JP2002080503A - Hollow polymer fine particle and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hollow polymer fine particle comprising a shell of single layer structure, having a high porosity by a short process and by a simple method. SOLUTION: A mixture of (i) a crosslinkable monomer (B) (or a mixture of the crosslinkable monomer (B) and a monofunctional monomer (B')), (ii) an initiator (C) and (iii) a slightly water-soluble solvent (D) having low solubility of a polymer obtained from the crosslinkable monomer (B) is dispersed in an aqueous solution of a dispersion stabilizer (A), and a suspension polymerization is carried out to give the hollow polymer fine particle comprising the shell of the single layer structure composed of the polymer of the crosslinkable monomer or a copolymer of the crosslinkable monomer and the monofunctional monomer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to hollow polymer microparticles, and more particularly to hollow polymer microparticles having a high porosity in which a shell is crosslinked and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, inorganic particles such as calcium carbonate and clay have been added to coating agents such as paints and paper coating compositions for the purpose of imparting concealing properties.

However, since these inorganic particles are heavy, hollow polymer particles have recently been used in place of the inorganic particles. The hollow polymer particles are lightweight because they are hollow, and have excellent optical properties such as concealing properties, whiteness, and gloss due to irregular reflection of light in the hollows, and furthermore, because of the presence of the hollow portions, heat insulation. It also has an effect.

Conventionally, as a method for producing hollow polymer fine particles,
The following two types of manufacturing methods are known. One method is a method described in JP-A-6-248012. This method comprises the steps of: a) 20 to 60% by weight of a carboxyl group-containing monomer and 80 to 40% by weight of a comonomer copolymerizable therewith.
A middle layer polymer consisting of a copolymer of 1 to 12% by weight of a carboxyl group-containing monomer and 99 to 88% by weight of a comonomer copolymerizable therewith; A base is added to a latex containing polymer particles having at least a three-layer structure consisting of a surface layer polymer composed of a monomer polymer containing no carboxyl group and a base to adjust the pH of the latex to 8 or more, And adding an acid to adjust the pH of the latex to 7 or less.

Another method is disclosed in Japanese Patent Application Laid-Open No. H8-20604.
It is a method described in the item. This method comprises the steps of dispersing the following (a) to (e) in the following hydrophilic organic solvent (f) to prepare a dispersion system;
In (e), the solubility of the water-insoluble monomer (a), the water-insoluble organic solvent (c), and the oil-soluble polymerization initiator (e) is reduced, so that the seed polymer particles (b) are Absorbing the water-insoluble monomer (a), the water-insoluble organic solvent (c) and the oil-soluble polymerization initiator (e), and the water-insoluble monomer in the seed polymer particles (b). (A) a step of selectively polymerizing (a): (a) a water-insoluble monomer containing a monomer having two or more polymerizable reactive groups; (B) a seed polymer particle that dissolves in or absorbs the water-insoluble monomer (a) and swells;
A polymer formed from the water-insoluble monomer (a) and a water-insoluble organic solvent that dissolves or swells the seed polymer particles (b), (d) a dispersion stabilizer, and (e) oil-soluble polymerization initiation (F) dissolving the water-insoluble monomer (a),
And a hydrophilic organic solvent that does not dissolve the polymer formed from the monomer and the seed polymer particles (b).

In this conventional method, first, a monomer (a) such as divinylbenzene and a monomer (a) such as toluene are mixed in a seed polymer particle (b) such as a polystyrene particle using a so-called dynamic swelling method. Water-insoluble organic solvent (c) and oil-soluble polymerization initiator such as azobisisobutyronitrile (e)
To swell or dissolve the seed polymer particles (b).

Thus, the water-insoluble organic solvent (c)
Dissolves the seed polymer particles (b), so that a solution of the seed polymer particles (b), the monomer (a), the water-insoluble organic solvent (c), and the oil-soluble polymerization initiator (e) Mixed droplets are obtained. When the temperature is raised in this state, since the oil-soluble polymerization initiator (e) is present, the monomer (a) in the droplets is polymerized (seed polymerization) to form a polymerized film of the monomer (a). A shell is formed, and a water-insoluble organic solvent (c) is formed therein.
There is a seed polymer (b) dissolved in the polymer. When the particles thus obtained are dried, the water-insoluble organic solvent (c) in the core part is obtained.
Volatilizes, and the seed polymer (b) adheres to the inside of the shell made of the polymerized film of the monomer (a) to form the second shell. As a result, hollow polymer fine particles having a shell having a two-layer structure are obtained.

