JPH0791348B2 - Method for producing crosslinked polymer particles - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing crosslinked polymer particles, and more particularly to a method for producing highly crosslinked polymer particles.

[Prior art]

Generally, the polymerization method of polymer particles is roughly classified into an emulsion polymerization method, a soap-free polymerization method and a suspension polymerization method. Among these, according to the emulsion polymerization method or soap-free polymerization method,
The obtained polymer particles have a relatively narrow particle size distribution, but the particle size is usually about 0.5 μm or less, and even under special conditions is about several μm or less, it is difficult to obtain polymer particles with a large particle size. Is. Further, according to the suspension polymerization method, polymer particles having a large particle size of several μm or more can be obtained, but the polymer particles produced have a very wide particle size distribution, and it is difficult to control the particle size. Is.

By the way, in order to obtain polymer particles excellent in hardness, strength, heat resistance or solvent resistance, a polymerizable monomer containing a considerable amount of a crosslinkable monomer may be polymerized to form a crosslinked polymer particle. However, in the case of producing crosslinked polymer particles by a conventionally known emulsion polymerization method or soap-free polymerization method, the stability of the polymerization reaction system becomes extremely poor when the proportion of the crosslinkable monomer in the monomer is 3% by weight or more. However, because of this, a large amount of coagulated product is generated and the production efficiency of the crosslinked polymer particles is extremely low, or the polymerization reaction product solidifies (gels) during the polymerization to actually produce the desired crosslinked polymer particles. There is a problem that you cannot do it.

In the polymerization mechanism in these methods, a particle nucleus is formed in the initial stage of the polymerization (the first stage of Smith-Evert theory), and the monomer is absorbed in the particle nucleus to polymerize (the second and third stages of the Smith-Evert theory). It is said that. However, in the polymerization reaction system in which the proportion of the crosslinkable monomer is large, the particle nuclei formed have almost no ability to absorb the monomer for the crosslinkable monomer, and therefore the reaction actually does not proceed after the second stage of the polymerization. In addition, a large amount of only minute polymer particles having an average particle size of about 0.05 μm or less are formed, and eventually the particle surface area in the polymerization reaction system becomes too large and the colloidal chemical stability of the system is lost.

Thus, by the emulsion polymerization method or soap-free polymerization method, it is not possible to increase the proportion of the crosslinkable monomer in the monomer, as a result of the difficulty in producing highly crosslinked polymer particles, This is an essential problem due to the particle formation mechanism.

On the other hand, when a polymerizable monomer containing a large amount of a crosslinkable monomer is polymerized by the suspension polymerization method, there is no problem in polymerization stability, but the crosslinked polymer particles formed are particles having a particle size of several μm or more. In addition, it is difficult to control the particle size, and the particle size distribution becomes very wide, so that practically useful crosslinked polymer particles could not be produced.

[Problems to be solved by the invention]

As described above, conventionally, it has been difficult to produce highly crosslinked polymer particles having a particle diameter in the range of 0.1 to several μm by the emulsion polymerization method.

INDUSTRIAL APPLICABILITY The present invention utilizes an emulsion polymerization method to obtain a crosslinked polymer particle having a particle size accurately controlled to a target particle size within a range of 0.1 to 3 μm and having a narrow particle size distribution, and comprising a crosslinked polymer. An object of the present invention is to provide a method for producing crosslinked polymer particles that can be industrially advantageously produced.

[Structure of Invention]

The method for producing crosslinked polymer particles according to the present invention is a seed polymer particle 1 having a weight average molecular weight in the range of 500 to 10,000.
Aqueous dispersion containing 10 parts by weight of crosslinkable monomer
By adding 2 to 500 parts by weight of the polymerizable monomer containing the above, the polymerizable monomer is absorbed by the seed polymer particles, and emulsion polymerization is performed in the presence of a persulfate to give a particle size of 0.
It is characterized in that crosslinked polymer particles of 1 to 3 μm are obtained.

The present invention will be specifically described below.

The method of the present invention is characterized in that polymer particles having a weight average molecular weight in a specific range are used as so-called seed polymer particles. That is, the seed polymer particles used in the present invention have a weight average molecular weight of 500 to 1
0,000, preferably 700-7,000, more preferably 1,000
Must be ~ 6,000.

In the present invention, the "weight average molecular weight" of the polymer particles is a weight average molecular weight measured by a usual method such as gel permeation chromatography (in terms of polystyrene) based on viscosity measurement or viscosity measurement of a solution of the polymer particles. is there.

When the weight average molecular weight of the seed polymer particles exceeds 10,000, the monomer absorption capacity of the seed polymer particles is small, and the monomer polymerizes independently without being absorbed by the seed polymer particles, so that a polymer having a particle diameter different from the intended one is used. A large amount of particles are produced, and the stability of the polymerization reaction system is deteriorated due to these different particles, and a large amount of coagulated products are generated during polymerization.

