Biodegradable spherical particles and method for producing the same

Abstract

To provide biodegradable spherical particles that maintain their initial satisfactory tactile properties and a method for producing the biodegradable spherical particles.SOLUTION: Biodegradable spherical particles are mainly composed of a biodegradable polymer. The biodegradable spherical particles have a coefficient of variation CV in particle diameter of 40% or less and a five-day biodegradability, as determined by a biodegradability test in accordance with OECD TG301F, of 40% or less. A cosmetic composition contains the biodegradable spherical particles. A method for producing the biodegradable spherical particles comprises mixing the biodegradable polymer, a plasticizer, and a water-soluble polymer to obtain a mixture, melt-kneading the mixture at a temperature of 200-280°C to obtain a kneaded mixture, and removing the water-soluble polymer from the kneaded mixture.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to biodegradable spherical particles and methods for producing the same. More specifically, this disclosure relates to biodegradable spherical particles for use in cosmetic compositions and methods for producing the same. [Background technology]

[0002] Traditionally, cosmetics have incorporated various polymer microparticles for purposes such as improving spreadability, altering texture, providing wrinkle-blurring effects, and enhancing the smoothness of foundations and other products. Microparticles with high sphericity, in particular, offer superior texture, and their physical properties and shape can produce a light-scattering (soft-focus) effect. When such microparticles are used in foundations and other products, they can fill in skin irregularities, smooth the skin, and scatter light in various directions, making wrinkles and other imperfections less noticeable (soft-focus effect).

[0003] For use in such cosmetics, microparticles made from synthetic polymers such as polyamide, polymethyl methacrylate (PMMA), polystyrene, polypropylene, and polyethylene have been used. However, in recent years, due to environmental concerns, there has been a demand for microparticles made from biodegradable materials that possess the necessary properties while having a low environmental impact, as an alternative to these synthetic polymers.

[0004] Patent Document 1 (Japanese Patent Publication No. 6872068) discloses resin beads mainly composed of cellulose, wherein the cumulative 50% particle diameter by volume is 50 μm or less, the sphericity is 0.7 to 1.0, the surface smoothness is 70 to 100%, the solidity is 50 to 100%, the 5-day biodegradation rate measured in accordance with JIS K6950 is 20% or more, and the cellulose content in the resin is 90 to 100% by mass.

[0005] Patent Document 2 discloses a spherical cellulose powder having an average primary particle diameter of 5 μm or less, with the primary particle diameter of 90% or more of the total particles being in the range of 2 to 7 μm, the ratio of the longest diameter to the shortest diameter of the sphere (longest diameter / shortest diameter) being in the range of 1.0 to 2.5, a haze value of 70% or more of 20% by mass of silicone oil paste, and a total transmittance of 95% or more.

[0006] Patent Document 3 describes a method of preparing a dispersion by kneading a resin component (A), such as a thermoplastic resin, with a water-soluble auxiliary component (B), eluting the auxiliary component (B) from this dispersion, and producing a molded article (for example, a porous body or spherical particles) composed of the resin component (A). The patent document also describes cellulose derivatives, polylactic acid, etc., as the resin component (A). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 6872068 [Patent Document 2] Japanese Patent Publication No. 2013-221000 [Patent Document 3] Japanese Patent Publication No. 2004-051942 [Overview of the project] [Problems that the invention aims to solve]

[0008] The particulate molded articles obtained by the manufacturing method described in Patent Document 3 have low sphericity, being only roughly spherical, and their biodegradability is not sufficient.

[0009] The cellulose-based microparticles disclosed in Patent Documents 1 and 2 exhibit excellent biodegradability. However, the spherical particles described in Patent Document 2 have poor surface smoothness and therefore cannot provide a good tactile feel. Furthermore, in cosmetics containing biodegradable microparticles, the feel may change after use due to the decomposition of the microparticles. Users are particularly sensitive to changes in tactile feel. There is a need for biodegradable microparticles that minimize changes in feel when incorporated into cosmetic compositions. The particles disclosed in Patent Document 1 cannot sufficiently suppress changes in feel.

[0010] The purpose of this disclosure is to provide biodegradable spherical particles and a method for producing the same, which can be used to obtain cosmetic compositions that have a good tactile feel and whose feel does not change in the short term. [Means for solving the problem]

[0011] The biodegradable spherical particles relating to this disclosure mainly consist of a biodegradable polymer. These biodegradable spherical particles have a particle size variation coefficient CV of 40% or less, and in a biodegradation test in accordance with OECD TG301F, the degree of biodegradation on day 5, calculated by the following formula, is 40% or less. Biodegradation degree (%)=(BOD-B) / TOD×100 (In the formula, BOD is the biochemical oxygen consumption by the test substance (mg), B is the biochemical oxygen consumption of the blank (mg), and TOD is the theoretical oxygen consumption by the test substance (mg).) [Effects of the Invention]

[0012] According to this disclosure, the biodegradable spherical particles exhibit a good tactile feel due to their narrow particle size distribution and nearly uniform particle size. These spherical particles have a low initial decomposition rate in a predetermined biodegradation test. In other words, these spherical particles decompose slowly and gradually. Cosmetic compositions containing these spherical particles avoid the deterioration of usability caused by the rapid decomposition of the spherical particles. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a scanning electron microscope (SEM) image (magnification: 800 times) of the particles of Example A-1. [Figure 2] Figure 2 is a scanning electron microscope (SEM) image (magnification: 5000 times or more) of the particles of Example A-1. [Figure 3] Figure 3 is a scanning electron microscope (SEM) image (magnification: 800 times) of the particles of Comparative Example A-2. [Figure 4] Figure 4 is a scanning electron microscope (SEM) image (magnification: 5000 times or more) of the particles of Comparative Example A-2. [Figure 5] Figure 5 is a scanning electron microscope (SEM) image (magnification: 800 times) of the particles of Example A-1 after decomposition treatment. [Figure 6] Figure 6 is a scanning electron microscope (SEM) image (magnification: 15000 times) of the particles of Example A-1 after decomposition treatment. [Figure 7] Figure 7 is a scanning electron microscope (SEM) image (magnification: 800 times) of the particles of Comparative Example A-2 after decomposition treatment. [Figure 8] Figure 8 is a scanning electron microscope (SEM) image (magnification: 5000 times) of the particles of Comparative Example A-2 after decomposition treatment.

Mode for Carrying Out the Invention

[0014] Hereinafter, the present disclosure will be described in detail based on preferred embodiments. Each configuration and their combinations in each embodiment are examples, and within the scope not departing from the gist of the present disclosure, addition, omission, substitution, and other changes of the configuration can be made as appropriate. The present disclosure is not limited by the embodiments, but is only limited by the scope of the claims. In addition, each aspect disclosed in this specification can be combined with any other features disclosed in this specification.

[0015] In the present specification, "X~Y" indicating a range means "X or more and Y or less", "ppm" means "weight ppm", and unless otherwise noted, all test temperatures are room temperature (20°C ± 5°C).

[0016] [Biodegradable spherical particles] The biodegradable spherical particles of this disclosure (hereinafter sometimes referred to as "spherical particles") are particles whose main component is a biodegradable polymer. Here, "main component" means that the most abundant component among the constituent components of the particle is a biodegradable polymer, and that its content is at least 50% by weight. Furthermore, "biodegradable polymer" means a polymer that is decomposed in soil or seawater or in living organisms. In this disclosure, "polymer" is defined as a compound composed of one or more constituent units repeatedly bonded together. It may be a synthetic polymer or a naturally derived polymer, as long as it exhibits the required biodegradability.

[0017] Furthermore, these spherical particles have a particle size variation coefficient (CV) of 40% or less, and in biodegradability tests compliant with OECD TG301F, the degree of biodegradation on day 5, calculated using the following formula, is 40% or less. Biodegradation degree (%)=(BOD-B) / TOD×100 (In the formula, BOD is the biochemical oxygen consumption by the test substance (mg), B is the biochemical oxygen consumption of the blank (mg), and TOD is the theoretical oxygen consumption by the test substance (mg).)

[0018] The spherical particles of this disclosure are made from a biodegradable material and have an extremely good tactile feel due to their shape and narrow particle size distribution. By incorporating these spherical particles, it is possible to obtain a cosmetic composition that is environmentally friendly and of high quality. Moreover, the spherical particles of this disclosure exhibit slower decomposition compared to particles made from conventional biodegradable materials. In cosmetic compositions incorporating these spherical particles, the feel, especially the tactile feel, does not change in the short term. In this specification, "tactile feel" includes not only the feel when directly touching the spherical particles, but also the feel and texture when they are incorporated into a cosmetic composition, for example.

[0019] The spherical particles of this disclosure are biodegradable, and their decomposition rate is controlled. The biodegradability of the spherical particles can be evaluated by a biodegradability test in accordance with OECD TG301F. Specifically, the test substance (spherical particles) is dispersed in a culture medium (water), an inoculation source (activated sludge from a sewage treatment plant) is added, and the culture is incubated at 22°C ± 2°C for 28 days. The amount of oxygen consumed by microorganisms to decompose the test substance (biochemical oxygen consumption) is measured over time, and the ratio to the theoretical oxygen consumption by the test substance is determined as the degree of biodegradation (%). The degree of biodegradation in this specification is determined with a test substance concentration of 100 mg / L, an inoculation source concentration of 30 mg / L, and a test solution volume of 100 mL. This degree of biodegradation (%) is calculated by the following formula. Biodegradation degree (%)=(BOD-B) / TOD×100 (In the formula, BOD is the biochemical oxygen consumption by the test substance (mg), B is the biochemical oxygen consumption of the blank (mg), and TOD is the theoretical oxygen consumption by the test substance (mg).)

