JPH03243666A - Ultraviolet ray shielding transparent flaky particle and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject particles useful as cosmetics, coatings, etc., for preventing sunburn by mixing a mixture solution of an organosiloxane, fine ZnO particles and an organic solvent with transparent flaky particles, drying the resultant mixture while stirring the mixture and then heating the dried mixture. CONSTITUTION:With 100 pts. wt. mixture solution of an organosiloxane in an amount of 5-30 wt.% expressed in terms of SiO2, 4-15 wt.% fine ZnO particles and 60-80 wt.% organic solvent, is mixed 40-300 pts. wt. transparent flaky particles. The resultant mixture is then dried while being stirred and subsequently heated to afford the objective particles coated with a layer containing the ZnO and organosiloxane.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is applicable to cosmetics for preventing sunburn, plastic films used in greenhouse horticulture, paints for preventing deterioration caused by ultraviolet rays, resin articles or surface protective films. UV-shielding transparent flake-like particles for use mixed in.

[Prior Art] In recent years, cosmetics containing fine flaky mica whose surface is coated with titanium oxide have been used to prevent sunburn. In the above-mentioned cosmetics, ultraviolet rays are prevented by the flaky mica particles whose surfaces are coated with titanium oxide, which are mixed into the emulsion, cream-like substance, or foundation.

However, when these titanium oxide crystals are anatase, they have a strong oxidizing effect on the skin due to the photocatalytic effect, and safety and health problems have been pointed out. Therefore, in order to transform the crystal form of titanium oxide into the rutile form, which has a relatively weak photocatalytic effect, a tin compound is added to the titanium oxide, and firing is usually performed at a temperature of 900°C or higher. . In this case, because the mica releases water little by little and decomposes during the above firing process at a temperature of 500°C or higher, the flaky form is distorted and the light of the product is
There was an inconvenience that R or smoothness was impaired.

In addition, in greenhouse horticulture using vinyl greenhouses, plastic films that can block ultraviolet light are being used, taking advantage of the fact that the behavior of pests is significantly reduced in environments where near-ultraviolet light from the sun is blocked. became. in this case,
Usually, organic materials such as hensifenone, hensitriazole, salicylic acid ester, or acrylonitrile are mixed into plastic films as UV absorbers, but these UV absorbers have problems with their longevity. .

Furthermore, the present inventors have previously proposed an ultraviolet-absorbing flake glass. (Unexamined Japanese Patent Publication No. 63-307142) In the above proposal, the UV absorbers are trivalent iron ions and trivalent cerium ions dissolved in the glass, so the above-mentioned disadvantages of the conventional technology in terms of safety and lifespan are eliminated. It has been resolved. However, if a particularly strong ultraviolet absorption effect is desired, it is necessary to increase the concentration of trivalent iron ions.

At this time, some of the absorption of the iron ions enters the visible light range, resulting in a disadvantage that the whiteness decreases.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problems of titanium mica in conventional sunburn prevention cosmetics, namely the photo-oxidation effect caused by anatase and the decomposition of mica caused by calcination. The purpose is to solve problems. In addition, conventional organic ultraviolet absorbers
The aim is to solve the problem of short lifespan due to decomposition by ultraviolet rays.

[Means for Solving the Problems] The present invention provides transparent flaky particles whose surfaces are made of zinc oxide (Zn
UV-shielding transparent flake-like particles coated with a layer containing O). The layer containing zinc oxide may be composed of 100% zinc oxide, but preferably contains 100% zinc oxide.
0~75! It contains 25 to 90% by weight of organopolysiloxane, calculated as % and 5102, respectively. The thickness of the layer is preferably 0.05 to 2 μm.

A layer of zinc oxide (ZnO) itself may be provided on the surface of the UV-shielding transparent flaky particles of the present invention. The layer of zinc oxide can be formed by pg deposition, sputtering, sol-gel method, pyrolysis method, etc. can. However, if the formed zinc oxide film is amorphous, it hardly absorbs ultraviolet rays, so it is necessary to convert it into a crystalline state by heat treatment or the like afterwards.