Further, when the weight average molecular weight of the seed polymer particles is less than 500, the molecular weight is too small, so that the monomer absorption capacity is also small and the same problem as described above occurs.

In addition, the particle size and particle size distribution of the seed polymer particles are
Since it affects the particle size and particle size distribution of the crosslinked polymer particles produced, it is preferable to use seed polymer particles having a uniform particle size and being controlled as narrow as possible. Specifically, the particle size is 0.
2-0.8 μm seed polymer particles having a narrow particle size distribution, for example, a coefficient of variation of 10% or less are preferably used.

The composition of the seed polymer particles is not particularly limited as long as it dissolves or swells in the monomer used for polymerization,
It is preferably of the same type as the monomer used for the polymerization. Specifically, polystyrene and other polymer particles are preferably used.

The method for obtaining such seed polymer particles is not particularly limited, but, for example, they can be synthesized by an emulsion polymerization method or a soap-free polymerization method using a relatively large amount of a mercaptan-based molecular weight modifier. . Also in the production of the seed polymer particles, it is preferable to utilize the seed polymerization method using the seed particles in order to control the particle diameter.

In the present invention, the crosslinkable monomer is two or more, preferably a non-conjugated divinyl compound typified by divinylbenzene, or a polyvalent acrylate compound typified by trimethylolpropane trimethacrylate or trimethylolpropane triacrylate, or the like. A compound having two copolymerizable double bonds can be preferably used.

Examples of the polyvalent acrylate compound that can be used in the present invention include the following compounds.

Diacrylate compound polyethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,6-hexane glycol diacrylate, neopentyl glycol diacrylate, polypropylene glycol diacrylate, 2,
2'-bis (4-acryloxyproproxyphenyl)
Propane, 2,2'-bis (4-acryloxydiethoxyphenyl) propane triacrylate compound Trimethylolpropane triacrylate, trimethylolethane triacrylate, tetramethylolmethane triacrylate tetraacrylate compound Tetramethylolmethane tetraacrylate dimethacrylate compound Ethylene Glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-
Butylene glycol dimethacrylate, 1,6-hexane glycol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate,
2,2'-Bis (4-methacryloxydiethoxyphenyl) propane trimethacrylate compound Trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate Among the above, divinylbenzene, ethylene glycol dimethacrylate or trimethylolpropane trimethacrylate is particularly used. It is preferable. Further, two or more kinds of these crosslinkable monomers can be mixed and used.

In the present invention, the proportion of the crosslinkable monomer needs to be 10 to 100% by weight based on all the monomers.

If the proportion of the crosslinkable monomer is too small, the resulting polymer particles will have problems in hardness, strength, heat resistance or solvent resistance.

In the present invention, the polymerizable monomer used with the crosslinkable monomer, styrene, α-methylstyrene, fluorostyrene, aromatic monovinyl compounds such as vinylpyrine, acrylonitrile, vinyl cyanide compounds such as methacrylonitrile, butyl acrylate, Two
-Ethylhexyl acrylate, methyl acrylate,
Acrylic ester monomers such as 2-hydroxyethyl acrylate, glycidyl acrylate, N, N'-dimethylaminoethyl acrylate, butyl methacrylate, 2-ethylhexyl methacrylate, methyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, N, N'- Methacrylic acid ester monomers such as dimethylaminoethyl methacrylate,
Acrylic acid, methacrylic acid, maleic acid, itaconic acid and other mono- or dicarboxylic acids and acid anhydrides of dicarboxylic acids, and amide monomers such as acrylamide and methacrylamide may be used. Further, within a range which is allowable in terms of polymerization rate and polymerization stability, conjugated double bond compounds such as butadiene and isoprene, vinyl ester compounds such as vinyl acetate, 4-methyl-1-pentene and other α-olefin compounds. Can also be used. You may use 2 or more types of these.

As the method of adding the monomer, there are a method of adding the monomer to the seed polymer particles at a time and a method of dividing the monomer while conducting the polymerization or continuously adding the monomer. The present invention requires that the seed polymer particles be imbibed with monomer before polymerization is initiated and substantially crosslinking occurs in the seed polymer particles.

When the monomer is added after the middle stage of the polymerization, the monomer is not absorbed by the polymer particles, so that a large amount of fine particles are generated, the polymerization stability is deteriorated, and the polymerization reaction cannot be maintained. Therefore, either add all the monomers to the seed polymer particles before starting the polymerization, or the polymerization yield is 30%.
It is preferred to finish the addition of all monomers before reaching the extent. In the present invention, it is particularly preferable to start the polymerization after the seed polymer particles have absorbed all the monomers.

