Method for producing modified cellulose fiber

Abstract

The present invention relates to a method for producing modified cellulose fibers. According to the present invention, it is possible to provide a method for producing a modified cellulose fiber, which comprises a modification step in which two or more types of amines having different molecular weights are amide-bonded to an anion-modified cellulose fiber having an average fiber diameter of 1 [mu] m to 100 [mu] m (inclusive), and the average fiber diameter of the anion-modified cellulose fiber is 1 [mu] m to 100 [mu] m (inclusive). In the modification step, the following step 2 is performed after the following step 1. Step 1: A step in which an amine containing an amine having the smallest molecular weight is amide-bonded to the anion-modified cellulose fibers. And step 2: a step in which, after step 1, an amine including an amine having the maximum molecular weight is amide-bonded to the anion-modified cellulose fibers.

Description

TECHNICAL FIELD

[0001] The present application relates to a manufacturing method of a modified cellulose fiber. BACKGROUND

[0002] In the past, plastic materials derived from petroleum, which is a limited resource, have been used frequently, but in recent years, technologies that have less load on the environment have attracted attention, and in this technical background, materials using cellulose fibers, which are biomass that exists in nature in large amounts, have received attention.

[0003] A modified cellulose fiber in which a modification group having high chemical stability is bonded to an anion-modified cellulose fiber having a cellulose I crystal structure via an amide bond is expected to exhibit excellent physical properties as a filler for daily sundries, home appliance parts, automobile parts, and the like.

[0004] For example, in Patent Literature 1, a fine cellulose fiber composite in which a fine cellulose fiber is connected to a polymer having an oxirane / propylene oxide copolymer portion or the like via an amide bond is proposed in order to improve the transparency, heat resistance, or mechanical strength of a resin composition.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Patent Application Laid-Open No. 2015-143337 SUMMARY

[0008] The present application relates to the following [1] to

[15] .

[0009] [1] A manufacturing method of a modified cellulose fiber, comprising a modification step of causing two or more amines having different molecular weights to amide-bond with an anion-modified cellulose fiber; and

[0010] the anion-modified cellulose fiber has an average fiber diameter of 1 μm or more and 100 μm or less,

[0011] in the modification step, after the following step 1, the following step 2 is performed,

[0012] Step 1: a step of causing an amine containing an amine having the smallest molecular weight to amide-bond with an anion-modified cellulose fiber

[0013] Step 2: a step of causing an amine containing an amine having the largest molecular weight to amide-bond with an anion-modified cellulose fiber after Step 1.

[0014] [2] The manufacturing method of a modified cellulose fiber according to the above [1], wherein the anion-modified cellulose fiber has an average fiber length of 1 μm or more and 1000 μm or less.

[0015] [3] The method for producing modified cellulose fiber as claimed in any one of [1] or [2] above, wherein the anion-modified cellulose fiber has a carboxyl group.

[0016] [4] The method for producing modified cellulose fiber as claimed in any one of [1] to [3] above, wherein in the modification step, the content of the anion-modified cellulose fiber in the reaction solution at the start of the step is 1 mass% or more.

[0017] [5] The method for producing modified cellulose fiber as claimed in any one of [1] to [4] above, wherein the amine has one or two or more kinds of modifying groups selected from a hydrocarbon group and a polymer group.

[0018] [6] The method for producing modified cellulose fiber as claimed in any one of [1] to [5] above, wherein the molecular weight of the amine having the smallest molecular weight is 20 or more and 2000 or less.

[0019] [7] The method for producing modified cellulose fiber as claimed in any one of [1] to [6] above, wherein the molecular weight of the amine having the largest molecular weight is 100 or more and 4000 or less.

[0020] [8] The method for producing modified cellulose fiber as claimed in any one of [1] to [7] above, wherein the ratio of the molecular weights of the amine having the largest molecular weight to the amine having the smallest molecular weight (molecular weight of the amine having the largest molecular weight / molecular weight of the amine having the smallest molecular weight) is more than 1 and 100 or less.

[0021] [9] The method for producing modified cellulose fiber as claimed in any one of [5] to [8] above, wherein the introduction rate of the modifying group in the modified cellulose fiber is 40 mole% or more and 100 mole% or less.

[0022]

[10] The method for producing modified cellulose fiber as claimed in any one of [5] to [9] above, wherein of the modifying groups introduced into the modified cellulose fiber, the introduction rate of the modifying group having the smallest molecular weight introduced by bonding of the amine having the smallest molecular weight is 10 mole% or more and 95 mole% or less.

[0023]

[11] The method for producing modified cellulose fiber as claimed in any one of [1] to

[10] above, wherein the amount of the amine in the step 1 is 0.01 mole equivalent or more and 10 mole equivalent or less.

[0024]

[12] The method for producing modified cellulose fiber as claimed in any one of [1] to

[11] above, wherein the amount of the amine in the step 2 is 0.01 mole equivalent or more and 10 mole equivalent or less.

[0025]

[13] The method for producing a modified cellulose fiber as claimed in any one of [5] to

[12] above, wherein the polymer group is one or two or more selected from a polyoxyalkylene structure and a polysiloxane structure.

[0026]

[14] The method for producing a modified cellulose fiber as claimed in any one of [5] to

[13] above, wherein the polymer group is a structure represented by the following formula.

[0027] [Chemical Formula 1]

[0028]

[0029] (In the formula, R 1 represents a hydrogen atom, a hydrocarbon group having a carbon number of 1 or more and 6 or less, or a -CH2CH(CH3)NH2 group; EO and PO are present in a random or block state, a is a positive number representing the average addition mole number of EO, and b is a positive number representing the average addition mole number of PO)

[0030]

[15] A method for producing a micronized modified cellulose fiber, comprising a step of micronizing the modified cellulose fiber obtained by the method for producing a modified cellulose fiber as claimed in any one of [1] to

[14] above. DETAILED DESCRIPTION

[0031] The present application relates to a novel method for producing a modified cellulose fiber in which a modifying group is bonded to an anionically modified cellulose fiber via an amide bond, the method being excellent in yield of the modified cellulose fiber and excellent in dispersibility when the obtained modified cellulose fiber is micronized.

[0032] According to the present application, a novel method for producing a modified cellulose fiber in which a modifying group is bonded to an anionically modified cellulose fiber via an amide bond can be provided, the method being excellent in yield of the modified cellulose fiber and excellent in dispersibility when the obtained modified cellulose fiber is micronized.

[0033] In Patent Literature 1, a micronized anionically modified cellulose fiber micronized to the nanometer level is subjected to a modification treatment (i.e., an amide bonding treatment).

[0034] The present inventors have studied a method for producing a modified cellulose fiber obtained by introducing a modifying group through an amidation reaction, and as a result, have for the first time found that, by using an anionically modified cellulose fiber having a specific average fiber diameter for the modification treatment, even when an anionically modified cellulose fiber having a higher concentration than in the past is used, the reaction can be performed without gelation, and thus a modified cellulose fiber can be produced in good yield.

[0035] Furthermore, it was discovered for the first time that, when using a method for producing anionic modified cellulose fibers having a specific average fiber diameter, the dispersibility of the micronized modified cellulose fibers obtained by subsequent micronization treatment can be unexpectedly improved by reacting an amine with a smaller molecular weight first and then an amine with a larger molecular weight.

[0036] Although the mechanism by which this effect is exerted is not clear, it is believed to be due to the following: amines with smaller molecular weight are uniformly bonded to the anionic modified cellulose fibers, improving their wettability in the medium. As a result, the bonds between the anionic modified cellulose fibers become loose. As a result, amines with larger molecular weight efficiently enter the interior of the anionic modified cellulose fibers and bond with them, which promotes a reduction in the cohesive force between the fibers caused by steric repulsion.

[0037] 1. Method for producing modified cellulose fiber

[0038] The method for producing modified cellulose fibers of the present invention comprises a modification step of amide bonding two or more amines having different molecular weights to anionic modified cellulose fibers; and

[0039] The average fiber diameter of the anionically modified cellulose fibers is 1 μm or more and 100 μm or less.

[0040] In the above-mentioned modification step, the following step 2 is performed after the following step 1.

[0041] Step 1: A step of amide-bonding an amine including an amine having the smallest molecular weight to an anionically modified cellulose fiber.

[0042] Step 2: After step 1, a step of subjecting an amine including an amine having the highest molecular weight to an anionically modified cellulose fiber to amide bonding.

[0043] [Anionic modified cellulose fiber]

[0044] The anionically modified cellulose fibers used in the production method of the present invention are cellulose fibers that have been anionically modified so as to contain anionic groups.

[0045] The average fiber diameter of the anionically modified cellulose fibers is, from the perspective of production efficiency, 1 μm or greater, preferably 5 μm or greater, more preferably 10 μm or greater, and even more preferably 20 μm or greater. From the same perspective, the average fiber diameter of the anionically modified cellulose fibers is 100 μm or less, preferably 60 μm or less, and more preferably 40 μm or less. The average fiber diameter of the anionically modified cellulose fibers can be measured by the method described in the Examples below.

[0046] The average fiber length of the anion-modified cellulose fiber is preferably 1 μm or more, more preferably 10 μm or more, further preferably 50 μm or more, and further preferably 100 μm or more from the viewpoint of production efficiency, and is preferably 1000 μm or less, more preferably 500 μm or less, and further preferably 400 μm or less from the same viewpoint. The average fiber length of the anion-modified cellulose fiber can be measured by the method described in the Examples below.

[0047] In the present application, the cellulose fiber or the anion-modified cellulose fiber as a raw material is preferably subjected to, for example, a thermal decomposition treatment, a biochemical treatment, and / or a chemical treatment, and the like, to adjust the length in such a manner as to have the average fiber length described above (also referred to as "short fiberization" in the present specification). As the thermal decomposition treatment, for example, a treatment in which an aqueous suspension of the cellulose fiber is stirred under temperature conditions of preferably 50°C or higher and 230°C or lower can be given. As the biochemical treatment, the agent used is not particularly limited, and for example, a treatment using an enzyme such as an endo-cellulase, an exo-cellulase, or a β-glucosidase can be given. As the chemical treatment, the agent used is not particularly limited, and for example, an acid hydrolysis treatment using hydrochloric acid or sulfuric acid, an oxidation treatment using hydrogen peroxide or ozone, or an alkali hydrolysis treatment using sodium hydroxide can be given. The conditions of the alkali hydrolysis treatment and the conditions of the acid hydrolysis treatment can be, for example, those described in paragraphs 0034 to 0035 of Japanese Patent Application Publication No. 2019-119983.

[0048] The content of the anionic group in the anion-modified cellulose fiber is preferably 0.1 mmol / g or more, more preferably 0.6 mmol / g or more, further preferably 0.8 mmol / g or more, and further preferably 1.0 mmol / g or more from the viewpoint of easily introducing a modification group while ensuring stable dispersibility, and is preferably 3.0 mmol / g or less, more preferably 2.5 mmol / g or less, and further preferably 2.0 mmol / g or less from the same viewpoint. The content of the anionic group can be measured by the method described in the Examples below.

[0049] The anionic group contained in the anion-modified cellulose fiber can include, for example, a sulfonic acid group, a (phospho)acid group, and the like, and a carboxyl group is included in order to introduce a modification group into the cellulose fiber.

[0050] As the ion (counter ion) that becomes the counter ion of the anionic group in the anion-modified cellulose fiber, for example, a metal ion such as a sodium ion, a potassium ion, a calcium ion, an aluminum ion, and the like, which is generated in the presence of an alkali at the time of production, or a proton generated by substituting these metal ions with an acid, and the like can be given.

[0051] Based on the viewpoint of the introduction of the modifying group, the anionically modified cellulose fiber is preferably an oxidized cellulose fiber obtained by oxidation of the hydroxyl group in the cellulose structural unit, and more preferably a cellulose fiber in which the C6 position of the cellulose structural unit is a carboxyl group.

[0052] The anionically modified cellulose fiber preferably has a cellulose I crystal structure. With respect to the crystallinity of the anionically modified cellulose fiber, based on the viewpoint of exhibiting high mechanical properties of the resin composition in the case of being compounded in the resin composition as a filler, it is preferably 10% or more, more preferably 15% or more, and further preferably 20% or more. In addition, based on the viewpoint of raw material availability, it is preferably 90% or less, more preferably 85% or less, and further preferably 80% or less. Note that in the present specification, the crystallinity of various cellulose fibers is the cellulose I crystallinity calculated from the diffraction intensity value measured by X-ray diffraction, and can be measured according to the method described in the Examples described later. Note that cellulose I is a crystal form of natural cellulose, and the cellulose I crystallinity refers to the proportion of the amount of the crystalline region in the entire cellulose fiber. The presence or absence of the cellulose I crystal structure can be determined by the presence of a peak at 2θ = 22.6° in X-ray diffraction measurement.

