JP2646620B2 - Method for producing hollow polymer particles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing hollow polymer fine particles. More specifically, the present invention relates to a method for producing hollow polymer fine particles having an inner hole useful as a light scattering agent or a light scattering auxiliary which can be used for a coating agent for paper, fiber, leather or the like, or various paints, or a microcapsule. It is.

<Prior Art> Polymer particles having pores inside the particles are used as microcapsule particles by including various substances in the inner hole, or hollow particles used as a light scattering agent by making the inner hole hollow. It is used as an organic material such as polymer particles.

Conventionally, the following method is known as a method for producing polymer particles having an inner hole.

(I) A method in which a foaming agent is contained in polymer particles, and then the foaming agent is foamed.

(II) A method of encapsulating a volatile substance such as butane in a polymer, and then gasifying and swelling the volatile substance.

(III) A method in which a polymer is melted, and a gaseous jet such as air is blown into the polymer to enclose air bubbles.

(IV) A method in which an alkali-swellable substance is permeated into polymer particles to swell the alkali-swellable substance.

(V) A method of preparing a w / o / w type monomer emulsion and conducting polymerization.

(VI) A method of polymerizing a monomer in a suspension in which a pigment is suspended in an unsaturated polyester solution.

(VII) A two-stage cross-linking method in which cross-linked polymer particles are used as seeds, and polymers having different compatibility are polymerized and cross-linked on the seeds.

(VIII) A method of producing a polymer by polymerizing shrinkage.

<Problems to be Solved by the Invention> However, in these production methods, it has been difficult to control production conditions or stably produce polymer particles having a desired inner pore. Further, conventional hollow fine particles, when added as a light scattering agent to the coating film forming material, had the required physical properties of opacity, but gloss, coating film strength, elasticity, adhesion, water resistance, and water resistance. The balance of physical properties such as alkalinity and weather resistance was poor. In particular, in the conventional method for producing polymer particles having internal pores, it is necessary to use a polymer having a high glass transition temperature as a shell polymer in order to develop internal pores in the polymer particles. There is a fatal problem that polymer particles having good inner porosity cannot be obtained.

The present invention provides a hollow fine particle that solves such problems of the conventional technology and a method for producing the same.

<Means for Solving the Problems> The present invention relates to (A) first hollow polymer fine particles having an average particle size in the range of 0.05 to 15 μm, and (B) 0.5 to 80% by weight of a polymerizable unsaturated carboxylic acid. (C) 5 parts by weight or less of an emulsifier and / or 5 parts by weight per 100 parts by weight of the total weight of the first hollow polymer fine particles (A) and the monomer mixture (B). Alternatively, it is subjected to polymerization in an aqueous medium in the presence of a dispersant to form a polymer film of the monomer mixture (B) on the surface of the first hollow polymer fine particles (A), and has an average particle size of 0.1 to 20 μm. And a method for producing hollow polymer fine particles characterized by forming the second hollow polymer fine particles in the range of (1).

 Hereinafter, the present invention will be described in detail.

(I) The component (A) of the present invention has an average particle size of 0.05 to 15
Regarding the first hollow polymer fine particles in the range of μm: The hollow fine particles of the component (A) can be produced by the methods (I) to (VIII) described in the section of the prior art and the methods thereof.

The average particle diameter of the first hollow fine particles (A) is 0.05 to 15 μm.
m, preferably 0.15 to 10 μm. Average particle size 0.05
If it is less than μm, it is difficult to produce, and even if it can be produced, it is not preferable because at least a part of polymer particles having no hollow is generated and contained. On the other hand, if the outer diameter exceeds 15 μm, the particle diameter distribution becomes broad, and the second hollow fine particles obtained by using this as the first hollow fine particles (A) cannot be obtained as having uniform particle diameters, which is not preferable. .

The ratio of the inner diameter to the outer diameter of the first hollow fine particles (A) is preferably 0.15 to 0.9 times. When the ratio is 0.15 times or more, hollow particles having the object properties of the present invention, which are more excellent, are preferably obtained. On the other hand, when the ratio exceeds 0.9 times, production of the first hollow particles (A) becomes difficult, and As a typical production,
Not preferred.

The preferred method for producing the first hollow fine particles (A) is the method (VII) described in the prior art section proposed in JP-A-61-62510 and JP-A-61-66710. Showa 61-8
No. 7734, JP-A-61-86941, JP-A-62-127336, JP-A-62-156387, and the like, and the method (VIII) shown in the section of the prior art. The second hollow fine particles obtained by using the first hollow fine particles (A) of these methods have excellent concealing properties. Particularly preferred is the method (VIII), in which the outer diameter and the inner diameter of the hollow fine particles can be easily controlled.
The second hollow fine particles obtained as the hollow fine particles (A) are excellent in concealing properties, solvent resistance and heat resistance.

The best method of the method (VIII) is described in
The first hollow fine particles (A) obtained by the method of No. 127336, which is excellent in polymerization stability and productivity in the polymerization of the first hollow fine particles (A). It has excellent concealing properties.

The preferred constituent composition of the first hollow fine particles (A) will be described below.

As the first hollow polymer fine particles (A), the polymer comprises (a) 20 to 99% by weight of a hydrophilic non-crosslinkable monomer, 1 to 80% by weight of a crosslinkable monomer, and another monomer copolymerizable with these monomers. (B) a polymer different from the above copolymer, and (c) 100 parts by weight of the above polymer (a) with respect to 100 parts by weight of the above polymer. (B) a composition having a composition of 1 to 100 parts by weight. More preferably, component (a) comprises 40 to 98% by weight of a non-crosslinkable monomer and 2 to 60% of a crosslinkable monomer.
% By weight and other monomers copolymerizable therewith.
70% by weight.

The type of the hydrophilic non-crosslinkable monomer in the component (a) is not particularly limited, but preferably comprises an unsaturated carboxylic acid and / or another hydrophilic monomer.

As the kind of the hydrophilic non-crosslinkable monomer in the component (a), more preferably, the hydrophilic non-crosslinkable monomer is composed of an unsaturated carboxylic acid and / or another hydrophilic monomer. It is composed of 70% by weight and other hydrophilic monomers 30 to 99.

By using the above-mentioned preferable and more preferable ones as the component (a) of the first hollow fine particles (A),
It is possible to produce a hollow fine particle having the object properties of the present invention which is more excellent.

