JP7265331B2 - Porous cellulose particles and cosmetics - Google Patents

Description

TECHNICAL FIELD The present invention relates to porous cellulose particles formed by aggregation of cellulose having good biodegradability, and more particularly to porous cellulose particles with high sphericity and cosmetics containing the same.

In recent years, plastic particles (for example, polyethylene particles) of several hundred micrometers have been blended into cosmetics to improve their tactile characteristics. Most petroleum-derived synthetic polymers (plastic particles) are not decomposed in the natural environment and tend to adsorb chemical substances such as insecticides. As a result, various environmental problems have arisen. For example, plastic products that have flowed into the water environment have accumulated, causing great harm to marine and lake ecosystems. In addition, bioaccumulation may affect the human body.

In recent years, fine plastics with a length of 5 mm or less to nano-level called microplastics have become a big problem. Microplastics include fine particles contained in cosmetics, etc., small lumps of plastic resin before processing, and substances that have become finer as large products float in the sea.

These matters have been pointed out by the United Nations Environment Program, etc., and various countries and industry groups are considering regulations. Therefore, biodegradable plastics, which are decomposed into water and carbon dioxide by microorganisms in the natural environment and incorporated into the carbon cycle of the natural world, have attracted attention.

In addition, there is growing interest in natural cosmetics and organic cosmetics, and guidelines (ISO16128) have been enacted on the display of natural/organic indexes for cosmetics. According to this guideline, raw materials in products are classified into natural raw materials, naturally derived raw materials, and non-natural raw materials, and an index is determined based on the content of each raw material. In the future, indices calculated according to this guideline will be displayed on products. Therefore, it is required to use naturally derived raw materials, and further natural raw materials.

Against this background, plant-derived cellulose particles with good biodegradability have attracted attention. Conventionally, it is known to obtain spherical regenerated cellulose particles of 9 to 400 nm by neutralizing a cuprammonium solution in which cellulose is dissolved with an acid (see, for example, Patent Document 1). It is also known to obtain spherical regenerated cellulose particles by spraying a solution of copper ethylenediamine in which cellulose is dissolved into a coagulation liquid (see, for example, Patent Document 2). These regenerated cellulose particles are produced using type II crystalline cellulose obtained by a process of intentional chemical modification. As defined in the aforementioned guidelines, such regenerated cellulose particles are classified as naturally occurring raw materials. On the other hand, it is also known to obtain type I crystalline cellulose by a process that does not involve intentional chemical modification, and apply cellulose particles formed using this to scrub agents and cosmetics (see, for example, Patent Documents 3).

WO2008/084854 International Publication JP 2013-133355 A JP 2017-88873 A

In order to use cellulose particles in cosmetics as an alternative to plastic beads, the following two points are required for cellulose particles.
(1) Being formed of type I crystalline form cellulose obtained by a process without intentional chemical modification in order to be considered a natural source;
(2) To have high sphericity and good fluidity, and to improve the feel characteristics of cosmetics.

The regenerated cellulose particles described in US Pat. In addition, the cellulose particles described in Patent Document 3 have a sphericity of 0.1 to 0.7, and could not provide cosmetics with good tactile characteristics.

Therefore, an object of the present invention is to realize porous cellulose particles having both high sphericity and good fluidity by using type I crystalline cellulose obtained by a process without intentional chemical modification. be. Cosmetics containing such porous cellulose particles are less likely to cause environmental problems, and can provide the same tactile characteristics as conventional plastic beads.

The porous cellulose particles according to the present invention are particles in which crystalline cellulose is aggregated, and have an average particle diameter d ₁ of 5 to less than 500 nm, a specific surface area of 25 to 1000 m ² /g, and a sphericity of 0.5 nm. 85 or more. Here, the crystalline cellulose has a type I crystal form with glucose molecules as constituent units.

Also, the pore volume PV is set in the range of 0.2 to 5.0 ml/g. Furthermore, the average pore diameter PD is set in the range of 2 to 100 nm. In addition, crystalline cellulose having an average particle diameter _d3 of 1 to 200 nm was used.

Furthermore, when the aqueous dispersion of porous cellulose particles was dispersed for 60 minutes using an ultrasonic disperser, the ratio of the average particle size _d2 after dispersion to the average particle size _d1 before dispersion ( _d2 / d ₁ ) is in the range of 0.95 to 1.05.

