Cellulose particles

Abstract

Provided are fine particles that have excellent biodegradablility, particularly marine biodegradablility, and are capable of expressing physical properties equivalent to or exceeding those of plastic-based fine particles, e.g., favorable texture, particularly low friction, as well as the ability to adjust moist feeling and smoothness, excellent optical properties, and excellent formability. The present invention relates to cellulose particles comprising: a ridge section (R) of a prescribed width (W) that is reticulately disposed on the entirety of the surface of the particles; and crater-like sunken sections (C) that are surrounded by the ridge section (R) and divided from each other by the ridge section (R).

Description

[Technical Field]

[0001] This invention relates to cellulose particles. [Background technology]

[0002] Microparticles are used in a wide range of fields. For example, cosmetics contain microparticles of various materials and forms, primarily for the purpose of improving texture or imparting optical properties. Generally, spherical microparticles made of plastic materials are frequently used. For example, spherical silicone microparticles are disclosed in Patent Document 1 below. In some cases, microparticles with special surface shapes are used to further improve tactile and optical properties. For example, Patent Document 2 below discloses silicone microparticles having a mesh-like structure on their surface. Patent Document 3 discloses silicone microparticles having polygonal recesses on their surface and further coated with fine microparticles. Patent document 4 below discloses silicone microparticles having micro-protrusions on their surface. In addition, various types of microparticles made from acrylic, urethane, polyolefin, and other materials and forms are used in a variety of applications.

[0003] In recent years, the use of non-biodegradable plastic microparticles has been discouraged and restricted from an environmental protection standpoint. The particles shown in the following Patent Documents 1-4 have the problem of not being biodegradable. In fields where non-biodegradable plastic microparticles have traditionally been used, there is a movement to replace them with microparticles made from natural or inorganic mineral materials, or microparticles made from biodegradable materials.

[0004] As a natural product / inorganic mineral-based material, for example, Patent Document 5 discloses spherical silica nanoparticles and a method for producing them. Although silica nanoparticles have excellent squeaky and slippery properties, they can sometimes be problematic in cosmetic applications due to their unique grittiness, slipperiness, and poor moldability.

[0005] In the case of biodegradable materials, rapid biodegradation, particularly in the ocean where waste ultimately flows in and accumulates, is becoming increasingly important. For example, Patent Document 6 discloses spherical cellulose microparticles. Patent Document 7 discloses cellulose microparticles having a wrinkled structure on the surface. Patent Document 8 discloses cellulose microparticles having an irregular, smooth shape. While cellulose microparticles have features such as rapid marine biodegradability and a soft feel, a unique squeaky texture can be a problem in cosmetic applications.

[0006] As biodegradable materials other than cellulose, for example, spherical cellulose acetate microparticles are disclosed in Patent Document 9 below. Also, cross-linked carboxymethylcellulose microparticles having crater-like depressions on their surface are disclosed in Patent Document 10 below. However, cellulose acetate microparticles and other biodegradable materials have the problem that they decompose slowly in the ocean and may remain in the environment for a long period of time. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 4860214 [Patent Document 2] Patent No. 5522859 [Patent Document 3] Patent No. 5859478 [Patent Document 4] Patent No. 6125276 [Patent Document 5] Japanese Patent Publication No. 128916 / 1983 [Patent Document 6] Patent No. 6872068 [Patent Document 7] International Publication No. 2019 / 151486 [Patent Document 8] Japanese Patent Application Publication No. 4-348131 [Patent Document 9] Japanese Patent No. 6609726 Publication [Patent Document 10] Japanese Unexamined Patent Application Publication No. 2022-135891 [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] As described above, fine particles that have good marine biodegradability and exhibit good physical properties comparable or superior to those of conventionally widely used non-biodegradable plastic fine particles have not yet been proposed, and new fine particle materials are desired. Further, for fine particles made of a material having good marine biodegradability, it cannot be said that sufficient studies have been conducted on improving physical properties focusing on the surface morphology of the fine particles. In view of the above background, the problem to be solved by the present invention is to provide fine particles that have excellent biodegradability, particularly marine biodegradability, and can exhibit physical properties comparable or superior to plastic fine particles, for example, have good feel, particularly reduced squeakiness, can be adjusted for moist feel and slip feel, have excellent optical properties, and excellent moldability. [Means for Solving the Problems]

[0009] As a result of intensive studies and repeated experiments by the inventors to solve the above-mentioned problems, they unexpectedly found that imparting a specific concavo-convex structure to the surface of cellulose fine particles can exert the desired effect, and thus completed the present invention.

[0010] That is, the present invention is as follows. [1] Cellulose particles, wherein the entire surface of the particles has ridges (R) of a predetermined width (W) arranged in a net shape, and crater-shaped depressions (C) surrounded by the ridges (R) and separated from each other by the ridges (R). [2] The number of depressions (C) separated from each other by the ridges (R) per 100 μm 2 of the surface of the cellulose particles is 20 or more and 200 or less, the cellulose particles according to [1] above. [3] The cellulose particles according to [1] or [2], wherein a predetermined width (W) of the ridge portion (R) is 0.1 µm or more and 2.0 µm or less, and a ratio W / D of the predetermined width (W) to a particle diameter (D) is 0.25 or less. [4] The cellulose particles according to any one of [1] to [3], wherein the circularity is 0.8 or more. [5] The cellulose particles according to any one of [1] to [4], wherein a crystallinity of cellulose constituting the cellulose particles is less than 70%. [6] The cellulose particles according to any one of [1] to [5], wherein the cellulose constituting the cellulose particles is regenerated cellulose of crystal structure type II. [7] The cellulose particles according to [6], wherein the regenerated cellulose of crystal structure type II is cuprammonium process regenerated cellulose (cupra). [8] The cellulose particles according to any one of [1] to [7], comprising at least one concave contour shape among contour shapes of depressed portions (C) separated from each other by the ridge portions (R). [9] The cellulose particles according to any one of [1] to [8], wherein a number ratio of concave contour shapes among contour shapes of depressed portions (C) separated from each other by the ridge portions (R) is 10% or more.

[10] The cellulose particles according to any one of [1] to [9], wherein light-scattering solid particles are supported inside or on a surface layer of the cellulose particles.

[11] The cellulose particles according to any one of [1] to

[10] , wherein the light-scattering solid particles are any one selected from the group consisting of titanium oxide, zinc oxide, aluminum oxide, magnesium oxide, zirconium oxide, tin oxide, cerium oxide, barium sulfate, silica, mica, sericite, talc, kaolin, mica, titanated mica, bismuth oxychloride, and boron nitride, or a combination thereof.

[12] A cellulose powder that is an aggregate of the cellulose particles according to any one of [1] to

[11] , wherein a volume average particle diameter (Dv50) of the cellulose particles is 1 µm or more and 50 µm or less.

[13] A cellulose powder which is an aggregate of cellulose particles as described in any of [1] to

[11] above, wherein the proportion of particles whose number ratio W / D to a particle diameter (D) of a predetermined width (W) is 0.15 or less is 50% or more.

[14] A cosmetic composition comprising cellulose particles as described in any of [1] to

[11] above, or cellulose powder as described in

[12] or

[13] above. [Effects of the Invention]

[0011] The cellulose particles according to the present invention have a good feel, especially with minimal squeaking, and their moistness and slipperiness can be adjusted. Furthermore, they have excellent optical properties, excellent moldability, and excellent biodegradability. Therefore, the cellulose particles according to the present invention can be suitably used in various fields such as cosmetic raw materials, texture improvers, light scattering agents, resin additives, various fillers, mold release agents, coatings, paints, scrubs, and cleansing agents, either as a substitute material for existing non-biodegradable plastic microparticles or as a novel material with superior properties compared to conventional materials. [Brief explanation of the drawing]

[0012] [Figure 1] This is an explanatory diagram of the surface structure of the cellulose particles in this embodiment. [Figure 2] This is an example of the optical property measurement results for cellulose particles in this embodiment. [Figure 3] This is a surface SEM image of cellulose particles from Example 4. [Figure 4] This is an SEM image of the cellulose particles from Example 7. [Figure 5] These are SEM images of cellulose particles from Comparative Example 4, at (a) a magnification of 10,000x and (b) a magnification of 30,000x. [Figure 6] This is a cross-sectional SEM image of cellulose particles from Example 7. [Figure 7] These are the optical property measurement results for the cellulose particles of Example 11. [Figure 8] This is a surface SEM image of cellulose particles from Example 12. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described in detail below.

[0014] [Surface structure] The cellulose particles of this embodiment have an uneven surface structure. This uneven surface structure (hereinafter also referred to as the specific uneven surface structure) is composed of ridges (R) of a predetermined width (W) arranged in a mesh-like pattern, and crater-shaped depressions (C) surrounded by and separated from each other by the ridges (R), as illustrated in Figure 1, which are distributed across the entire surface of the particles. At various points along the ridge (R), there are branching points (B) leading in three or more directions. The ridge (R) surrounds the depression (C), and is clearly distinguishable from the depression (C) by a certain height. The ridge line (RL) is defined as a line that bisects the width of the ridge (R). The closed curve drawn by the ridge line (RL) surrounding one depression (C) is defined as the contour line of the depression (C), and the figure formed by being enclosed by the contour line is defined as the contour shape of the depression (C). The predetermined width (W) of a ridge (R) is defined as the average value of the width of the ridge (R) at a point that bisects the length of the ridge line (RL) connecting two adjacent branching points (B) for a single particle.

