JP5231821B2 - Adhesive and adhesive sheet - Google Patents

Description

  The present invention uses an aqueous emulsion-type pressure-sensitive adhesive and the same pressure-sensitive adhesive that are excellent in adhesiveness to various adherends, in particular, condensate or wet adherends, and excellent in mechanical stability (high-speed coating stability). The present invention relates to an adhesive sheet.

The pressure-sensitive adhesive sheet does not require high pressure or energy even when a practical adhesive force is obtained like a normal adhesive, and when it is bonded with a pressure of about a finger pressure, it immediately exhibits a practical adhesive force. In recent years, it has been used in many fields because of its simplicity and good workability in use.
Examples of uses of the pressure-sensitive adhesive sheet include packaging / bundling, office / household use, bonding, coating masking, surface protection, anticorrosion / decoration, and labeling.
This pressure-sensitive adhesive sheet is generally composed of a base sheet, a pressure-sensitive adhesive layer formed on the surface thereof, and a release sheet provided on the pressure-sensitive adhesive layer as necessary. In use, the release sheet is provided. When it is, the release sheet is peeled off, and the pressure-sensitive adhesive layer is adhered to the adherend and applied. Examples of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer include acrylic, urethane-based, rubber-based, and silicone-based materials. Among these, performance and economy such as adhesive strength, holding power, weather resistance, and heat resistance are included. From the viewpoint of properties, acrylic pressure-sensitive adhesives are frequently used. Conventionally, as this acrylic adhesive, a solvent-type adhesive has been mainly used. However, in recent years, volatilization of an organic solvent at the time of forming an adhesive layer has been a problem in terms of environmental hygiene and safety. Even when the sheet is used, a slight amount of organic solvent remains in the pressure-sensitive adhesive layer, and it gradually evaporates during use, causing a problem in terms of environmental hygiene.
On the other hand, the water-based emulsion-type pressure-sensitive adhesive has no particular problems with respect to environmental hygiene and safety, and high-speed coating due to high concentration and cost reduction by not using an organic solvent are possible. Recently, a water-based emulsion type has been used instead of the solvent type. In particular, labels using solvent-free pressure-sensitive adhesives are preferably used for labels used in food products.
However, the water-based emulsion-type pressure-sensitive adhesive contains a large amount of hydrophilic components such as an emulsifier, and thus has a problem that it has poor adhesion or water-resistant adhesion to a condensed or wet adherend. For example, when a pressure-sensitive adhesive sheet prepared using a water-based emulsion-type pressure-sensitive adhesive is affixed to an adherend in a condensed or wet state, or when the pressure-sensitive adhesive sheet is immersed in water after application of the pressure-sensitive adhesive sheet, Peeling occurred, or peeling occurred at the interface between the base sheet and the pressure-sensitive adhesive layer. Emulsion-type adhesives that emphasize the adhesiveness to dew and wet surfaces and water-resistant adhesive strength, and reduce the amount of hydrophilic components such as emulsifiers, are poor in particle stability of emulsion particles and have high shearing force. In such an environment, aggregation of emulsion particles tends to occur.
On the other hand, as an aqueous acrylic emulsion-type pressure-sensitive adhesive having excellent water resistance, a pressure-sensitive adhesive obtained by emulsion polymerization of a specific monomer in the presence of a reactive nonionic emulsifier is disclosed (for example, Patent Documents 1 and 2). In addition, as a water-dispersed pressure-sensitive adhesive composition exhibiting a good initial adhesive force on a dew condensation surface or a wet surface, an acrylic or rubber-based water-dispersed pressure-sensitive adhesive and a weight average molecular weight of 20,000 A composition containing ˜5,000,000 polyalkylene glycol in a specific ratio (for example, see Patent Document 3), a composition containing a rosin having a specific softening temperature (for example, see Patent Document 4), hydrophilic A composition containing a functional polymer (see, for example, Patent Document 5) is disclosed.
However, these pressure-sensitive adhesives and pressure-sensitive adhesive compositions do not sufficiently satisfy all of low-temperature pressure-sensitive adhesive strength, condensation surface or wet surface pressure-sensitive adhesive strength, water-resistant pressure-sensitive adhesive strength, and curved surface stickiness when used for pressure-sensitive adhesive sheets. In addition, the mechanical stability is not sufficient.
In general, emulsion particles with a small amount of addition of a hydrophilic component such as a surfactant have low particle stability, and pressure-sensitive adhesives with a large amount of addition of a hydrophilic component have low adhesion to a condensation surface or a wet surface.

