Powder manufacturing method and powder

Abstract

To provide a technique for improving protein adsorbability.SOLUTION: There is provided a method of producing a powder containing a cellulose fiber, which comprises a step of spray-drying a slurry, wherein the slurry comprises a cellulose fiber having an anionic group and a solvent including an organic solvent, the cellulose fiber is dispersed in a solvent and the zeta potential is -40 mV or more and -20 mV or less. The powder containing a cellulose fiber has a cellulose fiber having an anionic group, a specific surface area of 50 m2 / g or more and 400 m2 / g or less and a total pore volume of 0.1 cm3 / g or more and 0.85 cm3 / g or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing powder and the powder. [Background technology]

[0002] Cellulose is a biodegradable, naturally occurring material known for its versatility and relatively high chemical and thermal stability. Because cellulose is resistant to nonspecific interactions and adsorption with biological substances such as proteins, it is used as a packing material for purification and separation columns, as well as a carrier, adsorbent, and membrane material for immobilizing enzymes, microorganisms, and cells.

[0003] Fine fibrous cellulose, also known as cellulose nanofibers, are nano-order cellulose fibers obtained by defibrating cellulosic raw materials such as wood. Research results have been reported on the adsorption properties of cellulose nanofibers toward biological substances such as proteins. For example, Non-Patent Document 1 describes the adsorption properties of proteins toward TEMPO-oxidized cellulose nanofibers. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Ramon Weishaupt, and 8 others “TEMPO-OxidizedNanofibrillated Cellulose as a High Density Carrier for Bioactive Molecules”, Biomacromolecules, 2015, 16, 11, 3640-3650 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the cellulose nanofibers described in Non-Patent Document 1 do not have sufficient protein adsorption capacity, and there is room for improvement. For this reason, there is a need for the development of a technology that can improve protein adsorption capacity. [Means for solving the problem]

[0006] The present invention can be realized in the following aspects.

[0007] (1) According to one aspect of the present invention, there is provided a method for producing a powder containing cellulose fibers, comprising spray-drying a slurry, the slurry containing cellulose fibers having anionic groups and a solvent containing an organic solvent, the cellulose fibers being dispersed in the solvent, and the slurry having a zeta potential of −40 mV or more and −20 mV or less.

[0008] (2) In the powder production method of the above aspect, the cellulose fiber may be contained in an amount of 0.01% by mass or more and 0.50% by mass or less in terms of solid content relative to the total mass of the slurry.

[0009] (3) In the method for producing a powder of the above aspect, the inlet temperature in the spray drying may be 120°C or higher and 180°C or lower.

[0010] (4) According to another aspect of the present invention, there is provided a powder containing cellulose fibers, the cellulose fibers having anionic groups and a specific surface area of ​​50 m 2 / g or more 400m 2 / g or less, and the total pore volume is 0.1 cm 3 / g or more 0.85cm 3 / g or less.

[0011] (5) In the powder of the above form, the cellulose fibers may be TEMPO-oxidized cellulose nanofibers.

[0012] (6) The powder in the above form may be used for adsorbing proteins.

[0013] The present invention can be realized in various forms, for example, as a protein adsorbent, a column packing material, an immobilization carrier, and the like. [Effects of the Invention]

[0014] According to the production method of this embodiment, a powder having excellent protein adsorption capacity can be produced. Furthermore, the powder of this embodiment has excellent protein adsorption capacity. DETAILED DESCRIPTION OF THE INVENTION

[0015] Preferred embodiments of the present invention will now be described in detail.

[0016] The method for producing a powder containing cellulose fibers according to the present embodiment includes a step of spray-drying a slurry containing cellulose fibers having anionic groups and a solvent containing an organic solvent, the cellulose fibers being dispersed in the solvent, and the slurry having a zeta potential of −40 mV or more and −20 mV or less.

[0017] [Cellulose fiber] The cellulose fibers used in this embodiment have anionic groups, which can enhance the protein adsorption capacity.

