Cellulose particles

Abstract

To provide a cellulosic particle that has high biodegradability combined with high flexibility.SOLUTION: A cellulosic particle includes: a cellulose-based core particle; a first coating layer covering the core particle and containing a polyamine compound; and a second coating layer covering the first coating layer and containing a wax.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to cellulose particles.

Background Art

[0002] Patent Document 1 proposes "resin beads having a volume-based cumulative 50% particle diameter of 50 μm or less, a sphericity of 0.7 to 1.0, a surface smoothness of 70 to 100%, and a crystallinity of 60% or less, obtained by surface-treating core beads formed of a resin containing cellulose as a main component with a solid surface treatment agent".

[0003] Patent Document 2 proposes "an oil-based solid cosmetic characterized by containing a surface-treated spherical cellulose powder having an average particle diameter of 1.0 to 30.0 μm".

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem of the present invention is to provide cellulose particles that have higher biodegradability and higher flexibility than cellulose particles, which are single-layer particles containing cellulose as a main component.

Means for Solving the Problems

[0006] The above problems are solved by the following means. That is <1> Mother particles containing cellulose as a main component, and a first coating layer that coats the mother particles and contains a polyamine compound, and A second coating layer covering the first coating layer, comprising at least one selected from the group consisting of wax, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds, Cellulose particles having the properties of cellulose. <2> The polyamine compound is at least one selected from the group consisting of polyethyleneimine and polylysine. <1> Cellulose particles as described above. <3> The wax is carnauba wax. <1> or <2> Cellulose particles as described above. <4> A straight-chain saturated fatty acid is a straight-chain saturated fatty acid with 14 to 22 carbon atoms. <1> ~ <3> Cellulose particles as described in any one of the items. <5> The second coating layer further contains a polyvalent metal salt <1> ~ <4> Cellulose particles as described in any one of the items. <6> At least one external additive selected from the group consisting of silicon-containing compound particles and metal soap particles is added externally. <1> ~ <5> Cellulose particles as described in any one of the items. <7> The silicon-containing compound particles include silica particles as an extraneous addition. <6> Cellulose particles as described above. <8> The volume-average particle diameter is 3 μm or more and less than 10 μm. <1> ~ <7> Cellulose particles as described in any one of the items. <9> The GSDv (Grain Size Distribution Index) on the larger diameter side is between 1.0 and 1.7. <1> ~ <8> Cellulose particles as described in any one of the items. <10> The sphericity is 0.9 or higher. <1> ~ <9> Cellulose particles as described in any one of the items. <11> The number-average molecular weight of the cellulose is 37,000 or more. <1> ~ <10> Cellulose particles as described in any one of the items. <12> The number-average molecular weight of the cellulose is 45,000 or more. <11> Cellulose particles as described above. <13> The surface smoothness is 80% or higher. <1> ~ <12> Cellulose particles as described in any one of the items. [Effects of the Invention]

[0007] <1> According to the invention, cellulose particles are provided that are more biodegradable and more flexible than cellulose particles, which are single-layer particles mainly composed of cellulose. <2> According to the invention, cellulose particles are provided that are more biodegradable and more flexible compared to cases where the polyamine compound is polyvinylamine. <3> According to the invention, cellulose particles are provided that are more biodegradable and more flexible compared to cases where the wax is candelilla wax. <4> According to the invention, cellulose particles are provided that are more biodegradable and flexible compared to cases where the number of carbon atoms in a straight-chain saturated fatty acid is less than 14 or more than 22. <5> According to the invention, cellulose particles are provided that are more biodegradable and more flexible compared to cases where the second coating layer does not contain polyvalent metal salts. <6> According to the invention, cellulose particles are provided that are more biodegradable and more flexible than those in which stearyl stearate particles or zinc oxide particles are added externally. <7> According to the invention, cellulose particles are provided that are more biodegradable and more flexible than those in which metal soap particles are added externally. <8> According to the invention, cellulose particles are provided that are more biodegradable and more flexible than those with a volume-average particle diameter of less than 3 μm or more than 10 μm. <9> According to the invention, cellulose particles are provided that are more biodegradable and more flexible compared to cases where the large diameter side particle size distribution index GSDv is less than 1.0 or greater than 1.7. <10> According to the invention, cellulose particles are provided that are more biodegradable and more flexible compared to those with a sphericity of less than 0.9. <11> According to the invention, cellulose particles are provided that are more biodegradable and more flexible than those in which the number-average molecular weight of cellulose is less than 37,000. <12> According to the invention, cellulose particles are provided that are more biodegradable and more flexible compared to cases where the number-average molecular weight of cellulose is less than 45,000. According to the invention according to <13>, cellulose particles with high biodegradability and high flexibility are provided as compared with the case where the surface smoothness is less than 80%.

