Porous cellulose particles

Abstract

Porous cellulose particles having a compressive elastic modulus of 50 MPa or less, a specific surface area of 100 m2 / g or more and less than 500 m2 / g, and a pore volume of 1.5 mL / g or more.

Description

Technical Field

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

[0002] It is known that functional polymer particles are used as additives for perfumes and cosmetics in order to impart a soft touch (elasticity), a dry touch, or a sebum-capturing function. Most of these polymer particles are compounded with synthetic polymers (microplastic beads) with a particle size of several μm. However, from an environmental perspective, the use of microplastic beads is expected to be restricted in the future.

[0003] Therefore, as particles that do not belong to microplastic beads, polymer particles of natural polymer materials with biodegradability have attracted attention. As one example of such polymer particles, cellulose particles that have not been chemically modified can be cited.

[0004] Porous cellulose particles are known as functional cellulose particles used in cosmetics. Porous cellulose particles are preferred because they can enclose the functional substances in the cosmetics in the particles.

[0005] For example, Patent Document 1 discloses porous microcellulose particles for use as a cosmetic additive, which have a crystal form of type I and a specific surface area of ​​20 m 2 / g or more and the volume of pores with a diameter of 0.01 μm or more is 0.3 cm 3 / g or more porous structure, with an average particle size of up to 100μm.

[0006] Patent Document 2 discloses a porous cellulose particle which is formed by agglomeration of crystalline cellulose of type I crystal form, has an average particle size d1 of less than 0.5 to 50 μm, and a specific surface area of ​​25 to 1000 m 2 / g, and a sphericity of 0.85 or more, and it is described that a cosmetic containing the porous cellulose particles has excellent touch properties.

[0007] Research has also been conducted on methods for producing porous cellulose particles. For example, Patent Document 3 describes a method for producing porous cellulose particles, which can be produced more simply without using a harmful solvent, and includes: preparing a cellulose diacetate solution by dissolving the cellulose diacetate in a solvent; dispersing the cellulose diacetate solution in a medium that is immiscible with the cellulose diacetate solution to obtain a dispersion; cooling the dispersion; precipitating cellulose diacetate particles by adding a poor solvent to the cooled dispersion; and saponifying the cellulose diacetate particles.

[0008] Patent document 4 discloses a method for producing porous cellulose beads, which is characterized in that a cellulose dispersion prepared by mixing an alkaline aqueous solution in a specified temperature range with cellulose is brought into contact with a coagulation solvent. It is described that porous cellulose beads with high mechanical strength can be produced without using toxic or highly corrosive by-raw materials and without going through industrially disadvantageous complicated processes.

[0009] Patent document 5 discloses that: cellulose is dissolved in an alkaline aqueous solution within a specified temperature range, and after preparing the cellulose solution, heating, emulsion preparation, and cellulose beads precipitation are carried out under specified conditions, followed by cross-linking. In this way, porous cross-linked cellulose beads having a pore structure suitable for antibody adsorption can be simply and efficiently manufactured without using highly toxic and corrosive by-raw materials and without going through industrially unfavorable complicated processes.

[0010] Patent Document 6 discloses a particle size of 1 to 2500 μm, an average pore size of 200 to 1000 μm, and a specific surface area of ​​500 to 800 m 2 / g, a water content of 86-93%, a pore volume of 1.00-5.00 ml / g, and a porosity of 90-95%, and a method for preparing the same.

[0011] Prior art literature

[0012] Patent Literature

[0013] Patent Document 1: Japanese Patent Application Laid-Open No. 2-84401

[0014] Patent Document 2: International Publication No. 2020 / 004604

[0015] Patent Document 3: International Publication No. 2015 / 029790

[0016] Patent Document 4: Japanese Patent Application Publication No. 2017-14528

[0017] Patent Document 5: Japanese Patent Application Publication No. 2021-161246

[0018] Patent Document 6: Chinese Patent Application Publication No. 101250267 Summary of the invention

[0019] Problems to be solved by the invention

[0020] Functional particles incorporated into cosmetics are required to impart excellent tactile properties such as soft touch and less roughness during application. In addition, in the case of porous particles, it is desired that the functional substance can be enclosed and that the particles can be disintegrated by the application action when the cosmetics are applied to the object, thereby slowly releasing the functional substance into the object.

[0021] The porous cellulose particles described in Patent Document 1 are crystalline cellulose of type I crystal form, and therefore are hard particles, and it is believed that a rough feeling is produced when the particles disintegrate due to the coating action. In addition, the pore capacity of the porous cellulose particles disclosed in the examples is all below 1 mL / g, and it is believed that the inclusion of the functional substance is insufficient.

[0022] The porous cellulose particles described in Patent Document 2 are also aggregates of crystalline cellulose of type I crystal form. The porous cellulose particles are described to have good tactile properties, but there is no description or suggestion of the inclusion and sustained release of functional substances. In addition, the pore capacity of the porous cellulose particles disclosed in the examples of Patent Document 2 is all below 1 mL / g, and it is believed that the inclusion of functional substances is insufficient.

[0023] The porous cellulose particles described in Patent Document 3 and the porous cellulose beads described in Patent Document 4 are both used for chromatographic fillers, etc., and have a large average particle size, so it is believed that they have poor tactile properties when used in cosmetics. In addition, the particles used in chromatographic fillers are preferably high in strength, so according to these documents, it is not conceivable that the porous cellulose particles disintegrate during coating.

[0024] The porous cross-linked cellulose beads described in Patent Document 5 are hard particles due to cross-linking treatment. In addition, it is also described that the cellulose beads are also suitable for chromatographic adsorbents, affinity adsorbents, etc., and have a lower porosity than particles for cosmetic applications that are assumed to disintegrate by coating.

[0025] The cellulose fine particles described in Patent Document 6 have a large specific surface area and a high water content.

[0026] The present invention relates to porous cellulose particles which can impart a soft touch when added to cosmetics, have less roughness when applied, and are excellent in the inclusion of functional substances and the disintegration of particles.

[0027] Means for solving problems

[0028] The present inventors have found that the above-mentioned problems can be solved by using porous cellulose particles having a compression elastic modulus, a specific surface area, and a pore volume within predetermined ranges.

[0029] That is, the present invention relates to the following contents.

[0030] [1] A porous cellulose particle having a compressive elastic modulus of 50 MPa or less and a specific surface area of ​​100 m 2 / g or more and less than 500m 2 / g, and the pore volume is 1.5mL / g or more.

[0031] [2] A cosmetic comprising the porous cellulose particles described in [1] above.

[0032] [3] A method for producing the porous cellulose particles according to [1], comprising the following steps (I) to (V) in order.

[0033] Step (I): a step of mixing raw material cellulose with an alkaline aqueous solution to prepare a cellulose aqueous solution

[0034] Step (II): a step of mixing the above-mentioned cellulose aqueous solution with an organic solvent to prepare a cellulose emulsion

[0035] Step (III): a step of mixing the cellulose emulsion with a solvent that does not dissolve cellulose to precipitate crude cellulose particles and obtain a suspension containing crude cellulose particles

[0036] Step (IV): After solid-liquid separation of the suspension containing crude cellulose particles, the obtained wet crude cellulose particles are washed to obtain purified wet cellulose particles.

[0037] Step (V): Drying the wet purified cellulose particles to obtain porous cellulose particles

[0038] Effects of the Invention

[0039] According to the present invention, there can be provided porous cellulose particles which can impart a soft touch when added to cosmetics, have less roughness when applied, and are excellent in the inclusion of functional substances and the disintegration of particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is an X-ray diffraction pattern of the raw material cellulose (cellulose I type crystal) used in the examples.

[0041] Figure 2 This is the X-ray diffraction pattern of the porous cellulose particles (cellulose II type crystals) obtained in Example 1.

[0042] Figure 3 This is the X-ray diffraction pattern of the porous cellulose particles (amorphous) obtained in Example 4. DETAILED DESCRIPTION

[0043] [Porous cellulose particles]

[0044] The porous cellulose particles of the present invention have a compression modulus of 50 MPa or less and a specific surface area of ​​100 m 2 / g or more and less than 500m 2 / g and porous cellulose particles with a pore volume of 1.5 mL / g or more.

[0045] The porous cellulose particles of the present invention have the above-mentioned structure, so that when formulated into cosmetics, they can provide a soft touch, less roughness during application, and are excellent in the inclusion of functional substances and the disintegration of particles. The reasons are not yet clear, but are believed to be as follows.

[0046] It is believed that by making the compression elastic modulus of the porous cellulose particles below a specified value, a soft touch can be imparted, the roughness when applied to an object is suppressed, and the object is easily disintegrated due to the application action. In addition, it is believed that by making the specific surface area and pore volume of the porous cellulose particles above a specified value, the inclusion of the functional substance is improved.

[0047] From the viewpoint of soft touch, less roughness when applied to an object, and improved disintegration caused by the application action on the object, the compressive elastic modulus of the porous cellulose particles is 50 MPa or less, preferably 40 MPa or less, more preferably 30 MPa or less, further preferably 20 MPa or less, further preferably 10 MPa or less, further preferably 7.0 MPa or less, further preferably 6.0 MPa or less, further preferably 5.3 MPa or less, further preferably 5.2 MPa or less, further preferably 5.0 MPa or less. In addition, from the viewpoint of suppressing the disintegration of the porous cellulose particles in the manufacturing process, it is preferably 1.0 MPa or more, more preferably 2.0 MPa or more, further preferably 3.0 MPa or more, further preferably 4.0 MPa or more, and further preferably 4.9 MPa or more. Furthermore, the compressive elastic modulus of the porous cellulose particles is 50 MPa or less, preferably 1.0 MPa or more and 50 MPa or less, more preferably 1.0 MPa or more and 40 MPa or less, further preferably 1.0 MPa or more and 30 MPa or less, further preferably 1.0 MPa or more and 20 MPa or less, further preferably 2.0 MPa or more and 10 MPa or less, further preferably 2.0 MPa or more and 7.0 MPa or less, further preferably 3.0 MPa or more and 6.0 MPa or less, further preferably 4.0 MPa or more and 5.3 MPa or less, further preferably 4.0 MPa or more and 5.2 MPa or less, further preferably 4.9 MPa or more and 5.0 MPa or less.

[0048] The compressive elastic modulus is the apparent compressive elastic modulus of a single particle measured using a micro compression tester, and can be specifically measured by the method described in Examples.

[0049] The compressive modulus of the porous cellulose particles can be adjusted, for example, by changing the degree of polymerization of the raw cellulose used in step (I) and the cellulose concentration in the aqueous solution prepared in step (I) in the method for producing the porous cellulose particles described later. Specifically, by using a raw cellulose with a high degree of polymerization in step (I) or increasing the cellulose concentration in the aqueous solution, the compressive modulus of the obtained porous cellulose particles becomes higher. In addition, by using a raw cellulose with a low degree of polymerization in step (I) or decreasing the cellulose concentration in the aqueous solution, porous cellulose particles with a low compressive modulus can be obtained.