[0015] In this specification, the term "crater-shaped depression (C)" refers to a portion surrounded by a network of ridges (R) of a predetermined width (W), separated from each other by the ridges (R), and which is a depression that has been indented from the surface of a substantially spherical particle. That is, the ridges (R) surrounding the crater-shaped depression (C) are preferably formed in a ridge-like manner and preferably formed continuously. The ridges (R) surrounding the crater-shaped depression (C) are formed integrally (continuously) on the periphery surrounding the crater-shaped depression (C), or in other words, it is preferable that the depression (C) is formed by the indentation of the surface of a substantially spherical particle, and as a result, the portion that was originally the surface of the substantially spherical particle remains as a ridge (R), thus forming the ridges (R). In that sense, it is preferable that the multiple protrusions formed on the surface of the roughly spherical particles do not overlap each other, and that they do not have the irregular uneven structure (groove-like ridges) seen in petal-shaped particles.

[0016] The three-dimensional shape of the crater-like depression (C) is not particularly limited and may be hemispherical, bowl-shaped, cylindrical, conical, frustum-shaped, elliptical prism, elliptical cone, elliptical frustum-shaped, polygonal prism, polygonal pyramidal, polygonal pyramidal, groove-shaped, etc.

[0017] The contour shape of the crater-like depression (C) is not particularly limited and may be circular, elliptical, concave, irregular, or striated. From the viewpoint of obtaining good feel and optical properties, the contour shape is preferably circular, elliptical, star-shaped, concave, or irregular, and more preferably concave. This includes polygons that are concave. Furthermore, it is preferable that the circularity of the contour shape is 0.80 or less.

[0018] A concave contour refers to a shape in which the contour line of a recessed portion (C) has an inwardly recessed portion. A concave contour may have one recess or it may be an intricate shape with two or more recesses. In this specification, a concave contour is defined as one in which the ratio S2 / S3 of the area of ​​the contour (S2) to the area of ​​the convex hull of the contour (S3) is 0.95 or less. From the viewpoint of obtaining good optical properties, it is preferable that at least one of the recessed portions (C) present in a single particle has a concave shape. Furthermore, it is preferable that the proportion of recessed portions (C) present in a single particle that have a concave shape is 10% or more, more preferably 20% or more, and even more preferably 25% or more. Furthermore, when viewed as a powder composed of aggregates of cellulose particles, it is preferable that the proportion of particles having a specific uneven structure that include a concave shape in the contour shape of the recessed portion (C) is 20% or more, and more preferably 50% or more.

[0019] The "circularity of the contour shape of the recessed area (C)" and "S2 / S3" can be measured and calculated according to the following procedure. 1. Using a scanning electron microscope (SEM), take an image at a magnification such that the depression (C) and its surrounding ridge (R) are included in the field of view. 2. When using the image analysis software ImageJ, and specifying an area in Freehand line mode to trace the contour line of the target depression (C), the values ​​calculated as Shape Descriptors are as follows: Circ. represents the circularity of the contour shape, and Solidity represents S2 / S3.

[0020] The "percentage of particles containing concave shapes as the contour shape of the depression (C)" can be measured and calculated according to the following procedure. 1. Using a scanning electron microscope (SEM), capture an image of a single particle with the specific surface structure to be measured, ensuring that the entire particle is within the field of view. 2. Using the image analysis software ImageJ, calculate the solidity of the contour shape for all depressions visible in the SEM image using the same procedure as described above. 3. Perform the same measurement procedure on a total of 10 randomly selected particles. 4. Calculate the percentage of the measured particles that have one or more contour shapes with a Solidity of 0.95 or less.

[0021] One effect of providing the aforementioned specific uneven surface structure to particles is that, for example, the feel of the particles may be improved. More specifically, dry particles with the specific uneven surface structure exhibit reduced squeaking compared to particles with a smooth surface without irregularities, and their feel, including moistness, friction, and softness, also changes. The reason why the feel of dry particles changes when the specific uneven surface structure is provided is not entirely clear, but it is thought to be due to the fact that the behavior of the contact points between individual particles and their surfaces, and / or between individual particles themselves, differs from that of particles with a smooth surface, resulting in differences in contact area, contact state, adhesion force (liquid crosslinking force, van der Waals force, electrostatic interaction, hydrophilic interaction), friction, fluidity, and compressive deformability. Furthermore, when particles with the specific uneven surface structure are moistened with a liquid such as water or oil, the liquid can be retained in the recessed areas (C), thus exhibiting effects such as reduced stickiness and improved makeup longevity compared to particles with a smooth surface without irregularities. Another effect of providing the aforementioned specific uneven structure on the surface of the particles is, for example, improved moldability. Because it has depressions (C), the bulk density of the powder layer is low when no compressive stress is applied, but when compressive stress is applied, the ridges (R) deform easily, so the powder layer is densely packed, and a molded product with high compressibility and high strength can be manufactured.

[0022] Another effect of creating the aforementioned specific surface irregularities on the particles is that optical properties can be improved. If the scale of the specific surface irregularities is on the order of the wavelength of light, the light scattering rate will improve. At the same time, if the particle size scale is sufficiently larger than the wavelength of light, the light transmittance will improve. Since the specific surface irregularities and particle size can be controlled independently, it is possible to adjust the balance between light scattering and light transmittance to the optimal level depending on the purpose. For example, when used as a cosmetic ingredient, it is expected to achieve both soft focus and a natural bare-skin feel through visible light scattering, improved UV protection performance (SPF and PA values) through ultraviolet scattering, and reduced skin damage through infrared scattering. Another effect of providing the aforementioned specific uneven structure on the surface of the particles is that the external specific surface area is increased compared to particles with a smooth surface, and the external specific surface area can be arbitrarily controlled. For example, when the cellulose particles of this embodiment are used as an adsorbent or column packing agent, a large amount of antibody or functional agent with adsorption capacity can be supported on the particle surface to exhibit effects such as high adsorption capacity and high adsorption rate. Furthermore, since the cellulose particles of this embodiment have good moldability, they are also suitable for use as excipients, where a large amount of drug components or active ingredients are supported or coated on the particle surface before compression molding.

[0023] The specific uneven structure of the cellulose particles in this embodiment may consist of smooth curved surfaces or rough curved surfaces with fine irregularities. When the specific uneven structure consists of smooth curved surfaces, a smooth and moist feel is easily obtained. When the specific uneven structure consists of rough curved surfaces with fine irregularities, a soft and light feel and a strong light scattering effect are easily obtained. However, if the fine irregularities include needle-like or fibrous structures, the feel may deteriorate, which is undesirable.

[0024] In the cellulose particles of this embodiment, the number of depressions (C) separated from each other by ridges (R) is the number of depressions (C) on the surface of the particle over 100 μm. 2 Preferably, there are between 20 and 200 depressions per unit area. The number of depressions (C) separated from each other by ridges (R) is 100 μm. 2 When the number of particles per unit area falls below 20, the particles become flattened, red blood cell-shaped or disc-shaped. Furthermore, particles tend to get stuck in the depressions, worsening the user experience. Additionally, the relative structural size of the depressions with respect to the wavelength of light increases, leading to a deterioration in light scattering, which is undesirable. On the other hand, when the number of depressions (C) separated from each other by the ridges (R) is 100 μm, 2 When the number of particles exceeds 200, the indentations of each individual particle are small, so the majority of the particle surface becomes composed of ridges (R). As a result, the surface structure becomes not much different from that of particles with a smooth surface that does not have a specific uneven structure, which leads to an increased squeaking sensation and a noticeable deterioration in light scattering properties, which is undesirable.

[0025] The number of depressions (C) separated from each other by ridges (R) can be measured and calculated according to the following procedure. 1. Using a scanning electron microscope (SEM), take an image so that the entire particle to be measured is included in the field of view. 2.1 Count the number of depressions (C) that can be confirmed from the SEM image in each particle (i.e., the number of depressions (C) located on one hemisphere side of a roughly spherical particle), and let this be N (particles). 3. Using the image analysis software ImageJ, calculate the area within the specified region by tracing the contour line of the particle in Freehand Selection mode, and determine the two-dimensional projected area A (μm²) of the particle. 2 ) 4. Calculate the number density of the depressions (C) based on the following formula. Number density of depressions (C) (number of depressions / 100μm 2 ) = N / A × 100 Furthermore, in the cellulose particles of this embodiment, the average number of "indentations (C) separated from each other by ridges (R)" of a total of 10 particles having a specific uneven structure that have been arbitrarily selected is 100 μm. 2 It is preferable that there be between 20 and 200 items per unit.

[0026] In the cellulose particles of this embodiment, it is preferable that the predetermined width (W) of the ridge portion (R) is 0.1 μm or more and 2.0 μm or less, and that the ratio W / D of the predetermined width (W) of the ridge portion (R) to the particle diameter (D) is 0.25 or less. When the predetermined width (W) of the ridge portion (R) is 0.1 μm or more, the mechanical strength of the ridge portion (R) is sufficient, and it is preferable that the specific uneven structure does not irreversibly deform or collapse during use, or that the light scattering properties do not decrease. It is preferable that the predetermined width (W) of the ridge portion (R) is 0.1 μm or more, and more preferably 0.2 μm or more. On the other hand, when the predetermined width (W) of the ridge portion (R) is 2.0 μm or less, the contact of the ridge portion (R) with other surfaces or other particles changes from planar to point-like or linear, and the effect of having a specific uneven structure is exhibited, so the squeaking sensation is reduced, which is preferable. The predetermined width (W) of the ridge (R) is preferably 2.0 μm or less, more preferably 1.5 μm or less, and even more preferably 1.3 μm or less. Furthermore, in the cellulose particles of this embodiment, a ratio W / D of the predetermined width (W) of the ridge portion (R) to the particle diameter (D) is preferable because the area ratio of the depression portion to the particle surface is sufficiently large, thereby reducing the squeaky feeling and achieving a light scattering effect. W / D is preferably 0.25 or less, more preferably 0.20 or less, and even more preferably 0.15 or less.