Mode for Carrying Out the Invention

[0008] Hereinafter, embodiments which are examples of the present invention will be described. These descriptions and examples are illustrative of the embodiments and do not limit the scope of the invention. In the numerical ranges described step by step in this specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other step-by-step descriptions. Further, in the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.

[0009] Each component may contain a plurality of corresponding substances. When referring to the amount of each component in the composition, when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified, it means the total amount of the plurality of substances present in the composition.

[0010] <Cellulose particles> The cellulose particles according to the present embodiment have a mother particle mainly composed of cellulose, a first coating layer covering the mother particle and containing a polyamine compound, and a second coating layer covering the first coating layer and containing at least one selected from the group consisting of wax, linear saturated fatty acid, hydroxy fatty acid and amino acid-based compound.

[0011] The cellulose particles according to the present embodiment have high biodegradability and high flexibility due to the above configuration. The reason is presumed as follows.

[0012] Due to the problem of marine litter, resin particles having biodegradability are required. Among them, cellulosic particles mainly composed of cellulose have high biodegradability in any environment of compost, activated sludge, and seawater, and have been put into practical use in various applications such as cosmetics. However, although conventional cellulose particles have high biodegradability, they are hard and lack flexibility.

[0013] On the other hand, by using particles mainly composed of cellulose as the mother particles and coating the mother particles with a first coating layer containing a polyamine compound, higher flexibility is exhibited compared to single-layer cellulose particles. On the other hand, polyamine compounds have poor biodegradability, and the biodegradability of cellulose particles decreases due to the coating. Therefore, the first coating layer is coated with a second coating layer containing at least one selected from the group consisting of wax, linear saturated fatty acids, hydroxy fatty acids, and amino acid-based compounds. Since wax, linear saturated fatty acids, hydroxy fatty acids, and amino acid-based compounds have biodegradability, when the wax starts biodegradation, the first coating layer strongly adhered to the wax is peeled off, ensuring fast biodegradability. In addition, since wax, linear saturated fatty acids, hydroxy fatty acids, and amino acid-based compounds self-aggregate or hydrocarbons repel each other, the coating rate of the first coating layer is not complete, and the first coating layer is exposed, so flexibility can be maintained.

[0014] From the above, it is presumed that the cellulose particles according to this embodiment have high biodegradability and high flexibility due to the above configuration. Specifically, since the cellulose particles according to this embodiment have high flexibility, for example, the touch such as slipperiness, moistness, and smoothness is good.

[0015] Hereinafter, the details of the cellulose particles according to this embodiment will be described.

[0016] (Mother particles) The mother particles are mainly composed of cellulose. Here, being mainly composed of cellulose means that the content of cellulose in the mother particles is 90% by mass or more.

[0017] The number average molecular weight of cellulose is preferably 37,000 or more, and more preferably 45,000 or more. The upper limit of the number-average molecular weight of cellulose is not particularly limited, but may be, for example, 100,000 or less.

[0018] By increasing the number-average molecular weight of cellulose to 37,000 or higher, it becomes easier to form cellulose particles that are highly biodegradable and highly flexible. The reason for this is presumed to be as follows: When the number-average molecular weight falls below 37,000, the number of terminal hydroxyl groups increases, which increases the number of hydroxyl groups per unit volume. This strengthens the number and bond strength of intramolecular and extramolecular hydrogen bonds, resulting in a tendency for the powder to become harder and less flexible. Based on the above, it can be inferred that it is more likely to form cellulose particles that are highly biodegradable and highly flexible.

[0019] 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.

