Method for producing microfibrillated modified cellulose fibers

Abstract

To provide methods for producing novel microfibrillated modified cellulose fibers that can reduce organic solvent usage and improve the dispersibility of the microfibrillated modified cellulose fibers compared to the traditional methods.SOLUTION: Methods for producing microfibrillated modified cellulose fibers include steps for (a) removing water by distillation from a mixture comprising modified cellulose fibers, water and an organic solvent and (b) microfibrillating the modified cellulose fibers in the mixture after water removal.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing finely divided modified cellulose fibers. [Background technology]

[0002] In recent years, attention has been drawn to the fact that the addition of fine cellulose fibers to materials such as resins significantly improves various mechanical properties of the materials. In general, the surface of fine cellulose fibers is hydrophilic, and therefore they will aggregate in non-aqueous solvents such as organic solvents or hydrophobic resins. Therefore, when using fine cellulose fibers in such hydrophobic systems, it is necessary to modify the fine cellulose fibers to be hydrophobic before dispersing them in the target medium.

[0003] On the other hand, natural cellulose fibers, which are the raw material for fine cellulose fibers, usually contain a large amount of water. Therefore, when dispersing fine cellulose fibers in various media, it is important to know how to remove this water. In existing technologies, the cellulose fibers are subjected to solid-liquid separation before dispersion, and the water is replaced with an organic solvent to remove the water associated with the cellulose fibers (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-188673 A Summary of the Invention [Problem to be solved by the invention]

[0005] The process of separating the cellulose fibers into solid and liquid and then replacing the solid with an organic solvent requires repeated operations, which is time-consuming and requires a correspondingly large amount of organic solvent to be used.

[0006] The present invention relates to a method for producing finely divided modified cellulose fibers, and a method for producing a composition containing the finely divided modified cellulose fibers and an organic solvent, and relates to providing a new method that can reduce the amount of organic solvent used and has superior dispersibility of the finely divided modified cellulose fibers compared to conventional methods. [Means for solving the problem]

[0007] That is, the present invention relates to the following [1] to [4]. [1] A step of distilling off water from a mixture containing modified cellulose fibers, water and an organic solvent; and micronizing the modified cellulose fibers in the mixture from which water has been distilled off; A method for producing finely divided modified cellulose fibers, comprising the steps of: [2] A method for producing finely divided modified cellulose fibers according to the above [1], wherein the modified cellulose fibers are obtained by bonding modifying groups to the anionic groups of anionically modified cellulose fibers in the presence of water and an organic solvent. [3] A step of distilling off water from a mixture containing modified cellulose fibers, water and an organic solvent; and micronizing the modified cellulose fibers in the mixture from which water has been distilled off; A method for producing a composition containing finely divided modified cellulose fibers and an organic solvent, comprising: [4] A method for producing the composition according to [3] above, wherein the modified cellulose fiber is obtained by bonding a modifying group to an anionic group of an anionically modified cellulose fiber in the presence of water and an organic solvent. Effect of the Invention

[0008] According to the present invention, it is possible to provide a novel method which can reduce the amount of organic solvent used and has superior dispersibility of finely divided modified cellulose fibers compared to conventional methods. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The method for producing the microfibrillated modified cellulose fiber of the present invention comprises the steps of: removing water from a mixture containing the modified cellulose fibers, water and an organic solvent; and micronizing the modified cellulose fibers in the mixture from which the water has been distilled off; Includes. Furthermore, the method for producing a composition containing finely divided modified cellulose fibers and an organic solvent of the present invention includes the steps of: removing water from a mixture containing the modified cellulose fibers, water and an organic solvent; and micronizing the modified cellulose fibers in the mixture from which the water has been distilled off; Includes.

[0010] According to the method of the present invention, the amount of organic solvent used can be reduced by a simple treatment of distilling off water from a mixture containing modified cellulose fiber, water and an organic solvent. In addition, the inventors unexpectedly found that the dispersibility of the finely divided modified cellulose fiber produced by the method of the present invention is higher than that of the finely divided modified cellulose fiber obtained through conventional solid-liquid separation and solvent replacement. Although the mechanism by which such an effect is exhibited is unclear, it is presumed that this is because, while in conventional solid-liquid separation and solvent replacement, hydrophilic cellulose fiber forms hydrogen bonds in an organic solvent and aggregates, in the method of the present invention, modification such as hydrophobization and mixing with an organic solvent are performed in the presence of water, and then the water is distilled off, making it difficult for the modified cellulose fiber to aggregate.

[0011] [Modified cellulose fibers] The modified cellulose fiber in the present invention is a cellulose fiber having a modifying group via an ionic bond or an amide bond. The modifying group is preferably bonded to some or all of the hydroxy groups of the cellulose fiber, or to a carboxy group obtained by converting the hydroxy groups to a carboxy group, more preferably to an anionic group of the anion-modified cellulose fiber, and even more preferably to a carboxy group obtained by converting the hydroxymethyl group (-CHOH) at the C6 position of the glucose unit to a carboxy group (-COOH). When the modifying group is bonded to a carboxy group via an ionic bond, for example, "-COO - H3N + When the modifying group is bonded to the carboxy group via an amide bond, the bonding pattern is, for example, "-CONH-modifying group."

[0012] The average fiber diameter of the modified cellulose fiber is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 15 μm or more from the viewpoint of improving the dispersibility of the fine modified cellulose fiber, while from the same viewpoint, it is preferably 300 μm or less, more preferably 100 μm or less, and even more preferably 60 μm or less. The average fiber length of the modified cellulose fiber is preferably 700 μm or more, more preferably 1,000 μm or more, more preferably 1,200 μm or more, and even more preferably 1,500 μm or more from the viewpoint of improving the dispersibility, availability, and economic efficiency of the fine modified cellulose fiber, while from the same viewpoint, it is preferably 10,000 μm or less, more preferably 5,000 μm or less, and even more preferably 3,000 μm or less. The average fiber diameter and average fiber length of the modified cellulose fiber can be measured according to the method described in the Examples below.

[0013] (modifying group) The modifying groups include (a) hydrocarbon groups and (b) polymer groups. These modifying groups may be attached to the anionically modified cellulose fibers alone or in combination of two or more.

[0014] (a) Hydrocarbon group Examples of the hydrocarbon group include monovalent hydrocarbon groups, such as linear or branched chain saturated hydrocarbon groups, linear or branched chain unsaturated hydrocarbon groups, cyclic saturated hydrocarbon groups, aryl groups, aralkyl groups, and heterocyclic aromatic hydrocarbon groups. From the viewpoint of improving the dispersibility of the refined modified cellulose fiber, the carbon number of the hydrocarbon group is 1 or more, preferably 3 or more, more preferably 8 or more, and even more preferably 10 or more, and from the same viewpoint, is preferably 30 or less, more preferably 22 or less, and even more preferably 18 or less. The hydrocarbon group may have a substituent described later, and a part of the hydrocarbon group may be substituted with a hydrogen nitride group.