[0027] The "predetermined width (W) of the ridge (R)" can be measured and calculated according to the following procedure. 1. Acquire an image at a magnification of 5000x using a scanning electron microscope (SEM). 2. Select one particle from among the particles within the field of view and identify one branching point (B). 3. Using the image analysis software ImageJ, draw the ridge line (RL) connecting the branch point (B) identified in step 2 with any adjacent branch point (B) in Freehand line mode, and measure its length. Identify the midpoint (the point that bisects the length) of the edge (RL) drawn in 4.3, and call this point M. 5. Measure the width of the ridge (R) passing through M and perpendicular to the ridge line (RL) at M. 6. Using a similar procedure, measure the width of all measurable furrows (R) within a single particle, and the average of these results is the predetermined width (W) of the furrow (R). In this embodiment, it is preferable that the average value of the "predetermined width (W) of the ridge (R)" of a total of 10 arbitrarily selected cellulose particles having a specific uneven structure is 0.1 μm or more and 2.0 μm or less.

[0028] The ratio W / D of the predetermined width (W) of the ridge (R) to the particle size (D) can be measured and calculated according to the following procedure. 1. Acquire an image at a magnification of 5000x using a scanning electron microscope (SEM). 2. Select one particle from among the particles within the field of view and calculate the predetermined width (W) of the ridge (R) using the same procedure as above. 3. If the entire particle to be measured is not contained within the field of view of the SEM image acquired in step 1 above, take an image at a magnification that allows the entire particle to be measured to be contained within the field of view. 4. Using the image analysis software ImageJ, in Freehand Selection mode, determine the Ferrey diameter (the distance of the longest straight line connecting any two points on the outer boundary of the selected area) of the specified region by tracing the contour line of the selected particle, and define this as the particle diameter (D). 5. Calculate the ratio W / D of the predetermined width (W) of the ridge (R) to the particle size (D). Furthermore, in this embodiment, the cellulose particles preferably have an average value of "ratio W / D of the particle diameter (D) to a predetermined width (W) of the ridge (R)" of a total of 10 arbitrarily selected particles having a specific uneven structure, which is 0.25 or less, more preferably 0.20 or less, and even more preferably 0.15 or less. Also, when viewed as a powder aggregate of cellulose particles, it is preferable that the proportion of particles having a specific uneven structure in which the ratio W / D of the particle diameter (D) to a predetermined width (W) is 0.15 or less is 50% or more.

[0029] A figure drawn by surrounding one crater-shaped depressed portion (C) with a ridgeline (RL), that is, the area (S2) of the contour shape, is preferably within a certain range for obtaining good feel and optical properties. The larger S2 is, the ridges (R) are arranged at wider intervals, so a good feel can be obtained. For example, the area (S2) of the region surrounding the depressed portion (C) by the ridgeline (RL) is 1 μm 2 or more, it is preferable. Alternatively, it is preferable that the ratio S2 / S1 of the area (S2) of the region surrounding the depressed portion (C) by the ridgeline (RL) to the area (S1) when the entire particle is two-dimensionally projected is 0.05 or more. On the other hand, if S2 is relatively large with respect to the particle diameter, the rolling of the particles may deteriorate and the feel may be impaired. Therefore, the ratio S2 / S1 of the area (S2) of the region surrounding the depressed portion (C) by the ridgeline (RL) to the area (S1) when the entire particle is two-dimensionally projected is preferably 0.50 or less, more preferably 0.25 or less, still more preferably 0.20 or less, and still more preferably 0.15 or less. Furthermore, for the cellulose particles of the present embodiment, the average value of "the area (S2) of the region surrounding the depressed portion (C) by the ridgeline (RL)" of a total of 10 particles having a specific uneven structure selected arbitrarily is 1 μm 2 or more, it is preferable. In addition, for the cellulose particles of the present embodiment, the average value of "the ratio S2 / S1 of the area (S2) of the region surrounding the depressed portion (C) by the ridgeline (RL) to the area (S1) when the entire particle is two-dimensionally projected" of a total of 10 particles having a specific uneven structure selected arbitrarily is preferably 0.05 or more and 0.50 or less, more preferably 0.05 or more and 0.25 or less, still more preferably 0.05 or more and 0.20 or less, and still more preferably 0.05 or more and 0.15 or less.

[0030] "The area (S1) when the entire particle is two-dimensionally projected" can be measured and calculated according to the procedure shown below. 1. An image is captured with a scanning electron microscope (SEM) at a magnification such that the entire single particle to be measured fits within the field of view. 2. Using the image analysis software ImageJ, calculate the area of ​​a specified region by tracing the contour line of the particle in Freehand line mode, and define this as S1.

[0031] The area (S2) of the region enclosed by the ridge (RL) around the depression (C) can be measured and calculated according to the following procedure. 1. Using a scanning electron microscope (SEM), take an image at a magnification such that the depression (C) and its surrounding ridge (R) are included in the field of view. 2. Using the image analysis software ImageJ, in Freehand line mode, calculate the area of ​​the region specified by tracing the contour line of the target depression (C), i.e., the ridge line (RL) surrounding the depression (C), and define this as S2.

[0032] [Roundness] The cellulose particles of this embodiment have a roughly spherical shape, preferably a spherical shape. A spherical or roughly spherical shape allows the particles to roll easily, resulting in a pleasant feel, as well as improved light scattering. The general shape of the particles can be determined from a two-dimensional projection image of the particles using the following formula:

number

[0033] [Particle size / particle size distribution] In this embodiment, the volume-average particle diameter (Dv50) of the cellulose particles is preferably 1 μm or more and 50 μm or less. In this specification, the volume-average particle diameter (Dv50) refers to the value of the particles in a dry state. To prevent the formation of aggregates and obtain a good feel and optical properties, the volume-average particle diameter (Dv50) is preferably 1 μm or more. On the other hand, to reduce grittiness and graininess and obtain a smooth feel, and to obtain sufficient light scattering properties, the volume-average particle diameter (Dv50) is preferably 50 μm or less.

[0034] There are no particular restrictions on the particle size distribution of the cellulose particles in this embodiment. After manufacturing the cellulose particles in this embodiment, classification and pulverization processes may be performed under conditions that do not destroy the specific uneven structure, and the particles may be used with any desired particle size distribution. From the viewpoint of obtaining a good feel, it is preferable that particles with a particle diameter of 75 μm or more constitute 5% or less by volume fraction, and more preferably 1% or less. Furthermore, from the viewpoint of preventing the formation of aggregates that change or deteriorate the feel and other physical properties, it is preferable that the primary particles are of a certain size or larger. Specifically, it is preferable that particles with a particle diameter of less than 1 μm constitute 20% or less by volume fraction, more preferably 10% or less, and even more preferably 5% or less.

[0035] [Internal structure] The cellulose particles of this embodiment may have a solid, hollow, or porous structure. From the viewpoint of maintaining their physical properties and resisting deformation when subjected to load during use, it is preferable for the cellulose particles to be solid. In applications where softness, moldability, and high liquid absorption are important, it is preferable for the cellulose particles to be hollow or porous. Furthermore, when light transmittance and transparency are desired, it is preferable for the cellulose particles to be solid, while when strong light scattering is desired, it is preferable for the cellulose particles to be hollow or porous.

[0036] [cellulose] The cellulose particles in this embodiment may be natural cellulose such as cotton, hemp, or pulp; regenerated cellulose such as viscose rayon, copper ammonia-processed regenerated cellulose (cupro), lyocell, or cellulose acetate, obtained by saponification; or bacterial cellulose produced by bacteria. These celluloses may also be chemically modified cellulose obtained by modifying them using hydroxyl groups. Furthermore, unmodified cellulose and chemically modified cellulose may be mixed, and other polysaccharides, their derivatives, and polymer compounds may also be included. From the viewpoint of rapid marine biodegradation, the weight fraction of unmodified cellulose is preferably 80 wt% or more, more preferably 90 wt% or more, and even more preferably 95 wt% or more.

[0037] The crystallinity of the cellulose constituting the cellulose particles in this embodiment is preferably less than 70%. From the viewpoint of obtaining a soft feel and rapid marine biodegradability, a crystallinity of less than 70% is preferred, less than 60% is more preferred, and less than 50% is even more preferred.

[0038] The cellulose constituting the cellulose particles in this embodiment is preferably regenerated cellulose with a crystalline structure of type II. Generally, cellulose crystal structures are known as Type I (natural cellulose) and Type II (most regenerated cellulose). Examples of Type I cellulose include cellulose nanofiber (CNF) and crystalline cellulose. Compared to Type II cellulose crystals, Type I cellulose crystals have higher elastic modulus and rigidity, so particles made from Type I cellulose tend to have a hard feel. Also, when particles made from Type I cellulose are granulated after mechanical and / or chemical crushing treatment without dissolving the raw material Type I cellulose, rigid fibrous material and coarse crystals remain during the crushing process, and these are exposed on the particle surface, forming a rough surface, which tends to produce a strong squeaky and rough feel. On the other hand, Type II cellulose has lower elastic modulus and rigidity compared to Type I cellulose crystals, so particles made from Type II cellulose tend to have a soft and moist feel. Also, since Type II cellulose is granulated after completely dissolving the raw material cellulose, the surface of the granulated material can be made smooth without fibrous material or coarse crystals, which reduces the squeaky and rough feel. For the reasons stated above, the cellulose constituting the cellulose particles in this embodiment is preferably regenerated cellulose with a crystalline structure of type II.

