found that a method for producing an aqueous pressure-sensitive adhesive composition characterized in that the time required to reach is substantially within 180 minutes.

That is, the present invention relates to a polymerizable monomer (A) containing (meth) acrylates and versatic in an aqueous medium in which acrylic polymer particles [X] having an average particle diameter of 10 to 300 nm are dispersed. A water-dispersed pressure-sensitive adhesive composition containing a water-dispersed acrylic polymer obtained by emulsion polymerization by charging polymerizable monomers containing an acid vinyl ester (B) , the (meth) acrylate The ratio of the polymerizable monomer component of the polymerizable monomer (A) having a main component to the vinyl acetate (B) is 99/1 to 70/30 (weight ratio), and Water dispersion characterized in that the weight ratio of the acrylic polymer particles [X] and the polymerizable monomer (A) containing the (meth) acrylates is in the range of 5/95 to 40/60. A mold pressure-sensitive adhesive composition is provided.

The present invention also relates to polymerizable monomers containing a polymerizable monomer (A) containing (meth) acrylates and a vinyl versatate (B) having an average particle size of 10 to 300 nm. The acrylic polymer particles [X], which is an aqueous medium in which the acrylic polymer particles [X] are dispersed, are charged all at once and emulsified by controlling the pressure in the closed pressure reaction vessel at the start of the reaction to normal pressure or higher. A method for producing a water-dispersed pressure-sensitive adhesive composition, characterized in that the polymerizable monomer (A) comprising the (meth) acrylates as a main component and a vinyl versatate (B) The ratio of the polymerizable monomer component is 99/1 to 70/30 (weight ratio), and the polymerizable monomer contains the acrylic polymer particles [X] and the (meth) acrylates. The weight ratio with (A) is 5 / 95-40 It provides a method for producing water-dispersed PSA composition, which is a range of 60.

  The present invention provides an aqueous pressure-sensitive adhesive composition excellent in both adhesion and holding power. In addition, a method for producing the aqueous pressure-sensitive adhesive composition with high production efficiency and more safely can be provided. Furthermore, the pressure-sensitive adhesive product of the present invention is excellent in adhesive strength and holding power, and is suitable as a pressure-sensitive adhesive label, pressure-sensitive adhesive tape, special pressure-sensitive adhesive sheet, and the like.

First, the aqueous pressure-sensitive adhesive composition of the present invention will be described.
The water-dispersed acrylic polymer used in the present invention is a polymerizable monomer having a polymerizable monomer (A) mainly composed of (meth) acrylates and a vinyl versatate (B) as essential components. Is obtained by emulsion polymerization. The ratio of the polymerizable monomer component of the (meth) acrylic acid alkyl ester (A) and the versatic acid vinyl ester (B) is preferably 99/1 to 70/30, more preferably (A ) / (B) = 95/5 to 85/15, a pressure-sensitive adhesive having excellent adhesion and holding power can be obtained. That is, when (A) / (B) = 95/5 or more, the cohesive force is remarkably improved and the holding force is greatly improved, and (A) / (B) = 85. In the case of / 15 or less, the cohesive force does not become too high as compared with it, and the adhesive force is large and preferable.

  As the polymerizable monomer (A) component mainly composed of (meth) acrylates used in the present invention, alkyl (meth) acrylate (a) having an alkyl group having 4 to 12 carbon atoms and carboxyl And an ethylenically unsaturated monomer (b) having a group. Moreover, the ethylenically unsaturated monomer (c) other than the above (a) and (b) can be copolymerized as necessary.

  Examples of the alkyl (meth) acrylate (a) having an alkyl group having 4 to 12 carbon atoms include n-butyl (meth) acrylate, i-butyl (meth) acrylate, n-hexyl (meth) acrylate, n -Octyl (meth) acrylate, i-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, i-nonyl (meth) acrylate, n-decyl (meth) acrylate, n-lauryl A (meth) acrylate etc. can be mentioned and these 1 type, or 2 or more types of mixtures can be used. Among these, an alkyl (meth) acrylate having an alkyl group having 4 to 9 carbon atoms is preferable because of good polymerizability. The amount of the alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms is preferably in an amount in the range of 45 to 99.5% by weight.

  The ethylenically unsaturated monomer (b) having a carboxyl group is not particularly limited as long as it has a carboxyl group and an ethylenically unsaturated group in the molecule. Examples of 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, it is particularly preferable to use acrylic acid or methacrylic acid in terms of excellent stability during polymerization of the monomer component and excellent adhesive properties. The amount of the ethylenically unsaturated monomer having a carboxyl group is preferably an amount in the range of 0.5 to 10% by weight.

  Examples of the ethylenically unsaturated monomer (c) other than (a) and (b) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, t-butyl (meth) acrylate, stearyl (meth) acrylate, phenyl (Meth) acrylates such as (meth) acrylate and benzyl (meth) acrylate; 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3-pentafluoropropyl (meth) acrylate, Fluorine-containing ethylenically unsaturated monomers such as perfluorocyclohexyl (meth) acrylate, 2,2,3,3-tetrafluoropropyl (meth) acrylate, β- (perfluorooctyl) ethyl (meth) acrylate; acetic acid Vinyl esters such as vinyl, vinyl propionate and vinyl butyrate; methyl Vinyl ethers such as nyl 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 toluene, vinyl anisole , Α-halostyrene, vinyl naphthalene, vinyl compounds having an aromatic ring such as divinylstyrene; isoprene, chloroprene, butadiene, ethylene, tetrafluoroethylene, vinylidene fluoride, N-vinylpyrrolidone and the like. Among these, it is preferable to use (meth) acrylic acid esters in terms of excellent stability during polymerization of the monomer component.