[0008]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 6-248.
In the method described in No. 012, as described above, at least three steps of a step of forming a center layer polymer, a step of forming an intermediate layer polymer, and a step of forming a surface layer polymer require at least three layers. There is still much room for improvement in the point that a latex containing a polymer particle having a structure is prepared, and the latex is subjected to a base treatment step and an acid treatment step, which requires complicated and numerous steps. The fine particles produced by this method have a shell thickness of 3 in the examples of the publication.
Although hollow particles having a shell with a three-layer structure of 0 to 45 nm are obtained, there is a problem that polymer particles having a laminated structure of at least three layers must be prepared first.

On the other hand, also in the method described in JP-A-8-20604, a step of dispersing the above (a) to (e) in the above hydrophilic organic solvent (f) to prepare a dispersion system, Swelling the seed polymer particles (b) by the method,
There is still room for improvement in that three steps of a subsequent seed polymerization step are required, and various raw materials and solvents including the seed polymer particles (b) are required.

[0010] In particular, the use of seed polymer particles (b) is indispensable. For example, Colloid & Polymer Science, Vol. 276, No. 7, (1)
998) The abstract column on page 638 to page 642, for example, page 638, states that when the above-mentioned dynamic swelling method is used, hollow polymer fine particles cannot be produced unless the seed polymer (b) (polystyrene) is present. Have been.

The hollow polymer fine particles obtained by the method of JP-A-8-20604 have a shell composed of a polymer film of the monomer (a) and a seed polymer formed inside the film. Since it has a two-layer structure with the film derived from b), the synthesis process is also complicated. In particular, in the synthesis, after the seed polymer has been synthesized in advance, it is dispersed after being mixed with the monomer,
It must go through a stage of conducting polymerization.

In some cases, it is desired that the hollow polymer particles have a high porosity.

Accordingly, an object of the present invention is to provide hollow polymer particles having a single-layer shell and a high porosity.

Another object of the present invention is to provide a method capable of producing such hollow polymer fine particles in a short process and by a simple method.

[0015]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above-mentioned object, and in particular, disclosed in JP-A-8-20 / 1990.
The study was repeated from the viewpoint of improving the method of No. 604. As a result, surprisingly, the crosslinkable monomer (B) (or the crosslinkable monomer (B)) can be obtained in an aqueous solution of the dispersion stabilizer (A) without using the seed polymer particles (b), which have been conventionally regarded as essential. A mixture of a monomer (B) and a monofunctional monomer (B ′)), an initiator (C) and a specific solvent (D),
It has been found that hollow polymer fine particles can be produced by a simple process of subjecting to a suspension polymerization reaction.

Further, the present inventors have found that the hollow polymer fine particles obtained by the above method have a shell in which the shell is a polymerized film of the crosslinkable monomer (B) or a crosslinkable monomer (B) and a monofunctional monomer (B ′). )) And a single-layer structure composed of a copolymer film of the mixture with (1), and a large porosity.

The present invention has been completed based on these findings and further studied and provides the following invention.

Item 1. Hollow high-molecular fine particles comprising a shell and a hollow portion, wherein the shell is a polymer or copolymer of at least one crosslinkable monomer, or at least one
Hollow polymer fine particles having a single-layer structure comprising a copolymer of at least one kind of crosslinkable monomer and at least one kind of monofunctional monomer.

Item 2 The thickness of the shell is 0.01 to 4 μm,
The porosity is 50 to 80%, and the average particle size is 0.1 to 3
Item 2. The hollow polymer fine particles according to Item 1, having a particle size of 0 μm.

Item 3. The shell is composed of at least one crosslinkable monomer of 10 to 100% by weight and a monofunctional monomer of 90 to 90% by weight.
Item 3. The hollow polymer fine particles according to Item 1 or 2, comprising 0% by weight of a polymer or a copolymer.

Item 4 The above item 1 wherein the shell comprises a polymer or copolymer of at least one kind of crosslinkable monomer.
4. The hollow polymer fine particles according to any one of 3.

Item 5: The crosslinkable monomer is at least one of polyfunctional monomers having two or more polymerizable double bonds (particularly, divinylbenzene, divinylbiphenyl, divinylnaphthalene, diallylphthalate, triallyl cyanurate, ethylene glycol). At least one member selected from the group consisting of dimethacrylate and tetraethylene glycol dimethacrylate), wherein the monofunctional monomer is a monovinyl aromatic monomer, an acrylic monomer, a vinyl ester monomer, or a vinyl ether monomer. 4. The hollow polymer fine particles according to any one of the above items 1 to 3, which are at least one selected from the group consisting of a monomer, a monoolefin monomer, a halogenated olefin monomer and a diolefin.

