Fine cellulose fiber composite

Abstract

To provide a fine cellulose fiber complex that can provide a resin composition having excellent heat resistance when blended in various resins, and a resin composition containing the complex.SOLUTION: The present invention provides a fine cellulose fiber complex that has a fine cellulose fiber with a carboxy group content of 0.1 mmol / g or more, the carboxy group bonded to a modifying group, where the fine cellulose fiber complex has an average aspect ratio of 1 or more and 150 or less. There is also provided a resin composition containing the fine cellulose fiber complex and a resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a fine cellulose fiber composite. More specifically, the present invention relates to a fine cellulose fiber composite that can be suitably incorporated as a nanofiller in daily necessities, home appliance parts, automobile parts, etc., and a resin composition containing the fine cellulose fiber composite. Furthermore, the present invention relates to a resin molded article obtained by molding the resin composition. [Background technology]

[0002] Traditionally, plastic materials derived from petroleum, a finite resource, have been widely used, but in recent years, technologies with less environmental impact have come into the spotlight. Against this technological backdrop, materials made from cellulose fiber, a naturally occurring biomass, have been attracting attention.

[0003] For example, Patent Document 1 reports that by blending a fine cellulose fiber composite with an adsorbed surfactant with various resins, a composite material having both high mechanical strength and transparency can be obtained. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-140738 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional composite materials are required to have further improved heat resistance when used in various molded products such as home appliance parts, automobile parts, and electronic materials.

[0006] The present invention relates to a fine cellulose fiber composite that can provide a resin composition having excellent heat resistance when blended with various resins, and a resin composition containing the composite. The present invention also relates to a resin molded article obtained by molding the resin composition. [Means for solving the problem]

[0007] As a result of intensive research to solve the above-mentioned problems, the inventors discovered that by mixing a surface-modified fine cellulose fiber composite having a specific aspect ratio with various resins, the resulting resin composition has excellent heat resistance, and thus completed the present invention.

[0008] That is, the present invention relates to the following [1] to [3]. [1] A fine cellulose fiber composite having an average aspect ratio of 1 or more and 150 or less, in which modifying groups are bonded to the carboxy groups of fine cellulose fibers having a carboxy group content of 0.1 mmol / g or more. [2] A resin composition containing a resin and the fine cellulose fiber composite described in [1]. [3] A resin molded product obtained by extrusion molding, injection molding, press molding, cast molding or solvent casting of the resin composition described in [2]. [Effects of the Invention]

[0009] The fine cellulose fiber composite of the present invention can provide a resin composition having excellent heat resistance when blended with various resins. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Fine cellulose fiber composite] The fine cellulose fiber composite of the present invention is a carboxy group-containing fine cellulose fiber in which a modifying group, which will be described later, is bonded to the carboxy group, and the composite has a specific aspect ratio.

[0011] Conventional microfibrillated cellulose fiber composites are typically prepared by conjugating microfibrillated cellulose fibers having an average aspect ratio of approximately 300 with various modifying groups. However, it has been found that while such composites exhibit excellent effects due to the modifying groups, their heat resistance is insufficient. On the other hand, the present inventors have discovered that when a composite having a modifying group has a specific average aspect ratio, the composite can become a material with excellent heat resistance without losing the effects of the modifying group. While the detailed reasons for this effect are unknown, it is presumed that microfibrillated cellulose fiber composites with an average aspect ratio within the above range exhibit excellent heat resistance because the weak parts present in natural cellulose fibers, such as amorphous regions, are cut and shortened to form short fibers, resulting in an increased overall distribution of crystalline regions. Furthermore, the short fiber length of the resulting composite improves dispersibility in the resin composition, fully demonstrating its filler effect and further enhancing the heat resistance while providing excellent mechanical strength.

[0012] <Fine cellulose fiber> (carboxyl group content) The fine cellulose fibers constituting the fine cellulose fiber composite of the present invention have a carboxy group content of 0.1 mmol / g or more, but from the viewpoint of stable micronization and introduction of modifying groups, it is preferably 0.4 mmol / g or more, more preferably 0.6 mmol / g or more, and even more preferably 0.8 mmol / g or more. Furthermore, from the viewpoint of improving handleability, it is preferably 3 mmol / g or less, more preferably 2 mmol / g or less, even more preferably 1.8 mmol / g or less, even more preferably 1.5 mmol / g or less, and even more preferably 1.2 mmol / g or less. The term "carboxy group content" refers to the total amount of carboxy groups in the cellulose constituting the fine cellulose fibers, and is specifically measured by the method described in the Examples below.

[0013] (average fiber diameter) The average fiber diameter of the fine cellulose fibers constituting the fine cellulose fiber composite of the present invention is preferably 0.1 nm or more, more preferably 0.5 nm or more, even more preferably 1 nm or more, even more preferably 2 nm or more, and still more preferably 3 nm or more, from the viewpoint of improving the heat resistance and mechanical strength when the composite is incorporated into a resin to form a resin composition. Also, from the viewpoint of improving the heat resistance when the composite is incorporated into a resin to form a resin composition, it is preferably 100 nm or less, more preferably 50 nm or less, even more preferably 20 nm or less, even more preferably 10 nm or less, even more preferably 6 nm or less, and still more preferably 5 nm or less.

[0014] (average fiber length) The length (average fiber length) of the fine cellulose fibers constituting the fine cellulose fiber composite of the present invention is preferably 150 nm or more, more preferably 200 nm or more, from the viewpoint of improving the heat resistance when the composite is incorporated into a resin to form a resin composition. Also, from the viewpoint of improving the heat resistance when the composite is incorporated into a resin to form a resin composition, the length (average fiber length) is preferably 1000 nm or less, more preferably 750 nm or less, even more preferably 500 nm or less, and even more preferably 400 nm or less.

[0015] (average aspect ratio) Furthermore, since the fine cellulose fiber composite of the present invention has a specific average aspect ratio, it is preferable that the constituent fine cellulose fibers also have a similar average aspect ratio. The average aspect ratio (fiber length / fiber diameter) of the fine cellulose fibers is preferably 1 or more, more preferably 10 or more, even more preferably 20 or more, even more preferably 40 or more, and even more preferably 50 or more from the viewpoint of improving heat resistance when the composite is incorporated into a resin to form a resin composition. From the viewpoint of improving heat resistance and mechanical strength when the composite is incorporated into a resin to form a resin composition, it is preferably 150 or less, more preferably 140 or less, even more preferably 130 or less, even more preferably 100 or less, even more preferably 95 or less, and even more preferably 90 or less. Furthermore, when the average aspect ratio is within the above range, the standard deviation of the aspect ratio is preferably 60 or less, more preferably 50 or less, and even more preferably 45 or less from the viewpoint of improving heat resistance when the composite is incorporated into a resin to form a resin composition. Although there is no particular lower limit, it is preferably 4 or more from the viewpoint of economic efficiency. In this specification, the average fiber diameter and average fiber length of cellulose fibers can be measured using an atomic force microscope (AFM), and the average aspect ratio can be calculated by dividing the average fiber length by the average fiber diameter. Specifically, this is measured by the method described in the Examples below. Generally, the smallest unit of cellulose nanofibers prepared from higher plants is a 6 × 6 molecular chain packed in an approximately square shape, and therefore the height analyzed in an AFM image can be considered the fiber width.

[0016] (crystallinity) The crystallinity of the fine cellulose fibers is preferably 30% or more, more preferably 35% or more, even more preferably 40% or more, and even more preferably 45% or more, from the viewpoint of improving heat resistance when the composite is incorporated into a resin to form a resin composition. Furthermore, from the viewpoint of improving reaction efficiency, it is preferably 95% or less, more preferably 90% or less, even more preferably 85% or less, and even more preferably 80% or less. In this specification, the crystallinity of cellulose is the cellulose type I crystallinity calculated by the Segal method from the diffraction intensity value obtained by X-ray diffraction, and is defined by the following calculation formula (A): Cellulose type I crystallinity (%) = [(I22.6 - I18.5) / I22.6] x 100 (A) (In the formula, I22.6 represents the diffraction intensity of the lattice plane (002 plane) (diffraction angle 2θ=22.6°) in X-ray diffraction, and I18.5 represents the diffraction intensity of the amorphous portion (diffraction angle 2θ=18.5°).) It should be noted that type I cellulose refers to the crystalline form of natural cellulose, and type I cellulose crystallinity refers to the proportion of crystalline regions in the total cellulose.

[0017] Such fine cellulose fibers may be known or may be prepared separately. For example, natural cellulose fibers may be subjected to an oxidation treatment to incorporate (i.e., introduce) carboxyl groups into the fibers, and then the fibers may be subjected to a known treatment, such as at least one treatment selected from biochemical, chemical, and mechanical treatments, to obtain fine cellulose fibers having a low aspect ratio. The treatment for achieving a low aspect ratio described above is also referred to as a "low aspect ratio treatment." Furthermore, as long as the composite treatment described below can be performed, fine cellulose fibers obtained by a known microfibrillation treatment may be used, and they do not necessarily have the low aspect ratio described above. In this specification, "low aspect ratio" refers to an aspect ratio of 150 or less, and "high aspect ratio" refers to an aspect ratio of more than 150.

[0018] Methods for introducing carboxyl groups into natural cellulose fibers include a method of converting the hydroxyl groups of cellulose into carboxyl groups by oxidizing them, and a method of reacting the hydroxyl groups of cellulose with at least one selected from the group consisting of compounds having carboxyl groups, acid anhydrides of compounds having carboxyl groups, and derivatives thereof.

[0019] The method for oxidizing the hydroxyl groups of the cellulose is not particularly limited, but specific examples include a method in which an N-oxyl compound is used as an oxidation catalyst and a co-oxidant is reacted with the cellulose, as described below, or a method in which the cellulose is heated at a high temperature of 100°C or higher.

[0020] The compound having a carboxy group is not particularly limited, but specific examples include halogenated acetic acids, and examples of halogenated acetic acids include chloroacetic acid.

[0021] The acid anhydrides of compounds having a carboxy group and derivatives thereof are not particularly limited, but examples thereof include acid anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, and adipic anhydride, imidized products of acid anhydrides of compounds having a carboxy group, and derivatives of acid anhydrides of compounds having a carboxyl group.

[0022] In the present invention, the method for introducing carboxyl groups into natural cellulose fibers is preferably a method of oxidizing the hydroxyl groups of cellulose, since this method has excellent selectivity for hydroxyl groups on the fiber surface and the reaction conditions are mild. In particular, a method in which an N-oxyl compound is used as an oxidation catalyst and a co-oxidant is used, as described below, is even more preferred.

[0023] Specifically, the aspect ratio reduction treatment can be carried out by one or more of the following known methods: acid hydrolysis, hydrothermal decomposition, oxidative decomposition, mechanical treatment, enzyme treatment, alkali treatment, UV treatment, and electron beam treatment. Among these, acid hydrolysis, hydrothermal decomposition, and mechanical treatment can be preferably carried out alone or in combination, more preferably, acid hydrolysis and hydrothermal decomposition can be carried out alone or in combination, and even more preferably, acid hydrolysis can be carried out. If the cellulose fibers are not sufficiently fined after the aspect ratio reduction treatment, further known fine-fining treatments can be carried out. Below, treatment methods for acid hydrolysis, hydrothermal treatment, and mechanical treatment are described as examples of aspect ratio reduction treatments.

[0024] Specifically, in the acid hydrolysis treatment, the raw cellulose fiber is brought into contact with an acid to cleave the glycosidic bonds in the cellulose. Preferred acids for contact include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, acetic acid, and citric acid.

[0025] The conditions for the acid hydrolysis can be appropriately set as long as the acid cleaves the glycosidic bonds of cellulose, and are not particularly limited. For example, the amount of acid added is preferably 0.01 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 10 parts by mass or more, relative to 100 parts by mass of the bone-dry mass of the raw cellulose fiber, from the viewpoint of reducing the aspect ratio of cellulose, and 400 parts by mass or less from the viewpoint of economic efficiency and improved yield. The pH of the solution during the treatment is preferably 4 or less, more preferably 2 or less, and even more preferably 1 or less, from the viewpoint of reducing the aspect ratio of cellulose. The treatment temperature is preferably 80°C or more, more preferably 90°C or more, and preferably 120°C or less, more preferably 110°C or less, from the viewpoint of reducing the aspect ratio of cellulose. The treatment time is preferably 0.1 hours or more, preferably 5 hours or less, and more preferably 3 hours or less, from the viewpoint of reducing the aspect ratio of cellulose.

[0026] In the hydrothermal decomposition treatment, specifically, a preferred embodiment is to immerse the raw cellulose fiber in water and heat it.