JP-A-9-143444 JP 2003-64338 A JP 2003-313525 A Japanese Patent Laid-Open No. 2005-220295 JP 2006-283034 A

  In this background, the present invention optimizes the carboxyl group-containing unsaturated monomer content, surfactant content, and alkali-soluble or alkali-swelled emulsion addition amount during copolymerization. It is an object of the present invention to provide a pressure-sensitive adhesive that achieves both particle stability, that is, mechanical stability (high-speed coating stability) and adhesion to a condensation surface or a wet surface, and a pressure-sensitive adhesive sheet using the same. And

  As a result of intensive studies, the present inventors have found that a large amount of an acrylic emulsion containing a small amount of a carboxyl group-containing unsaturated monomer unit and a small amount of an alkali-soluble type or alkali containing a large amount of a carboxyl group-containing unsaturated monomer unit. It has been found that the above problems can be solved by using a swelling emulsion as a component, and the present invention has been completed.

That is, the present invention provides an unsaturated monomer mixture consisting essentially of the following (1) (meth) acrylic acid alkyl ester and a carboxyl group-containing unsaturated monomer (content of carboxyl group-containing unsaturated monomer is 0 .3 to 0.8% by mass) Acrylic emulsion [A] obtained by emulsion polymerization in the presence of 0.4 to 1.2 parts by mass of a surfactant per 100 parts by mass, and the unsaturated monomer mixture. An aqueous emulsion-type pressure-sensitive adhesive containing 0.05 to 0.9 parts by mass of an alkali-soluble or alkali-swelled emulsion [B] per 100 parts by mass, wherein the residue by Marlon test is 1 g or less. Aqueous emulsion adhesive,
(2) The aqueous emulsion-type pressure-sensitive adhesive according to the above (1), wherein the alkali-soluble or alkali-swelling emulsion [B] is an emulsion obtained by copolymerizing ethyl acrylate and (meth) acrylic acid,
(3) The aqueous solution according to (1) or (2) above, wherein the alkali-soluble or alkali-swelling emulsion [B] is a polymer emulsion containing 10 to 30% by mass of a carboxyl group-containing unsaturated monomer unit. Emulsion-type adhesive,
(4) The aqueous emulsion-type pressure-sensitive adhesive according to any one of the above (1) to (3), wherein the (meth) acrylic acid alkyl ester comprises 2-ethylhexyl acrylate and butyl acrylate,
(5) The aqueous emulsion-type pressure-sensitive adhesive according to any one of (1) to (4), further including a tackifier,
(6) The aqueous emulsion-type pressure-sensitive adhesive according to any one of (1) to (5), wherein the solid content is 45 to 65% by mass,
(7) A pressure-sensitive adhesive sheet in which the water-based emulsion-type pressure-sensitive adhesive according to any one of the above (1) to (6) is applied to a base material to provide a pressure-sensitive adhesive layer, and (8) A pressure-sensitive adhesive sheet according to the above (7) is provided.

  The pressure-sensitive adhesive sheet using the water-based emulsion-type pressure-sensitive adhesive of the present invention is excellent in adhesiveness to various adherends, in particular, a condensed or wet adherend, and is coated at a high speed (about 150 to 500 m / min). Even in this case, there are few coating defects and excellent mechanical stability (high-speed coating stability).