The polymer (hereinafter, referred to as a heteropolymer) as the component (b) of the first hollow fine particles (A) is different from a copolymer obtained from the monomer represented by the component (a),
In addition, it is necessary that the compound be easily dissolved or swelled in the polymerizable monomer.

Specific examples of such heteropolymers include polystyrene, carboxy-modified polystyrene, carboxy-modified styrene-butadiene copolymer, styrene-butadiene copolymer, styrene-acryl ester copolymer, styrene-methacrylic ester copolymer, acrylic ester copolymer, methacrylic ester copolymer, and carboxy-modified styrene. An acrylic ester copolymer, a carboxy-modified styrene methacryl ester copolymer, a carboxy-modified acrylic ester copolymer, a carboxy-modified methacryl ester copolymer and the like are exemplified.

Of these, especially polystyrene or styrene component
Styrene copolymers containing greater than or equal to weight percent are preferred.

The amount of the heterogeneous polymer as the component (b) of the first hollow fine particles (A) is 1 to 100 parts by weight, preferably 2 to 50 parts by weight, based on 100 parts by weight of the copolymer of the component (a). More preferably, it is 5 to 20 parts by weight.

As described above, the first hollow fine particles (A) are preferably: (a) 20 to 99% by weight of a hydrophilic non-crosslinkable monomer, 1 to 80% by weight of a crosslinkable monomer, and a copolymerizable with these monomers. In the presence of (b) polymer fine particles of a different species from the copolymer obtained from the above monomer component, a monomer component comprising 0 to 70% by weight of the other monomer is added to the polymer fine particles per 100 parts by weight of the monomer component. It is produced by being present in a proportion of 100 parts by weight and subjecting it to polymerization in an aqueous medium to form first hollow polymer fine particles having an average particle size in the range of 0.05 to 15 μm.

At this time, the amount of the different polymer used as the component (b) is
It is preferably 2 to 50 parts by weight, more preferably 5 to 20 parts by weight, based on 100 parts by weight of the monomer (a). In any of the above methods, the amount of the heterogeneous polymer used is 1
If the amount is less than 100 parts by weight, the effect of forming the inner hole is small, and if the amount of the different polymer exceeds 100 parts by weight, the formation of the inner hole tends to be suppressed, which is not preferable.

Examples of the hydrophilic non-crosslinkable monomer of the component (a) include vinyl pyridine, glycidyl acrylate, glycidyl methacrylate, methyl acrylate, and the like.
Methyl methacrylate, acrylonitrile, acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, sodium styrenesulfonate, vinyl acetate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, 2
Vinyl monomers such as -hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate.

Of these, those preferably used are unsaturated carboxylic acids such as methacrylic acid, methyl methacrylate, vinyl pyridine, 2-hydroxyethyl methacrylate,
And so on. It is preferable that these hydrophilic non-crosslinkable monomers have a solubility in water of 0.5% by weight or more, especially 1% by weight or more.

Examples of the crosslinkable monomer of the component (a) include divinyl monomers such as divinylbenzene, ethylene glycol dimethacrylate, 1,3 butylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and allyl methacrylate, or trivinyl monomers. And particularly preferred are divinylbenzene, ethylene glycol dimethacrylate and trimethylolpropane trimethacrylate.

The other copolymerizable monomer of the component (a) is not particularly limited as long as it has radical polymerizability. For example, aromatic monomers such as styrene, α-methylstyrene, p-methylstyrene, and halogenated styrene can be used. Group vinyl monomers, vinyl esters such as vinyl propionate,
Ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-
Examples thereof include ethylenically unsaturated carboxylic acid alkyl esters such as ethylhexyl methacrylate, lauryl acrylate, and lauryl methacrylate, and conjugated dioles such as butadiene and isoprene. Styrene and ethylenically unsaturated carboxylic acid alkyl esters are particularly preferable.

More preferable composition ratio of each monomer in the component (a) is 40 to 98% by weight of a hydrophilic non-crosslinkable monomer, 2 to 60% by weight of a crosslinkable monomer, and 0 to 70% by weight of another copolymerizable monomer. It is.

If the amount of the hydrophilic monomer used is too small, the phase separation of the heterogeneous polymer may be insufficient, or the heterogeneous polymer may be exposed on the surface of the polymer particles, and the formation of the inner pore tends to be uncertain. Is not preferred. If the amount of the crosslinking monomer used is too small, the strength of the particles during polymerization becomes insufficient and the whole particles shrink, and the internal pores are not formed due to insufficient strain due to polymerization shrinkage inside the particles. However, even if polymer particles having inner pores are formed, problems such as a decrease in shell strength occur.

On the other hand, if the amount of the crosslinkable monomer used is too large, the heterogeneous polymer tends to be rejected to the outside of the polymer particles generated during the polymerization, and the resulting polymer particles do not have a true spherical shape and have irregularities. This creates a problem of certain agglomerated particles.

The first method for producing hollow fine particles (A) is disclosed in
It is obtained by polymerizing the monomer of the component (a) in the presence of the heterogeneous polymer of the component (b) as described above using the polymerization technique of No. 7336.

In the above-mentioned production method, fine particles are used as a heterogeneous polymer of the component (b), and the fine particles (seed polymer particles) absorb the monomer component of the component (a) and, if necessary, an oily substance, and then polymerize the monomer component. (B) dissolving the heterogeneous polymer of the component (b) in the monomer component of the component (a) and, if necessary, an oily substance to form an oily solution, and finely dispersing the oily solution in water; To form an oil-in-water emulsion and then polymerize the monomer component (b). In the above, the presence of the oily substance together with the heterogeneous polymer makes it easy to control the inner pore diameter of the polymer particles.

When the heterogeneous polymer is used in the form of particles by the method (a), the heterogeneous polymer functions as a seed polymer particle, and the polymerizable monomer and the oily substance are absorbed into the particle. It is preferable that the absorbability of the polymerizable monomer and the oily substance is good. For this purpose, the heterogeneous polymer preferably has a small molecular weight, for example, the number average molecular weight is 20,000.
Or less, preferably 10,000 or less, more preferably 700 to
7,000. In addition, the number average molecular weight here is obtained by dissolving a heterogeneous polymer in a good solvent, and using the resulting solution as a gel permeation chromatograph (GPC), an osmotic pressure molecular weight measurement device, a vapor pressure reduction molecular weight measurement device, or the like. It is obtained by the measurement according to the method described above.

