JP5358074B2 - Microcapsule, resin composition for coating film formation, coating film and method for producing microcapsule - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microcapsule excellent in dispersibility in a solvent and capable of obtaining a coating film having homogeneous holes and having high surface smoothness, a resin composition for forming a coating film using the microcapsule, a coating film, and a production method of the microcapsule. <P>SOLUTION: This microcapsule is one in which a shell having a uniforate structure contains a substance having a boiling point of 30 to 200&deg;C as a core agent and which has an average particle diameter of 1 to 10 &mu;m, an aspect ratio of 1 to 1.1, and a rate of change of the average particle diameter thereof after heating at a predetermined temperature of 30 to 200&deg;C for 10 minutes of within 100&plusmn;5%. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

The present invention is a microcapsule that has excellent dispersibility in a solvent, has uniform pores, and can obtain a coating film with high surface smoothness, and a resin composition for coating film formation using the microcapsule The present invention relates to a manufacturing method of a product, a coating film, and a microcapsule.

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 was insufficient, and it could not be suitably used for the various applications described above.
JP-A-5-285376 JP 2001-213727 A JP-A-5-237368

In view of the above-mentioned present situation, the present invention uses a microcapsule that is excellent in dispersibility in a solvent, has uniform pores, and can obtain a coating film having high surface smoothness, and the microcapsule. It is an object of the present invention to provide a method for producing a resin composition for forming a coating film, a coating film, and a microcapsule.

The present invention is a microcapsule in which a substance having a boiling point of 30 to 200 ° C. is encapsulated as a core agent in a shell having a single pore structure, and the average particle diameter is 1 to 10 μm, the aspect ratio is 1 to 1.1, and state, and are change rate within 5% ± the average particle diameter after heating for 10 minutes or more at a predetermined temperature of 30 to 200 ° C., the core agent, water and / or water solubility of 15 g / L It has more organic solvents, and the content of the core agent is der Ru microcapsules least 50 wt%.
The present invention is described in detail below.

The microcapsule of the present invention has a core agent having a boiling point of 30 to 200 ° C.
The core agent is not particularly limited as long as it has a boiling point of 30 to 200 ° C. and can be easily evaporated by heating, 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.
Especially, it is preferable to use the organic solvent whose solubility with respect to water and / or water is 15 g / L or more. Specifically, for example, dichloromethane, methanol, ethanol, n-propanol, isopropyl alcohol, 1-butanol, 2-butanol, isobutyl alcohol, t-butyl alcohol, n-pentanol, isopentyl alcohol, neopentyl alcohol, octanol, Examples include diethyl ether, dioxane, tetrahydrofuran, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl acetate, ethyl acetate, propyl acetate, nitromethane, nitroethane, acetonitrile, aniline, and 2-pyrrolidone.

The core agent has a boiling point of 30 ° C. and an upper limit of 200 ° C. If it is lower than 30 ° C., the core agent will boil at room temperature, resulting in extremely poor handling properties. When the temperature exceeds 200 ° C., the boiling point is too high, and thus the core agent may not be completely removed in the drying step, resulting in insufficient pore formation. A preferred lower limit is 50 ° C and a preferred 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%. If it is less than 50% by weight, for example, when the microcapsule of the present invention is used in a resin composition for forming a coating film, the microcapsule may float and the dispersibility of the microcapsule may be significantly impaired. A preferred upper limit is 60% by 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 such a problem that the ratio of the pores of the obtained coating film decreases due to penetration.
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 shell material is not particularly limited as long as it can have a single pore structure and can realize an average particle diameter and an aspect ratio within the above ranges. For example, a segment derived from a crosslinkable monomer and hydrophilic A copolymer having a segment derived from a functional monomer can be used.

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 microcapsules of the present invention. is there. If it 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.

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 it is less than 1N / mm ^2, when forming a porous coating film by coating a slurry of microcapsules, there is that the particles collapse in the drying step of the coating process and coating, 1000 N / mm ² If it exceeds 1, the flexibility of the coating film may be lost and the coating film may be cracked, or when the coating film is printed or embossed, the transferability may deteriorate.

