cellulose particles

Abstract

To provide a cellulose particle that has high biodegradability and changes little in particle size due to water absorption.SOLUTION: A cellulose particle contains 90 pts.mass or more and 99.5 pts.mass of cellulose, and 0.5 pt.mass or more and 10 pts.mass or less of a cellulose derivative.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to cellulose particles. [Background technology]

[0002] Patent Document 1 proposes "resin beads formed from a resin containing cellulose as a main component, which have a volume-based cumulative 50% particle size of 50 μm or less, a sphericity of 0.7 to 1.0, a surface smoothness of 70 to 100%, a solidity of 50 to 100%, a 5-day biodegradability measured in accordance with JIS K6950:2000 (ISO 14851:1999) of 20% or more, and a cellulose content of 90 to 100% by mass in the resin."

[0003] Patent Document 2 proposes "a method for producing cellulose acetate particles, comprising: (a) a step of dissolving cellulose acetate in an organic solvent to prepare a cellulose acetate solution; (b) a step of passing the cellulose acetate solution and an aqueous medium through a gap between an outer cylinder and an inner cylinder coaxially disposed within the outer cylinder, while rotating at least one of the outer cylinder and the inner cylinder, thereby obtaining an emulsion; and (c) a step of precipitating cellulose acetate particles from the emulsion." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6872068 [Patent Document 2] Japanese Patent Publication No. 2021-021044 Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to provide a composition that does not contain a cellulose derivative, or has a cellulose derivative content of less than 0.5 parts by mass or 10 parts by mass. exceedThe object of the present invention is to provide cellulose particles which are highly biodegradable and have little change in particle size due to water absorption, compared with the case where the cellulose particles are biodegradable. [Means for solving the problem]

[0006] The above problems are solved by the following means: <1> 90 parts by mass or more 99.5 parts by mass below of cellulose, 0.5 parts by mass or more and 10 parts by mass or less of a cellulose derivative; Cellulose particles containing. <2> The cellulose derivative is cellulose acylate. <1> The cellulose particles according to claim 1. <3> 90 parts by mass or more of the above 99.5 parts by mass below and 0.5 parts by mass or more and 10 parts by mass or less of the cellulose derivative; a coating layer that coats the base particles and contains at least one selected from the group consisting of polyamine compounds, waxes, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds; have <1> or <2> The cellulose particles according to claim 1. <4> The polyamine compound is at least one selected from the group consisting of polyethyleneimine and polylysine. <3> The cellulose particles according to claim 1. <5> The wax is carnauba wax <3> or <4> The cellulose particles according to claim 1. <6> the coating layer covers the base particles, and the polyamine compound, the linear saturated fatty acid, A first coating layer containing at least one selected from the group consisting of hydroxy fatty acids and amino acid compounds, and a second coating layer covering the first coating layer and containing a wax. <3> ~ <5> The cellulose particles according to any one of claims 1 to 4. <7> The second coating layer further contains a polyvalent metal salt. <6> The cellulose particles according to claim 1. <8> At least one external additive selected from the group consisting of silicon-containing compound particles and metal soap particles is added externally. <1> ~ <7> The cellulose particles according to any one of claims 1 to 4. <9> Silica particles are externally added as the silicon-containing compound particles. <8> The cellulose particles according to claim 1. <10> The volume average particle size is 3 μm or more and less than 10 μm <1> ~ <9> The cellulose particles according to any one of claims 1 to 4. <11> The large diameter side number particle size distribution index GSDv is 1.0 or more and 1.7 or less <1> ~ <10> The cellulose particles according to any one of claims 1 to 4. <12> Sphericity is 0.9 or more <1> ~ <11> The cellulose particles according to any one of claims 1 to 4. <13> The number average molecular weight of the cellulose is 37,000 or more. <1> ~ <12> The cellulose particles according to any one of claims 1 to 4. <14> The number average molecular weight of the cellulose is 45,000 or more. <13> The cellulose particles according to claim 1. <15> Surface smoothness is 80% or more <1> ~ <14> The cellulose particles according to any one of claims 1 to 4. [Effects of the Invention]

[0007] <1> According to the invention, the cellulose derivative is not contained, or the content of the cellulose derivative is less than 0.5 parts by mass or 10 parts by mass. exceed As compared with the case where the cellulose granules are prepared by the above method, the cellulose granules are highly biodegradable and undergo little change in particle size due to water absorption. <2> According to the present invention, cellulose particles are provided which are highly biodegradable and exhibit little change in particle size due to water absorption, compared to cellulose derivatives other than cellulose acylate, such as cellulose ether, hydroxyalkyl cellulose, and carboxymethyl cellulose. <3> According to the present invention, cellulose particles having a high biodegradability and a small change in particle size due to water absorption are provided compared to single-layer cellulose particles having cellulose as the main component. <4> According to the invention, cellulose particles are provided which are more biodegradable and show less change in particle size due to water absorption than when the polyamine compound is polyvinylamine. <5> According to the invention, cellulose particles are provided which are more biodegradable and have less change in particle size due to water absorption than when the wax is candelilla wax. <6> According to the invention, a coating layer covers the base particles, and cellulose particles are provided which are highly biodegradable and have less change in particle size due to water absorption compared to particles having only a first coating layer containing at least one selected from the group consisting of polyamine compounds, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds. <7> According to the invention, cellulose particles are provided which are highly biodegradable and show less change in particle size due to water absorption, compared to when the second coating layer does not contain a polyvalent metal salt. <8> According to the invention, cellulose particles are provided which are more biodegradable and have less change in particle size due to water absorption than when stearyl stearate particles or zinc oxide particles are externally added. <9> According to the present invention, cellulose particles are provided which are highly biodegradable and exhibit less change in particle size due to water absorption than those in which metal soap particles are externally added. <10> According to the present invention, cellulose particles are provided which are highly biodegradable and exhibit little change in particle size due to water absorption, compared to cellulose particles having a volume average particle size of less than 3 μm or greater than 10 μm. <11> According to the invention, the large diameter side number particle size distribution index GSDv is less than 1.0 or 1. Compared with cellulose particles having a molecular weight of more than 7, the resulting cellulose particles are highly biodegradable and undergo little change in particle size due to water absorption. <12> According to the invention, cellulose particles are provided which are highly biodegradable and exhibit less change in particle size due to water absorption than cellulose particles having a sphericity of less than 0.9. <13> According to the invention, cellulose particles are provided which are highly biodegradable and exhibit less change in particle size due to water absorption, compared to cellulose having a number average molecular weight of less than 37,000. <14> According to the present invention, cellulose particles are provided which are highly biodegradable and exhibit less change in particle size due to water absorption, compared to cellulose having a number average molecular weight of less than 45,000. <15> According to the invention, cellulose particles are provided which are highly biodegradable and have less change in particle size due to water absorption, compared to cellulose particles having a surface smoothness of less than 80%. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described. These descriptions and examples are intended to illustrate the embodiment and are not intended to limit the scope of the invention. In the present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of a numerical range may be replaced with a value shown in the examples.

[0009] Each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, the amount refers to the total amount of those multiple substances present in the composition, unless otherwise specified.

[0010] <Cellulose particles> The cellulose particles according to this embodiment contain 90 parts by mass or more and 99.5 parts by mass or less of cellulose and 0.5 parts by mass or more and 10 parts by mass or less of a cellulose derivative.

[0011] Due to the above-described structure, the cellulose particles according to this embodiment have high biodegradability and are less susceptible to particle size change due to water absorption. The reasons for this are presumed to be as follows.

[0012] Biodegradable resin particles are in demand due to the problem of marine litter. Cellulose particles, which are primarily composed of cellulose, are rapidly biodegradable in compost, activated sludge, and seawater, and are being used in a variety of applications, including cosmetics. It has also been reported that cellulose particles with a high biodegradability can be produced by forming cellulose acetate, which is soluble in organic solvents, into particles and saponifying the particles (for example, Patent Document 2, etc.). However, cellulose particles have high water absorption properties, and when they absorb moisture from the air or the product to which they are applied, they expand and their particle size increases.

[0013] In contrast, the cellulose particles according to this embodiment contain 0.5 to 10 parts by mass of the cellulose derivative with respect to 90 to 99.5 parts by mass of cellulose. Cellulose derivatives also absorb water and swell, but to a lesser extent than cellulose. When cellulose and a cellulose derivative coexist, it is generally thought that the amount of change in particle size will be between that of cellulose and the cellulose derivative. However, when cellulose and a cellulose derivative coexist in the above ratio, the amount of change in water absorption can be made smaller than that of particles of a cellulose derivative alone. This is because their structures are similar, so cellulose derivative islands are dispersed extremely uniformly in the cellulose sea, and the two are incompatible, so voids are formed uniformly between the sea-island particles. These voids absorb the swelling amount, thereby suppressing the change in particle size.

