Cellulose nanofiber-containing powder composition and method for producing the same

Abstract

To provide a cellulose nanofiber-containing powder (dried) composition that hardly forms flour coagulates (lumps) when being suspended in a dispersion medium and can be readily dispersed even if the lumps are formed, and a method of producing the same.SOLUTION: A powder composition of this invention is made by mixing powdery saccharide into dried powders of cellulose nanofibers. The saccharide is preferably sugar or dextrin, and the cellulose nanofibers are preferably anion modified cellulose nanofibers.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a powder composition containing cellulose nanofibers and a method for producing the same. More specifically, the present invention relates to a powder composition containing a powder of cellulose nanofibers and a powder of saccharides, which is less likely to leave lumps (strings, clumps, masses) when suspended in a dispersion medium, and a method for producing the same.

Background Art

[0002] Cellulose nanofibers are fine fibers obtained by refining cellulose fibers to a fiber diameter of about several nm to several hundred nm. Cellulose nanofibers are light, have high strength, are biodegradable, exhibit high viscosity in water, and have high water retention, and thus have been studied for application in various fields.

[0003] Cellulose nanofibers are usually produced as a low-concentration aqueous dispersion (wet state). As long as it remains in the low-concentration aqueous dispersion, there are risks such as high costs for transportation and storage, and susceptibility to contamination by various bacteria. Therefore, it is preferable to remove the dispersion medium (water) from the aqueous dispersion and store it as a dried product. However, when cellulose nanofibers are dried to obtain a dry solid, they do not readily mix with water and tend to form lumps when attempting to redisperse them in water or the like.

[0004] In order to address the problem of lumps caused by powders of cellulose-derived materials, for example, Patent Document 1 proposes producing water-soluble carboxymethyl cellulose sodium by adding 10 to 50% by weight of a lower alcohol to wet powdered carboxymethyl cellulose sodium, mixing water therewith, and then drying. Patent Document 2 describes that when a carboxymethyl cellulose salt is dissolved in water having a magnesium ion concentration of 1 to 30 ppm, the lumps become smaller and the carboxymethyl cellulose can be rapidly dissolved.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-261702 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-63427 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] The methods of Patent Documents 1 and 2 are for dealing with lumps caused by carboxymethyl cellulose powder, but not for dealing with lumps caused by cellulose nanofiber powder. An object of the present invention is to produce a powder (dry) composition containing cellulose nanofibers in which lumps (clumps, masses) are less likely to occur when introduced into a dispersion medium, or are easily eliminated even if they occur. [Means for Solving the Problems]

[0007] As a result of intensive studies, the present inventors found that when a cellulose nanofiber dispersion is dried to obtain powdery cellulose nanofibers (dried product) and then a powdery saccharide is mixed and suspended in a dispersion medium, compared with the case where the powdery cellulose nanofibers are suspended in the dispersion medium alone, lumps (clumps, masses) are less likely to occur, and the generated lumps are also easily eliminated. The present invention includes, but is not limited to, the following. [1] A powder composition containing a powder of cellulose nanofibers and a powder of saccharide. [2] The powder composition according to [1], wherein the saccharide is sugar. [3] The powder composition according to [1], wherein the saccharide is dextrin. [4] The powder composition according to any one of [1] to [3], wherein the cellulose nanofibers are anionic-modified cellulose nanofibers. [5] The powder composition according to [4], wherein the anionic-modified cellulose nanofibers are cellulose nanofibers having a carboxyl group or cellulose nanofibers having a carboxyalkyl group. [6] The powder composition as described in [5], wherein the anionic modified cellulose nanofiber is a carboxymethylated cellulose nanofiber having a degree of carboxymethyl substitution of 0.50 or less and a crystallinity of cellulose type I of 50% or more. [7] The powder composition according to any one of [1] to [6], having a water content of less than 10% by mass. [8] A food containing the powder composition according to any one of [1] to [6]. [9] A method for producing the powder composition according to [1] to [6], which includes mixing a powder of cellulose nanofiber and a powder of saccharide.

Advantages of the Invention

[0008] According to the present invention, when the powdered cellulose nanofiber is dispersed (or suspended) in a dispersion medium, it is difficult for lumps to form. Even if lumps form, they are small in size, and the lumps can be eliminated in a short time by normal stirring. The powder composition of the present invention is easy to handle and convenient when dispersed in various media for use.

Modes for Carrying Out the Invention

[0009] The present invention relates to a powder composition containing a powder of cellulose nanofiber and a powder of saccharide, which is less likely to form lumps (clumps, masses) when suspended in a dispersion medium and is easy to eliminate lumps, and a method for producing the same. Hereinafter, cellulose nanofiber may be described as "CNF".

[0010] (CNF) In this specification, "CNF" (cellulose nanofiber) refers to a material obtained by refining pulp or other cellulose-based raw materials to a fiber width at the nanometer level, and is a fine fiber of cellulose with a fiber width of about 3 to several hundred nm, for example, about 3 to 500 nm. The average fiber diameter of CNF is preferably about 3 to 500 nm, more preferably about 3 to 150 nm, and even more preferably about 3 to 20 nm. The aspect ratio can be calculated by dividing the average fiber length by the average fiber diameter. The aspect ratio is preferably 30 or more, more preferably 50 or more, and even more preferably 100 or more. The upper limit of the aspect ratio is not limited, but is about 500 or less.