When the number average molecular weight of the different polymer is larger than 20,000,
The amount of the monomer that is not absorbed by the seed polymer particles increases, and this polymerizes separately from the seed polymer particles in the aqueous dispersion. As a result, not only a large amount of fine particles that do not become polymer particles having internal pores are generated, but also the polymerization system becomes improper. A stable problem arises.

Further, the particle diameter of the heterogeneous polymer used as the seed polymer particles is preferably 0.3 to 0.8 times the outer diameter of the target polymer particles having inner pores.

The method for producing a heterogeneous polymer used as such seed polymer particles is not particularly limited, and for example, a production method such as emulsion polymerization or suspension polymerization using a relatively large amount of a chain transfer agent can be used.

When a heterogeneous polymer is used as the seed polymer particles, a high lipophilic substance having a solubility in water of 10 ^-3 % by weight or less is previously absorbed in the seed polymer particles so that the polymerizable monomer for the seed polymer particles can be absorbed. And the ability to absorb oily substances can be increased.

When the means for absorbing the highly lipophilic substance such as seed polymer particles is used, the number average molecular weight of the different polymer may exceed 20,000.

Examples of the highly lipophilic substance include 1-chlordodecane, octanoyl peroxide, 3,5,5-trimethylhexanoyl peroxide and the like.

In order to absorb these highly lipophilic substances into the seed polymer particles, an aqueous dispersion in which the highly lipophilic substance is finely dispersed is prepared, and this dispersion is mixed with an aqueous dispersion of the seed polymer particles. Preferably, the highly lipophilic substance is brought into contact with the seed polymer particles.

The particle size of the polymer particles having inner pores obtained when the seed polymer particles are used is approximately the same as the particle size of the particles in which the seed polymer particles have been enlarged by absorbing a polymerizable monomer and an oily substance. Therefore, by adjusting the particle size of the seed polymer particles, the relative amount of the seed polymer particles to the polymerizable monomer and the oily substance, and the like, it is possible to control the particle size of the generated polymer particles having inner pores.

Specifically, in the production of polymer particles having an inner hole, in order to obtain hollow polymer particles having a particle size of 0.1 to 0.6 μm excellent in whiteness and hidden power, 0.06 to 0.40 μm as seed polymer particles. What has a particle diameter may be used.

In addition, the use of seed polymer particles requires a particle diameter of 1 μm.
When polymer particles having an inner hole having a small particle diameter of not more than m are produced, it is particularly preferable because monomer droplets having a small particle diameter can be easily and stably formed.

When a different polymer is used in the method (b), the molecular weight of the different polymer is not particularly limited, and a polymer having a number average molecular weight of 20,000 or more can be preferably used.

In this production method, an oily substance can be used as necessary. Such an oily substance is not particularly limited as long as it has a solubility in water of 0.2% by weight or less, and any of vegetable oil, animal oil, mineral oil and synthetic oil can be used.

In this production method, polymer particles having an inner hole can be obtained without using an oily substance.However, it is possible to reliably control the diameter of the inner hole by using an oily substance and adjusting the amount used. it can.

Examples of the oily substance include lard oil, olive oil, coconut oil, castor oil, cottonseed oil, kerosene, benzene, toluene, xylene, butane, pentane, hexane, cyclohexane, carbon disulfide, carbon tetrachloride, and the like. .

Further, as the oily substance, high boiling point oils such as eugenol, geraniol, cyclamenaldehyde, citronellal, dioctyl phthalate and dibutyl phthalate can also be used. The use of these high-boiling oils gives capsule-shaped polymer particles containing a fragrance, a plasticizer and the like in the core.

The amount of the oily substance to be used is generally 0 to 1,000 parts by weight, preferably 0 to 300 parts by weight, based on 100 parts by weight of all components of the monomer. In addition, inert solvents that are usually contained in those supplied as the crosslinkable monomer material can also be included as the oily substance here. If the amount of the oily substance is excessively large, the monomer component becomes relatively short and the thickness of the outer shell of the polymer becomes thin, resulting in a problem that the capsule is insufficient in strength and is easily crushed.

Further, the concept of the oily substance may include the polymerizable monomer described above. In this case, in the polymerization step, the polymerization is stopped in a state where the polymerizable monomer remains in the generated polymer particles, so that the remaining monomer can be used as an oily substance. In this case, the polymerization yield needs to be 97% or less, preferably 95% or less. For this purpose, a method of performing polymerization by adding a small amount of a polymerization inhibitor, a method of lowering the temperature of the reaction system during the polymerization, or a method of stopping the polymerization by adding a polymerization terminator during the polymerization can be adopted. .

Further, in this production method, the capsule-shaped polymer particles containing an oily substance or the water-containing hollow polymer particles obtained by substituting the oily substance with water as described above are separated from the aqueous dispersion and subjected to a drying treatment, whereby the internal To obtain hollow polymer particles having a space.

The hollow fine particles of the component (A) obtained by using the above polymerization technique have the following advantages.

(I) The manufacturing process is simple and the productivity is excellent.

(Ii) Production control is easy, and hollow fine particles having the desired outer diameter and inner diameter can be obtained.

(Iii) Since the pH of the aqueous dispersion of the hollow fine particles can be freely selected, it can be used without any limitation as the polymer monomer formed on the surface of the hollow fine particles.

(Iv) Using the hollow fine particles as the first hollow fine particles (A) of the present invention, the obtained second hollow fine particles show much more excellent concealing property, gloss, adhesiveness, coating film and strength.

Regarding the component (B) of the present invention: Examples of the polymerizable unsaturated carboxylic acid of the component (B) include mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid, and dicarboxylic acids. Preferred are acid anhydrides of acids, monoalkyl esters of dicarboxylic acids, and monoamides of dicarboxylic acids. Among them, acrylic acid, methacrylic acid and itaconic acid are more preferred. As the unsaturated carboxylic acids other than those described above, unsaturated carboxylic acids having a molecular weight of 100 or more of unsaturated carboxylic acid monomer per carboxyl group can also be used. These examples are shown below by a general formula. When this unsaturated carboxylic acid is used, the strength adhesion of the second hollow fine particles is further improved.