Hereinafter, the water-based emulsion pressure-sensitive adhesive and pressure-sensitive adhesive sheet of the present invention will be described in detail.
First, the acrylic emulsion as the [A] component will be described.
The (meth) acrylic acid ester in the unsaturated monomer mixture in the component [A] constituting the aqueous emulsion-type pressure-sensitive adhesive of the present invention includes a methyl group, an ethyl group, a propyl group, n- It is an alkyl ester of acrylic acid or methacrylic acid having an alkyl group of about 1 to 20 carbon atoms such as butyl group, isobutyl group, isoamyl group, hexyl group, heptyl group, 2-ethylhexyl group, isooctyl group, isononyl group, isodecyl group, etc. is there.
Among these, those having 4 to 12 carbon atoms are preferable, and those having 4 to 8 carbon atoms are more preferable. Specific examples include butyl acrylate and 2-ethylhexyl acrylate. These (meth) acrylic acid esters may be used alone or as a mixture of two or more thereof, but a combination of butyl acrylate and 2-ethylhexyl acrylate is preferable from the viewpoint of performance.

Examples of the carboxyl group-containing unsaturated monomer in the unsaturated monomer mixture include acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, and the like. From the viewpoint of availability, polymerizability, etc. Acid and methacrylic acid are preferred.
In the unsaturated monomer mixture (100% by mass), the content of the carboxyl group-containing unsaturated monomer is 0.3 to 0.8% by mass, preferably 0.35 to 0.75% by mass. .
When the content of the carboxyl group-containing unsaturated monomer is less than 0.3% by mass, the mechanical stability, the adhesion to the condensation surface or the wet surface and the coating property are inferior, and when it exceeds 0.8% by mass, the mechanical stability is obtained. In addition, the coating property is excellent, but the adhesion to the dew condensation surface or the wet surface is reduced.
In the present invention, the dew-bonding surface or the wet surface adhesive force means that the polyethylene adherend left in an environment of 0 ° C. is allowed to stand in an environment of 23 ° C. and 50% RH for 30 seconds, and then the adherend in the same environment. The sample was measured by following a JIS Z-0237 peeling-off adhesive force measuring method of 180 ° immediately after applying the sample to a sample.

  In addition to the above, the unsaturated monomer mixture includes one kind of hydroxyl group-containing monomer such as hydroxyalkyl (meth) acrylate such as hydroxyethyl (meth) acrylate, vinyl acetate, styrene, etc. It can be used above.

In the aqueous emulsion type pressure-sensitive adhesive of the present invention, the unsaturated monomer mixture has a surface activity of 0.4 to 1.2 parts by weight, preferably 0.4 to 1.0 parts by weight, based on 100 parts by weight thereof. An acrylic emulsion of [A] component is obtained by emulsion polymerization in an aqueous solvent in the presence of an agent.
When the amount of the surfactant is less than 0.4 parts by mass, the adhesive strength to the dew condensation surface or the wet surface is excellent, but the mechanical stability and coating property are poor. When the amount exceeds 1.2 parts by mass, the mechanical stability and the coating property are excellent, but the adhesive force to the dew condensation surface or the wet surface decreases.