Item 6: In an aqueous solution of the dispersion stabilizer (A), (i)
At least one crosslinkable monomer (B) or a mixture of at least one crosslinkable monomer (B) and at least one monofunctional monomer (B ′); (ii) an initiator (C) and
(iii) a polymer or copolymer of at least one crosslinkable monomer (B), or a copolymer of at least one crosslinkable monomer (B) and at least one monofunctional monomer (B ′) Item 2. The method for producing hollow polymer fine particles according to Item 1, wherein a mixture comprising a poorly water-soluble solvent (D) having low compatibility with the coalesced is dispersed and subjected to suspension polymerization.

Item 7: The solvent (D) is a polymer or copolymer of at least one crosslinkable monomer (B) or at least one crosslinkable monomer (B) and at least one monofunctional monomer (B). ') Has a low compatibility with the copolymer with ()), and dissolves the interfacial tension (γ ^X ) between the solvent (D) and water and the crosslinkable monomer (B) in the solvent (D). Or a solution obtained by dissolving a mixture of a crosslinkable monomer (B) and a monofunctional monomer (B ') in a solvent (D), and subjecting the solution to suspension polymerization to obtain a solution between the polymer-adsorbed surface and water. In relation to the interfacial tension (γ ^P ) (mN / m), γ ^X ≧
The process according to Item 6 conditions, such as gamma ^P is a solvent which satisfies.

Item 8: The dispersion stabilizer (A) is a polymer dispersion stabilizer (particularly, polyvinyl alcohol), and the crosslinkable monomer (B) is a polyfunctional monomer having two or more polymerizable double bonds. At least one kind (particularly, at least one selected from the group consisting of divinylbenzene, divinylbiphenyl, divinylnaphthalene, diallylphthalate, triallyl cyanurate, ethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate)
Species), and the monofunctional monomer (B ′) is a monovinyl aromatic monomer, an acrylic monomer, a vinyl ester monomer, a vinyl ether monomer, a monoolefin monomer, or a halogenated monomer. At least one member selected from the group consisting of an olefin-based monomer and a diolefin, wherein the initiator (C) is soluble in the monomer, and is composed of azobisisobutyronitrile, cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, di-t
-Butyl peroxide, benzoyl peroxide, lauroyl peroxide or the like, or at least one initiator selected from photopolymerization initiators, and the solvent (D) contains 8 to 18 carbon atoms (particularly 12 to 18 carbon atoms). (8) The production method according to the above (6) or (7), which is a saturated hydrocarbon.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the production method of the present invention will be described first, and then the hollow polymer fine particles of the present invention will be described.

Method for Producing Hollow Polymer Fine Particles of the Present Invention The production method of the present invention comprises, as described above, (i) at least one crosslinkable monomer (B) in an aqueous solution of a dispersion stabilizer (A).
Or a mixture of at least one crosslinkable monomer (B) and at least one monofunctional monomer (B ′), (ii)
Polymers or copolymers of initiators (C) and (iii) at least one crosslinkable monomer (B) or at least one crosslinkable monomer (B) and at least one monofunctional monomer (B ') A process comprising dispersing a mixture composed of a poorly water-soluble solvent (D) having low compatibility with a copolymer of the above, and performing a suspension polymerization reaction. .

Dispersion Stabilizer (A) The dispersion stabilizer (A) used in the present invention is the crosslinkable monomer (B) (or a mixture of the crosslinkable monomer (B) and the monofunctional monomer (B ')). What has the effect of dispersing the mixture formed of the initiator (C) and the solvent (D) in water to prevent the droplets formed from coalescence can be used from a wide range, for example, polyvinyl alcohol, methyl cellulose, ethyl cellulose , Polyacrylic acid, polyacrylimide, polyethylene oxide, polymer dispersion stabilizer such as poly (hydroxystearic acid-g-methyl methacrylate-co-methacrylic acid) copolymer, nonionic surfactant, anionic interface Surfactants and amphoteric surfactants. Among these, a polymer dispersion stabilizer such as polyvinyl alcohol is preferable.

The amount of the dispersion stabilizer (A) to be used can be selected from a wide range, but is generally a crosslinkable monomer (B) or a mixture of the crosslinkable monomer (B) and the monofunctional monomer (B ′). + Initiator (C)
+ 0.001 to 1 part by weight, preferably 0.01 to 0.1 part by weight, based on 1 part by weight of the total amount of the solvent (D).

