JP7437218B2 - Emulsion particles, coating agents, dried products, and methods for producing emulsion particles - Google Patents

Description

The present invention relates to emulsion particles, a coating agent, a dried product, and a method for producing emulsion particles, and more particularly, the present invention relates to emulsion particles, a coating agent containing the emulsion particles, a dried product of the emulsion particles, and a method for producing the emulsion particles. .

Conventionally, emulsion 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, and fragrances.

Such emulsion particles include, for example, a core layer made of a polymer (A) prepared by polymerizing a vinyl monomer mixture (a) containing 5 to 80% by weight of an acidic group-containing vinyl monomer; A primary shell layer consisting of a polymer (B) prepared by polymerizing a vinyl monomer mixture (b) containing 0 to 10% by weight of monomers, a vinyl monomer mixture (B) that does not contain any acidic group-containing vinyl monomers ( c) is composed of a secondary shell layer that is permeable to a nonvolatile base and is made of a polymer (C) prepared by polymerizing in the presence of a nonionic surfactant and has a glass transition temperature of 50 ° C. or higher. By adding a nonvolatile base, emulsion particles have been proposed that have voids inside the particles when dried as a result of the base neutralizing the core and causing hydration and swelling (see, for example, Patent Document 1).

Further, as emulsion particles, cored multilayer emulsion particles have been proposed that have a core particle inside the particle and a void layer in the outer layer of the core particle (see, for example, Patent Document 2).

Japanese Patent Application Publication No. 6-73138 Japanese Patent Application Publication No. 4-211411

For example, when such emulsion particles are incorporated into a heat insulating layer of a heat-sensitive recording material, from the viewpoint of suppressing deterioration of printing due to heat and improving durability against drying at high temperatures, emulsion particles are requires heat resistance.

The present invention provides emulsion particles with excellent heat resistance, a coating agent containing the emulsion particles, a dried product of the emulsion particles, and a method for producing the emulsion particles.

The present invention [1] provides a first polymer that is a polymerization product of a first monomer component containing an acidic group-containing vinyl monomer, and a polymerization product of a second monomer component that does not substantially contain the acidic group-containing vinyl monomer. in the first monomer component, the acidic group-containing vinyl monomer accounts for 10% by mass or more and 80% by mass or less with respect to the first monomer component, and the glass transition of the second polymer An emulsion wherein the temperature is 112.0° C. or higher, at least a portion of the acid functional groups in the acidic group-containing vinyl monomer form a salt, and the first polymer is coated with the second polymer. It is a particle.

The present invention [2] is characterized in that the second monomer component contains (meth)acrylamide, and the content of (meth)acrylamide is more than 10% by mass and not more than 80% by mass with respect to the second monomer component. Contains the emulsion particles described in [1] above.

The present invention [3] is characterized in that the first monomer component contains methyl methacrylate, and the content of methyl methacrylate is 50% by mass or more based on the first monomer component. 2] contains the emulsion particles described in [2].

The present invention [4] provides any of the above [1] to [3], wherein the second monomer component contains styrene, and the content of styrene is 10% by mass or more with respect to the second monomer component. It contains the emulsion particles described in item 1.

The present invention [5] includes a third polymer that is a polymerization product of a third monomer component, the first polymer is coated with the third polymer, and the third polymer is coated with the second polymer. Contains the emulsion particles described in any one of [1] to [4] above.

The present invention [6] is characterized in that the third monomer component includes the acidic group-containing vinyl monomer, and in the third monomer component, the acidic group-containing vinyl monomer is 1% by mass or more and 10% by mass or less. Contains the emulsion particles described in [5].

The present invention [7] includes a fourth polymer that is a polymerization product of a fourth monomer component, and the fourth polymer is coated with the first polymer. Contains the emulsion particles described in Section.

The present invention [8] includes a coating agent containing the emulsion particles described in any one of [1] to [7] above.

The present invention [9] includes a dried product that is a dried product of the emulsion particles described in any one of the above [1] to [7].

The present invention [10] includes the dried product according to the above [9], which is hollow inside.

The present invention [11] includes a step of polymerizing a first monomer component containing an acidic group-containing vinyl monomer to prepare a first polymer, and a step of polymerizing a second monomer component not containing the acidic group-containing vinyl monomer, and and a step of neutralizing at least a portion of the acid functional groups in the acidic group-containing vinyl monomer, wherein in the first monomer component, the acidic group-containing vinyl monomer is The emulsion is 10% by mass or more and 80% by mass or less based on the ingredients, the glass transition temperature of the second polymer is 112.0° C. or more, and the first polymer is coated with the second polymer. This is a method for producing particles.

The emulsion particles of the present invention include a second polymer and a first polymer coated on the second polymer. That is, the outermost surface of the emulsion particles is the second polymer. Moreover, the glass transition temperature of the second polymer is 112.0° C. or higher. Therefore, this emulsion particle has excellent heat resistance.

Since the coating agent of the present invention contains the emulsion particles of the present invention, it has excellent heat resistance.

Since the dried product of the present invention is a dried product of the emulsion particles of the present invention, it has excellent heat resistance.

The method for producing emulsion particles of the present invention is a method for producing emulsion particles comprising a second polymer and a first polymer coated on the second polymer, wherein the second polymer has a glass transition temperature of 112.0°C or higher. be. Therefore, the emulsion particles obtained by this method for producing emulsion particles have excellent heat resistance.

FIG. 1 is a schematic diagram showing an embodiment of the method for producing emulsion particles of the present invention, and FIG. 1A shows a fourth polymer preparation step of polymerizing a fourth monomer component to prepare a fourth polymer, FIG. 1B shows a first polymer preparation step of polymerizing a first monomer component to prepare a first polymer, and FIG. 1C shows a third polymer preparation step of polymerizing a third monomer component to prepare a third polymer. 1D shows a neutralization step of neutralizing at least a portion of the acid functional groups in the acidic group-containing vinyl monomers in the first polymer and the third polymer, and FIG. 1E shows polymerizing the second monomer component, The second polymer preparation process of preparing the second polymer is shown. FIG. 2 shows the results of the heat resistance test of Example 9, FIG. 2A shows the results of scanning electron microscopy, and FIG. 2B shows the results of transmission electron microscopy. 3 shows the results of the heat resistance test of Example 13, FIG. 3A shows the results of scanning electron microscopy, and FIG. 3B shows the results of transmission electron microscopy. FIG. 4 shows the results of the heat resistance test of Comparative Example 2, FIG. 4A shows the results of scanning electron microscopy, and FIG. 4B shows the results of transmission electron microscopy.

The emulsion particles of the present invention include a first polymer and a second polymer as essential components, and a third polymer, a fourth polymer, and a fifth polymer as optional components.

In the following description, a case in which the emulsion particles include a first polymer, a second polymer, a third polymer, and a fourth polymer will be explained in detail.
1. First Polymer The first polymer is a polymerization product of the first monomer component.

The first monomer component includes an acidic group-containing vinyl monomer.

If the first monomer component includes an acidic group-containing vinyl monomer, the first polymer can be swollen in the neutralization step (described later).

The acidic group-containing vinyl monomer is a vinyl monomer containing an acidic group (eg, carboxyl group, sulfonic acid group, phosphoric acid group).

Examples of acidic group-containing vinyl monomers include carboxy group-containing vinyl monomers, sulfonic acid group-containing vinyl monomers, phosphoric acid group-containing vinyl monomers, and the like.

Examples of the carboxyl group-containing vinyl monomer include (meth)acrylic acid, maleic anhydride, fumaric acid, itaconic acid, and crotonic acid.

Examples of the sulfonic acid group-containing vinyl monomer include allylsulfonic acid and methallylsulfonic acid.

Examples of the phosphoric acid group-containing vinyl monomer include acid phosphooxyethyl (meth)acrylate.

The acidic group-containing vinyl monomers can be used alone or in combination of two or more types.

The acidic group-containing vinyl monomer is preferably a carboxyl group-containing vinyl monomer, more preferably (meth)acrylic acid, and still more preferably methacrylic acid.

In the first monomer component, the blending ratio of the acidic group-containing vinyl monomer is 10% by mass or more, preferably 30% by mass or more, and 80% by mass or less, preferably 50% by mass or more, based on the first monomer component. % by mass or less.

If the blending ratio of the acidic group-containing vinyl monomer is equal to or higher than the above lower limit, swelling will be improved, and accordingly, the internal porosity will be improved.

On the other hand, if the blending ratio of the acidic group-containing vinyl monomer is less than the above-mentioned lower limit, swelling will be insufficient and formation of a core-shell structure will be lacking.

Moreover, if the blending ratio of the acidic group-containing vinyl monomer is below the above upper limit, swelling will be improved, and accordingly, the internal porosity will be improved.

On the other hand, when the blending ratio of the acidic group-containing vinyl monomer exceeds the above upper limit, particle stability decreases and agglomeration and precipitation occur.

Further, the first monomer component preferably includes an alkyl (meth)acrylate ester.

Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate having 1 to 8 carbon atoms. Examples include (meth)acrylic acid alkyl esters having an alkyl moiety.

(Meth)acrylic acid alkyl esters can be used alone or in combination of two or more types.

The (meth)acrylic acid alkyl ester is preferably a (meth)acrylic acid alkyl ester having an alkyl moiety having 2 to 4 carbon atoms, more preferably methyl (meth)acrylate, n-butyl (meth)acrylate. or a combination thereof, more preferably methyl methacrylate, butyl acrylate, or a combination thereof, particularly preferably methyl methacrylate and butyl acrylate.

In the first monomer component, the blending ratio of the (meth)acrylic acid alkyl ester is, for example, 20% by mass or more, preferably 50% by mass or more, and, for example, 95% by mass or less, preferably 70% by mass. It is as follows.

In particular, when the (meth)acrylic acid alkyl ester contains methyl methacrylate (when the first monomer component contains methyl methacrylate), the blending ratio of methyl methacrylate to the first monomer component is For example, it is 40% by mass or more, preferably 50% by mass or more, and, for example, 70% by mass or less.

