WO2022025100A1 - Nanocellulose and dispersant of same, and method for producing same - Google Patents

Nanocellulose and dispersant of same, and method for producing same Download PDF

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Publication number
WO2022025100A1
WO2022025100A1 PCT/JP2021/027849 JP2021027849W WO2022025100A1 WO 2022025100 A1 WO2022025100 A1 WO 2022025100A1 JP 2021027849 W JP2021027849 W JP 2021027849W WO 2022025100 A1 WO2022025100 A1 WO 2022025100A1
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Prior art keywords
nanocellulose
less
fiber length
cellulose
range
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PCT/JP2021/027849
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French (fr)
Japanese (ja)
Inventor
詩路士 松木
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東亞合成株式会社
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Priority to JP2022539519A priority Critical patent/JPWO2022025100A1/ja
Publication of WO2022025100A1 publication Critical patent/WO2022025100A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B15/00—Preparation of other cellulose derivatives or modified cellulose, e.g. complexes
    • C08B15/02—Oxycellulose; Hydrocellulose; Cellulosehydrate, e.g. microcrystalline cellulose
    • C08B15/04—Carboxycellulose, e.g. prepared by oxidation with nitrogen dioxide
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D21H11/16—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only modified by a particular after-treatment
    • D21H11/18—Highly hydrated, swollen or fibrillatable fibres
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D21H11/16—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only modified by a particular after-treatment
    • D21H11/20—Chemically or biochemically modified fibres
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H15/00—Pulp or paper, comprising fibres or web-forming material characterised by features other than their chemical constitution
    • D21H15/02—Pulp or paper, comprising fibres or web-forming material characterised by features other than their chemical constitution characterised by configuration

