JPH0689154B2 - Polyamide composite particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to polyamide composite particles having enhanced reflectance with respect to ultraviolet rays and infrared rays. Further, the present invention relates to fine particles suitable for foundation useful as a sunscreen agent, when oils are easily dispersed when used as a cosmetic base material.

<Prior Art> When skin is exposed to ultraviolet rays, unfavorable cosmetic phenomena occur such as blackening of the skin and promotion of aging. For this reason, organic ultraviolet absorbers and inorganic titanium oxides are used in cosmetics for the purpose of blocking ultraviolet rays (Japanese Patent Publication No. 47-42502). In particular, it has been said that titanium oxide is excellent because it does not produce harmful substances upon irradiation with light.

<Problems to be Solved by the Invention> However, according to recent findings, titanium oxide does not reflect ultraviolet rays, but absorbs them, and thus causes a photochemical reaction in the presence of an electrolyte such as sweat, thereby deoxidizing hydrogen peroxide gas. A phenomenon has been discovered that causes skin roughness. It has been found that not only ultraviolet rays but also infrared rays are harmful to the skin.

The inventors diligently studied fine particles that have a large light-reflecting power in the visible region as well as in the ultraviolet region and the near-infrared region, and therefore have a large shielding effect and do not cause a photoreaction by ultraviolet rays. As a result, they have found that zirconium oxide has the desired properties, and have examined its use in sun care cosmetics. However, since zirconium oxide has a large specific gravity, it tends to settle in the cosmetic raw material, and it is difficult to maintain stable dispersion. Then, the method of lowering the specific gravity was further investigated, and the present invention was accomplished.

<Means for Solving Problems> That is, the present invention provides polyamide composite particles characterized in that zirconium oxide having an average particle size of 1 μm or less is carried on the surface layer of polyamide particles having an average particle size of 3 μm to 20 μm. To do.

The polyamide particles referred to in the present invention are homopolymerization or copolymerization of a salt of an aliphatic diamine and an aliphatic dicarboxylic acid represented by cyclic lactam represented by caprolactam or laurolactam, hexamethylene adipate, hexamethylene sebacate or the like. The particles produced by pulverizing the copolymer produced by pulverizing at low temperature can be used, but it is preferable that the above-mentioned cyclic lactam be produced by a solution precipitation method in the presence of an alkali polymerization catalyst. The particles have a good shape and zirconium oxide has good adhesion, and can be preferably used (JP-B-45-29832 and JP-B-47-251).
No. 57).

The smaller the average particle diameter of the polyamide in the present invention, the higher the hiding power, which is preferable. However, when the particle size is small, there are restrictions in production such as handling of particles becomes complicated. In addition, when the average particle size is large, it is not preferable because when it comes into contact with the skin, a foreign body feels.

Therefore, in the present invention, it is necessary to use polyamide particles of 3 to 20 μm.

As zirconium oxide, one produced by a usual method can be used. An example of the manufacturing method is as follows. That is, using zirconium oxychloride, zirconium nitrate, or zirconium alkoxide as a raw material, the well-known coprecipitation method is a thermal decomposition method, a hydrolysis method, a metal alkoxide method, a sol-gel method, a gas phase method, or the like. A powder having a nearly spherical shape is formed.

The particle size is controlled by the conditions of the powder forming process (concentration, pH, aging time, type of solvent, etc.) and the conditions of the process after powder formation (calcination temperature, etc.). After calcining, the zirconium oxide powder can be produced by dispersing it in a solvent, pulverizing it with a pulverizer such as a ball mill, and drying it.

The particle size of zirconium oxide used in the present invention is 1 μm.
It is necessary to be below, and preferably 0.1 to 0.8 μm. If the particle size is larger than 1 μm, the adhesion to the polyamide particles will decrease, and the rough feeling of the composite particles will be too strong to achieve the initial purpose.