[0011] The average fiber diameter and average fiber length of CNF can be measured by analyzing 200 randomly selected fibers using an atomic force microscope (AFM) when the diameter is less than 20 nm and a field emission scanning electron microscope (FE-SEM) when the diameter is 20 nm or more, and calculating the average.

[0012] CNF can be obtained by applying mechanical force to cellulose raw materials such as pulp for refinement, or by defibrating anionic modified cellulose such as carboxylated cellulose (also called oxidized cellulose), carboxymethylated cellulose, and cellulose introduced with a phosphate ester group.

[0013] (Cellulose raw material) The type of cellulose used as the raw material for CNF is not particularly limited. Cellulose is generally classified into natural cellulose, regenerated cellulose, microcrystalline cellulose, microcrystalline cellulose excluding the amorphous region, etc. from the origin, production method, etc. In the present invention, any of these celluloses can be used as the raw material for CNF.

[0014] Examples of natural cellulose include bleached pulp or unbleached pulp (bleached wood pulp or unbleached wood pulp); lint, purified lint; cellulose produced by microorganisms such as acetic acid bacteria, etc. The raw materials for bleached pulp or unbleached pulp are not particularly limited, and examples include wood, cotton, straw, bamboo, hemp, jute, kenaf, etc. Also, the manufacturing method of bleached pulp or unbleached pulp is not particularly limited, and it may be a mechanical method, a chemical method, or a method that combines the two in between. Examples of bleached pulp or unbleached pulp classified by the manufacturing method include mechanical pulp (thermomechanical pulp (TMP), groundwood pulp), chemical pulp (sulfite pulp such as softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP), kraft pulp such as softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), etc.). Furthermore, dissolving pulp may be used in addition to pulp for papermaking. Dissolving pulp is chemically purified pulp, which is mainly dissolved in chemicals and used as the main raw material for artificial fibers, cellophane, etc.

[0015] Examples of regenerated cellulose include those obtained by dissolving cellulose in a solvent such as a copper ammonia solution, a cellulose xanthate solution, a morpholine derivative, etc. and then spinning it again. Examples of microfibrillated cellulose include those obtained by depolymerizing cellulose-based materials such as the above natural cellulose and regenerated cellulose (for example, acid hydrolysis, alkaline hydrolysis, enzymatic hydrolysis, blasting treatment, vibration ball mill treatment, etc.), and those obtained by mechanically treating the cellulose-based materials.

[0016] (Anionic modified CNF) The above-mentioned cellulose raw material can be made into CNF by applying mechanical force to it for refinement. However, if an anionic group is introduced into the above-mentioned cellulose raw material before refinement to obtain an anionic-modified cellulose, less energy is required for refinement, which is preferable. In this specification, introducing an anionic group is called "anionic modification", the product obtained by introducing an anionic group into the above-mentioned cellulose raw material is called "anionic-modified cellulose", and the CNF obtained by defibrating the anionic-modified cellulose is called "anionic-modified CNF".

[0017] Specific examples of anionic modification include introducing an anionic group into the pyranose ring of cellulose by an oxidation or substitution reaction. The oxidation reaction refers to a reaction that directly oxidizes the hydroxyl group of the pyranose ring to a carboxyl group. The obtained anionic-modified cellulose becomes cellulose having a carboxyl group, and the CNF obtained by defibrating this becomes CNF having a carboxyl group. The substitution reaction refers to a reaction that introduces an anionic group into the pyranose ring by a substitution reaction other than oxidation. For example, introducing a carboxyalkyl group such as a carboxymethyl group as the anionic group is included. The obtained anionic-modified cellulose becomes cellulose having a carboxyalkyl group, and the CNF obtained by defibrating this becomes CNF having a carboxyalkyl group. In addition, examples of the anionic-modified cellulose and CNF include cellulose and CNF into which a phosphate ester group has been introduced.

[0018] As the anionic-modified cellulose serving as the raw material for anionic-modified CNF, those in which at least a part of the fibrous shape is maintained even when dispersed in water or a water-soluble organic solvent are used. If those in which the fibrous shape is not maintained (that is, those that dissolve in the dispersion medium) are used, nanofibers cannot be obtained. When at least a part of the fibrous shape is maintained upon dispersion, it means that when the dispersion of the anionic-modified cellulose is observed with an electron microscope, fibrous substances can be observed. Also, an anionic-modified cellulose capable of observing the peak of cellulose I-type crystal when measured by X-ray diffraction is preferable.

[0019] In anionic modified cellulose, the crystallinity of cellulose is preferably 50% or more, more preferably 60% or more in crystalline form I. By adjusting the crystallinity within the above range, crystalline cellulose fibers that do not dissolve even after fibrillation to refine the fibers can be sufficiently obtained. The crystallinity of anionic modified CNF in crystalline form I of cellulose is preferably 50% or more, more preferably 60% or more. The crystallinity of cellulose can be controlled by the crystallinity of the raw material cellulose and the degree of anionic modification. The measurement method of the crystallinity of anionic modified cellulose and anionic modified CNF is as follows: Place the sample in a glass cell and measure it using an X-ray diffractometer (LabX XRD-6000, manufactured by Shimadzu Corporation). The crystallinity is calculated using the method of Segal et al. Using the diffraction intensity in the range of 2θ = 10° to 30° in the X-ray diffraction pattern as the baseline, it is calculated from the diffraction intensity of the 002 plane at 2θ = 22.6° and the diffraction intensity of the amorphous part at 2θ = 18.5° by the following formula. Xc=(I002c-Ia) / I002c×100 Xc: Crystallinity of cellulose in crystalline form I (%) I002c: Diffraction intensity of the 002 plane at 2θ = 22.6° Ia: Diffraction intensity of the amorphous part at 2θ = 18.5°.