[0020] The mother particles may contain other components. Other components include, for example, plasticizers, flame retardants, compatibilizers, mold release agents, lightfasteners, weathering agents, colorants, pigments, modifiers, drip inhibitors, 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 to prevent acetic acid release (oxides such as magnesium oxide and aluminum oxide; metal hydroxides such as magnesium hydroxide, calcium hydroxide, aluminum hydroxide, hydrotalcite; calcium carbonate; talc; etc.), and reactive trapping agents (e.g., epoxy compounds, acid anhydride compounds, carbodiimide, etc.). The content of other components is preferably 0% by mass or more and 5% by mass or less, relative to the total amount of mother particles. Here, "0% by mass" means that no other components are present.

[0021] (covering layer) The coating layer has a first coating layer and a second coating layer.

[0022] -First coating layer- The first coating layer contains a polyamine compound. 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.

[0023] 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, it becomes even easier to form cellulose particles that are highly biodegradable and highly flexible. 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 attached to the surface of cellulose particles, the hydrocarbon chains tend to repel each other, creating voids and exposing themselves to the surface. Because of these appropriate voids, the flexibility of the particle surface increases through a sponge-like effect, resulting in increased particle flexibility. Furthermore, microorganisms can enter through these voids, so the excellent biodegradability of cellulose is reflected in the biodegradability of the particles. Based on the above, it can be inferred that it is more likely to form cellulose particles that are highly biodegradable and highly flexible.

[0024] 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.

[0025] 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.

[0026] -Second coating layer- The second coating layer contains at least one selected from the group consisting of wax, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds.

[0027] ·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.

[0028] Carnauba wax is preferred as the wax. Applying carnauba wax as the wax makes it easier to form cellulose particles that are highly biodegradable and flexible. The reason for this is presumed to be as follows: Carnauba wax contains components that exhibit strong self-aggregation, such as free fatty acids, and components with high repulsive force, such as hydrocarbons. Multiple self-aggregates repel each other, covering the surface like islands, while uncovered structures exist continuously like a sea. If the island portions have a certain thickness, they become flexible, increasing the flexibility of the particle surface. If these islands are relatively uniform, the flexibility of the particle increases. Furthermore, microorganisms can penetrate the gaps between the islands, i.e., the sea portions, thus achieving excellent biodegradability. Based on the above, it can be inferred that it is more likely to form cellulose particles that are highly biodegradable and highly flexible.

[0029] • Straight-chain saturated fatty acids Straight-chain saturated fatty acids are saturated fatty acids that have a linear structure. As for the straight-chain saturated fatty acid, it is preferable that it be a straight-chain saturated fatty acid with 14 to 22 carbon atoms, from the viewpoint of improving biodegradability and flexibility. Specific examples of straight-chain saturated fatty acids with 14 to 22 carbon atoms include behenic acid, arachidic acid, and palmitic acid. The reason why using linear saturated fatty acids as the second coating layer can increase particle flexibility and achieve excellent biodegradability is as follows: The terminal carboxylic acids develop an ionic affinity with the polyamine compound and can adhere to the particle surface. Linear hydrocarbon chains are exposed on the surface and repel each other, so the linear chains are arranged to stand upright on the outside of the particle. This part exhibits flexibility similar to that of polyolefins, increasing the flexibility of the particle. Furthermore, excellent biodegradability can be achieved by allowing microorganisms to enter through the gaps between the linear carbonate water chains. In straight-chain saturated fatty acids, when the number of carbon atoms is 14 or more, the vertical distance increases, improving flexibility. On the other hand, when the number of carbon atoms is 22 or less, the entanglement between hydrocarbon chains becomes looser, inhibiting microbial entry and improving biodegradability.

[0030] • Hydroxy fatty acids As for the hydroxy fatty acid, it is preferable that it is a hydroxy fatty acid having 12 to 20 carbon atoms, from the viewpoint of improving biodegradability and flexibility. Examples of hydroxy fatty acids with 12 to 20 carbon atoms include hydroxystearic acid, hydroxypaltimic acid, hydroxylauric acid, hydroxymyristic acid, and castor hydrogenated fatty acids. The reason why using hydroxy fatty acids as a coating layer enhances particle flexibility and achieves excellent biodegradability is as follows: The hydroxyl groups of hydroxy fatty acids are compatible with and adhere to polyamines. Because the fatty acid portion of the attached hydroxy fatty acids is fixed, it cannot repel the polyamines and covers the surface, forming an intertwined structure with voids, resulting in sponge-like flexibility. Microorganisms can penetrate the cellulose particles, enabling uniform biodegradation and achieving excellent biodegradability. In hydroxy fatty acids, when the number of carbon atoms is 12 or more, the fatty acid density increases, making it easier to form a sponge structure and improving flexibility. On the other hand, when the number of carbon atoms is 20 or less, the long chains are less likely to entangle, inhibiting the entry of microorganisms and improving biodegradability.

