Cellulose particles

Abstract

To provide cellulosic particles that are superior in biodegradability and less susceptible to flocculation.SOLUTION: Cellulosic particles are primarily composed of cellulose. When hydrophobically treated silica particles are attached to the cellulosic particles, the silica particles show an ultrasound detachment rate of 50% or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to cellulose particles.

Background Art

[0002] Patent Document 1 proposes "an oil-based solid cosmetic characterized by containing surface-treated spherical cellulose powder having an average particle diameter of 1.0 to 30.0 μm." Patent Document 2 proposes "resin beads formed of a resin containing cellulose as a main component, having a cumulative 50% particle diameter based on volume 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 biodegradation rate measured in accordance with JIS K6950:2000 (ISO 14851:1999) of 20% or more, and a cellulose content in the resin of 90 to 100% by mass."

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem of the present invention is to provide cellulose particles that are excellent in biodegradability and difficult to aggregate, compared with the case where the ultrasonic detachment rate of silica particles exceeds 50% when hydrophobicized silica particles are attached to cellulose particles containing cellulose as a main component.

Means for Solving the Problems

[0005] The above problems are solved by the following means. That is <1> It is mainly composed of cellulose, Cellulose particles in which the ultrasonic desorption rate of hydrophobized silica particles is 50% or less when the silica particles are attached to them. <2> The aforementioned mother particles mainly composed of cellulose, A coating layer that covers the aforementioned mother particles, comprising at least one selected from the group consisting of polyamine compounds, waxes, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds, has <1> Cellulose particles as described above. <3> The polyamine compound is at least one selected from the group consisting of polyethyleneimine and polylysine. <2> Cellulose particles as described above. <4> The wax is carnauba wax. <2> or <3> Cellulose particles as described above. <5> The coating layer comprises a first coating layer that coats the mother particles and contains at least one selected from the group consisting of the polyamine compound, the linear saturated fatty acid, the hydroxy fatty acid, and the amino acid compound, and a second coating layer that coats the first coating layer and contains wax. <2> ~ <4> Cellulose particles as described in any one of the following. <6> The second coating layer further contains a polyvalent metal salt <5> Cellulose particles as described above. <7> At least one external additive selected from the group consisting of silicon-containing compound particles and metal soap particles is added externally. <1> ~ <6> Cellulose particles as described in any one of the following. <8> The silicon-containing compound particles are silica particles. <7> Cellulose particles as described above. <9> The volume-average particle diameter is 3 μm or more and less than 10 μm. <1> ~ <8> Cellulose particles as described in any one of the following. <10> The GSDv (Grain Size Distribution Index) on the larger diameter side is between 1.0 and 1.7. <1> ~ <9> Cellulose particles as described in any one of the following. <11> The sphericity is 0.90 or higher. <1> ~ <10> Cellulose particles as described in any one of the following. <12> The number-average molecular weight of the cellulose is 37,000 or more. <1> ~ <11> Cellulose particles as described in any one of the following. <13> The number-average molecular weight of the cellulose is 45,000 or more. <12> Cellulose particles as described above. <14> The surface smoothness is 80% or higher. <1> ~ <13> Cellulose particles as described in any one of the following. [Effects of the Invention]

[0006] <1> , <2> , <5> , <7> , <8> , <9> , <12> , <13> , and <14> According to the invention, cellulose particles, which are mainly composed of cellulose, are provided that exhibit superior biodegradability and are less prone to aggregation compared to cases where hydrophobically treated silica particles are attached and the ultrasonic desorption rate of silica particles exceeds 50%. <3> According to the invention, cellulose particles that are more biodegradable and less prone to aggregation are provided compared to cases where the polyamine compound is polyvinylamine, polyvinyl alcohol, or polyvinylpyrrolidone. <4> According to the invention, cellulose particles are provided that are more biodegradable and less prone to aggregation compared to cases where the wax is a diester. <6> According to the invention, the second coating layer provides cellulose particles that are more biodegradable and less prone to aggregation compared to the case where polyvalent metal salts are not included. <10> According to the invention, cellulose particles that are highly biodegradable and less prone to aggregation are provided, compared to cases where the large diameter side particle size distribution index GSDv is less than 1.0 or greater than 1.7. <11> According to the invention, cellulose particles are provided that are more biodegradable and less prone to aggregation compared to cases where the sphericity is less than 0.90. [Modes for carrying out the invention]

[0007] The following describes an example embodiment of the present invention. These descriptions and examples are illustrative and do not limit the scope of the invention. In numerical ranges described stepwise within this specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. Furthermore, in numerical ranges described within this specification, the upper or lower limit of that range may be replaced with the values ​​shown in the examples.

[0008] Each component may contain multiple types of the relevant substance. When referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, unless otherwise specified, it refers to the total amount of those multiple substances present in the composition.

[0009] <Cellulose particles> The cellulose particles according to this embodiment are mainly composed of cellulose, and when hydrophobically treated silica particles are attached to them, the ultrasonic desorption rate of the silica particles is 50% or less.

[0010] The cellulose particles according to this embodiment, due to the above configuration, exhibit excellent biodegradability and are resistant to aggregation. The reason for this is presumed to be as follows.

[0011] Cellulose-containing particles (hereinafter referred to as cellulose particles) have the advantage of being highly biodegradable due to their cellulose content. However, because cellulose particles tend to aggregate, their applications have sometimes been limited. The aggregation of cellulose particles is thought to be due to the presence of hydroxyl groups on the surface of the cellulose particles, which then form hydrogen bonds.

[0012] In contrast, the cellulose particles according to this embodiment are mainly composed of cellulose, and when hydrophobically treated silica particles are attached to them, the ultrasonic desorption rate of the silica particles is 50% or less. The ultrasonic detachment rate of the above-mentioned silica particles being 50% or less indicates that the hydrophobicity of the cellulose particle surface tends to be high. This is presumably because the amount of hydroxy groups contained in the cellulose on the cellulose particle surface is small. Therefore, it becomes difficult to form hydrogen bonds of the hydroxy groups present on the cellulose particle surface.

[0013] From the above, it is presumed that the cellulose particles according to this embodiment are excellent in biodegradability and difficult to aggregate due to the above configuration.

[0014] (Cellulose) The cellulose particles according to this embodiment are mainly composed of cellulose. Here, the phrase "mainly composed of cellulose" means that the content of cellulose in the cellulose particles is 90% by mass or more.

[0015] The number average molecular weight of cellulose is preferably 37,000 or more, and more preferably 45,000 or more. The upper limit value of the number average molecular weight of cellulose is not particularly limited, but for example, it may be 100,000 or less.

