JP7421320B2 - resin particles - Google Patents

Description

The present invention relates to hollow resin particles, a heat-sensitive recording material, a method for producing hollow resin particles, and microcapsules, and more particularly, the present invention relates to hollow resin particles, a heat-sensitive recording material having a heat insulating layer containing hollow resin particles, a method for producing hollow resin particles, and a microcapsule comprising a core and a shell covering the core.

Conventionally, hollow resin particles have been used in many fields such as heat-sensitive recording materials such as heat-sensitive recording paper and heat transfer receiving paper, agricultural chemicals, medicines, fragrances, liquid crystals, and adhesives.

As such hollow resin particles, for example, hollow resin particles containing a polymer of a crosslinkable monomer containing one or more types of polyfunctional monomers having three or more polymerizable double bonds have been proposed (for example, (See Patent Document 1 below.)

Patent No. 6513273

In such hollow resin particles, it is considered to increase the hollowness ratio of the hollow resin particles from the viewpoint of improving heat insulation, lightness, optical properties, etc. However, increasing the hollowness ratio of the hollow resin particles Strength tends to decrease.

Further, for example, when coating a base material with a resin containing hollow resin particles, it is required that the hollow resin particles have a true spherical shape from the viewpoint of strength.

In addition, when using such hollow resin particles dispersed in a dispersion liquid, in the dispersion liquid, there are problems with handling during storage and production equipment, concentration unevenness during preparation of the mixed liquid, and uniformity of the coating film. From these points of view, dispersibility is required.

The present invention provides hollow resin particles that have a high proportion of true spheres, can have a high hollowness ratio while ensuring strength, and have excellent dispersibility, and a heat-sensitive recording material comprising a heat insulating layer containing the hollow resin particles. A method for producing hollow resin particles that can be obtained in a high proportion of true spherical shapes, can have a high hollowness ratio while ensuring strength, and has excellent dispersion stability; The object of the present invention is to provide microcapsules that have excellent dispersibility while ensuring strength.

The present invention [1] is a hollow resin particle having a hollow interior and containing a polymer of a crosslinkable monomer, wherein the crosslinkable monomer has three or more polymerizable double bonds, and has a carboxyl These are hollow resin particles containing one or more types of polyfunctional monomers (A) having groups.

The present invention [2] includes the hollow resin particles according to the above [1], wherein the crosslinkable monomer contains two or more types of the polyfunctional monomers (A) having different numbers of polymerizable double bonds. I'm here.

In the present invention [3], the crosslinking monomer further includes a polyfunctional monomer (B) having three or more polymerizable double bonds and having no carboxyl group, or [1] or [ 2] contains the hollow resin particles described in [2].

The present invention [4] provides the hollow according to the above [3], wherein the proportion of the polyfunctional monomer (A) to the total amount of the polyfunctional monomer (A) and the polyfunctional monomer (B) is 50% by mass or more. Contains resin particles.

The present invention [5] includes a support layer, a heat insulating layer, and a heat-sensitive recording layer in this order, and the heat insulating layer contains the hollow resin particles according to any one of [1] to [4] above. Contains heat-sensitive recording material.

The present invention [6] provides a step of mixing a crosslinking monomer and a hydrophobic solvent in water to obtain crosslinking monomer droplets in which the hydrophobic solvent is encapsulated by the crosslinking monomer; polymerizing the crosslinkable monomer to obtain resin particles containing a polymer of the crosslinkable monomer encapsulating the hydrophobic solvent; and removing the hydrophobic solvent encapsulated in the resin particles. the step of obtaining hollow resin particles containing a polymer of the crosslinkable monomer and having a hollow interior, the crosslinkable monomer having three or more polymerizable double bonds and a carboxyl group; This is a method for producing hollow resin particles containing one or more functional monomers (A).

The present invention [7] includes a core and a shell that covers the core and includes a polymer of a crosslinkable monomer, and the crosslinkable monomer has three or more polymerizable double bonds, and It contains microcapsules characterized by containing one or more types of polyfunctional monomers (A) having carboxyl groups.

The hollow resin particles of the present invention are hollow resin particles containing a polymer of a crosslinkable monomer, wherein the crosslinkable monomer is a polyfunctional monomer having three or more polymerizable double bonds and a carboxyl group. Contains one or more types of (A). Therefore, the proportion of true spheres is high, and while ensuring strength, excellent dispersibility and high hollowness can be achieved. Due to the high hollowness ratio, the internal space of the hollow resin particles can be increased, resulting in excellent heat insulation properties.

Since the heat-sensitive recording material of the present invention includes a heat insulating layer containing the hollow resin particles of the present invention, it has excellent heat insulation properties.

The method for producing hollow resin particles of the present invention involves polymerizing a crosslinking monomer having three or more polymerizable double bonds and containing one or more types of polyfunctional monomers having a carboxyl group, and using a hydrophobic solvent. The method includes a step of obtaining resin particles containing a polymer of a crosslinkable monomer encapsulating. Therefore, it is possible to obtain a high proportion of true spherical particles, and it is also possible to obtain hollow resin particles having a high hollowness ratio and excellent dispersibility while ensuring strength.

The microcapsule of the present invention comprises a core and a crosslinkable monomer covering the core, having three or more polymerizable double bonds, and containing one or more polyfunctional monomers (A) having a carboxyl group. and a shell containing a polymer.

Therefore, it has a high proportion of true spherical shapes, and has excellent dispersibility while ensuring strength.

FIG. 1 is a cross-sectional view showing one embodiment of the heat-sensitive recording material of the present invention.

Hollow resin particles are produced by mixing a crosslinking monomer and a hydrophobic solvent in water to obtain crosslinking monomer droplets in which the hydrophobic solvent is encapsulated by the crosslinking monomer, and polymerizing the crosslinking monomer in the crosslinking monomer droplets. to obtain resin particles containing a polymer of a crosslinkable monomer encapsulating a hydrophobic solvent; It can be obtained by a manufacturing method comprising a step of obtaining hollow resin particles having a hollow shape.

In the step of mixing a crosslinking monomer and a hydrophobic solvent in water to obtain crosslinking monomer droplets in which the hydrophobic solvent is encapsulated by the crosslinking monomer, first, the crosslinking monomer and the hydrophobic solvent are mixed together. Prepare the liquid.

The crosslinkable monomer has three or more polymerizable double bonds and contains one or more polyfunctional monomers (A) having a carboxyl group.