[0031] • Amino acid compounds Amino acid compounds refer to amino acids and amino acid derivatives. Examples of amino acid-based compounds include lauryl leucine, lauryl arginine, and myristyl leucine. The reason why using amino acid-based compounds in the coating layer enhances particle flexibility and achieves excellent biodegradability is as follows: Amino acid compounds tend to form flattened crystals after coating, and the increased specific surface area reflects their own flexibility in the particles, resulting in higher particle flexibility. In addition, gaps are created between the crystals, allowing for gradual invasion by microorganisms, which enables uniform biodegradation and achieves excellent biodegradability.

[0032] The total content of wax, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds is preferably 0.1% to 2% by mass, and more preferably 0.2% to 1% by mass, relative to the total amount of cellulose particles.

[0033] 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 flexible. The reason for this is presumed to be as follows: The wax, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds contained in the second layer have low adhesion to the layer below. Therefore, coating defects tend to form due to self-aggregation. By including polyvalent metal salts along with the wax in the second coating layer, the polyvalent metal salts uniformly adhere to the wax, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds. This causes uniform aggregation over a wide area, suppressing the occurrence of large coating defects due to self-aggregation and allowing the second coating layer to exhibit a greater degree of flexibility improvement. Furthermore, while large coating defects are suppressed, numerous small coating defects remain uniformly present, allowing for microbial invasion, and thus maintaining excellent biodegradability. Based on the above, it can be inferred that it is more likely to form cellulose particles that are highly biodegradable and highly flexible.

[0034] 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.

[0035] Examples of polyvalent metal salts include aluminum sulfate, polyaluminum chloride, iron chloride, and calcium hydroxide.

[0036] 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.

[0037] 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.

[0038] (External additive) 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.

[0039] 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 highly biodegradable and highly flexible. 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 deposition, and they have higher flexibility than similarly adhering metal oxide particles and aliphatic ester particles, resulting in a greater effect on improving flexibility. Due to their particle shape, there are sufficient gaps for microorganisms to enter, and they do not hinder the excellent biodegradability of cellulose. Based on the above, it can be inferred that it is more likely to form cellulose particles that are highly biodegradable and highly flexible.

[0040] 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.

[0041] 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.

[0042] By using silica particles as silicon-containing compound particles, it becomes easier to create cellulose particles that are highly biodegradable and flexible. The reason for this is presumed to be as follows: Silica exhibits particularly high electrostatic adhesion to cellulose particles and is also extremely flexible. For the reasons mentioned above, its texture changes very little over time, and it is highly biodegradable. Based on the above, it can be inferred that it is more likely to form cellulose particles that are highly biodegradable and highly flexible.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] As for metal oxides, oxides of metals other than silicon can be used. Examples of metal oxides include zinc oxide, magnesium oxide, iron oxide, and aluminum oxide.

[0049] From the viewpoint of texture (specifically, feel), the volume-average particle size of the external additive is preferably 1 nm to 100 nm, and more preferably 5 nm to 30 nm. The volume-average particle size of external additives is measured in a similar manner to that used for the volume-average particle size of cellulose.

[0050] 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).

[0051] (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.

[0052] 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 highly flexible. The reason for this is presumed to be as follows. If the volume-average particle size is 3 μm or larger, the particle diameter does not become too small, and deformation when subjected to external force is not severely hindered, resulting in a tendency towards higher flexibility. Furthermore, if the particle size is less than 10 μm, the surface area is moderately large, allowing for more uniform biodegradation from the surface, resulting in a tendency towards superior biodegradability. Based on the above, it can be inferred that it is more likely to form cellulose particles that are highly biodegradable and highly flexible.

[0053] 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.

[0054] 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 more biodegradable and flexible. 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) and coarse powder (large particles exceeding 10 μm) is small, which tends to reduce the decrease in flexibility caused by fine powder as described above. Also, the inhibition of biodegradation (because it decomposes from the surface) caused by coarse powder (large particles exceeding 10 μm) tends to be less likely. Based on the above, it can be inferred that it is more likely to form cellulose particles that are highly biodegradable and highly flexible.

