JP2002179708A - Method for producing polymer microparticle having many surface depressions - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for easily producing a golf ball-like polymer microparticle having many deep depressions or hollows on the surface. SOLUTION: This method for producing polymer microparticles comprises the steps of polymerizing a monomer (B) by seed dispersing polymerization method in a medium (M) in which microparticles of a seed polymer (PA) are dispersed, in the presence of (i) the monomer (B) soluble in the medium (M) giving a polymer (PB) which is different from the polymer (PA) and has a lower or equal compatibility to the medium (M) compared to the seed polymer (PA), (ii) an organic solvent (S) which is a poor solvent or non-solvent of the seed polymer (PA) but a good solvent of the polymer (PB) and non-soluble or partially soluble in the medium (M), (iii) a polymerization initiator and (iv) a dispersing agent, separating the obtained composite polymer microparticles and treating to remove the solvent (S).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing fine polymer particles, and more particularly to a method for producing fine polymer particles having a large number of deep depressions (recesses) on the surface of the fine particles.

[0002]

2. Description of the Related Art Conventionally, as a method for producing polymer fine particles having a large number of depressions (concave portions) on the surface, JP-A-6-287244 and JP-A-6-287244 proposed by the present inventors.
A method using a seed emulsion polymerization method described in -287245 is known.

In this method, polystyrene particles serving as seed particles are made to absorb alkyl acrylate and / or methacrylic acid ester as monomers in a mixed solvent of water-soluble organic solvent and water or in water. This is a method characterized by emulsion-polymerizing a monomer, whereby golf ball-like polymer composite fine particles can be produced.

More specifically, referring to FIG. 1, in this conventional method, first, as a polymerization medium, a mixed solvent obtained by adding a small amount of alcohol to water (for example, ethanol / water (10/90; weight ratio)) A)) or water,
Polystyrene (PS) as seed particles 1 in such a medium
In the dispersion liquid in which the particles are dispersed, the above monomer (for example,
Butyl acrylate). The system is stirred at a low temperature of about 5 ° C. to allow the monomer to be absorbed by the seed particles.
Thus, as shown in FIG. 1A, the seed particles 1
It is uniformly swollen with the above monomer (for example, butyl acrylate (BA)).

[0005] Next, a polymerization initiator is added, and seed emulsion polymerization is performed at a temperature lower than the glass transition temperature of the seed polystyrene, whereby the seed particles 1 swollen with the monomer (BA) are formed in the medium. Polymerization is initiated by the intrusion of the agent radical, and a polymer (eg, polybutyl acrylate (PBA)) derived from the above monomer (eg, butyl acrylate monomer (BA)) is formed on the particle surface and collects by phase separation. Then, domain 2 is formed on the particle surface (FIG. 1B). Monomer (B
A) is absorbed into domain 2 (FIG. 1c). At this time, the viscosity of the seed polystyrene portion increases because the swollen monomer (BA) rapidly decreases, the above domains are fixed, and a large number of monomer absorption domains 3 are dispersed on the surface of the polystyrene particles 1 as seed particles. It is formed in a shape.

As the monomer (butyl acrylate (BA)) absorbed in each domain 3 is polymerized, a polymer (polybutyl acrylate (PB)) obtained from the monomer is polymerized.
Since the density of (A)) is higher than that of the monomer (BA), the polymer (PBA) formed in domain 3 shrinks. As a result, as shown in FIG. 1D, a number of depressions or depressions 4 are formed on the surface of the seed particles, and golf ball-shaped polymer composite particles are obtained.

[0007]

In general, the deeper the recesses 4 are, the greater the specific surface area is, the efficiency of the surface of the useful substance and the recesses as a carrier material, the light scattering ability are improved, and the like. Is improved.

The conventional methods described in the above-mentioned JP-A-6-287244 and JP-A-6-287245 are epoch-making in that golf ball-like polymer fine particles having a large number of recesses or depressions on the surface of the polymer particles are formed. It was something.

However, in the above-mentioned conventional method, the control of the depth of the concave portion 4 is determined only by polymerization shrinkage. In order to obtain a deep concave portion, the post-polymerized polymer layer 5 (poly- By treating with a solvent that dissolves the butyl acrylate (PBA) -rich layer but does not dissolve the seed polymer 1, only the post-polymerized polymer (polybutyl acrylate (PBA) layer) is selectively dissolved. In addition, it is necessary to increase the depth of the depression or the depression.

In addition, in the above-mentioned conventional method, it is necessary to absorb the monomer into the seed particles before the polymerization reaction is carried out in order to form the concave portion, and thus the operation is complicated. .

Accordingly, it is an object of the present invention to provide a method for efficiently and easily producing golf ball-shaped composite polymer fine particles having deep recesses.

[0012]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, it has been found that instead of allowing the monomer to be absorbed in the seed particle polymer, the monomer is present in the medium. The present inventors have found that the above object can be achieved by performing seed dispersion polymerization in the presence of a specific organic solvent, and have completed the present invention.