  As the ethylenically unsaturated monomer (c), an ethylenically unsaturated monomer containing a crosslinkable reactive group other than a carbonyl group or a carboxyl group is used for the purpose of improving the holding power of the aqueous pressure-sensitive adhesive. Specifically, for example, glycidyl group-containing polymerizable monomers such as glycidyl (meth) acrylate and allyl glycidyl ether; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, Hydroxyl group-containing polymerizable monomers such as polyethylene glycol mono (meth) acrylate and glycerol mono (meth) acrylate; aminoethyl (meth) acrylate, N-monoalkylaminoalkyl (meth) acrylate, N, N-dialkylaminoalkyl ( Amino group-containing polymerizable monomers such as (meth) acrylate; N A methylolamide group such as methylol (meth) acrylamide, N-isopropoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-isobutoxymethyl (meth) acrylamide, or an alkoxylated-containing polymerizable monomer thereof; Vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropyltriethoxysilane, γ- ( (Meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxypropyltriisopropoxysilane, N-β- (N-vinylbenzylaminoethyl)- silyl group-containing polymerizable monomers such as γ-aminopropyltrimethoxysilane and its hydrochloride; aziridinyl group-containing polymerizable monomers such as 2-aziridinylethyl (meth) acrylate; (meth) acryloyl isocyanate, Isocyanate groups 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 Oxazoline group-containing polymerizable monomers such as (meth) acrylamide, N-monoalkyl (meth) acrylamide, and amide group-containing polymerizable monomers such as N, N-dialkyl (meth) acrylamide; dicyclopentenyl (meta ) Cyclopentenyl group-containing polymerizable monomers such as acrylate Body; allyl group-containing polymerizable monomers such as allyl (meth) acrylate; carbonyl group-containing polymerizable monomers such as acrolein and diacetone (meth) acrylamide; acetoacetyl group-containing polymerization such as acetoacetoxyethyl (meth) acrylate And other monomers.

  In addition, as the ethylenically unsaturated monomer (c), for the purpose of improving the stability during emulsion polymerization and the storage stability of the water-dispersed acrylic polymer, a sulfonic acid group and / or as required. Monomers containing sulfate groups (and / or salts thereof), phosphate groups and / or phosphate ester groups (and / or salts thereof) can be used, such as vinyl sulfonic acid, styrene sulfonic acid, etc. Vinylsulfonic acids or salts thereof, allyl group-containing sulfonic acids such as allylsulfonic acid and 2-methylallylsulfonic acid or salts thereof, (meth) acrylic acid 2-sulfoethyl, (meth) acrylic acid 2-sulfopropyl, etc. ) Acrylate group-containing sulfonic acids or salts thereof, (meth) acrylamide such as (meth) acrylamide-t-butylsulfonic acid Containing sulfonic acids or salts thereof. As a commercial item of the ethylenically unsaturated monomer which has a phosphoric acid group, "Adekalia soap PP-70, PPE-710" [Asahi Denka Kogyo Co., Ltd. product] etc. are mentioned.

  Examples of the versatic acid vinyl ester (B) include Veova 9, Veova 10 and Veova 11 (all manufactured by Japan Epoxy Resin Co., Ltd.).

  Next, the method for producing the aqueous pressure-sensitive adhesive composition of the present invention will be described. In general, the production method for obtaining a water-dispersed acrylic polymer by emulsion polymerization is as follows: (1) Polymerization by mixing water, an ethylenically unsaturated monomer, a polymerization initiator, and if necessary, an emulsifier and a dispersion stabilizer. And (2) 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. Among these, the aqueous pressure-sensitive adhesive of the present invention can be produced by a method in which (1) water, an ethylenically unsaturated monomer, a polymerization initiator, and if necessary, an emulsifier and a dispersion stabilizer are mixed and polymerized. Since an agent is easy to obtain, it is preferable.

  As a method for polymerizing by mixing water, an ethylenically unsaturated monomer, a polymerization initiator and, if necessary, an emulsifier and a dispersion stabilizer as described above, for example, as a water-soluble radical polymerization initiator, 2, 2- Using a low decomposition temperature such as azobis [2- (2-imidazolin-2-yl) propane], which is used at 0.001 to 0.05% by weight with respect to 100% by weight of the monomer component, In addition, there is a method for producing an aqueous pressure-sensitive adhesive composition, wherein emulsion polymerization is carried out by setting the polymerization temperature to substantially 20 to 60 ° C. This method requires a long reaction time to control the polymerization exotherm.

  In addition, as in the above production method, the monomer component containing (meth) acrylate as a main component is collectively charged into a closed pressure reaction vessel in which an aqueous medium is present and emulsion polymerization is performed. There is also a method for producing an aqueous pressure-sensitive adhesive composition characterized in that the time required for the polymerization conversion to reach 95% is substantially within 180 minutes. Compared with the method for controlling the exothermic polymerization in the previous period, the production method of the present invention is preferable because it is remarkably superior in terms of production efficiency.

  Specifically, the aqueous pressure-sensitive adhesive composition of the present invention comprises the polymerizable monomer (A) mainly composed of the above-mentioned (meth) acrylates and a versatic acid vinyl ester (B) as essential components. The polymerizable monomer is obtained by batch charging into a closed pressure reaction vessel in which an aqueous medium is present and emulsion polymerization. Furthermore, in this production method, it is preferable to set the reaction conditions so that the time required for the polymerization conversion rate of the monomer component to reach 95% is substantially within 180 minutes. Examples of means for setting the reaction conditions so as to be within 180 minutes include adjusting the monomer components and the temperature at the start of polymerization. The time required for the polymerization conversion rate of the monomer component to be 95% or more is particularly preferably 10 to 120 minutes from the viewpoint of safety and productivity.

  The polymerization conversion rate of the monomer component in the present invention is the total charge of the monomer component (that is, the weight when all the monomers are converted into a polymer) and the solid content weight in the water-dispersed acrylic polymer. It is a value obtained by calculation from

  Polymerization conversion rate (%) = 100 × (solid content concentration of water-dispersed acrylic polymer: measured value (%) − solid content concentration of raw materials other than monomer components: calculated value (%)) / (monomer Concentration of ingredients for all raw materials: Calculated value (%))

The time required for the polymerization conversion rate of the monomer component to reach 95% refers to the contents in the reaction vessel in order starting from the time when the polymerization exotherm is observed after adding the polymerization initiator to the reaction vessel. The polymerization conversion rate is obtained from the above-mentioned formula by sampling the product, and indicates the time required for the polymerization conversion rate to reach 95%.
The purpose of the present invention is to efficiently produce a water-dispersed acrylic polymer, and therefore the time required for the polymerization conversion rate of the monomer component to reach 95% is preferably within 180 minutes. .