[0055] 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.

[0056] (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.

[0057] By setting the sphericity of the cellulose particles according to this embodiment to 0.90 or higher, it becomes easier to obtain cellulose particles that are highly biodegradable and highly flexible. The reason for this is presumed to be as follows. If the sphericity is 0.9 or higher, when force is applied from the particle surface, the particle thickness does not become extremely thin, and flexibility does not tend to decrease. In addition, microbial decomposition can proceed from the surface to the center in the shortest possible time, resulting in superior biodegradability. Based on the above, it can be inferred that it is more likely to form cellulose particles that are highly biodegradable and highly flexible.

[0058] 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.

[0059] (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%.

[0060] 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 highly biodegradable and highly flexible. The reason for this is presumed to be as follows. If the smoothness is 80% or higher, localized stress concentration due to surface irregularities is less likely to occur, and flexibility tends to be higher. 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 superior biodegradability. Based on the above, it can be inferred that the material is likely to form cellulose particles that are highly biodegradable and flexible.

[0061] 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.

[0062] <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).

[0063] -Particle precursor manufacturing process- A particle precursor containing cellulose acylate is produced by one of the following methods (1) to (5).

[0064] (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.

[0065] Here, cellulose acylate is a cellulose derivative in which at least one of the hydroxyl groups in cellulose is substituted (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 ).

[0066] -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.

[0067] The saponification process is carried out, for example, by adding sodium hydroxide to a dispersion of particle precursors and stirring the dispersion.

[0068] -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.

[0069] 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.

[0070] 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 of the surface treatment polymer, thereby 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.

[0071] -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.

[0072] <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.

[0073] 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.

[0074] 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]

[0075] 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.

[0076] <Preparation of each ingredient> I prepared the following materials.

[0077] (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.

[0078] (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 10000 • 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 "Polyvinylamine", Polyvinylamine • Fir15: JNC "Polylysine 10", Polylysine ·Fir16: Ichimaru Falcos "Polylysine 10", Polylysine

[0079] -Polyvinyl alcohol and polyvinylpyrrolidone- ·Fir17: Mitsubishi Chemical "Gosenol N-300", polyvinyl alcohol • Fir18: Nippon Shokubai "K-30", polyvinylpyrrolidone

[0080] (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 Wax Sec9: Toa Chemical "TOWAX-4F3", Candelilla Wax • Sec10: Toa Chemical "TOWAX-4F4", Candelilla Wax Sec11: Toa Kasei "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

[0081] -Straight-chain saturated fatty acids- • Sec16: NOF Corporation "NAA-222S", Behenic acid (22 carbon atoms) • Sec17: Fujifilm Shonan Wako "Arachidic Acid", Arachidic Acid (20 carbon atoms) • Sec18: Fujifilm Shonan Wako "Paltimic Acid", Palmitic Acid (14 carbon atoms) • Sec19: Fujifilm Shonan Wako "Lauric Acid", Lauric Acid (12 carbon atoms) • Sec20: Fujifilm Shonan Wako "Lignoceric Acid", Lignoceric Acid (24 carbon atoms)

[0082] -Hydroxy fatty acids- •Sec21: Ito Oil Co., Ltd. "12-Hydroxystearic Acid", Hydroxystearic Acid •Sec22: NOF Corporation, "Hydrogenated Castor Fatty Acids", Hydrogenated Castor Fatty Acids

[0083] - Amino acid compounds - •Sec23: Ajinomoto "Amihope LL", Lauroyl Lithium

[0084] -Polyvalent metal salts- Sec31: Fujifilm Wako Pure Chemical Industries, Aluminum Sulfate Sec32: Fujifilm Wako Pure Chemical Industries, Polyaluminum Chloride •Sec33: Fujifilm Wako Pure Chemical Industries, Iron Chloride Sec34: Fujifilm Wako Pure Chemical Industries, Calcium Hydroxide

[0085] (External additive) -Silicon-containing compound particles- • Sur1: Japan Aerosil "AEROSIL R972", dimethylsilylated silica particles, average particle size = 16 nm • Sur2: Japan Aerosil "AEROSIL RY200S", dimethicone silica particles, average particle size = 12nm

[0086] -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

[0087] - Fatty acid ester particles - • Sur6: Kao "Excepearl SS", stearyl stearate particles, volume average particle size = 1000 nm -Metal oxide particles- • Sur7: Sakai Chemical "FINEX-50", zinc oxide particles, volume-average particle size = 15000nm

[0088] <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 3 hours (hereinafter referred to as the "first stirring time"). A solution of 4 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 this mixture, the residue was filtered, and then dispersed again in pure water to obtain a particle precursor dispersion (solid content concentration 10%).