[0014] From the above, it is presumed that the cellulose particles according to this embodiment have high biodegradability and little change in particle size due to water absorption due to the above-mentioned configuration. Specifically, the cellulose particles according to this embodiment undergo little change in particle size due to water absorption, and therefore, in cosmetic applications, it is possible to suppress changes in the feel on the skin (smoothness, moistness, smoothness, etc.), and in spacer applications, it is possible to suppress changes in the distance between substrates.

[0015] The cellulose particles according to this embodiment will be described in detail below.

[0016] (Cellulose / Cellulose Derivatives) The cellulose particles according to this embodiment contain 90 parts by mass or more and 99.5 parts by mass or less of cellulose and 0.5 parts by mass or more and 10 parts by mass or less of a cellulose derivative. From the viewpoint of improving biodegradability and suppressing particle size change, the cellulose particles contain 95 parts by mass or more and 99.5 parts by mass or less of cellulose. and 0.5 parts by mass or more and 5 parts by mass or less of a cellulose derivative. However, when the cellulose particles have a coating layer as described below, the mother particles coated with the coating layer contain cellulose and a cellulose derivative in the above-mentioned ratio.

[0017] From the viewpoint of biodegradability and suppression of particle size change, the cellulose content is preferably 90% by mass or more relative to the cellulose particles. However, when the cellulose particles have a coating layer as described below, the cellulose content is preferably 90% by mass or more relative to the base particles coated with the coating layer.

[0018] -cellulose- The number average molecular weight of the cellulose is preferably 37,000 or more, and more preferably 45,000 or more. The upper limit of the number average molecular weight of the cellulose is not particularly limited, but may be, for example, 100,000 or less.

[0019] By setting the number average molecular weight of cellulose to 37,000 or more, it becomes easier to obtain cellulose particles that are highly biodegradable and have little change in particle size due to water absorption. The reason for this is presumed to be as follows. When the number-average molecular weight of cellulose is 37,000 or higher, the increase in the number of terminal hydroxyl groups per unit volume of the particle is suppressed, the water absorption rate is lowered, and dimensional change due to water absorption also tends to be small. In addition, the reduction in terminal hydroxyl groups reduces the hydrogen bonding strength, making particle aggregation less likely to occur, and suppressing the decrease in biodegradability due to the decrease in specific surface area caused by aggregation. From the above, it is presumed that the cellulose particles are more likely to become highly biodegradable and have less change in particle size due to water absorption.

[0020] The number-average molecular weight of cellulose is measured by gel permeation chromatography (differential refractometer Optilab T-rEX, manufactured by Wyatt Technology; multi-angle light scattering detector DAWN HELEOS II, manufactured by Wyatt Technology; columns TSKgel α-M and α-3000, one each, manufactured by Tosoh Corporation) using dimethylacetamide (with 0.1 M lithium chloride added) as a solvent.

[0021] -Cellulose derivatives- Examples of the cellulose derivatives include cellulose acylate, cellulose ether, hydroxyalkyl cellulose, and carboxymethyl cellulose. Among these, cellulose acylate is preferred as the cellulose derivative, since cellulose acylate can be easily dispersed finely in cellulose and the change in particle size due to water absorption can be easily suppressed.

[0022] Cellulose acylate is a cellulose derivative in which at least some of the hydroxyl groups in cellulose are substituted with acyl groups (acylation). An acyl group is a group consisting of -CO-R AC (R AC represents a hydrogen atom or a hydrocarbon group.

[0023] Cellulose acylate is, for example, a cellulose derivative represented by the following general formula (CA).

[0024] [ka]

[0025] In the general formula (CA), A 1 , A 2 and A 3 each independently represents a hydrogen atom or an acyl group, and n represents an integer of 2 or more. 1 , n A 2 and n A's 3 At least some of the n A's in the molecule represent acyl groups.1 may be all the same, some of them may be the same, or they may be different from each other. 2 and n A's 3 may be all the same, some may be the same, or different from each other.

[0026] A 1 , A 2 and A 3 The hydrocarbon group in the acyl group represented by may be linear, branched, or cyclic, but is preferably linear or branched, and more preferably linear.

[0027] A 1 , A 2 and A 3 The hydrocarbon group in the acyl group represented by may be a saturated hydrocarbon group or an unsaturated hydrocarbon group, but is more preferably a saturated hydrocarbon group.

[0028] A 1 , A 2 and A 3 The acyl group represented by the formula (I) is preferably an acyl group having a carbon number of 1 to 6. That is, the cellulose acylate is preferably an acyl group having a carbon number of 1 to 6.

[0029] A 1 , A 2 and A 3 The acyl group represented by may be a group in which a hydrogen atom in the acyl group is substituted with a halogen atom (for example, a fluorine atom, a bromine atom, an iodine atom), an oxygen atom, a nitrogen atom, or the like, but is preferably unsubstituted.

[0030] A 1 , A 2 and A 3Examples of the acyl group represented by include a formyl group, an acetyl group, a propionyl group, a butyryl group (butanoyl group), a propenoyl group, a hexanoyl group, etc. Among these, from the viewpoint of improving the biodegradation rate of the resin particles, an acyl group having from 2 to 4 carbon atoms is more preferred, and an acyl group having 2 or 3 carbon atoms is even more preferred.

[0031] Examples of cellulose acylate include cellulose acetate (cellulose monoacetate, cellulose diacetate (DAC), cellulose triacetate), cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB).

[0032] The cellulose acylate is preferably cellulose acetate from the viewpoints of biodegradability and suppression of particle size change. The cellulose acylate may be used alone or in combination of two or more kinds.

[0033] The weight average degree of polymerization of the cellulose acylate is preferably 200 or more and 1,000 or less, more preferably 500 or more and 1,000 or less, and even more preferably 600 or more and 1,000 or less.

[0034] The weight-average degree of polymerization of cellulose acylate is determined from the weight-average molecular weight (Mw) by the following procedure. First, the weight average molecular weight (Mw) of cellulose acylate is measured in polystyrene equivalent using tetrahydrofuran with a gel permeation chromatography device (GPC device: HLC-8320GPC manufactured by Tosoh Corporation, column: TSKgel α-M). Next, the degree of polymerization of cellulose acylate is calculated by dividing the molecular weight by the molecular weight of the constituent unit of cellulose acylate. For example, when the substituent of cellulose acylate is an acetyl group, the molecular weight of the constituent unit is 263 when the substitution degree is 2.4, and 284 when the substitution degree is 2.9.

[0035] From the viewpoint of biodegradability, the degree of substitution of cellulose acylate is preferably from 1.7 to 2.9, more preferably from 1.9 to 2.6, even more preferably from 2.0 to 2.5, and particularly preferably from 2.1 to 2.4.

[0036] The degree of substitution of cellulose acylate is an index showing the degree to which hydroxyl groups in cellulose are substituted with acyl groups. In other words, the degree of substitution is an index showing the degree of acylation of cellulose acylate. Specifically, the degree of substitution means the intramolecular average number of hydroxyl groups in the D-glucopyranose unit of cellulose acylate that have been substituted with acyl groups. The degree of substitution is 1 The hydroxyl group content is determined from the integral ratio of the peaks of cellulose-derived hydrogen and acyl group-derived hydrogen by H-NMR (JMN-ECA / JEOL RESONANCE).

[0037] These cellulose acylates may be used alone or in combination of two or more.

[0038] (Other ingredients) The cellulose particles according to this embodiment may contain other components. However, when the cellulose particles have a coating layer as described below, the other components are contained in the base particles coated with the coating layer.

[0039] Examples of other components include plasticizers, flame retardants, compatibilizers, release agents, light resistance agents, weather resistance agents, colorants, pigments, modifiers, anti-drip agents, antistatic agents, hydrolysis inhibitors, fillers, reinforcing agents (glass fiber, carbon fiber, talc, clay, mica, glass flakes, milled glass, glass beads, crystalline silica, alumina, silicon nitride, aluminum nitride, boron nitride, etc.), acid acceptors for preventing acetic acid release (oxides such as magnesium oxide and aluminum oxide; metal hydroxides such as magnesium hydroxide, calcium hydroxide, aluminum hydroxide, and hydrotalcite; calcium carbonate; talc; etc.), and reactive trapping agents (for example, epoxy compounds, acid anhydride compounds, carbodiimides, etc.). The content of each of the other components is preferably 0% by mass or more and 5% by mass or less relative to the total amount of the cellulose particles (or base particles), where "0% by mass" means that no other components are included.

[0040] (Cellulose particles with coating layer) The cellulose particles according to this embodiment are preferably cellulose particles having base particles containing cellulose and a cellulose derivative in the above-mentioned ratio, and a coating layer covering the base particles, the coating layer containing at least one selected from the group consisting of polyamine compounds, waxes, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds (hereinafter also referred to as "cellulose particles having a coating layer").