In the aqueous solution of the dispersion stabilizer (A), the concentration of the dispersion stabilizer (A) may be appropriately selected so that the above-mentioned droplets do not coalesce. Generally,
The concentration of the aqueous dispersion stabilizer is 0.001 to 10% by weight, especially 0.1%.
It is preferable to adjust it to the range of 0.5% by weight.

Crosslinkable monomer (B) and monofunctional monomer
Examples of the (B ′) crosslinkable monomer (B) include a polyfunctional monomer having two or more (particularly 2 to 4) polymerizable double bonds, particularly a polymerizable reactive group. ,
Examples include divinyl biphenyl, divinyl naphthalene, diallyl phthalate, triallyl cyanurate, ethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate. These can be used alone or in combination of two or more.

The crosslinkable monomer (B) may be used in combination with the monofunctional monomer (B ′) having one polymerizable reactive group as long as the effect of the present invention is not impaired. Examples of the monofunctional monomer (B ′) include monovinyl aromatic monomers, acrylic monomers, vinyl ester monomers, vinyl ether monomers, monoolefin monomers, and halogenated olefins. System monomers, diolefins and the like. These can be used alone or in combination of two or more.

The monovinyl aromatic monomer includes a monovinyl aromatic hydrocarbon represented by the following general formula (1):
Examples thereof include vinyl biphenyl which may be substituted with a lower alkyl group, and vinyl naphthalene which may be substituted with a lower alkyl group.

[0034]

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[In the formula, R ¹ is a hydrogen atom, a lower alkyl group or a halogen atom, and R ² is a hydrogen atom, a lower alkyl group, a halogen atom, a —SO ₃ Na group, a lower alkoxy group, an amino group or Shows a carboxyl group. In the above general formula (1), R ¹ is preferably a hydrogen atom, a methyl group or a chlorine atom, and R ² is preferably a hydrogen atom, a chlorine atom, a methyl group or a —SO ₃ Na group.

Specific examples of the monovinyl aromatic hydrocarbon represented by the general formula (1) include styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene, o-
Chlorostyrene, m-chlorostyrene, p-chlorostyrene, sodium styrenesulfonate and the like can be mentioned.
Further, vinyl biphenyl optionally substituted with a lower alkyl group, vinyl naphthalene optionally substituted with a lower alkyl group include vinyl biphenyl, methyl group,
Examples thereof include vinyl biphenyl and vinyl naphthalene substituted with a lower alkyl group such as an ethyl group, and vinyl naphthalene substituted with a lower alkyl group such as a methyl group and an ethyl group. These monovinyl aromatic monomers can be used alone or in combination of two or more.

The acrylic monomer includes an acrylic monomer represented by the following general formula (2).

[0038]

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Wherein R ³ represents a hydrogen atom or a lower alkyl group; R ⁴ represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a phenyl group, a hydroxyalkyl group having 1 to 6 carbon atoms, a lower alkyl group; Aminoalkyl group or di (C1-C4 alkyl)
Indicates an amino- (C1-C4) alkyl group. In the general formula (2), R ³ is preferably a hydrogen atom or a methyl group, and R ⁴ is a hydrogen atom, having 1 to 8 carbon atoms.
Are preferably an alkyl group, a phenyl group, a lower hydroxyalkyl group, and a lower aminoalkyl group.

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

Examples of the vinyl ester monomer include those represented by the following general formula (3).

[0042]

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Wherein R ⁵ represents a hydrogen atom or a lower alkyl group. Specific examples of the vinyl ester monomer include vinyl formate, vinyl acetate, and vinyl propionate.

Examples of the vinyl ether monomer include a vinyl ether monomer represented by the following general formula (4).

[0045]

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[R ⁶ is an alkyl group having 1 to 12 carbon atoms,
It represents a phenyl group or a cyclohexyl group. Specific examples of the vinyl ether-based monomer include vinyl methyl ether, vinyl ethyl ether, vinyl n-butyl ether, vinyl phenyl ether, and vinyl cyclohexyl ether.

Examples of the monoolefin-based monomer include those represented by the following general formula (5).

[0048]

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[Wherein, R ⁷ and R ⁸ are a hydrogen atom or a lower alkyl group, which may be different or the same. Specific examples of the monoolefin-based monomer include ethylene, propylene, butene-1, pentene-1, and 4-methylpentene-1.

Examples of the halogenated olefin-based monomer include vinyl chloride and vinylidene chloride.

Further, diolefins such as butadiene, isoprene and chloroprene can be included in the monofunctional monomer.