[0020] According to OECD TG301F, test substances that exhibit a biodegradability of more than 60% after 28 days are generally considered "easily degradable." For example, microcrystalline cellulose exhibits a so-called sigmoid-type degradation behavior, where the degradation reaction proceeds rapidly during the first five days after the start of the test, and then the degradation rate decreases to reach equilibrium. The disclosers considered that this rapid degradation during the first five days after the start of the test is the cause of short-term changes in the texture of cosmetic compositions containing spherical particles. They found that by reducing the initial degradation rate of the biodegradable spherical particles, and setting the biodegradability to 40% or less on the fifth day in the biodegradability test compliant with the aforementioned OECD TG301F, short-term changes in the feel of use can be suppressed. In other words, the spherical particles of this disclosure differ from conventional biodegradable resin particles in that they exhibit a low initial degradation rate and mild degradation behavior. From the viewpoint of improving the stability of the feel of use, the biodegradability of the spherical particles on the fifth day is preferably 35% or less, and more preferably 30% or less. From the perspective of minimizing environmental impact, a biodegradation rate of 10% or more on the fifth day is preferable.

[0021] When the degree of biodegradation on day 5, measured according to a biodegradation test compliant with OECD TG301F, is defined as BD5 (%), and the degree of biodegradation on day 28 is defined as BD28 (%), from the viewpoint of suppressing fluctuations in usability while maintaining high biodegradability, the ratio BD5 / BD28 for these spherical particles may be 0.60 or less, 0.55 or less, 0.50 or less, or 0.45 or less. From the viewpoint of improving biodegradability, a preferred ratio BD5 / BD28 is 0.10 or higher.

[0022] From the perspective of suppressing fluctuations in usability while maintaining high biodegradability, it is preferable that the biodegradation degree BD5 on day 5 and the biodegradation degree BD28 on day 28, as measured by a biodegradation test in accordance with OECD TG301F, satisfy the following formula. (BD28 - BD5) / BD5 ≥ 0.50

[0023] For spherical particles where the ratio of the difference between BD28 and BD5 (BD28-BD5) to BD5 (BD28-BD5) / BD5 is 0.50 or higher, the decomposition reaction is suppressed during the 5-day biodegradation test, and the decomposition reaction proceeds from 5 to 28 days. From the viewpoint of improving biodegradability, this ratio (BD28-BD5) / BD5 may be 0.60 or higher, 0.70 or higher, or 0.80 or higher. From the viewpoint of minimizing the impact on the tactile feel in the initial stages of use, a preferred ratio (BD28-BD5) / BD5 is 2.0 or lower.

[0024] These spherical particles may satisfy the following formulas when measuring their biodegradability BD5 on day 5 and BD28 on day 28, as measured by a biodegradability test in accordance with OECD TG301F. (BD28 - BD5) / BD28 ≥ 0.30

[0025] For spherical particles where the ratio of the difference between BD28 and BD5 (BD28-BD5) to BD28 (BD28-BD5) / BD28 is 0.30 or higher, high biodegradability is achieved while suppressing fluctuations in tactile feel during the initial stages of use. From this perspective, this ratio (BD28-BD5) / BD28 may be 0.35 or higher, 0.40 or higher, 0.45 or higher, 1.0 or lower, or 0.90 or lower.

[0026] The coefficient of variation CV of the spherical particles is 40% or less. Spherical particles with a coefficient of variation CV of 40% or less exhibit little variation in particle size. These spherical particles have a good tactile feel. Furthermore, because of the small variation in particle size, the decomposition reaction proceeds almost uniformly in each particle. Therefore, even if the particle size decreases as the decomposition reaction progresses, a narrow particle size distribution is maintained. The tactile feel of the spherical particles of this disclosure does not deteriorate in the short term. From the viewpoint of stabilizing physical properties, the coefficient of change CV of the spherical particles is preferably 38% or less, and more preferably 35% or less. From the viewpoint of ease of manufacture, the coefficient of variation CV of the spherical particles may be 0% or more, and may be 2% or more. The coefficient of variation CV of the particle size is calculated using the average particle size and the standard deviation of the particle size of the spherical particles, as described later, by the following formula. Coefficient of variation of particle size CV (%) = Standard deviation of particle size / Average particle size × 100

[0027] The average particle size of the spherical particles may be 0.08 μm or larger, 0.1 μm or larger, 1.0 μm or larger, 2.0 μm or larger, or 4.0 μm or larger. It may also be 100 μm or smaller, 80 μm or smaller, 40 μm or smaller, 20 μm or smaller, or 10 μm or smaller. If the average particle size is too large, the tactile feel will be inferior, and the light scattering (soft focus) effect will be reduced. Conversely, if the average particle size is too small, manufacturing will be difficult.

[0028] The average particle diameter and the coefficient of variation of particle diameter can be measured using dynamic light scattering. Specifically, the procedure is as follows: First, spherical particles are added to pure water to a concentration of 100 ppm, and a sample is prepared by creating a pure water suspension using an ultrasonic vibrator. Then, the volume frequency particle size distribution is measured by laser diffraction (Horiba, Ltd. "Laser Diffraction / Scattering Particle Size Distribution Analyzer LA-960", ultrasonic treatment for 15 minutes, refractive index (1.500, medium (water; 1.333))). In this volume frequency particle size distribution, the particle diameter corresponding to 50% of the integrated scattering intensity is determined as the average particle diameter. That is, the average particle diameter (μm) in this specification is the volume-based median diameter. The coefficient of variation of particle diameter is calculated from this median diameter and the standard deviation of the particle diameter.

[0029] The sphericity of the spherical particles of this disclosure is preferably 0.7 or more and 1.0 or less, more preferably 0.8 or more and 1.0 or less, and even more preferably 0.9 or more and 1.0 or less. If the sphericity is less than 0.7, the texture is inferior, and for example, when incorporated into a cosmetic composition, the skin feel and soft-focus effect are reduced.

[0030] Sphericity can be measured by the following method: Using images of particles observed with a scanning electron microscope (SEM), the major and minor axes of 30 randomly selected particles are measured, the minor axis / major axis ratio for each particle is determined, and the average of these minor axis / major axis ratios is taken as the sphericity. The closer the sphericity is to 1, the more perfectly spherical the particle is considered to be. Details of the measurement method will be described later in the examples.

[0031] The surface smoothness of the spherical particles in this disclosure is 80% or more, preferably 85% or more, more preferably 90% or more, even more preferably 95% or more, and particularly preferably 98% or more, with an upper limit of 100%. If the surface smoothness is less than 80%, the desired tactile sensation cannot be obtained, and the feel during use may fluctuate in the short term. From the viewpoint of improving tactile sensation and stabilizing physical properties, the surface smoothness of the spherical particles may be 80-100%, 85-100%, 90-100%, 95-100%, or 98-100%.

[0032] The surface smoothness of spherical particles can be determined by taking scanning electron microscope images of the particles, observing the surface irregularities, and basing the determination on the area of ​​the depressions. Details of the surface smoothness measurement method will be described later in the examples.

[0033] The shape of the spherical particles in this disclosure is not particularly limited, and it is preferable that they have the sphericity and surface smoothness described above. However, from the viewpoint of suppressing the initial decomposition rate and providing mild decomposition behavior that does not affect tactile sensation, it is more preferable that the surface shape has fewer fine irregularities. The disclosers have focused on the fact that even particles with the same surface smoothness exhibit different decomposition behavior depending on their surface shape, and have found that fine irregularities on the particle surface, which cannot be evaluated by the aforementioned surface smoothness, affect the decomposition properties of these particles, especially the initial decomposition properties. For example, when observing a 0.5 mm × 0.5 mm field of view at a magnification of 5000x using a scanning electron microscope, if there are substantially no particles with micron-sized depressions on their surface, and when observing a 0.5 mm × 0.5 mm field of view at a magnification of 5000x, if there are substantially no particles with micron-sized protrusions that extend from a virtual circle drawn along the arc of the spherical particle, the initial decomposition rate is suppressed and mild decomposition behavior is achieved. Here, "micron size" refers to a range of 0.5 μm to less than 10 μm, meaning that a roughly circular recess would have a diameter of approximately 0.5 to 10 μm.

[0034] Here, "substantially absent" is defined in detail as follows: when observing 30 randomly sampled particles in a scanning electron microscope image at a magnification of 5000x or higher, the average number of micron-sized depressions observed on the surface of a spherical particle is 3 or less, preferably 1 or less. Furthermore, when observing 30 randomly sampled particles in a scanning electron microscope image at a magnification of 5000x or higher, the average number of micron-sized protrusions projecting from a virtual circle drawn along the arc of the spherical particle is 3 or less, preferably 1 or less.

[0035] The main component of the spherical particles in this disclosure may be a biodegradable polymer selected from the group consisting of polysaccharides, polysaccharide esters, and aliphatic polyesters. Within the range in which the effects of this disclosure are obtained, the spherical particles may further contain biodegradable polymers such as aliphatic polyols, aliphatic polycarbonates, and polyacid anhydrides.

[0036] Polysaccharides refer to high-molecular-weight compounds formed by the linkage of monosaccharides via glycosidic bonds. As long as the effects of this disclosure are obtained, the polysaccharides may be polymers of α-glucose or polymers of β-glucose. Examples include cellulose, hemicellulose, pullulan, amylose, agarose, chitin, chitosan, carrageenan, pectin, dextrin, starch, collagen, mannan, arabinogalactan, glycogen, inulin, hyaluronic acid, and modified forms thereof. Two or more polysaccharides may be used in combination. One or two polysaccharides selected from cellulose and starch are preferred, with cellulose being more preferred. As long as the effects of this disclosure are obtained, commercially available polysaccharides may be used, or polysaccharides obtained by hydrolyzing polysaccharide esters described later. For example, if cellulose is used, it may be a fully saponified product of a known cellulose diacetate.

[0037] The weight-average molecular weight of cellulose is not particularly limited as long as the effects of this disclosure are obtained. The weight-average molecular weight of cellulose may be 10,000 or more, 20,000 or more, 30,000 or more, and may be 500,000 or less, 400,000 or less, or 300,000 or less. The weight-average molecular weight of cellulose can be measured by size exclusion chromatography (GPC) (GPC-light scattering method), similar to aliphatic polyesters described later.

