JPH0737534B2 - Method for producing spherical thermoplastic resin powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Use) The present invention uses thermoplastic amorphous resin powder as a raw material, and has a particle size substantially the same as the volume average particle size distribution (hereinafter, simply referred to as particle size distribution) of the raw material resin powder. The present invention relates to a method for producing a spherical resin powder having a distribution and a median particle diameter of about 1 to 1000 microns, and its purpose is, for example, as a scrubbing agent to be blended into various cosmetics, or a raw material for a porous ceramic material. The material that can be effectively used as is provided.

(Prior Art) As a method for producing a spherical thermoplastic resin powder, a raw resin and a component incompatible with the raw resin are melt-mixed at a melting temperature of each other or higher, and then cooled to obtain a spherical thermoplastic resin powder. (JP-A-60-192728) or a method of dispersing and swirling a thermoplastic resin in a pressurized hot air stream to make it spherical (JP-A-53-140358) and the like are known.

In the former case, it is stated that particles with a particle size of 0.01 to 100 microns can be obtained, but it is difficult to obtain spherical particles with a particle size of 50 microns or more, and the particle size distribution is wide. There is. In the latter case, particles with a particle size of several tens of microns to 100 microns can be obtained, but since the operation of dispersing and swirling in a pressurized hot air flow is required, heat loss is large and the amount of energy consumed is large. It cannot be said that the method is industrially advantageous because the device is complicated.

Unlike the conventional method, the present invention uses an inexpensive thermoplastic resin powder pulverized and classified by, for example, a mechanical pulverization method, which is available at a low cost, as a raw material, and changes the shape of the resin powder from an amorphous shape to a spherical shape, and It provides a method for producing a spherical resin powder having substantially the same particle size distribution,
In addition, it has been difficult to manufacture in the past.
The inventors have found a method capable of producing spherical resin powder having a particle size of not more than micron by a simple operation.

(Problems to be Solved by the Invention) For example, a resin powder having a particle size of about 1 micron to 1000 microns produced by a mechanical pulverization method has an irregular shape,
Particles having a sharp portion are formed depending on the production conditions, and therefore when used as a scrubbing agent for cosmetics, it is not preferable because it has a rough feeling during use. Further, when it is used as a raw material of a porous ceramic material, it is difficult to perform the closest packing, and therefore the porosity cannot be increased, which is not preferable.

By the method of the present invention, since the amorphous thermoplastic resin powder of 1 micron or more and 1000 micron or less manufactured by the mechanical pulverization method or the like can be spheroidized, a spherical resin powder having a smooth feeling in use is provided. Is possible. Further, when it is used as a raw material of a porous ceramic material, the closest packing becomes possible, and as a result, a material having a large porosity can be obtained.

(Means for Solving Problems) The present inventors have conducted various studies on a method for producing a spherical thermoplastic resin powder having a medium particle size of 1 micron or more and 1000 microns or less, and as a result, the amorphous thermoplastic resin powder is used as a raw material. And using a solvent that is incompatible with this raw material resin powder as a medium,
In this, a dispersant, for example, in the presence of an ethylene-acrylic acid copolymer, heated to above the melting temperature of the raw material resin powder and stirred,
After that, it was found that a spherical thermoplastic resin powder can be obtained by cooling to below the melting temperature, and a patent application was filed.
(Japanese Patent Application No. 61-38125) However, the spherical thermoplastic resin powder thus obtained contains a small amount of ethylene-acrylic acid copolymer, and its use is restricted, for example, cosmetics. It causes inconvenience when used for. In view of such circumstances, as a result of further investigation, in place of the conventionally used dispersant, ethylene-acrylic acid copolymer, an inorganic substance having a particle diameter of 1 micron or less which is inert to the solvent and the raw material resin powder is used. It was found that the use of the dispersant has the same effect as the case of using the ethylene-acrylic acid copolymer, and that there is no restriction on the use of the product spherical resin powder, and the present invention has been completed.

In order to produce the target spherical resin powder, first, a solvent incompatible with the raw material resin powder is added, and the mixture is stirred and mixed at room temperature. At this time, a dispersant and, if necessary, an emulsifier are added. This is because the addition of the emulsifier is effective in dispersing the resin powder in the solvent and preventing secondary aggregation.

Subsequently, the raw material resin powder is heated to a melting temperature or higher under stirring, preferably from the melting temperature to a temperature of the melting temperature plus 50 ° C.,
Usually, the mixture is stirred for 1 to 10 minutes, preferably 1 to 5 minutes and then cooled. If necessary, heating time can be 10 minutes or more,
In some cases, fusion of the resin powder is likely to occur, which is not preferable. It is considered that the addition of the dispersant is effective in making the particles spherical when the resin powder is melted in the latter stage, and acts so that the rounded particles do not stick to each other. After cooling, filtration, washing with water and drying are carried out to obtain the desired spherical thermoplastic resin powder.