The preferred combination of the crosslinkable monomer (B) and the other monofunctional monomer (B ′) is, as the monofunctional monomer (B ′), styrene alone, acrylate ester, A combination of methacrylate alone, styrene and acrylate, styrene and methacrylate, acrylate and methacrylate, styrene, acrylate and methacrylate, and divinylbenzene as the crosslinkable monomer (B) Can be

When the above monofunctional monomer (B ′) is used in combination, the crosslinking monomer (B), that is, the polymerizable functional group
The content of the polyfunctional monomer having at least one monomer is 10% by weight or more of the crosslinkable monomer (B) based on the total amount of the monofunctional monomer (B ′) and the crosslinkable monomer (B). It is preferably at least 30% by weight.

The shell obtained by polymerizing these monomers forms the above-mentioned at least one crosslinkable monomer (B) 10
-100% by weight, in particular 30-100% by weight, and at least one monofunctional monomer (B ') from 90 to 0% by weight, especially 70 to 0% by weight, comprising a polymer or copolymer.

The amount of the crosslinkable monomer (B) used or the amount of the mixture of the crosslinkable monomer (B) and the monofunctional monomer (B ′) is determined by the particle size of the desired hollow polymer fine particles, Can be appropriately selected according to the thickness of the solvent (D), but is generally 0.1 to 2 parts by weight per 1 part by weight of the solvent (D),
In particular, it is preferably 0.5 to 1 part by weight.

Initiator (C) The initiator (C) used in the present invention comprises a crosslinkable monomer (B) or a crosslinkable monomer (B) and the above monofunctional monomer (B ′) in the above-mentioned droplets. To initiate polymerization of a mixture of the above, and oil-soluble polymerization initiators can be widely used. For example, an azo compound such as azobisisobutyronitrile which is a radical polymerization initiator, cumene hydroperoxide, t
-Butyl hydroperoxide, dicumyl peroxide,
Those soluble in monomers such as peroxides such as di-t-butyl peroxide, benzoyl peroxide, and lauroyl peroxide are exemplified. Further, a photopolymerization initiator that initiates polymerization by light such as ultraviolet light may be used. Such a photopolymerization initiator is not particularly limited as long as it is oil-soluble,
Conventionally used ones can be used.

The initiator (C) is used in an amount of 0.001 part by weight of the crosslinkable monomer (B) or 1 part by weight of the mixture of the crosslinkable monomer (B) and the monofunctional monomer (B ′).
It is preferably 5 to 0.1 part by weight, particularly preferably 0.01 to 0.05 part by weight.

Solvent (D) The solvent (D) used in the present invention comprises the crosslinkable monomer (B) or a mixture of the crosslinkable monomer (B) and the monofunctional monomer (B ′), and a polymerization initiator ( C) is dissolved, but a polymer or copolymer obtained from at least one crosslinkable monomer (B) or at least one crosslinkable monomer (B) and at least one monofunctional monomer (B ′) Has low compatibility with the copolymer of the polymer and the polymer, promotes phase separation of the polymer or the copolymer, and has a polymerized film of the crosslinkable monomer (B) or the crosslinkable monomer (B) and the monofunctional monomer (B Various organic solvents can be used as long as they do not prevent the formation of a polymerized film of the mixture with (1).

As the solvent (D), for example,
Examples thereof include saturated hydrocarbons having 8 to 18, especially 12 to 18 carbon atoms. Hexadecane is particularly preferred as the solvent (D).

In the present invention, the solvent (D) is
Not limited to the hydrocarbons, at least one type of crosslinkable
Nomer (B) polymer or copolymer or at least
One crosslinkable monomer (B) and at least one monofunctional
Low compatibility with copolymer with functional monomer (B ')
Has interfacial tension between solvent (D) and water
(Γ ^X) And a crosslinkable monomer under the conditions of the production method of the present invention.
A solution or a crosslinkable product obtained by dissolving (B) in a solvent (D)
A mixture of the monomer (B) and the monofunctional monomer (B ')
The solution obtained by dissolving in the medium (D) is subjected to suspension polymerization,
Interfacial tension between the polymer adsorption surface and water (γ^P) (MN / m)
In relation to^X≧ γ^PA condition such as
Medium can be widely used.

The amount of the solvent (D) to be used can be appropriately selected from a wide range, but is generally a monomer (ie, a crosslinkable monomer (B), or a crosslinkable monomer (B) and a monofunctional monomer (B ′). 1) 5 to 1 part by weight of the mixture
It is preferable to use 1 part by weight, especially 1-2 parts by weight.

