JP3090582B2 - Method for producing fine polymer particles of uniform size - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Fine polymer particles are required in various fields. In particular, polymer particles having a particle size in the range of 1 to 100 μm are a spacer, a slipperiness imparting agent,
Since it is suitable for use as a toner, a polishing agent for paint, a functional carrier, and the like, it is widely demanded in this field.
Among them, particularly those having a narrow particle size distribution and a uniform size are particularly useful. However, it has been difficult to provide particles suitable for satisfying this demand.

[0003] For example, everyone thinks that in order to produce fine polymer particles, monomers may be polymerized by an emulsion polymerization method. However, according to the emulsion polymerization method, the size of the particles is usually as fine as 1 μm or less, and
It is difficult to obtain particles having a size of m or more. On the other hand,
It is difficult to make the particle size uniform by the conventional suspension polymerization method. That is, if the monomer is added to the aqueous medium and the suspension is stirred with a normal high-speed rotary stirrer, the size of the monomer particles is reduced to a range of approximately 5 to 100 μm. However, the particle size is widely distributed in the range, and the particle size distribution is not concentrated in a narrow range.

[0004] A homomixer was generally used as a high-speed rotary stirrer. However, if the suspension is made with a homomixer, the suspension is performed in a batch system, so that the inside of the tank cannot be completely uniformly stirred and the liquid cannot be sheared.
Therefore, the size of the particles becomes uneven. In addition, a high-speed rotary stirrer has low shearing force. For this reason, the size of the particles obtained by the conventional suspension polymerization method has not been sufficiently uniform.

On the other hand, as a device for producing an emulsion, a suspension, and the like, there is a dispersing device sold under a trade name such as a nanomizer, a harmonizer, or a microfluidizer.
The purpose of this device is to pulverize suspended particles to make them finer. This device presses the liquid under high pressure onto the surface of a disk with two holes penetrating from the front to the back, causing the liquid to flow out of the two holes and to cause
The principle is that the individual liquid streams collide with each other and the impact causes the suspended particles contained therein to be crushed and refined, thereby producing a suspension of fine particles.

[0006] Japanese Patent Application Laid-Open No. 4-156555 discloses that a suspension is formed by making the suspended particles fine by collision of the liquid streams, and the suspension is subjected to suspension polymerization to prepare a toner for electrostatic development. It discloses how to make it. According to this publication, an ethylene-based monomer, a polymerization initiator soluble in this monomer, a surfactant, and a dispersion stabilizer are added to an aqueous medium, and the mixture is stirred to form monomer particles. A primary suspension is made, the primary suspension is passed through a microfluidizer, the primary suspension is divided into a plurality of streams under pressure, and the liquid streams thus obtained collide with each other to form monomer particles. Is further refined to form a secondary suspension,
Thereafter, the secondary suspension is subjected to suspension polymerization to obtain fine polymer particles.

[0007]

However, the polymer particles produced according to the teachings of the above publication have irregular sizes even if the particles are fine, and have a wide particle size distribution. Therefore, there has been a need to provide fine particles having a more uniform particle size, and thus having a narrow range of particle size distribution. The present invention is intended to provide fine polymer particles having such a uniform size.

[0008]

The present inventor has found the following as a result of repeatedly trying to produce fine polymer particles with reference to the teachings of the above publication. That is,
As taught by the above publication, if a surfactant is used in a large amount of about twice the critical micelle concentration, the size of the monomer particles in the suspension after passing through a microfluidizer is reduced. I noticed that it would not be aligned. Conversely, it has been found that when the amount of the surfactant used is reduced to 0.25 to 1 times the critical micelle concentration, the size of the particles in the suspension becomes uniform. At the same time, although the above-mentioned publication uses a dispersion stabilizer, the present inventor, when the amount of the surfactant used is reduced as described above, it is better not to use the dispersion stabilizer to make the particle size uniform. Was found to be convenient. The present invention has been completed based on such knowledge.

According to the present invention, a primary suspension of monomer particles is prepared by adding an ethylene monomer, a polymerization initiator soluble in the monomer and a surfactant to an aqueous medium and stirring the mixture. Pressure, applying pressure to the primary suspension, dividing the suspension into a plurality of liquid streams, and colliding the liquid streams to form a secondary suspension of monomer particles. In the method for producing polymer particles by suspension polymerization, a surfactant is used as a primary suspension of a monomer by using 0.25 to 1 times the critical micelle concentration thereof without using a dispersion stabilizer. , 10-3000kg for primary suspension
A method for producing fine polymer particles of uniform size, characterized in that monomer particles are pulverized into fine particles by applying a pressure of / cm ² .