The 10% K value is a smooth end face 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 compression rate of the base resin particles. It is a value obtained by compressing at 0.27 g / sec and a maximum test load of 10 g and by the following formula.
^{K = (3 / √2) ·} F · S -3/2 · R -1/2
In the formula, F represents a load value (kg) in 10% compression deformation of fine particles, S represents a compression displacement (mm) in 10% compression deformation of fine particles, and R represents a radius (mm) of the fine particles.

In the microcapsules of the present invention, the rate of change in average particle diameter after heating for 10 minutes at a predetermined temperature of 30 to 200 ° C. is within ± 5%.
That the rate of change of the average particle diameter is within ± 5% means that the average particle diameter does not change without thermal expansion at 30 to 200 ° C. When microcapsules that heat and expand at 30 to 200 ° C. are used, the coated particles coated with the microcapsules are dried to remove the core agent and obtain a porous coating. As a result, the smoothness of the coating film is lost.
In addition, about conditions other than the said temperature, the operating condition of a general sheet dryer is represented.

Moreover, the minimum of the average particle diameter of the microcapsule of this invention is 1 micrometer, and an upper limit is 10 micrometers. When the thickness is less than 1 μm, aggregation of the microcapsules of the present invention occurs, resulting in poor handleability. When the thickness exceeds 10 μm, the smoothness of a product obtained using the microcapsules of the present invention decreases. A preferred lower limit is 1.5 μm and a preferred upper limit is 5 μm.

In the microcapsule of the present invention, the lower limit of the aspect ratio (ratio of the length of the major axis to the length of the minor axis) is 1.0, and the upper limit is 1.1. When the aspect ratio is out of the above range, the microcapsules are crushed or sag in the process of forming the coating film. In addition, the smoothness of the product obtained using the microcapsules of the present invention is reduced. 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. A preferred lower limit is 1.00 and a preferred upper limit is 1.05.

The microcapsule of the present invention comprises a non-polymerizable substance having a boiling point of 0 to 200 ° C. in a monomer solution containing a crosslinkable monomer, a hydrophilic monomer having a solubility in water at 25 ° C. of 20 g / L or more, and a polymerization initiator. A primary emulsification step of preparing a primary emulsion in which droplets made of the non-polymerizable substance are dispersed in the monomer solution by adding and stirring; adding the primary emulsion to a solution insoluble in the monomer solution; A secondary emulsification step of preparing a secondary emulsified liquid in which droplets made of a monomer solution containing the non-polymerizable substance are dispersed in a solution insoluble in the monomer solution by stirring, and the crosslinkable monomer and a method for producing a microcapsule having a polymerization step of polymerizing a hydrophilic monomer, wherein the non-polymerizable material, 15 g is solubility in water and / or water An organic solvent or L, and in the primary emulsification process, the crosslinking monomer of 25 wt% or more, the hydrophilic monomer of 10 wt% or more, and, the addition of the non-polymerizable substance 50 wt% or more It can be manufactured using a method.
Such a method for producing microcapsules is also one aspect of the present invention.

In the method for producing a microcapsule of the present invention, first, a monomer solution containing a crosslinkable monomer, a hydrophilic monomer having a solubility in water at 25 ° C. of 20 g / L or more, and a polymerization initiator has a boiling point of 0 to 200 ° C. A primary emulsification step of preparing a primary emulsified liquid in which droplets made of the nonpolymerizable substance are dispersed in the monomer solution is performed by adding and stirring the nonpolymerizable substance.

Examples of the crosslinkable 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, trimethylolpropane tri (meth) acrylate, tetramethylolmethanetritri (meth) acrylate, tetramethylolpropanetetra (meth) acrylate, diallyl phthalate and its isomers, triallyl isocyanurate and its derivatives, divinylbenzene, etc. Is mentioned.
These crosslinkable monomers may be used alone or in combination of two or more.

In the primary emulsification step, the lower limit of the amount of the crosslinkable monomer added is 25% by weight with respect to the total amount of the primary emulsion. If it is less than 25% by weight, the resulting microcapsule shell is insufficiently crosslinked and the strength is insufficient, so that a microcapsule having a single-pore structure shell cannot be produced. Further, when heating or the like is performed, crushing or sag occurs, or the particles undergo thermal expansion due to the volatilized core agent. A preferred lower limit is 25% by weight and a preferred upper limit is 40% by weight.