[0038] Polysaccharide esters are defined as carboxylic acid esters of the aforementioned polysaccharides, in which some of the hydroxyl groups in the molecular chain are replaced by acyl groups. Esters of one or two polysaccharides selected from cellulose and starch are preferred, with cellulose esters being more preferred. Two or more polysaccharide esters may be used in combination. Other carboxylic acid esters of polysaccharides not specified herein may be used to the extent that the effects of this disclosure are obtained.

[0039] The total degree of substitution of the polysaccharide ester used in the spherical particles of this disclosure is appropriately selected within a range of greater than 0 and less than or equal to 3.0, depending on the type of polysaccharide and the type of substituent. The total degree of substitution of the polysaccharide ester may be 0.05 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.5 or more, 2.95 or less, 2.80 or less, 2.65 or less, 2.00 or less, 1.50 or less, 1.0 or less, and less than 0.7. The total degree of substitution of the polysaccharide ester is 13 C-NMR or 1 It can be measured using known methods with 1H-NMR.

[0040] From the viewpoint of being readily available and having excellent biodegradability, preferred polysaccharide esters are cellulose esters, and cellulose acylates having acyl groups with 2 or more carbon atoms are more preferred. The number of carbon atoms in the acyl groups of cellulose acylate may be 3 or more, 4 or more, 10 or less, or 8 or less. Cellulose acylates may have two or more acyl groups as substituents. In this disclosure, two or more cellulose acylates having acyl groups with different numbers of carbon atoms may be used in combination as biodegradable polymers.

[0041] Specific examples of cellulose acylates in this disclosure include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate. From the viewpoint of biodegradability and availability, cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate are preferred, with cellulose acetate being more preferred.

[0042] The total degree of substitution of cellulose acylate is appropriately selected within the range of 0 to 3.0, similar to the polysaccharide esters described above. However, from the viewpoint of obtaining good biodegradability, for example, the total degree of substitution of cellulose acylate having acyl groups with 2 to 10 carbon atoms is preferably greater than 0 and less than 1.0. The total degree of substitution of this cellulose acylate may be 0.05 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, and may also be 0.9 or less, 0.8 or less, or less than 0.7. Within the range in which the effects of this disclosure can be obtained, cellulose acylates with different total degrees of substitution may be used in combination, or cellulose acylates with a total degree of substitution greater than 1.0 and less than 3.0 may be mixed and used.

[0043] The degree of substitution of cellulose acylate can be measured by the following method. For example, it can be measured by NMR according to the method of Tezuka (Carbonydr. Res. 273, 83 (1995)). That is, the free hydroxyl group of cellulose acylate is acylated with a carboxylic acid anhydride in pyridine. The type of carboxylic acid anhydride used here should be selected according to the purpose of analysis; for example, acetic anhydride is suitable when analyzing the degree of propionyl substitution of cellulose propionate. The obtained sample is dissolved in deuterated chloroform, 13The 1C-NMR spectrum is measured. When analyzing the degree of propionyl substitution of cellulose acylate with or without a propionyl group by treating it with propionic anhydride, the signals of the carbonyl carbons of the propionyl group appear in the 172 ppm to 174 ppm region in the same order from the highest magnetic field, starting from the 2nd, 3rd, and 6th positions. Since the total degree of substitution of cellulose acylate treated with carboxylic anhydride by Tezuka's method or a similar method is 3.0, the sum of the areas of the carbonyl carbon signals of the acyl groups originally present in the cellulose acylate and the carbonyl signals of the acyl groups introduced by the carboxylic anhydride treatment is normalized to 3.0, and the relative abundance of each acyl group at the corresponding positions (in other words, the area ratio of each signal) can be determined to represent the degrees of acyl substitution at the 2nd, 3rd, and 6th positions of the glucose ring in the cellulose ester. Needless to say, the substituents containing acyl groups that can be analyzed by this method are only substituents that do not correspond to the carboxylic anhydride used in the analytical treatment. Also, 13 In addition to C-NMR, 1 It can also be analyzed using 1H-NMR.

[0044] The weight-average molecular weight of the cellulose acylate is not particularly limited as long as the effects of this disclosure are obtained. From the viewpoint of easily obtaining the desired shape, the weight-average molecular weight of the cellulose acylate is preferably 10,000 or more, more preferably 20,000 or more, and even more preferably 30,000 or more. From the viewpoint of high biodegradability and easily obtaining the desired spherical shape, the weight-average molecular weight of the cellulose acylate is preferably 500,000 or less, more preferably 400,000 or less, and even more preferably 300,000 or less. The weight-average molecular weight of the cellulose acylate can be measured by size exclusion chromatography (GPC) (GPC-light scattering method), similar to aliphatic polyesters described later.

[0045] The types of aliphatic polyesters are not particularly limited, but examples include polyhydroxyalkanoic acids having repeating units formed by the polycondensation of hydroxyalkanoic acids, and polymers having repeating units formed by the dehydration condensation of aliphatic dicarboxylic acids and aliphatic diols, from the viewpoint of polymer structure.

[0046] Examples of polyhydroxyalkanoates include polyglycolic acid, polylactic acid, poly(β-hydroxybutyric acid), poly(β-hydroxyvaleric acid), poly(lactic acid-co-glycolic acid), poly(β-hydroxybutyric acid-co-β-hydroxyvaleric acid), poly(β-propiolactone), and poly(ε-caprolactone). Examples of polymers with aliphatic dicarboxylic acids and aliphatic diols include polyethylene succinate, polybutylene succinate, and poly(butylene succinate-co-butylene adipate). Two or more types may be used in combination.

[0047] From the viewpoint of being readily available and having excellent biodegradability, preferred aliphatic polyesters are one or more selected from the group consisting of polycaprolactone, polyhydroxybutyric acid, and polylactic acid. Other aliphatic polyesters not specified herein may be used to the extent that the effects of this disclosure are obtained.

[0048] From the viewpoint of easily obtaining the desired particle shape, the weight-average molecular weight of the aliphatic polyester is preferably 10,000 or more, more preferably 20,000 or more, and even more preferably 50,000 or more. From the viewpoint of excellent biodegradability, the weight-average molecular weight of the aliphatic polyester is preferably 5,000,000 or less, more preferably 1,000,000 or less, even more preferably 500,000 or less, and particularly preferably 250,000 or less.

[0049] The weight-average molecular weight of aliphatic polyesters is determined by size exclusion chromatography (GPC) measurement using the following equipment and conditions (GPC-light scattering method). Equipment: Shodex GPC "SYSTEM-21H" Solvent: Acetone Columns: GMHxl (Tosoh) x 2, Guard column (Tosoh TSKgel guardcolumn HXL-H) Flow rate: 0.8ml / min Temperature: 29℃ Sample concentration: 0.25% (wt / vol) Injection volume: 100μl Detection: MALLS (Multi-angle light scattering detector) (Wyatt, "DAWN-EOS") MALLS correction standard material: PMMA (molecular weight 27600)

[0050] In another aspect of this disclosure, the spherical particles may contain a plasticizer. In this disclosure, a plasticizer means a compound that can increase the plasticity of the biodegradable polymer described above. The type of plasticizer is not particularly limited, and examples include dimethyl adipate, dibutyl adipate, diisostearyl adipate, diisodecyl adipate, diisononyl adipate, diisobutyl adipate, diisopropyl adipate, diethylhexyl adipate, dioctyl adipate, dioctyldodecyl adipate, dicapryl adipate, and dihexyldecyl adipate, di(ethylene glycol monoalkyl ether) adipate, and di(diethylene glycol) adipate. Adipate-based plasticizers including adipate esters such as di(triethylene glycol monomethyl ether), di(tetraethylene glycol monomethyl ether), di(pentaethylene glycol monomethyl ether), di(hexaethylene glycol monomethyl ether), di(propylene glycol monoalkyl ether), di(dipropylene glycol monomethyl ether), di(tripropylene glycol monomethyl ether), di(tetrapropylene glycol monomethyl ether), di(pentapropylene glycol monomethyl ether), di(hexapropylene glycol monomethyl ether), di(polyethylene glycol monoalkyl ether), di(polypropylene glycol monoalkyl ether), diphenyl adipate, dinaphthyl adipate, and dibenzyl adipate; acetyl tri(adipropylene glycol monomethyl ether), di(tetrapropylene glycol monomethyl ether), di(pentapropylene glycol monomethyl ether), di(hexapropylene glycol monomethyl ether), di(polyethylene glycol monoalkyl ether), di(polypropylene glycol monoalkyl ether), diphenyl adipate, dinaphthyl adipate, and dibenzyl adipate; acetyl tri(adipropylene glycol monomethyl ether); Citrate-based plasticizers containing citrate esters such as ethyl citrate, acetyl tributyl citrate, isodecyl citrate, isopropyl citrate, triethyl citrate, triethylhexyl citrate, and tributyl citrate; glutarate-based plasticizers containing glutarate esters such as diisobutyl glutarate, dioctyl glutarate, and dimethyl glutarate; succinate-based plasticizers containing succinate esters such as diisobutyl succinate, diethyl succinate, diethylhexyl succinate, and dioctyl succinate;Examples of polycarboxylic acid esters include sebacate-based plasticizers containing sebacate esters such as diisoamyl sebacate, diisooctyl sebacate, diisopropyl sebacate, diethyl sebacate, diethylhexyl sebacate, and dioctyl sebacate; and phthalate-based plasticizers containing phthalate esters such as ethyl phthalate, methyl phthalate, diaryl phthalate, diethyl phthalate, diethylhexyl phthalate, dioctyl phthalate, dibutyl phthalate, and dimethyl phthalate. These polycarboxylic acid esters may also be mixed polybasic acid esters.

[0051] Furthermore, examples of plasticizers contained in the spherical particles of this disclosure include glycerin-based plasticizers containing glycerin alkyl esters such as triacetin, diacetin, and monoacetin; neopentyl glycol; phosphate-based plasticizers containing phosphate esters such as trioleyl phosphate, tristearyl phosphate, and tricetyl phosphate; as well as di-2-methoxyethyl phthalate, dibutyl-O-benzoyl benzoate, ethyl phthalyl ethyl glycolate (EPEG), methylphthalyl ethyl glycolate (MPEG), N-ethyltoluenesulfonamide, triethyl p-toluenesulfonic acid O-cresyl phosphate (TEP), triphenyl phosphate (TPP), and tribrobionin. The spherical particles may contain one or more plasticizers.