Dispersion Step In the present invention, a crosslinkable monomer (B) (or a mixture of the crosslinkable monomer (B) and the monofunctional monomer (B ′)) is added to an aqueous solution of the dispersion stabilizer (A). A mixture containing the initiator (C) and the solvent (D) at the above-mentioned ratio is dispersed, and suspension polymerization is carried out.

A crosslinkable monomer (B) (or a mixture of the crosslinkable monomer (B) and the monofunctional monomer (B ′)),
The mixture of the initiator (C) and the solvent (D) is preferably a homogeneous solution, and is formed by mixing these three components. The temperature at the time of mixing is not particularly limited, and for example, mixing may be performed at about 0 to 30 ° C.

The crosslinkable monomer (B) thus obtained
(Or a mixture of the crosslinkable monomer (B) and the monofunctional monomer (B ')), a homogeneous solution of the initiator (C) and the solvent (D), and then an aqueous solution of the dispersion stabilizer (A) Disperse in.

The homogeneous solution is an aqueous solution 1 of the dispersion stabilizer (A).
It is preferable to use 1 to 50 parts by weight, particularly 3 to 20 parts by weight, per 100 parts by weight, but it is not particularly limited to this range.

As the dispersing method, various known methods such as a homogenizer and a dispersing method using mechanical shearing force such as a membrane emulsifying method can be adopted. The temperature condition at the time of dispersion is not limited as long as it is not higher than the temperature that affects the decomposition of the initiator used, but it is usually preferably around room temperature or lower, particularly about 0 to 30 ° C.

In the above dispersion method, the crosslinkable monomer (B)
(Or a mixture of the crosslinkable monomer (B) and the monofunctional monomer (B ')), the initiator (C) and the solvent (D) are dispersed. Instead of monodispersion, generally, droplets of various different particle sizes are mixed. Therefore, the finally obtained hollow polymer fine particles also have different particle diameters.

On the other hand, by selecting a dispersion method, the size of the droplets can be made uniform to obtain monodispersed droplets. As a method of obtaining such monodisperse droplets, for example, a method of producing monodisperse droplets by a film emulsification method using porous glass (SPG) can be mentioned. When such monodispersed droplets having a uniform particle diameter are prepared, the finally obtained hollow polymer fine particles are also monodisperse having a uniform particle diameter.

In any case, the average particle size of the droplets may be appropriately determined according to the desired average particle size of the hollow polymer fine particles, but is generally 0.1 to 30 μm, especially 0.5 to 30 μm.
It is preferable that the thickness be 10 μm.

Suspension polymerization The crosslinkable monomer (B) thus obtained (or a mixture of the crosslinkable monomer (B) and the monofunctional monomer (B ')), the initiator (C) and the solvent (D) In order to subject the aqueous solution of the dispersion stabilizer (A) in which the homogeneous mixture of the above is dispersed to suspension polymerization, the aqueous solution may be heated while stirring.

As the heating temperature, the crosslinking monomer (B)
(Or a mixture of a crosslinkable monomer (B) and the monofunctional monomer (B ')), a droplet of a homogeneous mixture of the initiator (C) and the solvent (D), the crosslinkable monomer (B) ( Or a mixture of the crosslinkable monomer (B) and the monofunctional monomer (B ')) is not particularly limited as long as it is at a temperature at which polymerization is initiated by the initiator (C).
C, especially 50-70C is preferred.

The suspension polymerization is performed until desired hollow polymer fine particles are obtained. The time required for suspension polymerization is as follows: the crosslinkable monomer (B) used (or a mixture of the crosslinkable monomer (B) and the monofunctional monomer (B ′)), the initiator (C) and the solvent (D) Varies depending on the type of
About 4 hours.

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

By carrying out the suspension polymerization in this way, the crosslinking monomer (B) (or a mixture of the crosslinking monomer (B) and the monofunctional monomer (B ′)), the initiator (C) and the solvent ( In the droplets of the homogeneous mixture of D), the crosslinkable monomer (B) (or a mixture of the crosslinkable monomer (B) and the monofunctional monomer (B ′)) is polymerized. In the obtained polymer of the crosslinkable monomer (B) (or a mixture of the crosslinkable monomer (B) and the monofunctional monomer (B ′)), phase separation is promoted by the presence of the solvent (D), As a result, a shell having a single-layer structure, that is, a shell composed of only a polymer of the crosslinkable monomer (B) (or a copolymer of the crosslinkable monomer (B) and the monofunctional monomer (B ′)) is formed. Is done. On the other hand, the core portion is in a state in which the solvent (D) is included.