Definitions

  • the present invention relates to nanocellulose, a dispersion thereof, and a method for producing the same. More specifically, nanocellulose having a specific range of average fiber length and average fiber width, and having a specific range of fiber length distribution or a specific range of fiber width distribution, nanocellulose dispersion containing the same, and nano. Regarding the method for producing cellulose.
  • Nanocellulose such as cellulose nanofibers (hereinafter, also referred to as "CNF") is produced by mechanically defibrating cellulose, oxidized cellulose, etc. in water, and is obtained as a viscous nanocellulose aqueous dispersion.
  • CNF cellulose nanofibers
  • the use of nanocellulose as a thickener, dispersant, binder, etc. is being studied by taking advantage of its viscosity, but the viscosity of nanocellulose water dispersion is related to the fiber shape such as fiber length and fiber width of nanocellulose. Is known to be.
  • the quality of the product may change when the viscosity stability of the slurry is poor.
  • Patent Document 1 describes the average fiber length and average of CNF as an acid (H) type carboxylated CNF having a high viscosity in a low shear region and an extremely short fiber length. CNFs that specify the fiber width and the viscosity of the CNF aqueous dispersion are described.
  • Patent Document 2 chemical pulp is mechanically treated to shorten the fibers, and then subjected to cellulase-based enzyme treatment, followed by high-speed rotary defibration treatment or high-pressure homogenizer treatment.
  • Patent Document 1 is a technique relating to an acid-type carboxylated CNF having a high viscosity in a low shear region, an average fiber length of 50 to 500 nm, and a ratio of having a fiber length of 300 nm or less is 50% or more.
  • CNF having a fiber length ratio of 600 nm or more and less than 20% is described, but there is a problem in the viscosity stability of the slurry containing this CNF.
  • Patent Document 2 describes only CNF having a fiber length in the micrometer unit, and does not describe a technique relating to fine cellulose having a fiber length distribution in the nanometer unit.
  • nanocellulose having excellent viscosity stability of a slurry containing nanocellulose.
  • the present inventor sets the standard deviation, kurtosis, skewness, or range as an index indicating the fiber length distribution or fiber width distribution of nanocellulose within a specific range. Therefore, they have found that the slurry containing nanocellulose has excellent viscosity stability, and have completed the present invention.
  • the first invention of the present invention is nanocellulose having an average fiber length of 100 nm or more and 500 nm or less and an average fiber width of 2.0 nm or more and 5.0 nm or less, and at least one of the following conditions A to H. Nanocellulose that meets the requirements.
  • Condition A The standard deviation of the fiber length is 600 nm or less
  • Condition B The kurtosis of the fiber length is 11 or more
  • Condition C The skewness of the fiber length is 3.0 or more
  • Condition D The range of the fiber length is 4000 nm
  • Condition E The standard deviation of the fiber width is 1.5 nm or less
  • F The kurtosis of the fiber width is 0.3 or more
  • G The skewness of the fiber width is 0.5 or more
  • H The fiber width range is 6.8 nm or less.
  • the second invention of the present invention is the nanocellulose according to the first invention, wherein the standard deviation of the fiber length is 10 nm or more and 500 nm or less.
  • the third invention of the present invention is the nanocellulose according to the first invention or the second invention, wherein the fiber length has a kurtosis of 12 or more and 30 or less.
  • the fourth invention of the present invention is the nanocellulose according to any one of the first to third inventions, wherein the fiber length skewness is 3.0 or more and 6.0 or less.
  • the fifth invention of the present invention is the nanocellulose according to any one of the first to fourth inventions, wherein the fiber length range is 450 nm or more and 4000 nm or less.
  • the sixth invention of the present invention is the nanocellulose according to any one of the first to fifth inventions, wherein the standard deviation of the fiber width is 0.5 nm or more and 1.5 nm or less.
  • the seventh invention of the present invention is the nanocellulose according to any one of the first to sixth inventions, wherein the fiber width has a kurtosis of 0.3 or more and 2.5 or less.
  • the eighth invention of the present invention is the nanocellulose according to any one of the first to seventh inventions, wherein the fiber width skewness is 0.5 or more and 1.5 or less.
  • the ninth invention of the present invention is the nanocellulose according to any one of the first to eighth inventions, wherein the fiber width range is 3.0 nm or more and 6.8 nm or less.
  • the tenth invention of the present invention is the nanocellulose according to any one of the first to ninth inventions, which comprises carboxylated nanocellulose.
  • the eleventh invention of the present invention is the nanocellulose according to any one of the first to tenth inventions, which does not substantially contain an N-oxyl compound.
  • the twelfth invention of the present invention is described in any one of the first to eleventh inventions, which is produced by defibrating cellulose oxide obtained by oxidizing a cellulose-based raw material with hypochlorous acid or a salt thereof. It is nanocellulose.
  • the thirteenth invention of the present invention is a nanocellulose dispersion liquid in which the nanocellulose according to any one of the first to twelfth inventions is dispersed in a dispersion medium.
  • the 14th invention of the present invention is any one of the 1st to 12th inventions, which comprises a step of defibrating a cellulose oxide obtained by oxidizing a cellulose-based raw material with hypochlorous acid or a salt thereof.
  • the standard deviation, kurtosis, skewness, or range of the fiber length of nanocellulose, or the standard deviation, kurtosis, skewness, or range of the fiber width of nanocellulose is set to a specific range. This makes it possible to improve the viscosity stability of the slurry containing nanocellulose. Since the slurry containing nanocellulose is excellent in viscosity stability, the nanocellulose of the present invention is useful for, for example, a thickener, a dispersant, a binder and the like.
  • Cellulose-based raw materials with 2,2,6,6-tetramethyl-1-piperidin-N-oxyradical hereinafter, also referred to as "TEMPO"
  • TEMPO 2,2,6,6-tetramethyl-1-piperidin-N-oxyradical
  • sodium bromide sodium bromide
  • sodium hypochlorite which is an inexpensive oxidizing agent.
  • carboxy radicals can be efficiently introduced on the surface of cellulose.
  • the oxidized cellulose into which this carboxy group is introduced with a mixer or the like it is possible to produce fine nanocellulose having a fiber length in the nanometer unit.
  • the cellulosic raw material is treated with hypochlorous acid or a salt thereof to obtain oxidized cellulose, and by defibrating this, fine nanocellulose can be obtained.
  • nanocellulose that does not substantially contain the N-oxyl compound obtained by the production method that does not use TEMPO is preferable.
  • substantially free of N-oxyl compound means that the residual nitrogen component derived from the N-oxyl compound contained in nanocellulose is 2.0 ppm or less as an increase from the raw material pulp. means.
  • the residual nitrogen component derived from the N-oxyl compound in the nanocellulose of the present specification is preferably 1.0 ppm or less as an increase from the raw material pulp.
  • N-oxyl compound is substantially contained. It means "not included”. Since the N-oxyl compound is not substantially contained, it is possible to suppress the residual of the N-oxyl compound, which is concerned about the influence on the environment and the human body, in the nanocellulose.
  • the content of the N-oxyl compound can be measured by a known means. As a known means, a method using a trace total nitrogen analyzer can be mentioned.
  • the nitrogen component derived from the N-oxyl compound in nanocellulose is measured as the amount of nitrogen using a trace total nitrogen analyzer (for example, manufactured by Mitsubishi Chemical Analytech Co., Ltd., device name: TN-2100H, etc.). be able to.
  • a trace total nitrogen analyzer for example, manufactured by Mitsubishi Chemical Analytech Co., Ltd., device name: TN-2100H, etc.
  • nanocellulose When cellulose is oxidized, a carboxy group is generated in at least a part of the constituent units constituting the cellulose molecular chain. Due to the electrostatic repulsive force and osmotic pressure effect generated by the carboxy group, defibration becomes possible with relatively weak energy, which contributes to the reduction of production cost. Nanocellulose obtained by this oxidation method is called carboxylated nanocellulose. Since the carboxy group improves the dispersibility in water and the like, the viscosity stability of the slurry containing nanocellulose is also improved. Therefore, the nanocellulose of the present invention preferably contains carboxylated nanocellulose.
  • the nanocellulose of the present invention is an aggregate of nanocellulose fibers.
  • the nanocellulose of the present invention contains carboxylated nanocellulose, it suffices to contain at least one carboxylated nanocellulose fiber, and it is preferable that the carboxylated nanocellulose is the main component.
  • the main component of the carboxylated nanocellulose fiber is that the ratio of the carboxylated nanocellulose to the total amount of nanocellulose exceeds 50% by mass, preferably exceeds 70% by mass, and more preferably 80% by mass. It means that it is over%.
  • the upper limit of the above ratio is 100% by mass, but it may be 98% by mass or 95% by mass.
  • the nanocellulose of the present invention has an average fiber length of 100 nm or more and 500 nm or less, and an average fiber width of 2.0 nm or more and 5.0 nm or less.
  • the average fiber length is preferably in the range of 100 nm or more and 450 nm or less, and more preferably in the range of 100 nm or more and 400 nm or less.
  • the average fiber length exceeds 500 nm, the slurry becomes violently thickened and handling becomes difficult. Further, when the average fiber length is smaller than 100 nm, it becomes difficult to develop the viscosity characteristic of nanocellulose.
  • the average fiber width is preferably in the range of 2.0 nm or more and 4.5 nm or less, and more preferably in the range of 2.5 nm or more and 4.0 nm or less. If the average fiber width is smaller than 2.0 nm, it becomes difficult to improve the strength when nanocellulose is added to the resin. Further, when the average fiber width is larger than 5.0 nm, it becomes difficult to improve the strength due to stress concentration.
  • the average fiber length and average fiber width are such that nanocellulose and water are mixed so that the concentration of nanocellulose is approximately 1 to 10 ppm, and a sufficiently diluted nanocellulose aqueous dispersion is naturally dried on a mica substrate.
  • Image processing software can be used to calculate such average fiber width and average fiber length. At this time, the image processing conditions are arbitrary, but the calculated values may differ depending on the image processing conditions even for the same image.
  • the range of the difference in values depending on the image processing conditions is preferably within the range of ⁇ 100 nm for the average fiber length.
  • the range of the difference in values depending on the conditions is preferably within the range of ⁇ 10 nm for the average fiber width.
  • the standard deviation of the fiber length is preferably 600 nm or less, more preferably 500 nm or less, and further preferably 10 nm or more and 500 nm or less.
  • the standard deviation of the fiber length exceeds 600 nm, the slurry using the nanocellulose tends to have a non-uniform portion of the nanocellulose concentration, and the state of the slurry, particularly the viscosity stability, deteriorates. Therefore, the smaller the standard deviation, the better.
  • the standard deviation is set to less than 10 nm, it is necessary to significantly increase the number of defibration, which is economically unfavorable.
  • the kurtosis of the fiber length is preferably 11 or more, more preferably 12 or more, and further preferably 12 or more and 30 or less.
  • the kurtosis is a numerical value indicating the concentration of the fiber length distribution, and a slurry using nanocellulose with a small kurtosis of less than 11 tends to have a non-uniform portion of the nanocellulose concentration, and the state of the slurry, especially the viscosity is stable. Sex is reduced. Therefore, the larger the kurtosis, the more preferable, but in order to make the kurtosis more than 30, it is necessary to significantly reduce the number of defibration, which is not preferable because the nanocellulose formation becomes insufficient.
  • the skewness (distribution shape) of the fiber length is preferably 3.0 or more, more preferably 3.0 or more and 6.0 or less, and 3.0 or more and 4.0 or less.
  • the range of is more preferred.
  • the mechanism is unknown, but the slurry using the nanocellulose has a high slurry state, particularly viscosity stability. If the skewness of the fiber length is less than 3.0, the viscosity stability is lowered, and if the skewness of the fiber length exceeds 6.0, it is necessary to significantly reduce the number of defibration, and nanocellulose formation is not possible. It is not preferable because it is sufficient.
  • the higher the skewness of the fiber length the more the fiber length distribution is biased toward the smaller width side.
  • the fiber length range (difference between the maximum value and the minimum value) is preferably 4000 nm or less, more preferably 450 nm or more and 4000 nm or less, and further preferably 500 nm or more and 4000 nm or less.
  • the range of 550 nm or more and 4000 nm or less is more preferable, and the range of 700 nm or more and 4000 nm or less is further preferable.
  • a slurry using nanocellulose having a fiber length range of more than 4000 nm a non-uniform portion of the nanocellulose concentration tends to occur, and the state of the slurry, particularly the viscosity stability, tends to decrease. Therefore, the smaller the fiber length range, the more preferable.
  • the standard deviation of the fiber width is 1.5 nm or less, preferably 0.5 nm or more and 1.5 nm or less, and more preferably 1.0 nm or more and 1.5 nm or less. ..
  • the standard deviation of the fiber width exceeds 1.5 nm, the slurry using nanocellulose tends to have a non-uniform portion of the nanocellulose concentration in the slurry, and the state of the slurry, especially the viscosity stability, tends to decrease. be. Therefore, the smaller the standard deviation, the better.
  • the fiber width sharpness is preferably 0.3 or more, more preferably 0.3 or more and 2.5 or less, and further preferably 0.7 or more and 2.5 or less. preferable.
  • the lower limit of the kurtosis of the fiber width is more preferably 0.35 or more, further preferably 0.4 or more, further preferably 0.5 or more, and even more preferably 0.6 or more.
  • a slurry using nanocellulose with a small fiber width tends to have a non-uniform portion of the nanocellulose concentration, and the state of the slurry, particularly the viscosity stability, tends to decrease. Therefore, the larger the kurtosis, the more preferable.
  • the kurtosis of the fiber width is to exceed 2.5, it is necessary to significantly reduce the number of defibration, which is not preferable because the nanocellulose formation becomes insufficient.
  • the skewness of the fiber width is preferably 0.5 or more, more preferably 0.6 or more, still more preferably 0.7 or more. It is more preferably 0.8 or more.
  • the range of the degree of skewness of the fiber width is preferably 0.5 or more and 1.5 or less, more preferably 0.6 or more and 1.5 or less, and further preferably 0.7 or more and 1.5 or less.
  • the range of 0.8 or more and 1.5 or less is more preferable, and the range of 0.85 or more and 1.5 or less is further preferable.
  • the fiber width skewness is less than 0.5, the viscosity stability is lowered, and if the fiber width skewness exceeds 1.5, the number of defibration must be significantly reduced, and nanocellulose formation is not possible. It is not preferable because it is sufficient. It should be noted that the higher the skewness of the fiber width, the more the fiber width distribution is biased toward the smaller width side.
  • the fiber width range (difference between the maximum value and the minimum value) is preferably 6.8 nm or less, more preferably 3.0 nm or more and 6.8 nm or less, and 4.0 nm.
  • the range of 6.8 nm or less is further preferable, the range of 5.0 nm or more and 6.8 nm or less is further preferable, and the range of 5.2 nm or more and 6.7 nm or less is further preferable.
  • the fiber width range is, the more preferable.
  • the average fiber length, average fiber width, standard deviation of fiber length, sharpness, strain, and range, and the standard deviation, sharpness, strain, and range of fiber width in the nanocellulose of the present invention are, for example, cellulose, respectively.
  • the methods for controlling the average fiber length, average fiber width, standard deviation of fiber length, kurtosis, skewness, and range, and the standard deviation, kurtosis, skewness, and range of fiber width in the nanocellulose of the present invention are, respectively.
  • the method is not limited to these, and two or more of these methods may be combined.
  • the standard deviation, kurtosis, skewness, and range of fiber width can be easily controlled within a predetermined range.
  • the standard deviation of the fiber length and the standard deviation of the fiber width in the present invention each indicate how wide the range of the statistically targeted values is from the average.
  • the standard deviation is obtained from the following equation (1), where n is the number of data and x is each data. Represents the arithmetic mean of a group of data n.
  • the kurtosis of the fiber length and the kurtosis of the fiber width have a sharp peak and a long thick hem when the kurtosis is large, and a more rounded peak when the kurtosis is small. It becomes a distribution with a short and thin hem.
  • the kurtosis of the fiber length and the kurtosis of the fiber width can be obtained from the following equation (2), where n is the number of data, xi is each data, and s is the standard deviation. Represents the arithmetic mean of a group of data n.
  • the skewness of fiber length and the skewness of fiber width each represent the asymmetry of both sides of the mean marginal distribution, and the positive skewness shows a distribution with an asymmetric tail that extends toward more positive values.
  • Negative skewness indicates a distribution with an asymmetric tail extending towards more negative values.
  • the skewness of the fiber length and the skewness of the fiber width can be obtained from the following equation (3), where n is the number of data, xi is each data, and s is the standard deviation. Represents the arithmetic mean of a group of data n.
  • the average fiber length, average fiber width, standard deviation of fiber length, kurtosis, skewness, and range, and the standard deviation, kurtosis, skewness, and range of fiber width in the nanocellulose of the present invention are commercially available table calculations. It may be obtained using software. For example, the STDEV function of Microsoft Excel can be used to calculate the standard deviation, the KURT function can be used to calculate the kurtosis, and the SKEW function can be used to calculate the skewness.
  • the fiber length distribution or fiber width distribution is narrow (small standard deviation, small range), and / or the fiber length distribution or fiber width distribution is sharp (high kurtosis).
  • the fiber length distribution or fiber width distribution is biased toward the smaller side (higher skewness)
  • non-uniform parts of the nanocellulose concentration in the slurry are less likely to occur, and the state of the slurry, especially the viscosity. It is thought that the stability will be high.
  • the fiber width or fiber width distribution is narrow (small standard deviation, small range) and / or sharp (high kurtosis) and / or fiber width distribution.
  • the fiber width distribution is biased toward a smaller size (skewness is large), it is considered that a non-uniform portion of the nanocellulose concentration in the slurry is less likely to occur, and the state of the slurry, particularly the stability of the viscosity, is improved.
  • nanocellulose of the present invention will be described by way of exemplifying a production method.
  • the nanocellulose of the present invention is not limited to these production methods.
  • the nanocellulose of the present invention can be produced, for example, by reacting a cellulosic raw material with sodium hypochlorite, which is an oxidizing agent, to produce cellulose oxide, and further defibrating the cellulose oxide.
  • sodium hypochlorite which is an oxidizing agent
  • nanocellulose is fibrous cellulose obtained by refining oxidized fibrous cellulose, it is also referred to as "fine cellulose fiber” or "CNF”.
  • nanocellulose is a general term for nano-sized cellulose, and includes cellulose nanofibers, cellulose nanocrystals, and the like.
  • the cellulosic raw material in the present invention is not particularly limited as long as it is a material mainly composed of cellulose, and examples thereof include pulp, natural cellulose, regenerated cellulose, and fine cellulose depolymerized by mechanically treating the cellulosic raw material. Be done.
  • the cellulose-based raw material a commercially available product such as crystalline cellulose made from pulp can be used as it is.
  • the cellulosic raw material may be subjected to a chemical treatment such as an alkali treatment in order to facilitate the penetration of the oxidizing agent used in the method described later.
  • the concentration of the cellulosic raw material at the time of the reaction is not particularly limited, but is preferably 10% by mass or less, and generally, the reaction is carried out in a state where the cellulosic raw material is added to the liquid containing the oxidizing agent.
  • the effective chlorine concentration of sodium hypochlorite in the reaction system is not particularly limited, but is preferably 6% by mass or more and 43% by mass or less, and more preferably 7% by mass or more and 43% by mass or less. It is more preferably 10% by mass or more and 43% by mass or less, and further preferably 14% by mass or more and 43% by mass or less. The higher the effective chlorine concentration in the reaction system, the smoother the reaction. On the other hand, sodium hypochlorite having an effective chlorine concentration of more than 43% by mass tends to be unstable.
  • hypochlorous acid such as sodium hypochlorite or a salt thereof
  • hypochlorous acid is a weak acid that exists only as an aqueous solution
  • hypochlorite is a compound in which hydrogen of hypochlorous acid is replaced with another cation.
  • sodium hypochlorite which is a hypochlorite
  • the amount of effective chlorine in the solution is measured, not the concentration of sodium hypochlorite.
  • the effective chlorine of sodium hypochlorite is sodium hypochlorite (NaClO) because the oxidizing power of the divalent oxygen atom generated by the decomposition of sodium hypochlorite corresponds to the diatomic equivalent of monovalent chlorine.
  • NaClO sodium hypochlorite
  • acetic acid two atoms of unbound chlorine (Cl 2 )
  • effective chlorine 2 ⁇ (chlorine in NaClO)
  • the sample is precisely weighed, water, potassium iodide, and acetic acid are added and left to stand, and the liberated iodine is titrated with a sodium thiosulfate solution using an aqueous starch solution as an indicator.
  • a method of concentrating the sodium hypochlorite aqueous solution having a low effective chlorine concentration and a sodium hypochlorite pentahydrate having an effective chlorine concentration of about 43% by mass There is a method of adjusting the crystals as they are or by diluting them with water.
  • the above-mentioned method can be mentioned as a method for adjusting the effective chlorine concentration to a preferable range of 6% by mass or more and 43% by mass or less.
  • the amount of the sodium hypochlorite aqueous solution used as the oxidizing agent can be selected within the range in which the oxidation reaction is promoted.
  • the method for mixing the cellulosic raw material and the sodium hypochlorite aqueous solution is not particularly limited, but it is preferable to add the cellulosic raw material to the sodium hypochlorite aqueous solution and mix them from the viewpoint of ease of operation.
  • the reaction temperature in the oxidation reaction is preferably 15 ° C. or higher and 100 ° C. or lower, and more preferably 20 ° C. or higher and 90 ° C. or lower.
  • the pH of the reaction system is preferably maintained at 5 or more and 14 or less, and more preferably 7 or more and 14 or less.
  • An alkaline agent such as sodium hydroxide and an acid such as hydrochloric acid can be added to adjust the pH.
  • the time of the oxidation reaction can be set according to the degree of progress of the oxidation, but for example, it is preferable to carry out the reaction for about 15 minutes or more and 50 hours or less.
  • the reaction time is preferably 20 minutes or longer, more preferably 20 minutes or longer, and even more preferably 25 minutes or longer.
  • the primary hydroxyl group of cellulose contained in the cellulose-based raw material is oxidized to a carboxy group to generate oxidized cellulose.
  • the cellulose oxide in the present invention can also be said to be cellulose oxide which is an oxide of a cellulosic raw material.
  • the oxidized cellulose can be said to be an oxide of the cellulose-based raw material by hypochloric acid or a salt thereof.
  • the amount of carboxy group of the oxidized cellulose is not particularly limited, but in the next step, when the oxidized cellulose is defibrated and nano-sized to produce nanocellulose, the amount of carboxy group per 1 g of oxidized cellulose is 0.2 mmol / g or more. It is preferably 3.0 mmol / g or less, more preferably 0.35 mmol / g or more and 3.0 mmol / g or less, still more preferably 0.4 mmol / g or more and 3.0 mmol / g or less.
  • the oxidation reaction may be carried out in two or more steps.
  • the higher the amount of carboxy groups in the nanocellulose the more preferably 0.4 mmol / g or more. It is preferably 0.8 mmol / g or less because the cost in the oxidation reaction is high.
  • the amount of carboxy group in oxidized cellulose or nanocellulose can be measured by the following method.
  • Pure water is added to a 0.5% by mass slurry of cellulose oxide or nanocellulose to prepare 60 ml, and a 0.1 M hydrochloric acid aqueous solution is added to adjust the pH to 2.5, and then a 0.05 N sodium hydroxide aqueous solution is added dropwise.
  • the electric conductivity is measured until the pH reaches 11, and it is calculated from the amount of sodium hydroxide (a) consumed in the neutralization step of a weak acid in which the change in electric conductivity is moderate, using the following formula.
  • Amount of carboxy group (mmol / g cellulose oxide or nanocellulose) a (ml) x 0.05 / mass of cellulose oxide or mass of nanocellulose (g)
  • the cellulosic raw material may contain a protein component
  • the mixed protein component can be removed by performing filtration and washing with water after the oxidation reaction is completed.
  • a known method can be applied. Further, by comparing the conductivity values of the water-washed water and the water-washed drainage, it can be used as a guideline for reaching the end point of the washing.
  • the salt type (-COO - X + : X + refers to a cation such as sodium, lithium, etc.) of at least a part of the carboxy group produced by the above can be changed to the proton type (-COO - H + ).
  • the proton type has a peak near 1720 cm -1
  • the salt type has a peak near 1600 cm -1 , so that they can be distinguished.
  • a base was added to improve the handleability when the solution was used for the subsequent use.
  • the solution containing cellulose oxide or nanocellulose may be used as a composition containing cellulose oxide or nanocellulose by substituting the solvent or the like.
  • the pH is set to an alkaline condition of 10 or more, and at least a part of the carboxy group is a salt type (-COO - X + : X + indicates a cation such as sodium or lithium. ).
  • the method for producing cellulose oxide or nanocellulose may further include a step of mixing the obtained cellulose oxide or nanocellulose with a compound having a modifying group in order to control the physical properties of the cellulose oxide.
  • the compound having a modifying group is not particularly limited as long as it is a compound having a modifying group capable of forming an ionic bond or a covalent bond with a carboxy group or a hydroxyl group of cellulose oxide or nanocellulose.
  • Examples of the compound having a modifying group capable of forming an ionic bond include a primary amine, a secondary amine, a tertiary amine, a quaternary ammonium compound, and a phosphonium compound.
  • Compounds having a modifying group capable of forming a covalent bond include, for example, alcohols, isocyanate compounds, and epoxy compounds.
  • the oxidized cellulose or nanocellulose includes the salt type, the proton type, and the modified type by a modifying group.
  • Stirring from the viewpoint of adjusting the average fiber length, average fiber width, standard deviation of fiber length, kurtosis, skewness, and range, standard deviation of fiber width, kurtosis, skewness, and range to the range of the present invention.
  • a propeller-type stirring blade or the like that can uniformly mix the reaction system.
  • the rotation speed of the propeller type stirring blade is preferably in the range of 50 rpm or more and 500 rpm or less, and preferably in the range of 80 rpm or more and 200 rpm or less.
  • the oxidized cellulose obtained above can be defibrated and nano-sized to produce nanocellulose.
  • the nanocellulose of the present invention includes nano-sized cellulose such as cellulose nanocrystals.
  • the defibration time can be shortened by performing weak stirring with a stirrer or the like in a solvent or mechanical defibration. However, if the mechanical defibration is too strong, the nanocellulose may break or break.
  • the method of mechanical defibration is not particularly limited, but can be appropriately selected depending on the intended purpose, for example, after the oxidized cellulose is sufficiently washed with a solvent.
  • Turbine type mixer homomixer under high speed rotation, high pressure homogenizer, ultra high pressure homogenizer, double cylindrical homogenizer, ultrasonic homogenizer, water flow counter-collision type disperser, beater, disc type refiner, conical type refiner, double disc type
  • Known mixing / stirring devices such as refiners, grinders, uniaxial or multiaxial kneaders can be mentioned, and by treating them alone or in combination of two or more in a solvent, oxidized cellulose is nano-sized to obtain nanocellulose. Can be manufactured.
  • the pressure during the defibration treatment is preferably 100 MPa or more, more preferably 120 MPa or more, still more preferably 150 MPa or more.
  • the number of times of defibration treatment is not particularly limited, but is preferably 2 times or more, and more preferably 3 times or more from the viewpoint of sufficiently advancing defibration.
  • the average fiber length, average fiber width, standard deviation of fiber length, kurtosis, and strain can be adjusted. Degrees and ranges, standard deviations of fiber width, kurtosis, strain, and ranges can be the scope of the invention.
  • the solvent used for the defibration treatment is not particularly limited and may be appropriately selected depending on the intended purpose. Water, alcohols, ethers, ketones, carbonic acid esters, acetonitrile, N-methyl-2-pyrrolidone. , N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide and the like, and these may be used alone or in combination of two or more.
  • Examples of the alcohols include methanol, ethanol, isopropanol, isobutanol, sec-butyl alcohol, tert-butyl alcohol, methyl cellosolve, ethylene glycol and glycerin.
  • Examples of the ethers include ethylene glycol dimethyl ether, 1,4-dioxane and tetrahydrofuran.
  • Examples of the ketones include acetone, methyl ethyl ketone and the like.
  • Examples of the carbonic acid esters include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, diphenyl carbonate and ethyl methyl carbonate.
  • an organic solvent as the solvent, it becomes easy to isolate the oxidized cellulose obtained in the above step and the nanocellulose obtained by defibrating it. Further, since nanocellulose dispersed in an organic solvent can be obtained, it becomes easy to mix with a resin that dissolves in the organic solvent, a resin raw material monomer, or the like.
  • ⁇ Evaluation method of viscosity stability For an aqueous slurry (50 g) containing titanium oxide R-820 (5% by mass) manufactured by Ishihara Sangyo Co., Ltd. and various nanocelluloses, the initial viscosity of the slurry shall be 300 mPa ⁇ s when the viscosity is measured by the method described below. It was prepared by changing the amount of nanocellulose added. In the mixing for preparing the slurry, a Shinky mixer "Awatori Rentaro ARE-310" (mix mode, revolution: 2000 rpm, rotation: 800 rpm, 20 minutes) was used.
  • Viscosity change rate (%) (viscosity of slurry after standing for 1 week) / (slurry viscosity immediately after preparation) ⁇ 100 Criteria for viscosity stability (absolute value of viscosity change rate) A: Less than 105% B: 105% or more, less than 110% C: 110% or more, less than 115% D: 115% or more The standing was indoors (23 ⁇ 2 ° C.).
  • ⁇ Viscosity measurement method> The initial viscosity of the slurry is 25 ° C. and 100 rpm (shear velocity 200s -1 ) with an E-type viscometer (TV-22) manufactured by Toki Sangyo Co., Ltd. after stirring with a spatula at a speed that does not allow bubbles to enter. Measured at. The viscosity after standing for one week was also measured with the above equipment under the same conditions.
  • ⁇ Measurement method of fiber length and fiber width of nanocellulose The obtained nanocellulose dispersion is diluted 1000 to 1,000,000 times with pure water, air-dried on a mica substrate, and AC mode is used using a scanning probe microscope "MFP-3D infinity” manufactured by Oxford Asylum. Then, the shape of nanocellulose was observed.
  • Example 1 As a cellulosic raw material, coniferous pulp (SIGMA-ALDRICH NIST RM 8495, bleached kraft pulp) is cut into 5 mm squares with scissors and treated with Osaka Chemical's "Wonder Blender WB-1" for 1 minute at 25,000 rpm. Then, it was mechanically defibrated into a cotton-like shape. 350 g of sodium hypochlorite pentahydrate crystal having an effective chlorine concentration of 42% by mass was placed in a beaker, pure water was added, and the mixture was stirred to bring the effective chlorine concentration to 21% by mass.
  • SIGMA-ALDRICH NIST RM 8495 bleached kraft pulp
  • aqueous solution having a pH of 11.
  • the sodium hypochlorite aqueous solution is heated to 30 ° C. in a constant temperature water bath while stirring at 100 rpm using a propeller type stirring blade with a stirrer (Three One Motor, BL600) manufactured by Shinto Kagaku Co., Ltd. 50 g of a cellulosic raw material was added. After supplying the cellulosic raw material, adjust the pH during the reaction to 11 while keeping the temperature at 30 ° C. in the same constant temperature water bath and adding 48% by mass sodium hydroxide, and stir for 30 minutes under the same conditions with a stirrer. Was done.
  • the product was solid-liquid separated by suction filtration using a PTFE mesh filter having an opening of 20 ⁇ m, and the obtained cellulose oxide was washed with pure water. Pure water was added to the oxidized cellulose to prepare a 5% dispersion, which was treated with an ultra-high pressure homogenizer "Starburst Lab HJP-25005" manufactured by Sugino Machine Limited at 200 MPa for 10 passes to obtain a nanocellulose aqueous dispersion.
  • the ultra-high pressure homogenizer the aqueous dispersion of cellulose oxide is circulated through the built-in ultra-high pressure defibration section to proceed with defibration. One pass through the defibration section is called one pass.
  • the residual nitrogen component derived from the N-oxyl compound in nanocellulose was measured as the amount of nitrogen using a trace total nitrogen analyzer (manufactured by Mitsubishi Chemical Analytech Co., Ltd., device name: TN-2100H), and the amount increased from the raw material pulp. As a result of calculating, it was 1 ppm or less.
  • Example 2 The conditions were the same as in Example 1 except that the number of passes in the ultra-high pressure homogenizer was set to 15 passes.
  • Example 3> The conditions were the same as in Example 1 except that powdered cellulose (KC Flock W-100GK) manufactured by Nippon Paper Industries, Ltd. was used as the cellulose-based raw material.
  • powdered cellulose KC Flock W-100GK manufactured by Nippon Paper Industries, Ltd. was used as the cellulose-based raw material.
  • Example 4 The conditions were the same as in Example 1 except that powdered cellulose (VP-1) manufactured by TDI was used as the cellulose-based raw material.
  • Example 5 The conditions were the same as in Example 1 except that the cellulose oxide concentration of the cellulose oxide dispersion liquid at the time of defibration was set to 2% by mass.
  • Example 6> The conditions were the same as in Example 3 except that the cellulose oxide concentration of the cellulose oxide dispersion liquid at the time of defibration was set to 2% by mass.
  • Example 7 The conditions were the same as in Example 3 except that the cellulose oxide concentration of the defibrated cellulose oxide dispersion was 2% by mass and the number of passes with the ultrahigh pressure homogenizer was 8 passes.
  • Example 8> The conditions were the same as in Example 3 except that the cellulose oxide concentration of the cellulose oxide dispersion liquid at the time of defibration was set to 3% by mass.
  • Example 1 The results of the nanocellulose obtained in Examples 1 to 8 and Comparative Examples 1 to 3 are summarized in Table 1 below.
  • the cellulosic raw materials in Table 1 are as follows.
  • -Conifer Conifer pulp (SIGMA-ALDRICH NIST RM 8495, bleached kraft pulp) mechanically defibrated into a cotton-like powder
  • KC Powdered cellulose manufactured by Nippon Paper Industries (KC Flock W-100GK)
  • VP Powdered cellulose (VP-1) from TDI