[0052] From the viewpoint of having a high effect in plasticizing biodegradable polymers, polycarboxylic acid-based plasticizers or glycerin-based plasticizers are preferred, and one or more selected from mixed polybasic acid esters or glycerin alkyl esters are more preferred. Examples of plasticizers for biodegradable polymers include "DAIFATTY-10" from Daihachi Chemical Industry Co., Ltd., "BIOCIZER," "Rikemar PL-004," "Poem G-002" from Riken Vitamin Co., Ltd., and "Polysizer," "Monosizer" from DIC Corporation.

[0053] If the spherical particles of this disclosure contain a plasticizer, the amount of plasticizer contained in the spherical particles is not particularly limited. For example, the amount of plasticizer in the spherical particles may be more than 0 parts by weight and 120 parts by weight or less, 2 parts by weight or more and 100 parts by weight or less, 10 parts by weight or more and 80 parts by weight or less, or 15 parts by weight or more and 50 parts by weight or less, per 100 parts by weight of biodegradable polymer. 1 This can be determined by 1H-NMR measurement.

[0054] In yet another aspect of this disclosure, part or all of the surface of the spherical particles may be coated with inorganic powder and / or an organic compound having a long-chain alkyl group. The inorganic powder and / or organic compound having a long-chain alkyl group present on the particle surface allows the spherical particles to obtain surface properties suitable for solvents and formulations used in cosmetic compositions. Spherical particles having inorganic powder and / or an organic compound having a long-chain alkyl group on their surface achieve high particle dispersibility in various solvents and formulations, improving the tactile feel of the resulting cosmetic composition. The inorganic powder and / or organic compound having a long-chain alkyl group and the spherical particles may be physically attached or chemically bonded.

[0055] As long as the effects of this disclosure are obtained, the particle shape of the inorganic powder is not particularly limited and may be spherical, plate-shaped, needle-shaped, granular, or irregularly shaped. The average particle diameter of the inorganic powder is preferably smaller than the average particle diameter of the spherical particles, for example, it may be 1 / 3 or less and 1 / 10 or less of the average particle diameter of the spherical particles. Here, the average particle diameter of the inorganic powder and the spherical particles means the median diameter based on volume.

[0056] The type of the inorganic powder is not particularly limited. For example, it may include titanium oxide, silicon oxide, aluminum oxide, zinc oxide, zirconium oxide, magnesium oxide, boron nitride, silicon nitride, barium sulfate, calcium sulfate, magnesium sulfate, calcium carbonate, magnesium carbonate, talc, mica, kaolin, sericite, mica, vermiculite, hydrillaite, bentonite, montmorillonite, hectorite, kaolinite, zeolite, ceramic powder, hydroxyapatite, calcium phosphate, silicic acid, aluminum silicate, magnesium silicate, aluminum magnesium silicate, calcium silicate, etc. Two or more of them may be used in combination. From the viewpoint of good adhesion to spherical particles and obtaining a good touch feeling, one or more selected from the group consisting of titanium oxide, silicon oxide, aluminum oxide, zinc oxide, and zirconium oxide are preferable.

[0057] The type of the organic compound having a long-chain alkyl group is not particularly limited. For example, the carbon number of the long-chain alkyl group may be 5 or more, 7 or more, 8 or more, and may also be 22 or less. The carbon number of the long-chain alkyl group may be 5 or more and 22 or less, 7 or more and 22 or less, 8 or more and 22 or less. Two or more organic compounds having different alkyl groups may be used in combination.

[0058] In the present disclosure, the organic compound having a long-chain alkyl group may be an amino acid derivative. As the amino acid derivative, Nε-lauroyl-L-lysine is preferable.

[0059] Also, in the present disclosure, the organic compound having a long-chain alkyl group may be a cationic surfactant. Examples of the cationic surfactant include quaternary ammonium salts and / or amine salts. From the viewpoint of improving the touch feeling and dispersibility, the quaternary ammonium salt represented by the following general formula (1) is preferable. R 1 R 2 R 3 R 4 N + X - (1) (In the formula, X- R is a halogen ion, 1 , R 2 , R 3 and R 4 Each of these is independently an alkyl group having 1 to 25 carbon atoms, which may have substituents, and R 1 , R 2 , R 3 and R 4 At least one of them is an alkyl group having 12 or more carbon atoms. Specific examples of cationic surfactants represented by formula (1) include stearyltrimethylammonium chloride, distearyldimethylammonium chloride, behenyltrimethylammonium chloride, distearyldiethylammonium chloride, decyltriethylammonium chloride, decyldimethylhydroxyethylammonium chloride, coconut oil trimethylammonium chloride, coconut oil methyldihydroxyethylammonium chloride, myristyltrimethylammonium chloride, lauryltrimethylammonium chloride, distearyldimethylammonium bromide, and stearyltrimethylammonium bromide.

[0060] Organic compounds having long-chain alkyl groups may also be metal soaps. Metal soaps are defined as non-alkali metal salts of higher fatty acids. Preferred higher fatty acids are fatty acids with 12 to 25 carbon atoms, and may be saturated or unsaturated fatty acids. Examples of such fatty acid soaps include zinc salts, calcium salts, magnesium salts, or aluminum salts of lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, α-linolenic acid, erucic acid, etc. Alkaline earth metal salts of fatty acids with 12 to 25 carbon atoms are preferred, zinc salts are more preferred, and zinc stearate is particularly preferred.

[0061] From the viewpoint of obtaining surface properties suitable for incorporation into cosmetic compositions, the amount of inorganic powder and / or organic compounds having long-chain alkyl groups added is preferably 1.0% by weight or more, more preferably 3.0% by weight or more, and particularly preferably 5.0% by weight or more. From the viewpoint of not inhibiting the physical properties of spherical particles, the amount of inorganic powder and / or organic compounds having long-chain alkyl groups added is preferably 50.0% by weight or less, more preferably 30.0% by weight or less, and particularly preferably 10.0% by weight or less. When two or more inorganic powders and / or organic compounds having long-chain alkyl groups are used in combination, it is preferable that their total amount satisfies the above range.

[0062] [Cosmetic composition] The biodegradable spherical particles of this disclosure can be suitably used in various cosmetic compositions. Cosmetic compositions containing these spherical particles have a soft-focus effect, as the shape of the spherical particles fills in and smooths skin irregularities and scatters light in various directions, making wrinkles and other imperfections less noticeable. Furthermore, because the spherical particles of this disclosure have a narrow particle size distribution and a nearly uniform particle size, they impart an unprecedentedly good tactile feel to the cosmetic composition. Moreover, compared to conventional spherical particles made of biodegradable polymers, the spherical particles of this disclosure have a slower initial decomposition rate. Therefore, changes in the feel due to the decomposition of the spherical particles are avoided. Even if the decomposition reaction of the spherical particles gradually progresses during use, the narrow particle size distribution of the spherical particles is maintained, so the user is less likely to notice a change in tactile feel. In this cosmetic composition, a good tactile feel is stably exhibited without fluctuations in feel over a short period of time.

[0063] Cosmetic compositions include foundations such as liquid foundations and powder foundations; concealers; sunscreens; makeup bases; lipsticks and lipstick bases; face powders such as body powders, solid face powders, and face powders; solid powder eyeshadows; wrinkle-concealing creams; and skincare lotions, and are not limited to external skin and hair preparations primarily for cosmetic purposes. Dosage forms may include liquid preparations such as aqueous solutions, emulsions, and suspensions; semi-solid preparations such as gels and creams; powdered solid preparations such as powders and granules; and oily solid preparations. They may also be emulsion preparations such as creams and emulsions; oil-gel preparations such as lipsticks; powder preparations such as foundations; and aerosol preparations such as hair styling products. Cosmetic compositions containing the spherical particles of this disclosure, in particular liquid foundations, exhibit excellent spreadability on the skin, pore coverage, and smoothness.

[0064] [Method for producing biodegradable spherical particles] The spherical particles of this disclosure can be obtained by sequentially performing the following steps. (1) A mixture is obtained by mixing a biodegradable polymer, a plasticizer, and a water-soluble polymer. (2) The obtained mixture is melted and kneaded at 200°C to 280°C to obtain a kneaded product. and (3) Remove water-soluble polymers from the resulting mixture.

[0065] Conventionally, the emulsion method has been a common method for obtaining spherical particles using polymer materials. For example, in the O / W emulsion method, the polymer material is dissolved in an organic solvent to form an oil phase, and this oil phase is emulsified and dispersed in an aqueous phase, thereby eluting the organic solvent from the droplet-like oil phase to form polymer particles. With this O / W emulsion method, irregularities caused by the elution pathway of the organic solvent are inevitably formed on the particle surface. In contrast, the spherical particles of this disclosure are obtained by a melt-kneading method that does not use organic solvents, so that no irregularities caused by solvent elution are formed on the particle surface, and extremely smooth spherical particles can be obtained. Here, the absence of irregularities on the particle surface means that when a scanning electron microscope is used to observe a 0.5 mm × 0.5 mm field of view at a magnification of 5000x, there are substantially no particles with micron-sized depressions on their surface, and when a scanning electron microscope is used to observe a 0.5 mm × 0.5 mm field of view at a magnification of 5000x, there are substantially no particles with micron-sized protrusions that extend from a virtual circle drawn along the arc of the spherical particle. The definition of "substantially non-existent" in this disclosure is as stated above.

[0066] The biodegradable polymer in the manufacturing method of this disclosure is one or more selected from polysaccharides, polysaccharide esters, and aliphatic polyesters. The aforementioned polysaccharides, polysaccharide esters, and aliphatic polyesters are used as appropriate for spherical particles. Polysaccharides, polysaccharide esters, and aliphatic polyesters can be produced by known methods. Commercially available biodegradable polymers may be used as long as the effects of this disclosure are obtained. Alternatively, polysaccharides may be obtained by hydrolyzing polysaccharide esters using known methods. For example, when the biodegradable polymer is a polysaccharide ester, in the step of removing the water-soluble polymer from the kneaded material, the kneaded material can be treated with alkali to completely saponify the polysaccharide ester and obtain spherical particles mainly composed of polysaccharides. Details of the alkali treatment will be described later.