The method for producing porous cellulose particles according to the present invention includes an emulsification step of preparing an emulsion containing emulsified liquid droplets by mixing a dispersion of crystalline cellulose in the type I crystal form, a surfactant, and a non-aqueous solvent. and a dehydration step for dehydrating the emulsified droplets, and a step for solid-liquid separation of the non-aqueous solvent dispersion obtained in the dehydration step to obtain porous cellulose particles as a solid matter.

Any of the porous cellulose particles described above can be blended with a cosmetic ingredient to prepare a cosmetic.

The porous cellulose particles according to the present invention are formed by aggregating crystalline cellulose having "type I crystalline form with glucose molecules as constituent units" (hereinafter simply referred to as "type I crystalline cellulose"). ing. The porous cellulose particles have an average particle diameter (d ₁ ) of 5 to less than 500 nm, a sphericity of 0.85 or more, and a specific surface area of 25 to 1000 m ² /g. Such particles provide tactile properties similar to plastic beads. The average particle size affects the tactile properties of cosmetics. If the average particle size is less than 5 nm, the fluidity of the particles is low, and uniform spreadability cannot be obtained, resulting in a marked reduction in touch feeling. On the other hand, when the average particle size is 500 nm or more, the spreadability is high, so that the soft and moist feeling cannot be obtained when the powder is touched. In particular, the average particle diameter (d ₁ ) is preferably 10-300 nm. Here, the average particle size (d ₁ ) was obtained by laser diffraction method.

Also, if the specific surface area of the particles is less than 25 m ² /g, they cannot biodegrade at a sufficient rate when released into an aqueous environment. On the other hand, when the specific surface area exceeds 1000 m ² /g, the particles become brittle and may collapse when applied to the skin. A specific surface area of 50 to 500 m ² /g is particularly preferred.

Also, a cosmetic containing particles having a sphericity of less than 0.85 does not have good rolling properties. A sphericity of 0.90 or more is particularly preferable. Here, the sphericity was obtained by an image analysis method from a scanning electron microscope photograph.

Furthermore, the particle variation coefficient (CV) of the porous cellulose particles is preferably 50% or less. If the coefficient of variation of particles exceeds 50%, uniform rolling properties cannot be obtained. Although the smaller the coefficient of variation of particles, the better, it is industrially difficult to obtain particles with a narrow distribution of less than 1%. If it is about 3% or more, there is no particular problem in manufacturing. The particle variation coefficient is preferably 3 to 40%, particularly 3 to 30%.

Furthermore, the pore volume (PV) is preferably 0.2-5.0 ml/g, and the average pore diameter (PD) is preferably 2-100 nm. Particles with a pore volume of less than 0.2 ml/g have low elasticity, and therefore it is difficult to obtain soft touch characteristics. On the other hand, particles exceeding 5.0 ml/g are fragile in strength and may disintegrate when applied to the skin. A pore volume of 0.2 to 2.0 ml/g is particularly preferred. On the other hand, when the average pore diameter is less than 2 nm, the biodegradability is lowered although the tactile properties are not significantly affected. On the other hand, if it exceeds 100 nm, the strength of the particles becomes brittle.

If the porous cellulose particles are disintegrated during the manufacturing process of the cosmetic, there is a risk that the initially assumed functions may not be obtained. Therefore, it is desirable that the average particle size does not change during the manufacturing process. Therefore, the porous cellulose particles were dispersed in distilled water, and ultrasonic waves were applied to this dispersion for 60 minutes using an ultrasonic disperser. The ratio (d ₂ /d ₁ ) between the average particle size d ₂ after the dispersion test and the average particle size d ₁ before the test is preferably 0.95 to 1.05. A ratio (d ₂ /d ₁ ) of less than 0.95 indicates that the strength of the particles is low. In other words, there is a possibility that the particles may collapse due to the mechanical load in the manufacturing process, and the effect of improving the texture may not be obtained. On the other hand, the fact that this ratio (d ₂ /d ₁ ) exceeds 1.05 indicates that the crystalline cellulose swells in water. Therefore, the cosmetics tend to thicken after the manufacturing process, and quality stability cannot be ensured. Furthermore, the tactile properties may also change. This ratio (d ₂ /d ₁ ) is particularly preferably 0.97 to 1.03.