[0016] By setting the number average molecular weight of cellulose to 37,000 or more, it is more likely to become cellulose particles that are excellent in biodegradability and difficult to aggregate. The reason is presumed as follows. By setting the number average molecular weight of cellulose to 37,000 or more, the number of terminal hydroxy groups per unit volume of the particles decreases, and the intermolecular and intramolecular hydrogen bonds are suppressed, making it difficult for the cellulose particles to aggregate. Regarding biodegradation, the specific surface area increases due to the suppression of the aggregation of cellulose particles, and the biodegradability also improves. From the above, it is presumed that it is more likely to become cellulose particles that are excellent in biodegradability and difficult to aggregate.

[0017] The number-average molecular weight of cellulose is measured using gel permeation chromatography (differential refractometer Optilab T-rEX / Wyatt Technology, multi-angle light scattering detector DAWN HELEOS II / Wyatt Technology, column TSKgel α-M and α-3000, one of each / Tosoh Corporation) with dimethylacetamide (with 0.1M lithium chloride added) as the solvent.

[0018] (Ultrasonic desorption rate) In this embodiment, the cellulose particles have an ultrasonic desorption rate of 50% or less of the silica particles when hydrophobically treated silica particles are attached to them.

[0019] The ultrasonic desorption rate of silica particles is measured as follows. Ten g of cellulose particles, the target of measurement, and two g of hydrophobized silica particles (AEROSIL R972, dimethylsilylated silica particles) were mixed for two minutes at 200 rpm using a sample mill SK-M10 (Kenis Corporation), thereby externally adding the hydrophobized silica particles to the cellulose particles. The net intensity of silicon atoms in the cellulose particles with the added silica particles was measured using an X-ray fluorescence analyzer (EA1400, Hitachi High-Tech Science Corporation), and this was determined as the amount of silica particles before ultrasonic treatment. The entire amount of cellulose particles with added silica particles is added to 500g of water and subjected to sonication (38kHz, 5 minutes) to obtain a dispersion after sonication. The dispersion after sonication is centrifuged (centrifuge: Kenis Corporation, model CF03, centrifugal force: 2000G, centrifugation time: 10 minutes), the supernatant is removed by decantation, and the precipitate is collected. The net intensity of silicon atoms in the collected precipitate is measured using an X-ray fluorescence analyzer, and this is determined as the amount of silica particles after sonication. Based on the measured amount of silica particles before and after ultrasonic treatment, the ultrasonic desorption rate of silica particles is calculated using the following formula A. Formula A: Ultrasonic desorption rate of silica particles (%) = (Amount of silica particles before ultrasonic treatment - Amount of silica particles after ultrasonic treatment) / Amount of silica particles before ultrasonic treatment × 100

[0020] From the viewpoint of producing cellulose particles that are less prone to aggregation, the ultrasonic desorption rate of silica particles is preferably 1% to 40%, more preferably 3% to 30%, and even more preferably 5% to 25%.

[0021] (Cellulose particles with a coating layer) In this embodiment, the cellulose particles are preferably cellulose particles having a mother particle mainly composed of cellulose, and a coating layer covering the mother particle, 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").

[0022] By using the above configuration for the cellulose particles according to this embodiment, it becomes even easier to obtain cellulose particles that are highly biodegradable and less prone to aggregation. The reason for this is presumed to be as follows. Polyamine compounds are compatible with the hydroxyl groups of cellulose and adhere to the surface of cellulose particles. However, the surface of the cellulose particles is not completely covered, and voids are created in places in the coating layer. The surface of the cellulose particles forms an uneven surface, with convex areas where the polyamine compound is applied and concave areas where it is not applied. This unevenness reduces the surface energy, which tends to further enhance the anti-aggregation effect. Although the biodegradability of polyamine compounds is inferior to that of cellulose, microorganisms can pass through the gaps in the surface coating layer, so the excellent biodegradability of cellulose is not impaired, resulting in excellent biodegradability. Waxes and linear saturated fatty acids possess strong water-repellent properties, which tend to improve the repulsive force on the surface of cellulose particles and promote the suppression of cellulose particle aggregation. This effect is particularly pronounced in water and organic solvents. Furthermore, because these compounds have a strong tendency to self-aggregate, they may partially self-aggregate on the surface of cellulose particles, resulting in gaps in the coating layer instead of complete coverage. Microorganisms can pass through these gaps, thus preserving the excellent biodegradability of cellulose, and since these compounds themselves are also biodegradable, excellent biodegradability can be achieved as particles. Hydroxy fatty acids, like straight-chain saturated fatty acids, are water-repellent and have an inhibitory effect on the aggregation of cellulose particles. Furthermore, because they have hydroxyl groups, they have excellent affinity for cellulose, and their aggregation inhibitory effect is well maintained even when subjected to strong impacts. Because hydroxy fatty acids readily self-aggregate, gaps can form in the coating layer, similar to straight-chain saturated fatty acids with 14 to 22 carbon atoms, thus enabling excellent biodegradability. In the case of amino acid compounds, after the formation of the coating layer, the amino acid compounds tend to form flattened crystals, resulting in a surface shape that is more uneven than that of cellulose particles with a coating layer containing polyamine compounds, thus enhancing the aggregation suppression effect. Because gaps are created between the crystals, gaps are more likely to form in the coating layer, and excellent biodegradability can also be achieved. Based on the above, it is presumed that the material is more likely to form cellulose particles that are highly biodegradable and less prone to aggregation.

[0023] -Mother particle- The mother particles are mainly composed of cellulose. The cellulose contained in the mother particles is synonymous with the cellulose described above, and the preferred range is also the same.

[0024] -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-based compounds.

[0025] • Polyamine compounds Polyamine compounds are a general term for aliphatic hydrocarbons that have two or more primary amino groups. Examples of polyamine compounds include polyalkyleneimines, polyallylamines, polyvinylamines, and polylysine. As for the polyalkylene imine, from the viewpoint of improving biodegradability, polyalkylene imines having constituent units with alkylene groups having 1 to 6 carbon atoms (preferably 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms) are preferred, and polyethyleneimine is more preferred. Examples of polyallylamines include homopolymers or copolymers of allylamine, allylamine amide sulfate, diallylamine, and dimethylallylamine. Examples of polyvinylamines include those produced by hydrolyzing poly(N-vinylformamide) with an alkali, specifically "PVAM-0595B" manufactured by Mitsubishi Chemical Corporation. Polylysine may be extracted from natural products, produced by transformed microorganisms, or chemically synthesized.

