JP2009185218A - Method for producing microcapsule aqueous dispersion and crosslinkable resin composition using microcapsule - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive composition that does not thicken and has a long pot life even if mixed with a crosslinking agent. <P>SOLUTION: The method for producing an aqueous dispersion of a microcapsule (B) having a specific particle diameter and including a crosslinking agent (b1) in a polymer shell formed from monomers (b3) and (b4) comprises dispersing a uniform homogeneous solution containing the crosslinking agent (b1), an organic solvent (b2) that is sparingly water-soluble and hardly dissolves a polymer formed from the monofunctional monomer (b4), a small amount of the polyfunctional monomer (b3), the monofunctional monomer (b4) and a polymerization initiator to an aqueous solution of a dispersion stabilizer to give a monomer dispersion having a specific particle diameter, then polymerizing the monomers (b3) and (b4). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing an aqueous dispersion of microcapsules. Specifically, the present invention relates to a method for producing an aqueous dispersion of microcapsules suitable for encapsulating a crosslinkable resin composition, specifically, a crosslinker for a pressure-sensitive adhesive composition. Furthermore, the present invention relates to a crosslinkable resin composition using an aqueous dispersion of microcapsules, specifically, a pressure-sensitive adhesive composition.

  Conventionally, in various applications such as coating materials such as paints, adhesives, adhesives, ink binders, overcoat varnishes, various functional surface treatment agents, fine particle dispersants such as organic and inorganic pigments, compatibilizers, etc. Various resistances such as heat resistance and water resistance are required. One method for clearing these resistances is the introduction of a crosslinked structure. In many cases, physical properties are dramatically improved by introducing a crosslinked structure.

  As a method for introducing a crosslinked structure, there is a method using a reaction between a main agent and a crosslinking agent (curing agent). Since the main agent and the cross-linking agent can react with each other, after mixing the main agent and the cross-linking agent, in the case of a coating material, it is necessary to apply the coating material to the coating material before the reaction between the two does not proceed. The better the reactivity between the main agent and the cross-linking agent, the easier the viscosity of the composition after mixing is, and the pot life (the pot life after mixing the main agent and the cross-linking agent) becomes shorter. For example, polycarbodiimide is rich in reactivity with a carboxyl group even at room temperature, but has a short pot life and needs to be used immediately after mixing.

  Ensuring prompt reactivity between the main agent and the cross-linking agent and securing the pot life as long as possible are one of the challenges for many years. In order to make the pot life longer, a method using a cross-linking agent whose periphery is coated with some partition wall material has been proposed.

Patent Document 1 discloses a method for producing a crosslinking agent emulsion obtained by emulsifying water by adding polycarbodiimide and a surfactant, and by emulsifying water by adding water to polycarbodiimide, an organic solvent, and a surfactant. A method for producing the cross-linking agent emulsion is disclosed. (Refer to Unexamined-Japanese-Patent No. 2004-277569).
Since the crosslinking agent emulsion according to the production method disclosed in Patent Document 1 is only protected around the crosslinking agent by a surfactant, if the crosslinking agent emulsion is stored for a long period of time such as one month, polycarbodiimide Some of them react with water and become inactive.

Patent Document 2 discloses a microcapsule-type phosphorus-based curing in which the core material is a phosphorus-based curing accelerator and a polymer whose main polymerization component is allyl glycidyl ether or glycidyl (meth) acrylate is the main component of the shell wall. An epoxy resin composition containing an accelerator, an epoxy resin and a crosslinking agent as essential components and a cured product thereof are disclosed (see JP-A-8-73566).
It is considered that by encapsulating the accelerator in the microcapsule, there is an effect of delaying the reaction with the epoxy resin and the crosslinking agent. However, although it is described in Patent Document 2 that the average particle size of the microcapsule-type phosphorus curing accelerator is preferably 0.1 to 500 μm, it is specifically described in the Example level of Patent Document 2. The average particle size of the microcapsules disclosed in 1) is 30 μm, and microcapsules of such a size are poor in stability per se, and will settle in about one week if left at room temperature.

Patent Document 3 discloses that a target component, a monomer component, an initiator, and an initiator are dispersed in an aqueous solution of a dispersion stabilizer in order to obtain fine particles that can be used for a long period of time or to release the target component at a predetermined time. Disclosed is a method for producing target component-containing fine particles, in which a mixture containing an auxiliary polymer is dispersed if necessary, and suspension polymerization is performed. [0069] exemplifies various solvents as one of the target components. (See JP 2003-96108 A). The production method disclosed in Patent Document 3 requires a polyfunctional monomer as a monomer and discloses the combined use of a monofunctional monomer, but no specific production method using a monofunctional monomer is described at all. Only the case where only a polyfunctional monomer (crosslinkable monomer) is used is described. And the invention which concerns on patent document 3 uses the auxiliary polymer which functions as a phase-separation promoter, or uses an auxiliary polymer, even if it uses only a polyfunctional monomer (crosslinkable monomer) without using a monofunctional monomer. Even if not, it is claimed that the target substance to be encapsulated has a specific property, so that a high-strength shell formed only from a polyfunctional monomer (crosslinkable monomer) can be formed and the target component can be encapsulated inside. (Patent Document 4: Japanese Patent No. 3785440).
In Patent Documents 3 and 4, there is no description or suggestion that a cross-linking agent for a pressure-sensitive adhesive composition is included as a target component. Since the production methods disclosed in Patent Documents 3 and 4 are directed to forming a shell using only a polyfunctional monomer (crosslinkable monomer), a crosslinking agent for a pressure-sensitive adhesive composition is temporarily used as a target component. Even if it can be included, the strength of the shell formed is very high. As a result, although the pot life as a composition mixed with the main agent is prolonged, the target component-containing fine particles cannot be easily destroyed at a general temperature of about 100 ° C. for applying and drying the pressure-sensitive adhesive composition. The reaction between the main agent and the crosslinking agent does not occur, and a pressure-sensitive adhesive sheet cannot be obtained.

