JPS619433A - Production of thermoplastic resin microsphere - Google Patents

Abstract

PURPOSE:To facilitate the production of the titled microspheres useful in the production of sintered microspheres, etc., by disintegrating a melt-blend of resin A and component B incompatible with resin A by immersion in a solvent which is a poor solvent for resin A but is a good solvent for component B and separating particles of resin A. CONSTITUTION:A matrix thermoplastic resin A (e.g., PE or PVC) is melt-blended with a component B incompatible with resin A (e.g., polyethylene oxide) at a temperature higher than any of the melting points of resin A and component B and a mixing ratio at which component B forms a continuous phase and resin A forms a dispersed phase. This melt blend is cooled directly or after it is heated at a temperature higher than any of the melting points of resin A and component B within 2hr. The obtained cooled blend is disintegrated by immersion in a solvent S which is a poor solvent for resin A but is a good solvent for component B (e.g., water) to obtain a suspension comprising solvent S in which component B is dissolved and particles of resin A are dispersed. The particles of resin A are separated from the dispersion. In this way, it is possible to obtain the titled microspheres of a particle diameter of 0.01-100mu suitable for use in, for example, sintered microfilters, fluidized bed coatings, electrostatic coatings, sol coatings, solid lubricants, and cosmetic additives.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing thermoplastic resin microspheres.

More specifically, it is used for applications such as sintered microfilters, sintered battery separators, fluidized immersion coatings, electrostatic coatings, sol coatings, materials for Hypuri and do (microcomposite materials), solid lubricants, and cosmetic additives. Particle size suitable for 0゜0
The present invention relates to a method for producing thermoplastic resin microspheres of 1 μm to 100 μm.

Conventionally, known methods for producing thermoplastic resin microspheres include a latex production method using an emulsion polymerization method, a mechanical crushing method, and a precipitation method in which a thermoplastic resin is dissolved in a solvent and then cooled.

However, the emulsion polymerization method is difficult to produce a large particle size latex with a particle size of 5 μm or more, and requires complicated means such as a freeze aggregation method and a pressure aggregation method. It is still difficult to isolate emulsion particles in their original particle size, and they tend to aggregate. Furthermore, in the emulsion polymerization method, it is difficult to add fillers, plasticizers, etc. inside the thermoplastic resin microspheres for the purpose of improving physical properties.

However, with mechanical crushing, it is difficult to obtain truly spherical microspheres, and it is also difficult to control the particle size.

The precipitation method requires a long period of time, requires strict control of conditions, tends to produce coarse lumps, and has an extremely low yield.

The present invention provides a method for producing thermoplastic resin microspheres without the above-mentioned drawbacks. That is, in the present invention, a base thermoplastic resin A and a component B that is incompatible with A are melted at a temperature equal to or higher than the melting temperature of A and B at a mixing ratio such that B forms a continuous phase and A forms a dispersed phase. The molten mixture is cooled as it is, or heat treated at a temperature higher than the melting temperature of A and B for up to 2 hours, then cooled, and immersed in a solvent S that is a poor solvent for A and a good solvent for B. , the molten mixture is disintegrated to obtain a suspension in which B is dissolved in a solvent S and particles of A are dispersed, and the particles of A are separated from the suspension; This is a method for producing thermoplastic resin microspheres.

Thermoplastic resin A in the present invention is a base material for forming microspheres. Preferred examples of thermoplastic resin A are:
Polyethylene, polypropylene, polyvinyl chloride polystyrene, polyamides such as nylon 6, nylon 6
6. Polyesters such as polyethylene terephthalate, polycarbonate, polymethyl methacrylate, polytetrafluoroethylene, polyvinylidene fluoride, polyhinyl acetate, polyacetal, polysulfone, acrylonitrile-styrene copolymer, ethylene-vinyl acetate copolymer, ethylene acrylic acid copolymer , ethylene-propylene copolymers, thermoplastic elastomers such as styrene-butadiene pro-7 copolymers, and the like.

Component B in the present invention forms a continuous phase in which the thermoplastic resin A is dispersed to form microspheres.

Preferred examples of component B include the above-mentioned thermoplastic resin A, as well as polyalkylene oxides such as polyethylene oxide, polyethylene glycol, polyvinyl alcohol, polybutene, wax, natural rubber, synthetic rubber, etc. Polybutadiene, styrene-butadiene copolymer rubber, petroleum resin, etc. can also be used.

However, not all of the exemplified thermoplastic resins A and component B can be used in any combination;
must choose incompatible combinations.

In the present invention, an incompatible combination of A and B may be selected as follows. Thermoplastic resin A30 by volume and component B 70 by volume are melt-mixed at a temperature higher than the melting temperature of A and B, and the molten mixture is heated and press-molded to a thickness of 0 to 5.
m'm sheet, immersed in solvent S, which is a poor solvent for A and a good solvent for B, and stirred for a period of time, and the sheet collapses to form a suspension, A and B are compatible. This is a combination without.

In the present invention, when the thermoplastic resin A or component B is dissolved in a solvent at the usage temperature to a concentration of 1% by weight or more, the solvent is said to be a good solvent for 8 or B, and is less than 1% by weight. A solvent is said to be a poor solvent for A or B if it dissolves only at a concentration of A or B.

In this dissolution test, a 0.5 mm thick sample is placed in a solvent at a specified temperature.
Judgment can be made by adding 1 weight of a film or powder sample of about 100 ml and thoroughly 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 at least 50 volume ratio and A is less than 50 volume ratio. This can be determined as follows. That is, A and B, which are not compatible, are melt-mixed at a predetermined mixing ratio at a temperature higher than the melting temperature of A and B, the molten mixture is hot press-molded to form a sheet with a thickness of 0.5 mm, and a poor solvent for A is formed. When the sheet is immersed in solvent S, which is a good solvent for B, and stirred for ] hours, and the sheet collapses to form a suspension, the mixing ratio is such that B forms a continuous phase and A forms a dispersed phase. It can be determined that the mixing ratio is the same.