The polyfunctional monomer (A) includes a reaction product of a tetrafunctional or higher functional monomer and an amino acid (hereinafter referred to as the first polyfunctional monomer (A1)), a reaction product of a trifunctional or higher functional monomer containing a hydroxyl group, and an acid anhydride. A reaction product (hereinafter referred to as a second polyfunctional monomer (A2)) can be mentioned.

Hereinafter, each of the first polyfunctional monomer (A1) and the second polyfunctional monomer (A2) will be explained in detail.

The first polyfunctional monomer (A1) is a reaction product of a tetrafunctional or higher functional monomer and an amino acid.

A tetrafunctional or higher functional monomer has four or more polymerizable double bonds. Examples of tetrafunctional or higher-functional monomers include tetrafunctional monomers such as ditrimethylolpropane tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate; pentafunctional monomers such as dipentaerythritol penta(meth)acrylate; Examples include hexafunctional monomers such as erythritol hexa(meth)acrylate.

Note that (meth)acrylate is defined as acrylate and/or methacrylate.

The tetrafunctional or higher functional monomers can be used alone or in combination of two or more.

Examples of the amino acid include glycine, alanine, glutamic acid, etc., and preferably glycine.

Amino acids can be used alone or in combination of two or more.

In order to react the tetrafunctional or higher functional monomer and the amino acid, the tetrafunctional or higher functional monomer and the amino acid are mixed.

In this reaction, one polymerizable double bond in a tetrafunctional or higher-functional monomer undergoes an addition reaction (Michael addition reaction) with an amino group in an amino acid.

In other words, the reaction product (first polyfunctional monomer (A1)) between a tetrafunctional or higher functional monomer having n (n≧4) polymerizable double bonds and an amino acid (first polyfunctional monomer (A1)) is ni (n≧4). 3, preferably i=1) and a carboxyl group.

That is, the first polyfunctional monomer (A1) contains a carboxyl group.

Since the first polyfunctional monomer (A1) contains a carboxyl group, it can suppress aggregation during polymerization and improve dispersibility.

In the above reaction, the ratio of the amino acid to 1 mol of the tetrafunctional or higher functional monomer is, for example, 0.1 mol or more and 1.2 mol or less, and preferably 1 mol. It is.

Furthermore, in the above reaction, a polymerization inhibitor (preferably hydroquinone monomethyl ether) may be blended in an appropriate ratio if necessary.

Furthermore, in the above reaction, a known organic solvent (preferably ethanol) may be blended if necessary.

Further, the reaction conditions for the above reaction are such that the reaction temperature is, for example, 20°C or higher and 120°C or lower, and the reaction time is, for example, 0.1 hour or more, and, for example, , 24 hours or less.

Thereby, the first polyfunctional monomer (A1) is obtained.

Among such first polyfunctional monomers (A1), preferably a reaction product of pentaerythritol tetraacrylate and glycine (glycine-modified pentaerythritol tetraacrylate (having three polymerizable double bonds)), ditrimethylol Reaction product of propanetetraacrylate and glycine (glycine modified ditrimethylolpropane tetraacrylate (having 3 polymerizable double bonds)), reaction product of dipentaerythritol pentaacrylate and glycine (glycine modified dipentaerythritol pentaacrylate) (having 4 polymerizable double bonds)), a reaction product of dipentaerythritol hexaacrylate and glycine (glycine-modified dipentaerythritol hexaacrylate (having 5 polymerizable double bonds)).

The first polyfunctional monomer (A1) can be used alone or in combination of two or more types.

When two or more types of first polyfunctional monomers (A1) are used together, preferably, the first polyfunctional monomers (A1) are two or more types of first polyfunctional monomers having different numbers of polymerizable double bonds. Contains (A1).

If the first polyfunctional monomer (A1) includes two or more types of first polyfunctional monomers (A1) having different numbers of polymerizable double bonds, the strength can be adjusted arbitrarily and a true spherical shape can be obtained. can.

Preferably, the first polyfunctional monomer (A1) includes a first polyfunctional monomer (A1) having n polymerizable double bonds and a first polyfunctional monomer (A1) having n+1 polymerizable double bonds. , preferably comprising glycine-modified dipentaerythritol pentaacrylate and glycine-modified dipentaerythritol hexaacrylate.

When the first polyfunctional monomer (A1) includes a first polyfunctional monomer (A1) having n polymerizable double bonds and a first polyfunctional monomer (A1) having n+1 polymerizable double bonds The blending ratio of the first polyfunctional monomer (A1) having n polymerizable double bonds is the first polyfunctional monomer (A1) having n polymerizable double bonds and n+1 polymerizable The amount is, for example, 5 parts by mass or more and, for example, 20 parts by mass or less, based on 100 parts by mass of the first polyfunctional monomer (A1) having a double bond. In addition, the blending ratio of the first polyfunctional monomer (A1) having n+1 polymerizable double bonds is as follows: The amount is, for example, 80 parts by mass or more and, for example, 95 parts by mass or less, based on 100 parts by mass of the first polyfunctional monomer (A1) having a double bond.

The second polyfunctional monomer (A2) is a reaction product of a hydroxyl group-containing trifunctional or higher functional monomer and an acid anhydride. That is, the second polyfunctional monomer (A2) is a reaction product obtained by acid-modifying a hydroxyl group-containing trifunctional or higher-functional monomer with an acid anhydride, and the second polyfunctional monomer (A2) contains a carboxyl group.

Since the second polyfunctional monomer (A2) contains a carboxyl group, it can suppress aggregation during polymerization and improve dispersibility.

The hydroxyl group-containing trifunctional or higher-functional monomer has a hydroxyl group and three or more polymerizable double bonds, such as pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate Examples include hydroxyl group-containing trifunctional monomers such as hydroxyl group-containing trifunctional monomers such as dipentaerythritol tetra(meth)acrylate, hydroxyl group-containing pentafunctional monomers such as dipentaerythritol penta(meth)acrylate, and the like, preferably. , hydroxyl group-containing trifunctional monomer, hydroxyl group-containing pentafunctional monomer, more preferably pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, still more preferably pentaerythritol triacrylate, dipentaerythritol pentaacrylate, especially Preferred is dipentaerythritol pentaacrylate.

The hydroxyl group-containing trifunctional or higher functional monomers can be used alone or in combination of two or more.