[0026] It is preferable that the polyamine compound is at least one selected from the group consisting of polyethyleneimine and polylysine. By applying at least one polyamine compound selected from the group consisting of polyethyleneimine and polylysine, the cellulose particles become even more biodegradable and less prone to aggregation. 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 surface area ratio, and when they adhere to the surface of cellulose particles, the hydrocarbon chains tend to be exposed on the surface, making particle aggregation less likely. Furthermore, because polyethyleneimine and polylysine have a relatively coarse structure rather than a dense one, they have gaps for microorganisms to enter and tend not to inhibit the excellent biodegradability of cellulose. Based on the above, it is presumed that the material is more likely to form cellulose particles that are highly biodegradable and less prone to aggregation.

[0027] The polyamine compound content is preferably 0.2% by mass or more and 2% by mass or less relative to the total amount of cellulose particles.

[0028] ·wax Examples of waxes include vegetable oils containing fatty acids, hydrocarbon waxes, and diesters. 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 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, wood 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 dodecanediic acid, and alcohols having 10 to 25 carbon atoms.

[0029] Carnauba wax is preferred as the wax. By applying carnauba wax as the wax, the cellulose particles become more biodegradable and less prone to aggregation. The reason for this is presumed to be as follows: Carnauba wax contains many water-repellent components such as free fatty acids and hydrocarbons, which prevents aggregation between particles. Furthermore, because it contains free alcohols, it forms weak hydrogen bonds with the hydroxyl groups of cellulose particles, causing it to adhere to them. However, because the adhesive force is relatively weak, there is a gap at the interface between the cellulose particle surface and the coating layer, allowing microorganisms to enter. Therefore, it is thought that the excellent biodegradability of cellulose is not impaired. Based on the above, it is presumed that the material is more likely to form cellulose particles that are highly biodegradable and less prone to aggregation.

[0030] 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, relative to the total amount of cellulose particles.

[0031] • Straight-chain saturated fatty acids Straight-chain saturated fatty acids are saturated fatty acids that have a linear structure. As for the linear saturated fatty acid, it is preferable that it be a linear saturated fatty acid with 14 to 22 carbon atoms, from the viewpoint of producing cellulose particles that are more biodegradable and less prone to aggregation. Specific examples of straight-chain saturated fatty acids with 14 to 22 carbon atoms include behenic acid, arachidic acid, and palmitic acid.

[0032] The reason why using linear saturated fatty acids in the coating layer prevents aggregation of cellulose particles and achieves excellent biodegradability is as follows: The terminal carboxylic acids can form covalent bonds or ionic affinity with the hydroxyl groups of cellulose and adhere to the surface of the cellulose particles. Linear hydrocarbon groups are exposed on the surface, and the repulsion between hydrocarbon groups prevents particle aggregation. On the other hand, even on the surface of the same particle, the repulsion between hydrocarbon groups creates gaps in the coating layer, allowing microorganisms to penetrate through these gaps, thus not impairing the excellent biodegradability of cellulose. In this case, by setting the number of carbon atoms in a linear saturated fatty acid to 14 or more, the repulsive force is improved, and both the anti-aggregation effect and biodegradability tend to improve. On the other hand, by setting the number of carbon atoms to 22 or less, the repulsive force does not become too strong, the adhesion to the surface of cellulose particles increases, and the anti-aggregation effect tends to improve.

[0033] The linear saturated fatty acid content is preferably 2% by mass or more and 15% by mass or less, and more preferably 5% by mass or more and 10% by mass or less, relative to the total amount of cellulose particles.

[0034] • Hydroxy fatty acids Hydroxy fatty acids are fatty acids that contain a hydroxyl group. As for hydroxy fatty acids, hydroxy fatty acids with 12 to 20 carbon atoms are preferred. Examples of hydroxy fatty acids include hydroxystearic acid, hydroxypaltimic acid, hydroxylauric acid, hydroxymyristic acid, and castor hydrogenated fatty acids.

[0035] The reason why using hydroxy fatty acids as a coating layer prevents the aggregation of cellulose particles and achieves excellent biodegradability is as follows: The hydroxyl groups of hydroxy fatty acids form weak hydrogen bonds with the hydroxyl groups of 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 cellulose particles, and the mutual repulsion suppresses the aggregation of cellulose particles. Since the hydrocarbon portion of the fatty acids has low affinity for cellulose, a gap is created between them, allowing microorganisms to penetrate the cellulose particles, thus not hindering the excellent biodegradability of cellulose. Here, when the number of carbon atoms in hydroxy fatty acids exceeds 12, the repulsive force between fatty acids increases, and the aggregation-inhibiting effect tends to improve. When the number of carbon atoms is 20 or less, the long chains become entangled, which inhibits the blocking of microbial entry routes and suppresses the decrease in biodegradability.

[0036] The hydroxy fatty acid content is preferably 1% by mass or more and 10% by mass or less, relative to the total cellulose particles, and more preferably 3% by mass or more and 10% by mass or less.

[0037] • Amino acid compounds Amino acid compounds refer to amino acids and amino acid derivatives. An amino acid derivative is a compound in which one or more hydrogen atoms or functional groups contained in an amino acid are replaced by other substituents. As for the amino acid-based compound, an amino acid derivative is preferred. Examples of amino acid-based compounds include lauryl leucine, lauryl arginine, and myristyl leucine.

[0038] The reason why using amino acid-based compounds in the coating layer prevents the aggregation of cellulose particles and achieves excellent biodegradability is as follows: The amide group has an ionic affinity with the hydroxyl group of cellulose, causing the amino acid-based compound to adhere to the surface of the cellulose particles. The hydrocarbon portion of the amino acid-based compound is exposed on the surface of the cellulose particles, and the repulsion between these two portions suppresses the aggregation of the cellulose particles. Furthermore, since amino acids are rapidly decomposed when attacked by microorganisms, the biodegradability is also extremely excellent.

[0039] The content of amino acid compounds is preferably 2% by mass or more and 10% by mass or less relative to the total amount of cellulose particles.

[0040] • Layer structure of the coating layer The coating layer may include a first coating layer that coats the mother 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.

[0041] In particular, it is preferable that the coating layer comprises a first coating layer that coats the mother particles and contains at least one selected from the group consisting of polyamine compounds, linear saturated fatty acids, hydroxy fatty acids, and amino acid-based compounds, and a second coating layer that coats the first coating layer and contains wax. The coating layer, having the first coating layer and the second coating layer, is more likely to form cellulose particles that are highly biodegradable and less prone to aggregation. The reason for this is presumed to be as follows.