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Abstract

The present invention provides nanocellulose that produces nanocellulose-containing slurry having stable viscosity, the nanocellulose having an average fiber length of 100-500 nm, an average fiber width of 2.0-5.0 nm, and satisfying at least one of the following conditions. Condition A: the standard deviation of the fiber length is 600 nm or less. Condition B: the kurtosis of the fiber length is 11 or greater. Condition C: the skewness of the fiber length is 3.0 or greater. Condition D: the range of the fiber length is 4000 nm or less. Condition E: the standard deviation of the fiber width is 1.5 nm or less. Condition F: the kurtosis of the fiber width is 0.3 or greater. Condition G: the skewness of the fiber width is 0.5 or greater. Condition H: the range of the fiber width is 6.8 nm or less.

Description

ナノセルロース及びその分散液並びにその製造方法Nanocellulose, its dispersion, and its manufacturing method
　本発明は、ナノセルロース及びその分散液並びにその製造方法に関する。さらに詳しくは、特定の範囲の平均繊維長と平均繊維幅を有し、かつ、特定の範囲の繊維長分布または特定の範囲の繊維幅分布を有するナノセルロース及びこれを含むナノセルロース分散液並びにナノセルロースの製造方法に関する。 The present invention relates to nanocellulose, a dispersion thereof, and a method for producing the same. More specifically, nanocellulose having a specific range of average fiber length and average fiber width, and having a specific range of fiber length distribution or a specific range of fiber width distribution, nanocellulose dispersion containing the same, and nano. Regarding the method for producing cellulose.
　セルロースナノファイバー（以下、「ＣＮＦ」ともいう）等のナノセルロースは、セルロースや酸化セルロースなどを水中で機械的に解繊処理することで製造され、粘性のあるナノセルロース水分散体として得られる。
　その粘性を活かしてナノセルロースを増粘剤、分散剤、バインダーなどへの使用が検討されているが、ナノセルロース水分散体の粘性はナノセルロースの繊維長や繊維幅などの繊維形状に関係していることが知られている。また、上記用途でナノセルロースと無機粒子を混合させてスラリーを作製する場合、そのスラリーの粘度安定性が悪いとき、製品としての品質に変化が生じる恐れがある。 Nanocellulose such as cellulose nanofibers (hereinafter, also referred to as "CNF") is produced by mechanically defibrating cellulose, oxidized cellulose, etc. in water, and is obtained as a viscous nanocellulose aqueous dispersion.
The use of nanocellulose as a thickener, dispersant, binder, etc. is being studied by taking advantage of its viscosity, but the viscosity of nanocellulose water dispersion is related to the fiber shape such as fiber length and fiber width of nanocellulose. Is known to be. Further, when nanocellulose and inorganic particles are mixed to prepare a slurry for the above-mentioned use, the quality of the product may change when the viscosity stability of the slurry is poor.
　例えば、特開２０１８－１６２５４９号公報（特許文献１）には、低ずり領域で高粘度であり、極めて短い繊維長を有する酸（Ｈ）型のカルボキシル化ＣＮＦとして、ＣＮＦの平均繊維長や平均繊維幅を特定し、またＣＮＦ水分散液の粘度を特定したＣＮＦが記載されている。 For example, Japanese Patent Application Laid-Open No. 2018-162549 (Patent Document 1) describes the average fiber length and average of CNF as an acid (H) type carboxylated CNF having a high viscosity in a low shear region and an extremely short fiber length. CNFs that specify the fiber width and the viscosity of the CNF aqueous dispersion are described.
　また、特許第５６５５４３２号公報（特許文献２）には、化学パルプを機械的処理することで短繊維化し、その後、セルラーゼ系酵素処理を行った後に、高速回転式解繊処理あるいは高圧ホモジナイザー処理、超音波処理などの微細化処理を行うことで、繊維幅が４～１００ｎｍであり、全繊維の３０％以上を占める繊維長が１～６００μｍである微細繊維状セルロースを得る方法が記載されている。 Further, in Japanese Patent No. 5655432 (Patent Document 2), chemical pulp is mechanically treated to shorten the fibers, and then subjected to cellulase-based enzyme treatment, followed by high-speed rotary defibration treatment or high-pressure homogenizer treatment. A method for obtaining fine fibrous cellulose having a fiber width of 4 to 100 nm and a fiber length of 1 to 600 μm, which occupies 30% or more of all fibers, is described by performing a micronization treatment such as ultrasonic treatment. ..
特開２０１８－１６２５４９号公報Japanese Unexamined Patent Publication No. 2018-162549 特許第５６５５４３２号公報Japanese Patent No. 5655432
　しかしながら、特許文献１は、低ずり領域で高粘度である酸型のカルボキシル化ＣＮＦに関する技術であり、また、平均繊維長が５０～５００ｎｍであり、３００ｎｍ以下の繊維長を有する割合が５０％以上、６００ｎｍ以上の繊維長の割合が２０％未満のＣＮＦが記載されているが、このＣＮＦを含むスラリーの粘度安定性に問題がある。
　また、特許文献２は、マイクロメートル単位の繊維長のＣＮＦについてのみ記載されており、ナノメートル単位の繊維長分布である微細セルロースに関する技術については記載されていない。 However, Patent Document 1 is a technique relating to an acid-type carboxylated CNF having a high viscosity in a low shear region, an average fiber length of 50 to 500 nm, and a ratio of having a fiber length of 300 nm or less is 50% or more. , CNF having a fiber length ratio of 600 nm or more and less than 20% is described, but there is a problem in the viscosity stability of the slurry containing this CNF.
Further, Patent Document 2 describes only CNF having a fiber length in the micrometer unit, and does not describe a technique relating to fine cellulose having a fiber length distribution in the nanometer unit.
　本発明は、上記の状況を鑑み、ナノセルロースを含むスラリーの粘度安定性に優れたナノセルロースを提供することを目的とする。 In view of the above situation, it is an object of the present invention to provide nanocellulose having excellent viscosity stability of a slurry containing nanocellulose.
　本発明者は、上記の課題を解決するために鋭意検討した結果、ナノセルロースの繊維長分布または繊維幅分布を示す指標として標準偏差、尖度、歪度、または範囲を特定の範囲にすることで、ナノセルロースを含むスラリーの粘度安定性が優れることを見出し、本発明を完成するに至った。 As a result of diligent studies to solve the above problems, the present inventor sets the standard deviation, kurtosis, skewness, or range as an index indicating the fiber length distribution or fiber width distribution of nanocellulose within a specific range. Therefore, they have found that the slurry containing nanocellulose has excellent viscosity stability, and have completed the present invention.
　すなわち、本発明の第１発明は、平均繊維長が１００ｎｍ以上５００ｎｍ以下であり、平均繊維幅が２．０ｎｍ以上５．０ｎｍ以下であるナノセルロースであって、下記条件Ａ～Ｈの少なくとも一つを満たすナノセルロースである。
条件Ａ：繊維長の標準偏差が６００ｎｍ以下である
条件Ｂ：繊維長の尖度が１１以上である
条件Ｃ：繊維長の歪度が３．０以上である
条件Ｄ：繊維長の範囲が４０００ｎｍ以下である
条件Ｅ：繊維幅の標準偏差が１．５ｎｍ以下である
条件Ｆ：繊維幅の尖度が０．３以上である
条件Ｇ：繊維幅の歪度が０．５以上である
条件Ｈ：繊維幅の範囲が６．８ｎｍ以下である That is, the first invention of the present invention is nanocellulose having an average fiber length of 100 nm or more and 500 nm or less and an average fiber width of 2.0 nm or more and 5.0 nm or less, and at least one of the following conditions A to H. Nanocellulose that meets the requirements.
Condition A: The standard deviation of the fiber length is 600 nm or less Condition B: The kurtosis of the fiber length is 11 or more Condition C: The skewness of the fiber length is 3.0 or more Condition D: The range of the fiber length is 4000 nm Condition E: The standard deviation of the fiber width is 1.5 nm or less F: The kurtosis of the fiber width is 0.3 or more G: The skewness of the fiber width is 0.5 or more H : The fiber width range is 6.8 nm or less.
　本発明の第２発明は、繊維長の標準偏差が１０ｎｍ以上５００ｎｍ以下である、第１発明に記載のナノセルロースである。 The second invention of the present invention is the nanocellulose according to the first invention, wherein the standard deviation of the fiber length is 10 nm or more and 500 nm or less.
　本発明の第３発明は、繊維長の尖度が１２以上３０以下である、第１発明または第２発明に記載のナノセルロースである。 The third invention of the present invention is the nanocellulose according to the first invention or the second invention, wherein the fiber length has a kurtosis of 12 or more and 30 or less.
　本発明の第４発明は、繊維長の歪度が３．０以上６．０以下である、第１発明～第３発明のいずれか１項に記載のナノセルロースである。 The fourth invention of the present invention is the nanocellulose according to any one of the first to third inventions, wherein the fiber length skewness is 3.0 or more and 6.0 or less.
　本発明の第５発明は、繊維長の範囲が４５０ｎｍ以上４０００ｎｍ以下である、第１発明～第４発明のいずれか１項に記載のナノセルロースである。 The fifth invention of the present invention is the nanocellulose according to any one of the first to fourth inventions, wherein the fiber length range is 450 nm or more and 4000 nm or less.
　本発明の第６発明は、繊維幅の標準偏差が０．５ｎｍ以上１．５ｎｍ以下である、第１発明～第５発明のいずれか１項に記載のナノセルロースである。 The sixth invention of the present invention is the nanocellulose according to any one of the first to fifth inventions, wherein the standard deviation of the fiber width is 0.5 nm or more and 1.5 nm or less.
　本発明の第７発明は、繊維幅の尖度が０．３以上２．５以下である、第１発明～第６発明のいずれか１項に記載のナノセルロースである。 The seventh invention of the present invention is the nanocellulose according to any one of the first to sixth inventions, wherein the fiber width has a kurtosis of 0.3 or more and 2.5 or less.
　本発明の第８発明は、繊維幅の歪度が０．５以上１．５以下である、第１発明～第７発明のいずれか１項に記載のナノセルロースである。 The eighth invention of the present invention is the nanocellulose according to any one of the first to seventh inventions, wherein the fiber width skewness is 0.5 or more and 1.5 or less.
　本発明の第９発明は、繊維幅の範囲が３．０ｎｍ以上６．８ｎｍ以下である、第１発明～第８発明のいずれか１項に記載のナノセルロースである。 The ninth invention of the present invention is the nanocellulose according to any one of the first to eighth inventions, wherein the fiber width range is 3.0 nm or more and 6.8 nm or less.
　本発明の第１０発明は、カルボキシル化ナノセルロースを含む、第１発明～第９発明のいずれか一項に記載のナノセルロースである。 The tenth invention of the present invention is the nanocellulose according to any one of the first to ninth inventions, which comprises carboxylated nanocellulose.
　本発明の第１１発明は、Ｎ－オキシル化合物を実質的に含まない、第１発明～第１０発明のいずれか１項に記載のナノセルロースである。 The eleventh invention of the present invention is the nanocellulose according to any one of the first to tenth inventions, which does not substantially contain an N-oxyl compound.
　本発明の第１２発明は、セルロース系原料を次亜塩素酸またはその塩で酸化して得られる酸化セルロースを解繊処理して作製する第１発明～第１１発明のいずれか１項に記載のナノセルロースである。 The twelfth invention of the present invention is described in any one of the first to eleventh inventions, which is produced by defibrating cellulose oxide obtained by oxidizing a cellulose-based raw material with hypochlorous acid or a salt thereof. It is nanocellulose.
　本発明の第１３発明は、第１発明～第１２発明のいずれか１項に記載のナノセルロースが分散媒に分散されたナノセルロース分散液。 The thirteenth invention of the present invention is a nanocellulose dispersion liquid in which the nanocellulose according to any one of the first to twelfth inventions is dispersed in a dispersion medium.
　また、本発明の第１４発明は、セルロース系原料を次亜塩素酸またはその塩で酸化して得られる酸化セルロースを解繊処理して作製する工程を含む第１発明～第１２発明のいずれか１項に記載のナノセルロースの製造方法である。 Further, the 14th invention of the present invention is any one of the 1st to 12th inventions, which comprises a step of defibrating a cellulose oxide obtained by oxidizing a cellulose-based raw material with hypochlorous acid or a salt thereof. The method for producing nanocellulose according to item 1.
　本発明によれば、ナノセルロースの繊維長の標準偏差、尖度、歪度、もしくは範囲、またはナノセルロースの繊維幅の標準偏差、尖度、歪度、もしくは範囲の数値を特定の範囲にすることで、ナノセルロースを含むスラリーの粘度安定性を高めることが出来る。
　ナノセルロースを含むスラリーの粘度安定性に優れているので、本発明のナノセルロースは、例えば、増粘剤、分散剤、バインダーなどに有用である。 According to the present invention, the standard deviation, kurtosis, skewness, or range of the fiber length of nanocellulose, or the standard deviation, kurtosis, skewness, or range of the fiber width of nanocellulose is set to a specific range. This makes it possible to improve the viscosity stability of the slurry containing nanocellulose.
Since the slurry containing nanocellulose is excellent in viscosity stability, the nanocellulose of the present invention is useful for, for example, a thickener, a dispersant, a binder and the like.
　セルロース系原料を２，２，６，６－テトラメチル－１－ピペリジン－Ｎ－オキシラジカル（以下、「ＴＥＭＰＯ」ともいう）、臭化ナトリウム、安価な酸化剤である次亜塩素酸ナトリウムとの共存下で処理すると、セルロースの表面にカルボキシ基を効率よく導入することができる。このカルボキシ基を導入した酸化セルロースをミキサー等で解繊処理することにより繊維長がナノメートル単位の微細なナノセルロースを製造することができる。また、ＴＥＭＰＯの非存在下、セルロース系原料を次亜塩素酸またはその塩で処理することで、酸化セルロースが得られ、これを解繊処理することで、微細なナノセルロースが得られる。 Cellulose-based raw materials with 2,2,6,6-tetramethyl-1-piperidin-N-oxyradical (hereinafter, also referred to as "TEMPO"), sodium bromide, and sodium hypochlorite, which is an inexpensive oxidizing agent. When treated in the coexistence, carboxy radicals can be efficiently introduced on the surface of cellulose. By defibrating the oxidized cellulose into which this carboxy group is introduced with a mixer or the like, it is possible to produce fine nanocellulose having a fiber length in the nanometer unit. Further, in the absence of TEMPO, the cellulosic raw material is treated with hypochlorous acid or a salt thereof to obtain oxidized cellulose, and by defibrating this, fine nanocellulose can be obtained.
　なお、ＴＥＭＰＯを使用すると、有害性のあるＮ－オキシル化合物がナノセルロースに残留する恐れがあるため、ＴＥＭＰＯを使用しない製造方法で得られるＮ－オキシル化合物を実質的に含まないナノセルロースが好ましい。
　本明細書において、Ｎ－オキシル化合物を実質的に含まないとは、ナノセルロース中に含まれるＮ－オキシル化合物由来の残留窒素成分が、原料パルプからの増加分として２．０ｐｐｍ以下であることを意味する。本明細書のナノセルロースにおけるＮ－オキシル化合物由来の残留窒素成分は、原料パルプからの増加分として１．０ｐｐｍ以下であることが好ましい。また、Ｎ－オキシル化合物の含有量が、セルロース系原料からの増加分として、好ましくは２．０質量ｐｐｍ以下、より好ましくは１．０質量ｐｐｍ以下である場合も、「Ｎ－オキシル化合物を実質的に含まない」ことを意味する。
　Ｎ－オキシル化合物を実質的に含んでいないことにより、環境や人体への影響が懸念されているＮ－オキシル化合物を、ナノセルロースに残留させることを抑制できる。Ｎ－オキシル化合物の含有量は、公知の手段で測定することができる。公知の手段としては、微量全窒素分析装置を用いる方法が挙げられる。具体的には、ナノセルロース中のＮ－オキシル化合物由来の窒素成分は、微量全窒素分析装置（例えば、三菱ケミカルアナリテック社製、装置名：ＴＮ－２１００Ｈ等）を用いて窒素量として測定することができる。 When TEMPO is used, harmful N-oxyl compounds may remain in the nanocellulose. Therefore, nanocellulose that does not substantially contain the N-oxyl compound obtained by the production method that does not use TEMPO is preferable.
In the present specification, substantially free of N-oxyl compound means that the residual nitrogen component derived from the N-oxyl compound contained in nanocellulose is 2.0 ppm or less as an increase from the raw material pulp. means. The residual nitrogen component derived from the N-oxyl compound in the nanocellulose of the present specification is preferably 1.0 ppm or less as an increase from the raw material pulp. Further, even when the content of the N-oxyl compound is preferably 2.0 mass ppm or less, more preferably 1.0 mass ppm or less as an increase from the cellulosic raw material, "N-oxyl compound is substantially contained. It means "not included".
Since the N-oxyl compound is not substantially contained, it is possible to suppress the residual of the N-oxyl compound, which is concerned about the influence on the environment and the human body, in the nanocellulose. The content of the N-oxyl compound can be measured by a known means. As a known means, a method using a trace total nitrogen analyzer can be mentioned. Specifically, the nitrogen component derived from the N-oxyl compound in nanocellulose is measured as the amount of nitrogen using a trace total nitrogen analyzer (for example, manufactured by Mitsubishi Chemical Analytech Co., Ltd., device name: TN-2100H, etc.). be able to.
　セルロースを酸化すると、そのセルロース分子鎖を構成する少なくとも一部の構成単位にカルボキシ基が生じる。そのカルボキシ基により生じる静電的斥力および浸透圧効果により、比較的弱いエネルギーで解繊が可能になり、生産コストの低減に寄与する。この酸化法により得られるナノセルロースをカルボキシル化ナノセルロースという。そして、そのカルボキシ基により水中などでの分散性が向上することから、ナノセルロースを含むスラリーの粘度安定性も高まるため、本願発明のナノセルロースとしては、カルボキシル化ナノセルロースを含むことが好ましい。 When cellulose is oxidized, a carboxy group is generated in at least a part of the constituent units constituting the cellulose molecular chain. Due to the electrostatic repulsive force and osmotic pressure effect generated by the carboxy group, defibration becomes possible with relatively weak energy, which contributes to the reduction of production cost. Nanocellulose obtained by this oxidation method is called carboxylated nanocellulose. Since the carboxy group improves the dispersibility in water and the like, the viscosity stability of the slurry containing nanocellulose is also improved. Therefore, the nanocellulose of the present invention preferably contains carboxylated nanocellulose.