Examples of the acid anhydride include organic carboxylic anhydrides such as succinic anhydride, maleic anhydride, glutaric anhydride, itaconic anhydride, and phthalic anhydride, and preferably succinic anhydride.

Acid anhydrides can be used alone or in combination of two or more.

In order to react the hydroxyl group-containing trifunctional or higher functional monomer with the acid anhydride, the acid anhydride is blended with the hydroxyl group containing trifunctional or higher functional monomer.

In this reaction, the acid anhydride is blended so that the hydroxyl group of the hydroxyl group-containing trifunctional or higher functional monomer becomes a carboxyl group. Specifically, the ratio of the acid anhydride to 1 mole of the hydroxyl group-containing trifunctional or higher functional monomer is, for example, more than 1, preferably 1 or more, and, for example, 1.2 or less. .

In the above reaction, a catalyst may be added if necessary.

Examples of the catalyst include N,N-dimethylbenzylamine, triethylamine, tributylamine, triethylenediamine, benzyltrimethylammonium chloride, benzyltriethylammonium bromide, tetramethylammonium bromide, cetyltrimethylammonium bromide, zinc oxide, and the like.

The catalyst can be used alone or in combination of two or more types.

Furthermore, in the above reaction, a polymerization inhibitor (preferably hydroquinone monomethyl ether) may be blended in an appropriate ratio if necessary.

Furthermore, in the above reaction, a known organic solvent (preferably toluene) may be blended if necessary.

Further, the reaction conditions for the above reaction are such that the reaction temperature is, for example, 30° C. or higher and 110° C. or lower, and the reaction time is, for example, 1 hour or more, and, for example, 48° C. less than an hour.

Thereby, the second polyfunctional monomer (A2) is obtained.

Among such second polyfunctional monomers (A2), preferably a reaction product of pentaerythritol triacrylate and succinic anhydride (succinic anhydride-modified pentaerythritol triacrylate), dipentaerythritol pentaacrylate and succinic anhydride ( succinic anhydride-modified dipentaerythritol pentaacrylate).

Moreover, as the second polyfunctional monomer (A2), succinic anhydride-modified dipentaerythritol pentaacrylate is more preferably used.

Furthermore, as the second polyfunctional monomer (A2), commercially available products can also be used. Specifically, M-510 (polybasic acid-modified acrylic oligomer having three or more polymerizable double bonds, acid value : 80 to 120 mgKOH/g, manufactured by Toagosei Co., Ltd.), M-520 (polybasic acid-modified acrylic oligomer having 3 or more polymerizable double bonds, acid value: 20 to 40 mgKOH/g, manufactured by Toagosei Co., Ltd.), etc. can be mentioned.

The second polyfunctional monomer (A2) can be used alone or in combination of two or more types.

When two or more types of second polyfunctional monomers (A2) are used together, preferably, the second polyfunctional monomers (A2) are two or more types of second polyfunctional monomers having different numbers of polymerizable double bonds. Contains (A2).

If the second polyfunctional monomer (A2) includes two or more types of second polyfunctional monomers (A2) having different numbers of polymerizable double bonds, the strength can be adjusted arbitrarily and a true spherical shape can be obtained. can.

The acid value of such a polyfunctional monomer (A) (the first polyfunctional monomer (A1) and the second polyfunctional monomer (A2) is, for example, 10 mgKOH/g or more, preferably 50 mgKOH/g or more, or more. Preferably, it is 80 mgKOH/g or more, and for example, 200 mgKOH/g or less, preferably 120 mgKOH/g or less, more preferably 95 mgKOH/g or less.

When the above acid value is equal to or higher than the above lower limit, the proportion of true spheres can be increased, and while ensuring strength, excellent dispersibility and hollowness can be achieved.

Note that the above acid value can be measured by neutralization titration or potentiometric titration.

The polyfunctional monomer (A) can be used alone or in combination of two or more types, and preferably, the first polyfunctional monomer (A1) is used alone and the second polyfunctional monomer (A2) is used alone.

The blending ratio of the polyfunctional monomer (A) is, for example, 15% by mass or more, preferably 25% by mass or more, more preferably 35% by mass or more, still more preferably 50% by mass or more, based on the crosslinkable monomer. , particularly preferably 65% by mass or more, most preferably 75% by mass or more, and, for example, 100% by mass or less, and further, for example, 99% by mass or less.

Moreover, the crosslinkable monomer may further contain a polyfunctional monomer (B) having three or more polymerizable double bonds and having no carboxyl group.

When the crosslinking monomer contains the polyfunctional monomer (B), the strength can be improved.

Examples of the polyfunctional monomer (B) include trifunctional monomers such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate; for example, the above-mentioned tetrafunctional monomers; for example, the above-mentioned pentafunctional monomers, e.g. , the above-mentioned hexafunctional monomers, and the like, preferably tetrafunctional monomers and hexafunctional monomers, more preferably pentaerythritol tetraacrylate and dipentaerythritol hexaacrylate.

The acid value of the polyfunctional monomer (B) is, for example, less than 10 mgKOH/g, preferably 5 mgKOH/g or less, more preferably 1 mgKOH/g or less, and, for example, 0.1 mgKOH/g or more.

The blending ratio of the polyfunctional monomer (B) is, for example, 1% by mass or more with respect to the crosslinkable monomer, and is, for example, 85% by mass or less, preferably 75% by mass or less, more preferably 65% by mass. % or less, more preferably 50% by weight or less, particularly preferably 35% by weight or less, most preferably 25% by weight or less.

The blending ratio of the polyfunctional monomer (A) to the total amount of the polyfunctional monomer (A) and the polyfunctional monomer (B) is, for example, 15% by mass or more, preferably 25% by mass or more, more preferably , 35% by mass or more, more preferably 50% by mass or more, particularly preferably 65% by mass or more, most preferably 75% by mass or more, and, for example, 100% by mass or less, and, for example, 99% by mass. % or less.

If the blending ratio of the polyfunctional monomer (A) is at least the above lower limit, the strength will be improved and the dispersibility will be excellent.

Further, the crosslinkable monomer includes a bifunctional monomer having two polymerizable double bonds, if necessary.

Examples of difunctional monomers include vinyl group-containing difunctional monomers such as divinylbenzene, divinylbiphenyl, and divinylnaphthalene, allyl group-containing difunctional monomers such as diallyl phthalate, and examples such as ethylene glycol di(meth)acrylate and tetraethylene. Examples include (meth)acryloyloxy group-containing bifunctional monomers such as glycol di(meth)acrylate.

