阅读说明：本技术 纤维素衍生物粒子、化妆品组合物及纤维素衍生物粒子的制造方法 (Cellulose derivative particles, cosmetic composition, and method for producing cellulose derivative particles ) 是由 小林慧子 大村雅也 于 2020-02-14 设计创作，主要内容包括：本发明涉及纤维素衍生物粒子、化妆品组合物及纤维素衍生物粒子的制造方法。本发明的目的在于提供含有纤维素衍生物的半合成聚合物、触感优异的微粒。纤维素衍生物粒子,其是具有碳原子数为2以上的烷氧基、或碳原子数为3以上的酰基的纤维素衍生物粒子,上述纤维素衍生物粒子的平均粒径为80nm以上且100μm以下,并且球形度为70％以上且100％以下,表面平滑度为80％以上且100％以下,上述纤维素衍生物的总取代度为0.7以上且3以下。(The present invention relates to cellulose derivative particles, a cosmetic composition, and a method for producing cellulose derivative particles. The purpose of the present invention is to provide fine particles which contain a semisynthetic polymer of a cellulose derivative and have excellent tactile sensation. Cellulose derivative particles having an alkoxy group having 2 or more carbon atoms or an acyl group having 3 or more carbon atoms, wherein the cellulose derivative particles have an average particle diameter of 80nm or more and 100 μm or less, a sphericity of 70% or more and 100% or less, a surface smoothness of 80% or more and 100% or less, and a total substitution degree of the cellulose derivative of 0.7 or more and 3 or less.)

1. Cellulose derivative particles having an alkoxy group having 2 or more carbon atoms or an acyl group having 3 or more carbon atoms,

the cellulose derivative particles have an average particle diameter of 80nm to 100 [ mu ] m, a sphericity of 70% to 100%, and a surface smoothness of 80% to 100%,

the cellulose derivative has a total substitution degree of 0.7 to 3.

2. The cellulose derivative particle according to claim 1, wherein the cellulose derivative has a total degree of substitution of 2.0 or more and less than 2.6.

3. The cellulose derivative particle according to claim 1 or 2, wherein the acyl group has 3 or more and 18 or less carbon atoms.

4. The cellulose derivative particle according to any one of claims 1 to 3, wherein the alkoxy group has 2 to 8 carbon atoms.

5. The cellulose derivative particle according to any one of claims 1 to 4, which has a true specific gravity of 1.04 or more.

6. The cellulose derivative particles according to any one of claims 1 to 5, wherein the cellulose derivative particles contain a plasticizer,

the content of the plasticizer is more than 0 wt% and 40 wt% or less with respect to the weight of the cellulose derivative particles.

7. The cellulose derivative particles according to claim 6, wherein the plasticizer is a glyceride-based plasticizer.

8. A cosmetic composition comprising the cellulose derivative particles according to any one of claims 1 to 7.

9. A method for producing cellulose derivative particles, comprising the steps of:

a step in which a cellulose derivative having a total substitution degree of 0.7 to 3 inclusive is kneaded with a water-soluble polymer at 200 to 280 ℃ to obtain a dispersion having the cellulose derivative as a dispersoid; and

and removing the water-soluble polymer from the dispersion.

10. The method for producing cellulose derivative particles according to claim 9,

the cellulose derivative having a total substitution degree of 0.7 to 3 is a cellulose derivative impregnated with a plasticizer,

the cellulose derivative impregnated with the plasticizer is obtained by melt-kneading the cellulose derivative having the total substitution degree of 0.7 to 3 with the plasticizer at a temperature of 20 ℃ to less than 200 ℃.

11. The method for producing cellulose derivative particles according to claim 10, wherein the plasticizer is a glyceride plasticizer.

12. The method for producing cellulose derivative particles according to claim 10, wherein the plasticizer is triacetin.

13. The method for producing cellulose derivative particles according to any one of claims 9 to 12, wherein the water-soluble polymer is polyvinyl alcohol or thermoplastic starch.

Technical Field

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

Background

In the past, various polymer fine particles suitable for the application have been proposed. For example, the purpose of fine particles contained in cosmetics is also various. The purpose of containing fine particles in cosmetics includes: improving the extensibility of the cosmetic; imparting a change to the feel; imparting a wrinkle-lightening effect; and improving smoothness of foundation and the like.