That is, the present invention provides the following method for producing a polymer fine particle having a large number of surface concave portions like a golf ball.

Item 1 In the medium (M) in which polymer (PA) fine particles are dispersed as seed particles, (i) a monomer dissolved in the medium (M), which is different from the seed particle polymer (PA) Together with the monomer (B) that gives the polymer (PB) having a lower or equivalent affinity to the medium (M) compared to the seed particle polymer (PA), and (ii) poor seed particle polymer (PA). Solvent or non-solvent, but a good solvent for the polymer (PB), and
Organic solvent insoluble or partially soluble in the above medium (M)
(S), (iii) a polymerization initiator soluble in the medium (M), and (i)
v) In the presence of a dispersant, monomer
(B) is polymerized, and the solvent in the obtained composite polymer fine particles (S)
A method for producing fine polymer particles having a large number of deep concave portions on the surface, characterized by performing a removal treatment.

Item 2. The method according to Item 1, wherein the polymer (PA) fine particles as seed particles are in a monodispersed state.

Item 3 The seed particle polymer (PA) is a C1-C8 alkyl ester of acrylic acid or a C1 alkyl ester of methacrylic acid.
A polymer or copolymer obtained (preferably by emulsion polymerization or dispersion polymerization) from at least one radically polymerizable monomer selected from aromatic vinyls such as -C8 alkyl esters and styrene, wherein the medium (M) is (a) A) a mixed solvent of at least one water-soluble organic solvent selected from acetone and a lower saturated aliphatic alcohol having 1 to 3 carbon atoms and a small amount of water, wherein the monomer (B) is a C
1-C8 alkyl ester, C1-C8 of methacrylic acid
Aromatic vinyl represented by alkyl ester, styrene, etc., vinyl cyanide, ethylenically unsaturated carboxylic acid, ethylenically unsaturated carboxylic acid ester, vinyl halide, conjugated diene, vinyl carboxylate and ethylenically unsaturated carboxylic acid A monomer that is at least one selected from the group consisting of amides and that gives a polymer (PB) different from the seed polymer (PA);
(S) is a poor solvent or non-solvent for the seed particle polymer (PA), but a good solvent for the polymer (PB), and
Item 3. The method according to Item 1 or 2, wherein the organic solvent is an organic solvent that is insoluble or partially soluble in the medium (M).

Item 4. The seed polymer (PA) is a C1-C8 alkyl ester of acrylic acid or a C1-C8 alkyl ester of methacrylic acid.
A polymer or copolymer obtained from at least one radical polymerizable monomer selected from aromatic vinyl such as 8-alkyl ester and styrene (preferably by emulsion polymerization or dispersion polymerization), wherein the medium (M) comprises (a) carbon Number 1
A mixed solvent of 80 to 70% by weight of at least one selected from lower saturated aliphatic alcohols and 20 to 30% by weight of water, wherein the monomer (B) is C1 of acrylic acid.
-C8 alkyl ester, C1-C8 alkyl ester of methacrylic acid and aromatic vinyl (for example, styrene)
And a monomer that gives a polymer (PB) different from the seed polymer (PA), and the organic solvent (S) is a poor polymer of the seed particle polymer (PA). Solvent or non-solvent, but the polymer (P
Item 4. The method according to any one of Items 1 to 3, which is a good solvent of B) and an organic solvent which is insoluble or partially soluble in the medium (M).

Item 5. The method according to any one of Items 1 to 4, wherein the high-molecular fine particles having a large number of concave portions on the surface have an average particle diameter of 50 nm to 50 μm.

Item 6. The seed polymer (PA) is a polymer of a C1-C8 alkyl (meth) acrylate, the monomer (B) is the aromatic vinyl such as styrene, and the organic solvent (S) is cyclohexane or the like. Is a monocyclic cycloalkane having about 5 to 8 carbon atoms or a bicyclic cyclic alkane having about 8 to 12 carbon atoms such as decalin, or the seed polymer (PA) is the aromatic compound such as styrene. Item 1 is a vinyl polymer, wherein the monomer (B) is a C1-C8 alkyl (meth) acrylate and the organic solvent (S) is a saturated aliphatic higher alcohol having about 7 to 12 carbon atoms such as octanol. 6. The production method according to any one of items 1 to 5,

According to the present invention, the polymer (PA), the medium (M), the monomer (B) and the organic solvent (S) as the seed particles are used.
By using in an appropriate combination, golf ball-shaped composite polymer fine particles having a deeper depression than before can be easily obtained.

In the present invention, the mechanism by which the golf ball-like polymer fine particles are formed in the above system has not been completely elucidated yet, but it is presumed to be due to the following mechanism.

That is, first, in the present invention, the seed particles 10
Medium (M) in which polymer (PA) fine particles are dispersed
In, a monomer (B), an organic solvent (S) and an initiator are dissolved,
Perform seed dispersion polymerization. At that time, the operation of absorbing the monomer (B) into the seed particles 10 is unnecessary. As the polymerization reaction proceeds, the monomer (B) is mainly polymerized in the medium (M). The produced polymer (PB) precipitates out, and the seed particles 10
(Fine particles of polymer (PA)).