[0020] (CNF having a carboxyl group) As an example of anionic modified CNF, CNF having a carboxyl group can be mentioned. In this specification, the carboxyl group refers to -COOH (acid type) and -COOM (metal salt type) (wherein M is a metal ion). CNF having a carboxyl group (hereinafter also referred to as carboxylated CNF) can be obtained by carboxylating (oxidizing) the above cellulose raw material by a known method to obtain cellulose having a carboxyl group (hereinafter also referred to as carboxylated cellulose), and defibrating it until it has a nanofiber diameter.

[0021] The amount of carboxyl groups in carboxylated cellulose and carboxylated CNF is not particularly limited, but is preferably 0.6 mmol / g to 3.0 mmol / g, more preferably 1.0 mmol / g to 2.0 mmol / g, based on the absolute dry mass of CNF having carboxyl groups. The amount of carboxyl groups in carboxylated cellulose and carboxylated CNF obtained by defibrating the carboxylated cellulose is usually the same. When the amount of carboxyl groups in carboxylated cellulose is within the above range, it is preferable because nanofibrillation can be performed with a small amount of energy.

[0022] The amount of carboxyl groups in carboxylated cellulose and carboxylated CNF can be measured by the following method: Prepare 60 ml of a 0.5 mass% slurry (aqueous dispersion) of a carboxylated cellulose sample, add 0.1 M hydrochloric acid aqueous solution to adjust the pH to 2.5, then dropwise add 0.05 N sodium hydroxide aqueous solution and measure the electrical conductivity until the pH reaches 11. From the amount of sodium hydroxide (a) consumed in the neutralization stage of the weak acid where the change in electrical conductivity is gentle, it is calculated using the following formula: Amount of carboxyl groups [mmol / g carboxylated cellulose] = a [ml] × 0.05 / mass of carboxylated cellulose [g].

[0023] As an example of the carboxylation (oxidation) method, a method of oxidizing a cellulose raw material in water using an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromides, iodides, and mixtures thereof can be mentioned. By this oxidation reaction, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized to obtain cellulose fibers having an aldehyde group and a carboxyl group (-COOH) or a carboxylate group (-COO - ) on the surface. The concentration of the cellulose raw material in water during the reaction is not particularly limited, but is preferably 5 mass% or less.

[0024] An N-oxyl compound refers to a compound capable of generating a nitroxyl radical. As the N-oxyl compound, any compound can be used as long as it promotes the target oxidation reaction. For example, 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and its derivatives (such as 4-hydroxy TEMPO) can be mentioned. The usage amount of the N-oxyl compound only needs to be a catalytic amount capable of oxidizing the cellulose raw material and is not particularly limited. For example, for 1 g of absolutely dry cellulose raw material, 0.01 mmol to 10 mmol is preferable, 0.01 mmol to 1 mmol is more preferable, and 0.05 mmol to 0.5 mmol is even more preferable. Also, about 0.1 mmol / L to 4 mmol / L is good for the reaction system.

[0025] A bromide is a compound containing bromine, and examples thereof include alkali metal bromides that can dissociate and ionize in water. Also, an iodide is a compound containing iodine, and examples thereof include alkali metal iodides. The usage amount of the bromide or iodide can be selected within a range capable of promoting the oxidation reaction. The total amount of the bromide and iodide is, for example, preferably 0.1 mmol to 100 mmol, more preferably 0.1 mmol to 10 mmol, and even more preferably 0.5 mmol to 5 mmol with respect to 1 g of absolutely dry cellulose raw material.

[0026] As the oxidizing agent, known ones can be used. For example, halogen, hypohalous acid, halous acid, perhalic acid or their salts, halogen oxides, peroxides, etc. can be used. Among them, sodium hypochlorite is preferable because it is inexpensive and has a small environmental load. The appropriate usage amount of the oxidizing agent is, for example, preferably 0.5 mmol to 500 mmol, more preferably 0.5 mmol to 50 mmol, even more preferably 1 mmol to 25 mmol, and most preferably 3 mmol to 10 mmol with respect to 1 g of absolutely dry cellulose raw material. Also, for example, 1 mol to 40 mol is preferable with respect to 1 mol of the N-oxyl compound.

[0027] The oxidation process of the cellulose raw material can proceed efficiently even under relatively mild conditions. Therefore, the reaction temperature is preferably 4°C to 40°C, and it may also be at room temperature of about 15°C to 30°C. As carboxyl groups are generated in the cellulose during the reaction, a decrease in the pH of the reaction solution is observed. In order to efficiently proceed with the oxidation reaction, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution at 8 to 12, preferably about 10 to 11. The reaction medium is preferably water in terms of ease of handling and difficulty in causing side reactions. The reaction time in the oxidation reaction can be appropriately set according to the degree of progress of oxidation, and is usually 0.5 hours to 6 hours, for example, about 0.5 hours to 4 hours.