[0042] While wax exhibits strong water repellency and resilience, it tends to self-aggregate, leading to larger defects in the coating layer. If these defects become too large, the particle aggregation suppression effect is reduced, requiring a certain amount of coating to avoid defects. On the other hand, excessive wax tends to decrease biodegradability. Conversely, polyamine compounds, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds, while less resilient than wax, exhibit high adhesion to cellulose particles, reducing coating defects. Furthermore, wax and these compounds have high mutual adhesion, making wax coating defects less likely. For these reasons, a coating layer comprising both the first and second coating layers is more likely to result in cellulose particles that are highly biodegradable and less prone to aggregation. Based on the above, it is presumed that the material is more likely to form cellulose particles that are highly biodegradable and less prone to aggregation.

[0043] • Polyvalent metal salts The second coating layer preferably contains a polyvalent metal salt. The second coating layer, containing polyvalent metal salts, is more likely to form cellulose particles that are highly biodegradable and less prone to aggregation. The reason for this is presumed to be as follows: The wax contained in the second layer has poor adhesion to the layer below. Therefore, it tends to develop coating defects due to self-aggregation. By including a polyvalent metal salt along with the wax in the second coating layer, the polyvalent metal salt adheres to the entire wax in a nearly uniform manner, and aggregation occurs uniformly over a wide area starting from that point. This suppresses the occurrence of coating defects due to self-aggregation and improves the adhesion of the second coating layer. Based on the above, it is presumed that the material is more likely to form cellulose particles that are highly biodegradable and less prone to aggregation.

[0044] A polyvalent metal salt is a compound composed of two or more valent metal ions and anions. Examples of metal ions with a valency of 2 or higher that constitute polyvalent metal salts include ions of calcium, magnesium, copper, nickel, zinc, barium, aluminum, titanium, strontium, chromium, cobalt, and iron. Anions that constitute polyvalent metal salts include inorganic ions and organic ions. Examples of inorganic ions include chloride ions, bromide ions, iodide ions, nitrate ions, sulfate ions, hydroxide ions, etc. Examples of organic ions include organic acid ions, such as carboxylate ions.

[0045] Examples of polyvalent metal salts include aluminum sulfate, polyaluminum chloride, iron chloride, and calcium hydroxide.

[0046] The content of polyvalent metal salts relative to the wax content 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.

[0047] • Content of components in the first and second coating layers The polyamine compound content relative to 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 wax and polyvalent metal salts relative to 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.

[0048] -External additives- The cellulose particles according to this embodiment may have 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.

[0049] In particular, it is preferable that the cellulose particles according to this embodiment are externally supplemented with at least one additive selected from the group consisting of silicon-containing compound particles and metal soap particles. The cellulose particles according to this embodiment, due to the addition of the above-mentioned external additive, are more likely to become cellulose particles that are highly biodegradable and less prone to aggregation. The reason for this is presumed to be as follows. Silicon-containing compound particles and metal soap particles can adhere to larger particles (e.g., cellulose particles) through electrostatic adhesion, and because they have significantly higher water repellency than metal oxide particles and aliphatic ester particles, aggregation inhibition is further promoted. Furthermore, because silicon-containing compound particles and metal soap particles are particle-shaped, their specific surface area is larger than that of the coating layer, and aggregation inhibition is further strengthened due to this shape effect. Because silicon-containing compound particles and metal soap particles are particle-shaped, there are sufficient gaps for microorganisms to enter, and they do not hinder the excellent biodegradability of cellulose. Based on the above, it is presumed that the material is more likely to form cellulose particles that are highly biodegradable and less prone to aggregation.

[0050] Silicon-containing compound particles refer to particles that contain silicon. The silicon-containing compound particles may be particles containing only silicon, or particles containing silicon and other elements.

[0051] The silicon-containing compound particles are preferably silica particles. Silica particles can be any particles whose main component is silica, i.e., SiO2, and may be crystalline or amorphous. Furthermore, silica particles may be particles manufactured using silicon compounds such as water glass or alkoxysilane as raw materials, or particles obtained by crushing quartz.

[0052] By using silica particles as silicon-containing compound particles, it becomes easier to create cellulose particles that are highly biodegradable and less prone to aggregation. The reason for this is presumed to be as follows: Silica tends to have high sphericity when formed into particles, and its high water repellency due to the silicon element gives it a particularly strong anti-aggregation effect. Furthermore, because silica particles are granular, there are sufficient gaps for microorganisms to penetrate, allowing them to attack cellulose particles in a uniform distribution, resulting in particularly excellent biodegradability. Based on the above, it is presumed that the material is more likely to form cellulose particles that are highly biodegradable and less prone to aggregation.

[0053] Metal soap particles are particles whose main component is metal soap. Here, particles whose main component is metal soap refer to particles in which the metal soap content is 90% by mass or more of the total particle size.

[0054] Metallic soaps are fatty acid metal salts formed by the bonding of fatty acids with metals. Examples of fatty acid metal salts include metal salts of fatty acids having 10 to 25 carbon atoms (preferably 12 to 22 carbon atoms). Examples of fatty acid metal salts having 10 to 25 carbon atoms include metal salts of stearic acid, palmitic acid, lauric acid, oleic acid, linoleic acid, and ricinoleic acid. Examples of metals in fatty acid metal salts include divalent metals. Examples of metals in fatty acid metal salts include magnesium, calcium, aluminum, barium, and zinc.

[0055] Fatty acid ester particles are particles whose main component is fatty acid ester particles. Here, particles whose main component is fatty acid ester particles refer to particles in which the content of fatty acid ester particles relative to the total particle is 90% by mass or more.

[0056] Examples of fatty acid esters include esterified products 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.

[0057] Metal oxide particles are particles whose main component is a metal oxide. Here, particles whose main component is metal oxide refer to particles in which the metal oxide content is 90% by mass or more of the total particle size.

[0058] As for metal oxides, oxides of metals other than silicon can be used. Examples of metal oxides include zinc oxide, magnesium oxide, iron oxide, aluminum oxide, and calcium oxide.

[0059] The amount of external additive added is preferably 0.1% by mass or more and 2% by mass or less, relative to the total mass of cellulose particles (cellulose particles without external additive).

[0060] (Volume-average particle size and large-diameter particle size distribution index GSDv) The volume-average particle diameter 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.