(Where R ₁ , R ₂ , and R ₃ are H or an alkyl group having 1 to 20 carbon atoms) (Where X is And Y is H or CH _3. (In the above two formulas, R ₄ , R ₅ , and R ₆ are H or an alkyl group having 1 to 12 carbon atoms, EO is an ethylene oxide group, and PO is a propylene oxide group.) (In the above two formulas, R ₇ and R ₈ are H or carbon 1 to
Among these higher carboxylic acid monomers, the following formula: Is preferred.

Examples of other copolymerizable monomers for the component (B) include aromatic vinyl compounds, vinyl cyanide compounds, ester aliphatic conjugated dienes of acrylic acid or methacrylic acid, organic acid vinyl compounds, α-olefins, and vinyl ethers. , Vinylidene halides, hydroxyl group-containing monomers, amino group-containing monomers, glycidyl group-containing monomers, amide monomers, crosslinkable monomers and the like are preferably used.

Examples of the aromatic vinyl compound include styrene, α-methylstyrene, methylstyrene, p-methylstyrene,
Vinyl xylene, monochlorostyrene, dichlorostyrene, monobromostyrene, dibromostyrene, fluorostyrene, p-tert-butylstyrene, ethylstyrene, vinylnaphthalene, and the like are preferred, and styrene and α-methylstyrene are particularly preferred.

As the vinyl cyanide compound, for example, acrylonitrile, methacrylonitrile and the like are preferable, and acrylonitrile is more preferable.

As the ester compound of acrylic acid or methacrylic acid, for example, methyl acrylate, ethyl acrylate,
Alkyl esters of acrylic acid such as propylene acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, cyclohexyl actylate, dodecyl acrylate, octadecyl acrylate, phenyl acrylate, and benzyl acrylate; methyl methacrylate, ethyl methacrylate, Propylene methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, phenyl methacrylate, alkyl methacrylate such as benzyl methacrylate is preferred. And the like. Among them, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-
Ethylhexyl acrylate is preferred.

As the aliphatic conjugated diene, for example, 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,
3-butadiene, 2-neopentyl-1,3-butadiene,
Preferred are 2-chloro-1,3-butadiene, 2-cyano-1,3-butadiene, substituted linear conjugated pentadienes, linear and side chain conjugated hexadienes, and the like. Of these, 1,3-
The use of butadiene is particularly preferred.

Preferred examples of the organic acid vinyl compound include vinyl acetate, vinyl propionate, and vinyl stearate.

In addition, for example, ethylene, propylene, butylene,
Α-olefins such as -methylpentene-1; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether and vinyl phenyl ether; vinylidene halides such as vinylidene chloride and vinylidene fluoride; vinyl methyl ketone; Vinyl pyridine, isobutylene, 1,1-fluorinated ethylene, vinyl chloride and the like are also used as other copolymerizable monomers of the component (B).

Examples of the hydroxyl group-containing monomer include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, n-hydroxyethylacrylamide,
Preferred are hydroxypropyl-acrylate or methacrylate, hydroxyethyl-acrylate or methacrylate, and the like.

Preferred examples of the glycidyl group-containing monomer include glycidyl acrylate, glycidyl methacrylate, and vinyl glycidyl ether.

Preferred examples of the amino group-containing monomer include amino group-containing acrylate or methacrylate, β-aminoethyl vinyl ether, dimethylaminoethyl vinyl ether, and the like.

As the amino group-containing acrylate or methacrylate, the following formula (I) Wherein R is H or CH ₂ , and R ¹ and R ² have 1 carbon atom
To 8, preferably a hydrocarbon group having 1 to 3 carbon atoms, and X is an alkylene group having 2 to 4 carbon atoms.

Specific examples of the acrylate of the general formula (I) include dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dipropylaminoethyl methacrylate, methylethylaminoethyl methacrylate, and dibutylaminoethyl. Examples include methacrylate, dibutylaminopropyl methacrylate, diethylaminobutyl methacrylate, dihexylaminoethyl methacrylate, and dioctylaminoethyl methacrylate.

Among these, preferred are dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dipropylaminoethyl methacrylate,
Methylethylaminoethyl methacrylate and the like can be mentioned.

As amide monomers, for example, acrylamide,
Methacrylamide, n-methylol methacrylamide,
Examples include diacetone acrylamide, ethacrylamide, crotonamide, itaconamide, methylitaconamide, maleic monoamide, and methylene diacrylamide. Acrylamide and methacrylamide are particularly preferred.

Examples of the crosslinkable monomer include divinylbenzene,
Examples thereof include divinyl monomers such as ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and allyl methacrylate, and trivinyl monomers. Particularly, divinylbenzene, ethylene glycol dimethacrylate and trimethylolpropane trimethacrylate are preferred.

The composition ratio of the polymerizable unsaturated carboxylic acid of the component (B) to the other copolymerizable monomer as described above is 0.5 to 80% by weight to 20%.
999.5% by weight, preferably 0.5-50% by weight to 50-9%.
9.5% by weight, more preferably 1-35% by weight to 65-9%
9% by weight.

When the amount of the unsaturated carboxylic acid exceeds 80% by weight, the polymerization stability and the fluidity of the obtained aqueous dispersion are poor, which hinders handling. Also, the opacity of hollow particles, adhesion, water resistance,
Poor physical properties of alkali resistance.

When the crosslinking monomer is used in an amount of 0.5 to 20% by weight, preferably 1 to 5% by weight, based on 100 parts by weight of the component (B), the second hollow fine particles have concealing properties, solvent resistance,
The balance of the water resistance strength is further improved.

Regarding the step (C) of the present invention: The step (C) of the present invention comprises the step of adding 5 parts by weight or less of an emulsifier and / or a dispersant per 100 parts by weight of the total of the first hollow fine particles (A) and the monomer mixture (B). By polymerizing in the aqueous medium in the presence, a polymer film of the monomer mixture (B) is formed on the surface of the first hollow polymer fine particles (A), and the first hollow polymer fine particles (A) have a mean particle size in the range of 0.1 to 20 μm. This is a step of forming the hollow polymer fine particles of No. 2.

In the above production method, when the monomer mixture (B) is a monomer mixture containing a polymerizable unsaturated carboxylic acid, the pH during the polymerization is particularly preferably 7 or less.