[0041] By configuring the cellulose particles according to this embodiment as described above, the cellulose particles are more likely to have high biodegradability and undergo little change in particle size due to water absorption. The reason for this is presumed to be as follows. Polyamine compounds exhibit less dimensional change due to water absorption than cellulose, and by adhering to the surface through affinity with the hydroxyl groups of cellulose, particle size change can be further suppressed. In this case, the polyamine compound does not completely coat the surface, leaving gaps here and there. Although the biodegradability of polyamines is inferior to that of cellulose, microorganisms can pass through the gaps on the surface, so the excellent biodegradability of cellulose is not impaired, and since the amount of polyamine added is very small, there is little adverse effect and excellent biodegradability can be achieved. Wax and linear saturated fatty acids have strong water repellency, and coating the surface with them can suppress water absorption by cellulose and further suppress particle size change. Furthermore, because these compounds have a strong tendency to self-aggregate, they can partially self-aggregate on the cellulose surface, resulting in incomplete coverage and creating gaps. Microorganisms can pass through these gaps, so the excellent biodegradability of cellulose is not impaired, and furthermore, because these compounds themselves are biodegradable, excellent biodegradability can be achieved as particles. Like straight-chain saturated fatty acids, hydroxy fatty acids are water-repellent and can better suppress particle size change. Furthermore, the presence of hydroxyl groups gives them excellent affinity with cellulose, and they are highly able to maintain particle size change even when subjected to strong impacts. Because the fatty acid moiety is prone to self-aggregation, the gap effect, like straight-chain saturated fatty acids, allows for excellent biodegradability. Amino acid compounds tend to form flat crystals after coating, making it easy to cover the surface of cellulose particles. Because their water absorption rate is lower than that of cellulose, they can better suppress dimensional changes in cellulose particles. Gaps are formed between the crystals, which also makes them highly biodegradable. From the above, it is presumed that the cellulose particles are more likely to become highly biodegradable and have less change in particle size due to water absorption.

[0042] In the cellulose particles according to this embodiment, for example, base particles mainly composed of cellulose are prepared by saponifying cellulose acylate, which causes hydroxyl groups to be concentrated on the surface, thereby enabling the base particles to be coated with a first coating layer containing a polyamine compound at a high coverage rate.

[0043] -Mother particle- The base particles are mainly composed of cellulose. The cellulose contained in the base particles has the same meaning as the cellulose described above, and the preferred range is also the same.

[0044] -Coating layer- The coating layer contains at least one selected from the group consisting of polyamine compounds, waxes, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds.

[0045] Polyamine compounds Polyamine compounds are a general term for aliphatic hydrocarbons having two or more primary amino groups. Examples of the polyamine compound include polyalkyleneimine, polyallylamine, polyvinylamine, and polylysine. From the viewpoint of improving biodegradability, the polyalkyleneimine is preferably a polyalkyleneimine having a structural unit with an alkylene group having 1 to 6 carbon atoms (preferably 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms), and more preferably polyethyleneimine. Examples of polyallylamine include homopolymers and copolymers of allylamine, allylamine amide sulfate, diallylamine, dimethylallylamine, and the like. The polyvinylamine is produced, for example, by hydrolyzing poly(N-vinylformamide) with an alkali, and specific examples thereof include "PVAM-0595B" manufactured by Mitsubishi Chemical Corporation. The polylysine may be extracted from a natural product, may be produced by a transformed microorganism, or may be chemically synthesized.

[0046] The polyamine compound is preferably at least one selected from the group consisting of polyethyleneimine and polylysine. By using at least one selected from the group consisting of polyethyleneimine and polylysine as the polyamine compound, it becomes easier to obtain cellulose particles that are highly biodegradable and undergo little change in particle size due to water absorption. The reason for this is presumed to be as follows. Polyethyleneimine and polylysine have a high cation density and functional groups that react with the hydroxyl groups of cellulose, allowing them to adhere firmly to cellulose particles. On the other hand, they have hydrocarbon chains with an appropriate area ratio, and when attached to the surface of cellulose particles, the hydrocarbon chains tend to be exposed on the surface, preventing water absorption by the cellulose particles and further suppressing particle size change. Furthermore, because polyethyleneimine and polylysine have a relatively coarse structure rather than a dense one, they have gaps through which microorganisms can penetrate, and tend not to inhibit the excellent biodegradability of cellulose. From the above, it is presumed that the cellulose particles are more likely to become highly biodegradable and have smaller particle size changes due to water absorption.

[0047] The content of the polyamine compound is preferably 0.2% by mass or more and 2% by mass or less based on the total mass of the cellulose particles.

[0048] ·wax Examples of waxes include vegetable oils containing fatty acids, hydrocarbon waxes, diesters, and the like. Examples of vegetable oils containing fatty acids include castor oil, tung oil, linseed oil, shortening, corn oil, soybean oil, sesame oil, rapeseed oil, sunflower oil, rice bran oil, camellia oil, coconut oil, palm oil, walnut oil, olive oil, peanut oil, almond oil, jojoba oil, cocoa butter, shea butter, neem oil, safflower oil, Japan wax, candelilla wax, rice wax, carnauba wax, and damask rose flower wax. Examples of hydrocarbon waxes include petroleum waxes (paraffin wax, microcrystalline wax, petrolatum wax, etc.) and synthetic hydrocarbon waxes (polyethylene wax, polypropylene wax, polybutene wax, Fischer-Tropsch wax, etc.). Examples of diesters include diesters of dibasic acids such as malic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedioic acid with alcohols having 10 to 25 carbon atoms.

[0049] The wax is preferably carnauba wax. By using carnauba wax as the wax, it becomes easier to produce cellulose particles that are highly biodegradable and have little change in particle size due to water absorption. The reason for this is presumed to be as follows. Carnauba wax contains many components with water-repellent structures, such as free fatty acids and hydrocarbons, so coating the surface with it prevents direct contact between water and cellulose, suppresses water absorption by cellulose particles, and reduces dimensional change. Furthermore, because it contains free alcohol, it forms weak hydrogen bonds with the hydroxyl groups of cellulose particles, adhering to the cellulose particles. However, because the adhesive strength is relatively weak, there are small gaps at the interface through which microorganisms can penetrate, which is thought to preserve the excellent biodegradability of cellulose. From the above, it is presumed that the cellulose particles are more likely to become highly biodegradable and have less change in particle size due to water absorption.

[0050] The wax content is preferably 0.1% by mass or more and 2% by mass or less, and more preferably 0.2% by mass or more and 1% by mass or less, based on the total mass of the cellulose particles.

[0051] ·Straight-chain saturated fatty acids A straight-chain saturated fatty acid is a straight-chain saturated fatty acid. From the viewpoint of improving biodegradability and suppressing particle size change, the straight-chain saturated fatty acid is preferably a straight-chain saturated fatty acid having from 14 to 22 carbon atoms. Specific examples of straight-chain saturated fatty acids having from 14 to 22 carbon atoms include behenic acid, arachidic acid, palmitic acid, etc. The reason why using straight-chain saturated fatty acids in the coating layer prevents particle size changes and achieves excellent biodegradability is thought to be as follows: The terminal carboxylic acids form covalent bonds or ionic affinity with the hydroxyl groups of cellulose, allowing them to adhere to the surface of cellulose particles. Straight-chain hydrocarbon groups are exposed on the surface, and the hydrocarbon structure is highly water-repellent, preventing cellulose from absorbing water and suppressing dimensional changes in the particles. Meanwhile, even on the surface of the same particle, hydrocarbon groups repel each other, creating gaps on the surface through which microorganisms can penetrate, without impairing the excellent biodegradability of cellulose. In the case of straight-chain saturated fatty acids, if the carbon number is 14 or more, the repulsion between the hydrocarbon groups is strong, sufficient gaps are created in the coating, and the penetration of microorganisms is suppressed, resulting in sufficient biodegradability. On the other hand, if the carbon number is 22 or less, the repulsion of excess hydrocarbon groups is suppressed, preventing a decrease in the coating area and increasing the effect of suppressing water absorption by cellulose, i.e., suppressing changes in particle size.

[0052] Hydroxy fatty acids The hydroxy fatty acid is preferably a hydroxy fatty acid having 12 to 20 carbon atoms from the viewpoint of improving biodegradability and suppressing particle size change. Examples of hydroxy fatty acids having 12 to 20 carbon atoms include hydroxystearic acid, hydroxypaltimic acid, hydroxylauric acid, hydroxymyristic acid, and hardened castor oil fatty acid. The reason why using hydroxy fatty acids in the coating layer prevents particle size changes and achieves excellent biodegradability is thought to be as follows: The hydroxyl groups of the hydroxy fatty acids form weak hydrogen bonds with the hydroxyl groups of the cellulose particles, causing the hydroxy fatty acids to adhere to the surface of the cellulose particles. The fatty acid portion of the attached hydroxy fatty acids faces outward from the particles, which prevents the cellulose from absorbing water and further suppresses particle size changes. Because the hydrocarbon portion of the fatty acid has low affinity for cellulose, gaps are formed between the two, allowing microorganisms to enter the cellulose particles through these gaps, thereby not inhibiting the excellent biodegradability of cellulose. When the carbon number of the hydroxy fatty acid is 12 or more, the fatty acid has a strong effect of suppressing water absorption by cellulose, i.e., suppressing particle size change. On the other hand, when the carbon number is 20 or less, the fatty acid is fixed to the surface of the cellulose particles by the hydroxyl groups, so the non-repulsive long chains are less likely to become entangled, which prevents the entry of microorganisms and tends to improve biodegradability.