[0039] Examples of regenerated cellulose with a crystal structure type II include viscose rayon, copper ammonia regenerated cellulose (cupro), lyocell, cellulose obtained by saponification of esterified cellulose such as cellulose acetate, cellulose regenerated from acid or alkaline solutions of specific concentrations, cellulose regenerated from aqueous solutions of inorganic salts such as zinc chloride, and cellulose regenerated from various ionic liquid solutions. Copper ammonia regenerated cellulose is the most preferred because it is easy to achieve a crystallinity of less than 70% of the cellulose particles and to impart microporosity derived from the phase separation structure, resulting in a soft feel and a faster marine biodegradation rate. The degree of polymerization of cellulose is not particularly limited. A low degree of polymerization is preferable when softness and moldability are desired, while a high degree of polymerization is preferable when hardness and robustness of the particle structure are desired.

[0040] [Method for manufacturing cellulose particles] The method for producing cellulose particles in this embodiment is not particularly limited as long as it can create a specific uneven structure on the surface of the fine particles. For example, a preferred method is one in which (i) first, a raw material liquid containing cellulose is formed into droplets, (ii) then, only the surface layer of the droplets is solidified to form a film, and the inside of the droplets is in a liquid or gel state with a low solid content concentration, and (iii) then, the volume contraction that occurs during the process of concentrating and solidifying the inside of the droplets is used as a driving force to form crater-like depressions (C) on the surface of the fine particles, thereby creating a specific uneven structure. (i) Methods for forming liquid droplets from the raw material include, for example, spraying, suspension, and emulsification. (ii) Methods for solidifying the surface of the droplets and forming a film include, for example, drying, coagulation, and derivatization. (iii) Methods for shrinking the volume of the droplets include, for example, drying, dehydration, solvent removal, and derivatization.

[0041] To produce the cellulose particles of this embodiment, methods (i) to (iii) can be arbitrarily combined depending on the purpose, but the spray-drying (SD) method is particularly preferred from the viewpoint of productivity, cost, and the ability to use commonly available equipment. The raw material liquid for the SD method can be selected from a dispersion of finely ground cellulose, a cellulose solution in which cellulose is completely dissolved, a solution in which a cellulose derivative is completely dissolved, etc., and is not particularly limited, but a cellulose solution or a cellulose derivative solution is desirable because the outermost surface of the formed film becomes smooth, and even at high concentrations, the viscosity of the raw material liquid can be kept low and it is easy to spray and dropletize. In particular, an aqueous copper ammonia cellulose solution is particularly preferred because it contains two solvents, ammonia and water, which have different vapor pressures, so the rapid volatilization of ammonia in the initial stages of drying can control the film formation process, and the delayed evaporation of water can control the volume shrinkage process, and as a result it is easy to control a specific uneven structure. In the powder obtained by this spray-drying method, it is crucial to set the spray-drying conditions such that the number proportion of cellulose particles having a specific uneven structure is preferably 50% or more, more preferably 70% or more, and even more preferably 90% or more. The optimal spray-drying conditions vary depending on the type of raw material liquid used and cannot be stated in general terms, but for example, when using an aqueous solution of copper ammonia cellulose, the inventors of this invention have found that the following conditions are appropriate.

[0042] The cellulose concentration of the copper ammonia cellulose aqueous solution, which is the raw material liquid, is not particularly limited, but it is preferably 1.5 wt% or more and 15.0 wt% or less. If the cellulose concentration is low, the predetermined width (W) of the ridges (R) may become small or disappear, which is undesirable. In order to obtain particles with a predetermined width (W) of ridges (R) of 0.1 μm or more, it is preferable to set the cellulose concentration to 1.5 wt% or more, more preferably to 2.0 wt% or more, and even more preferably to 2.5 wt% or more. On the other hand, if the cellulose concentration is high, nozzle clogging is likely to occur during granulation using the SD method, which is undesirable as it hinders stable operation. In order to stably granulate using the SD method, it is preferable to set the cellulose concentration to 15.0 wt% or less, and more preferably to 10.0 wt% or less.

[0043] The ammonia concentration of the copper ammonia cellulose aqueous solution, which is the raw material liquid, is not particularly limited as long as it is within the range that can dissolve cellulose, but it is preferably between 2.5 wt% and 15.0 wt%. If the ammonia concentration is low, the solubility of cellulose decreases and precipitates may form, which is undesirable. From the viewpoint of solubility of cellulose, an ammonia concentration of 2.5 wt% or higher is preferred, 3.0 wt% or higher is more preferred, and 4.0 wt% or higher is even more preferred. On the other hand, if the ammonia concentration is high, the ammonia vapor concentration inside the drying chamber of the spray dryer increases, which inhibits the film formation of spray droplets, causing the ridges (R) to disappear or the structure to become disordered, which is undesirable. From the viewpoint of imparting a specific uneven structure, an ammonia concentration of 15.0 wt% or less is preferred, 10.0 wt% or less is more preferred, 7.5 wt% or less is even more preferred, and 6.0 wt% or less is most preferred.

[0044] The copper concentration in the copper ammonia cellulose aqueous solution, which is the raw material, is not particularly limited as long as it is within the range that can dissolve the cellulose. However, if there is a large excess amount of copper in addition to the theoretical amount required to dissolve the cellulose, it may affect the dissolution stability of the solution and the granulation stability (nozzle clogging) in the SD method, which is undesirable.

[0045] The viscosity of the raw material liquid, an aqueous solution of copper ammonia cellulose, is not particularly limited as long as it can be sprayed and droplet-formed by a spray nozzle; for example, it should be between 0.1 mPa·s and 300 mPa·s. The atomization method is not particularly limited as long as it is a method that can form the copper ammonia cellulose aqueous solution into droplets. As for the atomizer, for example, a one-fluid nozzle, a two-fluid nozzle, a four-fluid nozzle, a disc atomizer, etc., can be selected according to the purpose, and are not limited to these.

[0046] The optimal operating conditions for a spray dryer vary depending on the composition of the copper ammonia cellulose aqueous solution and the specifications and structure of the spray dryer used, so it is difficult to give a general answer. However, for example, the inlet temperature is set between 80 and 300°C, and the outlet temperature is set between 0 and 150°C. The liquid flow rate and hot air supply rate are adjusted so that the set inlet and outlet temperatures are stably maintained. While there are no particular limitations on the set value of the inlet temperature, if the inlet temperature is too low, the drying rate will be slow, which may hinder film formation and prevent the formation of the predetermined uneven structure. Furthermore, the slow drying rate may result in low productivity and loss due to adhesion of undried material, leading to a decrease in yield. Therefore, the inlet temperature is preferably 80°C or higher, more preferably 100°C or higher, and even more preferably 130°C or higher. On the other hand, if the inlet temperature is too high, the drying rate will be fast, making it difficult to control the predetermined uneven structure as film formation and volume shrinkage proceed almost simultaneously. Furthermore, solidified material may form in the nozzle area, hindering stable granulation. Particles that come into contact with and adhere to the wall of the spray dryer may undergo thermal denaturation and discoloration. From this perspective, the inlet temperature is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower.

[0047] The outlet temperature is not particularly limited as long as it is lower than the inlet temperature. However, if the outlet temperature is too low, it may result in adhesion loss of undried material and a decrease in yield, and condensation may occur in the cyclone recovery section, leading to aggregation of product particles. Therefore, the outlet temperature is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. On the other hand, if the outlet temperature is too high, there is a concern that thermal decomposition of cellulose in the particles collected in the cyclone section may occur, leading to discoloration and a decrease in physical properties. From this viewpoint, the outlet temperature is preferably 150°C or lower, and more preferably 100°C or lower. On the other hand, when obtaining a specific uneven structure composed of a rough curved surface with fine irregularities, the outlet temperature is preferably 60°C or lower.

[0048] The difference between the inlet and outlet temperatures (ΔT) is not particularly limited as long as the spray droplets can be dried. However, if ΔT is too small, the ammonia vapor concentration and humidity inside the drying chamber of the spray dryer decrease, the drying rate increases, making it difficult to control the predetermined uneven structure and reducing productivity. Therefore, ΔT is preferably 10°C or higher, and more preferably 30°C or higher. On the other hand, if ΔT is too large, the ammonia vapor concentration and humidity inside the drying chamber of the spray dryer increase, inhibiting film formation, which can cause the ridges (R) to disappear or become disordered, and can lead to adhesion loss of undried material and a decrease in yield. Therefore, ΔT is preferably 100°C or lower.