At that time, the seed particles 10 (polymer (P
The surface layer of the particles (A)) is slightly swollen by the monomer (B), but the inside of the particles is in a high viscosity state. When the seed dispersion polymerization is performed at a temperature lower than the glass transition temperature of the seed polymer (PA), it is in a glassy state.

As the polymerization proceeds, as shown in FIG. 3, a large number of domains 12 are formed in the seed particle 10 from the surface to the inside. In these domains 12, the polymer (PB) produced by polymerization is
(S) is dissolved and exists. That is, the polymer (PB) assembled in the domain, the organic solvent (S) and the monomer
Since (B) has a high affinity, the organic solvent (S) and the monomer (B) are absorbed in the domain, and the monomer (B) thus absorbed is polymerized to form a polymer (PB), which is obtained. The polymer (PB) exists in the domain 12 while being dissolved in the organic solvent (S). Thus, the polymer (PB) and the organic solvent
Composite polymer fine particles, which are fine particles of a polymer (PA) in which a large number of domains containing (S) are formed on the surface layer, are generated.

After the completion of the seed dispersion polymerization, the solvent (S) in the obtained composite polymer fine particles is removed. As shown in FIG. 4, the organic solvent (S) is removed by volatilization and the like, and the polymer (S) is removed. The layer of (PB) 14 remains on the particles of the seed polymer (PA) and a number of recesses or depressions 16 are formed in the particles of the seed polymer (PA). As a result, the composite polymer fine particles 18 of the present invention having a large number of deep recesses or depressions 16 are obtained.

When the conventional method described in JP-A-6-287244 and JP-A-6-287245 is compared with the method of the present invention, there are the following fundamental differences. That is, in the conventional method, it is essential to perform the operation of absorbing the monomer in the seed particles prior to the polymerization reaction, and as the polymerization reaction proceeds, the monomer absorbed in the seed particles mainly becomes a domain. It is considered that as a result of being absorbed and polymerized, the density of the produced polymer is increased to form a concave portion.

On the other hand, in the present invention, the seed particles (P
Since the polymerization is carried out without performing the operation of absorbing the monomer (B) into the (A), the monomer (B) is not absorbed in the seed particles (PA). The surface layer only swells slightly with monomer (B).
As the polymerization reaction proceeds, the polymer (PB) generated in the medium (M) precipitates on the surface of the seed particles (PA) and aggregates to form a domain, and the domain forms a monomer (B) in the medium (M). Is absorbed and polymerized to produce a polymer (PB), and the organic solvent (S) is absorbed by the polymer (PB) in the domain, and is removed by the removal treatment of the solvent (S) after isolation to form a concave portion. it is conceivable that.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below more specifically.

Polymer (PA) as Seed Particles As the seed polymer (PA), any of vinyl polymers granulated by a conventionally known method, in particular, emulsion polymerization, dispersion polymerization or the like can be used. More specifically, C1-C8 alkyl esters (particularly C1-C4 alkyl esters) of acrylic acid such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, etc .; methyl methacrylate, ethyl methacrylate, methacrylic acid Propyl,
At least one selected from C1-C8 alkyl esters of methacrylic acid such as butyl methacrylate (particularly C1-C4 alkyl esters), and aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene and dimethylstyrene.
Examples include polymers or copolymers obtained from various radically polymerizable monomers.

The average particle diameter of the fine particles of the seed polymer (PA) is not particularly limited, and may be a submicron size of less than 1 μm (for example, about 50 to 900 nm). About 50 μm, especially 1 to 10 μm
It is preferably of the order of microns in size. Of course, a larger particle diameter may be used. The fine particles of the seed polymer (PA) are preferably in a monodispersed state having a uniform particle diameter, but need not be in a monodispersed state.

In the present specification, the average particle diameter of the seed particles and the fine particles of the present invention, such as polymer fine particles having a large number of surface depressions, is measured by an image processing method using an electron microscope photograph.

The fine particles of the seed polymer (PA) can be easily produced from the monomer (A) constituting the seed polymer by a conventionally known and commonly used emulsion polymerization method, dispersion polymerization method or the like. Also, conventionally known particles of monodispersed seed polymer (PA) particles, for example, Colloid & Polymer Science, 26
7 , 193 (1989).

The molecular weight range of the seed polymer (PA) is as follows:
The weight average molecular weight is not particularly limited and may be appropriately selected from a wide range.
It is preferably about 00000 to 500,000, but is not limited to this range.

Medium (M) The medium (M) used in the present invention is required to be a medium capable of dispersing the seed polymer (PA) fine particles without substantially dissolving them. .

Further, the medium (M) contains the seed polymer (PA)
Is required to have lower or equal affinity to the polymer (PB) obtained by polymerization of the monomer (B).