In the polymerization step, the method of adding the monomer mixture (B) is a method of stirring and mixing the first hollow polymer fine particles (A) and the monomer mixture (B) to polymerize, and the method of adding the monomer mixture (B) to the first hollow polymer. There is an incremental polymerization method in which the polymerization is carried out by continuously or dividedly supplying the polymerization system in which the fine particles (A) are present to perform polymerization. In order to efficiently copolymerize the polymerizable monomer on the surface of the polymer particles having inner pores, an increment polymerization method is preferable for stable polymerization.

In the polymerization of the hollow fine particles, an anionic emulsifier, a nonionic emulsifier, a cationic emulsifier, an amphoteric emulsifier, and / or a deoxidizer (suspension protective agent) are used. These can be used alone or in combination of two or more.

Examples of the emulsifier include rosinates such as potassium rosinate and sodium rosinate; sodium and potassium salts of fatty acids such as potassium oleate, potassium laurate, sodium laurate, sodium stearate and potassium stearate; sodium lauryl sulfate; Anionic emulsifiers such as alkyl allyl sulfonates such as sodium dodecylbenzenesulfonate, sodium dialkyl sulfosuccinate, and formalin condensates of naphthalenesulfonic acid; alkyl ester types of polyethylene glycol, alkyl ethers And nonionic emulsifiers such as alkyl phenyl ether type. Among them, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium dioctylsulfosuccinate, formalin condensate of naphthalenesulfonic acid, and alkylifenyl ether type of polyethylene glycol are preferable.

Examples of the cationic emulsifier include a quaternary ammonium salt type, and when the aqueous dispersion is a cationic type,
Used alone or in combination with nonions.

Examples of the dispersant include hydrophilic synthetic high molecular substances such as polyacrylic acid, polymethacrylic acid, polyvinyl sulfonic acid, polyvinyl alcohol, polyvinyl pyrrolidone and polyethylene glycol; natural hydrophilic high molecular substances such as gelatin and water-soluble starch; Examples include hydrophilic semi-synthetic polymer substances such as carboxymethyl cellulose.

The amount of the emulsifier and / or dispersant used is 5 parts by weight or less, preferably 2 parts by weight or less, more preferably 1 part by weight or less. If it exceeds 5 parts by weight, new particles are generated during polymerization,
It is not preferable because the production efficiency of the second hollow fine particles of the present invention is reduced, and the concealing property and the gloss are further reduced.

Examples of the polymerization initiator include organic hydroperoxides represented by, for example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramenthane hydroperoxide, and sugar-containing pyrophosphate, sulfoxylate, and sugar-containing pyrophosphate formulations. Redox initiators in combination with reducing agents represented by mixed / sulfoxylate formulations, etc .; further, persulfates such as potassium persulfate and ammonium persulfate; azobisisobutyronitrile, benzoyl peroxide And lauroyl peroxide can be used.

Preferably, a persulfate such as potassium persulfate or ammonium persulfate, azobisisobutyronitrile, or benzoyl peroxide is combined with a reducing agent, if necessary. Particularly preferred are persulfates such as potassium persulfate and ammonium persulfate. In these polymerization initiators, radicals tend to concentrate on the surface of the first hollow fine particles, so that a film is formed efficiently by the component (B). The polymerization initiator amount is preferably 0.05 to 2 parts by weight based on the total amount of the first hollow fine particles (A) and the monomer mixture (B),
More preferably, it is 0.05 to 0.8 parts by weight. When used in this range, second hollow polymer fine particles having excellent water resistance and alkali resistance can be obtained.

As the polymerization temperature, usually 5 to 95 ° C. is good, especially
50-90 ° C is preferred.

Other chain transfer agents can be used if necessary.

Examples of the chain transfer agent include mercaptans such as t-dodecyl mercaptan, octyl mercaptan, n-tetradecyl mercaptan, octyl mercaptan, t-hexyl mercaptan, and halogen compounds such as carbon tetrachloride and ethylene bromide. .

In the emulsion polymerization of the present invention, depending on the pH of the polymerization system, the polymerization stability and the particle size distribution of the second hollow fine particles, the inner diameter /
The outer diameter ratio is influenced by not a little. When the pH is 7 or less, the above items are satisfactory, and the desired second hollow fine particles are obtained. In the case where the pH exceeds 7, when the monomer mixture (B) does not contain a polymerizable unsaturated carboxylic acid, the above items are similarly satisfactory without any problem. It is not preferable because stability tends to decrease.

As the first hollow fine particles (A), the above-mentioned JP-A-62-1273 is used.
Using the aqueous dispersion of hollow fine particles obtained in 36,
Since the pH is 7 or less, a polymer monomer to be formed on the surface of the hollow fine particles can be used without limitation, which is extremely preferable.

On the other hand, since the pH of the aqueous dispersion obtained by the method of producing hollow fine particles by forming inner pores by alkali neutralization swelling naturally exceeds 7, the polymerizable unsaturated carboxylic acid is particularly added to the monomer mixture (B). When the water dispersion is contained, the use of the aqueous dispersion is not preferred. Also, to lower the pH of this one,
When a buffer or an acid such as sodium hydrogen carbonate is added, poor polymerization stability is caused. Therefore, it is not preferable to use particles produced by alkali neutralization swelling as the first hollow fine particles.

The aqueous dispersion (C) of the present invention obtained as described above
It is preferable that the outer diameter is 0.1 to 20 μm and the inner diameter is 0.1 to 0.85 times the outer diameter. Those having an outer diameter of less than 0.1 μm are inferior in opacity when used as a light-scattering aid, and those having an outer diameter of more than 20 μm have poor polymerization stability, and new particles are generated during polymerization, and the desired opacity is obtained. The balance between properties and various physical properties such as gloss cannot be maintained.

On the other hand, if the inner diameter is less than 0.1 times the outer diameter, the concealing property is considerably poor, which is not preferable. If the inner diameter is more than 0.85 times, the balance between the concealing property, adhesiveness, gloss and strength is poor, which is not preferable.

Although the solid content of the aqueous dispersion (C) of the present invention is not limited, it is usually preferably 10 to 65% in view of the solid content of the composition for each use.

In addition, it can be easily confirmed whether or not the polymer particles of the aqueous dispersion of the present invention have pores. It can generally be confirmed with a transmission electron microscope, or can be confirmed by measuring specific gravity.