[0028] Also, the oxidation reaction may be carried out in two steps. For example, the oxidized cellulose obtained by filtration after the completion of the first-stage reaction can be oxidized again under the same or different reaction conditions, so that it can be efficiently oxidized without being inhibited by the reaction of by-produced sodium chloride in the first-stage reaction.

[0029] As another example of the carboxylation (oxidation) method, a method of oxidizing by bringing a gas containing ozone into contact with the cellulose raw material can be mentioned. By this oxidation reaction, the hydroxyl groups at least at the 2-position and 6-position of the pyranose ring are oxidized, and decomposition of the cellulose chain occurs. The ozone concentration in the gas containing ozone is preferably 3 ~250 g / m 3 and preferably 3 ~220 g / m 3More preferably, it is as follows. When the solid content of the cellulose raw material is 100 parts by mass, the amount of ozone added to the cellulose raw material is preferably 0.1 part by mass to 30 parts by mass, and more preferably 5 parts by mass to 30 parts by mass. The ozone treatment temperature is preferably 0°C to 50°C, and more preferably 20°C to 50°C. The ozone treatment time is not particularly limited, but is about 1 minute to 360 minutes, and preferably about 30 minutes to 360 minutes. When the ozone treatment conditions are within these ranges, it is possible to prevent the cellulose from being excessively oxidized and decomposed, and the yield of oxidized cellulose becomes good. After the ozone treatment, a post-oxidation treatment may be performed using an oxidizing agent. The oxidizing agent used for the post-oxidation treatment is not particularly limited, and examples include chlorine-based compounds such as chlorine dioxide and sodium chlorite, and oxygen, hydrogen peroxide, persulfuric acid, peracetic acid, etc. For example, these oxidizing agents are dissolved in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and the post-oxidation treatment can be performed by immersing the cellulose raw material after ozone treatment in the solution.

[0030] The amount of carboxyl groups of the carboxylated cellulose can be adjusted by controlling reaction conditions such as the addition amount of the above-mentioned oxidizing agent and the reaction time. By defibrating the obtained carboxylated cellulose, carboxylated CNF can be obtained. The apparatus used for defibrillation is not particularly limited, and apparatuses such as a high-speed rotation type, a colloid mill type, a high-pressure type, a roll mill type, and an ultrasonic type can be used. Among them, it is preferable to use a wet high-pressure or ultra-high-pressure homogenizer that can apply a strong shearing force to the aqueous dispersion of carboxylated cellulose. In order to defibrillate efficiently, the pressure of the high-pressure homogenizer is preferably 50 MPa or more, more preferably 100 MPa or more, and even more preferably 140 MPa or more. Prior to defibrillation with a high-pressure homogenizer, if necessary, a known mixing, stirring, emulsifying, and dispersing apparatus such as a high-speed shearing mixer may be used to perform a pretreatment on the aqueous dispersion of carboxylated cellulose.

[0031] (CNF having a carboxyalkyl group) As an example of anionic-modified CNF, CNF having a carboxyalkyl group can be mentioned. In the present specification, the carboxyalkyl group refers to -RCOOH (acid form) and -RCOOM (metal salt form). Here, R is an alkylene group such as a methylene group or an ethylene group, and M is a metal ion.

[0032] Cellulose having a carboxyalkyl group (hereinafter also referred to as carboxyalkylated cellulose), which is a raw material for CNF having a carboxyalkyl group (hereinafter also referred to as carboxyalkylated CNF), may be obtained by a known method or may be a commercially available product. Carboxyalkylated CNF can be obtained by defibrating carboxyalkylated cellulose until it has a nanofiber diameter.

[0033] The degree of carboxyalkyl substitution per anhydroglucose unit of carboxyalkylated cellulose and carboxyalkylated CNF is preferably 0.50 or less, more preferably 0.40 or less. When the degree of carboxyalkyl substitution exceeds 0.50, it may dissolve in an aqueous dispersion medium. The lower limit of the degree of carboxyalkyl substitution is preferably 0.01 or more, more preferably 0.02 or more, more preferably 0.05 or more, more preferably 0.10 or more, more preferably 0.15 or more, more preferably 0.20 or more, and more preferably 0.25 or more. The degree of carboxyalkyl substitution of carboxyalkylated cellulose and carboxyalkylated CNF obtained by defibrating it is usually the same. When the degree of carboxyalkyl substitution of carboxyalkylated cellulose is within the above range, it is preferable because nanofibrillation can be performed with a small amount of energy. Note that the anhydroglucose unit means an individual anhydroglucose (glucose residue) constituting cellulose, and the degree of carboxyalkyl substitution indicates the ratio of the hydroxyl groups (-OH) in the glucose residue constituting cellulose that are substituted with carboxyalkyl ether groups (-ORCOOH or -ORCOOM) (the number of carboxyalkyl ether groups per glucose residue).