[0089] (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.

[0090] (Coating layer formation process) 1,000 parts of cellulose particles, which are the mother particles, and 10,000 parts of deionized water were mixed to obtain 500 parts of a mother particle dispersion. 5 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, 4 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.

[0091] <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.

[0092] <Examples 8-24> Cellulose particles having a coating layer were obtained using the same procedure as in Example 1, 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.

[0093] <Examples 25-38> Cellulose particles having the first and second coating layers were obtained using the same procedure as in Example 1, except that the type of wax used in the coating layer formation process was as shown in Table 1.

[0094] <Examples 39-41> Cellulose particles having first and second coating layers were obtained using the same procedure as in Example 1, 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.

[0095] <Example 42> (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 1.

[0096] (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.

[0097] <Examples 44-45, 47-50> Cellulose particles containing the external additive were obtained using the same procedure as in Example 42, except that the type and amount of the external additive were as shown in Table 1 during the external additive process.

[0098] <Examples 51-58> Cellulose particles containing external additives were obtained using the same procedure as in Example 1, 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.

[0099] <Comparative Examples 10-11> Cellulose particles having a coating layer were obtained using the same procedure as in Example 1 or 42, except that the step of adding 4 parts of Sec1 as a compound constituting the second coating layer to the mother particle dispersion and stirring was omitted in the coating layer formation step.

[0100] <Examples 61-64> Cellulose particles with external additives were obtained using the same procedure as in Example 42, 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.

[0101] <Examples 65-78> Cellulose particles having a coating layer were obtained using the same procedure as in the above example, except that the conditions shown in Table 1 were changed.

[0102] <Comparative Examples 1-5> 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.) Comparative Example 5: Cellflow TA25 CELLULOBEADS D-10 (manufactured by JNC Corporation; cellulose particles mainly composed of diacetylcellulose; without a coating layer or external additives.)

[0103] <Comparative Example 6> Cellulose particles were obtained according to the procedure described in Example 1 of Japanese Patent Publication No. 6921923. The cellulose particles consist of a mother particle mainly composed of cellulose and a coating layer containing zinc stearate, and contain no external additives. The specific manufacturing method is as follows. An oil phase was prepared by dissolving 150 parts by mass of dicellulose acetate (CA398-6, Eastman Chemical Co.) in 1350 parts by mass of ethyl acetate. An aqueous phase was prepared by dissolving 100 parts by mass of polyvinyl alcohol in 1250 parts of deionized water. The oil phase was added to the prepared aqueous phase and mixed, and the mixture was stirred at 1000 rpm for 3 minutes using a dissolver. The mixture was then stirred at 2000 rpm for 10 minutes to obtain a suspension in which oil droplets were uniformly dispersed. While stirring this suspension at 500 rpm, 2000 parts by mass of deionized water were added over 90 minutes to prepare a resin particle dispersion. After filtering and washing the resin particles, they were added to deionized water, stirred, filtered, and washed again, and the resulting resin particles were dispersed in 2500 parts of deionized water. Sodium hydroxide was added to adjust the pH to 13.0 or lower, and the mixture was heated to 50°C to hydrolyze it, followed by neutralization with hydrochloric acid. After filtering and washing the product, it was stirred in deionized water, filtered, washed again, dried, and crushed to obtain cellulose mother particles. 50 g of the obtained cellulose matrix particles and 1.5 g of zinc stearate (SPZ-100F, manufactured by Sakai Chemical Industry Co., Ltd.) were placed in a small mixer and mixed dry for 3 minutes to obtain cellulose particles obtained by surface-treating the cellulose matrix particles with zinc stearate.

[0104] <Comparative Example 7> Cellulose particles were obtained according to the procedure described in Example 2 of Japanese Patent Publication No. 6921923. These cellulose particles consist of a mother particle mainly composed of cellulose and a coating layer containing magnesium stearate, and contain no external additives. The specific manufacturing method is as follows.