[0015] The linear or branched chain saturated hydrocarbon group is preferably a linear chain saturated hydrocarbon group from the viewpoint of improving the dispersibility of the finely divided modified cellulose fiber. Examples of the linear saturated hydrocarbon group include a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, an isobutyl group, a pentyl group, a tert-pentyl group, an isopentyl group, a hexyl group, an isohexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, a dodecyl group, a tridecyl group, a tetradecyl group, an octadecyl group, a docosyl group, and an octacosanyl group.

[0016] Examples of the chain unsaturated hydrocarbon group include a propenyl group, a butenyl group, an isobutenyl group, an isoprenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, and an octadecenyl group.

[0017] Examples of cyclic saturated hydrocarbon groups include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, a cyclododecyl group, a cyclotridecyl group, a cyclotetradecyl group, and a cyclooctadecyl group.

[0018] Examples of the aryl group include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, a biphenyl group, a triphenyl group, a terphenyl group, and groups in which these groups are substituted with the substituents described below.

[0019] Examples of the aralkyl group include a benzyl group, a trityl group, a phenethyl group, a phenylpropyl group, a phenylpentyl group, a phenylhexyl group, a phenylheptyl group, a phenyloctyl group, and groups in which these groups are substituted with the substituents described below. Examples of the heterocyclic aromatic hydrocarbon group include an imidazole group, a methylimidazole group, an ethylimidazole group, a propylimidazole group, a 2-phenylimidazole group, a benzimidazole group, and groups in which these groups are substituted with a substituent.

[0020] (b) Polymer group The polymer group in the present invention is a functional group that contains a polymer structure. From the viewpoint of improving the dispersibility of the refined modified cellulose fiber, the formula weight (molecular weight) of the polymer group is preferably 100 or more, more preferably 200 or more, even more preferably 300 or more, even more preferably 500 or more, even more preferably 1,000 or more, and even more preferably 1,500 or more. From the same viewpoint, it is preferably 1,000,000 or less, more preferably 100,000 or less, even more preferably 10,000 or less, even more preferably 7,000 or less, even more preferably 5,000 or less, even more preferably 4,000 or less, even more preferably 3,500 or less, and even more preferably 2,500 or less.

[0021] From the viewpoint of improving the dispersibility of the microfibrillated modified cellulose fibres, the polymer group is preferably a functional group having a repeating structure linked by a structure having an oxygen atom, more preferably a functional group having a repeating structure linked by an oxygen atom, such as a polyoxyalkylene structure or a polysiloxane structure, more preferably a polyoxyalkylene structure, and even more preferably an alkoxypolyoxyalkylene group.

[0022] From the viewpoint of improving the dispersibility of the finely divided modified cellulose fibers, the polyoxyalkylene structure is preferably a (co)polymer structure of one or more oxyalkylenes selected from oxyalkylenes having 2 or more and 8 or less carbon atoms, more preferably a (co)polymer structure of one or more oxyalkylenes selected from oxyalkylenes having 2 or more and 4 or less carbon atoms, even more preferably a (co)polymer structure of one or two oxyalkylenes selected from ethylene oxide (EO) and propylene oxide (PO), and even more preferably a copolymer structure in which ethylene oxide and propylene oxide are polymerized randomly or in a block form (EO / PO copolymer structure).

[0023] An example of a copolymer structure in which ethylene oxide and propylene oxide are polymerized randomly or in a block form is a structure represented by the following formula.

[0024] [ka]

[0025] (In the formula, R 1 represents a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, or a -CH2CH(CH3)NH2 group. EO and PO are present randomly or in a block form, a is a positive number indicating the average number of moles of EO added, and b is a positive number indicating the average number of moles of PO added.

[0026] R 1 From the viewpoint of improving the dispersibility of the finely divided modified cellulose fibers, is preferably a linear or branched alkyl group having from 1 to 6 carbon atoms, and more preferably a methyl group.

[0027] From the viewpoint of enhancing the dispersibility of the refined modified cellulose fibers, a is preferably 1 or more, more preferably 3 or more, even more preferably 6 or more, even more preferably 11 or more, even more preferably 15 or more, even more preferably 20 or more, even more preferably 25 or more, and even more preferably 30 or more. From the same viewpoint, a is preferably 100 or less, more preferably 70 or less, even more preferably 60 or less, even more preferably 50 or less, and even more preferably 40 or less.

[0028] From the viewpoint of enhancing the dispersibility of the refined modified cellulose fibers, b is preferably 1 or more, more preferably 3 or more, and even more preferably 5 or more. From the same viewpoint, b is preferably 50 or less, more preferably 40 or less, even more preferably 30 or less, even more preferably 25 or less, even more preferably 20 or less, even more preferably 15 or less, and even more preferably 10 or less. In the above formula, a+b represents the average total number of moles of EO and PO added, and from the viewpoint of improving the dispersibility of the finely divided modified cellulose fiber, it is preferably 4 or more, more preferably 6 or more, and even more preferably 8 or more, and from the same viewpoint, it is preferably 100 or less, more preferably 70 or less.

[0029] The PO content (mol%) in the EO / PO copolymer structure can be calculated based on the above a and b, specifically, it can be obtained by b×100 / (a+b). From the viewpoint of enhancing the dispersibility of the finely refined modified cellulose fiber, the PO content is preferably 1 mol% or more, more preferably 5 mol% or more, even more preferably 7 mol% or more, even more preferably 10 mol% or more, and even more preferably 20 mol% or more. From the same viewpoint, it is preferably 100 mol% or less, more preferably 90 mol% or less, even more preferably 85 mol% or less, even more preferably 75 mol% or less, even more preferably 60 mol% or less, even more preferably 50 mol% or less, even more preferably 40 mol% or less, and even more preferably 30 mol% or less.

[0030] (c) Further Substituents The modifying group may further have a substituent. Examples of the substituent include alkoxy groups having 1 to 6 carbon atoms, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, isopentyloxy, and hexyloxy; methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, isobutoxycarbonyl, sec-butoxycarbonyl, and tert-butoxy. Examples of such groups include alkoxy-carbonyl groups having 1 to 6 carbon atoms in the alkoxy group, such as t-butoxycarbonyl, pentyloxycarbonyl, and isopentyloxycarbonyl groups; halogen atoms, such as fluorine, chlorine, bromine, and iodine atoms; acyl groups having 1 to 6 carbon atoms, such as acetyl and propionyl groups; aralkyl groups; aralkyloxy groups; alkylamino groups having 1 to 6 carbon atoms; dialkylamino groups having an alkyl group of 1 to 6 carbon atoms; and hydroxy groups.