[0018] The anionic group is not particularly limited, and examples thereof include at least one selected from the group consisting of a carboxyl group, a phosphate group, a sulfonic acid group, a nitrate group, a borate group, and a sulfate group. In this specification, the term "carboxyl group" is not limited to the acid form (-COOH) but also encompasses the salt form, i.e., a carboxylate group (-COOX, where X is a cation that forms a salt with a carboxylic acid), and the acid form and the salt form may be mixed. Similarly, the term "phosphate group, sulfonic acid group, nitrate group, borate group, and sulfate group" is not limited to the acid form but also encompasses the salt form, and the acid form and the salt form may be mixed. The salt is not particularly limited, and examples thereof include alkali metal salts such as sodium salts and potassium salts, alkaline earth metal salts such as magnesium salts and calcium salts, onium salts such as ammonium salts and phosphonium salts, and amine salts such as primary amines, secondary amines, and tertiary amines.

[0019] In one embodiment, the anionic group is preferably a carboxy group. Examples of cellulose fibers containing a carboxy group include, but are not limited to, oxidized cellulose fibers formed by oxidizing hydroxyl groups of glucose units in cellulose molecules, and carboxymethylated cellulose fibers formed by carboxymethylating hydroxyl groups of glucose units in cellulose molecules.

[0020] The amount of anionic groups in cellulose fibers is not particularly limited, but is preferably 0.5 to 3.0 mmol / g, and more preferably 1.5 to 2.0 mmol / g, relative to the dry mass of the cellulose fibers. For example, in the case of carboxy groups, the amount of anionic groups can be determined by preparing 60 mL of a 0.5 to 1% by mass slurry using cellulose fibers whose dry mass has been precisely weighed, adjusting the pH to approximately 2.5 with a 0.1 mol / L aqueous hydrochloric acid solution, adding a 0.05 mol / L aqueous sodium hydroxide solution dropwise, measuring the electrical conductivity, and continuing until the pH reaches approximately 11. The amount of sodium hydroxide (V) consumed during the neutralization stage of the weak acid, where the electrical conductivity changes slowly, can be used to determine the amount of anionic groups according to the following formula: Sulfate groups can also be measured by similar electrical conductivity measurements. Other anionic groups can also be measured by known methods. Amount of anionic group (mmol / g) = V (mL) × [0.05 / mass of cellulose fiber (g)]

[0021] The cellulose fibers used in this embodiment preferably have a type I crystal structure. Type I cellulose crystals are the crystalline form of natural cellulose, and the type I crystal structure makes the cellulose fibers water-insoluble, suppresses swelling in water, and increases durability. Therefore, by using cellulose fibers having a type I crystal structure, it is possible to provide a powder that has excellent protein adsorption capacity and high durability.

[0022] The fact that cellulose fibers have a type I crystal structure can be identified, for example, by the presence of typical peaks at two positions, around 2θ=14° to 17° and around 2θ=22° to 23°, in a diffraction profile obtained by wide-angle X-ray diffraction image measurement.

[0023] As the cellulose fibers, for example, fine fibrous cellulose (cellulose nanofibers) having an average fiber diameter of 3 nm to 500 nm may be used. The average fiber diameter of the fine fibrous cellulose is more preferably 3 nm to 100 nm, and even more preferably 3 nm to 30 nm.

[0024] The average fiber diameter of cellulose fibers can be measured as follows. Specifically, an aqueous dispersion of cellulose fibers with a solid content of 0.05 to 0.1% by mass is prepared, and the aqueous dispersion is cast onto a hydrophilically treated carbon film-coated grid to prepare a sample for observation with a transmission electron microscope (TEM). When fibers with large diameters are included, scanning electron microscope (SEM) images of the surface cast onto glass may be observed. The sample for observation may also be negatively stained, for example, with 2% uranyl acetate. Then, electron microscope images are observed at magnifications of 5,000x, 10,000x, or 50,000x, depending on the size of the fibers. In this case, an arbitrary axis of vertical and horizontal width is assumed within the obtained image, and the sample and observation conditions (magnification, etc.) are adjusted so that at least 20 fibers intersect with the axis. After obtaining an observation image that satisfies these conditions, two random axes are drawn vertically and horizontally per image, and the fiber diameters of the fibers intersecting the axes are visually determined. In this way, at least three non-overlapping images of the surface area are taken with an electron microscope, and the fiber diameter values ​​of the fibers intersecting each of the two axes are read (thus, information on the diameters of at least 20 fibers x 2 x 3 = 120 fibers is obtained). The arithmetic mean of the fiber diameters obtained in this way is taken as the average fiber diameter.

