JP2010149024A - Method of manufacturing microcapsule, microcapsule and optical sheet and skin material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a microcapsule having excellent dispersibility in a solvent and excellent elasticity, a microcapsule manufactured by the method, a resin composition for forming a coating film, a coating film, and an optical sheet and a skin material. <P>SOLUTION: The method of manufacturing a microcapsule consisting of a shell having a single-pore structure and involving a core agent includes a process of preparing an emulsion dispersed with droplets consisting of a monomer solution involving a non-polymerizable substance and a process of polymerizing the monomer in the monomer solution. The monomer solution contains 55-90 wt.% of a trifunctional or higher cross-linking monomer(s) with respect to the total amount of monomer ingredients. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a method for producing microcapsules having excellent dispersibility in a solvent and excellent elasticity. Moreover, this invention relates to the microcapsule manufactured by the manufacturing method of this microcapsule, the resin composition for coating-film formation, a coating film, an optical sheet, and a skin material.

Conventionally, hollow particles having voids inside the particles have been reduced in weight, pore formation, heat insulation, sound insulation, low dielectric property, impact resistance, rigidity improvement, texture improvement, anti-sink, paintability, etc. Various molded products such as injection molded products, extruded molded products, hollow molded products, film molded products, etc. for improvement, wallpaper, paints, sealing agents, adhesives, shoe soles, synthetic leather, tires, paper, cement, tiles, building materials It is used in a very wide range of fields such as artificial wood, FRP, and porous ceramic filters.

As such hollow particles, conventionally, foams mainly composed of inorganic microballoons such as glass balloons and shirasu balloons, and thermoplastic polymers having gas barrier properties such as nitrile polymers and vinylidene chloride as described in Patent Document 1. Resin fine particles, thermoplastic hollow resin particles described in Patent Document 2, and the like are known.

Moreover, hollow particles are also used when a porous coating film is further formed on a substrate such as a sheet-like molded body, or when sheet-like molded bodies such as wallpaper are bonded together. Specifically, a method is known in which a slurry in which hollow particles having no liquid impregnation property are dispersed in an aqueous medium is prepared, the slurry is applied to a substrate, and the aqueous medium is dried. When such a method is used, it is possible to impart performance such as heat insulation and cushioning properties to the base material.

However, in such a method, the hollow particles are suspended in the slurry at the time of coating, so that the dispersibility of the hollow particles is impaired. There was a problem that the pores of the coating became non-uniform.

On the other hand, in order to maintain the dispersibility of the particles in the slurry, after applying the slurry in which the foamed resin particles before heat expansion are dispersed, the slurry is dried and heated to form a porous coating film. Although a method has also been proposed, there has been a problem that the surface smoothness of the coating film deteriorates due to foaming of the particles, and only a sheet with poor design can be obtained.

Furthermore, a method using a liquid-encapsulated microcapsule that encloses a liquid that can be removed in the drying step instead of the hollow particles has been studied.
However, for example, when using the heat storage particles described in Patent Document 3, it is impossible to completely remove the encapsulated liquid in the drying process. Either the vacancy state of the coating film obtained after the drying step or the smoothness of the surface is insufficient, and it cannot be suitably used for the various applications described above.

Patent Document 4 describes hollow polymer fine particles whose shell is made of a polymer of a crosslinkable monomer. However, such hollow polymer fine particles have a high porosity, but have a too high degree of cross-linking of the shell, so that the rigidity becomes too high and they tend to be crushed or deformed. Therefore, when various molded bodies, coating films, and the like are produced using the obtained hollow polymer fine particles, the desired rigidity improving effect and flexibility have not been sufficiently realized.
JP-A-5-285376 JP 2001-213727 A JP-A-5-237368 Japanese Patent No. 3600845

In view of the above-described present situation, an object of the present invention is to provide a method for producing a microcapsule that is excellent in dispersibility in a solvent and has excellent elasticity. Another object of the present invention is to provide a microcapsule, a resin composition for forming a coating film, a coating film, an optical sheet and a skin material produced by the method for producing the microcapsule.

The present invention is a method for producing a microcapsule in which a core agent is encapsulated in a shell having a single pore structure, and a step of preparing an emulsion in which droplets composed of a monomer solution encapsulating a non-polymerizable substance are dispersed. And a step of polymerizing monomers in the monomer solution, wherein the monomer solution is a method for producing microcapsules containing 55 to 90% by weight of a trifunctional or higher functional crosslinkable monomer with respect to all monomer components.
The present invention is described in detail below.

In the method for producing a microcapsule of the present invention, first, a step of preparing an emulsion in which droplets composed of a monomer solution containing a non-polymerizable substance are dispersed.
As a method for preparing an emulsion in which droplets composed of a monomer solution containing the non-polymerizable substance are dispersed, for example, the monomer solution is prepared by adding the non-polymerizable substance to the monomer solution and stirring. Preparing a primary emulsion in which droplets of the non-polymerizable substance are dispersed, and then adding the obtained primary emulsion to a solution insoluble in the monomer solution and stirring the monomer. Examples thereof include a method of preparing a secondary emulsion (so-called W / O / W emulsion) in which droplets composed of a monomer solution containing the non-polymerizable substance are dispersed in a solution insoluble in the solution.

The monomer solution contains 55 to 90% by weight of a trifunctional or higher functional crosslinkable monomer with respect to all monomer components. By containing 55 to 90% by weight of the trifunctional or higher crosslinkable monomer, a moderately crosslinked shell can be formed, and as a result, a microcapsule having excellent elasticity can be produced.
When the addition amount of the trifunctional or higher functional crosslinkable monomer is less than 55% by weight based on the total monomer components, the resulting microcapsule shell is insufficiently crosslinked, resulting in insufficient strength. It is not possible to produce a microcapsule having a shell of Further, when heating or the like is performed, crushing or sag occurs, or the particles undergo thermal expansion due to the volatilized core agent. When the addition amount of the trifunctional or higher functional crosslinkable monomer exceeds 90% by weight with respect to the total monomer components, the crosslinking of the shell proceeds excessively, the elasticity of the resulting microcapsules is impaired, and it tends to be crushed.
The addition amount of the trifunctional or higher functional crosslinking monomer is preferably 60% by weight and preferably 88% by weight with respect to all monomer components.

Examples of the trifunctional or higher functional crosslinkable monomer include a crosslinkable monomer having three or more polymerizable unsaturated bonds. Examples of the crosslinkable monomer having three or more polymerizable unsaturated bonds include trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolpropane tetra (meth) acrylate, triallyl isocyanate. Examples thereof include nurate and derivatives thereof, pentaerythritol triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate.
These trifunctional or higher functional crosslinkable monomers may be used alone or in combination of two or more.

The monomer solution preferably contains a polymerizable monomer such as a monofunctional monomer or a bifunctional monomer in addition to the trifunctional or higher functional crosslinkable monomer.