[0027] The temperature for hydrothermal decomposition is preferably 70°C or higher, more preferably 100°C or higher, and even more preferably 140°C or higher, from the viewpoint of reducing the aspect ratio of cellulose. Furthermore, from the viewpoint of reducing the aspect ratio of cellulose and preventing decomposition, it is preferably 250°C or lower, more preferably 200°C or lower, and even more preferably 180°C or lower. Furthermore, from the viewpoint of reducing the aspect ratio of cellulose, the pressure during treatment is preferably 0.1 MPa [gage] or higher, more preferably 0.2 MPa [gage] or higher, and even more preferably 0.3 MPa [gage] or higher, and preferably 10 MPa [gage] or lower, more preferably 5 MPa [gage] or lower, and even more preferably 3 MPa [gage] or lower. Furthermore, the treatment time is determined based on the amount of pressure required to reduce the aspect ratio of cellulose. From the viewpoint of controlling the reaction ratio, the reaction time is preferably 15 minutes or more, more preferably 1 hour or more, and is preferably 4 hours or less, more preferably 2 hours or less.

[0028] Mechanical treatments include pulverization, and the machine used is, for example, preferably a container-driven media mill such as a planetary ball mill or a rod mill, more preferably a vibration mill, and even more preferably a vibration rod mill, from the viewpoint of treatment efficiency. The treatment time, which depends on the size of the machine used, is preferably 5 minutes or more, more preferably 10 minutes or more, and even more preferably 15 minutes or more from the viewpoint of reducing the aspect ratio of cellulose, and is preferably 12 hours or less, more preferably 4 hours or less, and even more preferably 1 hour or less from the viewpoint of economy,

[0029] After the treatment such as acid hydrolysis, it is preferable to carry out a known micronization treatment.

[0030] <Modification group> The fine cellulose fiber composite of the present invention refers to one in which a modifying group is bound to the surface of the above-mentioned fine cellulose fibers, and this can be obtained, for example, by ionic and / or covalently binding a compound having a modifying group to a carboxy group already present on the surface of the fine cellulose fibers. Examples of the bonding mode to the carboxy group include ionic and covalent bonding. Examples of the covalent bond here include an amide bond, an ester bond, and a urethane bond, and among these, from the viewpoint of obtaining a resin composition with excellent heat resistance, an amide bond is preferred. Therefore, from the viewpoint of obtaining a resin composition with excellent heat resistance, the fine cellulose fiber composite of the present invention is preferably obtained by ionic and / or amide bonding a compound having a modifying group to a carboxy group already present on the surface of the fine cellulose fibers.

[0031] (Compounds having modifying groups) The compound having a modifying group may be any compound having a modifying group as described below, and depending on the bonding mode, for example, the following compounds can be used. In the case of an ionic bond, any of primary amines, secondary amines, tertiary amines, quaternary ammonium compounds, and phosphonium compounds may be used. Among these, from the viewpoint of dispersibility, primary amines, secondary amines, tertiary amines, and quaternary ammonium compounds are preferred. Furthermore, from the viewpoint of reactivity, the anion component of the ammonium compound or phosphonium compound preferably includes halogen ions such as chloride ions and bromide ions, hydrogen sulfate ions, perchlorate ions, tetrafluoroborate ions, hexafluorophosphate ions, trifluoromethanesulfonate ions, and hydroxy ions, more preferably hydroxy ions. In the case of a covalent bond, the following compounds can be used depending on the functional group substituted. In the case of modification to a carboxy group, in the case of an amide bond, either primary amines or secondary amines may be used. In the case of an ester bond, alcohols are preferred, such as butanol, octanol, and dodecanol. In the case of a urethane bond, an isocyanate compound is preferred.

[0032] The modifying group in the present invention may be a hydrocarbon group, a copolymer moiety, or the like. These may be introduced into the fine cellulose fibers either alone or in combination of two or more. From the viewpoint of achieving the desired effect, a fine cellulose fiber composite in which two or more modifying groups are preferably introduced into the fine cellulose fibers is desirable.

[0033] (hydrocarbon group) Examples of the hydrocarbon group include a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, a cyclic saturated hydrocarbon group, and an aromatic hydrocarbon group. From the viewpoints of suppressing side reactions and stability, a chain saturated hydrocarbon group, a cyclic saturated hydrocarbon group, and an aromatic hydrocarbon group are preferred.

[0034] The chain saturated hydrocarbon group may be linear or branched. From the viewpoint of improving heat resistance when the composite is incorporated into a resin to form a resin composition, the number of carbon atoms in the chain saturated hydrocarbon group is preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, still more preferably 6 or more, and even more preferably 8 or more. From the same viewpoint, the number of carbon atoms is preferably 30 or less, more preferably 24 or less, still more preferably 18 or less, and even more preferably 16 or less. Hereinafter, the number of carbon atoms in the hydrocarbon group means the total number of carbon atoms in the entire modifying group.

[0035] Specific examples of the chain saturated hydrocarbon group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, an isobutyl group, a pentyl group, a tert-pentyl group, an isopentyl group, a hexyl group, an isohexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, a dodecyl group, a tridecyl group, a tetradecyl group, an octadecyl group, a docosyl group, and an octacosanyl group. From the viewpoint of improving the heat resistance when a resin composition is prepared by incorporating the group into the resin, preferred are propyl, isopropyl, butyl, sec-butyl, tert-butyl, isobutyl, pentyl, tert-pentyl, isopentyl, hexyl, isohexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, dodecyl, tridecyl, tetradecyl, octadecyl, docosyl, and octacosanyl groups. These may be incorporated alone or in any combination of two or more in any proportion.

[0036] The chain unsaturated hydrocarbon group may be linear or branched. From the viewpoint of handleability, the number of carbon atoms in the chain unsaturated hydrocarbon group is preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more. From the viewpoint of availability, the number of carbon atoms is preferably 30 or less, more preferably 18 or less, even more preferably 12 or less, and even more preferably 8 or less.

[0037] Specific examples of the chain unsaturated hydrocarbon group include ethylene, propylene, butene, isobutene, isoprene, pentene, hexene, heptene, octene, nonene, decene, dodecene, tridecene, tetradecene, and octadecene groups, and from the viewpoint of compatibility with the resin, ethylene, propylene, butene, isobutene, isoprene, pentene, hexene, heptene, octene, nonene, decene, and dodecene groups are preferred. These may be introduced alone or in any combination of two or more in any proportion.

[0038] From the viewpoint of ease of handling, the number of carbon atoms in the cyclic saturated hydrocarbon group is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more. From the viewpoint of availability, the number of carbon atoms is preferably 20 or less, more preferably 16 or less, even more preferably 12 or less, and even more preferably 8 or less.

[0039] Specific examples of cyclic saturated hydrocarbon groups include cyclopropane, cyclobutyl, cyclopentane, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, cyclododecyl, cyclotridecyl, cyclotetradecyl, and cyclooctadecyl groups, and from the viewpoint of compatibility with the resin, preferred are cyclopropane, cyclobutyl, cyclopentane, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, and cyclododecyl groups. These may be introduced alone or in any combination of two or more.

[0040] The aromatic hydrocarbon group is, for example, selected from the group consisting of an aryl group and an aralkyl group. In the aryl group and the aralkyl group, the aromatic ring itself may be substituted or unsubstituted.

[0041] The total number of carbon atoms in the aryl group may be 6 or more, and from the viewpoint of compatibility with the resin, it is preferably 24 or less, more preferably 20 or less, even more preferably 14 or less, even more preferably 12 or less, and even more preferably 10 or less.

[0042] The total number of carbon atoms in the aralkyl group is 7 or more, and from the viewpoint of compatibility with the resin, preferably 8 or more, and from the same viewpoint, preferably 24 or less, more preferably 20 or less, even more preferably 14 or less, even more preferably 13 or less, and even more preferably 11 or less.

[0043] Examples of the aryl group include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, a biphenyl group, a triphenyl group, a terphenyl group, and groups in which these groups are substituted with the substituents described below. These groups may be introduced singly or in any combination of two or more groups in any proportion. Among these, from the viewpoint of compatibility with resins, a phenyl group, a biphenyl group, and a terphenyl group are preferred.

[0044] Examples of aralkyl groups include benzyl, phenethyl, phenylpropyl, phenylpentyl, phenylhexyl, phenylheptyl, and phenyloctyl groups, and groups in which the aromatic group of these groups is substituted with a substituent described below. These groups may be introduced singly or in any combination of two or more groups in any proportion. Among these, benzyl, phenethyl, phenylpropyl, phenylpentyl, phenylhexyl, and phenylheptyl groups are preferred from the viewpoint of compatibility with the resin.

[0045] The primary amine, secondary amine, tertiary amine, quaternary ammonium compound, phosphonium compound, acid anhydride, and isocyanate compound having a hydrocarbon group are commercially available products, or can be prepared according to known methods.

[0046] Specific examples of primary to tertiary amines include ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, butylamine, dibutylamine, hexylamine, dihexylamine, octylamine, dioctylamine, trioctylamine, dodecylamine, didodecylamine, stearylamine, distearylamine, monoethanolamine, diethanolamine, triethanolamine, aniline, benzylamine, octadecylamine, and dimethylbehenylamine. Specific examples of quaternary ammonium compounds include tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetraethylammonium chloride, tetrapropylammonium hydroxide (TPAH), tetrabutylammonium hydroxide (TBAH), tetrabutylammonium chloride, lauryltrimethylammonium chloride, dilauryldimethylchloride, stearyltrimethylammonium chloride, distearyldimethylammonium chloride, cetyltrimethylammonium chloride, and alkylbenzyldimethylammonium chloride. Among these, from the viewpoints of dispersibility and heat resistance, preferred are propylamine, dipropylamine, butylamine, dibutylamine, hexylamine, dihexylamine, octylamine, dioctylamine, trioctylamine, dodecylamine, didodecylamine, distearylamine, tetraethylammonium hydroxide (TEAH), tetrabutylammonium hydroxide (TBAH), tetrapropylammonium hydroxide (TPAH), aniline, octadecylamine, and dimethylbehenylamine, and more preferred are propylamine, dodecylamine, tetrabutylammonium hydroxide (TBAH), aniline, octadecylamine, and dimethylbehenylamine.

[0047] The average bond amount of hydrocarbon groups in the fine cellulose fiber composite is preferably 0.01 mmol / g or more, more preferably 0.05 mmol / g or more, even more preferably 0.1 mmol / g or more, even more preferably 0.3 mmol / g or more, and even more preferably 0.5 mmol / g or more, from the viewpoint of improving heat resistance when the composite is incorporated into a resin to form a resin composition relative to the fine cellulose fibers. Furthermore, from the viewpoint of reactivity, it is preferably 3 mmol / g or less, more preferably 2.5 mmol / g or less, even more preferably 2 mmol / g or less, even more preferably 1.8 mmol / g or less, and even more preferably 1.5 mmol / g or less. Even when a hydrocarbon group selected from a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, and a cyclic saturated hydrocarbon group and an aromatic hydrocarbon group are simultaneously introduced, it is preferable that the individual average bond amounts are within the above-mentioned ranges.

[0048] Furthermore, the introduction rate of hydrocarbon groups, for any modifying group, is preferably 10% or more, more preferably 30% or more, even more preferably 50% or more, even more preferably 60% or more, and even more preferably 70% or more from the viewpoint of obtaining a resin composition with excellent heat resistance, and is preferably 99% or less, more preferably 97% or less, even more preferably 95% or less, and even more preferably 90% or less from the viewpoint of reactivity. Here, when a hydrocarbon group selected from a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, and a cyclic saturated hydrocarbon group and an aromatic hydrocarbon group are introduced simultaneously, it is preferable that the total introduction rate be within the above range, provided that it does not exceed the upper limit of 100%.

[0049] (Copolymerization part) In the present invention, the copolymerization moiety may be, for example, an ethylene oxide / propylene oxide (EO / PO) copolymerization moiety. Here, the EO / PO copolymerization moiety refers to a structure in which ethylene oxide (EO) and propylene oxide (PO) are polymerized randomly or in a block form. For example, when an amine having an EO / PO copolymerization moiety is represented by formula (i) described below, the ethylene oxide (EO) and propylene oxide (PO) have a random or block chain structure. However, when the amine has a structure represented by formula (ii) described below, (EO)a(PO)b, (EO)c(PO)d, and (EO)e(PO)f do not need to be chained.