[0061] By setting the volume-average particle diameter of the cellulose particles according to this embodiment to 3 μm or more and less than 10 μm, it becomes easier to obtain cellulose particles that are highly biodegradable and less prone to aggregation. The reason for this is presumed to be as follows. If the volume-average particle size of cellulose particles is 3 μm or larger, the surface area of ​​the cellulose particles does not become too large, and the repulsive force is maintained, resulting in a greater effect of suppressing aggregation between cellulose particles. On the other hand, if the volume-average particle size of cellulose particles is less than 10 μm, the surface area of ​​the cellulose particles becomes moderately large, so biodegradation from the surface proceeds more uniformly, and the material tends to have excellent biodegradability. Based on the above, it is presumed that the material is more likely to form cellulose particles that are highly biodegradable and less prone to aggregation.

[0062] In this embodiment, the GSDv (Grain Size Distribution Index) for the number of large-diameter cellulose particles 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.

[0063] By setting the GSDv (Grain Size Distribution Index) of the large-diameter side of the cellulose particles in this embodiment to 1.0 or more and 1.7 or less, the cellulose particles become even more biodegradable and less prone to aggregation. 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 cellulose particles with a volume-average particle diameter of less than 3 μm) is small, making aggregation between cellulose particles less likely. This also reduces the likelihood of biodegradation inhibition by coarse powder (large cellulose particles with a volume-average particle diameter exceeding 10 μm) (since decomposition begins from the surface of the cellulose particles, larger cellulose particles tend to have reduced biodegradability), thus enabling the achievement of excellent biodegradability. Based on the above, it is presumed that the material is more likely to form cellulose particles that are highly biodegradable and less prone to aggregation.

[0064] The volume-average particle size and the large-diameter particle size distribution index (GSDp) of cellulose particles are measured as follows: The particle size is measured using the 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 which the cumulative distribution reaches 50% is determined as the volume-average particle size. On the other hand, the cumulative particle size distribution is plotted from the smallest diameter side based on volume, and the particle size at which the cumulative distribution reaches 50% is defined as the number-average particle size D50v, and the particle size at which the cumulative distribution reaches 84% ​​is defined as the number-particle size D84v. Then, the large-diameter side number-particle size distribution index GSDv is given by the formula GSDv=(D84v / D50v) 1 / 2 It is calculated as follows.

[0065] (Sphericity) The sphericity of the cellulose particles according to this embodiment is preferably 0.90 or higher, more preferably 0.95 or higher, and even more preferably 0.97 or higher.

[0066] By setting the sphericity of the cellulose particles according to this embodiment to 0.90 or higher, the cellulose particles become even more biodegradable and less prone to aggregation. The reason for this is presumed to be as follows. If the sphericity is 0.90 or higher, it tends to prevent an increase in the contact area due to anisotropy, and the effect of suppressing the aggregation of cellulose particles tends to be higher. In addition, microbial decomposition can proceed from the surface to the center in the shortest possible time, and biodegradability tends to be superior. Based on the above, it is presumed that the material is more likely to form cellulose particles that are highly biodegradable and less prone to aggregation.

[0067] Sphericity is determined by (circular equivalent perimeter) / (perimeter) [(perimeter of a circle with the same projected area as the particle image) / (perimeter of the particle projection image)]. Specifically, it is a value measured by the following method. First, the cellulose particles to be measured are collected by suction, a flattened flow is formed, and a still image of the particles is captured by instantaneous strobe flashing. This particle image is then analyzed using a flow-type particle image analyzer (FPIA-3000 manufactured by Sysmex Corporation). The number of samples used to determine the sphericity is 3500. If 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. These cellulose particles are then used as the target for measurement.

[0068] (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%.

[0069] By setting the surface smoothness of the cellulose particles according to this embodiment to 80% or more, it is easier to obtain cellulose particles that are more biodegradable and less prone to aggregation. The reason for this is presumed to be as follows. If the surface smoothness is 80% or higher, the aggregation of cellulose particles tends to be suppressed because the specific surface area of ​​the cellulose particles is small. In addition, some microorganisms that promote biodegradation are relatively large, and because such large microorganisms can come into contact with the particle surface, the material tends to have excellent biodegradability. Based on the above, it is presumed that this will result in cellulose particles that are more biodegradable and less prone to aggregation.

[0070] Surface smoothness is measured using the following procedure. The smoothness M of individual cellulose particles is calculated using the following formula by observing SEM images (magnification 5,000x) of cellulose particles taken with a scanning electron microscope (SEM). The arithmetic mean of the smoothness M of 10 or more arbitrarily selected cellulose particles is then defined as the surface smoothness. The closer the smoothness M value is to 1, the smoother the surface of the cellulose particle is. M = (1 - (S3) / (S2)) × 100 In the above formula, S2 represents the area (projected area) occupied by the cellulose particles in the image, and S3 represents the sum of "the area outside the outline of the circle with the same projected area as S2, and inside the outline of the cellulose particles in the image" and "the area inside the outline of the circle with the same projected area as S2, and outside the outline of the cellulose particles in the image" when the cellulose particles in the image and a circle with the same projected area as S2 are superimposed. The method for superimposing the cellulose particles in the image with a circle having the same projected area as S2 is as follows. When superimposing the cellulose particles in the image with a circle having the same projected area as S2, the two images are superimposed in such a way that the area of ​​the overlapping region (the area inside the outline of the circle with the same projected area as S2, and inside the outline of the cellulose particles in the image) is maximized.

[0071] <Method for producing cellulose particles> A 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).

[0072] -Particle precursor manufacturing process- A particle precursor containing cellulose acylate is produced by one of the following methods (1) to (5).

[0073] (1) A kneading and grinding method in which each component is kneaded, the resulting kneaded material is ground and classified to obtain granular material. (2) Dry manufacturing method in which granular material obtained by the kneading and grinding method is changed in shape by mechanical impact force or thermal energy to obtain granular material. (3) Coagulation and coagulation method: Mixing particle dispersions of each component, agglomerating and heating the particles in the dispersion to obtain granular material. (4) Dissolution suspension method: The organic solvent in which each component is dissolved is suspended in an aqueous solvent to granulate a granular material containing each component. (5) A kneading and dissolving method in which each component and a binder are kneaded together, extruded to form pellets, and the resulting pellets are granulated by stirring them in a solvent that dissolves only the binder.

[0074] Here, cellulose acylate is a cellulose derivative in which at least one of the hydroxyl groups in cellulose is replaced (acylated) with an aliphatic acyl group. Specifically, at least one of the hydroxyl groups in cellulose is -CO-R AC (R AC represents an aliphatic hydrocarbon group. ) This is a cellulose derivative substituted with ).