[0050] From the viewpoint of suppressing the rough feeling when applied to an object, the median diameter (D 50 ) is preferably 75 μm or less, more preferably 70 μm or less, further preferably 65 μm or less, further preferably 55 μm or less, further preferably 40 μm or less, further preferably 30 μm or less. In addition, from the viewpoint of improving the disintegration caused by the coating action on the object, it is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 15 μm or more. In addition, the median particle size of the porous cellulose particles measured by the dry method is preferably 5 μm or more and 75 μm or less, more preferably 5 μm or more and 70 μm or less, further preferably 5 μm or more and 65 μm or less, further preferably 5 μm or more and 55 μm or less, further preferably 10 μm or more and 40 μm or less, and further preferably 15 μm or more and 30 μm or less.

[0051] The median particle size of the porous cellulose particles measured by a dry method refers to the 50% median particle size measured by a particle size distribution analyzer based on a laser diffraction / scattering method using dry particles as a measurement sample, and can be specifically measured by the method described in the Examples.

[0052] The median particle size of the porous cellulose particles can be adjusted, for example, by changing the stirring speed when the cellulose aqueous solution and the organic solvent are mixed in step (II) in the method for producing porous cellulose particles described later. Specifically, by increasing the stirring speed when the cellulose aqueous solution and the organic solvent are mixed in step (II), the diameter of the emulsion droplets of the obtained cellulose emulsion becomes smaller, and as a result, porous cellulose particles with a small median particle size can be obtained. In addition, by reducing the above stirring speed, the diameter of the emulsion droplets of the obtained cellulose emulsion becomes larger, and as a result, porous cellulose particles with a large median particle size can be obtained.

[0053] From the viewpoint of improving the inclusion of functional substances, the specific surface area of ​​porous cellulose particles is 100 m 2 / g or more, preferably 110m 2 / g or more, more preferably 120m 2 / g or more, more preferably 130m 2 / g or more, more preferably 135m 2 / g or more, more preferably 140m 2 / g or more, and more preferably 144m 2 / g or more. In addition, from the viewpoint of suppressing the disintegration of the porous cellulose particles during the production process, the particle size is less than 500 m 2 / g, preferably 200m 2 / g or less, more preferably 180m 2 / g or less, more preferably 150m 2 / g or less. In addition, the specific surface area of ​​the porous cellulose particles is 100m 2 / g or more and less than 500m 2 / g, preferably 100m 2 / g and above and 200m 2 / g or less, more preferably 110m 2 / g and above and 180m 2 / g or less, more preferably 120m 2 / g and above and 180m 2 / g or less, and more preferably 130m 2 / g and above and 150m 2 / g or less, and more preferably 135m 2 / g and above and 150m 2 / g or less, and more preferably 140m 2 / g and above and 150m 2 / g or less, and more preferably 144m 2 / g and above and 150m 2 / g or less.

[0054] The specific surface area is a value obtained by dividing the total surface area of ​​the microscopic surface inside the porous cellulose particles and the surface of the particles by the mass of the particles and normalizing the surface area by mercury porosimetry. Specifically, it can be measured by the method described in Examples.

[0055] The specific surface area of ​​the porous cellulose particles can be controlled, for example, by selecting the surface tension of the dispersion medium (organic solvent) used in the dispersion medium replacement performed as needed in step (IV) in the method for producing the porous cellulose particles described later, and the drying method in step (V). Specifically, if the surface tension of the organic solvent used in the dispersion medium replacement in step (IV) is small, the capillary force accompanying the volatilization of the organic solvent is small, which can suppress the shrinkage of the cellulose particles during drying, and porous cellulose particles with a large specific surface area can be obtained. In addition, in step (V), the shrinkage of the cellulose particles during drying can also be suppressed by a drying method such as freeze drying in which the capillary force caused by the surface tension of the organic solvent does not work, thereby obtaining porous cellulose particles with a large specific surface area.

[0056] From the viewpoint of improving the inclusion of functional substances, the pore capacity of the porous cellulose particles is 1.5 mL / g or more, preferably 2.0 mL / g or more, more preferably 2.5 mL / g or more, further preferably 3.0 mL / g or more, further preferably 3.5 mL / g or more, further preferably 4.0 mL / g or more. In addition, from the viewpoint of suppressing the disintegration of the porous cellulose particles during the manufacturing process, it is preferably 8.0 mL / g or less, more preferably 7.0 mL / g or less, further preferably 6.0 mL / g or less, and further preferably 5.0 mL / g or less. Furthermore, the pore capacity of the porous cellulose particles is 1.5 mL / g or more, preferably 1.5 mL / g or more and 8.0 mL / g or less, more preferably 2.0 mL / g or more and 7.0 mL / g or less, further preferably 2.5 mL / g or more and 6.0 mL / g or less, further preferably 3.0 mL / g or more and 5.0 mL / g or less, further preferably 3.5 mL / g or more and 5.0 mL / g or less, further preferably 4.0 mL / g or more and 5.0 mL / g or less.

[0057] The pore volume is a value obtained by dividing the total volume of mercury intruding into the pores inside the porous cellulose particles and the gaps between the particles by the mass of the particles and normalizing the total volume by mercury intrusion into the pores inside the porous cellulose particles by mercury intrusion ...

[0058] The pore capacity of the porous cellulose particles can be adjusted by, for example, selecting the surface tension of the dispersion medium (organic solvent) used for the dispersion medium replacement performed as needed in step (IV) and the drying method in step (V) in the method for producing the porous cellulose particles described later, and by the diameter of the emulsion droplets of the cellulose emulsion obtained in step (II). Specifically, if the diameter of the emulsion droplets of the cellulose emulsion is small, the median particle size and pore capacity of the obtained porous cellulose particles will also be small.

[0059] From the perspective of environmental considerations, the porous cellulose particles of the present invention are preferably chemically unmodified porous cellulose particles. In the present specification, "chemically unmodified" means (1) substantially no substituents are introduced into the hydroxyl groups in the cellulose constituting the porous cellulose particles, and (2) the surface of the porous cellulose particles is not coated with a surface treatment agent. The amount of substituents introduced into the hydroxyl groups in the cellulose constituting the porous cellulose particles is preferably 0.5 mol% or less, more preferably 0.1 mol% or less, and even more preferably 0 mol% of all hydroxyl groups.

[0060] In addition, from the perspective of imparting a soft touch, improving the inclusion of functional substances, and improving the disintegration caused by the coating action on the object, the porous cellulose particles are preferably non-crosslinked particles. Non-crosslinked particles refer to particles that are produced without an intentional crosslinking reaction and do not substantially have a crosslinked structure.

[0061] From the viewpoint of improving the inclusion of functional substances, the surface pore diameter of the porous cellulose particles is preferably 50 nm or more, more preferably 100 nm or more, and further preferably 200 nm or more, and from the viewpoint of having high particle strength and maintaining particle shape, it is preferably 800 nm or less, more preferably 600 nm or less, and further preferably 500 nm or less. Furthermore, the surface pore diameter of the porous cellulose particles is preferably 50 nm or more and 800 nm or less, more preferably 100 nm or more and 600 nm or less, and further preferably 200 nm or more and 500 nm or less.

[0062] The surface pore diameter is determined by mercury porosimetry, and specifically, can be measured by the method described in Examples.

[0063] From the viewpoint of improving the touch when applied to an object and the viewpoint of imparting appropriate particle disintegration, the sphericity of the porous cellulose particles is preferably 60% or more, more preferably 70% or more, and further preferably 80% or more. In addition, the upper limit of the sphericity is 100%, and can be 90% or less. It should be noted that the sphericity of the porous cellulose particles is a value defined by the following formula, which can be obtained by measuring using a dynamic image analysis device CAMSIZER X2 (made by MICROTRAC MRB). Sphericity can be specifically measured by the method described in the examples.

[0064] Sphericity (%) = 4π × particle area (m 2 ) / (Particle circumference (m)) 2 ×100

[0065] The cellulose constituting the porous cellulose particles preferably does not contain cellulose I type crystalline cellulose but contains cellulose II type crystalline cellulose or amorphous cellulose from the viewpoint of imparting a soft touch and improving disintegration properties caused by coating an object.

[0066] The crystal form of cellulose constituting the porous cellulose particles can be identified based on the diffraction angle and diffraction intensity based on the X-ray diffraction method. Cellulose II type crystalline cellulose shows a diffraction peak from the (11-0) plane at a diffraction angle of 2θ = 12.5° and a diffraction peak from the (110) plane at 2θ = 20.0°, and can be easily distinguished from cellulose I type crystalline cellulose. Cellulose II type crystallinity is defined by the following formula, and its value is not particularly limited.

[0067] Cellulose II crystallinity (%) = [(I 20.0 -I 15.0 ) / I 20.0 ]×100

[0068] (Here, I 20.0 is the diffraction intensity of the lattice plane (110 plane) (diffraction angle 2θ = 20.0°) in X-ray diffraction, I 15.0 is the diffraction intensity of the amorphous part (diffraction angle 2θ = 15.0).

[0069] The cellulose II type crystallinity can be measured by an X-ray diffraction method, specifically, the method described in Examples.

[0070] The crystal form (cellulose II type crystallinity) of the porous cellulose particles can be adjusted, for example, by the type of solvent contained in the wet purified cellulose particles when the particles are dried in step (V) in the method for producing the porous cellulose particles described below. Although the reason is not clear, if the wet purified cellulose particles are dried in step (V) in a state where the particles contain an aqueous solvent, the crystallinity becomes higher, while if the wet purified cellulose particles are dried in step (V) in a state where the particles contain a non-aqueous solvent, the crystallinity becomes lower.

[0071] The physical properties of the porous cellulose particles can be adjusted by, for example, selecting appropriate production conditions for the cellulose particles, the type of raw cellulose used in the production of the cellulose particles, etc. The details are as described above.

[0072] The porous cellulose particles preferably have a low content of compounds other than cellulose, such as impurities contained in the raw cellulose, solvents and additives used in the production, etc. That is, the content of cellulose in the porous cellulose particles is preferably 95% by mass or more, more preferably 99% by mass or more, and further preferably substantially 100% by mass.

[0073] [Method for producing porous cellulose particles]

[0074] The porous cellulose particles of the present invention can be preferably produced by a production method comprising the following steps (I) to (V) in order.

[0075] Step (I): a step of mixing raw material cellulose with an alkaline aqueous solution to prepare a cellulose aqueous solution

[0076] Step (II): a step of mixing the above-mentioned cellulose aqueous solution with an organic solvent to prepare a cellulose emulsion

[0077] Step (III): a step of mixing the cellulose emulsion with a solvent that does not dissolve cellulose to precipitate crude cellulose particles and obtain a suspension containing crude cellulose particles

[0078] Step (IV): After solid-liquid separation of the suspension containing crude cellulose particles, the obtained wet crude cellulose particles are washed to obtain purified wet cellulose particles.

[0079] Step (V): Drying the wet purified cellulose particles to obtain porous cellulose particles

[0080] The above-mentioned production method can easily produce porous cellulose particles having the above-mentioned physical properties.

[0081] <Process (I)>

[0082] In step (I), the raw material cellulose is mixed with an alkaline aqueous solution to prepare a cellulose aqueous solution. The cellulose aqueous solution prepared in step (I) is different from a cellulose suspension and is a solution in which cellulose is dissolved in an alkaline aqueous solution. Here, the state of "cellulose dissolution" means that the cellulose aqueous solution is transparent when viewed visually. It should be noted that a portion of the cellulose may be in a dispersed state.

[0083] It is considered that by preparing a cellulose aqueous solution in step (I) and subjecting the aqueous solution to step (II) and subsequent steps, the morphology inside the cellulose particles can be easily controlled, and porous cellulose particles having desired physical properties can be easily produced.