[0025] The average aspect ratio of the cellulose fibers is not particularly limited, but is preferably 50 or more and 1,000 or less, more preferably 100 or more and 800 or less, and even more preferably 200 or more and 500 or less.

[0026] The average aspect ratio of cellulose fibers can be measured as follows. Specifically, the average fiber diameter is calculated according to the method described above. The average fiber length of the cellulose fibers is also calculated from the same observation image. Specifically, the length from the start point to the end point of at least 10 fibers (fiber length) is visually read. The arithmetic mean of the fiber lengths thus obtained is calculated as the average fiber length. These values ​​are then used to calculate the average aspect ratio according to the following formula: Average aspect ratio = average fiber length (nm) / average fiber diameter (nm)

[0027] The fine fibrous cellulose may be obtained by a defibration treatment. The defibration treatment may be carried out after or before the introduction of anionic groups. The defibration treatment is not particularly limited, but may be carried out by treating an aqueous dispersion of cellulose fibers using, for example, a homomixer rotating at high speed, a high-pressure homogenizer, an ultrasonic dispersion processor, a beater, a disk refiner, a conical refiner, a double-disc refiner, a grinder, or the like, to obtain an aqueous dispersion of fine fibrous cellulose.

[0028] A preferred embodiment of the fine fibrous cellulose is oxidized fine fibrous cellulose in which the hydroxyl group at the C6 position of the glucose unit in the cellulose molecule is selectively oxidized to a carboxyl group. Oxidized fine fibrous cellulose can be obtained by oxidizing natural cellulose, such as wood pulp, with a co-oxidant in the presence of an N-oxyl compound and then defibrating (fine-graining) it. The N-oxyl compound is a compound having a nitroxy radical, which is commonly used as an oxidation catalyst, such as piperidine nitroxyoxy radical. Preferred N-oxyl compounds are 2,2,6,6-tetramethylpiperidinooxy radical (TEMPO) or 4-acetamido-TEMPO. Fine fibrous cellulose oxidized with TEMPO is generally referred to as TEMPO-oxidized cellulose nanofiber (hereinafter also referred to as TOCN). In this embodiment, the cellulose fiber is preferably fine fibrous cellulose, more preferably oxidized fine fibrous cellulose, and even more preferably TOCN. The oxidized fine fibrous cellulose may have an aldehyde group or a ketone group in addition to a carboxy group, but preferably does not substantially have an aldehyde group or a ketone group.

[0029] [solvent] The solvent in this embodiment includes an organic solvent. The organic solvent is not particularly limited, but examples thereof include alcohols, ketones, ethers, esters, etc. Examples of alcohols include methanol, ethanol, isopropanol, 1-propanol, etc. As the organic solvent, alcohols are preferably used from the viewpoint of having a relatively high dielectric constant and suppressing aggregation of cellulose fibers in the slurry, and methanol or ethanol is more preferably used. Furthermore, ethanol is particularly preferably used from the viewpoint of improving the protein adsorption ability of the powder obtained after spray drying. Furthermore, the solvent may contain water together with the organic solvent. One type of organic solvent may be used alone, or two or more types may be mixed and used. By including an organic solvent in the solvent, the pore state in the powder formed by spray drying can be maintained in an appropriate state.

[0030] The concentration of the organic solvent in the solvent is not particularly limited, but is preferably 75% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, and even more preferably 90% by mass or more and 100% by mass or less, with the remainder of the solvent being water.