[0105] Cellulose particles were obtained by surface-treating cellulose mother particles with magnesium stearate in the same manner as in Comparative Example 7, except that 1.5 g of magnesium stearate (SPX-100F, manufactured by Sakai Chemical Industry Co., Ltd.) was used instead of zinc stearate.

[0106] <Comparative Example 8> Cellulose particles were obtained according to the procedure described in Example 1 of Japanese Patent Publication No. 2021-021044. These cellulose particles are mainly composed of cellulose and do not have a coating layer or external additives. The specific manufacturing method is as follows.

[0107] 4.8 g of cyclohexanone was mixed with 0.2 g of diacetylcellulose (L20, manufactured by Daicel Corporation) and stirred. The mixture was further stirred at 60°C for 3 hours to prepare a solution with a diacetylcellulose concentration of 4% by mass, which was used as the dispersed phase. 50 g of pure water was mixed with 0.1 g of sodium dodecylbenzenesulfonate and 3.5 g of cyclohexanone, and the mixture was stirred. The temperature was further raised to 60°C to prepare an aqueous medium, which was used as the continuous phase. The dispersed phase was preheated to 60°C and injected at a rate of 1 mL / min using a syringe pump (high-pressure microfeeder JP-H, manufactured by Furue Science Co., Ltd.). The continuous phase was also preheated to 60°C and injected at a rate of 10 mL / min using a plunger pump (NP-KX-840, manufactured by Nippon Precision Science Co., Ltd.). Both were introduced into different inlets of an internal cylinder rotating device (internal cylinder outer diameter 78 mm, internal cylinder length 215 mm, internal cylinder inner diameter 80 mm, clearance 1 mm, manufactured by Chipton Co., Ltd.). Emulsification was performed at an internal cylinder rotation speed of 2000 rpm for 138 seconds to obtain an oil-in-water emulsion. This oil-in-water emulsion was cooled to 5°C and supplied to a double-tube confluencer. Pure water was then supplied at a rate of 10 mL / min to precipitate diacetylcellulose and obtain a particle slurry solution. The diacetylcellulose particles obtained were added to a mixture of 7 parts by mass of a 55% by mass methanol aqueous solution and 3.5 parts by mass of a 20% by mass sodium hydroxide aqueous solution, and the mixture was stirred at 35°C for 20 hours to saponify the diacetylcellulose particles and obtain cellulose particles.

[0108] <Comparative Example 9> Cellulose particles were obtained according to the procedure described in Example 1 of Japanese Patent Publication No. 2021-021045. These cellulose particles are mainly composed of cellulose and do not have a coating layer or external additives. The specific manufacturing method is as follows.

[0109] Diacetylcellulose (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 more than 3 hours to obtain a 10% by mass solution of diacetylcellulose. This was poured into 82.8g of 50°C pure water containing 0.18g of sodium dodecylbenzenesulfonate and 6.2g of ethyl acetate, and stirred at 300 rpm for 10 minutes to prepare a crude emulsion. A porous membrane (a cylindrical SPG membrane with an outer diameter of 10mm, a film thickness of 1mm, and a pore size of 50μm, manufactured by SPG Techno Co., Ltd.) was immersed in a container filled with 331.2g of 50°C pure water containing 0.71g of sodium dodecylbenzenesulfonate and 24.9g of ethyl acetate, and the container with the crude emulsion was connected to the inside of the porous membrane. The crude emulsion was pumped through the container with the crude emulsion under a pressure of 100kPa to emulsify it and obtain an oil-in-water droplet type incoming liquid. This was cooled to 20°C, at which point 444 mL of pure water was added dropwise to obtain spherical diacetylcellulose particles. The dispersion was then centrifuged and filtered, and the filtered diacetylcellulose particles were thoroughly washed with a large amount of water and filtered to obtain 2.8 g of diacetylcellulose particles. The obtained diacetylcellulose particles were added to a mixture of a 55% methanol aqueous solution (7 parts by mass) and a 20% sodium hydroxide aqueous solution (3.5 parts by mass), and the mixture was stirred at 35°C for 20 hours to saponify the diacetylcellulose and obtain cellulose particles.