Examples of the monofunctional monomer include carboxylic acids having a polymerizable unsaturated bond such as (meth) acrylic acid, itaconic acid, fumaric acid, crotonic acid and maleic acid, carboxylic acid esters and carboxylates, 2- Sulfonic acids having polymerizable unsaturated bonds such as (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, vinylsulfonic acid and styrenesulfonic acid , Sulfonic acid esters and sulfonates, (meth) acrylamide, N-substituted (meth) acrylamide, (meth) acrylonitrile, polyoxyethylene glycol (meth) acrylate, polyoxypropylene glycol (meth) acrylate, hydroxyethyl (meta ) Acrylate, H Rokishipuropiru (meth) acrylate, N- vinylpyrrolidone and the like. These monofunctional monomers may be used alone or in combination of two or more.

Examples of the bifunctional monomer include ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (Meth) acrylate, diallyl phthalate and its isomers, divinylbenzene and the like.

The non-polymerizable substance is liquid at the reaction temperature of the tri- or higher functional crosslinkable monomer and the polymerizable monomer, is not polymerized by the polymerization reaction, and can be easily evaporated by heating or the like. If it is, it will not specifically limit, For example, n-pentane, n-hexane, cyclohexane, n-heptane, n-octane, isooctane, benzene, toluene, xylene, water, dichloromethane, chloroform, methanol, ethanol, n-propanol, Isopropyl alcohol, 1-butanol, 2-butanol, isobutyl alcohol, t-butyl alcohol, n-pentanol, isopentyl alcohol, neopentyl alcohol, octanol, diethyl ether, dioxane, tetrahydrofuran, acetone, methyl ethyl ketone Methyl isobutyl ketone, cyclohexanone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, nitromethane, nitroethane, acetonitrile, aniline, 2-pyrrolidone, water and the like.

As for the addition amount of the non-polymerizable substance, a preferable lower limit is 100 parts by weight and a preferable upper limit is 1900 parts by weight with respect to 100 parts by weight of the monomer solution. If the amount of the non-polymerizable substance added is less than 100 parts by weight, the resulting microcapsule shell may be thick and the resulting microcapsule porosity may be reduced. If the amount of the non-polymerizable substance added exceeds 1900 parts by weight, the shape of the microcapsule may not be maintained, and the elasticity or strength may not be ensured.

The monomer solution preferably contains a polymerization initiator.
The polymerization initiator is not particularly limited and may be appropriately selected according to the type of monomer component used. For example, benzoyl peroxide, lauroyl peroxide, dibutyl peroxydicarbonate, α-cumylperoxyneodecano Organic peroxides such as ate, azo initiators such as azobisisobutyronitrile, and redox initiators.

The monomer solution preferably contains a lipophilic emulsifier. The lipophilic emulsifier has a role of further improving the emulsion stability of the obtained emulsion.
The lipophilic emulsifier is not particularly limited. For example, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, glycerin fatty acid ester, polyglycerin fatty acid ester, propylene glycol fatty acid ester, etc. Is mentioned.

As the solution insoluble with the monomer solution, the same non-polymerizable substance as that described above can be used. In addition, you may use a different thing from the said nonpolymerizable substance.

In the step of preparing an emulsion in which droplets composed of a monomer solution containing the non-polymerizable substance are dispersed, generation of new particles due to polymerization of the monomer in the monomer solution at a place other than oil droplets is suppressed. Therefore, an inorganic salt or a water-soluble polymerization inhibitor may be added to the monomer solution or a solution insoluble in the monomer solution.
The inorganic salt functions to reduce the solubility of the monomer component and suppress polymerization. Examples of the inorganic salt include sodium chloride, calcium chloride, sodium carbonate and the like. The water-soluble polymerization inhibitor is added for the purpose of suppressing polymerization in a solvent, and specific examples include sodium sulfite, copper chloride, iron chloride, titanium chloride, hydroquinone and the like.

In the step of preparing an emulsion in which droplets composed of a monomer solution containing the non-polymerizable substance are dispersed, the stirring method is not particularly limited, and examples thereof include a homomixer, a biomixer, an omni mixer, an ultrasonic homogenizer, The conventionally well-known method using a microfluidizer etc. is mentioned.

Next, in the method for producing microcapsules of the present invention, a step of polymerizing the monomers in the monomer solution is performed. Thereby, the shell part of the microcapsule is formed.
The method for polymerizing the monomer in the monomer solution is not particularly limited, and an optimum method may be selected as appropriate depending on the trifunctional or higher functional crosslinkable monomer and the type of the polymerizable monomer. Usually, heating is performed. Is preferred.

In the method for producing a microcapsule of the present invention, a microcapsule in which the non-polymerizable substance is encapsulated as a core agent in a shell having a single pore structure by performing a step of polymerizing the monomer in the monomer solution, Although a slurry dispersed in a monomer solution and an insoluble solution is obtained, a step of removing the monomer solution and the insoluble solution may be performed thereafter.
The method for removing the monomer solution and the insoluble solution is not particularly limited, and examples thereof include a method for drying by heating and a method for reducing the pressure of the entire system.

According to such a microcapsule production method of the present invention, a microcapsule in which a core agent is encapsulated in a shell having a single pore structure can be produced. Such microcapsules are also one aspect of the present invention.

The microcapsule of the present invention has a core agent.
Since the microcapsule of the present invention has the above core agent, it is excellent in dispersibility in a solvent and a composition as compared with hollow particles. Therefore, for example, after coating the base material with the resin composition for forming a coating film containing the microcapsules of the present invention, a desired coating film having uniform pores is obtained by removing the core agent by a drying process. Can be formed. However, after the core agent encapsulated in the microcapsules of the present invention is evaporated by heating or the like, a coating film-forming resin composition containing the obtained dry microcapsules is applied to a substrate, and a coating film is formed. It may be formed.
The core agent is not particularly limited as long as it can be easily evaporated by heating or the like. For example, the same core agent as that described above can be used.

The core agent has a preferable lower limit of boiling point of 30 ° C and a preferable upper limit of 200 ° C. If the boiling point is less than 30 ° C., the core agent will boil at room temperature, which may result in extremely poor handling properties. When the boiling point exceeds 200 ° C., for example, when forming a coating film using the microcapsules of the present invention, the boiling point is too high, so that the core agent is not completely removed in the drying step, and pore formation is insufficient. It may become. A more preferable lower limit of the boiling point of the core agent is 50 ° C., and a more preferable upper limit is 160 ° C.
In the present specification, the boiling point refers to the boiling point at 1 atm.

The minimum with preferable content of the said core agent in the microcapsule of this invention is 50 weight%. When the content of the core agent is less than 50% by weight, for example, when the microcapsule of the present invention is contained in a resin composition for forming a coating film, the microcapsule floats and the dispersibility of the microcapsule is remarkably high. It may be damaged. The upper limit with preferable content of the said core agent is 95 weight%.

The shell constituting the microcapsule of the present invention has a single-hole structure.
By having the single-hole structure, the void formed inside the shell is excellent in hermeticity, and when the microcapsule of the present invention is used for various applications, a binder component and other components are present in the void. It is possible to prevent problems such as penetration and a decrease in the percentage of holes.
In the present specification, the “single pore structure” refers to a structure having only one closed void, not including a plurality of voids such as a porous shape.