[0049] In this embodiment, when a method of spray-drying a copper ammonia cellulose aqueous solution is selected as the method for producing cellulose particles, a blue powder containing copper and cellulose is first obtained. The fine particles with residual copper may be used as is, but depending on the application, the presence of copper may not be acceptable. In that case, the copper can be removed by acid treatment. The method of acid treatment is not particularly limited, but for example, the fine particles may be immersed in sulfuric acid and then separated into solid and liquid by methods such as suction filtration and centrifugation. After removing copper using acid, the method of removing the acid can be arbitrarily selected, but for example, the fine particles after acid treatment may be immersed in pure water and then separated into solid and liquid by methods such as suction filtration and centrifugation. The fine particles after copper removal and deoxidation will be in a hydrated state, but they may be used in their hydrated state or dried before use. When drying, the drying method is not particularly limited, and known drying methods and equipment may be used. From the viewpoint of suppressing particle aggregation during drying, methods such as freeze-drying, spray-drying, and paddle-stirring drying are preferred. If particle aggregation after drying is a problem, a step may be provided to crush the aggregates of particles to the extent that it does not affect the specific uneven structure. In this embodiment, it is preferable to have low levels of residual copper and residual sulfuric acid in the cellulose particles. High levels of these can lead to effects such as particle aggregation, discoloration, and carbonization during drying, decreased strength and deterioration of physical properties during storage, reduced biodegradation rate, and skin irritation.

[0050] The cellulose particles of this embodiment can be further classified to remove fine powder, coarse powder, and particles that do not have a specific uneven structure.

[0051] The cellulose particles of this embodiment may be subjected to any surface treatment, derivatization, or modification for the purpose of improving or adjusting the feel and other physical properties. As surface treatment agents, those commonly used for surface treatment, such as pigments, may be used, and examples include, but are not limited to, metal soaps, fatty acids, amino acids, oils, surfactants, silicones, silane coupling agents, and solid fine particles. From the viewpoint of easy adsorption and immobilization to cellulose, surface treatment agents containing nitrogen atoms, such as cationic surfactants and amino acids, are preferred. From the viewpoint of strong immobilization with cellulose through covalent bonding, silane coupling agents are preferred. The cellulose particles obtained in this invention are biodegradable and decompose in compost, soil, and ocean. Biodegradation in ocean is particularly difficult due to the low number of microorganisms and low temperatures. Therefore, to increase the rate of biodegradation in ocean, it is preferable that the cellulose has not undergone surface treatment, derivatization, or modification. Furthermore, from the viewpoint of concerns about the safety of substances produced as a result of biodegradation, it is preferable that the cellulose has not undergone surface treatment, derivatization, or modification.

[0052] The cellulose particles of this embodiment may have various functional substances or active ingredients supported or compounded inside or on the surface of the particles. Examples of functional substances and active ingredients include, but are not limited to, organic substances, inorganic substances, polymer compounds, dyes, pigments, lakes, oils, and surfactants. Examples of inorganic substances include, but are not limited to, titanium dioxide, zinc oxide, barium sulfate, talc, mica, platinum, gold, Prussian blue and its analogues, iron oxide, red iron oxide, etc.

[0053] The cellulose particles of this embodiment may have light-scattering solid particles supported or compounded inside and / or on the surface of the particles. By supporting or compounding light-scattering solid particles, the scattering of ultraviolet light, visible light, infrared light, or a combination thereof can be improved for cellulose particles having a specific uneven structure. Furthermore, the light-scattering effect of the solid particles can be enhanced by the specific uneven structure. In addition, even light-scattering solid particles that have a poor feel on their own can be improved in feel by compounding them with cellulose particles having a specific uneven structure. Due to these characteristics, cellulose particles compounded with light-scattering solid particles can be suitably used in any composition that requires enhanced light-scattering properties and tactile characteristics. For example, when incorporated into cosmetic formulations, even light-scattering solid particles that have poor dispersibility in the formulation on their own can have their dispersibility improved by compounding them with cellulose particles having a specific uneven structure, resulting in effects such as improved feel of the formulation, improved light-scattering performance, and suppression of white cast. Examples of light-scattering solid particles include, but are not limited to, titanium dioxide, zinc oxide, aluminum oxide, magnesium oxide, zirconium oxide, tin oxide, cerium oxide, barium sulfate, silica, mica, sericite, talc, kaolin, mica, titanium mica, bismuth oxychloride, and boron nitride. The state in which the light-scattering solid particles are supported and composited is not particularly limited, but from the viewpoint of improving feel and optical properties, it is preferable that they are supported and composited in a dispersed manner without aggregation, both inside and / or on the surface of the particles. While there are no particular limitations on the method for supporting and compounding light-scattering solid particles, from the viewpoint of dispersing the light-scattering solid particles and imparting a specific uneven structure, a method is preferred in which the light-scattering solid particles are added to and dispersed in an aqueous copper ammonia cellulose solution, which is the raw material liquid, and then granulated by a spray-drying method. The content of light-scattering solid particles can be arbitrarily adjusted according to the desired physical properties.

[0054] The cellulose particles of this embodiment may be in a dry state, a wet state, or dispersed in any liquid or medium. [Examples]

[0055] The present invention will be specifically described below with reference to examples and comparative examples. First, we will explain the main manufacturing methods, manufacturing equipment, manufacturing conditions, measurement methods, measuring devices, and measurement conditions used in the examples and comparative examples.

[0056] [Particle production method] (granulation equipment) For the spray dryer, we used either the L-8i manufactured by Okawara Chemical Machinery (disc atomizer: Okawara Chemical Machinery MC-50, two-fluid nozzle: Okawara Chemical Machinery RJ-5) or the Palvis Mini Spray GB210-A manufactured by Yamato Scientific (two-fluid nozzle: 1A).

[0057] (filter paper) For suction filtration, AS ONE's Azfil qualitative filter paper (product number: 2-872-02, diameter: 9 mm, material: cellulose, maximum pore size: 10-15 μm) was used.

[0058] [Preparation of particle samples for structural analysis] For structural analysis of particles, prepare a dry powder sample. If the sample is already in the form of a dry powder, it can be used directly for structural analysis. If the sample is wet or dispersed in a liquid, the liquid is replaced with water and then dried to obtain a dry powder. Specifically, first, as much liquid as possible is removed by suction filtration. Next, 10 times the weight of water is added to the residue on the filter paper and stirred with a magnetic stirrer at room temperature for 10 minutes, then filtered by suction (first water replacement operation). The same water replacement operation is repeated a total of three times. The resulting wet cake is broken up with a spatula and spread on a stainless steel tray, and dried in a constant temperature drying oven at 80°C. When the dried material becomes a free-flowing powder or a flake-like substance with aggregated powder, and the moisture content is 10 wt% or less, the drying is stopped, and the material is removed from the constant temperature drying oven and subjected to structural analysis.

[0059] [Volume-averaged particle size (Dv50)] For dry particles, the volume-average particle size (Dv50) was measured using a laser diffraction particle size analyzer (Malvern Mastersizer 3000E). As a pretreatment, dispersion was performed using an Aero M at a dispersion pressure of 4 bar.

[0060] [Evaluation of particle surface structure] A small amount of cellulose particles were scattered onto a carbon tape, and as a pretreatment, a platinum coating was applied for 30 seconds using a sputtering device (Vacuum Devices, MSP-1S). The sample was observed using a scanning electron microscope to obtain SEM images of the particle surface. When observing and measuring specific surface irregularities, images were acquired under the following SEM observation conditions. SEM model: Hitachi High-Tech TM4000 II Magnification: 100~30,000x Electron detector: Backscattered electron detector Observation conditions: 5kV, Mode 3, Standard (H)

[0061] [Evaluation of particle cross-sectional structure] The cross-sectional structure of resin-embedded cellulose microparticles was evaluated by measuring the contour of the cross-section exposed by BIB (Broad Ion Beam) processing using the following procedure. The conditions below are just an example, and a technician familiar with this technology may change the observation conditions within a range that is not expected to change the results. Resin embedding of cellulose particles was carried out as follows. Quetrol-812, manufactured by Nissin EM Co., Ltd., was used as the epoxy resin. 10.6 mL of Quetrol-812 and 9.4 mL of MNA (manufactured by Nissin EM Co., Ltd.) were weighed and mixed to form a resin mixture, which was placed in a 50 mL beaker and stirred with a stirrer for 10 minutes. The stirring speed was 300 rpm / min. Next, 0.34 mL of DMP-30 (manufactured by Nissin EM Co., Ltd.) was added and stirred for another 5 minutes. After stirring, the resin mixture was placed in a vacuum dryer and degassed under reduced pressure for 20 minutes or more. Cellulose particles were added to the degassed resin mixture and stirred thoroughly, then it was placed in the vacuum dryer again and degassed under reduced pressure for 10 minutes or more. A commercially available cover glass (approximately 18 x 18 x 0.2 mm in size) was cut into eight rectangles. A resin mixture containing an appropriate amount of cellulose particles was dropped onto each cover glass, and another cover glass, also cut into eight rectangles, was placed on top of the resin mixture. The mixture was left to stand and allowed to spread between the cover glass pieces. After the resin mixture had spread sufficiently, it was heat-treated at 60°C for 24 hours.

[0062] The resin-embedded cellulose particles were cross-sectionally processed using a BIB processing device (IM4000+, Hitachi) under the following conditions. Acceleration voltage: 2.5kV Ion beam current: 20 μA Argon flow rate: 0.35 cm 3 / min Stage Mode: C6 Processing time: 6 hours Temperature: room temperature

[0063] The cross-section of the resin containing processed cellulose particles was observed using a scanning electron microscope (Regulus8220, Hitachi) under the following conditions, and SEM images were obtained. Magnification: 1,000 to 1,500x Electron detector: Secondary electron detector (SE(U), SE(L), LM, or a combination thereof) Acceleration voltage: 1kV Emission current: 10μA Condenser lens: 5~13 Probe current: Normal Working distance (WD): 8±0.2mm Image acquisition scanning method: Rapid

[0064] [Evaluation of circularity] The circularity of cellulose particles was measured using a particle shape image analyzer (PITA-04, manufactured by Seishin Corporation). 0.5 g of the particle sample and 25 g of purified water were placed in a 100 mL beaker, and after ultrasonic dispersion pretreatment, the entire sample was placed into the analyzer. Measurements were continued until the number of observed particles exceeded 10,000, and the average circularity of each particle was used as the evaluation result.