[0084] (Raw material cellulose)

[0085] From the viewpoint of environmental considerations, the raw material cellulose used in step (I) is preferably chemically pure cellulose that is not chemically modified. In addition, as the raw material cellulose, for example, various wood chips, pruned branches of various trees, thinned materials, branch wood, construction waste, factory waste and other wood; wood pulp made from wood, cotton linter pulp obtained from fibers around cotton seeds and other pulps; newspapers, corrugated paper, magazines, high-quality paper and other papers; plant stems and leaves such as rice straw and corn stalks; various cellulose-containing raw materials such as plant shells such as rice husks, palm shells, and coconut shells. Among them, from the viewpoint of cellulose purity in the raw material cellulose, the degree of polymerization of cellulose and the ease of obtaining, various wood chips, pruned branches of various trees, thinned materials, branch wood, construction waste, factory waste and other wood; wood pulp made from wood, cotton linter pulp obtained from fibers around cotton seeds and other pulps are preferred.

[0086] Examples of the shape of the raw material cellulose include powder, flake, and cotton. Among them, the raw material cellulose is preferably in a powdery form from the viewpoint of excellent solubility in an alkaline aqueous solution.

[0087] From the viewpoint of the strength of the obtained porous cellulose particles, the degree of polymerization of the raw material cellulose is preferably 10 or more, more preferably 50 or more, further preferably 100 or more, and further preferably 150 or more. From the viewpoint of improving the solubility in the alkaline aqueous solution, it is preferably 1000 or less, more preferably 500 or less, and further preferably 300 or less. Furthermore, the degree of polymerization of the raw material cellulose is preferably 10 or more and 1000 or less, more preferably 50 or more and 500 or less, further preferably 100 or more and 500 or less, and further preferably 150 or more and 300 or less.

[0088] The degree of polymerization of raw material cellulose is generally controlled by the acid hydrolysis conditions of raw material pulp. For example, if the acid hydrolysis time is prolonged, raw material cellulose with a low degree of polymerization can be obtained.

[0089] As the raw material cellulose, either crystalline cellulose or amorphous cellulose can be used, but from the viewpoint of obtaining porous cellulose particles having desired physical properties and from the viewpoint of easy availability, crystalline cellulose is preferred, and cellulose I type crystalline cellulose is more preferred.

[0090] When the raw material cellulose is in powder form, the median particle size of the raw material cellulose is preferably 10 μm or more, more preferably 20 μm or more, from the viewpoint of improving handleability, and is preferably 500 μm or less, more preferably 300 μm or less, further preferably 200 μm or less, and further preferably 150 μm or less, from the viewpoint of improving solubility in aqueous alkaline solution.

[0091] The median particle size of the raw material cellulose can be measured by the same method as described above.

[0092] (Alkaline aqueous solution)

[0093] The alkaline aqueous solution used in step (I) is not particularly limited as long as it is alkaline and can dissolve cellulose. Here, “dissolve cellulose” means, for example, mixing cellulose in an amount of 4 mass % in the alkaline aqueous solution and visually confirming dissolution.

[0094] As the alkaline compound used in the alkaline aqueous solution, both inorganic alkaline compounds and organic alkaline compounds can be used, and examples thereof include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; ammonia; and tertiary amines such as trimethylamine and triethylamine. Among them, from the viewpoint of easy availability and economy, alkali metal hydroxides are preferred, more preferably one or more selected from sodium hydroxide and potassium hydroxide, and further preferably sodium hydroxide.

[0095] The above-mentioned base compounds can be used alone or in combination of two or more.

[0096] From the viewpoint of improving the solubility of the raw cellulose and the stability of the obtained cellulose aqueous solution, the concentration of the alkali compound in the alkali aqueous solution is preferably 1% by mass or more, more preferably 2% by mass or more, and further preferably 3% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less, and further preferably 25% by mass or less. In addition, the concentration of the alkali compound in the alkali aqueous solution is preferably 1% by mass or more and 40% by mass or less, more preferably 2% by mass or more and 30% by mass or less, and further preferably 3% by mass or more and 25% by mass or less.

[0097] In step (I), from the viewpoint of improving production efficiency, solubility of the raw material cellulose, and stability of the obtained cellulose aqueous solution, aqueous alkali solutions of different concentrations may be mixed with the raw material cellulose in a plurality of times.

[0098] Specifically, in step (I), preferably, after mixing the raw material cellulose with an alkaline aqueous solution A having an alkali compound concentration of 1 mass % to 10 mass %, an alkaline aqueous solution B having an alkali compound concentration exceeding 10 mass % to 40 mass % is added and mixed to prepare the cellulose aqueous solution.

[0099] The concentration of the alkali compound in the aqueous alkali solution A is more preferably 2 mass % or more and 8 mass % or less, and further preferably 2 mass % or more and 5 mass % or less.

[0100] The concentration of the alkali compound in the aqueous alkali solution B is more preferably 15% by mass or more and 30% by mass or less, and further preferably 20% by mass or more and 25% by mass or less.

[0101] In step (I), when the alkaline aqueous solution A and the alkaline aqueous solution B are used, the ratio thereof is not particularly limited. However, from the viewpoint of improving the production efficiency and the viewpoint of improving the stability of the obtained cellulose aqueous solution, the mass ratio (A / B) of the alkaline aqueous solution A to the alkaline aqueous solution B is preferably in the range of 1 to 10, more preferably in the range of 2 to 8, and even more preferably in the range of 3 to 6.

[0102] The mixing of the raw material cellulose and the alkaline aqueous solution in the step (I) can be performed by adding the raw material cellulose to the alkaline aqueous solution and stirring the mixture using a known apparatus.

[0103] From the viewpoint of uniformly dispersing the raw material cellulose and efficiently dissolving it, the temperature when the raw material cellulose is mixed with the alkaline aqueous solution is preferably 10°C or lower, more preferably 5°C or lower, and even more preferably 0°C or lower. In addition, from the viewpoint of improving the solubility of cellulose without freezing, it is preferably -20°C or higher, more preferably -10°C or higher, and even more preferably -5°C or higher. Furthermore, the temperature when the raw material cellulose is mixed with the alkaline aqueous solution is preferably -20°C or higher and 10°C or lower, more preferably -10°C or higher and 5°C or lower, and even more preferably -5°C or higher and 0°C or lower.

[0104] When the alkaline aqueous solution A and the alkaline aqueous solution B are used, it is preferred that the raw material cellulose is added to the alkaline aqueous solution A and stirred and mixed, and then the temperature of the mixture is adjusted to the above range, and then the alkaline aqueous solution B is added and mixed.

[0105] The stirring time depends on the production scale, the concentration of the alkali compound in the alkali aqueous solution, and the temperature and can be appropriately set, so it is not particularly limited. Usually, stirring is performed until the raw material cellulose is visually observed to be dissolved.

[0106] From the viewpoint of improving the strength of the obtained porous cellulose particles, the cellulose concentration in the cellulose aqueous solution obtained in step (I) is preferably 0.5% by mass or more, more preferably 1% by mass or more, and further preferably 2% by mass or more. In addition, from the viewpoint of the viscosity that allows easy preparation of a cellulose emulsion when the cellulose aqueous solution is supplied to step (II), it is preferably 15% by mass or less, more preferably 10% by mass or less, further preferably 8% by mass or less, and further preferably 6% by mass or less. Furthermore, the cellulose concentration in the cellulose aqueous solution obtained in step (I) is preferably 0.5% by mass or more and 15% by mass or less, more preferably 1% by mass or more and 10% by mass or less, further preferably 1% by mass or more and 8% by mass or less, and further preferably 2% by mass or more and 6% by mass or less.

[0107] In addition, from the viewpoint of improving the solubility of the raw material cellulose and the stability of the obtained cellulose aqueous solution, the concentration of the alkali compound in the cellulose aqueous solution obtained in step (I) is preferably 0.5% by mass or more, more preferably 1% by mass or more, further preferably 2% by mass or more, further preferably 3% by mass or more, further preferably 5% by mass or more, and preferably 15% by mass or less, more preferably 12% by mass or less, further preferably 10% by mass or less. Furthermore, the concentration of the alkali compound in the cellulose aqueous solution obtained in step (I) is preferably 0.5% by mass or more and 15% by mass or less, more preferably 1% by mass or more and 15% by mass or less, further preferably 2% by mass or more and 12% by mass or less, further preferably 3% by mass or more and 10% by mass or less, further preferably 5% by mass or more and 10% by mass or less.

[0108] <Process (II)>

[0109] In step (II), the cellulose aqueous solution obtained in step (I) is mixed with an organic solvent to prepare a cellulose emulsion. By step (II), a water-in-oil type cellulose emulsion capable of producing porous cellulose particles having a desired median particle size can be prepared.

[0110] The organic solvent is not particularly limited as long as it is an organic solvent that is immiscible with water and can prepare a cellulose emulsion by mixing with the above-mentioned cellulose aqueous solution.

[0111] Preferred examples of the organic solvent used in step (II) include hydrocarbon solvents, ester solvents, halogen solvents, and the like.

[0112] Examples of the hydrocarbon solvent include chain aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons.

[0113] The number of carbon atoms in the chain aliphatic hydrocarbon is preferably 6 or more, more preferably 8 or more, and preferably 18 or less, more preferably 12 or less. The chain aliphatic hydrocarbon may be either a linear aliphatic hydrocarbon or a branched aliphatic hydrocarbon.

[0114] The carbon number of the alicyclic hydrocarbon and the aromatic hydrocarbon is preferably 6 or more and 18 or less, more preferably 6 or more and 12 or less.

[0115] Specific examples of the hydrocarbon solvent include n-pentane, n-hexane, n-heptane, n-octane, isooctane, n-decane, isodecane, n-dodecane, isododecane, tetradecane, hexadecane, octadecane, cyclohexane, methylcyclohexane, cycloheptane, methylcycloheptane, toluene, and xylene.

[0116] As the ester solvent, an ester having 4 to 10 carbon atoms is preferred, and examples thereof include ethyl acetate and butyl acetate.

[0117] Examples of the halogen-based solvent include dichloromethane, dichloroethane, and dichlorobenzene.

[0118] The above-mentioned organic solvents may be used alone or in combination of two or more.

[0119] From the viewpoint of being able to easily prepare a water-in-oil type cellulose emulsion, the above-mentioned organic solvent is preferably a hydrocarbon solvent, more preferably a chain aliphatic hydrocarbon, further preferably at least one selected from n-pentane, n-hexane, n-heptane, n-octane, isooctane, decane, isodecane, dodecane, isododecane, tetradecane, hexadecane and octadecane, and further preferably at least one selected from n-octane, isooctane, n-decane, isodecane, n-dodecane and isododecane.

[0120] In step (II), from the viewpoint of improving the emulsification stability of the water-in-oil type cellulose emulsion, the amount of the organic solvent mixed with the cellulose aqueous solution is preferably 80 parts by mass or more, more preferably 100 parts by mass or more, and further preferably 120 parts by mass or more, relative to 100 parts by mass of the cellulose aqueous solution. From the viewpoint of easily obtaining porous cellulose particles having a desired median particle size, it is preferably 1000 parts by mass or less, more preferably 800 parts by mass or less, further preferably 500 parts by mass or less, and further preferably 300 parts by mass or less. Furthermore, in step (II), the amount of the organic solvent mixed with the cellulose aqueous solution is preferably 80 parts by mass or more and 1000 parts by mass or less, more preferably 100 parts by mass or more and 800 parts by mass or less, further preferably 120 parts by mass or more and 500 parts by mass or less, and further preferably 120 parts by mass or more and 300 parts by mass or less, relative to 100 parts by mass of the cellulose aqueous solution.

