JPS61271330A - Production of microsphere of thermoplastic resin composition - Google Patents

Abstract

PURPOSE:To obtain microspheres suitable as, e.g., a toner, by grinding a thermoplastic resin, melt-blending the ground resin with an incompatible component, settling the blend to form stable spheres, solidify them and removing the incompatible component by dissolving in a solvent. CONSTITUTION:A thermoplastic resin A (e.g., nylon 6) ground to a desired particle size and component B (e.g., polyethylene glycol) incompatible with A are melt-blended at such a blending ratio that component B forms a continuous phase and component A forms a dispersed phase at a temperature higher than any of the m.p.'s components A and B to bring them to a state of dispersion in which the distance between A particles is sufficient. This dispersion is settled within 1hr to form stable spheres of component A and this mixture is solidified by cooling. The solidified produce is disintegrated by immersion in a solvent which is a poor solvent for component A but is a good solvent for component B to form a suspension in which component B is dissolved in the solvent and spherical microspheres of component A are dispersed in it. The microspheres of component A is separated from this dispersion.

Description

[Detailed description of the invention]

Using this manufacturing method, thermoplastic resin with a fine particle size is spheroidized, improving lubricity and stabilizing particle properties, which can be used as cosmetic additives, lubricants, micro spacers, biochemical carriers, toner carriers for copying machines, etc. There are other fields of application to further increase its value.

[Prior art and problems to be solved by the invention]

Conventionally, the only way to obtain spherical fine particles by mechanical crushing was to add shavings to the particles, but this did not yield a truly spherical shape, and the shavings caused significant wear and tear. .

[Means to solve the problem]