When the blending ratio of methyl methacrylate is equal to or higher than the above lower limit, stabilization of the particle size is excellent.

In addition, when the (meth)acrylic acid alkyl ester contains methyl methacrylate and butyl acrylate (when the first monomer component contains methyl methacrylate and butyl acrylate), the blending ratio of methyl methacrylate is is, for example, 80 parts by mass or more, preferably 85 parts by mass or more, and, for example, 95 parts by mass or less, based on 100 parts by mass of the total amount of methyl methacrylate and butyl acrylate. The blending ratio of butyl is, for example, 5 parts by mass or more and, for example, 20 parts by mass or less, preferably 15 parts by mass or less, based on 100 parts by mass of the total amount of methyl methacrylate and butyl acrylate.

Moreover, the first monomer component can contain a copolymerizable monomer (hereinafter referred to as a first copolymerizable monomer) that can be copolymerized with the acidic group-containing vinyl monomer and the alkyl (meth)acrylate ester.

Examples of the first copolymerizable monomer include functional group-containing vinyl monomers (excluding acidic group-containing vinyl monomers), vinyl esters, aromatic vinyl monomers, heterocyclic vinyl compounds, halogenated vinylidene compounds, and α-olefins. and dienes.

Examples of the functional group-containing vinyl monomer include a hydroxyl group-containing vinyl monomer, an amino group-containing vinyl monomer, a glycidyl group-containing vinyl monomer, a cyano group-containing vinyl monomer, and an acetoacetoxy group-containing vinyl monomer.

Examples of the hydroxyl group-containing vinyl monomer include 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate.

Examples of amino group-containing vinyl monomers include 2-aminoethyl (meth)acrylate, 2-(N-methylamino)ethyl (meth)acrylate, and 2-(N,N-dimethylamino) (meth)acrylate. Examples include ethyl.

Examples of the glycidyl group-containing vinyl monomer include glycidyl (meth)acrylate.

Examples of the cyano group-containing vinyl monomer include (meth)acrylonitrile.

Examples of the acetoacetoxy group-containing vinyl monomer include acetoacetoxyethyl (meth)acrylate.

Examples of vinyl esters include vinyl acetate and vinyl propionate.

Examples of the aromatic vinyl monomer include styrene and α-methylstyrene.

Examples of the heterocyclic vinyl compound include vinylpyrrolidone.

Examples of the vinylidene halide compound include vinylidene chloride and vinylidene fluoride.

Examples of α-olefins include ethylene and propylene.

Examples of dienes include butadiene.

Furthermore, a crosslinkable vinyl monomer can also be mentioned as the first copolymerizable monomer.

Examples of the crosslinkable vinyl monomer include compounds containing two or more vinyl groups, such as methylenebis(meth)acrylamide, divinylbenzene, and di(meth)acrylate containing a polyethylene glycol chain.

The first copolymerizable monomer can be used alone or in combination of two or more types.

The blending ratio of the first copolymerizable monomer is, for example, 0% by mass or more, preferably 1% by mass or more, more preferably 5% by mass or more, and, for example, 20% by mass or more, based on the first monomer component. % by mass or less.

The first monomer component preferably does not contain the first copolymerizable monomer and contains an acidic group-containing vinyl monomer and a (meth)acrylic acid alkyl ester, more preferably an acidic group-containing vinyl monomer and a (meth)acrylic acid alkyl ester. Consists of alkyl esters.

The first polymer is obtained by polymerizing the first monomer component by the method described below.

The blending ratio of the first polymer is, for example, 1 part by mass or more and, for example, 10 parts by mass or less with respect to 100 parts by mass of the total amount of the first polymer, second polymer, third polymer, and fourth polymer. be.
2. Second Polymer The second polymer is a polymerization product of the second monomer component.

The second monomer component does not substantially contain the acidic group-containing vinyl monomer described above.

"Not contained in the acidic group-containing vinyl monomer" means that the content of the acidic group-containing vinyl monomer is 0.1% by mass or less, preferably 0.01% by mass or less, more preferably 0.01% by mass or less, based on the second monomer component. means 0.001% by mass or less.

The second monomer component preferably contains the above-mentioned aromatic vinyl monomer and the above-mentioned hydroxyl group-containing vinyl monomer, or contains no hydroxyl group-containing vinyl monomer but an aromatic vinyl monomer, and more preferably contains an aromatic vinyl monomer. Contains monomers and hydroxyl group-containing vinyl monomers.

Examples of the aromatic vinyl monomer include the aromatic vinyl monomers listed for the first monomer component, and preferably styrene.

In the second monomer component, the blending ratio of the aromatic vinyl monomer is, for example, 10% by mass or more, preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, particularly preferably is 70% by mass or more and, for example, 90% by mass or less.

In particular, when the aromatic vinyl monomer contains styrene (when the second monomer component contains styrene), the blending ratio of styrene is preferably, for example, 10% by mass or more with respect to the second monomer component. is 40% by mass or more, more preferably 50% by mass or more, further preferably 60% by mass or more, particularly preferably 70% by mass or more, and, for example, 90% by mass or less.

If the blending ratio of styrene is at least the above lower limit, emulsification and polymerization stability will be excellent.

Examples of the hydroxyl group-containing vinyl monomer include the hydroxyl group-containing vinyl monomers listed for the first monomer component, preferably 2-hydroxyethyl (meth)acrylate, more preferably 2-hydroxyethyl methacrylate.

In the second monomer component, the blending ratio of the hydroxyl group-containing vinyl monomer is, for example, 1% by mass or more and, for example, 10% by mass or less.

Further, from the viewpoint of increasing the glass transition temperature (described later) of the second polymer, the second monomer component preferably contains (meth)acrylamide and/or isobornyl (meth)acrylate, and more preferably contains methacrylamide and/or isobornyl (meth)acrylate. Contains/or isobornyl methacrylate, more preferably either one of methacrylamide and isobornyl methacrylate.

When the second monomer component contains (meth)acrylamide, the blending ratio of (meth)acrylamide is, for example, more than 10% by mass, preferably 15% by mass or more, based on the second monomer component, Further, for example, it is 80% by mass or less, preferably 40% by mass or less, and more preferably 30% by mass or less.

When the blending ratio of (meth)acrylamide is at least the above lower limit, the glass transition temperature (described later) of the second polymer can be increased, and as a result, emulsion particles with excellent heat resistance can be obtained.

Moreover, if the blending ratio of (meth)acrylamide is below the above upper limit, emulsification and polymerization stability will be excellent.

Further, when the second monomer component contains isobornyl (meth)acrylate, the blending ratio of isobornyl (meth)acrylate is, for example, 15% by mass or more, preferably 25% by mass or more, based on the second monomer component. It is at least 80% by mass, preferably at most 50% by mass.

When the blending ratio of isobornyl (meth)acrylate is at least the above lower limit, the glass transition temperature (described later) of the second polymer can be increased, and as a result, emulsion particles with excellent heat resistance can be obtained.

Moreover, if the blending ratio of isobornyl (meth)acrylate is below the above upper limit, the polymerization stability will be excellent.

Further, the second monomer component may preferably further include the above-mentioned crosslinkable vinyl monomer (preferably divinylbenzene) from the viewpoint of increasing the glass transition temperature (described later) of the second polymer.

The blending ratio of the crosslinkable vinyl monomer is, for example, 0% by mass or more, preferably 1% by mass or more, more preferably 3% by mass or more, and, for example, 10% by mass, based on the second monomer component. It is as follows.

The second monomer component is a copolymerizable monomer (hereinafter referred to as a second copolymerizable monomer) that can be copolymerized with an aromatic vinyl monomer, a hydroxyl group-containing vinyl monomer, (meth)acrylamide, and isobornyl (meth)acrylate, and a crosslinkable vinyl monomer. (referred to as a functional monomer).

The second copolymerizable monomers include the above-mentioned (meth)acrylic acid alkyl esters, the above-mentioned functional group-containing vinyl monomers (excluding acidic group-containing vinyl monomers, hydroxyl group-containing vinyl monomers, and (meth)acrylamide), and the above-mentioned vinyl monomers. Examples include esters, the above-mentioned heterocyclic vinyl compounds, the above-mentioned vinylidene halides, the above-mentioned α-olefins, and the above-mentioned dienes.

The second copolymerizable monomer can be used alone or in combination of two or more types.

The blending ratio of the second copolymerizable monomer is, for example, 0% by mass or more, preferably 1% by mass or more, more preferably 5% by mass or more, and, for example, 20% by mass or more, based on the second monomer component. % by mass or less.

The second monomer component preferably does not contain the second copolymerizable monomer, but contains an aromatic vinyl monomer, a hydroxyl group-containing vinyl monomer, (meth)acrylamide, and, if necessary, a crosslinkable vinyl monomer, or , an aromatic vinyl monomer, a hydroxyl group-containing vinyl monomer, isobornyl (meth)acrylate, and optionally a crosslinkable vinyl monomer, more preferably an aromatic vinyl monomer, a hydroxyl group-containing vinyl monomer, and (meth)isobornyl acrylate. ) Acrylamide and, if necessary, a crosslinkable vinyl monomer, or an aromatic vinyl monomer, a hydroxyl group-containing vinyl monomer, isobornyl (meth)acrylate, and, if necessary, a crosslinkable vinyl monomer.

The second polymer is obtained by polymerizing the second monomer component by the method described below.

The glass transition temperature of the second polymer is 112.0°C or higher, preferably 113.0°C or higher, more preferably 115.0°C or higher, even more preferably 117.0°C or higher, and, for example, The temperature is 260°C or less.

When the glass transition temperature of the second polymer is equal to or higher than the above lower limit, emulsion particles having excellent heat resistance can be obtained.

