JPH05262804A - Production of fine polymer particle of good dispersibility - Google Patents

Abstract

PURPOSE:To produce fine polymer particles improved in dispersibility and the uniformity of particle diameters by polymerizing a vinyl monomer in a nonaqueous dispersion in the presence of a specified dispersion stabilizer. CONSTITUTION:0.1-30mol% vinylic polydimethylsiloxane of a molecular weight of 500-10000 is copolymerized with a vinyl monomer to obtain a dispersion stabilizer comprising a polymer containing polydimethylsiloxane as at the branch component. A vinyl monomer is polymerized in a nonaqueous dispersion in the presence of this stabilizer.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing fine polymer particles having a narrow particle size distribution and excellent dispersibility.

[0002]

2. Description of the Related Art In a dispersion polymerization method, a monomer is dissolved but
Polymer is a method in which a monomer is dissolved in a medium in which it is not dissolved, and an initiator is added to carry out radical polymerization to produce fine particles of the polymer. In this method, as a factor controlling the particle size of the polymer particles produced, the monomer
Although the concentration, the initiator concentration, the affinity between the medium and the polymer, etc. are related, a method of adding a dispersion stabilizer is known in order to obtain fine particles having excellent dispersibility and a uniform particle size. This dispersion stabilizer needs to be uniformly dissolved in the medium.
Although the mechanism of action of the dispersion stabilizer is not clear, it is considered that it is adsorbed on the surface of polymer fine particles that precipitate as the polymerization of the monomer progresses and prevents the association of these primary particles in the medium. .. Therefore, the chemical structure of the dispersion stabilizer is important, but the correlation with the polymer particles is not clear.

By the way, conventionally, in the dispersion polymerization of polymethyl methacrylate in a non-aqueous system, a block polymer of styrene and dimethyl siloxane or a block polymer of styrene and methyl methacrylate is used as a dispersion stabilizer. Is known [Makromol. ch
em. Makromol. symp. October 11, 48
3-501 (1987)]. As described in this document, in dispersion polymerization in a non-aqueous system, it is important to select an effective dispersion stabilizer in order to stably perform this polymerization and obtain fine particles having a uniform particle size. is there. In many conventional dispersion stabilizers, during dispersion polymerization, the stability of the polymerization system cannot be maintained within a certain monomer concentration range (10 to 35 wt%), and aggregation of polymer fine particles occurs. It has been known.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a dispersion polymerization method capable of stably polymerizing in a wide monomer concentration range and obtaining polymer fine particles having excellent dispersibility and particle size uniformity. The purpose is to provide.

[0005]

That is, the present invention provides a method for producing fine polymer particles by non-aqueous dispersion polymerization of a vinyl monomer, wherein the vinyl monomer is used as a dispersion stabilizer.
Is used as a main chain component and a polymer having polydimethylsiloxane as a branch component is used, which is a method for producing fine polymer particles having excellent dispersibility.

The present invention will be described in detail below. The present invention uses a specific dispersion stabilizer in a method for producing polymer fine particles by non-aqueous dispersion polymerization of a vinyl monomer. The feature of the dispersion stabilizer used in the present invention is a polymer having a vinyl monomer as a main chain component and polydimethylsiloxane as a branch component. That is,
The polymer used in the dispersion stabilizer of the present invention is a vinyl monomer.
Is a polymer having a graft-like structure in which a polydimethylsiloxane is branchedly bonded to the trunk (main chain). This copolymer is a polydimethylsiloxane having a vinyl group (abbreviated as PDMS macromer).
It is obtained by copolymerizing a vinyl monomer with a vinyl monomer.

The PDMS macromer is, for example,

[0008]

[Chemical 1]

A polydimethylsiloxane represented by the formula (wherein n is an integer),

[0010]

[Chemical 2]

Methacryloxypropyl-containing T-structure polydimethylsiloxane represented by the formula (wherein, 1, m, n
Is an integer) and so on.