The material of the shell is a polymer obtained by polymerizing monomers in a monomer solution containing 55 to 90% by weight of the trifunctional or higher functional crosslinkable monomer with respect to all monomer components, and has a single-pore structure. It is not particularly limited as long as it can be achieved and an average particle diameter, an aspect ratio, and the like within the ranges described below can be realized. The shell material is a polymer obtained by polymerizing a monomer in a monomer solution containing 55 to 90% by weight of the trifunctional or higher functional crosslinkable monomer with respect to all monomer components, and is appropriately crosslinked. Therefore, the microcapsule of the present invention has excellent elasticity.
Examples of the material of the shell include a copolymer having a segment derived from the trifunctional or higher functional crosslinkable monomer and a segment derived from the polymerizable monomer.

The preferable lower limit of the average particle diameter of the microcapsules of the present invention is 1 μm, and the preferable upper limit is 20 μm. When the average particle diameter is less than 1 μm, aggregation of the microcapsules of the present invention may occur, resulting in poor handling. When the average particle diameter exceeds 20 μm, for example, when the coating film is formed using the microcapsules of the present invention, the smoothness of the coating film obtained may be lowered. The microcapsules of the present invention have a more preferable lower limit of the average particle diameter of 1.5 μm and a more preferable upper limit of 10 μm.

In the microcapsules of the present invention, the preferred lower limit of the aspect ratio (ratio of the length of the major axis to the length of the minor axis) is 1, and the preferred upper limit is 1.1. When the aspect ratio is out of the above range, for example, when a coating film is formed using the microcapsule of the present invention, the microcapsule may be crushed or sag in the process of forming the coating film, Smoothness may decrease. The more preferable lower limit of the aspect ratio of the microcapsule of the present invention is 1.00, and the more preferable upper limit is 1.05.
The aspect ratio is a value obtained by dividing the length of the major axis by the length of the minor axis. The closer the value is to 1, the closer the shape is to a true sphere.

The microcapsules of the present invention preferably have a change rate of the average particle diameter within 100 ± 5% after heating at a predetermined temperature of 30 to 200 ° C. for 10 minutes.
That the change rate of the average particle diameter is within 100 ± 5% means that the average particle diameter does not change without thermal expansion at 30 to 200 ° C. When a microcapsule that heats and expands at 30 to 200 ° C. is used, for example, the coating film on which the resin composition for forming a coating film containing the microcapsule is applied is dried to remove the core agent, and is porous. When obtaining a coating film, the smoothness of the coating film may be lost due to the expanded particles.
In addition, when heating at the predetermined temperature of 30-200 degreeC, the operating condition of the dryer for general sheets is applied about conditions other than the said temperature.

In the microcapsule of the present invention, the preferable lower limit of the compressive elastic modulus (hereinafter also referred to as 10% K value) when the diameter at 23 ° C. is displaced by 10% is 1 N / mm ² and the preferable upper limit is 1000 N / mm ² . When the 10% K value is less than 1 N / mm ² , for example, when a porous coating film is formed by coating a resin composition for forming a coating film containing microcapsules, The microcapsules may be crushed during the drying process. When the 10% K value exceeds 1000 N / mm ² , for example, when a coating film is formed using a microcapsule, the coating film loses its flexibility and the coating film is cracked or printed or embossed. When processing is performed, transferability may be deteriorated.

The 10% K value is a smooth end surface of a diamond column having a diameter of 50 μm using a micro compression tester (for example, “PCT-200” manufactured by Shimadzu Corporation), and the microcapsules are compressed at a compression speed of 0. It is a value obtained by compressing at 27 g / second and a maximum test load of 10 g and by the following formula.
10% K value ^{= (3 / √2) · F} · S -3/2 · R -1/2
In the formula, F represents a load value (kg) in 10% compression deformation of the microcapsule, S represents a compression displacement (mm) in 10% compression deformation of the microcapsule, and R represents a radius (mm) of the microcapsule. .

In the microcapsules of the present invention, the preferable lower limit of the porosity is 50% by volume, and the preferable upper limit is 95% by volume. When the porosity is less than 50% by volume, it may not be possible to sufficiently impart weight reduction, pore formation, heat insulation, sound insulation, cushioning, etc. to a molded body using the obtained microcapsules. . If the porosity exceeds 95% by volume, the shape of the microcapsule may not be maintained, and the strength may not be ensured.
In the present specification, the porosity means the volume ratio of the void portion excluding the core agent in the total volume of the microcapsule, for example, based on a photograph taken with a transmission electron microscope. It can be measured by measuring the average particle diameter (outer diameter) and average inner pore diameter, and calculating the ratio of the volume of the void portion to the volume of the microcapsule.

The resin composition for forming a coating film containing the microcapsule, binder resin and solvent of the present invention has, for example, a shape and distribution of pores when applied to a substrate and the core agent is removed by a drying process. It is possible to form a coating film that is uniform, has high surface roughness, has high definition, and is excellent in flexibility. Such a resin composition for forming a coating film is also one aspect of the present invention.
Moreover, the coating film which uses the resin composition for coating-film formation of this invention is also one of this invention.

In the resin composition for forming a coating film of the present invention, the preferable lower limit of the content of the microcapsules of the present invention is 5% by weight, and the preferable upper limit is 90% by weight. When the content of the microcapsule of the present invention is less than 5% by weight, the ratio of pores in the obtained coating film may be extremely low. When the content of the microcapsule of the present invention exceeds 90% by weight, the durability of the obtained coating film may be lowered.
Moreover, the minimum with preferable content of the said binder resin is 0.1 weight%, and a preferable upper limit is 30 weight%. When the content of the binder resin is less than 0.1% by weight, the durability of the obtained coating film may be lowered. If the content of the binder resin exceeds 30% by weight, the ratio of pores in the obtained coating film may be extremely low.

Although it does not specifically limit as a use of the resin composition for film formation of this invention, For example, the skin material used for the material for manufacturing the optical sheet used for the backlight unit etc. of a liquid crystal display, a vehicle interior material, etc. Materials for manufacturing are mentioned. The resin composition for forming a coating film of the present invention has the above microcapsules of the present invention having excellent dispersibility in the solvent and the composition, and excellent elasticity. When the agent is removed, it is possible to form a coating film having a uniform shape and distribution of pores, less surface irregularities, high definition, and excellent flexibility.

An optical sheet having a porous layer containing the microcapsules of the present invention is also one aspect of the present invention.

The optical sheet of the present invention has a porous layer containing the microcapsules of the present invention.
Since the porous layer contains the microcapsules of the present invention, the porous layer has uniform pores and a sufficiently low refractive index. Therefore, for example, when the porous layer is used in a backlight unit of a liquid crystal display, effects such as prevention of luminance reduction can be satisfactorily exhibited. Furthermore, since the porous layer contains the microcapsules of the present invention, it has excellent flexibility.