[0121] In step (II), from the viewpoint of improving the emulsification stability of the water-in-oil type cellulose emulsion, it is preferred to further mix an emulsifier in addition to the cellulose aqueous solution and the organic solvent.

[0122] Examples of the emulsifier include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, etc. Among them, nonionic surfactants are preferred from the viewpoint of improving the emulsification of the water-in-oil type cellulose emulsion.

[0123] From the viewpoint of improving the emulsification stability of the water-in-oil type cellulose emulsion, the HLB (Hydrophile-Lipophile Balance) of the nonionic surfactant used as an emulsifier is preferably 1 to 10, more preferably 1 to 8, further preferably 1 to 6, further preferably 1 to 5, further preferably 1 to 4, further preferably 1 to 3.

[0124] Here, HLB is an index indicating the ratio of the relative affinity of a surfactant to two liquids in an oil-water system, and can be calculated by the following formula according to the Griffin method (J. Soc. Cosm. Chem., 1954, 5:249-256).

[0125] HLB = 20 × [(molecular weight of the hydrophilic group contained in the surfactant) / (molecular weight of the surfactant)]

[0126] Examples of the hydrophilic group contained in the surfactant include a hydroxyl group and an ethyleneoxy group.

[0127] It should be noted that the HLB of two or more nonionic surfactants can be calculated as follows: the HLB of each nonionic surfactant is multiplied by the mass fraction of each nonionic surfactant (i.e., the value obtained by dividing the mass of each nonionic surfactant by the total mass of the nonionic surfactants), and the total is calculated as a weighted average.

[0128] Examples of the nonionic surfactant used as an emulsifier include sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene glycerol fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene hydrogenated castor oil, polyglycerol fatty acid esters, sucrose fatty acid esters, and polyether-modified silicones. These may be used alone or in combination of two or more.

[0129] The carbon number of the fatty acid in sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerol fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyglycerol fatty acid ester and sucrose fatty acid ester, and the carbon number of the alkyl group in polyoxyethylene alkyl ether is preferably 12 or more, more preferably 16 or more, and further preferably 18 or more, and is preferably 24 or less, and more preferably 22 or less, from the viewpoint of making HLB preferably within the above range.

[0130] Examples of the sorbitan fatty acid ester include sorbitan monooleate, sorbitan monostearate, sorbitan sesquioleate, sorbitan coconut oil fatty acid ester, sorbitan monopalmitate, sorbitan tristearate, and sorbitan trioleate.

[0131] Examples of the polyoxyethylene sorbitan fatty acid esters include polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan trioleate.

[0132] Examples of the polyoxyethylene alkyl ether include polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, and the like.

[0133] Examples of the polyoxyethylene glyceryl fatty acid ester include monooleic acid polyoxyethylene glyceryl and the like.

[0134] Examples of the polyoxyethylene sorbitan fatty acid esters include polyoxyethylene sorbitan tetraoleate and the like.

[0135] Examples of the sucrose fatty acid ester include sucrose palmitate, sucrose oleate, sucrose stearate, sucrose erucate, and sucrose behenate.

[0136] Among them, from the viewpoint of further improving the emulsification stability of the water-in-oil type cellulose emulsion, the nonionic surfactant used as the emulsifier is preferably one or more selected from sorbitan fatty acid esters, polyoxyethylene alkyl ethers, sucrose fatty acid esters and polyether-modified silicones, more preferably sucrose fatty acid esters, further preferably one or more selected from sucrose palmitate, sucrose oleate, sucrose stearate, sucrose erucate and sucrose behenate, and even more preferably one or more selected from sucrose erucate and sucrose behenate.

[0137] In step (II), when an emulsifier is further mixed, from the viewpoint of further improving the emulsification stability of the water-in-oil type cellulose emulsion, the amount of the emulsifier mixed is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and further preferably 1.0 parts by mass or more, and is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and further preferably 5.0 parts by mass or less, relative to 100 parts by mass of the organic solvent. Furthermore, the amount of the emulsifier mixed is preferably 0.1 parts by mass or more and 20 parts by mass or less, more preferably 0.5 parts by mass or more and 10 parts by mass or less, and further preferably 1.0 parts by mass or more and 5.0 parts by mass or less.

[0138] The emulsifier may be added to either the aqueous cellulose solution or the organic solvent before mixing, or may be added after the aqueous cellulose solution and the organic solvent are mixed.

[0139] The cellulose emulsion can be prepared, for example, by adding an organic solvent and an emulsifier to an aqueous cellulose solution and stirring the solution using a known mixer such as a homomixer or a high-speed emulsifying disperser.

[0140] From the viewpoint of further improving the emulsification stability of the water-in-oil cellulose emulsion, the temperature at which the aqueous cellulose solution is mixed with the organic solvent is preferably 20°C or less, more preferably 10°C or less, and further preferably 5°C or less. In addition, from the viewpoint of preparing the water-in-oil cellulose emulsion without freezing, it is preferably -20°C or more, more preferably -10°C or more, and further preferably -5°C or more. Furthermore, the temperature at which the aqueous cellulose solution is mixed with the organic solvent is preferably -20°C or more and 20°C or less, more preferably -10°C or more and 10°C or less, and further preferably -5°C or more and 5°C or less.

[0141] The stirring speed when the cellulose aqueous solution is mixed with the organic solvent is appropriately selected according to the manufacturing scale, the device used, the viscosity of the cellulose emulsion, etc. From the viewpoint of controlling the diameter of the emulsion droplets and obtaining porous cellulose particles with a desired median particle size, it is preferably 1000 rpm or more, more preferably 3000 rpm or more, further preferably 5000 rpm or more, and further preferably 5500 rpm or more. In addition, it is preferably 15000 rpm or less, more preferably 12000 rpm or less, further preferably 10000 rpm or less, and further preferably 8500 rpm or less. In addition, the stirring speed when the cellulose aqueous solution is mixed with the organic solvent is preferably 1000 rpm or more and 15000 rpm or less, more preferably 3000 rpm or more and 12000 rpm or less, further preferably 5000 rpm or more and 10000 rpm or less, and further preferably 5500 rpm or more and 8500 rpm or less.

[0142] The mixing time of the aqueous cellulose solution and the organic solvent is appropriately selected depending on the production scale, the equipment to be used, the viscosity of the cellulose emulsion, and the like.

[0143] <Step (III)>

[0144] In the step (III), the cellulose emulsion obtained in the step (II) is mixed with a solvent in which cellulose is not dissolved to precipitate crude cellulose particles, thereby obtaining a suspension containing crude cellulose particles.

[0145] The solvent that does not dissolve cellulose is a so-called non-solvent for cellulose that has no ability to dissolve cellulose, and is a solvent that is compatible with the above-mentioned aqueous alkali solution and organic solvent. By mixing the solvent with the cellulose emulsion, the solvent that does not dissolve cellulose flows into the interior of the cellulose, and the organic solvent in the interior of the cellulose flows out, forming a phase separation structure. In this way, the morphology inside the cellulose particles can be controlled, and the cellulose can be coagulated in a state where a desired porous structure is formed, and precipitated in the form of particles.

[0146] The solvent that does not dissolve cellulose is preferably an alcohol solvent, and more preferably an alcohol having 4 or less carbon atoms.

[0147] Examples of the alcohol used as a solvent that does not dissolve cellulose include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, and tert-butanol. These can be used alone or in combination of two or more.

[0148] Among them, as a solvent that does not dissolve cellulose, from the viewpoint of making it easy to precipitate crude cellulose particles and controlling the internal morphology of the cellulose particles to obtain porous cellulose particles with desired physical properties, it is preferably one or more selected from ethanol, 2-propanol, 1-butanol, 2-butanol and 2-methyl-1-propanol, and ethanol is more preferred.

[0149] Regarding the mixing amount of the solvent that does not dissolve cellulose, from the viewpoint of making it easy to precipitate crude cellulose particles, controlling the morphology inside the cellulose particles to obtain porous cellulose particles with desired physical properties, and maintaining the stability of the emulsion, relative to 100 parts by mass of the cellulose emulsion, it is preferably 50 parts by mass or more, more preferably 100 parts by mass or more, and further preferably 200 parts by mass or more, and preferably 1000 parts by mass or less, more preferably 500 parts by mass or less, and further preferably 400 parts by mass or less. Furthermore, relative to 100 parts by mass of the cellulose emulsion, the mixing amount of the solvent that does not dissolve cellulose is preferably 50 parts by mass or more and 1000 parts by mass or less, more preferably 100 parts by mass or more and 500 parts by mass or less, and further preferably 200 parts by mass or more and 400 parts by mass or less.

[0150] In the step (III), it is preferred to further mix an acid from the viewpoint of neutralizing the alkaline compound remaining in the crude cellulose particles.

[0151] The acid may be either an inorganic acid or an organic acid, but from the viewpoint of solubility in a cellulose emulsion and a solvent in which cellulose is not dissolved, an organic acid is preferred, and a carboxylic acid having 4 or less carbon atoms is more preferred.

[0152] Examples of the carboxylic acid having 4 or less carbon atoms include monocarboxylic acids, dicarboxylic acids, and hydroxycarboxylic acids having 4 or less carbon atoms, such as formic acid, acetic acid, propionic acid, butyric acid, lactic acid, citric acid, malic acid, and succinic acid. Among them, from the viewpoint of solubility in a cellulose emulsion and a solvent that does not dissolve cellulose, preferably at least one selected from acetic acid, lactic acid, malic acid, and succinic acid, and more preferably acetic acid.

[0153] When an acid is used in step (III), the amount of the acid mixed is preferably 1.0 equivalent or more, more preferably 1.2 equivalent or more, and further preferably 1.4 equivalent or more, relative to the alkali compound used in step (I) from the viewpoint of neutralizing the alkali compound remaining in the crude cellulose particles, and is preferably 3.0 equivalents or less, more preferably 2.0 equivalents or less, and further preferably 1.8 equivalents or less from the viewpoint of economic efficiency. Furthermore, the amount of the acid mixed in step (III) is preferably 1.0 equivalent or more and 3.0 equivalents or less, more preferably 1.2 equivalents or more and 2.0 equivalents or less, and further preferably 1.4 equivalents or more and 1.8 equivalents or less, relative to the alkali compound used in step (I).

[0154] The mixing of the cellulose emulsion and the solvent in which cellulose is not dissolved can be carried out, for example, by adding the cellulose emulsion to the solvent in which cellulose is not dissolved and stirring using a known apparatus. When the cellulose emulsion is added to the solvent in which cellulose is not dissolved, it is preferred to add the cellulose emulsion and mix while stirring the solvent in which cellulose is not dissolved so that the emulsion droplets do not bind to each other.

