JP3165472B2 - Method for producing polymer particles containing inner pores - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Industrial applications] Organic pigments are superior in lightness and thermoplasticity compared to inorganic pigments.
Used in fields such as paint and coated paper. In recent years, polymer particles having an inner pore have been produced for the purpose of further improving the performance of an organic pigment such as lightness and opacity. The present invention relates to polymer particles containing such inner pores.

[0002]

2. Description of the Related Art Processes for producing polymer particles having an inner pore have been known for a long time. For example, JP-B-36-9168 and JP-B-37-14327 disclose that the solvent is contained in the inner hole by carrying out suspension polymerization or emulsion polymerization in the presence of a water-insoluble non-polymerizable organic solvent. It is disclosed that the resulting polymer particles are obtained. However, such a method has disadvantages such as that particles having inner pores cannot be obtained satisfactorily and that the particle diameter and the distribution of inner pore diameter become extremely large. Further, when such a method is used, JP-A Nos. 61-66710 and 62-127336 also describe that the method can be carried out in the presence of polymer particles as seed particles. However, also in the case of using seed particles, it is difficult to stably obtain polymer particles having inner pores, and it is difficult to control the particle diameter and inner pore diameter with respect to the method of using a non-polymerizable organic solvent. It is difficult to obtain a polymer particle having an inner hole having excellent strength, and there is a problem that the inner hole shrinks when a solvent contained in the particle is removed. .

Japanese Patent Application Laid-Open No. 63-135409 also discloses a method in which the core of core / shell type polymer particles is preferentially swelled with an organic solvent compatible with the polymer to develop inner pores when dried. Has been stated. However, in this method, the core / shell type polymer particles to be used need to be designed to have a solvent swelling property because they need to absorb only an organic solvent and swell. It is difficult to obtain polymer particles having pores, it is difficult to remove the solvent compatible with the polymer, and the polymer in the shell part is plasticized to some extent by the organic solvent used. However, when the solvent is removed or dried, the whole particles shrink and the inner pores are reduced and disappear.

On the other hand, several methods for producing polymer particles containing inner pores without using such an organic solvent are also known. For example, a basic substance is applied to polymer particles comprising an alkali-swellable core portion and a shell portion covering the core portion as disclosed in JP-A-56-32513 to cause the core portion to swell and expand, thereby forming an inner hole during drying. Japanese Patent Application Laid-Open No. 2-173101 discloses a method for obtaining particles expressing
In the above-mentioned publication, there is a method of hydrolyzing the core of a core / shell type polymer in which the core comprises a vinyl acetate polymer.
However, in these methods, since the shell portion needs to have plasticity in order for the core portion to expand, it is difficult to obtain a polymer particle having an inner hole excellent in strength, However, the water absorbed by the polymer is difficult to remove, so that there is a problem that the drying property when used for a predetermined application is poor.

Japanese Patent Application Laid-Open No. 61-62510 also discloses a method of polymerizing a monomer having a solubility parameter different from that of the seed particle by 0.1 or more. There was a problem that the inner hole diameter could not be obtained.

[0006]

As described above, the problem to be solved by the present invention is that, while easily controlling the particle diameter and the inner hole diameter, an inner hole larger than the particle diameter can be obtained, and When removing the inner hole does not shrink,
It also means that there has been no satisfactory method for obtaining polymer particles having inner pores excellent in strength.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present inventors have intensively studied a method for producing a polymer particle having an inner hole which can sufficiently satisfy these various problems. As a result, in a method of polymerizing a radical polymerizable monomer in the presence of a non-polymerizable organic solvent, it is possible to solve the above problem by polymerizing in the presence of specific polymer particles. They have found and completed the present invention. That is, the present invention is a method for producing polymer particles containing an inner hole, comprising the following steps (1), (2) and (3). (Step 1) The melt viscosity at 120 ° C. is 10 ⁵ Pa · S
(Pascal second) or less and the particle diameter is 0.1 to 2
μ of the water-dispersible particulate polymer (A). (Step 2) Using the particulate polymer (A) as seed particles, a monomer having a composition different from that at the time of polymerization of the seed particles is added to a dispersion medium and polymerized to have a particle size of 0.2 to 5 μm. Obtaining a water-dispersible particulate polymer (B) having a melt viscosity at 150 ° C. of 10 ⁴ Pa · S or more. (Step 3) In a dispersion medium containing 100 parts by weight of the particulate polymer (B), more than 10 and 1000
0 parts by weight or less, a polymerizable monomer comprising a crosslinkable monomer as necessary, and 1 to 10000 parts by weight of a non-polymerizable organic solvent which is substantially incompatible with the polymer particles having an inner pore. Adding at least a part of the polymerizable monomer and the organic solvent into the particulate polymer (B), and then polymerizing to obtain polymer particles containing water-dispersible inner pores. .