In particular, fine particles having a high sphericity have excellent touch feeling, and can obtain a light scattering (soft focus) effect depending on the physical properties and shape thereof. When such fine particles are used for foundation or the like, the following effects are expected: the unevenness of the skin is filled to be smooth, and wrinkles and the like are less likely to be conspicuous by scattering light in various directions (soft focus effect).

In order to achieve the object and effect of such cosmetics, fine particles to be blended in the cosmetics must have a narrow particle size distribution and a high degree of sphericity, and as such fine particles, fine particles formed of polyamide such as nylon 12, or synthetic polymer such as polymethyl methacrylate (PMMA), Polystyrene (PS), polypropylene (PP), and Polyethylene (PE) have been proposed.

However, the fine particles made of PP, PE, and the like in these synthetic polymers have a specific gravity of 1 or less, are light, and have an excessively small particle diameter, and therefore, they easily float in water and cannot be removed by sewage treatment facilities, and sometimes they flow into rivers directly or further through rivers and into the sea. Therefore, there is a problem that the sea and the like are contaminated with particles made of these synthetic polymers. In addition, fine particles made of PS in a synthetic polymer contain a phthalate plasticizer such as dioctyl phthalate as a main plasticizer. Phthalate plasticizers also contain substances suspected of being environmental hormones, and are not suitable for efflux into the ocean.

Further, since the fine particles formed of these synthetic polymers have a property of adsorbing a trace amount of chemical pollutants in the environment, there is a concern that various influences may be exerted, for example, plankton and fish may ingest the fine particles adsorbing the chemical pollutants and may also exert adverse influences on the human body.

Because of such concerns, attempts have been made to replace synthetic polymer microparticles for a wide variety of uses with other particles.

Cellulose or a cellulose derivative is excellent in that it can be obtained from natural materials such as wood, cotton and the like which do not compete with food and feed. It would therefore be advantageous if the microparticles of synthetic polymers could be replaced by microparticles of cellulose as a natural polymer or cellulose derivatives as semi-synthetic polymers. However, there are limited polymers that can be applied to the method for producing synthetic polymer microparticles, and it is difficult to apply the method to the production of microparticles of cellulose or cellulose derivatives.

Patent document 1 describes a method including the steps of: forming a polysaccharide ester product comprising a polysaccharide ester and a solvent by polysaccharide synthesis; diluting the polysaccharide ester product to obtain a polysaccharide ester stock solution; and forming a plurality of polysaccharide ester microspheres from the polysaccharide ester stock solution. Among them, cosmetic compositions are mentioned as articles which can contain polysaccharide ester microspheres.

Patent document 2 describes a cellulose acylate having a volume average particle diameter D50 of 72 μm or more and 100 μm or less, a polymerization degree of 131 or more and 350 or less, and a substitution degree of 2.1 or more and 2.6 or less, as measured by a laser diffraction particle size distribution measuring apparatus, and further, it describes that a method for producing the cellulose acylate including the following steps is preferable: an acylation step of acylating cellulose in the presence of sulfuric acid; and a deacylation step of deacylating the acylated cellulose in a polar solvent in the presence of acetic acid.

Patent document 3 describes that a molded article (for example, a porous body or spherical particles) composed of a resin component (a) is produced by kneading the 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; as the resin component (a), a cellulose derivative such as cellulose acetate is described.

Disclosure of Invention

Problems to be solved by the invention

However, the polysaccharide ester microspheres of patent document 1 are porous particles having a large particle diameter and a wide particle size distribution, and are not satisfactory as a substitute for synthetic polymer microparticles blended in cosmetics and the like. Cellulose acylate obtained by the production method described in patent document 2 is also porous particles having an irregular shape. The particle-shaped molded article obtained by the production method described in patent document 3 is also a particle having a low sphericity and a nearly spherical shape. Therefore, the conventional fine particles have poor touch.

The purpose of the present invention is to provide fine particles which contain a semisynthetic polymer of a cellulose derivative and have excellent tactile sensation.

Means for solving the problems

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

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

In the cellulose derivative particles, the acyl group may have 3 to 18 carbon atoms.

In the cellulose derivative particles, the number of carbon atoms of the alkoxy group may be 2 or more and 8 or less.

The cellulose derivative particles may have a true specific gravity of 1.04 or more.

The cellulose derivative particles may contain a plasticizer, and the content of the plasticizer may be more than 0% by weight and 40% by weight or less based on the weight of the cellulose derivative particles.