　本発明のナノセルロースは、ナノセルロース繊維の集合体である。本発明のナノセルロースがカルボキシル化ナノセルロースを含む場合、少なくとも１つのカルボキシル化されたナノセルロース繊維を含んでいればよく、カルボキシル化されたナノセルロースが主成分であることが好ましい。ここでカルボキシル化ナノセルロース繊維が主成分であるとは、ナノセルロース全量に占めるカルボキシル化ナノセルロースの割合が５０質量％超過であること、好ましくは７０質量％超過であること、より好ましくは８０質量％超過であることを指す。上記割合の上限は１００質量％であるが、９８質量％であってもよく、９５質量％であってもよい。 The nanocellulose of the present invention is an aggregate of nanocellulose fibers. When the nanocellulose of the present invention contains carboxylated nanocellulose, it suffices to contain at least one carboxylated nanocellulose fiber, and it is preferable that the carboxylated nanocellulose is the main component. Here, the main component of the carboxylated nanocellulose fiber is that the ratio of the carboxylated nanocellulose to the total amount of nanocellulose exceeds 50% by mass, preferably exceeds 70% by mass, and more preferably 80% by mass. It means that it is over%. The upper limit of the above ratio is 100% by mass, but it may be 98% by mass or 95% by mass.
　本発明のナノセルロースは、平均繊維長が１００ｎｍ以上５００ｎｍ以下であり、平均繊維幅が２．０ｎｍ以上５．０ｎｍ以下である。
　平均繊維長は１００ｎｍ以上４５０ｎｍ以下の範囲が好ましく、１００ｎｍ以上４００ｎｍ以下の範囲がより好ましい。平均繊維長が５００ｎｍを超える場合、スラリーが激しく増粘しハンドリングが難しくなる。また、平均繊維長が１００ｎｍより小さいとナノセルロースの特長である粘性が発現し難くなる。 The nanocellulose of the present invention has an average fiber length of 100 nm or more and 500 nm or less, and an average fiber width of 2.0 nm or more and 5.0 nm or less.
The average fiber length is preferably in the range of 100 nm or more and 450 nm or less, and more preferably in the range of 100 nm or more and 400 nm or less. When the average fiber length exceeds 500 nm, the slurry becomes violently thickened and handling becomes difficult. Further, when the average fiber length is smaller than 100 nm, it becomes difficult to develop the viscosity characteristic of nanocellulose.
　平均繊維幅は２.０ｎｍ以上４．５ｎｍ以下の範囲が好ましく、２．５ｎｍ以上４．０ｎｍ以下の範囲がより好ましい。平均繊維幅が２．０ｎｍより小さいとナノセルロースを樹脂に添加した際の強度向上が発現し難くなる。また、平均繊維幅が５．０ｎｍより大きいと応力集中により同様に強度向上が発現し難くなる。 The average fiber width is preferably in the range of 2.0 nm or more and 4.5 nm or less, and more preferably in the range of 2.5 nm or more and 4.0 nm or less. If the average fiber width is smaller than 2.0 nm, it becomes difficult to improve the strength when nanocellulose is added to the resin. Further, when the average fiber width is larger than 5.0 nm, it becomes difficult to improve the strength due to stress concentration.
　なお、平均繊維長および平均繊維幅は、ナノセルロースの濃度が概ね１～１０ｐｐｍとなるようにナノセルロースと水とを混合し、十分希釈したナノセルロース水分散体をマイカ基材上で自然乾燥させ、走査型プローブ顕微鏡を用いてナノセルロースの形状観察を行い、得られた像より任意の本数の繊維を無作為に選択し、形状像の断面高さ＝繊維幅とし、周囲長÷２＝繊維長とすることにより算出した値である。このような平均繊維幅及び平均繊維長の算出には、画像処理のソフトウェアを用いることができる。このとき画像処理の条件は任意であるが、画像処理の条件によって同一画像であっても算出される値に差が生じる場合がある。画像処理の条件による値の差の範囲は、平均繊維長については±１００ｎｍの範囲内であることが好ましい。条件による値の差の範囲は、平均繊維幅については±１０ｎｍの範囲内であることが好ましい。より詳細な測定方法は、後述の実施例に記載の方法に従う。 The average fiber length and average fiber width are such that nanocellulose and water are mixed so that the concentration of nanocellulose is approximately 1 to 10 ppm, and a sufficiently diluted nanocellulose aqueous dispersion is naturally dried on a mica substrate. , The shape of nanocellulose was observed using a scanning probe microscope, and an arbitrary number of fibers were randomly selected from the obtained images, and the cross-sectional height of the shape image = fiber width, and the peripheral length ÷ 2 = fiber. It is a value calculated by setting the length. Image processing software can be used to calculate such average fiber width and average fiber length. At this time, the image processing conditions are arbitrary, but the calculated values may differ depending on the image processing conditions even for the same image. The range of the difference in values depending on the image processing conditions is preferably within the range of ± 100 nm for the average fiber length. The range of the difference in values depending on the conditions is preferably within the range of ± 10 nm for the average fiber width. A more detailed measurement method follows the method described in Examples described later.
　本発明のナノセルロースに関して、繊維長の標準偏差が６００ｎｍ以下であることが好ましく、５００ｎｍ以下であることがより好ましく、１０ｎｍ以上５００ｎｍ以下の範囲がさらに好ましい。
　繊維長の標準偏差が６００ｎｍを超える場合、そのナノセルロースを使用したスラリーは、ナノセルロース濃度の不均一な部分が生じ易くなり、スラリーの状態、特に粘度安定性が低下する。そのため、標準偏差は小さいほど好ましい。但し、標準偏差を１０ｎｍ未満にしようとすると解繊回数を大幅に増やす必要があり、経済的に好ましくない。 Regarding the nanocellulose of the present invention, the standard deviation of the fiber length is preferably 600 nm or less, more preferably 500 nm or less, and further preferably 10 nm or more and 500 nm or less.
When the standard deviation of the fiber length exceeds 600 nm, the slurry using the nanocellulose tends to have a non-uniform portion of the nanocellulose concentration, and the state of the slurry, particularly the viscosity stability, deteriorates. Therefore, the smaller the standard deviation, the better. However, if the standard deviation is set to less than 10 nm, it is necessary to significantly increase the number of defibration, which is economically unfavorable.
　本発明のナノセルロースに関して、繊維長の尖度が１１以上であることが好ましく、１２以上がより好ましく、１２以上３０以下の範囲がさらに好ましい。
　尖度は繊維長分布の集中度を示す数値であり、１１未満の尖度が小さなナノセルロースを使用したスラリーは、ナノセルロース濃度の不均一な部分が生じ易くなり、スラリーの状態、特に粘度安定性が低下する。そのため、尖度は大きいほど好ましいが、３０を超える尖度にするためには、解繊回数を大幅に減らす必要があり、ナノセルロース化が不十分となるため好ましくない。 Regarding the nanocellulose of the present invention, the kurtosis of the fiber length is preferably 11 or more, more preferably 12 or more, and further preferably 12 or more and 30 or less.
The kurtosis is a numerical value indicating the concentration of the fiber length distribution, and a slurry using nanocellulose with a small kurtosis of less than 11 tends to have a non-uniform portion of the nanocellulose concentration, and the state of the slurry, especially the viscosity is stable. Sex is reduced. Therefore, the larger the kurtosis, the more preferable, but in order to make the kurtosis more than 30, it is necessary to significantly reduce the number of defibration, which is not preferable because the nanocellulose formation becomes insufficient.
　本発明のナノセルロースに関して、繊維長の歪度（分布の形状）が３．０以上であることが好ましく、３．０以上６．０以下の範囲がより好ましく、３．０以上４．０以下の範囲がさらに好ましい。
　繊維長の歪度が一定範囲内であると、メカニズムは不明であるが、そのナノセルロースを使用したスラリーは、スラリーの状態、特に粘度安定性が高い。
　繊維長の歪度が３．０未満であると粘度安定性が低下し、繊維長の歪度が６．０を超える場合は、解繊回数を大幅に減らす必要があり、ナノセルロース化が不十分となるため好ましくない。
　なお、繊維長の歪度が高いほど、繊維長分布が幅の小さい側に偏っていることを示している。 Regarding the nanocellulose of the present invention, the skewness (distribution shape) of the fiber length is preferably 3.0 or more, more preferably 3.0 or more and 6.0 or less, and 3.0 or more and 4.0 or less. The range of is more preferred.
When the skewness of the fiber length is within a certain range, the mechanism is unknown, but the slurry using the nanocellulose has a high slurry state, particularly viscosity stability.
If the skewness of the fiber length is less than 3.0, the viscosity stability is lowered, and if the skewness of the fiber length exceeds 6.0, it is necessary to significantly reduce the number of defibration, and nanocellulose formation is not possible. It is not preferable because it is sufficient.
It should be noted that the higher the skewness of the fiber length, the more the fiber length distribution is biased toward the smaller width side.
　また、本発明のナノセルロースに関して、繊維長の範囲（最大値と最小値の差）が４０００ｎｍ以下であることが好ましく、４５０ｎｍ以上４０００ｎｍ以下であることがより好ましく、５００ｎｍ以上４０００ｎｍ以下の範囲がさらに好ましく、５５０ｎｍ以上４０００ｎｍ以下の範囲がよりさらに好ましく、７００ｎｍ以上４０００ｎｍ以下の範囲が一層好ましい。
　繊維長の範囲が４０００ｎｍを超えるナノセルロースを使用したスラリーは、ナノセルロース濃度の不均一な部分が生じ易くなり、スラリーの状態、特に粘度安定性が低下する傾向にある。そのため、繊維長の範囲は小さいほど好ましい。但し、繊維長の範囲の下限を５００ｎｍ未満にするためには、解繊回数を大幅に増やす必要があり、経済的に好ましくない。 Further, regarding the nanocellulose of the present invention, the fiber length range (difference between the maximum value and the minimum value) is preferably 4000 nm or less, more preferably 450 nm or more and 4000 nm or less, and further preferably 500 nm or more and 4000 nm or less. The range of 550 nm or more and 4000 nm or less is more preferable, and the range of 700 nm or more and 4000 nm or less is further preferable.
In a slurry using nanocellulose having a fiber length range of more than 4000 nm, a non-uniform portion of the nanocellulose concentration tends to occur, and the state of the slurry, particularly the viscosity stability, tends to decrease. Therefore, the smaller the fiber length range, the more preferable. However, in order to make the lower limit of the fiber length range less than 500 nm, it is necessary to significantly increase the number of defibration, which is economically unfavorable.
　本発明のナノセルロースに関して、繊維幅の標準偏差は１．５ｎｍ以下であり、好ましくは０．５ｎｍ以上１．５ｎｍ以下の範囲であり、より好ましくは１．０ｎｍ以上１．５ｎｍ以下の範囲である。
　繊維幅の標準偏差が１．５ｎｍを超えると、ナノセルロースを使用したスラリーは、スラリー中のナノセルロース濃度の不均一な部分が生じ易くなり、スラリーの状態、特に粘度安定性が低下する傾向にある。そのため、標準偏差は小さいほど好ましい。但し、標準偏差を１．０ｎｍ未満にするためには解繊回数を大幅に増やす必要があり、経済的に好ましくない。 With respect to the nanocellulose of the present invention, the standard deviation of the fiber width is 1.5 nm or less, preferably 0.5 nm or more and 1.5 nm or less, and more preferably 1.0 nm or more and 1.5 nm or less. ..
When the standard deviation of the fiber width exceeds 1.5 nm, the slurry using nanocellulose tends to have a non-uniform portion of the nanocellulose concentration in the slurry, and the state of the slurry, especially the viscosity stability, tends to decrease. be. Therefore, the smaller the standard deviation, the better. However, in order to make the standard deviation less than 1.0 nm, it is necessary to significantly increase the number of defibration, which is economically unfavorable.
　本発明のナノセルロースに関して、繊維幅の尖度が０．３以上であることが好ましく、０．３以上２．５以下の範囲がさらに好ましく、０．７以上２．５以下の範囲がよりさらに好ましい。繊維幅の尖度の下限は、０．３５以上がより好ましく、０．４以上がさらに好ましく、０．５以上がよりさらに好ましく、０．６以上が一層好ましくい。
　繊維幅の尖度の小さなナノセルロースを使用したスラリーは、ナノセルロース濃度の不均一な部分が生じ易くなり、スラリーの状態、特に粘度安定性が低下する傾向にある。そのため、尖度は大きいほど好ましい。但し、繊維幅の尖度を２．５超過にしようとすると解繊回数を大幅に減らす必要があり、ナノセルロース化が不十分となるため好ましくない。 Regarding the nanocellulose of the present invention, the fiber width sharpness is preferably 0.3 or more, more preferably 0.3 or more and 2.5 or less, and further preferably 0.7 or more and 2.5 or less. preferable. The lower limit of the kurtosis of the fiber width is more preferably 0.35 or more, further preferably 0.4 or more, further preferably 0.5 or more, and even more preferably 0.6 or more.
A slurry using nanocellulose with a small fiber width tends to have a non-uniform portion of the nanocellulose concentration, and the state of the slurry, particularly the viscosity stability, tends to decrease. Therefore, the larger the kurtosis, the more preferable. However, if the kurtosis of the fiber width is to exceed 2.5, it is necessary to significantly reduce the number of defibration, which is not preferable because the nanocellulose formation becomes insufficient.
　本発明のナノセルロースに関して、繊維幅の歪度（分布の形状）が０．５以上であることが好ましく、０．６以上であることがより好ましく、０．７以上であることがさらに好ましく、０．８以上であることがよりさらに好ましい。繊維幅の歪度の範囲は、０．５以上１．５以下の範囲が好ましく、０．６以上１．５以下の範囲がより好ましく、０．７以上１．５以下の範囲がさらに好ましく、０．８以上１．５以下の範囲がよりさらに好ましく、０．８５以上１．５以下の範囲が一層好ましい。
　繊維幅の歪度が０．５以上であると、メカニズムは不明であるが、そのナノセルロースを使用したスラリーは、スラリーの状態、特に粘度安定性が高い。
　繊維幅の歪度が０．５未満であると粘度安定性が低下し、繊維幅の歪度が１．５を超える場合は、解繊回数を大幅に減らす必要があり、ナノセルロース化が不十分となるため好ましくない。
　なお、繊維幅の歪度が高いほど、繊維幅分布が幅の小さい側に偏っていることを示している。 Regarding the nanocellulose of the present invention, the skewness of the fiber width (shape of distribution) is preferably 0.5 or more, more preferably 0.6 or more, still more preferably 0.7 or more. It is more preferably 0.8 or more. The range of the degree of skewness of the fiber width is preferably 0.5 or more and 1.5 or less, more preferably 0.6 or more and 1.5 or less, and further preferably 0.7 or more and 1.5 or less. The range of 0.8 or more and 1.5 or less is more preferable, and the range of 0.85 or more and 1.5 or less is further preferable.
When the skewness of the fiber width is 0.5 or more, the mechanism is unknown, but the slurry using the nanocellulose has a high slurry state, particularly viscosity stability.
If the fiber width skewness is less than 0.5, the viscosity stability is lowered, and if the fiber width skewness exceeds 1.5, the number of defibration must be significantly reduced, and nanocellulose formation is not possible. It is not preferable because it is sufficient.
It should be noted that the higher the skewness of the fiber width, the more the fiber width distribution is biased toward the smaller width side.
　さらに、本発明のナノセルロースに関して、繊維幅の範囲（最大値と最小値の差）が６．８ｎｍ以下であることが好ましく、３．０ｎｍ以上６．８ｎｍ以下の範囲がより好ましく、４．０ｎｍ以上６．８ｎｍ以下の範囲がさらに好ましく、５．０ｎｍ以上６．８ｎｍ以下の範囲がよりさらに好ましく、５．２ｎｍ以上６．７ｎｍ以下の範囲がさらにより好ましい。
　繊維幅の範囲の大きなナノセルロースを使用したスラリーは、ナノセルロース濃度の不均一な部分が生じ易くなり、スラリーの状態、特に粘度安定性が低下する傾向にある。そのため、繊維幅の範囲は小さいほど好ましい。但し、繊維幅の範囲の下限を３．０ｎｍ未満にするためには、解繊回数を大幅に増やす必要があり、経済的に好ましくない。 Further, regarding the nanocellulose of the present invention, the fiber width range (difference between the maximum value and the minimum value) is preferably 6.8 nm or less, more preferably 3.0 nm or more and 6.8 nm or less, and 4.0 nm. The range of 6.8 nm or less is further preferable, the range of 5.0 nm or more and 6.8 nm or less is further preferable, and the range of 5.2 nm or more and 6.7 nm or less is further preferable.
In a slurry using nanocellulose having a large fiber width range, a non-uniform portion of the nanocellulose concentration tends to occur, and the state of the slurry, particularly the viscosity stability, tends to decrease. Therefore, the smaller the fiber width range is, the more preferable. However, in order to make the lower limit of the fiber width range less than 3.0 nm, it is necessary to significantly increase the number of defibration, which is economically unfavorable.
　本発明のナノセルロースにおける平均繊維長、平均繊維幅、繊維長の標準偏差、尖度、歪度、および範囲、ならびに繊維幅の標準偏差、尖度、歪度、および範囲はそれぞれ、例えば、セルロース系原料の種類の選択、ナノセルロースのカルボキシル化の程度を制御すること、具体的には、酸化反応の時間を制御すること；酸化反応の撹拌を調整すること；解繊処理の方法を制御すること；酸化反応後に酸化セルロースを固液分離する際に用いるフィルターの目開きを調整すること；などによって、所定の範囲に制御することができる。本発明のナノセルロースにおける平均繊維長、平均繊維幅、繊維長の標準偏差、尖度、歪度、および範囲、ならびに繊維幅の標準偏差、尖度、歪度、および範囲の制御方法はそれぞれ、これらに限定されず、また、これらの方法の２つ以上を組み合わせて行ってもよい。
　フィルターの目開きを調整する方法においては、目開きを大きくすることにより、細かな繊維が除かれて、平均繊維長、平均繊維幅、繊維長の標準偏差、尖度、歪度、および範囲、ならびに繊維幅の標準偏差、尖度、歪度、および範囲が所定の範囲に制御しやすい。 The average fiber length, average fiber width, standard deviation of fiber length, sharpness, strain, and range, and the standard deviation, sharpness, strain, and range of fiber width in the nanocellulose of the present invention are, for example, cellulose, respectively. Select the type of raw material, control the degree of carboxylation of nanocellulose, specifically, control the time of the oxidation reaction; adjust the agitation of the oxidation reaction; control the method of defibration treatment. It can be controlled within a predetermined range by adjusting the opening of the filter used for solid-liquid separation of the oxidized cellulose after the oxidation reaction. The methods for controlling the average fiber length, average fiber width, standard deviation of fiber length, kurtosis, skewness, and range, and the standard deviation, kurtosis, skewness, and range of fiber width in the nanocellulose of the present invention are, respectively. The method is not limited to these, and two or more of these methods may be combined.
In the method of adjusting the opening of the filter, by increasing the opening, fine fibers are removed, and the average fiber length, average fiber width, standard deviation of fiber length, kurtosis, skewness, and range, Also, the standard deviation, kurtosis, skewness, and range of fiber width can be easily controlled within a predetermined range.
　なお、本発明における繊維長の標準偏差および繊維幅の標準偏差はそれぞれ、統計的な対象となる値がその平均からどれだけ広い範囲に分布しているかを表すものである。標準偏差は、データ数をｎ、各データをｘとすれば、下記式（１）から求められる。
Figure JPOXMLDOC01-appb-M000001
  