Here, it is determined whether or not the condition that the affinity of the polymer (PB) with the medium (M) is lower or equal to that of the seed particle polymer (PA) is satisfied as compared with the seed particle polymer (PA). For example, assuming that the interfacial tension between a 0.01% by weight toluene solution of seed particle polymer (PA) and a medium (M) is γ ^A ,
The interfacial tension between 0.01 wt% toluene solution and medium (PB) (M) in the case of the gamma ^B, or a ^{γ A <γ B γ A =} γ
^This can be done by confirming whether the relationship ^B is satisfied.

Further, the medium (M) is required not to dissolve the organic solvent (S) at all or to not substantially dissolve the organic solvent (S). That is, the medium (M) does not dissolve or partially dissolves the organic solvent (S).

As the medium (M), for example, a mixture of a water-soluble organic solvent and a small amount of water can be exemplified. As the water-soluble organic solvent, acetone, alcohols, in particular, lower saturated aliphatic alcohols having 1 to 3 carbon atoms such as methanol and ethanol can be used, and these can be used alone or in combination of two or more. They can be used in combination. Among the above mixed solvents, a mixed solvent composed of 80 to 70% by weight of a lower saturated aliphatic alcohol having 1 to 3 carbon atoms (particularly methanol or ethanol) and 20 to 30% by weight of water is particularly preferable.

The amount of the medium (M) is not particularly limited and can be appropriately selected from a wide range. Generally, 500 to 500 parts by weight per 100 parts by weight of the seed polymer (PA) fine particles are used.
It is preferably 0 parts by weight, particularly preferably 1000 to 2000 parts by weight.

In order to disperse the fine particles of the polymer (PA) as the seed particles in the medium (M), the dispersant may be used in an amount of about 5% by weight based on the seed particles and dispersed according to a conventional method. . The dispersant can be used without any particular limitation as long as it is commonly used in this field. For example, polyvinyl alcohol, polyvinylpyrrolidone, and the like are preferably used.

The dispersant is preferably the same as the dispersant used in the dispersion polymerization, but may be different.

Monomer (B) The monomer (B) used in the post-polymerization in the present invention is a monomer satisfying the following conditions: (i) a monomer soluble in the medium (M); ii) the polymer (PB) obtained from the monomer (B) has a lower or equal affinity to the medium (M) as compared to the seed particle polymer (PA), and (iii) The polymer obtained from the monomer (B) (P
B) is different from seed particle polymer (PA).

Here, the polymer (PB) is a seed particle polymer
The determination as to whether or not the condition that the affinity with the medium (M) is lower or equivalent to that of (PA) is satisfied,
It can be carried out as described in the section of “Medium (M)”.

The monomer (B) is a seed particle polymer
(PA) and a polymer (PB) that is different from that of the seed particle polymer (PA), and particularly, a polymer that gives a different polymer (PB) in the type and / or composition of the constituent monomer can be preferably used. .

More specifically, as the monomer (B),
C1-C8 alkyl ester of acrylic acid, C1-C8 alkyl ester of methacrylic acid, aromatic vinyl represented by styrene, vinyl cyanide, ethylenically unsaturated carboxylic acid, ethylenically unsaturated carboxylic acid ester, vinyl halide And conjugated dienes, carboxylic acid vinyl esters and ethylenically unsaturated carboxylic acid amides. These can be used alone or in combination of two or more.

Among the above monomers, particularly,
(B) includes methyl acrylate, ethyl acrylate,
C1-C8 alkyl esters of acrylic acid (especially C1-C4 alkyl esters) such as propyl acrylate and butyl acrylate; C1-C8 alkyl esters of methacrylic acid such as methyl methacrylate, ethyl methacrylate, propyl methacrylate and butyl methacrylate Esters (especially C1-
Preferred are aromatic vinyls such as C4 alkyl ester), styrene, α-methylstyrene, vinyltoluene, and dimethylstyrene.

The amount of the monomer (B) is not particularly limited and can be appropriately selected from a wide range, but is generally from 10 to 200 parts by weight, especially from 30 to 70 parts by weight, per 100 parts by weight of the seed polymer particles. It is preferred that

Organic Solvent (S) The organic solvent (S) used in the present invention is a poor solvent or non-solvent for the seed polymer (PA), but may be a good solvent for the polymer (PB) to be post-polymerized. First you need. In other words, the organic solvent (S) is hardly absorbed by the seed polymer (PA),
It is an organic solvent that can be absorbed by the polymer (PB) obtained by post-polymerization.

The polymer (P) which is post-polymerized with the seed polymer (PA)
For certain combinations of B), any organic solvent
The determination as to whether or not the organic solvent (S) of the present invention can be used is made by adding the separately prepared polymer (PA) and polymer (PB) to the organic solvent (S) and dissolving only one of them. Can be performed by observing Typically, poor solvents are solvents that do not completely dissolve but slightly swell the seed polymer (PA), and non-solvents are solvents that do not substantially dissolve the seed polymer (PA). A good solvent is a solvent that completely dissolves the polymer (PB).

