JPH06220110A - Production of vinyl particles having uniform size - Google Patents

Abstract

PURPOSE:To produce polymer particles having particle size uniformized within a specific range, high slipperiness and thermal stability and excellent quality by polymerizing a vinyl monomer together with a phosphorous acid ester and an inorganic compound used as dispersion agents. CONSTITUTION:A vinyl monomer is polymerized in an aqueous medium containing a dispersion agent consisting of fine powder of an inorganic compound and a phosphorous acid ester or a partial ester of phosphoric acid. The produced particles have particle diameters uniformized within the range of 1-100mum. The inorganic compound is e.g. barium carbonate, silica or talc and preferably added in the form of fine powder having particle diameter of 0.01-1mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing vinyl polymer particles of uniform size.

[0002]

2. Description of the Related Art Vinyl polymer particles of uniform size are
It is needed in many ways. Among them, particularly fine polymer particles are required for various applications. For example, in the field of cosmetics, fine particles within a range of 8 to 20 μm are required as a slipperiness imparting agent, and toner within an electronic copying machine requires particles within a range of 5 to 20 μm.
Particles in the range of 5 to 50 μm are required as the polish for the paint, and particles in the range of 2 to 100 μm are required as the light diffusing agent. In order to make such fine particles, it is possible to make large particles and then grind them, but it is not easy to grind them to such sizes. Moreover, the pulverization results in an angular particle shape, which makes it unsuitable for applications requiring slipperiness.

Since vinyl polymer particles form a particulate polymer by the polymerization of monomers, it is desirable that the particles have a desired size within the range of the polymerization process.
Therefore, an attempt was made to immediately obtain particles of uniform size by polymerizing the monomers.

There are various methods for polymerizing vinyl monomers. For example, there are emulsion polymerization method, soap-free polymerization method, dispersion polymerization method, suspension polymerization method, swelling polymerization method and the like. Among them, the emulsion polymerization method and the soap-free polymerization method generate small particles having a particle size of 2 μm or less, and therefore the particles are too fine and are not suitable for the above-mentioned applications. Further, the dispersion polymerization and the swelling polymerization are not suitable for industrial production because the operations are complicated and it takes a long time to complete the polymerization. As a result, only the suspension polymerization method is considered to be suitable for obtaining polymer particles of uniform size, and therefore various methods for producing polymer particles by the suspension polymerization method have been proposed.

The suspension polymerization method is a method in which a vinyl monomer is dispersed in an aqueous medium containing a dispersant, and a polymerization reaction is carried out inside the dispersed monomer particles to obtain polymer particles. The dispersant is required to disperse the vinyl-based monomer as particles in the aqueous medium. Further, since the polymerization is an exothermic reaction and external heating is required to accelerate the polymerization, it is necessary to stir the aqueous medium in order to uniformly proceed the polymerization. . Due to this stirring, the monomer particles that were finely dispersed at the beginning of the polymerization,
During the polymerization process, they collided and coalesced to form giant particles. Therefore, in order to produce fine particles of uniform size, it was necessary to prevent coalescence of dispersed particles during the polymerization process. It is thought that this prevention of coalescence can be achieved by the coexisting dispersant, and therefore it has been proposed to use various dispersants.

Japanese Unexamined Patent Publication (Kokai) No. 55-34247 discloses the name of suspension stabilizer, and this suspension stabilizer corresponds to the above-mentioned dispersant. This publication recommends the use of a magnesium silicate compound having a molar ratio of SiO ₂ and MgO within a certain range as a suspension stabilizer.
This dispersant belongs to the inorganic powder. This publication describes that fine vinyl polymer particles can be efficiently obtained by using this compound as a dispersant. However, the particles obtained have an average particle diameter within the range of 1 mm to 0.1 mm. In fact, it is difficult to make the average particle size finer than this because of coalescence of particles during the polymerization process.

Japanese Patent Publication No. 62-51962 proposes suspension polymerization of a vinyl monomer by using a special tricalcium phosphate and an anionic surfactant as a dispersant. This publication describes that a good quality polymer having an arbitrary particle size can be obtained, but the particle size is 200
It is said to be within the range of -1240 μm. In fact, according to this method, particles are coalesced during the polymerization process, so that it is difficult to make the particle size 100 μm or less.

JP-A-1-146910 discloses that when a methacrylic acid ester is suspension-polymerized by using a polyvinyl alcohol having a specific saponification degree as a dispersant, a narrow particle size distribution between 1 and 20 μm is obtained. It is described that the polymer particles of In addition, JP-A-2-14560
No. 4 also discloses that when polyvinyl alcohol prepared by a special method using a special solvent is used as a dispersant to polymerize the vinyl monomer by suspension polymerization, polymer particles having a narrow particle size distribution can be obtained. It has been described. However, if an organic polymer dispersant such as polyvinyl alcohol is used,
This serves as a nucleus to form a graft polymer, and the generated graft polymer is mixed into the intended vinyl polymer particles, resulting in the result that the thermal stability of the obtained polymer is deteriorated. , The product gets worse.