[0031] [Method for producing modified cellulose fibers] The modified cellulose fiber can be produced, for example, by introducing anionic groups into raw cellulose fiber to produce anionically modified cellulose fiber (step 1), and then bonding modifying groups to the anionic groups of the anionically modified cellulose fiber in the presence of water and an organic solvent (step 2).

[0032] (Process 1) Raw cellulose fiber As the cellulose fiber that is the raw material for the anion-modified cellulose fiber, natural cellulose is preferred from an environmental perspective, and examples thereof include wood pulp such as coniferous pulp and broadleaf pulp; cotton pulp such as cotton linter and cotton lint; non-wood pulp such as straw pulp and bagasse pulp; bacterial cellulose, etc., and these can be used alone or in combination of two or more.

[0033] The average fiber diameter of the raw cellulose fibers is not particularly limited, but from the viewpoints of handleability and cost, it is preferably 5 μm or more, more preferably 7 μm or more, and from the same viewpoints, it is preferably 500 μm or less, more preferably 300 μm or less. The average fiber diameter of the raw cellulose fibers is determined by the method described in the Examples below.

[0034] The average fiber length of the raw cellulose fibers is not particularly limited, but from the viewpoints of availability and cost, it is preferably 5 μm or more, more preferably 25 μm or more, and from the same viewpoints, it is preferably 5,000 μm or less, more preferably 3,000 μm or less. The average fiber length of the raw cellulose fibers is determined by the method described in the Examples below.

[0035] Method for introducing anionic groups Methods for introducing carboxy groups as anionic groups into cellulose fibers include, for example, a method of oxidizing hydroxy groups of the cellulose fibers to convert them into carboxy groups, and a method of reacting the hydroxy groups of the cellulose fibers with at least one selected from the group consisting of compounds having a carboxy group, acid anhydrides of compounds having a carboxy group, and derivatives thereof.

[0036] Examples of methods for oxidizing hydroxy groups in cellulose fibers include a method described in JP 2015-143336 A or JP 2015-143337 A in which an oxidizing agent such as sodium hypochlorite and a bromide such as sodium bromide are reacted with raw cellulose fibers using 2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) as a catalyst. By oxidizing cellulose fibers using TEMPO as a catalyst, the hydroxymethyl group at the C6 position of glucose in the cellulose fiber constituent unit is selectively converted to a carboxy group, and the TEMPO-oxidized cellulose fibers described below can be obtained.

[0037] As a method for introducing sulfonic acid groups as anionic groups into cellulose fibers, a method of adding sulfuric acid to cellulose fibers and heating the fibers can be given. Methods for introducing phosphorous acid groups as anionic groups into cellulose fibers include a method of mixing a powder or an aqueous solution of phosphorous acid or a phosphorous acid derivative with dry or wet cellulose fibers, a method of adding an aqueous solution of phosphorous acid or a phosphorous acid derivative to a dispersion of cellulose fibers, etc. When these methods are adopted, in general, after mixing or adding a powder or an aqueous solution of phosphorous acid or a phosphorous acid derivative, a dehydration treatment, a heat treatment, etc. are carried out.

[0038] Anionically modified cellulose fibers Anion-modified cellulose fibers are cellulose fibers having an anionic group, such as one or more groups selected from the group consisting of a carboxy group, a (phosphorous) group, and a sulfonic acid group, in the molecule. The introduction of anionic groups into cellulose fibers can be achieved by the above-mentioned method. From the viewpoint of availability and effectiveness, anion-modified cellulose fibers having a carboxy group as the anionic group (referred to as "oxidized cellulose fibers") are preferred, and anion-modified cellulose fibers in which the hydroxymethyl group at the C6 position of the glucose unit constituting the cellulose fiber is selectively converted to a carboxy group (referred to as "TEMPO-oxidized cellulose fibers") are more preferred. The ion (counter ion) that is paired with the anionic group is preferably a proton.

[0039] The anionic group content in the anion-modified cellulose fiber is preferably 0.1 mmol / g or more, more preferably 0.4 mmol / g or more, even more preferably 0.6 mmol / g or more, even more preferably 0.7 mmol / g or more, and even more preferably 0.8 mmol / g or more, from the viewpoint of stable introduction of a modifying group and increasing the dispersibility of the finely refined modified cellulose fiber by the introduction of the modifying group. Also, from the viewpoint of improving the handleability, it is preferably 3 mmol / g or less, more preferably 2.5 mmol / g or less, even more preferably 2 mmol / g or less, and even more preferably 1.9 mmol / g or less. The "anionic group content" means the total amount of anionic groups in the glucose constituting the cellulose fiber, and is specifically measured by the method described in the Examples below.

[0040] The modification group is bonded to the anionic group of the anion-modified cellulose fiber, which means that the modification group is bonded to the anionic group, preferably the carboxy group, of the anion-modified cellulose fiber. The bond between the modification group and the anionic group can be an ionic bond and / or a covalent bond. Examples of the covalent bond include an amide bond, an ester bond, and a urethane bond.

[0041] (Process 2) The introduction of modifying groups into the anionic groups of the anion-modified cellulose fiber is achieved by reacting a compound for introducing modifying groups into the anionic groups (referred to as a "modifying compound") with the anion-modified cellulose fiber in the presence of water and an organic solvent. The modified cellulose fiber in the present invention is preferably one obtained by such step 2. As a method for introducing a modifying group, (1) when introducing via an ionic bond, JP 2015-143336 A can be referenced, and (2) when introducing via an amide bond, JP 2015-143337 A can be referenced.

[0042] For example, when an EO / PO copolymer structure is introduced as a modifying group via an ionic bond, preferred modifying compounds include, for example, amines having an EO / PO copolymer structure (specifically, JEFFAMINE M600 and JEFFAMINE M2070 manufactured by HUNTSMAN, etc.).

[0043] After completion of step 2, post-treatment may be appropriately carried out in order to remove unreacted compounds, etc. Examples of methods for the post-treatment include filtration, centrifugation, dialysis, etc.

[0044] 〔water〕 Water is one of the components constituting the mixture in the present invention, and can be present as a medium in step 2 above, etc.

[0045] [Organic solvent] The organic solvent is one of the components constituting the mixture in the present invention, and is used as a medium in the above step 2 and in the step of micronizing the modified cellulose fiber.