[0050] From the viewpoint of obtaining a resin composition having excellent heat resistance, the PO content (mol %) in the EO / PO copolymerization portion is preferably 1 mol % or more, more preferably 5 mol % or more, even more preferably 7 mol % or more, and even more preferably 10 mol % or more, and from the same viewpoint, it is preferably 100 mol % or less, more preferably 90 mol % or less, even more preferably 85 mol % or less, even more preferably 75 mol % or less, even more preferably 60 mol % or less, even more preferably 50 mol % or less, even more preferably 40 mol % or less, and even more preferably 30 mol % or less. Note that a PO content of 100 mol % means that the EO / PO copolymerization portion is composed only of PO, and in the present invention, a PO polymerization portion may be introduced.

[0051] From the viewpoint of obtaining a resin composition with excellent heat resistance, the molecular weight of the EO / PO copolymer moiety is preferably 500 or more, more preferably 1,000 or more, and even more preferably 1,500 or more. From the same viewpoint, it is preferably 10,000 or less, 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. For example, in the case of an amine having a structure represented by formula (ii) described below, the total molecular weight of (EO)a(PO)b + (EO)c(PO)d + (EO)e(PO)f is defined as the molecular weight of the EO / PO copolymer moiety. The PO content (mol %) in the EO / PO copolymer moiety and the molecular weight of the EO / PO copolymer moiety can be calculated from the average number of moles added during the production of the amine.

[0052] The EO / PO copolymer moiety and the amine are preferably bonded directly or via a linking group. The linking group is preferably a hydrocarbon group, and is preferably an alkylene group having 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms. For example, an ethylene group or a propylene group is preferred.

[0053] Examples of such amines having an EO / PO copolymer moiety include those represented by the following formula (i):

[0054] [ka]

[0055] [In the formula, R1 represents a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a -CH2CH(CH3)NH2 group, or a group represented by the following formula (ii), EO and PO are present randomly or in a block form, a is a positive number indicating the average number of moles of EO added, and b is a positive number indicating the average number of moles of PO added] Examples of the compound include compounds represented by the following formula:

[0056] Formula (ii):

[0057] [ka]

[0058] [In the formula, n is 0 or 1; R2 represents a phenyl group, a hydrogen atom, or a linear or branched alkyl group having 1 to 3 carbon atoms; EO and PO are present randomly or in a block form; c and e represent the average number of moles of EO added and are independently a number from 0 to 50; and d and f represent the average number of moles of PO added and are independently a number from 1 to 50.]

[0059] In formula (i), a represents the average number of moles of EO added, and from the viewpoint of obtaining a resin composition having excellent heat resistance, it is preferably 11 or more, more preferably 15 or more, even more preferably 20 or more, even more preferably 25 or more, and even more preferably 30 or more; from the same viewpoint, it is preferably 100 or less, more preferably 70 or less, even more preferably 60 or less, even more preferably 50 or less, and even more preferably 40 or less.

[0060] In formula (i), b represents the average number of moles of PO added, and from the viewpoint of obtaining a resin composition having excellent heat resistance, it is preferably 1 or more, more preferably 3 or more, and even more preferably 5 or more; from the same viewpoint, it is preferably 50 or less, more preferably 40 or less, even more preferably 30 or less, even more preferably 25 or less, even more preferably 20 or less, even more preferably 15 or less, and even more preferably 10 or less.

[0061] When the amine is represented by the formula (i), the PO content (mol %) in the EO / PO copolymerization portion can be calculated from the above-mentioned a and b, and can be obtained from the formula: b × 100 / (a + b). When the amine is represented by the formulas (i) and (ii), the PO content can be similarly obtained from the formula: (b + d + f) × 100 / (a + b + c + d + e + f). The preferred ranges are as described above.

[0062] In formula (i), R1 represents a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a -CH2CH(CH3)NH2 group, or a group represented by formula (ii), but from the viewpoint of obtaining a resin composition having excellent heat resistance, a hydrogen atom is preferred. The linear or branched alkyl group having 1 to 6 carbon atoms is preferably a methyl group, an ethyl group, or an iso- or normal-propyl group.

[0063] Furthermore, when R1 in formula (i) is a group represented by formula (ii), the linear or branched alkyl group having 1 to 3 carbon atoms for R2 in formula (ii) is preferably a methyl group or an ethyl group. When R2 is a methyl group or an ethyl group, n is preferably 1, and when R2 is a hydrogen atom, n is preferably 0. Furthermore, c and e in formula (ii) are independently preferably 10 to 30, and d and f are independently preferably 5 to 25.

[0064] The amine having an EO / PO copolymer moiety represented by formula (i) can be prepared by known methods. For example, a desired amount of ethylene oxide and propylene oxide may be added to a propylene glycol alkyl ether, followed by aminating the hydroxyl terminal. If necessary, the alkyl ether may be cleaved with an acid to convert the terminal to a hydrogen atom. For these production methods, see JP-A-3-181448.

[0065] The amine having an EO / PO copolymerization portion may be, for example, a commercially available product. Specific examples include Jeffamine M-2070, Jeffamine M-2005, Jeffamine M-2095, Jeffamine M-1000, Surfoamine B200, Surfoamine L100, Surfoamine L200, Surfoamine L207, Surfoamine L300, XTJ-501, XTJ-506, XTJ-507, and XTJ-508, manufactured by HUNTSMAN; and Jeffamine M3000, Jeffamine ED-900, Jeffamine ED-2003, Jeffamine D-2000, Jeffamine D-4000, XTJ-510, and Jeffamine ED-2003, manufactured by BASF. Examples of suitable surfactants include Jeffamine T-3000, Jeffamine T-5000, XTJ-502, XTJ-509, and XTJ-510. Among these, from the viewpoint of heat resistance, preferred are Jeffamine M-2070, Jeffamine M-2005, Jeffamine M-1000, Jeffamine M-600, Surfoamine L100, Surfoamine L200, Surfoamine L207, and Surfoamine L300. These may be used alone or in combination of two or more.

[0066] From the viewpoint of obtaining a resin composition having excellent heat resistance, the average bonding amount of the EO / PO copolymer moiety in the fine cellulose fiber composite is preferably 0.01 mmol / g or more, more preferably 0.05 mmol / g or more, even more preferably 0.1 mmol / g or more, even more preferably 0.3 mmol / g or more, and even more preferably 0.5 mmol / g or more. From the viewpoint of reactivity, it is preferably 3 mmol / g or less, more preferably 2.5 mmol / g or less, even more preferably 2 mmol / g or less, even more preferably 1.8 mmol / g or less, and even more preferably 1.5 mmol / g or less. When two or more types of hydrocarbon groups and copolymer moieties are introduced as modifying groups, the average bonding amount of each modifying group is preferably within the above-mentioned range.

[0067] Furthermore, from the viewpoint of obtaining a resin composition having excellent heat resistance, the modification rate of the EO / PO copolymer portion in the fine cellulose fiber composite is preferably 10% or more, more preferably 20% or more, even more preferably 30% or more, even more preferably 40% or more, even more preferably 50% or more, even more preferably 60% or more, even more preferably 70% or more, and from the viewpoint of obtaining a resin composition having excellent heat resistance, it is preferably 95% or less.

[0068] The modifying group may have a substituent, and in the case of a hydrocarbon group, for example, the total number of carbon atoms in the entire modifying group, including the substituent, is preferably within the above range. Examples of the substituent include alkoxy groups having 1 to 6 carbon atoms, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, isopentyloxy, and hexyloxy; methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, isobutoxycarbonyl, and sec-butoxycarbonyl; Examples of the hydrocarbon group include alkoxycarbonyl groups having 1 to 6 carbon atoms, such as a carboxyl group, tert-butoxycarbonyl group, pentyloxycarbonyl group, and isopentyloxycarbonyl group; halogen atoms such as a fluorine atom, chlorine atom, bromine atom, and iodine atom; acyl groups having 1 to 6 carbon atoms, such as an acetyl group and a propionyl group; aralkyl groups; aralkyloxy groups; alkylamino groups having 1 to 6 carbon atoms; and dialkylamino groups having an alkyl group with 1 to 6 carbon atoms. The hydrocarbon groups themselves may be bonded as substituents.

[0069] In this specification, the average bond amount of the modifying group can be adjusted by the amount of compound having the modifying group added, the type of compound having the modifying group, the reaction temperature, the reaction time, the solvent, etc. The average bond amount (mmol / g) and introduction rate (%) of the modifying group in the fine cellulose fiber composite refer to the amount and proportion of the modifying group introduced into the carboxyl groups on the surface of the fine cellulose fiber, and can be calculated by measuring the carboxyl group content of the fine cellulose fiber according to a known method (for example, titration, IR measurement, etc.).

[0070] <Microcrystalline cellulose fiber composite and method for producing the same> The fine cellulose fiber composite of the present invention can be produced according to any known method, as long as it is possible to introduce a modifying group into the fine cellulose fibers described above. For example, a reaction to introduce a modifying group may be performed on pre-prepared fine cellulose fibers having a low aspect ratio, or a reaction to introduce a modifying group into fine cellulose fibers having an average aspect ratio outside the above range may be performed followed by a treatment to reduce the aspect ratio, or a reaction to introduce a modifying group may be performed when preparing a fine cellulose fiber composite with a low aspect ratio. The fine cellulose fibers referred to here can be prepared by known methods, such as the method described in JP 2011-140632 A, to which 0.1 mmol / g or more of carboxy groups have been introduced. Alternatively, a mixture of natural cellulose, a mixture of a lower alcohol such as isopropyl alcohol and water, and a catalyst such as sodium hydroxide may be mixed, followed by the addition of a carboxy-introducing agent such as sodium chloroacetate, and the reaction is carried out. Subsequent micronization treatment using a known method can yield fine cellulose fibers to which 0.1 mmol / g or more of carboxy groups have been introduced via ether bonds.

[0071] Specific production methods include the following two modes depending on the mode of introduction of the modifying group into the fine cellulose fibers. That is, modes (mode A) in which the modifying group is bonded to the fine cellulose fibers by an ionic bond, and modes (mode B) in which the modifying group is bonded to the fine cellulose fibers by a covalent bond are included. The following shows the case where the covalent bond is an amide bond. [Aspect A] Step (1): A step of oxidizing natural cellulose fibers in the presence of an N-oxyl compound to obtain carboxyl group-containing cellulose fibers. Step (2A): A step of mixing the carboxyl group-containing cellulose fiber obtained in step (1) with a compound having a modifying group. [Aspect B] Step (1): A step of oxidizing natural cellulose fibers in the presence of an N-oxyl compound to obtain carboxyl group-containing cellulose fibers. Step (2B): A step of amidating the carboxyl group-containing cellulose fiber obtained in step (1) with a compound having a modifying group. The method for introducing the modifying group can be carried out, for example, by referring to the method described in JP 2015-143336 A for Aspect A and the method described in JP 2015-143337 A for Aspect B. Furthermore, in the present invention, there are two methods (first production mode) in which a micronization step and / or a low-aspect-ratio treatment step described below is carried out after step (1) to obtain carboxyl group-containing low-aspect-ratio fine cellulose fibers, followed by step (2A or 2B). Another method (second production mode) in which step (1) is followed by step (2A or 2B), followed by a micronization step and / or a low-aspect-ratio treatment step to obtain the fine cellulose fiber composite of the present invention is also included. From the viewpoint of efficient aspect ratio reduction and modification, the first production mode is preferred. That is, it is preferable to obtain carboxyl group-containing low-aspect-ratio fine cellulose fibers in step (1).

[0072] Hereinafter, a method for producing a fine cellulose fiber composite will be described based on the first production form of Aspect A.

[0073] [Step (1)] In step (1), natural cellulose fibers are oxidized in the presence of an N-oxyl compound to obtain carboxyl group-containing cellulose fibers. Specifically, the natural cellulose fibers are subjected to an oxidation treatment step (e.g., oxidation treatment using 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)) and a purification step (if necessary) as described in JP-A-2015-143336 or JP-A-2015-143337, thereby obtaining carboxyl group-containing cellulose fibers having a carboxyl group content of preferably 0.1 mmol / g or more. By oxidizing natural cellulose fibers using TEMPO as a catalyst, the group (-CHOH) at the C6 position of the cellulose structural unit is selectively converted to a carboxy group. Therefore, a preferred embodiment of the carboxy group-containing cellulose fiber of the present invention is a cellulose fiber in which the C6 position of the cellulose structural unit is a carboxy group.

[0074] Examples of natural cellulose fibers as raw materials include wood pulps such as softwood pulp and hardwood pulp; cotton pulps such as cotton linter and cotton lint; non-wood pulps such as straw pulp and bagasse pulp; and bacterial cellulose. These may be used alone or in combination. The natural cellulose fibers may be subjected to a treatment such as beating to increase the surface area. The cellulose type I crystallinity of the commercially available pulps is usually 80% or more.