[0009]

As described above, the particles have a uniform size within the fine range of 1 to 100 μm and are not inferior in physical properties such as thermal stability.
There was no suitable method for obtaining vinyl polymer particles. Therefore, the present invention is intended to provide a method suitable for obtaining vinyl polymer particles of generally uniform size by a suspension polymerization method. Particularly, this invention is 1-100.
An object of the present invention is to provide a method for obtaining polymer particles having a uniform size within the range of fine particles of μm.

[0010]

The method according to the present invention is characterized in that a phosphite ester or a partial ester of phosphoric acid is used as a dispersant, and this dispersant is used together with a fine powder of an inorganic compound. .

That is, according to the present invention, when polymerizing a vinyl monomer in an aqueous medium containing a dispersant, a phosphorous acid ester or a partial ester of phosphoric acid is used as a dispersant together with a fine powder of an inorganic compound. Characterized by,
It is intended to provide a method for producing vinyl polymer particles of uniform size.

The present invention is characterized most by using a phosphorous acid ester or a partial ester of phosphoric acid as a dispersant. Among them, the phosphite ester is phosphite H ₃ PO.
It is an ester of ₃ . Phosphorous acid

[0013]

[Chemical 1] Therefore, it has two hydroxyl groups that can be ester-substituted. The phosphite ester is one in which the two hydroxyl groups are all esterified by reacting with alcohols,

[0014]

[Chemical 2] Is a compound represented by. That is, the phosphorous acid ester means only a complete ester of phosphorous acid and does not include a partial ester. Here, R ₁ and R ₂ represent an alkyl group. R ₁ and R ₂ represent an alkyl group having 1 to 14 carbon atoms. R ₁ and R ₂ may be the same or unsaturated. A preferred example of a phosphite is dibutyl hydrogen phosphite.

Further, the partial ester of phosphoric acid used in the present invention is a partial ester of phosphoric acid represented by H ₃ PO ₄ . Phosphoric acid

[0016]

[Chemical 3] Therefore, it has three hydroxyl groups that can be ester-substituted. The partial ester of phosphoric acid is one in which only one or two of the three hydroxyl groups are esterified by reacting with an alcohol,

[0017]

[Chemical 4] Is a compound represented by. Here, R ₁ and R ₂ represent the above. That is, the complete ester of phosphoric acid is excluded. Suitable examples of the partial ester of phosphoric acid are caprolactone EO-modified phosphoric acid dimethacrylate, monoisodecyl phosphate, 2-ethylhexyl acid phosphate, isodecyl acid phosphate and the like. Here, the caprolactone EO-modified phosphoric acid dimethacrylate is

[0018]

[Chemical 5] The compound represented by is sold under the trade name of PM-21 by Nippon Kayaku Co., Ltd.

In the present invention, a fine powder of an inorganic compound is used as a dispersant together with the above-mentioned phosphite ester or partial ester of phosphoric acid (hereinafter, both are collectively referred to as esters). As the inorganic compound, it is possible to use sparingly water-soluble salts such as barium carbonate, calcium carbonate, calcium phosphate and calcium sulfate, and inorganic polymer substances such as talc, bentonite, silicic acid, diatomaceous earth and clay. Of these, sparingly soluble salts are preferably used. These inorganic compounds are used as a fine powder of 0.01 to 10 μm, and particularly preferably 0.01 to 1 μm.

The esters can be used either separately or as a mixture. The amount of the ester used is preferably 0.01 to 0.4% by weight based on the vinyl monomer. Among them, 0.03 to 0.2% by weight is particularly preferable. The reason is that if the amount of ester exceeds 0.4% by weight, the product used will be adversely affected, and conversely, if the amount of ester is 0.01
This is because if it is less than wt%, the effect of preventing the dispersed particles from being coalesced during the polymerization process becomes poor. The amount of the inorganic compound fine powder added is 0.1 to 20 with respect to the vinyl monomer.
It is preferable to set the content by weight, but among them, 0.5 to 1
It is particularly preferable to set it to 0% by weight. The reason for this is that if the amount of the inorganic compound exceeds 20% by weight, the viscosity of the solution will be too high and the whole system will not flow, thus making suspension polymerization difficult. This is because they cannot be protected and coalescence occurs.