[0046] From the viewpoint of improving the dispersibility of the refined modified cellulose fibers, the melting point of the organic solvent is preferably less than 0° C., more preferably −50° C. or less, and even more preferably −60° C. or less. From the same viewpoint, on the other hand, those having a melting point of −100° C. or more are preferred. From the viewpoint of improving the dispersibility of the refined modified cellulose fibers, the boiling point of the organic solvent is preferably 150° C. or less, more preferably 100° C. or less, and even more preferably 90° C. or less. On the other hand, from the viewpoint of reducing the amount of the organic solvent used, those with a boiling point of 70° C. or more are preferred.

[0047] Specific examples of the organic solvent include alcohols having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, such as methanol, ethanol, propanol, and 1-methoxy-2-propanol (PGME); ketones having 3 to 6 carbon atoms, such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; formic acid esters of alkyl groups having 1 to 4 carbon atoms, such as methyl formate and ethyl formate; acetate esters of alkyl groups having 1 to 4 carbon atoms, such as methyl acetate and ethyl acetate; propionic acid esters of alkyl groups having 1 to 4 carbon atoms, such as methyl propionate and ethyl propionate; butyric acid esters of alkyl groups having 1 to 4 carbon atoms, such as methyl butyrate and ethyl butyrate; P-based glycol ethers such as 2-methoxy-1-methylethyl acetate (PGMEA); saturated or unsaturated hydrocarbons having 1 to 6 carbon atoms; aromatic hydrocarbons such as benzene and toluene; halogenated hydrocarbons such as methylene chloride and chloroform; lower alkyl ethers having 2 to 5 carbon atoms; and polar solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide, and dimethylsulfoxide. These may be used alone or in combination of two or more.

[0048] [Other ingredients] The mixture may contain known components such as a polymerization initiator, a plasticizer, a stabilizer, a lubricant, a surfactant, an inorganic filler, etc. The amount of such components is not particularly limited, and an appropriate amount may be appropriately adopted.

[0049] [Step of distilling off water from the mixture] One of the features of the production method of the present invention is that it includes a step of distilling off water from a mixture containing modified cellulose fiber, water, and an organic solvent. The amount of water to be distilled off is at least a part or all of the water contained in the mixture, and is preferably an amount that satisfies the value described below in "Amount of water in the mixture after water is distilled off".

[0050] The mixture in the present invention contains the modified cellulose fiber, water, an organic solvent, and may further contain other components. The mixture is subjected to a step of distilling off the water.

[0051] The amount of modified cellulose fiber in the mixture subjected to the water removal step is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, from the viewpoint of increasing the dispersibility of the finely divided modified cellulose fiber, while from the same viewpoint, it is preferably 50% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less.

[0052] The amount of modified cellulose fiber in the mixture subjected to the water removal step is, from the viewpoint of increasing the dispersibility of the finely divided modified cellulose fiber, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 30 parts by mass or more, and even more preferably 50 parts by mass per 100 parts by mass of water; from the same viewpoint, on the other hand, the amount is preferably 90 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 75 parts by mass or less, per 100 parts by mass of water.

[0053] The amount of water in the mixture subjected to the water removal step is, from the viewpoint of improving the dispersibility of the finely divided modified cellulose fiber, preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1.0% by mass or more, while from the same viewpoint, it is preferably 50% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less.

[0054] The amount of organic solvent in the mixture subjected to the water removal step is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, from the viewpoint of increasing the dispersibility of the finely divided modified cellulose fiber, while it is preferably 99% by mass or less, more preferably 98.5% by mass or less, and even more preferably 98% by mass or less, from the viewpoint of reducing the amount of organic solvent used.

[0055] The amount of organic solvent in the mixture subjected to the water removal step is, from the viewpoint of improving the dispersibility of the finely divided modified cellulose fiber, preferably 100 parts by mass or more, more preferably 500 parts by mass or more, and even more preferably 1000 parts by mass or more, per 100 parts by mass of water; on the other hand, from the viewpoint of reducing the amount of organic solvent used, the amount is preferably 1000 parts by mass or less, more preferably 9000 parts by mass or less, and even more preferably 8000 parts by mass or less, per 100 parts by mass of water.

[0056] The temperature conditions for distilling off water from the mixture are, from the viewpoint of efficiently distilling off water, preferably not less than the melting point of the organic solvent in the mixture, more preferably not less than 25°C, and even more preferably not less than 30°C, and from the viewpoint of reducing the load on facilities and the environmental load, preferably not more than the boiling point of the organic solvent in the mixture, more preferably not more than 100°C, and even more preferably not more than 80°C.

[0057] The pressure condition when distilling off water from the mixture may be normal pressure or reduced pressure. From the viewpoint of distilling off water at a lower temperature, it is preferable to distill off water under reduced pressure. When distilling off water under reduced pressure, the upper limit of the pressure is preferably 60 kPa (absolute pressure) or less, more preferably 50 kPa (absolute pressure) or less.

[0058] The specific apparatus for distilling off water from the mixture is not particularly limited as long as it satisfies the above-mentioned temperature and pressure conditions, and examples thereof include a batch simple distillation apparatus, a reduced pressure distillation apparatus, a thin film distillation apparatus such as a flash evaporator, a rotary distillation apparatus, a stirring evaporator, etc. Specific examples thereof include a rotary vacuum distillation apparatus such as a rotary evaporator, a stirred tank thin film evaporator, a continuous multistage distillation apparatus, a batch multistage distillation apparatus, etc.

[0059] The amount of water in the mixture after the water has been distilled off is preferably as small as possible from the viewpoint of compatibility with resins, etc. Specifically, the amount of water in the mixture after the water has been distilled off is preferably 1% by mass or less, more preferably 0.5% by mass or less. The amount of water in the mixture containing the modified cellulose fibers and the like can be determined by the Karl Fischer method described in the Examples below. The organic solvent contained in the mixture may be partially distilled off along with the distillation of water. If necessary, the organic solvent may be added to the mixture after the water distillation step.

[0060] [Refining process] By pulverizing the modified cellulose fibers contained in the mixture after distilling off the water, the cellulose fibers of the micrometer scale can be pulverized to the nanometer scale. By reducing the average fiber diameter to the nanometer size, the dispersibility in the resin is improved, which is preferable.

[0061] In addition, from the viewpoint of improving the dispersibility of the refined modified cellulose fiber in the resin, the solids concentration in the mixture during the refinement process is preferably 50% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, and the lower the concentration, the better. On the other hand, from the viewpoint of reducing the amount of non-aqueous solvent used and reducing the environmental load, it is preferable to first remove water by distillation from a mixture having a high solids concentration. Therefore, from the viewpoints of improving the dispersibility of the refined modified cellulose fiber in the resin, reducing the amount of non-aqueous solvent used, and reducing the environmental load, it is preferable that the refinement process is carried out after the process of distilling off water from the mixture.