[0067] When using a cellulose acylate with a total substitution degree greater than 0 and less than or equal to 3.0 as the polysaccharide ester, this cellulose acylate is obtained through the following steps: activating the raw material pulp (cellulose); acyling the activated cellulose with an esterifying agent (acyling agent); deactivating the acyling agent after the acyling reaction is complete; and maturing (saponification, hydrolysis) the resulting cellulose acylate to adjust it to the desired total substitution degree. Alternatively, before the activation step, there may be a pretreatment step in which the raw material pulp is disintegrated and crushed, and then sprayed and mixed with acetic acid. After the maturation (saponification, hydrolysis) step, there may be a posttreatment step of precipitation separation, purification, stabilization, and drying.

[0068] The total degree of substitution in cellulose acylate can be adjusted by controlling the conditions of the maturation process (time, temperature, etc.). It is also possible to obtain fully saponified cellulose by substantially reducing the total degree of substitution to zero. The type of substituent can be determined by the selection of an esterifying agent. Examples of substituents include acetyl groups, propionyl groups, and butyryl groups. Depending on the application, two or more substituents can be introduced at the desired degree of substitution.

[0069] The plasticizer used in the manufacturing method of this disclosure is not limited to any particular type, as long as it has a plasticizing effect in the melt extrusion of the biodegradable polymer. It can be appropriately selected depending on the type and physical properties of the biodegradable polymer used. Specifically, the aforementioned plasticizers can be used individually or in combination of two or more as plasticizers contained in the spherical particles. From the viewpoint of having a high plasticizing effect on biodegradable polymers, polycarboxylic acid-based plasticizers or glycerin-based plasticizers are preferred, and one or more selected from mixed polybasic acid esters or glycerin alkyl esters are more preferred.

[0070] The amount of plasticizer added may be more than 0 parts by weight and 120 parts by weight or less, 2 parts by weight or more and 100 parts by weight or less, 10 parts by weight or more and 80 parts by weight or less, or 15 parts by weight or more and 50 parts by weight or less, per 100 parts by weight of biodegradable polymer. If the amount is too small, the sphericity of the resulting spherical particles tends to decrease, and if the amount is too large, the particle shape cannot be maintained, and the desired spherical particles may not be obtained.

[0071] The type of water-soluble polymer used in the manufacturing method of this disclosure is not particularly limited. Here, "water-soluble" means that when 1 g of polymer is dissolved in 100 g of water at 25°C, the insoluble content is less than 50% by weight. In this disclosure, preferably, the water-soluble polymer is thermoplastic. "Thermoplastic" means the property of softening and becoming fluid when heated and solidifying when cooled.

[0072] Examples of water-soluble polymers include polyvinyl alcohol, polyethylene glycol, sodium polyacrylate, polyvinylpyrrolidone, polypropylene oxide, polyglycerin, polyethylene oxide, polyvinyl acetate, modified starch, thermoplastic starch, methylcellulose, ethylcellulose, hydroxyethylcellulose, and hydroxypropylcellulose. Thermoplastic starch can be obtained by known methods. For example, it can be produced by mixing tapioca starch with about 20% glycerin as a plasticizer and then kneading it in a twin-screw extruder, referring to Japanese Patent Publication No. 6-6307, WO92 / 04408, etc.

[0073] In the manufacturing method of this disclosure, the water-soluble polymer is preferably one or more selected from the group consisting of polyvinyl alcohol, sodium polyacrylate, polyvinylpyrrolidone, and thermoplastic starch, and more preferably one or more selected from the group consisting of polyvinyl alcohol and thermoplastic starch. The weight-average molecular weight of the polyvinyl alcohol is preferably 500 or more and 50,000 or less.

[0074] The amount of water-soluble polymer blended is preferably 110 parts by weight or more and 15,000 parts by weight or less, more preferably 180 parts by weight or more and 1,200 parts by weight or less, and even more preferably 200 parts by weight or more and 800 parts by weight or less, per 100 parts by weight of biodegradable polymer. If the amount is less than 110 parts by weight, the surface smoothness will be low and irregularly shaped particles may be generated. If it exceeds 15,000 parts by weight, the particle size of the resulting spherical particles may become too small.

[0075] As long as the effects of this disclosure are obtained, the mixing of the biodegradable polymer, plasticizer, and water-soluble polymer may be carried out in one step or in multiple steps. Furthermore, the mixing of the biodegradable polymer, plasticizer, and water-soluble polymer may be carried out by melt kneading. For example, a first mixture may be obtained by mixing or melt kneading the biodegradable polymer and plasticizer, and then the water-soluble polymer may be added to this first mixture and mixed or melt kneaded.

[0076] The mixing of biodegradable polymers and plasticizers, or the mixing of biodegradable polymers, plasticizers, and water-soluble polymers, can be carried out dry or wet using a mixer such as a Henschel mixer. When using a mixer such as a Henschel mixer, the temperature inside the mixer is preferably in the range of 20°C to less than 200°C, which is a temperature at which the biodegradable polymer does not melt or decompose.

[0077] Furthermore, when mixing biodegradable polymers and plasticizers, or mixing biodegradable polymers, plasticizers, and water-soluble polymers by melt kneading, the mixture may be mixed using a Henschel mixer or similar device at a temperature range of 20°C to less than 200°C before melt kneading. This allows the biodegradable polymers and plasticizers, or biodegradable polymers, plasticizers, and water-soluble polymers, to blend more uniformly and quickly, resulting in a higher surface smoothness of the final spherical particles and improved tactile feel.

[0078] Alternatively, melt mixing may be performed by heating and mixing in an extruder. The mixing temperature (cylinder temperature) of the extruder may be in the range of 200°C to 230°C. Plasticization and a uniform mixture can be obtained even at temperatures within this range. If the mixing temperature is too low, the sphericity and surface smoothness of the resulting particles may decrease, potentially reducing tactile properties and optical properties. Conversely, if the mixing temperature is too high, thermal deterioration and discoloration of the mixture may occur. Furthermore, high mixing temperatures reduce the viscosity of the molten material, which may result in insufficient mixing of the resin within the twin-screw extruder.

[0079] For example, when using cellulose acylate as the biodegradable polymer, the kneading temperature (cylinder temperature) of the twin-screw extruder may be 200°C. The kneaded material may be extruded into strands and then cut to form pellets. In this case, the die temperature may be around 220°C.

[0080] In the manufacturing method of this disclosure, a mixture containing a biodegradable polymer, a plasticizer, and a water-soluble polymer is melt-kneaded at 200°C to 280°C to obtain a kneaded product. When the mixing of the biodegradable polymer, plasticizer, and water-soluble polymer described above is carried out by melt-kneading at 200°C to 280°C, the kneaded product obtained by the mixing may be used as is in the next step.

[0081] For melt-mixing the mixture, an extruder such as a twin-screw extruder can be used. When using an extruder, the mixing temperature refers to the cylinder temperature. The mixture containing biodegradable polymers, etc., may be extruded in a string-like form from a die attached to the tip of the extruder, and then cut into pellets. In this case, the die temperature may be between 220°C and 300°C.

[0082] A mixture containing a biodegradable polymer, a plasticizer, and a water-soluble polymer is melt-kneaded at a temperature of 200°C to 280°C to obtain a dispersion in which the water-soluble polymer is the dispersion medium and the mixture of the biodegradable polymer and plasticizer is the dispersed phase. In other words, the kneaded product of this disclosure is a dispersion in which substantially spherical particles containing the biodegradable polymer and plasticizer are dispersed in a matrix made of a water-soluble polymer.

[0083] By removing the water-soluble polymer from this compound, spherical particles are obtained that mainly contain a biodegradable polymer, have a particle size variation coefficient (CV) of 40% or less, and exhibit a biodegradation rate of 40% or less on day 5 of a biodegradation test in accordance with OECD TG301F.

[0084] One method for removing water-soluble polymers is to contact the pressurized kneaded material with a suitable solvent for the water-soluble polymer, thereby eluting the polymer into the solvent. Examples of such solvents include water; alcohols such as methanol, ethanol, and isopropanol; or mixtures thereof. Specifically, the pressurized kneaded material can be mixed with the solvent to elute the water-soluble polymer into the solvent, and then the resulting filtrate can be filtered to remove the water-soluble polymer from the pressurized kneaded material.

[0085] In the process of removing the water-soluble polymer from the pressurized mixture, the plasticizer may or may not be removed along with the water-soluble polymer. Therefore, the resulting spherical particles may or may not contain the plasticizer.

[0086] From the viewpoint of achieving high removal efficiency of water-soluble polymers, the mixing ratio of the kneaded material to the solvent is preferably 0.01% to 20% by weight of the kneaded material, more preferably 2% to 15% by weight, and even more preferably 4% to 13% by weight, relative to the total weight of the kneaded material and solvent. If the amount of kneaded material is greater than 20% by weight, it may not be possible to sufficiently remove the water-soluble polymers. In addition, it may be difficult to separate the solid component containing spherical particles from the liquid component in which the water-soluble polymers are dissolved by operations such as filtration and centrifugation.

[0087] From the viewpoint of achieving high removal efficiency of water-soluble polymers, the mixing temperature of the kneaded material and the solvent is preferably 0°C to 200°C, more preferably 20°C to 110°C, and even more preferably 40°C to 80°C. Below 0°C, the dissolution of water-soluble polymers may be insufficient, making removal difficult. Furthermore, at temperatures exceeding 200°C, particle deformation and aggregation may occur, making it difficult to obtain the desired particle shape.

[0088] The mixing time between the compound and the solvent is not particularly limited and can be adjusted as appropriate, but for example, it may be 0.5 hours or more, 1 hour or more, 3 hours or more, 5 hours or more, or 6 hours or less.