[0031] [slurry] The slurry is a dispersion of cellulose fibers having anionic groups in a solvent containing an organic solvent. A slurry in which the cellulose fibers are dispersed in the solvent can be obtained by mixing and stirring the solvent and the cellulose fibers. The content of the cellulose fibers relative to the total mass of the slurry is not particularly limited, but is preferably 0.01% by mass to 0.50% by mass, more preferably 0.02% by mass to 0.50% by mass, even more preferably 0.04% by mass to 0.50% by mass, even more preferably 0.04% by mass to 0.40% by mass, and particularly preferably 0.04% by mass to 0.20% by mass. Setting the content above the lower limit can improve production efficiency. Setting the content below the upper limit can prevent the viscosity of the slurry from increasing excessively, thereby preventing nozzle clogging during spray drying and, as a result, preventing a decrease in production efficiency.

[0032] The zeta potential of the slurry in this embodiment is -40 mV or more and -20 mV or less. Zeta potential refers to the potential at the sliding surface of an electric double layer and is also called the interfacial kinetic potential. The zeta potential of the slurry is more preferably -40 mV or more and -25 mV or less. By setting the zeta potential at or above the lower limit, the protein adsorption capacity of the powder obtained after spray drying can be improved. Furthermore, by setting the zeta potential at or below the upper limit, a decrease in the dispersibility of cellulose fibers in the slurry can be suppressed, thereby suppressing nozzle clogging during spray drying and, as a result, suppressing a decrease in production efficiency. The zeta potential can be measured by electrophoretic light scattering. More specifically, it can be measured using a zeta potential measuring device under conditions of 0.2 mg / mL in pure water at pH 7.0 and a temperature of 25°C.

[0033] [Spray drying] The method for producing powder according to this embodiment includes a step of spray-drying a slurry in which cellulose fibers having anionic groups are dispersed in a solvent containing an organic solvent.

[0034] The spray drying method is not particularly limited, but may be, for example, a nozzle method such as a two-fluid or four-fluid method for spray drying the slurry, or a rotating disk method. The inlet temperature during spray drying is not particularly limited, but is preferably 100°C to 200°C, more preferably 120°C to 180°C, and even more preferably 120°C to 150°C. By keeping the temperature within the above range, the protein adsorption capacity of the powder obtained after spray drying can be further improved. As used herein, the "inlet temperature during spray drying" refers to the temperature measured at the junction between the drying chamber of the spray drying apparatus and the piping for introducing gas into the drying chamber. The slurry flow rate during spray drying is not particularly limited, but is preferably 1 mL / min to 10 mL / min when using, for example, a BUCHI Mini Spray Dryer B-290. The gas flow rate during spray drying is not particularly limited, but is preferably 1 L / min to 10 L / min. Examples of gases that can be used for spray drying include rare gases and nitrogen gas.

[0035] [powder] The above-mentioned manufacturing method can produce a powder containing cellulose fibers. This powder has a specific surface area of ​​50 m 2 / g or more 400m 2 / g or less, and the total pore volume is 0.1 cm 3 / g or more 0.85cm 3 / g or less.

[0036] The specific surface area of ​​the powder is 50m 2 / g or more 400m 2 / g or less is more preferable, and 100m 2 / g or more 300m 2 / g or less is more preferable. By setting the specific surface area at or above the lower limit, the protein adsorption capacity can be improved. Furthermore, by setting the specific surface area at or below the upper limit, the physical strength of the powder can be imparted. In this specification, "specific surface area" means the nitrogen adsorption specific surface area determined by the BET method. The specific surface area of ​​the powder can be determined by measuring the nitrogen adsorption isotherm at 77K using a capacitance measuring device.

[0037] The total pore volume of the powder is 0.1 cm 3 / g or more 0.85cm 3 / g or less is more preferable, and 0.2 cm 3 / g or more 0.75cm 3 / g or less is more preferable. By setting the adsorption capacity at or above the lower limit, the protein adsorption capacity can be improved. Furthermore, by setting the adsorption capacity at or below the upper limit, the physical strength of the powder can be imparted. In this specification, "total pore volume" means the sum of the volumes of all pores. The total pore volume of a powder can be measured by converting the amount of adsorbed gas into a liquid when the relative pressure is sufficiently close to 1.

