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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