[0034] The degree of carboxyalkyl substitution per glucose unit can be measured by the following method: Weigh accurately about 2.0 g of the carboxyalkylated cellulose sample (bone-dry) and place it in a 300 mL conical flask with a stopper. Add 100 mL of nitric acid methanol (a solution prepared by adding 100 mL of special grade concentrated nitric acid to 1000 mL of methanol), shake for 3 hours to convert the salt of carboxyalkylated cellulose to the hydrogen form. Weigh accurately 1.5 g to 2.0 g of the hydrogen form sample (bone-dry) and place it in a 300 mL conical flask with a stopper. Moisten the hydrogen form sample with 15 mL of 80% by mass methanol, add 100 mL of 0.1 N NaOH, and shake at room temperature for 3 hours. Using phenolphthalein as an indicator, back-titrate the excess NaOH with 0.1 N H 2 SO 4 Calculate the degree of carboxyalkyl substitution (DS) by the following formula: A = [(100 × F’ - (0.1 N of H 2 SO 4 )(mL) × F) × 0.1] / (bone-dry mass of the hydrogen form sample (g)) DS = 0.162 × A / (1 - 0.058 × A) A: Amount of 1 N NaOH (mL) required for neutralizing 1 g of the hydrogen form sample F: Factor of 0.1 N of H 2 SO 4 F’: Factor of 0.1 N of NaOH.

[0035] As an example of a method for producing carboxyalkylated cellulose, a method including the following steps can be mentioned. i) A step of mixing a starting material, a solvent, and a mercerizing agent, and performing a mercerizing treatment at a reaction temperature of 0 to 70 °C, preferably 10 to 60 °C, and a reaction time of 15 minutes to 8 hours, preferably 30 minutes to 7 hours. ii) Next, add 0.05 to 10.0 times the molar amount of the carboxyalkylating agent per glucose residue, and perform an etherification reaction at a reaction temperature of 30 to 90 °C, preferably 40 to 80 °C, and a reaction time of 30 minutes to 10 hours, preferably 1 hour to 4 hours.

[0036] ​As the starting material, the above-mentioned cellulose raw material can be used. As the solvent, water or a lower alcohol in an amount of 3 to 20 times by mass can be used, specifically, water, methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, etc. alone, or a mixed medium of two or more thereof can be used. When mixing a lower alcohol, the mixing ratio is preferably 60 to 95% by mass. As the mercerizing agent, an alkali metal hydroxide in an amount of 0.5 to 20 times the molar amount per anhydrous glucose residue of the starting material is preferably used, specifically, sodium hydroxide or potassium hydroxide. Examples of the carboxyalkylating agent include monochloroacetic acid, sodium monochloroacetate, methyl monochloroacetate, ethyl monochloroacetate, isopropyl monochloroacetate, etc. Among these, monochloroacetic acid or sodium monochloroacetate is preferred in terms of easy availability of the raw materials.

[0037] By defibrating the obtained carboxyalkylated cellulose, carboxyalkylated CNF can be obtained. The apparatus and method used for defibrillation are the same as those described in the column of CNF having a carboxyl group.

[0038] Among the carboxyalkylated CNFs, CNF having a carboxymethyl group (also referred to as "carboxymethylated CNF" in this specification) is preferred. In particular, carboxymethylated CNF having a degree of carboxymethyl substitution of 0.50 or less and a crystallinity of cellulose type I of 40% or more is preferred.

[0039] (Powder of CNF) By removing (drying) the dispersion medium from the dispersion of the CNF or anion-modified CNF obtained above, a powder of CNF can be obtained. As the drying method, known methods can be used and are not particularly limited. For example, spray drying, pressing, air drying, hot air drying, and vacuum drying can be mentioned. The drying device is not particularly limited, but continuous tunnel drying devices, band drying devices, vertical drying devices, vertical turbo drying devices, multi-stage disk drying devices, ventilation drying devices, rotary drying devices, pneumatic drying devices, spray dryer drying devices, spray drying devices, cylindrical drying devices, drum drying devices, belt drying devices, screw conveyor drying devices, rotary drying devices with heating tubes, vibration transport drying devices, batch box-type drying devices, ventilation drying devices, vacuum box-type drying devices, and stirring drying devices, etc. can be used alone or in combination of two or more.

[0040] After drying, if necessary, it may be pulverized. Examples of the device used for pulverization include, but are not limited to, cutting mills, impact mills, pneumatic mills, and media mills. These can be used alone or in combination, and further, several stages of processing can be performed with the same model. Among these, pneumatic mills are preferred. Examples of cutting mills include mesh mills (manufactured by Horai Co., Ltd.), Atoms (manufactured by Yamamoto Hyakuba Seisakusho Co., Ltd.), knife mills (manufactured by Pallmann), granulators (manufactured by Herbold), rotary cutter mills (manufactured by Nara Kikai Seisakusho Co., Ltd.), etc. Examples of impact mills include pulpizers (manufactured by Hosokawa Micron Corporation), fine impact mills (manufactured by Hosokawa Micron Corporation), super micron mills (manufactured by Hosokawa Micron Corporation), sample mills (manufactured by Seishin Co., Ltd.), bantam mills (manufactured by Seishin Co., Ltd.), atomizers (manufactured by Seishin Co., Ltd.), tornado mills (manufactured by Nikkiso Co., Ltd.), turbo mills (manufactured by Turbo Kogyo Co., Ltd.), bevel impactors (manufactured by Aikawa Tekko Co., Ltd.), etc. Examples of pneumatic mills include CGS type jet mills (manufactured by Mitsui Mining Co., Ltd.), jet mills (manufactured by Sanjo Industry Co., Ltd.), Ebara jet micronizers (manufactured by Ebara Corporation), Selenmirror (manufactured by Masayuki Sangyo Co., Ltd.), supersonic jet mills (manufactured by Nippon Pneumatic Mfg. Co., Ltd.), etc. Examples of media mills include vibration ball mills, etc.