In the present invention, when A and B are melted and mixed, it is necessary to perform the melting at a temperature higher than the melting temperature of A and B.

Otherwise, 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, Roll, Banbury mixer, Nigoo,
This can be carried out using a single-screw extruder, a twin-screw extruder, or the like.

In the present invention, after cooling the molten mixture of A and B,
It may be immersed 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 pulverized with a mill, pelletizer, etc., pelletized with a pelletizer, or formed into a pellet shape with an extruder, roll, etc., and then immersed in the solvent S.

In fact, a molten mixture of A and B may be heat-treated at a temperature higher than the melting temperature of A(!:B) for up to 2 hours in a state where no shear deformation force is applied, and then immersed in the solvent S.

In this case, during the heat treatment in the molten state, the A phase becomes more perfectly spherical, and the A phases coagulate with each other to grow into a true spherical shape with a large particle size.

Therefore, by controlling the heat treatment time, the particle size can be easily controlled.

The heat treatment method is not particularly limited. For example, the molten mixture is formed into a shape such as a pulverized product, a pellet, a sheet, etc., and placed in a constant temperature bath set at a predetermined temperature higher than the melting temperature of A and B, and allowed to stand for a predetermined period of time. In this case, it may be in air, but if the time is long, it may be in nitrogen gas or A.
Deterioration can be prevented by heat treatment in a poor solvent of and B.

As an excellent heat treatment method, a molten mixture of A and B is formed into a sheet or strand shape by extrusion molding, inflation molding, roll molding, etc., and the time in which the molded product is cooled and solidified is controlled by controlling the cooling conditions. It may be adjusted by grinding or heating. It should be noted that if the heat treatment time is 2 hours or more, deterioration will occur, which is not preferable.

In the present invention, when the molten mixture of A and B is immersed in the solvent S and stirred, the molten mixture collapses because the component B forming the continuous phase dissolves, and the thermoplastic resin A
A suspension of microspheres is obtained.

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.

In the present invention, in addition to thermoplastic resin A and component B,
If necessary, fillers such as calcium carbonate, silicon dioxide, titanium dioxide, clay, calcium sulfate, carbon plastic, and glue, plasticizers, antioxidants, ultraviolet absorbers, colorants, crosslinking agents, etc. are added as appropriate. By adding a certain amount, it is also possible to produce microspheres of type A containing the additive.

In order to facilitate the formation of microspheres,
Appropriate amounts of surfactants, polymers, oligomers, etc. may be added.

Next, the present invention will be explained in more detail with reference to Examples.

(Example = 1) The compounding recipe shown in Table 1 was kneaded under the melt mixing conditions shown in Table 2. After cooling the molten mixture, it was ground in a crusher and poured into the solvent S shown in Table 2. Soak and stir for about 30 minutes to obtain a suspension. This suspension was filtered through a microfilter to obtain nylon 6 microspheres with a sharp particle size distribution as shown in Table 2.

(Example-2) With the formulation shown in Table 2, first, polyvinyl chloride,
DOP, diptyltin malate, VT, and TN-5 (manufactured by Yoken Fine Chemical ■, lubricant) were tri-blended and left for 1 hour to impregnate the polyvinyl chloride with DOP.
The mixture was kneaded with polyethylene oxide under the melt-mixing conditions shown in Table 2, and the molten mixture was cooled, crushed with a cracker and shear, and formed into a sheet with a thickness of 1 mm using an extruder and a T-die. This sheet was immersed in the solvent S shown in Table 2 and stirred for about 20 minutes to obtain a suspension.

This suspension was filtered to obtain polyvinyl chloride microspheres having the particle size distribution shown in Table 2.

(Example-3) The T-die molded sort of Example 2 was heat-treated for 0 minutes in an air constant temperature bath at 190°C, and after cooling, the same solvent treatment as in Example 2 was carried out to obtain microscopic particles of polyvinyl chloride. I got a sphere.
These microspheres had a more perfect spherical shape than those of Example 2, and had a particle size of 1 to 6 μm, and were larger than those of Example 2, indicating that they had grown.

(Example-4) The T-die molded sheet of Example 2 was heat-treated in an air constant temperature bath at 190°C for 30 minutes, and after cooling, polyvinyl chloride with a particle size of 5 to 20 μm was prepared in the same manner as in Example 3. Microspheres were obtained. It can be seen that these microspheres grew even larger than those in Example 3. In the same manner as in Example 3, polyvinyl chloride microspheres with a particle size of 50 to 100 μm were obtained. It can be seen that these microspheres grew even larger than those of Example 4.

(Example-6 to Example-10) Using the formulation shown in Table 1, carrying out the same procedure as in Example-1 under the melt mixing conditions and solvent treatment conditions shown in Table 2,
Microspheres of thermoplastic resin A having the particle size distribution shown in Table 2 were obtained.

Claims (1)

[Claims] A base thermoplastic resin A, a component B that is not compatible with A,
is continuous and A forms a dispersed phase, melt-mixes A and B at a temperature higher than their melting temperature, cools the molten mixture as it is, or heat-treats it at a temperature higher than the melting temperature of A and B within 2 hours. After that, it is cooled and immersed in a solvent S, which is a poor solvent for A and a good solvent for B, to disintegrate the molten mixture, thereby obtaining a suspension in which B is dissolved in the solvent S and particles of A are dispersed. A method for producing thermoplastic resin microspheres having a particle size of 0.01 μm to 100 μm, which comprises separating the particles of A from the suspension.