JP3178199B2 - Method for producing spherical particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing spherical particles.

[0002]

2. Description of the Related Art Conventionally, micron-sized spherical particles have been produced by means such as suspension polymerization, swelling polymerization, emulsion seed polymerization, and dispersion polymerization. However, these manufacturing means have the following technical problems. In other words, since these means mainly use a radical polymerization reaction, polymerization takes time, and further, large particles cannot be produced by swelling polymerization, emulsion seed polymerization, or dispersion polymerization. There is a problem that swelling polymerization and emulsion seed polymerization, which are difficult, generate minute new particles. In addition, it is difficult to impart functions such as coloring and magnetism in the polymerization process other than suspension polymerization.

[0003]

On the basis of these conventional technical problems, the present inventor can easily control the particle size in a wide range, narrow the particle size distribution, and impart functions such as coloring and magnetism. The present inventors have intensively studied a method for producing a fine spherical particle.

[0004]

That is, the present invention is characterized in that a liquid medium is flowed into an ejector, a photocurable substance is extruded through a capillary through a throat of the ejector, and the produced droplet is irradiated with light to be cured. And a method of producing spherical particles having a particle size of 1 to 200 μm and a narrow particle size distribution.

The photocurable substance used in the present invention includes cyclized polyisoprene, cyclized polybutadiene, poly (meth) acrylate of polyether, which is generally known as a photosensitive resin or a photocurable resin.
Examples include cinnamic acid esters of polyvinyl alcohol, novolak resins, polyglycidyl methacrylate, and chlorinated polymethylstyrene.

[0006] These photocurable substances are diluted with a solvent or a polymerizable monomer, and a photocrosslinking agent or a photopolymerization initiator is added. Examples of the photocrosslinking agent or photopolymerization initiator include azide compounds such as aromatic azides and trichloromethyltriazide, silver halides, bisimidazole derivatives, cyanine dyes, and ketocoumarin dyes. In addition, azo radical polymerization initiators such as azobisisobutyronitrile and azobisdimethylvaleronitrile can be used.

Examples of the polymerizable monomer include vinyl aromatic monomers such as styrene, α-methylstyrene, vinyltoluene, chlorostyrene, and divinylbenzene; (meth) acrylic acid; methyl (meth) acrylate; ) N-butyl acrylate, hydroxyethyl (meth) acrylate,
Ethylene glycol di (meth) acrylate,
Acrylic monomers such as (meth) acrylonitrile; vinyl ester monomers such as vinyl formate and vinyl acetate;
Examples include vinyl halide monomers such as vinyl chloride and vinylidene chloride, and diallyl phthalate and triallyl cyanurate. These polymerizable monomers may be used alone or in combination of two or more. Preferred polymerizable monomers are styrene, ethyl (meth) acrylate, and divinylbenzene. If divinylbenzene is used in an amount of 30% by weight or more based on the total polymerizable monomer, even if the produced particles are brought into contact with an organic substance, the dye contained therein no longer migrates and elutes, and the particles are heated. Therefore, it can be suitably used as a liquid crystal spacer particle for a liquid crystal display device.

[0008] The wavelength of the light is from ultraviolet to 480 nm, especially 28
0 to 410 nm is preferred. The size of the droplet of the photocurable substance is 1 to 200 μm. If it exceeds 200 μm, the curing reaction does not proceed sufficiently and the particles may aggregate. If it is less than 1 μm, the particle size distribution becomes wide.

In order to make a droplet of a photocurable substance, FIG.
And a photoreactor equipped with an ejector shown in FIG. In FIG. 1 or FIG. 2, the liquid medium fed from the inlet 1 is accelerated by the throat section 2 and sent out to the quartz tube exposure section 3. On the other hand, the container 4 containing the photocurable substance is placed in the pressurized container 5 and sent to the throat section through the capillary 6 by compressed gas. The photocurable material is now separated from the capillary by the accelerated liquid medium, becomes fine droplets and is exposed at 3 to spherical solid particles.