Moreover, the porous cellulose particles may have a hollow structure in which a cavity is formed inside the outer shell. Since such hollow particles are lighter than solid particles of the same diameter, the number of particles contained in the same weight is greater than that of solid particles. Here, the outer shell is porous, and preferably has porosity to the extent that nitrogen gas can pass through. Furthermore, the ratio (T/OD) of the outer shell thickness T to the outer diameter OD of the porous cellulose particles is preferably in the range of 0.02 to 0.45. When this ratio (T/OD) exceeds 0.45, it becomes substantially equivalent to solid particles. On the other hand, if this ratio is less than 0.02, the particles tend to disintegrate. The ratio (T/OD) is particularly preferably in the range of 0.04-0.30.

The type I crystalline cellulose that forms the porous cellulose particles preferably has an average particle size _d3 in the range of 1 to 200 nm. Porous cellulose particles formed of particles with a fine average particle size exhibit good biodegradability.

Crystalline cellulose having type I crystals can be obtained by subjecting cellulose fibers obtained by cooking plant fibers or commercially available cellulose powder (Seolus (registered trademark) PH-101 manufactured by Asahi Kasei Co., Ltd.) to mechanical processing such as a water jet method or TEMPO. Obtained by fibrillation by chemical treatment such as oxidation method. In addition, cellulose nanofibers and cellulose nanocrystals are suitable. Alternatively, commercially available aqueous dispersions (e.g., Ceolus RC manufactured by Asahi Kasei Corporation, Rheocrysta (registered trademark) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., BiNFi-s (registered trademark) manufactured by Sugino Machine Co., Ltd., Fibnano manufactured by Kusano Sakuko Co., Ltd., etc.) It may be used as a type of crystalline cellulose.

Here, the porous cellulose particles may contain not only type I crystalline cellulose but also other types II to IV crystalline cellulose. However, it is desirable to contain 50% by weight or more of type I crystalline cellulose. The content of type I crystalline cellulose is preferably 75% or more, more preferably 90% or more. The higher the content, the higher the naturalness index according to the aforementioned guidelines. The crystalline form of cellulose can be identified by infrared spectroscopy, and strong absorption is observed at 3365 to 3370 cm ^-1 in the type I crystalline form. In addition, it can be identified from the difference in chemical shift by solid-state 13C-NMR method and the diffraction angle by X-ray diffraction method. The crystal form may be either Iα or Iβ, or a mixture.

<Method for producing porous cellulose particles>
Next, a method for producing porous cellulose particles will be described. First, a dispersion of type I crystalline cellulose, a surfactant, and a non-aqueous solvent are mixed and emulsified (emulsification step). As a result, an emulsified liquid containing emulsified droplets is obtained. Next, the emulsion is dehydrated (dehydration step). This removes the water in the emulsified droplets. Next, solid-liquid separation is performed to take out the porous cellulose particles as a solid (solid-liquid separation step). By drying and pulverizing this solid (drying step), a powder of porous cellulose particles is obtained. The sphericity of the obtained porous cellulose particles is 0.85 or more.

Each step will be described in detail below.

[Emulsification process]
First, a dispersion of type I crystalline cellulose is prepared. The solid content concentration of this dispersion is adjusted in the range of 0.01 to 5% to obtain a dispersion with an appropriate viscosity. If the solids concentration exceeds 5%, the viscosity usually increases and the homogeneity of the emulsified droplets may be impaired. Solids concentrations of less than 0.01% are not economically viable and offer no particular advantage. The solid content concentration of the dispersion liquid is particularly preferably 0.1 to 3.0%. Water is preferable as the solvent for the dispersion.

This dispersion is mixed with a non-aqueous solvent and a surfactant. The non-aqueous solvent is necessary for emulsification and should be incompatible with water. Common hydrocarbon solvents can be used as the non-aqueous solution. Surfactants are added to form water-in-oil emulsified droplets. The HLB value of the surfactant is suitable in the range of 1-10. An optimum HLB value may be selected according to the polarity of the non-aqueous solvent. The HLB value is particularly preferably in the range of 1-5. Also, surfactants with different HLB values may be combined.