[0053] Amino acid compounds Examples of amino acid compounds include lauryl leucine, lauryl arginine, and myristyl leucine. The reason why using amino acid compounds in the coating layer prevents particle size changes and achieves excellent biodegradability is thought to be as follows: The amide groups have ionic affinity with the hydroxyl groups of cellulose, allowing the amino acid compounds to adhere to the surface of the cellulose particles. The hydrocarbon portion of the amino acid is exposed on the surface, which prevents the cellulose from absorbing water and suppresses particle size changes. Furthermore, amino acids are quickly decomposed by microorganisms, resulting in extremely good biodegradability.

[0054] Layer structure of the coating layer The coating layer may include a first coating layer that coats the base particles and contains at least one selected from the group consisting of polyamine compounds, polyvinyl alcohol, polyvinylpyrrolidone, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds, and a second coating layer that coats the first coating layer and contains wax.

[0055] In particular, it is preferable that the coating layer has a first coating layer that coats the base particles and contains a polyamine compound, a linear saturated fatty acid, a hydroxy fatty acid, and an amino acid-based compound, and a second coating layer that coats the first coating layer and contains a wax. By having the coating layer comprise the first coating layer and the second coating layer, the cellulose particles are more likely to have high biodegradability and undergo less change in particle size due to water absorption. The reason for this is presumed to be as follows. Wax has strong water repellency, but it tends to self-aggregate, which can easily cause defects in the coating layer. If these become too large, the cellulose's water absorption, i.e., its ability to inhibit particle size change, tends to decrease. Therefore, a certain amount of wax needs to be coated to avoid defects, and if the amount is too large, biodegradability tends to decrease. On the other hand, polyamine compounds, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds have inferior water repellency to wax, but have high adhesion to cellulose particles and can reduce defects in the coating layer. Wax and polyamine compounds, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds have high adhesion to each other, making it difficult for wax coating defects to occur. For the above reasons, it is presumed that when the coating layer has the first coating layer and the second coating layer, the cellulose particles are more likely to be highly biodegradable and have less change in particle size due to water absorption.

[0056] Polyvalent metal salts The second coating layer preferably contains a polyvalent metal salt. When the second coating layer contains a polyvalent metal salt, the cellulose particles are more likely to have high biodegradability and undergo less particle size change due to water absorption. The reason for this is presumed to be as follows. The wax contained in the second layer has relatively low adhesion to the lower layer. Therefore, it is prone to self-aggregation, which can lead to coating defects. By including a polyvalent metal salt in the second coating layer along with the wax, the polyvalent metal salt is spread evenly throughout the wax, and aggregation occurs uniformly over a wide area starting from this point. This suppresses the occurrence of coating defects due to self-aggregation and improves the adhesion of the second coating layer. From the above, it is presumed that the cellulose particles are more likely to become highly biodegradable and have less change in particle size due to water absorption.

[0057] A polyvalent metal salt is a compound composed of a divalent or higher metal ion and an anion. Examples of divalent or higher metal ions that constitute polyvalent metal salts include ions of calcium, magnesium, copper, nickel, zinc, barium, aluminum, titanium, strontium, chromium, cobalt, iron, and the like. Examples of anions constituting polyvalent metal salts include inorganic ions and organic ions. Examples of inorganic ions include chloride ions, bromide ions, iodide ions, nitrate ions, sulfate ions, and hydroxide ions. Examples of organic ions include organic acid ions, such as carboxylate ions.

[0058] Examples of polyvalent metal salts include aluminum sulfate, polyaluminum chloride, iron chloride, and calcium hydroxide.

[0059] The content of the polyvalent metal salt relative to the content of the wax is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.2% by mass or more and 5% by mass or less, and even more preferably 0.3% by mass or more and 1% by mass or less.

[0060] - Content of the components in the first and second coating layers The content of polyamine compounds, polyvinyl alcohol, polyvinylpyrrolidone, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds in the entire first coating layer is preferably 90% by mass or more and 100% by mass or less, and more preferably 95% by mass or more and 100% by mass or less. The total content of the wax and the polyvalent metal salt in the entire second coating layer is preferably 90% by mass or more and 100% by mass or less, and more preferably 95% by mass or more and 100% by mass or less.

[0061] -External additives- The cellulose particles according to this embodiment may be externally added with at least one external additive selected from the group consisting of silicon-containing compound particles, metal soap particles, fatty acid ester particles, and metal oxide particles.

[0062] In particular, the cellulose particles according to this embodiment preferably have at least one external additive selected from the group consisting of silicon-containing compound particles and metal soap particles added thereto. The cellulose particles according to this embodiment, which contain the external additive, are more likely to be highly biodegradable and have less change in particle size due to water absorption. The reason for this is presumed to be as follows. Silicon-containing compound particles and metal soap particles can adhere to larger particles through electrostatic adhesion, and are much more water-repellent than metal oxide particles and aliphatic ester particles, which also adhere to them, further promoting cellulose's water absorption, i.e., suppressing particle size change. Furthermore, because of their particulate shape, they have a larger specific surface area than coating materials, and this shape effect also enhances their water absorption, i.e., suppressing particle size change. Because of their particulate shape, there are sufficient gaps for microorganisms to enter, and they do not inhibit the excellent biodegradability of cellulose. From the above, it is presumed that the cellulose particles are more likely to be degraded and have less change in particle size due to water absorption.

[0063] The silicon-containing compound particles refer to particles containing silicon. The silicon-containing compound particles may be particles containing only silicon, or particles containing silicon and other elements.

[0064] The silicon-containing compound particles are preferably silica particles. The silica particles may be crystalline or amorphous as long as they are particles containing silica, i.e., SiO2, as the main component. The silica particles may be particles produced from silicon compounds such as water glass or alkoxysilane, or may be particles obtained by crushing quartz.

[0065] By using silica particles as the silicon-containing compound particles, it becomes easier to obtain cellulose particles that are highly biodegradable and undergo little change in particle size due to water absorption. The reason for this is presumed to be as follows. Silica tends to have high sphericality when granulated, and since the silicon element has high water repellency, it has a particularly strong effect in inhibiting particle size change, and since microorganisms can attack cellulose particles in a uniform distribution, it also has particularly excellent biodegradability. From the above, it is presumed that the cellulose particles are more likely to become highly biodegradable and have less change in particle size due to water absorption.

[0066] Metal soap particles are particles whose main component is metal soap. Here, particles containing metal soap as a main component refer to particles in which the content of metal soap in the particles is 90 mass % or more.

[0067] Metal soaps are fatty acid metal salts in which fatty acids and metals are bonded together. Examples of fatty acid metal salts include metal salts of fatty acids having from 10 to 25 carbon atoms (preferably from 12 to 22). Examples of metal salts of fatty acids having from 10 to 25 carbon atoms include metal salts of stearic acid, metal salts of palmitic acid, metal salts of lauric acid, metal salts of oleic acid, metal salts of linoleic acid, and metal salts of ricinoleic acid. The metal in the fatty acid metal salt may be a divalent metal. Examples of metals in fatty acid metal salts include magnesium, calcium, aluminum, barium, and zinc.

[0068] The fatty acid ester particles are particles containing fatty acid ester particles as a main component. Here, particles containing fatty acid ester particles as a main component refer to particles in which the content of fatty acid ester particles relative to the total particle content is 90 mass % or more.

[0069] Examples of fatty acid esters include esters of saturated fatty acids having 10 to 25 carbon atoms and alcohols having 10 to 25 carbon atoms. Examples of fatty acid esters include stearyl stearate, stearyl laurate, and stearyl palmitate.

[0070] Metal oxide particles are particles whose main component is a metal oxide. Here, particles containing metal oxide as a main component refer to particles in which the content of metal oxide in the particles is 90 mass % or more.

[0071] As the metal oxide, oxides of metals other than silicon can be used. Examples of metal oxides include zinc oxide, magnesium oxide, iron oxide, and aluminum oxide.

[0072] From the viewpoint of texture (specifically, feel on the skin), the volume average particle size of the external additive is preferably 1 nm or more and 100 nm or less, and more preferably 5 nm or more and 30 nm or less. The volume average particle size of the external additive is measured in the same manner as the volume average particle size of the cellulose.

[0073] The amount of the external additive added is preferably 0.1% by mass or more and 2% by mass or less with respect to the total mass of the cellulose particles (cellulose particles to which no external additive has been added).

[0074] (Volume average particle size and large particle size distribution index GSDv) The volume average particle size of the cellulose particles according to this embodiment is preferably 3 μm or more and less than 10 μm, more preferably 4 μm or more and 9 μm or less, and even more preferably 5 μm or more and 8 μm or less.