The curing reaction is mainly carried out in an aqueous medium, but a substance having a low solubility of the photocurable substance, for example, n-hexane, isooctane, cyclohexane or the like may be used as a decomposition medium. In addition, if an organic medium having high solubility in water, such as acetone or ethanol, is dissolved in the photocurable substance, it is possible to adjust the particle size to a smaller one by transferring it to the aqueous medium. .
In order to improve the dispersibility of the photocurable substance in the aqueous medium, a dispersion stabilizer is dissolved in the aqueous medium and used as necessary. As the dispersion stabilizer, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, polyacrylamide, polymer dispersion stabilizer such as polyethylene oxide,
Anionic surfactants, cationic surfactants, nonionic surfactants and the like are used.

The average particle size of the particles can be controlled by the difference in the amount of the soluble substance such as the flow rate of the liquid medium passing through the throat, the amount of the photocurable substance fed, and the amount of acetone added. The diameter of the throat is 1 to 3 mm, preferably 1.2 to 2 mm. If it is less than 1 mm, the flow velocity becomes too large even if the flow rate of the liquid medium is reduced, and the particle size distribution of the generated particles becomes wide. On the other hand, if it exceeds 3 mm, the flow rate of the liquid medium becomes too large, and not only does the curing reaction slow, but also it becomes difficult to collect the generated particles. The flow rate of the liquid medium passing through the throat section is 0.5 to 200 c / sec.
m, preferably 1 to 100 cm. The higher the flow rate, the smaller the average particle size. When the flow rate is less than 0.5 cm, the size of the droplet exceeds 200 μm, and the curing reaction becomes insufficient. On the other hand, when the flow velocity exceeds 200 cm, the particle size distribution becomes extremely wide, and the advantage of using the ejector for droplet formation is lost.

The inner diameter of the capillary is 0.15 to 0.5
mm is preferable, and the length is about 30 cm to 1 m. The flow rate of the photocurable substance is controlled by the inner diameter and length of the capillary and the pressure applied to the pressure vessel.
An exposure time of 1 to 10 seconds is sufficient for curing the droplets having an average particle diameter of 200 μm or less of the exemplified photocurable substance. The length of the exposed part of the quartz tube may be 20-50 cm,
The exposure time can be adjusted by changing the thickness.

[Operation] A photocurable substance is dispersed by an accelerated dispersion medium passing through a throat portion of an ejector, and cured by light to produce spherical particles having a controlled particle size in an extremely short time. can do.

[0014]

Next, the present invention will be described more specifically with reference to examples. Example 1 In FIG. 1 and FIG. 2, an ejector having a throat having a diameter of 1.25 mm and a length of 1 mm, and an inner diameter of 0.19
mm, an outer diameter of 0.41 mm, and a length of 1 m were used. Water was flowed through the throat at a flow rate of 10 cm per second.
The flow rate is about 30 ml per minute. On the other hand, a polyether acrylate-based photocurable substance (manufactured by Nippon Synthetic Rubber
A 60% ethanol solution of SCR-200) was put into a pressurized container, and pressurized to ² kg / cm ² with compressed air. At this time, the extruded amount of the photocurable substance is about 0.1 per minute.
It was 5 g.

Example 2 Spherical particles were obtained in the same manner as in Example 1 except that the flow rate of water was 30 cm / sec and 50 cm / sec. The average particle size and standard deviation were 7.5 μm and 0.25 μm, 3.4 μm and 0.19 μm, respectively.

[0016]

According to the present invention, a liquid medium is caused to flow through an ejector, a photocurable substance is extruded through a capillary into a narrow portion (throat) of the ejector, and the generated droplets are irradiated with light to be cured, whereby the particle size can be reduced in an extremely short time. Can be produced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an outline of an apparatus used in an embodiment of the present invention.

FIG. 2 is a diagram showing a structure of an ejector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Entrance of liquid medium 2 Throat part of ejector 3 Exposure part made of quartz tube 4 Container containing photocurable substance 5 Pressurized container 6 Capillary 7 Light source 8 Liquid sending pump 9 Ejector

Claims (1)

(57) [Claims] 1. A method for producing spherical particles, comprising flowing a liquid medium through an ejector, extruding a photocurable substance through a capillary through a throat of the ejector, and irradiating the generated droplets with light to cure the particles.