[0075] (Refining process) In the first production mode, the carboxy group-containing cellulose fibers obtained in step (1) are then subjected to a step of micronizing after the purification step to obtain carboxy group-containing low aspect ratio micronized cellulose fibers. In the micronizing step, it is preferable to disperse the carboxy group-containing cellulose fibers that have been subjected to the purification step in a solvent and perform a micronization treatment.

[0076] Examples of the solvent as the dispersion medium include, in addition to water, alcohols having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, such as methanol, ethanol, propanol, and isopropanol; ketones having 3 to 6 carbon atoms, such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; esters having 3 to 6 carbon atoms, such as ethyl acetate and butyl acetate; linear or branched saturated or unsaturated hydrocarbons having 1 to 6 carbon atoms; aromatic hydrocarbons such as benzene and toluene; halogenated hydrocarbons such as methylene chloride, chloroform, and chlorobenzene; lower alkyl ethers having 2 to 5 carbon atoms, such as tetrahydrofuran; aprotic polar solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, and acetonitrile; and hydrocarbon solvents such as hexane, squalane, and paraffin. These can be used alone or in combination of two or more, but from the viewpoint of operability of the micronization treatment, polar solvents such as water, alcohols having 1 to 6 carbon atoms, ketones having 3 to 6 carbon atoms, lower alkyl ethers having 2 to 5 carbon atoms, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, etc. The amount of solvent used is not particularly limited as long as it is an effective amount that can disperse the carboxy group-containing cellulose fibers, but it is more preferable to use an amount that is preferably 1 to 500 times by mass, more preferably 2 to 200 times by mass, relative to the carboxy group-containing cellulose fibers.

[0077] As the apparatus used in the micronization treatment, a known disperser is preferably used. For example, a disintegrator, a beater, a low-pressure homogenizer, a high-pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a single-screw extruder, a twin-screw extruder, an ultrasonic agitator, a household juicer mixer, etc. can be used. In addition, the solid content concentration of the reaction product fiber in the micronization treatment is preferably 50 mass% or less.

[0078] (Low aspect ratio processing process) In the first production method, to efficiently obtain a composite having a low aspect ratio, carboxyl group-containing cellulose fibers are subjected to at least one aspect ratio reduction treatment selected from biochemical treatment, chemical treatment, and mechanical treatment to obtain carboxyl group-containing low-aspect ratio fine cellulose fibers. Examples of aspect ratio reduction treatments include acid hydrolysis, hydrothermal decomposition, oxidative decomposition, mechanical treatment using a planetary ball mill or rod mill, enzyme treatment, alkali treatment, UV treatment, and electron beam treatment. These treatments shorten the cellulose fibers, allowing the micronization process to be carried out more efficiently, thereby achieving an average aspect ratio within the above-mentioned range. For details, see the section on the preparation method of low-aspect ratio fine cellulose fibers described above. In the present invention, as long as the resulting micronized cellulose fibers have a low aspect ratio, either the aspect ratio reduction treatment or the micronization treatment may be carried out alone, or both may be carried out. If both are carried out, the order in which they are carried out does not matter. Furthermore, in the present invention, in order to set the average aspect ratio within the desired range, for example, fine cellulose fibers having a low aspect ratio may be mixed with fine cellulose fibers having a high aspect ratio of more than 150. The mixing ratio (mass of fine cellulose fibers having a high aspect ratio / mass of fine cellulose fibers having a low aspect ratio) is preferably 1 or less, more preferably 0.4 or less, even more preferably 0.1 or less, even more preferably 0.05 or less, and even more preferably 0.01 or less, from the viewpoint of improving the heat resistance and mechanical strength when the composite is incorporated into a resin to form a resin composition.

[0079] The obtained low aspect ratio fine cellulose fibers may be in the form of a suspension with an adjusted solid content (visually colorless, transparent or opaque liquid), or a dried powder (however, this refers to a powder in which the fine cellulose fibers are aggregated, and does not mean cellulose particles). When forming the fine cellulose fibers in the form of a suspension, water alone may be used as the dispersion medium, or a mixed solvent of water with other organic solvents (for example, alcohols such as ethanol), surfactants, acids, bases, etc. may be used.

[0080] Thus, the hydroxyl group at the C6 position of the cellulose structural unit is selectively oxidized to a carboxy group via an aldehyde group, and it is possible to obtain fine cellulose fibers having a low aspect ratio, which are made of cellulose having a carboxy group content of 0.1 mmol / g or more, preferably finely divided with an average fiber diameter of 0.1 to 200 nm, preferably with a crystallinity of 30% or more, and preferably with an average aspect ratio of 1 to 150. Here, the carboxy group-containing fine cellulose fibers have a cellulose type I crystal structure. This means that the carboxy group-containing fine cellulose fibers used in the present invention are fibers obtained by surface-oxidizing and finely dividing a naturally occurring solid cellulose raw material having a type I crystal structure.

[0081] [Process (2A)] In the first production form, step (2A) is a step of mixing the carboxyl group-containing low-aspect ratio fine cellulose fibers obtained through the above-mentioned microfibrillation step with a compound having a modifying group to obtain a microfibrillated cellulose fiber composite. Specifically, the carboxyl group-containing low-aspect ratio fine cellulose fibers and the compound having a modifying group are mixed in a solvent, and the composite can be produced, for example, according to the method described in JP 2015-143336 A.

[0082] The compound having a modifying group used in step (2A) includes those mentioned above for the fine cellulose fiber composite. When two or more types of modifying groups are to be introduced, two or more compounds having a modifying group can be used in this step to produce a fine cellulose fiber composite into which two or more types of modifying groups have been introduced.

[0083] The amount of the compound used can be determined based on the desired binding amount of modifying groups in the fine cellulose fiber composite. From the viewpoint of reactivity, the amount of amine groups is preferably 0.01 mol or more, more preferably 0.1 mol or more, even more preferably 0.5 mol or more, even more preferably 0.7 mol or more, and even more preferably 1 mol or more per mol of carboxyl groups contained in the carboxyl group-containing low aspect ratio fine cellulose fibers. From the viewpoint of product purity, the amount used is preferably 50 mol or less, more preferably 20 mol or less, and even more preferably 10 mol or less. Note that the amount of compound within the above range may be reacted all at once or in portions. When the compound is a monoamine, the above-mentioned amine group and amine are the same. When a compound having two or more types of modifying groups is used, the amount of compound used is the total amount of each compound.

[0084] As the solvent, it is preferable to select a solvent in which the compound to be used dissolves, and examples thereof include methanol, ethanol, isopropanol (IPA), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N,N-dimethylacetamide, tetrahydrofuran (THF), acetone, methyl ethyl ketone (MEK), acetonitrile, dichloromethane, chloroform, toluene, acetic acid, water, etc., and these can be used alone or in combination of two or more. Among these polar solvents, methanol, ethanol, IPA, DMF, DMSO, MEK, and water are preferred.

[0085] The temperature during mixing is preferably 0°C or higher, more preferably 5°C or higher, and even more preferably 10°C or higher, from the viewpoint of the reactivity of the compound. Furthermore, from the viewpoint of coloration of the composite, it is preferably 50°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower. The mixing time can be appropriately set depending on the type of compound and solvent used, but from the viewpoint of the reactivity of the compound, it is preferably 0.01 hour or higher, more preferably 0.1 hour or higher, and even more preferably 1 hour or higher, and is preferably 48 hours or lower, and more preferably 24 hours or lower.

[0086] After the salt formation, post-treatment may be carried out as appropriate to remove unreacted compounds, etc. Examples of methods for the post-treatment include filtration, centrifugation, dialysis, etc.

[0087] In addition, in the production method of Aspect B, step (1) can be carried out in the same manner as in Aspect A, and therefore, step (2B) in the first production mode will be described below. In addition, for example, it can be produced by the method described in JP 2013-151661 A.

[0088] [Process (2B)] In the first production form, step (2B) is a step of obtaining a fine cellulose fiber composite by amidation reaction of the carboxy group-containing low aspect ratio fine cellulose fibers obtained through the above-mentioned microfibrillation step with a compound having a modifying group. The mixing method is not particularly problematic as long as it is sufficient to react the raw materials. Specifically, the raw materials are mixed in the presence of a condensing agent, and the carboxy groups contained in the carboxy group-containing low aspect ratio fine cellulose fibers are condensed with the amino groups of the compound having a modifying group to form amide bonds.

[0089] The compound having a modifying group used in step (2B) includes those mentioned above for the fine cellulose fiber composite. When two or more types of modifying groups are to be introduced, two or more compounds having a modifying group can be used in this step to produce a fine cellulose fiber composite into which two or more types of modifying groups have been introduced.

[0090] In step (2B), the carboxy group-containing low aspect ratio fine cellulose fibers and a compound having a modifying group are amidated in the presence of a condensing agent.

[0091] The amount of the compound having the modifying group used is, from the viewpoint of reactivity, preferably 0.1 mol or more, more preferably 0.5 mol or more, of amine groups per mol of carboxy groups contained in the carboxy group-containing low-aspect ratio fine cellulose fibers, and from the viewpoint of product purity, preferably 50 mol or less, more preferably 20 mol or less, and even more preferably 10 mol or less. Note that the amount of the compound within the above range may be subjected to the reaction all at once or in portions. When compounds having two or more types of modifying groups are used, the amount of the compounds used is the total amount of each compound.

[0092] The condensing agent is not particularly limited, but includes those described in Synthetic Chemistry Series, Peptide Synthesis (Maruzensha), p. 116, or Tetrahedron, 57, 1551 (2001), such as 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (hereinafter sometimes referred to as "DMT-MM").

[0093] In the amidation reaction, the solvent used in the micronization step can be used, and it is preferable to select a solvent that dissolves the compound used.

[0094] The reaction time and reaction temperature for the amidation reaction can be appropriately selected depending on the type of compound and solvent used, but are preferably 1 to 24 hours, more preferably 10 to 20 hours, from the viewpoint of reaction rate. Furthermore, from the viewpoint of reactivity, the reaction temperature is preferably 0°C or higher, more preferably 5°C or higher, and even more preferably 10°C or higher. Furthermore, from the viewpoint of coloration of the composite, the reaction temperature is preferably 200°C or lower, more preferably 80°C or lower, and even more preferably 30°C or lower.

[0095] After the reaction, post-treatment may be carried out as appropriate to remove unreacted compounds, condensing agents, etc. Examples of methods that can be used for the post-treatment include filtration, centrifugation, dialysis, etc.

[0096] In both Aspect A and B, the second manufacturing method can be carried out in the same manner as the first manufacturing method, except that the above-mentioned steps are carried out in the following order: step (1), step (2A) or step (2B), and the micronization step.

[0097] The fine cellulose fiber composite may also be obtained by combining Mode A and Mode B, i.e., a fine cellulose fiber composite having a modifying group linked via an ionic bond and a modifying group linked via an amide bond. In this case, either step (2A) or step (2B) may be carried out first.

[0098] Thus, a fine cellulose fiber composite having a low aspect ratio can be obtained in which modifying groups are bonded to the fine cellulose fibers via ionic and / or covalent bonds.

[0099] The average fiber diameter of the obtained fine cellulose fiber composite is preferably 0.1 nm or more, more preferably 0.5 nm or more, even more preferably 1 nm or more, even more preferably 2 nm or more, and still more preferably 3 nm or more from the viewpoint of improving the heat resistance and mechanical strength when the composite is incorporated into a resin to form a resin composition. Also, from the viewpoint of improving the heat resistance when the composite is incorporated into a resin to form a resin composition, the average fiber diameter is preferably 100 nm or less, more preferably 50 nm or less, even more preferably 20 nm or less, even more preferably 10 nm or less, even more preferably 6 nm or less, and still more preferably 5 nm or less.

[0100] The length (average fiber length) of the obtained fine cellulose fiber composite is preferably 150 nm or more, more preferably 200 nm or more, from the viewpoint of improving the heat resistance when the composite is incorporated into a resin to form a resin composition, and is preferably 1000 nm or less, more preferably 750 nm or less, even more preferably 500 nm or less, and even more preferably 400 nm or less, from the viewpoint of improving the heat resistance when the composite is incorporated into a resin to form a resin composition.