The glass transition temperature of the second polymer is determined by the glass transition point Tgi of the homopolymer of each monomer described in Polymer Handbook, 2 Volumes Set, 4th Edition and the homopolymer mass of each monomer added during polymerization. It can be calculated from the rate xi according to the formula below.
(1/Tg)=Σ(xi/Tgi) (1)
The blending ratio of the second polymer is, for example, 5 parts by mass or more, preferably 30 parts by mass or more, based on 100 parts by mass of the total amount of the first polymer, second polymer, third polymer, and fourth polymer, and , for example, 90 parts by mass or less, preferably 70 parts by mass or less.
3. Third Polymer The third polymer is a polymerization product of the third monomer component.

The third monomer component contains the acidic group-containing vinyl monomer described above.

Examples of the acidic group-containing vinyl monomer include the acidic group-containing vinyl monomers listed for the first monomer component, preferably carboxy group-containing vinyl monomers, more preferably (meth)acrylic acid, and still more preferably methacrylic acid. Can be mentioned.

The blending ratio of the acidic group-containing vinyl monomer to the third monomer component is lower than the blending ratio of the acidic group-containing vinyl monomer to the first monomer component.

As a result, as will be described in detail later, when the first polymer swells in the neutralization step described below, a rapid increase in viscosity can be suppressed.

Specifically, the blending ratio of the acidic group-containing vinyl monomer to the third monomer component is, for example, 1% by mass or more, preferably 5% by mass or more, and, for example, 10% by mass or less.

Further, the third monomer component preferably contains the above-described (meth)acrylic acid alkyl ester and the above-described aromatic vinyl monomer.

Examples of the (meth)acrylic acid alkyl ester include the (meth)acrylic acid alkyl esters listed in the first monomer component, and preferably methyl methacrylate.

In the third monomer component, the blending ratio of the (meth)acrylic acid alkyl ester is, for example, 60% by mass or more, preferably 70% by mass or more, and, for example, 95% by mass or less, preferably 85% by mass. It is as follows.

Examples of the aromatic vinyl monomer include the aromatic vinyl monomers listed for the first monomer component, and preferably styrene.

In the third monomer component, the blending ratio of the aromatic vinyl monomer is, for example, 5% by mass or more, preferably 15% by mass or more, and, for example, 40% by mass or less, preferably 30% by mass or less. .

Further, the third monomer component is a copolymerizable monomer (hereinafter referred to as a third copolymerizable monomer) that can be copolymerized with the (meth)acrylic acid alkyl ester, the aromatic vinyl monomer, and the acidic group-containing vinyl monomer. can contain.

Examples of the third copolymerizable monomer include the above-mentioned functional group-containing vinyl monomers (excluding acidic group-containing vinyl monomers), the above-mentioned vinyl esters, the above-mentioned heterocyclic vinyl compounds, the above-mentioned vinylidene halides compounds, Examples include the above-mentioned α-olefins, the above-mentioned dienes, and the above-mentioned crosslinkable vinyl monomers.

The third copolymerizable monomer can be used alone or in combination of two or more types.

The blending ratio of the third copolymerizable monomer is, for example, 0% by mass or more, preferably 1% by mass or more, more preferably 5% by mass or more, and, for example, 20% by mass or more, based on the third monomer component. % by mass or less.

The third monomer component preferably does not contain a third copolymerizable monomer and contains a (meth)acrylic acid alkyl ester, an aromatic vinyl monomer, and an acidic group-containing vinyl monomer, and more preferably (meth) It consists of an acrylic acid alkyl ester, an aromatic vinyl monomer, and an acidic group-containing vinyl monomer.

The third polymer is obtained by polymerizing the third monomer component by the method described below.

The blending ratio of the third polymer is, for example, 5 parts by mass or more, preferably 20 parts by mass or more, based on 100 parts by mass of the total amount of the first polymer, second polymer, third polymer, and fourth polymer, and , for example, 50 parts by mass or less, preferably 40 parts by mass or less.
4. Fourth Polymer The fourth polymer is a polymerization product of the fourth monomer component.

The fourth monomer component preferably includes the aromatic vinyl monomer described above, the hydroxyl group-containing vinyl monomer described above, and the crosslinkable vinyl monomer described above.

Examples of the aromatic vinyl monomer include the aromatic vinyl monomers listed for the first monomer component, and preferably styrene.

In the fourth monomer component, the blending ratio of the aromatic vinyl monomer is, for example, 80% by mass or more, preferably 90% by mass or more, and, for example, 99% by mass or less.

Examples of the hydroxyl group-containing vinyl monomer include the hydroxyl group-containing vinyl monomers listed for the first monomer component, preferably 2-hydroxyethyl (meth)acrylate, more preferably 2-hydroxyethyl methacrylate.

In the fourth monomer component, the blending ratio of the hydroxyl group-containing vinyl monomer is, for example, 1% by mass or more and, for example, 10% by mass or less, based on the fourth monomer component.

Examples of the crosslinkable vinyl monomer include the crosslinkable vinyl monomers listed for the first monomer component, and preferably divinylbenzene.

In the fourth monomer component, the blending ratio of the crosslinkable vinyl monomer is, for example, 1% by mass or more and, for example, 10% by mass or less.

Further, the fourth monomer component may contain an aromatic vinyl monomer, a hydroxyl group-containing vinyl monomer, and a copolymerizable monomer (hereinafter referred to as a fourth copolymerizable monomer) that can be copolymerized with the crosslinkable vinyl monomer. I can do it.

As the fourth copolymerizable monomer, the above-mentioned (meth)acrylic acid alkyl ester, the above-mentioned functional group-containing vinyl monomer (excluding the hydroxyl group-containing vinyl monomer), the above-mentioned vinyl esters, the above-mentioned heterocyclic vinyl compound, Examples include the above-mentioned vinylidene halides, the above-mentioned α-olefins, and the above-mentioned dienes.

The fourth copolymerizable monomer can be used alone or in combination of two or more types.

The blending ratio of the fourth copolymerizable monomer is, for example, 0% by mass or more, preferably 1% by mass or more, more preferably 5% by mass or more, and, for example, 20% by mass or more, based on the fourth monomer component. % by mass or less.

The fourth monomer component preferably does not contain the fourth copolymerizable monomer, but contains an aromatic vinyl monomer, a hydroxyl group-containing vinyl monomer, and a crosslinkable vinyl monomer, and preferably contains an aromatic vinyl monomer, a hydroxyl group-containing vinyl monomer, and a crosslinkable vinyl monomer. , a crosslinkable vinyl monomer.

The fourth polymer is obtained by polymerizing the fourth monomer component by the method described below.

The blending ratio of the fourth polymer is, for example, 1 part by mass or more and, for example, 10 parts by mass or less, based on 100 parts by mass of the total amount of the first polymer, second polymer, third polymer, and fourth polymer. Preferably, it is 5 parts by mass or less.
5. Method for producing emulsion particles The method for producing emulsion particles includes a fourth polymer preparation step of polymerizing a fourth monomer component to prepare a fourth polymer, and a first polymer preparation step of polymerizing a first monomer component to prepare a first polymer. a third polymer preparation step of polymerizing a third monomer component to prepare a third polymer; a neutralization step of neutralizing at least a portion of the acid functional groups in the acidic group-containing vinyl monomer; and a second polymer preparation step of polymerizing monomer components to prepare a second polymer.

Hereinafter, a method for manufacturing emulsion particles will be explained with reference to FIG. 1.

In the fourth polymer preparation step, a fourth monomer component is polymerized to prepare a fourth polymer.

Specifically, first, an aqueous solution of a polymerization initiator is prepared.

Examples of polymerization initiators include, but are not limited to, persulfates (ammonium persulfate, potassium persulfate, etc.), hydrogen peroxide, organic hydroperoxides, 4,4'-azobis(4-cyanovaleric acid) acid, etc. Water-soluble initiators such as benzoyl peroxide, oil-soluble initiators such as azobisisobutyronitrile, and redox initiators are preferably used. Examples include sulfates.

The polymerization initiators can be used alone or in combination of two or more.

The blending ratio of the polymerization initiator is appropriately set depending on the purpose and use.

To prepare an aqueous solution of a polymerization initiator, the polymerization initiator is mixed with water and heated to, for example, 50° C. or higher and 80° C. or lower.

In this way, an aqueous solution of a polymerization initiator is prepared.

Separately, an emulsion of the fourth monomer component is prepared.

To prepare an emulsion of the fourth monomer component, the fourth monomer component is mixed into an emulsifier (surfactant) while stirring.

Examples of the emulsifier (surfactant) include anionic surfactants such as sodium dodecylbenzenesulfonate and sodium lauryl sulfate, preferably sodium lauryl sulfate.

Moreover, the emulsifier (surfactant) can also be diluted with water.

Emulsifiers (surfactants) can be used alone or in combination of two or more.

The blending ratio of the emulsifier (surfactant) is appropriately set depending on the purpose and use.

In this way, an emulsion of the fourth monomer component is prepared.

Next, an emulsion of the fourth monomer component is added to the aqueous solution of the polymerization initiator, and the fourth monomer component is polymerized.

The emulsion of the fourth monomer component can be blended in portions or can be blended all at once.

As for the polymerization conditions, under normal pressure, the polymerization temperature is, for example, 30°C or higher, preferably 50°C or higher, and, for example, 95°C or lower, preferably 85°C or lower. Further, the polymerization time is, for example, 2 hours or more, and is, for example, 12 hours or less, preferably 8 hours or less.

Thereby, as shown in FIG. 1A, an aqueous dispersion containing the fourth polymer (specifically, particles made of the fourth polymer (hereinafter referred to as core particles 1)) is obtained.

The average particle diameter of the core particles 1 is, for example, 0.1 μm or more and, for example, 0.3 μm or less.

The method for measuring the average particle diameter will be described in detail in the examples below.

In the first polymer preparation step, a first monomer component is polymerized to prepare a first polymer.

Specifically, first, a polymerization initiator is added to an aqueous dispersion of the fourth polymer, and the mixture is heated to, for example, 50° C. or higher and 80° C. or lower.