[0062] The micronization treatment can be carried out by a known micronization treatment method. For example, in order to obtain micronized modified cellulose fibers having an average fiber diameter of nanometer size, a treatment method using a grinder such as a mass colloider or a treatment method using a high-pressure homogenizer in a medium may be carried out.

[0063] The medium may be one or more of the above organic solvents. The amount of the medium used may be any amount that can disperse the modified cellulose fiber, and is preferably at least 1 time, more preferably at least 2 times, and preferably at most 500 times, and more preferably at most 200 times, the mass of the modified cellulose fiber.

[0064] As the device used in the micronization treatment, a known dispersing machine is preferably used in addition to the high-pressure homogenizer. For example, a disintegrator, a beater, a low-pressure homogenizer, a grinder, a mass colloider, a cutter mill, a ball mill, a jet mill, a single-screw extruder, a twin-screw extruder, an ultrasonic agitator, a household juicer mixer, etc. can be used. In addition, the solid content concentration of the modified cellulose fiber in the micronization treatment is preferably 50 mass% or less.

[0065] [Short fiber processing] At any stage of the production method according to the present invention, various cellulose fibers, i.e., raw cellulose fibers, anion-modified cellulose fibers, modified cellulose fibers, and finely divided modified cellulose fibers, may be subjected to a fiber shortening treatment. By carrying out such a fiber shortening treatment, the dispersibility of the finely divided modified cellulose fibers can be improved. The fiber shortening process can be carried out by subjecting the target cellulose fibers to one or more treatment methods selected from the group consisting of (i) alkali treatment, (ii) acid treatment, and (iii) heat treatment, ultraviolet treatment, electron beam treatment, mechanical treatment, and enzyme treatment.

[0066] [Properties of finely divided modified cellulose fibers] The main properties of the finely divided modified cellulose fiber of the present invention are as follows:

[0067] (Crystal structure) The finely refined and modified cellulose fibers preferably have a cellulose I type crystal structure from the viewpoint of enhancing the dispersibility of the finely refined and modified cellulose fibers. The crystallinity of the finely refined and modified cellulose fibers is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more from the viewpoint of enhancing the dispersibility of the finely refined and modified cellulose fibers. In addition, from the viewpoint of raw material availability, it is preferably 90% or less, more preferably 85% or less, even more preferably 80% or less, and even more preferably 75% or less. In this specification, the crystallinity of various cellulose fibers is the cellulose I type crystallinity calculated from the diffraction intensity value by the X-ray diffraction method, and can be measured according to the method described in the examples below. In addition, the cellulose I type refers to the crystalline form of natural cellulose, and the cellulose I type crystallinity refers to the proportion of the amount of crystalline regions in the entire cellulose fiber. The presence or absence of the cellulose I type crystal structure can be determined by the presence of a peak at 2θ=22.6° in X-ray diffraction measurement.

[0068] (Average fiber diameter) The finely divided modified cellulose fibers are those that have been subjected to a finely divided treatment to have a nanometer size. Therefore, the average fiber diameter of the finely divided modified cellulose fibers is preferably 1 nm or more, more preferably 2 nm or more, and even more preferably 3 nm or more from the viewpoints of handling, availability, and cost, and is preferably 300 nm or less, more preferably 200 nm or less, more preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 10 nm or less from the viewpoints of improving handling and dispersibility.

[0069] (average fiber length) The average fiber length of the finely divided modified cellulose fibers is preferably 10 nm or more, more preferably 30 nm or more, and even more preferably 50 nm or more, from the viewpoint of improving the dispersibility of the finely divided modified cellulose fibers, while it is preferably 1000 nm or less, more preferably 500 nm or less, more preferably 300 nm or less, and even more preferably 200 nm or less, from the viewpoint of improving the extrusion property and the dispersibility of the finely divided modified cellulose fibers.

[0070] (average aspect ratio) The average aspect ratio of the finely divided modified cellulose fibers is preferably 5 or more, more preferably 10 or more, and even more preferably 20 or more, from the viewpoint of improving the dispersibility of the finely divided modified cellulose fibers, while it is preferably 300 or less, more preferably 200 or less, more preferably 100 or less, and even more preferably 60 or less, from the viewpoint of improving the extrusion property and the dispersibility of the finely divided modified cellulose fibers. By setting the average aspect ratio within the above range, both improvement in mechanical properties of the resin and good dispersibility can be achieved, which is preferable. The average fiber diameter, average fiber length and average aspect ratio of the finely divided modified cellulose fiber can be determined by the method described in the Examples below.

[0071] (Amount of modified group bonded and introduction rate) The amount of the modifying group bonded to the fine modified cellulose fiber is preferably 0.01 mmol / g or more from the viewpoint of improving the dispersibility of the fine modified cellulose fiber, and from the same viewpoint, is preferably 3.0 mmol / g or less. When any two or more kinds of modifying groups are simultaneously introduced into the fine modified cellulose fiber as the modifying groups, the amount of the modifying groups bonded is preferably within the above range.

[0072] The introduction rate of the modifying group in the finely divided modified cellulose fiber is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 25 mol% or more from the viewpoint of improving the dispersibility of the finely divided modified cellulose fiber, and from the same viewpoint, is preferably 100 mol% or less, more preferably 50 mol% or less, and even more preferably 40 mol% or less. When any two or more types of modifying groups are simultaneously introduced as the modifying group, it is preferable that the introduction rate is within the above range as long as the total introduction rate does not exceed the upper limit of 100 mol%.

[0073] The bonded amount and introduction rate of the modifying group can be adjusted by the type and amount of the modifying compound, reaction temperature, reaction time, type of solvent, etc. The bonded amount (mmol / g) and introduction rate (mol%) of the modifying group refer to the amount and ratio of the modifying group introduced (bonded) to the anionic group in the finely refined modified cellulose fiber. For example, when the anionic group is a carboxy group, the bonded amount and introduction rate of the modifying group in the finely refined modified cellulose fiber are calculated by the method described in the Examples below.

[0074] The amount of glucose moiety in the finely divided modified cellulose fiber in the composition of the present invention is preferably 0.1 mass% or more in the composition of the present invention, more preferably 0.2 mass% or more, and even more preferably 0.3 mass% or more, from the viewpoint of improving the dispersibility of the finely divided modified cellulose fiber, while from the viewpoint of handling during production, it is preferably 10 mass% or less in the composition of the present invention, more preferably 5 mass% or less, and even more preferably 4 mass% or less.