In the present invention, the particulate polymer (A) obtained in the step (1) is usually an aromatic vinyl compound such as styrene, α-methylstyrene and p-methylstyrene, and a conjugated diene such as butadiene. Olefins, and vinyl chloride, chlorine-containing vinyl compounds such as vinylidene chloride, and acetates such as vinyl acetate, and acrylonitrile, unsaturated nitrile compounds such as methacrylonitrile, and methyl methacrylate, ethyl methacrylate, propyl methacrylate, Butyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate,
Methacrylates such as allyl methacrylate,
And acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, glycidyl acrylate, allyl acrylate, and acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid Using monomers such as unsaturated acids such as acids and unsaturated amides such as acrylamide and methacrylamide, t-dodecyl mercaptan, mercaptans such as octyl mercaptan, or carbon tetrachloride, ethylene bromide, if necessary. And the like, or a chain transfer agent such as ethylhexyl thioglycolate or α-methylstyrene dimer, and the particle weight obtained by a generally known method such as emulsion polymerization or suspension polymerization. It is a body. Particulate polymer (A)
Has a particle size of 0.1 to 2 μm, and the smaller the particle size distribution, the better. The melt viscosity of the particulate polymer (A) at 120 ° C is 10 ⁵ Pa · S or less, and its glass transition temperature is preferably 110 ° C or less, more preferably 100 ° C or less. Further, the particulate polymer (A) is preferably substantially non-crosslinked. Here, the melt viscosity of the particulate polymer (A) at 120 ° C. is 1
If it exceeds 0 ⁵ Pa · S, the following steps (2) and (3)
In this case, it is difficult to obtain polymer particles having an inner pore.

[0009] In the present invention, the particulate polymer (B) obtained in the step (2) is defined as a particle comprising the particulate polymer (A) as a seed particle in a dispersion medium. It is a particulate polymer obtained by polymerizing a monomer having a composition different from the monomer composition by a generally known method such as emulsion polymerization or suspension polymerization. Examples of the type of monomer to be used include those exemplified above as monomers usable when polymerizing the particulate polymer (A), and divinylbenzene, trivinylbenzene, ethylene glycol dimethacrylate, and ethylene glycol dimethacrylate. Acrylate, 1,3-butanediol dimethacrylate, 1,3-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1,
There are crosslinkable monomers such as 4-butanediol diacrylate, 1,6-hexanediol dimethacrylate, 1,6-hexanediol diacrylate, triallyl isocyanurate and the like. As the chain transfer agent, those exemplified above as chain transfer agents that can be used when polymerizing the particulate polymer (A) are used as necessary. The particle size of the particulate polymer (B) is from 0.2 to 5 μm, but the distribution of the particle size is preferably small. The weight fraction of the particulate polymer (A) in the particulate polymer (B) is not particularly limited, but is preferably 5 to 70%, and more preferably 10 to 50%. The melt viscosity of the particulate polymer (B) is 10 ⁴ Pa · S at 150 ° C.
That is all. The melt viscosity of the particulate polymer (B) is 150 ° C
If it is not more than 10 ⁴ Pa · S in the following step (3)
When it is carried out, it becomes difficult to obtain polymer particles containing inner pores, and when removing the non-polymerizable organic solvent from the obtained polymer particles containing inner pores as necessary, the inner pores are formed. It is easy to shrink. A particulate polymer (B) obtained by using the particulate polymer (A) as seed particles and polymerizing a monomer having a composition different from that of the particulate polymer (A) is generally a uniform polymer particle. However, it is a so-called core / shell type polymer particle in which the particulate polymer (A) is used as a core and a polymer that is polymerized later covers the core. preferable. When the glass transition temperature of such a particulate polymer (B) is measured, the two glass transition temperatures of the one caused by the particulate polymer (A) and the one caused by the polymer polymerized later are usually two. Although it is observed, the glass transition temperature due to the polymer polymerized later is preferably 80 ° C. or higher, and more preferably 1 ° C.
It is 00 ° C or higher. The polymer polymerized later does not need to be a crosslinked structure, but is preferably a crosslinked structure. There is no problem in introducing another polymer so as to further cover the outside of the particulate polymer (B).
In this case, the polymer does not necessarily have to completely cover the surface of the particulate polymer (B).
May exist in the form of islands on the surface. The particle size of the particulate polymers (A) and (B) can be measured, for example, by observation with an electron microscope. The melt viscosity of the particulate polymer is, for example, a flow tester CFT-500 manufactured by Shimadzu Corporation.
It can be measured using a shape, a nozzle having a diameter of 0.5 mm and a length of 1 mm, under the conditions of a load of 100 kgf and a heating rate of 3 ° C./min. The glass transition temperature can be measured using, for example, a viscoelasticity measuring device or a differential thermal analyzer.