The present invention consists of the following steps to obtain particles with a particle size of 0.01 μm to 11 μm.
000Ii thermoplastic resin composition microspheres. That is, a thermoplastic resin composition A that has been mechanically pulverized to a desired particle size in advance, and a component B that is incompatible with A,
A and B are melt-mixed above their melting temperature at a mixing ratio where B forms a continuous phase and A forms a dispersed phase, and A is in a dispersed state with a mutual particle spacing. A first step in which each particle of A forms a stable spherical shape, and then the mixture is cooled and solidified, and this is immersed in a solvent S, which is a poor solvent for A and a good solvent for B, to disintegrate it. , a second step in which B is dissolved in the solvent S to obtain a suspension in which spherical particles of A are dispersed, and a third step in which microspheres of A are separated from the suspension, and the particle size is 0.01 μm. Thermoplastic resin microspheres of 1000 μm are obtained. Thermoplastic resin A in the present invention is a base material for forming microspheres. Preferred examples of thermoplastic resin A include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyamides such as nylon 6, nylon 66, polyesters such as polyethylene terephthalate, polycarbonate, polymethyl methacrylate, polytetrafluoroethylene, polybutylene, etc. Examples include vinylidene dihydride, polyvinyl acetate, polyacetal, polysulfone, acrylonitrile-styrene copolymer, ethylene to vinyl acetate copolymer, ethylene to acrylic acid copolymer, ethylene to propylene copolymer, thermoplastic elastomer such as styrene to butadiene brosoxypolymer, and the like. Component B in the present invention forms a continuous phase for dispersing thermoplastic resin A to form microspheres. Preferred examples of component B include, in addition to the above-mentioned thermoplastic resin A, polyalkylene oxides such as polyethylene oxide, polyethylene glycol, polyvinyl alcohol, polyvinyl alcohol, polyvinyl alcohol, wax, natural rubber, synthetic rubber such as polybutadiene, Styrene-butadiene copolymer rubber, petroleum resins, etc. can also be used singly or in combination. However, not all of the exemplified thermoplastic resins A and component B can be used in any combination, but combinations in which A and B are incompatible must be selected. In the present invention, an incompatible combination of A and B may be selected as follows. 30 volume units of thermoplastic resin A and 70 volume units of component B are melt-mixed at a temperature higher than the melting temperature of A and B, and the molten mixture is hot press molded to a thickness of Q, 5.
m m sheet, immersed in solvent S, which is a poor solvent for A and a good solvent for B, and stirred for 1 hour, and the sheet collapses to form a suspension, A and B are compatible. This is a unique combination. In the present invention, when the thermoplastic resin A or component B is dissolved in the solvent at the use temperature to a concentration of 1 weight or more,
A solvent is said to be a good solvent for A or B, and a solvent is said to be a poor solvent for A or B if it dissolves at a concentration of less than 1 ml. This dissolution test is performed using a 0.5 m thick film in a solvent at a given temperature.
Judgment can be made by adding 1% by weight of a film or powder sample of about 200 m in size and stirring for 2 hours. In the present invention, the mixing ratio in which B forms a continuous phase and A forms a dispersed phase is usually a mixing ratio in which B is 50 volume units or more and A is less than 50 volume units. This can be determined as follows. A and B, which are not compatible with ready-to-plate, are melt-mixed at a predetermined mixing ratio at a temperature higher than the melting temperature of A and B, and the molten mixture is hot press-molded to a thickness Q,
A 5 mm sheet is immersed in solvent S, which is a poor solvent for A and a good solvent for B, and stirred for 1 hour.When the sheet collapses to form a suspension, the mixing ratio is such that B is continuous. Even if it can be determined that the mixing ratio is such that A forms a dispersed phase, it is necessary to melt and mix A and B at a temperature higher than the melting temperature of A and B in the present invention. you should do,
The structure of the mixture in which A becomes fine microspheres and is dispersed in phase B cannot be changed. In the present invention, the method of melt-mixing is not particularly limited. For example, it can be carried out using a roll, a Banbury mixer, a kneader, a single-screw extruder, a twin-screw extruder, or the like. In the present invention, the molten mixture of A and B may be cooled and then immersed as it is in a solvent S that is a poor solvent for A and a good solvent for B. In this case, the molten mixture may be cooled and then crushed using a crusher or the like, pelletized using a pelletizer, formed into a sheet using an extruder, a roll, etc., and then immersed in the solvent S. In addition, when the molten mixture of A and B is heated above the melting temperature of A and B,
It may be immersed in the solvent S after being heat treated in a state where no shear deformation force is applied for up to 2 hours. In this case, during the heat treatment in the molten state, the A phase becomes a perfect sphere, and the human phase particles aggregate to form a perfect sphere as the particle size increases. Therefore, by controlling the heat treatment time, the particle size can be increased. The heat treatment method is not particularly limited. For example, the molten mixture is shaped into a crusher-pulverized product, pellet, sheet, etc., placed in a constant temperature bath set at a predetermined temperature higher than the melting temperatures of A and B, and left to stand for a predetermined period of time. In this case, air may be used, but if the time is long, deterioration can be prevented by heat treatment in nitrogen gas or a poor solvent of A and B. In addition, as heat treatment methods, A and B
The molten mixture is formed into a sheet or strand by extrusion molding, inflation molding, roll molding, etc.
The time required for the molded product to cool and solidify may be adjusted by controlling the cooling conditions or by heating. It should be noted that if the heat treatment time is longer than 1 hour, deterioration will occur, which is not preferable. In the present invention, when a molten mixture of A and B is immersed in a solvent S and stirred, the molten mixture collapses into microspheres of thermoplastic resin A because component B forming the continuous phase is dissolved. You can get a cloudy suspension. The method for separating the microspheres of A from the suspension is as follows:
Not particularly limited. For example, it can be carried out by a centrifugation method, a filtration method, a sedimentation method, a floating separation method, an evaporation method, etc. At this time, it is desirable to wash with solvent S several times. The shape and particle size of the microspheres of A thus obtained are as follows:
It can be observed and measured using a scanning electron microscope, transmission electron microscope, etc. Example-1 1.3 Ky polyethylene glycol powder was added to 6-nylon powder 1 of 1 μm to 10 μm that had been mechanically crushed in advance, and after being dispersed as uniformly as possible in a blender, the mixture was heated in a unit set at 230°C. This was formed into a sheet using a screw extruder. After leaving the sheet in a constant temperature bath at 230°C for 30 minutes, it was dissolved in water and 1μ of nylon 6 was added.
A suspension in which beautiful true spheres of m to 10 μm were suspended was obtained. Example-2 1.8 KP polyethylene oxide powder was added to 1 second of Teflon powder of 2 μm to 6 μm that had been mechanically crushed in advance, and after being dispersed as uniformly as possible in a blender, it was placed in a kneader set at 320°C. knead for 5 minutes,
This mass was dissolved in water to obtain a suspension in which beautiful Teflon spheres of 2 μm to 6 μm were suspended.

Claims (1)

[Claims] Thermoplastic resin composition A, which has been mechanically pulverized in advance to a desired particle size, and component B, which is incompatible with A, are mixed at a mixing ratio such that B forms a continuous phase and A forms a dispersed phase. Then, A and B are melted and mixed at a temperature higher than the melting temperature of A and B, so that A is in a dispersed state with a mutual particle spacing, and then this is left to stand for less than 1 hour, so that each particle of A forms a stable spherical shape. First step: Next, the mixture is cooled and solidified, and it is immersed in a solvent S, which is a poor solvent for A and a good solvent for B, to disintegrate it, so that B is dissolved in the solvent S, and the spherical particles of A are dissolved. A method for producing thermoplastic resin microspheres, which comprises sequentially performing a second step of obtaining a suspension in which A is dispersed, and a third step of separating the microspheres of A from the suspension.