は、データ数ｎの集団の算術平均を表す。 The standard deviation of the fiber length and the standard deviation of the fiber width in the present invention each indicate how wide the range of the statistically targeted values is from the average. The standard deviation is obtained from the following equation (1), where n is the number of data and x is each data.
Figure JPOXMLDOC01-appb-M000001
Represents the arithmetic mean of a group of data n.
Figure JPOXMLDOC01-appb-M000002
  
Figure JPOXMLDOC01-appb-M000002
  
　なお、繊維長の尖度および繊維幅の尖度のそれぞれについて、正規分布と比べて、尖度が大きければ鋭いピークと長く太い裾を持った分布となり、尖度が小さければより丸みがかったピークと短く細い裾を持つ分布となる。
　繊維長の尖度および繊維幅の尖度はそれぞれ、データ数をｎ、各データをｘi、標準偏差をｓとすれば、下記式（２）から求められる。
Figure JPOXMLDOC01-appb-M000003
  
は、データ数ｎの集団の算術平均を表す。 Compared to the normal distribution, the kurtosis of the fiber length and the kurtosis of the fiber width have a sharp peak and a long thick hem when the kurtosis is large, and a more rounded peak when the kurtosis is small. It becomes a distribution with a short and thin hem.
The kurtosis of the fiber length and the kurtosis of the fiber width can be obtained from the following equation (2), where n is the number of data, xi is each data, and s is the standard deviation.
Figure JPOXMLDOC01-appb-M000003
Represents the arithmetic mean of a group of data n.
Figure JPOXMLDOC01-appb-M000004
  
Figure JPOXMLDOC01-appb-M000004
  
　繊維長の歪度および繊維幅の歪度はそれぞれ、平均値周辺分布の両側の非対称度を表すもので、正の歪度は、より正の値に向かって広がる非対称のテールを持つ分布を示し、負の歪度は、より負の値に向かって伸びる非対称テールを持つ分布を示す。
　繊維長の歪度および繊維幅の歪度はそれぞれ、データ数をｎ、各データをｘi、標準偏差をｓとすれば、下記式（３）から求められる。
Figure JPOXMLDOC01-appb-M000005
  
は、データ数ｎの集団の算術平均を表す。 The skewness of fiber length and the skewness of fiber width each represent the asymmetry of both sides of the mean marginal distribution, and the positive skewness shows a distribution with an asymmetric tail that extends toward more positive values. Negative skewness indicates a distribution with an asymmetric tail extending towards more negative values.
The skewness of the fiber length and the skewness of the fiber width can be obtained from the following equation (3), where n is the number of data, xi is each data, and s is the standard deviation.
Figure JPOXMLDOC01-appb-M000005
Represents the arithmetic mean of a group of data n.
Figure JPOXMLDOC01-appb-M000006
  