In the present invention, the polymerizable vinyl monomer used in step (3) is not particularly limited as long as it is capable of radical polymerization, and examples thereof include styrene, α-methylstyrene, p-methylstyrene and the like. Aromatic vinyl compounds, conjugated diolefins such as butadiene, and vinyl chloride compounds such as vinyl chloride and vinylidene chloride, and acetates such as vinyl acetate, and unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile And methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate,
Methacrylates such as 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, allyl methacrylate, and methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, glycidyl acrylate, Examples include acrylates such as allyl acrylate and unsaturated acids such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid and maleic acid, and unsaturated amides such as acrylamide and methacrylamide. Next, the crosslinkable monomer is not particularly limited as long as it has two or more functional groups capable of radical polymerization in one molecule, and examples thereof include divinylbenzene, trivinylbenzene, ethylene glycol dimethacrylate, and ethylene. Glycol diacrylate, 1,3-butanediol dimethacrylate, 1,3-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,6
-Hexanediol dimethacrylate, 1,6-hexanediol diacrylate, triallyl isocyanurate and the like. These polymerizable vinyl monomers and crosslinkable monomers can be used singly or in combination of two or more. However, those which give a robust polymer having a high glass transition temperature are preferable. Further, it is preferable that the polymer has excellent compatibility with the particulate polymer (B). It is not necessary to use a crosslinkable monomer, but by using a crosslinkable monomer, it is possible to obtain polymer particles having more excellent inner pores in terms of strength. The amount of the crosslinkable monomer used is preferably 0.1 to 20% by weight based on all monomers. The amount of the polymerizable vinyl monomer and the optional crosslinkable monomer used is more than 10 and not more than 10,000 parts by weight, preferably not more than 10 parts by weight, per 100 parts by weight of the particulate polymer (B). And more than 5000 parts by weight, more preferably more than 10 and less than 1000 parts by weight. When the amount of the polymerizable monomer is 10,000 parts by weight or more, the effect of using the particulate polymer (B) is reduced, or it is difficult to obtain polymer particles containing an inner hole, or It becomes difficult to control the inner hole diameter and the state of the inner hole.

