JPH0311297B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention uses nylon 12 and nylon produced by reprecipitation method.
11, relates to a method for producing spherical powder of synthetic linear polyamide such as nylon 12/11. [Prior Art] Polyamide powder has great industrial value as a raw material for powder coatings, adsorbents, cosmetic bases, sintered molded products, and the like. In particular, the appearance of spherical powders is desired because of their handling advantages and the expansion of their range of use. Typical methods for turning polyamide into powder include mechanically pulverizing pellets or other lumps, or the so-called reprecipitation method, in which a suitable solvent is used to take advantage of the solubility difference due to temperature, or a poor solvent is added to precipitate. It is true. Mechanical pulverization methods are applicable to coarse pulverization, but they have limitations in making polyamides finer and have the disadvantage that the resulting powder is angular and has many irregularities or whisker-like protrusions. The reprecipitation method can generally produce powder with a finer particle size, and several methods have been proposed so far. [Problems to be Solved by the Invention] It is known that ethanol, butanol, propylene glycol, benzyl alcohol, and the like can be used as solvents in the reprecipitation method. However, when lower alcohols such as ethanol and butanol are used, there are drawbacks such as the need for high pressure or the addition of special inorganic compounds. Furthermore, polyamide powder obtained using propylene glycol, benzyl alcohol, etc. has the disadvantage that the powder contains a large amount of amorphous secondary agglomerated particles. [Means for Solving the Problems] As a result of repeated experiments in order to improve the above-mentioned drawbacks in the reprecipitation method, the present inventor found that the viscosity of the medium affects the shape of the polyamide powder. That is, they discovered that by increasing the viscosity of the medium, the shape of the powder becomes more spherical, and based on this knowledge, they completed the present invention. The present invention uses an ester solvent in which 2.0 to 10.0 wt% of ethyl hydroxyethyl cellulose is dissolved as a medium, adds bulk polyamide such as pellets to the medium, and stirs the polyamide at a temperature higher than the melting point of the polyamide to thoroughly mix and disperse the mixture. The method for producing spherical polyamide powder is characterized in that the molten polyamide is solidified by cooling and then separated from the medium. It is therefore an object of the present invention to provide a method for producing substantially spherical polyamide microparticles. Polyamides used in the present invention include homopolymers or interpolymers of nylon 11, nylon 12, nylon 12/11, and the like. Examples of ester solvents used in the present invention include 2-ethylhexyl acetate, butyl benzoate, dimethyl phthalate, diethyl phthalate, and dibutyl phthalate. These may be used alone or in combination of two or more. Ethyl hydroxyethyl cellulose, which increases the viscosity of the medium by adding and dissolving it in these solvents, is manufactured by Hercules Co., Ltd.
There are EHEC-High, ETHC-EXTraHigh, etc. The concentration of these ethylhydroxyethylcellulose compounds ranges from 2.0wt% to 10.0wt% in the medium;
Preferably 3.0wt% to 7.0wt. If it is less than 2.0wt%, the viscosity of the medium cannot be increased sufficiently and the resulting nylon powder will have a spherical shape that is different from the spherical shape.If it exceeds 10.0wt%, the viscosity of the medium will become high and stirring will be difficult. As a result, sufficient dispersion cannot be achieved, resulting in unsatisfactory atomization. The mixing ratio of the medium and polyamide used in the present invention is not particularly limited, but generally 1 to 50 wt% of the polyamide and 50 to 99 wt% of the medium are mixed. According to the present invention, the shape and particle size distribution of the powder can be controlled by appropriately selecting and combining the polyamide mixing ratio, medium viscosity, stirring conditions, etc. The polyamide and the medium can be separated directly or by diluting with ethanol or acetone to lower the viscosity and then filtering.The filtered powder is then thoroughly washed with water, ethanol, acetone, etc., and then dried in a vacuum dryer. I can do things. Example 1 Nylon 12 (Daicel product name L-21400) 15
g and 85 g of dimethyl phthalate dissolved with 3.5 g of ethyl hydroxyethyl cellulose (trade name: EHECHigh, manufactured by Hercules), stirred at 200°C for 30 minutes, cooled while stirring, and filtered under reduced pressure at approximately 100°C. The filtered powder was thoroughly washed with ethanol and then dried in a vacuum dryer at 60°C for 3 hours. When 14.9 g of the obtained nylon powder was observed under an electron microscope, it was found to be spherical fine particles with a size of 10 to 60 microns. Examples 2 to 4 Experiments similar to those in Example 1 were conducted by changing the composition of the medium. The results are shown in Table-1. Comparative example 1 Nylon 12 (product name L-21400 manufactured by Daicel) 15
g with 85 g of dimethyl phthalate and heated at 200℃ for 30
After stirring for a minute, the mixture was cooled while being stirred, but during cooling, the entire nylon that had been melted and dispersed gelled into lumps. Comparative Example 2 Table 1 shows the results of an experiment similar to Comparative Example 1 using dibutyl benzoate instead of dimethyl phthalate.
Shown below.

【table】

〔Effect of the invention〕

Since the polyamide powder obtained according to the method of the present invention is a homogeneous spherical powder, it has good fluidity and is easy to handle, unlike the conventional powder with a uniform shape. It's advantageous. Such homogeneous spherical particles are suitable as powder coatings, cosmetic bases, and solid lubricants for sliding parts.

Claims (1)

[Claims] 1 Using an ester solvent in which 2.0 to 10% by weight of ethylhydroxyethyl cellulose is dissolved as a medium, add polyamide to this, stir at a temperature higher than the melting point of the polyamide to thoroughly mix and disperse, and then cool. A method for producing spherical polyamide powder, which comprises solidifying the molten polyamide and then separating it from a medium.