Further, in order to coat the surface of the transparent flaky particles with a layer containing zinc oxide, the following method is preferably used: S i 0
5 to 30 weight percent organosiloxane, 4 to 15 weight percent ZnO fine particle crystals,
And 40 to 3,001 parts of transparent flaky particles such as flaky glass, mica, or synthetic mica particles per 100 parts of γN mixture of 60 to 80 weight percent of an organic solvent such as alcohol or ester! It is obtained by mixing I, drying with stirring, and then heating and holding at 80°C to 500°C at 2 degrees for several minutes to several hours. When forming a film in this manner, a maximum film thickness of about 60 μm can be obtained. In this case, organopolysiloxane and ZnO
A film is formed with the fine particle crystals of ZnO, and the organopolysiloxane has some alkyl groups left inside.
The fine crystal particles are dispersed in the organopolysiloxane.

The organosiloxane used in the present invention has the general formula R,' -S, (OR5)4-0 (wherein R4 is a hydrocarbon group having 1 to 3 carbon atoms, and R5 is a hydrocarbon group having 1 to 3 carbon atoms.
is a hydrocarbon group, C is 1 or 2. ) or a hydrolyzate thereof is preferably used. Examples of the organosilicon compound represented by this general formula include the following. That is, dimethyldimethoxysilane, methyltrimethoxysilane, ethyltriethoxysilane and the like. Since the organopolysiloxane film has a binder function, it is possible to form a film containing Zn0m particles and the like.

This type of material is already available on the market as a paint. (For example, Shinto Paint Circle product name ``Graceram''
).

In the organosiloxane solution enriched with ZnO fine particles that meets the preferred U pattern of the present invention, the organosiloxane content of 5 to 30 weight percent in terms of S i 02 should be less than 5%. However, the amount of solvent is increased, which is unavoidable, and the thickness of the coating obtained in the second coating operation is less than 0.1 μm.
The amount of binder for fixing nO fine particles to flake-like particles is low and insufficient. Moreover, if the concentration exceeds 30%, not only will the stability of the above-mentioned mixed liquid deteriorate, but also the viscosity of the above-mentioned liquid will increase, resulting in a film thickness exceeding 2 μm, which is compared to the thickness of flaky particles. This is because the thickness becomes too large and the particles become coarse, making it unsuitable as a material for cosmetics, for example.

The reason why the ZnO fine particles are contained in the above liquid in an amount of 4 to 15 weight percent is that at the lower limit, the ultraviolet absorption effect decreases, and when the upper limit is exceeded, the stability of the liquid decreases and precipitates are likely to form. Furthermore, the reason why the proportion of the solvent such as alcohol and ester is set to 60 to 80 weight percent is to keep the range within which coating workability on flaky particles is good. Further, if it is below the lower limit, it becomes uneconomical. As the ZnO fine particles, crystals having a diameter of 5 to 1100 nm can be used, and generally commercially available products can be used.

Further, the above-mentioned final heat treatment is necessary for film formation by dehydration and dealcoholization of the organosiloxane, and curing is insufficient at 80° C. or lower, and slipperiness decreases at 500° C. or higher. The time required for heat treatment is several hours at 80°C, for example, about 3 hours when the amount of flake particles is 1 kg.
About 0 minutes is sufficient, and at 500°C, several minutes is sufficient.

For example, when the amount of flaky glass particles is 500 g, even if they are charged into a crucible and held at 500°C for 1 hour, the slipperiness is not lost, but when the temperature reaches 550°C, the slipperiness disappears in 10 minutes or more. The reason for the slipperiness is not well understood, but it is thought to be due to the action of the remaining alkyl groups.

As the transparent flake particles used in the present invention, glass flakes, mica, or synthetic mica particles are suitable.
~4μm, diameter 2~100μm, aspect ratio 2~
100 is usually used. Mica or synthetic mica particles usually have a thickness of 0.1 to 1 μm, a diameter of 10 to 100 μm, an aspect ratio of 5 to 100
is usually used.

[Function] The surface of the flaky particles produced by the method of the present invention is coated with a ZnO film or has fine particles (particle size, for example, 20 to 30 nm) fixed thereon, and therefore is transparent and has no ultraviolet absorption effect. have In particular, when organopolysiloxane is contained, the surface of the flake-like particles becomes more slippery, so when used as a cosmetic material such as a foundation, it spreads well on the skin, and the flake-like particles are smoother due to warm air. ZnO particles do not cause secondary aggregation, and ZnO itself is safe for the human body. Furthermore, the membrane containing organopolysiloxane is
Since it has excellent chemical durability and water resistance, even if the flaky glass particles contain an alkali metal oxide, there is no need to worry about the effects on the skin due to alkali elution.