In the present invention, the amount of the monomer used relative to 1 part by weight of the seed polymer particles is 2 to 500 parts by weight, preferably 3 to 1 part.
The amount is 00 parts by weight, more preferably 4 to 19 parts by weight.

When the amount of this monomer used is less than 2 parts by weight, the ratio of the soft seed polymer particles to the whole becomes high, so that the crosslinked polymer particles finally obtained may have sufficient hardness and strength. However, since the phase separation occurs in the seed polymer particles, the finally obtained crosslinked polymer particles have a distorted shape, and it is not possible to obtain true spherical crosslinked polymer particles.

If the amount of the monomer used exceeds 500 parts by weight,
The monomer absorption capacity of the seed polymer particles is insufficient, and the amount of the monomer not absorbed by the seed polymer particles increases, so that it becomes difficult to control the particle diameter.

In the present invention, the particle diameter of the finally obtained crosslinked polymer particles can be controlled by adjusting the amount of seed polymer particles and the amount of monomers. Specifically, when the weight of the seed polymer particles is W _s , the number average particle diameter thereof is D _s , the amount of monomer is M, and this polymerization conversion rate is X (%), the number average seed diameter of the crosslinked polymer particles obtained is D is calculated by the following formula, and is practically realized with relatively high accuracy.

However, d _m is the specific gravity of the monomer, and d is the specific gravity of the crosslinked polymer particles.

In the present invention, the polymerizable monomer absorbed by the seed polymer particles is polymerized by the emulsion polymerization method. In this emulsion polymerization reaction, a water-soluble radical polymerization initiator made of persulfate is used as the polymerization initiator.

Further, in the emulsion polymerization reaction, a surfactant is used in order to increase the stability of the polymerization reaction system, but the concentration of this surfactant must be below the limit micelle formation concentration (CMC). Is. Here, a usual surfactant can be used, and examples thereof include anionic emulsifiers such as sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium dialkylsulfosuccinate, and a formalin condensate of naphthalenesulfonic acid. .

Furthermore, polyoxyethylene nonyl phenyl ether,
It is also possible to use a nonionic surfactant such as polyethylene glycol monostearate or sorbitan monostearate together.

The cross-linked polymer particles obtained by the method of the present invention have a high degree of cross-linking, so that cross-linked polymer particles having extremely high hardness, strength, heat resistance or solvent resistance can be obtained.
The crosslinked polymer particles can be used in various fields by utilizing such characteristics.

To give an example of the use of the crosslinked polymer particles according to the invention,
Lubricants, spacers, antiblocking agents, powder fluidity improvers, powder lubricants, cosmetic particles, abrasives, rubber compounding agents, plastic pigments, filter media and filter aids, gelling agents, flocculants, paints. Additives, gloss control agents, release agents,
There are column packing materials for chromatography, particles for microcapsules, particles for adding synthetic fibers and the like.

The crosslinked polymer particles according to the method of the present invention are particularly effective as an auxiliary agent for electrophotographic toners. For example, 1 to 10% by weight of the crosslinked polymer particles according to the method of the present invention are added together with a base resin and various toner additives during the production of toner. When melted and crushed, the energy required for crushing is reduced because the crushability is improved, and the crushed product has a narrow particle size distribution, which has the advantage of reducing the classification burden.
Further, it is possible to improve the balance between the fixing property as a toner and the blocking resistance. Further, when the crosslinked polymer particles according to the present invention are blended in the toner by dry mixing at a ratio of 1 to 20% by weight, the toner has improved blocking resistance, improved fluidity, reduced contamination on the photosensitive drum, and further improved fog. Further, it is possible to prevent a decrease in image density due to deterioration of the toner over time.

〔Example〕

Examples of the present invention will be described below. In the following description, "part" is part by weight.

Example 1 Styrene 98 parts Methacrylic acid 2 parts t-Dodecyl mercaptan 10 parts Sodium dodecylbenzene sulfonate 0.05 parts Potassium persulfate 0.4 parts Water 200 parts The above substances are put into a flask having a volume of 2 l and stirred into nitrogen gas. The temperature was raised to 70 ° C. and the polymerization was carried out for 6 hours. As a result, seed polymer particles A having a particle size of 0.45 μm and a standard deviation of the particle size of 0.015 μm were obtained at a polymerization yield of 98%.
Here, the particle diameter is an average value of values measured for 100 polymer particles by a transmission electron microscope photograph. The seed polymer particles A had a toluene solubility of 98% and a molecular weight measured by gel permeation chromatography was: weight average molecular weight (Mw) = 5,000 and number average molecular weight (Mn) = 3,100.