[0089] As a method for mixing a compound with a solvent to elute water-soluble polymers, for example, stirring devices such as ultrasonic homogenizers and three-way motors can be used. For example, when using a three-way motor as a stirring device, the rotation speed during mixing of the compound and solvent may be between 5 rpm and 3000 rpm. This allows for efficient removal of water-soluble polymers from the compound. It also allows for efficient removal of plasticizers from the compound.

[0090] When the biodegradable polymer is a polysaccharide ester, as mentioned above, the kneaded mixture may be treated with alkali in the step of removing the water-soluble polymer from the mixture. This alkali treatment saponifies the polysaccharide ester in the mixture, yielding a polysaccharide ester with the desired degree of substitution. Furthermore, by performing alkali treatment under conditions that result in complete saponification, polysaccharides with a degree of substitution of 0 can be obtained.

[0091] Alkali treatment is carried out in the step of removing water-soluble polymers from the kneaded material by mixing the kneaded material with a solvent containing one or more metal compounds selected from alkali metal compounds and alkaline earth metal compounds. In other words, when the biodegradable polymer is a polysaccharide ester, this manufacturing method further includes hydrolyzing the polysaccharide ester by mixing the kneaded material with a solvent containing one or more metal compounds selected from alkali metal compounds and alkaline earth metal compounds. This solvent may be an aqueous solution of one or more metal compounds selected from alkali metal compounds and alkaline earth metal compounds. By washing the kneaded material with this metal compound solution, water-soluble polymers can be removed and the polysaccharide ester can be adjusted to a desired degree of substitution.

[0092] Examples of alkali metal compounds and alkaline earth metal compounds include compounds of alkali metals such as sodium, lithium, and potassium, or alkaline earth metals such as calcium, magnesium, and barium. Hydroxides, oxides, or carbonates of alkali metals or alkaline earth metals are preferred, and hydroxides of alkali metals or alkaline earth metals are more preferred. Examples of such metal compounds include sodium hydroxide, magnesium hydroxide, and calcium hydroxide.

[0093] The amount of metal compound added is appropriately selected depending on the type of polysaccharide ester and the degree of substitution. Furthermore, when removing water-soluble polymers by repeatedly stirring and mixing the kneaded mixture and solvent and filtering, it is preferable to wash with a solution containing the metal compound at least once, and it is more preferable to wash with a solution containing the metal compound at the end of the removal process.

[0094] In another embodiment, the manufacturing method of the present disclosure may include adding and mixing inorganic powder to spherical particles obtained by removing a water-soluble polymer from a kneaded material. This results in spherical particles in which part or all of their surface is coated with inorganic powder. These spherical particles further improve tactile properties.

[0095] From the viewpoint of obtaining a good tactile feel, the inorganic powder is preferably one or more selected from the group consisting of titanium dioxide, silicon dioxide, aluminum oxide, zinc oxide, and zirconium oxide. The amount of inorganic powder added is preferably 0.01 parts by weight or more and 1.0 part by weight or less per 100 parts by weight of biodegradable polymer.

[0096] There are no particular limitations on the method of adding inorganic powder to spherical particles obtained by removing water-soluble polymers and mixing them; known mixing methods can be appropriately selected and used. The mixing may be dry or wet. For example, if dry mixing is used, mixing devices such as ball mills, sand mills, bead mills, homogenizers, planetary mixers, and film mixers can be used. Furthermore, there are no particular limitations on the order in which the spherical particles and inorganic powder are mixed. The spherical particles and inorganic powder may be introduced into the mixing device at the same time, or a predetermined amount of inorganic powder may be introduced into the mixing device and stirred (or ground simultaneously with stirring), and then the spherical particles may be introduced and mixed.

[0097] If necessary, the manufacturing method of the present disclosure may include a step of drying the obtained spherical particles after removing the water-soluble polymer and / or after adding and mixing the inorganic powder. The drying method is not particularly limited, and known methods such as heat drying, reduced pressure drying, and vacuum drying can be used. From the viewpoint of high drying efficiency, the drying temperature is preferably above room temperature, may be 50°C or higher, and may be 60°C or higher. From the viewpoint of suppressing thermal degradation, the preferred drying temperature is 120°C or lower. [Examples]

[0098] The present disclosure will be described in detail below with reference to examples, but the technical scope of the present disclosure is not limited by these examples. Each configuration and combination thereof in each embodiment is an example, and additions, omissions, substitutions, and other modifications can be made as appropriate without departing from the spirit of the present disclosure.

[0099] (Example A-1) 100 parts by weight of cellulose acetate (manufactured by Daicel Corporation, total substitution degree = 2.4) as a biodegradable polymer and 25 parts by weight of triacetin (manufactured by Daicel Corporation) as a plasticizer were blended in a dry state, dried at 80°C for 12 hours or more, and then stirred and mixed using a Henschel mixer to obtain a mixture of biodegradable polymer and plasticizer. The obtained mixture was supplied to a twin-screw extruder (PCM30 manufactured by Ikegai Co., Ltd., cylinder temperature: 200°C, die temperature: 220°C), melt-kneaded and extruded to obtain pellets.

[0100] 30 parts by weight of the obtained pellets were blended with 70 parts by weight of polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Co., Ltd., melting point 190°C, degree of saponification 99.1%) as a water-soluble polymer in a dry state. The mixture was then supplied to a twin-screw extruder (PCM30 manufactured by Ikegai Co., Ltd., cylinder temperature 220°C, die temperature 220°C), melt-kneaded and extruded to obtain a compound containing a biodegradable polymer, a plasticizer, and a water-soluble polymer.

[0101] Separately, a 4.7% by weight sodium hydroxide aqueous solution was prepared by dissolving sodium hydroxide (manufactured by Nacalai Tesque) in pure water as a solvent.

[0102] Next, the resulting mixture was mixed with the aforementioned sodium hydroxide aqueous solution (solvent) so that the amount of the mixture was 5% by weight or less (= weight of mixture / (weight of mixture + weight of solvent) × 100), and stirred for 3 hours at a temperature of 80°C and a rotation speed of 100 rpm using a Three One Motor (BL-3000, manufactured by Shinto Kagaku Co., Ltd.). The stirred solution was filtered using filter paper (No. 5A, manufactured by ADVANTEC), and the filtrate was removed. The removed filtrate was mixed again with pure water, and the mixture was adjusted so that the amount of the mixture was 5% by weight or less, and stirred again at a temperature of 80°C and a rotation speed of 100 rpm for 3 hours. After filtering, the process of stirring the filtrate in water was repeated at least three times to obtain the spherical particles of Example A-1.

[0103] The obtained spherical particles 1¹H-NMR analysis revealed an acetyl substitution degree of 0.01, confirming that the main component of Example A-1 was substantially cellulose. Furthermore, the sample of Example A-1 was observed using a scanning electron microscope (Hitachi High-Technologies Corporation, product name "TM3000"). Figure 1 shows an example of an 800x magnification SEM image of Example A-1. The scale bar length in Figure 1 is 50.0 μm. Additionally, a 0.5 mm × 0.5 mm field of view was observed at 5000x magnification, confirming the absence of particles with micron-sized depressions on their surface, and particles with micron-sized protrusions extending from a virtual circle drawn along the arc of the spherical particle. The results are shown in Table 1 below as "SEM observation (magnification 5000x)". Furthermore, the number of micron-sized depressions and micron-sized protrusions was measured for 30 randomly sampled particles in SEM images at magnifications of 5000x or higher, and the average values ​​were 0.50 and 0.47, respectively. A portion of the SEM images of the sampled spherical particles is shown in Figure 2. In each image in Figure 2, the areas circled are micron-sized recesses, and the areas indicated by arrows are micron-sized protrusions that extend from a virtual circle drawn along the arc of the approximately spherical particle.

[0104] The average particle size (μm), coefficient of variation (%), sphericity (%), and surface smoothness (%) of the spherical particles in Example A-1 were measured, and their biodegradability and tactile properties were evaluated. Tactile properties were evaluated as tactile property 1 immediately after manufacturing and tactile property 2 after decomposition treatment. The evaluation results are shown in Table 1. The measurement or evaluation of average particle size, coefficient of variation, sphericity, surface smoothness, biodegradability, tactile property 1, and tactile property 2 were performed using the following methods.

[0105] <Average particle diameter and coefficient of variation (CV) of particle diameter> The particles were added to pure water to adjust the concentration to approximately 100 ppm, and a suspension was prepared using an ultrasonic vibration device. Subsequently, the volume frequency particle size distribution was determined by laser diffraction (using a HORIBA LA-960 laser diffraction / scattering particle size distribution analyzer, with 15 minutes of ultrasonic treatment and a refractive index of 1.500, medium (water; 1.333)), and the average particle size was measured. The average particle size (μm) was defined as the particle size corresponding to 50% of the cumulative scattering intensity in the volume frequency particle size distribution (volume-based median diameter). The coefficient of variation CV (%) was calculated as the standard deviation of particle size / average particle size × 100. The obtained results are shown in Table 1 below.

[0106] <Sphericity> Using images of particles observed with a scanning electron microscope (SEM), the major and minor axes of 30 randomly selected particles were measured, the minor axis / major axis ratio for each particle was determined, and the average of these minor axis / major axis ratios was defined as the sphericity. The results are shown in Table 1 below.

[0107] <Surface smoothness> Images of particles observed with a scanning electron microscope (SEM) were binarized using the Winroof image processing system (manufactured by Mitani Corporation). From the binarized images, a region containing the center and / or vicinity of the center of a single particle was randomly selected, and the area ratio of the concave portion (shaded area) of the surface irregularities in that region was calculated. The surface smoothness (%) of that single particle was then calculated using the following formula. Surface smoothness of a single particle (%) = (1 - percentage of concave area) × 100 Area ratio of the concave area = Area of ​​the concave area in the arbitrary region / Area of ​​the arbitrary region The average surface smoothness of 10 randomly selected particle samples (n1 to n10) was defined as the surface smoothness percentage (%). A higher value indicates higher surface smoothness of the particle. The area used to calculate the area percentage may be any area smaller than the particle, including the center and / or vicinity of the center of a single particle. The size of this area may be 5 μm square when the particle diameter is 15 μm.