[0075] By adjusting the volume average particle size of the cellulose particles according to this embodiment to 3 μm or more and less than 10 μm, the cellulose particles are more likely to have high biodegradability and little change in particle size due to water absorption. The reason for this is presumed to be as follows. If the volume average particle size is 3 μm or more, the particle surface area will not be too large, which will suppress water absorption from the cellulose surface and reduce particle size change. Also, if it is less than 10 μm, the surface area will be appropriately large, which will facilitate uniform biodegradation from the surface and tend to result in excellent biodegradability. From the above, it is presumed that the cellulose particles are more likely to become highly biodegradable and have less change in particle size due to water absorption.

[0076] The large diameter number particle size distribution index GSDv of the cellulose particles according to this embodiment is preferably 1.0 or more and 1.7 or less, more preferably 1.0 or more and 1.5 or less, and even more preferably 1.0 or more and 1.3 or less.

[0077] By setting the large-diameter number particle size distribution index GSDv of the cellulose particles according to this embodiment to 1.0 or more and 1.7 or less, the cellulose particles are more likely to have high biodegradability and little change in particle size due to water absorption. The reason for this is presumed to be as follows. If the GSDv is between 1.0 and 1.7, the amount of fine powder (small particles less than 3 μm) is small, so the cellulose is less likely to absorb water due to the remaining fine powder, resulting in small changes in particle size. In addition, coarse powder (large particles over 10 μm) is less likely to inhibit biodegradation (because decomposition begins from the surface), which tends to achieve excellent biodegradability. From the above, it is presumed that the cellulose particles are more likely to become highly biodegradable and have less change in particle size due to water absorption.

[0078] The volume average particle size and the large particle size distribution index GSDp of the cellulose particles are measured as follows. The particle size is measured using an LS particle size distribution analyzer "Beckman Coulter LS13 320 (manufactured by Beckman Coulter)" and the cumulative particle size distribution is plotted from the smallest diameter side on a volume basis. The particle size at 50% of the cumulative distribution is determined as the volume average particle size. On the other hand, the cumulative particle size distribution is plotted from the small diameter side on a volume basis, and the particle size at 50% of the cumulative distribution is defined as the number average particle size D50v, and the particle size at 84% of the cumulative distribution is defined as the number particle size D84v. The large diameter side number particle size distribution index GSDv is calculated using the formula GSDv = (D84v / D50v) 1 / 2 Calculated as follows.

[0079] (Sphericity) The sphericity of the cellulose particles according to this embodiment is preferably 0.90 or more, more preferably 0.95 or more, and even more preferably 0.97 or more.

[0080] By setting the sphericity of the cellulose particles according to this embodiment to 0.90 or more, the cellulose particles are more likely to have high biodegradability and little change in particle size due to water absorption. The reason for this is presumed to be as follows. If the sphericity is 0.9 or higher, the anisotropy of dimensional change is small and averaged in all directions, resulting in small particle size changes. Also, microbial decomposition can proceed from the surface to the center in the shortest possible time, which tends to result in excellent biodegradability. From the above, it is presumed that the cellulose particles are more likely to become highly biodegradable and have less change in particle size due to water absorption.

[0081] The sphericity is calculated by (circular equivalent perimeter) / (perimeter) [(perimeter of a circle having the same projected area as the particle image) / (perimeter of the particle projected image)]. Specifically, it is a value measured by the following method. First, the cellulose particles to be measured are collected by suction, flattened, and instantaneously flashed to capture a still image of the particles, which is then analyzed using a flow-type particle image analyzer (FPIA-3000, manufactured by Sysmex Corporation). The number of samples taken to determine the sphericity is 3,500. When the cellulose particles contain external additives, the cellulose particles to be measured are dispersed in water containing a surfactant, and then ultrasonically treated to remove the external additives, resulting in cellulose particles that are used as the measurement subject.

[0082] (Surface smoothness) The surface smoothness of the cellulose particles according to this embodiment is preferably 80% or more, more preferably 82% to 99%, and even more preferably 84% to 98%.

[0083] By making the surface smoothness of the cellulose particles according to this embodiment 80% or more, the cellulose particles tend to be highly biodegradable and have little change in particle size due to water absorption. The reason for this is presumed to be as follows. If the smoothness is 80% or more, the particle surface area becomes relatively small, which reduces the water absorption of cellulose and reduces the change in particle size. Also, although some microorganisms that promote biodegradation are relatively large, such large microorganisms can come into contact with the particle surface, which tends to result in excellent biodegradability. From the above, it is assumed that the cellulose particles are likely to be highly biodegradable and undergo little change in particle size due to water absorption.

[0084] The surface smoothness is measured by the following procedure. SEM images (magnification 5,000x) of cellulose particles taken with a scanning electron microscope (SEM) are observed, and the smoothness M of each cellulose particle is calculated using the following formula. The arithmetic mean value of the smoothness M of 10 or more arbitrarily selected cellulose particles is then taken as the surface smoothness. The closer the smoothness M value is to 1, the smoother the surface of the cellulose particle. M = (1-(S3) / (S2)) × 100 In the above formula, S2 represents the area (projected area) of the cellulose particle in the image, and S3 represents the sum of the "area outside the outline of the circle having the same projected area as S2 and inside the outline of the cellulose particle in the image" and the "area inside the outline of the circle having the same projected area as S2 and outside the outline of the cellulose particle in the image" when the cellulose particle in the image is superimposed on a circle having the same projected area as S2. The method for superimposing the cellulose particles in the image onto a circle having the same projected area as S2 is as follows. When the cellulose particles in the image are superimposed on a circle with the same projected area as S2, the two images are superimposed so that the area of ​​the overlapping region (the area inside the outline of the circle with the same projected area as S2 and the area inside the outline of the cellulose particles in the image) is maximized.

[0085] <Method of manufacturing cellulose particles> The method for producing cellulose particles preferably includes a step of producing a particle precursor containing cellulose acylate (particle precursor production step) and a step of saponifying the cellulose acylate contained in the particle precursor (saponification step).

[0086] -Particle precursor manufacturing process- A particle precursor containing cellulose acylate is produced by any one of the following methods (1) to (5).

[0087] (1) A kneading and crushing method in which the components are kneaded, and the resulting kneaded mixture is crushed and classified to obtain granules; (2) A dry manufacturing method in which the shape of granules obtained by the kneading and grinding method is changed by mechanical impact force or thermal energy to obtain granules. (3) A method of agglomeration and coalescence in which particle dispersions of each component are mixed, the particles in the dispersion are agglomerated, and heat-fused to obtain granules. (4) A dissolution suspension method in which an organic solvent in which each component is dissolved is suspended in an aqueous solvent to form granules containing each component. (5) A kneading and dissolving method in which each component and a binder are kneaded and extruded to form pellets, and the resulting pellets are stirred in a solvent that dissolves only the binder to form granules.

[0088] Here, cellulose acylate is a cellulose derivative in which at least one hydroxy group in cellulose is substituted (acylated) with an aliphatic acyl group. Specifically, at least one hydroxy group in cellulose is substituted (acylated) with an aliphatic acyl group. AC (R AC represents an aliphatic hydrocarbon group.) is a cellulose derivative substituted with.

[0089] -Saponification process- Subsequently, the cellulose acylate contained in the particle precursor is saponified. Through this step, the aliphatic acyl groups in the cellulose acylate are hydrolyzed, and the cellulose is converted into cellulose.

[0090] The saponification step is carried out, for example, by adding sodium hydroxide to a dispersion of the particle precursor and stirring the dispersion.

[0091] -Coating layer formation process- When producing cellulose particles having a coating layer, it is preferable to include a step of forming a coating layer (coating layer forming step) after the saponification step. Here, when the coating layer forming step is carried out, the particles obtained through the saponification step are used as base particles to form a coating layer.

[0092] First, an aqueous dispersion of the base particles is prepared. Before preparing the aqueous dispersion, the base particles are preferably washed with an acid.

[0093] Next, the aqueous dispersion in which the base particles are dispersed is mixed with an aqueous solution containing the compound that constitutes the first coating layer. As a result, for example, the hydroxyl groups of the resin contained in the base particles react with the amine sites, carboxyl groups, amino groups, etc. of the surface-treated polymer, or the hydroxyl groups form hydrogen bonds, thereby forming the first coating layer. Then, the aqueous dispersion in which the base particles with the first coating layer formed thereon are dispersed is mixed with an emulsion containing the compound that constitutes the second coating layer. As a result, the second coating layer is formed. The cellulose particles having a coating layer are then extracted from the mixture. The extraction of the cellulose particles having a coating layer is carried out, for example, by filtering the mixture. The extracted cellulose particles having a coating layer are preferably washed with water. This allows the removal of unreacted surface-treating polymer. The cellulose particles having a coating layer are then dried to obtain the cellulose particles according to this embodiment.

[0094] -External addition process- An external additive may be added to the obtained cellulose particles. The external addition step may be, for example, a process of adding an external additive to cellulose particles using a mixing mill, a V-type blender, a Henschel mixer, a Loedige mixer, or the like.

