JPS61233019A - Fine polyamide particle - Google Patents

Abstract

PURPOSE:Fine polyamide particles in spherical or almost spherical shape having many recessed parts of almost spherical surface on the surface and improved adhesion to additives and useful as a cosmetic binder, etc. CONSTITUTION:Fine polyamide particles obtained by alkali polymerizing a 6-12C cyclic lactam, e.g. omega-laurolactam, and an alkylene addition lactam, preferably an adduct of caprolactam with ethylene oxide having 1,000-20,000 molecular weight, etc., together in the presence of an alkali metal salt as a catalyst and an acyllactam or phosphorus trihalide, as a cocatalyst in a liquid paraffin medium.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to polyamide fine particles having spherical concave portions on the surface, and is applicable to binders and microcapsule base materials effective in the fields of cosmetics, pharmaceuticals, and diagnostic agents. It is something that

<Prior art> Cyclic lactams are dispersed in a suitable inert solvent, and if necessary, a dispersion aid is added, and while stirring, an alkaline substance is added as a catalyst, and if necessary, a polymerization accelerator is added. It is known that a polymer can be obtained at a temperature above the melting point of the lactam and below the softening point of the polyamide (Japanese Patent Publication No. 45-29832).

Further, the produced polymer is separated from the solvent as a powder or granules, and washed with alcohol or hot water as necessary to remove residual catalyst and unreacted substances, thereby producing a product.

Polyamide powder produced by these methods is a perfectly spherical fine particle with good sliding properties and a good feel, so it is widely used as a base material for cosmetics.

<Problems to be Solved by the Invention> Although the above polyamide fine particles have a smooth surface and good sliding properties, they have poor adhesion to pigments, ultraviolet absorbers, medicinal ingredients, etc.

Therefore, the inventors of the present invention have carried out extensive research in search of fine particles with improved adhesion of additives by changing the surface structure of the fine particles. As a result, polyamide fine particles having approximately spherical concave portions on the surface were discovered and the present invention was achieved.

Means for Solving the Problems> That is, an object of the present invention is to provide spherical or approximately spherical polyamide fine particles having a large number of approximately spherical recesses on the surface. The polyamide referred to in the present invention has 6 carbon atoms.
It is a polymer obtained from ~12 cyclic lactams, and may be either a homopolymer or a copolymer.

These cyclic lactams can be subjected to alkali polymerization using an alkali metal salt as a catalyst and an acyl lactam, phosphorus trihalide, or the like as a promoter. When polymerization is carried out in a poor solvent for polyamides, such as liquid paraffin, spherical polymer particles are produced. The present inventors investigated the copolymerization of a polyalkylene oxide-adducted lactam during the polymerization of a cyclic lactam in a liquid paraffin medium, and arrived at the present invention. That is, when ω-2 urolactam was anionically polymerized in the coexistence of polyalkylene oxide, especially polyethylene oxide-adducted 2-cutam, and polyamide powder was obtained through passing, washing, and drying steps in a conventional manner, the particles were It was discovered that it has the surface structure shown in Figure 1. The polyalkylene oxide preferably has a molecular weight of 1,000 to 20,000, and the lactam is preferably caprolactam or laurolactam. The fine particles in the present invention mean particles having a particle size of substantially 1 to 100 μm, and the particle size distribution and average particle size are not limited.

In the above polymerization method, it is possible to change the particle diameter by changing the polymerization temperature, the amount of polymerization catalyst, and the concentration of the polymerization solution. Powders with different particle sizes obtained by selecting polymerization conditions have various sensations on the skin. Even if particles with a large diameter are smooth, they give a strange feeling of being squeezed. They can be used differently depending on their purpose.

The particles having substantially spherical concave portions on their surfaces refer to golf pole-shaped particles as shown in FIG. Powder made of fine particles having such a shape, like powder made of particles with a smooth surface (see Figure 2), gives a soft and smooth feel when rubbed against the surface of the skin. Moreover, since various medicinal ingredients, ultraviolet absorbers, etc. are adsorbed in the recessed portions, it can be effectively used as a holder for these substances. One of the methods for producing such a shape was shown in Examples.

<Example> Example 1 Liquid paraffin 1201r was placed in a reactor equipped with a stirrer, and 1
It was heated at 40°C for 3 hours to dehumidify it.

Dried omega-lacro-lactam 190fr and polyethylene oxide addition lactam compound (Sanyo Chemical, Nippon M
W 8000-9000) 10 fr, X potassium tearate 3.8 fr was added and stirred to disperse well. Subsequently, after heating to 160'C, potassium lactam 7,
61r and phosphorus trichloride L12d were sequentially added to initiate polymerization. The polymerization was completed by stirring at 160'C for 2 hours.

After cooling, the polyamide powder produced was separated by P. The solvent and alkaline components were removed by washing with alcohol and hot water. After drying, a powder of 150 #r was obtained. The particle surface condition of the obtained powder was observed using a scanning microscope. FIG. 1 a is an overall photograph of the fine particles, and FIG. 1 is an enlarged photograph of the surface of the fine particles.

Many depressions are observed on the surface of the spherical particles.

Comparative Example 1 200 yr of ω-laurolactam was polymerized in the same manner as in Example 1 without adding the polyethylene oxide-adducted lactam compound. After similar solid-liquid separation and washing, the surface condition of the particles was observed. Figure 2 shows an overall photograph of the fine particles. The surface condition is very smooth with no depressions.

<Effects of the Invention> The polyamide fine particles of the present invention have many concavities on the surface, making it easy for pigments, ultraviolet absorbers, medicinal ingredients, etc. to adhere to them, making them effective as binders and microcapsule base materials in the cosmetics and pharmaceutical fields. Available.

[Brief explanation of the drawing]

Figure 1a is an overall enlarged photograph (1000x) showing the structure of the polyamide fine particles obtained in the present invention, b: an enlarged surface photograph (50x) showing the structure of the polyamide fine particles obtained in the civil engineering invention.
Figure 2a is an enlarged overall photograph (1000x) showing the structure of conventional polyamide fine particles, and Figure 2b is an enlarged surface photograph (1000x) showing the structure of conventional polyamide fine particles. Patent application Daitoshi Co., Ltd. Figure 1 α

Claims (1)

[Claims] Spherical or approximately spherical polyamide fine particles having a large number of approximately spherical concave portions on the surface.