Examples of the polymerization initiator include the polymerization initiators mentioned in the fourth polymer preparation step, preferably persulfates.

This prepares an aqueous dispersion.

Separately, an emulsion of the first monomer component is prepared.

To prepare an emulsion of the first monomer component, the first monomer component is mixed into an emulsifier (surfactant) while stirring.

Examples of the emulsifier (surfactant) include the emulsifiers (surfactants) mentioned in the fourth polymer preparation step, preferably sodium lauryl sulfate.

In this way, an emulsion of the first monomer component is prepared.

Next, an emulsion of the first monomer component is added to the aqueous dispersion, and the first monomer component is polymerized. That is, the first monomer component is polymerized in the presence of the fourth polymer.

The emulsion of the first monomer component can be blended in portions or can be blended all at once.

As for the polymerization conditions, under normal pressure, the polymerization temperature is, for example, 30°C or higher, preferably 50°C or higher, and, for example, 95°C or lower, preferably 85°C or lower. Further, the polymerization time is, for example, 2 hours or more, and is, for example, 12 hours or less, preferably 8 hours or less.

As a result, a first polymer is obtained. Specifically, the first polymer is formed to cover the fourth polymer. That is, as shown in FIG. 1B, the first coated particles include a layer made of a first polymer (hereinafter referred to as the first polymer layer 2) and a core particle 1 coated on the first polymer layer 2. An aqueous dispersion is obtained.

Then, such first polymer layer 2 is swollen by a neutralizing agent in a neutralization step described below.

In the third polymer preparation step, a third monomer component is polymerized to prepare a third polymer.

Specifically, first, a polymerization initiator is added to an aqueous dispersion containing the first coated particles, and the mixture is heated to, for example, 50° C. or higher and 80° C. or lower.

Examples of the polymerization initiator include the polymerization initiators mentioned in the fourth polymer preparation step, preferably persulfates.

This prepares an aqueous dispersion.

Separately, an emulsion of the third monomer component is prepared.

To prepare an emulsion of the third monomer component, the third monomer component is mixed into an emulsifier (surfactant) while stirring.

Examples of the emulsifier (surfactant) include the emulsifiers (surfactants) mentioned in the fourth polymer preparation step, preferably sodium lauryl sulfate.

In this way, an emulsion of the third monomer component is prepared.

Next, an emulsion of the third monomer component is added to the aqueous dispersion, and the third monomer component is polymerized. That is, the third monomer component is polymerized in the presence of the first coated particles (first polymer and fourth polymer).

The emulsion of the third monomer component can be blended in portions or can be blended all at once.

As for the polymerization conditions, under normal pressure, the polymerization temperature is, for example, 30°C or higher, preferably 50°C or higher, and, for example, 95°C or lower, preferably 85°C or lower. Further, the polymerization time is, for example, 2 hours or more, and is, for example, 12 hours or less, preferably 8 hours or less.

A third polymer is thus obtained. Specifically, the third polymer is formed to coat the first coated particles. That is, as shown in FIG. 1C, a layer made of a third polymer (hereinafter referred to as the third polymer layer 3), a first polymer layer 2 covered with the third polymer layer 3, and a first polymer layer 2 An aqueous dispersion containing the second coated particles and the core particles 1 coated with the second coated particles is obtained.

As described above, the blending ratio of the acidic group-containing vinyl monomer to the third monomer component is lower than the blending ratio of the acidic group-containing vinyl monomer to the first monomer component.

Therefore, the concentration of the acidic group-containing vinyl monomer decreases from the first polymer layer 2 toward the third polymer layer 3. Thereby, in the neutralization step described later, when the first polymer layer 2 and the third polymer layer 3 are swollen, a sudden increase in viscosity can be suppressed.

In the neutralization step, at least a portion of the acid functional groups of the acidic group-containing vinyl monomers in the first polymer and the third polymer are neutralized.

Specifically, a neutralizing agent is added to the aqueous dispersion containing the second coated particles, and the mixture is maintained at a predetermined temperature for a predetermined period of time.

Examples of the neutralizing agent include alkali metal hydroxides (sodium hydroxide, potassium hydroxide, etc.), amines, ammonia, and the like. Further, the neutralizing agent is preferably used as saline water, and specific examples thereof include aqueous solutions of alkali metal hydroxides, aqueous ammonia, and the like. These neutralizing agents can be used alone or in combination of two or more.

Preferable neutralizing agents include sodium hydroxide and ammonia.

The blending ratio of the neutralizing agent is, for example, 20 mol or more, preferably 25 mol or more, more preferably 30 mol or more, and, for example, 200 mol or less, preferably , 150 mol or less, more preferably 120 mol or less.

As for the holding conditions after adding the neutralizing agent, the holding temperature is, for example, 40°C or higher, preferably 50°C or higher, and, for example, 90°C or lower, preferably 80°C or lower. Further, the holding time is, for example, 30 minutes or more, preferably 1 hour or more, and, for example, 12 hours or less, preferably 10 hours or less.

As a result, at least a portion of the acid functional groups of the acidic group-containing vinyl monomers in the first polymer and the third polymer are neutralized to form a salt. As a result, as shown in FIG. 1D, the salt takes up water, causing the first and third polymers to swell.

In the second polymer preparation step, a second monomer component is polymerized to prepare a second polymer.

Specifically, first, a polymerization initiator is added to an aqueous dispersion containing the second coated particles, and the mixture is heated to, for example, 50° C. or higher and 95° C. or lower.

Examples of the polymerization initiator include the polymerization initiators mentioned in the fourth polymer preparation step, preferably persulfates.

This prepares an aqueous dispersion.

Separately, an emulsion of the second monomer component is prepared.

To prepare an emulsion of the second monomer component, the second monomer component is mixed into an emulsifier (surfactant) while stirring.

Examples of the emulsifier (surfactant) include the emulsifiers (surfactants) mentioned in the fourth polymer preparation step, preferably sodium lauryl sulfate.

In this way, an emulsion of the second monomer component is prepared.

Next, an emulsion of the second monomer component is added to the aqueous dispersion, and the second monomer component is polymerized. That is, the second monomer component is polymerized in the presence of the second coated particles (first polymer, third polymer, and fourth polymer).

The emulsion of the second monomer component can be blended in portions or can be blended all at once.

As for the polymerization conditions, under normal pressure, the polymerization temperature is, for example, 30°C or higher, preferably 50°C or higher, and, for example, 95°C or lower, preferably 85°C or lower. Further, the polymerization time is, for example, 2 hours or more, and is, for example, 12 hours or less, preferably 8 hours or less.

A second polymer is thus obtained. Specifically, the second polymer is formed to coat the second coated particles. That is, as shown in FIG. 1E, the outer layer made of the second polymer (hereinafter referred to as the second polymer layer 5), the third polymer layer 3 covered with the second polymer layer 5, and the third polymer layer 3 An aqueous dispersion containing emulsion particles 6 comprising a first polymer layer 2 coated with the first polymer layer 2 and a core particle 1 coated with the first polymer layer 2 is obtained.

The average particle diameter of the emulsion particles 6 is, for example, 0.1 μm or more, preferably 0.5 μm or more, and is, for example, 5 μm or less, preferably 1 μm or less.

Such emulsion particles 6 include a core particle 1 (fourth polymer) coated with a first polymer layer 2 (first polymer).

Therefore, the polymerization stability of the first polymer layer 2 of the emulsion particles 6 can be improved.

Further, such emulsion particles 6 include a third polymer layer 3 (third polymer) coated with the second polymer layer 5 (second polymer) and covering the first polymer layer 2 (first polymer).

Therefore, in the neutralization step, when the first polymer layer 2 and the third polymer layer 3 are swollen, it is possible to suppress the generation of aggregates and increase in viscosity when the neutralizing agent is added.

Further, such emulsion particles 6 include a second polymer layer 5 (second polymer) covering the first polymer layer 2 (first polymer) and the third polymer layer 3 (third polymer).

Specifically, in such emulsion particles 6, the first polymer layer 2 (first polymer) is coated with the second polymer layer 5 (second polymer) via the third polymer layer 3 (third polymer). ing.

That is, the outermost surface of the emulsion particles 6 is the second polymer layer 5 (second polymer). Moreover, the glass transition temperature of the second polymer layer 5 (second polymer) is 112.0° C. or higher.

Therefore, the emulsion particles 6 have excellent heat resistance.

Since the emulsion particles 6 have excellent heat resistance, they can be suitably used for a heat insulating layer in a heat-sensitive recording material.
6. Modifications In the above description, the emulsion particles 6 include the fourth polymer, but the emulsion particles 6 may not include the fourth polymer. In other words, the emulsion particles 6 do not need to include the core particles 1.

In such a case, the emulsion particles 6 include the second polymer layer 5, the third polymer layer 3 coated on the second polymer layer 5, and the first polymer layer 2 coated on the third polymer layer 3. Equipped with

Further, in the above description, the emulsion particles 6 include the third polymer, but the emulsion particles 6 may not include the third polymer.

Furthermore, in the above description, the emulsion particles 6 include the second polymer layer 5, the third polymer layer 3 coated on the second polymer layer 5, and the first polymer layer 2 coated on the third polymer layer 3. , and the core particles 1 covered with the first polymer layer 2. However, a layer made of a fifth polymer may be further disposed between the second polymer layer 5 and the third polymer layer 3.

The fifth polymer is a polymerization product of the fifth monomer component.

The fifth monomer component does not substantially contain the acidic group-containing vinyl monomer described above.

"Not contained in the acidic group-containing vinyl monomer" means that the content of the acidic group-containing vinyl monomer is 0.1% by mass or less, preferably 0.01% by mass or less, more preferably 0.01% by mass or less, based on the fifth monomer component. means 0.001% by mass or less.

The fifth monomer component preferably contains the above-described aromatic vinyl monomer and the above-described hydroxyl group-containing vinyl monomer.

Examples of the aromatic vinyl monomer include the aromatic vinyl monomers listed for the first monomer component, and preferably styrene.