Vinyl-based monomers that can be used in the present invention include styrene-based monomers such as α-methylstyrene, methyl acrylate, acrylates such as butyl acrylate, and methyl methacrylate. , Methacrylic acid esters such as butyl methacrylate. These can be used alone or in combination.
In addition, other monomers which can be copolymerized with these monomers can be mixed and used.

The aqueous medium which can be used in the present invention may contain a surfactant, if necessary, in addition to the above-mentioned dispersant. As the surfactant, any of cationic, anionic, nonionic and amphoteric surfactants can be used. The amount used is 500 with respect to the aqueous medium.
It should be 0 ppm or less. For example, an anionic surfactant such as sodium lauryl sulfate can be used at 2000 ppm or less.

In the present invention, a polymerization initiator is added to accelerate the polymerization of the vinyl monomer. As the polymerization initiator, a polymerization initiator soluble in the vinyl-based monomer that has been used to carry out suspension polymerization of the vinyl-based monomer is used. For example, a peroxide such as benzoyl peroxide or dicumyl peroxide, or an azo compound such as azobisisobutyronitrile is used. This polymerization initiator is
It is used by dissolving it in a vinyl-based monomer, and the amount used is within the range that has been used so far.

The method of the present invention does not impose any particular restrictions on the order of mixing the above materials. However, the mixing order is preferably as follows. First, the fine powder of the inorganic compound and the surfactant are preliminarily dissolved in water, while the esters and the polymerization initiator are preliminarily dissolved in the vinyl monomer, and then both are mixed. It is preferable to disperse the vinyl monomer in the aqueous medium by stirring the obtained mixture. At this time, the stirring speed is adjusted to observe the particle size of the dispersed vinyl-based polymer, and when the particle size reaches a desired size, the stirring speed is kept constant, and then the stirring is continued at that speed. It is preferable to continue.

To carry out the method of the present invention, it is preferable to use an autoclave as a container. The autoclave is equipped with a stirrer, and is preferably equipped with a jacket for heating and cooling. It is heated to 50-100 ° C. at the beginning of the polymerization, maintained at a temperature in this range thereafter, and continuously stirred during the polymerization period. Then, the vinyl monomer is polymerized into a polymer within a few hours. During that time, the dispersed monomer particles hardly cause the particles to coalesce with each other, resulting in a polymer having a desired particle size. Whether or not coalescence has occurred can be easily determined by taking a part of the obtained polymer particles and observing under a microscope.

[0026]

According to the method of the present invention, since ethesul and a fine powder of an inorganic compound are used as the dispersant, polymer particles can be formed by suspension polymerization without causing coalescence of vinyl monomers. Obtainable. Therefore, it is possible to complete the polymerization in a state close to the initial dispersion state of the vinyl monomer in the aqueous medium, therefore, the proportion of the vinyl monomer in the aqueous medium, the amount of the dispersant used, and stirring. By adjusting the dispersion rate of the vinyl-based monomer at the initial stage of polymerization by adjusting the speed, etc.
Within the range of 00 μm, polymer particles of uniform size can be obtained. Further, in this method, the polymer particles are not contaminated and the physical properties are not deteriorated due to the inorganic powder and the esters. Thus, according to the method of the present invention, good quality polymer particles having a desired size can be obtained. Therefore, it is possible to meet the demands from the various fields mentioned above. In this respect, the profit of the present invention is great.

Hereinafter, the reason why the method of the present invention is excellent will be specifically described with reference to Examples and Comparative Examples. In the following Examples and Comparative Examples, the average particle size is the value measured by a Coulter counter, and the presence or absence of coalescence of particles is based on the result of observation under a microscope.

[0028]

Example 1 An aqueous medium prepared by dissolving 60 g of magnesium pyrophosphate as an inorganic compound in 3000 g of water was placed in a jacket-type autoclave with a stirrer and a capacity of 5 liters. Separately, 50 g of ethylene glycol dimethacrylate and 0.9 g of azobisisobutyronitrile were added to 950 g of methyl methacrylate, and caprolactone EO-modified phosphate dimethacrylate (manufactured by Nippon Kayaku Co., Ltd., trade name PM-21 ) Was added at a ratio of 500 ppm / monomer to prepare a monomer solution. This monomer solution was placed in the autoclave.

While maintaining the temperature in the autoclave at 70 ° C., high speed stirring was carried out to carry out suspension polymerization for 6 hours. After that, it was cooled, filtered, washed, and dried. The obtained particles were uniform in size, the average particle size was 8.5 μm, and no coalescence of particles was observed.

[0030]

EXAMPLE 2 This example was carried out in the same manner as in Example 1, except that 2-ethylhexyl acid phosphate (manufactured by Daihachi Chemical Industry Co., Ltd., AP, instead of caprolactone EO-modified phosphoric acid dimethacrylate as an ester) was used. −
8) was only different in that it was used at a ratio of 500 ppm / monomer.