[0155] The temperature at which the cellulose emulsion is mixed with the solvent in which cellulose is not dissolved is preferably 0°C or higher, more preferably 5°C or higher, and even more preferably 15°C or higher, and is preferably 50°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower. Furthermore, the temperature at which the cellulose emulsion is mixed with the solvent in which cellulose is not dissolved is preferably 0°C or higher and 50°C or lower, more preferably 5°C or higher and 40°C or lower, and even more preferably 15°C or higher and 30°C or lower.

[0156] When the acid is mixed in step (III), the acid may be mixed simultaneously with the mixing of the cellulose emulsion and the solvent in which the cellulose is not dissolved, or may be mixed after the cellulose emulsion and the solvent in which the cellulose is not dissolved are mixed. From the viewpoint of efficiently neutralizing the alkali compound remaining in the crude cellulose particles (including the neutralization salt as impurities and the above-mentioned emulsifier), it is preferred to mix the acid after the cellulose emulsion and the solvent in which the cellulose is not dissolved are mixed.

[0157] The stirring speed when the cellulose emulsion is mixed with the solvent that does not dissolve cellulose is also appropriately set depending on the production scale and temperature. From the perspective of fully separating the crude cellulose particles and controlling the internal morphology of the cellulose particles to obtain porous cellulose particles with desired physical properties, it is preferably 100 rpm or more, more preferably 200 rpm or more, and preferably 2000 rpm or less, more preferably 1500 rpm or less, further preferably 1000 rpm or less, and further preferably 800 rpm or less. In addition, the stirring speed when the cellulose emulsion is mixed with the solvent that does not dissolve cellulose is preferably 100 rpm or more and 2000 rpm or less, more preferably 200 rpm or more and 1500 rpm or less, further preferably 200 rpm or more and 1000 rpm or less, and further preferably 200 rpm or more and 800 rpm or less.

[0158] The stirring time when the cellulose emulsion is mixed with the solvent that does not dissolve cellulose is also appropriately set depending on the production scale and temperature. From the perspective of fully precipitating the crude cellulose particles and controlling the internal morphology of the cellulose particles to obtain porous cellulose particles with the desired physical properties, it is usually 0.2 hours to 12 hours, preferably 0.5 hours to 6 hours.

[0159] <Step (IV)>

[0160] In step (IV), the suspension containing the crude cellulose particles obtained in step (III) is subjected to solid-liquid separation, and then the obtained wet crude cellulose particles are washed to obtain wet purified cellulose particles.

[0161] The solid-liquid separation of the suspension containing crude cellulose particles can be performed by centrifugation, filtration, decantation, or a combination thereof.

[0162] Next, in order to remove impurities such as the organic solvent and emulsifier used in step (II) and the neutralization salt produced in step (III) from the wet crude cellulose particles obtained after solid-liquid separation, the wet crude cellulose particles are washed. The washing treatment of the wet crude cellulose particles can be carried out using water, an organic solvent, or a combination thereof. In order to remove hydrophobic impurities such as the organic solvent and emulsifier used in step (II), it is preferred to use an organic solvent, and in order to remove water-soluble impurities such as the neutralization salt, it is preferred to use water.

[0163] As the organic solvent used in the washing treatment of the wet crude cellulose particles in step (IV), it is preferred that a solvent be capable of dissolving the organic solvent and emulsifier used in step (II) and be easily dried, examples of which include ketone solvents having a carbon number of 6 or less, such as acetone and methyl isobutyl ketone, and alcohol solvents having a carbon number of 6 or less, such as ethanol and 2-propanol.

[0164] When drying by reduced pressure drying is performed, after the washing treatment, it is preferred to further disperse the washed cellulose particles in a dispersion medium to perform dispersion medium replacement from the viewpoint of suppressing shrinkage of the obtained porous cellulose particles during drying.

[0165] From the viewpoint of suppressing shrinkage of the obtained porous cellulose particles during drying, the dispersion medium used in the dispersion medium replacement is preferably an organic solvent with low surface tension, preferably an organic solvent having a surface tension of 20 mN / m or less, more preferably 18 mN / m or less at 25°C.

[0166] The surface tension is a surface tension value measured at 25° C. using an automatic surface tensiometer (K100 manufactured by KRUSS Corporation).

[0167] As the organic solvent with low surface tension, for example, in addition to aliphatic hydrocarbons having 7 or less carbon atoms such as pentane, hexane, and heptane, ether compounds having 4 or less carbon atoms such as ethyl methyl ether and diethyl ether can be mentioned, and these can be used alone or in combination of two or more. Among them, pentane is preferred from the viewpoint of suppressing the shrinkage of the obtained porous cellulose particles during drying.

[0168] The amount of the dispersion medium used in the dispersion medium replacement is preferably 100 parts by mass or more, more preferably 200 parts by mass or more, and preferably 2000 parts by mass or less, more preferably 1000 parts by mass or less, and further preferably 600 parts by mass or less, relative to 100 parts by mass of the cellulose particles after the above-mentioned washing treatment. Furthermore, the amount of the dispersion medium used in the dispersion medium replacement is preferably 100 parts by mass or more and 2000 parts by mass or less, more preferably 200 parts by mass or more and 1000 parts by mass or less, and further preferably 200 parts by mass or more and 600 parts by mass or less, relative to 100 parts by mass of the cellulose particles after the above-mentioned washing treatment.

[0169] The dispersion medium replacement can be performed, for example, by adding the above-mentioned washed cellulose particles to the dispersion medium and stirring using a known device. The temperature at which the washed cellulose particles are mixed with the dispersion medium is preferably 0°C or higher, more preferably 5°C or higher, and further preferably 15°C or higher, and is preferably 50°C or lower, more preferably 40°C or lower, and further preferably 30°C or lower. Furthermore, the temperature at which the washed cellulose particles are mixed with the dispersion medium is preferably 0°C or higher and 50°C or lower, more preferably 5°C or higher and 40°C or lower, and further preferably 15°C or higher and 30°C or lower.

[0170] The stirring speed when the washed cellulose particles are mixed with the dispersion medium is also appropriately set depending on the production scale and temperature. From the viewpoint of fully dispersing the cellulose particles, it is preferably 100 rpm or more, more preferably 200 rpm or more, and preferably 2000 rpm or less, more preferably 1500 rpm or less, further preferably 1000 rpm or less, and further preferably 800 rpm or less. Furthermore, the stirring speed when the washed cellulose particles are mixed with the dispersion medium is preferably 100 rpm or more and 2000 rpm or less, more preferably 200 rpm or more and 1500 rpm or less, further preferably 200 rpm or more and 1000 rpm or less, and further preferably 200 rpm or more and 800 rpm or less.

[0171] The stirring time when mixing the washed cellulose particles and the dispersion medium is appropriately set depending on the production scale and temperature, and is usually 0.2 hours to 12 hours, preferably 0.5 hours to 6 hours.

[0172] By performing the above-mentioned dispersion medium replacement, a suspension containing purified cellulose particles can be obtained. The suspension can be subjected to solid-liquid separation in the same manner as described above to recover the purified cellulose wet particles.

[0173] <Process (V)>

[0174] In step (V), the wet purified cellulose particles obtained in step (IV) are dried to obtain dry porous cellulose particles.

[0175] As a method for drying the purified cellulose wet particles, freeze drying is preferably used from the viewpoint of suppressing shrinkage of the particles during drying and maintaining a porous structure. In addition, when the dispersion medium is replaced in step (IV), the drying treatment may also be performed by reduced pressure drying, drying using supercritical carbon dioxide, or the like.

[0176] Freeze drying is preferably performed by pre-freezing the purified cellulose wet particles and then performing primary drying and secondary drying.

[0177] The pre-freezing is preferably carried out by rapid freezing at a temperature of -200°C to -50°C under normal pressure. Furthermore, it is preferred to carry out primary drying to sublime ice in the pre-frozen product under a vacuum of 0.1 Pa to 100 Pa and at a temperature of -20°C to -5°C, and then, it is preferred to carry out secondary drying under a vacuum of 0.1 Pa to 100 Pa and at a temperature of 20°C to 40°C.

[0178] [cosmetic]

[0179] The present invention also provides a cosmetic comprising the porous cellulose particles.

[0180] The cosmetics of the present invention can provide a good touch by including the porous cellulose particles. In addition, the porous cellulose particles have excellent inclusion of functional substances and particle disintegration properties, so the cosmetics including the porous cellulose particles can slowly release the functional substances to the object by coating.

[0181] From the viewpoint of effectively exerting the above-mentioned effects, the cosmetics of the present invention are preferably skin cosmetics, and examples of the skin cosmetics include foundation, base makeup, sunscreen, emulsion, lotion, and the like.

[0182] The content of the porous cellulose particles in the cosmetic may be an amount that can exhibit desired performance, and may be appropriately selected depending on the type and form of the cosmetic, and is generally in the range of 0.01% by mass to 80% by mass in the cosmetic.

[0183] <Application>

[0184] The porous cellulose particles of the present invention can be blended or used for purposes other than cosmetics, such as toiletries, oral care products, quasi-drugs, pharmaceuticals, household products, agricultural products, and the like.

[0185] In addition, the porous cellulose particles of the present invention are composed of cellulose derived from natural plants and are therefore environmentally friendly and can also be suitably used as a substitute material for microplastics.

[0186] In addition to the above-mentioned embodiments, the present invention also discloses the following contents.

[0187] <1>

[0188] A porous cellulose particle having a compression elastic modulus of 50 MPa or less,

[0189] The specific surface area is 100m 2 / g or more and less than 500m 2 / g,

[0190] The pore volume is 1.5 mL / g or more.

[0191] <2>

[0192] The porous cellulose particles according to <1>, wherein the compressive elastic modulus of the above-mentioned porous cellulose particles is preferably 40 MPa or less, more preferably 30 MPa or less, further preferably 20 MPa or less, further preferably 10 MPa or less, further preferably 7.0 MPa or less, further preferably 6.0 MPa or less, further preferably 5.0 MPa or less, further preferably 5.3 MPa or less, further preferably 5.2 MPa or less.

[0193] <3>

[0194] The porous cellulose particles according to <1> or <2>, wherein the compressive elastic modulus of the porous cellulose particles is preferably 1.0 MPa or more, more preferably 2.0 MPa or more, further preferably 3.0 MPa or more, further preferably 4.0 MPa or more, further preferably 4.9 MPa or more.

[0195] <4>

[0196] The porous cellulose particles according to any one of <1> to <3>, wherein the porous cellulose particles have a median particle size of 75 μm or less as measured by a dry method.

[0197] <5>

[0198] The porous cellulose particles according to any one of <1> to <4>, wherein the median diameter (D 50 ) is preferably 75 μm or less, more preferably 70 μm or less, further preferably 65 μm or less, further preferably 55 μm or less, further preferably 40 μm or less, further preferably 30 μm or less.

[0199] <6>

[0200] The porous cellulose particles according to any one of <1> to <5>, wherein the median diameter (D 50 ) is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 15 μm or more.

[0201] <7>

[0202] The porous cellulose particles according to any one of <1> to <6>, wherein the specific surface area of ​​the porous cellulose particles is preferably 110 m 2 / g or more, more preferably 120m 2 / g or more, more preferably 130m 2 / g or more, more preferably 135m 2 / g or more, more preferably 140m 2 / g or more, and more preferably 144m 2 / g or above.

[0203] <8>

[0204] The porous cellulose particles according to any one of <1> to <7>, wherein the specific surface area of ​​the porous cellulose particles is preferably 200 m 2 / g or less, more preferably 180m 2 / g or less, more preferably 150m 2 / g or less.