Here, the water-based pressure-sensitive adhesive composition of the present invention includes isoprene, chloroprene, butadiene, ethylene, tetrafluoroethylene, vinylidene fluoride, N as ethylenically unsaturated monomers (c) other than (a) and (b). As described above, vinylpyrrolidone and the like can be used. However, in the case of using the production method of the present invention, it is necessary to consider that when a monomer other than these (meth) acrylates is used in combination, the polymerization rate during emulsion polymerization is not significantly reduced. That is, in the production method for obtaining the aqueous pressure-sensitive adhesive of the present invention, when the monomer component mainly composed of (meth) acrylate is emulsion-polymerized, the polymerization conversion rate of the monomer component reaches 95%. The time required for this is substantially within 180 minutes, and in order to increase productivity, it is preferable to use a combination of highly reactive monomer components.

  Next, the sealed pressure reaction vessel used in the present invention refers to a pressure-resistant sealed reaction vessel such as an autoclave, and is preferably provided with a stirrer, a pressure increasing / decreasing device, and an inert gas inlet. Furthermore, when the material of the inner surface of the closed pressure reaction vessel is made of glass lining, the amount of aggregates generated during the emulsion polymerization of the monomer component is reduced, or the aggregates are difficult to adhere in the container. Or, even when aggregates adhere to the container, it is easy to remove the aggregates, the maintenance in the container is easy, and the productivity when water-dispersed acrylic polymer is continuously produced in the same sealed pressure reaction container (Time required for maintenance can be shortened) is preferable.

  In the present invention, the aqueous medium for emulsion polymerization of the monomer component is not particularly limited, but only water may be used, or a mixed solution of water and a water-soluble solvent may be used. May be. Examples of the water-soluble solvent used here include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl carbitol, ethyl cellosolve, and butyl cellosolve, and polar solvents such as N-methylpyrrolidone. A mixture of two or more can be used.

  The amount of the water-soluble solvent used in the case of using a mixture of water and the water-soluble solvent can be arbitrarily selected from the viewpoint of stability during polymerization, but there is a risk of ignition of the resulting polymer aqueous dispersion. From the viewpoints of safety and health and safety, it is preferable to reduce the amount of water-soluble solvent as much as possible. For these reasons, it is particularly preferable to use water alone.

  Further, in the method for producing a water-dispersed pressure-sensitive adhesive composition of the present invention, when an aqueous medium in which polymer particles [X] having an average particle diameter of 10 to 300 nm are dispersed is used as an aqueous medium, it occurs during emulsion polymerization. This is preferable because the amount of aggregates to be reduced can be suppressed to a very low level, and the particle diameter of the obtained water-dispersed acrylic polymer can be easily controlled within a practical range (50 to 1000 nm). Since water-dispersed acrylic polymers generally increase in viscosity when the particle size decreases, when obtaining a water-dispersed acrylic polymer with a high solid content concentration, the particle size should be controlled to a certain size. is required.

  Here, the solid content concentration of the water-dispersed pressure-sensitive adhesive composition of the present invention is not particularly limited, but the workability and transportation cost during production and the aqueous pressure-sensitive adhesive composition are used after being dried. From the point of being excellent in drying property when performing, it is preferable that the solid content concentration is 40 to 70% by weight.

  The type of the polymer particles [X] is not particularly limited. For example, a polymer (hereinafter referred to as a polymer obtained by radical polymerization of an ethylenically unsaturated monomer such as an acrylic polymer or a butadiene polymer). , An ethylenic polymer), a polyurethane resin and a polyester resin containing a polymer having a urea bond and a urethane bond. In addition, a mixture of these various polymers, for example, an acrylic polymer / polyurethane resin mixture, a grafted (blocked) product of various polymers, for example, an unsaturated polyester polymer or an alkyd resin, Examples include grafted products. In particular, the polymer particle [X] is preferably an ethylenic polymer from the viewpoint that the adjustment of the particle diameter and the polymer design are easy and the polymer particle [X] can be easily produced by the method described later. In particular, when the polymer particle [X] is an acrylic polymer obtained by emulsion polymerization of a monomer component mainly composed of (meth) acrylate in an aqueous medium, emulsification is performed in the presence thereof. Water-dispersed acrylic system that is compatible with the monomer component that contains (meth) acrylate as the main component and that is compatible with the polymer that is produced by the polymerization of the monomer component, and has good dispersion stability This is preferable because a polymer is easily obtained.

  The production method of polymer particles [X], which is an acrylic polymer, is as follows: (1) Raw materials such as water, monomer components, polymerization initiator, and (if necessary, emulsifier and dispersion stabilizer) are charged together. It can be produced by a polymerization method, (2) a so-called pre-emulsion method in which water, a monomer component and an emulsifier are mixed in advance, or (3) a monomer dropping method. Among these, the method of batch charging and polymerizing the raw materials of (1) is particularly preferable because the polymer particles [X] can be efficiently produced in a short time.

Moreover, what was illustrated as the above-mentioned monomer component can be used as (meth) acrylate and other monomers used in the case of superposition | polymerization.

  Furthermore, when producing polymer particles [X] composed of acrylic polymers, emulsifiers and other dispersion stabilizers may be used, and polymerization initiators and chain transfer agents may be used. it can. As these specific examples, those similar to those used at the time of emulsion polymerization of the monomer components described later can be used.

  The ratio of the polymerizable monomer component containing the polymer particle [X] and the (meth) acrylate is not particularly limited, but the polymer particle [X] (weight of solids) is not limited. ) / Monomer component = in the range of 5/95 to 40/60, maintains high productivity during emulsion polymerization of the monomer component, and suppresses the amount of aggregates to stably disperse in water Type acrylic polymer is preferable because it can be produced.