[0075] -Saponification process- Next, the cellulose acylate contained in the particle precursor is saponified. Through this process, the aliphatic acyl groups in cellulose acylate are hydrolyzed, and cellulose is converted back into cellulose.

[0076] The saponification process is carried out, for example, by adding sodium hydroxide to a dispersion of particle precursors and stirring the dispersion.

[0077] -Coating layer formation process- When producing cellulose particles having a coating layer, it is preferable to include a step of forming the coating layer (coating layer formation step) after the saponification step. In this process, when forming a coating layer, the particles obtained through the saponification process are used as the base particles to form the coating layer.

[0078] First, prepare an aqueous dispersion in which the mother particles are dispersed. Before preparing the aqueous dispersion, it is advisable to acid wash the mother particles.

[0079] Next, the aqueous dispersion containing the mother particles is mixed with an aqueous solution containing the compounds that constitute the first coating layer. This causes a reaction between, for example, the hydroxyl groups of the resin contained in the mother particles and the amine sites and carboxylic acid sites of the surface treatment polymer, forming the first coating layer. Then, the aqueous dispersion containing the mother particles with the first coating layer is mixed with an emulsion containing the compounds that constitute the second coating layer. This forms the second coating layer. Then, cellulose particles having a coating layer are extracted from the mixture. The extraction of 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 removes any unreacted surface treatment polymer. Then, the cellulose particles according to this embodiment are obtained by drying the cellulose particles having a coating layer. -External addition process- External additives may be added to the obtained cellulose particles. External additive processes include, for example, adding external additives to cellulose particles using a mixing mill, V-type blender, Henschel mixer, or Rejdigge mixer.

[0080] <Application> Applications of the cellulose particles according to this embodiment include cosmetics, rolling agents, abrasives, scrubbing agents, display spacers, bead molding materials, light diffusing particles, resin reinforcing agents, refractive index control agents, biodegradation accelerators, fertilizers, water-absorbing particles, toner particles, and antiblocking particles in granular form.

[0081] The cellulose particles according to this embodiment are preferably used in cosmetics. In particular, cosmetic additives are preferred as the primary use of cellulose particles according to this embodiment. Because the cellulose particles according to this embodiment have excellent flexibility, when used as a cosmetic additive, they tend to spread well on the skin when the cosmetic is applied to the skin.

[0082] The cellulose particles according to this embodiment can be used as cosmetic additives in, for example, base makeup cosmetics (e.g., makeup base, concealer, foundation, face powder, etc.); makeup cosmetics (e.g., lipstick, gloss, lip liner, blush, eyeshadow, eyeliner, mascara, eyebrow products, nail products, nail care cosmetics, etc.); and skincare cosmetics (e.g., facial cleansers, makeup removers, lotions, emulsions, serums, packs, face masks, eye and lip care cosmetics, etc.). In particular, from the viewpoint of requiring flexibility and biodegradability, the resin particles according to this embodiment are preferably used as cosmetic additives in makeup cosmetics. [Examples]

[0083] Examples are described below, but the present invention is not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" all refer to mass.

[0084] <Preparation of each ingredient> I prepared the following materials.

[0085] (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 15000.

[0086] (Compounds that constitute 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 1000 • Fir6: Nippon Shokubai "Epomin HM-2000", polyethyleneimine, molecular weight 30000 • Fir7: Nippon Shokubai "Epomin P-1000", polyethyleneimine, molecular weight 70,000 • Fir8: Nitto Boseki Medical "PAA-01", polyallylamine, molecular weight 1600 • Fir9: Nitto Boseki Medical "PAA-03", polyallylamine, molecular weight 3000 • Fir10: Nitto Boseki Medical "PAA-05", polyallylamine, molecular weight 5000 • Fir11: Nitto Boseki Medical "PAA-08", polyallylamine, molecular weight 8000 • Fir12: Nitto Boseki Medical "PAA-15C", polyallylamine, molecular weight 15000 • Fir13: Nitto Boseki Medical "PAA-25", polyallylamine, molecular weight 25000 ·Fir14: Mitsubishi Chemical "Gosenol N-300", polyvinyl alcohol • Fir15: JNC "Polylysine 10", Polylysine ·Fir16: Ichimaru Falcos "Polylysine 10", Polylysine

[0087] -Straight-chain saturated fatty acids- • Fir19: NOF Corporation "NAA-222S", behenic acid (22 carbon atoms) • Fir20: Fujifilm Wako Pure Chemical Industries, arachidic acid (20 carbon atoms) • Fir21: Fujifilm Wako Pure Chemical Industries, palmitic acid (14 carbon atoms) • Fir22: Fujifilm Wako Pure Chemical Industries, Lauric Acid (12 carbon atoms) • Fir23: Fujifilm Wako Pure Chemical Industries, Lignoceric Acid (24 carbon atoms)

[0088] -Hydroxy fatty acids- • Fir24: Ito Oil Co., Ltd. "12-Hydroxystearic Acid", Hydroxystearic Acid • Fir25: NOF Corporation, hydrogenated castor fatty acids

[0089] - Amino acid compounds - ·Fir26: Ajinomoto "Amihope LL", Lauroyl Lysine

[0090] -Polyvinyl alcohol and polyvinylpyrrolidone- ·Fir17: Mitsubishi Chemical "Gosenol N-300", polyvinyl alcohol • Fir18: Nippon Shokubai "K-30", polyvinylpyrrolidone

[0091] (Compounds that constitute the second coating layer) -wax- • Sec1: Senka "CN-100", Carnauba wax •Second Section: Toa Chemical "TOWAX-1F3", Carnauba wax • Sec3: Toa Chemical "TOWAX-1F6", Carnauba wax • Sec4: Toa Chemical "TOWAX-1F8", Carnauba wax • Sec5: Toa Chemical "TOWAX-1F12", Carnauba wax • Sec6: Toa Chemical "TOWAX-5B2", Carnauba wax • Sec7: Toa Chemical "TOWAX-1B4", Carnauba wax • Sec8: Toa Chemical "TOWAX-4F2", Candelilla Rough • Sec9: Toa Chemical "TOWAX-4F3", Candelilla Rough • Sec10: Toa Chemical "TOWAX-4F4", Candelilla wax Sec11: Toa Chemical "TOWAX-6B2", Damask rose flower wax • Sec12: Toa Chemical "TOWAX-6F2", sunflower seed wax Sec13: Ogura Synthetic Industries, Rice Wax Sec14: Boso Oils "SS-1", rice wax • Sec15: Nisshin Oillio "Cosmoll 222", Diisostearyl Malate