Next, this mixed solution is emulsified by an emulsifier. At this time, emulsification conditions are set so as to obtain an emulsified liquid containing emulsified droplets with an average diameter of 5 nm to 5 μm. Type I crystalline cellulose dispersed in water is present in the emulsified droplets. A common high-speed shearing device can be used for the emulsifying device. In addition, known devices such as a high-pressure emulsifier capable of obtaining finer emulsified droplets, a membrane emulsifier capable of obtaining more uniform emulsified droplets, and a microchannel emulsifier can be selected according to the purpose.

The average diameter of emulsified droplets was measured as follows. An emulsified liquid is dropped onto a slide glass, and a cover glass is placed thereon. Using a digital microscope (VHX-600, manufactured by Keyence Corporation), images are taken through a cover glass at a magnification of 30 to 2000 times to obtain a photographic projection of the emulsified droplets. 50 droplets are arbitrarily selected from this photographic projection, and the equivalent circle diameter is calculated by the attached software. The average value of these 50 equivalent circle diameters was taken as the average diameter (average droplet diameter).

[Dehydration process]
Next, the emulsified liquid obtained in the emulsifying step is dehydrated. Water is evaporated by heating under normal or reduced pressure. As a result, water is removed from the emulsified droplets, and a non-aqueous solvent dispersion containing porous cellulose particles (aggregates of type I crystalline cellulose) having a particle size of 5 to less than 500 nm is obtained.

For example, in the heat dehydration method under normal pressure, a separable flask equipped with a cooling tube is heated to perform dehydration while recovering the non-aqueous solvent. In the heat dehydration method under reduced pressure, dehydration is performed by heating under reduced pressure using a rotary evaporator, an evaporator, or the like, while recovering the non-aqueous solvent. It is preferable to perform dehydration to such an extent that the porous cellulose particles can be taken out as a solid matter from the non-aqueous solvent dispersion in the solid-liquid separation step described later. If the dehydration is insufficient, the form of spherical particles cannot be maintained in the solid-liquid separation step.

[Solid-liquid separation step]
In the solid-liquid separation step, a solid content is separated from the non-aqueous solvent dispersion obtained in the dehydration step by a conventionally known method such as filtration or centrifugation. This gives a cake of porous cellulose particles.

Furthermore, the obtained cake-like substance may be washed. Thereby, the surfactant can be removed. When the porous cellulose particles are incorporated into a liquid preparation such as an emulsion, the surfactant may impede long-term stability. Therefore, the residual amount of the surfactant contained in the porous cellulose particles is preferably 500 ppm or less. In order to reduce the amount of surfactant, it is preferable to wash with an organic solvent.

[Drying process]
In the drying step, the non-aqueous solvent contained in the cake-like substance obtained in the solid-liquid separation step is evaporated by heating under normal pressure or reduced pressure. As a result, a dry powder of porous cellulose particles having a sphericity of 0.85 or more and an average particle diameter of 5 to less than 500 nm is obtained.

Further, the dehydration step may be performed after cooling the emulsion liquid obtained in the emulsification step to within the range of -50 to 0°C. That is, the water in the emulsified droplets is frozen to form a frozen emulsion. After returning the frozen emulsion to room temperature, the dehydration step is performed. When the freezing temperature is -50°C to -10°C, solid porous cellulose particles are obtained. When the temperature is -10 to 0°C, porous cellulose particles having a hollow structure are obtained. At a temperature of about -10 to 0°C, ice crystals grow gradually. As the crystal grows, the crystalline cellulose (primary particles) in the droplet is expelled to the periphery of the droplet. Therefore, a cavity is formed inside the outer shell.

<Cosmetics>
Cosmetics can be prepared by blending the porous cellulose particles described above and various cosmetic ingredients. Such a cosmetic provides the same rolling feeling as that of inorganic particles (silica particles) of a single component, the durability of the rolling feeling, and uniform spreadability, and the same soft and moist feeling as that of plastic beads. Obtainable. That is, it is possible to satisfy the typical feel properties required for feel improvers for cosmetics.

Specific cosmetics are exemplified in Table 1 by category. Such cosmetics can be produced by conventionally known general methods. Cosmetics are used in various forms such as powder, cake, pencil, stick, cream, gel, mousse, liquid and cream.