  Next, in the present invention, when the monomer component is emulsion-polymerized in an aqueous medium, it can be polymerized using an emulsifier or other dispersion stabilizer. Further, as described above, when the monomer component is emulsion polymerized in the presence of the polymer particles [X], it is possible to stably emulsion polymerize without using an emulsifier and other dispersion stabilizers. In addition, when the obtained water-dispersed acrylic polymer is formed into a film, it is preferable because various physical properties such as water resistance of the film are improved.

  Here, as an emulsifier that can be used in the present invention, known anionic emulsifiers, nonionic emulsifiers, and cationic emulsifiers can be used. Examples of the anionic emulsifier used in the present invention include sulfates of higher alcohols and salts thereof, alkylbenzene sulfonates, polyoxyethylene alkylphenyl sulfonates, polyoxyethylene alkyl diphenyl ether sulfonates, alkyl diphenyl ether disulfonic acids. And nonionic emulsifiers include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene diphenyl ether, polyoxyethylene-polyoxypropylene block copolymer Etc., and one or a mixture of two or more of these can be used.

  Furthermore, an emulsifier having a polymerizable unsaturated group in the molecule generally called “reactive emulsifier” can also be used. As reactive emulsifiers that can be used in the present invention, for example, “Latemul S-180” (manufactured by Kao Corporation) having a sulfonic acid group and a salt thereof, “Eleminol JS-2, RS-30” (Sanyo Chemical Industries ( "Aqualon HS-10, HS-20, KH-05, KH-10" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), "Adekaria soap SE-10, SE-20, SR-10N, SR-20N "(Asahi Denka Kogyo Co., Ltd.), etc .;" New Frontier A-229E "having a phosphate group (Daiichi Kogyo Seiyaku Co., Ltd.), etc .; nonionic “AQUALON RN-10, RN-20, RN-30, RN-50, ER-10, ER-20, ER-30, ER-40” (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) etc. having a hydrophilic group One or a mixture of two or more of these can be used.

  Other dispersion stabilizers other than the emulsifier that can be used in the present invention include, for example, polyvinyl alcohol, fiber ether, starch, maleated polybutadiene, maleated alkyd resin, polyacrylic acid (salt), polyacrylamide. Synthetic or natural water-soluble polymer substances such as water-based acrylic resins, water-based polyester resins, water-based polyamide resins, and water-based polyurethane resins can be used, and one or a mixture of two or more of these can be used.

  In the present invention, the monomer component is emulsion-polymerized using a sealed pressure reaction vessel. At that time, the emulsion polymerization is performed under the condition that the dissolved oxygen concentration in the liquid in the sealed pressure reaction vessel is 3 ppm or less. Inhibition of radical polymerization by oxygen can be avoided, and emulsion polymerization can proceed smoothly to produce a water-dispersed acrylic polymer efficiently. As a method for reducing the dissolved oxygen concentration in the liquid in the sealed reaction vessel, the aqueous medium, the monomer component, and the polymerization initiator are each reduced in a separate vessel, and then these are mixed together. , An aqueous medium, a monomer component, and a polymerization initiator are charged into a sealed pressure reaction vessel, and then a method of reducing dissolved oxygen is mentioned. A method can be appropriately selected according to the apparatus to be used. Also in this method, it is preferable that the dissolved oxygen concentration in the liquid in the closed pressure reaction vessel at the start of emulsion polymerization is 3 ppm or less. Specifically, the dissolved oxygen concentration in the liquid (a mixture of an aqueous medium or, in some cases, an aqueous medium containing polymer particles [A] or an emulsifier, a monomer component, and a polymerization initiator) is reduced. Specifically, (1) while stirring in the container, an inert gas is continuously blown or bubbled from one mouth of the container, and an inert gas and oxygen are blown out from the other mouth. (2) A method of lowering the dissolved oxygen concentration by boiling the liquid in the vessel once and then cooling it under an inert gas atmosphere. Examples of the method include reducing the dissolved oxygen concentration by lowering the partial pressure of oxygen in the container by lowering the pressure in the container after the inside of the container is stirred and pressurized with an inert gas. Among these, in order to reduce the dissolved oxygen in the liquid in the container, (3) the method of repeating the operation of lowering the pressure in the container after pressurizing and filling with an inert gas is efficient. Since dissolved oxygen can be reduced, it is preferable. The step of lowering the pressure in the container after pressurizing and filling with the inert gas is preferably repeated 2 to 10 times. The greater the number of repetitions of this step, the lower the dissolved oxygen concentration. Since the oxygen concentration is difficult to decrease, the efficiency is deteriorated.

  When the inert gas is pressure-filled into the sealed pressure reaction vessel, for example, the pressure is filled at 0.1 to 2.0 MPa, preferably 0.2 to 1.5 MPa. When the pressure is lower than this range, the number of repetitions may be increased to make the dissolved oxygen concentration 3 ppm or less, or it may not be possible to make it 3 ppm or less. Moreover, when lowering the pressure in the reaction vessel, for example, the pressure is reduced to -0.04 to -0.09 MPa. If the degree of vacuum is lower than this range, the number of repetitions may be increased to make the dissolved oxygen concentration 3 ppm or less, or the existing oxygen concentration may not be made 3 ppm or less. Furthermore, the pressure in the reaction vessel at the time of emulsion polymerization of the monomer component can be carried out by normal pressure or pressurization with an inert gas depending on the reaction temperature at the time of emulsion polymerization described later. . The pressure here does not mean an absolute pressure but a differential pressure obtained by setting the normal pressure to 0 MPa. Moreover, as inert gas, noble gases, such as nitrogen gas, helium, and argon, can be mentioned, You may use these 1 type or in mixture of 2 or more types. As the type of inert gas, nitrogen gas is particularly preferable from the viewpoints of economy and versatility. The purity of the inert gas is usually 95% or more, preferably 98% or more.