Japanese Patent Application Laid-Open No. 62-127336 discloses a method for producing polymer particles in which an oily substance such as toluene is incorporated in an inner hole. Patent Document 5, page 3, lower right column can contain the oily substance contained in the inner hole as it is, or after removing the oily substance in the inner hole to obtain hollow polymer particles, It is described that capsule-like polymer particles can be obtained by absorbing the target substance. A means for enclosing various useful components in the hollow polymer particles from the outside of the hollow polymer particles is described in Patent Document 5, page 8, upper right column. On the other hand, Patent Document 5, page 6, lower right column describes that various components that require physical protection by encapsulation can be dissolved in an oily substance.
However, Patent Document 5 merely describes what can be incorporated in the inner hole as an oily substance, and does not provide any disclosure or suggestion regarding the internal organs of the crosslinking agent for the pressure-sensitive adhesive composition. Further, in the case of the production method of Patent Document 5, in order to obtain polymer particles having inner pores, it is necessary to have a different polymer different from the polymer constituting the partition walls. In the pressure-sensitive adhesive composition, since components other than the crosslinking agent become impurities, there is a concern that the performance of the pressure-sensitive adhesive sheet after the reaction between the main agent and the crosslinking agent (curing agent) is adversely affected.

In Patent Documents 6 and 7, a monofunctional hydrophilic monomer, a crosslinkable monomer, and an oily substance are dispersed in an aqueous medium and polymerized to obtain polymer particles encapsulating the oily substance, and the oily substance encapsulated from the polymer particles. It is described that hollow polymer particles can be obtained by removing the substance. However, Patent Documents 6 and 7 merely describe what can be incorporated in the inner hole as an oily substance, and do not provide any disclosure or suggestion regarding the internal organs of the crosslinking agent for the pressure-sensitive adhesive composition.
And the 4th page and the upper left column of patent document 6 and the 3rd page and the upper right column of patent document 7 disclose oily substances such as toluene, respectively.
Further, Example 6 in the lower left column on page 6 of Patent Document 6 describes a case where isoamyl acetate was used as the oily substance and no heterogeneous polymer was used. From page 4 of Patent Document 7, the lower left column. Example 1, which begins, describes the case where toluene is used as the oily substance and no different polymer is used.
JP 2004-277469 A JP-A-8-73566 JP 2003-96108 A Japanese Patent No. 3785440 JP 62-127336 A JP 02-255704 A JP 61-087734 A

  An object of the present invention is to obtain a pressure-sensitive adhesive composition that does not thicken even when a crosslinking agent is blended and has a long pot life.

  As a result of examining the inclusion of a crosslinking agent in microcapsules in order to solve the above problems, the present inventor, as long as it is an aqueous dispersion of microcapsules produced under specific conditions, over a long period of time after mixing with the main agent, It is possible to suppress the reaction between the main agent and the crosslinking agent, and to suppress the increase in viscosity as a pressure-sensitive adhesive composition, and to ensure the performance as a pressure-sensitive adhesive sheet even after long-term storage as a pressure-sensitive adhesive composition. I found.

That is, the present invention relates to a dispersion stabilizer aqueous solution, a crosslinking agent (b1), an organic solvent (b2), a polyfunctional monomer (b3) having two or more polymerizable unsaturated double bonds, a polymerizable unsaturated double bond. A homogeneous solution containing a monofunctional monomer (b4) having one bond and a polymerization initiator is dispersed to obtain a dispersion having a volume average particle diameter of droplets of 0.1 to 10 μm, and then the monomer (b3), ( polymerizing b4),
A method for producing an aqueous dispersion of microcapsules (B) having a volume average particle size of 0.1 to 10 μm, wherein a crosslinking agent (b1) is encapsulated in a polymer shell formed from the monomers (b3) and (b4). Because
<1> The dispersion stabilizer is 0.1 to 10 weights with respect to a total of 100 parts by weight of the crosslinking agent (b1), the organic solvent (b2), the polyfunctional monomer (b3), and the monofunctional monomer (b4). And the cross-linking agent (b1) has a functional group capable of reacting with at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, a glycidyl group, and a carbonyl group. And <3> the content of the polyfunctional monomer (b3) in a total of 100 wt% of the polyfunctional monomer (b3) and the monofunctional monomer (b4) is 1 to 20 wt%, and <4> The solubility of the organic solvent (b2) in 100 parts by weight of water at 20 to 25 ° C. is 20 parts by weight or less, and
<5> The monofunctional monomer (b4) is a monomer capable of forming a polymer having a solubility of 1 part by weight or less with respect to 100 parts by weight of the organic solvent (b2) at 20 to 25 ° C. The present invention relates to a method for producing an aqueous dispersion of microcapsules (B).

  The present invention relates to an aqueous dispersion of microcapsules (B) obtained by the production method described in the above invention.

The present invention also provides a resin (A) having at least one crosslinkable functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, a glycidyl group, and a carbonyl group, and the microcapsule (B )), The crosslinkable resin composition containing
An acrylic resin is preferably used as the resin (A) having a crosslinkable functional group.
When the glass transition temperature of the acrylic resin is −60 to 0 ° C., the crosslinkable resin composition of the invention can be used as a pressure sensitive adhesive.

  Furthermore, the present invention relates to a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the crosslinkable resin composition for pressure-sensitive adhesives described in the above invention on at least one surface of a sheet-like substrate.

  Furthermore, in the present invention, at least one surface of the sheet-like base material is coated with the crosslinkable resin composition for a pressure-sensitive adhesive described in the above invention, and dried under conditions capable of breaking the microcapsule (B). In addition, the present invention relates to a method for producing a pressure-sensitive adhesive sheet, wherein the microcapsule (B) is destroyed and the resin (A) having a crosslinkable functional group is reacted with the crosslinking agent (b1).

  By using an aqueous dispersion of microcapsules encapsulating a crosslinking agent according to the production method of the present invention, the reaction between the main agent and the crosslinking agent is suppressed for a long time after mixing with the main agent, and as a pressure-sensitive adhesive composition Not only can the increase in viscosity be suppressed, but even when the pressure-sensitive adhesive composition is stored for a long period of time, a pressure-sensitive adhesive sheet having performance comparable to that before storage can be obtained.

A method for producing an aqueous dispersion of microcapsules (B) containing the crosslinking agent (b1) will be described.
Crosslinker (b1), organic solvent (b2), polyfunctional monomer (b3) having two or more polymerizable unsaturated double bonds, monofunctional monomer (b4) having one polymerizable unsaturated double bond and polymerization Mix the initiator to obtain a homogeneous solution. The homogeneous solution is dispersed in an aqueous solution containing a dispersion stabilizer to obtain a dispersion having a volume average particle diameter of 0.1 to 10 μm, and the monomers (b3) and (b4) are polymerized. In the method for producing an aqueous dispersion of microcapsules (B) of the present invention, it is important that (b1) to (b4) and the like satisfy the following conditions <1> to <5>.