In the fifth monomer component, the blending ratio of the aromatic vinyl monomer is, for example, 80% by mass or more, preferably 90% by mass or more, more preferably 99% by mass or more, and, for example, 99.5% by mass. It is as follows.

Examples of the hydroxyl group-containing vinyl monomer include the hydroxyl group-containing vinyl monomers listed for the first monomer component, preferably 2-hydroxyethyl (meth)acrylate, more preferably 2-hydroxyethyl methacrylate.

In the fifth monomer component, the blending ratio of the hydroxyl group-containing vinyl monomer is, for example, 0.5% by mass or more, and for example, 20% by mass or less, preferably 10% by mass or less, and more preferably 1% by mass. It is as follows.

Further, the fifth monomer component can contain a copolymerizable monomer (hereinafter referred to as a fifth copolymerizable monomer) that can be copolymerized with the aromatic vinyl monomer and the hydroxyl group-containing vinyl monomer.

The fifth copolymerizable monomer includes the above-mentioned (meth)acrylic acid alkyl ester, the above-mentioned functional group-containing vinyl monomer (excluding acidic group-containing vinyl monomers and hydroxyl group-containing vinyl monomers), the above-mentioned vinyl esters, and the above-mentioned vinyl monomers. Examples include heterocyclic vinyl compounds, the above-mentioned vinylidene halides, the above-mentioned α-olefins, the above-mentioned dienes, and the above-mentioned crosslinkable vinyl monomers.

The fifth copolymerizable monomer can be used alone or in combination of two or more types.

The blending ratio of the fifth copolymerizable monomer is, for example, 0% by mass or more, preferably 1% by mass or more, more preferably 5% by mass or more, and, for example, 20% by mass or more, based on the fifth monomer component. % by mass or less.

The fifth monomer component preferably does not contain the fifth copolymerizable monomer and contains an aromatic vinyl monomer and a hydroxyl group-containing vinyl monomer, and more preferably consists of an aromatic vinyl monomer and a hydroxyl group-containing vinyl monomer. .

The fifth polymer is obtained by polymerizing the fifth monomer component in the same manner as the above-described polymerization of the second monomer component.

Specifically, after the neutralization step and before the second polymer preparation step, the fifth monomer component is polymerized (the fifth polymer preparation step is carried out), or after the third polymer preparation step, the neutralization step is carried out. Before this, the fifth monomer component is polymerized (the fifth polymer preparation step is carried out).

Moreover, in the above description, the second polymer preparation step was carried out after the neutralization step, but the neutralization step can also be carried out after the second polymer preparation step.
7. Coating agent and dry product The coating agent of the present invention contains the above emulsion particles.

Therefore, the coating film obtained with this coating agent has excellent heat resistance.

The object to be coated with such a coating agent is not particularly limited, and paper is preferably used.

Moreover, the dried product of the present invention is a dried product of the above-mentioned emulsion particles. Therefore, this dried product has excellent heat resistance.

Further, by drying to remove water inside the emulsion particles, the dried product can be made into hollow particles.

Since such a dried product is hollow inside, it has better heat insulation properties.

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. can 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. Component details ST: Styrene DVB: Divinylbenzene MMA: Methyl methacrylate HEMA: 2-hydroxyethyl methacrylate BA: Butyl acrylate MAC: Methacrylic acid MAM: Methacrylamide AM: Acrylamide IBNMA: Isobornyl methacrylate AN: Acrylonitrile Table 1 and Table 2 show the prescription of the monomers contained in each monomer component (first monomer component to fifth monomer component) when each monomer component is 100 parts by mass.
2. Production of emulsion particles Example 1
(First polymer preparation step)
2,200 parts by mass of water was charged into a separable flask equipped with a stirrer, a thermometer, and a reflux condenser, and the mixture was stirred while purging with nitrogen, and the temperature was raised to 80°C. The internal temperature was maintained at 80°C, and 0.5 parts by mass of ammonium persulfate was added as a polymerization initiator and dissolved. In this way, an aqueous solution of a polymerization initiator was prepared.

Separately, 50 parts by mass of methyl methacrylate, 10 parts by mass of butyl acrylate, and 40 parts by mass of methacrylic acid were added to a surfactant (0.2 parts by mass of sodium lauryl sulfate and 50 parts by mass of water) with stirring. An emulsion of monomer components was prepared.

A part (0.5%) of the emulsion of the first monomer component was added to the aqueous solution of the polymerization initiator, and the mixture was reacted for 30 minutes, and then the remaining part was continuously added over 3 hours to react. . After the addition was completed, the mixture was aged for 2 hours.

Thereby, an aqueous dispersion of the first polymer was obtained.
(Third polymer preparation step)
70 parts by mass of water and 9 parts by mass of ammonium persulfate as a polymerization initiator were added to the above aqueous dispersion.

Separately, 630 parts by mass of methyl methacrylate and 70 parts by mass of styrene were added to a surfactant (0.6 parts by mass and 350 parts by mass of sodium lauryl sulfate) with stirring to prepare an emulsion of the third monomer component.

The emulsion of the third monomer component was continuously added to the aqueous dispersion containing the polymerization initiator over a period of 3 hours to cause a reaction. After the addition was completed, the mixture was aged for 1 hour.

In this way, a third polymer was obtained. Specifically, an aqueous dispersion of particles comprising a third polymer and a first polymer coated on the third polymer was obtained.
(Second polymer preparation step)
28 parts by mass of water and 2.8 parts by mass of ammonium persulfate as a polymerization initiator were added to the above aqueous dispersion.

Separately, 1092 parts by mass of styrene, 280 parts by mass of methacrylamide, and 28 parts by mass of 2-hydroxyethyl methacrylate were added to a surfactant (1600 parts by mass of water and 14 parts by mass of sodium lauryl sulfate) with stirring, and the second monomer was added. An emulsion of the ingredients was prepared.

The emulsion of the second monomer component was continuously added to the aqueous dispersion containing the polymerization initiator over a period of 3 hours to cause a reaction. After the addition was completed, the mixture was aged for 2 hours.

In this way, a second polymer was obtained. Specifically, an aqueous dispersion of particles comprising a second polymer, a third polymer coated on the second polymer, and a first polymer coated on the third polymer was obtained.
(neutralization process)
80 parts by mass of a 20% aqueous sodium hydroxide solution was added to the above aqueous dispersion, and the mixture was further maintained for 3 hours. As a result, at least a portion of the acid functional groups of the acidic group-containing vinyl monomers in the first polymer and the third polymer were neutralized to form salts. Then, the first polymer and the third polymer were swollen. Thereby, an aqueous dispersion of emulsion particles comprising the second polymer, the third polymer coated on the second polymer, and the first polymer coated on the third polymer was obtained.

The solid content concentration of the aqueous dispersion was 33% by mass.

Example 2
(First polymer preparation step)
Based on the same procedure as in Example 1, an aqueous dispersion of the first polymer was obtained.
(Second polymer preparation step)
A separable flask equipped with a stirrer, a thermometer, and a reflux condenser was charged with 2,350.7 parts by mass of the aqueous dispersion of the first polymer, stirred while purging with nitrogen, and heated to 80°C. The internal temperature was maintained at 80° C., and 98 parts by mass of water and 11.8 parts by mass of ammonium persulfate as a polymerization initiator were added to prepare an aqueous dispersion.

Separately, 630 parts by mass of methyl methacrylate, 1162 parts by mass of styrene, 280 parts by mass of methacrylamide, and 28 parts by mass of 2-hydroxyethyl methacrylate were stirred into a surfactant (1950 parts by mass of water and 14.6 parts by mass of sodium lauryl sulfate). In addition, an emulsion of the second monomer component was prepared.

The emulsion of the second monomer component was continuously added to the above aqueous dispersion over a period of 3 hours to cause a reaction. After the addition was completed, the mixture was aged for 2 hours.

In this way, a second polymer was obtained. Specifically, an aqueous dispersion of particles containing a second polymer and a first polymer coated on the second polymer was obtained.
(neutralization process)
25 parts by mass of a 28% ammonia aqueous solution was added to the above aqueous dispersion, and the mixture was further maintained for 3 hours. This neutralized at least a portion of the acid functional groups of the acid group-containing vinyl monomer in the first polymer to form a salt. The first polymer was then swollen. Then, an aqueous dispersion of emulsion particles including a second polymer and a first polymer coated with the second polymer was obtained.

The solid content concentration of the aqueous dispersion was 33% by mass.

Example 3
(Fourth polymer preparation step)
A separable flask equipped with a stirrer, a thermometer, and a reflux condenser was charged with 365 parts by mass of water, stirred while purging with nitrogen, and heated to 80°C. The internal temperature was maintained at 80° C., and 0.4 parts by mass of potassium persulfate was added as a polymerization initiator and dissolved. In this way, an aqueous solution of a polymerization initiator was prepared.

Separately, 98 parts by mass of styrene, 2 parts by mass of 2-hydroxyethyl methacrylate, and 5 parts by mass of divinylbenzene were added to a surfactant (0.05 parts by mass of sodium lauryl sulfate and 40 parts by mass of water) with stirring. An emulsion containing four monomer components was prepared.

A part (0.5%) of the emulsion of the fourth monomer component was added to the aqueous solution of the polymerization initiator, and the mixture was reacted for 30 minutes, and then the remaining part was continuously added over 4 hours to react. . After the addition was completed, the mixture was aged for 2 hours.

Thereby, an aqueous dispersion (solid content concentration: 20% by mass) of the fourth polymer was obtained.
(First polymer preparation step)
960 parts by mass of water was added to 137.5 parts by mass of the aqueous dispersion of the fourth polymer, stirred while substituting with nitrogen, and heated to 78°C. The internal temperature was maintained at 78° C., and 0.1 part by mass of ammonium persulfate was added as a polymerization initiator to prepare an aqueous dispersion.