  In the present invention, since the monomer component is subjected to emulsion polymerization in a closed pressure reaction vessel, the temperature in the vessel at the time of emulsion polymerization is not particularly limited. For example, it is safe even under conditions that exceed the boiling point of water as a medium. It is possible to emulsion polymerize. In the case of a reaction vessel attached to a condenser, which is used when producing an ordinary acrylic polymer by emulsion polymerization, if the reaction vessel boils, the content may blow out from the reaction vessel, or the reaction vessel will boil. However, since a closed pressure reaction vessel is used in the present invention, these problems can be avoided. In particular, when emulsion polymerization is performed at a high temperature (a temperature higher than the boiling point of the mixture of the aqueous medium and the monomer component), if the reaction vessel is pressurized with an inert gas, boiling in the reaction vessel can be suppressed. From the viewpoint that the generation of aggregates can be prevented. The pressure when pressurizing with an inert gas to suppress boiling in the reaction vessel is the liquid in the reaction vessel at the highest temperature reached within the reaction vessel during emulsion polymerization (mixture of aqueous medium and monomer components). It is preferable to set the pressure to be equal to or higher than the vapor pressure, and if the pressure equal to or higher than the vapor pressure is maintained, boiling in the reaction vessel can be completely suppressed.

  In the present invention, as described above, the polymerization temperature at the time of emulsion polymerization is not limited, but it is preferable to start the emulsion polymerization from a low temperature, particularly when it is desired to increase the molecular weight of the resulting water-dispersed acrylic polymer. . Specifically, when emulsion polymerization is started from a temperature within the range of 10 to 50 ° C., a high molecular weight polymer is easily obtained. When the polymerization start temperature is lower than this range, it is difficult for the polymerization to proceed smoothly. On the other hand, when the polymerization start temperature is higher than this range, it may be difficult to obtain a high molecular weight polymer.

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

  In the emulsion polymerization of the monomer component, it can be obtained by radical polymerization using only these peroxides, or by a redox polymerization initiator in which a reducing agent is used in combination with the above peroxides.

  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 polymerization initiators, in particular, a redox polymerization initiator using a combination of persulfates and / or organic peroxides and a reducing agent can smoothly promote emulsion polymerization even at a low temperature. Thus, when it is desired to obtain a high molecular weight water-dispersed acrylic polymer, it is preferable because emulsion polymerization can be started from a temperature within the range of 10 to 50 ° C.

  Specific examples of persulfates include potassium persulfate, sodium persulfate, and ammonium persulfate. Specific examples of organic peroxides include benzoyl peroxide, lauroyl peroxide, and decanoyl peroxide. Diacyl peroxides such as oxide, dialkyl peroxides such as t-butylcumyl peroxide and dicumyl peroxide, peroxyesters such as t-butylperoxylaurate and t-butylperoxybenzoate, cumene hydroper Examples thereof include hydroperoxides such as oxide, 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, Examples include sodium thiosulfate, sodium bisulfite, and ferric chloride.

  These polymerization initiators may be used in amounts that allow the polymerization to proceed smoothly. However, if water resistance is required for the obtained water-dispersed acrylic polymer film or the like, the amount used is minimized. The amount used is preferably 0.3% by weight or less based on the weight of the monomer component (in the case of a redox polymerization initiator in combination with a reducing agent, the total amount of an oxidizing agent and a reducing agent) and It is preferable to do.

In the present invention, when it is necessary to adjust the molecular weight of the water-dispersed acrylic polymer, a compound having a chain transfer ability as a molecular weight adjusting agent in emulsion polymerization of the monomer component, for example, lauryl mercaptan, octyl mercaptan, Mercaptans such as dodecyl mercaptan, 2-mercaptoethanol, octyl thioglycolate, 3-mercaptopropionic acid, thioglycerin, or α-methylstyrene dimer may be added.

  The aqueous pressure-sensitive adhesive composition of the present invention thus obtained can be used by adding a water-soluble or water-dispersible crosslinking agent as necessary. In this case, examples of the crosslinking agent include a polyfunctional melamine compound, a polyfunctional polyamine compound, a polyfunctional polyethyleneimine compound, a polyfunctional (block) isocyanate compound, a metal salt compound, and the like. In addition to being able to be used as a mixture of two or more kinds, a water-soluble or water-dispersible thermosetting resin, for example, a phenol resin, a urea resin, a melamine resin, a urethane resin, etc. can be mixed and used. .

  In addition, the aqueous pressure-sensitive adhesive composition of the present invention includes a filler, a pigment, a pH adjuster, a film forming aid, a leveling agent, a thickener, as long as the desired effect of the present invention is not impaired as necessary. Known materials such as water repellents, tackifiers and antifoaming agents can be appropriately added and used.

  That is, in the production method for obtaining the aqueous pressure-sensitive adhesive composition of the present invention, as one of preferred methods, a monomer component mainly composed of (meth) acrylate is an acrylic having an average particle size of 10 to 300 nm. In a manufacturing method in which an aqueous medium in which an aqueous medium in which polymer particles [X] of a polymer are dispersed is present is charged all at once and emulsion polymerization is performed, the dissolved oxygen concentration of the aqueous medium is 3 ppm or less, and the polymerization initiator Time required to start emulsion polymerization by using a redox polymerization initiator and set the temperature at the start of polymerization within the range of 10 to 50 ° C., and the polymerization conversion rate of the monomer component reaches 95% Is substantially within 180 minutes.

The aqueous pressure-sensitive adhesive composition of the present invention can be used for various pressure-sensitive adhesive products.
The pressure-sensitive adhesive product is composed of a base material and a layer of the aqueous pressure-sensitive adhesive composition. Examples of such a substrate include paper, plastic film, and nonwoven fabric.

As a method for forming a layer of the pressure-sensitive adhesive composition using the aqueous pressure-sensitive adhesive composition of the present invention, a direct method in which the water-based pressure-sensitive adhesive composition is directly coated on the substrate and dried, silicone or the like The aqueous pressure-sensitive adhesive composition is applied onto a release material such as paper or plastic film that has been subjected to release treatment in step 1 and dried to form a pressure-sensitive adhesive layer. There is a transfer method in which the materials are stacked and pressed to transfer the pressure-sensitive adhesive layer onto the substrate.
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 aqueous pressure-sensitive adhesive composition 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 about 6 to 9. 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, a thing with a viscosity of 300-10,000 mPa * s (same as the above) is preferable.

  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 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.