Further, as the bifunctional monomer, a reaction product of the above-mentioned trifunctional monomer and the above-mentioned amino acid (hereinafter referred to as an amino acid-modified bifunctional monomer) can also be used.

Trifunctional monomers and amino acids undergo an addition reaction (Michael addition reaction) between one polymerizable double bond in the trifunctional monomer and the amino group in the amino acid, similar to the reaction between the above-mentioned tetrafunctional or higher functional monomers and amino acids. do.

Therefore, the amino acid-modified bifunctional monomer has two polymerizable double bonds.

Such an amino acid-modified bifunctional monomer preferably includes a reaction product of pentaerythritol triacrylate and glycine (glycine-modified pentaerythritol triacrylate).

The acid value of the amino acid-modified bifunctional monomer is, for example, 10 mgKOH/g or more, preferably 50 mgKOH/g or more, more preferably 80 mgKOH/g or more, still more preferably 120 mgKOH/g or more, and, for example, 200 mgKOH/g or more. /g or less, preferably 160 mgKOH/g or less.

The bifunctional monomer preferably includes an amino acid-modified bifunctional monomer, more preferably a glycine-modified pentaerythritol triacrylate.

The blending ratio of the bifunctional monomer is, for example, 1 part by mass or more, preferably 5 parts by mass or more, based on 100 parts by mass of the total amount of the polyfunctional monomer (A) and the bifunctional monomer, and for example, 20 parts by mass or more. It is not more than 10 parts by weight, preferably not more than 10 parts by weight.

The proportion of the bifunctional monomer is, for example, 1% by mass or more, preferably 5% by mass or more, and, for example, 20% by mass or less, preferably 10% by mass or less, based on the crosslinkable monomer. It is.

The bifunctional monomers can be used alone or in combination of two or more types.

The crosslinking monomer preferably does not contain a difunctional monomer and preferably consists of a polyfunctional monomer (A) or a polyfunctional monomer (A) and a polyfunctional monomer (B).

Examples of hydrophobic solvents include esters such as ethyl acetate and butyl acetate, ether esters such as propylene glycol monomethyl ether acetate and propylene glycol monoethyl ether acetate, aromatic hydrocarbons such as benzene, toluene, and xylene, and hexane. , 2-ethylhexyl, cyclohexane, methylcyclohexane, and other aliphatic hydrocarbons, preferably esters, aromatic hydrocarbons, aliphatic hydrocarbons, and more preferably toluene. .

Hydrophobic solvents can be used alone or in combination of two or more.

Then, the crosslinking monomer and the hydrophobic solvent are mixed to prepare a mixed solution.

The blending ratio of the hydrophobic solvent is, for example, 80 parts by mass or more, preferably 200 parts by mass or more, more preferably 350 parts by mass or more, and, for example, 600 parts by mass or more. below.

In addition to the crosslinkable monomer, a monofunctional monomer having one polymerizable double bond can be blended into the mixed solution as a monomer constituting the polymer.

By blending a monofunctional monomer, a decrease in the reactivity of the vinyl group due to steric hindrance can be suppressed, the strength can be improved, and as a result, the volumetric hollowness can be increased.

Examples of the monofunctional monomer include (meth)acryloyloxy group-containing monofunctional monomers, vinyl group-containing monofunctional monomers, and monoolefins.

(Meth)acryloyloxy group-containing monofunctional monomers include (meth)acrylic acid, such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-(meth)acrylate. (meth)acrylic acid alkyl esters such as ethylexyl, for example, cyclohexyl (meth)acrylate, ring structure-containing (meth)acrylic esters such as phenyl (meth)acrylate, for example, β-hydroxyethyl (meth)acrylate; (meth)acrylic acid hydroxyalkyl esters such as γ-hydroxybutyl (meth)acrylate and δ-hydroxybutyl (meth)acrylate, such as γ-aminopropyl (meth)acrylate, γ-N (meth)acrylate , (meth)acrylic acid aminoalkyl esters such as N-diethylaminopropyl.

Vinyl group-containing monofunctional monomers include, for example, styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, sodium styrene sulfonate, vinylbiphenyl, vinylnaphthalene. Aromatic vinyl monomers such as, for example, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl n-butyl ether, vinyl phenyl ether, vinyl cyclohexyl ether, halogenated vinyl monomers such as vinyl chloride, vinylidene chloride, etc. .

Examples of the monoolefin include ethylene, propylene, 1-butene, 1-pentene, and 4-methyl-1-pentene.

The blending ratio of the monofunctional monomer is, for example, 2 parts by mass or more, and 8 parts by mass or less, based on 100 parts by mass of the total amount of the crosslinking monomer and the monofunctional monomer.

Monofunctional monomers can be used alone or in combination of two or more types.

Moreover, a polymerization initiator can also be blended into the liquid mixture.

Examples of the polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(2-methylbutyronitrile). , azo compounds such as azobisisobutyronitrile, peroxide compounds such as cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, di-t-butyl peroxide, such as benzoyl peroxide, lauroyl peroxide, etc. Examples include oil-soluble polymerization initiators such as organic peroxides, preferably azo compounds, and more preferably 2,2'-azobis(2-methylbutyronitrile).

The blending ratio of the polymerization initiator is, for example, 0.1 part by mass or more, preferably 1 part by mass or more, and, for example, 5 parts by mass or less, based on 100 parts by mass of the crosslinkable monomer.

The mixture is then added to the water and stirred.

The addition ratio of the mixed liquid is, for example, 20 parts by mass or more and, for example, 120 parts by mass or less, preferably 90 parts by mass or less, and more preferably 50 parts by mass or less, based on 100 parts of water. .

A dispersant is preferably added to the water in advance.

Examples of the dispersant include polymers such as polyvinyl alcohol, methyl cellulose, ethyl cellulose, polyacrylic acid, polyacrylimide, polyethylene oxide, and poly(hydroxystearic acid-g-methyl methacrylate-co-methacrylic acid) copolymer. Examples of dispersants include nonionic surfactants, anionic surfactants such as amphoteric surfactants, and preferably polymeric dispersants, more preferably polyvinyl alcohol.

The blending ratio of the dispersant is, for example, 1 part by mass or more, preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and, for example, 30 parts by mass, based on 100 parts by mass of the crosslinkable monomer. It is as follows.