In the cellulose derivative particles, the plasticizer may be a glyceride plasticizer.

The 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, comprising the steps of: a step in which a cellulose derivative having a total substitution degree of 0.7 to 3 inclusive is kneaded with a water-soluble polymer at 200 to 280 ℃ to obtain a dispersion having 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 more and 3 or less may be a cellulose derivative impregnated with a plasticizer, and the cellulose derivative impregnated with the plasticizer may be obtained by melt-kneading the cellulose derivative having a total substitution degree of 0.7 or more and 3 or less and the plasticizer at 20 ℃ or higher and lower than 200 ℃.

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

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

In the method for producing 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 semisynthetic polymer of a cellulose derivative and having excellent tactile sensation can be provided.

Drawings

FIG. 1 is a drawing for explaining a method of evaluating surface smoothness (%).

FIG. 2 is a drawing explaining a method of evaluating surface smoothness (%).

Detailed Description

[ cellulose derivative particles ]

The cellulose derivative particles of the present invention are cellulose derivative particles having an alkoxy group having 2 or more carbon atoms or an acyl group having 3 or more carbon atoms, and the cellulose derivative particles have an average particle diameter of 80nm or more and 100 μm or less, a sphericity of 70% or more and 100% or less, a surface smoothness of 80% or more and 100% or less, and a total substitution degree of the cellulose derivative of 0.7 or more and 3 or less.

The case where the cellulose derivative particles have an alkoxy group having 2 or more carbon atoms will be described. The number of carbon atoms of the alkoxy group is not particularly limited, and may be 3 or more, or 5 or more. Further, it may be 20 or less, preferably 8 or less.

The cellulose derivative particles may have both an alkoxy group having 2 or more carbon atoms and an alkoxy group (methoxy group) having 1 carbon atom.

Examples of the alkoxy group having 2 or more carbon atoms include an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, and an octyloxy group.

The case where the cellulose derivative particles have an acyl group having 3 or more carbon atoms will be described. The number of carbon atoms of the acyl group is not particularly limited as long as it is 3 or more, and may be 4 or more, 10 or more, or 14 or more. The content may be 40 or less, preferably 18 or less. The greater the number of carbon atoms of the acyl group, the more the flexibility of the cellulose derivative particle increases.

The cellulose derivative particles may have both an acyl group having 3 or more carbon atoms and an acyl group having 2 carbon atoms (acetyl group).

Examples of the acyl group having 3 or more carbon atoms include propionyl group, butyryl group, valeryl group, hexanoyl group, heptanoyl group, octanoyl group, nonanoyl group, undecanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group (myristoyl group), pentadecanoyl group, hexadecanoyl group, heptadecanoyl group, and octadecanoyl group (stearoyl group).

When the average particle diameter of the cellulose derivative particles of the present invention is 80nm or more and 100 μm or less, the average particle diameter may be 100nm or more, 1 μm or more, 2 μm or more, or 4 μm or more. The thickness may be 80 μm or less, 40 μm or less, 20 μm or less, or 14 μm or less. When the average particle size is too large, the feeling is poor and the light scattering (soft focus) effect is also reduced. In addition, when the average particle size is too small, the production is difficult. The feel may be, for example, skin feel or feel when the cellulose derivative particles are mixed in a cosmetic composition, in addition to the case of direct contact with the cellulose derivative particles.

The average particle diameter can be measured by a dynamic light scattering method. Specifically, the following is described. First, a sample was prepared by using an ultrasonic vibration device to prepare a pure water suspension of 100ppm concentration of cellulose derivative particles. Then, the average particle diameter was measured by measuring the volume frequency particle size distribution by a laser diffraction method (laser diffraction/scattering particle size distribution measuring device LA-960, manufactured by horiba, Ltd., ultrasonic treatment for 15 minutes, refractive index (1.500, medium (water; 1.333)) and the average particle diameter was measured, and the average particle diameter referred to herein is a particle diameter corresponding to a cumulative 50% of the scattering intensity in the particle size distribution.

The coefficient of variation in particle size of the cellulose derivative particles of the present invention may be 0% to 60%, or 2% to 50%.

The coefficient of variation (%) in particle size can be calculated from the standard deviation of particle size/average particle size × 100.