In the present invention, the non-polymerizable organic solvent used in step (3) is not particularly limited as long as it does not have radical polymerizability and is substantially insoluble in polymer particles having an inner pore. Not restricted. The meaning of “substantially incompatible with polymer particles containing inner pores” means that the non-polymerizable organic solvent used is in the form of particles swollen with polymerizable monomers during the polymerization process. Even if it can be compatible with the polymer, it cannot be compatible with the particulate polymer as the polymerization proceeds, and when the polymerization is completed, almost all of the non-polymerizable organic solvent used has an inner hole. That is, it is phase-separated from the contained polymer particles. Under the conditions of the present invention, it is considered that the non-polymerizable organic solvent used is phase-separated inside the polymer particles containing the inner pore, so that the inner pore is formed. The type of such a solvent includes the composition and molecular weight of the polymer constituting the particulate polymer (B) to be used, the type and amount of the polymerizable vinyl monomer and optionally the crosslinkable monomer, and the finished polymer. Is influenced by the composition and molecular weight of
Typical examples include aliphatic hydrocarbons such as butane, pentane, hexane, heptane, octane, and isooctane, and alicyclic hydrocarbons such as cyclohexane. Group hydrocarbons are preferred. These solvents may be used alone or in a combination of two or more. The amount of the non-polymerizable organic solvent used is required to be 1 to 10,000 parts by weight, preferably 5 to 1000 parts by weight, more preferably 10 to 500 parts by weight, per 100 parts by weight of the particulate polymer (B). . If the amount is less than 1 part by weight, the size of the obtained inner hole is too small,
When the amount is more than 00 parts by weight, it becomes difficult to obtain polymer particles having inner pores.

Next, the manufacturing method of the present invention will be described.
The production of the particulate polymers (A) and (B) in (Step 1) and (Step 2) can be carried out by a conventionally known method of emulsion polymerization or suspension polymerization. The production of the polymer particles having an inner pore in (Step 3) can also be carried out by a generally known emulsion polymerization or suspension polymerization method except that a non-polymerizable organic solvent is used. The step (3) will be specifically described as an example. That is, a dispersion medium such as water, a particulate polymer (B), and a surfactant or Add stabilizer. A polymerizable vinyl monomer, a crosslinking monomer, a non-polymerizable organic solvent, and a polymerization initiator are added to the mixture, and the mixture is stirred at a predetermined temperature for a predetermined time to complete the polymerization. It is a way. The polymerizable vinyl monomer, the crosslinkable monomer, the non-polymerizable organic solvent and the polymerization initiator may be added all at once, may be added continuously, or may be partially added. A method of adding all at once and continuously adding the remaining amount may be used. When adding continuously, the rate of addition may be changed halfway. As a preferred example of the production method, when a water-soluble polymerization initiator is used, for example, water, a particulate polymer (B) and, if necessary, a dispersion medium in a container equipped with a stirrer, a thermometer, and the like. Add surfactant, dispersion stabilizer, etc., and add polymerizable vinyl monomer, if necessary, crosslinkable monomer, non-polymerizable organic solvent, and polymerization initiator at a specified temperature and for a specified time. After the addition, stirring is further continued at a predetermined temperature for a predetermined time to complete the polymerization. When an oil-soluble polymerization initiator is used, the initiator is previously dissolved in a polymerizable vinyl monomer, a cross-linkable monomer to be used as required, or a non-polymerizable organic solvent, and these are dissolved in a particulate polymer. Coalescing (B)
Is added to the dispersion medium containing, and the mixture is stirred for a predetermined time at a temperature at which the initiator does not substantially act, and then the temperature is raised to a temperature higher than the temperature at which the initiator acts or a reducing agent is added. To complete the polymerization.

The polymerizable vinyl monomer, a crosslinking monomer used as required, a non-polymerizable organic solvent, and a polymerization initiator may be added to the initial charge as they are, but may be finely dispersed in a dispersion medium in advance. In some cases, it may be better to add those that have been used. Examples of the method of finely dispersing in a dispersion medium in advance include a method using a mechanical disperser such as a homomixer or a biomixer or an ultrasonic homogenizer, and the like. The reaction is carried out using one kind or a combination of two or more kinds. If necessary, a poorly water-soluble substance such as dodecyl chloride can also be used. The amount of the surfactant used for fine dispersion is usually 0.1% as an active ingredient based on the weight of the polymerizable vinyl monomer, the crosslinkable monomer used as required, and the non-polymerizable organic solvent. Or 10%. In the case of fine dispersion in advance, the degree of the fine dispersion is usually about 10 μm or less as the particle diameter of the oil droplet, but the smaller the degree, the more preferable.