The solvent (S) must be an organic solvent that is insoluble or partially soluble in the medium (M). When the solvent (S) is completely dissolved in the medium (M), the polymer
It is more present in the medium (M) than is absorbed by (PB), and in general, there is a tendency that a large deep recess cannot be formed.

It is preferable that the organic solvent (S) also dissolves the monomer (B).

As the organic solvent (S) satisfying the above conditions, a wide range of organic solvents can be used depending on the combination of the seed polymer (PA) and the monomer (B). In particular, seed polymers
When (PA) is a polymer of a C1-C8 alkyl (meth) acrylate and the monomer (B) is the above-mentioned aromatic vinyl such as styrene, the organic solvent (S) may have a carbon number of 5 to 5 such as cyclohexane. Bicyclic cyclic alkanes having about 8 to 12 carbon atoms such as about 8 monocyclic alkanes or decalin can be preferably used. Seed polymer (P
A) is a polymer of the aromatic vinyl such as styrene,
When the monomer (B) is a C1-C8 alkyl (meth) acrylate, a saturated aliphatic higher alcohol having about 7 to 12 carbon atoms, such as octanol, can be preferably used as the organic solvent (S).

The amount of the organic solvent (S) to be used may be appropriately selected from a wide range, but is generally from 10 to 1,000 parts by weight, especially from 50 to 100 parts by weight, per 100 parts by weight of the seed polymer (PA) fine particles. It is preferably 300 parts by weight, particularly preferably 100 to 200 parts by weight.

Initiator The initiator used in the present invention can be used without any particular limitation as long as it is an initiator that dissolves in the medium (M) and initiates the polymerization of the radically polymerizable monomer.

Examples of the initiator include azo compounds such as azoisobutyronitrile, persulfates such as potassium persulfate, tert-
A peroxide such as butyl peroxide, a redox initiator and the like can be used.

The amount of the polymerization initiator used is not particularly limited as long as it is an amount effective for the polymerization of the monomer (B), and can be appropriately selected from a wide range. , 0.1 to 5 parts by weight, especially 0.5 to 2 parts by weight.

Dispersant The dispersant used in the present invention is used for the purpose of stabilizing the dispersed state of the seed particles. As the dispersant, any dispersant conventionally used in performing dispersion polymerization can be used, and in particular, polyvinylpyrrolidone, polyvinyl alcohol and the like can be used, but not limited thereto.

As the above-mentioned dispersant, the dispersant used for producing the seed particles can be used as it is, or may be additionally added after the production of the seed particles.

The amount of the dispersant to be used can be appropriately selected from a wide range, but is generally preferably 1 to 20 parts by weight, particularly preferably 3 to 10 parts by weight, per 100 parts by weight of the seed particles.

Seed Dispersion Polymerization In the present invention, unlike the above-mentioned conventional method, seed dispersion polymerization is carried out without performing the step of absorbing the monomer (B) into the seed polymer (PA). That is, a monomer (B), a medium (M) in which fine particles of the polymer (PA) as the seed particles are dispersed,
The organic solvent (S), the polymerization initiator and the dispersant are added, and the resulting system is subjected to a seed dispersion polymerization method to polymerize the monomer (B).

The polymerization is carried out by heating the above system under stirring. The stirring conditions are not particularly limited, for example,
It is preferable to use a stirrer having a rotation speed of about 50 to 200 rpm. The polymerization temperature can be selected from a wide range depending on the type of the monomer (B) to be used and the like, but is generally preferably 30 to 90 ° C, particularly preferably 40 to 70 ° C. The polymerization time can vary depending on the polymerization conditions, but is generally about 3 to 24 hours. The polymerization is preferably performed in an atmosphere of an inert gas, for example, nitrogen gas, argon gas or the like.

By this polymerization reaction, composite polymer fine particles which are fine particles of the polymer (PA) having a large number of domains containing the polymer (PB) and the organic solvent (S) formed on the surface layer are generated. After completion of the seed dispersion polymerization reaction, the obtained composite polymer fine particles are isolated from the polymerization reaction mixture. As the isolation method, a conventionally used method such as filtration and centrifugation can be used.

After isolation, from the obtained composite polymer fine particles,
The solvent (S) is removed. As the removal treatment, any method may be used as long as the solvent (S) can be removed from the isolated composite polymer fine particles, and for example, a drying treatment, a washing or extraction treatment using a solvent, or the like can be employed.

The drying treatment may be carried out by any method as long as the organic solvent (S) evaporates from the domain 12 and the polymer (PB) layer adheres to the bottom of the domain 12 to form a recess 16 without a recess. Conditions, for example,
An example is a method of drying at a temperature of about 0 to 90 ° C. and a reduced pressure or a normal pressure of about 1 to 1 × 10 ⁵ Pa until a recess having a desired depth is formed.

In the washing or extraction treatment using the above-mentioned solvent, the composite polymer fine particles are immersed in an organic solvent which is compatible with the above-mentioned solvent (S) until a concave portion having a desired depth is formed. And the like.