The aqueous dispersion obtained in the present invention can be powdered by drying. Powdering can be performed by a commonly used powdering method of an aqueous dispersion, for example, 130 to 1
Spray drying at 60 ° C, in hot air atmosphere, for example, 50-70
And tray drying at ℃. The solid content of the aqueous dispersion before drying is preferably 20% or more. The particle size of the obtained powder of the aqueous dispersion of the present invention is substantially equal to the particle size of the used aqueous dispersion.

If the powder thus obtained is insoluble in an organic solvent, it can be used for an organic solvent-based paint.

The above-mentioned aqueous dispersion of the present invention and the particles thereof are a plastic pigment (organic resin pigment) having an excellent balance between concealing properties and various physical properties such as gloss, adhesion, water resistance, solvent resistance, heat resistance, and the like. And it can be applied to paints, paper coatings, inks, adhesives, adhesives, primers, leather treatments and the like. In addition, utilizing the encapsulation property, the fragrance, medicine, pesticide, dye, detergent, oil and fat, food, enzyme,
Liquid crystals, rust preventives, catalysts, flame retardants, anti-aging agents, adhesives, etc. can be filled with the effective components according to the application by means of immersion treatment, reduced pressure, pressure immersion treatment, etc., and useful components contained inside Can be used for various purposes.

[Examples] Next, the present invention will be described in more detail with reference to Examples.
This does not limit the present invention. In the following description, "%" and "part" represent% by weight and part by weight.

Production of first hollow fine particles (A): (1) Production of A-1 Production of heterogeneous polymer (b) (b-1) 80 parts of styrene, 17 parts of methyl methacrylate, 3 parts of methacrylic acid and t-dodecyl mercaptan 7 parts, 200 parts of water, 0.5 part of sodium lauryl sulfate and 1.0 part of potassium persulfate
The resulting mixture was placed in a dissolved aqueous solution and polymerized at 70 ° C. for 4 hours with stirring to obtain polymer particles. The polymer particles had an average particle size of 0.2 μm and a number average molecular weight of 6,000 in terms of polystyrene by GPC. This is designated as b-1.

Production of First Hollow Fine Particles (A) (A-1) Next, this polymer particle dispersion (b-1) is used as seed polymer particles, and the polymer particles are 10 parts by solid content of polyoxyethylene nonylphenyl. 0.1 part of ether, 0.3 part of sodium lauryl sulfate and 0.5 part of potassium persulfate and water
390 parts were charged into a reaction vessel. When a mixture of 75 parts of methyl methacrylate, 20 parts of divinylbenzene (in terms of pure product) and 5 parts of acrylic acid was added thereto and stirred at 30 ° C. for 1 hour, the substance was almost completely absorbed by the seed polymer particles. When this was polymerized while stirring at 70 ° C. for 5 hours,
A dispersion of capsule particles containing water inside the particles was obtained with a polymerization yield of 99%. When this dispersion was dried and observed with a transmission electron microscope, the polymer particles were completely spherical hollow polymer particles having a transparent central portion. The hollow particles had an outer diameter of 0.4 μm and an inner diameter of 0.3 μm. This was designated as A-1.

The first hollow fine particles (A) thus obtained were used as seeds in the production of the hollow fine particles of the present invention described below.

(2) Production of A-2 to 6, 8, 9, 11, 13 and b-2 to 7: The amount of the monomer and the amount of the heterogeneous polymer used in the method for producing the heterogeneous polymer particles b-1 and the hollow microparticles A-1 are determined. Except for changing to those shown in the table, polymerization was carried out in the same manner as in b-1 and A-1, and A-2 to 6, 8, 9, 11, 13 and heterogeneous polymers b-2 to 7 were converted. Obtained.

Here, A-5 and A-6 are each different polymer b
In the case of -2 (10 parts), the former was absorbed in 10 parts of toluene, and the latter was absorbed in 15 parts of dibutyl phthalate and then polymerized. The polymerization conditions and results are shown in Table 1.

(3) Production of A-7 Monomer component: 4-vinylpyridine; 50 parts Divinylbenzene; 2 parts Styrene; 28 parts Butyl acrylate; 20 parts Oily substance of core material: toluene; 10 parts Polymerization initiator: 3,5, 5-trimethylhexanoyl peroxide 2 parts [Perloyl 355, manufactured by NOF CORPORATION] The above substances were mixed to prepare an oily solution. Then, the oily solution was mixed with polyvinyl alcohol (Gohsenol GH).
20, manufactured by Nippon Synthetic Chemical Co., Ltd.) was added to 350 parts of dissolved water, and the system was stirred for 15 minutes at 5,000 rpm with a propeller type stirring blade having a diameter of 5 cm to obtain the oily solution. The solution was dispersed in water so that the oil droplets had a diameter of 5 to 15 μm. The suspension obtained in this way is
At a rotation speed of 120 r. Under a nitrogen atmosphere.
Polymerization was carried out at 70 ° C. for 15 hours while stirring the suspension at pm to produce polymer particles. The polymerization yield in this reaction was 98%.

Observation of the obtained polymer particles with an optical microscope revealed that the particles were hollow polymer particles. This hollow particle
The outer diameter was 13 μm and the inner diameter was 9 μm. This was designated as A-7.

(4) Production of A-10 and A-12 A-7 except that the monomer composition and the amount of the oily substance toluene used in the production method of A-7 were changed to those shown in Table 1.
Polymerization was carried out in the same manner as in the above to obtain A-10 and A-12.

Production of Second Hollow Fine Particles (Hollow Fine Particles of the Present Invention): Example 1 The hollow particle aqueous dispersion A-1 prepared by the above method was used as seed particles, and a solid content of 20 parts, water of 127 parts, 0.7 part of potassium persulfate was placed in the reaction vessel No. 2, the temperature was raised to 85 ° C. under a nitrogen atmosphere, and the next monomer emulsion was continuously dropped over 3 hours.