[0041] After drying, if necessary, it may be adjusted to a specific particle size by passing it through a mesh (sieve) having a predetermined aperture. The median diameter of the CNF powder is preferably 1 cm or less, more preferably 500 μm or less, still more preferably 150 μm or less, still more preferably 130 μm or less, still more preferably 120 μm or less, and still more preferably 100 μm or less, although it is not limited thereto. For example, the median diameter of the CNF powder is preferably 10 to 150 μm, more preferably 30 to 130 μm, and still more preferably 50 to 120 μm.

[0042] When forming the CNF powder, a water-soluble polymer may be added to the CNF dispersion, and then the dispersion medium may be removed from the dispersion containing CNF and the water-soluble polymer so that the CNF powder contains the water-soluble polymer. When the CNF powder contains the water-soluble polymer, aggregation between CNFs is less likely to occur when the CNF powder is redispersed in the dispersion medium. Examples of such water-soluble polymers include water-soluble carboxymethyl cellulose. As the water-soluble carboxymethyl cellulose, those having a carboxymethyl substitution degree of 0.55 to 1.60 are preferable, those having a carboxymethyl substitution degree of 0.55 to 1.10 are more preferable, and those having a carboxymethyl substitution degree of 0.65 to 1.10 are even more preferable. Also, those having a long molecule and showing a high viscosity when dispersed in water are preferable, and those having a B-type viscosity of 3 to 14000 mPa·s at 25°C and 60 rpm in a 1 mass% aqueous solution are preferable, those having a B-type viscosity of 7 to 14000 mPa·s are more preferable, and those having a B-type viscosity of 1000 to 8000 mPa·s are even more preferable. The blending amount of carboxymethyl cellulose when carboxymethyl cellulose is contained in the CNF powder is not particularly limited, but is preferably 5 to 300 mass% with respect to CNF (absolute dry solid content), more preferably 20 to 300 mass%, even more preferably 20 to 100 mass%, and even more preferably 20 to 50 mass%. Here, the carboxymethyl cellulose referred to herein is a water-soluble polymer having a high carboxymethyl substitution degree, which is different from the above-mentioned carboxymethylated CNF and is also different from the carboxymethylated cellulose that maintains a fibrous shape in water prepared for producing carboxymethylated CNF.

[0043] (Powder of saccharide) The powder composition of the present invention contains the CNF powder obtained above and the powder of saccharide. As the powder of saccharide, ordinary, for example, commercially available, powdered saccharides can be used. The median diameter, etc. of the powder of saccharide are not particularly limited.

[0044] As used herein, the term "saccharide" refers to monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Examples of monosaccharides include glucose, mannose, galactose, fructose, etc., and examples of disaccharides include sucrose, maltose, lactose, trehalose, etc. As used herein, oligosaccharides refer to those formed by the linkage of about 3 to 20 monosaccharides, and polysaccharides refer to those formed by the linkage of about several tens to several hundreds of monosaccharides. As the polysaccharide, one with a not-too-high molecular weight and soluble in water can be used, for example, water-soluble dextrin.

[0045] Among saccharides, sugar mainly composed of sucrose or dextrin, which is a water-soluble polysaccharide, is preferred because of its high inhibitory effect on mamako. The type of sugar is not particularly limited, and ordinary edible sweeteners such as sugar obtained from sugarcane and sugar beet can be used. The degree of purification and shape of the sugar are not particularly limited either, but it is preferably in powder or granular form. Preferably, it is refined sugar (purified sugar) with a high purity of sucrose, and preferably granulated sugar. The type and shape of dextrin are not particularly limited, but it is preferably in powder or granular form.

[0046] (Powder composition) The powder composition of the present invention can be obtained by mixing the above-mentioned CNF powder and the saccharide powder. The means used for mixing is not particularly limited, and any means capable of mixing powders can be used. For example, a container rotary mixing device, a paddle mixer, an air flow type mixing device, a vibration type mixing device, etc. can be mentioned. Also, a device for stirring does not necessarily have to be used. The CNF powder and the saccharide powder do not necessarily have to be uniformly mixed, and the powder composition of the present invention only needs to contain the CNF powder and the saccharide powder.

[0047] The blending ratio of the CNF powder and the saccharide powder in the powder composition is not particularly limited. For example, the CNF powder:saccharide powder (mass ratio) is 1:99 to 99:1, preferably 10:90 to 90:10, more preferably 15:85 to 60:40, still more preferably 20:80 to 50:50, and still more preferably 25:75 to 45:55. When a water-soluble polymer such as carboxymethyl cellulose is added when forming the CNF powder, the mass of the CNF powder referred to here means the total of the mass of the CNF and the mass of the water-soluble polymer. The ratio of the mass of the CNF alone to the mass of the saccharide is not limited to this, but the CNF:saccharide (mass ratio) is preferably 1:99 to 90:10, more preferably 5:95 to 85:15, still more preferably 10:90 to 55:45, still more preferably 15:85 to 45:55, and still more preferably 15:85 to 35:65.

[0048] In this specification, when referring to a "powder composition", it means a composition obtained by mixing powdery or granular substances. Those in a state where the powdery or granular substances adsorb surrounding moisture and the like and partially aggregate to form somewhat larger lumps are also included in the powder composition.