Examples of the hydrophilic monomer having a solubility in water at 25 ° C. of 20 g / L or more (hereinafter also simply referred to as a hydrophilic monomer) include (meth) acrylic acid, itaconic acid, fumaric acid, crotonic acid, maleic acid and the like. Carboxylic acid having a polymerizable unsaturated bond, carboxylic acid ester, carboxylate, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2- (meth) acrylamido-2-methylpropane Sulfonic acid having a polymerizable unsaturated bond such as sulfonic acid, vinyl sulfonic acid, styrene sulfonic acid, sulfonic acid ester, sulfonate, (meth) acrylamide, N-substituted (meth) acrylamide, (meth) acrylonitrile, polyoxy Ethylene glycol (meth) acrylate, polyoxypropylene Glycol (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, N- vinylpyrrolidone and the like. These hydrophilic monomers may be used independently and may use 2 or more types together.

The lower limit of the solubility of the hydrophilic monomer in water at 25 ° C. is 20 g / L. When it is less than 20 g / L, it is difficult to obtain particles having a single pore structure.

In the primary emulsification step, the lower limit of the addition amount of the hydrophilic monomer is 10% by weight with respect to the total amount of the primary emulsion. When the content is less than 10% by weight, it becomes difficult to obtain particles having a single pore structure. A preferred lower limit is 10% by weight and a preferred upper limit is 25% by weight.

The non-polymerizable substance is not particularly limited as long as it is liquid at the reaction temperature between the crosslinkable monomer and the hydrophilic monomer, does not polymerize by the polymerization reaction, and can be easily evaporated by heating or the like. For example, the same core agent can be used.
In the primary emulsification step, the lower limit of the amount of the non-polymerizable substance added is 50% by weight with respect to the total amount of the primary emulsion. When it is less than 50% by weight, the shell of the resulting microcapsule becomes thick, and the porosity of the obtained microcapsule decreases. A preferred lower limit is 50% by weight and a preferred upper limit is 95% by weight.

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; redox initiators and the like.

The monomer solution preferably contains a lipophilic emulsifier. The lipophilic emulsifier has a role of further improving the emulsion stability. 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.

In the method for producing a microcapsule according to the present invention, the primary emulsion is then added to and stirred in a solution insoluble in the monomer solution, and droplets composed of the monomer solution containing the non-polymerizable substance are converted into the monomer. A secondary emulsification step of preparing a secondary emulsion (so-called W / O / W emulsion) dispersed in a solution and an insoluble solution is performed.

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 primary emulsification step and the secondary emulsification step, in order to suppress generation of new particles due to polymerization of the monomer solution at a place other than oil droplets, an inorganic salt or a salt insoluble in the monomer solution or the monomer solution. A water-soluble polymerization inhibitor may be added.
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 primary emulsification step and the secondary emulsification step, the stirring method is not particularly limited, and examples thereof include conventionally known methods using a homomixer, a biomixer, an omni mixer, an ultrasonic homogenizer, a microfluidizer, and the like.

Next, in the method for producing a microcapsule of the present invention, a polymerization step of polymerizing the crosslinkable monomer and the hydrophilic monomer is performed. Thereby, the shell part of the microcapsule is formed. The polymerization method is not particularly limited, and an optimal method may be selected as appropriate depending on the types of the crosslinkable monomer and the hydrophilic monomer, but heating is usually preferable.

In the method for producing a microcapsule of the present invention, a slurry having microcapsules in a solution insoluble in the monomer solution is obtained by performing the polymerization step, and then a step of removing the solution insoluble in the monomer solution. May be performed.
The method for removing the monomer solution and the insoluble solution is not particularly limited, and examples thereof include a method of drying by heating; a method of decompressing the entire system, and the like.

According to the method for producing a microcapsule of the present invention, a microcapsule in which a substance having a boiling point of 30 to 200 ° C. is included as a core agent in a shell having a single pore structure, and an average particle diameter is 1 to 10 μm. In addition, microcapsules having an aspect ratio of 1 to 1.1 and a change rate of an average particle diameter within ± 5% when heated at a predetermined temperature of 30 to 200 ° C. for 10 minutes can be produced.