Table 2 shows representative classifications and components of various cosmetic ingredients. In addition, the Standards for Quasi-drug Ingredients 2006 (published by Yakuji Nippo Co., Ltd., June 16, 2006), International Cosmetic Ingredient Dictionary and Handbook (published by The Cosmetic, Toiletry, and Fragrance Association, Eleventh Edition 2006), etc. You may mix the cosmetic ingredients listed in.

Examples of the present invention will be specifically described below.

[Example 1]
First, a dispersion of type I crystalline cellulose is prepared. In this example, 50 g of I-type cellulose (Seolus PH-101 manufactured by Asahi Kasei Co., Ltd.) was suspended in 4950 g of pure water. This suspension was passed through a microfluidizer (M-7250-30 manufactured by Microfluidex Co., Ltd.) 200 times to prepare a dispersion having a solid concentration of 1%.

This dispersion is mixed with a water-insoluble solvent and a surfactant. In this example, 200 g of this dispersion was added to a mixed solution of 3346 g of heptane (manufactured by Kanto Chemical Co., Ltd.) and 25 g of surfactant AO-10V (manufactured by Kao Corporation). This mixed solution was passed through a microfluidizer at a pressure of 100 MPa. This resulted in an emulsified liquid containing emulsified droplets. This emulsion was heated at 60° C. for 16 hours to dehydrate the emulsified droplets. Furthermore, centrifugation treatment was performed at 10000 G for 10 minutes for solid-liquid separation. The sediment obtained was dispersed in heptane and centrifuged again. This operation was repeated three times to remove the surfactant. The resulting cake was dried at 60°C for 12 hours. This dry powder was sieved through a 250 mesh sieve (JIS test standard sieve) to obtain a powder of porous cellulose particles.

Table 3 shows the preparation conditions of the porous cellulose particles. Further, the physical properties of the powder of porous cellulose particles were measured by the following methods. Table 4 shows the results.

(1) Average particle size of each particle (d ₁ , d ₃ )
The particle size distribution of each particle was measured using a laser diffraction method. The median value was obtained from this particle size distribution and used as the average particle size. Thus, the average particle size d1 of the porous cellulose particles and the average particle size d3 of the type I crystalline cellulose were obtained. Here, the particle size distribution was measured using a laser diffraction/scattering particle size distribution analyzer LA-950v2 (manufactured by HORIBA, Ltd.). However, for the average particle size d3 of fibrous type I crystalline cellulose represented by cellulose nanofibers, cellulose nanocrystals, etc., using the formula "average particle size = 6000 ÷ (true density × specific surface area)" The average particle size in terms of equivalent spheres was calculated.

(2) Average Particle Size Ratio Before and After Ultrasonic Dispersion Dispersion was performed with a laser diffraction/scattering particle size distribution analyzer (LA-950v2) under the dispersing condition of "ultrasonic wave for 60 minutes". The particle size distribution of the dispersed porous cellulose particles was measured. The median value of this particle size distribution was defined as the average particle size _d2 after ultrasonic dispersion. From this, the ratio (d ₂ /d ₁ ) of the average particle size before and after ultrasonic dispersion was obtained.

(3) Sphericality of Porous Cellulose Particles Using a transmission electron microscope (manufactured by Hitachi Ltd., H-8000), photographs are taken at a magnification of 2000 to 250,000 times to obtain photographic projections. Arbitrarily selected 50 particles from this photographic projection, the maximum diameter DL and the short diameter DS perpendicular thereto were measured to obtain the ratio (DS/DL). Their average value was taken as the sphericity.

(4) Specific Surface Area of Porous Cellulose Particles About 30 ml of the powder of porous cellulose particles was collected in a magnetic crucible (B-2 type), dried at a temperature of 105° C. for 2 hours, placed in a desiccator and cooled to room temperature. . Next, 1 g of a sample was taken, and the specific surface area (m ² /g) was measured by the BET method using a fully automatic surface area measuring device (manufactured by Yuasa Ionics, Multisorb Model 12). The density of type I crystalline cellulose (1.5 g/cm ³ ) blended in the porous cellulose particles was used as a conversion value to determine the specific surface area per unit volume.