<1> The dispersion stabilizer is 0.1 to 10 parts by weight with respect to 100 parts by weight in total of the crosslinking agent (b1), the organic solvent (b2), the polyfunctional monomer (b3), and the monofunctional monomer (b4). 0.5 to 8 parts by weight is preferable.
The dispersion stabilizer has a function of dispersing the oily component composed of (b1) to (b4) in water and dispersing the polymerized microcapsules (B) in water. Accordingly, if the amount is too small, the particles cannot be dispersed. On the other hand, when too much, the water resistance after bridge | crosslinking the crosslinkable resin composition mentioned later falls.

  Examples of the dispersion stabilizer used in the present invention include polyvinyl alcohol, methyl cellulose, ethyl cellulose, polyacrylic acid, polyacrylimide, polyethylene oxide, poly (hydroxystearic acid-g-methyl methacrylate-co-methacrylic acid). Examples thereof include polymer dispersion stabilizers such as copolymers, nonionic surfactants, anionic surfactants, and amphoteric surfactants. Among these, polymer dispersion stabilizers such as polyvinyl alcohol are preferable.

<2> The crosslinking agent (b1) has a functional group capable of reacting with at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, a glycidyl group, and a carbonyl group.
As described later, the main resin (A) constituting the crosslinkable resin composition has at least one crosslinkable functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, a glycidyl group, and a carbonyl group. . The microcapsule (B) functions as a crosslinking agent with respect to the main resin (A). Therefore, the crosslinking agent (b1) included in the microcapsule (B) is at least one selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, a glycidyl group, and a carbonyl group so that it can react with the resin (A). It has a functional group capable of reacting with a species functional group.

<3> The content of the polyfunctional monomer (b3) in the total of 100% by weight of the polyfunctional monomer (b3) and the monofunctional monomer (b4) is 1 to 20% by weight, and 5 to 15% by weight. Is preferred.
The polymer formed from the polyfunctional monomer (b3) and the monofunctional monomer (b4) protects the encapsulated crosslinking agent (b1) as the shell portion of the microcapsule (B). Therefore, if the polyfunctional monomer (b3) is too small, the strength of the shell is insufficient, and the encapsulated crosslinking agent (b1) cannot be protected over a long period of time. On the other hand, when there are too many polyfunctional monomers (b3), when manufacturing the aqueous dispersion of a microcapsule (B), the whole dispersion will aggregate.

<4> The organic solvent (b2) dissolves only 20 parts by weight or less with respect to 100 parts by weight of water at 20 to 25 ° C., and the solubility is preferably 10 parts by weight or less.
The organic solvent (b2) is considered to be a component that assists the phase separation of the cross-linking agent (b1) from the polyfunctional monomer (b3) and the monofunctional monomer (b4) and transfer to the inside of the formed microcapsules. Therefore, it must be rich in poor water solubility.
Accordingly, the present inventor initially cannot diffuse the aqueous dispersion of the microcapsule (B) because the organic solvent (b2) diffuses into water when the solubility of the organic solvent (b2) in water is high. I thought. However, even when an organic solvent having a high solubility in water such as methanol is used, the microcapsule aqueous dispersion itself can be produced, and the microcapsule aqueous dispersion has a crosslinkable functional group described later. It has been found that the crosslinkable resin composition mixed with (A) does not thicken even when stored for a long time.

However, when a hydrophilic organic solvent such as methanol is used, the crosslinkable resin composition is excellent in viscosity stability, but the crosslinkable resin composition after long-term storage is equivalent to that before long-term storage. The performance of can not be demonstrated. Although the detailed mechanism is still unclear, when methanol is used, the cross-linking agent (b1) partially migrates from the microcapsule into the aqueous medium during the polymerization of the microcapsule, and water and the cross-linking agent ( It is considered that the breaking strength of the microcapsules increases due to the reaction of b1).
Therefore, in order to maintain the function of the crosslinking agent (b1) encapsulated in the microcapsule for a long time and to exhibit the same as in the initial stage, the organic solvent (b2) used at the time of producing the microcapsule is not rich in water solubility. It should be at most 20% by weight soluble in 100 parts by weight of water at 20-25 ° C.

  As an organic solvent (b) having a solubility of 20 parts by weight or less with respect to 100 parts by weight of water at 20 to 25 ° C., n-butanol (7.2% by weight), cyclohexane (0.01% by weight), toluene (0.05% by weight) and the like.

<5> It is important that the monofunctional monomer (b4) is a monomer capable of forming a polymer having a solubility of 1 part by weight or less with respect to 100 parts by weight of the organic solvent (b2) at 20 to 25 ° C.
The copolymer formed from the polyfunctional monomer (b3) and the monofunctional monomer (b4) serves as a shell part of the microcapsule (B), and the shell part is formed as described in <3> above. The main component is the functional monomer (b4). When the solubility of the polymer formed only from the monofunctional monomer (b4), excluding the polyfunctional monomer (b3), in the organic solvent (b) determines the ease of dissolution of the shell portion in the organic solvent (b) Conceivable. In addition, the organic solvent (b2) promotes the formation of the shell portion and is considered to be included inside the microcapsule together with the crosslinking agent (b1). Therefore, if the organic solvent (b) easily dissolves the shell portion, the encapsulated crosslinking agent (b1) cannot be sufficiently protected, and the microcapsules are considered to be fragile.

  Therefore, in the present invention, a polymer formed from only the monofunctional monomer (b4) is used as the monofunctional monomer (b4) for forming the shell portion so that the shell portion is not dissolved in the organic solvent (b2) as much as possible. It is important to use a monomer that does not dissolve in b2) as much as possible, specifically, a monomer capable of forming a polymer having a solubility of 1 part by weight or less with respect to 100 parts by weight of the organic solvent (b2) at 20 to 25 ° C. . In other words, it is important to select an organic solvent (b2) satisfying the condition <4> that is difficult to dissolve a polymer formed only from the monofunctional monomer (b4).