[0205] <9>

[0206] The porous cellulose particles according to any one of <1> to <8>, wherein the pore volume of the porous cellulose particles is preferably 2.0 mL / g or more, more preferably 2.5 mL / g or more, further preferably 3.0 mL / g or more, further preferably 3.5 mL / g or more, further preferably 4.0 mL / g or more.

[0207] <10>

[0208] The porous cellulose particles according to any one of <1> to <9>, wherein the pore volume of the porous cellulose particles is preferably 8.0 mL / g or less, more preferably 7.0 mL / g or less, further preferably 6.0 mL / g or less, and further preferably 5.0 mL / g or less.

[0209] <11>

[0210] The porous cellulose particles according to any one of <1> to <10>, wherein the sphericity of the porous cellulose particles is preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more.

[0211] <12>

[0212] The porous cellulose particles according to any one of <1> to <11>, wherein the surface pore diameter of the porous cellulose particles is preferably 50 nm or more, more preferably 100 nm or more, and even more preferably 200 nm or more.

[0213] <13>

[0214] The porous cellulose particles according to any one of <1> to <12>, wherein the surface pore diameter of the porous cellulose particles is preferably 800 nm or less, more preferably 600 nm or less, and even more preferably 500 nm or less.

[0215] <14>

[0216] The porous cellulose particles according to any one of <1> to <13>, wherein the porous cellulose particles are chemically unmodified porous cellulose particles.

[0217] <15>

[0218] The porous cellulose particles according to any one of <1> to <14>, wherein the porous cellulose particles are non-crosslinked particles.

[0219] <16>

[0220] The porous cellulose particles according to any one of <1> to <15>, wherein the cellulose constituting the porous cellulose particles comprises cellulose II type crystalline cellulose or amorphous cellulose.

[0221] <17>

[0222] The porous cellulose particles according to any one of <1> to <16>, wherein the content of cellulose in the porous cellulose particles is preferably 95% by mass or more, more preferably 99% by mass or more, and even more preferably substantially 100% by mass.

[0223] <18>

[0224] A cosmetic comprising the porous cellulose particles according to any one of <1> to <17>.

[0225] <19>

[0226] The method for producing porous cellulose particles according to any one of <1> to <17> comprises the following steps (I) to (V) in order.

[0227] Step (I): a step of mixing raw material cellulose with an alkaline aqueous solution to prepare a cellulose aqueous solution

[0228] Step (II): Mixing the cellulose aqueous solution with an organic solvent to prepare a cellulose emulsion

[0229] Step (III): a step of mixing the cellulose emulsion with a solvent that does not dissolve cellulose to precipitate crude cellulose particles and obtain a suspension containing crude cellulose particles

[0230] Step (IV): After solid-liquid separation of the suspension containing crude cellulose particles, the obtained wet crude cellulose particles are washed to obtain purified wet cellulose particles.

[0231] Step (V): a step of drying the wet purified cellulose particles

[0232] <20>

[0233] The method for producing porous cellulose particles according to <19>, wherein the raw material cellulose used in the step (I) is preferably chemically pure cellulose that has not been chemically modified, and more preferably wood or pulp.

[0234] <21>

[0235] The method for producing porous cellulose particles according to <19> or <20>, wherein the raw material cellulose used in the step (I) is in the form of powder, flake, or cotton, preferably powder.

[0236] <22>

[0237] The method for producing porous cellulose particles according to any one of <19> to <21>, wherein the degree of polymerization of the raw cellulose used in the above step (I) is preferably 10 or more, more preferably 50 or more, further preferably 100 or more, further preferably 150 or more, and is preferably 1000 or less, more preferably 500 or less, further preferably 300 or less.

[0238] <23>

[0239] The method for producing porous cellulose particles according to any one of <19> to <22>, wherein the raw material cellulose used in the step (I) is preferably crystalline cellulose, more preferably type I crystalline cellulose.

[0240] <24>

[0241] A method for producing porous cellulose particles according to any one of <19> to <23>, wherein the raw cellulose used in the above step (I) is in powder form, and the median particle size of the raw cellulose is preferably 10 μm or more, more preferably 20 μm or more, and is preferably 500 μm or less, more preferably 300 μm or less, further preferably 200 μm or less, and further preferably 150 μm or less.

[0242] <25>

[0243] The method for producing porous cellulose particles according to any one of <19> to <24>, wherein in the step (I), the alkali compound used in the aqueous alkali solution is preferably an alkali metal hydroxide, more preferably at least one selected from sodium hydroxide and potassium hydroxide, and even more preferably sodium hydroxide.

[0244] <26>

[0245] The method for producing porous cellulose particles according to any one of <19> to <25>, wherein the concentration of the alkali compound in the alkali aqueous solution used in the above step (I) is preferably 1 mass % or more, more preferably 2 mass % or more, further preferably 3 mass % or more, and is preferably 40 mass % or less, more preferably 30 mass % or less, further preferably 25 mass % or less.

[0246] <27>

[0247] The method for producing porous cellulose particles according to any one of <19> to <26>, wherein in the step (I), the aqueous alkali solutions having different concentrations are mixed with the raw material cellulose in a plurality of times.

[0248] <28>

[0249] A method for producing porous cellulose particles according to any one of <19> to <27>, wherein in the above step (I), after mixing the raw material cellulose with an alkaline aqueous solution A having an alkali compound concentration of 1% by mass to 10% by mass, an alkaline aqueous solution B having an alkali compound concentration of more than 10% by mass to 40% by mass is added and mixed to prepare a cellulose aqueous solution.

[0250] <29>

[0251] The method for producing porous cellulose particles according to <28>, wherein the concentration of the alkali compound in the aqueous alkali solution A is more preferably 2 mass % to 8 mass %, and further preferably 2 mass % to 5 mass %.

[0252] <30>

[0253] The method for producing porous cellulose particles according to <28> or <29>, wherein the concentration of the alkali compound in the aqueous alkali solution B is more preferably 15 mass % to 30 mass %, and further preferably 20 mass % to 25 mass %.

[0254] <31>

[0255] The method for producing porous cellulose particles according to any one of <28> to <30>, wherein the mass ratio (A / B) of the aqueous alkaline solution A to the aqueous alkaline solution B is preferably 1 to 10, more preferably 2 to 8, and even more preferably 3 to 6.

[0256] <32>

[0257] The method for producing porous cellulose particles according to any one of <19> to <31>, wherein in the step (I), the temperature at which the raw material cellulose and the alkaline aqueous solution are mixed is preferably 10°C or lower, more preferably 5°C or lower, further preferably 0°C or lower, and is preferably -20°C or higher, more preferably -10°C or higher, further preferably -5°C or higher.

[0258] <33>

[0259] A method for producing porous cellulose particles according to any one of <28> to <30>, wherein in the step (I), the raw material cellulose is added to the alkaline aqueous solution A and stirred and mixed, and then the temperature of the mixture is adjusted to preferably 10°C or less, more preferably 5°C or less, further preferably 0°C or less, and preferably -20°C or more, more preferably -10°C or more, further preferably -5°C or more, before adding the alkaline aqueous solution B and mixing.

[0260] <34>

[0261] The method for producing porous cellulose particles according to any one of <19> to <33>, wherein the cellulose aqueous solution obtained in the step (I) has a cellulose concentration of 1 mass % to 8 mass %.

[0262] <35>

[0263] A method for producing porous cellulose particles according to any one of <19> to <34>, wherein the concentration of the alkali compound in the cellulose aqueous solution obtained in the above step (I) is preferably 0.5% by mass or more, more preferably 1% by mass or more, further preferably 2% by mass or more, further preferably 3% by mass or more, further preferably 5% by mass or more, and is preferably 15% by mass or less, more preferably 12% by mass or less, further preferably 10% by mass or less.

[0264] <36>

[0265] The method for producing porous cellulose particles according to any one of <19> to <35>, wherein the organic solvent used in the above step (II) is a hydrocarbon solvent, more preferably a chain aliphatic hydrocarbon, further preferably at least one selected from n-pentane, n-hexane, n-heptane, n-octane, isooctane, decane, isodecane, dodecane, isododecane, tetradecane, hexadecane and octadecane, and further preferably at least one selected from n-octane, isooctane, n-decane, isodecane, n-dodecane and isododecane.

[0266] <37>

[0267] The method for producing porous cellulose particles according to any one of <19> to <36>, wherein an emulsifier is further mixed in the step (II).

[0268] <38>

[0269] According to the method for producing porous cellulose particles of <37>, the emulsifier is a nonionic surfactant, preferably at least one selected from sorbitan fatty acid esters, polyoxyethylene alkyl ethers, sucrose fatty acid esters and polyether-modified silicones, more preferably sucrose fatty acid esters, further preferably at least one selected from sucrose palmitate, sucrose oleate, sucrose stearate, sucrose erucate and sucrose behenate, and further preferably at least one selected from sucrose erucate and sucrose behenate.

[0270] <39>

[0271] According to the method for producing porous cellulose particles of <38>, the HLB of the nonionic surfactant used as an emulsifier is preferably greater than 1 and less than 10, more preferably greater than 1 and less than 8, further preferably greater than 1 and less than 6, further preferably greater than 1 and less than 5, further preferably greater than 1 and less than 4, further preferably greater than 1 and less than 3.

[0272] <40>

[0273] A method for producing porous cellulose particles according to any one of <37> to <39>, wherein the amount of the emulsifier mixed in the above step (II) is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, further preferably 1.0 parts by mass or more, relative to 100 parts by mass of the above organic solvent, and is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, further preferably 5.0 parts by mass or less.

[0274] <41>

[0275] A method for producing porous cellulose particles according to any one of <19> to <40>, wherein in the above step (II), the temperature when the cellulose aqueous solution and the organic solvent are mixed is preferably 20°C or less, more preferably 10°C or less, further preferably 5°C or less, and is preferably -20°C or more, more preferably -10°C or more, further preferably -5°C or more.

[0276] <42>

[0277] A method for producing porous cellulose particles according to any one of <19> to <41>, wherein in the above-mentioned step (II), the stirring speed when mixing the cellulose aqueous solution and the organic solvent is preferably 1000 rpm or more, more preferably 3000 rpm or more, further preferably 5000 rpm or more, further preferably 5500 rpm or more, and is preferably 15000 rpm or less, more preferably 12000 rpm or less, further preferably 10000 rpm or less, further preferably 8500 rpm or less.

[0278] <43>

[0279] The method for producing porous cellulose particles according to any one of <19> to <42>, wherein the solvent insoluble in cellulose used in the step (III) is an alcohol having 4 or less carbon atoms.

[0280] <44>

[0281] The method for producing porous cellulose particles according to any one of <19> to <43>, wherein the solvent insoluble to cellulose used in the step (III) is preferably at least one selected from ethanol, 2-propanol, 1-butanol, 2-butanol and 2-methyl-1-propanol, more preferably ethanol.

[0282] <45>

[0283] A method for producing porous cellulose particles according to any one of <19> to <44>, wherein the mixing amount of the solvent insoluble in cellulose used in the above step (III) is preferably 50 parts by mass or more, more preferably 100 parts by mass or more, further preferably 200 parts by mass or more, relative to 100 parts by mass of the cellulose emulsion, and is preferably 1000 parts by mass or less, more preferably 500 parts by mass or less, further preferably 400 parts by mass or less.