[0065] [Evaluation of crystallinity] The crystallinity of cellulose was measured and calculated using the WAXS transmission method and the Isogai method. Particles were sealed in cells made with double-sided tape and polyetherimide film, and 1 mm thick samples were used for measurement. Measurements were performed under the following conditions. Equipment: Rigaku Corporation NANOPIX X-ray wavelength: 0.154nm X-ray incidence direction: Normal direction to film Optical system: Point collimation (1st: 0.55mm, 2nd: Open, Guard: 0.35mm) Beam stopper: φ2.0mm Detector: Hypix-6000 (2D semiconductor detector) Camera length: WAXS: 86.1mm (measured with 4 overlapping sections) Exposure time: WAXS: 10 min * 4 / sample

[0066] For the scattering pattern I(2θ,φ) measured by the 2D detector, the following equation (1):

number

[0067] The one-dimensional profile calculated using equation (1) includes scattering from sources other than the sample, such as window material and air scattering, in addition to scattering originating from the sample. Furthermore, the scattering intensity depends on the instrument and sample thickness. To correct for these factors, use the following equation (2):

number

[0068] The degree of crystallinity is determined according to the Isogai method, using the following formula (3):

number

[0069] In formula (3), I (1-10) This is the peak intensity originating from the (1-10) plane, and I (1-10)B This represents the background intensity at the peak location originating from the (1-10) plane. I in equation (3) (1-10) and I (1-10)B The following procedure was used to calculate it. (i) The following equation (4) is obtained by adding the linear background and the Lorentz function in the range of 10° < 2θ < 15° of the WAXS profile:

number

[0070] [Example 1: Copperammonium spray-dried particles] Granulation: A copper-ammonia-cellulose aqueous solution was prepared with 3.5 wt% cellulose, 4.0 wt% ammonia, 1.3 wt% copper, and 91.2 wt% water. This solution was spray-dried using an RJ-5 under the conditions of a spray pressure of 0.3 MPa, a liquid supply rate of 1.3 kg / h, an inlet temperature of 130°C, and an outlet temperature of 65°C, and the blue powder was recovered in the cyclone section. Pickling (copper removal): 50 g of the blue powder obtained in Example 1 was added to 1000 g of 7.5 wt% sulfuric acid and dispersed. After stirring with a magnetic stirrer for 10 minutes, the slurry was filtered by suction to obtain a wet cake. Subsequently, the wet cake was added to 1000 g of fresh 7.5 wt% sulfuric acid and redispersed. After stirring with a magnetic stirrer for 10 minutes, the slurry was filtered by suction to obtain a wet cake. The same pickling and suction filtration procedure was repeated until the wet cake was sufficiently copper-removed and turned white. Washing (deacidification): The wet cake was dispersed in 1000g of pure water and stirred with a magnetic stirrer for 10 minutes. The slurry was then filtered by suction to obtain the wet cake. The same washing and suction filtration procedure was repeated until the pH of the filtrate became neutral. Drying: The wet cake was broken up with a spatula and spread on a stainless steel tray, then dried in a constant-temperature drying oven at 80°C. Drying was stopped when the material became a free-flowing powder or a flake-like substance with aggregated powder, and the moisture content was 10 wt% or less, at which point it was removed from the constant-temperature drying oven. Grinding and Classification: The sample was thoroughly ground using a mortar and pestle, and then passed through a sieve with a mesh size of 75 μm to remove coarse particles and obtain cellulose particles. The volume-average particle size (Dv50) was 6.4 μm. The particle surface showed a specific uneven structure, and the outermost layer was smooth without any fibrous or needle-like structures.

[0071] [Examples 2-10: Copperammonium spray-dried particles] Cellulose particles were obtained in the same manner as in Example 1, except that the granulation conditions were changed as shown in Table 1 below. Figure 3 shows a surface SEM image of the particles obtained in Example 4. The particle surface showed a specific uneven structure, and the outermost layer was smooth without any fibrous or needle-like structures. Figure 4 shows a surface SEM image of the particles obtained in Example 7. The particle surface showed a specific uneven structure, and the outermost layer was smooth without any fibrous or needle-like structures. Figure 6 shows a cross-sectional SEM image of the particles obtained in Example 7. The inside of the particles was solid (however, this does not negate the existence of microscopic pores on a scale that cannot be observed by SEM). In addition, the contour line of the cross-section showed a shape in which U-shaped depressions / papillary protrusions alternated around the entire circumference, originating from the specific uneven structure.

[0072] [Example 11: Spray-dried copper ammonium particles supported with a light-scattering solid] Cellulose particles were obtained in the same manner as in Example 1, except that a slurry of titanium dioxide particles (manufactured by Fuji Titanium Industries, TA-300D) dispersed in water was mixed with an aqueous solution of copper ammonia cellulose to prepare a solution containing 3.9 wt% cellulose, 5.7 wt% ammonia, 1.4 wt% copper, 3.9 wt% titanium dioxide, and 85.1 wt% water, and the granulation conditions were changed as shown in Table 1 below.

[0073] [Example 12: Copperammonium spray-dried particles] Cellulose particles were obtained in the same manner as in Example 1, except that the granulation conditions were changed as shown in Table 1 below. Figure 8 shows a surface SEM image of the particles obtained in Example 12. The surface of the particles obtained in Example 12 showed a specific uneven structure, which consisted of a rough curved surface with fine irregularities.

[0074] [Comparative Examples 1, 12, 13, 14: Copperammonium spray-dried particles] Cellulose particles were obtained in the same manner as in Example 1, except that the granulation conditions were changed as shown in Table 1 below.

[0075] [Comparative Example 4: CNF dispersion spray-dried particles] A commercially available cellulose nanofiber dispersion (BiNFi-s Ima-00002, manufactured by Sugino Machine, cellulose concentration 2 wt%) was diluted twice with pure water to obtain a CNF dispersion with a cellulose concentration of 1.0 wt%. This CNF dispersion was sprayed under the conditions of a disk rotation speed of 30,000 rpm, a liquid supply rate of 1.0 kg / h, an inlet temperature of 180°C, and an outlet temperature of 95°C. The white powder was collected in the cyclone section to obtain cellulose particles. The volume-average particle diameter (Dv50) was 10.5 μm. As shown in Figure 5, the surface structure was observed by SEM and found to have a wrinkled structure, but the start and end points of the ridges (R) were not clear, making it difficult to identify the branching points (B). Furthermore, there were no crater-like depressions (C) surrounded by the ridges (R), and it did not have a specific uneven structure. Needle-like and fibrous structures were also observed on the outermost layer of the particles, resulting in a rough surface.

[0076] [Comparative Example 15: Cross-linked carboxymethylcellulose particles] A 2 wt% aqueous solution of carboxymethylcellulose ammonium (manufactured by Nichirin Chemical Industry Co., Ltd., NA-3L) was prepared. This solution was spray-dried using a GB210-A under the conditions of a spray pressure of 0.15 MPa, a liquid supply rate of 0.35 kg / h, an inlet temperature of 185°C, and an outlet temperature of 100°C, and the powder was recovered in the cyclone section. The obtained powder was heated in a constant temperature dryer (Yamato Scientific Co., Ltd., DKN602) at 110°C for 16 hours to obtain cross-linked carboxymethylcellulose particles.

[0077] [Comparative Example 16: Crosslinked Carboxymethylcellulose Particles] Cross-linked carboxymethylcellulose particles were obtained in the same manner as in Comparative Example 15, except that the granulation conditions were changed to an inlet temperature of 120°C and an outlet temperature of 60°C.

[0078] Table 1 below shows the stock solution composition, spray drying conditions, and average particle size of the cellulose particles obtained in Examples 1-12 and Comparative Examples 1, 4, and 12-16.

[0079] [Table 1]

[0080] [Comparative Example 2: Copper Ammonium Spray Wet Solidification Particles] An aqueous copper-ammonia-cellulose solution was prepared using 5.0 wt% cellulose, 4.0 wt% ammonia, 1.8 wt% copper, and 89.2 wt% water. This solution was sprayed using a two-fluid nozzle (SETO 07507S303+TS303, manufactured by Kirinoikeuchi) at a spray pressure of 0.1 MPa and a liquid supply rate of 1.2 kg / h. A trough was set up facing the two-fluid nozzle and inclined to receive a 10 wt% NaOH aqueous solution from the top of the trough to constantly refresh the liquid level. The mist droplets discharged from the two-fluid nozzle were received in the trough, causing the cellulose to coagulate, and the slurry was collected at the bottom of the trough. The obtained slurry was filtered by suction, and the wet cake was thoroughly washed with pure water. Then, as in Example 1, pickling, washing, drying, grinding, and classification were performed to obtain cellulose particles. The volume-average particle size (Dv50) was 11.0 μm. SEM observation of the surface structure revealed that the particles were approximately spherical with a smooth surface, and no ridges (R) or depressions (C) were observed.