[0092] -Polyvalent metal salts- Sec21: Fujifilm Wako Pure Chemical Industries, Aluminum Sulfate Sec22: Fujifilm Wako Pure Chemical Industries, Polyaluminum Chloride Sec23: Fujifilm Wako Pure Chemical Industries, Iron Chloride Sec24: Fujifilm Wako Pure Chemical Industries, Calcium Hydroxide

[0093] (External additive) -Silicon-containing compound particles- • Sur1: Japan Aerosil "AEROSIL R972", Dimethylsilylated Silica Particles • Sur2: Japan Aerosil "AEROSIL RY200S", dimethicone silica particles

[0094] -Metal soap particles- • Sur3: NOF "MZ-2", zinc stearate particles • Sur4: NOF "Magnesium Stearate S", magnesium stearate particles - Fatty acid ester particles - • Sur6: Kao "Excepearl SS", stearyl stearate particles -Metal oxide particles- • Sur7: Sakai Chemical "FINEX-50", zinc oxide particles

[0095] <Example 1> (Particle precursor production process) 130 parts of Cel1 as cellulose acylate were completely dissolved in 870 parts of ethyl acetate. This was added to an aqueous solution containing 45 parts of calcium carbonate and 500 parts of pure water and stirred for 5 hours (hereinafter referred to as the "first stirring time"). A solution of 5 parts of carboxymethylcellulose (hereinafter also referred to as "CMC") and 200 parts of methyl ethyl ketone dispersed in 600 parts of pure water was added and stirred for 5 minutes using a high-speed emulsifier. 10 parts of sodium hydroxide were added, and the mixture was heated to 80°C and stirred for 3 hours to remove ethyl acetate and methyl ethyl ketone. An equal amount of dilute hydrochloric acid was added to the mixture, the residue was filtered, and then dispersed again in pure water to obtain a particle precursor dispersion (solid content concentration 10%).

[0096] (saponification process) 500 parts of particle precursor dispersion were mixed with 17.5 parts of a 20% sodium hydroxide aqueous solution, and the mixture was stirred for 6 hours at a saponification temperature of 30°C. After saponification, hydrochloric acid was added to the slurry to adjust the pH to 7, and the mixture was filtered and washed repeatedly until the conductivity of the filtrate was 10 μs / cm or less, thereby obtaining cellulose particles.

[0097] <Examples 2-7> Cellulose particles were obtained using the same procedure as in Example 1, except that the type of cellulose acylate used in the particle precursor manufacturing process was as shown in Table 1.

[0098] <Example 8> (Particle precursor manufacturing process), and (Saponification process) Cellulose particles were obtained using the same procedure as in Example 1.

[0099] (Coating layer formation process) A mother particle dispersion was obtained by mixing 1,000 parts of cellulose particles, which are the mother particles, with 10,000 parts of deionized water. Five parts of Fir16 were added to the mother particle dispersion as a compound constituting the first coating layer, and the mixture was stirred for 1 hour to form a coating layer. The cellulose particles with the coating layer were filtered and washed repeatedly until the conductivity of the filtrate was 10 μs / cm or less, thereby obtaining cellulose particles with a coating layer.

[0100] <Examples 9-25> Cellulose particles having a coating layer were obtained using the same procedure as in Example 8, except that the type of compound constituting the first coating layer (referred to as "first layer compound" in Table 1) was as shown in Table 1 during the coating layer formation process.

[0101] <Example 26> (Particle precursor manufacturing process), and (Saponification process) Cellulose particles were obtained using the same procedure as in Example 1.

[0102] (Coating layer formation process) A mother particle dispersion was obtained by mixing 1,000 parts of cellulose particles, which are the mother particles, with 10,000 parts of deionized water. 7 parts of Fir16 were added to the mother particle dispersion as a compound constituting the first coating layer, and the mixture was stirred for 1 hour to form the first coating layer, thus obtaining a cellulose particle dispersion having the first coating layer. Next, 6 parts of Sec1 as wax and 50 parts of pure water were stirred in a high-speed emulsifier to prepare a second coating layer forming emulsion. The entirety 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 the second coating layer, thereby obtaining a cellulose particle dispersion having both the first and second coating layers. Cellulose particles having a first and second coating layer were repeatedly filtered and washed until the conductivity of the filtrate was 10 μs / cm or less, thereby obtaining cellulose particles having a first and second coating layer.

[0103] <Examples 27-40> Cellulose particles having the first and second coating layers were obtained using the same procedure as in Example 26, except that the type of wax used in the coating layer formation process was as shown in Table 1.

[0104] <Examples 41-43> Cellulose particles having first and second coating layers were obtained using the same procedure as in Example 26, except that the amount of compound and wax added to the first coating layer in the coating layer formation process was as shown in Table 1.

[0105] <Example 44> (Particle precursor manufacturing process), (Saponification process), and (Coating layer formation process) Cellulose particles having first and second coating layers were obtained using the same procedure as in Example 26.

[0106] (External addition process) To 30 parts of cellulose particles having a first and second coating layer, 0.6 parts of Sur1 was added as an external additive, and the mixture was combined in a mixing mill (Wonder Crusher, manufactured by Osaka Chemical Co., Ltd.) to obtain cellulose particles containing the external additive.

[0107] <Examples 45-51> Cellulose particles containing the external additive were obtained using the same procedure as in Example 44, except that the type and amount of the external additive were as shown in Table 1 during the external additive process.

[0108] <Examples 52-59> Cellulose particles containing external additives were obtained using the same procedure as in Example 26, except that the amount of calcium carbonate added, the first stirring time, the amount of carboxymethylcellulose added, and the amount of sodium hydroxide added were as shown in Table 1 during the particle precursor manufacturing process.

[0109] <Example 60> Cellulose particles having a coating layer were obtained using the same procedure as in Example 26, except that the step of adding 5 parts of Fir16 as a compound constituting the first coating layer to the mother particle dispersion and stirring for 1 hour was omitted in the coating layer formation step.

[0110] <Examples 61-64> Cellulose particles with external additives were obtained using the same procedure as in Example 44, except that the type of wax was changed as shown in Table 1 during the coating layer formation process, and the polyvalent metal salts listed in Table 1 were added along with the wax and pure water in the amounts shown in Table 1 when preparing the second coating layer forming emulsion.

[0111] <Examples 65-74> Cellulose particles having a coating layer were obtained using the same procedure as in Example 8, except that the type of compound constituting the first coating layer (referred to as "first layer compound" in Table 1) and the amount of compound added to the first coating layer were as shown in Table 1 during the coating layer formation process.