As a method of stirring water, for example, a dispersing machine such as a homomixer, an ultrasonic homogenizer, a pressurized homogenizer, a milder, a porous membrane press-in dispersion machine, etc. is used, and preferably a homomixer is used.

Stirring conditions are set appropriately, and when using a homomixer, the rotation speed is set to, for example, 500 rpm or more and 30,000 rpm or less, for example. The stirring time is, for example, 1 minute or more, preferably 2 minutes or more, and, for example, 1 hour or less. The stirring temperature is, for example, 20°C or higher and, for example, 30°C or lower.

At this time, while the hydrophobic solvent is dispersed in water, the hydrophobic solvent has no affinity with water, and the crosslinking monomer and the monofunctional monomer blended as necessary have a relative affinity with water than the hydrophobic solvent. Therefore, the crosslinking monomer and the monofunctional monomer blended if necessary are interposed between the water and the hydrophobic solvent. Then, as the above stirring is continued, the crosslinking monomer interposed between the water and the hydrophobic solvent and the monofunctional monomer blended as necessary form droplets so as to surround the hydrophobic solvent.

As a result, crosslinkable monomer droplets containing a hydrophobic solvent are obtained by the crosslinkable monomer and a monofunctional monomer blended as necessary.

Moreover, such crosslinkable monomer droplets are dispersed in water. In other words, an aqueous dispersion containing crosslinkable monomer droplets is obtained.

Furthermore, when a porous membrane press-in dispersion machine is used, crosslinkable monomer droplets with a small particle size distribution can be obtained, and the volume average particle size distribution of the resulting hollow resin particles (described later) is also small.

The average particle diameter of the crosslinkable monomer droplets is, for example, 0.1 μm or more, preferably 0.5 μm or more, and, for example, 50 μm or less, preferably 30 μm or less.

The above average particle diameter can be determined by a dynamic light scattering method.

Subsequently, in the step of polymerizing the crosslinking monomer in the crosslinking monomer droplets to obtain resin particles containing a polymer of the crosslinking monomer encapsulating a hydrophobic solvent, the crosslinking monomer in the crosslinking monomer droplets and, if necessary, The monofunctional monomers to be blended are polymerized.

In order to polymerize the crosslinkable monomer and the monofunctional monomer blended if necessary, the aqueous dispersion is heated under an inert gas atmosphere (eg, nitrogen gas, argon, etc.) while stirring.

The heating temperature is, for example, 30°C or higher, preferably 50°C or higher, and is, for example, 90°C or lower, preferably 80°C or lower, and the heating time is, for example, 3 hours or higher, preferably is 12 hours or more and, for example, 36 hours or less.

In this polymerization, a crosslinking monomer and a monofunctional monomer blended as necessary are polymerized at the interface between the hydrophobic solvent and water. That is, the crosslinkable monomer on the surface of the crosslinkable monomer droplet and the monofunctional monomer blended if necessary are polymerized.

Therefore, by this polymerization, resin particles containing a polymer of a crosslinkable monomer encapsulating a hydrophobic solvent are obtained.

Such resin particles are dispersed in water.

Finally, in the step of removing the hydrophobic solvent encapsulated in the resin particles to obtain hollow resin particles containing a polymer of crosslinkable monomer and having a hollow interior, the hydrophobic solvent encapsulated in the resin particles is removed. remove.

To remove the hydrophobic solvent encapsulated in the resin particles, the pressure of the aqueous dispersion is reduced to vaporize the hydrophobic solvent encapsulated in the crosslinkable monomer polymer and replace it with air. As a result, the interior of the resin particle becomes hollow.

As a result, hollow resin particles containing the polymer of the crosslinking monomer and having a hollow interior are obtained.

Such hollow resin particles are dispersed in water.

This hollow resin particle is hollow inside. The hollow resin particles are hollow resin particles containing a polymer of a crosslinkable monomer, and the crosslinkable monomer contains one or more types of polyfunctional monomers having three or more polymerizable double bonds, and , because of the presence of carboxyl groups, a three-dimensional network of hyperlinks is formed, which increases the strength of the particles and allows them to withstand the negative pressure created when removing hydrophobic solvents, resulting in a high proportion of truly spherical particles. It has a high percentage of true spherical shapes.

Specifically, the proportion of truly spherical hollow resin particles is, for example, 80% or more, preferably 90% or more, and, for example, 100% or less, based on the obtained hollow resin particles.

Note that the method for measuring the proportion of truly spherical hollow resin particles will be described in detail in Examples described later.

If the shape of the hollow resin particles is truly spherical, the strength can be improved.

Therefore, for example, even if a calendering treatment is performed after applying a resin containing hollow resin particles to a base material, destruction of the hollow resin particles can be suppressed.

Moreover, since the strength is high, the volumetric hollowness ratio can be increased. Since the volumetric hollowness is high, the internal space of the hollow resin particles can be enlarged, resulting in excellent heat insulation properties.

Specifically, the volume hollowness of the hollow resin particles is, for example, 30% or more, preferably 60% or more, more preferably 75% or more, and, for example, 95% or less, preferably 85%. It is as follows.

If the volume hollowness of the hollow resin particles is equal to or less than the above upper limit, the strength will be excellent.

If the volume hollowness of the hollow resin particles is equal to or greater than the above lower limit, the heat insulation properties will be excellent.

Note that the method for measuring the volumetric hollowness will be described in detail in Examples described later.

Further, the hollow resin particles have excellent dispersibility from the viewpoint of ionization of carboxyl groups and reduction of the volume average particle diameter.

Therefore, such hollow resin particles can be suitably used when dispersed in a dispersion liquid.

The volume average particle diameter of the hollow resin particles is, for example, 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, and, for example, 50 μm or less, preferably 30 μm or less, or more. Preferably it is 20 μm or less, more preferably 10 μm or less.

Note that the method for measuring the volume average particle diameter will be described in detail in Examples described later.

The hollow resin particles thus obtained may be used in the form of a dispersion, or, if necessary, may be filtered, washed with water, dried, and used in the form of a powder for various purposes.

In the above explanation, a mixed solution was prepared by mixing a crosslinking monomer, a hydrophobic solvent, and a polymerization initiator, and the mixed solution was added to water. They can also be added separately to the water without prior mixing.