[0081] [Comparative Example 3: Coagulated particles after ammonium copper W / O emulsification] An aqueous solution of copper ammonia cellulose was prepared containing 5.0 wt% cellulose, 4.0 wt% ammonia, 1.8 wt% copper, and 89.2 wt% water. 10 mL of the aqueous copper ammonia cellulose solution was placed in a beaker with 300 mL of silicone oil (Shin-Etsu Chemical Co., Ltd., KF96-10CS), and 1 mL of Triton® X-100 (Sigma-Aldrich Co., Ltd.) was added. This mixture was emulsified by stirring at 8500 rpm for more than 5 minutes using a homogenizer (IKA ULTRA TURRAX T25 easy clean, shaft generator: S25N-18G). While continuing to stir in the homogenizer, 10 mL of acetone (Kanto Chemical Co., Ltd., reagent grade) was added, and stirring in the homogenizer was continued for another 5 minutes to coagulate the cellulose. The resulting slurry was filtered by suction, and then pickled, washed with water, dried, pulverized, and classified in the same manner as in Example 1 to obtain cellulose particles. The volume-average particle size (Dv50) was 4.2 μm. Surface structure observation by SEM revealed that the particles were approximately spherical with a smooth surface, and no ridges (R) or depressions (C) were observed.

[0082] [Comparative Example 5: Cellulose Particles] I obtained commercially available cellulose particles (Cellulobees D-10 manufactured by Daito Chemical Industries).

[0083] [Comparative Example 6: Cellulose Particles] I obtained commercially available cellulose particles (JNC Cellflow C-25).

[0084] [Comparative Example 7: Cellulose Particles] I obtained commercially available cellulose particles (VIVAPUR CS Sensory 5 manufactured by Rettenmeyer).

[0085] [Comparative Example 8: Silica Particles] I obtained commercially available silica particles (Cosmetic Silica CQ10 manufactured by Fuji Silicia Chemical).

[0086] [Comparative Example 9: Cellulose Acetate Particles] I obtained commercially available cellulose acetate particles (Daicel's Belosea S7).

[0087] [Comparative Example 10: Silicone Particles] I obtained commercially available silicone particles (MSP-S110, manufactured by Nikko Rica).

[0088] [Comparative Example 11: Nylon-12 Particles] I obtained commercially available nylon-12 particles (Toray SP-10).

[0089] Furthermore, the measurement results of the particle structure of the particles in Examples 1 to 12 and Comparative Examples 1 to 16 are shown in Table 2 below.

[0090] [Table 2]

[0091] [Evaluation of feel] A sensory evaluation of the feel of the fine particles was conducted using a panel test with 10 participants. The fine particle samples were conditioned overnight in a room at 25°C and 60% humidity to prepare the evaluation samples. Particulates evaluated the feel of the evaluation samples when a small amount was pinched between their fingers and rubbed with their fingertips, from the perspectives of "squeakiness," "moisture," and "slipperiness." Each participant scored the samples relatively on a range of +3 to -3 points, and the average score was calculated from the results. For "squeakiness," the sample with the least squeaky feeling was scored +3 points, and the sample with the strongest squeaky feeling was scored -3 points. For "moisture," the sample with the most moist feel was scored +3 points, and the sample with the driest feel was scored -3 points. For "slipperiness," the sample with the smoothest feel was scored +3 points, and the sample with the most friction was scored -3 points. Regarding the "squeaky feeling," the feel of the particles in Comparative Example 8 was used as a benchmark equivalent to +3 points, and the feel of the particles in Comparative Example 7 was used as a benchmark equivalent to -3 points. These were confirmed before evaluating the other particles. The evaluation results for the particles of Examples 1-12 and Comparative Examples 1-16 are shown in Table 3 below.

[0092] [Table 3]

[0093] The cellulose particles in Examples 1-12 received positive scores for squeaking (low squeaking), while the particles in Comparative Examples 1-7 received negative scores for squeaking (high squeaking), indicating that the cellulose particles of this embodiment have improved squeaking properties. Furthermore, it can be seen that the cellulose particles of this embodiment allow for adjustment of both moistness and slipperiness by controlling specific uneven structures.

[0094] [Evaluation of optical properties] Double-sided tape (Nichiban Nicetack NW-40) was attached to black drawing paper (Maruai PI-N46D), and the fine particle sample was sprinkled onto the double-sided tape. After evenly applying the sample with a makeup brush, any excess powder that did not adhere to the double-sided tape was brushed off to prepare the sample for optical property evaluation. A barium sulfate white plate (Murakami Shikisai Kogyo, 50mm x 50mm) was used as the standard sample. The visible light reflectance of the barium sulfate white plate was measured using a bending-angle photometer (Murakami Shikisai Kogyo GP-5) at an incident angle of -45°. After normalizing the reflected light intensity in the 0° direction to 90 (reference), the relative reflected light intensity of each sample was measured. Five samples for light scattering measurement were prepared for each type of fine particle sample. The average value of the relative reflected light intensity of the five samples was calculated, and the average values ​​of the relative reflected light intensity at each reflection angle were plotted.

[0095] Figure 2 shows the results for the particles of Example 1 and Comparative Examples 5, 6, 8, and 11. From Figure 2, it can be seen that the cellulose particles of Example 1 scatter incident light uniformly in all directions and have a moderate reflected light intensity, meaning they have a certain degree of light transmittance. These results indicate that they have good optical properties. When used, for example, as a cosmetic ingredient, the particles of this embodiment can achieve both soft focus and a natural, bare-skin look.

[0096] The results for the particles in Example 11 are shown in Figure 7. Cellulose particles have strong retroreflectivity, and when used as a cosmetic ingredient, for example, they can suitably exhibit optical properties such as matte finish, soft focus, and UV protection.

[0097] [Tablet Forming Test] A sample powder was prepared by mixing 10 parts by weight of the particle samples described in Examples 1-8 and Comparative Examples 1-11, 55 parts by weight of talc (food additive grade, manufactured by Kosakai Pharmaceutical Co., Ltd.), and 35 parts by weight of mica (synthetic mica pearl interference red RXD, manufactured by Nippon Koken Kogyo Co., Ltd.). 230 mg of the sample powder was filled into a φ6 mm flat tablet mold, and tablet molding was performed using a molding device (Aiko Engineering Co., Ltd., MODEL-1325VCW) under conditions of a compression pressure of 19 kN and holding for 10 seconds. The presence or absence of lateral cracking in the molded products was visually confirmed. As a result, lateral cracking occurred only in the molded product made from the sample powder containing the particles of Comparative Example 8, while lateral cracking did not occur in the other molded products (not shown).

[0098] [Stress at 10% deformation] A compression test of a single cellulose particle was conducted using a microparticle crushing force measuring device (NS-A300, manufactured by NanoSeeds Co., Ltd.). A small amount of the microparticle sample was scattered on the lower pressure plate, and particles with a diameter of approximately 10 μm were selected under microscopic observation to measure the stress at 10% deformation. Measurements were performed on 10 particles per sample, and the average value of the stress at 10% deformation was calculated.

[0099] [Measurement of shear force in powder layers] Using a powder layer shear force measuring device (NS-S500, manufactured by NanoSeeds Co., Ltd.), powder layer shear force measurements were performed, and various physical properties related to moldability were obtained. A particle sample was filled into a shear cell, the top surface of the powder layer was flattened, and then a shear test was conducted with the target indentation load as the indentation control condition. The measurement conditions were as follows: Sample filling amount: 2.5g Sampling frequency: 10Hz Powder layer inner diameter: 15mm Pressing speed: 0.20 mm / second Indentation control conditions: Indentation load: 50N, 100N, or 150N Shear rate: 10 μm / second Shear initiation delay: 100 seconds (after the compression control condition is met) The measured load at the point when the target indentation load was reached and indentation stopped was recorded as the instantaneous maximum vertical load. From the bottom load and indentation load just before shearing began, the following formula was used: Stress transfer rate (%) = (Bottom load / Indentation load) × 100 The stress transfer coefficient was calculated accordingly. A higher stress transfer coefficient indicates less friction between the powder layer and the inner wall of the filling cell, which is preferable when performing compression molding. The compressibility was calculated from the height of the powder layer during initial filling of the particle sample into the shear cell and the height of the powder layer immediately before shearing began. Furthermore, the data obtained from a series of measurements were plotted with vertical stress on the horizontal axis and shear stress on the vertical axis. From this, the powder layer failure envelope PYL was generated, and the maximum principal stress, uniaxial collapse stress, and kinetic friction coefficient were determined. The maximum principal stress refers to the pressure at which a cylindrical compressed powder layer breaks when pressure is applied from above and below while hydrostatic pressure is applied to the sides. The uniaxial collapse stress refers to the pressure at which a cylindrical compressed powder layer breaks when a load is applied from above the cylinder with the side walls removed. Both the maximum principal stress and uniaxial collapse stress are indicators of the strength of the molded body, and the larger the maximum principal stress and uniaxial collapse stress when the same load is applied, the better the moldability of the powder can be judged.

[0100] The results of the 10% deformation stress and powder layer shear force measurements for Example 4, Comparative Examples 5 and 6 are shown in Table 4 below.

[0101] [Table 4]

[0102] The cellulose particles of this embodiment can exhibit higher maximum principal stress and uniaxial collapse stress, particularly uniaxial collapse stress, when compressed and molded under the same target load, compared to existing cellulose particles, thus enabling the development of good moldability.

[0103] [Degree of crystallinity] The crystallinity of the particles in Example 1 was 0.42.