[Measurement method of adhesive strength]
The pressure-sensitive adhesive sheet was prepared by applying the aqueous pressure-sensitive adhesive composition obtained in Examples below so that the film thickness after drying was 25 μm on the surface of a polyethylene terephthalate film having a thickness of 25 μm and drying at 100 ° C. for 2 minutes. did. 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.

[Method of measuring holding force]
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 slips off under a load of 500 g at 40 ° C. The holding time was defined as holding power. In addition, when it was retained after 24 hours, the retention time was set to 24 hours or longer.

[Tack measurement method]
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
(1) Manufacture of polymer particles [X] (aqueous dispersion) Sealed type with internal volume of 2L, equipped with stirrer, pressurizable nitrogen inlet tube, pressure reducing tube (pressure reducing pump), raw material charging port, thermometer A pressure reaction vessel (material in the vessel: made of glass lining) was charged with 560 parts of deionized water at 25 ° C., and nitrogen gas was introduced into the reaction vessel from the nitrogen introduction tube with stirring, and the pressure in the reaction vessel was increased over 1 minute. Was pressurized to 0.3 MPa. Thereafter, the pressure in the reaction vessel was reduced to −0.08 MPa over 5 minutes using a vacuum pump from the vacuum tube. After repeating this operation three times, the dissolved oxygen concentration in the deionized water in the reaction vessel was measured and found to be 0.5 ppm. Under stirring in the reaction vessel, 2 parts of Aqualon KH-10 [Daiichi Kogyo Seiyaku Co., Ltd .: active ingredient 100%], 136 parts of 2-ethylhexyl acrylate, 16 parts of methyl methacrylate and 8 parts of methacrylic acid were charged. Subsequently, 16.4 parts of a 2.4% aqueous solution of sodium bisulfite was charged, nitrogen gas was introduced into the reaction vessel from a nitrogen introduction tube, and the pressure inside the reaction vessel was increased to 0.3 MPa over 1 minute. Thereafter, the pressure in the reaction vessel is reduced from the pressure reducing tube to −0.08 MPa over 5 minutes, and this operation is repeated three times, and then the reaction vessel pressure is increased to 0.05 MPa. Pressed. During this time, the temperature in the reaction vessel was adjusted to 30 ° C.

  Next, 16.8 parts of a 4.8% aqueous solution of ammonium persulfate was charged into another sealed pressure vessel having an internal volume of 0.2 L, and pressurized so that the internal pressure of the vessel became 0.3 MPa over 10 seconds. did. Then, using a vacuum pump from the vacuum tube, the pressure in the container is reduced to -0.08 MPa over 20 seconds, this operation is repeated three times, and then the pressure in the container is increased to 0.15 MPa. did.

  After confirming that the internal temperature of the sealed pressure reaction vessel was 30 ° C., a pressure vessel containing ammonium persulfate was placed in the raw material charging port, and an aqueous ammonium persulfate solution was pressed into the closed pressure reaction vessel. Immediately after the injection of the ammonium persulfate aqueous solution, the temperature inside the reaction vessel started to rise, and it was confirmed that emulsion polymerization was started. After 45 minutes from the start of the emulsion polymerization, the temperature rise in the reaction vessel stopped at 45 ° C. During this time, the temperature adjustment operation of the reaction vessel was not performed. Thereafter, the temperature in the reaction vessel was adjusted to 55 ° C. and held for 60 minutes. Thereafter, the contents were cooled, the pressure in the reaction vessel was returned to normal pressure, and then filtered through a 200 mesh wire mesh to obtain polymer particles [X] of the present invention. The polymer particles [X] obtained here had a solid content concentration of 21.6%, a viscosity of 5 mPa · s, an average particle diameter of 160 nm, and a polymerization conversion rate of 100%.

(2) Manufacture of water-dispersed acrylic polymer Sealed pressure reaction vessel (container with internal volume of 2L, equipped with stirrer, pressurizable nitrogen inlet tube, pressure reducing tube (pressure reducing pump), raw material charging port, thermometer The polymer particles [X] (aqueous dispersion) at 25 ° C. are charged into the inner material (made of glass lining), nitrogen gas is introduced into the reaction vessel from the nitrogen introduction tube with stirring, and the reaction vessel is allowed to take 1 minute. The internal pressure was increased to 0.3 MPa. Thereafter, the pressure in the reaction vessel was reduced to −0.08 MPa over 5 minutes using a vacuum pump from the vacuum tube. After repeating this operation three times, the dissolved oxygen concentration of the polymer particles [A] (aqueous dispersion) in the reaction vessel was measured and found to be 0.5 ppm. While stirring the reaction vessel, 528 parts of 2-ethylhexyl acrylate, 32 parts of methyl methacrylate, 16 parts of methacrylic acid, 0.8 part of lauryl mercaptan, and 64 parts of Veova 10 were charged. Subsequently, 32.8 parts of a 2.4% aqueous solution of sodium bisulfite was charged, nitrogen gas was introduced into the reaction vessel from the nitrogen introduction tube, and the pressure in the reaction vessel was increased to 0.3 MPa over 1 minute. . Thereafter, the pressure in the reaction vessel is reduced from the pressure reducing pipe to a pressure of -0.08 MPa over 5 minutes by using a pressure reduction pump, this operation is repeated three times, and then the pressure in the reaction vessel is reduced to 0.30 MPa. Pressurized. During this time, the temperature in the reaction vessel was adjusted to 40 ° C. Next, 33.6 parts of a 4.8% aqueous solution of ammonium persulfate was charged into another sealed pressure vessel with an internal volume of 0.2 L and pressurized so that the internal pressure of the vessel became 0.3 MPa over 10 seconds. did. After that, the pressure inside the container is reduced to -0.08 MPa over 20 seconds using a pressure reducing pump, and this operation is repeated three times, and then the pressure inside the container is increased to 0.40 MPa. did. After confirming that the internal temperature of the sealed pressure reaction vessel was 40 ° C., a pressure vessel containing ammonium persulfate was placed in the raw material charging port, and an aqueous ammonium persulfate solution was pressed into the sealed pressure reaction vessel. Five minutes after immediately after the injection of the ammonium persulfate aqueous solution, the temperature inside the reaction vessel started to increase, and it was confirmed that the emulsion polymerization was started. After 40 minutes from the start of the emulsion polymerization, the increase in the reaction vessel temperature stopped at 97 ° C. During this time, the temperature adjustment operation of the reaction vessel was not performed. Thereafter, the temperature in the reaction vessel was adjusted to 90 ° C. and held for 90 minutes. Meanwhile, after confirming the start of emulsion polymerization, sampling was performed at intervals of 10 minutes, the polymerization conversion rate was measured, and the time until the polymerization conversion rate reached 95% was determined. The time required for the polymerization conversion to reach 95% was 60 minutes after confirming the start of emulsion polymerization. Thereafter, the contents were cooled and adjusted with aqueous ammonia (active ingredient 10%) so that the pH was 8.0. It was confirmed that the polymerization conversion rate reached 100% before cooling. After pH adjustment, the mixture was filtered through a 200 mesh wire mesh to obtain the water-dispersed acrylic polymer of the present invention. The water-dispersed acrylic polymer obtained here had a solid content concentration of 54.5%, a viscosity of 250 mPa · s, and an average particle size of 210 nm.