Examples of the surfactant that can be used include anionic and nonionic emulsifiers. Specific examples of the anionic emulsifier include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, and the like. Examples of nonionic emulsifiers include polyoxyethylene alkyl ether and polyoxyethylene alkyl phenyl ether. A radical polymerizable reactive emulsifier into which a propenyl group, an acryloyl group or the like is introduced can also be used. These emulsifiers can be used alone or in combination.
The reactive emulsifier is not particularly limited as long as it is a reactive emulsifier. For example, anionic and nonionic reactive emulsifiers are used. Specifically, as an anionic reactive emulsifier, “Adekalia Soap SE-20N”, “Adekalia Soap SE-10N”, “Adekalia Soap PP-70”, “Adekalia Soap PP-710”, “Adekalia” “Soap SR-10”, “Adekaria Soap SR-20” (manufactured by Asahi Denka Kogyo Co., Ltd.), “Eleminol JS-2”, “Eleminol RS-30” (manufactured by Sanyo Kasei Kogyo Co., Ltd.), “Latemle E -118B "," Latemul S-180A "," Latemul S-180 "," Latemul PD-104 "(manufactured by Kao Corporation)," Aqualon BC-05 "," Aqualon BC-10 "," Aqualon BC- 20 "," Aqualon HS-05 "," Aquaron HS-10 "," Aquaron HS-20 "," New Frontier S-510 "," Aquaron K " -05 "," Aqualon KH-10 "(manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)," Phosfinol TX "(manufactured by Toho Chemical Co., Ltd.)," Adekalia Soap NE-10 "as a nonionic reactive emulsifier, “Adekaria soap NE-20”, “Adekaria soap NE-30”, “Adekaria soap NE-40”, “Adekaria soap ER-10”, “Adekaria soap ER-20”, “Adekaria soap ER” -30 "," Adekaria Soap ER-40 "(manufactured by Asahi Denka Kogyo Co., Ltd.)," Aqualon RN-10 "," Aquaron RN-20 "," Aquaron RN-30 "," Aquaron RN-50 "[ As mentioned above, commercial products such as those manufactured by Daiichi Kogyo Seiyaku Co., Ltd. may be mentioned.

  The conditions for the emulsion polymerization of the acrylic emulsion [A] are not particularly limited, and the conditions applied in normal 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 the acrylic emulsion [A] is prepared by an emulsion polymerization method, a polymerization initiator is usually used. As polymerization initiators, azo compounds such as 2,2′-azobis (2-methylpropionamidine) dihydrochloride, 2,2′-azobis (2-amidinopropane) dihydrochloride, potassium persulfate, ammonium persulfate and the like Peroxides such as sulfate, benzoyl peroxide, t-butyl hydroperoxide, and hydrogen peroxide can be used. A redox initiator comprising a combination of persulfate and sodium bisulfite or a combination of peroxide and sodium ascorbate can also be used. These polymerization initiators are usually added in a predetermined amount at each stage of the emulsion polymerization to cause the polymerization reaction.

When the acrylic emulsion [A] is prepared by an emulsion polymerization method, a tackifier (tackifier) may be further used. By using a tackifier, it is possible to obtain an adhesive having excellent adhesion to a dew condensation surface or a wet surface.
The amount of tackifier used is about 1 to 15 parts by mass (in terms of solid content), preferably 3 to 10 parts by mass (same as above) with respect to 100 parts by mass of the unsaturated monomer mixture. When the amount of tackifier used is less than 1 part by mass, the adhesive force on the dew condensation surface or wet surface is inferior.
As the tackifier, rosin resin, petroleum resin, terpene resin, alkylphenol resin, coumarone resin, coumarone indene resin, styrene resin, xylene resin and the like are used.
The rosin resin refers to rosin and rosin derivatives. Rosin is gum rosin, wood rosin, tall oil rosin. Examples of rosin derivatives include polymerized rosin, disproportionated rosin, hydrogenated rosin, reinforced rosin, rosin ester, polymerized rosin ester, rosin phenol, and polyhydric alcohols used for esterification include ethylene glycol, diethylene glycol, Glycerin, pentaerythritol, etc. can be used.
Examples of petroleum resins include C5 petroleum resins, C9 petroleum resins, C5-C9 copolymer petroleum resins, coumarone resins, coumarone-indene resins, pure monomer resins, dicyclopentadiene petroleum resins, and hydrides thereof. Is mentioned.
Examples of the terpene resin include a terpene polymer, a β-pinene polymer, a terpene phenol resin, and an aromatic modified terpene polymer. Examples of the alkylphenol resin and xylene resin include alkylphenol-modified xylene resin and rosin-modified xylene resin.