When the above-described removal processing is performed, the domain 1 in FIG.
The organic solvent (S) is removed from the polymer layer 2 and the polymer (PB) layer adheres to the bottom of the domain 12 to form a concave or concave 1
Thus, golf ball-like polymer fine particles 18 having a large number of surface concave portions of the present invention can be easily produced.

Golf ball-shaped polymer fine particles of the present invention The golf ball-shaped polymer fine particles of the present invention thus obtained have a large number of recesses or depressions on the surface. The term "many" refers to two or more, but the golf ball-shaped polymer fine particles of the present invention generally have about 50 to 400, particularly about 60 to 200, concave or concave cavities per fine particle. are doing.

Further, the large number of recesses or depressions are almost regularly arranged on the surface of the fine particles of the present invention. The form of the recess or the depression is a form in which the particle is dented like a bowl toward the center of the particle.

The depressions and depressions are composed of a mixture of depressions having various diameters from the small diameter to the large diameter of the opening (the diameter of the opening on the surface of the polymer fine particles). The average diameter (the average diameter of the openings on the surface of the polymer fine particles) is generally about 10 to 500 nm, particularly 50 to 400 nm. The average depth of the depressions or depressions is about 5 to 250 nm, especially 25 to 200 n.
m.

In this specification, the average diameter and the average depth of the concave portions are values obtained by an image analysis method of an electron micrograph of an ultrathin section of a particle.

The golf ball-shaped polymer fine particles having concave portions according to the present invention are characterized in that the concave portions are deeper than conventional products. That is, in the golf ball-shaped fine particles manufactured by the conventional method, compared with the opening diameter of the concave portion (d),
The depth (f) is as small as about 1/4 or less, and f / d is about 0.25.
Hereinafter, the ratio of the depth (F) to the diameter of the concave portion (D) is almost the same regardless of the diameter of the concave portion in the polymer microparticles of the present invention, particularly, about 0.1 to 0.25. The ratio F / D of the depth (F) to the diameter (D) of the concave portion is constant, and is usually 0.5 or more, especially about 0.5 to 1.

As described above, in the golf ball-shaped polymer fine particles obtained in the present invention, the size and depth of the depressions and depressions are sufficient, so that the polymer (PB) layer is formed as in the conventional method. The step of dissolving and removing with a solvent that selectively dissolves is unnecessary. Of course, such a process may be performed,
Usually the need is low.

In the production method of the present invention, the average particle size of the obtained golf ball-shaped fine particles is generally almost the same as or slightly larger than the average particle size of the seed polymer (PA) used as a raw material. Therefore, in the present invention, golf ball-shaped polymer fine particles having a submicron size (for example, about 50 to 900 nm) of less than 1 μm can be produced.
Micron-sized golf ball-shaped polymer fine particles having an average particle diameter of about 1 to 50 μm, particularly about 1 to 10 μm can also be produced. Even larger particles can be produced.

The golf ball-shaped polymer fine particles of the present invention are:
Compared to spherical organic pigments, it has high light scattering ability and high whiteness, high hiding power, is useful as an organic pigment, and has a large number of recesses and depressions, resulting in a large specific surface area. Since it becomes large, it can be advantageously used in the carrier for diagnostic agents, cosmetics field, and the like.

[0075]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 Production of Golf Ball-Like Polymer Fine Particles of the Present Invention As seed polymer (PA), polymethyl methacrylate particles produced by a dispersion polymerization method (average particle diameter = 1.64 μm)
m, weight average molecular weight = 300,000)
It was dispersed in 12 g of a mixed medium of methanol / water (4/1, W / W) as (M). 0.03 g of polyvinylpyrrolidone was used as a dispersant. In the obtained dispersion, 0.3 g of styrene as the monomer (B), 0.9 g of decalin as the organic solvent (S), and 0.02 g of azobisisobutyronitrile as an initiator were dissolved. Next, the mixture was stirred at 50 ° C. for 24 hours in a nitrogen gas atmosphere to complete seed dispersion polymerization.

From the resulting polymerization reaction mixture, the resulting polymer fine particles were isolated using a centrifuge, and the pressure was 1 × 10 ⁵ P
a, By drying under reduced pressure at a temperature of 25 ° C., polymer fine particles having a large number of concave portions of the present invention were obtained.

FIG. 5 shows an SEM photograph of the obtained polymer fine particles. The obtained polymer fine particles had an average particle diameter of 2 μm, an average number of concave portions per one polymer fine particle of 130, an average concave portion diameter of 100 nm, and an average concave portion depth of 1/2 or more of the average concave portion diameter (the maximum depth was (About 1 times the average diameter of the concave portion).

Comparative Example 1 Dispersion polymerization was carried out in the same manner as in Example 1 except that decalin as the organic solvent (S) was not used, and polymer fine particles produced were isolated from the polymerization reaction mixture in the same manner as in Example 1. Dried. In the polymer fine particles thus obtained, no surface concave portions were observed.