Such hollow resin particles can be used, for example, in the fields of heat-sensitive recording materials, agricultural chemicals, medicines, fragrances, liquid crystals, adhesives, etc., and are particularly suitable for use in heat-sensitive recording materials.

Therefore, in a heat-sensitive recording material that includes a support layer, a heat-insulating layer, and a heat-sensitive recording layer in this order, it is preferable that the hollow resin particles are contained in the heat-insulating layer.

Specifically, in FIG. 1, a heat-sensitive recording material 1 includes a support layer 2, a heat-insulating layer 3, and a heat-sensitive recording layer 4 in this order.

The heat-sensitive recording material 1 is a material that changes color with heat, and includes, for example, heat-sensitive recording paper, thermal transfer receiving paper, and the like.

Examples of the support layer 2 include paper and plastic sheets. The thickness of the support layer 2 is appropriately set depending on the purpose and use.

The heat insulating layer 3 is a layer that prevents the heat applied from the thermal head from dissipating to cause the thermal recording layer 4 to develop color.

The heat insulating layer 3 includes the hollow resin particles described above and a binder resin such as polyvinyl alcohol, polyacrylamide, styrene/butadiene emulsion, or acrylic emulsion.

The blending ratio of the hollow resin particles and the binder resin is appropriately set depending on the purpose and use.

The thickness of the heat insulating layer 3 is appropriately set depending on the purpose and use.

The thermosensitive recording layer 4 contains the above binder resin, dye, and color developer.

Examples of the dye include known basic organic dyes such as fluoran organic dyes, triallylmethane organic dyes, and phenoxyazine organic dyes.

The color developer is not particularly limited, and examples thereof include known color developers such as phenolic compounds and aromatic carboxylic acids.

The blending ratio of the binder resin, dye, and color developer is appropriately set according to the purpose and use. The thickness of the heat-sensitive recording layer 4 is appropriately set according to the purpose and use.

To manufacture the heat-sensitive recording material 1, first, the heat insulating layer 3 is formed on the support layer 2.

To form the heat insulating layer 3, a mixture of hollow resin particles and a binder resin is applied by a known coating method such as a curtain coating method, a roll coating method, or a blade coating method, and then dried.

Next, a thermosensitive recording layer 4 is formed on the heat insulating layer 3.

To form the heat-sensitive recording layer 4, a mixture of the above binder resin, dye, and color developer is applied by a known coating method such as a curtain coating method, a roll coating method, or a blade coating method, and then ,dry.

As a result, a thermosensitive recording material 1 is obtained.

In such a heat-sensitive recording material 1, the heat insulating layer 3 contains the hollow resin particles described above. Therefore, the heat-sensitive recording material 1 has excellent heat insulation properties.

In the above description, the heat-sensitive recording material 1 is composed of the support layer 2, the heat-insulating layer 3, and the heat-sensitive recording layer 4. 4, an intermediate layer (not shown) may be interposed between the two layers.

Further, an overcoat layer (not shown) may be disposed on the heat-sensitive recording layer 4. In such a case, the heat-sensitive recording material 1 includes a support layer 2, a heat-insulating layer 3, a heat-sensitive recording layer 4, and an overcoat layer (not shown) in this order.

Further, a back coat layer (not shown) may be disposed under the support layer 2. In such a case, the heat-sensitive recording material 1 includes a back coat layer (not shown), a support layer 2, a heat insulating layer 3, and a heat-sensitive recording layer 4 in this order.

Further, the heat-sensitive recording material 1 can also include both the above-mentioned overcoat layer (not shown) and the above-mentioned backcoat layer (not shown). In such a case, the heat-sensitive recording material 1 includes, in order, a back coat layer (not shown), a support layer 2, a heat insulating layer 3, a heat-sensitive recording layer 4, and an overcoat layer (not shown). .

In addition, in the process of obtaining the resin particles described above, by blending oil-soluble components such as pharmaceuticals, agricultural chemicals, cosmetics, organic/inorganic pigments, dyes, fragrances, and lubricating oils with hydrophobic solvents, the inside of the resin particles can be improved. Additionally, microcapsules encapsulating oil-soluble components can also be prepared.

Such microcapsules include a core made of an oil-soluble component and a shell covering the core and containing a polymer of the above-mentioned crosslinkable monomer.

In this microcapsule, since the shell contains a polymer of a crosslinking monomer, the shell has a high proportion of true spheres, and has excellent dispersibility while ensuring strength.

Microcapsules can be suitably used as a stabilizer and sustained release agent for oil-soluble components.

Specific numerical values such as blending ratios (content ratios), physical property values, parameters, etc. used in the following description are the corresponding blending ratios (content ratios) described in the above "Details of Carrying Out the Invention". ), physical property values, parameters, etc. may be replaced by the upper limit value (value defined as "less than" or "less than") or lower limit value (value defined as "more than" or "exceeding"). can. Furthermore, in the following description, unless otherwise specified, "parts" and "%" are based on mass.

1. Details of Components Each component used in each Example and each Comparative Example is described below.
PETTA-gly: Glycine-modified pentaerythritol tetraacrylate DPPA-gly: Glycine-modified dipentaerythritol pentaacrylate DPHA-gly: Glycine-modified dipentaerythritol hexaacrylate DTMPTA-gly: Glycine-modified ditrimethylolpropane tetraacrylate PETA-suc: Succinic anhydride Modified pentaerythritol triacrylate DPPA-suc: Succinic anhydride modified dipentaerythritol pentaacrylate M-510: Polybasic acid-modified acrylic oligomer having 3 or more polymerizable double bonds, acid value: 80-120 mgKOH/g, Toa M-520 manufactured by Gosei Co., Ltd.: Polybasic acid-modified acrylic oligomer having 3 or more polymerizable double bonds, acid value: 20 to 40 mgKOH/g, manufactured by Toagosei Co., Ltd. PETTA: Pentaerythritol tetraacrylate DPHA: Dipentaerythritol hexa Acrylate TMPTA-gly: Glycine-modified trimethylolpropane triacrylate PETA-gly: Glycine-modified pentaerythritol triacrylate MAA: Methacrylic acid AES: 2-acryloyloxyethylsuccinic acid PVA 9-88: Polyvinyl alcohol, manufactured by Kuraray Co., Ltd. AIBN: 2 ,2-azobis(isobutyronitrile)
2. Preparation of first polyfunctional monomer (A1) and second polyfunctional monomer (A2) (Preparation of first polyfunctional monomer)
In a reaction vessel equipped with a reflux device and a stirrer, 41.2 parts of pentaerythritol tetraacrylate (number of polymerizable double bonds per molecule, molecular weight 352) was mixed with a compound having a primary amino group and a carboxyl group. 8.7 parts of certain glycine (1 mole relative to pentaerythritol tetraacrylate), 0.1 part of hydroquinone monomethyl ether as a polymerization inhibitor, and 50 parts of ethanol as an organic solvent were mixed. Next, the mixture was stirred while blowing air and allowed to react at 70° C. for 5 hours. Then, while blowing air, ethanol and water were distilled off under reduced pressure to obtain glycine-modified pentaerythritol tetraacrylate.