When the sphericity of the cellulose derivative particles of the present invention is 70% to 100%, it is preferably 80% to 100%, more preferably 90% to 100%, and still more preferably 95% to 100%. When the sphericity is less than 70%, the feel to the touch is poor, and for example, when the sphericity is incorporated in a cosmetic composition, the skin feeling and soft focus effect are also reduced.

The sphericity can be measured by the following method. Using the particle images observed by a Scanning Electron Microscope (SEM), the major and minor diameters of 30 particles selected at random were measured, and the minor diameter/major diameter ratio of each particle was determined, and the average of the minor diameter/major diameter ratio was defined as the sphericity (%). The closer the sphericity is to 100%, the more the sphericity can be determined as a sphere.

When the surface smoothness of the cellulose derivative particles of the present invention is 80% or more and 100% or less, it is preferably 85% or more and 100% or less, and more preferably 90% or more and 100% or less. When the surface smoothness is less than 80%, the touch is poor. From the viewpoint of the touch, the closer to 100% the surface smoothness is, the more preferable.

The surface smoothness can be obtained by taking a scanning electron micrograph of the particles, observing the irregularities on the particle surface, and based on the area of the recesses.

When the total substitution degree of the cellulose derivative particles of the present invention is 0.7 or more and 3 or less, it is preferably 1.0 or more and 3 or less, more preferably 1.4 or more and 3 or less, and still more preferably 2.0 or more and 3 or less. This is because spherical particles having excellent moldability and high sphericity can be easily produced.

When the total substitution degree is less than 0.7, the water solubility is high, and in a step of extracting particles in the production of cellulose derivative particles described later, particularly in a step of removing the water-soluble polymer from the dispersion, the cellulose derivative may be easily eluted, and the sphericity of the obtained particles may be reduced, and thus the feel may be poor. When the total substitution degree is closer to 3, the biodegradability of the cellulose derivative particles is inferior.

The total degree of substitution of the cellulose derivative can be measured by the following method. First, the total degree of substitution of the cellulose derivative is the sum of the degrees of substitution at the 2-, 3-and 6-positions of the glucose ring of the cellulose derivative, and the degrees of substitution at the 2-, 3-and 6-positions of the glucose ring of the cellulose derivative can be measured by the NMR method according to the method of Otsuka (Tezuka, Carboydr. Res.273, 83 (1995)). That is, in pyridine, the free hydroxyl group of the cellulose derivative is acylated with a carboxylic anhydride. The kind of carboxylic anhydride used herein is selected according to the purpose of analysis, and for example, acetic anhydride is suitable when the substitution degree of propionyl group of cellulose acetate propionate is analyzed, and propionic anhydride is suitable when the substitution degree of acetyl group is analyzed. The solvent and acid anhydride for the acylation reaction may be appropriately selected depending on the cellulose derivative to be analyzed.

The sample obtained by acylation was dissolved in deuterated chloroform, and the 13C-NMR spectrum was measured. When the substituent is acetyl, propionyl or butyryl, for example, the carbon signal of acetyl appears in the order of 2, 3 and 6 from the high magnetic field in the region of 169ppm to 171ppm, the signal of carbonyl carbon of propionyl appears in the same order in the region of 172ppm to 174ppm, and the carbon signal of butyryl appears in the order of 2, 3 and 6 from the high magnetic field side in the region of 171ppm to 173 ppm. For another example, when a cellulose derivative having propionyl groups or a cellulose derivative not having propionyl groups is treated with propionic anhydride for analysis purposes to analyze the substitution degree of propionyl groups, signals of carbonyl carbons of propionyl groups appear in the same order in the region of 172ppm to 174 ppm.

Since the total degree of substitution of a cellulose derivative obtained by treatment with a carboxylic anhydride using the manual method or the method conforming to the manual method is 3.0, the degrees of substitution of the respective acyl groups at the 2-, 3-and 6-positions of the glucose ring in the original cellulose derivative can be determined by normalizing the sum of the areas of the carbonyl carbon signal of the acyl group originally present in the cellulose derivative and the carbonyl signal of the acyl group introduced by the carboxylic anhydride treatment to 3.0 and determining the presence ratio (area ratio of the respective signals) of the acetyl group and the propionyl group at the respective corresponding positions. Incidentally, the substituents including the acyl group which can be analyzed by this method are not necessarily the only substituents which do not correspond to the carboxylic anhydride used for the purpose of analysis.