[0095] <Application> Applications of the cellulose particles according to this embodiment include granular materials such as cosmetics, rolling agents, abrasives, scrubbing agents, display spacers, materials for forming beads, light diffusing particles, resin reinforcing agents, refractive index control agents, biodegradation accelerators, fertilizers, water-absorbing particles, toner particles, and anti-blocking particles.

[0096] The cellulose particles according to this embodiment are preferably used in cosmetics. Among these, the cellulose particles according to this embodiment are preferably used as cosmetic additives. The cellulose particles according to this embodiment have excellent flexibility, and therefore when used as a cosmetic additive, the cosmetic tends to spread well on the skin when applied to the skin.

[0097] The cellulose particles according to this embodiment can be used as a cosmetic additive in, for example, base makeup cosmetics (e.g., makeup base, concealer, foundation, face powder, etc.); makeup cosmetics (e.g., lipstick, gloss, lip liner, blush, eye shadow, eyeliner, mascara, eyebrow, nail, nail care cosmetics, etc.); skin care cosmetics (e.g., facial cleanser, cleanser, lotion, emulsion, serum, pack, face mask, eye and mouth care cosmetics, etc.); etc. In particular, since cosmetic additives for makeup cosmetics are required to be flexible and biodegradable, the resin particles according to this embodiment are preferably used as cosmetic additives for makeup cosmetics. [Example]

[0098] Examples will be described below, but the present invention is not limited to these examples. In the following description, unless otherwise specified, all "parts" and "%" are by mass.

[0099] <Preparing each ingredient> The following materials were prepared:

[0100] (Cellulose acylate) Cel1: Daicel "L-20", cellulose acetate, number average molecular weight 47,000. Cel2: Daicel "L-50", cellulose acetate, number average molecular weight 58,000. Cel3: Eastman Chemical "CAP482-20", cellulose acetate propionate, number average molecular weight 75,000. Cel4: Eastman Chemical "CAB381-20", cellulose acetate butyrate, number average molecular weight 70,000. Cel5: Eastman Chemical "CA398-6", cellulose acetate, number average molecular weight 35,000. Cel6: Eastman Chemical "CAP482-0.5", cellulose acetate propionate, number average molecular weight 25,000. Cel7: Eastman Chemical "CAP-504-0.2", cellulose acetate propionate, number average molecular weight 15,000. Cel8: Shin-Etsu Chemical "Metolose 60SH-4000", hydroxypropyl methylcellulose, number average molecular weight 47,000

[0101] (Compounds constituting the first coating layer) -Polyamine compounds- Fir1: Nippon Shokubai "Epomin SP-003", polyethyleneimine, molecular weight 300 Fir2: Nippon Shokubai "Epomin SP-006", polyethyleneimine, molecular weight 600 Fir3: Nippon Shokubai "Epomin SP-012", polyethyleneimine, molecular weight 1200 Fir4: Nippon Shokubai "Epomin SP-018", polyethyleneimine, molecular weight 1800 Fir5: Nippon Shokubai "Epomin SP-200", polyethyleneimine, molecular weight 10,000 Fir6: Nippon Shokubai "Epomin HM-2000", polyethyleneimine, molecular weight 30,000 Fir7: Nippon Shokubai "Epomin P-1000", polyethyleneimine, molecular weight 70,000 Fir8: Nittobo Medical "PAA-01", polyallylamine, molecular weight 1600 Fir9: Nittobo Medical "PAA-03", polyallylamine, molecular weight 3000 Fir10: Nittobo Medical "PAA-05", polyallylamine, molecular weight 5000 Fir11: Nittobo Medical "PAA-08", polyallylamine, molecular weight 8000 Fir12: Nittobo Medical "PAA-15C", polyallylamine, molecular weight 15,000 Fir13: Nittobo Medical "PAA-25", polyallylamine, molecular weight 25,000 Fir14: Mitsubishi Chemical "Polyvinylamine", Polyvinylamine Fir15: JNC "Polylysine 10", Polylysine Fir16: Ichimaru Falcos "Polylysine 10", Polylysine

[0102] -Polyvinyl alcohol and polyvinylpyrrolidone- Fir17: Mitsubishi Chemical "Gohsenol N-300", polyvinyl alcohol Fir18: Nippon Shokubai "K-30", polyvinylpyrrolidone

[0103] -Straight-chain saturated fatty acids- Fir19: NOF "NAA-222S", behenic acid (carbon number 22) Fir20: Fujifilm Shonan Wako Pure Chemical "Arachidic acid", arachidic acid (carbon number 20) Fir21: Fujifilm Shonan Wako Pure Chemical "Paltimic acid", palmitic acid (carbon number 14) Fir22: Fujifilm Shonan Wako Pure Chemical "Lauric Acid", lauric acid (carbon number 12) Fir23: Fujifilm Shonan Wako Pure Chemical "Lignoceric Acid", Lignoceric acid (carbon number 24)

[0104] -Hydroxy fatty acids- Fir24: Ito Oil "12-hydroxystearic acid", hydroxystearic acid Fir25 oil, "castor hydrogenated fatty acid", castor hydrogenated fatty acid

[0105] -Amino acid compounds- Fir26: Ajinomoto "Amihope LL", Lauroyl Lysine

[0106] (Compounds constituting the second coating layer) -wax- Sec1: Senka "CN-100", Carnauba wax Sec2: Toa Kasei "TOWAX-1F3", Carnauba wax Sec3: Toa Kasei "TOWAX-1F6", Carnauba wax Sec4: Toa Kasei "TOWAX-1F8", Carnauba wax Sec5: Toa Kasei "TOWAX-1F12", Carnauba wax Sec6: Toa Kasei "TOWAX-5B2", Carnauba wax Sec7: Toa Kasei "TOWAX-1B4", Carnauba wax Sec8: Toa Kasei "TOWAX-4F2", Candelilla wax Sec9: Toa Kasei "TOWAX-4F3", Candelilla wax Sec10: Toa Kasei "TOWAX-4F4", Candelilla wax Sec11: Toa Kasei "TOWAX-6B2", Damask rose flower wax Sec12: Toa Kasei "TOWAX-6F2", sunflower seed wax Sec13: Ogura Synthetic Industries, Rice Wax Sec14: Boso Oils & Fat "SS-1", Rice Wax Sec15: Nisshin Oillio "Cosmol 222", Diisostearyl Malate

[0107] -Polyvalent metal salts- Sec21: Fujifilm Wako Pure Chemical Industries, aluminum sulfate Sec22: Fujifilm Wako Pure Chemical Industries, polyaluminum chloride Sec23: Fujifilm Wako Pure Chemical, iron chloride Sec24: Fujifilm Wako Pure Chemicals, calcium hydroxide

[0108] (external additives) -Silicon-containing compound particles- Sur1: Nippon Aerosil "AEROSIL R972", dimethyl silylated silica particles, average particle size = 16 nm Sur2: Nippon Aerosil "AEROSIL RY200S", dimethicone silicate particles, average particle size = 12 nm

[0109] -Metal soap particles- Sur3: NOF "MZ-2", zinc stearate particles, volume average particle size = 1500 nm Sur4: NOF "Magnesium Stearate S", magnesium stearate particles, volume average particle size = 1000 nm

[0110] -Fatty acid ester particles- Sur6: Kao "Excepal SS", stearyl stearate particles, volume average particle size = 1000 nm

[0111] -Metal oxide particles- Sur7: Sakai Chemical "FINEX-50", zinc oxide particles, volume average particle size = 1500 nm

[0112] The volume average particle size of the external additive was measured by the same procedure as that for the volume average particle size of the cellulose particles.

[0113] Example 1 (Particle precursor production process) 130 parts of cellulose acylate (Cel1) were completely dissolved in 870 parts of ethyl acetate. This was added to an aqueous liquid containing 50 parts of calcium carbonate and 500 parts of pure water and stirred for 3 hours (hereinafter referred to as the "first stirring period"). A solution of 4 parts of carboxymethyl cellulose (hereinafter also referred to as "CMC") and 200 parts of methyl ethyl ketone dispersed in 600 parts of pure water was added to this and stirred for 5 minutes using a high-speed emulsifier. 10 parts of sodium hydroxide was added to this, heated to 80°C, and stirred for 3 hours to remove the ethyl acetate and methyl ethyl ketone. An equal amount of dilute hydrochloric acid as the sodium hydroxide was added to this, and the residue was filtered and then dispersed again in pure water to obtain a particle precursor dispersion (solid concentration 10%).

[0114] (saponification process) 15 parts of a 20% aqueous sodium hydroxide solution was added to 500 parts of the particle precursor dispersion, and the mixture was stirred for 2 hours at a saponification temperature of 30° C. Hydrochloric acid was added to the saponified slurry to adjust the pH to 7, followed by repeated filtration and washing until the conductivity of the filtrate reached 10 μs / cm or less, yielding cellulose particles.