A uniform solution (b1) to (b4) that satisfies the conditions <1> to <5> above is dispersed in an aqueous solution containing a dispersion stabilizer, and the volume average particle diameter of the droplets is 0.1 to 10 μm. A liquid, preferably a 1-5 μm dispersion, is obtained. Droplets having a volume average particle diameter of 0.1 to 10 μm can be obtained by controlling the stirring conditions and the like according to a conventional method. Next, the monomers (b3) and (b4) are polymerized to obtain an aqueous dispersion of microcapsules (B) having a volume average particle diameter of 0.1 to 10 μm, preferably 1 to 5 μm.
When the volume average particle diameter of the microcapsules is less than 0.1 μm, the shell thickness of the microcapsules becomes thin, and the encapsulated crosslinking agent (b1) cannot be sufficiently protected, and the microcapsules are considered to be fragile. . On the other hand, when the volume average particle diameter of the microcapsules is larger than 10 μm, when the macrocapsule aqueous dispersion itself is stored for a long period of time, the resin (A) having a crosslinkable functional group and the macrocapsule aqueous dispersion were mixed. When the crosslinkable resin composition is stored for a long period of time, the microcapsules will settle in either case.

  The crosslinking agent (b1) will be described. The crosslinking agent (b1) is at least one functional selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, a glycidyl group, and a carbonyl group so that it can react with the resin (A) having a crosslinking functional group described later. It has a functional group that can react with the group. Examples of the crosslinking agent (b1) include carbodiimide crosslinking agents, epoxy crosslinking agents, amine crosslinking agents, aziridine crosslinking agents, chelate crosslinking agents, melamine crosslinking agents, and hydrazino crosslinking agents.

As the carbodiimide-based crosslinking agent, a high molecular weight polycarbodiimide produced by a decarboxylation condensation reaction of diisocyanate in the presence of a carbodiimidization catalyst can also be used.
Examples of such compounds include those obtained by decarboxylation condensation reaction of the following diisocyanates. As the diisocyanate, 4,4′-diphenylmethane diisocyanate, 3,3′-dimethoxy-4,4′-diphenylmethane diisocyanate, 3,3′-dimethyl-4,4′-diphenylmethane diisocyanate, 4,4′-diphenyl ether diisocyanate, 3,3′-dimethyl-4,4′-diphenyl ether diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, isophorone diisocyanate, 4,4′- One kind of dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate or a mixture thereof can be used. As the carbodiimidization catalyst, 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1-ethyl-3-methyl-2-phospholene-1-oxide, 1-ethyl- Phosphorene oxides such as 2-phospholene-1-oxide or their 3-phospholene isomers can be used.

  Epoxy crosslinking agents include bisphenol A-epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl. Ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane, etc. Can be mentioned.

  Examples of the amine-based crosslinking agent include aliphatic diamines, aliphatic polyamines, aliphatic polyamines containing aromatic rings, alicyclic and cyclic polyamines, aromatic primary amines and the like.

  Examples of the aziridine-based crosslinking agent include N, N′-hexamethylene-1,6-bis (1-aziridinecarboxamide), N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxyamide), tri Examples include methylolpropane-tri-β-aziridinylpropionate.

  As the oxazoline-based crosslinking agent, 2,2′-bis- (2-oxazoline), 2,2′-methylene-bis- (2-oxazoline), 2,2′-ethylene-bis- (2-oxazoline), 2,2′-trimethylene-bis- (2-oxazoline), 2,2′-tetramethylene-bis- (2-oxazoline), 2,2′-hexamethylene-bis- (2-oxazoline), 2,2 '-Octamethylene-bis- (2-oxazoline), 2,2'-ethylene-bis- (4,4'-dimethyl-2-oxazoline), 2,2'-p-phenylene-bis- (2-oxazoline) ), 2,2'-m-phenylene-bis- (4,4'-dimethyl-2-oxazoline), bis- (2-oxazolinylcyclohexane) sulfide, bis- (2-oxazolinyl norbornane) sulfide, etc. But It is shown.

  Examples of the chelate-based crosslinking agent include aluminum chelates such as aluminum tris (acetylacetonate); acetylacetone compounds such as titanium, zirconium, copper, cobalt, and zinc; and ammonia coordination compounds such as polyamine.

  The melamine-based crosslinking agent is a compound having a triazine ring in the molecule, and examples include melamine, benzoguanamine, cyclohexanecarboguanamine, methylguanamine, vinylguanamine, hexamethoxymethylmelamine, tetramethoxymethylbenzoguanamine and the like. These low-condensates, alkyl etherified formaldehyde resins and aminoplast resins may also be used.

  Examples of the hydrazino crosslinking agent include dihydrazides of polyvalent carboxylic acids having 1 to 18 carbon atoms such as succinic acid dihydrazide, adipic acid dihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, maleic acid dihydrazide, sebacic acid dihydrazide, and itaconic acid. Examples include dihydrazide, trimellitic acid di or trihydrazide, 1,3-bis (hydrazinocarboethyl) -5-isopropylhydantoin, and the like.

  The polyfunctional monomer (b3) will be described. Examples of the polyfunctional monomer include polymerizable unsaturated double bonds, specifically, polyfunctional monomers having 2 or more (especially 2 to 4) ethylenically unsaturated double bonds. Examples thereof include divinylbenzene, divinylbiphenyl, divinylnaphthalene, diallyl phthalate, triallyl cyanurate, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and the like. In particular, divinylbenzene, ethylene glycol dimethacrylate and the like are preferable, and divinylbenzene is most preferable. These can be used alone or in admixture of two or more.

  The monofunctional monomer (b4) will be described. Examples of monofunctional monomers include monovinyl aromatic monomers, acrylic monomers, vinyl ester monomers, vinyl ether monomers, monoolefin monomers, halogenated olefin monomers, A diolefin etc. are mentioned. These can be used alone or in admixture of two or more.

  Monovinyl aromatic monomers include monovinyl aromatic hydrocarbons, vinyl biphenyl optionally substituted with a lower (carbon number 1 to 4) alkyl group, and lower (carbon numbers 1 to 4) alkyl group. Specific examples thereof include styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, sodium styrenesulfonate, and the like. Can be mentioned. Furthermore, vinyl biphenyl which may be substituted with a lower alkyl group, and vinyl naphthalene which may be substituted with a lower alkyl group include vinyl biphenyl substituted with a lower alkyl group such as vinyl biphenyl, methyl group and ethyl group. And vinylnaphthalene substituted with a lower alkyl group such as vinylnaphthalene, methyl group, and ethyl group. These monovinyl aromatic monomers can be used alone or in combination of two or more.