The vinyl monomer copolymerizable with the PDMS macromer is styrene, α-methylstyrene, p-
Styrene-based monomers such as chlorostyrene; methacrylate-based monomers such as methyl methacrylate and ethyl methacrylate; methyl acrylate and ethyl acrylate,
Acrylate monomers such as butyl acrylate; known vinyl monomers such as acrylic acid, methacrylic acid, acrylonitrile, acrylamide, vinyl acetate, maleic anhydride, vinyl chloride, vinylidene chloride and vinyl pyridin can be used. The copolymerization of PDMS macromer and vinyl monomer can be carried out by radical polymerization.

However, as the vinyl monomer to be copolymerized with the PDMS macromer, it is preferable to use the same vinyl monomer as the vinyl monomer constituting the desired polymer fine particles. The reason for this is not clear, but it is considered that during the non-aqueous dispersion polymerization, the above-mentioned copolymer, which is a dispersion stabilizer, is easily adsorbed on the surface of polymer fine particles produced by the dispersion polymerization. The copolymerization ratio of the PDMS macromer and the vinyl monomer is an important factor together with the molecular weight of the polydimethylsiloxane side chain. Generally, when the molecular weight of polydimethylsiloxane is large, PDMS in the copolymer
The mole fraction of the macromer may be small, and conversely, when the molecular weight of polydimethylsiloxane is small, the mole fraction needs to be increased.

According to the results of studies by the present inventors, the molecular weight of polydimethylsiloxane is 500 to 10,000, preferably 500 to 5,000. The mole fraction of PDMS macromer in the copolymer is 0.1 to 30 mol%,
It is preferably in the range of 0.5 to 15 mol%. When the molecular weight of polydimethylsiloxane and the mole fraction of PDMS macromer are out of the above ranges, it is difficult to stably produce polymer particles having excellent dispersibility and having a uniform particle size.

The method of the present invention can be applied to a known dispersion polymerization method for producing polymer fine particles by dispersing and polymerizing a vinyl monomer in a non-aqueous system. As the vinyl monomer to be dispersed and polymerized, in addition to the vinyl monomer described above, divinyl benzene, ethylene glycol dimethacrylate, and other divinyl monomers, and fluorinated (meth) acrylate monomers can also be used. it can. In this case, since the divinyl monomer acts as a crosslinking agent, it is often used as a copolymer component with other monofunctional vinyl monomer.

When dispersion polymerization is carried out using the dispersion stabilizer of the present invention, the average particle diameter of several tens of nm to several tens of μm, which is excellent in dispersibility by radical polymerization in a non-aqueous system than a known vinyl monomer, is obtained. Uniform fine particles can be obtained. Since the polymer fine particles obtained by the method of the present invention have the above-mentioned excellent properties, they are widely used industrially such as fillers for paints, cosmetics, recording materials such as toners, fluidity improvers and surface treatment agents.

The preferred embodiment of the present invention is as follows. 1. The main component of the vinyl monomer constituting the main chain component of the polymer is the same vinyl monomer as the polymer component of the polymer fine particles.
The method for producing polymer fine particles according to claim 1, wherein 2.
The vinyl monomer is a (meth) acrylate.
A method for producing the polymer fine particles described.

[0018]

The present invention will be described in more detail with reference to the following examples. Production Example of Dispersion Stabilizer 40 parts by weight of polydimethylsiloxane (molecular weight 1000) having one terminal methacryloyloxypropyl and 40 parts by weight of methyl methacrylate (MMA) were dissolved in 100 parts by weight of toluene to prepare benzoyl peroxide 1. 2 weight was added as an initiator, and polymerization was carried out at 90 ° C. for 5 hours in a 3 liter flask equipped with a stirrer. This polymerization solution was added to a large amount of methanol, and the polymer was precipitated and recovered to obtain a copolymer. The obtained copolymer was a graft copolymer in which a polymer mainly composed of methyl methacrylate forms a trunk portion (main chain) and polydimethylsiloxane serves as a branch portion.