[0112] <Example 75> Cellulose particles having first and second coating layers were obtained using the same procedure as in Example 26, except that the type of compound constituting the first coating layer, the amount of compound constituting the first coating layer added, and the amount of wax added were as shown in Table 1 during the coating layer formation process.

[0113] <Example 76> Cellulose particles having the first and second coating layers were obtained using the same procedure as in Example 75, except that in the coating layer formation process, when preparing the second coating layer forming emulsion, the polyvalent metal salts listed in Table 1 were added along with wax and pure water in the amounts listed in Table 1.

[0114] <Example 77> (Particle precursor manufacturing process), (Saponification process), and (Coating layer formation process) Cellulose particles having first and second coating layers were obtained using the same procedure as in Example 76.

[0115] (External addition process) To 30 parts of cellulose particles having a first and second coating layer, 0.6 parts of Sur1 was added as an external additive, and the mixture was combined in a mixing mill (Wonder Crusher, manufactured by Osaka Chemical Co., Ltd.) to obtain cellulose particles containing the external additive.

[0116] <Comparative Examples 1-4> The following particles were used as cellulose particles in each example. Comparative Example 1: CELLULOBEADS D10 (manufactured by Daito Chemical Co., Ltd., cellulose particles with cellulose as the main component. It does not have a coating layer or external additives.) Comparative Example 2: OTS-0.5A CELLULOBEADS D10 (manufactured by Daito Chemical Co., Ltd., cellulose particles having a mother particle mainly composed of cellulose and a coating layer containing triethoxyoctylsilane. No external additives are used.) Comparative Example 3: S-STM CELLULOBEADS D-5 (manufactured by Daito Chemical Co., Ltd., cellulose particles having a mother particle mainly composed of cellulose and a coating layer containing magnesium stearate. No external additives are used.) Comparative Example 4: Self-Flow C25 (manufactured by JNC Corporation; cellulose particles with cellulose as the main component; without a coating layer or external additives.)

[0117] <Comparative Examples 5-8> Cellulose particles were obtained for each example following the procedure below. Comparative Example 5: Cellulose particles were obtained according to the procedure described in Example 1 of Japanese Patent Publication No. 6872068. These cellulose particles consist of a mother particle mainly composed of cellulose and a coating layer containing zinc stearate, and do not contain any external additives. Comparative Example 6: Cellulose particles were obtained according to the procedure described in Example 2 of Japanese Patent Publication No. 6872068. These cellulose particles consist of a mother particle mainly composed of cellulose and a coating layer containing magnesium stearate, and do not contain any external additives. Comparative Example 7: Cellulose particles were obtained according to the procedure described in Example 1 of Japanese Patent Publication No. 2021-021044. These cellulose particles mainly consist of cellulose and do not have a coating layer or external additives. Comparative Example 8: Cellulose particles were obtained according to the procedure described in Example 1 of Japanese Patent Publication No. 2021-021045. These cellulose particles mainly consist of cellulose and do not have a coating layer or external additives.

[0118] <Rating> The cellulose particles obtained in each example were used to evaluate their biodegradability and degree of aggregation.

[0119] (biodegradable) The biodegradation rate after 60 days was measured and calculated in accordance with JIS K6950:2000 (ISO 14851:1999).

[0120] (Cohesion degree) The dispersion state of cellulose particles was evaluated after a certain period of time under the following conditions, in the following states: cellulose particles in powder form (hereinafter referred to as "powder state"), cellulose particles in water (hereinafter referred to as "water state"), and cellulose particles in an organic solvent (hereinafter referred to as "oil state"). Specifically, the volume-average particle diameter of cellulose particles was measured before and after treatment under the following conditions, and the degree of cohesion was calculated from the following formula (B). The volume-average particle diameter of cellulose particles was measured according to the method described above. Equation (B): Degree of cohesion = (Volume-average particle diameter of cellulose particles after the treatment below) / (Volume-average particle diameter of cellulose particles before the treatment below)

[0121] -Processing in powder form- The cellulose particles obtained in each example were left to stand for 72 hours under high temperature and high humidity conditions of 50°C and 80% relative humidity. -Processing underwater- The cellulose particles obtained in each example were stirred in water at 50°C for 48 hours. -Processing in an oil- The cellulose particles obtained in each example were stirred in isopropyl alcohol at a temperature of 40°C for 48 hours.

[0122] [Table 1-1]

[0123] [Table 1-2]

[0124] [Table 1-3]

[0125] [Table 2-1]

[0126] [Table 2-2]

[0127] [Table 2-3]

[0128] [Table 2-4]

[0129] In Table 2, "Particle Main Component" refers to the main component of the cellulose particle or mother particle (i.e., the component whose content relative to the cellulose particle or mother particle is 90% by mass or more).

[0130] From the above results, it can be seen that the cellulose particles of this embodiment are highly biodegradable and resistant to aggregation.

Claims

1. It is mainly composed of cellulose, Cellulose particles having an ultrasonic desorption rate of 50% or less when hydrophobized silica particles are attached, The aforementioned mother particles mainly composed of cellulose, A coating layer that covers the aforementioned mother particles, comprising at least one selected from the group consisting of polyamine compounds, waxes, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds, It has, The coating layer comprises a first coating layer that coats the mother particles and contains at least one selected from the group consisting of the polyamine compound, the linear saturated fatty acid, the hydroxy fatty acid, and the amino acid compound, and a second coating layer that coats the first coating layer and contains wax. The second coating layer further contains a polyvalent metal salt, The aforementioned polyvalent metal salt is a compound composed of a metal ion with two or more valencies and an anion. Cellulose particles.

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

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

4. Cellulose particles according to any one of claims 1 to 3, wherein at least one external additive selected from the group consisting of silicon-containing compound particles and metal soap particles is added externally.

5. The cellulose particles according to claim 4, wherein the silicon-containing compound particles are silica particles.

6. Cellulose particles according to any one of claims 1 to 5, wherein the volume-average particle diameter is 3 μm or more and less than 10 μm.

7. Cellulose particles according to any one of claims 1 to 6, wherein the large diameter side particle size distribution index GSDv is 1.0 or more and 1.7 or less.

8. Cellulose particles according to any one of claims 1 to 7, wherein the sphericity is 0.90 or higher.

9. The cellulose particles according to any one of claims 1 to 8, wherein the number-average molecular weight of the cellulose is 37,000 or more.

10. The cellulose particles according to claim 9, wherein the number-average molecular weight of the cellulose is 45,000 or more.

11. Cellulose particles according to any one of claims 1 to 10, wherein the surface smoothness is 80% or more.

Images