[0101] The average aspect ratio (fiber length / fiber diameter) of the obtained fine cellulose fiber composite is 1 or more and 150 or less, but from the viewpoint of improving heat resistance when incorporated into a resin to form a resin composition, it is preferably 10 or more, more preferably 20 or more, even more preferably 40 or more, and even more preferably 50 or more. From the viewpoint of improving heat resistance and mechanical strength when incorporated into a resin to form a resin composition, it is preferably 140 or less, more preferably 130 or less, even more preferably 100 or less, even more preferably 95 or less, and even more preferably 90 or less. Furthermore, when the average aspect ratio is within the above range, the standard deviation of the aspect ratio is preferably 60 or less, more preferably 50 or less, and even more preferably 45 or less from the viewpoint of improving heat resistance when incorporated into a resin to form a resin composition. There is no particular lower limit, but from the viewpoint of economy, it is preferably 4 or more. The fine cellulose fiber composite having the low aspect ratio not only has excellent heat resistance, but also has excellent dispersibility in the resin composition, and a resin composition having high mechanical strength and being resistant to brittle fracture can be obtained.

[0102] In this specification, the average fiber diameter, average fiber length, average aspect ratio, and degree of crystallinity of the fine cellulose fiber composite can be determined by the same measuring methods as those described for the fine cellulose fiber.

[0103] The obtained fine cellulose fiber composite can be used in the state of a dispersion after the above-mentioned post-treatment, or the solvent can be removed from the dispersion by drying treatment or the like to obtain a dried powdery fine cellulose fiber composite, which can then be used. Here, "powdered" refers to a powdery form in which the fine cellulose fiber composite is agglomerated, and does not mean cellulose particles.

[0104] Examples of the powdered fine cellulose fiber composite include a dried product obtained by drying the dispersion of the fine cellulose fiber composite as is, a dried product obtained by powdering the dried product through mechanical processing, a dispersion of the fine cellulose fiber composite obtained by powdering using a known spray drying method, and a dispersion of the fine cellulose fiber composite obtained by powdering using a known freeze drying method. The spray drying method is a method in which the dispersion of the fine cellulose fiber composite is sprayed in the atmosphere and dried.

[0105] In addition, the microfibrillated cellulose fiber composite preferably has a degree of crystallinity similar to that of the microfibrillated cellulose fiber, since the crystallinity is not reduced by the reaction in step (2A) or step (2B).

[0106] The fine cellulose fiber composite of the present invention can be suitably used to provide a resin composition having excellent heat resistance. Furthermore, since the fine cellulose fiber composite of the present invention has excellent dispersion stability in organic solvents and resins, it can also be used as a thickener, gelling agent, rheology adjuster, emulsifier, dispersant, etc.

[0107] [Resin composition] [resin] As the resin in the present invention, a thermoplastic resin, a curable resin, a cellulose-based resin, or a rubber-based resin can be used.

[0108] Examples of thermoplastic resins include saturated polyester resins such as polylactic acid resins, olefin resins such as polyethylene resins and polypropylene resins, vinyl chloride resins, styrene resins, (meth)acrylic resins, vinyl ether resins, polyvinyl alcohol resins, polyvinyl acetal resins, polyvinyl acetate resins, polyamide resins, polycarbonate resins, and polysulfone resins. These thermoplastic resins may be used alone or in combination of two or more. Among these, saturated polyester resins, olefin resins, vinyl chloride resins, styrene resins, (meth)acrylic resins, and polyamide resins are preferred because they provide resin compositions with excellent heat resistance. In this specification, (meth)acrylic resins refer to resins including methacrylic resins and acrylic resins.

[0109] The (meth)acrylic resin is preferably one containing 50% by weight or more of methyl (meth)acrylate as a monomer unit based on the total monomer units of all polymers constituting the resin, and a methacrylic resin is more preferred.

[0110] Methacrylic resins can be produced by copolymerizing methyl methacrylate with other monomers copolymerizable therewith. The polymerization method is not particularly limited, and examples thereof include bulk polymerization, solution polymerization, suspension polymerization, and cast polymerization (e.g., cell-cast polymerization). From the viewpoint of productivity, cast polymerization (e.g., cell-cast polymerization) is preferred. Furthermore, a methacrylic resin with excellent heat resistance can be obtained by polymerizing a polymerizable mixture containing the monomer mixture and a radical polymerization initiator.

[0111] The curable resin is preferably a photocurable resin and / or a thermosetting resin.

[0112] The photocurable resin undergoes a polymerization reaction by using a photopolymerization initiator that generates radicals or cations when irradiated with active energy rays such as ultraviolet rays or electron beams.

[0113] Examples of the photopolymerization initiator include acetophenones, benzophenones, ketals, anthraquinones, thioxanthones, azo compounds, peroxides, 2,3-dialkylthiones, disulfide compounds, thiuram compounds, and fluoroamine compounds. More specifically, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one, benzyl methyl ketone, 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-hydroxy-2-methylpropan-1-one, and benzophenone are preferred. Among these, 1-hydroxycyclohexylphenyl ketone is preferred from the viewpoints of improving antistatic properties, water resistance, transparency, and scratch resistance.

[0114] A photopolymerization initiator can polymerize, for example, a monomer (monofunctional monomer, polyfunctional monomer), an oligomer or a resin having a reactive unsaturated group, or the like.

[0115] Examples of monofunctional monomers include (meth)acrylic monomers such as (meth)acrylic acid esters, vinyl monomers such as vinylpyrrolidone, and (meth)acrylates having a bridged cyclic hydrocarbon group such as isobornyl (meth)acrylate and adamantyl (meth)acrylate. Polyfunctional monomers include polyfunctional monomers having about 2 to 8 polymerizable groups, and examples of bifunctional monomers include di(meth)acrylates having a bridged cyclic hydrocarbon group such as ethylene glycol di(meth)acrylate and propylene glycol di(meth)acrylate. Examples of tri- to octafunctional monomers include glycerin tri(meth)acrylate.

[0116] Examples of oligomers or resins having a reactive unsaturated group include (meth)acrylates of bisphenol A-alkylene oxide adducts, epoxy (meth)acrylates (such as bisphenol A-type epoxy (meth)acrylates and novolac-type epoxy (meth)acrylates), polyester (meth)acrylates (such as aliphatic polyester (meth)acrylates and aromatic polyester (meth)acrylates), urethane (meth)acrylates (such as polyester-type urethane (meth)acrylates and polyether-type urethane (meth)acrylates), and silicone (meth)acrylates. These oligomers or resins may be used together with the above-mentioned monomers.

[0117] Photocurable resins are preferred from the viewpoint of obtaining a resin composition with little aggregates and excellent transparency.

[0118] Examples of thermosetting resins include epoxy resins, phenolic resins, urea resins, melamine resins, unsaturated polyester resins, diallyl phthalate resins, polyurethane resins, silicon resins, and polyimide resins. The thermosetting resins can be used singly or in combination of two or more. Among these, epoxy resins, phenolic resins, urea resins, melamine resins, unsaturated polyester resins, and polyurethane resins are preferred, as they provide resin compositions with excellent heat resistance, and epoxy resins are more preferred.

[0119] When an epoxy resin is used as the resin component, it is preferable to use a curing agent. By blending the curing agent, the molding material obtained from the resin composition can be molded firmly and the mechanical strength can be improved. The content of the curing agent can be appropriately set depending on the type of curing agent used.

[0120] Examples of cellulose-based resins include organic acid esters such as cellulose acetate (cellulose acetate) and mixed cellulose acylates such as cellulose acetate propionate; inorganic acid esters such as cellulose nitrate and cellulose phosphate; organic acid-inorganic acid mixed acid esters such as cellulose nitrate acetate; and cellulose ether esters such as acetylated hydroxypropyl cellulose. Examples of cellulose acetate include cellulose triacetate (acetyl substitution degree 2.6 to 3), cellulose diacetate (acetyl substitution degree 2 or more but less than 2.6), and cellulose monoacetate. Among the above cellulose-based resins, organic acid esters of cellulose are preferred, and cellulose acetate (e.g., cellulose triacetate, cellulose diacetate) is more preferred, as they provide resin compositions with excellent heat resistance. The cellulose-based resins may be used alone or in combination of two or more.

[0121] Furthermore, in the present invention, a rubber-based resin can be used. Rubber-based resins are generally formulated with carbon black as a reinforcing material to increase their strength, but this reinforcing effect is thought to have limitations. However, in the present invention, by blending the fine cellulose fiber composite of the present invention with a rubber-based resin, the resulting rubber composition has excellent dispersibility, making it possible to provide a resin composition with excellent mechanical strength and heat resistance.

[0122] As the rubber-based resin, diene-based rubber and non-diene-based rubber are preferred.

[0123] Examples of diene rubbers include natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, butyl rubber, butadiene-acrylonitrile copolymer rubber, chloroprene rubber, and modified natural rubber. Examples of modified natural rubbers include epoxidized natural rubber and hydrogenated natural rubber. Examples of non-diene rubbers include butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, urethane rubber, silicone rubber, fluororubber, acrylic rubber, polysulfide rubber, and epichlorohydrin rubber. These may be used alone or in combination of two or more. Among these, from the viewpoint of achieving both good processability and high impact resilience of the rubber composition, one or more selected from natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, chloroprene rubber, and modified natural rubber are preferred, and one or more selected from natural rubber, styrene-butadiene copolymer rubber, and modified natural rubber are more preferred.

[0124] The content of the resin in the resin composition, the amount of the fine cellulose fiber composite relative to the resin, and the amount of the fine cellulose fibers relative to the resin (converted amount) vary depending on the type of resin, but are as follows.

[0125] From the viewpoint of producing a molded article, the resin content in the resin composition of the present invention is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 85% by mass or more. Also, from the viewpoint of incorporating a fine cellulose fiber composite or the like, the resin content is preferably 99% by mass or less, more preferably 98% by mass or less, even more preferably 95% by mass or less, and even more preferably 90% by mass or less.

[0126] The content of the fine cellulose fiber composite in the resin composition of the present invention is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, even more preferably 2% by mass or more, even more preferably 5% by mass or more, and even more preferably 10% by mass or more, from the viewpoint of the mechanical strength, dimensional stability, and heat resistance of the resulting resin composition. Also, from the viewpoint of the transparency of the resulting resin composition, it is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, even more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0127] The amount of fine cellulose fiber composite in the resin composition of the present invention is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, even more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of resin, from the viewpoint of the mechanical strength, dimensional stability, and heat resistance of the resulting resin composition; and from the viewpoint of the transparency of the resulting resin composition, it is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, even more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less.

[0128] In the resin composition of the present invention, the amount of fine cellulose fibers (equivalent amount) is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more, relative to 100 parts by mass of resin, from the viewpoint of the mechanical strength of the resulting resin composition, and from the viewpoint of the transparency of the resulting resin composition, it is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, even more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less. Note that the amount of fine cellulose fibers (equivalent amount) in this specification is specifically measured by the method described in the examples below.

[0129] The resin composition of the present invention may contain a plasticizer in addition to the above components.

[0130] The plasticizer is not particularly limited, and examples thereof include conventional plasticizers such as polycarboxylic acid esters, such as phthalates, succinates, and adipates, and fatty acid esters of aliphatic polyols, such as glycerin. Among these, preferred are ester compounds having two or more ester groups in the molecule, in which at least one of the alcohol components constituting the ester compound is an alcohol to which an average of 0.5 to 5 moles of alkylene oxide having 2 to 3 carbon atoms per hydroxyl group has been added. Specific examples include the plasticizers described in JP-A-2008-174718 and JP-A-2008-115372.

[0131] The content of the plasticizer is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the resin, from the viewpoint of improving the transparency of the molded article when it is formed into a molded article, and from the same viewpoint, it is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less.

[0132] The fine cellulose fiber composite of the present invention has few aggregates and excellent transparency when dispersed in a plasticizer, and therefore can be suitably used in the production of a resin composition containing the above-mentioned thermoplastic resin or curable resin and a fine cellulose fiber composite.

[0133] The resin composition of the present invention may contain other components in addition to those described above, such as nucleating agents, fillers (inorganic fillers, organic fillers), hydrolysis inhibitors, flame retardants, antioxidants, lubricants such as hydrocarbon waxes and anionic surfactants, UV absorbers, antistatic agents, antifogging agents, light stabilizers, pigments, mildew inhibitors, antibacterial agents, foaming agents, surfactants; polysaccharides such as starches and alginic acid; natural proteins such as gelatin, glue, and casein; inorganic compounds such as tannins, zeolites, ceramics, and metal powders; fragrances; flow control agents; leveling agents; conductive agents; UV dispersants; and deodorizers, as long as the effects of the present invention are not impaired. Similarly, other polymeric materials and other resin compositions may also be added as long as the effects of the present invention are not impaired. The content of optional additives may be appropriately adjusted as long as the effects of the present invention are not impaired. For example, the content of the optional additives is preferably about 10% by mass or less of the resin composition, and more preferably about 5% by mass or less.