[0053] [Method for producing anionically modified cellulose fiber]

[0054] The anionically modified cellulose fiber used in the production method of the present application can be obtained by introducing at least one or more anionic groups by subjecting a cellulose fiber as a raw material to oxidation treatment or addition treatment of an anionic group.

[0055] [Cellulose fiber as a raw material]

[0056] With respect to the cellulose fiber as a raw material of the anionically modified cellulose fiber, based on the viewpoint of having a cellulose I crystal structure and the viewpoint of environmental load, it is preferable to use a natural cellulose fiber. As the natural cellulose fiber, for example, wood pulp such as coniferous pulp, broad-leaved pulp, and the like; cotton pulp such as cotton linter and cotton lint; non-wood pulp such as wheat straw pulp, sugar cane pulp, and the like; bacterial cellulose; and the like can be given. One of these or two or more of these can be used in combination.

[0057] As the average fiber diameter of the cellulose fiber as a raw material, for example, from the viewpoint of ease of acquisition, it is preferably 1 μm or more, and from the same viewpoint, it is preferably 100 μm or less. As the average fiber length, for example, from the viewpoint of ease of acquisition, it is preferably 1000 μm or more, and from the same viewpoint, it is preferably 10000 μm or less. The average fiber diameter or the average fiber length of the cellulose fiber as a raw material can be measured by the method described in the Examples described later.

[0058] [Method of introducing an anionic group]

[0059] As the method of introducing an anionic group into the cellulose fiber, for example, there can be mentioned a method of oxidizing a hydroxyl group of the cellulose fiber to convert it into a carboxyl group, or a method of reacting a hydroxyl group of the cellulose fiber with one or two or more selected from a compound having an anionic group, an anhydride of a compound having an anionic group, and a derivative of these.

[0060] As the method of performing oxidation treatment on a hydroxyl group of the cellulose fiber, for example, there can be mentioned the method described in Japanese Patent Application Publication No. 2015-143336 or Japanese Patent Application Publication No. 2015-143337, that is, a method of reacting an oxidizing agent such as sodium hypochlorite and a bromide such as sodium bromide with the cellulose fiber as a raw material using 2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) as a catalyst. By performing oxidation treatment of the cellulose fiber using TEMPO as a catalyst, a hydroxymethyl group (-CH2OH) at the C6 position of the cellulose structural unit is selectively converted into a carboxyl group. In particular, this method is advantageous in that it is excellent in selectivity for a hydroxyl group at the C6 position on the surface of the cellulose fiber as a raw material that becomes an oxidation target, and the reaction conditions are also stable.

[0061] As the compound having an anionic group used for introducing an anionic group into the cellulose fiber, specifically, as a haloacetic acid, there can be mentioned chloroacetic acid and the like, and as an anhydride of a dicarboxylic acid compound, there can be mentioned maleic anhydride, succinic anhydride, phthalic anhydride, adipic anhydride, and the like. These compounds can be substituted with a hydrophobic group.

[0062] [Amine]

[0063] The amine in the present specification is a compound having a modification group and at least one amino group or imino group in the molecule.

[0064] [Modification group]

[0065] As the modifying group, (a) a hydrocarbon group and (b) a polymer group can be mentioned. By causing two or more amines having different molecular weights to amide-bond with the anion-modified cellulose fiber, the modifying group possessed by each amine is introduced into the anion-modified cellulose fiber, and a modified cellulose fiber having two or more modifying groups is synthesized. As the combination of two or more modifying groups, a combination of two or more hydrocarbon groups, a combination of a hydrocarbon group and a polymer group, and a combination of two or more polymer groups can be mentioned, and from the viewpoint of dispersibility of the modified cellulose fiber, a combination of a hydrocarbon group and a polymer group is preferred.

[0066] In the present application, regarding the ratio of the molecular weight of the amine having the largest molecular weight to the molecular weight of the amine having the smallest molecular weight (molecular weight of the amine having the largest molecular weight / molecular weight of the amine having the smallest molecular weight) bonded to the anion-modified cellulose, from the viewpoint of ensuring the chemical stability of the modified cellulose fiber and the dispersion stability as a filler, a value exceeding 1 is preferred, a value of 1.5 or more is more preferred, and a value of 2 or more is further preferred. From the same viewpoint, a value of 100 or less is preferred, a value of 50 or less is more preferred, and a value of 20 or less is further preferred.

[0067] Regarding the molecular weight of the amine having the smallest molecular weight, from the viewpoint of ensuring the chemical stability of the modified cellulose fiber and the dispersion stability as a filler, a value of 20 or more is preferred, a value of 50 or more is more preferred, and a value of 80 or more is further preferred. From the same viewpoint, a value of 2000 or less is preferred, a value of 1000 or less is more preferred, and a value of 300 or less is further preferred. In the case where the amine has a polymer group, the molecular weight is the average molecular weight.

[0068] Regarding the molecular weight of the amine having the largest molecular weight, from the viewpoint of ensuring the chemical stability of the modified cellulose fiber and the dispersion stability as a filler, a value of 100 or more is preferred, a value of 200 or more is more preferred, and a value of 1000 or more is further preferred. From the same viewpoint, a value of 4000 or less is preferred, a value of 3000 or less is more preferred, and a value of 2000 or less is further preferred. In the case where the amine has a polymer group, the molecular weight is the average molecular weight.

[0069] (a) a hydrocarbon group

[0070] As the hydrocarbon group, a monovalent hydrocarbon group such as a straight-chain or branched-chain aliphatic saturated hydrocarbon group, a straight-chain or branched-chain aliphatic unsaturated hydrocarbon group, a cyclic saturated hydrocarbon group, an aryl group, and an aralkyl group can be mentioned, and from the viewpoint of ensuring the chemical stability of the modified cellulose fiber and the dispersion stability as a filler, one or two or more selected from the group consisting of a straight-chain or branched-chain aliphatic saturated hydrocarbon group and an aralkyl group is preferred, and one or two or more selected from the group consisting of a straight-chain or branched-chain alkyl group is further preferred.

[0071] The number of carbons of the hydrocarbon group is preferably 1 or more, more preferably 3 or more, and even more preferably 6 or more, and on the other hand, is preferably 30 or less, more preferably 22 or less, even more preferably 18 or less, and even more preferably 10 or less. The hydrocarbon group can have a substituent described later, and a part of the hydrocarbon group can be replaced with a hydridonitrogen group.

[0072] Based on the viewpoint of ensuring the chemical stability of the modified cellulose fiber and the dispersion stability as a filler, the chain saturated hydrocarbon group is preferably a linear chain saturated hydrocarbon group.

[0073] Based on the viewpoint of ensuring the chemical stability of the modified cellulose fiber and the dispersion stability as a filler, the aralkyl group is preferably an alkyl group in which a hydrogen atom is replaced with a phenyl group. Specifically, a benzyl group and a phenylethyl group can be given.

[0074] (b) Polymer group

[0075] The polymer group in the present application is a functional group containing a polymer structure.

[0076] Regarding the formula weight (molecular weight) of the polymer group, based on the viewpoint of ensuring the chemical stability of the modified cellulose fiber and the dispersion stability as a filler, it 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 1000 or more, and even more preferably 1500 or more. Based on 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.

[0077] Based on the viewpoint of ensuring the chemical stability of the modified cellulose fiber and the dispersion stability as a filler, the polymer group preferably has a functional group having a repeating structure linked by a structure containing an oxygen atom, more preferably has a functional group having a repeating structure linked by an oxygen atom such as a polyoxyalkylene structure, a polysiloxane structure, and the like, and even more preferably has a polyoxyalkylene structure, and even more preferably an alkoxy polyoxyalkylene group.

[0078] From the viewpoint of ensuring the chemical stability of the modified cellulose fiber and the dispersion stability as a filler, the polyoxyalkylene structure is preferably a (co)polymer structure of one or two or more kinds of oxyalkylene groups having a carbon number of 2 or more and 8 or less, more preferably a (co)polymer structure of one or two or more kinds of oxyalkylene groups having a carbon number of 2 or more and 4 or less, further preferably a (co)polymer structure of one or two kinds of oxyalkylene groups selected from the group consisting of ethylene oxide (EO) and propylene oxide (PO), further preferably a copolymer structure in which ethylene oxide and propylene oxide are randomly or blockwise polymerized (EO / PO copolymer structure).

[0079] As the copolymer structure in which ethylene oxide and propylene oxide are randomly or blockwise polymerized, for example, the following formula can be given:

[0080] [Chemical Formula 2]

[0081]

[0082] (In the formula, R 1 represents a hydrogen atom, a hydrocarbon group having a carbon number of 1 or more and 6 or less, or a -CH2CH(CH3)NH2 group; EO and PO are present in a random or blockwise manner, and a is a positive number representing the average addition mole number of EO, and b is a positive number representing the average addition mole number of PO). The structure represented by the above formula is a preferable example of the polymer group.

[0083] From the viewpoint of ensuring the chemical stability of the modified cellulose fiber and the dispersion stability as a filler, R 1 A linear or branched alkyl group having a carbon number of 1 or more and 6 or less is preferable, and a methyl group is more preferable.

[0084] From the viewpoint of ensuring the chemical stability of the modified cellulose fiber and the dispersion stability as a filler, a is preferably 1 or more, more preferably 3 or more, further preferably 6 or more, further preferably 11 or more, further preferably 15 or more, further preferably 20 or more, further preferably 25 or more, further preferably 30 or more. From the same viewpoint, a is preferably 100 or less, more preferably 70 or less, further preferably 60 or less, further preferably 50 or less, further preferably 40 or less.

[0085] From the viewpoint of ensuring the chemical stability of the modified cellulose fiber and the dispersion stability as a filler, b is preferably 1 or more, more preferably 3 or more, further preferably 5 or more. From the same viewpoint, b is preferably 50 or less, more preferably 40 or less, further preferably 30 or less, further preferably 25 or less, further preferably 20 or less, further preferably 15 or less, further preferably 10 or less.

[0086] a+b in the above formula represents the total of the average addition mole numbers of EO and PO, and is preferably 4 or more, more preferably 6 or more, and further preferably 8 or more, from the viewpoint of ensuring the chemical stability of the modified cellulose fiber and the dispersion stability as a filler, and is preferably 100 or less, more preferably 70 or less, from the same viewpoint.

[0087] The content of PO in the EO / PO copolymer structure (mole %) can be calculated based on a and b described above, and specifically can be calculated by b x 100 / (a+b). The content of PO is preferably 1 mole % or more, more preferably 5 mole % or more, further preferably 7 mole % or more, further preferably 10 mole % or more, and further preferably 20 mole % or more, from the viewpoint of ensuring the chemical stability of the modified cellulose fiber and the dispersion stability as a filler, and is preferably 100 mole % or less, more preferably 90 mole % or less, further preferably 85 mole % or less, further preferably 75 mole % or less, further preferably 60 mole % or less, further preferably 50 mole % or less, further preferably 40 mole % or less, and further preferably 30 mole % or less, from the same viewpoint.

[0088] (c) further substituent

[0089] Note that the modification group can further have a substituent. As the substituent, for example, there can be mentioned: methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, pentoxy group, isopentoxy group, hexyloxy group, and the like; alkoxy-carbonyl groups in which the carbon number of the alkoxy group is 1 or more and 6 or less, such as methoxy-carbonyl group, ethoxy-carbonyl group, propoxy-carbonyl group, isopropoxy-carbonyl group, butoxy-carbonyl group, isobutoxy-carbonyl group, sec-butoxy-carbonyl group, tert-butoxy-carbonyl group, pentoxy-carbonyl group, and isopentoxy-carbonyl group; halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom; acyl groups in which the carbon number is 1 or more and 6 or less, such as acetyl group and propionyl group; aralkyl group; aralkoxy group; alkylamino group in which the carbon number is 1 or more and 6 or less; dialkylamino group in which the carbon number of the alkyl group is 1 or more and 6 or less; and hydroxy group.

[0090] [Specific examples of amine]

[0091] As the compound having a modification group, any one of primary amine, secondary amine, and tertiary amine can be used.

[0092] (a) compound having a hydrocarbon group

[0093] As specific examples of the compound having a hydrocarbon group, as primary amines, secondary amines, tertiary amines, for example, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, butylamine, dibutylamine, hexylamine, 2-ethylhexylamine, dihexylamine, trihexylamine, octylamine, dioctylamine, trioctylamine, dodecylamine, bis-dodecylamine, stearylamine, distearylamine, monoethanolamine, diethanolamine, triethanolamine, oleylamine, aniline, octadecylamine, dimethylamylamine, benzylamine, dibenzylamine, tritylamine, naphthylamine, and the like can be given.

[0094] The compound having a hydrocarbon group can be produced using a commercially available product or according to a publicly known method.