[0115] <Examples 2 to 7> Cellulose particles were obtained in the same manner as in Example 1, except that the type of cellulose acylate used in the particle precursor production step was as shown in Table 1.

[0116] <Examples 8 and 9> Cellulose particles were obtained in the same manner as in Example 1, except that in the saponification step, a 20% aqueous sodium hydroxide solution and stirring time were as shown in Table 1.

[0117] <Comparative Benefits 1-2> Cellulose particles were obtained in the same manner as in Example 1, except that in the saponification step, a 20% aqueous sodium hydroxide solution and stirring time were as shown in Table 1.

[0118] Example 10 (Particle precursor production process), and (Saponification process) Cellulose particles were obtained in the same manner as in Example 1.

[0119] (Coating layer formation process) A base particle dispersion was obtained by mixing 1,000 parts of cellulose particles (base particles) with 10,000 parts of ion-exchanged water. Seven parts of Fir16, a compound that forms the first coating layer, were added to the base particle dispersion and stirred for one hour to form a coating layer. The cellulose particles with the coating layer were repeatedly filtered and washed until the conductivity of the filtrate reached 10 μs / cm or less, yielding cellulose particles with a coating layer.

[0120] <Examples 11 to 27> In the coating layer formation process, cellulose particles having a coating layer were obtained using the same procedure as in Example 10, except that the type of compound constituting the first coating layer ("first layer compound" in Table 1) was as shown in Table 1.

[0121] Example 28 (Particle precursor production process), and (Saponification process) Cellulose particles were obtained in the same manner as in Example 1.

[0122] (Coating layer formation process) A base particle dispersion was obtained by mixing 1,000 parts of cellulose particles as base particles with 10,000 parts of ion-exchanged water. 7 parts of Fir16, a compound that forms a first coating layer, was added to the base particle dispersion and stirred for 1 hour to form a first coating layer, yielding a cellulose particle dispersion having a first coating layer. Next, 1:6 parts of Sec as a wax and 50 parts of pure water were stirred in a high-speed emulsifier to prepare a second coating layer forming emulsion. The entire amount of the second coating layer forming emulsion was added to the cellulose particle dispersion having the first coating layer, and the mixture was stirred for 24 hours to form a second coating layer, thereby obtaining a cellulose particle dispersion having the first and second coating layers. The cellulose particles having the first and second coating layers were repeatedly filtered and washed until the conductivity of the filtrate reached 10 μs / cm or less, yielding cellulose particles having the first and second coating layers.

[0123] <Examples 29 to 42> Cellulose particles having first and second coating layers were obtained in the same procedure as in Example 28, except that the types of wax used in the coating layer formation step were as shown in Table 1.

[0124] <Example 43> (Particle precursor production process), (Saponification process), and (Coating layer formation process) Cellulose particles having first and second coating layers were obtained in the same manner as in Example 28.

[0125] (External addition process) 0.6 parts of Sur1 was added as an external additive to 30 parts of cellulose particles having the first and second coating layers, and mixed in a mixing mill (Wonder Crusher, manufactured by Osaka Chemical Co., Ltd.) to obtain cellulose particles having an external additive.

[0126] <Examples 44 to 46, 48 to 49> Cellulose particles having external additives were obtained in the same manner as in Example 43, except that in the external addition step, the types and amounts of external additives added were as shown in Table 1.

[0127] <Examples 52 to 53> Cellulose particles were obtained in the same manner as in Example 43, except that in the saponification step, a 20% aqueous sodium hydroxide solution and stirring time were as shown in Table 1.

[0128] <Comparative Examples 3 and 4> Cellulose particles were obtained in the same manner as in Example 43, except that in the saponification step, a 20% aqueous sodium hydroxide solution and stirring time were as shown in Table 1.

[0129] <Examples 54 to 61> Cellulose particles containing external additives were obtained using the same procedure as in Example 28, except that in the particle precursor manufacturing process, the amount of calcium carbonate added, the first stirring time, the amount of carboxymethyl cellulose added, and the amount of sodium hydroxide added were as shown in Table 1.

[0130] <Examples 62 to 65> Cellulose particles with external additives were obtained using the same procedure as in Example 43, except that in the coating layer formation process, the type of wax was changed as shown in Table 1, and when preparing the second coating layer formation emulsion, the polyvalent metal salt shown in Table 1 was added together with the wax and pure water in the amount shown in Table 1.

[0131] <Examples 66 to 81> Cellulose particles were obtained in the same manner as in the above example, except that the conditions were changed as shown in Table 1. However, in Example 66, Cel1 and Cel8 were used as cellulose acylates in a mass ratio (Cel1:Cel8) of 49:1.

[0132] <Comparative Examples 5 to 9> The following particles were used as cellulose particles for each example. Comparative Example 5: CELLULOBEADS D10 (manufactured by Daito Kasei Co., Ltd., cellulose particles with a saponification rate of 100% and 100% by mass of cellulose. No coating layer or external additives.) Comparative Example 6: OTS-0.5A CELLULOBEADS D10 (manufactured by Daito Kasei Co., Ltd.; cellulose particles having base particles with a saponification rate of 100% and 100% by mass of cellulose and a coating layer containing triethoxyoctylsilane; no external additives). Comparative Example 7: S-STM CELLULOBEADS D-5 (manufactured by Daito Kasei Co., Ltd.; cellulose particles having base particles with a saponification rate of 100% and 100% by mass of cellulose and a coating layer containing magnesium stearate; no external additives). Comparative Example 8: CELLUFLOW TA25 CELLULOBEADS D-10 (manufactured by JNC Corporation, cellulose particles with a saponification rate of 0% and diacetyl cellulose of 100% by mass. No coating layer or external additives.) Comparative Example 9: Celluflow C25 (manufactured by JNC Corporation, cellulose particles containing 100% saponification rate and 100% by mass of cellulose as the main component. No coating layer or external additives are included.)

[0133] <Comparative Example 10> Cellulose particles were obtained according to the procedure described in Example 1 of Japanese Patent No. 6872068. The cellulose particles had a saponification rate of 100% and were 100% by mass of cellulose, and contained no external additives. The specific production method was as follows.

[0134] An oil phase was prepared by dissolving 250 parts by mass of diacetyl cellulose (CA398-3, manufactured by Eastman Chemical Co.) in 2,500 parts by mass of ethyl acetate. An aqueous phase was prepared by dissolving 200 parts by mass of polyvinyl alcohol in 2,300 parts by mass of ion-exchanged water. The oil phase was added to the prepared aqueous phase and mixed, followed by stirring at 1,000 rpm for 3 minutes using a dissolver. Further stirring was carried out at 1,800 rpm for 10 minutes using a dissolver to obtain a suspension in which the oil phase was uniformly dispersed. While stirring the resulting suspension at 500 rpm, 112,500 parts by mass of ion-exchanged water was poured into it over 75 minutes to obtain a resin particle dispersion. The resin particles were filtered, washed, and then stirred in the ion-exchanged water. The resin particles obtained after filtration and washing were dispersed in 2,500 parts by mass of ion-exchanged water. Sodium hydroxide was added to adjust the pH to 13.0 or less, and the mixture was heated to 60°C for hydrolysis and neutralized with hydrochloric acid. The product was filtered, washed, and then immersed in ion-exchanged water. After filtering and washing, the mixture was dried and crushed to obtain cellulose particles.

[0135] <Comparative Example 11> Cellulose particles were obtained according to the procedure described in Example 2 of Japanese Patent No. 6872068. The cellulose particles had a saponification rate of 100% and were 100% by mass of cellulose, and contained no external additives. The specific production method was as follows.

[0136] An oil phase was prepared by dissolving 250 parts by mass of cellulose acetate propionate (CAP504-0.2, manufactured by Eastman Chemical Co.) in 1,000 parts by mass of ethyl acetate. 100 parts by mass of polyvinyl alcohol was dissolved in 1,088 parts of ion-exchanged water, and 62.5 parts of ethyl acetate was added and stirred to prepare an aqueous phase. The oil phase was added to the prepared aqueous phase and mixed, followed by stirring at 1,000 rpm for 3 minutes using a dissolver. Stirring was then continued for another 5 minutes at 1,500 rpm to obtain a suspension in which oil droplets were uniformly dispersed. While stirring the suspension at 500 rpm, 21,250 parts by mass of ion-exchanged water was added over 60 minutes to obtain a resin particle dispersion. The resin particles were filtered, washed, and immersed in ion-exchanged water and stirred. After filtering and washing, they were dried and crushed to obtain resin particles. The obtained resin particles were dispersed in 5,000 parts by mass of ion-exchanged water. Sodium hydroxide was added to adjust the pH to 13.0 or less, and the mixture was heated to 40°C for hydrolysis, followed by neutralization with acetic acid. The product was filtered and washed to obtain cellulose particles.

[0137] <Comparative Example 12> Cellulose particles were obtained according to the procedure described in Example 1 of JP 2021-021044 A. The cellulose particles had a saponification rate of 100% and were 100% by mass of cellulose, and did not have a coating layer or external additives. The specific manufacturing method was as follows.