Figure JPOXMLDOC01-appb-M000006
  
　本発明のナノセルロースにおける平均繊維長、平均繊維幅、繊維長の標準偏差、尖度、歪度、および範囲、ならびに繊維幅の標準偏差、尖度、歪度、および範囲は、市販の表計算ソフトを用いて求めてもよい。例えば、標準偏差の算出には、マイクロソフト社エクセルのSTDEV関数を用いることができ、尖度の算出には、KURT関数を用いることができ、歪度の算出にはSKEW関数を用いることができる。 The average fiber length, average fiber width, standard deviation of fiber length, kurtosis, skewness, and range, and the standard deviation, kurtosis, skewness, and range of fiber width in the nanocellulose of the present invention are commercially available table calculations. It may be obtained using software. For example, the STDEV function of Microsoft Excel can be used to calculate the standard deviation, the KURT function can be used to calculate the kurtosis, and the SKEW function can be used to calculate the skewness.
　平均繊維長が比較的短く、繊維長分布または繊維幅分布が狭い（標準偏差が小さい、範囲が小さい）、および/または、繊維長分布または繊維幅分布が尖っている（尖度が大きい）と、および/または、繊維長分布または繊維幅分布が小さい方へ偏っている（歪度が大きい）と、スラリー中のナノセルロース濃度の不均一な部分が生じ難くなり、スラリーの状態、特に粘度の安定性が高くなると考えられる。
　同様に、繊維幅もしくは繊維幅分布は、その分布が狭い（標準偏差が小さい、範囲が小さい）、および/または、その分布が尖っている（尖度が大きい）、および/または、繊維幅分布もしくは繊維幅分布が小さい方へ偏っている（歪度が大きい）と、スラリー中のナノセルロース濃度の不均一な部分が生じ難くなり、スラリーの状態、特に粘度の安定性が高くなると考えられる。 When the average fiber length is relatively short, the fiber length distribution or fiber width distribution is narrow (small standard deviation, small range), and / or the fiber length distribution or fiber width distribution is sharp (high kurtosis). , And / or if the fiber length distribution or fiber width distribution is biased toward the smaller side (higher skewness), non-uniform parts of the nanocellulose concentration in the slurry are less likely to occur, and the state of the slurry, especially the viscosity. It is thought that the stability will be high.
Similarly, the fiber width or fiber width distribution is narrow (small standard deviation, small range) and / or sharp (high kurtosis) and / or fiber width distribution. Alternatively, if the fiber width distribution is biased toward a smaller size (skewness is large), it is considered that a non-uniform portion of the nanocellulose concentration in the slurry is less likely to occur, and the state of the slurry, particularly the stability of the viscosity, is improved.
　以下、本発明のナノセルロースについて、製造方法を例示して説明する。なお、本発明のナノセルロースは、これらの製造方法に限定されるものではない。
　本発明のナノセルロースは、例えば、セルロース系原料を酸化剤である次亜塩素酸ナトリウムと反応させて酸化セルロースを製造し、さらに酸化セルロースを解繊することで製造することができる。
　なお、「ナノセルロース」は、酸化された繊維状セルロースを微細化した繊維状セルロースであるため、「微細セルロース繊維」や「ＣＮＦ」とも称する。また、ナノセルロースは、セルロースをナノ化したものの総称を表し、セルロースナノファイバーやセルロースナノクリスタル等を含む。 Hereinafter, the nanocellulose of the present invention will be described by way of exemplifying a production method. The nanocellulose of the present invention is not limited to these production methods.
The nanocellulose of the present invention can be produced, for example, by reacting a cellulosic raw material with sodium hypochlorite, which is an oxidizing agent, to produce cellulose oxide, and further defibrating the cellulose oxide.
Since "nanocellulose" is fibrous cellulose obtained by refining oxidized fibrous cellulose, it is also referred to as "fine cellulose fiber" or "CNF". In addition, nanocellulose is a general term for nano-sized cellulose, and includes cellulose nanofibers, cellulose nanocrystals, and the like.
　本発明におけるセルロース系原料は、セルロースを主体とした材料であれば特に限定されず、例えば、パルプ、天然セルロース、再生セルロース、セルロース原料を機械的に処理することで解重合した微細セルロースなどが挙げられる。
　なお、セルロース系原料として、パルプを原料とする結晶セルロースなどの市販品をそのまま使用することもできる。セルロース系原料は、後述する方法で使用する酸化剤を浸透しやすくするためにアルカリ処理等の化学処理を行ってもよい。 The cellulosic raw material in the present invention is not particularly limited as long as it is a material mainly composed of cellulose, and examples thereof include pulp, natural cellulose, regenerated cellulose, and fine cellulose depolymerized by mechanically treating the cellulosic raw material. Be done.
As the cellulose-based raw material, a commercially available product such as crystalline cellulose made from pulp can be used as it is. The cellulosic raw material may be subjected to a chemical treatment such as an alkali treatment in order to facilitate the penetration of the oxidizing agent used in the method described later.
＜酸化セルロースを製造する工程＞
　反応時におけるセルロース系原料濃度は特に限定されないが、１０質量％以下が好ましく、一般的には、酸化剤を含む液にセルロース原料が添加された状態で反応させる。
　また、反応系内における次亜塩素酸ナトリウムの有効塩素濃度は、特に限定されないが、６質量％以上４３質量％以下であることが好ましく、７質量％以上４３質量％以下であることがより好ましく、１０質量％以上４３質量％以下であることが更に好ましく、１４質量％以上４３質量％以下であることがより更に好ましい。反応系内の有効塩素濃度が高いほど反応が円滑に進む利点がある。一方、有効塩素濃度が４３質量％を超える次亜塩素酸ナトリウムは不安定になりやすい。 <Process for producing oxidized cellulose>
The concentration of the cellulosic raw material at the time of the reaction is not particularly limited, but is preferably 10% by mass or less, and generally, the reaction is carried out in a state where the cellulosic raw material is added to the liquid containing the oxidizing agent.
The effective chlorine concentration of sodium hypochlorite in the reaction system is not particularly limited, but is preferably 6% by mass or more and 43% by mass or less, and more preferably 7% by mass or more and 43% by mass or less. It is more preferably 10% by mass or more and 43% by mass or less, and further preferably 14% by mass or more and 43% by mass or less. The higher the effective chlorine concentration in the reaction system, the smoother the reaction. On the other hand, sodium hypochlorite having an effective chlorine concentration of more than 43% by mass tends to be unstable.
　次亜塩素酸ナトリウムなどの次亜塩素酸またはその塩における有効塩素濃度はよく知られた概念であり、以下のように定義される。
　次亜塩素酸は水溶液としてのみ存在する弱酸であり、次亜塩素酸塩は次亜塩素酸の水素が他の陽イオンに置換された化合物である。
　例えば、次亜塩素酸塩である次亜塩素酸ナトリウムは溶液中にしか存在しないため、次亜塩素酸ナトリウムの濃度ではなく、溶液中の有効塩素量を測定する。次亜塩素酸ナトリウムの有効塩素とは、次亜塩素酸ナトリウムの分解により生成する２価の酸素原子の酸化力が１価の塩素の２原子当量に相当するため、次亜塩素酸ナトリウム（ＮａＣｌＯ）の結合塩素原子は、非結合塩素（Ｃｌ２）の２原子と同じ酸化力を持っていて、有効塩素＝２×（ＮａＣｌＯ中の塩素）となる。
　具体的な有効塩素濃度の測定は、試料を精秤し、水、ヨウ化カリウム、酢酸を加えて放置し、遊離したヨウ素についてデンプン水溶液を指示薬としてチオ硫酸ナトリウム溶液で滴定し測定する。 The effective chlorine concentration in hypochlorous acid such as sodium hypochlorite or a salt thereof is a well-known concept and is defined as follows.
Hypochlorous acid is a weak acid that exists only as an aqueous solution, and hypochlorite is a compound in which hydrogen of hypochlorous acid is replaced with another cation.
For example, since sodium hypochlorite, which is a hypochlorite, is present only in the solution, the amount of effective chlorine in the solution is measured, not the concentration of sodium hypochlorite. The effective chlorine of sodium hypochlorite is sodium hypochlorite (NaClO) because the oxidizing power of the divalent oxygen atom generated by the decomposition of sodium hypochlorite corresponds to the diatomic equivalent of monovalent chlorine. ) Has the same oxidizing power as the two atoms of unbound chlorine (Cl 2 ), and effective chlorine = 2 × (chlorine in NaClO).
To measure the specific effective chlorine concentration, the sample is precisely weighed, water, potassium iodide, and acetic acid are added and left to stand, and the liberated iodine is titrated with a sodium thiosulfate solution using an aqueous starch solution as an indicator.
　次亜塩素酸ナトリウム水溶液の有効塩素濃度の調整としては、有効塩素濃度が低い次亜塩素酸ナトリウム水溶液を濃縮する方法、有効塩素濃度が約４３質量％である次亜塩素酸ナトリウム５水和物結晶をそのまま、または水で希釈して調整する方法がある。
　有効塩素濃度を好ましい範囲である６質量％以上４３質量％以下の範囲に調整する方法は前記の方法が挙げられる。これらの中でも、次亜塩素酸ナトリウム５水和物を用いて、酸化剤として有効塩素濃度に調整することが、自己分解が少ない、すなわち有効塩素濃度の低下が少なく、調整が簡便であるため好ましい。 To adjust the effective chlorine concentration of the sodium hypochlorite aqueous solution, a method of concentrating the sodium hypochlorite aqueous solution having a low effective chlorine concentration and a sodium hypochlorite pentahydrate having an effective chlorine concentration of about 43% by mass. There is a method of adjusting the crystals as they are or by diluting them with water.
The above-mentioned method can be mentioned as a method for adjusting the effective chlorine concentration to a preferable range of 6% by mass or more and 43% by mass or less. Among these, it is preferable to adjust the effective chlorine concentration as an oxidizing agent by using sodium hypochlorite pentahydrate because the self-decomposition is small, that is, the decrease in the effective chlorine concentration is small and the adjustment is easy. ..
　酸化剤である次亜塩素酸ナトリウム水溶液の使用量は、酸化反応が促進する範囲で選択することができる。
　セルロース系原料と次亜塩素酸ナトリウム水溶液の混合方法は、特に限定はないが、操作の容易さの面から、次亜塩素酸ナトリウム水溶液にセルロース系原料を加えて混合させることが好ましい。 The amount of the sodium hypochlorite aqueous solution used as the oxidizing agent can be selected within the range in which the oxidation reaction is promoted.
The method for mixing the cellulosic raw material and the sodium hypochlorite aqueous solution is not particularly limited, but it is preferable to add the cellulosic raw material to the sodium hypochlorite aqueous solution and mix them from the viewpoint of ease of operation.
　前記酸化反応における反応温度は、１５℃以上１００℃以下であることが好ましく、２０℃以上９０℃以下であることがより好ましい。酸化反応を効率的に進めるために、反応系のｐＨを５以上１４以下に維持することが好ましく、７以上１４以下に維持することがより好ましい。ｐＨを調整するために水酸化ナトリウムなどのアルカリ剤、塩酸などの酸を添加することができる。
　酸化反応の時間は、酸化の進行の程度に従って設定することができるが、例えば、１５分以上５０時間以下程度反応させることが好ましい。
　平均繊維長、平均繊維幅、繊維長の標準偏差、尖度、歪度、および範囲、繊維幅の標準偏差、尖度、歪度、および範囲などを本発明の範囲に調整する観点から、酸化反応時間は、２０分以上とすることが好ましく、２０分超過とすることがより好ましく、２５分以上とすることがさらに好ましい。 The reaction temperature in the oxidation reaction is preferably 15 ° C. or higher and 100 ° C. or lower, and more preferably 20 ° C. or higher and 90 ° C. or lower. In order to efficiently proceed with the oxidation reaction, the pH of the reaction system is preferably maintained at 5 or more and 14 or less, and more preferably 7 or more and 14 or less. An alkaline agent such as sodium hydroxide and an acid such as hydrochloric acid can be added to adjust the pH.
The time of the oxidation reaction can be set according to the degree of progress of the oxidation, but for example, it is preferable to carry out the reaction for about 15 minutes or more and 50 hours or less.
Oxidation from the viewpoint of adjusting the average fiber length, average fiber width, standard deviation of fiber length, kurtosis, skewness, and range, standard deviation of fiber width, kurtosis, skewness, and range to the range of the present invention. The reaction time is preferably 20 minutes or longer, more preferably 20 minutes or longer, and even more preferably 25 minutes or longer.
　前記酸化反応では、セルロース系原料に含まれるセルロースの１級水酸基がカルボキシ基に酸化されて酸化セルロースが生成する。本発明における酸化セルロースは、セルロース系原料の酸化物である酸化セルロースともいえる。また、セルロース系原料を次亜塩素酸またはその塩で酸化して酸化セルロースを得る場合、該酸化セルロースは、次亜塩素酸又はその塩によるセルロース系原料の酸化物である酸化セルロースともいえる。該酸化セルロースのカルボキシ基量は特に限定されないが、次工程で酸化セルロースを解繊してナノ化させてナノセルロースを製造するに際し、酸化セルロース１ｇ当たりのカルボキシ基量は、０．２ｍｍｏｌ／ｇ以上３．０ｍｍｏｌ／ｇ以下であることが好ましく、０．３５ｍｍｏｌ／ｇ以上３．０ｍｍｏｌ／ｇ以下であることがより好ましく、０．４ｍｍｏｌ／ｇ以上３．０ｍｍｏｌ／ｇ以下であることが更に好ましく、０．５ｍｍｏｌ／ｇ以上３．０ｍｍｏｌ／ｇ以下であることが一層好ましく、０．５５ｍｍｏｌ／ｇ以上２．０ｍｍｏｌ／ｇ以下であることがより一層好ましい。また、前記酸化反応は２段階に以上に分けて実施してもよい。 In the oxidation reaction, the primary hydroxyl group of cellulose contained in the cellulose-based raw material is oxidized to a carboxy group to generate oxidized cellulose. The cellulose oxide in the present invention can also be said to be cellulose oxide which is an oxide of a cellulosic raw material. Further, when a cellulosic raw material is oxidized with hypochlorous acid or a salt thereof to obtain oxidized cellulose, the oxidized cellulose can be said to be an oxide of the cellulose-based raw material by hypochloric acid or a salt thereof. The amount of carboxy group of the oxidized cellulose is not particularly limited, but in the next step, when the oxidized cellulose is defibrated and nano-sized to produce nanocellulose, the amount of carboxy group per 1 g of oxidized cellulose is 0.2 mmol / g or more. It is preferably 3.0 mmol / g or less, more preferably 0.35 mmol / g or more and 3.0 mmol / g or less, still more preferably 0.4 mmol / g or more and 3.0 mmol / g or less. It is more preferably 0.5 mmol / g or more and 3.0 mmol / g or less, and even more preferably 0.55 mmol / g or more and 2.0 mmol / g or less. Further, the oxidation reaction may be carried out in two or more steps.
　また、ナノセルロースを含むスラリーの粘度安定性を高めるためには、ナノセルロース中のカルボキシ基量は高いほど好ましく、０．４ｍｍｏｌ／ｇ以上であることが好ましい。酸化反応でのコストが高くなることから、０．８ｍｍｏｌ／ｇ以下であることが好ましい。
　なお、酸化セルロースまたはナノセルロース中のカルボキシ基量は、次の方法で測定することができる。 Further, in order to enhance the viscosity stability of the slurry containing nanocellulose, the higher the amount of carboxy groups in the nanocellulose, the more preferably 0.4 mmol / g or more. It is preferably 0.8 mmol / g or less because the cost in the oxidation reaction is high.
The amount of carboxy group in oxidized cellulose or nanocellulose can be measured by the following method.
　酸化セルロースまたはナノセルロースの０．５質量％スラリーに純水を加えて６０ｍｌに調製し、０．１Ｍ塩酸水溶液を加えてｐＨ２．５にした後、０．０５Ｎの水酸化ナトリウム水溶液を滴下して、ｐＨが１１になるまで電気伝導度を測定し、電気伝導度の変化が穏やかな弱酸の中和段階において消費された水酸化ナトリウム量（ａ）から、下記式を用いて算出する。
カルボキシ基量（ｍｍｏｌ／ｇ酸化セルロースまたはナノセルロース）＝ａ（ｍｌ）×０．０５／酸化セルロース質量またはナノセルロース質量（ｇ） Pure water is added to a 0.5% by mass slurry of cellulose oxide or nanocellulose to prepare 60 ml, and a 0.1 M hydrochloric acid aqueous solution is added to adjust the pH to 2.5, and then a 0.05 N sodium hydroxide aqueous solution is added dropwise. , The electric conductivity is measured until the pH reaches 11, and it is calculated from the amount of sodium hydroxide (a) consumed in the neutralization step of a weak acid in which the change in electric conductivity is moderate, using the following formula.
Amount of carboxy group (mmol / g cellulose oxide or nanocellulose) = a (ml) x 0.05 / mass of cellulose oxide or mass of nanocellulose (g)
　なお、セルロース系原料にはタンパク質分が含まれる場合があるが、前記酸化反応が終了した後にろ過および水洗を行うことで混在するタンパク質分を取り除くことができる。ろ過および水洗の方法は、公知の方法が適用できる。
　また、水洗水と水洗排水の導電率値などを比較することで、洗浄の終点到達の目安とすることができる。 Although the cellulosic raw material may contain a protein component, the mixed protein component can be removed by performing filtration and washing with water after the oxidation reaction is completed. As the method of filtration and washing with water, a known method can be applied.
Further, by comparing the conductivity values of the water-washed water and the water-washed drainage, it can be used as a guideline for reaching the end point of the washing.
　上記ろ過等の単離処理の前に、単離処理のろ過性や収率を向上させる観点から、酸化セルロースまたはナノセルロースを含む溶液に酸を添加し、例えばｐＨを４．０以下とし、酸化によって生成したカルボキシ基の少なくとも一部の塩型（－ＣＯＯ－　Ｘ＋：Ｘ＋はナトリウム、リチウム等の陽イオンを指す）からプロトン型（－ＣＯＯ－Ｈ+）とすることができる。
　なお、赤外吸収スペクトルにおいて、プロトン型は１７２０ｃｍ－１付近に、塩型は１６００ｃｍ－１付近にピークが見られることから、それらを区別することができる。 Prior to the isolation treatment such as filtration, an acid is added to a solution containing oxidized cellulose or nanocellulose from the viewpoint of improving the filterability and yield of the isolation treatment, for example, the pH is set to 4.0 or less, and oxidation is performed. The salt type (-COO - X + : X + refers to a cation such as sodium, lithium, etc.) of at least a part of the carboxy group produced by the above can be changed to the proton type (-COO - H + ).
In the infrared absorption spectrum, the proton type has a peak near 1720 cm -1 , and the salt type has a peak near 1600 cm -1 , so that they can be distinguished.
　酸化セルロースまたはナノセルロースを含む溶液において、単離処理のためにｐＨを４．０以下としていた場合には、その後の用に供する際の取り扱い性を向上させるために、例えば塩基を添加してｐＨを６．０以上とし、カルボキシ基の少なくとも一部を塩型（－ＣＯＯ－　Ｘ＋：Ｘ＋はナトリウム、リチウム等の陽イオンを指す）とすることができる。また、酸化セルロースまたはナノセルロースを含む溶液は、その溶媒を置換等することによって、酸化セルロースまたはナノセルロースを含む組成物としてもよい。酸化セルロースまたはナノセルロースを含む組成物においても、例えばｐＨを１０以上のアルカリ条件とし、カルボキシ基の少なくとも一部を塩型（－ＣＯＯ－　Ｘ＋：Ｘ＋はナトリウム、リチウム等の陽イオンを指す）とすることができる。 In a solution containing cellulose oxide or nanocellulose, when the pH was set to 4.0 or less for the isolation treatment, for example, a base was added to improve the handleability when the solution was used for the subsequent use. Can be 6.0 or more, and at least a part of the carboxy group can be in the salt type (-COO - X + : X + indicates a cation such as sodium or lithium). Further, the solution containing cellulose oxide or nanocellulose may be used as a composition containing cellulose oxide or nanocellulose by substituting the solvent or the like. Even in a composition containing cellulose oxide or nanocellulose, for example, the pH is set to an alkaline condition of 10 or more, and at least a part of the carboxy group is a salt type (-COO - X + : X + indicates a cation such as sodium or lithium. ).
　酸化セルロースまたはナノセルロースの製造方法は、酸化セルロースの物性を制御するため、得られた酸化セルロースまたはナノセルロースと、修飾基を有する化合物とを混合する工程をさらに含んでもよい。修飾基を有する化合物としては、酸化セルロースまたはナノセルロースが有するカルボキシ基や水酸基とイオン結合又は共有結合を形成し得る修飾基を有する化合物であれば、特に限定されない。イオン結合を形成し得る修飾基を有する化合物として、例えば第１級アミン、第２級アミン、第３級アミン、第４級アンモニウム化合物、及びホスホニウム化合物が挙げられる。共有結合を形成し得る修飾基を有する化合物として、例えばアルコール、イソシアネート化合物、及びエポキシ化合物が挙げられる。
　以上のとおり、酸化セルロースまたはナノセルロースは、塩型、プロトン型、及び修飾基による変性型の態様を包含する。 The method for producing cellulose oxide or nanocellulose may further include a step of mixing the obtained cellulose oxide or nanocellulose with a compound having a modifying group in order to control the physical properties of the cellulose oxide. The compound having a modifying group is not particularly limited as long as it is a compound having a modifying group capable of forming an ionic bond or a covalent bond with a carboxy group or a hydroxyl group of cellulose oxide or nanocellulose. Examples of the compound having a modifying group capable of forming an ionic bond include a primary amine, a secondary amine, a tertiary amine, a quaternary ammonium compound, and a phosphonium compound. Compounds having a modifying group capable of forming a covalent bond include, for example, alcohols, isocyanate compounds, and epoxy compounds.
As described above, the oxidized cellulose or nanocellulose includes the salt type, the proton type, and the modified type by a modifying group.
　平均繊維長、平均繊維幅、繊維長の標準偏差、尖度、歪度、および範囲、繊維幅の標準偏差、尖度、歪度、および範囲などを本発明の範囲に調整する観点から、撹拌の際に反応系を均一に混ぜられるプロペラ型撹拌羽根等を使用することが好ましい。また、プロペラ型撹拌羽根の回転数は、５０ｒｐｍ以上５００ｒｐｍ以下の範囲とすることが好ましく、８０ｒｐｍ以上２００ｒｐｍ以下の範囲とすることが好ましい。 Stirring from the viewpoint of adjusting the average fiber length, average fiber width, standard deviation of fiber length, kurtosis, skewness, and range, standard deviation of fiber width, kurtosis, skewness, and range to the range of the present invention. At this time, it is preferable to use a propeller-type stirring blade or the like that can uniformly mix the reaction system. The rotation speed of the propeller type stirring blade is preferably in the range of 50 rpm or more and 500 rpm or less, and preferably in the range of 80 rpm or more and 200 rpm or less.