Next, the alkali-soluble or alkali-swelling emulsion that is the [B] component in the aqueous emulsion-type pressure-sensitive adhesive of the present invention will be described.
Component [B] is an emulsion containing a polymer having a large amount of carboxyl groups, and polymer particles dispersed in water are dissolved or swelled by the addition of an alkali such as aqueous ammonia, so that the viscosity is significantly increased. Specifically, it is used as a viscosity improver, a gelling agent, a thixotropic additive, etc. for uses such as water-based paints, paper coating liquids, and water-based inks.
In the aqueous emulsion type pressure-sensitive adhesive of the present invention, this alkali-soluble type or alkali-swelling type emulsion is not used as a conventional viscosity improver, but is used for the purpose of improving the stability of emulsion particles.
The [B] component, an alkali-soluble or alkali-swelled emulsion, generally contains a (meth) acrylic acid alkyl ester such as ethyl (meth) acrylate as the main component, and includes acrylic acid and methacrylic acid ( It can be prepared by emulsion polymerization by adding a large amount of a monomer having a carboxyl group such as (meth) acrylic acid and further adding a small amount of a monomer such as a polyfunctional monomer as required.
Polyfunctional monomers such as (poly) ethylene glycol di (meth) acrylate, methylenebisacrylamide, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, divinylbenzene, etc. And one or more selected from these groups can be used. The content of the unit derived from the polyfunctional monomer is preferably 0 to 2% by mass in all monomer units constituting the [B] component. When the content exceeds 2% by mass, the adhesive strength to the dew condensation surface or the wet surface decreases.

In some cases, an associative monomer such as alkoxy polyethylene glycol (meth) acrylate is emulsion-copolymerized. The main component is a monomer having a carboxyl group such as (meth) acrylic acid and a (meth) acrylic acid alkyl ester such as ethyl (meth) acrylate. Since the alkali-soluble type or the alkali-swelling type is excellent, as the emulsion polymerization step, about 20 to 40% by mass of an active ingredient is produced and sold by a polymerizable monomer dropping method or a pre-emulsion dropping method. Yes. The amount of the monomer having a carboxyl group such as (meth) acrylic acid is 10 to 30% by mass, preferably about 20% by mass. When the content is less than 10% by mass, the polymerization stability is improved, but the alkali-soluble or alkali-swelling property of the resulting polymer having many carboxyl groups may be lowered. If it exceeds 30% by mass, the polymerization stability is lowered, and the increase in viscosity is increased in an alkaline environment, which is not preferable.
This alkali-soluble or alkali-swelled emulsion can be adjusted in cross-linkability depending on the amount and type of the polyfunctional monomer, the molecular weight of the resulting polymer, and the type of the associative monomer, and is thus intended. It is possible to adjust the mechanical stability and the adhesive force to the dew condensation surface or the wet surface.
[B] Component-soluble alkali-soluble or alkali-swelled emulsions are commercially available. For example, “Aron B-300K”, “Aron A-7075” manufactured by Toa Gosei Co., Ltd., Rohm and Haas ( "Primal TT-615" manufactured by Co., Ltd.

In the aqueous emulsion type pressure-sensitive adhesive of the present invention, the blending ratio of the [A] component and the [B] component is such that the [B] component is 0.05 to 100 parts by mass of the unsaturated monomer mixture in the [A] component. 0.9 parts by mass.
When the blending amount of the component [B] is less than 0.05 parts by weight and more than 0.9 parts by weight, both have excellent adhesion to the condensation surface or wet surface, but mechanical stability and coatability Decreases.