The porous layer preferably contains a binder resin for the purpose of dispersing the microcapsules of the present invention and for bonding with the microcapsules of the present invention or other layers described later.
The binder resin is not particularly limited as long as it is a transparent and film-forming material, and examples thereof include organic materials such as acrylic resins, polyurethanes, polyesters, fluorine resins, silicone resins, polyamideimides, and epoxy resins. Can be mentioned.

In the porous layer, the content of the binder resin is not particularly limited, but a preferable lower limit is 0.1 parts by weight and a preferable upper limit is 50 parts by weight with respect to 100 parts by weight of the microcapsules of the present invention. When the content of the binder resin is less than 0.1 parts by weight, the adhesion of the resulting porous layer may be lost, and the mechanical strength of the optical sheet of the present invention may be lowered. When the content of the binder resin exceeds 50 parts by weight, a porous layer having a sufficiently low refractive index may not be obtained.

The method for laminating the porous layer is not particularly limited. For example, the resin composition is prepared by dispersing the microcapsules of the present invention and the binder resin in a solvent, and the resin composition is prepared by a general preparation method. Examples of the method include preparing a coating liquid by performing a dispersion treatment, applying the coating liquid to a base material or another layer described later, and drying.

The optical sheet of the present invention preferably has a plurality of other layers in addition to the porous layer. The other layers are not particularly limited and may be appropriately selected according to the performance of the obtained optical sheet. Examples thereof include a prism layer, a light diffusion layer, and a polarizing film layer.

Furthermore, a skin material containing the microcapsules of the present invention is also one aspect of the present invention.
The skin material of the present invention has excellent flexibility because it contains the microcapsules of the present invention, and therefore can be used, for example, as a vehicle interior material, artificial leather, or the like.

The material constituting the skin material of the present invention is not particularly limited as long as it is a transparent and film-forming material. For example, soft polyvinyl chloride resin, polyvinyl chloride resin and acrylonitrile-butadiene-styrene copolymer And mixtures thereof, thermoplastic polyolefin resins, polyurethane resins, other thermoplastic resins, elastomers and the like.

The method for producing the skin material of the present invention is not particularly limited. For example, the resin composition is prepared by dispersing the microcapsules of the present invention and the above materials in a solvent, and the resin composition is prepared by a general preparation method. A method of forming a sheet by preparing a coating liquid by performing a dispersion treatment, applying the coating liquid to a substrate, and drying the coating liquid may be mentioned.

ADVANTAGE OF THE INVENTION According to this invention, while being excellent in the dispersibility in a solvent, the manufacturing method of the microcapsule which has the outstanding elasticity can be provided. Moreover, the microcapsule manufactured by the manufacturing method of this microcapsule, the resin composition for coating-film formation, a coating film, an optical sheet, and a skin material can be provided.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
(1) Preparation of microcapsules 60 parts by weight of trimethylolpropane triacrylate as a trifunctional or higher functional crosslinkable monomer and polyethylene glycol dimethacrylate (Polyoxyethylene unit number = 1, manufactured by NOF Corporation “Blenmer PDE-” 50R ") 40 parts by weight, azobisisobutyronitrile (AIBN) 0.25 part by weight as a polymerization initiator, and 2 parts by weight of glycerin monostearate as a lipophilic emulsifier are mixed and stirred to prepare a monomer solution. Prepared.

A sodium chloride-sodium nitrite aqueous solution was prepared by adding 1% by weight of sodium chloride to ion-exchanged water and 0.02% by weight of sodium nitrite as a water-soluble polymerization inhibitor. Next, 100 parts by weight of a sodium chloride-sodium nitrite aqueous solution was added to the obtained monomer solution, followed by stirring with a stirring and dispersing device to prepare a primary emulsion of water-in-oil (W / O) emulsion.

Thereafter, the obtained primary emulsion is added to 600 parts by weight of an ion exchange aqueous solution containing 1% by weight of polyvinyl alcohol (PVA) as a dispersant and 0.02% by weight of sodium nitrite as a water-soluble polymerization inhibitor. By stirring using a stirring and dispersing device, a secondary emulsion composed of a (W / O / W) type composite emulsion in which oil droplets enclosing water was dispersed in an aqueous medium was obtained.

Using a 20-liter polymerization vessel equipped with a stirrer, jacket, reflux condenser and thermometer, the inside of the polymerization vessel was depressurized and deoxygenated in the vessel, and then the atmosphere inside the polymerization vessel was changed to a nitrogen atmosphere by replacing with nitrogen. . Thereafter, the secondary emulsion was added all at once, and the polymerization vessel was heated to 60 ° C. to initiate polymerization. After polymerization for 4 hours, the temperature was raised to 80 ° C., and after an aging period of 1 hour, the polymerization vessel was cooled to room temperature to obtain a slurry containing water-encapsulated microcapsules. The solvent of the obtained slurry was replaced with isopropanol (IPA) using a centrifuge, and an isopropanol (IPA) dispersion slurry of water-encapsulated microcapsules was obtained.

(2) Preparation of coating sample
A coating film was formed by mixing 300 parts by weight of the water-containing microcapsule-containing slurry (129 parts by weight of microcapsules, 58 parts by weight of solid content) and 500 parts by weight of a toluene solution containing 10% by weight of an acrylic resin. A resin composition was obtained. After coating the obtained resin composition for forming a coating film on a PET sheet as a substrate to a thickness of 15 μm (solid content) using a gravure coat, it is heated and dried with a hot air dryer at 120 ° C. for 1 minute. By doing, the coating film was formed.

(Example 2)
(1) Preparation of microcapsules 40 parts by weight of pentaerythritol tetraacrylate and 30 parts by weight of trimethylolpropane triacrylate as a trifunctional or higher functional crosslinking monomer, and polyethylene glycol dimethacrylate (the number of polyoxyethylene units = 1, "Blenmer PDE-50R" manufactured by NOF Corporation), 50 parts by weight of ethyl acetate and 350 parts by weight of cyclohexane as a non-polymerizable substance, and 0.3 parts by weight of azobisisobutyronitrile (AIBN) as a polymerization initiator Were mixed and stirred to prepare an ethyl acetate-cyclohexane dispersed primary emulsion.

Thereafter, the obtained primary emulsion is added to 370 parts by weight of an ion exchange aqueous solution containing 1% by weight of polyvinyl alcohol (PVA) as a dispersant and 0.02% by weight of sodium nitrite as a water-soluble polymerization inhibitor. Then, the mixture was stirred using a stirring and dispersing device to obtain a secondary emulsion composed of a composite emulsion in which oil droplets containing ethyl acetate-cyclohexane were dispersed in an aqueous medium.

Using a 20-liter polymerization vessel equipped with a stirrer, jacket, reflux condenser and thermometer, the inside of the polymerization vessel was depressurized and deoxygenated in the vessel, and then the atmosphere inside the polymerization vessel was changed to a nitrogen atmosphere by replacing with nitrogen. . Thereafter, the secondary emulsion was added all at once, and the polymerization vessel was heated to 60 ° C. to initiate polymerization. After polymerization for 4 hours, the polymerization vessel was cooled to room temperature to obtain a slurry containing solvent-encapsulated microcapsules. The solvent of the obtained slurry was replaced with isopropanol (IPA) using a centrifuge, and an isopropanol (IPA) dispersion slurry of solvent-encapsulated microcapsules was obtained.