[0038] The average particle size of the powder is not particularly limited, but is more preferably 0.1 μm or more and 100 μm or less, and even more preferably 1 μm or more and 50 μm or less. By setting the size above the lower limit, dusting during handling of the powder can be suppressed. Furthermore, by setting the size below the upper limit, the filling amount during handling of the powder can be increased. The average particle size of the powder can be confirmed by observing a scanning electron microscope (SEM) image. In this specification, the "average particle size of the powder" can be calculated by using an SEM image to measure the maximum diameter of at least 20 particles and calculating the average value.

[0039] [Protein adsorption method, etc.] The powder according to this embodiment has excellent protein adsorption ability and can be suitably used for adsorbing proteins, and can be suitably used, for example, as a protein adsorbent, column packing material, immobilization carrier, etc. The method for adsorbing proteins to the powder according to this embodiment is not particularly limited, and for example, the powder may be immersed in a solution containing the protein, or may be subjected to stirring or shaking. Alternatively, for example, the protein may be adsorbed to the powder by flowing a solution containing the protein into a container containing the powder according to this embodiment.

[0040] In this embodiment, the protein to be adsorbed is not particularly limited, and examples thereof include various proteins such as enzymes, antibodies, hormones, etc. Furthermore, the solvent in which such proteins are contained is also not particularly limited, and various buffer solutions (phosphate buffer, citrate buffer, Tris, HEPES, etc.) are preferably used. [Example]

[0041] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0042] [Raw materials] TOCN: TEMPO-oxidized cellulose nanofiber (Rheocrysta I-2SX, Daiichi Kogyo Seiyaku Co., Ltd., cellulose concentration: 2% by mass, cellulose type I crystal structure: "present," number-average fiber diameter: 4 nm, average aspect ratio: 280, carboxyl group content: 1.9 mmol / g) Cellulose particles (comparison example): Cellufine c-500 (manufactured by JNC Corporation) ·ethanol ·methanol Isopropanol

[0043] [Powder preparation] The following amount of TOCN was added to 50 mL of solvent and stirred for 60 minutes using a disperser (IKA Homogenizer T10 basic) at 70 W, Power 6, and 30,000 rpm to prepare a slurry in which cellulose fibers were dispersed in the solvent. The slurry was spray-dried using a spray dryer (BUCHI Mini Spray Dryer B-290). Spray drying was performed at the inlet temperature shown below, with a liquid feed rate of 2.5 mL / min, a gas flow rate of 6 L / min, and droplet diameters of 10 to 200 μm. This yielded a powder containing TOCN.

[0044] (1) Effect of solvent concentration As shown in Table 1 below, the effect of solvent concentration when ethanol was used as the solvent was investigated. The ethanol concentration was expressed as mass %, with the remainder being water. For Samples 1 to 5, the ethanol concentration in the slurry was the value shown in Table 1, and the TOCN concentration relative to the total mass of the slurry was 0.08 mass % in terms of solid content. The inlet temperature for spray drying was 120°C. Sample 6 is TOCN in a state before being dispersed in a solvent, and Sample 7 is general-purpose cellulose particles.

[0045] The zeta potential was measured for the slurry solutions of Samples 1 to 5 before spray drying. The zeta potential was also measured for solutions in which the powders obtained by spray drying (Samples 1 to 5), Samples 6, and Sample 7 were each dispersed in water. The specific surface area (BET value), total pore volume, and lysozyme adsorption amount were also measured for the powders obtained by spray drying (Samples 1 to 5), Samples 6, and Sample 7. The measurement results are shown in Table 1 below.

[0046] [Measurement method] Zeta potential The zeta potential (mV) was measured using a Malvern Zetasizer nano zs. The measurement was carried out in pure water at pH 7.0, with a powder concentration of 0.2 mg / mL, at a temperature of 25°C.