The aqueous emulsion-type pressure-sensitive adhesive of the present invention is characterized in that the residue by the Marlon test is 1 g or less.
As described above, even when coating is performed at a high speed (about 150 to 500 m / min), if the residue by the Marlon test is 1 g or less, the generation of coating streaks due to the generation of aggregates is reduced, and the machine of the coating machine It can be determined that the stability is good.
The Marlon test in the present invention was carried out using a Marlon mechanical stability tester (manufactured by Tester Sangyo Co., Ltd.), using 50 g of an aqueous emulsion adhesive as a sample, a load of 294 N (30 kg), a rotation speed of 1000 rpm, and a share application time of 30 minutes. This is a mechanical stability test conducted under the conditions of (1): the amount (g) obtained by filtering the aggregates with a 300 mesh SUS filter after the test and measuring the dry weight of the residue (105 ° C. for 60 minutes). .

  In the aqueous emulsion type pressure-sensitive adhesive of the present invention, various additives such as a plasticizer, a softener, a filler, a pigment, a dye, an anti-aging agent, an increase agent are used as long as they do not affect the effects of the present invention. A sticking agent, an antifoaming agent, a preservative, etc. can be mix | blended.

Moreover, in the aqueous | water-based emulsion type adhesive of this invention, solid content concentration becomes like this. Preferably it is 45-65 mass%, More preferably, it is 50-60 mass%.
The viscosity is 50 to 5,000 mPa · s, preferably 100 to 2,000 mPa · s (BM type viscometer, 60 rotations, 25 ° C.). Furthermore, the pH is in the range of 7.2 to 9.0.

Next, the base material in the adhesive sheet of this invention is demonstrated in detail.
As a base material, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyetherimide, polyaramid, polyetherketone, polyetheretherketone, polyphenylene sulfide, poly (4-methylpentene-1) and other resin sheets and films Paper substrates such as fine paper, coated paper, glassine paper, and laminate paper are used.
Although the thickness of a base material changes a little with materials to be used, it is about 5-300 micrometers normally, Preferably, it is about 10-100 micrometers.

  In order to apply an aqueous emulsion type adhesive to a substrate or a release sheet to be described later, an emulsion of the same adhesive is prepared and applied to a gravure coating method, a bar coating method, a spray coating method, a spin method, or the like. The coating method, roll coating method, die coating method, knife coating method, air knife coating method, lip coating method, curtain coating method and the like can be used.

  The thickness of the pressure-sensitive adhesive layer formed on the substrate after drying and curing is usually about 3 to 50 μm, and preferably about 5 to 40 μm. By setting the thickness of the pressure-sensitive adhesive layer to 3 μm or more, it is possible to ensure the condensation or wet pressure-sensitive adhesive force necessary for the pressure-sensitive adhesive sheet of the present invention. Is prevented from protruding from the end.

Next, the release sheet will be described in detail.
As a release sheet for protecting the pressure-sensitive adhesive layer formed on the substrate, a resin film such as polyethylene terephthalate, polyethylene, or polypropylene coated with a release agent such as a fluororesin, a silicone resin, or a long-chain alkyl group-containing carbamate Alternatively, a release sheet obtained by coating the release agent on a paper substrate such as high-quality paper, glassine paper, or laminate paper can be used. The thickness of the release sheet varies somewhat depending on the material used, but is usually 10 to 250 μm, preferably 20 to 200 μm. The thickness of the release agent layer is usually about 0.1 to 5 μm, preferably about 0.5 to 2 μm.

  The pressure-sensitive adhesive sheet of the present invention is obtained by directly applying an aqueous emulsion-type pressure-sensitive adhesive on the base material and then drying it according to a conventional method for producing pressure-sensitive adhesive sheets, or by peeling the release sheet. After coating on the adhesive layer and drying, an adhesive layer is formed by transferring onto the base material, and a sheet or tape-like roll or laminate, or a single sheet and a release sheet. Adhesive sheets in the form of affixed can be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to a following example. Further, in the following description, the term “parts” or “%” means all parts by mass or mass%.