According to the present invention, a primary suspension of monomer particles is prepared by adding an ethylene-based monomer, a polymerization initiator soluble in the monomer, and a surfactant to an aqueous medium and stirring the mixture. Is similar to the disclosure in JP-A-4-156555, but differs from the disclosure in the above-mentioned publication in that no dispersion stabilizer is used. Further, the disclosure of the above-mentioned publication discloses that the surfactant is used at a critical micelle concentration of 0.5 to 2.0.
In contrast to the necessity of using a large amount as much as twice, the present invention is characterized in that a small portion thereof and a small amount exceeding the lower limit thereof are 0.25 to 1 times the critical micelle concentration. This is different from the disclosure of the above publication.

It is preferable to use an anionic surfactant. Preferred anionic surfactants are, for example, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene lauryl ether sulfate, sodium dioctylsulfosuccinate and the like.

In general, a surfactant is molecularly dispersed while it is only dissolved in a small amount of water to form a low concentration aqueous solution. However, when the concentration of the surfactant exceeds a certain concentration, the molecules of the surfactant aggregate to form a colloid-sized aggregate called a micelle in an aqueous solution. The concentration at which such micelle formation occurs is called the critical micelle concentration. Surfactants rapidly change physicochemical properties such as osmotic pressure, electrical conductivity and surface tension of an aqueous solution at a critical micelle concentration. The critical micelle concentration is a unique value for each surfactant. For example, sodium lauryl sulfate has a critical micelle concentration of 0.23% by weight.

In the present invention, in order to prepare a primary suspension, a device having a mechanism for dispersing particles by shearing force is used as in the conventional method. For this purpose, a high-speed rotating stirrer such as a homomixer is used. In the primary suspension, the size of the monomer particles in the primary suspension does not need to be particularly fine, and the size of the particles does not need to be particularly uniform. The primary suspension may be of a level which has hitherto been commonly referred to as a suspension.

In the present invention, the primary suspension obtained as described above is passed through a dispersing device called a microfluidizer or a nanomizer used in JP-A-4-156555. This device flows the primary suspension into a plurality of streams under pressure, as described above,
This is an apparatus in which the plurality of streams collide with each other, and the suspended particles are pulverized by the collision to make them finer.

An apparatus called a nanomizer has a main part constituted by a part as shown in FIG. In FIG. 1, the disk 1 has two through holes 11 and 12 penetrating from the front surface to the rear surface, and has a groove 13 connecting the holes 11 and 12 on the rear surface facing the disk 2. Disk 2
Also has two through holes 21 and 22 like the disk 1,
A groove 23 connecting holes 21 and 22 is provided on the back surface facing the disk 1. The disc 1 is pressed against the disc 2 by the presser 3, and the disc 2 is pressed toward the disc 1 by the presser 4, so that the disc 1 and the disc 2 come into close contact with each other. I have. However, the hole 11 and the hole 12 are not positioned so as to overlap with the hole 21 and the hole 22, but are arranged so that the groove 13 and the groove 23 intersect each other and extend vertically.

The primary suspension is introduced into the presser 3, and a pressure in the range of 10 to 3000 kg / cm ² is applied to the suspension, and the suspension is transferred to the holes 11 and 12 of the disc 1. From 2
It flows out as individual liquid flows. The outflowing liquid streams collide with the disk 2 and change directions, flow along the grooves 13 and collide with each other at the center thereof. The colliding suspension moves to the disk 2 side, collides with the center of the groove 23 of the disk 2, and then divides into two, flows toward both ends of the groove 23, and collides with the end of the groove 23. Through the holes 21 and 22 and into the presser 4, where it merges and flows. In this way, the suspension is disc 1 and disc 2
While passing, the monomer particles therein are pulverized by the impact of the collision to be refined.

A dispersing device called a microfluidizer or a nanomizer is generally designed to pulverize and pulverize particles in a suspension. When the surfactant is contained in the primary suspension in an amount of 0.5 to 2.0 times the critical micelle concentration and further contains a dispersion stabilizer, the finely divided particles are relatively large, and It has a broad particle size distribution. However, when the surfactant is present in the primary suspension only in an amount of 0.25 to 1 times the critical micelle concentration and when no dispersion stabilizer is present, the finely divided particles become relatively small, Moreover, the particles have a uniform size and a narrow particle size distribution. Thus, a secondary suspension having a fine particle size in the range of, for example, 1 to 3 μm is obtained.