When the resin composition for forming a coating film containing the microcapsules, binder resin and solvent of the present invention is applied to a substrate such as wallpaper, for example, the shape and distribution of the pores are uniform and the unevenness of the surface is small. A high-definition coating film can be formed. 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. If it is less than 5% by weight, the ratio of pores in the resulting coating film may be extremely low, and if it exceeds 90% by weight, the durability of the 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 is less than 0.1% by weight, the durability of the coating film may be lowered. When the content exceeds 30% by weight, the ratio of pores in the obtained coating film may be extremely low.

According to the present invention, a microcapsule having excellent dispersibility in a solvent and having uniform pores and capable of obtaining a coating film having high surface smoothness, and a coating film formation using the microcapsule A resin composition, a coating film, and a method for producing a microcapsule 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 20 parts by weight of acrylonitrile as a hydrophilic monomer, 50 parts by weight of polypropylene glycol dimethacrylate as a crosslinkable monomer (polyoxyethylene unit number = 7; manufactured by NOF Corporation, Blenmer PDP-400), trimethylol 30 parts by weight of propane triacrylate, 0.25 parts by weight of azobisisobutyronitrile (AIBN) as a polymerization initiator, and 2 parts by weight of glycerol monostearate as a lipophilic emulsifier are mixed and stirred, and a monomer solution is prepared. 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 monomer solution, and the mixture was stirred with a stirring and dispersing device to prepare a primary emulsion of water-in-oil (W / O) emulsion.

Thereafter, the obtained primary emulsion was 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 apparatus, 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 purging 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.

(2) Preparation of coating sample
A resin for forming a coating film is prepared by mixing 100 parts by weight of the obtained water-encapsulated microcapsule-containing slurry (25 parts by weight of microcapsules, 10 parts by weight of solids) and 50 parts by weight of an aqueous solution containing 20% by weight of PVA. A 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.

( Reference Example 2)
(1) Preparation of microcapsules 25 parts by weight of methacrylic acid and 25 parts by weight of methacrylonitrile as hydrophilic monomers and polyethylene glycol dimethacrylate (number of polyoxyethylene units = 1; manufactured by NOF Corporation, Blemmer PDE) -50R) 10 parts by weight, 40 parts by weight of trimethylolpropane triacrylate, 145 parts by weight of normal hexane as a non-polymerizable substance, and 0.3 parts by weight of azobisisobutyronitrile (AIBN) as a polymerization initiator are mixed and stirred. Then, a normal hexane dispersion type primary emulsion was prepared.

Thereafter, the obtained primary emulsion was 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. By stirring using a stirring and dispersing device, a secondary emulsion composed of a composite emulsion in which oil droplets containing normal hexane 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 purging 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.

(2) Preparation of coating sample
By mixing 1750 parts by weight of the resulting solvent-encapsulated microcapsule-containing slurry (700 parts by weight of microcapsules, 285.7 parts by weight of solid content) and 50 parts by weight of an aqueous solution containing 20% by weight of PVA, a coating film is formed. 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 25 parts by weight of acrylonitrile as a hydrophilic monomer, 25 parts by weight of polyethylene glycol dimethacrylate (polyoxyethylene unit number = 1; manufactured by NOF Corporation, Blemmer PDE-50R) as a crosslinkable monomer, tri 50 parts by weight of methylolpropane triacrylate, 145 parts by weight of cyclohexane as a non-polymerizable substance, 40 parts by weight of ethyl acetate and 0.3 part by weight of azobisisobutyronitrile (AIBN) as a polymerization initiator are mixed and stirred. A dispersion type primary emulsion was prepared.

Thereafter, the obtained primary emulsion was 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. By stirring using a stirring and dispersing device, a secondary emulsion composed of a composite emulsion in which oil droplets encapsulating cyclohexane 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 purging with nitrogen. . Thereafter, the emulsion suspension was added all at once, and the polymerization was started by raising the temperature of the polymerization vessel to 60 ° C. After polymerization for 4 hours, the polymerization vessel was cooled to room temperature to obtain a slurry containing solvent-encapsulated microcapsules.