Examples 1 to 3 Dispersion polymerization of fine particles of polymethylmethacrylate in a non-aqueous system was carried out by using the copolymer synthesized in Production Example as a dispersion stabilizer. The polymerization conditions are as follows. 1) Dispersion stabilizer / methyl methacrylate (MMA) = 1
/ 20 (weight ratio) 2) Initiator (AIBN) / MMA = 1/50
(Weight ratio) 3) Medium: cyclohexane 4) Polymerization temperature: 70 ° C

A predetermined amount of the medium was charged into a separable flask having a three-necked capacity of 1 liter equipped with a stirring rod to dissolve the dispersion stabilizer. Then azoisobutyronitrile (AIB
M) in which N) was dissolved was added to the flask with stirring, and the polymerization was carried out at 70 ° C. with stirring. As the polymerization proceeded, fine polymer particles were precipitated and the system became cloudy. After the polymerization rate reached 90% or more, the polymerization system was cooled, the polymer particles were filtered, and washed with excess cyclohexane. The fine particles having a small particle diameter of 1 part were collected as polymer fine particles by a centrifuge.

In this embodiment, the polymerization system methyl methacrylate monomer concentration was 20 wt% and 40 wt% with respect to the medium.
% And 50 wt%, but both were excellent in dispersion stability. The dispersion stability was evaluated by observing fine particles with an optical microscope or a scanning electron microscope, and the average particle system was measured by a centrifugal separation method (Shimadzu SA-CP).
3 form). The results are shown in Table 1. 1 and 2 are micrographs of particles obtained when the monomer concentration was 50 wt%. From these results, it can be seen that fine particles having a uniform particle size and excellent dispersion stability were obtained.

[0022]

[Table 1]

Examples 4 to 8 Various polymer fine particles were synthesized in the same manner as in Example 3 except that the type of the monomer was changed by using the dispersion stabilizer polymerized in the Production Example. The results are summarized in Table 2.

[0024]

[Table 2]

In Table 2, the numerical values in parentheses are monomers.
Is the weight% with respect to the medium. EDMA: ethylene glycol dimethacrylate BA: butyl acrylate 3FM:

[0026]

[Chemical 3]

St: Styrene DVB: Divinylbenzene

Comparative Example 1 Methyl methacrylate polymer fine particles were synthesized in the same manner as in Example 3 using a copolymer of ethylene and vinyl acetate (vinyl acetate content 28 mol%) as a dispersion stabilizer. The obtained fine particles had a wide particle size distribution of 0.3 to 4 μm, and as shown in FIGS. 3 and 4, the particles were agglomerated and the dispersion stability was poor.

[0029]

According to the present invention, in the method for producing fine polymer particles by non-aqueous dispersion polymerization of a vinyl monomer, the specific dispersion stabilizer is used. It is possible to stably produce polymer fine particles having an average particle diameter of. Further, the particle size distribution is narrow, and particularly when (meth) acrylate is used as a vinyl monomer as a polymerization raw material, fine particles having a uniform particle size can be obtained. Therefore, by adopting the method of the present invention, it is possible to provide fine particles useful for various industrial purposes as a fluidity improver, a surface modifier, a binder for powder molding, an additive for a toner and the like.

[Brief description of drawings]

1 is a methyl methacrylate obtained according to Example 3. FIG.
It is an optical microscope photograph (400 times) of the polymer fine particles.

2 is a methyl methacrylate obtained according to Example 3. FIG.
3 is a scanning electron microscopic photograph of polymer particles.

3 is a methyl methacrylate obtained in Comparative Example 1. FIG.
It is an optical microscope photograph (400 times) of the polymer fine particles.

4 is a methyl methacrylate obtained in Comparative Example 1. FIG.
3 is a scanning electron microscopic photograph of polymer particles.

Claims (1)

[Claims] 1. A method for producing fine polymer particles by non-aqueous dispersion polymerization of a vinyl monomer, wherein a polymer having vinyl monomer as a main chain component and polydimethylsiloxane as a branch component is used as a dispersion stabilizer. A method for producing polymer fine particles having excellent dispersibility.