[0075] In this specification, the term "glucose portion" refers to a portion consisting of glucose units in various cellulose fibers, and in the case of unmodified cellulose fibers, it refers to the entire glucose unit, in the case of anionically modified cellulose fibers, it refers to the entire glucose unit including the anionic group bonded to the glucose unit, and in the case of (micronized) modified cellulose fibers, it refers to the entire glucose unit excluding the modifying group bonded to the glucose unit. That is, the glucose unit in this specification also includes glucose units in which the hydroxymethyl group has been converted to a carboxy group.

[0076] The amount of organic solvent in the composition of the present invention, calculated in terms of the blending amount, is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, from the viewpoint of improving the dispersibility of the finely divided modified cellulose fiber, and from the same viewpoint, is preferably 99.9% by mass or less, more preferably 99.5% by mass or less, and even more preferably 99% by mass or less. EXAMPLES

[0077] The present invention will be specifically described below with reference to examples. Note that the following examples are merely illustrative of the present invention and do not imply any limitations. Note that "normal pressure" refers to 101.3 kPa, and "normal temperature" refers to 25°C.

[0078] [Average fiber diameter and average fiber length of cellulose fibers, (shortened) anion-modified cellulose fibers, modified cellulose fibers, and finely divided modified cellulose fibers] Depending on the size of the cellulose fibers to be measured, one of the following two measurement methods was selected for measurement. (1) Deionized water or N,N-dimethylformamide (DMF) was added to the cellulose fiber to be measured or to a dispersion containing the cellulose fiber to be measured to prepare a dispersion with a content of 0.0001% by mass. The dispersion was dropped onto mica and dried to prepare an observation sample, and the fiber height (height difference between where the fiber is present and where it is not present) of the cellulose fiber in the observation sample was measured using an atomic force microscope (AFM) (Nanoscope II Tapping mode AFM manufactured by Digital Instrument; the probe used was Point Probe (NCH) manufactured by Nanosensors). At that time, 100 cellulose fibers were extracted from the microscope image in which the cellulose fiber could be confirmed, and the average fiber diameter was calculated from the fiber height. The average fiber length was calculated from the distance in the fiber direction.

[0079] (2) Deionized water was added to the cellulose fiber to be measured or a suspension containing the cellulose fiber to be measured to prepare a dispersion with a content of 0.01% by mass. The dispersion was measured using a wet dispersion type image analysis particle size distribution meter (manufactured by JUSCO International, product name: IF-3200) under the following conditions: front lens: 2x, telecentric zoom lens: 1x, image resolution: 0.835 μm / pixel, syringe inner diameter: 6515 μm, spacer thickness: 500 μm, image recognition mode: ghost, threshold: 8, analysis sample amount: 1 mL, sampling: 15%. The length of the short axis of the cellulose fiber when it is approximated as a rectangle was taken as the fiber diameter, and the length of the long axis was taken as the fiber length. The respective values ​​were measured for 100 cellulose fibers, and the average values ​​were calculated.

[0080] [Anionic Group Content of Anion-Modified Cellulose Fiber] Cellulose fibers to be measured with a dry mass of 0.5 g were placed in a beaker, and deionized water or a mixed solvent of methanol / deionized water = 2 / 1 (volume ratio) was added to make a total of 55 mL, to which 5 mL of 0.01 M sodium chloride aqueous solution was added to prepare a dispersion. The dispersion was stirred until the cellulose fibers to be measured were sufficiently dispersed. 0.1 M hydrochloric acid was added to the dispersion to adjust the pH to 2.5 to 3, and an automatic titration device (manufactured by DKK-TOA, AUT-701) was used to drop 0.05 M sodium hydroxide aqueous solution into the dispersion under the condition of a waiting time of 60 seconds, and the conductivity and pH value were measured every minute. The measurement was continued until the pH was about 11, and a conductivity curve was obtained. The sodium hydroxide titration amount was determined from this conductivity curve, and the anionic group content of the cellulose fibers to be measured was calculated by the following formula. Anionic group content (mmol / g) = [amount of sodium hydroxide solution titrated (mL) × concentration of sodium hydroxide solution (0.05M)] / [mass of cellulose fiber to be measured (0.5g)]

[0081] [Amount of modified groups bonded and introduction rate of modified cellulose fibers and fine modified cellulose fibers] The bonded amount of the modifying group in the modified cellulose fibers and the fine modified cellulose fibers was determined by the following IR measurement method, and the bonded amount and introduction rate were calculated by the following formula. Specifically, the IR measurement was performed by measuring the infrared absorption spectrum of the dried cellulose fibers to be measured by the ATR method using an infrared absorption spectrometer (IR) (Nicolet 6700, manufactured by Thermo Fisher Scientific), and the bonded amount and introduction rate of the modifying group were calculated by formula A. The following shows the case where the anionic group is a carboxy group, i.e., the case of oxidized cellulose fibers. The following "1720 cm" -1 The peak intensity of "is the peak intensity derived from the carbonyl group. In the case of an anionic group other than a carboxy group, the value of the wave number is appropriately changed, and the bond amount and introduction rate of the modifying group can be calculated. <Formula A> Amount of modified group bound (mmol / g) = a × (bc) ÷ b a: Carboxylic group content of oxidized cellulose fiber (mmol / g) b: 1720 cm of oxidized cellulose fiber -1 Peak intensity of c: 1720 cm of modified cellulose fiber and fine modified cellulose fiber -1 Peak intensity of <Formula B> Modification group introduction rate (mol%) = 100 × f / g f: Amount of modified group bound (mmol / g) g: Carboxylic group content of oxidized cellulose fiber (mmol / g)

[0082] [Content of each ingredient] The content of each component was calculated from the blended amount of each component. Regarding the mass of the glucose portion, it was assumed that all of the shortened anion-modified cellulose fiber and the modifying compound blended during the preparation of the modified cellulose fiber were ionically bonded, and the mass of the shortened anion-modified cellulose fiber contained in the blended modified cellulose fiber was regarded as the mass of the glucose portion in the calculation. The water content in the dispersion or suspension was measured by Karl Fischer titration using a Mitsubishi Analytech CA-200. The solid content concentration of anion-modified cellulose fiber and short fiber anion-modified cellulose fiber was calculated from the difference from 100% by mass by measuring the moisture concentration in the sample using an infrared moisture meter (Shimadzu Corporation, MOC-120H). The moisture concentration was measured every 30 seconds at a constant temperature of 150°C for 1 g of sample, and the value displayed when the mass loss in 30 seconds became 0.1% or less was used.

[0083] [Measurement of electrical conductivity of filtrate] The electrical conductivity of the filtrate was measured using a compact electrical conductivity meter (HORIBA, Ltd., LAQUAtwin EC-33B).