[0047] Specific surface area (BET value) Specific surface area (m 2 / g) was measured by measuring the nitrogen adsorption isotherm at 77 K using a capacitance measuring device (BEL, BELSORP28SA).

[0048] Total pore volume Total pore volume (cm 3 / g) was measured using a volumetric capacity measuring device (BEL, BELSORP28SA) as the liquid equivalent of the amount of gas adsorbed when the relative pressure was sufficiently close to 1.

[0049] Lysozyme adsorption amount The amount of lysozyme adsorption (mg Lys / g TOCN) was measured using the following method. Chicken egg white lysozyme (MP Biomedical, zeta potential: 7.8 mV, size: 4.5 × 3.0 × 3.0 nm, isoelectric point: 11) was used. First, 10–40 mg of lysozyme was added to 50 mL of water and stirred for 30 minutes on a shaker. Then, 10 mg of the powder, TOCN, or cellulose particles was added and stirred for 120 minutes on a shaker. The mixture was then centrifuged (15,000 rpm, 5 minutes). The absorbance of the supernatant was measured by UV-Vis-NIR spectroscopy (281 nm). The amount of free protein in the supernatant was quantified by comparing it with a separately prepared calibration curve. The mass of lysozyme adsorbed to the sample was calculated by subtracting the amount of free protein in the supernatant from the mass of lysozyme added. The amount of lysozyme adsorption (mg Lys / g TOCN) was defined as the mass of lysozyme adsorbed per solid mass of cellulose fiber in the sample.

[0050] [Table 1]

[0051] [Measurement results] As shown in Table 1, the specific surface area and total pore volume of the powder obtained by spray drying tended to increase with increasing solvent concentration. Furthermore, the lysozyme adsorption capacity of the powder obtained by spray drying tended to increase with increasing solvent concentration. Sample 1, which contained only water, and comparative samples 6 and 7 showed low lysozyme adsorption capacity. In contrast, samples containing organic solvents showed increased lysozyme adsorption capacity of the powder obtained by spray drying. Samples 4 and 5, whose pre-drying slurries had zeta potentials between -40 mV and -20 mV, showed particularly high lysozyme adsorption capacity, indicating that powders with excellent protein adsorption capacity were obtained. Furthermore, the absolute values ​​of the zeta potentials of the solutions in which the spray-dried powders were dispersed in water increased compared to the absolute values ​​of the zeta potentials of the slurry solutions before spray drying for Samples 4 and 5. This suggests that the powders obtained by spray drying in Samples 4 and 5, in which the zeta potential of the pre-drying slurry was −40 mV or more and −20 mV or less, were well dispersed in water.

[0052] (2) Effect of spray drying temperature The effect of the inlet temperature during spray drying was investigated as shown in Table 2 below. For Samples 8 to 13, 100% ethanol was used as the solvent, the TOCN concentration relative to the total mass of the slurry was 0.08 mass% in terms of solid content, and the inlet temperature during spray drying was set to the values ​​shown in Table 2. The specific surface area and total pore volume of the powder obtained by spray drying were measured using the same methods as above. The measurement results are shown in Table 2.

[0053] [Table 2]

[0054] [Measurement results] As shown in Table 2, regardless of the inlet temperature in spray drying, the specific surface area of ​​50 m 2 / g or more 400m 2 / g or less, and the total pore volume is 0.1 cm 3 / g or more 0.85cm 3It was also shown that it was possible to produce powders with a specific surface area and total pore volume of 1 / g or less. In addition, samples 8 to 11, in which the inlet temperature in spray drying was set to 150°C or less, tended to have larger specific surface areas and larger total pore volumes than samples 12 and 13, in which the inlet temperature in spray drying was set to 180°C.