<Examples 1-8>
(1) Preparation of pressure-sensitive adhesive 40 parts by mass of 2-ethylhexyl acrylate (abbreviation 2-EHA in the table), 60 parts by mass of butyl acrylate (abbreviation BA in the table), acrylic acid (carboxyl group) of each part described in Table 1 A terpene phenol resin [trade name “Tamanol 901” manufactured by Arakawa Chemical Industries, Ltd.] which is a tackifier (abbreviation TF in the table) to an unsaturated monomer mixture comprising the unsaturated monomer contained, abbreviation AA in the table) 6 parts by mass was put into a reaction vessel having a stirrer, a thermometer, a reflux condenser and a dropping funnel, and stirred and dissolved for 30 minutes while maintaining at about 30 ° C.
After homogeneously dissolving the above components, the anionic surfactant in the number of parts listed in Table 1 at the same temperature [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name “New Frontier A-229E”] was added in 57 parts by mass of ion-exchanged water. The dispersion liquid dispersed in was added and stirred for 30 minutes to prepare an emulsion containing an unsaturated monomer mixture and the like.
Separately, 40 parts of deionized water is put into a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen introduction tube, and a dropping funnel, and the temperature in the reaction vessel is raised to 80 ° C. while introducing nitrogen. Then, 4 parts of potassium persulfate was charged and dissolved so that the concentration became 5% by mass. A solution containing the unsaturated monomer mixture and the like prepared in advance was added dropwise over 3 hours while maintaining the temperature at about 80 ° C.
In parallel with the dropping of the emulsion, 4 parts of an aqueous potassium persulfate solution having a concentration of 5% by mass was dropped, and emulsion polymerization was carried out by stirring for 3 hours while maintaining the temperature in the reaction vessel at 80 to 83 ° C.
After completion of dropping, 1 part by weight of potassium persulfate was added at 1 hour and 2 hours respectively to complete the polymerization. After aging at the same temperature for 3 hours, the mixture was cooled to room temperature and then the acrylic component [A] An emulsion was prepared.
Subsequently, 25 mass% ammonia water was added and adjusted so that pH might be set to 8.0, Furthermore, the alkali-soluble type or alkali swelling type emulsion [ethyl acrylate 100 which is the [B] component of the number of parts described in Table 1) Emulsion copolymerization of 20 parts by mass and 20 parts by mass of methacrylic acid in the presence of 0.2 parts by mass of dodecyl mercaptan, solid content concentration of 25% by mass] to add an aqueous emulsion type adhesive (solid content concentration of 55% by mass) Obtained.

(2) Manufacture of pressure-sensitive adhesive sheet and observation of pressure-sensitive adhesive surface Aqueous emulsion type obtained in the above example on a release sheet (length 5000 m) surface-treated with a silicone-based release agent on one side of glassine paper having a width of 1 m The pressure-sensitive adhesive and the comparative aqueous emulsion-type pressure-sensitive adhesive obtained in the following comparative examples were coated at a coating speed of 250 m / min using a gravure coater so that the thickness after drying was 20 μm, and dried at 100 ° C. Then, it was bonded to a high-quality paper having a basis weight of 55 g / m ² as a base material, and the formed pressure-sensitive adhesive layer was transferred to the high-quality paper side to produce a pressure-sensitive adhesive sheet. The state of the pressure-sensitive adhesive layer surface, which was peeled off from the produced pressure-sensitive adhesive sheet (10 m) and transferred to the high-quality paper, was observed.
The evaluation criteria of the state (high-speed coating property) of the pressure-sensitive adhesive layer surface in Table 1 are as follows.
○: No coating streaks are observed.
Δ: 1 to 3 coating stripes are observed in 1 m width.
X: Four or more coating stripes are observed in 1 m width.

[Comparative Examples 1-6]
Acrylic acid and an anionic emulsifier in the amounts shown in Table 1 were mixed with an unsaturated monomer mixture and subjected to emulsion polymerization. After the emulsion polymerization, an alkali-soluble or alkali-swelling emulsion in the amount shown in Table 1 was added. Was carried out in the same manner as in Example, and a comparative water-based emulsion type pressure-sensitive adhesive was obtained.
The performance evaluation results of the comparative aqueous emulsion-type pressure-sensitive adhesive and pressure-sensitive adhesive sheet are shown together in Table 1.