＜酸化セルロースを解繊処理してナノセルロースを製造する工程＞
　前記で得られた酸化セルロースは、解繊してナノ化することにより、ナノセルロースを製造することができる。本発明のナノセルロースには、セルロースナノクリスタルなどセルロースをナノ化したものを含む。
　前記酸化セルロースを解繊する方法では、溶媒中でスターラーなどの弱い撹拌や、機械的解繊を行うことで、解繊時間の短縮が可能になる。ただし、機械的解繊が強すぎると、ナノセルロースが折れたり、切れたりする場合がある。 <Process of defibrating cellulose oxide to produce nanocellulose>
The oxidized cellulose obtained above can be defibrated and nano-sized to produce nanocellulose. The nanocellulose of the present invention includes nano-sized cellulose such as cellulose nanocrystals.
In the method for defibrating oxidized cellulose, the defibration time can be shortened by performing weak stirring with a stirrer or the like in a solvent or mechanical defibration. However, if the mechanical defibration is too strong, the nanocellulose may break or break.
　前記機械的解繊の方法は、特に限定されないが、例えば、酸化セルロースを十分に溶媒で洗浄した後、目的に応じて適宜選択することができ、例えば、スクリュー型ミキサー、パドルミキサー、ディスパー型ミキサー、タービン型ミキサー、高速回転下でのホモミキサー、高圧ホモジナイザー、超高圧ホモジナイザー、二重円筒型ホモジナイザー、超音波ホモジナイザー、水流対抗衝突型分散機、ビーター、ディスク型リファイナー、コニカル型リファイナー、ダブルディスク型リファイナー、グラインダー、一軸または多軸混錬機などの公知の混合・撹拌装置が挙げられ、これらを単独または２種類以上組合せて溶媒中で処理することで、酸化セルロースをナノ化して、ナノセルロースを製造することができる。
　平均繊維長、平均繊維幅、繊維長の標準偏差、尖度、歪度、および範囲、繊維幅の標準偏差、尖度、歪度、および範囲などを本発明の範囲に調整する観点から、超高圧ホモジナイザーを用いることが好ましい。
　超高圧ホモジナイザーにより解繊を行う場合、解繊処理時の圧力は、好ましくは１００ＭＰａ以上であり、より好ましくは１２０ＭＰａ以上であり、さらに好ましくは１５０ＭＰａ以上である。解繊処理回数は特に限定されないが、解繊を十分に進行させる観点から好ましくは２回以上、より好ましくは３回以上である。
　また、機械解繊時の解繊処理回数、酸化セルロース分散液の酸化セルロースの濃度などの解繊条件を調整することで、平均繊維長、平均繊維幅、繊維長の標準偏差、尖度、歪度、および範囲、繊維幅の標準偏差、尖度、歪度、および範囲などを本発明の範囲とすることができる。 The method of mechanical defibration is not particularly limited, but can be appropriately selected depending on the intended purpose, for example, after the oxidized cellulose is sufficiently washed with a solvent. , Turbine type mixer, homomixer under high speed rotation, high pressure homogenizer, ultra high pressure homogenizer, double cylindrical homogenizer, ultrasonic homogenizer, water flow counter-collision type disperser, beater, disc type refiner, conical type refiner, double disc type Known mixing / stirring devices such as refiners, grinders, uniaxial or multiaxial kneaders can be mentioned, and by treating them alone or in combination of two or more in a solvent, oxidized cellulose is nano-sized to obtain nanocellulose. Can be manufactured.
From the viewpoint of adjusting the average fiber length, average fiber width, standard deviation of fiber length, kurtosis, skewness, and range, standard deviation of fiber width, kurtosis, skewness, and range, etc. to the scope of the present invention, it is super. It is preferable to use a high pressure homogenizer.
When defibrating with an ultra-high pressure homogenizer, the pressure during the defibration treatment is preferably 100 MPa or more, more preferably 120 MPa or more, still more preferably 150 MPa or more. The number of times of defibration treatment is not particularly limited, but is preferably 2 times or more, and more preferably 3 times or more from the viewpoint of sufficiently advancing defibration.
In addition, by adjusting the defibration conditions such as the number of defibration treatments during mechanical defibration and the concentration of defibrated cellulose in the oxidative cellulose dispersion, the average fiber length, average fiber width, standard deviation of fiber length, kurtosis, and strain can be adjusted. Degrees and ranges, standard deviations of fiber width, kurtosis, strain, and ranges can be the scope of the invention.
　解繊処理に使用する溶媒としては、特に制限はなく、目的に応じて適宜選択することができ、水、アルコール類、エーテル類、ケトン類、炭酸エステル類、アセトニトリル、Ｎ－メチル－２－ピロリドン、Ｎ，Ｎ－ジメチルホルムアミド、Ｎ，Ｎ－ジメチルアセトアミド、ジメチルスルホキサイドなどが挙げられ、これらを単独で使用してもよいし、２種類以上を併用してもよい。 The solvent used for the defibration treatment is not particularly limited and may be appropriately selected depending on the intended purpose. Water, alcohols, ethers, ketones, carbonic acid esters, acetonitrile, N-methyl-2-pyrrolidone. , N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide and the like, and these may be used alone or in combination of two or more.
　前記アルコール類としては、メタノール、エタノール、イソプロパノール、イソブタノール、ｓｅｃ－ブチルアルコール、ｔｅｒｔ－ブチルアルコール、メチルセロソルブ、エチレングリコールおよびグリセリン等が挙げられる。
　前記エーテル類としては、エチレングリコールジメチルエーテル、１，４－ジオキサンおよびテトラヒドロフラン等が挙げられる。
　前記ケトン類としては、アセトンおよびメチルエチルケトン等が挙げられる。
　前記炭酸エステル類としては、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、ジフェニルカーボネートおよびエチルメチルカーボネート等が挙げられる。 Examples of the alcohols include methanol, ethanol, isopropanol, isobutanol, sec-butyl alcohol, tert-butyl alcohol, methyl cellosolve, ethylene glycol and glycerin.
Examples of the ethers include ethylene glycol dimethyl ether, 1,4-dioxane and tetrahydrofuran.
Examples of the ketones include acetone, methyl ethyl ketone and the like.
Examples of the carbonic acid esters include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, diphenyl carbonate and ethyl methyl carbonate.
　溶媒として有機溶剤を選択することにより、前記工程で得られた酸化セルロースおよびそれを解繊して得られたナノセルロースの単離が容易となる。また、有機溶剤中に分散したナノセルロースが得られるため、有機溶剤に溶解する樹脂やその樹脂原料モノマー等との混合が容易となる。 By selecting an organic solvent as the solvent, it becomes easy to isolate the oxidized cellulose obtained in the above step and the nanocellulose obtained by defibrating it. Further, since nanocellulose dispersed in an organic solvent can be obtained, it becomes easy to mix with a resin that dissolves in the organic solvent, a resin raw material monomer, or the like.
　以下、実施例および比較例により、本発明を具体的に説明するが、本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.
＜粘度安定性の評価方法＞
　石原産業社製酸化チタンＲ－８２０（５質量％）および各種ナノセルロースを含む水系スラリー（５０ｇ）について、スラリーの初期粘度が、以下に記載する方法で粘度測定した際に３００ｍＰａ・ｓとなるようにナノセルロース添加量を変えて作製した。スラリーを作製するための混合ではシンキー社のミキサー「あわとり練太郎ＡＲＥ－３１０」（ミックスモード、公転：２０００ｒｐｍ、自転：８００ｒｐｍ、２０分間）を使用した。
　そして、作製直後（初期粘度）と１週間静置後の粘度を測定し、下記式より粘度変化率を算出すると共に、以下の判定基準に従って粘度安定性を判定した。
粘度変化率（％）＝（１週間静置後のスラリーの粘度）/（作製直後のスラリー粘度）×１００
粘度安定性の判定基準（粘度変化率の絶対値）
Ａ：１０５％未満
Ｂ：１０５％以上、１１０％未満
Ｃ：１１０％以上、１１５％未満
Ｄ：１１５％以上
なお、静置は室内（２３±２℃）とした。 <Evaluation method of viscosity stability>
For an aqueous slurry (50 g) containing titanium oxide R-820 (5% by mass) manufactured by Ishihara Sangyo Co., Ltd. and various nanocelluloses, the initial viscosity of the slurry shall be 300 mPa · s when the viscosity is measured by the method described below. It was prepared by changing the amount of nanocellulose added. In the mixing for preparing the slurry, a Shinky mixer "Awatori Rentaro ARE-310" (mix mode, revolution: 2000 rpm, rotation: 800 rpm, 20 minutes) was used.
Then, the viscosity immediately after production (initial viscosity) and after standing for one week were measured, the viscosity change rate was calculated from the following formula, and the viscosity stability was determined according to the following criteria.
Viscosity change rate (%) = (viscosity of slurry after standing for 1 week) / (slurry viscosity immediately after preparation) × 100
Criteria for viscosity stability (absolute value of viscosity change rate)
A: Less than 105% B: 105% or more, less than 110% C: 110% or more, less than 115% D: 115% or more The standing was indoors (23 ± 2 ° C.).
＜粘度測定方法＞
　スラリーの初期粘度は、スパチュラで泡が入らない程度の速さで撹拌した後、東機産業社のＥ型粘度計（ＴＶ－２２）にて２５℃、１００ｒｐｍ（せん断速度２００ｓ-1）の条件で測定した。１週間静置後の粘度も、上記機器にて同条件で測定した。 <Viscosity measurement method>
The initial viscosity of the slurry is 25 ° C. and 100 rpm (shear velocity 200s -1 ) with an E-type viscometer (TV-22) manufactured by Toki Sangyo Co., Ltd. after stirring with a spatula at a speed that does not allow bubbles to enter. Measured at. The viscosity after standing for one week was also measured with the above equipment under the same conditions.
＜ナノセルロースの繊維長と繊維幅の測定方法＞
　得られたナノセルロース分散液を純水で１０００～１００００００倍に希釈し、それをマイカ基材上で自然乾燥させ、オックスフォード・アサイラム製走査型ブローブ顕微鏡「ＭＦＰ－３Ｄ　ｉｎｆｉｎｉｔｙ」を用いて、ＡＣモードで、ナノセルロースの形状観察を行った。
　繊維長については、得られた画像を画像処理ソフトウェア「ＩｍａｇｅＪ」を用いて二値化し解析を行った。繊維１００本以上について、繊維長＝「周囲長」÷２として数平均繊維長を求めた。
　繊維幅については、「ＭＦＰ－３Ｄ　ｉｎｆｉｎｉｔｙ」に付属されているソフトウェアを用いて、繊維５０本以上について、形状像の断面高さ＝繊維幅として数平均繊維幅を求めた。 <Measurement method of fiber length and fiber width of nanocellulose>
The obtained nanocellulose dispersion is diluted 1000 to 1,000,000 times with pure water, air-dried on a mica substrate, and AC mode is used using a scanning probe microscope "MFP-3D infinity" manufactured by Oxford Asylum. Then, the shape of nanocellulose was observed.
The fiber length was quantified using the image processing software "ImageJ" and analyzed. For 100 or more fibers, the number average fiber length was calculated by setting fiber length = "peripheral length" / 2.
Regarding the fiber width, the software attached to "MFP-3D infinity" was used to obtain the number average fiber width as the cross-sectional height of the shape image = the fiber width for 50 or more fibers.
＜実施例１＞
　セルロース系原料として、針葉樹パルプ（ＳＩＧＭＡ－ＡＬＤＲＩＣＨ社　ＮＩＳＴ ＲＭ ８４９５, ｂｌｅａｃｈｅｄ ｋｒａｆｔ ｐｕｌｐ）を５ｍｍ角にハサミで切断し、大阪ケミカル社製「ワンダーブレンダーＷＢ－１」にて、２５，０００ｒｐｍで１分間処理して、綿状に機械解繊した。
　ビーカーに、有効塩素濃度が４２質量％である次亜塩素酸ナトリウム５水和物結晶を３５０ｇ入れ、純水を加えて撹拌し有効塩素濃度を２１質量％とした。そこへ、３５質量％塩酸を加えて撹拌し、ｐＨ１１の水溶液とした。
　前記次亜塩素酸ナトリウム水溶液を新東科学社製の撹拌機（スリーワンモータ、ＢＬ６００）にてプロペラ型撹拌羽根を使用して１００ｒｐｍで撹拌しながら恒温水浴にて３０℃に加温した後、前記セルロース系原料を５０ｇ加えた。
　セルロース系原料を供給後、同じ恒温水槽で３０℃に保温しながら、４８質量％水酸化ナトリウムを添加しながら反応中のｐＨを１１に調整して、３０分間、撹拌機にて同条件で撹拌を行った。
　反応終了後、目開き２０μｍのＰＴＦＥ製メッシュフィルターを使用して、吸引ろ過により生成物を固液分離し、得られた酸化セルロースを純水で洗浄した。
　酸化セルロースに純水を加え５％分散液を作製し、スギノマシン社製の超高圧ホモジナイザー「スターバースト　ラボ　ＨＪＰ－２５００５」にて２００ＭＰａで、１０パス処理し、ナノセルロース水分散体を得た。
　なお、超高圧ホモジナイザーでは、内蔵された超高圧解繊部に酸化セルロース水分散液を循環通液させて解繊を進める。その解繊部への通液１回分を１パスと呼んでいる。
　ナノセルロース中のＮ－オキシル化合物由来の残留窒素成分は、微量全窒素分析装置（三菱ケミカルアナリテック社製、装置名：ＴＮ-２１００Ｈ）を用いて窒素量として測定し、原料パルプからの増加分を算出した結果、１ｐｐｍ以下であった。 <Example 1>
As a cellulosic raw material, coniferous pulp (SIGMA-ALDRICH NIST RM 8495, bleached kraft pulp) is cut into 5 mm squares with scissors and treated with Osaka Chemical's "Wonder Blender WB-1" for 1 minute at 25,000 rpm. Then, it was mechanically defibrated into a cotton-like shape.
350 g of sodium hypochlorite pentahydrate crystal having an effective chlorine concentration of 42% by mass was placed in a beaker, pure water was added, and the mixture was stirred to bring the effective chlorine concentration to 21% by mass. To this, 35% by mass hydrochloric acid was added and stirred to prepare an aqueous solution having a pH of 11.
The sodium hypochlorite aqueous solution is heated to 30 ° C. in a constant temperature water bath while stirring at 100 rpm using a propeller type stirring blade with a stirrer (Three One Motor, BL600) manufactured by Shinto Kagaku Co., Ltd. 50 g of a cellulosic raw material was added.
After supplying the cellulosic raw material, adjust the pH during the reaction to 11 while keeping the temperature at 30 ° C. in the same constant temperature water bath and adding 48% by mass sodium hydroxide, and stir for 30 minutes under the same conditions with a stirrer. Was done.
After completion of the reaction, the product was solid-liquid separated by suction filtration using a PTFE mesh filter having an opening of 20 μm, and the obtained cellulose oxide was washed with pure water.
Pure water was added to the oxidized cellulose to prepare a 5% dispersion, which was treated with an ultra-high pressure homogenizer "Starburst Lab HJP-25005" manufactured by Sugino Machine Limited at 200 MPa for 10 passes to obtain a nanocellulose aqueous dispersion.
In the ultra-high pressure homogenizer, the aqueous dispersion of cellulose oxide is circulated through the built-in ultra-high pressure defibration section to proceed with defibration. One pass through the defibration section is called one pass.
The residual nitrogen component derived from the N-oxyl compound in nanocellulose was measured as the amount of nitrogen using a trace total nitrogen analyzer (manufactured by Mitsubishi Chemical Analytech Co., Ltd., device name: TN-2100H), and the amount increased from the raw material pulp. As a result of calculating, it was 1 ppm or less.
＜実施例２＞
　超高圧ホモジナイザーでのパス回数を１５パスにした以外は実施例１と同条件とした。 <Example 2>
The conditions were the same as in Example 1 except that the number of passes in the ultra-high pressure homogenizer was set to 15 passes.
＜実施例３＞
　セルロース系原料として、日本製紙社製の粉末セルロース（ＫＣフロックＷ－１００ＧＫ）を使用した以外は実施例１と同条件とした。 <Example 3>
The conditions were the same as in Example 1 except that powdered cellulose (KC Flock W-100GK) manufactured by Nippon Paper Industries, Ltd. was used as the cellulose-based raw material.
＜実施例４＞
　セルロース系原料として、ティーディーアイ社の粉末セルロース（ＶＰ－１）を使用した以外は実施例１と同条件とした。 <Example 4>
The conditions were the same as in Example 1 except that powdered cellulose (VP-1) manufactured by TDI was used as the cellulose-based raw material.
＜実施例５＞
　解繊する際の酸化セルロース分散液の酸化セルロース濃度を２質量％にした以外は実施例１と同条件とした。 <Example 5>
The conditions were the same as in Example 1 except that the cellulose oxide concentration of the cellulose oxide dispersion liquid at the time of defibration was set to 2% by mass.
＜実施例６＞
　解繊する際の酸化セルロース分散液の酸化セルロース濃度を２質量％にした以外は実施例３と同条件とした。 <Example 6>
The conditions were the same as in Example 3 except that the cellulose oxide concentration of the cellulose oxide dispersion liquid at the time of defibration was set to 2% by mass.
＜実施例７＞
　解繊する際の酸化セルロース分散液の酸化セルロース濃度を２質量％に、超高圧ホモジナイザーでのパス回数を８パスにした以外は、実施例３と同条件とした。 <Example 7>
The conditions were the same as in Example 3 except that the cellulose oxide concentration of the defibrated cellulose oxide dispersion was 2% by mass and the number of passes with the ultrahigh pressure homogenizer was 8 passes.
＜実施例８＞
　解繊する際の酸化セルロース分散液の酸化セルロース濃度を３質量％にした以外は実施例３と同条件とした。 <Example 8>
The conditions were the same as in Example 3 except that the cellulose oxide concentration of the cellulose oxide dispersion liquid at the time of defibration was set to 3% by mass.
＜比較例１＞
　酸化反応時の撹拌をスターラーで撹拌させたこと、酸化セルロースに純水を加えて１％分散液を作製し、ヒールッシャー社製の超音波ホモジナイザー「ＵＰ－４００Ｓ」にてＣＹＣＬＥ０．５、ＡＭＰＬＩＹＵＤＥ５０の条件で１０分間解繊した以外は実施例１と同条件とした。
　なお、超音波ホモジナイザーでは、容器に入れた酸化セルロース水分散液に超音波発振部を浸漬し、発振される超音波にて解繊を進めた。 <Comparative Example 1>
Stirrer was used for stirring during the oxidation reaction, and pure water was added to the oxidized cellulose to prepare a 1% dispersion, and the conditions were CYCLE 0.5 and AMPLIYUDE 50 using an ultrasonic homogenizer "UP-400S" manufactured by Heelscher. The conditions were the same as in Example 1 except that the fibers were defibrated for 10 minutes.
In the ultrasonic homogenizer, the ultrasonic oscillating part was immersed in the aqueous dispersion of cellulose oxide in a container, and the defibration was proceeded by the oscillated ultrasonic waves.
＜比較例２＞
　酸化反応の時間を２０分にした以外は、実施例４と同条件とした。 <Comparative Example 2>
The conditions were the same as in Example 4 except that the oxidation reaction time was set to 20 minutes.
＜比較例３（ＴＥＭＰＯ酸化）＞
　ビーカーに、２,２,６,６－テトラメチル－１－ピペリジン－Ｎ－オキシラジカル（ＴＥＭＰＯ、Ｓｉｇｍａ－Ａｌｄｒｉｃｈ社）０．８ｇ、臭化ナトリウム（富士フィルム和光純薬社）５ｇを入れ、純水５０００mLを加えて新東科学社製の撹拌機（スリーワンモータ、ＢＬ６００）にてプロペラ型撹拌羽根を使用して２００ｒｐｍで撹拌し溶解させた。
　恒温水浴にて２５℃に加温した後、セルロース系原料として、針葉樹パルプ（ＳＩＧＭＡ－ＡＬＤＲＩＣＨ社　ＮＩＳＴ ＲＭ ８４９５, ｂｌｅａｃｈｅｄ ｋｒａｆｔ ｐｕｌｐ）を綿状に機械解繊したものを５０ｇ加え、０．１Ｍ-水酸化ナトリウム溶液を加え、ｐＨ１０の水溶液とした。次いで、次亜塩素酸ナトリウム水溶液（工業用グレード）１３１.５ｇを加え反応を開始させた。次亜塩素酸ナトリウム水溶液を供給後、同じ恒温水槽で２５℃に保温しながら、０．１Ｍ水酸化ナトリウムを添加しながら反応中のｐＨを１０に調整して、１２０分間、撹拌機にて同条件で撹拌を行った。
　反応終了後、目開き２０μｍのＰＴＦＥ製メッシュフィルターを使用して、吸引ろ過により生成物を固液分離し、得られた酸化セルロースを純水で洗浄した。
　酸化セルロースに純水を加え０．５％分散液を作製し、スギノマシン社製の超高圧ホモジナイザー「スターバーストラボ」にて２００ＭＰａで３パス処理し、ナノセルロース水分散体を得た。なお、ナノセルロース中のＮ－オキシル化合物由来の残留窒素成分は、実施例１と同様の条件で窒素量として測定し、原料パルプからの増加分を算出した結果、５ｐｐｍであった。 <Comparative Example 3 (TEMPO Oxidation)>
In a beaker, add 0.8 g of 2,2,6,6-tetramethyl-1-piperidine-N-oxy radical (TEMPO, Sigma-Aldrich) and 5 g of sodium bromide (Fuji Film Wako Pure Chemical Industries, Ltd.) to make it pure. 5000 mL of water was added, and the mixture was stirred and dissolved at 200 rpm using a propeller type stirring blade with a stirrer (Three One Motor, BL600) manufactured by Shinto Kagaku Co., Ltd.
After heating to 25 ° C in a constant temperature water bath, 50 g of cotton-like mechanically defibrated softwood pulp (SIGMA-ALDRICH NIST RM 8495, bleached kraft pull) was added as a cellulosic raw material, and 0.1 M-water was added. A sodium oxide solution was added to prepare an aqueous solution having a pH of 10. Then, 131.5 g of an aqueous sodium hypochlorite solution (industrial grade) was added to initiate the reaction. After supplying the sodium hypochlorite aqueous solution, adjust the pH during the reaction to 10 while keeping the temperature at 25 ° C. in the same constant temperature water bath and adding 0.1 M sodium hydroxide, and use the same stirrer for 120 minutes. Stirring was performed under the conditions.
After completion of the reaction, the product was solid-liquid separated by suction filtration using a PTFE mesh filter having an opening of 20 μm, and the obtained cellulose oxide was washed with pure water.
Pure water was added to the oxidized cellulose to prepare a 0.5% dispersion, which was treated with an ultra-high pressure homogenizer "Starburst Lab" manufactured by Sugino Machine Limited at 200 MPa for 3 passes to obtain a nanocellulose aqueous dispersion. The residual nitrogen component derived from the N-oxyl compound in the nanocellulose was measured as the amount of nitrogen under the same conditions as in Example 1, and the increase from the raw material pulp was calculated to be 5 ppm.
　実施例１～８および比較例１～３で得られたナノセルロースについて、下記表１に結果をまとめた。
　なお、表１におけるセルロース系原料は以下のとおりである。
・針葉樹：針葉樹パルプ（ＳＩＧＭＡ－ＡＬＤＲＩＣＨ社　ＮＩＳＴ ＲＭ ８４９５, ｂｌｅａｃｈｅｄ ｋｒａｆｔ ｐｕｌｐ）を綿状に機械解繊したもの
・ＫＣ：日本製紙社製の粉末セルロース（ＫＣフロックＷ－１００ＧＫ）
・ＶＰ：ティーディーアイ社の粉末セルロース（ＶＰ－１） The results of the nanocellulose obtained in Examples 1 to 8 and Comparative Examples 1 to 3 are summarized in Table 1 below.
The cellulosic raw materials in Table 1 are as follows.
-Conifer: Conifer pulp (SIGMA-ALDRICH NIST RM 8495, bleached kraft pulp) mechanically defibrated into a cotton-like powder-KC: Powdered cellulose manufactured by Nippon Paper Industries (KC Flock W-100GK)
-VP: Powdered cellulose (VP-1) from TDI
Figure JPOXMLDOC01-appb-T000007
  