Separately, 12.4 parts by mass of methyl methacrylate and 4.1 parts by mass of methacrylic acid were added to a surfactant (9.6 parts by mass of water and 0.1 parts by mass of sodium lauryl sulfate) with stirring, and the first monomer was added. An emulsion of the ingredients was prepared.

The emulsion of the first monomer component was continuously added to the aqueous dispersion over 30 minutes to react. After the addition was completed, the mixture was aged for 2 hours.

As a result, a first polymer was obtained. Specifically, an aqueous dispersion of particles containing a first polymer and a fourth polymer coated on the first polymer was obtained.
(Third polymer preparation step)
To the above aqueous dispersion, 0.9 parts by mass of ammonium persulfate was added as a polymerization initiator and dissolved.

Separately, 140 parts by mass of methyl methacrylate, 31.5 parts by mass of styrene, and 3.5 parts by mass of methacrylic acid were added to a surfactant (72 parts by mass of water and 0.6 parts by mass of sodium lauryl sulfate) with stirring, An emulsion of the third monomer component was prepared.

The emulsion of the third monomer component was continuously added to the aqueous dispersion over a period of 2 hours to cause a reaction. After the addition was completed, the mixture was aged for 2 hours.

In this way, a third polymer was obtained. Specifically, an aqueous dispersion of particles containing a third polymer, a first polymer coated on the third polymer, and a fourth polymer coated on the first polymer was obtained.
(neutralization process)
The temperature of the above aqueous dispersion was set to 90° C., 13.9 parts by mass of 28% aqueous ammonia was added with stirring, and the mixture was stirred for 2 hours. As a result, at least a portion of the acid functional groups of the acidic group-containing vinyl monomers in the first polymer and the third polymer were neutralized to form salts. Then, the first polymer and the third polymer were swollen.
(Second polymer preparation step)
While maintaining the temperature of the aqueous dispersion at 90° C., 4.4 parts by mass of ammonium persulfate was added as a polymerization initiator and dissolved.

Separately, 704 parts by mass of styrene and 176 parts by mass of methacrylamide were added to a surfactant (1056 parts by mass of water and 3.6 parts by mass of sodium lauryl sulfate) with stirring to prepare an emulsion of the second monomer component.

The emulsion of the second monomer component was continuously added to the aqueous dispersion over a period of 3 hours to cause a reaction. After the addition was completed, the mixture was aged for 2 hours.

As a result, the second polymer is obtained, the second polymer, the third polymer coated on the second polymer, the first polymer coated on the third polymer, and the fourth polymer coated on the first polymer. An aqueous dispersion of emulsion particles was obtained.

The solid content concentration of the aqueous dispersion was 33% by mass.

Example 4
(Fourth polymer preparation step)
Based on the same procedure as in Example 3, an aqueous dispersion of the fourth polymer was obtained.
(First polymer preparation step)
A separable flask equipped with a stirrer, a thermometer, and a reflux condenser was charged with 500 parts by mass of the aqueous dispersion of the fourth polymer and 1280 parts by mass of water, stirred while purging with nitrogen, and heated to 80°C. The internal temperature was maintained at 80° C., and 1 part by mass of ammonium persulfate was added as a polymerization initiator to prepare an aqueous dispersion.

Separately, 110 parts by mass of methyl methacrylate, 10 parts by mass of butyl acrylate, and 80 parts by mass of methacrylic acid were added to a surfactant (80 parts by mass of water and 0.2 parts by mass of sodium lauryl sulfate) with stirring. An emulsion of monomer components was prepared.

The emulsion of the first monomer component was continuously added to the aqueous dispersion over a period of 3 hours, and reacted. After the addition was completed, the mixture was aged for 2 hours.

As a result, a first polymer was obtained. Specifically, an aqueous dispersion of particles containing a first polymer and a fourth polymer coated on the first polymer was obtained.
(Third polymer preparation step)
3,250 parts by mass of water and 1.8 parts by mass of ammonium persulfate were added to the above aqueous dispersion.

Separately, 675 parts by mass of methyl methacrylate, 180 parts by mass of styrene, and 45 parts by mass of methacrylic acid were added to a surfactant (350 parts by mass of water and 1.35 parts by mass of sodium lauryl sulfate) with stirring, and the third monomer component An emulsion was prepared.

The emulsion of the third monomer component was continuously added to the aqueous dispersion over a period of 3 hours to cause a reaction. After the addition was completed, the mixture was aged for 1 hour.

In this way, a third polymer was obtained. Specifically, an aqueous dispersion of particles containing a third polymer, a first polymer coated on the third polymer, and a fourth polymer coated on the first polymer was obtained.
(neutralization process)
8,800 parts by mass of water was added to the above aqueous dispersion, 55 parts by mass of a 28% ammonia aqueous solution was added while the internal temperature was kept at 80°C, and after holding for 3 hours, 25 parts by mass of a 28% ammonia aqueous solution was added. was added and held for an additional 3 hours. This neutralized at least a portion of the acid functional groups of the acid group-containing vinyl monomer in the first polymer to form a salt. Then, the first polymer and the third polymer were swollen.
(Second polymer preparation step)
11 parts by mass of ammonium persulfate was added to the above aqueous dispersion.

Separately, 1738 parts by mass of styrene, 440 parts by mass of methacrylamide, and 22 parts by mass of 2-hydroxyethyl methacrylate were added to a surfactant (2200 parts by mass of water and 3.6 parts by mass of sodium lauryl sulfate) with stirring. An emulsion of two monomer components was prepared.

The emulsion of the second monomer component was continuously added to the aqueous dispersion over a period of 3 hours to cause a reaction. After the addition was completed, the mixture was aged for 2 hours.

As a result, the second polymer is obtained, the second polymer, the third polymer coated on the second polymer, the first polymer coated on the third polymer, and the fourth polymer coated on the first polymer. An aqueous dispersion of emulsion particles was obtained.

The solid content concentration of the aqueous dispersion was 26% by mass.

Example 5
In the following steps, an aqueous dispersion of emulsion particles was obtained in the same manner as in Example 4, except that the procedure and prescription were changed. The solid content concentration of the aqueous dispersion was 26% by mass.

In the third polymer preparation step, 7790 parts by mass of water and 3.8 parts by mass of ammonium persulfate were added to the aqueous dispersion, and methacrylic acid was added to the surfactant (760 parts by mass of water and 2.85 parts by mass of sodium lauryl sulfate). 1425 parts by mass of methyl, 380 parts by mass of styrene, and 95 parts by mass of methacrylic acid were added with stirring to prepare an emulsion of the third monomer component.

In the neutralization step, 77 parts by mass of a 28% ammonia aqueous solution was added to the aqueous dispersion.

In the second polymer preparation step, 1738 parts by mass of styrene, 440 parts by mass of methacrylamide, and 22 parts by mass of 2-hydroxyethyl methacrylate were stirred into a surfactant (2200 parts by mass of water and 2.2 parts by mass of sodium lauryl sulfate). In addition, an emulsion of the second monomer component was prepared.

Example 6
In the following steps, an aqueous dispersion of emulsion particles was obtained in the same manner as in Example 4, except that the procedure and prescription were changed. The solid content concentration of the aqueous dispersion was 26% by mass.

In the third polymer preparation step, 7790 parts by mass of water and 3.8 parts by mass of ammonium persulfate were added to the aqueous dispersion, and methacrylic acid was added to the surfactant (760 parts by mass of water and 2.85 parts by mass of sodium lauryl sulfate). 1425 parts by mass of methyl, 380 parts by mass of styrene, and 95 parts by mass of methacrylic acid were added with stirring to prepare an emulsion of the third monomer component.

In the neutralization step, 4400 parts by mass of water and 77 parts by mass of a 28% aqueous ammonia solution were added to the aqueous dispersion.

In the second polymer preparation step, 22 parts by mass of ammonium persulfate was added to the aqueous dispersion, and 3476 parts by mass of styrene and 880 parts by mass of methacrylamide were added to the surfactant (4400 parts by mass of water and 4.4 parts by mass of sodium lauryl sulfate). and 44 parts by mass of 2-hydroxyethyl methacrylate were added with stirring to prepare an emulsion of the second monomer component.

Example 7
(Fourth polymer preparation step)
Based on the same procedure as in Example 4, an aqueous dispersion of the fourth polymer was obtained.
(First polymer preparation step)
Based on the same procedure as in Example 4, an aqueous dispersion of particles containing a first polymer and a fourth polymer coated on the first polymer was obtained.
(Third polymer preparation step)
7,790 parts by mass of water and 3.8 parts by mass of ammonium persulfate were added to the above aqueous dispersion.

Separately, 1425 parts by mass of methyl methacrylate, 380 parts by mass of styrene, and 95 parts by mass of methacrylic acid were added to a surfactant (760 parts by mass of water and 2.85 parts by mass of sodium lauryl sulfate) with stirring, and the third monomer component An emulsion was prepared.

The emulsion of the third monomer component was continuously added to the aqueous dispersion over a period of 3 hours to cause a reaction. After the addition was completed, the mixture was aged for 1 hour.

In this way, a third polymer was obtained. Specifically, an aqueous dispersion of particles containing a third polymer, a first polymer coated on the third polymer, and a fourth polymer coated on the first polymer was obtained.
(neutralization process)
To the above aqueous dispersion, 3,696 parts by mass of water was added, and 77 parts by mass of a 28% ammonia aqueous solution was added while keeping the internal temperature at 80°C, and after further holding for 3 hours, 25 parts by mass of a 28% ammonia aqueous solution was added. was added and held for an additional 3 hours. As a result, at least a portion of the acid functional groups of the acidic group-containing vinyl monomers in the first polymer and the third polymer were neutralized to form salts. Then, the first polymer and the third polymer were swollen.
(Fifth polymer preparation step)
6.16 parts by mass of ammonium persulfate was added to the above aqueous dispersion.

Separately, 3049 parts by mass of styrene and 30.8 parts by mass of 2-hydroxyethyl methacrylate were added to a surfactant (1232 parts by mass of water and 3.08 parts by mass of sodium lauryl sulfate) with stirring, and the fifth monomer component was added. An emulsion was prepared.