[0095] (b) Compound having a polymer group

[0096] The polymer group in the compound having a polymer group is preferably bonded directly or via a linking group to the nitrogen atom of the compound. As the linking group, a hydrocarbon group is preferred, and an alkylene group having a carbon number of preferably 1 or more and 6 or less, more preferably 1 or more and 3 or less, can be given. As the alkylene group, for example, ethylene group, propylene group is preferred.

[0097] As the compound having a polymer group, from the viewpoint of ensuring chemical stability of the modified cellulose fiber and dispersion stability as a filler, one or two or more selected from the group consisting of an amine having a polyoxyalkylene structure and an amine having a polysiloxane structure is preferred, one or two or more selected from the group consisting of a polyoxyalkylene alkyl ether amine, a polyoxyalkylene glycol amine, and an amino-modified polysiloxane is more preferred, and one or two or more selected from the group consisting of a poly(oxyethylene / oxypropylene) alkyl ether amine and a poly(oxyethylene / oxypropylene) glycol amine is further preferred.

[0098] As the poly(oxyethylene / oxypropylene) alkyl ether amine or the poly(oxyethylene / oxypropylene) glycol amine, for example, the following formula (i) can be given:

[0099] [Chemical Formula 3]

[0100]

[0101] The compound represented by the formula. EO and PO are present in a random or block manner, R 1 , a and b are the same as R 1 , a and b in the formula representing one example of the structure of the EO / PO copolymer described above.

[0102] The amine having a polyoxyalkylene structure can be produced according to known methods. For example, it is possible to add as much ethylene oxide or propylene oxide as desired to a propylene glycol alkyl ether, and then to aminate the hydroxyl terminal. The terminal can be made into a hydrogen atom by cleaving the alkyl ether with an acid, as desired. These production methods can be referred to in Japanese Patent Application Publication No. 3-181448, and the details of the amine are described, for example, in Japanese Patent No. 6105139.

[0103] The amine having a polyoxyalkylene structure can be produced according to known methods. For example, it is possible to add as much ethylene oxide or propylene oxide as desired to a propylene glycol alkyl ether, and then to aminate the hydroxyl terminal. The terminal can be made into a hydrogen atom by cleaving the alkyl ether with an acid, as desired. These production methods can be referred to in Japanese Patent Application Publication No. 3-181448, and the details of the amine are described, for example, in Japanese Patent No. 6105139.

[0104] The amine having a polyoxyalkylene structure can be produced according to known methods. For example, it is possible to add as much ethylene oxide or propylene oxide as desired to a propylene glycol alkyl ether, and then to aminate the hydroxyl terminal. The terminal can be made into a hydrogen atom by cleaving the alkyl ether with an acid, as desired. These production methods can be referred to in Japanese Patent Application Publication No. 3-181448, and the details of the amine are described, for example, in Japanese Patent No. 6105139.

[0105] The amine having a polyoxyalkylene structure can be produced according to known methods. For example, it is possible to add as much ethylene oxide or propylene oxide as desired to a propylene glycol alkyl ether, and then to aminate the hydroxyl terminal. The terminal can be made into a hydrogen atom by cleaving the alkyl ether with an acid, as desired. These production methods can be referred to in Japanese Patent Application Publication No. 3-181448, and the details of the amine are described, for example, in Japanese Patent No. 6105139.

[0106] The amine having a polyoxyalkylene structure can be produced according to known methods. For example, it is possible to add as much ethylene oxide or propylene oxide as desired to a propylene glycol alkyl ether, and then to aminate the hydroxyl terminal. The terminal can be made into a hydrogen atom by cleaving the alkyl ether with an acid, as desired. These production methods can be referred to in Japanese Patent Application Publication No. 3-181448, and the details of the amine are described, for example, in Japanese Patent No. 6105139.

[0107] As specific examples of the amine having a polysiloxane structure, TSF4703, TSF4708, manufactured by Momentive Performance Materials Co., Ltd., SS-3551, SF8457C, SF8417, SF8452C, BY16-209, BY16-892, BY16-898), FZ-3760, BY16-213, manufactured by Dow Corning Toray Silicone Co., Ltd., KF-8002, KF-8004, KF-8005, KF-867, KF-864, KF-859, and the like manufactured by Shin-Etsu Chemical Co., Ltd. can be given. One of these or two or more of these can be used in combination.

[0108] [Modified cellulose fiber]

[0109] The modified cellulose fiber in the present application is one in which two or more amines are bonded to an anionically modified cellulose fiber via an amide bond.

[0110] The average fiber length, average fiber diameter, and cellulose I crystallinity of the modified cellulose fiber in the present application are preferably the same as the average fiber length, average fiber diameter, and cellulose I crystallinity of the anionically modified cellulose fiber described above.

[0111] From the viewpoint of ensuring the chemical stability of the modified cellulose fiber and the dispersion stability as a filler, the introduction rate of the modifying group in the modified cellulose fiber is preferably 40 mol% or more, more preferably 50 mol% or more, and further preferably 60 mol% or more. On the other hand, from the viewpoint of production efficiency, the introduction rate is preferably 100 mol% or less, and more preferably 90 mol% or less. The introduction rate (mol%) of the modifying group refers to the proportion of the modifying group introduced (bonded) to the anionic group in the modified cellulose fiber. The introduction rate of the modifying group in the modified cellulose fiber is measured by the method described in the Examples below.

[0112] From the viewpoint of efficient acquisition, the introduction rate of the modifying group having the smallest molecular weight among the introduced modifying groups is preferably 10 mol% or more, more preferably 20 mol% or more, and further preferably 30 mol% or more. From the viewpoint of ensuring the dispersibility of the modified cellulose fiber, the introduction rate of the modifying group having the smallest molecular weight among the introduced modifying groups is preferably 95 mol% or less, more preferably 90 mol% or less, and further preferably 85 mol% or less. This modifying group having the smallest molecular weight is introduced by bonding of the amine having the smallest molecular weight.

[0113] [Modification step: step of performing amide reaction]

[0114] One of the features of the present application is that the production method of the present application includes a modification step, the above modification step is an amidation reaction of anionically modified cellulose fiber and two or more kinds of amines having different molecular weights in the presence of a condensing agent, and in the above modification step, process 2 is performed after process 1.

[0115] Process 1: a process of causing an amine containing an amine having the smallest molecular weight to amide bond with anionically modified cellulose fiber.

[0116] Process 2: a process of causing an amine containing an amine having the largest molecular weight to amide bond with anionically modified cellulose fiber after process 1.

[0117] In the present application, two or more kinds of amines having different molecular weights are used. An amine containing an amine having the smallest molecular weight among the plurality of amines is used in process 1, and an amine containing an amine having the largest molecular weight among the plurality of amines is used in process 2 after process 1.

[0118] From the viewpoint of efficiently obtaining a modified cellulose fiber, the amine used in process 1 preferably has a hydrocarbon group, more preferably has a monovalent hydrocarbon group, further preferably has one or two or more selected from a linear or branched chain saturated hydrocarbon group and an aralkyl group, further preferably has a linear or branched chain saturated hydrocarbon group, further preferably has one or two or more selected from a linear or branched alkyl group.

[0119] For example, a method in which the above (a) amine having a hydrocarbon group is first caused to amide bond, and then (b) amine having a polymer group is caused to amide bond can be mentioned.

[0120] From the viewpoint of efficiently obtaining a modified cellulose fiber, the amine used in process 2 is preferably the above amine having a polymer group, more preferably one or two or more selected from an amine having a polyoxyalkylene structure and an amine having a polysiloxane structure, further preferably one or two or more selected from a polyoxyalkylene alkyl ether amine, a polyoxyalkylene glycol amine, and an amino-modified polysiloxane, further preferably one or two or more selected from a poly(oxyethylene / oxypropylene) alkyl ether amine and a poly(oxyethylene / oxypropylene) glycol amine.

[0121] After the amidation reaction is completed, post-treatment can be appropriately performed to remove unreacted compounds and the like. As a method of post-treatment, for example, filtration, centrifugal separation, dialysis, and the like can be used.

[0122] From the viewpoint of ensuring the chemical stability of the modified cellulose fiber and the dispersion stability as a filler, the specific bonding pattern of the compound having a modifying group and the anionic group is amide bonding. With regard to the amidation reaction, for example, Japanese Patent Application Publication No. 2015-143337 can be referred to.

[0123] For example, in the case where oxidized cellulose fibers are used as the anionically modified cellulose fibers, and a primary amine having a modifying group is used as the compound having a modifying group, the modifying group can be introduced to the carboxyl group at the C6 position of the glucose constituting the cellulose fiber via an amide bond as shown in the following formula (in the formula, C 6 is the carbon atom at the 6 position of the glucose constituting the cellulose fiber, and R is a modifying group).

[0124] [Chemical Formula 4]

[0125]

[0126] As the amount of the amine, the amount of the amine in Step 1 is preferably 0.01 mole equivalent or more, more preferably 0.1 mole equivalent or more, and further preferably 0.5 mole equivalent or more, from the viewpoint of efficiently obtaining the modified cellulose fibers. On the other hand, the amount of the amine in Step 1 is preferably 10 mole equivalent or less, more preferably 5 mole equivalent or less, and further preferably 2 mole equivalent or less, from the viewpoint of ensuring the dispersibility of the modified cellulose fibers.

[0127] As the amine in Step 1, only one kind of amine having the smallest molecular weight can be used, or an amine having a larger molecular weight than the amine can be included. In the latter case, the proportion of the amine having the smallest molecular weight in the total amount of the amine in Step 1 is preferably 51 mole% or more, and more preferably 75 mole% or more.

[0128] The amount of the amine in Step 2 is preferably 0.01 mole equivalent or more, more preferably 0.1 mole equivalent or more, and further preferably 0.5 mole equivalent or more, from the viewpoint of forming an amide bond and ensuring the dispersibility of the modified cellulose fibers. On the other hand, the amount of the amine in Step 2 is 10 mole equivalent or less, preferably 5 mole equivalent or less, and more preferably 2 mole equivalent or less, from the viewpoint of efficiently obtaining the modified cellulose fibers.

[0129] As the amine in Step 2, only one kind of amine having the largest molecular weight can be used, or an amine having a smaller molecular weight than the amine can be included. In the latter case, the proportion of the amine having the largest molecular weight in the total amount of the amine in Step 2 is preferably 51 mole% or more, and more preferably 75 mole% or more.

[0130] In the case where the amine has a plurality of amino groups or imino groups, the amino groups or imino groups are present in a total of the above-mentioned molar amount. In the present specification, "0.01 mole equivalent of the compound having a modifying group" means "0.01 mole of the compound having a modifying group with respect to 1 mole of the anionic group of the anionically modified cellulose fiber, in terms of the amino groups or imino groups of the compound having a modifying group".

[0131] As the reaction time of the amidation reaction, each of the process 1 and the process 2 is preferably 1 hour or more, more preferably 10 hours or more from the viewpoint of reactivity, and is preferably 24 hours or less, more preferably 20 hours or less from the viewpoint of production efficiency. Also, as the reaction temperature of the amidation reaction, each of the process 1 and the process 2 is preferably 0°C or more, more preferably 20°C or more, further preferably 40°C or more, further preferably 50°C or more from the viewpoint of reactivity. Also, it is preferably 200°C or less, more preferably 150°C or less, further preferably 100°C or less from the viewpoint of suppressing side reactions.

[0132] In order to make the amine undergo amide bonding, that is, to introduce the modifying group via an amide bond, it is only necessary to mix the anionically modified cellulose fiber and the amine, that is, the compound having the modifying group, in the presence of a condensing agent, whereby an amide bond is formed between the anionic group and the amino group of the compound having the modifying group.

[0133] As the condensing agent, there is no particular limitation, and examples that can be given include triazine-based compounds (for example, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium hydrochloride (DMTMM) and the like), carbodiimide-based compounds (for example, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC), N,N'-dicyclohexylcarbodiimide (DCC), N,N'-diisopropylcarbodiimide (DIC), and the like), imidazole-based compounds (for example, carbonyldiimidazole (CDI), carbonyl di-(1,2,4-triazole) (CDT), and the like), phosphonium-based compounds (for example, 1H-benzotriazole-1-yloxytris(dimethylamino)phosphonium hexafluorophosphate (BOP), 1H-benzotriazole-1-yloxytripyrrolidino phosphonium hexafluorophosphate (PyBOP), and the like), uronium-based compounds (for example, O-(benzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HBTU), O-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU), and the like), and halogenated uronium-based compounds (for example, 2-chloro-1,3-dimethylimidazolinium hexafluorophosphate (CIP), 1-(chloro-1-pyrrolidinylmethylene)pyrrolidinium hexafluorophosphate (PyCIU), and the like), of which DMTMM is preferred from the viewpoint of reactivity.

[0134] A catalyst can be used at the time of amidation.