Example 2 (1) Production of Seed Polymer Fine Particles 24 g of methyl methacrylate, 2,2′-azobis (2,
A system consisting of 0.36 g of 4-dimethylvaleronitrile), 5.6 g of polyvinylpyrrolidone, 1.6 g of tricapryltrimethylammonium chloride, 179.2 g of methanol and 44.8 g of water was placed in a nitrogen atmosphere at 46 ° C.
Polymerization was performed for 24 hours under stirring conditions of 120 rpm to obtain seed polymer fine particles (average particle size = 1.64 μm).
m, weight average molecular weight = 300,000).

(2) Production of Golf Ball-Like Polymer Fine Particles of the Present Invention As the seed polymer (PA), the polymethyl methacrylate particles produced in the above (1) (average particle diameter = 1.64 μm, weight average molecular weight = 300000) was dispersed in a mixed medium consisting of 9.6 g of methanol as a medium (M) and 2.4 g of water. As a dispersant, 0.03 g of polyvinylpyrrolidone was used.

To the obtained dispersion, 0.3 g of styrene as the monomer (B) and 0.3 g of decalin as the organic solvent (S) were added.
(a), 0.6 g (b), 0.9 g (c) or 1.2 g (d) and 4.7 mg of azobisisobutyronitrile as an initiator were dissolved.

The mixture was stirred in a nitrogen gas atmosphere at 60 ° C. under stirring conditions of 120 rpm for 24 hours to complete the seed dispersion polymerization.

From the resulting polymerization reaction mixture, the resulting polymer fine particles were isolated using a centrifuge, and the pressure was 1 × 10 ⁵ P
a, By drying under reduced pressure at a temperature of 25 ° C., polymer fine particles having a large number of concave portions of the present invention were obtained.

FIG. 6 shows an SEM photograph of the obtained polymer fine particles.
(a) to (d). 6 (a) to 6 (d) show the amount of decalin used.
FIG. 6 corresponds to (a) to (d). In FIG. 6, the weight ratio of polymethyl methacrylate / decalin is (a) 2/1,
(b) 1/1, (c) 2/3 and (d) 1/2. FIG. 7 is an enlarged view of FIG. In addition, these (a) to (d)
Table 1 below shows the average particle size of the polymer fine particles, the average number of concave portions per polymer fine particle, the average diameter of the concave portions, and the average depth of the concave portions obtained at the weight ratio of

[0086]

[Table 1]

As can be seen from FIGS. 6 (a) to 6 (d) and Table 1, from the viewpoint of obtaining golf ball-like polymer fine particles having clear recesses and depressions, the amount of decalin used is determined by the amount of the seed polymer.
It is understood that the amount is preferably 50 to 200 parts by weight or more based on 100 parts by weight of (PA).

Comparative Example 2 According to the method of Example 2 in JP-A-6-287244,
The following operation was performed to produce conventional golf ball-like polymer composite fine particles. (1) Preparation of polystyrene particles Styrene is emulsion-polymerized in a water / ethanol (25/75, weight / weight) mixed medium at 70 ° C. in an N ₂ atmosphere without an emulsifier to obtain an emulsion of polystyrene particles. Was. (2) Seed polymerization of butyl acrylate Emulsion 6 of polystyrene fine particles obtained in (1) above
g (in terms of solid content) was mixed with 2570 mg of butyl acrylate, and allowed to stand at 0 ° C. for 24 hours to absorb butyl acrylate into polystyrene particles to obtain swollen fine particles. afterwards,
70 ° C. in a mixed medium of ethanol / water (10/90, weight / weight) using 200 mg of potassium persulfate as an initiator,
Polymerization was performed for 24 hours to obtain polystyrene / polybutyl acrylate composite fine particles.

The physical properties of the fine particles were as follows: average particle size: 600 n
m, average number of concave portions: 50, average concave portion diameter: 80 nm, average concave portion depth: 20 nm.

[0090]

According to the present invention, the following excellent effects are exhibited: (1) In the golf ball-like polymer fine particles obtained by the production method of the present invention, the size and depth of the depressions and depressions are sufficient. It is something.

(2) Therefore, in the production method of the present invention,
The step of dissolving and removing the polymer (PB) layer with a solvent that selectively dissolves the polymer (PB) is substantially unnecessary.

(3) Further, since the recesses and pits obtained by the production method of the present invention are deep, the light scattering property is high and the specific surface area is high. Therefore, when the golf ball-shaped polymer fine particles obtained by the production method of the present invention are used as an organic pigment, the whiteness and the hiding power are high, the ability to adsorb a substance is high, and the utility as a carrier is high.

(4) Since the seed polymer (PA) does not need to absorb the monomer (B), the golf ball-shaped polymer can be easily and efficiently obtained simply by performing seed dispersion polymerization using the above-mentioned components. Fine particles can be produced.