After adding 1.2 parts of Surfinol 420 [manufactured by Air Products Japan Co., Ltd .: active ingredient 100%] as a leveling agent to the above water-dispersed acrylic polymer, the mixture is filtered through a 100 mesh wire mesh, and the present invention. An acrylic aqueous pressure-sensitive adhesive composition was obtained.
Table 1 shows the evaluation results of the adhesive strength, holding strength, and tack of the pressure-sensitive adhesive sheet using this aqueous pressure-sensitive adhesive composition.

Examples 2-4
An aqueous 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 average particle diameter (50% median diameter), solid content concentration, and viscosity of the polymer particles contained in this aqueous pressure-sensitive adhesive composition were as described in Table 1. Table 1 shows the evaluation results of the adhesive strength, holding strength, and tack of the pressure-sensitive adhesive sheet obtained using this aqueous pressure-sensitive adhesive composition.

Comparative Example 1
An aqueous pressure-sensitive adhesive composition was obtained in exactly the same manner as in Examples 1 to 4, except that the vinyl mixture of Versatic acid was not used as the monomer mixture, and those shown in Table 1 were used. The average particle diameter (50% median diameter), solid content concentration, and viscosity of the polymer particles contained in this aqueous pressure-sensitive adhesive composition were as described in Table 1. Table 1 shows the evaluation results of the adhesive strength, holding strength, and tack of the pressure-sensitive adhesive sheet obtained using this aqueous pressure-sensitive adhesive composition.

Comparative Example 2
A reaction vessel equipped with a stirrer, a nitrogen introduction tube, a condenser (cooling tube), a raw material charging port, and a thermometer was charged with 280 parts of deionized water at 25 ° C., and 50 mL / Nitrogen gas was introduced at a flow rate of min. After 120 minutes, the dissolved oxygen concentration in the reaction vessel was measured and found to be 2.3 ppm. While introducing nitrogen gas under stirring in the reaction vessel, 7.5 parts of polyoxyethylene alkylphenyl ether sulfate ammonium salt, 237.5 parts of butyl acrylate, 10 parts of acrylonitrile, 2.5 parts of acrylic acid were charged. Emulsified uniformly. Thereafter, the temperature in the reaction vessel was adjusted to 40 ° C. Next, after confirming that the temperature in the reaction vessel was 40 ° C., 0.25 part of a 5 wt% methanol solution of 2,2-azobis [2- (2-imidazolin-2-yl) propane] was added, and 40 The emulsion polymerization was carried out by maintaining at 12 ° C. for 12 hours. The polymerization conversion rate was 95.1%. Thereafter, 0.1 part of the above 5 wt% methanol solution was further added and maintained at 40 ° C. for 24 hours. Thereafter, the contents were cooled, adjusted with aqueous ammonia (active ingredient 10%) so that the pH was 8.0, and then filtered through a 200 mesh wire net to obtain the water-dispersed acrylic polymer of the present invention. The water-dispersed acrylic polymer obtained here had a solid content concentration of 46.6%, a viscosity of 180 mPa · s, an average particle size of 220 nm, and a polymerization conversion rate of 100%.

After adding 1.2 parts of Surfinol 420 [manufactured by Air Products Japan Co., Ltd .: active ingredient 100%] as a leveling agent to the above water-dispersed acrylic polymer, the mixture is filtered through a 100 mesh wire mesh and acrylic. An aqueous pressure-sensitive adhesive composition was obtained.
Table 1 shows the evaluation results of the adhesive strength, holding strength, and tack of the pressure-sensitive adhesive sheet obtained using this aqueous pressure-sensitive adhesive composition.

Comparative Example 3
A reaction vessel equipped with a stirrer, a nitrogen inlet tube, a condenser (cooling tube), a raw material charging port, and a thermometer was charged with 300 parts of deionized water at 25 ° C., and 50 mL / Nitrogen gas was introduced at a flow rate of min. After 120 minutes, the dissolved oxygen concentration in the reaction vessel was measured and found to be 2.3 ppm. While introducing nitrogen gas while stirring in the reaction vessel, 2 parts of polyoxyethylene nonylphenyl ether [HLB: 14], 2 parts of sodium dodecylbenzenesulfonate, 140 parts of 2-ethylhexyl acrylate, 54 parts of ethyl acrylate, acrylic 6 parts of acid was charged and the whole was uniformly emulsified. Thereafter, the temperature in the reaction vessel was adjusted to 50 ° C. Next, after confirming that the temperature in the reaction vessel was 50 ° C., 0.04 part of 2,2-azobis [2-methyl-N- (phenylmethyl) -propionamidine] dihydrochloride was added, and the mixture was heated to 50 ° C. The emulsion was subjected to emulsion polymerization while maintaining for 8 hours to obtain a first dispersion B. The polymerization rate was 99.8% by weight.