(2) Preparation of coating sample
A coating film was formed by mixing 200 parts by weight of the resulting slurry containing microcapsules in the solvent (57 parts by weight of microcapsules, 12 parts by weight of solids) and 500 parts by weight of a toluene solution containing 10% by weight of acrylic resin. A resin composition was obtained. After coating the obtained resin composition for forming a coating film on a PET sheet as a substrate to a thickness of 15 μm (solid content) using a gravure coat, it is heated and dried with a hot air dryer at 120 ° C. for 1 minute. By doing, the coating film was formed.

(Example 3)
(1) Preparation of microcapsules 60 parts by weight of trimethylolpropane triacrylate as a trifunctional or higher functional crosslinking monomer, 40 parts by weight of acrylonitrile as a polymerizable monomer, 40 parts by weight of ethyl acetate and 120 parts by weight of heptane as non-polymerizable substances And 0.3 part by weight of azobisisobutyronitrile (AIBN) as a polymerization initiator were mixed and stirred to prepare an ethyl acetate-heptane dispersion type primary emulsion.

Thereafter, the obtained primary emulsion is added to 300 parts by weight of an ion exchange aqueous solution containing 1% by weight of polyvinyl alcohol (PVA) as a dispersant and 0.02% by weight of sodium nitrite as a water-soluble polymerization inhibitor. Then, the mixture was stirred using a stirring and dispersing device to obtain a secondary emulsion composed of a composite emulsion in which oil droplets containing ethyl acetate-heptane were dispersed in an aqueous medium.

Using a 20-liter polymerization vessel equipped with a stirrer, jacket, reflux condenser and thermometer, the inside of the polymerization vessel was depressurized and deoxygenated in the vessel, and then the atmosphere inside the polymerization vessel was changed to a nitrogen atmosphere by replacing with nitrogen. . Thereafter, the secondary emulsion was added all at once, and the polymerization vessel was heated to 60 ° C. to initiate polymerization. After polymerization for 4 hours, the polymerization vessel was cooled to room temperature to obtain a slurry containing solvent-encapsulated microcapsules. The resulting slurry containing the solvent-encapsulated microcapsules was dried using a spray dryer to obtain powdery dry microcapsules.

(2) Preparation of coating sample
A resin composition for forming a coating film was obtained by mixing 100 parts by weight of the obtained dry microcapsule and 500 parts by weight of a toluene solution containing 10% by weight of an acrylic resin. After coating the obtained resin composition for forming a coating film on a PET sheet as a substrate to a thickness of 15 μm (solid content) using a gravure coat, it is heated and dried with a hot air dryer at 120 ° C. for 1 minute. By doing, the coating film was formed.

Example 4
(1) Preparation of microcapsules 35 parts by weight of pentaerythritol tetraacrylate and 50 parts by weight of trimethylolpropane triacrylate as a trifunctional or higher functional crosslinking monomer, 15 parts by weight of methyl methacrylate as a polymerizable monomer, and as a non-polymerizable substance 10 parts by weight of ethyl acetate, 40 parts by weight of cyclohexane and 150 parts by weight of normal hexane and 0.3 parts by weight of azobisisobutyronitrile (AIBN) as a polymerization initiator are mixed and stirred, and ethyl acetate-cyclohexane-normal hexane is mixed. A dispersion type primary emulsion was prepared.

Thereafter, the obtained primary emulsion is added to 300 parts by weight of an ion exchange aqueous solution containing 1% by weight of polyvinyl alcohol (PVA) as a dispersant and 0.02% by weight of sodium nitrite as a water-soluble polymerization inhibitor. Then, the mixture was stirred using a stirring and dispersing device to obtain a secondary emulsion composed of a composite emulsion in which oil droplets containing ethyl acetate-cyclohexane-normal hexane were dispersed in an aqueous medium.

Using a 20-liter polymerization vessel equipped with a stirrer, jacket, reflux condenser and thermometer, the inside of the polymerization vessel was depressurized and deoxygenated in the vessel, and then the atmosphere inside the polymerization vessel was changed to a nitrogen atmosphere by replacing with nitrogen. . Thereafter, the secondary emulsion was added all at once, and the polymerization vessel was heated to 60 ° C. to initiate polymerization. After polymerization for 4 hours, the polymerization vessel was cooled to room temperature to obtain a slurry containing solvent-encapsulated microcapsules. The solvent of the obtained slurry was replaced with isopropanol (IPA) using a centrifuge, and an isopropanol (IPA) dispersion slurry of solvent-encapsulated microcapsules was obtained.

(2) Preparation of coating sample
A coating film was formed by mixing 210 parts by weight of the resulting solvent-encapsulated microcapsule-containing slurry (95 parts by weight of microcapsules, 29 parts by weight of solids) and 500 parts by weight of a toluene solution containing 10% by weight of an acrylic resin. A resin composition was obtained. After coating the obtained resin composition for forming a coating film on a PET sheet as a substrate to a thickness of 15 μm (solid content) using a gravure coat, it is heated and dried with a hot air dryer at 120 ° C. for 1 minute. By doing, the coating film was formed.

(Comparative Example 1)
(1) Preparation of microcapsule 10 parts by weight of trimethylolpropane triacrylate as a trifunctional or higher functional crosslinkable monomer, and polypropylene glycol dimethacrylate as a polymerizable monomer (number of polyoxypropylene units = approximately 7, “Blemmer PDP-” manufactured by NOF Corporation) 400 ") 60 parts by weight and 30 parts by weight of methyl methacrylate, 100 parts by weight of heptane as a non-polymerizable substance, and 0.3 parts by weight of azobisisobutyronitrile (AIBN) as a polymerization initiator are mixed and stirred. A heptane-dispersed primary emulsion was prepared.

Thereafter, the obtained primary emulsion is added to 400 parts by weight of an ion exchange aqueous solution containing 1% by weight of polyvinyl alcohol (PVA) as a dispersant and 0.02% by weight of sodium nitrite as a water-soluble polymerization inhibitor. Then, the mixture was stirred using a stirring and dispersing device to obtain a secondary emulsion composed of a composite emulsion in which oil droplets containing heptane were dispersed in an aqueous medium.

Using a 20-liter polymerization vessel equipped with a stirrer, jacket, reflux condenser and thermometer, the inside of the polymerization vessel was depressurized and deoxygenated in the vessel, and then the atmosphere inside the polymerization vessel was changed to a nitrogen atmosphere by replacing with nitrogen. . Thereafter, the secondary emulsion was added all at once, and the polymerization vessel was heated to 60 ° C. to initiate polymerization. After polymerization for 8 hours, the polymerization vessel was cooled to room temperature to obtain a slurry containing solvent-encapsulated microcapsules. The solvent of the obtained slurry was replaced with isopropanol (IPA) using a centrifuge, and an isopropanol (IPA) dispersion slurry of solvent-encapsulated microcapsules was obtained.