[0134] Furthermore, when the resin composition of the present invention contains a rubber-based resin, other components than those described above may be blended, if desired, in conventional amounts within the scope of the object of the present invention, such as reinforcing fillers commonly used in the rubber industry, such as carbon black and silica, various chemicals, for example, vulcanizing agents, vulcanization accelerators, antioxidants, scorch inhibitors, zinc oxide, stearic acid, process oil, vegetable oils and plasticizers, and various other additives blended in tires and other general rubbers.

[0135] The resin composition of the present invention can be prepared without any particular limitation as long as it contains a thermoplastic resin or a curable resin and a fine cellulose fiber composite. For example, raw materials containing a thermoplastic resin or a curable resin and a fine cellulose fiber composite, and further various additives as necessary, can be mixed by stirring using a Henschel mixer, a planetary centrifugal mixer, or the like, or by melt-kneading using a known kneader such as an internal kneader, a single-screw or twin-screw extruder, or an open-roll kneader.

[0136] One of the features of the resin composition of the present invention is its excellent heat resistance. Specifically, the weight loss rate after heating by a predetermined method is preferably 3.7% by weight or less, more preferably 3.5% by weight or less, even more preferably 3.0% by weight or less, and preferably 0.2% by weight or more, more preferably 0.3% by weight or more, even more preferably 0.4% by weight or more. The weight loss rate can be measured according to the method described in the Examples below.

[0137] The resin composition of the present invention has good processability and excellent heat resistance, and therefore can be suitably used in various applications such as daily necessities, home appliance parts, automobile parts, etc. Specifically, for example, the resin composition can be suitably used as a packaging material for daily necessities, cosmetics, home appliances, etc., as an electronic material for constituting electronic parts, etc., as food containers such as blister packs, trays, and lunch box lids, as industrial trays used for transporting and protecting industrial parts, and as automobile parts such as dashboards, instrument panels, and floors.

[0138] [Resin molding] The resin molded article can be prepared by appropriately using a known molding method such as extrusion molding, injection molding, press molding, cast molding, solvent casting, etc. For example, a molded article suitable for the intended use can be obtained by injecting or applying the resin composition of the present invention into a package, a substrate, etc., followed by drying and curing.

[0139] When preparing a sheet-like molded product, from the viewpoint of processability, the thickness is preferably 0.01 mm or more, more preferably 0.03 mm or more, more preferably 0.05 mm or more, more preferably 0.08 mm or more, and even more preferably 0.1 mm or more, and is preferably 1.5 mm or less, more preferably 1.0 mm or less, and even more preferably 0.5 mm or less.

[0140] The molded article of the resin composition of the present invention thus obtained has excellent mechanical strength, heat resistance and dimensional stability as described below, and can therefore be suitably used in the various applications mentioned for the resin composition.

[0141] One of the features of the molded article of the resin composition of the present invention is excellent mechanical strength. Specifically, the storage modulus at 30°C is preferably 2.5 GPa or more, more preferably 2.8 GPa or more, even more preferably 3.0 GPa or more, and preferably 10.0 GPa or less, more preferably 8.0 GPa or less, even more preferably 6.0 GPa or less. The storage modulus at 30°C can be measured according to the method described in the Examples below.

[0142] One of the features of the molded article of the resin composition of the present invention is excellent heat resistance. Specifically, the storage modulus at 200°C is preferably 205 MPa or more, more preferably 220 MPa or more, even more preferably 250 MPa or more, and preferably 2000 MPa or less, more preferably 1000 MPa or less, even more preferably 550 MPa or less. The storage modulus at 200°C can be measured according to the method described in the Examples below.

[0143] One of the features of the molded article of the resin composition of the present invention is excellent dimensional stability. Specifically, the linear thermal expansion coefficient is preferably 63 ppm / K or less, more preferably 60 ppm / K or less, even more preferably 55 ppm / K or less, and is preferably 0.5 ppm / K or more, more preferably 3.0 ppm / K or more, even more preferably 15 ppm / K or more. The linear thermal expansion coefficient can be measured according to the method described in the Examples below.

[0144] In addition, in relation to the above-described embodiment, the present invention further discloses the following fine cellulose fiber composite, a resin composition containing the same, and use thereof.

[0145] <1> A fine cellulose fiber composite having an average aspect ratio of 1 or more and 150 or less, which is obtained by bonding modifying groups to carboxy groups of fine cellulose fibers having a carboxy group content of 0.1 mmol / g or more.

[0146] <2> The carboxyl group content of the fine cellulose fibers is preferably 0.4 mmol / g or more, more preferably 0.6 mmol / g or more, even more preferably 0.8 mmol / g or more, and is preferably 3 mmol / g or less, more preferably 2 mmol / g or less, even more preferably 1.8 mmol / g or less, even more preferably 1.5 mmol / g or less, even more preferably 1.2 mmol / g or less. <1> The fine cellulose fiber composite described above. <3> The carboxyl group content of the fine cellulose fibers is 0.4 mmol / g or more. <1> The fine cellulose fiber composite described above. <4> The carboxyl group content of the fine cellulose fibers is 0.6 mmol / g or more. <1> The fine cellulose fiber composite described above. <5> The carboxyl group content of the fine cellulose fibers is 2 mmol / g or less. <1> The fine cellulose fiber composite described above. <6> The carboxyl group content of the fine cellulose fibers is 1.8 mmol / g or less. <1> The fine cellulose fiber composite described above. <7> The average fiber diameter of the fine cellulose fibers is preferably 0.1 nm or more, more preferably 0.5 nm or more, even more preferably 1 nm or more, even more preferably 2 nm or more, still more preferably 3 nm or more, and is preferably 100 nm or less, more preferably 50 nm or less, even more preferably 20 nm or less, even more preferably 10 nm or less, even more preferably 6 nm or less, and still more preferably 5 nm or less. <1> ~ <6> The fine cellulose fiber composite according to any one of the preceding claims. <8> The average fiber diameter of the fine cellulose fibers is 100 nm or less. <1> ~ <6> The fine cellulose fiber composite according to any one of the preceding claims. <9> The average fiber diameter of the fine cellulose fibers is 10 nm or less. <1> ~ <6> The fine cellulose fiber composite according to any one of the preceding claims. <10> The average fiber length of the fine cellulose fibers is preferably 150 nm or more, more preferably 200 nm or more, and is preferably 1000 nm or less, more preferably 750 nm or less, even more preferably 500 nm or less, and even more preferably 400 nm or less. <1> ~ <9> The fine cellulose fiber composite according to any one of the preceding claims. <11> The average aspect ratio (fiber length / fiber diameter) of the fine cellulose fibers is preferably 1 or more, more preferably 10 or more, even more preferably 20 or more, even more preferably 40 or more, even more preferably 50 or more, and is preferably 150 or less, more preferably 140 or less, even more preferably 130 or less, even more preferably 100 or less, even more preferably 95 or less, even more preferably 90 or less. <1> ~ <10> The fine cellulose fiber composite according to any one of the preceding claims. <12> The average aspect ratio (fiber length / fiber diameter) of the fine cellulose fibers is 20 or more. <1> ~ <10> The fine cellulose fiber composite according to any one of the preceding claims. <13> The average aspect ratio (fiber length / fiber diameter) of the fine cellulose fibers is 40 or more. <1> ~ <10> The fine cellulose fiber composite according to any one of the preceding claims. <14> The average aspect ratio (fiber length / fiber diameter) of the fine cellulose fibers is 50 or more. <1> ~ <10> The fine cellulose fiber composite according to any one of the preceding claims. <15> The average aspect ratio (fiber length / fiber diameter) of the fine cellulose fibers is 130 or less. <1> ~ <10> The fine cellulose fiber composite according to any one of the preceding claims. <16> The average aspect ratio (fiber length / fiber diameter) of the fine cellulose fibers is 100 or less. <1> ~ <10> The fine cellulose fiber composite according to any one of the preceding claims. <17> The average aspect ratio (fiber length / fiber diameter) of the fine cellulose fibers is 90 or less. <1> ~ <10> The fine cellulose fiber composite according to any one of the preceding claims. <18> The standard deviation of the average aspect ratio of the fine cellulose fibers is preferably 60 or less, more preferably 50 or less, even more preferably 45 or less, and is preferably 4 or more. <1> ~ <17> The fine cellulose fiber composite according to any one of the preceding claims. <19> The fine cellulose fibers are obtained by subjecting cellulose fibers that have been previously subjected to an oxidation treatment to incorporate carboxyl groups to at least one aspect ratio reduction treatment selected from biochemical treatment, chemical treatment, and mechanical treatment (one or more of acid hydrolysis, hydrothermal decomposition, oxidative decomposition, mechanical treatment, enzyme treatment, alkali treatment, UV treatment, and electron beam treatment), preferably one or more of acid hydrolysis, hydrothermal decomposition, oxidative decomposition, and mechanical treatments, more preferably one or more of acid hydrolysis and hydrothermal decomposition, and even more preferably acid hydrolysis. <1> ~ <18> The fine cellulose fiber composite according to any one of the preceding claims. <20> The above-mentioned compound is obtained by ionic and / or covalent bonding (amide bond, ester bond, ether bond such as carboxymethylation or carboxyethylation, urethane bond) of a compound having a modifying group to the carboxy group already present on the surface of fine cellulose fibers. <1> ~ <19> The fine cellulose fiber composite according to any one of the preceding claims.