[0138] 0.2 g of diacetyl cellulose (L20, manufactured by Daicel Corporation) was added to 4.8 g of cyclohexanone and stirred. The mixture was further stirred at 60° C. for 3 hours to prepare a solution with a diacetyl cellulose concentration of 4% by mass, which was used as the dispersed phase. 0.1 g of sodium dodecylbenzenesulfonate and 3.5 g of cyclohexanone were added to 50 g of pure water and stirred. The temperature was further increased to 60 °C to prepare an aqueous medium, which served as the continuous phase. The dispersed phase was preheated to 60 °C and fed at 1 mL / min using a syringe pump (High-Pressure Microfeeder JP-H, Furue Science Co., Ltd.). The continuous phase was preheated to 60 °C and fed at 10 mL / min using a plunger pump (NP-KX-840, Nippon Seimitsu Kagaku Co., Ltd.) into different inlets of an inner cylinder rotating device (inner cylinder outer diameter 78 mm, inner cylinder length 215 mm, inner cylinder inner diameter 80 mm, clearance 1 mm, Tipton). The inner cylinder was rotated at 2000 rpm and emulsified for 138 seconds to obtain an oil-in-water emulsion. This oil-in-water emulsion was cooled to 5°C and fed into a double-pipe confluence vessel, and purified water was further fed at 10 mL / min to precipitate diacetyl cellulose, thereby obtaining a particle slurry solution. The obtained diacetyl cellulose particles were added to a mixture of 7 parts by mass of 55% by mass aqueous methanol solution and 3.5 parts by mass of 20% by mass aqueous sodium hydroxide solution, and stirred at 35°C for 20 hours to saponify the diacetyl cellulose particles and obtain cellulose particles.

[0139] <Comparative Example 13> Cellulose particles were obtained according to the procedure described in Example 1 of JP 2021-021045 A. The cellulose particles had a saponification rate of 100% and were 100% by mass of cellulose, and did not have a coating layer or external additives. The specific manufacturing method was as follows.

[0140] Diacetyl cellulose (L20, manufactured by Daicel Corporation) was added to 64 g of ethyl acetate and 16 g of acetone, and the mixture was stirred at 50° C. for 3 hours or more to obtain a diacetyl cellulose solution with a concentration of 10% by mass. This was poured into 82.8 g of 50 ° C pure water containing 0.18 g of sodium dodecylbenzenesulfonate and 6.2 g of ethyl acetate, and stirred at 300 rpm for 10 minutes to prepare a crude emulsion. A porous membrane (cylindrical, 10 mm outer diameter, 1 mm membrane thickness, 50 μm pore size SPG membrane / SPG Techno Co., Ltd.) was immersed in a container containing 331.2 g of 50 ° C pure water containing 0.71 g of sodium dodecylbenzenesulfonate and 24.9 g of ethyl acetate. The container containing the crude emulsion was connected to the inside of the porous membrane. The crude emulsion was pumped into the container containing the crude emulsion at 100 kPa pressure and emulsified through the membrane, resulting in an oil-in-water type incoming liquid. This was cooled, and when it reached 20°C, 444 mL of pure water was added dropwise to obtain spherical diacetyl cellulose particles. Thereafter, the dispersion was centrifuged and filtered, and the filtered diacetyl cellulose particles were thoroughly washed with a large amount of water and filtered to obtain 2.8 g of diacetyl cellulose particles. The obtained diacetyl cellulose particles were added to a mixture of 55% aqueous methanol solution (7 parts by mass) and 20% aqueous sodium hydroxide solution (3.5 parts by mass), and stirred at 35°C for 20 hours to saponify the diacetyl cellulose and obtain cellulose particles.

[0141] <Evaluation> The cellulose granules obtained in each example were measured for the following particle properties according to the methods described above. Parts by mass of cellulose and cellulose derivatives: After vacuum-drying the cellulose particles before coating (or the cellulose particles from which the coating layer has been removed) at 40°C for 8 hours, 10 g was weighed out and placed in 200 g of tetrahydrofuran and stirred at 50°C for 8 hours. The insoluble particles were then recovered by filtration and vacuum-dried again at 40°C for 8 hours. The weight of the particles measured was taken as Wr (g). The parts by mass of cellulose in the particles were calculated using (Equation 1), and the parts by mass of the cellulose derivatives were calculated using (Equation 2). (Equation 1) Parts by mass of cellulose = (Wr / 10) x 100 (Equation 2) Parts by mass of cellulose derivative = ((10 - Wr) / 10) x 100

[0142] Volume average particle size of cellulose particles (referred to as "particle size" in the table) - Number particle size distribution index of the large diameter side of cellulose particles (referred to as "GSDv" in the table) - Sphericity of cellulose particles Number average molecular weight of cellulose in cellulose particles (referred to as "Mn" in the table) ·Surface smoothness of cellulose granules

[0143] (biodegradation rate) The biodegradation rate (60-day biodegradation rate) of the obtained cellulose particles was measured and calculated in accordance with JIS K6950:2000 (ISO 14851:1999). Specifically, the biodegradability is calculated using the following formula from the oxygen demand of the cellulose particles to be measured (hereinafter referred to as the target substance) and the reference substance. A biodegradability rate of 60% or higher was determined to be highly biodegradable. Biodegradation rate (%)=(AB) / C×100 A (mg): Biochemical oxygen demand of the target substance B (mg): Average biochemical oxygen demand of the control substance C (mg): The theoretical maximum amount of oxygen required to oxidize the target substance

[0144] The oxygen demand is measured using a closed system oxygen consumption measuring device under the following conditions. Inoculum source: Aerobic reactor sludge from sewage treatment plants that mainly treat domestic wastewater Control material: microcrystalline cellulose Target substance concentration: 100mg / L Control substance concentration: 100 mg / L Inoculum concentration: 150mg / L Test liquid volume: 300 mL Test temperature: 25±1℃ Culture period: 30 days

[0145] (particle size change rate) The resulting cellulose particles were vacuum dried at 40°C to remove moisture, and immediately thereafter, their particle size was measured using a laser diffraction / scattering particle size analyzer (Microtrac MT3300EX, Microtrac Bell Corporation). Methanol was used as the dispersant for the measurement, and 0.2 g of cellulose particles was added and the measurement was carried out. The particle size obtained at 50% of the cumulative sedimentation was taken as the (dry particle size). The same measurement was carried out immediately after immersion in 30°C water for 48 hours, and the particle size change rate was calculated using (Equation 3). (Equation 3) Particle size change rate (%) = ((particle size absorbed - dry particle size) / (dry particle size)) x 100

[0146] [Table 1-1]

[0147] [Table 1-2]

[0148] [Table 1-3]

[0149] [Table 1-4]

[0150] [Table 1-5]

[0151] [Table 1-6]

[0152] [Table 2-1]

[0153] [Table 2-2]

[0154] [Table 2-3]

[0155] [Table 2-4]

[0156] The above results show that the cellulose particles of this example have higher biodegradability and show less change in particle size due to water absorption than the cellulose particles of the comparative example.

Claims

1. mother particles containing 90 parts by mass or more and 99.5 parts by mass or less of cellulose and 0.5 parts by mass or more and 10 parts by mass or less of a cellulose derivative; a coating layer that coats the base particles and contains at least one selected from the group consisting of polyamine compounds, waxes, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds; and The cellulose particles, wherein the cellulose derivative is cellulose acylate.

2. 2. The cellulose particles according to claim 1, wherein the polyamine compound is at least one selected from the group consisting of polyethyleneimine and polylysine.

3. 3. The cellulose particles according to claim 1 or 2, wherein the wax is carnauba wax.

4. The cellulose particles according to any one of claims 1 to 3, wherein the coating layer comprises: a first coating layer that coats the base particles and contains at least one compound selected from the group consisting of polyamine compounds, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds; and a second coating layer that coats the first coating layer and contains a wax.

5. The cellulose particles according to claim 4, wherein the second coating layer further comprises a polyvalent metal salt.

6. The cellulose particles according to any one of claims 1 to 5, further comprising at least one external additive selected from the group consisting of silicon-containing compound particles and metal soap particles.

7. The cellulose particles according to claim 6, wherein silica particles are externally added as the silicon-containing compound particles.

8. The cellulose particles according to any one of claims 1 to 7, wherein the volume average particle diameter is 3 µm or more and less than 10 µm.

9. 9. The cellulose particles according to claim 1, wherein the large diameter side number particle size distribution index GSDv is 1.0 or more and 1.7 or less.

10. The cellulose particles according to any one of claims 1 to 9, which have a sphericity of 0.9 or more.

11. The cellulose particles according to any one of claims 1 to 10, wherein the number average molecular weight of the cellulose is 37,000 or more.

12. The cellulose particles according to claim 11, wherein the number average molecular weight of the cellulose is 45,000 or more.

13. The cellulose particles according to any one of claims 1 to 12, which have a surface smoothness of 80% or more.

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