  Examples of acrylic monomers include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, and acrylic acid. Examples include β-hydroxyethyl, γ-hydroxybutyl acrylate, δ-hydroxybutyl acrylate, β-hydroxyethyl methacrylate, γ-aminopropyl acrylate, γ-N acrylate, N-diethylaminopropyl, and the like.

Examples of vinyl ester monomers include vinyl formate, vinyl acetate, and vinyl propionate.
Examples of the vinyl ether monomer include vinyl methyl ether, vinyl ethyl ether, vinyl n-butyl ether, vinyl phenyl ether, vinyl cyclohexyl ether and the like.
Examples of the monoolefin monomer include ethylene, propylene, butene-1, pentene-1, 4-methylpentene-1, and the like.
Examples of the halogenated olefin monomer include vinyl chloride and vinylidene chloride.
Furthermore, diolefins such as butadiene, isoprene and chloroprene can also be included in the monofunctional monomer. These can be used alone or in admixture of two or more.

  The amount of the monomers (b3) and (4) to be used can be appropriately selected according to the average particle diameter of the microcapsules, the thickness of the shell, the inner diameter, etc. Generally, the crosslinking agent (b1) and the organic solvent (b2) The total amount is preferably 1 to 100 parts by weight, more preferably about 3 to 70 parts by weight, and particularly preferably 5 to 50 parts by weight.

  The polymerization initiator will be described. The polymerization initiator used in the present invention starts polymerization of the monomer component in the droplets, and oil-soluble polymerization initiators can be widely used. For example, azo compounds such as azobisisobutyronitrile which is a radical polymerization initiator, cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, di-t-butyl peroxide, benzoyl peroxide, lauroyl peroxide, etc. Those soluble in monomers such as peroxides. Moreover, you may use the photoinitiator which starts superposition | polymerization by light, such as an ultraviolet-ray. Such a photopolymerization initiator is not particularly limited as long as it is oil-soluble, and includes those conventionally used.

  The amount of the polymerization initiator used is preferably about 0.5 to 10 parts by weight, particularly about 1 to 5 parts by weight, based on 100 parts by weight of the total monomer components.

The method for producing the aqueous dispersion of the microcapsule (B) of the present invention will be described more specifically.
A homogeneous solution containing a crosslinking agent (b1), an organic solvent (b2), monomer components (b3), (b4) and a polymerization initiator is obtained.
Separately, an aqueous solution of a dispersion stabilizer is obtained. What is necessary is just to select suitably the density | concentration of the dispersion stabilizer in the aqueous solution of a dispersion stabilizer so that it may become a density | concentration which the droplet of the said uniform solution does not unite. In general, the dispersion stabilizer is preferably adjusted to about 0.05 to 50 parts by weight, particularly about 0.1 to 10 parts by weight with respect to 100 parts by weight of water.

  It is preferable that about 1 to 200 parts by weight of the homogeneous solution containing the crosslinking agent (b1), the organic solvent (b2) and the like is dispersed per 100 parts by weight of the aqueous solution of the dispersion stabilizer. It is more preferable to disperse to a certain extent.

  As the dispersion method, various known methods such as a dispersion method using mechanical shearing force such as a homogenizer or a membrane emulsification method can be employed. The temperature condition during the dispersion is not limited as long as it is equal to or lower than the temperature that affects the decomposition of the target component and initiator used, but it is preferably about 0 to 40 ° C.

  As described above, the volume average particle size of the dispersed droplets is 0.1 to 10 μm, and preferably 0.5 to 5 μm. The viscosity of the homogeneous solution consisting of the crosslinking agent (b1), the organic solvent (b2), the monomer component, and the initiator, the amount of dispersion stabilizer used, the viscosity of the dispersion stabilizer aqueous solution, the dispersion method and dispersion conditions are appropriately set within the above ranges. By doing so, the average particle diameter of the droplets in the above range is obtained. In order to use in suspension polymerization an aqueous solution of a dispersion stabilizer in which a homogeneous solution composed of a crosslinking agent (b1), an organic solvent (b2), a monomer component, and an initiator is dispersed, the aqueous solution is heated while stirring. Good.

  The heating temperature is particularly a temperature that allows the monomer component to be polymerized by the initiator in a droplet of a uniform solution composed of the crosslinking agent (b1), the organic solvent (b2), the monomer component, and the initiator. Although not limited, generally, about 30 to 100 ° C, particularly about 40 to 90 ° C is preferable.

  Suspension polymerization is performed until a desired target component-encapsulated fine particle is obtained. The time required for the suspension polymerization varies depending on the purpose component, the monomer component and the type of initiator used, but is generally about 3 to 48 hours.

  The suspension polymerization is preferably performed in an inert gas atmosphere such as nitrogen gas or argon gas.

  As the polymerization of the monomer component proceeds, the presence of the cross-linking agent (b1) and the organic solvent (b2) causes the polymer to be formed to be separated to the aqueous phase side, and as a result, a shell, that is, a shell composed of the polymer is formed. The On the other hand, the core part is in a state in which the crosslinking agent (b1) and the organic solvent (b2) are included.

  When the crosslinking agent (b1) is solid at room temperature, it is dissolved in the organic solvent (b2) and the monomer components (b3) and (b4) at the initial stage of polymerization. However, as the polymerization of the monomer components proceeds, the microcapsules There is a tendency to deposit inside.

Next, utilization of the aqueous dispersion of microcapsules (B) obtained by the above production method will be described.
That is, the aqueous dispersion of the microcapsule (B) is mixed with a resin (A) having at least one crosslinkable functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, a glycidyl group, and a carbonyl group. By doing so, it is possible to obtain a crosslinkable resin composition that can be used for various purposes and applications such as paints and adhesives.
As the resin (A) having a crosslinkable functional group, a known resin can be used as long as it has the functional group capable of reacting with the crosslinker (b1) in the microcapsule (B). In particular, an acrylic resin, a polyester resin, an epoxy resin, and a polyurethane resin are preferable.