(5) Pore Volume and Average Pore Diameter of Porous Cellulose Particles 10 g of porous cellulose particle powder was placed in a crucible, dried at 105° C. for 1 hour, placed in a desiccator and cooled to room temperature. Then, a 0.15 g sample is placed in the cleaned cell, and nitrogen gas is adsorbed onto the sample while vacuum deaeration is performed using Belsorp mini II (manufactured by Bell Japan), followed by desorption. From the obtained adsorption isotherm, the average pore diameter is calculated by the BJH method. Also, the pore volume was calculated from the formula “pore volume (ml/g)=(0.001567×(V−Vc)/W)”. Here, V is the standard adsorption amount (ml) at a pressure of 735 mmHg, Vc is the cell blank capacity (ml) at a pressure of 735 mmHg, and W is the mass of the sample (g). Also, the density ratio of nitrogen gas to liquid nitrogen was set to 0.001567.

[Example 2]
In the same manner as in Example 1, a dispersion of type I crystalline cellulose having a solid concentration of 1% was prepared. 200 g of this dispersion, 3346 g of heptane and 25 g of surfactant (AO-10V) were mixed. This mixed solution was emulsified by passing it through a microfluidizer at a pressure of 100 MPa. The emulsified liquid thus obtained was allowed to stand in a constant temperature bath at -5°C for 72 hours to freeze the water in the emulsified droplets. After that, the temperature was raised to normal temperature and thawed. Furthermore, centrifugation treatment was performed in the same manner as in Example 1, and washing was repeated with heptane to remove the surfactant. A powder of porous cellulose particles was obtained from the obtained cake-like substance in the same manner as in Example 1, and the physical properties of this powder were measured.

The internal structure of the porous cellulose particles obtained in this example was examined. After uniformly mixing 0.1 g of powder with about 1 g of epoxy resin (EPO-KWICK manufactured by BUEHLHER) and curing at room temperature, a sample was prepared using an FIB processing apparatus (FB-2100 manufactured by Hitachi, Ltd.). . Using a transmission electron microscope (HF-2200, manufactured by Hitachi, Ltd.), an SEM image of this sample was taken under the condition of an acceleration voltage of 200 kV. As a result, the particles had a hollow structure in which a cavity was formed inside the outer shell. From this SEM image, the thickness T and the outer diameter OD of the outer shell were measured to obtain the outer shell thickness ratio (T/OD).

[Example 3]
An emulsion was prepared in the same manner as in Example 2. This emulsion was allowed to stand in a freezer at -25°C for 72 hours. Thereafter, porous cellulose particles were prepared in the same manner as in Example 2, and physical properties were measured.

[Example 4]
Using BiNFi-s WMa-10002 (manufactured by Sugino Machine Co., Ltd.) as type I cellulose in place of Ceolus PH-101 in Example 1, a dispersion having a solid concentration of 1% was prepared. Thereafter, porous cellulose particles were prepared in the same manner as in Example 1, and physical properties were measured.

[Example 5]
In this example, the mixed solution was passed through a microfluidizer at a pressure of 50 MPa during emulsification. Except for this, porous cellulose particles were prepared in the same manner as in Example 1, and physical properties were measured.

[Example 6]
Using I-2SP manufactured by Daiichi Kogyo Seiyaku Co., Ltd. as I-type cellulose instead of Ceolus PH-101 in Example 1, a dispersion having a solid concentration of 1% was prepared. Also, the number of times the liquid was passed through the microfluidizer during emulsification was changed to 5 times. Except for this, porous cellulose particles were prepared in the same manner as in Example 1, and physical properties were measured.

[Comparative Example 1]
Porous cellulose particles were prepared in the same manner as in Example 4, except that the emulsion was dehydrated at 40° C. for 4 hours, and its physical properties were measured.