When the total degree of substitution at the 2-, 3-and 6-positions of the glucose ring of the cellulose derivative as the sample is known to be 3.0 and all the substituents are limited to acetyl, propionyl, and the like, the sample may be directly dissolved in deuterated chloroform without performing the acylation step to measure the NMR spectrum. When all the substituents are acetyl groups and propionyl groups, as in the case of the step involving acylation, since carbon signals of acetyl groups appear in the order of 2-, 3-, and 6-positions from a high magnetic field in the region of 169ppm to 171ppm and carbon signals of propionyl groups appear in the same order in the region of 172ppm to 174ppm, the degrees of substitution such as the degrees of substitution of the acetyl groups and propionyl groups at the 2-, 3-, and 6-positions of the glucose ring in the cellulose derivative can be determined from the presence ratio of the acetyl groups and propionyl groups at the corresponding positions (in other words, the area ratio of the signals).

The cellulose derivative particles of the present invention may have a bulk specific gravity of 0.1 to 0.9, 0.5 to 0.9, or 0.6 to 0.9. For example, in the case where the particles are blended in a cosmetic, the higher the bulk specific gravity of the particles, the better the fluidity of the cosmetic composition. The bulk specific gravity can be measured by a method in accordance with JIS K1201-1.

The cellulose derivative particles of the present invention have a true specific gravity of preferably more than 1, more preferably 1.04 or more, still more preferably 1.1 or more, and most preferably 1.2 or more. The sphericity of the cellulose derivative fine particles may be 1.35 or less from the viewpoint of 70% or more. The true specific gravity can be measured by the measuring method based on a pycnometer (liquid: water) according to JIS Z8807 and 1976 "method for measuring specific gravity of solids".

The true specific gravity is the density of water at 4 ℃: 0.999973g/cm-³Is the basis specific gravity.

The cellulose derivative particles of the present invention may or may not contain a plasticizer. In the present invention, the plasticizer is a compound capable of increasing the plasticity of the cellulose derivative. The plasticizer is not particularly limited, and examples thereof include: adipic acid plasticizers containing adipic acid esters such as dimethyl adipate, dibutyl adipate, diisostearyl adipate, diisodecyl adipate, diisononyl adipate, diisobutyl adipate, diisopropyl adipate, diethylhexyl adipate, dioctyl adipate, dioctyldodecyl adipate, dioctyl adipate, and dihexyldecyl adipate; citric acid plasticizers comprising citric acid esters such as acetyl triethyl citrate, acetyl tributyl citrate, isodecyl citrate, isopropyl citrate, triethyl citrate, triethylhexyl citrate, and tributyl citrate; glutaric acid plasticizers containing glutaric acid esters such as diisobutyl glutarate, dioctyl glutarate, and dimethyl glutarate; succinic acid plasticizers containing succinic acid esters such as diisobutyl succinate, diethyl succinate, diethylhexyl succinate, and dioctyl succinate; sebacic acid plasticizers containing sebacic acid esters such as diisoamyl sebacate, diisooctyl sebacate, diisopropyl sebacate, diethyl sebacate, diethylhexyl sebacate, and dioctyl sebacate; a glyceride plasticizer containing glycerin alkyl esters such as triacetin, diacetin, and monoacetin; neopentyl glycol; and a phosphoric acid plasticizer containing phosphoric acid esters such as trioleyl phosphate, tristearyl phosphate, and tricetyl phosphate. These plasticizers may be used alone, or 2 or more kinds of plasticizers may be used in combination.

Among these, preferred are citric acid plasticizers selected from the group consisting of citric acid esters including triethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate; a glyceride plasticizer containing glycerin alkyl esters such as triacetin, diacetin, and monoacetin; and an adipic acid plasticizer such as diisononyl adipate, more preferably at least one member selected from the group consisting of triethyl citrate, acetyl tributyl citrate, triacetin, and diisononyl adipate, and still more preferably at least one member selected from the group consisting of acetyl triethyl citrate, triacetin, and diacetin. Although the phthalic acid plasticizer can be used, attention is required in use in consideration of the similarity with environmental hormones.