(2) Preparation of coating sample
Forming a coating film by mixing 300 parts by weight of the resulting slurry containing microcapsules in the solvent (129 parts by weight of microcapsules, 58 parts by weight of solid) and 500 parts by weight of a toluene solution containing 10% by weight of acrylic resin A resin composition was obtained. After coating the obtained resin composition for forming a coating film on a PET sheet as a substrate to a thickness of 15 μm (solid content) using a gravure coat, it is heated and dried with a hot air dryer at 120 ° C. for 1 minute. By doing, the coating film was formed.

(Comparative Example 2)
(1) Preparation of microcapsules 25 parts by weight of pentaerythritol tetraacrylate and 25 parts by weight of trimethylolpropane triacrylate as trifunctional or more crosslinkable monomers, 10 parts by weight of acrylonitrile, 10 parts by weight of methacrylonitrile, 20 parts by weight of methyl acid and 10 parts by weight of polyethylene glycol dimethacrylate (polyoxyethylene unit number = 1, “Blenmer PDE-50R” manufactured by NOF Corporation), 110 parts by weight of cyclohexane as a non-polymerizable substance, and as a polymerization initiator A cyclohexane-dispersed primary emulsion was prepared by mixing and stirring with 0.3 part by weight of azobisisobutyronitrile (AIBN).

Thereafter, the obtained primary emulsion is added to 1133 parts by weight of an ion exchange aqueous solution containing 2% by weight of sodium dodecylbenzenesulfonate as a dispersant, and stirred using an ultrasonic homogenizer, whereby cyclohexane is added to the aqueous medium. A secondary emulsified liquid composed of a composite emulsion in which oil droplets encapsulating therein were dispersed was obtained.

Using a 20-liter polymerization vessel equipped with a stirrer, jacket, reflux condenser and thermometer, the inside of the polymerization vessel was depressurized and deoxygenated in the vessel, and then the atmosphere inside the polymerization vessel was changed to a nitrogen atmosphere by replacing with nitrogen. . Thereafter, the secondary emulsion was added all at once, and the polymerization vessel was heated to 60 ° C. to initiate polymerization. After polymerization for 8 hours, the polymerization vessel was cooled to room temperature to obtain a slurry containing solvent-encapsulated microcapsules. The solvent of the obtained slurry was replaced with isopropanol (IPA) using a centrifuge, and an isopropanol (IPA) dispersion slurry of solvent-encapsulated microcapsules was obtained.

(2) Preparation of coating sample: 400 parts by weight of the solvent-encapsulated microcapsule-containing slurry obtained (138 parts by weight of microcapsules, 66 parts by weight of solid content), 500 parts by weight of a toluene solution containing 10% by weight of an acrylic resin, Was mixed to obtain a resin composition for forming a coating film. After coating the obtained resin composition for forming a coating film on a PET sheet as a substrate to a thickness of 15 μm (solid content) using a gravure coat, it is heated and dried with a hot air dryer at 120 ° C. for 1 minute. By doing, the coating film was formed.

(Comparative Example 3)
(1) Preparation of microcapsules 25 parts by weight of pentaerythritol tetraacrylate and 25 parts by weight of trimethylolpropane triacrylate as trifunctional or more crosslinkable monomers, 10 parts by weight of acrylonitrile, 10 parts by weight of methacrylonitrile, 20 parts by weight of methyl acid and 10 parts by weight of polyethylene glycol dimethacrylate (polyoxyethylene unit number = 1, “Blenmer PDE-50R” manufactured by NOF Corporation), 110 parts by weight of cyclohexane as a non-polymerizable substance, and as a polymerization initiator A cyclohexane-dispersed primary emulsion was prepared by mixing and stirring with 0.3 part by weight of azobisisobutyronitrile (AIBN).

Thereafter, the obtained primary emulsion is added to 455 parts by weight of an ion exchange aqueous solution containing 1% by weight of polyvinyl alcohol (PVA) as a dispersant and 0.02% by weight of sodium nitrite as a water-soluble polymerization inhibitor. By stirring using a stirring and dispersing device, a secondary emulsion composed of a composite emulsion in which oil droplets containing cyclohexane were dispersed in an aqueous medium was obtained.

Using a 20-liter polymerization vessel equipped with a stirrer, jacket, reflux condenser and thermometer, the inside of the polymerization vessel was depressurized and deoxygenated in the vessel, and then the atmosphere inside the polymerization vessel was changed to a nitrogen atmosphere by replacing with nitrogen. . Thereafter, the secondary emulsion was added all at once, and the polymerization vessel was heated to 60 ° C. to initiate polymerization. After polymerization for 8 hours, the polymerization vessel was cooled to room temperature to obtain a slurry containing solvent-encapsulated microcapsules. The resulting slurry containing the solvent-encapsulated microcapsules was dried using a spray dryer to obtain powdery dry microcapsules.

(2) Preparation of coating sample
By mixing 129 parts by weight of the obtained dry microcapsules and 500 parts by weight of a toluene solution containing 10% by weight of an acrylic resin, a resin composition for forming a coating film was obtained. After coating the obtained resin composition for forming a coating film on a PET sheet as a substrate to a thickness of 15 μm (solid content) using a gravure coat, it is heated and dried with a hot air dryer at 120 ° C. for 1 minute. By doing, the coating film was formed.

(Comparative Example 4)
(1) Preparation of microcapsules 5 parts by weight of pentaerythritol tetraacrylate and 10 parts by weight of trimethylolpropane triacrylate as tri- or more functional crosslinkable monomers, 35 parts by weight of methyl methacrylate and polypropylene glycol dimethacrylate (poly Number of oxypropylene units = approximately 7, 50 parts by weight of “Blenmer PDP-400” manufactured by NOF Corporation, 50 parts by weight of ethyl acetate and 50 parts by weight of cyclohexane as non-polymerizable substances, and azobisisobutyro as a polymerization initiator Nitrile (AIBN) 0.5 part by weight was mixed and stirred to prepare an ethyl acetate-cyclohexane dispersion type primary emulsion.

Thereafter, the obtained primary emulsion is added to 455 parts by weight of an ion exchange aqueous solution containing 1% by weight of polyvinyl alcohol (PVA) as a dispersant and 0.02% by weight of sodium nitrite as a water-soluble polymerization inhibitor. Then, the mixture was stirred using a stirring and dispersing device to obtain a secondary emulsion composed of a composite emulsion in which oil droplets containing ethyl acetate-cyclohexane were dispersed in an aqueous medium.

Using a 20-liter polymerization vessel equipped with a stirrer, jacket, reflux condenser and thermometer, the inside of the polymerization vessel was depressurized and deoxygenated in the vessel, and then the atmosphere inside the polymerization vessel was changed to a nitrogen atmosphere by replacing with nitrogen. . Thereafter, the secondary emulsion was added all at once, and the polymerization vessel was heated to 60 ° C. to initiate polymerization. After polymerization for 8 hours, the polymerization vessel was cooled to room temperature to obtain a slurry containing solvent-encapsulated microcapsules. The solvent of the obtained slurry was replaced with isopropanol (IPA) using a centrifuge, and an isopropanol (IPA) dispersion slurry of solvent-encapsulated microcapsules was obtained.