The time required for the polymerization depends on the composition and molecular weight of each polymer constituting the particulate polymer (B) to be used, the type and amount of the polymerizable vinyl monomer and the optional crosslinkable monomer, and It depends on the temperature of the system, but usually 1
Within 2 hours. The polymerization temperature varies depending on the composition and molecular weight of each polymer constituting the particulate polymer (B) to be used, the type and amount of the initiator, and the like, but is usually in the range of 30 ° C to 120 ° C.

The surfactants used as required include anionic, cationic, nonionic, amphoteric, and reactive surfactants, and oligosoaps. One of these surfactants may be used. Alternatively, two or more types may be used in combination. Examples of the anionic surfactant include an alkali metal salt of alkyl benzene sulfonic acid, an alkali metal salt of alkyl sulfate, an alkali metal salt of polyoxyethylene alkylphenol sulfate, an alkali metal salt of alkyl diphenyl ether disulfonate, and an alkali metal salt of dialkyl sulfosuccinic acid. it can. As the nonionic surfactant, for example, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ether, polyoxyethylene higher fatty acid ester, ethylene oxide-propylene oxide block copolymer and the like can be used.

As the dispersion stabilizer, a polymer compound having a function as a protective colloid such as polyvinyl alcohol, hydroxyethylcellulose and hydroxypropylcellulose can be used. As the polymerization initiator, a compound that generates a radical at a predetermined temperature is used. Examples of the water-soluble initiator include persulfates such as sodium persulfate, potassium persulfate and ammonium persulfate, and peroxides such as hydrogen peroxide. Examples of the oil-soluble initiator include benzoyl peroxide And organic peroxides such as cumene hydroperoxide, lauroyl peroxide, tert-butyl peroxide and tert-butylperoxy-2-ethylhexanoate, and azo compounds such as azobisisobutyronitrile. These can also be used as a so-called redox initiator in combination with a reducing agent.

It is to be noted that various additives may be used at the time of or after the polymerization. Such additives include surfactants, dispersion stabilizers, p
H regulators, antioxidants, antioxidants, preservatives and the like. Although the reason why the polymer particles containing inner pores can be easily obtained in the production method of the present invention is not necessarily clear, the part of the particulate polymer (A) present in the particulate polymer (B) is polymerized. Under the conditions, it has considerable fluidity, so that it facilitates the phase separation of non-polymerizable organic solvents that are substantially incompatible with the polymer particles containing the inner pores. Since the polymer portion polymerized later in (B) is excellent in strength, it is presumed that it functions to prevent the separated organic solvent from being extruded out of the particles and to maintain the inner hole. Is done. In addition, when such a particulate polymer (B) is used, the efficiency of use of the non-polymerizable organic solvent that forms inner pores by layer separation increases, and the size of the resulting inner pores depends on the amount of non-polymerizable organic solvent used. Can be easily controlled.

In the state where the polymerization is substantially completed,
The non-polymerizable organic solvent used is present in the inner pores of the polymer particles containing the inner pores, and this solvent is removed by a method such as steam or blowing gas such as nitrogen or air as necessary. be able to. Further, polymer particles containing an inner pore obtained by the production method of the present invention,
It can be dried and provided for use as a powder.

[0019]

The present invention will be specifically described below with reference to examples. In the examples, parts and percentages are by weight unless otherwise specified. The reaction was performed under a nitrogen atmosphere.

[0020]

EXAMPLE 1 1.6 parts of seed particles having a particle size of 0.05 μm and 100 parts of ion-exchanged water were placed in a flask equipped with a stirrer, a reflux condenser, and a thermometer, and the internal temperature was reduced to 80 ° C. Heated and stirred until it was. A mixture of 78 parts of styrene, 20 parts of butyl acrylate, 2 parts of acrylic acid, 2 parts of t-dodecyl mercaptan and 0.8 part of sodium persulfate dissolved in 20 parts of ion-exchanged water was added over 4 hours. Thereafter, the mixture was further stirred at 80 ° C. for 2 hours and then cooled. The obtained particulate polymer is referred to as particulate polymer (A). The solid content concentration of the obtained particulate polymer (A) dispersion was 46.5%, and the particle size of the particulate polymer (A) was 0.2 μ as observed with an electron microscope.
The obtained dispersion was dried to obtain a powder of the particulate polymer (A). Using a flow tester, using a nozzle having a diameter of 0.5 mm and a length of 1 mm, a load of 100 kgf and a temperature rising rate of 3 ° C. / When the melt viscosity was measured under the conditions of
Was 3 × 10 ⁴ Pa · S.