[0135] As the catalyst, for example, one or two or more kinds of compounds selected from the group consisting of N-methylmorpholine (NMM), N-hydroxysuccinimide (NHS), 1-hydroxybenzotriazole (HOBt), 1-hydroxy-7-azabenzotriazole (HOAt), and ethyl cyano(hydroxyimino)acetate (Oxyma) can be mentioned.

[0136] In the amidation reaction, a solvent can be used or not used. As a specific example of the solvent in the case of using a solvent, for example, methanol, ethanol, isopropyl alcohol (IPA), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N,N-dimethylacetamide, tetrahydrofuran (THF), acetone, methyl ethyl ketone (MEK), cyclohexanone, ethyl acetate, acetonitrile, dichloromethane, chloroform, toluene, acetic acid, 1-methoxy-2-propanol (PGME), water, and the like can be mentioned, and one of these or two or more kinds thereof can be used in combination, and the solvent used is preferably N,N-dimethylformamide from the viewpoint of efficiently performing the reaction.

[0137] By using the anion-modified cellulose fiber having an average fiber diameter of 1 μm or more and 100 μm or less, the modification process can be performed at a higher content ratio of the anion-modified cellulose fiber than in the past. The present inventors have found that, in the case where the average fiber diameter of the anion-modified cellulose fiber is outside the above range, there is a tendency that the viscosity of the reaction liquid containing the anion-modified cellulose fiber and the like in the modification process becomes high or further gels. In order to prevent the gelling of the reaction liquid, it is necessary to reduce the content ratio of the anion-modified cellulose fiber in the reaction liquid, and as a result, the production yield of the modified cellulose fiber is reduced.

[0138] Specifically, in the modification process, the content ratio of the anion-modified cellulose fiber in the reaction liquid at the start of the process is preferably 1% by mass or more, more preferably 2% by mass or more, and further preferably 3% by mass or more, from the viewpoint of improving the productivity of the modified cellulose fiber, and on the other hand, the content ratio is preferably 50% by mass or less, more preferably 10% by mass or less, and further preferably 7% by mass or less, from the viewpoint of being able to produce the modified cellulose fiber with good yield.

[0139] The reaction liquid at the start of the process of the modification process contains the anion-modified cellulose fiber, the amine, and the condensing agent, and can contain a solvent and / or a catalyst as necessary.

[0140] The content ratio of the anion-modified cellulose fiber in the reaction liquid at the start of the process is calculated from the amounts of the respective components contained in the reaction liquid.

[0141] 2. Method for producing a finely modified cellulose fiber

[0142] The modified cellulose fiber can be further refined by the production method of the present application, and a refined modified cellulose fiber can be produced.

[0143] The refined modified cellulose fiber can be produced, for example, by a method including a step of refining the modified cellulose fiber by a publicly known method. For example, the refining step described in Japanese Patent Application Publication No. 2013-151661 can be implemented.

[0144] [Refined modified cellulose fiber]

[0145] The average fiber diameter of the refined modified cellulose fiber is in the nanometer range regardless of the type of the modifying group. The average fiber diameter of the refined modified cellulose fiber is preferably 0.1 nm or more, more preferably 1 nm or more, and further preferably 5 nm or more from the viewpoint of production efficiency, and is preferably 300 nm or less, more preferably 100 nm or less, and further preferably 60 nm or less, and further preferably 40 nm or less from the viewpoint of the effect of the addition as a filler.

[0146] The average fiber length of the refined modified cellulose fiber is preferably 10 nm or more, more preferably 20 nm or more, and further preferably 50 nm or more from the viewpoint of the effect of the addition as a filler, and is preferably 500 nm or less, more preferably 400 nm or less, and further preferably 300 nm or less from the viewpoint of improving dispersibility.

[0147] The average fiber diameter and the average fiber length of the refined modified cellulose fiber are measured by the methods described in the Examples below.

[0148] The preferable crystallinity of the refined modified cellulose fiber and the preferable introduction rate of the modifying group are the same as those of the above-described modified cellulose fiber.

[0149] [Dispersion]

[0150] The dispersion in the present application contains the above-described refined modified cellulose fiber and a dispersion medium.

[0151] The content rate of the refined modified cellulose fiber in the dispersion is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and further preferably 1% by mass or more from the viewpoint of exhibiting high mechanical properties of the resin composition when the dispersion is a resin, and is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 4% by mass or less from the viewpoint of improving the dispersibility of the modified cellulose fiber in the dispersion.

[0152] The content of the glucose moiety in the microfibrillated modified cellulose fiber as a dispersion is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and further preferably 0.5% by mass or more, from the viewpoint of exhibiting high mechanical properties of the resin composition when the dispersion is used as a resin, and is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 2% by mass or less, from the viewpoint of improving the dispersibility of the modified cellulose fiber in the dispersion.

[0153] The "glucose moiety" in the present specification refers to a moiety derived from an anionically modified cellulose fiber in an anionically modified cellulose fiber, a modified cellulose fiber, or a microfibrillated modified cellulose fiber, and refers to the anionically modified cellulose fiber itself in the case of an anionically modified cellulose fiber, and refers to a moiety remaining by removing an amine through hydrolysis of a modified cellulose fiber or the like in the case of a modified cellulose fiber or a microfibrillated modified cellulose fiber.

[0154] [Dispersion medium]

[0155] As the dispersion medium, a solvent and / or a resin can be given.

[0156] (a) Solvent

[0157] As the solvent, the solvents given as the specific examples of the solvent in the amidation reaction described above can be used.

[0158] (b) Resin

[0159] From the viewpoint of water resistance, the resin in the present application is preferably a non-water-soluble resin that is not dissolved in water or has extremely low solubility in water. Specifically, a resin having a solubility of 1 mg or less in 100 g of water at 25°C is referred to as a non-water-soluble resin.

[0160] The solubility described above is measured in the following manner.

[0161] To 100 mL (25°C) of water, 100 mg of the resin is added, and after stirring for 24 hours using a stirrer or the like stirring device, the solution (or suspension) is centrifuged at 25°C, 3000 x g for 30 minutes, and the insoluble residue is collected. The residue is dried at 105°C for 3 days, and the mass after drying (dried mass) is measured. Furthermore, a resin having a dried mass of less than 99 mg is judged to be water-soluble, and a resin having a dried mass of 99 mg or more is judged to be non-water-soluble.

[0162] As specific examples of the resin, there are mentioned acrylic resins such as methyl methacrylate polymers, silicone resins such as polydimethylsiloxanes, epoxy resins, polyurethane resins, vinyl chloride resins, phenoxy resins, phenol resins, urea resins, melamine resins, polyimide resins, unsaturated polyester resins, diallyl phthalate resins, and rubber-based resins. These resins correspond to the above-mentioned non-water-soluble resin.

[0163] The resin can be used alone or in the form of a mixed resin of two or more kinds.

[0164] The dispersion can contain, as required, a curing agent, a curing accelerator, a polymerization initiator, a plasticizer, a stabilizer, a lubricant, a surfactant, an inorganic filler, and the like. The amounts of these components are not particularly limited, and appropriate amounts can be used as appropriate.

[0165] As the method for producing the dispersion, there is mentioned a method including a step of mixing the above-mentioned finely modified cellulose fiber and a dispersion medium.

[0166] By molding the dispersion containing the resin, it can be used as an information home appliance component, a packaging material for an information home appliance component, a motor vehicle component, a three-dimensional modeling material, a cushioning material, a repair material, a sealing material, a thermal insulation material, an acoustic absorbing material, and the like.

[0167] With respect to the above-mentioned embodiment, the present application further discloses the following production method of modified cellulose fiber, production method of finely modified cellulose fiber, and dispersion.

[0168] <1> A production method of modified cellulose fiber, comprising a modification step of amide-bonding two or more kinds of amines having different molecular weights to anionically modified cellulose fiber; and

[0169] The above-mentioned anionically modified cellulose fiber has an average fiber diameter of 1 μm or more and 100 μm or less,

[0170] In the above-mentioned modification step, after the following step 1, the following step 2 is performed,

[0171] Step 1: a step of amide-bonding an amine containing an amine having the smallest molecular weight to anionically modified cellulose fiber

[0172] Step 2: a step of amide-bonding an amine containing an amine having the largest molecular weight to anionically modified cellulose fiber after Step 1.

[0173] <2> The method for producing a modified cellulose fiber according to any one of <1> to <5>, wherein the average fiber diameter of the anionically modified cellulose fiber is preferably 1 μm or more, more preferably 5 μm or more, further preferably 10 μm or more, further preferably 20 μm or more, and is preferably 100 μm or less, more preferably 60 μm or less, further preferably 40 μm or less, and the average fiber length of the anionically modified cellulose fiber is preferably 1 μm or more, more preferably 10 μm or more, further preferably 50 μm or more, further preferably 100 μm or more, and is preferably 1000 μm or less, more preferably 500 μm or less, further preferably 400 μm or less.

[0174] <3> The method for producing a modified cellulose fiber according to <1> or <2>, wherein the content of the anionic group in the anionically modified cellulose fiber is preferably 0.1 mmol / g or more, more preferably 0.6 mmol / g or more, further preferably 0.8 mmol / g or more, further preferably 1.0 mmol / g or more, and is preferably 3.0 mmol / g or less, more preferably 2.5 mmol / g or less, further preferably 2.0 mmol / g or less.

[0175] <4> The method for producing a modified cellulose fiber according to any one of <1> to <3>, wherein the anionically modified cellulose fiber is preferably an oxidized cellulose fiber obtained by oxidation of the hydroxyl group in the cellulose structural unit, more preferably has a carboxyl group, further preferably a cellulose fiber in which the C6 position of the cellulose structural unit is a carboxyl group.

[0176] <5> The method for producing a modified cellulose fiber according to any one of <1> to <4>, wherein the modifying group introduced to the anionically modified cellulose fiber in the modification step is preferably a combination of two or more hydrocarbon groups, a combination of a hydrocarbon group and a polymer group, or a combination of two or more polymer groups, more preferably a combination of a hydrocarbon group and a polymer group.

[0177] <6> The method for producing a modified cellulose fiber according to any one of <1> to <5>, wherein the ratio of the molecular weight of the largest amine to the molecular weight of the smallest amine (molecular weight of the largest amine / molecular weight of the smallest amine) is preferably more than 1, more preferably 1.5 or more, further preferably 2 or more, and is preferably 100 or less, more preferably 50 or less, further preferably 20 or less.

[0178] <7> The production method of the modified cellulose fiber according to any one of <1> to <6>, wherein the molecular weight of the smallest amine is preferably 20 or more, more preferably 50 or more, further preferably 80 or more, and is preferably 2000 or less, more preferably 1000 or less, further preferably 300 or less, and the molecular weight of the largest amine is preferably 100 or more, more preferably 200 or more, further preferably 1000 or more, and is preferably 4000 or less, more preferably 3000 or less, further preferably 2000 or less.

[0179] <8> The production method of the modified cellulose fiber according to any one of <1> to <7>, wherein the hydrocarbon group is preferably a monovalent hydrocarbon group, more preferably one or more selected from the group consisting of a linear or branched chain saturated hydrocarbon group, a linear or branched chain unsaturated hydrocarbon group, a cyclic saturated hydrocarbon group, an aryl group, and an aralkyl group, further preferably one or more selected from the group consisting of a linear or branched chain saturated hydrocarbon group and an aralkyl group, further preferably one or more selected from the group consisting of a linear or branched alkyl group, further preferably a linear chain saturated hydrocarbon group, and the polymer group is preferably a functional group having a repeating structure linked by a structure containing an oxygen atom, more preferably a functional group having a repeating structure linked by an oxygen atom such as a polyoxyalkylene structure, a polysiloxane structure, and the like, further preferably a group having a polyoxyalkylene structure, further preferably an alkoxy polyoxyalkylene group.

[0180] <9> The production method of the modified cellulose fiber according to any one of <1> to <8>, wherein the number of carbon atoms of the hydrocarbon group is preferably 1 or more, more preferably 3 or more, further preferably 6 or more, and is preferably 30 or less, more preferably 22 or less, further preferably 18 or less, further preferably 10 or less.

[0181] <10> The production method of the modified cellulose fiber according to any one of <1> to <9>, wherein the aralkyl group is preferably an alkyl group substituted with a phenyl group, more preferably a benzyl group and a phenethyl group.

[0182] <11> The production method of the modified cellulose fiber according to any one of <1> to <10>, wherein the hydrocarbon group preferably further has a substituent or a part of the hydrocarbon group is substituted with a nitrogen hydride group.