The emulsion of the fifth monomer component was continuously added to the above aqueous dispersion over a period of 3 hours, and reacted. After the addition was completed, the mixture was aged for 2 hours.

As a result, a fifth polymer is obtained, and the fifth polymer, the third polymer coated with the fifth polymer, the first polymer coated with the third polymer, and the fourth polymer coated with the first polymer are separated. An aqueous dispersion of the particles was obtained.

The solid content concentration of the aqueous dispersion was 26% by mass.
(Second polymer preparation step)
2.64 parts by mass of ammonium persulfate was added to the above aqueous dispersion.

Separately, 488.4 parts by mass of styrene, 818.4 parts by mass of methacrylamide, and 13.2 parts by mass of 2-hydroxyethyl methacrylate were stirred into a surfactant (4092 parts by mass of water and 1.32 parts by mass of sodium lauryl sulfate). In addition, an emulsion of the second monomer component was prepared.

The emulsion of the second monomer component was continuously added to the aqueous dispersion over a period of 3 hours to cause a reaction. After the addition was completed, the mixture was aged for 2 hours.

As a result, a second polymer is obtained, a second polymer, a fifth polymer coated on the second polymer, a third polymer coated on the fifth polymer, a first polymer coated on the third polymer, An aqueous dispersion of emulsion particles comprising a fourth polymer coated on a first polymer was obtained.

The solid content concentration of the aqueous dispersion was 25% by mass.

Example 8
(Fourth polymer preparation step)
A separable flask equipped with a stirrer, a thermometer, and a reflux condenser was charged with 365 parts by mass of water, stirred while purging with nitrogen, and heated to 70°C. The internal temperature was maintained at 70°C, and 0.4 parts by mass of potassium persulfate was added as a polymerization initiator and dissolved. In this way, an aqueous solution of a polymerization initiator was prepared.

Separately, 98 parts by mass of styrene, 2 parts by mass of 2-hydroxyethyl methacrylate, and 5 parts by mass of divinylbenzene were added to a surfactant (0.07 parts by mass of sodium lauryl sulfate and 40 parts by mass of water) with stirring. An emulsion containing four monomer components was prepared.

A part (0.5%) of the emulsion of the fourth monomer component was added to the aqueous solution of the polymerization initiator, and the mixture was reacted for 30 minutes, and then the remaining part was continuously added over 4 hours to react. . After the addition was completed, the mixture was aged for 2 hours.

Thereby, an aqueous dispersion (solid content concentration: 20% by mass) of the fourth polymer was obtained.
(First polymer preparation step)
80 parts by mass of water was added to 500 parts by mass of the aqueous dispersion of the fourth polymer, stirred while substituting with nitrogen, and heated to 80°C. The internal temperature was maintained at 80° C., and 1 part by mass of ammonium persulfate was added as a polymerization initiator to prepare an aqueous dispersion.

Separately, 110 parts by mass of methyl methacrylate, 10 parts by mass of butyl acrylate, and 80 parts by mass of methacrylic acid were added to a surfactant (80 parts by mass of water and 0.2 parts by mass of sodium lauryl sulfate) with stirring. An emulsion of monomer components was prepared.

The emulsion of the first monomer component was continuously added to the aqueous dispersion over a period of 3 hours, and reacted. After the addition was completed, the mixture was aged for 2 hours.

As a result, a first polymer was obtained. Specifically, an aqueous dispersion of particles containing a first polymer and a fourth polymer coated on the first polymer was obtained.
(Third polymer preparation step)
To the above aqueous dispersion, 7790 parts by mass of water and 3.8 parts by mass of ammonium persulfate as a polymerization initiator were added and dissolved.

Separately, 1425 parts by mass of methyl methacrylate, 380 parts by mass of styrene, and 95 parts by mass of methacrylic acid were added to a surfactant (760 parts by mass of water and 2.85 parts by mass of sodium lauryl sulfate) with stirring, and the third monomer component An emulsion was prepared.

The emulsion of the third monomer component was continuously added to the aqueous dispersion over a period of 3 hours to cause a reaction. After the addition was completed, the mixture was aged for 1 hour.

In this way, a third polymer was obtained. Specifically, an aqueous dispersion of particles containing a third polymer, a first polymer coated on the third polymer, and a fourth polymer coated on the first polymer was obtained.
(neutralization process)
4400 parts by mass of water was added to the above aqueous dispersion, and while the temperature of the aqueous dispersion was kept at 80° C., 77 parts by mass of 28% aqueous ammonia was added with stirring and maintained for 3 hours. As a result, at least a portion of the acid functional groups of the acidic group-containing vinyl monomers in the first polymer and the third polymer were neutralized to form salts. Then, the first polymer and the third polymer were swollen.
(Second polymer preparation step)
While maintaining the temperature of the aqueous dispersion at 80° C., 22 parts by mass of ammonium persulfate was added as a polymerization initiator and dissolved.

Separately, 3476 parts by mass of styrene, 880 parts by mass of methacrylamide and 44 parts by mass of 2-hydroxyethyl methacrylate were added to a surfactant (4400 parts by mass of water and 4.4 parts by mass of sodium lauryl sulfate) with stirring. An emulsion of two monomer components was prepared.

The emulsion of the second monomer component was continuously added to the aqueous dispersion over a period of 3 hours to cause a reaction. After the addition was completed, the mixture was aged for 2 hours.

As a result, the second polymer is obtained, the second polymer, the third polymer coated on the second polymer, the first polymer coated on the third polymer, and the fourth polymer coated on the first polymer. An aqueous dispersion of emulsion particles was obtained.

The solid content concentration of the aqueous dispersion was 26% by mass.

Example 9
In the following steps, an aqueous dispersion of emulsion particles was obtained in the same manner as in Example 4, except that the procedure and prescription were changed. The solid content concentration of the aqueous dispersion was 26% by mass.

In the first polymer preparation step, 500 parts by mass of the aqueous dispersion of the fourth polymer, 2240 parts by mass of water, and 2 parts by mass of ammonium persulfate are added to a separable flask equipped with a stirrer, a thermometer, and a reflux condenser. 220 parts by mass of methyl methacrylate, 20 parts by mass of butyl acrylate, and 160 parts by mass of methacrylic acid were added to a surfactant (160 parts by mass of water and 0.4 parts by mass of sodium lauryl sulfate) with stirring. An emulsion containing one monomer component was prepared.

In the third polymer preparation step, 12,710 parts by mass of water and 6.2 parts by mass of ammonium persulfate were added to the aqueous dispersion, and methacrylic acid was added to the surfactant (1240 parts by mass of water and 3.1 parts by mass of sodium lauryl sulfate). 2,325 parts by mass of methyl, 620 parts by mass of styrene, and 155 parts by mass of methacrylic acid were added with stirring to prepare an emulsion of the third monomer component.

In the neutralization step, 7100 parts by mass of water and 138 parts by mass of a 28% ammonia aqueous solution were added to the aqueous dispersion.

In the second polymer preparation step, 35.5 parts by mass of ammonium persulfate was added to the aqueous dispersion, and 5609 parts by mass of styrene and methacrylamide were added to the surfactant (7100 parts by mass of water and 7.1 parts by mass of sodium lauryl sulfate). 1420 parts by mass and 71 parts by mass of 2-hydroxyethyl methacrylate were added with stirring to prepare an emulsion of the second monomer component.

Example 10
In the following steps, an aqueous dispersion of emulsion particles was obtained in the same manner as in Example 8, except that the procedure and prescription were changed. The solid content concentration of the aqueous dispersion was 26% by mass.

In the first polymer preparation step, 500 parts by mass of the aqueous dispersion of the fourth polymer, 2240 parts by mass of water, and 2 parts by mass of ammonium persulfate are added to a separable flask equipped with a stirrer, a thermometer, and a reflux condenser. 220 parts by mass of methyl methacrylate, 20 parts by mass of butyl acrylate, and 160 parts by mass of methacrylic acid were added to a surfactant (160 parts by mass of water and 0.4 parts by mass of sodium lauryl sulfate) with stirring. An emulsion containing one monomer component was prepared.

In the third polymer preparation step, 12,710 parts by mass of water and 6.2 parts by mass of ammonium persulfate were added to the aqueous dispersion, and methacrylic acid was added to the surfactant (1240 parts by mass of water and 3.1 parts by mass of sodium lauryl sulfate). 2,325 parts by mass of methyl, 620 parts by mass of styrene, and 155 parts by mass of methacrylic acid were added with stirring to prepare an emulsion of the third monomer component.

In the neutralization step, 7100 parts by mass of water and 138 parts by mass of a 28% ammonia aqueous solution were added to the aqueous dispersion.

In the second polymer preparation step, 35.5 parts by mass of ammonium persulfate was added to the aqueous dispersion, and 5609 parts by mass of styrene and methacrylamide were added to the surfactant (7100 parts by mass of water and 7.1 parts by mass of sodium lauryl sulfate). 1420 parts by mass and 71 parts by mass of 2-hydroxyethyl methacrylate were added with stirring to prepare an emulsion of the second monomer component.

Example 11
In the following steps, an aqueous dispersion of emulsion particles was obtained in the same manner as in Example 9, except that the procedure and prescription were changed. The solid content concentration of the aqueous dispersion was 26% by mass.

In the neutralization step, 7100 parts by mass of water and 138 parts by mass of a 28% ammonia aqueous solution were added to the aqueous dispersion.

In the second polymer preparation step, 35.5 parts by mass of ammonium persulfate was added to the aqueous dispersion, and 5609 parts by mass of styrene and methacrylamide were added to the surfactant (7100 parts by mass of water and 7.1 parts by mass of sodium lauryl sulfate). 1065 parts by mass, 71 parts by mass of 2-hydroxyethyl methacrylate, and 444 parts by mass of divinylbenzene were added with stirring to prepare an emulsion of the second monomer component.