In a flask equipped with a stirrer, a reflux condenser, and a thermometer, 30 parts of the particulate polymer (A) and 110 parts of ion-exchanged water are placed, and heated and stirred until the internal temperature reaches 80 ° C. I'm sorry. 70 parts of a monomer mixture composed of 48% of styrene, 45% of methyl methacrylate, 4% of acrylic acid and 3% of ethylene glycol dimethacrylate and 0.6 part of sodium persulfate dissolved in 20 parts of ion-exchanged water. Was added over 3 hours, and the mixture was further stirred at 80 ° C. for 2 hours and then cooled. The obtained particulate polymer is referred to as a particulate polymer (B). The solid content concentration of the obtained particulate polymer (B) dispersion was 43.6%, and the particle size of the particulate polymer (B) was 0.3 μ as observed with an electron microscope. The obtained dispersion was dried to obtain a powder of the particulate polymer (B), and the melt viscosity was measured under the same conditions using a flow tester.
The melt viscosity at 50 ° C. was 3 × 10 ⁵ Pa · S.

In a flask equipped with a stirrer, a reflux condenser, and a thermometer, 100 parts of the particulate polymer (B) and 400 parts of ion-exchanged water are placed, and heated until the internal temperature becomes 80 ° C.
I was agitated. A mixture of 185 parts of styrene, 100 parts of methyl methacrylate, 10 parts of acrylic acid, 5 parts of divinylbenzene and 50 parts of heptane and 2.5 parts of sodium persulfate dissolved in 100 parts of ion-exchanged water was each taken for 4 hours. The mixture was further stirred at 80 ° C. for 2 hours and then cooled. The solid content concentration of the obtained dispersion was 42.2%, and the particle size of the polymer particles was 0.50 μm. When a cross section of the obtained polymer particles was observed with an electron microscope, a pore of 0.22 μ was observed. The obtained dispersion was kept at 80 ° C., and nitrogen gas was blown into the dispersion to remove the non-polymerizable organic solvent, and the cross section of the polymer particles was observed with an electron microscope. By drying the dispersion of polymer particles containing the inner pores from which the non-polymerizable organic solvent has been removed with a spray dryer,
A powder of polymer particles containing inner pores was obtained.

[0023]

Example 2 100 parts of the particulate polymer (B) used in Example 1 and 400 parts of ion-exchanged water were placed in a flask equipped with a stirrer, a reflux condenser, and a thermometer. The mixture was heated and stirred until the temperature reached 80 ° C. 180 parts of styrene, 100 parts of methyl methacrylate, 10 parts of acrylic acid, 10 parts of divinylbenzene and 100 parts of heptane
And a solution prepared by dissolving 2.5 parts of sodium persulfate in 100 parts of ion-exchanged water was added over 4 hours, followed by stirring at 80 ° C. for 2 hours and cooling. The solid content concentration of the obtained dispersion is 40.1%,
The particle size of the polymer particles was 0.52 μm. When the cross section of the obtained polymer particle was observed with an electron microscope, it was found to be 0.27.
μ pores were observed.

[0024]

Comparative Example 1 Into a flask equipped with a stirrer, a reflux condenser, and a thermometer, 3 parts of seed particles having a particle diameter of 0.1 μm and 100 parts of ion-exchanged water were added until the internal temperature reached 80 ° C. heating,
I was agitated. Then, a mixture of 57 parts of styrene, 31.5 parts of methyl methacrylate, 8 parts of butyl acrylate, 3.5 parts of acrylic acid, 0.8 parts of t-dodecylmercaptan and 0.8 parts of sodium persulfate were added to 20 parts of ion-exchanged water. The dissolved substances were added over 4 hours, and then stirred at 80 ° C. for 2 hours and cooled. The solid content concentration of the obtained particulate polymer dispersion was 46.5%, and the particle size of the particulate polymer was 0.3 when observed with an electron microscope.
2μ.