When the cellulose derivative particles contain a plasticizer, the content of the plasticizer contained in the cellulose derivative particles is not particularly limited. For example, the content may be more than 0 wt% and 40 wt% or less, may be 0.01 wt% or more and 40 wt% or less, may be 0.05 wt% or more and 35 wt% or less, may be 0.1 wt% or more and 30 wt% or less, may be 0.4 wt% or more and 20 wt% or less, may be 0.4 wt% or more and 15 wt% or less, may be 0.4 wt% or more and 10 wt% or less, may be 0.4 wt% or more and 5 wt% or less, and may be 0.4 wt% or more and 2.5 wt% or less, based on the weight of the cellulose derivative particles. The smaller the content of the plasticizer, the better, but a large amount is allowable as long as the object of the present invention is not impaired.

The content of the plasticizer in the cellulose derivative particles is determined by dissolving the cellulose derivative particles in a solvent capable of dissolving the cellulose derivative particles, and subjecting the solution to¹H-NMR was measured.

The cellulose derivative particles of the present invention can be produced by the production method described below.

The cellulose derivative particles of the present invention are excellent in touch feeling, and therefore can be suitably used in, for example, a cosmetic composition. Further, since the spherical shape has a high sphericity, when incorporated in a cosmetic composition, the effects of filling in the irregularities of the skin to smooth the irregularities, and preventing wrinkles and the like from becoming conspicuous (soft focus) by scattering light in various directions can be obtained.

As cosmetic compositions, foundations such as liquid foundations and powder foundations; concealing the concealer; sun protection; isolating; priming lipstick and lipstick; body powder, solid powder, loose powder, and the like: solid powder eye shadow; anti-wrinkle cream; and skin and hair external preparations mainly for cosmetic purposes such as skin care lotions, and the dosage forms thereof are not limited. The dosage form may be aqueous solution, emulsion, suspension, etc.; semisolid agents such as gels and creams; any of solid agents such as powder, granule and solid. In addition, the emulsion can also be in the form of cream, emulsion and the like; oil gel formulations such as lipstick; powder formulations such as foundation; and aerosol formulations such as hair styling agents.

The cosmetic composition, particularly a liquid foundation, containing the cellulose derivative particles of the present invention is excellent in spreading to the skin, coverage of stains and freckles, and smoothness.

[ Process for producing cellulose derivative particles ]

The method for producing cellulose derivative particles of the present invention comprises the steps of: a step in which a cellulose derivative having a total substitution degree of 0.7 to 3 inclusive is kneaded with a water-soluble polymer at 200 to 280 ℃ to obtain a dispersion having the cellulose derivative as a dispersoid; and removing the water-soluble polymer from the dispersion.

(step of obtaining Dispersion)

In the step of obtaining the dispersion, a cellulose derivative having a total substitution degree of 0.7 to 3 is kneaded with a water-soluble polymer at 200 to 280 ℃ to obtain a dispersion containing the cellulose derivative as a dispersoid.

The cellulose derivative and the water-soluble polymer can be kneaded using an extruder such as a twin-screw extruder. The temperature of mixing is referred to as barrel temperature.

The dispersion may be extruded in a strand form from a die attached to the tip of an extruder such as a twin-screw extruder, and then cut to prepare pellets. In this case, the mold temperature may be 220 ℃ or higher and 300 ℃ or lower.

When the total degree of substitution of the cellulose acetate is 0.7 or more and 3 or less, it is preferably 1.0 or more and 3 or less, more preferably 1.4 or more and 3 or less, and still more preferably 2.0 or more and 3 or less. The total substitution degree can be adjusted by adjusting the conditions (time, temperature, and the like) of the aging step.

The amount of the water-soluble polymer to be blended may be 55 parts by weight or more and 99 parts by weight or less based on 100 parts by weight of the total amount of the cellulose derivative and the water-soluble polymer. Preferably 60 parts by weight or more and 90 parts by weight or less, and more preferably 65 parts by weight or more and 85 parts by weight or less.

The water-soluble polymer in the present specification means a polymer having an insoluble content of less than 50% by weight when 1g of the polymer is dissolved in 100g of water at 25 ℃. Examples of the water-soluble polymer include polyvinyl alcohol, polyethylene glycol, sodium polyacrylate, polyvinylpyrrolidone, polypropylene oxide, polyglycerol, polyethylene oxide, vinyl acetate, modified starch, thermoplastic starch, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose. Among these, polyvinyl alcohol, polyethylene glycol and thermoplastic starch are preferable, and polyvinyl alcohol and thermoplastic starch are particularly preferable. It should be noted that thermoplastic starch can be obtained by known methods. For example, Japanese examined patent publication (Kokoku) No. 6-6307 and WO92/04408 can be cited, and more specifically, for example, a mixture of tapioca starch and about 20% of glycerin as a plasticizer and kneaded by using a twin-screw extruder can be used.

