JPH075742B2 - 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 volume average particle size distribution (hereinafter, simply referred to as particle size distribution) of the raw material resin powder having substantially the same particle size. 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 as a scrubbing agent to be blended into various cosmetics and also as an ink, paint, adhesive, etc. A material that can be effectively used as a raw material is provided.

(Prior Art) As a method for producing a spherical thermoplastic resin powder, a raw resin and components that are incompatible with the raw resin are melt-mixed at a melting temperature above each other 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 (JP-A-53-140358) is 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, 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 stream is required, heat loss is large and energy consumption 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 crushed and classified by, for example, a mechanical crushing method as a raw material, and changes the spherical shape of the resin powder from an amorphous shape to a spherical shape. The present invention provides a method for producing spherical resin powder having substantially the same particle size distribution,
Further, the inventors have found a method for producing spherical resin powder of 1 micron or more and 1000 micron or less, which has been conventionally difficult to produce, by a simple operation.

(Problems to be solved by the invention) The resin powder having a particle size of about 1 to 1000 microns manufactured by the mechanical pulverization method has an irregular shape, and particles having a sharp portion may be formed depending on the manufacturing conditions. When used as a scrubbing agent, it does not give a rough feeling when used. Further, when it is used as a raw material for inks, paints, pressure-sensitive adhesives, etc., there may be a problem in smoothness during coating, 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 sphericalized, a spherical resin powder having a smooth feeling in use is provided. Is possible.

(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, an amorphous thermoplastic resin powder was used as a raw material. And using a solvent that is incompatible with this raw material resin powder as the medium,
In the presence of ethylene-acrylic acid copolymer, which is a dispersant, is hypothesized to stir above the melting temperature of the raw material resin powder, preferably from the melting temperature to the melting temperature plus 50 ° C, and then cool to below the melting temperature. As a result, they found that spherical thermoplastic resin powder was obtained, and completed the present invention.

In order to produce the desired 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 additives is effective in dispersing the resin powder in the solvent and preventing secondary agglomeration.

Subsequently, the raw material resin powder is heated to a temperature higher than the melting temperature with stirring, usually 1 to 10 minutes, preferably 1 to 5 minutes, and then cooled. The heating time can be 10 minutes or more, but 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 spheroidizing the particles 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,
Wash with water and dry 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 an indefinite shape resin powder obtained by mechanical pulverization, freeze pulverization or the like. Types of resin include polyethylene, polypropylene, ethylene-propylene copolymer, polystyrene, nylon, styrene-acrylic copolymer, ethylene-acrylic acid copolymer, etc. , Acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacryl Examples include nitrile and acrylamide.

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 incompatible with the raw material resin powder may be any solvent which does not substantially swell or dissolve the raw material resin powder used. For example, when polyethylene is used as the raw material resin, other than water,
Ethylene glycol, propylene glycol, etc., among which water can be used most advantageously.

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 when the amount of action is 50 parts by weight or less, the resin concentration is too high and it is difficult to stir and mix sufficiently, and the use of 2000 parts by weight or more reduces the production amount compared to the size of the equipment. It is not preferable.

The ethylene-acrylic acid copolymer as the dispersant used in the present invention is a polymer obtained by polymerizing ethylene and acrylic acid under high pressure, for example. It has the structure of and acrylic acid is irregularly bonded to ethylene.
It contains 3 to 20% by weight of acrylic acid. The amount of the dispersant used is preferably in the range of 0.5 to 50 parts by weight with respect to 100 parts by weight of the raw material resin powder. If the addition amount is less than that, the effect of preventing the resins from sticking to each other during melting does not appear. It is uneconomical since the effect does not change even if added above.

The ethylene-acrylic acid copolymer may be partially neutralized with caustic soda, caustic potash, ammonia or the like. The degree of neutralization at that time is 0 to 90% of the carboxyl group of acrylic acid contained in the ethylene-acrylic acid copolymer.
It is preferably about the same.

Neutralization is preferably performed in a separate container in advance, but after the ethylene-acrylic acid polymer is placed in a container for spheroidizing the resin, the neutralizing agent should be added in the required amount. You can also

In order to stabilize the resin powder in the solvent, it is often effective to use an emulsifier, for example, a commercially available surfactant which is usually used, 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 a temperature at which the resin starts to have fluidity in a solvent that is incompatible with the raw material resin powder. In industrial practice, it is preferable to appropriately select the combination of the raw material resin powder and the solvent so that the melting temperature does not exceed the boiling point of the solvent, but there is no particular limitation 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 to obtain the product spherical resin powder.