The acrylic resin having the functional group can be obtained by polymerizing the monomer having the functional group as an essential component.
Examples of the acrylic resin include polymerizable unsaturated carboxylic acids such as (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid or anhydrides thereof, methyl (meth) acrylate, and ethyl (meth) acrylate. , (Meth) acrylic acid esters such as butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylamide (Meth) acrylic monomers other than (meth) acrylic acid such as acrylontolyl and, if necessary, styrene, α-methylstyrene, vinyl acetate and the like by copolymerization methods such as milk polymerization, solution polymerization and bulk polymerization. An acrylic resin obtained by polymerization may be mentioned.

  As the epoxy resin, the epoxy resin is not particularly limited as long as it is a compound having two or more epoxy groups in one molecule, but glycidyl ether type epoxy resin, for example, glycidyl ether of bisphenol A, glycidyl ether of bisphenol F, Resorcin glycidyl ether, glycerin glycidyl ether, polyalkylene oxide glycidyl ether, brominated bisphenol A glycidyl ether and oligomers thereof, phenolic novolac glycidyl ether and the like, phenols, orthocresols and And / or epoxidized products of condensates of naphthols and the like with formalins, aliphatic and aromatic aldehydes or ketones, alicyclic epoxy resins such as alicyclic diepoxy Tar, alicyclic diepoxy adipate, alicyclic diepoxy carboxylate and the like.

  Examples of the polyester-based resin include a polyester resin obtained by chain-extending a glycol or a polyester glycol having a terminal hydroxyl group and a tetracarboxylic dianhydride by a selective monoesterification reaction.

  As the polyurethane-based resin, for example, a urethane-based prepolymer obtained from an isocyanate compound, polyols and / or amino acids and polyols is reacted with a basic organic compound and an extender in the presence of a solvent and / or water, And a polyurethane resin obtained by removing the solvent under reduced pressure.

  The resin (A) having a crosslinkable functional group can be used in a state dissolved in an organic solvent, or in a state dissolved or dispersed in water, but storage stability after mixing the aqueous dispersion of microcapsules (B). From the viewpoint of properties, it is preferably used in a state dissolved or dispersed in water.

  In the present invention, an acrylic resin is preferably used as the resin (A) having a crosslinkable functional group, and when an acrylic resin having a glass transition temperature of −60 to 0 ° C. is used, The crosslinkable resin composition can be used as a pressure sensitive adhesive.

A pressure-sensitive adhesive sheet can be obtained using the crosslinkable resin composition for pressure-sensitive adhesives of the present invention. That is, the crosslinkable resin composition for pressure-sensitive adhesive is applied to at least one surface of the sheet-like base material, and dried under conditions that can break the microcapsule (B). By destroying and reacting the resin (A) having a crosslinkable functional group and the crosslinking agent (b1), a pressure-sensitive adhesive layer can be formed on at least one surface of the sheet-like substrate.
The microcapsules (B) in the aqueous dispersion of microcapsules (B) produced by the production method of the present invention are destroyed mainly by heating. In many cases, the pressure-sensitive adhesive applied to the sheet-like base material is dried and reacted with the main agent and the cross-linking agent at around 100 ° C., and further proceeds with the reaction between the main agent and the cross-linking agent at around room temperature. (Aging) A pressure-sensitive adhesive sheet is obtained. The pressure-sensitive adhesive using the microcapsule (B) according to the production method of the present invention does not thicken even when stored for a long time, does not require special conditions such as special high temperature and high pressure, and pressure-sensitive adhesive It is possible to provide a pressure-sensitive adhesive sheet in which the main agent and the cross-linking agent are reacted under general production conditions of the sheet, that is, by drying and curing at around 100 ° C.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited only to a following example. The following “parts” and “%” are values based on weight.

Example 1
Carbodilite V-05 (carbodiimide-based crosslinking agent, solid content: 100%, manufactured by Nisshinbo Co., Ltd.) 108 g as the crosslinking agent (b1), n-butanol (solubility in water: 7.2%) as the organic solvent (b2): 12 g Then, 3 g of divinylbenzene as the polyfunctional monomer (b3), 27 g of styrene as the monofunctional monomer (b4), and 0.3 g of benzoyl peroxide (purity 70%) as the polymerization initiator were mixed to obtain a uniform solution. In addition, the solubility with respect to 100 parts of n-butanol of polystyrene (molecular weight 100,000) is less than 0.1 part.
As a dispersion stabilizer, polyvinyl alcohol (polymerization degree 1700, saponification degree 88%): 7.5 g of water is dissolved in 236.7 g of water, and the homogeneous solution is added to the solution at room temperature using a homogenizer. Stirring was performed at a stirring speed of 8000 rpm for 5 minutes to obtain a suspension having a volume average particle diameter of 1 μm.

Next, the suspension was placed in a 2 L four-necked flask equipped with a reflux condenser, a stirrer, a thermometer, a nitrogen inlet tube, and a raw material inlet under a nitrogen gas atmosphere, and nitrogen was introduced. While stirring, the mixture was heated to 80 ° C. and subjected to suspension polymerization for 6 hours to obtain an aqueous dispersion of microcapsules (B) having a volume average particle diameter of 1 μm (solid content: about 37%).
The average particle size of the pre-polymerization droplets containing the crosslinking agent (b1) and the like and the dispersed particles of the aqueous dispersion of the microcapsules (B) after the polymerization are volume average particles determined by a dynamic light scattering method. Is the diameter.

  As the resin (A) having a crosslinkable functional group, an aqueous dispersion of an acrylic resin having a carboxyl group-containing glass transition temperature of −50 ° C. is used in a solid content of 100 parts, and superester E650 which is a tackifying resin is used for this. The aqueous dispersion of 8.9 parts and the prepared microcapsule (B) was blended so as to have a solid content of 2 parts to obtain an aqueous pressure-sensitive adhesive composition having a solid content of about 60%.

[Examples 2 to 6]
An aqueous pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that the raw materials used for the production of the microcapsule (B) were changed to the formulation shown in Table 1.

[Comparative Example 1]
An aqueous dispersion of microcapsules (B) was obtained in the same manner as in Example 1 except that no polyfunctional monomer (b3) was used, and an aqueous pressure-sensitive adhesive composition was obtained in the same manner.