[Comparative Example 2]
In this comparative example, aggregated particles of crystalline cellulose were produced by a spray drying method without using an emulsifying method. First, 20 g of Asahi Kasei Seilus PH-101, 75 g of urea, 23 g of lithium hydroxide and 5000 g of distilled water were mixed. This mixture was cooled in a constant temperature bath at -25°C for 2 hours. By raising the temperature to room temperature and thawing, a solution in which cellulose is dissolved is obtained. This solution was used as a spray liquid and spray-dried with a spray dryer (NIRO-ATMIZER manufactured by NIRO). That is, in a dry air stream with an inlet temperature of 150 ° C. and an outlet temperature of 50 to 55 ° C., the liquid is sprayed from one of the two-fluid nozzles at a flow rate of 2 L / hr, and the gas is sprayed from the other nozzle at a pressure of 0.15 MPa. It was fed and spray dried. The dry powder thus obtained is cellulose with a type II crystalline form. This was suspended in pure water and centrifuged at 10,000 G for 10 minutes for solid-liquid separation. The sediment obtained was dispersed in pure water and centrifuged again. This operation was repeated 5 times to obtain a cake-like substance. This cake-like material was dried at 120° C. for 16 hours and then sieved through a 250-mesh sieve (JIS test standard sieve) to obtain a powder of porous cellulose particles. The physical properties of this powder were measured in the same manner as in Example 1.

[Features of Porous Cellulose Particle Powder]
Next, the tactile properties of the powders obtained in each example and comparative example were evaluated. Each powder was subjected to a sensory test by a panel of 20 specialists, and was evaluated in seven categories: smoothness, moistness, rollability, uniform spreadability, adhesion to skin, durability of rollability, and softness. An interview survey was conducted regarding the items. Each person's evaluation points based on the evaluation point criteria (a) were totaled, and the tactile characteristics were evaluated based on the evaluation criteria (b). Table 5 shows the results. As a result, it was found that the powders of each example are extremely excellent as feel-improving materials for cosmetics, but the powders of comparative examples are not suitable as feel-improving materials.
Evaluation point criteria (a)
5 points: very good 4 points: excellent 3 points: average 2 points: poor 1 point: very poor Criterion (b)
◎: Total score is 80 or more ○: Total score is 60 or more and less than 80 △: Total score is 40 or more and less than 60 ▲: Total score is 20 or more and less than 40 ×: Total score is less than 20

[Usage of powder foundation]
A powder foundation was prepared using the powder of porous cellulose particles so as to have a blending ratio (% by weight) shown in Table 6. That is, the powder of each example was used as component (1), and the components (2) to (9) were placed in a mixer and stirred to uniformly mix. Next, the cosmetic ingredients (10) to (12) were added to the mixer and stirred to mix evenly. After pulverizing the obtained cake-like material, about 12 g was taken out of the material, placed in a square plate of 46 mm×54 mm×4 mm, and press-molded. The powder foundation thus obtained was subjected to a sensory test by 20 expert panelists. Interviews were conducted on six evaluation items: uniform spread, moist feeling, and smoothness during application to the skin, and uniformity, moist feeling, and softness of the cosmetic film after application to the skin. Each person's evaluation points based on the evaluation point criteria (a) described above were totaled, and the feeling of use of the foundation was evaluated based on the evaluation criteria (b) described above. Table 7 shows the results. It was found that the cosmetics A to F according to Examples had an excellent feeling during use and after application. However, it was found that the cosmetics a and b of the comparative examples did not give a good feeling when used.

Claims (7)

Porous cellulose particles formed by aggregation of crystalline cellulose,
The crystalline cellulose is a type I crystal form with glucose molecules as constituent units,
The porous cellulose particles have an average particle diameter (d ₁ ) of 5 to less than 500 nm, a specific surface area of 25 to 1000 m ² /g, and a sphericity of 0.85 or more. 2. Porous cellulose particles according to claim 1, characterized in that the pore volume (PV) is between 0.2 and 5.0 ml/g. 3. The porous cellulose particles according to claim 1, wherein the average pore diameter (PD) is 2-100 nm. When the aqueous dispersion of the porous cellulose particles was dispersed for 60 minutes using an ultrasonic disperser, the ratio of the average particle size _d2 after dispersion to the average particle size _d1 before dispersion ( _d2 /d ₁ ) is in the range of 0.95 to 1.05. The porous cellulose particles according to any one of claims 1 to 4, wherein the average particle diameter (d ₃ ) of the crystalline cellulose is in the range of 1 to 200 nm. 6. The porous cellulose particles according to any one of claims 1 to 5, wherein the porous cellulose particles are hollow particles having a cavity inside an outer shell. A cosmetic containing the porous cellulose particles according to any one of claims 1 to 6.