In the present invention, the secondary suspension obtained above is subjected to suspension polymerization. Since the secondary suspension already contains the polymerization initiator, the polymerization can be started only by heating this. The heating is performed at an appropriate temperature depending on the type of the polymerization initiator and the type of the monomer, but is usually in the range of 25 to 100 ° C, and preferably in the range of 50 to 90 ° C. When the secondary suspension is polymerized in this way, the ethylene monomer becomes a polymer with the particle size as it exists in the secondary suspension. Therefore, a polymer having a uniform particle size can be obtained.

After the polymerization, the suspension is filtered or centrifuged to separate the polymer particles from the aqueous medium, washed with water or a solvent, dried and used as a powder.

The ethylene monomers usable in the present invention include, for example, styrene, p-methylstyrene, p-methylstyrene and p-methylstyrene.
-Styrene monomers such as chlorostyrene; acrylate monomers such as ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate; methacrylate esters such as methyl methacrylate, ethyl methacrylate and butyl methacrylate Alkyl vinyl ethers such as polyethylene glycol mono (meth) acrylate and methyl vinyl ether; vinyl ester monomers such as vinyl acetate and vinyl butyrate; N-methylacrylamide, N
N-alkyl-substituted acrylamides such as ethyl acrylamide; nitrile monomers such as acrylonitrile and methacrylonitrile; and polyfunctional monomers such as divinylbenzene, ethylene glycol (meth) acrylate and trimethylolpropane triacrylate. These monomers can be used alone or as a mixture of two or more, if necessary.

As the polymerization initiator that can be used in the present invention, an oil-soluble polymerization catalyst generally used for polymerization of an ethylene monomer can be used, and it is not particularly limited. For example, benzoyl peroxide, lauroyl peroxide, t
Peroxide catalysts such as -butyl peroxyoctoate,
Azo catalysts such as azobisisobutyronitrile and azobisisovaleronitrile can be used.

In general, when an ethylene monomer is subjected to suspension polymerization, as a dispersion stabilizer, protective colloids such as polyvinyl alcohol, methyl cellulose, polyvinyl pyrrolidone, and gelatin, barium sulfate, calcium sulfate,
Although poorly water-soluble inorganic salts such as magnesium carbonate, calcium phosphate and magnesium pyrophosphate are used, in the present invention, such a dispersion stabilizer is not used.

[0023]

In general, an ethylene-based monomer, a polymerization initiator soluble in this monomer, a surfactant, and a dispersion stabilizer are added to an aqueous medium and stirred to form a monomer particle. In the conventional method of preparing a primary suspension, according to the method of the present invention, a dispersion stabilizer is not used, and the amount of a surfactant is reduced to 0.25 to 1 times the critical micelle concentration. Since the primary suspension is prepared, the preparation of the primary suspension can be easily performed without much difference from the conventional method. The primary suspension thus obtained is passed through a dispersing device such as a nanomizer,
A pressure of 10 to 3000 kg / cm ² is applied to the primary suspension to divide the suspension into a plurality of streams, and the liquid streams collide with each other to pulverize and atomize the monomer particles to form a secondary suspension. Therefore, the preparation of the secondary suspension is also easy. Since the secondary suspension is polymerized only by heating it, fine polymer particles can be easily obtained according to the method of the present invention. Moreover,
The obtained particles have a uniform particle size within the range of 1 to 3 μm and have a narrow particle size distribution. Since these particles are fine and their particle size distribution is confined to a narrow range, they are suitable for use as a spacer, a slip imparting agent, a toner, a polishing agent for paints, and the like. Therefore, the present invention is useful as providing polymer particles suitable for such uses.

[0024]

Next, the advantages of the present invention will be specifically described with reference to examples and comparative examples.

[0025]

Example 1 175 g of styrene in which 1 g of benzoyl peroxide was dissolved, 25 g of divinylbenzene (80% pure), 1.6 g of sodium lauryl sulfate (critical micelle concentration: 0.1 g).
23% by weight) and 800 g of water.

Next, Nanomizer L manufactured by Nanomizer Co., Ltd.
Using an A-31 type, one-pass treatment was performed at a treatment pressure of 1300 kg / cm ² to obtain an emulsion. Next, this emulsion was charged into a polymerization reaction tank having an internal volume of 2 liters, and reacted at 80 ° C. for 6 hours under gentle stirring at 200 rpm with an irrigated stirring blade.

FIG. 2 shows the results of measuring the particle size of the obtained polymer particles using a laser diffraction type particle size distribution analyzer SALD-2000 (manufactured by Shimadzu Corporation). The polymer particles had a narrow particle size distribution as shown in FIG. 2, and had a median particle size of about 1.1 μm.