[Comparative Example 2]
An aqueous dispersion of microcapsules (B) was obtained in the same manner as in Example 1 except that the polyfunctional monomer (b3) was 70% by weight in 100% by weight of the total monomers. Since the polymerization stability was lowered and the particles were coalesced and aggregated, an aqueous pressure-sensitive adhesive composition could not be obtained.

[Comparative Examples 3 and 4]
Instead of the aqueous dispersion of microcapsules obtained in Example 1, in Comparative Example 3, in order to increase the solid content concentration of the aqueous dispersion, half of the water was withdrawn before stirring and stirred at room temperature using a homogenizer. An aqueous dispersion of microcapsules (B) having a volume average particle size of 0.05 μm obtained by adding water extracted after stirring at a speed of 13,000 rpm for 5 minutes was used in Comparative Example 4 at room temperature using a homogenizer. An aqueous pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that each of the microcapsule (B) aqueous dispersions having a volume average particle size of 50 μm obtained by stirring at 2000 rpm for 5 minutes was used. It was.

[Comparative Examples 5 to 7]
Instead of n-butanol, which was used in obtaining the aqueous dispersion of microcapsules in Example 1,
In Comparative Example 5, toluene (solubility 0.05 part in 100 parts of water, polystyrene (molecular weight: 100,000) solubility in 100 parts of toluene 10 parts or more),
In Comparative Example 6, isoamyl acetate (solubility 0.2 part in 100 parts water, polystyrene (molecular weight: 100,000) solubility in 100 parts isoamyl acetate 100 parts or more),
In Comparative Example 7, methanol (more than 50 parts solubility in 100 parts water, less than 0.1 part solubility in polystyrene (molecular weight: 100,000) in 100 parts methanol)
An aqueous dispersion of microcapsules (B) was obtained in the same manner as in Example 1 except that each was used, and an aqueous pressure-sensitive adhesive composition was obtained in the same manner.

[Comparative Example 8]
Carrying out except that 2 parts of carbodilite V-04 (carbodiimide-based water-soluble crosslinking agent, active ingredient 40%, manufactured by Nisshinbo Co., Ltd.) was used as an active ingredient instead of the aqueous dispersion of microcapsules obtained in Example 1. An aqueous pressure-sensitive adhesive composition was obtained in the same manner as in Example 1.

[Comparative Example 9]
An aqueous pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that the aqueous dispersion of microcapsules obtained in Example 1 was not used.

<Viscosity stability test>
The aqueous pressure-sensitive adhesive composition was allowed to stand in an oven at 40 ° C. for 1 month, and the change in viscosity was examined. When there was no change in viscosity, it was marked as ◯, and when gelled, it was marked as x. In the case where there was no change in viscosity, the evaluation was further conducted by a temperature rising holding force test. The evaluation results are shown in Table 1.

The aqueous pressure-sensitive adhesive composition obtained in each example and comparative example was coated on a release paper with an applicator so as to have a dry film thickness of 60 g / m ² , dried in a drying oven at 100 ° C. for 3 minutes, and adhered. The agent layer (1) was formed.

Next, a 50 μm-thick polyethylene terephthalate (hereinafter referred to as PET) was bonded to the pressure-sensitive adhesive layer provided on the release paper to obtain a laminate having a configuration of “release paper / pressure-sensitive adhesive layer (1) / PET”. .
The resulting laminate was left to stand for 24 hours or more in a 23 ° C.-65% RH atmosphere to complete the crosslinking reaction of the pressure-sensitive adhesive layer (1) to obtain a pressure-sensitive adhesive sheet.

[Evaluation of adhesive sheet]
<Initial temperature retention test after storage at 40 ° C. for 1 month>
The obtained adhesive sheet is cut into strips each having a width of 25 mm and a length of 100 mm, the release paper is peeled off, and a portion of 25 mm width × 80 mm length is bonded to a stainless steel plate (hereinafter abbreviated as “SUS plate”). A sample for measurement was obtained by reciprocating once with a 2 kg roll.
The obtained sample for measurement was left in an atmosphere of 23 ° C.-50% RH for 24 hours, and a weight of 310 g was hung on the end of the adhesive sheet where it was not pasted, at a rate of 3 ° C./5 min. The temperature was raised from ℃ to 152 ℃, and the temperature at which the SUS plate was peeled off was measured. When the acrylic resin having a carboxyl group and the crosslinking agent (b1) in the microcapsule (B) react when obtaining the pressure-sensitive adhesive sheet, a crosslinked structure is formed in the pressure-sensitive adhesive layer, so that the pressure-sensitive type Heat resistance as an adhesive sheet can be secured. The above evaluation results are shown in Table 1.

  Comparative Example 9 is a case where no cross-linking agent is contained, and the viscosity of the aqueous pressure-sensitive adhesive composition does not change even after long-term storage, but the sensitivity is not affected either before or after long-term storage. The heat resistance as a pressure type adhesive sheet cannot be exhibited.

  On the other hand, as shown in Comparative Example 8, when a cross-linking agent is included, before the aqueous pressure-sensitive adhesive composition is stored for a long period of time, when a pressure-sensitive adhesive sheet is obtained, a cross-linked structure is present in the pressure-sensitive adhesive layer. Since it is formed, heat resistance as a pressure-sensitive adhesive sheet can be secured. However, in the case of Comparative Example 8, unlike the microcapsules of the present invention, since the crosslinking agent is not protected by a protective wall, the viscosity change as an aqueous pressure-sensitive adhesive composition is significant, and after storage for a long time, it is no longer necessary. The coating could not be performed, and the pressure-sensitive adhesive sheet itself could not be obtained.

  In Comparative Example 1, since the shell constituting the microcapsule does not have a crosslinked structure of the polyfunctional monomer (b3), the function as a protective wall is weak with respect to the crosslinking agent (b1), and the same results as in Comparative Example 8 Presents.

  Comparative Example 3 is a case where the volume average particle diameter of the microcapsules is small. Since the shell thickness of the microcapsule is reduced, the encapsulated crosslinking agent (b1) cannot be sufficiently protected, and the same result as in Comparative Example 8 is obtained.