[0055] (3) Effect of cellulose fiber concentration in the slurry The effect of cellulose fiber concentration in the slurry was investigated, as shown in Table 3 below. For Samples 14 to 17, 100% ethanol was used as the solvent, the TOCN concentration (solid content equivalent) relative to the total mass of the slurry was set to the values ​​shown in Table 3, and the inlet temperature for spray drying was set to 120°C. The specific surface area and total pore volume of the powder obtained by spray drying were measured using the same methods as above. The measurement results are shown in Table 3.

[0056] [Table 3]

[0057] [Measurement results] As shown in Table 3, in all samples, the specific surface area was 50 m 2 / g or more 400m 2 / g or less, and the total pore volume is 0.1 cm 3 / g or more 0.85cm 3 It was shown that it is possible to produce powders with a density of 1 / g or less.

[0058] (4) Effect of solvent type The effect of the type of solvent was investigated, as shown in Table 4 below. For Samples 18 to 20, the solvents shown in Table 4 were used, the TOCN concentration relative to the total mass of the slurry was 0.08 mass% in terms of solid content, and the inlet temperature for spray drying was 120°C. The zeta potential of the slurry solution before spray drying, the zeta potential of a solution in which the powder obtained by spray drying was dispersed in water, and the specific surface area, total pore volume, and lysozyme adsorption amount of the powder obtained by spray drying were measured using the same methods as above. The measurement results are shown in Table 4.

[0059] [Table 4]

[0060] [Measurement results] As shown in Table 4, the zeta potential of the slurry solution before spray drying was −40 mV or more and −20 mV or less for all samples. 2 / g or more 400m 2 / g or less, and the total pore volume is 0.1 cm 3 / g or more 0.85cm 3 / g or less. Furthermore, it was found that the lysozyme adsorption amount was extremely large in all samples, and powders with excellent protein adsorption properties could be produced.

[0061] (5) Effect of solvent type on TOCN dispersibility and spray state As shown in Table 5 below, the effect of the type of solvent on TOCN dispersion and spraying condition The TOCN dispersibility was evaluated for Samples 21 to 23, using the solvents (100%) shown in Table 5, with a TOCN concentration of 0.08% by mass (solid content) relative to the total mass of the slurry. Furthermore, the spray state was evaluated when the inlet temperature for spray drying was set to 120°C. The zeta potential of the slurry solution before spray drying and the zeta potential of a solution in which the powder obtained by spray drying was dispersed in water were measured using the same method as above. The evaluation and measurement results are shown in Table 5. Table 5 also shows the boiling point and dielectric constant of each organic solvent.

[0062] [Table 5]

[0063] [Evaluation results] As shown in Table 5, the higher the dielectric constant of the solvent, the better the dispersibility of TOCN in the slurry. Furthermore, the spray state during spray drying was good when using methanol and ethanol. It is believed that the good dispersibility of TOCN prevented nozzle clogging during spray drying. Therefore, it was suggested that using a solvent with good dispersibility of cellulose fibers could prevent a decrease in powder production efficiency.

[0064] The present invention is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit of the present invention. For example, the technical features in the embodiments and examples corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.

Claims

1. A method for producing a powder containing cellulose fibers, comprising: spray drying the slurry; The slurry is The present invention relates to a method for producing a cellulose fiber dispersion comprising: dispersing cellulose fibers having anionic groups in a solvent containing an organic solvent; The zeta potential is -40 mV or more and -20 mV or less, The method for producing a powder, wherein the inlet temperature in the spray drying is 120°C or higher and 180°C or lower.

2. The method for producing powder according to claim 1, The method for producing a powder, wherein the cellulose fiber is contained in an amount of 0.01 mass % or more and 0.50 mass % or less in terms of solid content relative to the total mass of the slurry.

3. A powder containing cellulose fibers, The cellulose fiber has an anionic group and a specific surface area of ​​181 m ２ / g or more 227m ２ / g or less, and the total pore volume is 0.583 cm ３ / g or more 0.772cm ３ / g or less.

4. The powder according to claim 3, A powder, wherein the cellulose fibers are TEMPO-oxidized cellulose nanofibers.

5. The powder according to claim 3 or claim 4, A powder used to adsorb proteins.

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