(5) By selecting the particle size of the seed polymer (PA), not only golf ball-like polymer fine particles having a small average particle size of submicron size but also an average particle size of 1 to 50 μm, especially Golf ball-shaped polymer fine particles of 1 to 10 μm can be produced. When the seed polymer (PA) is used in a monodispersed state, the obtained golf ball-shaped polymer fine particles of the present invention can also be in a monodispersed state.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a mechanism for producing golf ball-shaped fine particles by a conventional seed emulsion polymerization method.

FIG. 2 shows the results of the seed dispersion polymerization method of the present invention.
FIG. 4 is a schematic diagram showing a state in which a polymer (PB) precipitates and adheres to seed particles with the polymerization of (B).

FIG. 3 is a schematic diagram showing seed polymer particles and domains that have entered inside from the surface in the seed dispersion polymerization method of the present invention.

FIG. 4 is a schematic diagram of polymer fine particles having concave portions on the surface, obtained by the seed dispersion polymerization method of the present invention.

FIG. 5 is a photograph substituted for a drawing showing the structure of the polymer fine particles having concave portions on the surface of the present invention obtained in Example 1.

FIG. 6 is a photograph substituted for a drawing showing the structure of the polymer fine particles having concave portions on the surface of the present invention obtained in Example 2;
(A), (b), (c) and (d) are respectively the weight ratio of polymethyl methacrylate / decalin = 2/1, 1/1, 2/3
And the polymer fine particles obtained in 1/2.

FIG. 7 is an enlarged view of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Seed particle 2 Domain 3 Monomer absorption domain 4 Indentation 10 Seed particle 12 Domain 14 Polymer (PB) layer 16 Indentation without depression 18 Golf ball-like polymer fine particles of the present invention

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J011 HA07 HA08 HB14 HB28 PA69 4J026 AA17 AA45 AC09 BA05 BA09 BA24 BA27 BA31 BA32 BA46 BA47 DB03 DB09 DB10 DB12 DB22 DB27 EA04 FA01 GA08

Claims (5)

[Claims] 1. A medium (M) in which fine particles of a polymer (PA) are dispersed as seed particles, wherein (i) a monomer dissolved in the medium (M), and A monomer (B) that provides a polymer (PB) having a lower or equivalent affinity with the medium (M) as compared to the seed particle polymer (PA), which is different, and (ii) a seed particle polymer (PA). A poor solvent or non-solvent, but a good solvent for the polymer (PB), and the medium
(M) an organic solvent (S) insoluble or partially soluble in (M), (iii) a polymerization initiator soluble in the medium (M), and (iv) a dispersant is present, and a monomer ( The solvent in the composite polymer fine particles obtained by polymerizing B)
A method for producing polymer fine particles having a large number of concave portions on the surface, which comprises removing (S). 2. The method according to claim 1, wherein the polymer (PA) fine particles as seed particles are in a monodispersed state. 3. The seed particle polymer (PA) is a C1-C8 alkyl ester of acrylic acid or a C1-C8 alkyl ester of methacrylic acid.
A polymer or copolymer obtained from at least one radically polymerizable monomer selected from 8 alkyl esters and aromatic vinyls, wherein the medium (M) is (a) acetone or a lower saturated aliphatic alcohol having 1 to 3 carbon atoms. A mixed solvent of at least one selected water-soluble organic solvent and a small amount of water, wherein the monomer (B) is a C1-C8 alkyl ester of acrylic acid, a C1-C8 alkyl ester of methacrylic acid, an aromatic vinyl, At least one selected from the group consisting of vinyl cyanide, ethylenically unsaturated carboxylic acid, ethylenically unsaturated carboxylic acid ester, vinyl halide, conjugated diene, carboxylic acid vinyl ester and ethylenically unsaturated carboxylic acid amide; , And the seed polymer (P
A) is a monomer that gives a polymer (PB) different from (A), and the organic solvent (S) is a poor solvent or a non-solvent for the seed particle polymer (PA), but is a good solvent for the polymer (PB). The production method according to claim 1, wherein the organic solvent is an organic solvent that is insoluble or partially soluble in the medium (M). 4. A method according to claim 1, wherein the seed polymer (PA) is C1 of acrylic acid.
A polymer or copolymer obtained from at least one radically polymerizable monomer selected from a C8 alkyl ester, a C1-C8 alkyl ester of methacrylic acid and an aromatic vinyl, wherein the medium (M) comprises (a) a carbon number of 1 to 80 to 70% by weight of at least one selected from lower saturated aliphatic alcohols and water 2
0 to 30% by weight, wherein the monomer (B) is at least one selected from the group consisting of C1-C8 alkyl esters of acrylic acid, C1-C8 alkyl esters of methacrylic acid, and aromatic vinyl. Polymer that is different from seed polymer (PA)
(PB) is a monomer, the organic solvent (S) is a poor solvent or non-solvent of the seed particle polymer (PA), but a good solvent of the polymer (PB), and the medium 4. The method according to claim 1, wherein the organic solvent is insoluble or partially soluble in (M). 5. The method according to claim 1, wherein the average particle diameter of the fine polymer particles having a large number of concave portions on the surface is 50 nm to 50 μm.