Example 1 Organosiloxane (mixture of methyltrimethoxysilane and ethyltrimethoxysilane) 30% (approximately 27% in terms of SiO2) and isopropyl alcohol 70%
A mixed solution consisting of %
00) To 100 parts, add 12 parts of ZnO crystal fine particles (Sumitomo Cement H 2 particle size 20 to 40 nm) and disperse 350 g of Kake 8I liquid using an ultrasonic homogenizer to make glass flakes (manufactured by Nippon Glass Fiber ■, trade name). Glass flakes RCFFX5, thickness 1.5 μm x width 5 μm) 500g
In addition, isopropyl alcohol was evaporated while stirring in a mortar. Incidentally, if the drying at this time is insufficient, clumps will occur due to secondary aggregation of flake-like particles after the subsequent curing treatment, and it will be necessary to lightly re-grind again. Now, the flaky glass particles dried as described above are in a smooth state. This was kept in a dryer at 180° C. for 15 minutes and then taken out to obtain UV-shielding transparent flaky particles.

The surface of these flaky particles has a thickness of about 0.08 μm.
A layer consisting of ZnO and organopolysiloxane (Zn
O301% by weight, organopolysiloxane 70% by weight)
was covered with. The ultraviolet absorbance of the flaky particles was calculated from the surface area of the glass flakes and the amount of the ZnO fine particle suspension used. ZnO per surface area
Measurements were carried out on samples in which the above suspended AI liquid was coated on a slide glass so that the amounts were equal. As a result, the ultraviolet absorption rate per flake-like particle was 30% (wavelength 3
60 nm). The visible light transmittance was approximately 100% excluding reflection. The ultraviolet absorbance of the uncoated glass flakes was about 1% (wavelength: 360 nm).

Example 2 Mixture liquid consisting of 30% organosiloxane and 70% isopropyl alcohol (Graceram #300) 10
0 parts, 15 parts of ZnO111 particles were added, and 400 g of a suspension was dispersed using an ultrasonic homogenizer.
After drying in the same manner as in Example 1, the sample was kept at 150° C. for 1 hour in a miss dryer. Approximately 0.11μ is present on the surface of these flaky particles.
m thickness, eyebrows made of ZnO and organopolysiloxane (35% ZnO, 6% organopolysiloxane)
5% by weight). The ultraviolet absorption rate of these flaky particles was determined in the same manner as in Example 1, and was 40% per mica particle (wavelength 360 nm).
The visible light transmittance was about 100%. Through the above processing,
The slipperiness of the mica powder was further improved, so much so that it took on a white smoke-like appearance when dropped from above.

[Effect] As detailed above, the ultraviolet-shielding transparent flaky particles of the present invention absorb ultraviolet rays with a wavelength of 385 parts m or less, but do not absorb light in the visible light range, so whiteness is required. It is particularly suitable when

In addition, when the film contains organopolysiloxane in addition to ZnO, the slipperiness of the particles is significantly improved, so when used as a cosmetic material, for example, it has the advantage of being easier to spread on the skin, and has a long lifespan. There is no need to worry about secondary aggregation due to moisture during long-term storage. Furthermore, since the flake-like particles are in the form of thin flakes, they have an excellent coating effect on the base when used as a paint filler or cosmetics. Furthermore, plastic film, wA! When a filler such as II reinforced plastic is used, it has a large aspect ratio and thus has a reinforcing effect, and also has the advantage of preventing deterioration of the matrix resin due to ultraviolet rays.

Claims (1)

[Scope of Claims] 1) Ultraviolet-shielding transparent flake particles whose surfaces are coated with a layer containing zinc oxide. 2) The ultraviolet shielding according to claim 1, wherein the layer containing zinc oxide contains 10 to 75% by weight of zinc oxide and 25 to 90% by weight of organopolysiloxane in terms of SiO_2. Transparent flake particles. 3) The UV-shielding transparent flaky particles according to claim 1, wherein the layer has a thickness of 0.05 to 2 μm. 4) 40 to 3 parts by weight of transparent flaky particles to 100 parts by weight of a mixed solution of 5 to 30 weight percent organosiloxane, 4 to 15 weight percent ZnO fine particles, and 60 to 80 weight percent organic solvent in terms of SiO_2.
A method for producing UV-shielding transparent flake-like particles coated with a layer containing ZnO and organopolysiloxane, characterized in that 00 parts by weight are mixed, the mixture is dried with stirring, and then heated.