JPH0717833B2 - Method for treating polyamide particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a treatment method for obtaining polyamide spherical particles having a smooth surface and a good feel.

[Conventional technology]

Polyamide fine particles are conventionally known as, for example, base particles for cosmetics.

The fine particles can be obtained, for example, by rapidly polymerizing laurolactam in the presence of an alkali metal catalyst or by precipitating polyamide in a powder form from a solvent.

[Problems to be Solved by the Invention]

Polyamide spherical particles are used as a raw material for cosmetics because they have a moist feel when touched by hand as compared with inorganic fine particles such as silica powder.

However, when used as dispersed particles such as lotion, it is desirable to further improve the ride on the skin and the slimy feel, and to prevent the solidification of the powder itself and the solidification of the powder in the powder dispersion liquid. ing.

The present invention provides a treatment method for improving these points, for obtaining polyamide particles which have a moist feel and do not cause powder solidification.

[Means for Solving the Problems]

That is, the method for treating polyamide particles of the present invention has an average particle size of 0.
It is characterized in that the surface of polyamide spherical particles having a particle size of 1 to 30 μm is coated with polysiloxane and then heat-treated at 100 ° C. or higher.

Hereinafter, the present invention will be specifically described.

The polyamide in the present invention is a polyamide having a repeating unit having 6 or more carbon atoms, such as nylon 6,
Nylon 66, Nylon 610, Nylon 611, Nylon 612, Nylon 11, Nylon 12 and their copolymers, etc. can be mentioned, but due to the ease of making spherical particles and the wide range of applications,
Nylon 12 is preferred.

For example, in the case of nylon 12, polyamide spherical particles can be obtained by polymerizing laurolactam using liquid paraffin as a solvent and an alkali metal or phosphorus-based initiator.

The average particle diameter of the polyamide spherical particles needs to be 0.1 to 30 μm, and preferably 3 to 20 μm. The average particle size is 0.
If it is less than 1 μm, the characteristics of the spherical particles cannot be exhibited, and the touch feeling when touched with the hand becomes poor, and if it exceeds 30 μm, a foreign body sensation is felt.

The polysiloxane in the present invention is not particularly limited, and those commercially available as silicone oil can be used.

Polysiloxane is generally With a repeating unit of R, R'is hydrogen, an alkyl group,
It can be modified into an active one by changing it to an amino group or the like, but in the present invention, dimethylpolysiloxane which is chemically inactive and is thermally stable is preferable.

Polysiloxane has various viscosities depending on its molecular weight, and various kinds of polysiloxane are commercially available.
(25 ° C) is preferable, more preferably 1,000 to 8,000 CS
(25 ° C). The polysiloxane having a viscosity of 500 CS or less tends to reduce the caking property-preventing effect, and the polysiloxane having a viscosity of more than 10,000 CS makes it difficult to uniformly coat the surface of fine particles.

Examples of the method for coating the surface of the polyamide spherical particles with polysiloxane include a dry blending method and a wet blending method.

The dry blending method is a method of kneading polyamide particles and polysiloxane in a Henschel mixer or the like, and is effective in the case of polysiloxane having a relatively low viscosity.

The wet blending method is a method in which polysiloxane is diluted with, for example, a fluorine-based, aromatic-based or aliphatic-based solvent, the polyamide particles are kneaded in a mixer, and then the solvent is removed. This method is effective for a polysiloxane having a relatively high viscosity.

The amount of polysiloxane used is preferably 1 to 50% by weight, more preferably 4 to 15% by weight, and particularly preferably 6 to 10% by weight, based on the polyamide particles. If it is less than 1% by weight, the effect of coating the surface of the particles to improve the touch is poor, and if it is more than 50% by weight, the sticky feeling is preceded and the feeling of the powder is lost.

In the treatment method of the present invention, it is necessary to heat treat the particles by the above-mentioned dry blending or after wet blending.

The temperature of this heat treatment is 100 to 150 ° C and the time is 1
-50 hours, especially 5-30 hours are preferred. Although it is unknown what kind of change is caused by the heat treatment, experimentally, if the heat treatment is not performed, the feel is not improved and the effect of preventing caking is not obtained.

If the treatment temperature is less than 100 ° C, there is no anti-caking effect,
Further, when the temperature exceeds 150 ° C, the polyamide particles are discolored and the commercial value is lost.

This heat treatment can be performed under normal pressure, but it is more preferable to perform under reduced pressure.

[Work]

By heating the polyamide particles coated with polysiloxane, a small amount of low molecular weight substances in the polysiloxane may be removed, and this phenomenon is considered to be large when heat-treated under reduced pressure. Further, in dimethylpolysiloxane or the like, it may be considered that the water repellency may be produced by directing the methyl group to the surface. Further, in the case of polysiloxane having hydrogen, amino groups, etc., some chemical reaction with polyamide may occur.

Although neither has been confirmed, simply coating the polysiloxane does not provide the moist feel and anti-caking effect, which are the objects of the present invention.

〔Example〕

Example 1 The amount of dimethylpolysiloxane (“SH200” manufactured by Toray Silicone Co., Ltd.) and 5,000CS (25 ° C.) was changed as shown in Table 1, and polyamide particles (“SP-500” manufactured by Toray Co., Ltd.) were averaged. After mixing with a Henschel mixer for 5 minutes at room temperature with 100 parts by weight of a particle size of 5 μm, 120 ° C. for 24 hours in a 5 Torr vacuum dryer.
It heat-processed and the result of Table 1 was obtained.

Moisture: Sensory test by human O: Good, Δ: Slightly good, X: Poor Caking property: Particles were put in a glass container as a 20% dispersion liquid in 55% ethanol and shaken for 50 hours.

○ ... Caking does not occur only by sedimentation.

Δ: Caking occurs, but re-disperses due to re-vibration.

X: Caking occurred and redispersion was difficult. Example 2 The same operation as in Example 1 was performed except that the viscosity of silicone was changed and the addition amount was 8%.

The results are shown in Table 2.

Example 3 The same operation as in Example 1 was performed except that the amount of silicone added was 8% by weight and the heat treatment temperature and time were changed.

The results are shown in Table 3.

However, particles of Run Nos. 9 and 10 treated with 150 ° C turned yellow.

〔The invention's effect〕

The treated polyamide particles of the present invention give a moist feel and prevent caking, and are therefore particularly suitable as a cosmetic material.

Claims (1)

[Claims] 1. A method for treating polyamide particles, which comprises coating the surface of spherical polyamide particles having an average particle diameter of 0.1 to 30 μm with polysiloxane and then heat-treating at 100 ° C. or higher.