(2) Preparation of coating sample 310 parts by weight of the slurry containing the encapsulated solvent-encapsulated microcapsules (140 parts by weight of microcapsules, 70 parts by weight of solids), 500 parts by weight of a toluene solution containing 10% by weight of acrylic resin, Was mixed to obtain a resin composition for forming a coating film. After coating the obtained resin composition for forming a coating film on a PET sheet as a substrate to a thickness of 15 μm (solid content) using a gravure coat, it is heated and dried with a hot air dryer at 120 ° C. for 1 minute. By doing, the coating film was formed.

(Comparative Example 5)
(1) Preparation of microcapsules 0.003 part by weight of trimethylolpropane triacrylate as a trifunctional or higher functional crosslinkable monomer, 90 parts by weight of acrylonitrile and 10 parts by weight of methacrylonitrile as a polymerizable monomer, and normal as a non-polymerizable substance 200 parts by weight of hexane and 0.3 parts by weight of azobisisobutyronitrile (AIBN) as a polymerization initiator were mixed and stirred to prepare a normal hexane dispersion type primary emulsion.

Thereafter, the obtained primary emulsion is added to 455 parts by weight of an ion exchange aqueous solution containing 1% by weight of polyvinyl alcohol (PVA) as a dispersant and 0.02% by weight of sodium nitrite as a water-soluble polymerization inhibitor. Then, the mixture was stirred using a stirring and dispersing device to obtain a secondary emulsion composed of a composite emulsion in which oil droplets containing normal hexane were dispersed in an aqueous medium.

Using a 20-liter polymerization vessel equipped with a stirrer, jacket, reflux condenser and thermometer, the inside of the polymerization vessel was depressurized and deoxygenated in the vessel, and then the atmosphere inside the polymerization vessel was changed to a nitrogen atmosphere by replacing with nitrogen. . Thereafter, the secondary emulsion was added all at once, and the polymerization vessel was heated to 60 ° C. to initiate polymerization. After polymerization for 8 hours, the polymerization vessel was cooled to room temperature to obtain a slurry containing solvent-encapsulated microcapsules. The solvent of the obtained slurry was replaced with isopropanol (IPA) using a centrifuge, and an isopropanol (IPA) dispersion slurry of solvent-encapsulated microcapsules was obtained.

(2) Preparation of coating sample 200 parts by weight of the slurry containing the encapsulated solvent-containing microcapsules (150 parts by weight of microcapsules, 68 parts by weight of solid content), 500 parts by weight of a toluene solution containing 10% by weight of acrylic resin, Was mixed to obtain a resin composition for forming a coating film. After coating the obtained microcapsule composition on a PET sheet as a substrate to a thickness of 15 μm (solid content) using a gravure coat, heat drying at 120 ° C. for 1 minute with a hot air dryer Thus, a coating film was formed.

(Comparative Example 6)
(1) Preparation of microcapsules 20 parts by weight of pentaerythritol tetraacrylate and 10 parts by weight of trimethylolpropane triacrylate as a trifunctional or higher functional crosslinking monomer, 60 parts by weight of methyl methacrylate and polypropylene glycol dimethacrylate (poly Number of oxypropylene units = approximately 7, 10 parts by weight of “Blenmer PDP-400” manufactured by NOF Corporation, 400 parts by weight of cyclohexane as a non-polymerizable substance, and 0. azobisisobutyronitrile (AIBN) as a polymerization initiator. 3 parts by weight was mixed and stirred to prepare a cyclohexane-dispersed primary emulsion.

Thereafter, the obtained primary emulsion is added to 455 parts by weight of an ion exchange aqueous solution containing 1% by weight of polyvinyl alcohol (PVA) as a dispersant and 0.02% by weight of sodium nitrite as a water-soluble polymerization inhibitor. By stirring using a stirring and dispersing device, a secondary emulsion composed of a composite emulsion in which oil droplets containing cyclohexane were dispersed in an aqueous medium was obtained.

Using a 20-liter polymerization vessel equipped with a stirrer, jacket, reflux condenser and thermometer, the inside of the polymerization vessel was depressurized and deoxygenated in the vessel, and then the atmosphere inside the polymerization vessel was changed to a nitrogen atmosphere by replacing with nitrogen. . Thereafter, the secondary emulsion was added all at once, and the polymerization vessel was heated to 60 ° C. to initiate polymerization. After polymerization for 8 hours, the polymerization vessel was cooled to room temperature to obtain a slurry containing solvent-encapsulated microcapsules. The resulting slurry containing the solvent-encapsulated microcapsules was dried using a spray dryer to obtain powdery dry microcapsules.

(2) Preparation of coating sample
A resin composition for forming a coating film was obtained by mixing 67 parts by weight of the obtained dry microcapsules and 500 parts by weight of a toluene solution containing 10% by weight of an acrylic resin. After coating the obtained resin composition for forming a coating film on a PET sheet as a substrate to a thickness of 15 μm (solid content) using a gravure coat, it is heated and dried with a hot air dryer at 120 ° C. for 1 minute. By doing, the coating film was formed.

(Comparative Example 7)
(1) Preparation of microcapsules As a trifunctional or higher functional crosslinkable monomer, 40 parts by weight of pentaerythritol tetraacrylate and 60 parts by weight of trimethylolpropane triacrylate, 50 parts by weight of ethyl acetate and 140 parts by weight of heptane as non-polymerizable substances, As a polymerization initiator, 0.3 part by weight of azobisisobutyronitrile (AIBN) was mixed and stirred to prepare an ethyl acetate-heptane dispersion type primary emulsion.

Thereafter, the obtained primary emulsion is added to 455 parts by weight of an ion exchange aqueous solution containing 1% by weight of polyvinyl alcohol (PVA) as a dispersant and 0.02% by weight of sodium nitrite as a water-soluble polymerization inhibitor. Then, the mixture was stirred using a stirring and dispersing device to obtain a secondary emulsion composed of a composite emulsion in which oil droplets containing ethyl acetate-heptane were dispersed in an aqueous medium.

Using a 20-liter polymerization vessel equipped with a stirrer, jacket, reflux condenser and thermometer, the inside of the polymerization vessel was depressurized and deoxygenated in the vessel, and then the atmosphere inside the polymerization vessel was changed to a nitrogen atmosphere by replacing with nitrogen. . Thereafter, the secondary emulsion was added all at once, and the polymerization vessel was heated to 60 ° C. to initiate polymerization. After polymerization for 8 hours, the polymerization vessel was cooled to room temperature to obtain a slurry containing solvent-encapsulated microcapsules. The solvent of the obtained slurry was replaced with isopropanol (IPA) using a centrifuge, and an isopropanol (IPA) dispersion slurry of solvent-encapsulated microcapsules was obtained.