[0147] <21> In the case where the compound having a modifying group is an ionic bond, it is one or more selected from primary amines, secondary amines, tertiary amines, quaternary ammonium compounds, and phosphonium compounds, preferably a primary amine, a secondary amine, a tertiary amine, or a quaternary ammonium compound, and in the case where it is an amide bond, it may be either a primary amine or a secondary amine. <20> The fine cellulose fiber composite described above. <22> The modifying group may be a hydrocarbon group or a copolymer moiety. <1> ~ <21> The fine cellulose fiber composite according to any one of the preceding claims. <23> Examples of the hydrocarbon group include a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, a cyclic saturated hydrocarbon group, and an aromatic hydrocarbon group, and the chain saturated hydrocarbon group, the cyclic saturated hydrocarbon group, and the aromatic hydrocarbon group are preferred. <22> The fine cellulose fiber composite described above. <24> The total number of carbon atoms in the chain saturated hydrocarbon group is preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, still more preferably 6 or more, still more preferably 8 or more, and is preferably 30 or less, more preferably 24 or less, still more preferably 18 or less, and even more preferably 16 or less. <23> The fine cellulose fiber composite described above. <25> The total number of carbon atoms in the chain unsaturated hydrocarbon group is preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more, and is preferably 30 or less, more preferably 18 or less, even more preferably 12 or less, and even more preferably 8 or less. <23> The fine cellulose fiber composite described above. <26> The total number of carbon atoms in the cyclic saturated hydrocarbon group is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more, and is preferably 20 or less, more preferably 16 or less, even more preferably 12 or less, and even more preferably 8 or less. <23> The fine cellulose fiber composite described above. <27> As the aromatic hydrocarbon group, the total number of carbon atoms in the aryl group may be 6 or more, and preferably 24 or less, more preferably 20 or less, even more preferably 14 or less, even more preferably 12 or less, and even more preferably 10 or less, and the total number of carbon atoms in the aralkyl group may be 7 or more, and preferably 8 or more, and preferably 24 or less, more preferably 20 or less, even more preferably 14 or less, even more preferably 13 or less, and even more preferably 11 or less. <23> The fine cellulose fiber composite described above. <28> The average bonding amount of hydrocarbon groups in the fine cellulose fiber composite is preferably 0.01 mmol / g or more, more preferably 0.05 mmol / g or more, even more preferably 0.1 mmol / g or more, even more preferably 0.3 mmol / g or more, even more preferably 0.5 mmol / g or more, and is preferably 3 mmol / g or less, more preferably 2.5 mmol / g or less, even more preferably 2 mmol / g or less, even more preferably 1.8 mmol / g or less, even more preferably 1.5 mmol / g or less. <22> ~ <27> The fine cellulose fiber composite according to any one of the preceding claims. <29> The copolymerization portion may be an ethylene oxide / propylene oxide (EO / PO) copolymerization portion. <22> The fine cellulose fiber composite described above. <30> The PO content (mol%) in the EO / PO copolymer portion is preferably 1 mol% or more, more preferably 5 mol% or more, even more preferably 7 mol% or more, and even more preferably 10 mol% or more, and is preferably 100 mol% or less, more preferably 90 mol% or less, even more preferably 85 mol% or less, even more preferably 75 mol% or less, even more preferably 60 mol% or less, even more preferably 50 mol% or less, even more preferably 40 mol% or less, and even more preferably 30 mol% or less. <29> The fine cellulose fiber composite described above. <31> The molecular weight of the EO / PO copolymer portion is preferably 500 or more, more preferably 1,000 or more, even more preferably 1,500 or more, and is preferably 10,000 or less, 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, even more preferably 2,500 or less. <29> or <30> The fine cellulose fiber composite described above. <32> the average number of moles of EO added is preferably 11 or more, more preferably 15 or more, even more preferably 20 or more, even more preferably 25 or more, even more preferably 30 or more, and is preferably 100 or less, more preferably 70 or less, even more preferably 60 or less, even more preferably 50 or less, even more preferably 40 or less; <29> ~ <31> The fine cellulose fiber composite according to any one of the preceding claims. <33> the average number of moles of PO added is preferably 1 or more, more preferably 3 or more, even more preferably 5 or more, and is preferably 50 or less, more preferably 40 or less, even more preferably 30 or less, even more preferably 25 or less, even more preferably 20 or less, even more preferably 15 or less, even more preferably 10 or less; <29> ~ <32> The fine cellulose fiber composite according to any one of the preceding claims. <34> The average bonding amount of the EO / PO copolymer moiety in the fine cellulose fiber composite is preferably 0.01 mmol / g or more, more preferably 0.05 mmol / g or more, even more preferably 0.1 mmol / g or more, even more preferably 0.3 mmol / g or more, even more preferably 0.5 mmol / g or more, and is preferably 3 mmol / g or less, more preferably 2.5 mmol / g or less, even more preferably 2 mmol / g or less, even more preferably 1.8 mmol / g or less, even more preferably 1.5 mmol / g or less. <29> ~ <33> The fine cellulose fiber composite according to any one of the preceding claims. <35> The above-mentioned, which is obtained by a manufacturing method including the following steps: <1> ~ <34> The fine cellulose fiber composite according to any one of the preceding claims. Step (1): A step of oxidizing natural cellulose fibers in the presence of an N-oxyl compound to obtain carboxyl group-containing cellulose fibers. Step (2A): A step of mixing the carboxyl group-containing cellulose fiber obtained in step (1) with a compound having a modifying group. <36> The above-mentioned, which is obtained by a manufacturing method including the following steps: <1> ~ <34> The fine cellulose fiber composite according to any one of the preceding claims. Step (1): A step of oxidizing natural cellulose fibers in the presence of an N-oxyl compound to obtain carboxyl group-containing cellulose fibers. Step (2B): A step of amidating the carboxyl group-containing cellulose fiber obtained in step (1) with a compound having a modifying group. <37> After the step (1), a pulverization step and / or a treatment step for reducing the aspect ratio is carried out to obtain carboxyl group-containing low aspect ratio fine cellulose fibers, and then the step (2A or 2B) is carried out. <35> or <36> The fine cellulose fiber composite described above. <38> The average fiber diameter of the fine cellulose fiber composite is preferably 0.1 nm or more, more preferably 0.5 nm or more, even more preferably 1 nm or more, even more preferably 2 nm or more, and still more preferably 3 nm or more, and is preferably 100 nm or less, more preferably 50 nm or less, even more preferably 20 nm or less, even more preferably 10 nm or less, even more preferably 6 nm or less, and still more preferably 5 nm or less. <1> ~ <37> The fine cellulose fiber composite according to any one of the preceding claims. <39> The length (average fiber length) of the fine cellulose fiber composite is preferably 150 nm or more, more preferably 200 nm or more, and preferably 1000 nm or less, more preferably 750 nm or less, even more preferably 500 nm or less, and even more preferably 400 nm or less. <1> ~ <38> The fine cellulose fiber composite according to any one of the preceding claims. <40> The average aspect ratio (fiber length / fiber diameter) of the fine cellulose fiber composite is preferably 10 or more, more preferably 20 or more, even more preferably 40 or more, even more preferably 50 or more, and is preferably 140 or less, more preferably 130 or less, even more preferably 100 or less, even more preferably 95 or less, even more preferably 90 or less. <1> ~ <39> The fine cellulose fiber composite according to any one of the preceding claims.

[0148] <41> The standard deviation of the average aspect ratio of the fine cellulose fiber composite is preferably 60 or less, more preferably 50 or less, even more preferably 45 or less, and is preferably 4 or more. <1> ~ <40> The fine cellulose fiber composite according to any one of the preceding claims. <42> The fine cellulose fiber composite can be used in the form of a dispersion, or in the form of a dried powder obtained by removing the solvent from the dispersion by drying treatment or the like. <1> ~ <41> The fine cellulose fiber composite according to any one of the preceding claims. <43> The aforementioned <1> ~ <42> A resin composition comprising the fine cellulose fiber composite according to any one of claims 1 to 4 and a resin. <44> The resin is one or more selected from thermoplastic resins, curable resins, cellulose-based resins, and rubber-based resins. <43> The resin composition described above. <45> The thermoplastic resin may be selected from saturated polyester resins such as polylactic acid resins; olefin resins such as polyethylene resins and polypropylene resins; vinyl chloride resins, styrene resins, (meth)acrylic resins, vinyl ether resins, polyvinyl alcohol resins, polyamide resins, polycarbonate resins, and polysulfone resins, and may be used alone or as a mixture of two or more of the above resins. <44> The resin composition described above. <46> The curable resin is preferably a photocurable resin and / or a thermosetting resin. <44> The resin composition described above. <47> The thermosetting resin may be selected from the group consisting of epoxy resins, phenolic resins, urea resins, melamine resins, unsaturated polyester resins, diallyl phthalate resins, polyurethane resins, silicon resins, and polyimide resins, and may be used singly or in combination of two or more thereof. <46> The resin composition described above. <48> The cellulose-based resin may be selected from organic acid esters such as cellulose acetate, cellulose acetate propionate, and other cellulose mixed acylates; inorganic acid esters such as cellulose nitrate and cellulose phosphate; organic acid / inorganic acid mixed acid esters such as cellulose nitrate acetate; and cellulose ether esters such as acetylated hydroxypropyl cellulose, and may be used singly or in combination of two or more. <44> The resin composition described above. <49> As the rubber-based resin, diene rubber or non-diene rubber can be used. As the diene rubber, one or more types selected from natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, butyl rubber, butadiene-acrylonitrile copolymer rubber, chloroprene rubber, modified natural rubber, etc. can be used. As the non-diene rubber, one or more types selected from butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, urethane rubber, silicone rubber, fluororubber, acrylic rubber, polysulfide rubber, epichlorohydrin rubber can be used in combination. <44> The resin composition described above. <50> The content of the resin in the resin composition is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 85% by mass or more, and is preferably 99% by mass or less, more preferably 98% by mass or less, even more preferably 95% by mass or less, even more preferably 90% by mass or less. <43> ~ <49> The resin composition according to any one of the above. <51> The content of the fine cellulose fiber composite in the resin composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, even more preferably 2% by mass or more, even more preferably 5% by mass or more, even more preferably 10% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, even more preferably 20% by mass or less, even more preferably 15% by mass or less. <43> ~ <50> The resin composition according to any one of the above. <52> The amount of the fine cellulose fiber composite in the resin composition is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, even more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, and is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, even more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, relative to 100 parts by mass of the resin. <43> ~ <51> The resin composition according to any one of the above. <53> The amount of fine cellulose fibers (equivalent amount) in the resin composition is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more, relative to 100 parts by mass of the resin, and is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, even more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less. <43> ~ <52> The resin composition according to any one of the above. <54> Furthermore, the above-mentioned composition may contain plasticizers, crystal nucleating agents, fillers (inorganic fillers, organic fillers), hydrolysis inhibitors, flame retardants, antioxidants, lubricants such as hydrocarbon waxes and anionic surfactants, UV absorbers, antistatic agents, antifogging agents, light stabilizers, pigments, mildew inhibitors, antibacterial agents, foaming agents, surfactants; polysaccharides such as starches and alginic acid; natural proteins such as gelatin, glue, and casein; inorganic compounds such as tannins, zeolites, ceramics, and metal powders; fragrances; flow adjusters; leveling agents; conductive agents; UV dispersants; and deodorizers. <43> ~ <53> The resin composition according to any one of the above. <55> The above-mentioned composite material is obtained by melt-kneading a thermoplastic resin or a curable resin, a fine cellulose fiber composite, and a raw material containing various additives as required. <43> ~ <54> The resin composition according to any one of the above. <56> The present invention can be suitably used for various purposes such as daily necessities, home appliance parts, and automobile parts, and can be suitably used as packaging materials for daily necessities, cosmetics, and home appliances, as electronic materials for constituting electronic parts, as food containers such as blister packs, trays, and lunch box lids, as industrial trays used for transporting and protecting industrial parts, and as automobile parts such as dashboards, instrument panels, and floors. <43> ~ <55> The resin composition according to any one of the above. <57> The aforementioned <43> ~ <56> A resin molded article obtained by extrusion molding, injection molding, press molding, cast molding or solvent casting of any of the resin compositions described above. <58> The thickness of the sheet-like material is preferably 0.01 mm or more, more preferably 0.03 mm or more, even more preferably 0.05 mm or more, even more preferably 0.08 mm or more, even more preferably 0.1 mm or more, and is preferably 1.5 mm or less, more preferably 1.0 mm or less, even more preferably 0.5 mm or less. <57> The resin molded article described above. [Example]

[0149] The present invention will be specifically explained below by showing examples. Note that these examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention in any way. Parts in the examples are parts by mass unless otherwise specified. Note that "normal pressure" refers to 101.3 kPa, and "normal temperature" refers to 25°C.

[0150] [Average fiber diameter, average fiber length, and average aspect ratio of fine cellulose fibers and fine cellulose fiber composites] Water is added to fine cellulose fibers or fine cellulose fiber composites to prepare a dispersion with a concentration of 0.0001% by mass. The dispersion is then dropped onto mica and dried to serve as an observation sample. The fiber height of the cellulose fibers or fine cellulose fiber composites in the observation sample is measured using an atomic force microscope (AFM, Nanoscope III Tapping mode AFM, manufactured by Digital Instruments, Inc., using a Nanosensors Point Probe (NCH) probe). At this time, 100 or more fine cellulose fibers or fine cellulose fiber composites are extracted from a microscopic image in which the cellulose fibers or cellulose fiber composites can be seen, and the average fiber diameter is calculated from the height of these fibers or fiber composites. The average fiber length is calculated from the distance in the fiber direction. The average aspect ratio is calculated from the average fiber length / average fiber diameter, and the standard deviation is also calculated.

[0151] [Carboxy group content of fine cellulose fiber and fine cellulose fiber composite] A 100 mL beaker was filled with 0.5 g of dry fine cellulose fibers or a fine cellulose fiber composite, and 5 mL of 0.01 M sodium chloride solution was added to make a 55 mL dispersion. The dispersion was stirred until the fine cellulose fibers or fine cellulose fiber composite were fully dispersed. 0.1 M hydrochloric acid was added to the dispersion to adjust the pH to 2.5-3. Using an automatic titrator (DKK-TOA Corporation, trade name "AUT-710"), 0.05 M sodium hydroxide solution was added dropwise to the dispersion with a waiting time of 60 seconds. The conductivity and pH were measured every minute, and measurements were continued until the pH reached approximately 11, obtaining a conductivity curve. The sodium hydroxide titration volume was determined from the conductivity curve, and the carboxyl group content of the fine cellulose fibers or fine cellulose fiber composite was calculated using the following formula: Carboxylic group content (mmol / g) = sodium hydroxide titration amount × sodium hydroxide aqueous solution concentration (0.05M) / cellulose fiber mass (0.5g)

[0152] [Average bond amount and introduction rate (ionic bond) of modifying groups in fine cellulose fiber composites] The amount of bonded modifying groups is determined by the following IR measurement method, and the average bonded amount and introduction rate are calculated using the following formula: Specifically, the IR measurement is performed by measuring dried fine cellulose fibers or fine cellulose fiber composites by the ATR method using an infrared absorption spectrometer (IR) Nicolet 6700 (manufactured by Thermo Fisher Scientific), and the average bonded amount and introduction rate of modifying groups are calculated using the following formula. Amount of modified group bonded (mmol / g) = [carboxyl group content of fine cellulose fiber (mmol / g)] × [(1720 cm of fine cellulose fiber -1 Peak intensity - after introduction of modification group of the fine cellulose fiber composite at 1720 cm -1 (peak intensity of 1720 cm) of fine cellulose fiber -1 Peak intensity] 1720cm -1 Peak intensity: Peak intensity derived from the carbonyl group of carboxylic acid Modification group introduction rate (%) = {bonded amount of modification group (mmol / g) / carboxyl group content in fine cellulose fiber before introduction (mmol / g)} × 100

[0153] [Amount of fine cellulose fiber in fine cellulose fiber composite (equivalent amount) (ionic bond)] (1) When only one compound with a modifying group is added The amount of fine cellulose fibers (equivalent amount) is calculated using the following formula. Amount of fine cellulose fiber (g) = Amount of fine cellulose fiber composite (g) / [1 + Molecular weight of compound with modifying group (g / mol) × Bond amount of modifying group (mmol / g) × 0.001] Here, the molecular weight of the compound having a modifying group is the "molecular weight of the entire compound having a modifying group, including the copolymerization portion," when the compound having a modifying group is a primary amine, secondary amine, or tertiary amine; and is the "molecular weight of the entire compound having a modifying group, including the copolymerization portion, minus the molecular weight of the anion component," when the compound having a modifying group is a quaternary ammonium compound or a phosphonium compound.