Figure JPOXMLDOC01-appb-T000007
  
Figure JPOXMLDOC01-appb-T000008
  
Figure JPOXMLDOC01-appb-T000008
  

Claims (14)

  1. 　平均繊維長が１００ｎｍ以上５００ｎｍ以下であり、平均繊維幅が２．０ｎｍ以上５．０ｎｍ以下であるナノセルロースであって、下記条件Ａ～Ｈの少なくとも一つを満たすナノセルロース。
    条件Ａ：繊維長の標準偏差が６００ｎｍ以下である
    条件Ｂ：繊維長の尖度が１１以上である
    条件Ｃ：繊維長の歪度が３．０以上である
    条件Ｄ：繊維長の範囲が４０００ｎｍ以下である
    条件Ｅ：繊維幅の標準偏差が１．５ｎｍ以下である
    条件Ｆ：繊維幅の尖度が０．３以上である
    条件Ｇ：繊維幅の歪度が０．５以上である
    条件Ｈ：繊維幅の範囲が６．８ｎｍ以下である     Nanocellulose having an average fiber length of 100 nm or more and 500 nm or less and an average fiber width of 2.0 nm or more and 5.0 nm or less, and satisfying at least one of the following conditions A to H.
    Condition A: The standard deviation of the fiber length is 600 nm or less Condition B: The kurtosis of the fiber length is 11 or more Condition C: The skewness of the fiber length is 3.0 or more Condition D: The range of the fiber length is 4000 nm Condition E: The standard deviation of the fiber width is 1.5 nm or less F: The kurtosis of the fiber width is 0.3 or more G: The skewness of the fiber width is 0.5 or more H : The fiber width range is 6.8 nm or less.
  2. 　繊維長の標準偏差が１０ｎｍ以上５００ｎｍ以下である、請求項１に記載のナノセルロース。 The nanocellulose according to claim 1, wherein the standard deviation of the fiber length is 10 nm or more and 500 nm or less.
  3. 　繊維長の尖度が１２以上３０以下である、請求項１または２に記載のナノセルロース。 The nanocellulose according to claim 1 or 2, wherein the fiber length has a kurtosis of 12 or more and 30 or less.
  4. 　繊維長の歪度が３．０以上６．０以下である、請求項１～３のいずれか１項に記載のナノセルロース。 The nanocellulose according to any one of claims 1 to 3, wherein the fiber length skewness is 3.0 or more and 6.0 or less.
  5. 　繊維長の範囲が４５０ｎｍ以上４０００ｎｍ以下である、請求項１～４のいずれか１項に記載のナノセルロース。 The nanocellulose according to any one of claims 1 to 4, wherein the fiber length range is 450 nm or more and 4000 nm or less.
  6. 　繊維幅の標準偏差が０．５ｎｍ以上１．５ｎｍ以下である、請求項１～５のいずれか１項に記載のナノセルロース。 The nanocellulose according to any one of claims 1 to 5, wherein the standard deviation of the fiber width is 0.5 nm or more and 1.5 nm or less.
  7. 　繊維幅の尖度が０．３以上２．５以下である、請求項１～６のいずれか１項に記載のナノセルロース。 The nanocellulose according to any one of claims 1 to 6, wherein the fiber width has a kurtosis of 0.3 or more and 2.5 or less.
  8. 　繊維幅の歪度が０．５以上１．５以下である、請求項１～７のいずれか１項に記載のナノセルロース。 The nanocellulose according to any one of claims 1 to 7, wherein the fiber width skewness is 0.5 or more and 1.5 or less.
  9. 　繊維幅の範囲が３．０ｎｍ以上６．８ｎｍ以下である、請求項１～８のいずれか１項に記載のナノセルロース。 The nanocellulose according to any one of claims 1 to 8, wherein the fiber width range is 3.0 nm or more and 6.8 nm or less.
  10. 　カルボキシル化ナノセルロースを含む、請求項１～９のいずれか１項に記載のナノセルロース。 The nanocellulose according to any one of claims 1 to 9, which comprises carboxylated nanocellulose.
  11. 　Ｎ－オキシル化合物を実質的に含まない、請求項１～１０のいずれか１項に記載のナノセルロース。 The nanocellulose according to any one of claims 1 to 10, which does not substantially contain an N-oxyl compound.
  12. 　セルロース系原料を次亜塩素酸またはその塩で酸化して得られる酸化セルロースを解繊処理して作製する請求項１～１１のいずれか１項に記載のナノセルロース。 The nanocellulose according to any one of claims 1 to 11, which is produced by defibrating the oxidized cellulose obtained by oxidizing a cellulose-based raw material with hypochlorous acid or a salt thereof.
  13. 　請求項１～１２のいずれか１項に記載のナノセルロースが分散媒に分散されたナノセルロース分散液。 A nanocellulose dispersion liquid in which the nanocellulose according to any one of claims 1 to 12 is dispersed in a dispersion medium.
  14. 　セルロース系原料を次亜塩素酸またはその塩で酸化して得られる酸化セルロースを解繊処理して作製する工程を含む請求項１～１２のいずれか１項に記載のナノセルロースの製造方法。 The method for producing nanocellulose according to any one of claims 1 to 12, which comprises a step of defibrating the oxidized cellulose obtained by oxidizing a cellulose-based raw material with hypochlorous acid or a salt thereof.
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