[0049] Both the CNF powder and the saccharide powder forming the powder composition of the present invention are hygroscopic, and the powder composition may contain a small amount of moisture. It is preferable that the moisture content (water content rate) of the powder composition is small. The water content rate of the powder composition is preferably less than 10% by mass, more preferably less than 5% by mass, still more preferably less than 3% by mass, and still more preferably less than 2% by mass. The water content rate in the powder composition can be measured by the following procedure: The powder composition is dried in an oven at 105°C for 12 hours, and the water content rate of the powder composition is calculated from the mass before and after drying. The water content rate (%) of the powder composition = {1 - (mass after drying / mass before drying)} × 100.

[0050] When the powder composition of the present invention is put into a dispersion medium, it is characterized in that it is difficult for lumps to form, and the formed lumps are easily eliminated. "Lumps" refers to a state in which, when the powder is put into a dispersion medium (liquid), the powder does not conform to the dispersion medium (does not disperse) and remains solid in the form of powder. That it is difficult for lumps to form includes the case where no lumps are generated or, even if they are generated, the size is small. That lumps are easily eliminated includes the case where the lumps disappear (become invisible) by stirring for a short time. The type of the dispersion medium is not particularly limited, but water or a water-soluble organic solvent is preferable from the viewpoint of high lump suppression effect. The water-soluble organic solvent is an organic solvent that can be arbitrarily mixed with water, and examples thereof include methanol, ethanol, isopropanol, isobutanol, sec-butanol, tert-butanol, methyl cellosolve, ethyl cellosolve, ethylene glycol, glycerin, ethylene glycol dimethyl ether, 1,4-dioxane, tetrahydrofuran, acetone, methyl ethyl ketone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and the like. A mixture of a plurality of types of water and the water-soluble organic solvent may be used as the dispersion medium, or a single type may be used. Among these dispersion media, water is most preferable.

[0051] (Use of the powder composition) The above-mentioned powder composition can be used as a thickener, a gelling agent, a paste, a food additive, an excipient, a paint additive, an adhesive additive, a paper-making additive, an abrasive, a compounding material for rubber / plastic, a water retention agent, a shape retention agent, a viscosity modifier, an emulsion stabilizer, a foam stabilizer, a dispersion stabilizer, a mud conditioner, a filtration aid, a mud overflow prevention agent, etc. in various fields where additives are generally used, such as food, beverage, cosmetics, pharmaceuticals, paper-making, various chemical products, paints, inks, sprays, feeds, agricultural chemicals, glazes, civil engineering, construction, electronic materials, flame retardants, household goods, adhesives, detergents, fragrances, lubricating compositions, etc.

[0052] Since the powder composition of the present invention contains saccharides in particular, it is optimal for imparting sweetness, thickening property, shape retention property, dispersion stability, etc. to food and drink products. The powder composition of the present invention can be used, for example, as an additive for foods, although not limited thereto. Such additives include, but are not limited to, water retention agents for foods, shape retention agents, viscosity modifiers, emulsion stabilizers, texture improvers, foam stabilizers, and dispersion stabilizers. Examples of foods that can be used include, but are not limited to, beverages (such as cocoa, juice with fiber and pulp, shiru, amazake, lactic acid bacteria beverages, fruit milk, soft drinks, carbonated beverages, alcoholic beverages, etc.), soups (such as corn soup, ramen soup, miso soup, consommé, etc.), sauces, dressings, ketchup, mayonnaise, jam, yogurt, whipped cream, dried foods (such as dried processed foods, instant ramen, pasta noodles, etc.), gluten-free pasta, ice cream, monaka, sherbet, polydius, confectioneries (such as gummies, soft candies, jelly, cookies, etc.), swallowable foods (such as gel-like foods like thickening agents and medication-assisting jelly), oblat, agar, glass noodles, pullulan, water candy, meringue, bread (such as melon bread, cream bread, etc.), gluten-free bread, fillings, hot cakes, kneaded products, frozen foods, processed meat products, processed fish products, processed rice products (such as mochi, senbei, arare), edible films, etc.

[0053] The addition amount of the powder composition to food and drink products can be appropriately adjusted according to the desired use and is not particularly limited. (Method for producing the powder composition) The powder composition of the present invention is prepared by preparing a powder of CNF and a powder of saccharides and mixing them. As a method for producing a dry product of CNF, a method has been proposed in which an agent for promoting redispersion is added to an aqueous dispersion of CNF, and the dispersion medium is removed from the aqueous dispersion containing CNF and the redispersion promoter to produce a dry product containing CNF and the redispersion promoter. However, the powder composition of the present invention requires mixing CNF and saccharides in a dry powder state, rather than in a wet state. The powder composition thus obtained has the advantages that when suspended in a dispersion medium, it has good compatibility with the dispersion medium, and it is less likely to form lumps or the formed lumps are easily eliminated.