In a similar manner, glycine-modified dipentaerythritol pentaacrylate, glycine-modified dipentaerythritol hexaacrylate, and glycine-modified ditrimethylolpropane tetraacrylate were prepared.

(Preparation of second polyfunctional monomer)
In a reaction vessel equipped with a reflux device and a stirrer, 33.3 parts of pentaerythritol triacrylate (3 polymerizable double bonds per molecule, molecular weight 298), 11.1 parts of succinic anhydride (pentaerythritol triacrylate) 1 mole), 0.1 part of hydroquinone monomethyl ether as a polymerization inhibitor, and 55.5 parts of toluene as a solvent were mixed. Next, the mixture was stirred while blowing air and allowed to react at 70°C for 12 hours. Next, while blowing air, toluene was distilled off under reduced pressure to obtain succinic anhydride-modified pentaerythritol triacrylate.

In a similar manner, succinic anhydride modified dipentaerythritol pentaacrylate was prepared.

3. Preparation of hollow resin particles Example 1
A mixed solution was prepared by mixing 19 parts by mass of PETTA-gly as a polyfunctional monomer (A), 0.4 parts by mass of AIBN as a polymerization initiator, and 80 parts by mass of toluene as a hydrophobic solvent. Then, this mixture was mixed with 400 parts by mass of distilled water containing 5 parts by mass of PVA9-88 as a dispersant, and then stirred using a homogenizer at a stirring speed of 5000 rpm and room temperature (25°C). An aqueous dispersion was obtained.

The average particle diameter of the obtained crosslinkable monomer droplets was about 4 μm.

Next, the aqueous dispersion was heated at 70° C. under a nitrogen gas atmosphere with stirring, and polymerized for 24 hours. As a result, an aqueous dispersion containing resin particles containing a hydrophobic solvent was obtained.

The pressure of the resulting aqueous dispersion was reduced, and the hydrophobic solvent encapsulated in the resin particles was distilled off to obtain an aqueous dispersion containing hollow resin particles.

Examples 2 to 9, Comparative Examples 1 to 4
An aqueous dispersion containing hollow resin particles was obtained in the same manner as in Example 1, except that the formulation was changed according to the description in Table 1.

3. Evaluation (acid value)
The acid value of the polyfunctional monomer (A) used in each Example and each Comparative Example was measured by neutralization titration method (JISK 0070). The results are shown in Table 1.
(Volume average particle diameter)
The volume average particle diameter of the hollow resin particles was measured for each of the hollow resin particles of each Example and each Comparative Example. Specifically, 1 g of sample and 10 g of distilled water were collected in a 30 mL glass sample bottle, stirred for 5 minutes using a magnetic stirrer, and then the particle size was determined using a particle size analyzer Microtrac HRA (manufactured by Nikkiso Co., Ltd.) under the following conditions. Distribution measurements were performed.

Particle Transparency=Transp
Spherical Particles=Yes
Particle Refractive Index=1.50
Fluid Refractive Index =1.333
The results are shown in Table 1.
(shape and volumetric hollowness)
Regarding the hollow resin particles of each Example and each Comparative Example, the shape of the hollow resin particles was observed, and the volume hollowness was measured. Specifically, an aqueous dispersion containing hollow resin particles was applied onto aluminum foil and dried at 40° C. for 12 hours or more to obtain a coating film. Next, this coating film was immersed in liquid nitrogen to freeze it, and then immediately cut, and the obtained cut surface was observed using an electron microscope. The particle diameter and the diameter of the hollow portion of 10 randomly selected hollow resin particles were measured, and the volumetric hollowness ratio was calculated. The average value of the obtained volumetric hollowness was taken as the volumetric hollowness of the hollow resin particles.

The results are shown in Table 1.
(Percentage of true spherical hollow resin particles)
The proportion of truly spherical hollow resin particles was calculated for the hollow resin particles of each Example and each Comparative Example. Specifically, an aqueous dispersion containing hollow resin particles was applied onto aluminum foil and dried at 40° C. for 12 hours or more to obtain a coating film. The surface of the resulting coating film was observed using an electron microscope, and the proportion of particles that maintained a true spherical shape among 50 randomly selected hollow resin particles was calculated. The results are shown in Table 1.
(dispersibility)
70 mL (concentration 10% by mass) of the dispersion liquid of each Example and each Comparative Example was put into a 100 mL screw tube (diameter 4 cm), and after 2 weeks of standing at room temperature, it precipitated and agglomerated (hollow resin particles) on the bottom surface, or It was measured by the height of the floating agglomerates (resin particles) on the surface.

Dispersibility was evaluated based on the following criteria. The results are shown in Table 1.
◎: The height of the aggregate was 0 cm or more and 1 cm or less.
Good: The height of the aggregate was more than 1 cm and less than 2 cm.
Δ: The height of the aggregate was more than 2 cm and less than 3 cm.
x: The height of the aggregate was over 3 cm.
(Strength evaluation: Calendar test)
The strength of the hollow resin particles of each Example and each Comparative Example was measured. Specifically, an aqueous dispersion containing hollow resin particles whose nonvolatile content was adjusted to 10% with distilled water was coated on one side of commercially available coated paper (basis weight 74 g/m ² ) so that the coating amount after drying was 2 g/m ^{2 .} It was coated so that . This coated paper was subjected to calender treatment using a calender device ("desktop calender single plate type" manufactured by Yuri Roll Co., Ltd.) at room temperature, linear pressure of 200 kg/cm, and processing speed of 2 m/min. The surface of the coated paper after the calender treatment on the hollow resin particle layer side and the cut surface of the hollow resin particle layer were observed using a scanning electron microscope at a magnification of 2000 times. The cut surface of the hollow resin particle layer was obtained by immersing the coated paper in liquid nitrogen, freezing it, and then immediately cutting it.