The hollow polymer fine particles thus obtained may be used as a dispersion liquid (suspension), or may be filtered, washed with water as necessary, and then used in various forms in the form of powder. Can be provided to Further, the hollow polymer particles in the form of a suspension or powder are subjected to a temperature of 20 to 3
The solvent (D) existing in the hollow portion may be removed by a method of drying under conditions of 00 ° C. and a pressure of about 1 to 100,000 Pa, spontaneous evaporation, a reduced pressure treatment, and the like, to provide various uses.

In the present invention, the term “hollow hollow polymer particles” refers to not only the case where air exists in the hollow portion but also the case where air is present in the hollow portion.
This is intended to include the case where the solvent (D) or the like is present in the hollow portion. This is because, even if a solvent or the like is present in the hollow portion, the polymer pigment has a hiding effect and a gloss effect as a polymer pigment.

[0077] The hollow polymer fine particles obtained by the process of the hollow polymer fine particles present invention of the present invention, as described above, the shell is substantially crosslinking monomer (B)
(Or a copolymer of the crosslinkable monomer (B) and the monofunctional monomer (B ′)), and in this regard, the three-layer structure or the two-layer structure obtained by the conventional method is preferred. It is significantly different from hollow polymer fine particles having a layer structure.

The polymer constituting the shell comprises 10 to 100% by weight of the at least one crosslinkable monomer (B),
It is particularly preferable that the polymer or copolymer is composed of 30 to 100% by weight and 90 to 0% by weight, particularly 70 to 0% by weight of the at least one monofunctional monomer (B ').
The polymer constituting the shell is at least one of the above.
It may be a polymer or copolymer of a kind of crosslinking monomer (B).

In the present invention, although it depends on the amount of the crosslinkable monomer (B) used, the shell is generally characterized by a strong shell and a high porosity. Typically, the thickness of the shell of the hollow polymer fine particles of the present invention is 0.01 to 4 μm, particularly 0.05 to 1 μm.
μm. The porosity is 50-80%, especially 60-70%
It is.

Here, in this specification, “porosity”
Is calculated according to the following equation.

Porosity (%) = (r _h / r _p ) ³ × 100 (where _rh is the radius of the hollow particle (（of the outer diameter of the shell))
And _rp is the radius of the hollow part (1/2 of the inner diameter of the shell)
It is. Further, the particle size of the hollow polymer fine particles of the present invention can be adjusted by changing the size of the droplet, but generally, the average particle size of the hollow polymer fine particles of the present invention is 0.1. It is preferably in the range of from 30 to 30 μm, especially from 0.5 to 10 μm. The particle diameter of the hollow polymer particles in this case is a particle diameter measured by an electron microscope or an optical microscope.

As described above, if the monodisperse droplets having a uniform particle diameter are prepared before the suspension polymerization, the obtained hollow polymer fine particles of the present invention can be formed into a monodisperse particle having a uniform particle diameter. Become.

[0083]

The hollow polymer fine particles of the present invention can be used as an organic white pigment, as a polymer pigment added to a paper coating agent, or as a microcapsule carrier.

In particular, since the hollow polymer fine particles of the present invention have a large particle size and a large porosity, a large amount of air can be contained in the hollow portion, and as a result, properties such as heat insulation and sound insulation are obtained. Can also be given.

Further, the hollow polymer particles obtained by the present invention have a function of diffusing a low molecular weight substance from the inside to the outside of the particles because the porosity is large and the film is thin. Therefore, the hollow polymer particles obtained by the present invention,
It can also be used as a drug delivery system or as a microcapsule encapsulating a fragrance or the like.

The production method of the present invention does not require an alkali treatment or the like, and thus the obtained hollow polymer particles have excellent properties such as alkali resistance.

Further, the method for producing the hollow polymer particles of the present invention is as follows:
It does not require special equipment or equipment, can be easily performed at low cost, and can easily provide high-performance hollow polymer particles.

[0088]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. These embodiments are for the purpose of facilitating the understanding of the present invention, and do not limit the present invention, and various modifications are possible.

Example 1 (a) 15 g of an aqueous solution obtained by dissolving 50 mg of polyvinyl alcohol (polymerization degree: 1700, saponification degree: 88%) as a dispersion stabilizer (A) in water, and divinyl as a crosslinkable monomer (B) 250 mg of benzene, 5 mg of benzoyl peroxide as an initiator (C), and hexadecane 2 as a solvent (D)
A solution obtained by uniformly mixing 50 mg was suspended.