The obtained dispersion is a dispersion in which a water-soluble polymer is used as a dispersion medium and the cellulose derivative is used as a dispersoid. In other words, the water-soluble polymer may be a sea component and the cellulose derivative may be an island component. In the dispersion, the kneaded material constituting the island component contains a cellulose derivative and is mainly spherical.

The cellulose derivative having a degree of substitution of 0.7 or more and 3 or less can be produced by a known method for producing the derivative. When the cellulose derivative is a cellulose ester, it can be produced, for example, by the following steps: a step of activating the raw material pulp (cellulose); acylating the activated cellulose with an esterifying agent (acylating agent); deactivating the acylating agent after the completion of the acylation reaction; and (3) aging (saponification and hydrolysis) the cellulose acylate thus produced. Before the step of activation, the following pretreatment steps may be provided: the raw material slurry was dissociated and pulverized, and then acetic acid was dispersed and mixed. After the step of aging (saponification and hydrolysis), the following post-treatment step may be provided: separating the precipitate, purifying, stabilizing and drying.

In addition, when the cellulose derivative is a cellulose ether, it can be produced through the following steps: a step of impregnating a raw material slurry (cellulose) with a mixed solution of a lower aliphatic alcohol such as isopropyl alcohol (IPA) or tert-butyl alcohol (TBA), water, and an alkali metal hydroxide such as sodium hydroxide to obtain alkali cellulose which is a precursor of cellulose ether; and a step of further adding an etherifying agent to form a slurry (precipitation). The method may further comprise, before the step of obtaining alkali cellulose, the following pretreatment steps: the raw material slurry was dissociated and pulverized, and then acetic acid was dispersed and mixed. After the step of slurrying (precipitating), the following post-treatment steps may be provided: separating the precipitate, purifying, stabilizing and drying.

(step of removing Water-soluble Polymer)

The step of removing the water-soluble polymer from the dispersion will be described.

The method for removing the water-soluble polymer is not particularly limited as long as the water-soluble polymer can be dissolved and removed from the particles, and examples thereof include the following methods: the water-soluble polymer of the dispersion is dissolved and removed using a solvent such as water, an alcohol such as methanol, ethanol, or isopropyl alcohol, or a mixed solution thereof. Specifically, for example, the following methods can be mentioned: the water-soluble polymer is removed from the dispersion by mixing the dispersion with the solvent, filtering, and taking out the filtrate.

As described later, in the case where the cellulose derivative impregnated with the plasticizer is prepared by mixing a cellulose derivative having a total substitution degree of 0.7 to 3 with a plasticizer before the step of obtaining a dispersion, the plasticizer may or may not be removed from the dispersion together with the water-soluble polymer in the step of removing the water-soluble polymer from the dispersion. Therefore, the obtained cellulose derivative particles may or may not contain a plasticizer.

The mixing ratio of the dispersion and the solvent is preferably 0.01 wt% or more and 20 wt% or less, more preferably 2 wt% or more and 15 wt% or less, and further preferably 4 wt% or more and 13 wt% or less, based on the total weight of the dispersion and the solvent. When the amount of the dispersion is more than 20% by weight, the dissolution of the water-soluble polymer becomes insufficient and the water-soluble polymer cannot be removed by washing, or it is difficult to separate cellulose derivative particles which are not dissolved in the solvent from the water-soluble polymer dissolved in the solvent by filtration, centrifugation or the like.

The mixing temperature of the dispersion and the solvent is preferably 0 ℃ to 200 ℃, more preferably 20 ℃ to 110 ℃, and still more preferably 40 ℃ to 80 ℃. When the temperature is lower than 0 ℃, the solubility of the water-soluble polymer becomes insufficient and it is difficult to remove the polymer by washing, and when the temperature exceeds 200 ℃, deformation, aggregation, and the like of the particles occur, and it is difficult to take out the particles while maintaining a desired particle shape.

The mixing time of the dispersion and the solvent is not particularly limited, and may be appropriately adjusted, and for example, may be 0.5 hours or more, 1 hour or more, 3 hours or more, 5 hours or more, or 6 hours or less.

The method of mixing is not limited as long as the water-soluble polymer can be dissolved, and for example, the water-soluble polymer can be efficiently removed from the dispersion at room temperature by using a stirring device such as an ultrasonic homogenizer or a three-in-one motor.