[0183] <12> The method for producing the modified cellulose fiber according to any one of <1> to <11> above, wherein the formula weight (molecular weight) of the polymer group is preferably 100 or more, more preferably 200 or more, further preferably 300 or more, further preferably 500 or more, further preferably 1000 or more, further preferably 1500 or more, and is preferably 1,000,000 or less, more preferably 100,000 or less, further preferably 10,000 or less, further preferably 7,000 or less, further preferably 5,000 or less, further preferably 4,000 or less, further preferably 3,500 or less, further preferably 2,500 or less.

[0184] <13> The method for producing the modified cellulose fiber according to any one of <1> to <12> above, wherein the polyoxyalkylene structure is preferably a (co)polymer structure of one or two or more kinds of oxyalkylene groups having a carbon number of 2 or more and 8 or less, more preferably a (co)polymer structure of one or two or more kinds of oxyalkylene groups having a carbon number of 2 or more and 4 or less, further preferably a (co)polymer structure of one or two kinds of oxyalkylene groups selected from the group consisting of ethylene oxide (EO) and propylene oxide (PO), further preferably a copolymer structure in which ethylene oxide and propylene oxide are randomly or blockwise polymerized (EO / PO copolymer structure).

[0185] <14> The method for producing the modified cellulose fiber according to any one of <1> to <13> above, wherein the copolymer structure in which ethylene oxide and propylene oxide are randomly or blockwise polymerized is preferably a structure represented by the following formula:

[0186] [Chemical Formula 5]

[0187]

[0188] (In the formula, R 1a is preferably 1 or more, more preferably 3 or more, further preferably 6 or more, further preferably 11 or more, further preferably 15 or more, further preferably 20 or more, further preferably 25 or more, further preferably 30 or more, and is preferably 100 or less, more preferably 70 or less, further preferably 60 or less, further preferably 50 or less, further preferably 40 or less, b is preferably 1 or more, more preferably 3 or more, further preferably 5 or more, and is preferably 50 or less, more preferably 40 or less, further preferably 30 or less, further preferably 25 or less, further preferably 20 or less, further preferably 15 or less, further preferably 10 or less, and a+b is preferably 4 or more, more preferably 6 or more, further preferably 8 or more, and is preferably 100 or less, more preferably 70 or less.

[0189] <15> The method for producing the modified cellulose fiber according to any one of <1> to <14> above, wherein the content ratio (mol%) of PO in the EO / PO copolymer structure is preferably 1 mol% or more, more preferably 5 mol% or more, further preferably 7 mol% or more, further preferably 10 mol% or more, further preferably 20 mol% or more, and is preferably 100 mol% or less, more preferably 90 mol% or less, further preferably 85 mol% or less, further preferably 75 mol% or less, further preferably 60 mol% or less, further preferably 50 mol% or less, further preferably 40 mol% or less, further preferably 30 mol% or less.

[0190] <16> The method for producing the modified cellulose fiber according to any one of <1> to <15> above, wherein the amine is preferably a compound having a hydrocarbon group and / or a compound having a polymer group, the preferred compound having a hydrocarbon group is ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, butylamine, dibutylamine, hexylamine, 2-ethylhexylamine, dihexylamine, trihexylamine, octylamine, dioctylamine, trioctylamine, dodecylamine, didodecylamine, stearylamine, distearylamine, monoethanolamine, diethanolamine, triethanolamine, oleylamine, aniline, octadecylamine, dimethylbezylamine, benzylamine, benzyldimethylamine, benzylamine, and naphthylamine, and the preferred compound having a polymer group is one or two or more selected from the group consisting of an amine having a polyoxyalkylene structure and an amine having a polysiloxane structure, the more preferred compound having a polymer group is one or two or more selected from the group consisting of a polyoxyalkylene alkyl ether amine, a polyoxyalkylene glycol amine, and an amino-modified polysiloxane, and the further preferred compound having a polymer group is one or two or more selected from the group consisting of a poly(oxyethylene / oxypropylene) alkyl ether amine and a poly(oxyethylene / oxypropylene) glycol amine.

[0191] <17> The method for producing the modified cellulose fiber according to any one of <1> to <16> above, wherein the polymer group in the compound having a polymer group is preferably bonded directly or via a linking group to the nitrogen atom of the compound, the linking group is preferably an alkylene group having a carbon number of preferably 1 or more and 6 or less, and more preferably 1 or more and 3 or less, and the alkylene group is preferably an ethylene group or a propylene group.

[0192] <18> The method for producing the modified cellulose fiber according to any one of <1> to <17>, wherein the amine having an EO / PO copolymer structure and possibly having a hydrocarbon group is preferably selected from one or more of Jeffamine M-2070, Jeffamine M-2005, Jeffamine M-2095, Jeffamine M-1000, Jeffamine M-600, Surfoamine B200, Surfoamine L100, Surfoamine L200, Surfoamine L207, Surfoamine L300, Surfoamine B-100, XTJ-501, XTJ-506, XTJ-507, XTJ-508, M3000, Jeffamine ED-600, Jeffamine ED-900, Jeffamine ED-2003, Jeffamine D-230, Jeffamine D-400, Jeffamine D-2000, Jeffamine D-4000, XTJ-510, Jeffamine T-3000, Jeffamine T-5000, XTJ-502, XTJ-509, and XTJ-510 manufactured by Huntsman Corporation.

[0193] <19> The method for producing the modified cellulose fiber according to any one of <1> to <18>, wherein the average fiber length, the average fiber diameter, and the cellulose I crystallinity of the modified cellulose fiber are preferably the same as the average fiber length, the average fiber diameter, and the cellulose I crystallinity of the anion-modified cellulose fiber.

[0194] <20> The method for producing the modified cellulose fiber according to any one of <1> to <19>, wherein the introduction rate of the modification group in the modified cellulose fiber is preferably 40 mol% or more, more preferably 50 mol% or more, and further preferably 60 mol% or more, and is preferably 100 mol% or less, more preferably 90 mol% or less, and further preferably 85 mol% or less, the introduction rate of the modification group having the smallest molecular weight among the introduced modification groups is preferably 10 mol% or more, more preferably 20 mol% or more, and further preferably 30 mol% or more, and is preferably 95 mol% or less, more preferably 90 mol% or less, and further preferably 85 mol% or less.

[0195] <21> The production method of the modified cellulose fiber according to any one of <1> to <20> above, wherein the amine used in Step 1 is preferably an amine having a hydrocarbon group, more preferably an amine having a monovalent hydrocarbon group, further preferably an amine having one or more selected from the group consisting of a linear or branched chain saturated hydrocarbon group and an aralkyl group, further preferably an amine having a linear or branched chain saturated hydrocarbon group, further preferably an amine having one or more selected from the group consisting of a linear or branched alkyl group, and the amine used in Step 2 is preferably an amine having a polymer group, more preferably one or more selected from the group consisting of an amine having a polyoxyalkylene structure and an amine having a polysiloxane structure, further preferably one or more selected from the group consisting of a polyoxyalkylene alkyl ether amine, a polyoxyalkylene glycol amine, and an amino-modified polysiloxane, further preferably one or more selected from the group consisting of a poly(oxyethylene / oxypropylene) alkyl ether amine and a poly(oxyethylene / oxypropylene) glycol amine.

[0196] <22> The production method of the modified cellulose fiber according to any one of <1> to <21> above, wherein the amount of the amine in Step 1 is preferably 0.01 or more, more preferably 0.1 or more, further preferably 0.5 or more, and is preferably 10 or less, more preferably 5 or less, further preferably 2 or less, and the amount of the amine in Step 2 is preferably 0.01 or more, more preferably 0.1 or more, further preferably 0.5 or more, and is preferably 10 or less, more preferably 5 or less, further preferably 2 or less.

[0197] <23> The production method of the modified cellulose fiber according to any one of <1> to <22> above, wherein the reaction time of the amidation reaction is preferably 1 hour or more, more preferably 10 hours or more, and is preferably 24 hours or less, more preferably 20 hours or less, in each of Step 1 and Step 2, and the reaction temperature of the amidation reaction is preferably 0°C or more, more preferably 20°C or more, further preferably 40°C or more, further preferably 50°C or more, and is preferably 200°C or less, more preferably 150°C or less, further preferably 100°C or less, in each of Step 1 and Step 2.

[0198] <24> The production method of the modified cellulose fiber according to any one of <1> to <23> above, wherein the mixing of the anion-modified cellulose fiber and the amine, i.e., the compound having a modifying group, is performed in the presence of a condensing agent.

[0199] <25> The method for producing the modified cellulose fiber according to any one of <1> to <24> above, wherein the condensing agent is preferably a triazine compound (e.g., 4-(4,6-dimethoxy-l,3,5-triazin-2-yl)-4-methylmorpholinium hydrochloride (DMTMM) or the like), a carbodiimide compound (e.g., l-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC), N,N'-dicyclohexylcarbodiimide (DCC), N,N'-diisopropylcarbodiimide (DIC) or the like), an imidazole compound (e.g., carbonyldiimidazole (CDI), carbonyl di-(l,2,4-triazole) (CDT) or the like), a phosphonium compound (e.g., lH-benzotriazole-l-yloxytris(dimethylamino)phosphonium hexafluorophosphate (BOP), lH-benzotriazole-l-yloxytripyrrolidinophosphonium hexafluorophosphate (PyBOP) or the like), a uronium compound (e.g., O-(benzotriazol-l-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HBTU), O-(7-azabenzotriazol-l-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU) or the like), and a halogenated uronium compound (e.g., 2-chloro-l,3-dimethylimidazolinium hexafluorophosphate (CIP), l-(chloro-l-pyrrolidinylmethylene)pyrrolidinium hexafluorophosphate (PyCIU) or the like), and more preferably DMTMM.

[0200] <26> The method for producing the modified cellulose fiber according to any one of <1> to <25> above, wherein a catalyst is preferably used at the time of amidation, and the preferred catalyst is one or more compounds selected from the group consisting of N-methylmorpholine (NMM), N-hydroxysuccinimide (NHS), l-hydroxybenzotriazole (HOBt), l-hydroxy-7-azabenzotriazole (HOAt), and ethyl cyano(hydroxyimino)acetate (Oxyma).

[0201] <27> The method for producing the modified cellulose fiber according to any one of <1> to <26> above, wherein the content of the anion-modified cellulose fiber in the reaction solution at the start of the modification step is preferably 1% by mass or more, more preferably 2% by mass or more, and further preferably 3% by mass or more, and is preferably 50% by mass or less, more preferably 10% by mass or less, and further preferably 7% by mass or less.

[0202] <28> The method for producing the modified cellulose fiber according to any one of <1> to <27> above, wherein a step of subjecting the anion-modified cellulose fiber to a thermal decomposition treatment, a biochemical treatment, and / or a chemical treatment is performed before the modification step.

[0203] <29> The production method of the modified cellulose fiber according to any one of <1> to <28>, wherein the ratio of the molecular weight of the largest molecular weight amine to the smallest molecular weight amine (molecular weight of the largest molecular weight amine / molecular weight of the smallest molecular weight amine) is preferably more than 1, more preferably 1.5 or more, further preferably 2 or more, and is preferably 100 or less, more preferably 50 or less, further preferably 20 or less, the molecular weight of the smallest molecular weight amine is preferably 20 or more, more preferably 50 or more, further preferably 80 or more, and is preferably 2000 or less, more preferably 1000 or less, further preferably 300 or less, the molecular weight of the largest molecular weight amine is preferably 100 or more, more preferably 200 or more, further preferably 1000 or more, and is preferably 4000 or less, more preferably 3000 or less, further preferably 2000 or less.

[0204] <30> The production method of the modified cellulose fiber according to any one of <1> to <29>, wherein the average fiber diameter of the anion-modified cellulose fiber is preferably 1 μm or more and 100 μm or less, more preferably 5 μm or more and 60 μm or less, further preferably 10 μm or more and 40 μm or less, further preferably 20 μm or more and 40 μm or less, and the average fiber length of the anion-modified cellulose fiber is preferably 1 μm or more and 1000 μm or less, more preferably 10 μm or more and 500 μm or less, further preferably 50 μm or more and 400 μm or less, further preferably 100 μm or more and 400 μm or less.

[0205] <31> The production method of the modified cellulose fiber according to any one of <1> to <30>, wherein the content of the anionic group in the anion-modified cellulose fiber is preferably 0.1 mmol / g or more and 3.0 mmol / g or less, more preferably 0.6 mmol / g or more and 2.5 mmol / g or less, further preferably 0.8 mmol / g or more and 2.0 mmol / g or less, further preferably 1.0 mmol / g or more and 2.0 mmol / g or less.

[0206] <32> The production method of the modified cellulose fiber according to any one of <1> to <31>, wherein the ratio of the molecular weight of the largest molecular weight amine to the smallest molecular weight amine (molecular weight of the largest molecular weight amine / molecular weight of the smallest molecular weight amine) is preferably more than 1 and 100 or less, more preferably 1.5 or more and 50 or less, further preferably 2 or more and 20 or less.