(2) Preparation of coating sample
By mixing 30 parts by weight of the resulting solvent-encapsulated microcapsule-containing slurry (15 parts by weight of microcapsules, 5.3 parts by weight of solids) and 50 parts by weight of an aqueous solution containing 20% by weight of PVA, a resin composition for forming a coating film I got a thing. 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 The slurry containing the solvent-encapsulated microcapsules obtained in Example 3 was dried using a spray dryer to obtain dry powder microcapsules.

(2) Preparation of coating sample
A resin composition for forming a coating film was obtained by mixing 12.5 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 1)
As monomer components, 50 parts by weight of polypropylene glycol dimethacrylate (polyoxypropylene unit number = approximately 7; manufactured by NOF Corporation, Blenmer PDP-400), 30 parts by weight of methyl methacrylate, 20 parts by weight of trimethylolpropane trimethacrylate, non-polymerized 100 parts by weight of heptane as the active substance and 0.3 parts by weight of azobisisobutyronitrile (AIBN) as the polymerization initiator were mixed and stirred to prepare a heptane-dispersed primary emulsion.

Thereafter, the obtained primary emulsion was 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. By stirring using a stirring and dispersing device, a secondary emulsion composed of a composite emulsion in which oil droplets containing heptane 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 purging 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.

(2) Preparation of coating sample
By mixing 100 parts by weight of the resulting solvent-encapsulated microcapsule-containing slurry (33 parts by weight of microcapsules, 17 parts by weight of solids) and 50 parts by weight of an aqueous solution containing 20% by weight of PVA, a resin composition for coating film formation I got a thing. 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 methacrylic acid and 25 parts by weight of methacrylonitrile as hydrophilic monomers and polyethylene glycol dimethacrylate (number of polyoxyethylene units = 1; manufactured by NOF Corporation, Blemmer PDE) -50R) 10 parts by weight, 40 parts by weight of trimethylolpropane triacrylate, 100 parts by weight of cyclohexane as a non-polymerizable substance and 0.3 parts by weight of azobisisobutyronitrile (AIBN) as a polymerization initiator are mixed and stirred. A cyclohexane-dispersed primary emulsion was prepared.

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 purging 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.

(2) Preparation of coating sample: 300 parts by weight of the solvent-encapsulated microcapsule-containing slurry obtained (45 parts by weight of microcapsules, 22.5 parts by weight of solid content) and 50 parts by weight of an aqueous solution containing 20% by weight of PVA. The resin composition for coating-film formation was obtained by mixing. 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 As monomer components, polypropylene glycol dimethacrylate (number of polyoxypropylene units = about 7; manufactured by Nippon Oil & Fats Co., Ltd., Blemmer PDP-400) 10 parts by weight, methacrylonitrile 40 parts by weight, methacrylic acid 40 parts by weight 1 part by weight, 10 parts by weight of trimethylolpropane trimethacrylate, 145 parts by weight of normal hexane as a non-polymerizable substance, and 0.3 part by weight of azobisisobutyronitrile (AIBN) as a polymerization initiator are mixed and stirred, and a normal hexane dispersion type A primary emulsion was prepared.

Thereafter, the obtained primary emulsion was 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 normal hexane 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 purging 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.

(2) Preparation of coating sample
By mixing 1800 parts by weight of the resulting solvent-encapsulated microcapsule-containing slurry (630 parts by weight of microcapsules, 257 parts by weight of solid content) and 50 parts by weight of an aqueous solution containing 20% by weight of PVA, a resin composition for forming a coating film I got a thing. 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 Paraffin wax (SCP-0028) composed of 98 parts by weight of methyl methacrylate as monomer components, 2 parts by weight of trimethylolpropane trimethacrylate, and aliphatic hydrocarbons melted at 50 ° C. as non-polymerizable substances 100 parts by weight of Nippon Seiwa Co., Ltd .: melting point 28.1 ° C.) and 0.5 parts by weight of azobisisobutyronitrile (AIBN) as a polymerization initiator are mixed and stirred, and then 93.3 parts by weight of ion-exchanged water. 1.5 parts by weight of DBSNa (sodium dodecylbenzenesulfonate) as a dispersant was added and stirred to prepare an emulsified monomer solution.