[0108] <Biodegradable> In accordance with OECD TG301F, the biodegradability of the particles was tested under the following conditions. Source of seeds: Returned sludge from urban sewage treatment plants Target substance: Microcrystalline cellulose Test substance concentration: 100 mg / L Target substance concentration: 100 mg / L Inoculum concentration: 30mg / L Test solution volume: 100 mL Test temperature: 22℃±2℃ Culture period: 28 days

[0109] Subsequently, the biodegradation rate after 5 days (BD5%) and after 28 days (BD28%) was calculated using the following formula. The results are shown in Table 1 below. Biodegradation degree (%)=(BOD-B) / TOD×100 (In the formula, BOD is the biochemical oxygen consumption (mg) by the test substance (particles), B is the biochemical oxygen consumption (mg) of the blank, and TOD is the theoretical oxygen consumption (mg) by the test substance.)

[0110] <Touch 1> The tactile feel of the particles immediately after manufacturing was evaluated through a panel test involving 20 participants. Participants were asked to touch the particles, and their smoothness and moistness were comprehensively rated on a 5-point scale according to the following criteria. The average score of the 20 participants is shown in Table 1 below as "Tactile Feel 1". Good: 5, Fairly Good: 4, Average: 3, Fairly Poor: 2, Poor: 1

[0111] <Touch 2> Assuming that bacteria were contaminated into a cosmetic composition containing particles due to some factor, cellulase was added to simulate a decomposition process, and the changes in the texture of the particles before and after decomposition were evaluated.

[0112] First, 3.0 g of particles was collected in a 100 mL screw-capacity tube, and 0.0030 g of cellulase (MP Biomedicals) and 30 mL of buffer solution (pH 5.0) were added. After immersion in a constant temperature bath set to 40°C for 24 hours, the supernatant was removed, and the particles after decomposition were obtained by drying in a vacuum dryer at 80°C. Figures 5 and 6 are examples of SEM images of Example A-1 after decomposition at magnifications of 800x and 15000x, respectively. The scale bar length in Figure 5 is 50.0 μm, and the scale bar length in Figure 6 is 3.00 μm.

[0113] 5.0 g of particles before decomposition and 5.0 g of particles after 24 hours of decomposition were taken and added to 100 mL of water and stirred to prepare suspensions. Using these suspensions, sensory evaluations were conducted by a panel test of 20 people before and after decomposition. For each suspension, both smoothness and moistness were evaluated comprehensively on a scale of 5 points, according to the following criteria. The average scores of the 20 people were calculated and shown in Table 1 below as "Tactile Sensitivity 2 (Before Decomposition / After Decomposition)". Good: 5, Fairly Good: 4, Average: 3, Fairly Poor: 2, Poor: 1

[0114] (Examples A-2 to A-4) Spherical particles of Examples A-2 to A-4 were obtained in the same manner as in Example A-1, except that the concentrations of the sodium hydroxide aqueous solution were changed to 4.1% by weight, 3.7% by weight, and 3.2% by weight, respectively. 1 Table 1 below shows the total degree of substitution (DS) measured by 1H-NMR analysis, the physical properties of each particle evaluated by the method described above, and the results of SEM observation. In Table 1, "None" under "SEM observation (5000x)" means that when a 0.5 mm × 0.5 mm field of view was observed at a magnification of 5000x, there were virtually no particles with micron-sized depressions or protrusions on the surface.

[0115] (Examples A-5 and A-7) Spherical particles of Examples A-5 to A-7 were obtained in the same manner as in Example A-1, except that the biodegradable polymer was changed to one shown in Table 2 below, and distilled water was used instead of sodium hydroxide solution. The average particle size (μm), coefficient of variation (%), sphericity (%), surface smoothness (%), biodegradability, and tactile properties of each particle evaluated by the method described above, along with the results of SEM observation, are shown in Table 2 below. In Table 2, "None" under "SEM observation (5000x)" means that when a 0.5 mm × 0.5 mm field of view was observed at a magnification of 5000x, there were substantially no particles with micron-sized depressions or protrusions on the surface.

[0116] (Comparative example A-1) Commercially available microcrystalline cellulose (Asahi Kasei Corporation's product name "Ceolus-PH-101") was used as the particle size for Comparative Example A-1. These particles of Comparative Example A-1 were used as the control substance and subjected to the biodegradability test described above. The average particle size (μm), coefficient of variation of particle size (%), sphericity (%), surface smoothness (%), biodegradability, and tactile feel, evaluated by the method described above, along with the results of SEM observation, are shown in Table 2 below. In Table 2, "Unmeasurable" under "SEM observation (5000x)" means that the surface shape could not be evaluated because the particle shape was irregular.

[0117] (Comparative example A-2) A cellulose acetate solution was prepared by dissolving 250 parts by weight of cellulose acetate (manufactured by Daicel Corporation, total acetyl substitution degree 2.4) in 2250 parts by weight of acetone (manufactured by Nacalai Tesque). A medium phase was prepared by dissolving 200 parts by weight of polyvinyl alcohol (manufactured by Kuraray Co., Ltd.) in 2300 parts by weight of deionized water. The entire cellulose acetate solution was added to the medium phase and mixed. The mixture was stirred at 3000 rpm for 3 minutes using a homodisperser, and then stirred again at 2000 rpm for 10 minutes to obtain a suspension in which the cellulose acetate solution was uniformly dispersed in droplets. While stirring this suspension at 500 rpm using a homodisperser, 112500 parts by weight of deionized water was added over 75 minutes to obtain a dispersion of cellulose acetate resin particles. These resin particles were filtered and washed, and then dispersed in 2500 parts by weight of deionized water. Sodium hydroxide was added to this dispersion to adjust the pH to 13.0 or lower, and the mixture was heated to 60°C to carry out a hydrolysis reaction. After the hydrolysis reaction was complete, the mixture was neutralized with hydrochloric acid, the product was filtered and washed, and then gelatinized with deionized water. Further filtering and washing were performed, followed by drying and crushing to obtain the particles of Comparative Example A-2.

[0118] The obtained particles 1¹H-NMR analysis was performed to confirm that the main component of Comparative Example A-2 is substantially cellulose. Table 2 shows the average particle size (μm), coefficient of particle size variation (%), sphericity (%), surface smoothness (%), biodegradability, tactile feel 1, and tactile feel 2, as well as the results of SEM observation, as evaluated by the methods described above. Figure 3 is an example of an SEM image of Comparative Example A-2 taken at 800x magnification. The scale bar length in Figure 3 is 50.0 μm. In Table 2, "Yes" under "SEM observation (5000x)" means that when a 0.5 mm × 0.5 mm field of view was observed at 5000x magnification, multiple particles with micron-sized depressions or protrusions on the surface were observed. Specifically, for 30 randomly sampled particles, the number of micron-sized depressions and micron-sized protrusions was measured in SEM images at 5000x magnification or higher, and the average values ​​were 3.47 and 3.87, respectively. A portion of the SEM images of the sampled spherical particles is shown in Figure 4. In each image in Figure 4, the areas circled are micron-sized recesses, and the areas indicated by arrows are micron-sized protrusions that extend from a virtual circle drawn along the arc of the approximately spherical particle.

[0119] [Table 1]

[0120] [Table 2]

[0121] Details of the compounds shown in Table 1-2 are as follows: CA: Saponified cellulose acetate (total substitution degree 2.4, weight-average molecular weight 47,000) manufactured by Daicel Corporation. CA0: Fully saponified cellulose acetate (total substitution degree 2.4, weight-average molecular weight 47,000) manufactured by Daicel Corporation. CAP: Saponified cellulose acetate propionate (Eastman Chemical Co., Ltd.: CAP-482-0.5, acetyl substitution degree = 0.18, propionyl substitution degree = 2.40) PCL: Polycaprolactone manufactured by Daicel Corporation (weight-average molecular weight 50,000) PHB: Polyhydroxybutyrate (weight-average molecular weight 550,000) manufactured by Good Fellow.

[0122] As shown in Table 1-2, all of the spherical particles in the examples had a good tactile feel and were found to exhibit slower biodegradability compared to the particles in the comparative example. Furthermore, as shown in Figure 1-8, in the examples, the spherical particles were decomposed by cellulase from the surface and maintained a nearly spherical shape even after the decomposition treatment, resulting in only a 0.3-point decrease in tactile feel 2. In contrast, in the comparative example, decomposition progressed from areas with pronounced irregularities, and as a result of increased non-uniformity of particle shape, tactile feel 2 decreased by a further 0.6 points.

[0123] (Example B-1) Preparation of liquid foundation After mixing the components shown in Table 3, the mixture was thoroughly stirred and filled into containers to prepare liquid foundation. The texture of the resulting liquid foundation was evaluated using the method described below. The results are shown in Table 11.

[0124] [Table 3]

[0125] <Tactile sensation> A sensory evaluation was conducted on the compositions immediately after the particles were formulated and prepared, using a panel test with 20 participants. Each composition was used, and both smoothness and moisturizing properties were evaluated comprehensively on a 5-point scale according to the following criteria. The average score of the 20 participants was calculated. Good: 5, Fairly Good: 4, Average: 3, Fairly Poor: 2, Poor: 1

[0126] (Example B-2) sunscreen preparation After mixing the ingredients shown in Table 4, the mixture was thoroughly stirred and filled into containers to prepare sunscreen. The texture of the resulting sunscreen was evaluated using the method described above. The results are shown in Table 11.

[0127] [Table 4]

[0128] (Example B-3) Preparation of powder foundation After coarsely mixing component A shown in Table 5 using a Henschel mixer, component B, which had been uniformly dissolved, was added and thoroughly stirred. The mixture was then filled into containers to prepare the powder foundation. The texture of the obtained powder foundation was evaluated using the method described above. The results are shown in Table 11.

[0129] [Table 5]

[0130] (Examples B-4 to B-6 and Comparative Examples B-1 to B-2) Liquid foundations were prepared in the same manner as in Example B-1, except that the spherical particles in Example A-1 in Table 3 were replaced with the particles in Examples A-4 to A-6 and Comparative Examples A-1 to A-2. The tactile properties of each were evaluated using the method described above. The results are shown in Table 11.