Example

[0054] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. <Production of CNF Powder 1> Into a 5 L twin-screw kneader with the rotation speed adjusted to 100 rpm, 1089 parts of isopropanol (IPA) and a solution of 31 parts of sodium hydroxide dissolved in 121 parts of water were added, and 200 parts were charged based on the dry mass when hardwood pulp (LBKP, manufactured by Nippon Paper Industries Co., Ltd.) was dried at 100 °C for 60 minutes. Stirring and mixing were carried out at 30 °C for 60 minutes to prepare mercerized cellulose. While further stirring, 117 parts of sodium monochloroacetate were added, and after stirring at 30 °C for 30 minutes, the temperature was raised to 70 °C over 30 minutes, and a carboxymethylation reaction was carried out at 70 °C for 60 minutes. The proportion of water in the reaction medium during the mercerization reaction and the carboxymethylation reaction was 10% by mass. After completion of the reaction, it was neutralized, washed with 65% water-containing methanol, de-liquored, dried, and pulverized to obtain a sodium salt of carboxymethylated cellulose with a carboxymethyl substitution degree of 0.27 and a crystallinity of cellulose I type of 64%. The measurement methods for the carboxymethyl substitution degree and the crystallinity of cellulose I type are as described above.

[0055] The obtained sodium salt of carboxymethylated cellulose was dispersed in water to form a 1% (w / v) aqueous dispersion. This was treated 3 times with a high-pressure homogenizer at 150 MPa to obtain a dispersion of nanofibers of carboxymethylated cellulose.

[0056] The obtained carboxymethylated cellulose nanofiber was made into a dispersion with a solid content of 0.7% by mass in water, and carboxymethyl cellulose (trade name: F350HC-4, viscosity (1% by mass, 25 °C, 60 rpm) about 3000 mPa·s, degree of carboxymethyl substitution about 0.90) was added at 40% by mass with respect to the carboxymethylated cellulose nanofiber (that is, when the solid content of the carboxymethylated cellulose nanofiber was 100 parts by mass, the solid content of carboxymethyl cellulose was 40 parts by mass), and stirred with a TK homomixer (12,000 rpm) for 60 minutes. The pH of this dispersion was about 7 to 8.

[0057] To this dispersion, 0.5% by mass of an aqueous sodium hydroxide solution was added to adjust the pH to 9, then it was applied to the drum surface of a drum dryer D0405 (manufactured by Katsuragi Kogyo Co., Ltd.) and dried at 140 °C for 1 minute. The obtained dried product was scraped off, and then the dried product was pulverized at a speed of 10 kg per hour using an impact mill to obtain a dried pulverized product with a moisture content of 5% by mass. The obtained pulverized product was classified using a 30-mesh sieve to obtain a powder containing carboxymethylated cellulose nanofiber (CNF powder 1).

[0058] <Production of Powder Composition 1> 3 g of the CNF powder 1 obtained above was mixed with 7 g of sugar (Granulated Sugar, manufactured by Nissin Sugar Co., Ltd., trade name) to obtain Powder Composition 1.

[0059] <Production of Powder Composition 2> 3 g of the CNF powder 1 obtained above was mixed with 7 g of dextrin (TK-16, manufactured by Matsutani Chemical Co., Ltd., molecular weight about 1020) to obtain Powder Composition 2.

[0060] <Example 1> 300 mL of water was put into a 600 mL polyethylene container, and while stirring at 500 rpm using a homodisper, each of Powder Composition 1, Powder Composition 2, and CNF powder 1 was gradually added over 10 seconds. The state of the mama ko of each sample immediately after the addition and after stirring for 1 minute after the addition was visually observed and evaluated according to the following criteria. 6 points: There is no mama ko. 5 points: The size of the largest mamako is less than 1 mm. 4 points: The size of the largest mamako is 1 mm or more and less than 2 mm. 3 points: The size of the largest mamako is 2 mm or more and less than 5 mm. 2 points: The size of the largest mamako is 5 mm or more and less than 10 mm. 1 point: There is a mamako with a size of 10 mm or more.

[0061] <Example 2> The state of the mamako was evaluated in the same manner as in Example 1, except that each powder was gradually introduced over 60 seconds.

[0062] <Example 3> The state of the mamako was evaluated in the same manner as in Example 2, except that the stirring speed of the homodisper was changed to 1000 rpm.

[0063] The results are shown in Table 1. From the results in Table 1, it can be seen that in powder compositions 1 and 2 in which CNF and saccharides are mixed, even with a low stirring force such as 500 to 1000 rpm, mamako is less likely to occur compared to those without mixing saccharides, and the generated mamako is also easily eliminated by short-time stirring.

[0064]

Table 1

Claims

Manufacturing a powder composition by mixing a powder of cellulose nanofibers having a median diameter of 10 to 150 μm and a powder of sugar such that the ratio of the mass of the cellulose nanofibers to the mass of the sugar is in the range of 15:85 to 90:10, and suspending the powder composition obtained by the mixing in a dispersion medium for food and drink A method for manufacturing food and drink, comprising the above steps. The method for manufacturing food and drink according to claim 1, wherein the cellulose nanofibers are anion-modified cellulose nanofibers. The method for manufacturing food and drink according to claim 2, wherein the anion-modified cellulose nanofibers are cellulose nanofibers having a carboxyl group or cellulose nanofibers having a carboxyalkyl group. The method for manufacturing food and drink according to claim 3, wherein the anion-modified cellulose nanofibers are carboxymethylated cellulose nanofibers having a degree of carboxymethyl substitution of 0.50 or less and a crystallinity of cellulose type I of 50% or more. The method for manufacturing food and drink according to any one of claims 1 to 4, wherein the water content of the powder composition is less than 10% by mass.

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