[0104] [Marine biodegradation rate] Biodegradation tests of particulate matter in seawater were conducted in accordance with ASTM D6691. The particulate matter was placed in seawater, and the amount of oxygen consumed during cellulose decomposition was measured for 28 days to evaluate the decomposition rate. At the same time, the decomposition rate of a reference material (Sigma-Aldrich microcrystalline cellulose Avicel PH-101) was evaluated in parallel. After 28 days from the start of the test, samples showing a biodegradation rate of 90% or more compared to the biodegradation rate of the reference material were marked as "○" (sufficiently fast biodegradation rate), and samples showing a biodegradation rate of less than 90% were marked as "×" (slow biodegradation rate), and the marine biodegradation rate was evaluated. Evaluations for both particulate matter and reference material were performed with n=2, and the average value was adopted as the result. The results for Examples 1-12 and Comparative Examples 1-14 are shown in Table 5 below.

[0105] [Table 5]

[0106] The cellulose particles in Examples 1-12 exhibited rapid marine biodegradability.

[0107] [Evaluation of oil absorption ratio] Approximately 0.2 g of the powder sample was weighed onto a petri dish, and commercially available edible salad oil was added drop by drop, mixing with a spatula. The amount of salad oil added (W1) until the sample formed a smooth paste that could be spread without crumbling was measured, and the oil absorption ratio relative to the weight of the powder sample (W2) was calculated using the following formula: Oil absorption rate = W1 / W2×100 (%) It was calculated using [this method].

[0108] [Evaluation of water absorption ratio] Except for replacing salad oil with pure water, the water absorption ratio was calculated using the same method and formula as described above for evaluating the oil absorption ratio. The results for Examples 4, 9, and 12, and Comparative Examples 5-9 and 11 are shown in Table 6 below. The water absorption ratio of Comparative Example 11 could not be measured because the particles were water-repellent.

[0109] [Table 6]

[0110] [Cosmetic composition 1: Sun care composition] Cosmetic composition 1 was obtained by adding various particles in the weight ratios listed in Table 7 to a commercially available sun care product (Atopita Moisturizing UV Cream 29, manufactured by Tanpei Pharmaceutical Co., Ltd.) and mixing thoroughly. The UV-cutting performance and feel upon application of cosmetic composition 1 were evaluated. For UV-cutting performance evaluation, a sunscreen analyzer (UV-2000S, manufactured by Labsphere Co., Ltd.) was used, and a PMMA plate (HELIOPLATE SB6, manufactured by Helioscreen Co., Ltd.) was used as the coating substrate to measure SPF and PA values. The evaluation results for cosmetic composition 1 are shown in Table 7 below.

[0111] [Table 7]

[0112] Cosmetic compositions 1-1 and 1-2, which contained cellulose particles with a specific uneven structure, showed improved SPF and PA values ​​compared to commercially available sun care products, and had a good feel when applied. Cosmetic composition 1-3, which contained cellulose particles without a specific uneven structure, did not show any improvement in SPF value. Cosmetic composition 1-4, which contained fine titanium dioxide particles, showed improved UV protection performance, but had poor spreadability and a sticky feeling when applied to the skin.

[0113] [Cosmetic composition 2: Solid foundation composition] Cosmetic composition 2 was manufactured by mixing various ingredients conventionally used as raw materials for cosmetics. Specifically, each powder was blended in the weight proportions shown in Table 8, mixed in a blender, and then a binder was added and mixed in the weight proportions shown in Table 8 below.

[0114] [Table 8]

[0115] After crushing the material in a crusher, it was passed through a sieve, filled into containers, and then press-molded. No cracks or other defects were observed in the molded products. A sensory evaluation was conducted on the feel of cosmetic composition 2 when applied to the skin. The results showed that cosmetic compositions 2-1, 2-2, and 2-3 had little squeaky feeling and were good, but cosmetic composition 2-4 had a squeaky feeling and was poor. Visual evaluation of the concealment and soft-focus properties when applied to the skin showed that cosmetic composition 2-1 had good soft-focus properties, making fine lines on the skin less noticeable, and cosmetic composition 2-2 showed improved concealment in addition to soft-focus properties. On the other hand, cosmetic compositions 2-3 and 2-4 made fine lines on the skin more noticeable, and their concealment and soft-focus properties were insufficient.

[0116] [Cosmetic composition 3: O / W emulsion type foundation composition] Cosmetic composition 3 was prepared by mixing various ingredients conventionally used as raw materials for cosmetics. Specifically, bentonite, propylene glycol, and purified water were mixed in the weight ratios shown in Table 9 below and subjected to homomixing at 70°C. The remaining aqueous phase components were then added and thoroughly stirred. The thoroughly mixed powder portion was added while stirring and subjected to homomixing at 70°C. Next, the oil phase, which had been heated and dissolved at 70-80°C, was gradually added and subjected to homomixing at 70°C. The resulting mixture was cooled to room temperature while stirring and degassed to obtain cosmetic composition 3.

[0117] [Table 9]

[0118] A sensory evaluation was conducted on the feel of the film after applying cosmetic composition 3 to the skin and allowing it to dry. The results showed that cosmetic compositions 3-1 and 3-2 had a slightly rough texture, but cosmetic composition 3-3 had a reduced rough texture, and cosmetic composition 3-4 had a further reduced rough texture. Visual evaluation of the soft-focus properties also showed that cosmetic compositions 3-3 and 3-4 exhibited better soft-focus properties compared to cosmetic compositions 3-1 and 3-2, with fine lines on the skin being less noticeable.

[0119] [Cosmetic composition 4: W / O emulsion type foundation composition] Cosmetic composition 4 was prepared by mixing various ingredients conventionally used as raw materials for cosmetics. Specifically, in the weight proportions shown in Table 10 below, the aqueous phase was stirred, the thoroughly mixed powder portion was added and subjected to homomixer treatment, the dissolved oil phase was added and subjected to homomixer treatment again, and then degassed to obtain cosmetic composition 4.

[0120] [Table 10]

[0121] Visual evaluation of the soft-focus properties of cosmetic composition 4 upon application to the skin revealed that cosmetic compositions 4-1 and 4-2 exhibited good soft-focus properties, minimizing the appearance of fine lines on the skin. However, cosmetic compositions 4-3 and 4-4 were found to have insufficient soft-focus properties, making fine lines more noticeable. [Industrial applicability]

[0122] The cellulose particles according to the present invention have low squeaking properties, adjustable moistness and slipperiness, excellent optical properties, excellent moldability, and excellent biodegradability. Therefore, the cellulose particles according to the present invention can be suitably used in a variety of fields, such as cosmetic raw materials, texture improvers, visible light scattering agents, infrared scattering agents, resin additives, various fillers, mold release agents, coating agents, paints, scrubbing agents, cleansing agents, adsorbent carriers, filter media, filtration aids, column packing materials, and excipients. [Explanation of Symbols]

[0123] R ridge C. Crater-like depression B. Branch point of the ridge (R) The ridge line (RL) connects two branching points (B) such that it bisects the width of the ridge (R). S1 Area when the entire particle is projected in two dimensions S2 Area of ​​the figure (outline shape) drawn by surrounding a single crater-like depression (C) with a ridge line (RL) Area of ​​the convex hull of the contour shape S3 W Predetermined width of the ridge (R) D Particle size

Claims

1. Cellulose particles having a network of ridges (R) of a predetermined width (W) arranged across the entire surface of the particles, and crater-shaped depressions (C) surrounded by and separated from each other by the ridges (R), wherein branching points (B) to three or more directions exist at various points on the ridges (R).

2. The number of depressions (C) separated from each other by the aforementioned ridges (R) is equal to the surface area of ​​the cellulose particles within 100 μm. ２ The cellulose particles according to claim 1, wherein there are 20 or more and 200 or fewer particles per unit.

3. The cellulose particle according to claim 1 or 2, wherein the predetermined width (W) of the ridge portion (R) is 0.1 μm or more and 2.0 μm or less, and the ratio W / D of the predetermined width (W) to the particle diameter (D) is 0.25 or less.

4. Cellulose particles according to claim 1 or 2, wherein the circularity is 0.8 or greater.

5. The cellulose particle according to claim 1 or 2, wherein the degree of crystallinity of the cellulose constituting the cellulose particle is less than 70%.

6. The cellulose particles according to claim 1 or 2, wherein the cellulose constituting the cellulose particles is regenerated cellulose with a crystal structure of type II.

7. The cellulose particles according to claim 6, wherein the regenerated cellulose has a crystal structure of type II, and the regenerated cellulose is regenerated by the copper ammonia method (cupro).

8. The cellulose particle according to claim 1 or 2, wherein at least one of the contour shapes of the depressions (C) separated from each other by the aforementioned ridges (R) is concave.

9. The cellulose particles according to claim 1 or 2, wherein the proportion of concave shapes among the contour shapes of the depressions (C) separated from each other by the aforementioned ridges (R) is 10% or more.

10. The cellulose particle according to claim 1 or 2, wherein light-scattering solid particles are supported inside or on the surface of the cellulose particle.

11. The cellulose particles according to claim 10, wherein the light-scattering solid particles are any or a combination thereof of titanium oxide, zinc oxide, aluminum oxide, magnesium oxide, zirconium oxide, tin oxide, cerium oxide, barium sulfate, silica, mica, sericite, talc, kaolin, mica, titanium mica, bismuth oxychloride, boron nitride.

12. A cellulose powder which is an aggregate of cellulose particles according to claim 1 or 2, wherein the volume average particle diameter (Dv50) of the cellulose particles is 1 μm or more and 50 μm or less.

13. A cellulose powder which is an aggregate of cellulose particles according to claim 1 or 2, wherein the number proportion of particles having a ratio W / D of 0.15 or less to a particle diameter (D) of a predetermined width (W) is 50% or more.

14. A cosmetic composition comprising the cellulose powder described in claim 12.

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