The raw material resin powder used in the present invention is a resin powder which is indefinite during polymerization, or a resin powder having an indefinite shape obtained by mechanical pulverization, freeze pulverization and the like.

The types of resin include polyethylene, polypropylene,
An ethylene-propylene copolymer, polystyrene, nylon, a styrene-acrylic copolymer, an ethylene-acrylic acid copolymer, etc., and acrylic monomers that copolymerize with styrene include acrylic acid, methyl acrylate, and acrylic acid. Ethyl, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate,
Methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, and the like.

Inorganic pigments such as carbon black, titanium oxide, iron oxide, and silica, metal powders such as iron, copper, nickel, and cobalt, and organic substances such as ultraviolet absorbers and heat stabilizers may be contained in the raw material resin powder. The solvent which is not compatible with the raw material resin powder may be a solvent which does not substantially swell or dissolve the raw material resin powder to be used. For example, when polyethylene is used as the raw material resin, other than water,
Ethylene glycol, propylene glycol, etc., of which water is most advantageously used.

The amount of solvent used is 50 to 200 with respect to 100 parts by weight of the raw material resin powder.
0 parts by weight is preferable, and if the amount used is 50 parts by weight or less, the resin concentration is too high and it is difficult to sufficiently stir and mix, and if 2000 parts by weight or more is used, the production amount becomes smaller than the size of the apparatus. It is not preferable.

The dispersant used in the present invention is an inorganic substance having a particle diameter of 1 micron or less, preferably 300 millimicron or less, which is inert to the solvent and the raw material resin powder, and its type is hydrophobic anhydrous. Examples thereof include silicic acid, aluminum oxide, titanium oxide, magnesium oxide, and the like. Various studies have been conducted on hydrophilic silicic acid anhydride, but the effects of the present invention cannot be achieved. The method of hydrophobizing the hydrophilic silicic acid anhydride is not particularly limited, but the hydrophobic silicic acid anhydride can be obtained by, for example, treating with alkylsilane or alkyl silicone oil. Among these dispersants,
From the point that the obtained spherical resin powder is not colored,
The hydrophobic silicic acid anhydride can be used most advantageously. The amount of the dispersant used depends on the combination of the raw material amorphous thermoplastic resin powder and the solvent, but generally the raw material resin powder 100
Good results are obtained by using an amount of 3 parts by weight or more and 100 parts by weight or less based on parts by weight.

The method of adding the dispersant can be directly charged into the processing container together with the solvent, the raw material resin powder, and the emulsifier described below, but when the method of adding the previously prepared dispersion is preferable. There is also.

In order to stabilize the resin powder in the solvent, it is often effective to use an emulsifier, for example, a commonly used commercially available surfactant, and the effect becomes remarkable especially when water is used as the solvent.

The spheroidizing treatment is performed at a temperature equal to or higher than the melting temperature of the raw material resin powder, that is, equal to or higher than the temperature at which the resin starts to have fluidity in a solvent that is incompatible with the raw material resin powder. However, raising the temperature more than necessary is not preferable because decomposition of the resin may occur.
In industrial practice, it is preferable to appropriately select the combination of the raw material resin powder and the solvent, and consider that the melting temperature does not exceed the boiling point of the solvent, but is not particularly limited as long as the container can withstand pressurization. It does not mean that

It is not necessary to use a special structure to stir the contents, and any ordinary stirrer can be used.

The treatment liquid containing the spherical resin powder obtained by the melting and stirring operation is then cooled to a temperature below the melting temperature of the resin, and this is filtered and dried, whereby the product spherical resin powder can be taken out.

(Examples) The present invention will be specifically described with reference to Examples.

Example 1 100 g of propylene glycol in a 300 ml four-necked flask,
Emulsifier (Nippon Oil & Fats, trade name; Rapisol B-80) 1.5
g, hydrophobic silicic acid anhydride having an average particle size of 16 mm as a dispersant (manufactured by Nippon Aerosil, trade name; Aerosil R-97
2) Charge 2.5g and 25g of irregular polyethylene powder, stir,
Mixed. After that, the temperature is raised until the internal temperature reaches 110 ° C. while continuing stirring. Stir for 10 minutes while maintaining the internal temperature at 110 ° C, and then cool to 80 ° C. After filtration, washing with water and drying, a spherical polyethylene powder having a particle size distribution substantially the same as the particle size distribution of the raw material resin powder was obtained. The particle size distribution of the amorphous polyethylene powder used as a raw material and the obtained spherical polyethylene powder is shown in Table 1 below.