[0110] <Rating> The following particle properties were measured for the cellulose particles obtained in each example according to the method described above. Biodegradation rate of less than 20% in 5 days, and biodegradation rate of less than 20% in 60 days • Volume-average particle size of cellulose particles (indicated as "particle size" in the table) • Large diameter particle size distribution index of cellulose particles (indicated as "GSDv" in the table) • Sphericity of cellulose particles • Number-average molecular weight of cellulose in cellulose particles (indicated as "Mn" in the table) • Surface smoothness of cellulose granules

[0111] (biodegradation rate) In accordance with JIS K6950:2000 (ISO 14851:1999), the biodegradation rate of the obtained cellulose particles (biodegradation rate after 28 days) was measured and calculated. Specifically, the biodegradability rate is calculated using the following formula based on the oxygen demand of the cellulose particles being measured (hereinafter referred to as the target substance) and the reference substance. A biodegradability rate of 60% or higher was considered to indicate high biodegradability. 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.

[0112] The oxygen demand is then measured using a closed-system oxygen consumption meter under the following conditions. Source of grafts: Sludge in aerobic reaction tanks of sewage treatment plants that primarily treat household wastewater. Control substance: Microcrystalline cellulose Target substance concentration: 100 mg / L Control substance concentration: 100 mg / L Inoculum concentration: 150mg / L Test solution volume: 300 mL Test temperature: 25±1℃ Culture period: 30 days

[0113] (Flexibility) The Young's modulus of the obtained cellulose particles was calculated using a microcompression tester (MCT-510, manufactured by Shimadzu Corporation). Specifically, cellulose particles were scattered on a sample stage, and the initial position was adjusted so that a single particle was contained within the tip of the indenter while observing with an optical microscope. Compression was performed at a sample stage movement speed of 0.2 μm / s, and the test force corresponding to the displacement was continuously detected. The measurement was terminated when the particles were completely crushed. The obtained stress-strain curve was represented by two straight lines with different slopes. The intersection of these two lines is defined as the yield point (εy, σy), and the slope of the line from the origin is defined as the apparent Young's modulus Ey, as shown in the following equation. Equation: Ey = σy / εy The flexibility of the cellulose particles was evaluated based on the obtained Young's modulus. A lower Young's modulus indicates greater flexibility. A Young's modulus of less than 80 MPa was considered highly flexible.

[0114] [Table 1-1]

[0115] [Table 1-2]

[0116] [Table 1-3]

[0117] [Table 1-4]

[0118] [Table 1-5]

[0119] [Table 2-1]

[0120] [Table 2-2]

[0121] [Table 2-3]

[0122] From the above results, it can be seen that the cellulose particles of this embodiment have higher biodegradability and flexibility compared to the cellulose particles of the comparative example.

Claims

1. Mother particles mainly composed of cellulose, The aforementioned mother particles are coated with a first coating layer containing a polyamine compound, A second coating layer covering the first coating layer, comprising at least one selected from the group consisting of wax, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds, It has, Cellulose particles wherein the linear saturated fatty acid is a linear saturated fatty acid having 14 to 22 carbon atoms.

2. A mother particle mainly composed of cellulose, The aforementioned mother particles are coated with a first coating layer containing a polyamine compound, A second coating layer covering the first coating layer, comprising at least one selected from the group consisting of wax, linear saturated fatty acids, hydroxy fatty acids, and amino acid compounds, It has, The second coating layer further contains cellulose particles containing a polyvalent metal salt.

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

4. The cellulose particles according to any one of claims 1 to 3, wherein the wax is carnauba wax.

5. The cellulose particles according to claim 2, wherein the linear saturated fatty acid is a linear saturated fatty acid having 14 or more carbon atoms and 22 or fewer carbon atoms.

6. The cellulose particles according to claim 1, further comprising a polyvalent metal salt in the second coating layer.

7. Cellulose particles according to any one of claims 1 to 6, wherein at least one external additive selected from the group consisting of silicon-containing compound particles and metal soap particles is added externally.

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

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

10. Cellulose particles according to any one of claims 1 to 9, wherein the large diameter side particle size distribution index GSDv is 1.0 or more and 1.7 or less.

11. Cellulose particles according to any one of claims 1 to 10, wherein the sphericity is 0.9 or greater.

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

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

14. Cellulose particles according to any one of claims 1 to 13, wherein the surface smoothness is 80% or more.

Images