Next, seed polymer particles A (solid content) 8 parts Sodium lauryl sulfate 0.2 parts Potassium persulfate 0.5 parts Water 500 parts Styrene 80 parts Divinylbenzene 20 parts Mix and stir at 30 ° C for 10 minutes to form seed polymer particles. Absorbed monomer.

Next, when this was heated to 70 ° C. and polymerized for 3 hours,
The polymerization yield was 99% and the amount of the polymerized coagulation remaining on the 200-mesh filter was 0.02% (relative to the polymerized solid content), and crosslinked polymer particles were obtained with high polymerization stability.

The crosslinked polymer particles were particles having an average particle diameter of 1.02 μm and a standard deviation value of particle diameter of 0.05 μm, which were very well aligned and were true spheres.

When the crosslinked polymer particles were subjected to a differential thermal analysis and a thermobalance analysis, they did not melt or soften until ashed at room temperature to 450 ° C, and the thermal loss up to 400 ° C was 2% by weight or less.

Examples 2 to 4 and Comparative Examples 1 to 3 t in the production of seed polymer particles in Example 1
-The amount of dodecyl mercaptan used is 0 parts, 2 parts, 5 parts,
Seed polymer particles A except for 20 parts, 50 parts and 100 parts
Similarly, the weight average molecular weights are 120,000 and 15,
A total of 6 kinds of seed polymer particles BG of 000, 8,900, 3,050, 710 and 320 were synthesized.

Then, a crosslinked polymer particle was produced by the same treatment as in Example 1 except that each of these seed polymer particles was used.

Table 1 shows the proportion and polymerization yield of the polymerized coagulated product in each of the above-mentioned polymerization reactions, and the average particle diameter of the obtained crosslinked polymer particles and the standard deviation thereof.

As is clear from Table 1, Comparative Example 1 and Comparative Example 3
Then, the reaction system gelled during the polymerization, and in Comparative Example 2, the polymerization was achieved but the amount of the produced coagulated product was excessive, and the obtained polymer particles were particles having a particle diameter of about 0.8 μm, which was close to the target particle diameter. , A mixture of a large number of microparticles with a particle size of 0.05 to 0.1 μm and particles with a particle size of 10 to 100 μm produced by polymerization of monomer droplets that are not absorbed by seed polymer particles as they are. Was very broad.

8 parts of the seed polymer particles A of Example 1 as a solid content,
Polymerization was performed in the same manner as in Example 1 except that 40 parts of styrene and 10 parts of divinylbenzene were used as monomers to obtain crosslinked polymer particles.

Example 6 8 parts as a solid content of the seed polymer particles A of Example 1,
Polymerization was performed in the same manner as in Example 1 except that 60 parts of styrene and 40 parts of divinylbenzene were used as the monomers to obtain crosslinked polymer particles.

Example 7 8 parts of the seed polymer particles A of Example 1 as a solid content,
Polymerization was performed in the same manner as in Example 1 except that 80 parts of methyl methacrylate was used as the monomer instead of styrene, and 20 parts of ethylene glycol dimethacrylate was used instead of divinylbenzene to obtain crosslinked polymer particles.

[Effects of the Invention] The method of the present invention is to obtain cross-linked polymer particles by an emulsion polymerization method using seed polymer particles according to specific conditions. Therefore, a polymerizable monomer containing a cross-linkable monomer is subjected to an emulsion polymerization method. Despite polymerization, high stability can be achieved in the polymerization reaction system, and as a result, highly crosslinked crosslinked polymer particles can be reliably obtained, and the particle size can be easily controlled. Therefore, it is possible to produce crosslinked polymer particles having a narrow particle size distribution in a relatively small particle size range of 0.1 to 3 μm.

Further, since the obtained crosslinked polymer particles are highly crosslinked, they have excellent hardness, strength, heat resistance and solvent resistance, and have a uniform particle size, and particles of any size can be selected. Therefore, it is expected that the characteristics expected in various applications will be excellently exhibited, and that it will also be favorably used in new applications.

Front page continuation (72) Inventor Shiro Yasukawa 2-11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd. (72) Hiroshi Tatenuma 2-11-24 Tsukiji, Chuo-ku, Tokyo Japan Incorporated Rubber Co., Ltd. (56) Reference JP 60-206803 (JP, A) JP 59-18705 (JP, A)

Claims (1)

[Claims] 1. An aqueous dispersion containing 1 part by weight of seed polymer particles having a weight average molecular weight in the range of 500 to 10,000,
Polymerizable monomer containing 10% by weight or more of crosslinkable monomer 2
Cross-linked polymer particles having a particle diameter of 0.1 to 3 μm are obtained by adding 500 parts by weight to allow the seed polymer particles to absorb a polymerizable monomer and emulsion-polymerizing in the presence of persulfate. Method for producing particles.