[0084] [Confirmation of crystal structures in various cellulose fibers] The crystal structures of various cellulose fibers, such as cellulose fiber, anion-modified cellulose fiber, modified cellulose fiber, and fine modified cellulose fiber, were confirmed by measurement under the following conditions using a diffractometer (MiniFlexII, manufactured by Rigaku Corporation). Measurement pellet preparation conditions: A pressure of 10 to 20 MPa was applied to the target cellulose fiber using a tablet forming machine to produce pellets with an area of ​​320 mm 2 Smooth pellets measuring ×1 mm in thickness were prepared. X-ray diffraction analysis conditions: step angle 0.01°, scan speed 10° / min, measurement range: diffraction angle 2θ=5~40° X-ray source: Cu / Kα-radiation, tube voltage: 15kv, tube current: 30mA Peak splitting conditions: After removing background noise, the peaks were fitted with a Gaussian function so that the error between 2θ=13° and 23° was within 5%.

[0085] The degree of crystallinity of the cellulose type I crystal structure was calculated based on the following formula (A) using the area of ​​the X-ray diffraction peak obtained by the above-mentioned peak division. Cellulose type I crystallinity (%) = [I cr / (I cr +I am )]×100 (A) [In the formula, I cris the area of ​​the diffraction peak of the lattice plane (002 plane) (diffraction angle 2θ = 22-23°) in X-ray diffraction, I am indicates the area of ​​the diffraction peak of the amorphous part (diffraction angle 2θ = 18.5°).

[0086] [Measurement of the average polymerization degree of anionically modified cellulose fibers] The average degree of polymerization of the anionically modified cellulose fiber was measured as follows. (1) Preparation of measurement solution 0.06 g of anion-modified cellulose fiber to be measured (dry mass) was precisely weighed and placed in a 50 mL beaker, and water was added so that the solid content concentration was 1% by mass. 0.006 g of sodium borohydride was added, and the mixture was stirred at room temperature for 2 hours, after which 18 g of acetone was added, and then centrifuged at 10 ° C, 10000 G, and 1 minute using a high-speed refrigerated centrifuge (Koki Holdings Co., Ltd., CR21G III) to remove the supernatant. 18 g of ethanol was added to the residue, and the process of centrifuging and removing the supernatant was repeated three times to obtain a precipitate washed with ethanol. The obtained precipitate was vacuum-dried at 40 ° C for 12 hours to obtain reduced pulp in which the aldehyde groups in the anion-modified cellulose fiber were reduced. To 0.03 g of dried reduced pulp, 15 mL of 0.5 M copper ethylenediamine solution was added and stirred for 1 hour until the cellulose fibers were completely dissolved to prepare a measurement solution.

[0087] (2) Measurement of average degree of polymerization The measurement solution obtained in (1) above was placed in an Ubbelohde viscometer and allowed to stand in a thermostatic bath (20±0.1)°C for 1 hour. The flow time of the liquid (t (seconds)) and the flow time of the copper ethylenediamine solution without added cellulose (t0 (seconds)) were then measured, and the intrinsic viscosity [η] (dL / g) was calculated using the following formula.

[0088] [η]=[(t / t0-1) / c] / [1+0.28×(t / t0-1)] (c: Cellulose concentration (g / dL))

[0089] From the obtained intrinsic viscosity [η], the average degree of polymerization (DP) of the anion-modified cellulose fiber was calculated using the following formula: v ) was calculated.

[0090] [η] = 0.094 × 162 × DP v 0.67

[0091] [Transmittance of Dispersion] Using an ultraviolet-visible spectrophotometer (AS ONE, ASV11D-H), the transmittance at 660 nm of the dispersion of the finely divided modified cellulose fiber obtained in the examples and comparative examples (i.e., the composition of the finely divided modified cellulose fiber) was measured. The transmittance in each example is shown with the transmittance at 660 nm of only the medium constituting the dispersion, which does not contain the finely divided modified cellulose fiber, set as 100%. The higher the transmittance, the higher the dispersibility of the finely divided modified cellulose fiber.

[0092] [Anion-modified cellulose fiber] Anionically modified cellulose fibers 1 and anionically modified cellulose fibers 2 having the physical property values ​​shown in Table 1 were used as raw materials.

[0093] [Table 1]

[0094] Such anionically modified cellulose fiber 1 can be prepared, for example, by the TEMPO oxidation treatment described below.

[0095] [TEMPO oxidation treatment] In a 2L PP beaker equipped with a mechanical stirrer and stirring blades, 10 g of bleached kraft pulp fiber of coniferous wood as the raw material natural cellulose fiber and 990 g of deionized water are weighed and stirred at 25 ° C and 100 rpm for 30 minutes. Next, 0.13 g of TEMPO, 1.3 g of sodium bromide, and 35.5 g of 10.5 mass% sodium hypochlorite aqueous solution are added in this order to 10 g of the pulp fiber. Then, pH stat titration is performed using an automatic titration device, and 0.5 M sodium hydroxide aqueous solution is dropped to maintain the pH at 10.5. The reaction is performed at 25 ° C for 120 minutes at a stirring speed of 100 rpm. Then, while stirring, 0.01 M hydrochloric acid is added to it to make the pH of the suspension 2. Then, the solid content is filtered out by suction filtration. The solids are dispersed in deionized water and filtered off by suction filtration. This operation is repeated until the conductivity of the filtrate is 200 μs / cm or less. The resulting solids are dehydrated to obtain anion-modified cellulose fibers.

[0096] The anion-modified cellulose fiber 2 shown in Table 1 can be prepared, for example, by subjecting the anion-modified cellulose fiber obtained by the above-mentioned TEMPO oxidation treatment to the following alkaline hydrolysis treatment. [Alkaline hydrolysis treatment] The suspension of anion-modified cellulose fibers obtained by the TEMPO oxidation treatment (solid content: 144.5 g) is diluted with 1000 g of deionized water, to which 1.4 g of 35% hydrogen peroxide (1 part by mass of hydrogen peroxide per 100 parts by mass of the solid content of the raw cellulose fibers) is added, and the pH is adjusted to 12 with 1 M aqueous sodium hydroxide solution. Then, an alkaline hydrolysis treatment is performed at 80° C. for 2 hours (solid content concentration of the suspension of anion-modified cellulose fibers: 4.3% by mass). After cooling the suspension to room temperature, 0.01 M hydrochloric acid is added to adjust the pH of the suspension to 2. The solid content of the suspension is filtered out by suction filtration. The operation of dispersing the solid content in deionized water and filtering out the solid content by suction filtration is repeated until the conductivity of the filtrate is 200 μS / cm or less. The obtained solid content is dehydrated to obtain anion-modified cellulose fibers 2.