For example, when a three-in-one motor is used as the stirring device, the rotation speed at the time of mixing the dispersion and the solvent may be, for example, 5rpm to 3000 rpm. This enables the water-soluble polymer to be removed from the dispersion more efficiently. In addition, efficient removal of the plasticizer from the dispersion is also enabled.

(optional step: step of obtaining a cellulose derivative impregnated with a plasticizer)

The cellulose derivative having a total substitution degree of 0.7 or more and 3 or less may be a cellulose derivative impregnated with a plasticizer, and the method may further include, before the step of obtaining the dispersion, the steps of: the plasticizer-impregnated cellulose derivative is obtained by mixing a cellulose derivative having a total substitution degree of 0.7 to 3 with a plasticizer. In this step, a cellulose derivative having a total substitution degree of 0.7 or more and 3 or less is mixed with a plasticizer.

The plasticizer is not particularly limited as long as it has a plasticizing effect in melt extrusion processing of the cellulose derivative, and specifically, the above-mentioned plasticizers exemplified as the plasticizer contained in the cellulose derivative particles may be used alone or in combination of two or more kinds of plasticizers.

Among the above plasticizers, preferred are citric acid-based plasticizers selected from the group consisting of citric acid esters including triethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate; a glyceride plasticizer containing glycerin alkyl esters such as triacetin, diacetin, and monoacetin; and an adipic acid plasticizer such as diisononyl adipate, more preferably at least one member selected from the group consisting of triethyl citrate, acetyl tributyl citrate, triacetin, and diisononyl adipate, and still more preferably at least one member selected from the group consisting of acetyl triethyl citrate, triacetin, and diacetin. In the case of a phthalic acid plasticizer, attention is required in use in view of the similarity with environmental hormones.

The amount of the plasticizer to be blended may be more than 0 part by weight and 40 parts by weight or less, 2 parts by weight or more and 40 parts by weight or less, 10 parts by weight or more and 30 parts by weight or less, and 15 parts by weight or more and 20 parts by weight or less, based on 100 parts by weight of the total amount of the cellulose derivative and the plasticizer. When the amount of the plasticizer is too small, the sphericity of the obtained cellulose derivative particles tends to decrease, and when the amount of the plasticizer is too large, the shape of the particles cannot be maintained, and the sphericity tends to decrease.

The mixing of the cellulose acetate derivative with the plasticizer can be carried out in a dry or wet manner using a mixer such as a henschel mixer. When a mixer such as a henschel mixer is used, the temperature in the mixer may be a temperature at which the cellulose derivative does not melt, for example, a temperature in the range of 20 ℃ or higher and lower than 200 ℃.

The cellulose derivative and the plasticizer may be mixed by melt kneading. In addition, the melt kneading may be carried out in combination with mixing using a mixer such as a henschel mixer, and in this case, it is preferable to carry out melt kneading after mixing at a temperature condition of 20 ℃ or higher and lower than 200 ℃ using a mixer such as a henschel mixer. By fusing the plasticizer and the cellulose derivative more uniformly and in a short time, the sphericity of the cellulose derivative particles which can be finally produced is improved, and the touch comfort are improved.

The melt-kneading is preferably carried out by heating and mixing using an extruder. The mixing temperature (barrel temperature) of the extruder may be in the range of 200 ℃ to 230 ℃. Even at a temperature within this range, the resulting mixture can be plasticized to obtain a uniform kneaded product. If the temperature is too low, the sphericity of the particles obtained decreases, and therefore the feeling and the touch comfort are reduced, and if the temperature is too high, the kneaded product may be thermally deteriorated or colored. In addition, the viscosity of the melt may decrease, and the kneading of the resin in the twin-screw extruder may be insufficient.

This is because the melting point of the cellulose derivative is generally 230 to 280 ℃ and close to the decomposition temperature of the cellulose derivative, although it depends on the substitution degree, and therefore melt kneading is generally difficult in this temperature range, but the plasticizing temperature of the cellulose derivative (sheet) impregnated with the plasticizer can be lowered. The kneading temperature (cylinder temperature) may be, for example, 200 ℃ in the case of using a twin-screw extruder. The kneaded product may be extruded in a strand-like form and formed into a pellet-like form by thermal cutting or the like. The mold temperature in this case may be about 220 ℃.