40 parts by weight of ion exchange water was added to the polymerization vessel, and stirring was started. After depressurizing the inside of the polymerization vessel and deoxidizing the inside of the container, the pressure was returned to atmospheric pressure with nitrogen to make the inside nitrogen atmosphere, and then the emulsified monomer solution was charged all at once. The polymerization tank was heated to 80 ° C. and polymerization was started. Polymerization was completed in 30 minutes, and after a aging period of 1 hour, the polymerization tank was cooled to room temperature to obtain a slurry containing wax-encapsulated microcapsules. The time required for the polymerization step from completion of the temperature increase to completion of the ripening from the start of the polymerization was about 1.5 hours.

(2) Preparation of coating sample 750 parts by weight of slurry containing microcapsules containing wax (450 parts by weight of microcapsules, 225 parts by weight of solid content) and 50 parts by weight of an aqueous solution containing 20% by weight of PVA The resin composition for coating-film formation was obtained by mixing. 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 5)
(1) Preparation of microcapsules 70 parts by weight of acrylonitrile, 30 parts by weight of methacrylonitrile, 0.003 parts by weight of trimethylolpropane trimethacrylate, 20 parts by weight of normal pentane as a non-polymerizable substance, and azobis as a polymerization initiator Isobutyronitrile (AIBN) 0.3 parts by weight was mixed and stirred to prepare a normal pentane dispersion type primary emulsion.

Subsequently, 7300 parts by weight of deionized water, 1260 parts by weight of silica dispersion (solid content 20% by weight), 45 parts by weight of potassium dichromate (2.5% by weight solution), 8 parts by weight of polyvinylpyrrolidone, 2200 parts by weight of sodium chloride And 8.5 parts by weight of hydrochloric acid were mixed to prepare an aqueous mixture. Add the total amount of the resulting primary emulsion to the aqueous mixture, stir using a stirring and dispersing device, and prepare a secondary emulsion consisting of a composite emulsion in which oil droplets containing normal pentane are dispersed in the aqueous mixture. Obtained.

The total amount of the obtained secondary emulsion was put into a pressure polymerization reactor (20 L) purged with nitrogen, pressurized to 1.0 MPa, and reacted at 60 ° C. for 16 hours. Thereafter, filtration and washing with water of the obtained reaction product were repeated to obtain solvent-encapsulated microcapsules.

(2) Preparation of coating sample A resin composition for forming a coating film was obtained by mixing 25 parts by weight of the obtained solvent-encapsulated microcapsules and 50 parts by weight of an aqueous solution containing 20% by weight of PVA. 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 The solvent-encapsulated microcapsules obtained in Comparative Example 4 were heated at 150 ° C. for 1 minute to obtain foamed products. A classified microcapsule was obtained by excluding foamed particles having an average particle diameter of 10 μm or more using a classifier.

(2) Preparation of coating sample
A resin composition for forming a coating film was obtained by mixing 3 parts by weight of the obtained classified microcapsules and 50 parts by weight of an aqueous solution containing 20% by weight of PVA. 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 Classified microcapsules were prepared in the same manner as in Comparative Example 5.

(2) Preparation of coating sample
A resin composition for forming a coating film was obtained by mixing 0.5 parts by weight of the obtained classified microcapsules and 50 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.

(Evaluation)
(1) Average particle size, rate of change in average particle size after heating, ratio of major axis to minor axis Microcapsules obtained in each Example , Reference Example and Comparative Example, and oven with an inner temperature of 200 ° C. The microcapsules after heating for 10 minutes were photographed with a dropping 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 ratio of the major axis to the minor axis was calculated by dividing the major axis by the minor axis, and the number average was calculated.
Moreover, the change rate of the particle diameter 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)

(2) Porosity The microcapsules of each Example , Reference Example and Comparative Example were photographed with a transmission electron microscope, 350 photographs were randomly extracted from the obtained photographs, and the pore size in the particles was measured. The number average was obtained.
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.

(3) Observation of inner pore structure state The microcapsules from which the core agent had been removed were embedded in an epoxy resin and cut, and the cross section was observed with a scanning electron microscope.

(4) 10% K Value Using “PCT-200” manufactured by Shimadzu Corporation, the 10% K value of the microcapsules obtained in Examples , Reference Examples and Comparative Examples was determined by the following formula (2).
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 conductive fine particles (N)
S: Compression displacement (mm) in 10% compression deformation of conductive fine particles
R: Radius of conductive fine particles (mm)

(5) State of the resin composition for coating film formation The solution state of the resin composition for coating film formation obtained by the Example , the reference example, and the comparative example was confirmed visually.

