TECHNICAL FIELD

The present invention relates to cellulose derivative particles, a cosmetic composition, and a method for producing cellulose derivative particles.

BACKGROUND ART

To date, various polymer fine particles according to the application have been proposed. For example, the purpose of fine particles contained in cosmetics also varies. The purpose of adding fine particles in cosmetics includes improving the spread of the cosmetic, changing the tactile sensation, imparting a wrinkle blurring effect, and improving the slipperiness of the product, such as a foundation.

In particular, fine particles having high sphericity are excellent in tactile sensation and provide a light scattering (soft focus) effect depending on the physical properties and shape thereof. Such fine particles when used in a foundation or the like fill and smooth the roughness of the skin to scatter the light in various directions, and thus an effect of making wrinkles and the like less noticeable (soft focus) can be expected.

For such a purpose and an effect of cosmetics, fine particles to be contained in cosmetics need to have a narrow particle size distribution and high sphericity. Such fine particles include fine particles made of a synthetic polymer, which have been proposed in the art, such as nylon 12; polymethyl methacrylate (PMMA); polystyrene (PS); polypropylene (PP); and polyethylene (PE).

However, among these synthetic polymers, fine particles made of PP, PE, or the like are light with a specific gravity of 1 or less and have too small particle size, thus easily float in water and may not be removed at a sewage treatment facility, and may flow as they are into the river and further into the sea through the river. Thus, there is a problem that the ocean and the like are contaminated with fine particles made of these synthetic polymers. Furthermore, fine particles made of PS, among synthetic polymers, contain a phthalate ester-based plasticizer, such as dioctyl phthalate, as the main plasticizer. Some phthalate ester-based plasticizers are suspected of being environmental hormones, and it is not preferred that they flow into the ocean.

Furthermore, fine particles made of these synthetic polymers have the property of adsorbing trace amounts of chemical contaminants in the environment, and this leads to concerns about various effects to be caused; for example, planktons and fish swallow fine particles that have adsorbed the chemical contaminants, which can also negatively affect the human body.

From such concerns, attempts have been made to replace fine particles of synthetic polymers used in various applications with other particles.

Cellulose or cellulose derivatives are excellent in that they can be obtained from natural materials, such as wood or cotton flowers, which do not compete with food or feed. Thus, it would be beneficial if fine particles of synthetic polymers can be substituted with fine particles of cellulose, which is a natural polymer, or a cellulose derivative, which is a semi-synthetic polymer. However, polymers to which a production method of fine particles of synthetic polymers can be applied are limited, and it is difficult to apply such a production method to production of fine particles of cellulose or a cellulose derivative.

Patent Document 1 describes a method including: forming a polysaccharide ester product from a polysaccharide synthesis, wherein the polysaccharide ester product contains a polysaccharide ester and a solvent; diluting the polysaccharide ester product and thereby forming a polysaccharide ester dope; and forming a plurality of polysaccharide ester microspheres from the polysaccharide ester dope; and describes a cosmetic composition as an article that can contain a polysaccharide ester microsphere.

Patent Document 2 describes a cellulose acylate having a volume average particle size D50 as measured using a laser diffraction particle size distribution measuring device of 72 μm or greater and 100 μm or less, a degree of polymerization of 131 or greater and 350 or less, and a substitution degree of 2.1 or greater and 2.6 or less; and also describes that a method for producing the cellulose acylate is preferably a method for producing a cellulose acylate, the method including: acylating cellulose in the presence of sulfuric acid; and deacylating the acylated cellulose in a polar solvent in the presence of acetic acid.

Patent Document 3 describes kneading a resin component (A), such as a thermoplastic resin, and a water soluble auxiliary component (B) to prepare a dispersion; and eluting the auxiliary component (B) from the dispersion to produce a molded article constituted of the resin component (A) (for example, a porous article or spherical particles); and also describes a cellulose derivative, such as a cellulose acetate, as the resin component (A).

CITATION LIST

Patent Document

Patent Document 1: JP 2016-500129 A

Patent Document 2: JP 6187653 B

Patent Document 3: JP 2004-051942 A

SUMMARY OF INVENTION

Technical Problem

However, the polysaccharide ester microspheres of Patent Document 1 are porous particles having a large particle size and a broad particle size distribution, and thus are not sufficient as an alternative to fine particles of synthetic polymers to be contained in products, such as cosmetics. In addition, the cellulose acylates obtained by the production method described in Patent Document 2 are also amorphous porous particles. Furthermore, the particulate molded article obtained by the production method described in Patent Document 3 also has a low sphericity and is particles that are approximately spherical. Thus, known fine particles have poor tactile sensation.

An object of the present invention is to provide fine particles containing a semi-synthetic polymer of a cellulose derivative and excellent in tactile sensation.

Solution to Problem

A first aspect of the present invention relates to cellulose derivative particles including an alkoxy group having 2 or more carbons or an acyl group having 3 or more carbons, wherein the cellulose derivative particles have an average particle size of 80 nm or greater and 100 μm or less, a sphericity of 70% or greater and 100% or less, and a surface smoothness of 80% or greater and 100% or less; and a total substitution degree of the cellulose derivative is 0.7 or greater and 3 or less.

In the cellulose derivative particles, the total substitution degree of the cellulose derivative may be 2.0 or greater and less than 2.6.

In the cellulose derivative particles, the acyl group may have 3 or more and 18 or less carbons.

In the cellulose derivative particles, the alkoxy group may have 2 or more and 8 or less carbons.

In the cellulose derivative particles, the true specific gravity may be 1.04 or greater.

In the cellulose derivative particles, the cellulose derivative particles may contain a plasticizer, and the content of the plasticizer may be greater than 0 wt. % and 40 wt. % or less relative to a weight of the cellulose derivative particles.

In the cellulose derivative particles, the plasticizer may be a glycerin ester-based plasticizer.

A second aspect of the present invention relates to a cosmetic composition containing cellulose derivative particles.

A third aspect of the present invention relates to a method for producing cellulose derivative particles, the method including: kneading a cellulose derivative having a total substitution degree of 0.7 or greater and 3 or less and a water-soluble polymer at 200° C. or higher and 280° C. or lower to obtain a dispersion containing the cellulose derivative as a dispersoid; and removing the water-soluble polymer from the dispersion.

In the method for producing cellulose derivative particles, the cellulose derivative having a total substitution degree of 0.7 or greater and 3 or less may be a cellulose derivative impregnated with a plasticizer; and the cellulose derivative impregnated with a plasticizer is a product formed by melt-kneading the cellulose derivative having a total substitution degree of 0.7 or greater and 3 or less and the plasticizer in a range of 20° C. or higher and lower than 200° C.

In the method for producing the cellulose derivative particles, the plasticizer may be a glycerin ester-based plasticizer.

In the method for producing the cellulose derivative particles, the plasticizer may be triacetin.

In the method for producing the cellulose derivative particles, the water-soluble polymer may be polyvinyl alcohol or thermoplastic starch.

Advantageous Effects of Invention

According to the present invention, fine particles containing a semi-synthetic polymer of a cellulose derivative and excellent in tactile sensation can be provided.