[0097] [Preparation of Short Anion-Modified Cellulose Fibers] Using each cake of anion-modified cellulose fiber 1 and anion-modified cellulose fiber 2 having the physical property values ​​shown in Table 1, shortened anion-modified cellulose fiber 1 and shortened anion-modified cellulose fiber 2 were obtained. Specifically, 214 g of the anion-modified cellulose fiber cake (solid content 75 g) was taken, and deionized water was added until the solid content concentration reached 5 mass% from the value shown in Table 2. The diluted suspension was stirred at 95°C for the time shown in Table 2 to obtain an aqueous suspension of shortened anion-modified cellulose fiber. The suspension was centrifuged at 25°C, 10,000G, and 1 minute using a high-speed refrigerated centrifuge (Koki Holdings Co., Ltd., CR21G III) to obtain the shortened anion-modified cellulose fiber shown in Table 2 as a precipitate.

[0098] [Table 2]

[0099] Examples 1 to 4 [Preparation of modified cellulose fibers] Each of the shortened anionically modified cellulose fibers obtained as the precipitates was placed in a beaker, and a modifying compound and an organic solvent were added so as to obtain the composition shown in Table 3. The mixture was then stirred overnight at room temperature to obtain a suspension of modified cellulose fibers in which modifying groups were bonded to the anionic groups of the anionically modified cellulose fibers via ionic bonds. By using the following M600 and M2070 as modifying compounds, the above-mentioned EO / PO copolymer structure was provided to the modified cellulose fibers as modifying groups.

[0100] [Water removal] The obtained suspension was concentrated using a rotary evaporator (manufactured by BUCHI) while heating in a water bath at the temperature shown in Table 3, within the pressure range shown in Table 3, until the total mass of the suspension became one-third of the original mass, and water was distilled off together with the organic solvent. Then, the same mass and type of organic solvent as the evaporated mass was added.

[0101] [Micronization treatment] Next, the mixture was subjected to a micronization treatment five times at 150 MPa using a high-pressure homogenizer (Nano-Vita L-ES, manufactured by Yoshida Kikai Kogyo Co., Ltd.) to obtain a dispersion of the micronized modified cellulose fibers shown in Table 5.

[0102] [Table 3]

[0103] Comparative Examples 1 to 4 [Solvent replacement] Each of the shortened anion-modified cellulose fibers obtained as the precipitates was suspended in 30 g of acetone per 1.5 g of solid content, and the supernatant was removed by centrifugation. This procedure was repeated twice. The same procedure was then repeated twice using the organic solvents shown in Table 4 to replace the water contained in the shortened anion-modified cellulose fibers with the solvents shown in Table 4.

[0104] [Preparation of modified cellulose fibers] The shortened anion-modified cellulose fibers obtained after the solvent replacement were placed in a beaker, and a modifying compound and an organic solvent were added to obtain the composition shown in Table 4. The mixture was then stirred overnight at room temperature to obtain a suspension of modified cellulose fibers in which modifying groups were bound to the anionic groups of the anion-modified cellulose fibers via ionic bonds.

[0105] [Micronization treatment] The obtained suspension was subjected to a micronization treatment five times at 150 MPa using a high-pressure homogenizer (Nano-Vita L-ES, manufactured by Yoshida Kikai Kogyo Co., Ltd.) to obtain a dispersion of the micronized modified cellulose fibers shown in Table 5.

[0106] [Table 4]

[0107] Table 5 shows the composition and transmittance of the dispersion of finely divided modified cellulose fibers (i.e., the composition containing finely divided modified cellulose fibers and an organic solvent) obtained in each of the above examples and comparative examples.

[0108] [Table 5]

[0109] In the method of the present invention (Examples 1 to 4), it was possible to disperse finely refined modified cellulose fibers in an organic solvent without performing solvent replacement, and therefore the amount of organic solvent used could be significantly reduced compared to the methods in which solvent replacement was performed (Comparative Examples 1 to 4). Furthermore, it was found from Table 5 that the permeability of the compositions containing the finely divided modified cellulose fibers produced by the method of the present invention (Examples 1 to 4) was clearly higher than the permeability of the compositions produced in the corresponding Comparative Examples 1 to 4. This means that the finely divided modified cellulose fibers produced by the method of the present invention have high dispersibility in a hydrophobic medium.

[0110] 〔reagent〕 In the above examples, the following reagents were used without any special purification. 0.1M hydrochloric acid: 0.1mol / L hydrochloric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 0.5M copper ethylenediamine solution: copper ethylenediamine II solution (Merck) Acetone: Acetone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), melting point: -94.6°C, boiling point: 56.5°C [Organic solvents] Ethyl acetate: Ethyl acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), melting point: -83.6°C, boiling point: 77.1°C MEK: Methyl ethyl ketone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), melting point: -87.3°C, boiling point: 79.6°C PGMEA: 2-methoxy-1-methylethyl acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), melting point: -61.7°C, boiling point: 146.4°C [Modification compound] M600: methoxypoly(oxyethylene / oxypropylene)-2-propylamine (HUNTSMAN, Jeffamine M600, Mw=600, EO:PO=1:9) M2070: methoxypoly(oxyethylene / oxypropylene)-2-propylamine (HUNTSMAN, Jeffamine M2070, Mw=2000, EO:PO=31:10) [Industrial Applicability]

[0111] By further mixing the finely divided modified cellulose fibers with a resin or the like, the fibers can be used as a material for various molded articles having improved mechanical strength.

Claims

1. A step of distilling off water from a mixture containing modified cellulose fibers, water and an organic solvent, and a step of refining the modified cellulose fibers in the mixture from which the water has been distilled off, A method for producing refined modified cellulose fibers, comprising the steps of:

2. The method for producing refined modified cellulose fibers according to Claim 1, wherein the melting point of the organic solvent is less than 0°C.

3. The method for producing refined modified cellulose fibers according to Claim 1, wherein the boiling point of the organic solvent is 150°C or lower.

4. The method for producing refined modified cellulose fibers according to Claim 1, wherein the modified cellulose fibers are obtained by bonding a modifying group to an anionic group of an anionic modified cellulose fiber in the presence of water and an organic solvent.

5. A step of distilling off water from a mixture containing modified cellulose fibers, water and an organic solvent, and a step of refining the modified cellulose fibers in the mixture from which the water has been distilled off, A method for producing a composition containing refined modified cellulose fibers and an organic solvent, comprising the steps of:

6. The method for producing a composition according to Claim 5, wherein the modified cellulose fibers are obtained by bonding a modifying group to an anionic group of an anionic modified cellulose fiber in the presence of water and an organic solvent.