(6) Internal state of coating film The cross sections of the coating films obtained in Examples , Reference Examples and Comparative Examples were observed using a scanning electron microscope (SEM) to evaluate the state of pores in the coating film.

(7) Surface state of coating film The surface of the coating film obtained in Examples , Reference Examples and Comparative Examples was observed using SEM, and the smoothness of the surface was evaluated. The case of having smoothness was evaluated as x when the surface was not smooth.

As shown in Table 1, when the microcapsules obtained in Examples 1 , 3, 4, and Reference Example 2 were used, it was found that a coating film having uniform pores and excellent surface smoothness was obtained. .
On the other hand, when the microcapsule having a porous structure obtained in Comparative Example 1 is used, the shape cannot be maintained due to the impregnation of the binder resin in the shell portion of the microcapsule, and the average particle size is large. It can be seen that the surface smoothness is deteriorated.
When the microcapsule obtained in Comparative Example 2 is used, the microcapsule is deformed into a flat shape due to insufficient crosslinking degree of the shell portion, and the microcapsule is crushed, resulting in uneven pore shape. It was.
When the microcapsule obtained in Comparative Example 3 was used, the solvent contained therein had a high boiling point, so that it could not be removed in the drying step, and no pores were obtained.
When the microcapsules obtained in Comparative Example 4 were used, a decrease in surface smoothness was observed due to foaming in the drying process.
When the microcapsules obtained in Comparative Example 5 were used, the microcapsules floated in the coating film-forming resin composition, and the dispersibility was significantly impaired, so that the coating could not be performed. In addition, when the microcapsules obtained in Comparative Example 5 were dispersed in a 10% by weight acrylic resin toluene solution as in Comparative Example 6, the problem of dispersibility was solved and coating was possible. Particle collapse was observed due to the lack of degree of cross-linking of the part.

According to the present invention, a microcapsule having excellent dispersibility in a solvent and having uniform pores and capable of obtaining a coating film having high surface smoothness, and a coating film formation using the microcapsule A resin composition, a coating film, and a method for producing a microcapsule can be provided.

Claims (6)

A microcapsule in which a shell having a single pore structure is encapsulated with a substance having a boiling point of 30 to 200 ° C. as a core agent,
The average particle size is 1-10 μm,
An aspect ratio of 1 to 1.1, and
30-200 Ri Der change ratio within 5% ± the average particle diameter after heating for 10 minutes at a predetermined temperature of ° C.,
The core agent, solubility in water and / or water has an organic solvent or 15 g / L, and the content of the core agent is Ru der least 50 wt%
A microcapsule characterized by that. Microcapsules according to claim 1 Symbol mounting K value is equal to or is 1~1000N / mm ² at 23 ° C.. Claim 1 or 2 microcapsule according coating forming resin composition characterized by containing a binder resin and a solvent. The resin composition for forming a coating film according to claim 3 , comprising 5 to 90% by weight of the microcapsule according to claim 1 or 2 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 3 or 4 . By adding and stirring a non-polymerizable substance having a boiling point of 0 to 200 ° C. to a monomer solution containing a crosslinkable monomer, a hydrophilic monomer having a solubility in water at 25 ° C. of 20 g / L or more, and a polymerization initiator, A primary emulsification step of preparing a primary emulsified liquid in which droplets of the non-polymerizable substance are dispersed in the monomer solution;
By adding and stirring the primary emulsified liquid in a solution insoluble in the monomer solution, secondary droplets in which the monomer solution containing the non-polymerizable substance is dispersed in the monomer solution and the insoluble solution are dispersed. A secondary emulsification step of preparing an emulsion, and
A method for producing a microcapsule having a polymerization step of polymerizing the crosslinkable monomer and a hydrophilic monomer,
The non-polymerizable substance is water and / or an organic solvent having a solubility in water of 15 g / L or more, and
In the primary emulsification step, 25% by weight or more of the crosslinkable monomer, 10% by weight or more of the hydrophilic monomer, and 50% by weight or more of the non-polymerizable substance are added to the total amount of the primary emulsion. A method for producing a microcapsule characterized by the above.