Example 12
In the following steps, an aqueous dispersion of emulsion particles was obtained in the same manner as in Example 9, except that the procedure and prescription were changed. The solid content concentration of the aqueous dispersion was 26% by mass.

In the neutralization step, 7100 parts by mass of water and 138 parts by mass of a 28% ammonia aqueous solution were added to the aqueous dispersion.

In the second polymer preparation step, 35.5 parts by mass of ammonium persulfate was added to the aqueous dispersion, and 5609 parts by mass of styrene and methacrylamide were added to the surfactant (7100 parts by mass of water and 7.1 parts by mass of sodium lauryl sulfate). 1065 parts by mass and 71 parts by mass of 2-hydroxyethyl methacrylate were added with stirring to prepare an emulsion of the second monomer component.

Example 13
In the following steps, an aqueous dispersion of emulsion particles was obtained in the same manner as in Example 9, except that the procedure and prescription were changed. The solid content concentration of the aqueous dispersion was 26% by mass.

In the neutralization step, 9940 parts by mass of water and 138 parts by mass of 28% ammonia aqueous solution were added to the aqueous dispersion.

In the second polymer preparation step, 35.5 parts by mass of ammonium persulfate was added to the aqueous dispersion, and 4,899 parts by mass of styrene and methacrylic acid were added to the surfactant (4260 parts by mass of water and 7.1 parts by mass of sodium lauryl sulfate). 2,130 parts by mass of isobornyl and 71 parts by mass of 2-hydroxyethyl methacrylate were added with stirring to prepare an emulsion of the second monomer component.

Example 14
In the following steps, an aqueous dispersion of emulsion particles was obtained in the same manner as in Example 4, except that the procedure and prescription were changed. The solid content concentration of the aqueous dispersion was 26% by mass.

In the first polymer preparation step, 500 parts by mass of the aqueous dispersion of the fourth polymer, 8610 parts by mass of water, and 10.5 parts by mass of ammonium persulfate were added to a separable flask equipped with a stirrer, a thermometer, and a reflux condenser. A liquid was prepared, and 1470 parts by mass of methyl methacrylate, 315 parts by mass of styrene, 105 parts by mass of butyl acrylate, and 210 parts by mass of methacrylic acid were added to a surfactant (840 parts by mass of water and 2.1 parts by mass of sodium lauryl sulfate). The mixture was added while stirring to prepare an emulsion of the first monomer component.

In the neutralization step, 440 parts by mass of water and 77 parts by mass of a 28% ammonia aqueous solution were added to the aqueous dispersion.

In the second polymer preparation step, 11 parts by mass of ammonium persulfate was added to the aqueous dispersion, and 1738 parts by mass of styrene and 440 parts by mass of methacrylamide were added to the surfactant (2200 parts by mass of water and 2.2 parts by mass of sodium lauryl sulfate). 1 part and 22 parts by mass of 2-hydroxyethyl methacrylate were added with stirring to prepare an emulsion of the second monomer component.

The third polymer preparation step was not performed.

Comparative example 1
In the following steps, an aqueous dispersion of emulsion particles was obtained in the same manner as in Example 1, except that the procedure and prescription were changed. The solid content concentration of the aqueous dispersion was 33% by mass.

In the second polymer preparation step, 1232 parts by mass of styrene, 140 parts by mass of methacrylamide, and 28 parts by mass of 2-hydroxyethyl methacrylate were added to the surfactant (1600 parts by mass of water and 14 parts by mass of sodium lauryl sulfate) with stirring. An emulsion of the second monomer component was prepared.

Comparative example 2
In the following steps, an aqueous dispersion of emulsion particles was obtained in the same manner as in Example 9, except that the procedure and prescription were changed. The solid content concentration of the aqueous dispersion was 34% by mass.

In the neutralization step, 1420 parts by mass of water and 138 parts by mass of a 28% ammonia aqueous solution were added to the aqueous dispersion.

In the second polymer preparation step, 14.2 parts by mass of ammonium persulfate was added to the aqueous dispersion, and 7029 parts by mass of styrene and methacrylic acid were added to the surfactant (2840 parts by mass of water and 7.1 parts by mass of sodium lauryl sulfate). 71 parts by mass of 2-hydroxyethyl was added with stirring to prepare an emulsion of the second monomer component.

Comparative example 3
In the following steps, an aqueous dispersion of emulsion particles was obtained in the same manner as in Example 9, except that the procedure and prescription were changed. The solid content concentration of the aqueous dispersion was 26% by mass.

In the neutralization step, 7100 parts by mass of water and 138 parts by mass of a 28% ammonia aqueous solution were added to the aqueous dispersion.

In the second polymer preparation step, 35.5 parts by mass of ammonium persulfate was added to the aqueous dispersion, and 4899 parts by mass of styrene and 2130 parts by mass of acrylonitrile were added to the surfactant (7100 parts by mass of water and 7.1 parts by mass of sodium lauryl sulfate). 71 parts by mass of 2-hydroxyethyl methacrylate were added with stirring to prepare an emulsion of the second monomer component.
3. Evaluation <average particle diameter>
The average particle diameter was measured using a particle diameter measuring device FPAR1000 (manufactured by Otsuka Electronics). The results are shown in Tables 1 and 2.
<Internal structure>
The emulsion particles of each Example and each Comparative Example were dried at 40° C. for 12 hours, and the inside of the emulsion particles was observed using a transmission electron microscope H-7650 (manufactured by Hitachi High-Tech). The internal structure was evaluated using the following criteria. The results are shown in Tables 1 and 2.
○: The inside was hollow.
×: The inside was not hollow.
<Heat resistance>
In an aluminum cup with a diameter of about 5 cm, 3 g of an aqueous dispersion of emulsion particles of each Example and each Comparative Example, which had been adjusted to a solid content concentration of 20%, was weighed and left to stand in a dryer at 150° C. for 1 hour.

Thereafter, the surface of the emulsion particles was observed using a scanning electron microscope JSM-6380 (manufactured by JEOL), and the internal mass of the emulsion particles was observed using a transmission electron microscope H-7650 (manufactured by Hitachi High-Tech). Observed. Heat resistance was evaluated using the following criteria. The results are shown in Tables 1 and 2. Further, FIG. 2A shows the results of scanning electron microscopy observation of Example 9, FIG. 2B shows the results of transmission electron microscopy observation of Example 9, and FIG. 3A shows the results of scanning electron microscopy of Example 13. 3B shows the results of transmission electron microscopy of Example 13, FIG. 4A shows the results of scanning electron microscopy of Comparative Example 2, and FIG. 4B shows the results of scanning electron microscopy of Comparative Example 2. shows the results of transmission electron microscopy observation of Example 9.
◎: The particles were hardly melted on the surface of the particles, and the insides of the particles were hardly collapsed.
○: The particles were slightly melted on the surface of the particles, and the interior of the particles was hardly collapsed.
Δ: The particles were slightly melted on the surface of the particles, and the insides of the particles were slightly collapsed.
×: Most of the particles were melted on the surface of the particles, and the interior of the particles was almost completely collapsed.

Claims (10)

a first polymer that is a polymerization product of a first monomer component containing an acidic group-containing vinyl monomer;
a second polymer that is a polymerization product of a second monomer component that does not substantially contain the acidic group-containing vinyl monomer;
In the first monomer component, the acidic group-containing vinyl monomer is 10% by mass or more and 80% by mass or less with respect to the first monomer component,
The glass transition temperature of the second polymer is 112.0°C or higher,
At least a part of the acid functional groups in the acidic group-containing vinyl monomer form a salt,
the first polymer is coated with the second polymer,
the second monomer component includes (meth)acrylamide,
The content ratio of the (meth)acrylamide is more than 10% by mass and not more than 80% by mass with respect to the second monomer component,
An emulsion particle characterized in that, in the second monomer component that does not substantially contain the acidic group-containing vinyl monomer, the content of the acidic group-containing vinyl monomer is 0.1% by mass or less . the first monomer component includes methyl methacrylate,
The emulsion particles according to claim 1 , wherein the content of methyl methacrylate is 50% by mass or more based on the first monomer component. the second monomer component contains styrene,
The emulsion particles according to claim 1 or 2 , wherein the content of styrene is 10% by mass or more based on the second monomer component. comprising a third polymer that is a polymerization product of a third monomer component;
the first polymer is coated with the third polymer,
Emulsion particles according to any one of claims 1 to 3 , characterized in that the third polymer is coated with the second polymer. the third monomer component includes the acidic group-containing vinyl monomer,
5. The emulsion particles according to claim 4 , wherein in the third monomer component, the acidic group-containing vinyl monomer accounts for 1% by mass or more and 10% by mass or less. comprising a fourth polymer that is a polymerization product of a fourth monomer component;
The emulsion particle according to any one of claims 1 to 5 , characterized in that the fourth polymer is coated with the first polymer. A coating agent comprising the emulsion particles according to any one of claims 1 to 6 . A dried product, characterized in that it is a dried product of the emulsion particles according to any one of claims 1 to 6 . The dried product according to claim 8 , characterized in that the inside is hollow. Polymerizing a first monomer component containing an acidic group-containing vinyl monomer to prepare a first polymer;
Polymerizing a second monomer component that does not substantially contain the acidic group-containing vinyl monomer to prepare a second polymer;
neutralizing at least a portion of the acid functional groups in the acidic group-containing vinyl monomer,
In the first monomer component, the acidic group-containing vinyl monomer is 10% by mass or more and 80% by mass or less with respect to the first monomer component,
The glass transition temperature of the second polymer is 112.0°C or higher,
the first polymer is coated with the second polymer,
the second monomer component includes (meth)acrylamide,
The content ratio of the (meth)acrylamide is more than 10% by mass and not more than 80% by mass with respect to the second monomer component,
A method for producing emulsion particles, characterized in that the content of the acidic group-containing vinyl monomer in the second monomer component that does not substantially contain the acidic group-containing vinyl monomer is 0.1% by mass or less. .

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