  After obtaining aqueous dispersion B in this manner, a solution prepared by dissolving 0.4 part of ammonium persulfate in 20 parts of water was added to the polymerization system as a second step, and the mixture was heated to 70 ° C. while purging with nitrogen. did. To this, homogenize 140 parts of 2-ethylhexyl acrylate, 54 parts of ethyl acrylate, 6 parts of acrylic acid, 2 parts of sodium dodecylbenzenesulfonate, 2 parts of polyoxyethylene nonylphenyl ether (HLB: 14), and 140 parts of deionized water. A water emulsion uniformly emulsified with a mixer was added dropwise over 3 hours, and after completion of the addition, the mixture was maintained at the same temperature for 2 hours to carry out emulsion polymerization. Thereafter, the contents were cooled, adjusted with aqueous ammonia (active ingredient 10%) so that the pH was 8.0, and then filtered through a 200 mesh wire net to obtain the water-dispersed acrylic polymer of the present invention. The water-dispersed acrylic polymer obtained here had a solid content concentration of 50.9%, a viscosity of 230 mPa · s, an average particle size of 210 nm, and a polymerization conversion rate of 100%.

Surfinol 420 [Air Products Japan Co., Ltd .: active ingredient 100%] 1.2 parts as leveling agent, 1.2 parts of epoxy crosslinker TEPIC [Nissan Chemical Industry Co., Ltd.] After adding an aqueous solution in which 0.05 part was dissolved in 1 part of water, the mixture was filtered through a 100-mesh wire mesh to obtain an acrylic aqueous pressure-sensitive adhesive composition.
Table 1 shows the evaluation results of the adhesive strength, holding strength, and tack of the pressure-sensitive adhesive sheet obtained using this aqueous pressure-sensitive adhesive composition.

The official names of the abbreviations in Table 1 are shown below.
2-EHA; 2-ethylhexyl acrylate BA; n-butyl acrylate EA; ethyl acrylate AN; acrylonitrile MMA; methyl methacrylate MAA; methacrylic acid AA; acrylic acid DAAM; Vinyl ester)
L-SH; Lauryl mercaptan WS-500; EPOCROSS WS-500 manufactured by Nippon Shokubai Co., Ltd.
ADH: adipic acid dihydrazide The amounts of monomers and crosslinking agents used in Table 1 are expressed in parts by weight of solid content.

Further, in the part of the manufacturing method in Table 1, what is indicated as batch and dripping is as follows.
Manufacturing method in the present invention in which monomers are charged in a batch and emulsion polymerization is performed; Manufacturing method in which monomers are supplied dropwise and emulsion polymerization is performed

Furthermore, the contents of the terms shown in the polymerization conditions in Table 1 are as follows.
Polymerization start temperature; temperature in the reaction system when a polymerization initiator is added to the monomer and polymerization exotherm starts.
Exothermic stop temperature; temperature in the reaction system when the polymerization exotherm stops.
Exothermic time: Time required for the polymerization exotherm to start and stop.
Reaction time: Total reaction time required to obtain the polymer [X] or the aqueous adhesive polymer.

Claims (8)

A polymerizable monomer (A) containing a (meth) acrylate and a vinyl versatate (B) in an aqueous medium in which acrylic polymer particles [X] having an average particle size of 10 to 300 nm are dispersed. Is a water-dispersed pressure-sensitive adhesive composition containing a water-dispersed acrylic polymer obtained by emulsion polymerization and containing the above-mentioned (meth) acrylates as a main component. The ratio of the polymerizable monomer component of the polymerizable monomer (A) to the vinyl versatate (B) is 99/1 to 70/30 (weight ratio), and the acrylic polymer particles [ X] and the polymerizable monomer (A) containing the (meth) acrylates are in the range of 5/95 to 40/60, and the water-dispersed pressure-sensitive adhesive composition. The polymerizable monomers are charged all at once into a closed pressure reaction vessel in which an aqueous medium in which acrylic polymer particles [X] having an average particle size of 10 to 300 nm are dispersed, and sealed at the start of the reaction. The water-dispersed pressure-sensitive adhesive composition according to claim 1, wherein emulsion polymerization is carried out by controlling the pressure in the mold pressure reaction vessel to normal pressure or higher. 3. The water-dispersed pressure-sensitive adhesive composition according to claim 2 , wherein polymerization is carried out by pressurizing the pressure in the sealed pressure vessel so as to exceed a vapor pressure of a mixture of an aqueous medium and the polymerizable monomer. The water-dispersed pressure-sensitive adhesive composition according to claim 2 , wherein the polymerization reaction is advanced so that the polymerization conversion rate of the polymerizable monomer component becomes 95% or more within 180 minutes from the start of the reaction. The water-dispersed pressure-sensitive adhesive composition according to claim 2, which is emulsion-polymerized under a condition that the dissolved oxygen concentration in the liquid in the closed pressure reaction vessel is 3 ppm or less. The water-dispersed pressure-sensitive adhesive composition according to claim 2 , wherein a redox-based polymerization initiator is used as the polymerization initiator, and the polymerization is initiated and emulsion polymerization is performed with the temperature at the start of polymerization being in the range of 10 to 50 ° C. A pressure-sensitive adhesive product comprising the water-dispersed pressure-sensitive adhesive composition according to any one of claims 1 to 6 and a base material. Acrylic polymer having an average particle diameter of 10 to 300 nm for polymerizable monomers containing a polymerizable monomer (A) containing (meth) acrylates and a vinyl versatate (B). It is characterized in that it is charged all at once in a closed pressure reaction vessel in which an aqueous medium in which particles [X] are dispersed is present, and emulsion polymerization is carried out by controlling the pressure in the closed pressure reaction vessel at the start of the reaction to normal pressure or higher. A method for producing a water-dispersed pressure-sensitive adhesive composition , comprising a polymerizable monomer (A) comprising the (meth) acrylate as a main component and a polymerizable monomer component of a vinyl versatate (B) The weight of the acrylic polymer particles [X] and the polymerizable monomer (A) containing the (meth) acrylates is 99/1 to 70/30 (weight ratio) The ratio is in the range of 5/95 to 40/60 Method of producing a water-dispersed PSA composition, characterized in that.