In a flask equipped with a stirrer, a reflux condenser, and a thermometer, 100 parts of the particulate polymer and 400 parts of ion-exchanged water are placed, and heated and stirred until the internal temperature reaches 80 ° C. did. 185 parts of styrene, 100 parts of methyl methacrylate, 10 parts of acrylic acid, 5 parts of divinylbenzene
And a mixture of 50 parts of heptane and 2.5 parts of sodium persulfate dissolved in 100 parts of ion-exchanged water were added over 4 hours, followed by stirring at 80 ° C. for 2 hours and cooling. The solid content concentration of the obtained dispersion was 42.2%, and the particle size of the polymer particles was 0.50 μm. When a cross section of the obtained polymer particles was observed with an electron microscope, no holes were observed.

[0026]

Comparative Example 2 The same operation as in Example 1 was carried out except that heptane was changed to toluene. The solid content concentration of the obtained dispersion was 42.2%, and the particle size of the polymer particles was 0.50 μm. Example 1 was obtained from the obtained polymer particles.
After removing toluene by the same method as described above, the cross section of the polymer particles was observed with an electron microscope, and no holes were observed.

Comparative Example 3 A particulate polymer (A) 3 used in Example 1 was placed in a flask equipped with a stirrer, a reflux condenser, and a thermometer.
0 parts and 110 parts of ion-exchanged water were added, and the mixture was heated and stirred until the internal temperature reached 80 ° C. To this, 70 parts of a monomer mixture composed of 51% of styrene, 45% of methyl methacrylate and 4% of acrylic acid and 0.6 part of sodium persulfate dissolved in 20 parts of ion-exchanged water were added over 3 hours. Then, after further stirring at 80 ° C. for 8 hours,
Cool. The obtained particulate polymer is referred to as a particulate polymer (B ′). The solid content concentration of the obtained particulate polymer (B ′) dispersion was 43.4%, and the particle size of the particulate polymer (B ′) was 0.3 when observed with an electron microscope.
μ. The obtained dispersion was dried to obtain a powder of the particulate polymer (B ′), and the melt viscosity was measured under the same conditions as in Example 1 using a flow tester.
The melt viscosity at ℃ was 4 × 10 ³ Pa · S. In a flask equipped with a stirrer, reflux condenser, and thermometer,
100 parts of the particulate polymer (B ′) and 400 parts of ion-exchanged water were added, and the mixture was heated and stirred until the internal temperature reached 80 ° C. 185 parts of styrene, 100 parts of methyl methacrylate,
A mixture of 10 parts of acrylic acid, 5 parts of divinylbenzene, and 50 parts of heptane and 2.5 parts of sodium persulfate dissolved in 100 parts of ion-exchanged water are added over 4 hours, and then added at 80 ° C. for 2 hours. After stirring, the mixture was cooled. The solid content concentration of the obtained dispersion was 42.1%, and the particle size of the particulate polymer was 0.49 μm. When a cross section of the obtained particulate polymer was observed with an electron microscope, a pore of 0.23 μ was observed. The resulting dispersion was
The cross section of the particulate polymer, which was kept at 0 ° C. and blown with nitrogen gas to remove the non-polymerizable organic solvent, was observed with an electron microscope. The results are summarized in Table 1.