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

Example 1 In a 500 ml four-necked flask, 200 g of ethylene glycol, 2.5 g of an emulsifier (manufactured by NOF Corporation, trade name; Rapisol B-80), a dispersant (manufactured by Iron Manufacturing Chemical Co., trade name: Zyksen N, ethylene-acrylic acid co-weighing) As a combined product, 48 g of a 25% by weight aqueous acid solution containing 20% by weight of acrylic acid and having a concentration of 25% by weight of the carboxyl groups in the acrylic acid portion neutralized, and 40 g of amorphous polyethylene powder were mixed and stirred. After that, while continuing stirring, the internal temperature
Heat up to 110 ° C.

Stir for 10 minutes while maintaining the internal temperature at 110 ° C, then cool to 80 ° C. After filtration, washing with water and drying, a spherical ethylene powder having a particle size distribution substantially the same as that 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 In a 500 ml four-necked flask, 200 g of propylene glycol, 2.5 g of an emulsifier (manufactured by NOF CORPORATION, trade name; Pyrazole B-80), 48 g of a dispersant (manufactured by Iron Manufacturing Chemical Co., Ltd., trade name: Saixen N), amorphous polypropylene powder 40 g was charged and mixed by stirring.

Then, the temperature was raised until the internal temperature reached 170 ° C. while continuing stirring. Stir for 10 minutes while maintaining the internal temperature at 170 ℃, then
Cooled to 0 ° C. After filtration, washing with water and drying, a shaped polypropylene powder having substantially the same particle size distribution as 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 spherical polypropylene powder obtained.

Examples 3 to 6 Example 2 except that the type of the amorphous thermoplastic resin powder was changed and the spheroidizing temperature was set to 10 to 20 ° C. higher than the melting temperature of the raw material resin.
Spherical thermoplastic resin powder was obtained by performing the same treatment as described above. 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 7 400 g of water, 40 g of emulsifier (Asahi Denka, trade name; Pluronic F108), dispersant (Dow Chemical, trade name; EAA XO-2375-33) 4 g, amorphous polyethylene powder 80 g in the stainless steel autoclave of Example 1 Were charged and mixed with stirring. Then, the temperature was raised until the internal temperature reached 110 ° C while continuing stirring. The mixture was stirred for 10 minutes while maintaining the internal temperature at 110 ° C, and then cooled to 80 ° C. After filtration, it was washed with water and dried to obtain spherical polyethylene powder. The particle size distribution of the spherical polyethylene powder was substantially the same as that of the raw polyethylene powder.

(Effects of the Invention) In the present invention, a simple operation of dispersing and melting 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 Since it is possible to produce a spherical resin powder having a particle size distribution similar to that of the raw material resin powder, its industrial significance is great.

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. It is also expected to be used as a raw material for inks, paints and adhesives.

[Brief description of drawings]

FIG. 1 is an 80 × 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.

Continuation of the front page (56) References JP-A 61-31435 (JP, A) JP-A 60-13816 (JP, A)

Claims (9)

[Claims] 1. 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, using an amorphous thermoplastic resin powder as a raw material,
Spherical heat characterized by using a solvent that is not compatible with the raw material resin powder as a medium, in the presence of an ethylene-acrylic acid copolymer that is a dispersant, by heating and stirring above the melting temperature of the raw material resin powder, and then cooling. Manufacturing method of plastic resin powder. 2. The method according to claim 1, wherein the amorphous thermoplastic resin powder is polyethylene. 3. The method according to claim 1, wherein the amorphous thermoplastic resin powder is polypropylene. 4. The method according to claim 1, wherein the amorphous thermoplastic resin powder is polystyrene. 5. The method according to claim 1, wherein the amorphous thermoplastic resin powder is nylon. 6. The method according to claim 1, wherein the amorphous thermoplastic resin powder is a styrene-acrylic copolymer. 7. The method according to claim 1, wherein the amorphous thermoplastic resin powder is an ethylene-acrylic acid copolymer. 8. The medium particle size of the amorphous thermoplastic resin powder is 1.
The method according to claim (1), wherein the method is not less than micron and not more than 1000 micron. 9. The method according to claim 1, wherein the solvent incompatible with the amorphous thermoplastic resin powder is water.