[0284] <46>

[0285] The method for producing porous cellulose particles according to any one of <19> to <45>, wherein an acid is further mixed in the step (III).

[0286] <47>

[0287] The method for producing porous cellulose particles according to <46>, wherein the acid mixed in the step (III) is preferably an organic acid, more preferably a carboxylic acid having 4 or less carbon atoms.

[0288] <48>

[0289] The method for producing porous cellulose particles according to <46> or <47>, wherein the amount of the acid mixed in the step (III) is preferably 1.0 equivalent or more, more preferably 1.2 equivalents or more, further preferably 1.4 equivalents or more, relative to the alkaline compound used in the step (I), and is preferably 3.0 equivalents or less, more preferably 2.0 equivalents or less, further preferably 1.8 equivalents or less.

[0290] <49>

[0291] The method for producing porous cellulose particles according to any one of <46> to <48>, wherein in the step (III), the cellulose emulsion is mixed with a solvent that does not dissolve cellulose and then the acid is mixed.

[0292] <50>

[0293] A method for producing porous cellulose particles according to any one of <19> to <49>, wherein in the above step (III), the temperature at which the cellulose emulsion is mixed with a solvent that does not dissolve cellulose is preferably 0°C or higher, more preferably 5°C or higher, further preferably 15°C or higher, and preferably 50°C or lower, more preferably 40°C or lower, further preferably 30°C or lower.

[0294] <51>

[0295] A method for producing porous cellulose particles according to any one of <19> to <50>, wherein in the above-mentioned step (III), the stirring speed when the cellulose emulsion is mixed with the solvent in which the cellulose is not dissolved is preferably 100 rpm or more, more preferably 200 rpm or more, and is preferably 2000 rpm or less, more preferably 1500 rpm or less, further preferably 1000 rpm or less, and further preferably 800 rpm or less.

[0296] <52>

[0297] The method for producing porous cellulose particles according to any one of <19> to <51>, wherein in the step (III), the stirring time when the cellulose emulsion and the solvent insoluble in cellulose are mixed is 0.2 hours to 12 hours, preferably 0.5 hours to 6 hours.

[0298] <53>

[0299] The method for producing porous cellulose particles according to any one of <19> to <52>, wherein in the step (IV), solid-liquid separation of the suspension containing the crude cellulose particles obtained in the step (III) is performed by centrifugation, filtration, decantation, or a combination thereof.

[0300] <54>

[0301] The method for producing porous cellulose particles according to any one of <19> to <53>, wherein in the step (IV), the wet crude cellulose particles obtained after the solid-liquid separation are washed with water, an organic solvent, or a combination thereof.

[0302] <55>

[0303] The method for producing porous cellulose particles according to <54>, wherein the organic solvent is a ketone solvent having 6 or less carbon atoms or an alcohol solvent having 6 or less carbon atoms, preferably acetone, methyl isobutyl ketone, ethanol or 2-propanol.

[0304] <56>

[0305] The method for producing porous cellulose particles according to any one of <19> to <55>, wherein in the step (IV), the cellulose particles obtained after the washing treatment are dispersed in a dispersion medium to perform dispersion medium replacement, and further dried under reduced pressure.

[0306] <57>

[0307] The method for producing porous cellulose particles according to <56>, wherein in the step (IV), the dispersion medium used in the dispersion medium replacement is an organic solvent having a surface tension at 25° C. of preferably 20 mN / m or less, more preferably 18 mN / m or less, and preferably pentane.

[0308] <58>

[0309] The method for producing porous cellulose particles according to <56> or <57>, wherein in the above-mentioned step (IV), the amount of the dispersion medium used in the above-mentioned dispersion medium replacement is preferably 100 parts by mass or more, more preferably 200 parts by mass or more, and is preferably 2000 parts by mass or less, more preferably 1000 parts by mass or less, and further preferably 600 parts by mass or less, relative to 100 parts by mass of the cellulose particles after the above-mentioned washing treatment.

[0310] <59>

[0311] A method for producing porous cellulose particles according to any one of <56> to <58>, wherein in the step (IV), the temperature at which the washed cellulose particles are mixed with the dispersion medium is preferably 0°C or higher, more preferably 5°C or higher, further preferably 15°C or higher, and preferably 50°C or lower, more preferably 40°C or lower, further preferably 30°C or lower.

[0312] <60>

[0313] A method for producing porous cellulose particles according to any one of <56> to <59>, wherein in the step (IV), the stirring speed when mixing the washed cellulose particles with the dispersion medium is preferably 100 rpm or more, more preferably 200 rpm or more, and is preferably 2000 rpm or less, more preferably 1500 rpm or less, further preferably 1000 rpm or less, and further preferably 800 rpm or less.

[0314] <61>

[0315] The method for producing porous cellulose particles according to any one of <56> to <60>, wherein in the step (IV), the suspension obtained by the dispersion medium replacement is subjected to solid-liquid separation to recover and purify the wet cellulose particles.

[0316] <62>

[0317] The method for producing porous cellulose particles according to any one of <19> to <61>, wherein in the step (V), the drying treatment is performed by freeze drying.

[0318] <63>

[0319] The method for producing porous cellulose particles according to <62>, wherein the freeze-drying method is a method in which the wet purified cellulose particles are pre-frozen and then subjected to primary drying and secondary drying.

[0320] <64>

[0321] According to the method for producing porous cellulose particles <63>, in the above-mentioned pre-freezing, rapid freezing is carried out at normal pressure and a temperature of not less than -200°C and not more than -50°C, and a first drying is preferably carried out under a vacuum of not less than 0.1 Pa and not more than 100 Pa and at a temperature of not less than -20°C and not more than -5°C to allow ice in the pre-frozen material to sublime, and then a second drying is carried out under a vacuum of not less than 0.1 Pa and not more than 100 Pa and at a temperature raised to not less than 20°C and not more than 40°C.

[0322] Example

[0323] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples at all.

[0324] Various measurement and evaluation methods are described below.

[0325] <X-ray diffraction intensity>

[0326] The X-ray diffraction intensity was measured under the following conditions using an X-ray diffraction apparatus (“MiniFlex-II” manufactured by Rigaku Corporation).

[0327] The measurement conditions are as follows.

[0328] X-ray source: Cu / Kα-radiation

[0329] Measuring range: 2θ = 5 to 50°

[0330] The sample for measurement is compressed to an area of ​​320mm 2 The X-ray scanning speed was 5° / min.

[0331] Cellulose II crystals have a peak corresponding to the 110 face at a diffraction angle of 2θ = 20.0° (I 20.0 The cellulose II crystallinity (X [%]) was calculated using the peak intensity at 2θ = 15.0°, which reflects the amorphous part (I 15.0 ), is obtained by the following formula.

[0332] X=[(I 20.0 -I 15.0 ) / I 20.0 ]×100

[0333] <Compression elastic modulus>

[0334] The compressive elastic modulus of cellulose particles was measured using a micro compression tester ("MCT-510" manufactured by Shimadzu Corporation). Specifically, cellulose particles were placed on a measuring table attached to the above device, and the diameter d was measured. The indenter (Φ50 μm) was lowered at a constant loading rate (mN / sec) to compress the particles until a predetermined test force (0.98 mN) was reached. The compressive stress was calculated using the following formula based on the particle diameter d (μm) and the test force P (mN).

[0335] Compressive stress (MPa) = 2.48 × P (mN) / (π × (d (μm)) 2 )

[0336] The compressive strain was calculated from the displacement x (μm) and the particle size d (μm) using the following formula.

[0337] Compression strain (%) = x (μm) / d (μm) × 100

[0338] A stress-strain curve was prepared from the calculated compressive stress and compressive strain, and the compressive elastic modulus was calculated from the slope of the elastic region (0-10%). The measurement was performed 7 times, and the average value of the 5 times excluding the maximum and minimum values ​​was taken as the test result.

[0339] <Median particle size>

[0340] The median particle size of cellulose particles (D 50 ) was measured using a laser scattering particle size distribution measuring machine ("LS 13 320" manufactured by Beckman Coulter Co., Ltd.). Specifically, 50 mg of dried cellulose particles were weighed in a measuring cell and measured using a cyclone drying powder sample module (Japanese: トルネードドライパウダーモジュール) to find the particle size that reaches 50% in the volume distribution of the particle size. During the measurement, the refractive index of cellulose was input as the measured value of 1.469.

[0341] <Specific surface area>

[0342] The specific surface area of ​​cellulose particles was measured by the following method. Mercury was pressed into the cellulose particles by mercury intrusion using a mercury porosimeter ("Auto Pore IV 9500" manufactured by Shimadzu Corporation) to determine the total surface area X (m2) of the fine surface inside the cellulose particles and the surface of the particles. 2 Specifically, about 0.05 g of cellulose particles were added to the sample cell of the mercury porosimeter, and the mercury intrusion method was used to perform measurement at a pressure ranging from 0.01 MPa to 210 MPa to obtain the above X (m 2 ) value. Let the mass of the cellulose particles used as the measurement sample be Y (g), and X (m 2 The value of ) / Y(g) was taken as the specific surface area of ​​the cellulose particles.

[0343] <Pore capacity>

[0344] The pore capacity of cellulose particles is measured by the following method. Using a mercury porosimeter ("Auto Pore IV 9500" manufactured by Shimadzu Corporation), mercury is pressed into the cellulose particles by mercury intrusion, and the total volume of mercury that penetrates the pores in the cellulose particles and the gaps between the cellulose particles is calculated, Z (mL). Specifically, about 0.05 g of cellulose particles are added to the sample cell of the mercury porosimeter, and a measurement based on mercury intrusion is performed within the measurement pressure range of 0.01 MPa to 210 MPa to calculate the value of the above Z (mL). The mass of the cellulose particles used as the measurement sample is set to Y (g), and the value of Z (mL) / Y (g) is set to the pore capacity of the cellulose particles.

[0345] <Surface pore diameter>

[0346] The surface pore size of the cellulose particles is measured by the following method. Using a mercury porosimeter ("Auto Pore IV 9500" manufactured by Shimadzu Corporation), mercury is pressed into the cellulose particles by the mercury intrusion method to obtain the pore distribution in the cellulose particles. Specifically, first, about 0.05 g of cellulose particles are added to the sample cell of the mercury porosimeter, and a measurement based on the mercury intrusion method is performed in the range of measuring pressure of 0.01 MPa to 210 MPa. The pore capacity of the cellulose particles is obtained by the same method as above: Z (mL) / Y (g). The horizontal axis is set to the pore diameter (nm), and the vertical axis is set to the pore capacity (mL / g) to obtain a cumulative pore distribution curve. Next, the value obtained by differentiating the above (cumulative) pore capacity by the pore diameter, that is, the increase in pore capacity at each pore diameter, is taken as the differential pore capacity (mL / g). The horizontal axis is set to the pore diameter (nm), and the vertical axis is set to the differential pore capacity (mL / g) to obtain a pore distribution curve. In the obtained pore distribution curve, the mode value of the pore diameter in the region of pore diameters of 1000 nm or less was taken as the surface pore diameter of the particle.