The numerical value of the component amount excluding [A] in Table 1 indicates the effective component amount with respect to 100 parts by mass of the total monomer components of [A].
The abbreviations in the used [A] component are as follows.
2EHA: 2-ethylhexyl acrylate BA: n-butyl acrylate MAA: methacrylic acid

From Table 1, the following is clear.
(1) The water-based emulsion type adhesives in Examples 1 to 9 have high mechanical stability and good coatability, and also have high adhesion to the dew (wet) surface.
(2) In Comparative Example 1, since the amount of acrylic acid in the [A] component is small, the mechanical stability of the aqueous emulsion-type pressure-sensitive adhesive is low, and the amount of aggregates generated is large. In addition, the adhesion to the dew condensation (wet) surface is low.
(3) In Comparative Example 2, since the amount of acrylic acid in the [A] component is large, the mechanical stability of the water-based emulsion-type adhesive is good, but the adhesion to the dew (wet) surface is low.
(4) In Comparative Example 3, since the amount of emulsifier used in the component [A] is small, the adhesion to the dew (wet) surface is similar to that in the example, but the mechanical stability is low and the amount of aggregates generated is large.
(5) In Comparative Example 4, since the amount of the emulsifier used in the component [A] is large, the mechanical stability is high and the amount of aggregates is small, but the adhesion to the dew (wet) surface is low.
(6) In Comparative Example 5, since the amount of the [B] component used is 0, the adhesion to the dew (wet) surface is the same as in the examples, but the mechanical stability is low and the amount of aggregates generated is large.
(7) In Comparative Example 6, since the amount of the [B] component used is large, the adhesion to the dew (wet) surface is the same as in the examples, but the mechanical stability is low and the amount of aggregates generated is large.

Claims (9)

(Meth) unsaturated monomer mixture containing an acrylic acid alkyl ester and a carboxyl group-containing unsaturated monomer (content 0.3 to 0.8% by weight of the carboxyl group-containing unsaturated monomer) 100 parts by weight per An acrylic emulsion [A] obtained by emulsion polymerization in the presence of 0.4 to 1.2 parts by mass of a surfactant and an alkali-soluble or alkali-swelled emulsion per 100 parts by mass of the unsaturated monomer mixture An aqueous emulsion-type pressure-sensitive adhesive containing 0.05 to 0.6 parts by mass of [B], wherein a residue by a Marlon test is 1 g or less.   The aqueous emulsion-type pressure-sensitive adhesive according to claim 1, wherein the alkali-soluble or alkali-swelling emulsion [B] is an emulsion obtained by copolymerizing ethyl acrylate and (meth) acrylic acid.   The aqueous emulsion-type pressure-sensitive adhesive according to claim 1 or 2, wherein the alkali-soluble or alkali-swelling emulsion [B] is a polymer emulsion containing 10 to 30% by mass of a carboxyl group-containing unsaturated monomer unit.   The aqueous emulsion-type pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the (meth) acrylic acid alkyl ester comprises 2-ethylhexyl acrylate and butyl acrylate.   Furthermore, the water-based emulsion-type adhesive in any one of Claims 1-4 containing a tackifier.   Solid content is 45-65 mass%, The aqueous | water-based emulsion adhesive in any one of Claims 1-5. The acrylic emulsion [A] is an emulsion obtained by emulsion polymerization in the presence of 0.4 to 1.0 part by mass of the surfactant per 100 parts by mass of the unsaturated monomer mixture. The aqueous emulsion adhesive in any one of -6. Claim 1-7 an aqueous emulsion type adhesive is applied to a substrate pressure-sensitive adhesive sheet formed by providing an adhesive layer according to any one of the. The pressure-sensitive adhesive sheet according to claim 8 , which is used for sticking a dew condensation surface or a wet surface.