[0131] (Example B-7) Preparation of makeup base Component C, shown in Table 6, was dispersed in component A and thoroughly mixed. Then, component B was added and mixed, and the mixture was filled into a container to prepare a makeup base. The texture of the obtained makeup base was evaluated using the method described above. The results are shown in Table 11.

[0132] [Table 6]

[0133] (Example B-8) Lipstick preparation Component B, shown in Table 7, was heated to 60°C and thoroughly mixed. Component C was added and thoroughly dispersed, then component A was added and dissolved using a microwave oven, followed by thorough mixing. After that, it was heated and dissolved again using a microwave oven, poured into a mold, and cooled and solidified. This was then set in a lipstick container to prepare lipstick. The texture of the obtained lipstick was evaluated using the method described above. The results are shown in Table 11.

[0134] [Table 7]

[0135] (Example B-9) Preparation of face powder The components A shown in Table 8 were thoroughly mixed using a mixer. The resulting powder was filled into a container to prepare face powder. The texture of the resulting face powder was evaluated using the method described above. The results are shown in Table 11.

[0136] [Table 8]

[0137] (Example B-10) Preparation of solid face powder The talc and coloring pigments shown in Table 9 were mixed in a blender. The spherical particles from Example A-1 (CA0 spherical particles) and all the powder components containing the coloring pigments and talc previously mixed in the blender were then stirred using a Henschel mixer. Afterward, oil (a binder) was added, the mixture was heated to 70°C, and further stirring was performed. A grinding process was then carried out as needed. This mixture was then compressed into a metal dish to prepare a solid white powder. The texture of the obtained solid white powder was evaluated using the method described above. The results are shown in Table 11.

[0138] [Table 9]

[0139] (Example B-11) Preparation of solid powder eyeshadow After thoroughly mixing the powders shown in Table 10, the binder was uniformly dissolved and added to the powder mixture, which was then further mixed. The mixture was then compressed to prepare a solid powder eyeshadow. The texture of the obtained solid powder eyeshadow was evaluated using the method described above. The results are shown in Table 11.

[0140] [Table 10]

[0141] [Table 11]

[0142] As shown in Table 11, the cosmetic compositions of Examples B-1 to B-11 containing the spherical particles of this disclosure all had a good tactile feel. From the results in Table 1-2, it can be inferred that even if the decomposition reaction of the spherical particles progresses, there will be no abrupt change in tactile feel.

[0143] [Disclosure items] Each of the following items discloses a preferred embodiment.

[0144] [Item 1] It contains biodegradable polymers as its main component. The coefficient of variation (CV) of particle size is 40% or less. Biodegradable spherical particles in which the degree of biodegradation on day 5, calculated by the following formula in a biodegradation test compliant with OECD TG301F, is 40% or less. Biodegradation degree (%)=(BOD-B) / TOD×100 (In the formula, BOD is the biochemical oxygen consumption by the test substance (mg), B is the biochemical oxygen consumption of the blank (mg), and TOD is the theoretical oxygen consumption by the test substance (mg).)

[0145] [Item 2] Biodegradable spherical particles as described in item 1, wherein the ratio BD5 / BD28 of the biodegradation level BD5 on day 5 to the biodegradation level BD28 on day 28, as measured by a biodegradation test in accordance with OECD TG301F, is 0.60 or less.

[0146] [Item 3] Biodegradable spherical particles as described in item 1 or 2, wherein the biodegradation level BD5 on day 5 and the biodegradation level BD28 on day 28, as measured by a biodegradation test in accordance with OECD TG301F, satisfy the following formula. (BD28 - BD5) / BD5 ≥ 0.50

[0147] [Item 4] Biodegradable spherical particles as described in any of items 1 to 3, wherein, when observed using a scanning electron microscope at a magnification of 5000x over a 0.5 mm x 0.5 mm field of view, there are substantially no particles with micron-sized depressions on their surface.

[0148] [Item 5] Biodegradable spherical particles as described in any of items 1 to 4, wherein, when observed using a scanning electron microscope at a magnification of 5000x in a 0.5 mm × 0.5 mm field of view, there are substantially no particles in which micron-sized protrusions protruding from a virtual circle drawn along the arc of the spherical particle are observed.

[0149] [Item 6] The biodegradable spherical particles according to any one of items 1 to 5, wherein the biodegradable polymer is selected from the group consisting of polysaccharides, polysaccharide esters, and aliphatic polyesters.

[0150] [Item 7] The biodegradable spherical particles according to item 6, wherein the polysaccharide is one or two selected from cellulose and starch.

[0151] [Item 8] The biodegradable spherical particles according to item 6 or 7, wherein the total degree of substitution of the polysaccharide ester is greater than 0 and 3.0 or less.

[0152] [Item 9] The biodegradable spherical particles according to any one of items 6 to 8, wherein the polysaccharide ester is a cellulose acylate having acyl groups with 2 to 10 carbon atoms, and the total degree of substitution of the cellulose acylate is greater than 0 and less than or equal to 1.0.

[0153] [Item 10] The biodegradable spherical particles according to any one of items 6 to 9, wherein the aliphatic polyester is a polyhydroxyalkanoic acid or a polymer of an aliphatic dicarboxylic acid and an aliphatic diol.

[0154] [Item 11] The biodegradable spherical particles according to any one of items 6 to 10, wherein the aliphatic polyester is one or more selected from the group consisting of polycaprolactone, polyhydroxybutyric acid, and polylactic acid.

[0155] [Item 12] A cosmetic composition comprising biodegradable spherical particles as described in any of items 1 to 11.

[0156] [Item 13] A mixture is obtained by mixing a biodegradable polymer, a plasticizer, and a water-soluble polymer. The mixture is melted and kneaded at a temperature of 200°C to 280°C to obtain a kneaded product. and A method for producing biodegradable spherical particles according to item 1, comprising removing the water-soluble polymer from the kneaded mixture.

[0157] [Item 14] The method for producing biodegradable spherical particles according to item 13, wherein, in the step of removing the water-soluble polymer from the kneaded product, the kneaded product is further mixed with a solvent containing one or more metal compounds selected from alkali metal compounds and alkaline earth metal compounds to hydrolyze the polysaccharide ester.

[0158] [Item 15] A method for producing biodegradable spherical particles according to item 14, wherein the solvent is an aqueous solution of the metal compound.

[0159] [Item 16] A method for producing biodegradable spherical particles according to item 14 or 15, wherein the metal compound is a hydroxide of an alkali metal or alkaline earth metal.

Claims

1. It contains biodegradable polymers as its main component, and in a biodegradation test in accordance with OECD TG301F, the degree of biodegradation on day 5, calculated by the following formula, is 40% or less. The biodegradable polymer is selected from the group consisting of polysaccharides (excluding polysaccharide esters), polysaccharide esters, and aliphatic polyesters. Here, the total degree of substitution of the polysaccharide ester is greater than 0 and less than 0.7, The ratio BD5 / BD28 of the biodegradation level BD5 on day 5 to the biodegradation level BD28 on day 28, as measured by a biodegradation test in accordance with OECD TG301F, is 0.60 or less. The average particle diameter is 0.08 μm or more and 40 μm or less. The sphericity is 0.9 or higher. The surface smoothness is 80% or higher. Biodegradable spherical particles. Biodegradability (%) = (BOD-B) / TOD x 100 (In the formula, BOD is the biochemical oxygen consumption by the test substance (mg), B is the biochemical oxygen consumption of the blank (mg), and TOD is the theoretical oxygen consumption by the test substance (mg).)

2. The biodegradable spherical particles according to claim 1, wherein the coefficient of variation CV of the particle size of the biodegradable spherical particles is 40% or less.

3. The biodegradable spherical particles according to claim 1, wherein the biodegradation degree BD5 on day 5 and the biodegradation degree BD28 on day 28, as measured by a biodegradation test in accordance with OECD TG301F, satisfy the following formula. (BD28-BD5) / BD5 ≧ 0.50

4. The biodegradable spherical particles according to claim 1, wherein, when a 0.5 mm × 0.5 mm field of view is observed at a magnification of 5000x using a scanning electron microscope, substantially no particles with micron-sized depressions on their surface are observed.

5. The biodegradable spherical particles according to claim 1, wherein, when a scanning electron microscope is used to observe a 0.5 mm × 0.5 mm field of view at a magnification of 5000x, there are substantially no particles in which a micron-sized protrusion protruding from a virtual circle drawn along the arc of the spherical particle is observed.

6. The biodegradable spherical particles according to claim 1, wherein the polysaccharide (excluding polysaccharide esters) is one or two selected from cellulose and starch.

7. The biodegradable spherical particles according to claim 1, wherein the aliphatic polyester is a polyhydroxyalkanoic acid or a polymer of an aliphatic dicarboxylic acid and an aliphatic diol.

8. The biodegradable spherical particles according to claim 1, wherein the aliphatic polyester is one or more selected from the group consisting of polycaprolactone, polyhydroxybutyric acid, and polylactic acid.

9. A cosmetic composition comprising the biodegradable spherical particles described in claim 1.

10. A mixture is obtained by mixing a biodegradable polymer, a plasticizer, and a water-soluble polymer. The mixture is melted and kneaded at a temperature of 200°C to 280°C to obtain a kneaded product. and A method for producing biodegradable spherical particles according to claim 1, comprising removing the water-soluble polymer from the kneaded mixture.

11. The method for producing biodegradable spherical particles according to claim 10, wherein, in the step of removing the water-soluble polymer from the kneaded product, the kneaded product is further mixed with a solvent containing one or more metal compounds selected from alkali metal compounds and alkaline earth metal compounds to hydrolyze the polysaccharide ester.

12. The method for producing biodegradable spherical particles according to claim 11, wherein the solvent is an aqueous solution of the metal compound.

13. The method for producing biodegradable spherical particles according to claim 11, wherein the metal compound is a hydroxide of an alkali metal or an alkaline earth metal.

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