As a result, the obtained particles 1 had a uniform size, the average particle size was 8.0 μm, and no coalescence was observed.

[0032]

Example 3 This example was carried out in the same manner as in Example 1, except that monobutyl phosphate (manufactured by Daihachi Chemical Industry Co., Ltd., MP-4) was used as an ester instead of caprolactone EO-modified dimethacrylate phosphate. ) To 500pp
They were used in a ratio of m / monomer, and were different in that sodium lauryl sulfate as a surfactant was added at a ratio of 200 ppm / water.

The obtained particles were uniform in size, the average particle size was 9.0 μm, and no coalescence was observed.

[0034]

Example 4 This example was carried out in the same manner as in Example 1, except that monoisodecyl phosphate (manufactured by Daihachi Chemical Industry Co., Ltd., MP- 10) to 50
It was carried out with the only difference being that it was used at a ratio of 0 ppm / monomer.

The obtained particles were uniform in size, the average particle size was 8.2 μm, and no coalescence was observed.

[0036]

EXAMPLE 5 This example was carried out in the same manner as in Example 1, except that dibutyl hydrogen phosphite (manufactured by Daihachi Chemical Industry Co., Ltd., DBP, instead of caprolactone EO-modified phosphoric acid dimethacrylate as an ester) was used. −
I) is used at a ratio of 1000 ppm / monomer, and 200 pp of sodium lauryl sulfate is used as a surfactant.
Only the difference was added in the ratio of m / water.

The obtained particles were uniform in size, the average particle size was 8.5 μm, and no coalescence was observed.

[0038]

Example 6 This example was carried out in the same manner as in Example 1, except that the amount of caprolactone EO-modified phosphoric acid dimethacrylate used as the ester was increased to 1000 ppm.
/ Monomer ratio, and other than that, the same procedure as in Example 1 was carried out.

The particles obtained were of uniform size, the average particle size was 8.5 μm, and no coalescence was observed.

[0040]

COMPARATIVE EXAMPLE 1 In this comparative example, caprolactone EO-modified phosphoric acid dimethacrylate was not used as the ester in Example 1, but sodium lauryl sulfate was used as a surfactant at a ratio of 200 ppm / water. Except for this, the same procedure as in Example 1 was carried out. In other words, this comparative example corresponds to one carried out in exactly the same manner as in Example 3, except that the monobutyl phosphate used as the ester in Example 3 was not used.

The size of the obtained particles was not uniform, the average particle size was 9.8 μm, and it was recognized that there was a lot of coalescence.

[0042]

COMPARATIVE EXAMPLE 2 In this comparative example, 500 ppm of tricresyl phosphate, that is, a complete ester of phosphoric acid (trade name TCP manufactured by Daihachi Chemical Industry Co., Ltd.) was used instead of caprolactone EO-modified phosphoric acid dimethacrylate in Example 1.
In the same manner as in Example 1, except that the ratio of / monomer was used and sodium lauryl sulfate as a surfactant was used at a ratio of 200 ppm / water.

The obtained particles were not uniform in size, the average particle size was 10.5 μm, and it was recognized that there was a large amount of coalescence.

[0044]

Comparative Example 3 In this comparative example, instead of the caprolactone EO-modified phosphoric acid dimethacrylate used as the ester in Example 1, tri-2-ethylhexyl phosphate, that is, a complete ester of phosphoric acid (manufactured by Daihachi Chemical Industry Co., Ltd., TOP) at a ratio of 500 ppm / monomer, and 200% sodium lauryl sulfate as a surfactant.
Example 1 except that the ppm / water ratio was used.
It carried out exactly like the above.

The obtained particles were not uniform in size, the average particle diameter was 2.6 μm, and it was recognized that there was a lot of coalescence.

[0046]

COMPARATIVE EXAMPLE 4 In this comparative example, instead of caprolactone EO-modified phosphoric acid dimethacrylate in Example 1, tridecyl phosphate, that is, a complete ester of phosphoric acid (TTDP-I manufactured by Daihachi Chemical Industry Co., Ltd.) was used at 500 ppm / unit. The same procedure as in Example 1 was carried out except that the proportion of the monomer was used and that sodium lauryl sulfate was used as the surfactant in the proportion of 200 ppm / water.

The obtained particles were not uniform in size and a lot of coalescence was observed, and the average particle size was 10.2 μm.

Claims (1)

[Claims] 1. When polymerizing a vinyl monomer in an aqueous medium containing a dispersant, a phosphorous acid ester or a partial ester of phosphoric acid is used as a dispersant together with a fine powder of an inorganic compound. , A method for producing vinyl polymer particles of uniform size.