[0207] <33> The method for producing modified cellulose fiber according to any one of <1> to <32> above, wherein the molecular weight of the smallest amine is preferably 20 or more and 2000 or less, more preferably 50 or more and 1000 or less, further preferably 80 or more and 300 or less, and the molecular weight of the largest amine is preferably 100 or more and 4000 or less, more preferably 200 or more and 3000 or less, further preferably 1000 or more and 2000 or less.

[0208] <34> The method for producing modified cellulose fiber according to any one of <1> to <33> above, wherein the number of carbons of the hydrocarbon group is preferably 1 or more and 30 or less, more preferably 3 or more and 22 or less, further preferably 6 or more and 18 or less, further preferably 6 or more and 10 or less.

[0209] <35> The method for producing modified cellulose fiber according to any one of <1> to <34> above, wherein the formula weight (molecular weight) of the polymer group is preferably 100 or more and 1000000 or less, more preferably 200 or more and 100000 or less, further preferably 300 or more and 10000 or less, further preferably 500 or more and 7000 or less, further preferably 1000 or more and 5000 or less, further preferably 1500 or more and 4000 or less, further preferably 1500 or more and 3500 or less, further preferably 1500 or more and 2500 or less.

[0210] <36> The method for producing modified cellulose fiber according to any one of <1> to <35> above, wherein a in the copolymer structure is preferably 1 or more and 100 or less, more preferably 3 or more and 70 or less, further preferably 6 or more and 60 or less, further preferably 11 or more and 50 or less, further preferably 15 or more and 40 or less, further preferably 20 or more and 40 or less, further preferably 25 or more and 40 or less, further preferably 30 or more and 40 or less, b is preferably 1 or more and 50 or less, more preferably 3 or more and 40 or less, further preferably 5 or more and 30 or less, further preferably 5 or more and 25 or less, further preferably 5 or more and 20 or less, further preferably 5 or more and 15 or less, further preferably 5 or more and 10 or less, and a+b is preferably 4 or more and 100 or less, more preferably 6 or more and 70 or less, further preferably 8 or more and 70 or less.

[0211] <37> The method for producing the modified cellulose fiber according to any one of <1> to <36> above, wherein the content ratio of PO in the EO / PO copolymer structure is preferably 1 mol% or more and 100 mol% or less, more preferably 5 mol% or more and 90 mol% or less, further preferably 7 mol% or more and 85 mol% or less, further preferably 10 mol% or more and 75 mol% or less, further preferably 20 mol% or more and 60 mol% or less, further preferably 20 mol% or more and 50 mol% or less, further preferably 20 mol% or more and 40 mol% or less, further preferably 20 mol% or more and 30 mol% or less.

[0212] <38> The method for producing the modified cellulose fiber according to any one of <1> to <37> above, wherein the introduction ratio of the modification group in the modified cellulose fiber is preferably 40 mol% or more and 100 mol% or less, more preferably 50 mol% or more and 90 mol% or less, further preferably 60 mol% or more and 90 mol% or less, and the introduction ratio of the modification group having the smallest molecular weight among the introduced modification groups is preferably 10 mol% or more and 95 mol% or less, more preferably 20 mol% or more and 90 mol% or less, further preferably 30 mol% or more and 85 mol% or less.

[0213] <39> The method for producing the modified cellulose fiber according to any one of <1> to <38> above, wherein the amount of the amine in the step 1 is preferably 0.01 mol equivalent or more and 10 mol equivalent or less, more preferably 0.1 mol equivalent or more and 5 mol equivalent or less, further preferably 0.5 mol equivalent or more and 2 mol equivalent or less, and the amount of the amine in the step 2 is preferably 0.01 mol equivalent or more and 10 mol equivalent or less, more preferably 0.1 mol equivalent or more and 5 mol equivalent or less, further preferably 0.5 mol equivalent or more and 2 mol equivalent or less.

[0214] <40> The method for producing the modified cellulose fiber according to any one of <1> to <39> above, wherein the reaction time of the amidation reaction is preferably 1 hour or more and 24 hours or less, more preferably 10 hours or more and 20 hours or less, in each of the step 1 and the step 2, and the reaction temperature of the amidation reaction is preferably 0°C or more and 200°C or less, more preferably 20°C or more and 150°C or less, further preferably 40°C or more and 100°C or less, further preferably 50°C or more and 100°C or less, in each of the step 1 and the step 2.

[0215] <41> The production method of the modified cellulose fiber according to any one of <1> to <40> above, wherein the content of the anion-modified cellulose fiber in the reaction solution at the start of the modification step is preferably 1% by mass or more and 50% by mass or less, more preferably 2% by mass or more and 10% by mass or less, and further preferably 3% by mass or more and 7% by mass or less.

[0216] <42> The production method of the modified cellulose fiber according to any one of <1> to <41> above, wherein the ratio of the molecular weight of the largest amine to the molecular weight of the smallest amine (molecular weight of the largest amine / molecular weight of the smallest amine) is preferably more than 1 and 100 or less, more preferably 1.5 or more and 50 or less, and further preferably 2 or more and 20 or less, the molecular weight of the smallest amine is preferably 20 or more and 2000 or less, more preferably 50 or more and 1000 or less, and further preferably 80 or more and 300 or less, and the molecular weight of the largest amine is preferably 100 or more and 4000 or less, more preferably 200 or more and 3000 or less, and further preferably 1000 or more and 2000 or less.

[0217] <43> A production method of a micronized modified cellulose fiber, which has a step of micronizing the modified cellulose fiber obtained by the production method of the modified cellulose fiber according to any one of <1> to <42> above, and wherein the average fiber diameter of the micronized modified cellulose fiber is preferably 0.1 nm or more and 300 nm or less, more preferably 1 nm or more and 100 nm or less, and further preferably 5 nm or more and 60 nm or less, and further preferably 5 nm or more and 40 nm or less, the average fiber length of the micronized modified cellulose fiber is preferably 10 nm or more and 500 nm or less, more preferably 20 nm or more and 400 nm or less, and further preferably 50 nm or more and 300 nm or less, and the preferable crystallinity and the preferable introduction rate of the modification group of the micronized modified cellulose fiber are the same as those of the modified cellulose fiber.

[0218] <44> A dispersion containing the microfibrillated modified cellulose fiber obtained by the production method of the microfibrillated modified cellulose fiber described in the above <43>, and a dispersion medium, and the dispersion medium is a solvent and / or a resin, the above solvent is preferably selected from one or more of methanol, ethanol, isopropyl alcohol (IPA), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N,N-dimethylacetamide, tetrahydrofuran (THF), acetone, methyl ethyl ketone (MEK), cyclohexanone, ethyl acetate, acetonitrile, dichloromethane, chloroform, toluene, acetic acid, 1-methoxy-2-propanol (PGME), and water, more preferably N,N-dimethylformamide, and the above resin is preferably an acrylic resin such as methyl methacrylate polymer, a silicone resin such as polydimethylsiloxane, an epoxy resin, a polyurethane resin, a vinyl chloride resin, a phenoxy resin, a phenol resin, a urea resin, a melamine resin, a polyimide resin, an unsaturated polyester resin, a diallyl phthalate resin, and a rubber-based resin.

[0219] Examples

[0220] Hereinafter, the present application will be specifically described by showing examples and comparative examples, but the present application is not limited by the following examples. Note that "normal pressure" means 101.3 kPa, and "normal temperature" means 25°C.

[0221] [Mean fiber diameter, mean fiber length, and mean aspect ratio of various cellulose fibers]

[0222] Depending on the size of the cellulose fiber to be measured, either of the following two measurement methods is selected and measured.

[0223] (1) Deionized water or N,N-dimethylformamide (DMF) was added to the cellulose fiber to be measured to prepare a dispersion liquid having a cellulose fiber content of 0.0001 mass%. The dispersion liquid was dropped on mica and dried to obtain an observation sample, and an atomic force microscope (AFM) (Nanoscope II Tapping mode AFM manufactured by Digital instrument; probe: Point Probe (NCH) manufactured by NANOSENSORS) was used to measure the fiber height (height difference between the presence of the fiber and the absence of the fiber) of the cellulose fiber in the observation sample. At this time, in the microscope image in which the cellulose fiber could be confirmed, 100 cellulose fibers were selected, and the mean fiber diameter was calculated from the fiber height thereof. The mean fiber length was calculated from the distance in the fiber direction. The mean aspect ratio was calculated from the mean fiber length / mean fiber diameter. The height analyzed from the image obtained by AFM was regarded as the fiber diameter.

[0224] (2) To the cellulose fiber as the measurement target, deionized water was added to prepare a dispersion liquid having a cellulose fiber content of 0.01 mass%. The dispersion liquid was measured using a wet dispersion type image analysis particle size distribution meter (manufactured by JASCO INTERNATIONAL Co., Ltd., IF-3200) under the following conditions: front lens, 2 times; telecentric zoom lens, 1 time; image resolution, 0.835 μm / pixel; syringe inner diameter, 6515 μm; spacer thickness, 500 μm; image recognition mode, ghost; threshold value, 8; analysis sample amount, 1 mL; and sampling, 15%. Further, when the cellulose fiber was approximated to a rectangle, the length of the short axis was taken as the fiber diameter, and the length of the long axis was taken as the fiber length, and each value was measured for 100 cellulose fibers, and the average value was calculated.

[0225] [Anionic group content of various cellulose fibers]

[0226] A 0.5 g sample of the cellulose fiber as the measurement target was placed in a beaker, deionized water or a mixed solvent of methanol / deionized water = 2 / 1 (volume ratio) was added to make the total 55 mL, and 5 mL of a 0.01 M sodium chloride aqueous solution was added thereto to prepare a dispersion liquid. The dispersion liquid was stirred until the cellulose fiber as the measurement target was sufficiently dispersed. To the dispersion liquid, 0.1 M hydrochloric acid was added to adjust the pH to 2.5 to 3, and using an automatic titrator (manufactured by Toa DKK Co., Ltd., AUT-701), a 0.05 M sodium hydroxide aqueous solution was added dropwise to the dispersion liquid under the condition that the waiting time was 60 seconds, and the conductivity and the pH were measured every 1 minute. The measurement was continued until the pH became about 11, and a conductivity curve was obtained. From the conductivity curve, the sodium hydroxide titration amount was calculated, and the anionic group content of the cellulose fiber as the measurement target was calculated by the following equation.

[0227] Anionic group content (mmol / g) = [sodium hydroxide aqueous solution titration amount (mL) x sodium hydroxide aqueous solution concentration (0.05 M)] / [mass of the cellulose fiber as the measurement target (0.5 g)]

[0228] [Confirmation of crystal structure in various cellulose fibers]

[0229] The crystal structure of various cellulose fibers such as cellulose fiber, anion-modified cellulose fiber, or modified cellulose fiber was confirmed by measuring using a diffractometer (manufactured by RIGAKU Co., Ltd., MiniFlex II) under the following conditions.

[0230] Measurement of pellet preparation conditions: The cellulose fiber as the target was subjected to pressure in the range of 10 to 20 MPa using a tablet molding machine to prepare a tablet having an area of 320 mm 2X: Smoothed pellets with a thickness of 1 mm.

[0231] X-ray diffraction analysis conditions: Step angle 0.01°, scan speed 10° / minute, measurement range: diffraction angle 2θ = 5-40°

[0232] X-ray source: Cu / Kα radiation, tube voltage: 15 kv, tube current: 30 mA

[0233] Peak splitting conditions: After removing background noise, fitting was performed using a Gaussian function so that the error between 2θ = 13-23° would be within 5%.

[0234] The crystallinity of the cellulose I crystal structure was calculated using the area of the X-ray diffraction peak obtained by the above peak splitting, based on the following formula (A).

[0235] Cellulose I crystallinity (%) = [I cr / (I cr + I am )] x 100 (A)

[0236] [Note that I cr represents the area of the diffraction peak of the crystal plane (002 plane) (diffraction angle 2θ = 22-23°) in X-ray diffraction, and I am represents the area of the diffraction peak of the amorphous portion (diffraction angle 2θ = 18.5°)]

[0237] [Modified cellulose fibers and introduction rate of modified groups in microfibrillated modified cellulose fibers]

[0238] After drying the modified cellulose fibers or the microfibrillated modified cellulose fibers using a freeze dryer (manufactured by Tokyo Rikakikai Co., Ltd.; FDU-2110) for 16 hours, pellets with a diameter of 7 mm were produced using a pelletizer (manufactured by ST Japan Co., Ltd.; Pixie tabletop small oil press) at a pressure of about 2 tons. The FTIR (Fourier Transform Infrared) spectrum of the obtained pellets was measured using a Fourier transform infrared spectrometer (manufactured by Thermo Co.; NICOLET iS5). For the C=O stretching vibration of the carboxylic acid occurring around 1730 cm -1 , the amide occurring around 1660 cm -1 , and the C=O stretching vibration of the amide occurring around 1620 cm -1The spectrum of the O-H bending vibration of water in the vicinity was separated into components by fitting analysis using an analysis software (manufactured by HULINKS Corporation; igor pro 8) with the formula shown in the following Formula 1. Then, the total of the obtained peak area ratio of each of the carboxylic acid and the amide was set to 100 mol%, and the introduction rate (mol%) of the modified group in the modified cellulose fiber or the fibrillated modified cellulose fiber was calculated by the following formula.