Example 2 Polyethylene glycol (PEG
-200) 200 g, emulsifier (Atlas, trade name; Tween-20) 2.
5 g, hydrophobic silicic acid anhydride having a mean particle size of 16 mm as a dispersant (manufactured by Nippon Aerosil, trade name; Aerosil R-97
2) 6 g and 40 g of amorphous polypropylene powder were charged and mixed by stirring. Then, the temperature was raised until the internal temperature reached 190 ° C while continuing stirring. The mixture was stirred for 10 minutes while maintaining the internal temperature at 190 ° C, and then cooled to 80 ° C. After filtration, washing with water and drying, a spherical polypropylene powder having a particle size distribution substantially the same as that of the raw material resin powder was obtained. Table 2 shows the particle size distribution of the amorphous polypropylene powder used as the raw material and the obtained spherical polypropylene powder.

Examples 3 to 6 Example 1 except that the type of the amorphous thermoplastic resin powder was changed and the spheroidizing temperature was raised by 10 to 20 ° C above the melting temperature of the raw material resin.
The same treatment as above was performed to obtain a spherical thermoplastic resin powder. The particle size distribution was substantially the same as the distribution of the raw material amorphous resin powder. Table 3 shows the types of resin powder and the spheroidizing temperature.

Example 7 As a dispersant, hydrophilic titanium oxide having an average particle size of 20 millimicrons (manufactured by Nippon Aerosil Co., Ltd., trade name; Titanium Oxide p-2
A spherical polyethylene powder was obtained in the same manner as in Example 1 except that 5) was used. The particle size distribution of the amorphous polyethylene powder used as a raw material and the obtained spherical polyethylene powder is shown in Table 4 below.

Example 8 1 320 g of water in an autoclave, 4.8 g of an emulsifier (manufactured by NOF CORPORATION, trade name; Rapisol B-80), and an average particle size as a dispersant
20 g of hydrophilic titanium oxide (manufactured by Nippon Aerosil Co., Ltd., trade name; Titanium Oxide P-25) of 20 mm and amorphous polyethylene powder of 80 g were charged, and the same procedure as in Example 1 was carried out to obtain spherical polyethylene. The particle size distribution of the amorphous polyethylene powder used as the raw material and the obtained spherical polyethylene powder is shown in Table 5 below.

Example 9 A spherical polyethylene was obtained in the same manner as in Example 7 except that hydrophilic titanium oxide having an average particle size of 0.3 micron (manufactured by Ishihara Sangyo Co., Ltd., trade name: A-100) was used as a dispersant. The particle size distribution of the obtained spherical polyethylene was about the same as in Table 4.

(Effects of the Invention) In the present invention, an amorphous thermoplastic resin powder having a median particle size of 1 micron or more and 1000 micron or less obtained by, for example, a mechanical pulverization method is used as a raw material, and a Spherical resin powder having a particle size distribution similar to that of the raw material resin powder can be produced by an operation, and therefore has great industrial significance.

The spherical resin powder produced according to the present invention exerts a sufficient effect by, for example, being added to various cosmetics as a scrubbing agent. Further, it can be expected to be used as a raw material of a porous ceramic material.

[Brief description of drawings]

FIG. 1 is a 24 × photomicrograph showing the particle structure of the amorphous polyethylene powder used as the raw material in Example 1 and FIG. 2 showing the particle structure of the spherical polyethylene powder obtained in Example 1.

Claims (10)

[Claims] 1. An amorphous thermoplastic resin powder is used as a raw material,
In obtaining a spherical thermoplastic resin powder having a volume average particle size distribution substantially the same as the volume average particle size distribution of the raw material resin powder, a solvent that is incompatible with the raw material resin powder is used as a medium and is inert to the solvent and the raw material resin powder. An inorganic dispersant having a particle size of 1 micron or less is added to 100 parts by weight of the raw material resin powder.
A method for producing a spherical thermoplastic resin powder, which comprises presenting 3 parts by weight or more and 100 parts by weight or less, heating and stirring above the melting temperature of the raw material resin powder, and then cooling. 2. The method according to claim 1, wherein the inorganic dispersant is a hydrophobic silicic acid anhydride. 3. The method according to claim 1, wherein the inorganic dispersant is titanium oxide. 4. The method according to claim 1, wherein the amorphous thermoplastic resin powder is polyethylene. 5. The method according to claim 1, wherein the amorphous thermoplastic resin powder is polypropylene. 6. The method according to claim 1, wherein the amorphous thermoplastic resin powder is polystyrene. 7. The method according to claim 1, wherein the amorphous thermoplastic resin powder is nylon. 8. The method according to claim 1, wherein the amorphous thermoplastic resin powder is a styrene-acrylic copolymer. 9. The method according to claim 1, wherein the amorphous thermoplastic resin powder is an ethylene-acrylic acid copolymer. 10. The method according to claim 1, wherein the median particle diameter of the amorphous thermoplastic resin powder is 1 micron or more and 1000 micron or less.