Monomer emulsion: 40 parts of water, 5 parts of butyl acrylate, 89 parts of methyl methacrylate, 5 parts of methacrylic acid, 1 part of N-methylol methacrylamide and 0.3 part of sodium dodecylbenzenesulfonate. Then it was cooled.
No coagulated product was found in the obtained dispersion. The particle diameter of the dispersion was measured with a Nanosizer (Coulter, N-4 model) and found to be 0.63 μm. Drying the resulting dispersion,
Observation with a transmission electron microscope revealed that the surface of the first hollow fine particles was coated with a polymer layer. The hollow particles had an outer diameter of 0.63 μm and an inner diameter of 0.3 μm. No new particles were generated, and all the particles had hollows. The production conditions and results are shown in Table 2.

Examples 2, 3, 6, 9 and Comparative Examples 1 to 5 In Example 1, some conditions were changed to those of Example 2 in Table 2 below.
Polymerization was carried out in exactly the same manner as in Example 1 except that the conditions described in 3, 6, 9 and Comparative Examples 1 to 5 were changed.

Example 4 150 parts of water, 1.0 part of potassium persulfate, 0.4 part of sodium bisulfite, 0.5 part of sodium dodecylbenzenesulfonate, 0.1 part of polyoxyethylene nonylphenyl ether (EO = 30 mol) in a 100 stainless steel pressure vessel, Then, 40 parts of the above-mentioned A-3 in terms of solid content was charged as seed particles, and the temperature was raised to 70 ° C. under a nitrogen atmosphere with stirring, and the following monomer mixture was continuously dropped over 12 hours.

Monomer mixture: 50 parts of styrene, 40 parts of 1,3-butadiene, 5 parts of methacrylic acid and 5 parts of acrylester HH Further, the mixture was aged at 80 ° C. for 5 hours after completion of addition of the monomer, and then cooled. No coagulated product was found in the obtained dispersion. The particle diameter of the dispersion was 0.55 μm, and the polymer particles after drying were hollow particles having an outer diameter of 0.54 μm and an inner diameter of 0.3 μm, and no new particles were generated.

Examples 5, 7 and 8 In Example 4, some conditions were changed to those of Example 5 in Table 2 below.
Polymerization was carried out in exactly the same manner as in Example 4, except that the conditions described in columns 7 and 8 were changed.

Example 10 Using the aqueous dispersion A-1 of a hollow particle as a seed particle, 500 parts in solid content, 1400 parts of water, 0.7 part of sodium dodecylbenzenesulfonate, 0.1 part of polyoxyethylene nonylphenyl ether (EO = 30 mol) 0.1 Parts were placed in 2 reaction vessels. A mixture of 5 parts of n-butyl acrylate, 89 parts of methyl methacrylate and 6 parts of methacrylic acid was added thereto, and the mixture was heated at 40 ° C.
For 1 hour, and the monomer mixture was almost completely absorbed by the seed hollow polymer particles. To this were added 1.0 part of benzoyl peroxide and 0.5 part of sodium bisulfite, the temperature was raised to 70 ° C., polymerization was carried out for 5 hours, and then the mixture was cooled.
There was no coagulated product in the obtained dispersion, and the dried polymer particles were hollow particles having an outer diameter of 0.41 μm and an inner diameter of 0.3 μm, and no new particles were generated.

Comparative Examples 6 and 7 Instead of the first hollow fine particle dispersion of Example 1, the following ordinary polymer particle dispersion was used,
The obtained polymer particles had a particle size of 0.64 μm and had no inner hole. This is referred to as Comparative Example 6.

Seed polymer particle dispersion C-1; aqueous dispersion produced by ordinary emulsion polymerization.

 Particle size 0.4 μm, pH 7.2, solid content 40%.

The composition is butyl acrylate / methyl methacrylate / styrene / acrylic acid = 45/10/42/3, and there is no inner hole.

Comparative Example 7 was obtained by changing the kind and amount of the polymer particles of the seed in the above method to those shown in Table 2 and the following.

Seed polymer particle dispersion C-2; aqueous dispersion produced by conventional suspension polymerization.

 Particle size 4 μm, pH 7.8 solid content 45%.

The composition is ethyl acrylate / styrene / acrylic acid = 20
At / 79/1, there is no lumen.

Comparative Examples 8, 9 and 10 The hollow fine particles of A-1 and commercially available polymer fine particles (OP-84 (D-1) manufactured by Rohm. & Haas) and Plastic Pigment AK8801 (D-2) manufactured by Asahi Kasei Corp. The examples used were Comparative Examples 8, 9 and 10, respectively.

[Application Examples] 60 parts by weight of each of the aqueous dispersions of Examples 1 to 10 and Comparative Examples 1 to 10, 40 parts by weight of a 71% aqueous dispersion of rutile-type titanium dioxide, and an acrylic copolymer as a binder Emulsion (JSRAE315, manufactured by Japan Synthetic Rubber Co., Ltd.)
Part, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (Texanol CS-12 manufactured by Chitso Corporation) 7
, 3 parts of ethylene glycol, 2 parts of sodium salt of β-naphthalenesulfonic acid formalin condensate, 1.5 parts of hydroxyethyl cellulose, and 150 parts of water, and the mixture was stirred until the viscosity became constant. Thus, each coating composition was prepared.

The above-mentioned various paints were applied on a Morest secret banknote and a glass plate, and were air-dried for 3 days without a coating film having the same thickness. Table 2 shows the physical properties of these coatings.
The test conditions are as follows.

(Test conditions) (I) Opacity; Opacity test paper (manufactured by Nippon Test Panel Kogyo Co., Ltd.) was applied using a 6-mil aliquoter, and was applied at 20 ° C. and 60% RH for 5 hours.
After drying in the sun, the gloss of 45 ゜ / 0 に つ い て was measured for the black and white portions on the test using a Murakami gloss meter, and the ratio was calculated using the following formula. (JIS K-5400) (2) Gloss (glass plate): After the produced paint was left for one day, it was applied to a glass plate with a 3 mil applicator, dried at 20 ° C. and 60% RH for 5 days, and measured with a Murakami gloss meter. .

(3) Water resistance; The glass plate coating film prepared in (2) was dried for one day, immersed in water at room temperature for 14 days, and visually judged.