[0239] [Formula 1]

[0240]

[0241] Here, v and v c are the wave number and the center wave number of the peak, respectively, and ω is the width of the peak. In addition, Abs0 and a are the intercept and the slope of the baseline correction, respectively.

[0242] [Solid content ratio in dispersion, dispersion body, suspension, or mixture]

[0243] The sample was heated under normal pressure at 150°C, and the mass of the sample was measured every 30 seconds. The heating was ended at the time point at which the mass reduction rate of the sample reached 0.1% or less, and the residual fraction at that time point was taken as the solid content amount. The percentage of the value obtained by dividing the solid content amount by the mass of the sample before heating was taken as the solid content ratio.

[0244] [Glucose portion content ratio in mixture, dispersion body, or dispersion]

[0245] The glucose portion content ratio in the mixture, the dispersion body, or the dispersion was calculated by the following formula. Note that, for convenience of explanation, Step 1 is referred to as “1st amide reaction”, and Step 2 is referred to as “2nd amide reaction”. In addition, the amine used in the 1st amide reaction is referred to as “1st amine”, and the amine used in the 2nd amide reaction is referred to as “2nd amine”.

[0246] Glucose portion content ratio (mass%) in dispersion or mixture after 1st amide reaction

[0247] = 1000 x 100 x solid content ratio (mass%) in dispersion / [1000 x 100 + molecular weight (g / mol) of 1st amine x anionic group content (mmol / g) of short fiberized anionically modified cellulose fiber x modified group introduction rate (mol%) at the end of 1st amide reaction] ··· (Formula 2)

[0248] Glucose portion content ratio (mass%) in dispersion body or dispersion after 2nd amide reaction

[0249] = 1000 x 100 x solid content in the dispersion or dispersion liquid (% by mass) / [1000 x 100 + molecular weight of the 1st amine (g / mol) x anionic group content of the short-fiberized anionically modified cellulose fiber (mmol / g) x modification group introduction rate at the end of the 1st amidation reaction (mol%) + molecular weight of the 2nd amine (g / mol) x anionic group content of the short-fiberized anionically modified cellulose fiber (mmol / g) x increase in modification group introduction rate by the 2nd amidation reaction (mol%)] (Formula 3)

[0250] [Transmittance of dispersion]

[0251] The transmittance of the dispersion in each of the examples and comparative examples was measured in the following manner, and the transparency thereof was evaluated. The measurement of the transmittance was performed at normal temperature and pressure.

[0252] Specifically, 3 mL of the dispersion to be measured was added to a quartz cell having an optical path length of 10 mm, and immediately thereafter, the absorbance at a wavelength of 660 nm was measured using a double-beam spectrophotometer (manufactured by Hitachi High-Tech Science, "U-2910"). The medium used for the preparation of each dispersion was used as a blank sample (i.e., light transmittance of 100%), and the light transmittance (%) was calculated from the absorbance of each dispersion.

[0253] [Anionically modified cellulose fiber]

[0254] An anionically modified cellulose fiber having the physical property values described in Table 1 was used as a raw material.

[0255] [Table 1]

[0256]

[0257] The anionically modified cellulose fiber can be prepared, for example, by the following TEMPO oxidation treatment.

[0258] [TEMPO oxidation treatment]

[0259] A bleached kraft pulp fiber 10 g of a conifer as a natural cellulose fiber, which is a raw material, and deionized water 990 g were weighed into a 2-L PP (polypropylene) beaker equipped with a mechanical stirrer and stirring blade, and stirred at 25°C and 100 rpm for 30 minutes. Then, to the pulp fiber 10 g, TEMPO 0.13 g, sodium bromide 1.3 g, and 10.5 mass% sodium hypochlorite aqueous solution 35.5 g were added in this order. Then, constant pH titration was performed using an automatic titrator, and 0.5M sodium hydroxide aqueous solution was added to maintain the pH at 10.5. The reaction was performed at 25°C and 100 rpm for 120 minutes. Then, while stirring, 0.01M hydrochloric acid was added to the suspension to make the pH 2. Then, the solid component was separated by suction filtration. The operation of dispersing the solid component in deionized water and separating the solid component by suction filtration was repeated until the conductivity of the filtrate became 200 μS / cm or less. The obtained solid component can be subjected to dewatering treatment to obtain an anion-modified cellulose fiber.

[0260] [Preparation of a water suspension of a short-fiberized anion-modified cellulose fiber]

[0261] An anion-modified cellulose fiber having the physical property values described in Table 1 was subjected to a short-fiberization treatment to prepare a suspension of a short-fiberized anion-modified cellulose fiber having the physical property values described in Table 2. This short-fiberized anion-modified cellulose fiber was used as a raw material of a modified cellulose fiber.

[0262] [Table 2]

[0263]

[0264] Note that since the content ratio of the glucose portion in the above suspension is the content ratio before the amidation reaction, the solid component content ratio in the suspension is regarded as the content ratio of the glucose portion in the suspension.

[0265] (Suspension of a short-fiberized anion-modified cellulose fiber 1)

[0266] The short-fiberized anion-modified cellulose fiber 1 can be prepared by the following method.

[0267] A suspension of 144.5 g of an anion-modified cellulose fiber having the property values described in Table 1 in an amount of 1000 g of deionized water was diluted, 1.4 g of 35% hydrogen peroxide water (1 part by mass of hydrogen peroxide with respect to 100 parts by mass of the solid content of the raw cellulose fiber) was added thereto, and the pH was adjusted to 12 using a 1 M sodium hydroxide aqueous solution. Then, alkaline hydrolysis treatment was performed at 80°C for 2 hours (the solid content in the suspension of the anion-modified cellulose fiber was 4.3% by mass). After the suspension was cooled to room temperature, the solid content was separated by suction filtration. The operation of dispersing the solid content in deionized water and then separating the solid content by suction filtration was repeated until the conductivity of the filtrate became 200 μS / cm or less. In a manner such that the solid content in the suspension became 5% by mass, deionized water was added to the suspension, and stirring was performed at 95°C for 12 hours, after which it was cooled to room temperature. The water suspension obtained was subjected to centrifugal separation to remove the supernatant, whereby a suspension of short-fiberized anion-modified cellulose fiber 1 described in Table 2 was obtained.

[0268] (Suspension of short-fiberized anion-modified cellulose fiber 2)

[0269] To a suspension of an anion-modified cellulose fiber having the property values described in Table 1, deionized water was added in a manner such that the solid content in the suspension became 5% by mass, and stirring was performed at 95°C for 24 hours, after which it was cooled to 25°C. The supernatant was removed by centrifugal separation (manufactured by Hitachi Koki Co., Ltd., CR21G III, centrifugal acceleration 10000 G, 1 minute, and the same conditions below) of the water suspension obtained. To the suspension obtained by removing the supernatant, 840 g of water was added so that the solid content in the mixture became 4% by mass, and stirring was performed for 3 hours. To this, 4 g of sodium borohydride was added and stirring was performed for 3 hours, and the supernatant was removed by centrifugal separation. Further, the operation of adding 360 g of water to the precipitate obtained so as to suspend it and then removing the supernatant by centrifugal separation was repeated three times, and a water suspension of short-fiberized anion-modified cellulose fiber having a solid content of 23.8% by mass was obtained.

[0270] To the water suspension 6.3 g, 30 g of 1-methoxy-2-propanol (PGME) was added so as to suspend it, and the supernatant was removed by centrifugal separation. Further, the operation of adding 30 g of PGME to the precipitate obtained so as to suspend it and then removing the supernatant by centrifugal separation was repeated three times, and a suspension of short-fiberized anion-modified cellulose fiber 2 having a solid content of 16.5% by mass was obtained.

[0271] Example 1, Example 2, Comparative Example 1

[0272] (1st amide reaction)

[0273] To a beaker equipped with a magnetic stirrer, a stirring bar, was added 6.0 g of the suspension of the short-fiberized anion-modified cellulose fiber 1 described in Table 3 or Table 4, and 1 equivalent of the 1st amine described in Table 3 or Table 4 with respect to the carboxyl group of the short-fiberized anion-modified cellulose fiber, 1 equivalent of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM) as a condensing agent, and 0.5 equivalent of N-methylmorpholine (NMM) as a catalyst, and further, 24 g of PGME was added to obtain a mixture. The content ratio of the anion-modified cellulose fiber (i.e., the glucose moiety itself) in the mixture, i.e., in the reaction solution at the start of the modification step, was 5.0 mass%.

[0274] The obtained mixture was stirred at 25°C for 16 hours to perform the 1st amidation reaction. After the completion of the reaction, the supernatant was removed from the obtained mixture by centrifugal separation to obtain a suspension.

[0275] (1st purification)

[0276] The suspension obtained by the above 1st amidation reaction was suspended by adding 30 g of a 0.1M aqueous hydrochloric acid solution, and the supernatant was removed by centrifugal separation to thereby remove the unreacted amine. Further, the operation of suspending the obtained suspension by adding 30 g of methyl ethyl ketone (MEK) and removing the supernatant by centrifugal separation was repeated three times to obtain a suspension of modified cellulose fiber in which the 1st amine was bonded to the anion-modified cellulose fiber via an amide bond.

[0277] (2nd amidation reaction)

[0278] To a beaker equipped with a magnetic stirrer, a stirring bar, was added the MEK suspension of the modified cellulose fiber after the above 1st purification, and 1 equivalent of the amine described in Table 3 or Table 4 with respect to the total of the carboxyl group and the amide group of the modified cellulose fiber added as a raw material for the 2nd amidation reaction, 1 equivalent of DMTMM, and 0.5 equivalent of NMM, and further, MEK was added until the content ratio of the glucose moiety in the mixture became 5.0 mass%. Note that the total of the carboxyl group and the amide group of the above modified cellulose fiber was calculated assuming that all of the carboxyl groups that reacted in the 1st amidation reaction were converted into amide groups.

[0279] The obtained mixture was stirred at 25°C for 16 hours to perform the 2nd amidation reaction. After the completion of the reaction, the supernatant was removed from the obtained mixture by centrifugal separation to obtain a suspension.

[0280] (2nd purification)

[0281] The suspension obtained by the second amidation reaction was suspended by adding 30 g of a 0.1 M aqueous hydrochloric acid solution, and the supernatant was removed by centrifugation. Furthermore, the procedure of adding 30 g of PGME to the suspension and then removing the supernatant by centrifugation was repeated three times to wash the suspension. This yielded a suspension of modified cellulose fibers in which two amines were bonded to the anionic modified cellulose fibers via amide bonds.

[0282] (Micro-processing)

[0283] Utilize PGME to dilute the suspension of the modified cellulose fiber obtained by the above-mentioned second purification, confirm the solid content rate of the suspension obtained. Then, in a manner that the suspension contains modified cellulose fiber (1g in terms of glucose portion), PGME 49.5g, the above-mentioned suspension and PGME are mixed. 49.5g of epoxy resin is added thereto. Using a high-pressure homogenizer, the obtained mixture is subjected to 5 dispersion treatments at 150MPa, thereby obtaining an epoxy resin PGME solution dispersion of the micronized modified cellulose fiber with a glucose portion content of 1% by mass.

[0284] Comparative Example 2

[0285] In Comparative Example 1, except that the second amidation reaction and the second purification were not performed and the suspension of modified cellulose fibers obtained after the first purification was subjected to a micronization treatment, an epoxy resin PGME solution dispersion of modified cellulose fibers having a glucose moiety content of 1% by mass was obtained by the same operation as in Comparative Example 1.

[0286] Comparative Example 3

[0287] In Example 2, except that the second amidation reaction and the second purification were not carried out and the suspension of modified cellulose fibers obtained after the first purification was subjected to a micronization treatment, an epoxy resin PGME solution dispersion of modified cellulose fibers having a glucose moiety content of 1% by mass was obtained by the same operation as in Example 2.

[0288] Comparative Example 4

[0289] An epoxy resin DMF solution dispersion of modified cellulose fibers having a glucose moiety content of 1% by mass was obtained by the same operation as in Comparative Example 3, except that N,N-dimethylformamide (DMF) was used instead of PGME during the micronization treatment.

[0290] Example 3

[0291] (First Amidation Reaction)

[0292] The first amidation reaction was performed by the same method as the first amidation reaction of Example 1, except that the first amine was changed to the amine of Table 3. After the reaction was completed, a suspension was obtained by removing the supernatant from the obtained mixture by centrifugal separation.