A so-called dry blending method is effective as a method for supporting the zirconium oxide particles on the surface layer portion of the polyamide particles. Zirconium oxide particles and polyamide particles have good affinity, and by mixing both particles, the former adheres to the surface of the latter, and the polyamide is melted by friction heat,
Enter the inside. For this reason, both particles are firmly bonded by a suitable mixing time.

The weight ratio of the zirconium oxide particles supported on the surface layer of the polyamide particles is saturated at about 3: 1. Therefore, composite particles in which 10 to 35% by weight of the zirconium oxide particles are supported on the polyamide particles are preferable.

The composite particles thus formed have both the properties of the zirconium oxide particles arranged on the surface and the properties of the polyamide inside. That is, the specific gravity was close to that of polyamide, and the property against light was close to that of zirconium oxide particles, and the object of the present invention could be achieved. That is, the specific gravity is close to that of polyamide, the property against light is close to that of zirconium oxide particles, and when mixed with cosmetic raw materials, good mixing characteristics are exhibited without causing phenomena such as sedimentation and separation, and the object of the present invention is achieved. I was able to.

<Examples> Hereinafter, the present invention will be described in detail with reference to Examples.

Example 1 Production of Zirconium Oxide Particles About 99.9% pure aqueous solution of zirconium oxychloride was added.
Gradually heat to 100 ° C, hold at that temperature for about 150 hours to remove water, and then about 1000 ° C at a heating rate of about 100 ° C / hour.
The mixture was heated to ° C and kept at that temperature for about 3 hours to obtain a calcined powder. Further, the calcined powder was pulverized in a ball mill lined with urethane and then dried to obtain zirconium oxide particles having an average particle diameter of 0.3 μm and a nearly spherical shape.

Support of zirconium oxide particles 6 parts of zirconium oxide particles obtained by the above method and particle size 5
20 parts of a nylon powder (SP-500 manufactured by Toray Industries, Inc.) having a diameter of μm was mixed in an automatic mortar for 1 hour and 3 hours. Electron micrographs of the obtained composite particles are shown in FIGS. 1 and 2. From the figure, it can be seen that zirconium oxide particles are supported on the surface layer of the nylon particles. The light reflection characteristics of the composite particles are shown in FIG.

Comparative Example 1 6 parts of titanium oxide powder (TA-500 manufactured by Fuji Titanium Co., Ltd.) having an average particle diameter of 0.5 μm and 20 parts of the nylon particles used in Example 1 were treated in the same manner as in Example 1. The light reflection characteristics of the obtained composite particles are shown in FIG.

As can be seen from the graph of FIG. 3, the composite particles of the present invention have a higher reflectance in the near infrared region with a wavelength of about 2 μm than the powder to which titanium oxide is attached as shown in the comparative example. That is, it can be said that the reflectance of heat rays is high. In addition, the wavelength is 0.3-0.4μ
It shows that the reflectance is high in the ultraviolet region of m and that it has a property of blocking ultraviolet rays well.

<Effects of the Invention> The composite particles of the present invention produced by adhering fine particles of zirconium oxide to the surface layer of polyamide particles can reflect light in a wide range from ultraviolet rays to near infrared rays. In addition, the particles have a smaller specific gravity than zirconium oxide, and improved compatibility with cosmetic raw materials. Furthermore, zirconium oxide has a lower coefficient of friction than titanium oxide, and the powder has good sliding properties. It has a wide range of properties and can be widely used as a sunscreen agent.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and FIG. 2 are electron microscope photographs of polyamide composite particles after mixing for 1 hour and 3 hours in Example 1, and FIG. 3 shows photoreaction characteristics of the composite particles. It is a graph shown. 1 ... skin, 2 ... nylon particles 3 ... titanium oxide composite nylon particles 4 ... zirconium oxide composite nylon particles

Claims (1)

[Claims] 1. A polyamide composite particle comprising zirconium oxide having an average particle diameter of 1 μm or less supported on the surface layer of polyamide particles having an average particle diameter of 3 μm to 20 μm.