The suspension was carried out using a homogenizer as an apparatus under the conditions of a stirring speed of 1000 rpm and room temperature.
Droplets of the obtained suspension had an average particle diameter of about 10 μm.

(B) Next, the suspension was heated at 70 ° C. with stirring under a nitrogen gas atmosphere to carry out suspension polymerization for 24 hours.

When the obtained dispersion was observed with a microscope,
True spherical hollow polymer particles having an average particle diameter of about 10 μm were obtained. Hexadecane was included in the core. The shell thickness is about 1μm and the porosity is about 60%
Met. FIG. 1 shows a micrograph of the hollow polymer particles thus obtained.

(C) The dispersion obtained above is filtered using a filter paper to isolate hollow polymer fine particles, and dried under conditions of a temperature of about 70 ° C. and a pressure of about 100,000 Pa (atmospheric pressure). Then, hexadecane in the core portion was evaporated, and hollow polymer fine particles containing air inside were obtained.

Microscopic observation of the obtained hollow polymer fine particles revealed that spherical hollow polymer fine particles having an average particle diameter of about 10 μm were obtained. Air was contained in the core. The thickness of the shell was about 1 μm. The porosity is about 6
It was 0%.

Example 2 (a) As a dispersion stabilizer (A), 15 mg of an aqueous solution obtained by dissolving 50 mg of polyvinyl alcohol (polymerization degree: 1700, saponification degree: 88%) in water was mixed with the crosslinkable monomer (B). As a mixture with the functional monomer (B '), 51.7% by weight of divinyl biphenyl, 23.
250 mg of a mixture consisting of 6% by weight, 6.2% by weight of methylvinylbiphenyl, 5.8% by weight of vinylbiphenyl and 12.7% by weight of other non-polymerizable components (diethylbiphenyl, ethylbiphenyl, etc.), as initiator (C) 5 mg of benzoyl peroxide, hexadecane 2 as solvent (D)
A solution obtained by uniformly mixing 50 mg was suspended.

The suspension was carried out by using a homogenizer as an apparatus and at a stirring speed of 1000 rpm at room temperature.
Droplets of the obtained suspension had an average particle diameter of about 10 μm.

(B) Next, the suspension was heated at 70 ° C. with stirring under a nitrogen gas atmosphere to carry out suspension polymerization for 24 hours.

When the obtained dispersion was observed with a microscope,
True spherical hollow polymer particles having an average particle diameter of about 10 μm were obtained. Hexadecane was included in the core. The shell thickness is about 1μm and the porosity is about 60%
Met. FIG. 2 shows a micrograph of the hollow polymer particles thus obtained.

(C) The dispersion obtained above is filtered using a filter paper to isolate hollow polymer fine particles, and dried under conditions of a temperature of about 70 ° C. and a pressure of about 100,000 Pa (atmospheric pressure). Then, hexadecane in the core portion was evaporated, and hollow polymer fine particles containing air inside were obtained.

Microscopic observation of the obtained hollow polymer fine particles revealed that spherical hollow polymer fine particles having an average particle diameter of about 10 μm were obtained. Air was contained in the core. The thickness of the shell was about 1 μm. The porosity is about 6
It was 0%.

[Brief description of the drawings]

FIG. 1 is a drawing-substitute photograph (micrograph) showing the particle structure of the hollow polymer fine particles of the present invention produced in Example 1.

FIG. 2 is a drawing-substituting photograph (micrograph) showing the particle structure of the hollow polymer fine particles of the present invention produced in Example 2.

Claims (2)

[Claims] 1. A hollow polymer fine particle comprising a shell and a hollow portion, wherein the shell is a polymer or copolymer of at least one type of crosslinkable monomer, or at least one type of crosslinkable monomer and at least one type of crosslinkable monomer. Hollow polymer microparticles having a monolayer structure composed of a copolymer with a monofunctional monomer. 2. In an aqueous solution of a dispersion stabilizer (A), (i) at least one crosslinkable monomer (B), or at least one crosslinkable monomer (B) and at least one monofunctional monomer. A mixture with monomer (B '), (ii) initiators (C) and (i)
ii) A polymer or copolymer obtained from at least one crosslinkable monomer (B) or a copolymer of at least one crosslinkable monomer (B) and at least one monofunctional monomer (B ′) The method for producing hollow polymer fine particles according to claim 1, wherein a mixture comprising a poorly water-soluble solvent (D) having low compatibility with the mixture is dispersed, and suspension polymerization is performed.