[0293] (first purification)

[0294] The same operation as the first purification of Example 1 was performed, except that PGME was used instead of MEK, to obtain a PGME suspension of modified cellulose fibers in which the first amine was bonded to the anionically modified cellulose fibers via an amide bond.

[0295] (second amidation reaction)

[0296] The second amidation reaction was performed under the same conditions as the method described in Example 1, using the PGME suspension of the modified cellulose fibers after the first purification described above as the raw material for the second amidation reaction, the second amine described in Table 3, and using PGME instead of MEK, to obtain a suspension.

[0297] (second purification)

[0298] The same operation as the second purification of Example 1 was performed, using DMF instead of PGME, for the precipitate obtained by removing the supernatant after the reaction was completed by centrifugal separation, to obtain a suspension of modified cellulose fibers in which two kinds of amines were bonded to the anionically modified cellulose fibers via amide bonds.

[0299] (minutization treatment)

[0300] The same operation as the second purification of Example 1 was performed, using DMF instead of PGME, for the suspension of modified cellulose fibers obtained by the above-mentioned second purification, to obtain an epoxy resin DMF solution dispersion of minutized modified cellulose fibers having a glucose portion content of 1 mass%.

[0301] Example 4

[0302] In Example 1, MEK was used instead of PGME at the time of the first amidation reaction, and the first amine was changed to the amine described in Table 3, and the first amidation reaction, the first purification, the second amidation reaction, the second purification, and the minutization treatment were performed by the same method as Example 1, to obtain an epoxy resin PGME solution dispersion of modified cellulose fibers having a glucose portion content of 1 mass%.

[0303] Comparative Example 5

[0304] In Example 1, in the 1st amidation reaction, MEK was used instead of PGME, and the 1st amine and the 2nd amine were changed to the amines described in Table 4, and, except for this, the 1st amidation reaction, the 1st purification, the 2nd amidation reaction, the 2nd purification, and the fine treatment were performed by the same method as in Example 1, to obtain an epoxy resin PGME solution dispersion of modified cellulose fiber having a glucose moiety content of 1 mass%.

[0305] Comparative Example 6

[0306] In Example 4, the suspension of the modified cellulose fiber obtained after the 1st purification was subjected to the fine treatment without performing the 2nd amidation reaction and the 2nd purification, and, except for this, an epoxy resin PGME solution dispersion of modified cellulose fiber having a glucose moiety content of 1 mass% was obtained by the same operation as in Example 4.

[0307] Example 5

[0308] (1st amidation reaction)

[0309] The 1st amidation reaction was performed by the same method as in the 1st amidation reaction of Example 1, except for changing the 1st amine to the amine in Table 3 and using a suspension of 9.1 g of the short-fiberized anion-modified cellulose fiber 2.

[0310] (1st purification)

[0311] The same operation as in the 1st purification of Example 1 was performed, except for using DMF instead of MEK, to obtain a DMF suspension of modified cellulose fiber in which the 1st amine was bonded to the anion-modified cellulose fiber via an amide bond.

[0312] (2nd amidation reaction)

[0313] A DMF suspension of the modified cellulose fiber after the 1st purification described above was used as a raw material for the 2nd amidation reaction, and the 2nd amine described in Table 3 was used, and DMF was used instead of MEK, and, except for this, the 2nd amidation reaction was performed under the same conditions as described in Example 1 to obtain a suspension.

[0314] (2nd purification)

[0315] For the precipitate obtained by removing the supernatant by centrifugal separation after the reaction, the same operation as in the 2nd purification of Example 1 was performed, except for using acetone instead of PGME, to obtain a suspension of modified cellulose fiber in which two kinds of amines were bonded to the anion-modified cellulose fiber via amide bonds.

[0316] (Fine treatment)

[0317] The suspension of the modified cellulose fiber obtained by the above-mentioned second purification was diluted with acetone, and the glucose portion content of the obtained suspension was confirmed. The above-mentioned suspension and acetone were mixed so as to become a suspension containing the modified cellulose fiber (1 g in terms of the glucose portion), and 999 g of acetone. The obtained suspension was subjected to dispersion treatment 5 times at 150 MPa using a high-pressure homogenizer (manufactured by YOSHIDAMA-CHINERY CO., LTD., NanoVater L-ES), whereby an acetone dispersion of the modified cellulose fiber was obtained. To the obtained dispersion, 99 g of a mercaptan compound was added and stirred for 10 minutes.

[0318] The obtained dispersion was charged in an Erlenmeyer flask, the Erlenmeyer flask was heated by a water bath at 90°C, and the Erlenmeyer flask was stirred using a rotary evaporator, and acetone was removed under the condition of an absolute pressure of 2 kPa, whereby a mercaptan compound dispersion of the modified cellulose fiber having a glucose portion content of 1 mass% was obtained.

[0319] Comparative Example 7

[0320] (minutization treatment)

[0321] To a water suspension of the anion-modified cellulose fiber 1 having the physical property values described in Table 1, 10577 g of deionized water was added, and a water suspension having a solid content of 0.5 mass% was obtained. To the water suspension, sodium hydroxide was added at 1 equivalent relative to the carboxyl group of the anion-modified cellulose fiber. The obtained water suspension was subjected to dispersion treatment 2 times at 150 MPa using a high-pressure homogenizer (manufactured by YOSHIDAMA-CHINERY CO., LTD., NanoVater L-ES), whereby a water dispersion of the minutized anion-modified cellulose fiber was obtained.

[0322] Then, 245 g of a 1M aqueous hydrochloric acid solution was added, and the reaction was performed at ordinary temperature for 1 hour. After the completion of the reaction, reprecipitation was performed using acetone and filtration, and then washing was performed using acetone / deionized water (mass ratio: 1 / 1), and hydrochloric acid and salts were removed. Finally, PGME was added and filtration was performed, and a precipitate of the minutized anion-modified cellulose fiber (anion-modified cellulose fiber content of 5.0 mass%) was obtained. The average fiber diameter of the minutized anion-modified cellulose fiber contained in the precipitate was 3 nm, and the average fiber length was 600 nm.

[0323] (amidation reaction)

[0324] A mixture of the microfibrillated anion-modified cellulose fiber having a glucose moiety content of 5.0 mass% was produced under the same conditions as the first amidation reaction of Example 1, using the precipitate of the microfibrillated anion-modified cellulose fiber described above instead of the suspension of the short-fiberized anion-modified cellulose fiber, and without adding PGME. However, the reaction liquid gelled at the time of mixing and stirring could not be performed. Therefore, the amidation reaction could not be completed.

[0325] The main reaction conditions and results are shown in Table 3 and Table 4.

[0326] [Table 3]

[0327]

[0328] [Table 4]

[0329]

[0330] As is apparent from Table 3, according to the production method of the present application, it is possible to produce microfibrillated modified cellulose fibers having high transmittance, that is, high dispersibility (Example 1, Example 2).

[0331] On the other hand, it is known that in Comparative Example 1, in which modified cellulose fibers were produced by first modifying using an amine having a larger molecular weight and then modifying using an amine having a smaller molecular weight, the transmittance of the obtained dispersion was inferior to that of Example 1, Comparative Example 2 (in which an amine having a larger molecular weight was used alone), and the dispersibility of the obtained microfibrillated modified cellulose fibers was low. Furthermore, since the introduction rate of the modification group was also lower than that of Example 1, it is known that the efficiency of amidation was also inferior to that of Example 1.

[0332] Furthermore, as is apparent from Comparative Example 3, if an anion-modified cellulose fiber having an average fiber diameter of less than 1 μm is used, the reaction liquid gels and the amine cannot be bonded by an amide bond, and the production of the modified cellulose fiber itself is extremely difficult. Note that if the amount of the anion-modified cellulose fiber in the reaction liquid is reduced, gelling does not occur. From this, it is known that by selecting an anion-modified cellulose fiber having a prescribed average fiber diameter for the bonding by an amide bond, it is possible to produce a modified cellulose fiber with good yield.

[0333] Details of each component are described below.

[0334] DMTMM: manufactured by Suzhou Haofan Biological Co., Ltd., 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride

[0335] NMM: manufactured by FUJIFILM and Otsuka Pharmaceutical Co., Ltd., N-methylmorpholine

[0336] Epoxy resin: manufactured by Mitsubishi Chemical Corporation, jER-828

[0337] Thiol compound: manufactured by Fuji Pharma Wako Pure Chemical Industries, Ltd., pentaerythritol tetrakis (3-mercaptopropionate), molecular weight 488

[0338] ·amine

[0339] Octylamine: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., molecular weight 129.24

[0340] Benzylamine: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., molecular weight 107.15

[0341] Diphenylpropylamine: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., molecular weight 211.31

[0342] EOPO amine 1: manufactured by Huntsman Corporation, JEFFAMINE M2070, molecular weight 2000

[0343] EOPO amine 2: manufactured by Huntsman, JEFFAMINE M3000, molecular weight 3000

[0344] EOPO amine 3: manufactured by Huntsman, JEFFAMINE M1000, molecular weight 1000

[0345] Industrial applicability

[0346] The modified cellulose fibers and micronized modified cellulose fibers produced by the production method of the present invention have high dispersibility and, when blended with resins and molded, exhibit an effect that enhances mechanical strength, making them suitable for various fillers and the like. Furthermore, resin compositions containing dispersions of these micronized modified cellulose fibers are suitable for various industrial applications, including daily necessities, home appliance parts, packaging materials for home appliance parts, and automotive parts.

Claims

1. A method for producing modified cellulose fibers, comprising a modification step of amide bonding two or more amines having different molecular weights to anionic modified cellulose fibers; and The average fiber diameter of the anionically modified cellulose fibers is 1 μm or more and 100 μm or less, In the modification step, the following step 2 is performed after the following step 1, Step 1: A step of amide bonding an amine including an amine with the smallest molecular weight to an anionically modified cellulose fiber Step 2: After step 1, a step of subjecting an amine including an amine having the highest molecular weight to an anionically modified cellulose fiber to amide bonding.

2. The method for producing modified cellulose fibers according to claim 1, wherein: The anionically modified cellulose fibers have an average fiber length of 1 μm or more and 1000 μm or less.

3. The method for producing modified cellulose fibers according to claim 1 or 2, wherein: Anionically modified cellulose fibers have carboxyl groups.

4. The method for producing modified cellulose fibers according to any one of claims 1 to 3, wherein: In the modification step, the content of the anionically modified cellulose fibers in the reaction solution at the start of the step is 1% by mass or more.

5. The method for producing modified cellulose fibers according to any one of claims 1 to 4, wherein: The amine has one or more modifying groups selected from hydrocarbon groups and polymer groups.

6. The method for producing modified cellulose fibers according to any one of claims 1 to 5, wherein: The molecular weight of the amine with the smallest molecular weight is 20 or more and 2000 or less.

7. The method for producing modified cellulose fibers according to any one of claims 1 to 6, wherein: The molecular weight of the amine having the highest molecular weight is 100 or more and 4000 or less.

8. The method for producing modified cellulose fibers according to any one of claims 1 to 7, wherein: The molecular weight ratio of the amine with the largest molecular weight to the amine with the smallest molecular weight, that is, the molecular weight of the amine with the largest molecular weight / the molecular weight of the amine with the smallest molecular weight, is greater than 1 and 100 or less.

9. The method for producing modified cellulose fibers according to any one of claims 5 to 8, wherein: The introduction rate of the modifying groups in the modified cellulose fibers is 40 mol % or more and 100 mol % or less.

10. The method for producing modified cellulose fibers according to any one of claims 5 to 9, wherein: Among the modifying groups introduced into the modified cellulose fiber, the introduction rate of the modifying group with the smallest molecular weight introduced through bonding with the amine with the smallest molecular weight is 10 mol % or more and 95 mol % or less.

11. The method for producing modified cellulose fibers according to any one of claims 1 to 10, wherein: The amount of amine in the step 1 is 0.01 molar equivalents or more and 10 molar equivalents or less.

12. The method for producing modified cellulose fibers according to any one of claims 1 to 11, wherein: The amount of amine in the step 2 is 0.01 molar equivalents or more and 10 molar equivalents or less.

13. The method for producing modified cellulose fibers according to any one of claims 5 to 12, wherein: The polymer group is one or more selected from a polyoxyalkylene structure and a polysiloxane structure.

14. The method for producing modified cellulose fibers according to any one of claims 5 to 13, wherein: The polymer group is a structure represented by the following formula: Where 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 blocks, a is a positive number representing the average added mole number of EO, and b is a positive number representing the average added mole number of PO. 15 . A method for producing micronized modified cellulose fibers, comprising the step of micronizing the modified cellulose fibers obtained by the production method according to claim 1 .

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