(4) Adhesion; (Adhesion) Apply the prepared paint twice to a flexible board with a brush (200 g / m ² ), dry for 5 days, make a 2mm square goban with a razor, and use cellophane tape. A peel test was performed. (JISA-6910) (5) Film strength; A 0.5 mm coating film dried for 5 days was punched out with a dumbbell No. 2, and evaluated by an autograph. (20 ° C., 60% RH) Examples 1 to 10 show excellent concealing properties, gloss, adhesion, water resistance, and strength. For example, compared with Comparative Examples 6 and 7 in which non-hollow polymer particles were used for polymerization, they exhibited excellent concealing properties and gloss that were incomparable, and were also made of plastic pigment, commercially available hollow fine particles (D-1), and prototypes. When the hollow fine particles (first hollow fine particles (A-1)) alone were compared with each other, as is clear from Comparative Examples 8 to 10,
It showed excellent hiding, gloss, adhesion and water resistance.

In particular, the hollow fine particles of Examples 1 to 5 and 7 to 10 are much more excellent in concealing property, gloss, water resistance, etc., and are particularly preferable and remarkable.

In Comparative Example 1, the amount of the carboxylic acid monomer in the monomer mixture (B) was more than 80 parts by weight. Particularly, the polymerization stability was poor, and opacity, gloss, and water resistance were observed, in which new particles were generated. Properties, adhesion and film strength are remarkably inferior.

In Comparative Examples 2 and 3, the particle diameter of the obtained aqueous dispersion was 0.1
In this case, the opacity, gloss, and adhesion are remarkably poor, polymerization stability is poor, and new particles are generated, which is not preferable.

In Comparative Example 4, the emulsifier and / or dispersant at the time of polymerization was used as the total weight of the first hollow fine particles (A) and the monomer mixture (B).
This is an example in which an amount exceeding 5 parts by weight per 100 parts by weight is used, so that many new particles having no internal pores can be formed, and therefore, the opacity and gloss are extremely poor, which is not preferable. Comparative Example 5 is an example in which the particle size of the obtained hollow microparticles is large, and polymerization stability, new particles being generated during polymerization, and various physical properties such as concealing properties and luster are inferior.

The hollow fine particles obtained by the method of the present invention are in the form of an aqueous dispersion, and can be used as they are, or dried,
It can also be used as a powder. Especially in the case of solvent-based paints, etc.
Powders are preferred and are obtained by the following method.

(Drying method) 5 kg of the aqueous dispersion of Example 1 (solid content: 42%) was sprayed with a spray dryer (mobile minor type for research and development, Anzawanilo Atomizer Co., Ltd.) to obtain an inlet temperature.
2.1 kg of powder was obtained in about 3.5 hours at a temperature of 130 to 180 ° C. and a dropping rate of 1.5 kg / hr.

Tables 3 and 4 show the results obtained by pulverizing Examples 3 and 5 in the same manner.

<Effects of the Invention> According to the present invention, the opacity which has been impossible by the simple process of polymerizing the hollow fine particles in an aqueous medium can be produced with good stability and industrially. The present invention provides a method for producing hollow fine particles that dramatically improves the properties, gloss, adhesion, and coating film strength.

The hollow fine particles of the present invention have the above-described specific optical performance, and have excellent opacity, gloss, adhesion, and coating strength. Used as etc. For example, for paint, paper coating,
It can be widely used as an internal additive for inks, carpets and papers, and is useful because of the above-mentioned characteristics which cannot be exhibited by ordinary hollow particles.

Further, taking advantage of the characteristics of the capsule function, it can not only contain substances such as solvents, plasticizers, fragrances, inks, agricultural chemicals, and medicines, but also has the merit of freely modifying the surface of hollow polymer particles. Therefore, at present, there is no modification technology such as the adhesiveness of commercially available hollow polymer particles, and the present invention, which has hardly been applied, has been studied more specifically in the above-mentioned applications and / or various application fields. Can be applied.

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Claims (5)

(57) [Claims] (A) first hollow polymer fine particles having an average particle size in the range of 0.05 to 15 μm; and (B) 0.5 to 80% by weight of a polymerizable unsaturated carboxylic acid and another copolymerizable monomer (20). (C) in the presence of 5 parts by weight or less of an emulsifier and / or dispersant per 100 parts by weight of the total of the first hollow polymer fine particles (A) and the monomer mixture (B). The first hollow polymer particles (A) are polymerized in an aqueous medium to form a polymer film of the monomer mixture (B) on the surface of the first hollow polymer fine particles (A), and the second hollow polymer particles have an average particle size in the range of 0.1 to 20 μm. A method for producing hollow polymer fine particles, comprising forming hollow polymer fine particles. 2. The polymer of the first hollow polymer fine particles (A) comprises (a) 20 to 99% by weight of a hydrophilic non-crosslinkable monomer, 1 to 80% by weight of a crosslinkable monomer and copolymerizable with these monomers. (B) a polymer different from the above-mentioned copolymer, and (c) 100 parts by weight of the above-mentioned copolymer (a) The method according to claim 1, wherein the composition has a composition of 1 to 100 parts by weight of the polymer (b). 3. The method according to claim 2, wherein the hydrophilic non-crosslinkable monomer is an unsaturated carboxylic acid and / or another hydrophilic monomer. 4. The hydrophilic non-crosslinkable monomer comprises 1 to 70% by weight of an unsaturated carboxylic acid and 30 to 30% by weight of another hydrophilic monomer.
3. The method according to claim 2, comprising 99% by weight. 5. (1) (a) a hydrophilic non-crosslinkable monomer
20-99% by weight, crosslinkable monomer 1-80% by weight and other monomers copolymerizable with these monomers 0-70% by weight
(B) in the presence of polymer fine particles of a species different from the copolymer obtained from the monomer component, in a proportion of 1 to 100 parts by weight of the polymer fine particles per 100 parts by weight of the monomer components. Subjecting it to polymerization in an aqueous medium to form first hollow polymer fine particles having an average particle size in the range of 0.05 to 15 μm, and then (2) (A) the first hollow polymer fine particles, and (B) A monomer mixture comprising 0.5 to 50% by weight of a polymerizable unsaturated carboxylic acid and 50 to 99.5% by weight of another copolymerizable monomer, (C) the first hollow polymer fine particles (A) and the monomer mixture (B) Is subjected to emulsion polymerization in an aqueous medium in the presence of 5 parts by weight or less of an emulsifier and / or dispersant per 100 parts by weight of the total weight of the first hollow polymer fine particles (A ) Surface Preparation of hollow polymer particles, characterized in that the average particle size yielding polymer coating of the monomer mixture (B) forms a second hollow polymer particles in the range of 0.1 to 20 [mu] m.