Comparative Example 4 1.6 parts of seed particles having a particle diameter of 0.05 μm and 100 parts of ion-exchanged water were placed in a flask equipped with a stirrer, a reflux condenser, and a thermometer, and heated until the internal temperature reached 80 ° C. And stirred. A mixture of 78 parts of styrene, 20 parts of butyl acrylate, 2 parts of acrylic acid, 0.3 part of t-dodecyl mercaptan and 0.8 part of sodium persulfate dissolved in 20 parts of ion-exchanged water was taken for 4 hours each. The mixture was further stirred at 80 ° C. for 2 hours, and then cooled. The particulate polymer obtained here is referred to as particulate polymer (A ′). The solid content concentration of the obtained particulate polymer (A ′) dispersion was 46.4%, and the particle size of the particulate polymer (A ′) was 0.2 when observed with an electron microscope.
μ. The obtained dispersion was dried to obtain a powder of the particulate polymer (A ′). The melt viscosity was measured under the same conditions as in Example 1 using a flow tester.
The melt viscosity at ℃ was 6 × 10 ⁵ Pa · S. In a flask equipped with a stirrer, reflux condenser, and thermometer,
30 parts of the particulate polymer (A ′) and 110 parts of ion-exchanged water were added, and the mixture was heated and stirred until the internal temperature reached 80 ° C. This includes styrene 48%, methyl methacrylate 45%, acrylic acid 4% and ethylene glycol dimethacrylate 3
% Of a monomer mixture and 0.6 parts of sodium persulfate dissolved in 20 parts of ion-exchanged water were added over 3 hours, followed by further stirring at 80 ° C. for 2 hours and cooling. . The obtained particulate polymer obtained here is designated as particulate polymer (B ''). The solid content concentration of the obtained particulate polymer (B ″) dispersion was 43.6%, and the particle size of the particulate polymer (B ″) was 0.31 μ as observed with an electron microscope. Was. When the cross section of the obtained particulate polymer was observed with an electron microscope, it was found to be 0.23.
μ pores were observed. The obtained dispersion is dried to obtain a powder of the particulate polymer (B ′), and using a flow tester,
When the melt viscosity was measured under the same conditions, the melt viscosity at 150 ° C. was 9 × 10 ⁵ Pa · S. Stirrer,
A flask equipped with a reflux condenser and a thermometer was charged with 100 parts of the particulate polymer (B ″) and 400 parts of ion-exchanged water, and heated and stirred until the internal temperature reached 80 ° C. 185 parts of styrene, 100 parts of methyl methacrylate, 10 parts of acrylic acid, 5 parts of divinylbenzene and 5 parts of heptane
A mixture obtained by dissolving 0 parts of the mixture and 2.5 parts of sodium persulfate in 100 parts of ion-exchanged water was added over 4 hours, and the mixture was further stirred at 80 ° C. for 2 hours and then cooled. The solid content concentration of the obtained dispersion is 42.2%,
The particle size of the particulate polymer was 0.47 μm. When a cross section of the obtained particulate polymer was observed with an electron microscope, no pore was observed. The results are summarized in Table 1.

[Table 1]

[0027]

According to the production method of the present invention, polymer particles containing inner pores can be obtained stably, the inner pore diameter can be easily controlled, the strength is excellent, and the inner pores having a large particle diameter are large. Can be obtained. In addition, the polymer particles containing inner pores produced by this method do not shrink the inner pores when the solvent is removed, have excellent drying properties, and are excellent as hollow organic pigments in paints and coated papers. Has performance.

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Claims (1)

(57) [Claims] 1. A process for producing a particulate polymer having an inner pore, comprising the following steps (1), (2) and (3). (Step 1) The melt viscosity at 120 ° C. is 10 ⁵ Pa · S
(Pascal second) or less and the particle diameter is 0.1 to 2
μ of the water-dispersible particulate polymer (A). (Step 2) Using the particulate polymer (A) as seed particles, a monomer having a composition different from that at the time of polymerization of the seed particles is added to a dispersion medium and polymerized to have a particle size of 0.2 to 5 μm. Obtaining a water-dispersible particulate polymer (B) having a melt viscosity at 150 ° C. of 10 ⁴ Pa · S or more. (Step 3) In a dispersion medium containing 100 parts by weight of the particulate polymer (B), more than 10 and 1000
0 parts by weight or less, a polymerizable monomer comprising a crosslinkable monomer as necessary, and 1 to 10000 parts by weight of a non-polymerizable organic solvent which is substantially incompatible with the polymer particles having an inner pore. Adding at least a part of the polymerizable monomer and the organic solvent into the particulate polymer (B), and then polymerizing to obtain polymer particles containing water-dispersible inner pores. .