On the other hand, Comparative Example 4 is a case where the volume average particle diameter of the microcapsules is large. Even if the volume average particle size of the microcapsules is large, a cross-linked structure is formed in the pressure-sensitive adhesive layer when the pressure-sensitive adhesive sheet is obtained before long-term storage of the water-based pressure-sensitive adhesive composition. The heat resistance as a pressure-sensitive adhesive sheet can be secured.
However, when the macrocapsule aqueous dispersion itself is stored for a long time, the crosslinkable resin composition obtained by mixing the resin (A) having a crosslinkable functional group and the macrocapsule aqueous dispersion is stored for a long time. Also, the microcapsules will settle. As a result of sedimentation, when the macrocapsule aqueous dispersion itself is stored for a long period of time, the microcapsules that have settled cannot be redispersed and cannot be mixed with the adhesive. On the other hand, when the crosslinkable resin composition mixed with the aqueous dispersion of macrocapsules is stored for a long time, the microcapsules in the pressure-sensitive adhesive have settled, so the pressure-sensitive adhesive partially gels, It can no longer be applied.

In Comparative Examples 5 and 6, when obtaining microcapsules, toluene or isoamyl acetate having a low solubility in water was used instead of n-butanol. The organic solvent (b2) is considered to have a function of assisting the cross-linking agent (b1) to migrate to the inside of the formed microcapsule at the time of shell formation accompanying polymerization. It is considered preferable to be rich in.
However, as shown in Comparative Example 5, when the aqueous pressure-sensitive adhesive composition is stored for a long period of time, the heat resistance as a pressure-sensitive adhesive sheet cannot be secured. I thought that the shell that protected the cross-linking agent (b1) was destroyed during storage and the cross-linking agent (b1) was deactivated, but the encapsulated cross-linking agent (b1) was The protection by the shell is supported by the absence of viscosity change.

  A poorly water-soluble organic solvent such as toluene can be used from the viewpoint of producing the microcapsules themselves. However, on the other hand, since it has a high affinity for the shell mainly composed of polystyrene, although the shell is crosslinked by the polyfunctional monomer (b3), a part of the shell is gradually dissolved by the encapsulated toluene, A part of the crosslinking agent (b1) leaks to the outside. When the crosslinking agent (b1) quickly leaks out of the microcapsule as in Comparative Example 1, a marked increase in viscosity of the aqueous pressure-sensitive adhesive composition is observed. Since b1) gradually leaks, it is considered that the carbodiimide leaked to the outside of the microcapsule reacts with water and the shell is reinforced by the product. Therefore, after long-term storage, the microcapsules are not destroyed at a general temperature of about 100 ° C. when obtaining a pressure-sensitive adhesive sheet, and it is considered that heat resistance as a pressure-sensitive adhesive sheet cannot be secured. Is done.

In Comparative Example 7, when microcapsules were obtained, methanol having high water solubility was used instead of n-butanol. It was thought that the production of microcapsules requires a poorly water-soluble organic solvent. Surprisingly, however, an aqueous dispersion of microcapsules itself can be produced using an organic solvent having a high solubility in water such as methanol, and the aqueous pressure-sensitive adhesive composition can be stored for a long period of time. Also does not thicken.
However, the water-based pressure-sensitive adhesive composition after long-term storage cannot exhibit the same performance as that before long-term storage. Although the detailed mechanism is still unclear, when methanol is used, the cross-linking agent (b1) partially migrates from the microcapsule into the aqueous medium during the polymerization of the microcapsule, and water and the cross-linking agent ( It is considered that the breaking strength of the microcapsules increases due to the reaction of b1).

  As described above, the aqueous dispersion of microcapsules having a long pot life in the true sense, which is excellent not only in viscosity stability but also in terms of performance in terms of long-term storage, satisfies the conditions <1> to <5> It is necessary to have a specific volume average particle diameter obtained by a production method that satisfies the above.

  The aqueous dispersion of microcapsules produced by the production method of the present invention is useful as a crosslinking agent for pressure-sensitive adhesive compositions, and can also be used for various crosslinking resin compositions such as other adhesives and paints.

Claims (7)

In the aqueous dispersion stabilizer solution, a crosslinking agent (b1), an organic solvent (b2), a polyfunctional monomer (b3) having two or more polymerizable unsaturated double bonds, and a single monomer having one polymerizable unsaturated double bond. Dispersing a homogeneous solution containing the functional monomer (b4) and the polymerization initiator to obtain a dispersion having a volume average particle size of droplets of 0.1 to 10 μm, then polymerizing the monomers (b3) and (b4),
A method for producing an aqueous dispersion of microcapsules (B) having a volume average particle size of 0.1 to 10 μm, wherein a crosslinking agent (b1) is encapsulated in a polymer shell formed from the monomers (b3) and (b4). Because
<1> The dispersion stabilizer is 0.1 to 10 weights with respect to a total of 100 parts by weight of the crosslinking agent (b1), the organic solvent (b2), the polyfunctional monomer (b3), and the monofunctional monomer (b4). And the cross-linking agent (b1) has a functional group capable of reacting with at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, a glycidyl group, and a carbonyl group. And <3> the content of the polyfunctional monomer (b3) in a total of 100 wt% of the polyfunctional monomer (b3) and the monofunctional monomer (b4) is 1 to 20 wt%, and <4> The solubility of the organic solvent (b2) in 100 parts by weight of water at 20 to 25 ° C. is 20 parts by weight or less, and
<5> The monofunctional monomer (b4) is a monomer capable of forming a polymer having a solubility of 1 part by weight or less with respect to 100 parts by weight of the organic solvent (b2) at 20 to 25 ° C. A method for producing an aqueous dispersion of microcapsules (B).   An aqueous dispersion of microcapsules (B) obtained by the production method according to claim 1.   An aqueous dispersion of a resin (A) having at least one crosslinkable functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, a glycidyl group and a carbonyl group, and the microcapsule (B) according to claim 2. A crosslinkable resin composition to be contained.   The crosslinkable resin composition according to claim 3, wherein the resin (A) having a crosslinkable functional group is an acrylic resin.   The crosslinkable resin composition according to claim 4, wherein the acrylic resin has a glass transition temperature of -60 to 0 ° C and is used for a pressure-sensitive adhesive.   A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the crosslinkable resin composition for a pressure-sensitive adhesive according to claim 5 on at least one surface of the sheet-like substrate.   The crosslinkable resin composition for pressure-sensitive adhesive according to claim 5 is applied to at least one surface of the sheet-like substrate, and dried under conditions that can break the microcapsule (B). And a resin (A) having a crosslinkable functional group is allowed to react with the crosslinking agent (b1).