(2) Preparation of coating sample
Forming a coating film by mixing 280 parts by weight of the resulting solvent-encapsulated microcapsule-containing slurry (100 parts by weight of microcapsules, 35 parts by weight of solid content) and 500 parts by weight of a toluene solution containing 10% by weight of acrylic resin A resin composition was obtained. After coating the obtained resin composition for forming a coating film on a PET sheet as a substrate to a thickness of 15 μm (solid content) using a gravure coat, it is heated and dried with a hot air dryer at 120 ° C. for 1 minute. By doing, the coating film was formed.

(Evaluation)
(1) Observation of inner-hole structure state After removing the core agent of the microcapsules obtained in each Example and Comparative Example, the microcapsule was embedded in an epoxy resin and cut, and the cross section was observed with a scanning electron microscope.

(2) Average particle diameter, rate of change in average particle diameter after heating, aspect ratio After microcapsules obtained in each Example and Comparative Example and the same sample were heated in an oven at an internal temperature of 200 ° C. for 10 minutes The microcapsules were photographed with a drop-type electron microscope, 350 photographs were randomly extracted from the obtained photographs, and the major axis and minor axis were measured.
The major axis was taken as the particle diameter, and the number average was taken as the average particle diameter. Moreover, the aspect ratio was calculated by dividing the major axis by the minor axis, and the number average was calculated.
Moreover, the average particle diameter change rate by heating was computed using following formula (1).
Average particle size change rate after heating at 200 ° C for 10 minutes (%)
= (Average particle diameter after heating / Average particle diameter before heating) × 100 (1)

(3) 10% K Value Using “PCT-200” manufactured by Shimadzu Corporation, the 10% K value of the microcapsules obtained in each Example and Comparative Example was determined by the following formula (2).
10% K value (N / mm ² ) = (3/2 ^1/2 ) · F · S ⁻³ / ² · R ^−1/2 (2)
F: Load value at 10% compression deformation of microcapsule (N)
S: Compression displacement (mm) in 10% compression deformation of microcapsules
R: Radius of microcapsule (mm)

(4) Porosity Microcapsules of each Example and Comparative Example were photographed with a transmission electron microscope, 350 photographs were randomly extracted from the obtained photographs, and the pore diameters in the particles were measured. The average was calculated.
Then, assuming that the obtained microcapsules are true spheres, and determining the volumes from the average particle diameter (outer diameter) and the average inner pore diameter, respectively, {(pore volume / microcapsule volume) × 100} By calculating, the porosity was obtained.

(5) State of the resin composition for forming a coating film The solution state of the resin composition for forming a coating film obtained in each Example and Comparative Example was visually confirmed.

(6) Cross-sectional state of coating film The cross-sections of the coating films obtained in each Example and Comparative Example were observed using a scanning electron microscope (SEM), and the state of pores in the coating film was evaluated.

(7) Coating surface condition (smoothness)
The surface of the coating film obtained by each Example and the comparative example was observed using the scanning electron microscope (SEM), and the smoothness of the surface was evaluated. The case of having smoothness was marked with ◯, and the case of not having smoothness was marked with ×.

(8) Compression deformation recovery rate On the coating film obtained in each of Examples and Comparative Examples on a smooth end face of a diamond column having a diameter of 50 μm using a micro compression tester (Shimadzu Corporation “PCT-200”). The 10 measurement points were compressed at a compression rate of 0.27 g / sec and a maximum test load of 10 g, and the load was applied to 10 mN and then unloaded to 1 mN. For each measurement location, the compression deformation recovery rate was calculated by the following formula (3) using the displacement at 10 mN load and the displacement at 1 mN load, and the number average was calculated.
Compression deformation recovery rate (%)
= 100-(Displacement at 1 mN load / 10 Displacement at 10 mN load) x 100 (3)

As shown in Table 1, the coating films obtained using the microcapsules obtained in Examples 1 to 4 have uniform pores, excellent surface smoothness, and flexibility (compression deformation recovery) Rate).
On the other hand, in the coating film obtained using the microcapsule obtained in Comparative Example 1, the microcapsule has a porous structure, and the pores cannot be retained due to the impregnation of the binder resin inside the shell. The surface smoothness was also poor.
The microcapsules obtained in Comparative Example 2 were agglomerated in the coating film forming composition because the average particle size was too small, and collapsed because the shell was thin. Therefore, the coating film obtained using the microcapsules obtained in Comparative Example 2 had an uneven pore shape.
The coating film obtained using the microcapsules obtained in Comparative Example 3 had poor surface smoothness because the average particle diameter of the microcapsules was too large.
The microcapsule obtained in Comparative Example 4 was deformed into a flat shape when dried after solvent substitution due to insufficient crosslinking of the polymer forming the shell, resulting in crushing. Therefore, the coating film obtained using the microcapsules obtained in Comparative Example 4 did not retain pores.
The microcapsule obtained in Comparative Example 5 was deformed into a flat shape during polymer polymerization and collapsed due to a significant lack of the degree of crosslinking of the polymer forming the shell. Therefore, the coating film obtained using the microcapsules obtained in Comparative Example 5 did not retain pores.
The coating film obtained using the microcapsules obtained in Comparative Example 6 did not have sufficient flexibility (compression recovery rate) due to the very low 10% K value of the microcapsules.
The microcapsules obtained in Comparative Example 7 were embrittled because the degree of crosslinking of the polymer forming the shell was too high. Therefore, sufficient flexibility (compression deformation recovery rate) could not be obtained.

ADVANTAGE OF THE INVENTION According to this invention, while being excellent in the dispersibility in a solvent, the manufacturing method of the microcapsule which has the outstanding elasticity can be provided. Moreover, the microcapsule manufactured by the manufacturing method of this microcapsule, the resin composition for coating-film formation, a coating film, an optical sheet, and a skin material can be provided.

Claims (10)

A method for producing a microcapsule in which a core agent is encapsulated in a shell having a single pore structure,
Having a step of preparing an emulsion in which droplets composed of a monomer solution containing a non-polymerizable substance are dispersed and a step of polymerizing the monomer in the monomer solution,
The monomer solution contains 55 to 90% by weight of a trifunctional or higher functional crosslinkable monomer with respect to all monomer components. A microcapsule produced by the method for producing a microcapsule according to claim 1. The average particle diameter is 1 to 20 μm, the aspect ratio is 1 to 1.1, and the rate of change of the average particle diameter after heating at a predetermined temperature of 30 to 200 ° C. for 10 minutes is within 100 ± 5%. The microcapsule according to claim 2. The microcapsule according to claim 2 or 3, which contains 50% by weight or more of a core agent. The microcapsule according to claim 2, 3 or 4, wherein a 10% K value at 23 ° C is 1-1000 N / mm ² . A resin composition for forming a coating film, comprising the microcapsule according to claim 2, 3, 4, or 5, a binder resin, and a solvent. 7. The resin composition for forming a coating film according to claim 6, comprising 5 to 90% by weight of the microcapsules according to claim 2, 3, 4 or 5, and 0.1 to 30% by weight of a binder resin. A coating film comprising the resin composition for forming a coating film according to claim 6 or 7. An optical sheet comprising a porous layer containing the microcapsules according to claim 2, 3, 4 or 5. A skin material comprising the microcapsule according to claim 2, 3, 4 or 5.