[0028]

Example 2 The same crude dispersion as shown in Example 1 was treated with a Nanomizer LA-31 type at a processing pressure of 300 kg / kg.
The same operation as in Example 1 was performed, except that cm ² was used.
FIG. 3 shows the result of measuring the particle size of the obtained polymer particles using a laser diffraction type particle size distribution analyzer. The polymer particles exhibited a narrow particle size distribution as shown in FIG. 3, and had a median particle size of about 1.7 μm.

[0029]

Example 3 The same operation as in Example 1 was carried out except that the same crude dispersion as in Example 1 was treated at a processing pressure of 10 kg / cm ² using a Harmonizer LEH-I (manufactured by Nanomizer). Was. FIG. 4 shows the result of measuring the particle size of the obtained polymer particles using a laser diffraction type particle size distribution analyzer.
Shown in The polymer particles had a narrow particle size distribution as shown in FIG. 4, and had a median particle size of about 2.9 μm.

[0030]

[Comparative Example 1] In Example 1, the dispersion was performed using a TK homomixer MARK II 2.5 type (manufactured by Tokushu Kika Kogyo).
Suspension polymerization was performed under the same conditions except that the treatment was performed at 2000 rpm for 10 minutes. When the dispersion after the fine dispersion treatment was observed with a microscope, the oil droplets had a wide distribution having a center diameter of 3 to 5 μm. After the temperature was raised to 80 ° C., as the polymerization proceeded, the particles aggregated and fused to form coarse particles of about 100 μm, and good spherical fine particles could not be obtained.

[0031]

Comparative Example 2 The same operation as in Example 1 was performed, except that the same crude dispersion as in Example 1 was treated with an ultrasonic homogenizer (Sonifier II Model 450 output, 400 W, 400 W, manufactured by Branson) for 10 minutes. FIG. 5 shows the results of measuring the particle size of the obtained polymer particles using a laser diffraction type particle size distribution analyzer. Although the polymer particles have a median particle size of about 2.1 μm, as shown in FIG.
It had a broad distribution of 10 μm.

[0032]

Example 4 A crude dispersion containing 190 g of methyl methacrylate in which 0.6 g of azobisisovaleronitrile was dissolved, 10 g of ethylene glycol dimethacrylate, 1.6 g of sodium lauryl sulfate, and 800 g of water was used.
The same operation as in Example 1 was performed, and the reaction was performed at 50 ° C. for 6 hours. FIG. 6 shows the result of measuring the particle size of the obtained polymer particles using a laser diffraction type particle size distribution analyzer. The polymer particles had a narrow particle size distribution, as shown in FIG. 6, and had a median particle size of about 1.2 μm.

[0033]

Comparative Example 3 The same crude dispersion as shown in Example 4 was applied to TK
12000r using homomixer MARKII2.5
Suspension polymerization was performed under the same conditions except that the treatment was performed at pm for 10 minutes. When the dispersion after the fine dispersion treatment was observed with a microscope, the oil droplets had a wide distribution having a center diameter of 5 to 8 μm. After the temperature was raised to 50 ° C., as the polymerization proceeded, the particles aggregated and fused to form coarse particles of about 100 μm,
Good spherical fine particles were not obtained.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a main part of an apparatus used for producing a secondary suspension according to the present invention.

FIG. 2 is a graph showing the particle size distribution of polymer particles obtained in Example 1.

FIG. 3 is a graph showing the particle size distribution of the polymer particles obtained in Example 2.

FIG. 4 is a graph showing the particle size distribution of the polymer particles obtained in Example 3.

FIG. 5 is a graph showing the particle size distribution of the polymer particles obtained in Comparative Example 2.

FIG. 6 is a graph showing the particle size distribution of the polymer particles obtained in Example 4.

[Description of Signs] 1 disk 2 disk 3 retainer 4 retainer 11 hole 12 hole 13 groove 21 hole 22 hole 23 groove

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C08F 2/18-2/20

Claims (1)

(57) [Claims] 1. An ethylene-based monomer, a polymerization initiator soluble in this monomer, and a surfactant are added to an aqueous medium and stirred to form a primary suspension of monomer particles. Pressure is applied to the primary suspension to divide the suspension into a plurality of liquid streams, and the liquid streams collide with each other to form a secondary suspension of monomer particles. The secondary suspension is suspended. In the method for producing polymer particles by suspension polymerization, a surfactant is used as a primary suspension of a monomer using a surfactant in an amount of 0.25 to 1 times its critical micelle concentration without using a dispersion stabilizer, A method for producing fine polymer particles of uniform size, characterized in that monomer particles are pulverized into fine particles by applying a pressure of 10 to 3000 kg / cm ^{2 to} the suspension.