Strength was evaluated based on the following criteria. The results are shown in Table 1.
◎: Particles on the surface maintain their shape ○: Particles on the surface almost maintain their shape △: Approximately half of the particles on the surface are crushed ×: All particles on the surface are crushed ( amount of aggregates after synthesis)
The amount of aggregates generated was measured for the hollow resin particles of each Example and each Comparative Example. Specifically, 100 g of the synthesized emulsion was filtered through a 300 mesh stainless wire mesh, dried at 150°C for 20 minutes, the weight of the residue was measured, and the amount of aggregates was obtained by calculating the weight ratio to the filtered emulsion. . The results are shown in Table 1.
4. Discussion Examples 1 to 9, in which the crosslinkable monomer has three or more polymerizable double bonds and contains one or more polyfunctional monomers (A) having a carboxyl group, are The ratio is high, and while ensuring strength, it has excellent dispersibility and a high volumetric hollowness.

On the other hand, in Comparative Examples 3 and 4, in which the crosslinking monomer did not contain a polyfunctional monomer having three or more polymerizable double bonds, volume hollowness, strength, and dispersibility were reduced.

Moreover, in Comparative Examples 1 and 2, in which the crosslinking monomer did not have a carboxyl group, the strength and dispersibility decreased.

From this, if the crosslinking monomer contains a polyfunctional monomer (A) having three or more polymerizable double bonds and a carboxyl group, it will have excellent strength and volumetric hollowness, and will have excellent dispersion. It can be seen that it was possible to obtain truly spherical hollow resin particles with excellent properties.

Claims (7)

Hollow resin particles having a hollow interior and containing a polymer of a crosslinkable monomer,
The crosslinkable monomer has three or more polymerizable double bonds and contains one or more polyfunctional monomers (A) having a carboxyl group,
The polyfunctional monomer (A) is a reaction product of a tetrafunctional or higher functional monomer and an amino acid, and/or a reaction product of a hydroxyl group-containing trifunctional or higher monomer and an acid anhydride,
The tetrafunctional or higher functional monomer is selected from the group consisting of ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. at least one;
The hydroxyl group-containing trifunctional or higher functional monomer is at least one selected from the group consisting of pentaerythritol tri(meth)acrylate and dipentaerythritol penta(meth)acrylate,
The reaction product of the tetrafunctional or higher functional monomer and the amino acid is a reaction product of a Michael addition reaction between one polymerizable double bond in the tetrafunctional or higher functional monomer and an amino group in the amino acid,
A hollow resin characterized in that the reaction product of the hydroxyl group-containing trifunctional or higher-functional monomer and the acid anhydride is a reaction product of an ester reaction between the hydroxyl group-containing trifunctional or higher-functional monomer and the acid anhydride. particle. The hollow resin particle according to claim 1, wherein the crosslinkable monomer contains two or more types of the polyfunctional monomer (A) having different numbers of polymerizable double bonds. 3. The crosslinking monomer according to claim 1 or 2, further comprising a polyfunctional monomer (B) having three or more polymerizable double bonds and having no carboxyl group. Hollow resin particles. The hollow resin particle according to claim 3, wherein the proportion of the polyfunctional monomer (A) to the total amount of the polyfunctional monomer (A) and the polyfunctional monomer (B) is 50% by mass or more. A supporting layer, a heat insulating layer, and a heat-sensitive recording layer are provided in this order,
A heat-sensitive recording material, wherein the heat-insulating layer contains the hollow resin particles according to any one of claims 1 to 4. mixing a crosslinking monomer and a hydrophobic solvent in water to obtain crosslinking monomer droplets encapsulating the hydrophobic solvent with the crosslinking monomer;
polymerizing the crosslinking monomer in the crosslinking monomer droplets to obtain resin particles containing a polymer of the crosslinking monomer encapsulating the hydrophobic solvent;
a step of removing the hydrophobic solvent encapsulated in the resin particles to obtain hollow resin particles containing the polymer of the crosslinkable monomer and having a hollow interior;
The crosslinkable monomer has three or more polymerizable double bonds and contains one or more polyfunctional monomers (A) having a carboxyl group,
The polyfunctional monomer (A) is a reaction product of a tetrafunctional or higher functional monomer and an amino acid, and/or a reaction product of a hydroxyl group-containing trifunctional or higher monomer and an acid anhydride,
The tetrafunctional or higher functional monomer is selected from the group consisting of ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. at least one;
The hydroxyl group-containing trifunctional or higher functional monomer is at least one selected from the group consisting of pentaerythritol tri(meth)acrylate and dipentaerythritol penta(meth)acrylate,
The reaction product of the tetrafunctional or higher functional monomer and the amino acid is a reaction product of a Michael addition reaction between one polymerizable double bond in the tetrafunctional or higher functional monomer and an amino group in the amino acid,
A hollow resin characterized in that the reaction product of the hydroxyl group-containing trifunctional or higher-functional monomer and the acid anhydride is a reaction product of an ester reaction between the hydroxyl group-containing trifunctional or higher-functional monomer and the acid anhydride. Method of manufacturing particles. comprising a core and a shell covering the core and containing a polymer of a crosslinkable monomer,
The crosslinkable monomer has three or more polymerizable double bonds and contains one or more polyfunctional monomers (A) having a carboxyl group,
The polyfunctional monomer (A) is a reaction product of a tetrafunctional or higher functional monomer and an amino acid, and/or a reaction product of a hydroxyl group-containing trifunctional or higher monomer and an acid anhydride,
The tetrafunctional or higher functional monomer is selected from the group consisting of ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. at least one;
The hydroxyl group-containing trifunctional or higher functional monomer is at least one selected from the group consisting of pentaerythritol tri(meth)acrylate and dipentaerythritol penta(meth)acrylate,
The reaction product of the tetrafunctional or higher functional monomer and the amino acid is a reaction product of a Michael addition reaction between one polymerizable double bond in the tetrafunctional or higher functional monomer and an amino group in the amino acid,
A microcapsule, characterized in that the reaction product of the hydroxyl group-containing trifunctional or higher-functional monomer and the acid anhydride is a reaction product of an ester reaction between the hydroxyl group-containing trifunctional or higher-functional monomer and the acid anhydride. .

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