[0347] <Sphericity>

[0348] The sphericity of cellulose particles was measured by a dynamic image analyzer (CAMSIZERX2 manufactured by MICROTRAC MRB). Specifically, 20 mg of dried cellulose particles were put into the feeder of the device, and the particles were dispersed at an air dispersion pressure of 30 kPa. The dispersion was added to the above-mentioned dynamic image analyzer to obtain an image. The sphericity (%) of one particle was calculated from the image according to the following formula. The average value of about 5,000 images obtained was taken as the sphericity.

[0349] Sphericity (%) = 4π × particle area (m 2 ) / (Particle circumference (m)) 2 ×100

[0350] <Touch>

[0351] About 5 mg of cellulose particles were applied to the right forearm of the professional evaluator in an area of ​​4 cm × 5 cm to a concentration of 0.25 mg / cm 2 The softness and the degree of roughness at this time were evaluated by sensory evaluation according to the following criteria.

[0352] 5: Very soft and smooth, 4: Soft and smooth, 3: No hardness or roughness, 2: Hard and roughness, 1: Very hard and roughness

[0353] <Inclusion rate of functional substances (Nile Red)>

[0354] About 50 mg of cellulose particles were weighed and mixed with a solution of about 50 mg of Nile Red (manufactured by Tokyo Chemical Industry Co., Ltd.) as a functional substance dissolved in 20 mL of ethanol. After stirring overnight, the mixture was vacuum dried at 60°C and the ethanol was distilled off to obtain composite particles containing cellulose particles and Nile Red. The obtained composite particles were taken out and the Nile Red contained in the particles was extracted using 50 mL of o-xylene. The amount of Nile Red extracted was quantified by ultraviolet-visible absorption measurement, and the inclusion rate was calculated according to the following formula.

[0355] Encapsulation rate (%) = (amount of Nile red extracted (mg)) / (amount of Nile red used (mg)) × 100

[0356] The above insourcing ratio is scored according to the following criteria.

[0357] 5: 80% or more, 4: 60% or more and less than 80%, 3: 40% or more and less than 60%, 2: 20% or more and less than 40%, 1: less than 20%

[0358] <Disintegration due to friction>

[0359] About 20 mg of cellulose particles were weighed and placed on artificial leather (Laforet S2923, 5 cm × 4 cm). A surface tester (TriboGear TYPE14 manufactured by Shinto Science Co., Ltd.) was used to apply a vertical load of 200 g, which was equivalent to the coating action, and 20 reciprocating frictions were performed at a moving distance of 50 mm and a moving speed of 2000 mm / min. The cellulose particles remaining on the surface of the artificial leather were observed using a scanning electron microscope (SEM, JEOL Ltd. "JSM-IT-500HR") at an accelerating voltage of 5.0 kV and an observation magnification of 500 times. The proportion of particles that were flattened (disintegrated) due to friction among the 20 cellulose particles in the observed image was calculated as the disintegration rate, and the score was given according to the following criteria.

[0360] 5: 80% or more, 4: 60% or more and less than 80%, 3: 40% or more and less than 60%, 2: 20% or more and less than 40%, 1: less than 20%

[0361] Example 1 (Production and Evaluation of Porous Cellulose Particles)

[0362] (Process (I))

[0363] As the raw material cellulose, cellulose type I crystalline cellulose powder ("Avicel PH-101" manufactured by Asahi Kasei Corporation, degree of polymerization: 170, median particle size: 50 μm, moisture content 6%) was used.

[0364] 10.6 g of the cellulose powder was added to 189.4 g of a dilute NaOH aqueous solution (NaOH concentration: 4.2 mass %), and the mixture was cooled to -2° C. Then, 50 g of a concentrated NaOH aqueous solution (NaOH concentration: 22 mass %) was added while the mixture was kept at -2° C., and the mixture was stirred for 1 hour to dissolve the raw material cellulose, thereby obtaining a cellulose aqueous solution.

[0365] The cellulose concentration in the obtained cellulose aqueous solution was 4% by mass and the NaOH concentration was 7.6% by mass.

[0366] (Process (II))

[0367] 350 g of isododecane and 3.5 g of sucrose erucate ("RYOTO Sugar Ester ER-290" manufactured by Mitsubishi Chemical Co., Ltd., HLB: 2, monoester content: about 2%) as an emulsifier were added to the above cellulose aqueous solution. The mixture was stirred at 5°C and 7000 rpm for 5 minutes using a homomixer ("MARK II 2.5" manufactured by PRIMIX Co., Ltd.) to emulsify the mixture, thereby obtaining a water-in-oil emulsion of cellulose. The particle size distribution was measured using a laser diffraction / scattering particle size analyzer ("LA-960V2" manufactured by Horiba, Ltd.), and the diameter of the emulsion droplets in the emulsion was 10 to 80 μm.

[0368] (Step (III))

[0369] The total amount of the emulsion obtained in the above step (II) was added to 1500 g of alcohol (ethanol) as a solvent that does not dissolve cellulose, and stirred at 400 rpm for 1 hour at room temperature (25° C.) using a stirring blade to precipitate crude cellulose particles. Next, 42.8 g of acetic acid (1.5 equivalents relative to NaOH) was added for neutralization to obtain a suspension containing crude cellulose particles.

[0370] (Process (IV))

[0371] The suspension obtained in the above step (III) is filtered under reduced pressure (700 hPa) using filter paper ("OMNIPORE DISC PTFE PHILIC 1.0μM 90MM WH PLN 25 / PK" manufactured by Millipore, with a mesh size of 1μm) to perform solid-liquid separation. For the recovered wet particles, acetone (300 parts by mass relative to 100 parts by mass of cellulose wet particles) is added, and after stirring at room temperature for 1 hour, solid-liquid separation is performed again. This operation is repeated twice. Next, water (300 parts by mass relative to 100 parts by mass of cellulose wet particles) is added, and after stirring at room temperature for 1 hour, solid-liquid separation is performed again. This operation is repeated twice. After the above-mentioned washing step, the obtained suspension is subjected to solid-liquid separation again to recover the wet particles of purified cellulose.

[0372] (Process (V))

[0373] The wet particles of purified cellulose recovered in the above step (IV) were rapidly frozen in a dry ice / ethanol bath at -72°C and then freeze-dried under a vacuum of 100 Pa or less to obtain dry particles of purified porous cellulose.

[0374] The obtained porous cellulose particles were evaluated by the above-mentioned method. The results are shown in Table 1.

[0375] Embodiments 2-3, 5-6

[0376] In Example 1, porous cellulose particles were produced and evaluated in the same manner as in Example 1 except that the conditions of the above steps (I) to (V) were changed as shown in Table 1. The results are shown in Table 1.

[0377] Example 4

[0378] After carrying out steps (I) to (IV) in the same manner as in Example 1, the following operations were further carried out to produce porous cellulose particles, which were then evaluated. The results are shown in Table 1.

[0379] Pentane (300 parts by mass relative to the wet cellulose particles) was added to the wet particles of purified cellulose recovered in the above step (IV), and stirred at 400 rpm for 1 hour at room temperature using a stirring blade, and then solid-liquid separation was performed again in the same manner as above. This operation was repeated twice. After the above operation, the obtained wet particles of purified cellulose were dried under reduced pressure at a vacuum of 50 kPa or less overnight to obtain dried particles of purified porous cellulose.

[0380] Comparative Examples 1 to 3

[0381] Evaluation was performed using commercially available cellulose particles listed in Table 1 as cellulose particles. Table 1 shows the results.

[0382] [Table 1]

[0383]

[0384] As shown in Table 1, the porous cellulose particles of this example have a good feel when applied to the skin, and are excellent in the inclusion of functional substances and the disintegration of the particles during application. In contrast, the cellulose particles of the comparative example are inferior in any of the above properties.

[0385] Figures 1 to 3 The X-ray diffraction patterns of the raw cellulose (cellulose type I crystal) used in the examples, the porous cellulose particles obtained in Example 1 (cellulose type II crystal), and the porous cellulose particles (amorphous) obtained in Example 4 are shown respectively. Figure 2 , a diffraction peak from the (11-0) plane is shown at a diffraction angle of 2θ = 12.5°, and a diffraction peak from the (110) plane is shown at a diffraction angle of 2θ = 20.0°. Therefore, the porous cellulose particles obtained in Example 1 can be attributed to cellulose type II crystals. Figure 3 Since a broad peak is shown in the graphene, the porous cellulose particles obtained in Example 4 can be attributed to amorphous cellulose.

[0386] Industrial Applicability

[0387] According to the present invention, there can be provided porous cellulose particles which can impart a soft touch when added to cosmetics, have less roughness when applied, and are excellent in the inclusion of functional substances and the disintegration of particles.

Claims

1. A porous cellulose particle having a compressive elastic modulus of 50 MPa or less, The specific surface area is 100m 2 / g or more and less than 500m 2 / g, The pore volume is 1.5 mL / g or more.

2. The porous cellulose particles according to claim 1, wherein The porous cellulose particles have a median particle size of 75 μm or less as measured by a dry method.

3. The porous cellulose particles according to claim 1 or 2, wherein The porous cellulose particles are porous cellulose particles that are not chemically modified.

4. The porous cellulose particles according to any one of claims 1 to 3, wherein The cellulose constituting the porous cellulose particles includes cellulose II type crystalline cellulose or amorphous cellulose.

5. The porous cellulose particles according to any one of claims 1 to 4, wherein The porous cellulose particles contain cellulose in an amount of 95% by mass or more.

6. The porous cellulose particles according to any one of claims 1 to 5, wherein The porous cellulose particles have a surface pore diameter of 50 nm or more and 800 nm or less.

7. The porous cellulose particles according to any one of claims 1 to 6, wherein The sphericity of the porous cellulose particles is greater than 60%. 8 . A cosmetic comprising the porous cellulose particles according to claim 1 .

9. A method for producing porous cellulose particles according to any one of claims 1 to 7, comprising the following steps (I) to (V) in sequence: Step (I): a step of mixing a raw material cellulose with an alkaline aqueous solution to prepare a cellulose aqueous solution; Step (II): a step of mixing the cellulose aqueous solution with an organic solvent to prepare a cellulose emulsion; Step (III): a step of mixing the cellulose emulsion with a solvent that does not dissolve cellulose to precipitate crude cellulose particles, thereby obtaining a suspension containing crude cellulose particles; Step (IV): after solid-liquid separation of the suspension containing crude cellulose particles, washing the obtained wet crude cellulose particles to obtain purified wet cellulose particles; Step (V): a step of drying the wet purified cellulose particles to obtain porous cellulose particles.

10. The method for producing porous cellulose particles according to claim 9, wherein: The raw material cellulose used in the step (I) is cellulose I type crystalline cellulose.

11. The method for producing porous cellulose particles according to claim 9 or 10, wherein: The cellulose aqueous solution obtained in the step (I) has a cellulose concentration of 1 mass % or more and 8 mass % or less.

12. The method for producing porous cellulose particles according to any one of claims 9 to 11, wherein: The organic solvent used in the step (II) is a hydrocarbon solvent.

13. The method for producing porous cellulose particles according to any one of claims 9 to 12, wherein: In the step (II), an emulsifier is further mixed.

14. The method for producing porous cellulose particles according to any one of claims 9 to 13, wherein: The solvent insoluble in cellulose used in the step (III) is an alcohol having 4 or less carbon atoms.

15. The method for producing porous cellulose particles according to any one of claims 9 to 14, wherein In the step (III), an acid is further mixed.

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