[0154] (2) When two or more compounds having modifying groups are added The amount of fine cellulose fiber (equivalent amount) is calculated taking into consideration the molar ratio of the amount of each compound having a modifying group added (i.e., the molar ratio when the total molar amount of each compound having a modifying group added is 1). The following formula is a formula for calculating the amount of fine cellulose fiber (equivalent amount) when there are two types of compounds having a modifying group (i.e., a first compound and a second compound) and the molar ratio of the first compound to the second compound is first compound:second compound = 0.8:0.2. Amount of fine cellulose fiber (g) = Amount of fine cellulose fiber composite (g) / [1 + Molecular weight of first compound (g / mol) × 0.8 × Bond amount of modifying group (mmol / g) × 0.001 + Molecular weight of second compound (g / mol) × 0.2 × Bond amount of modifying group (mmol / g) × 0.001] Here, the molecular weight of the compound having a modifying group is the "molecular weight of the entire compound having a modifying group, including the copolymerization portion," when the compound having a modifying group is a primary amine, secondary amine, or tertiary amine; and is the "molecular weight of the entire compound having a modifying group, including the copolymerization portion, minus the molecular weight of the anion component," when the compound having a modifying group is a quaternary ammonium compound or a phosphonium compound.

[0155] [Average bond amount and introduction rate of modifying groups (amide bond) in fine cellulose fiber composites] The average bond amount of the modifying group is calculated by the following formula. Amount of modified group bonded (mmol / g) = Carboxy group content in fine cellulose fiber before modification group introduction (mmol / g) - Carboxy group content in fine cellulose fiber composite after modification group introduction (mmol / g) Modification group introduction rate (%) = {bonded amount of modification group (mmol / g) / carboxyl group content in fine cellulose fiber before introduction (mmol / g)} × 100

[0156] [Amount of fine cellulose fiber in fine cellulose fiber composite (equivalent amount) (amide bond)] (1) When only one compound with a modifying group is added The amount of fine cellulose fibers (equivalent amount) is calculated using the following formula. Amount of fine cellulose fiber (g) = Amount of fine cellulose fiber composite (g) / [1 + Molecular weight of compound with modifying group (g / mol) × Bond amount of modifying group (mmol / g) × 0.001] Here, when the compound having a modifying group is a primary amine or a secondary amine, the molecular weight of the compound having a modifying group is "the molecular weight of the entire compound having a modifying group, including the copolymerized portion, minus 18."

[0157] (2) When two or more compounds having modifying groups are added The amount of fine cellulose fiber (equivalent amount) is calculated taking into consideration the molar ratio of the amount of each compound having a modifying group added (i.e., the molar ratio when the total molar amount of each compound having a modifying group added is 1). The following formula is a formula for calculating the amount of fine cellulose fiber (equivalent amount) when there are two types of compounds having a modifying group (i.e., a first compound and a second compound) and the molar ratio of the first compound to the second compound is first compound:second compound = 0.8:0.2. Amount of fine cellulose fiber (g) = Amount of fine cellulose fiber composite (g) / [1 + Molecular weight of first compound (g / mol) × 0.8 × Bond amount of modifying group (mmol / g) × 0.001 + Molecular weight of second compound (g / mol) × 0.2 × Bond amount of modifying group (mmol / g) × 0.001] Here, when the compound having a modifying group is a primary amine or a secondary amine, the molecular weight of the compound having a modifying group is "the molecular weight of the entire compound having a modifying group, including the copolymerized portion, minus 18."

[0158] Preparation example 1 of fine cellulose fiber (oxidized softwood pulp) Bleached coniferous kraft pulp (Fletcher Challenge Canada, trade name "Machenzie", CSF 650 ml) was used as the natural cellulose fiber. A commercially available TEMPO (Aldrich, free radical, 98% by mass) was used. A commercially available sodium hypochlorite (Wako Pure Chemical Industries, Ltd.) was used. A commercially available sodium bromide (Wako Pure Chemical Industries, Ltd.) was used.

[0159] First, 100 g of bleached softwood kraft pulp fiber was thoroughly stirred with 9900 g of ion-exchanged water, and then 1.6% by mass of TEMPO, 10% by mass of sodium bromide, and 28.4% by mass of sodium hypochlorite were added in this order relative to the pulp mass. Using a pH-stat titration system (AUT-701 automatic titrator, manufactured by DKK-TOA Corporation), 0.5 M sodium hydroxide was added dropwise to maintain the pH at 10.5. After the reaction was carried out for 120 minutes (20°C), the addition of sodium hydroxide was stopped to obtain oxidized pulp. The obtained oxidized pulp was thoroughly washed with ion-exchanged water and then dehydrated to obtain oxidized pulp with a solids content of 34.6%. Subsequently, 1.04 g of the oxidized pulp and 34.8 g of ion-exchanged water were subjected to 10 rounds of micronization treatment at 150 MPa using a high-pressure homogenizer to obtain a carboxyl group-containing microfine cellulose fiber dispersion (solids concentration: 1.0% by mass). The average fiber diameter of the fine cellulose fibers was 2.7 nm, the average fiber length was 578 nm, the average aspect ratio was 214, and the carboxyl group content was 1.2 mmol / g.

[0160] Preparation example 2 of fine cellulose fiber (oxidized hardwood pulp) Oxidized pulp was produced in the same manner as in Preparation Example 1, except that eucalyptus-derived hardwood bleached kraft pulp (manufactured by CENIBRA) was used. The obtained oxidized pulp was subjected to the same pulping treatment as in Preparation Example 1 to obtain a carboxyl group-containing fine cellulose fiber dispersion (solid content concentration: 1.0 mass %). The average fiber diameter of the fine cellulose fibers was 3.5 nm, the average fiber length was 674 nm, the average aspect ratio was 193, and the carboxyl group content was 1.0 mmol / g.

[0161] Preparation example 3 of fine cellulose fibers (reducing the aspect ratio of oxidized softwood pulp) 92.54 g of the dehydrated oxidized pulp obtained in Preparation Example 1 was diluted with 1,000 g of ion-exchanged water, and 346 g of concentrated hydrochloric acid (389 parts by mass per 100 parts by mass of the bone-dry mass of the cellulosic raw material) was added to prepare a dispersion with an oxidized pulp solids concentration of 2.34 wt% and a hydrochloric acid concentration of 2.5 M (pH 1 or less). This dispersion was refluxed at 105°C for 10 minutes for acid hydrolysis. The resulting oxidized pulp was thoroughly washed to obtain acid-hydrolyzed TEMPO-oxidized pulp with a solids content of 41%. Subsequently, 0.88 g of the oxidized pulp and 35.12 g of ion-exchanged water were subjected to a high-pressure homogenizer at 150 MPa for 10 cycles to obtain a dispersion of carboxyl-containing, low-aspect-ratio fine cellulose fibers (solids concentration 1.0% by mass). The average fiber diameter of the fine cellulose fibers was 4.6 nm, the average fiber length was 331 nm, the average aspect ratio was 72, and the carboxyl group content was 1.1 mmol / g.

[0162] Preparation example 4 of fine cellulose fibers (reducing the aspect ratio of oxidized softwood pulp) Carboxy group-containing fine cellulose fibers with a low aspect ratio were produced in the same manner as in Preparation Example 3, except that the reflux time was changed to 60 minutes. The fine cellulose fibers had an average fiber diameter of 6.1 nm, an average fiber length of 284 nm, an average aspect ratio of 47, and a carboxy group content of 1.1 mmol / g.

[0163] Preparation example 5 of fine cellulose fiber (reducing aspect ratio of oxidized softwood pulp) Carboxy group-containing, low aspect ratio fine cellulose fibers were produced in the same manner as in Preparation Example 3, except that the reflux time was changed to 120 minutes. The average fiber diameter of the fine cellulose fibers was 7.5 nm, the average fiber length was 237 nm, the average aspect ratio was 32, and the carboxy group content was 1.1 mmol / g.

[0164] Preparation example 6 of fine cellulose fiber (reducing aspect ratio of oxidized hardwood pulp) Carboxy group-containing fine cellulose fibers with a low aspect ratio were produced in the same manner as in Preparation Example 3, except that the oxidized pulp obtained in Preparation Example 2 was used. The average fiber diameter of the fine cellulose fibers was 8.2 nm, the average fiber length was 213 nm, the average aspect ratio was 26, and the carboxy group content was 1.0 mmol / g.

[0165] Preparation example 7 of fine cellulose fibers (reducing the aspect ratio of oxidized softwood pulp) 14.5 g (solids content 5 g) of the dehydrated oxidized pulp obtained in Preparation Example 1 and 33.3 g of deionized water were placed in a metal pressure device (manufactured by Taiatsu Glass Industries Co., Ltd., product name: "Portable Reactor TVSN2 Type"), and the inside of the metal pressure device was pressurized with 0.4 MPa [gage] of nitrogen gas, and then returned to atmospheric pressure (101 kPa [abs]) (hereinafter, this operation is referred to as nitrogen substitution). The contents were then purged with nitrogen four more times and then sealed. The vessel was then heated to 150°C in an oil bath heated to 180°C without stirring, and the temperature of the oil bath was then adjusted to maintain the vessel at 150°C for 1 hour. After cooling, the contents were removed, 120 g of ion-exchanged water was added, and the mixture was stirred. Then, filtration and separation using a PTFE membrane filter were performed to obtain 21.2 g of impregnated fine cellulose fibers. The average fiber diameter of the fine cellulose fibers was 6.3 nm, the average fiber length was 250 nm, the average aspect ratio was 40, and the carboxyl group content was 1.1 mmol / g.

[0166] Preparation example 8 of fine cellulose fiber (reducing aspect ratio of oxidized softwood pulp) Carboxy group-containing fine cellulose fibers with a low aspect ratio were produced in the same manner as in Preparation Example 3, except that the reflux time was changed to 5 minutes. The fine cellulose fibers had an average fiber diameter of 3.5 nm, an average fiber length of 458 nm, an average aspect ratio of 131, and a carboxy group content of 1.1 mmol / g.

[0167] Preparation example 9 of fine cellulose fiber (reducing aspect ratio of oxidized softwood pulp) 14.5 g of the dehydrated oxidized pulp (5 g solids) obtained in Preparation Example 1 was weighed out as a 5 g dry mass and placed in a planetary ball mill (Fritsch P-6, Germany: using a zirconia pod and 300 g of 10 mm diameter zirconia balls) and mechanically ground at 400 rpm for 5 minutes. The resulting oxidized pulp was thoroughly washed to obtain an oxidized pulp with a solids content of 41%. 0.88 g of the resulting oxidized pulp and 35.12 g of ion-exchanged water were subjected to 10 cycles of micronization at 150 MPa using a high-pressure homogenizer to obtain a dispersion of carboxyl-containing, low-aspect-ratio microfibrillated cellulose fibers (solids concentration: 1.0% by mass). The microfibrillated cellulose fibers had an average fiber diameter of 3.9 nm, an average fiber length of 336 nm, an average aspect ratio of 86, and a carboxyl group content of 1.1 mmol / g.

[0168] Preparation example of fine cellulose fiber 10 (reducing aspect ratio of oxidized softwood pulp) 14.5 g of the dehydrated oxidized pulp obtained in Preparation Example 1 (solid content: 5 g) was weighed out as a dry mass of 5 g and placed in a batch vibration mill ("MB-1" manufactured by Chuo Kakoki Co., Ltd.: total container volume: 3.5 L, rods: 13 SUS304 rods with a diameter of 30 mm, length of 218 mm, and a circular cross-section; rod filling rate: 57%). Mechanical processing was performed by grinding for 10 minutes. The resulting oxidized pulp was thoroughly washed to obtain an oxidized pulp with a solid content of 41%. 0.88 g of the resulting oxidized pulp and 35.12 g of ion-exchanged water were subjected to a high-pressure homogenizer at 150 MPa for 10 cycles to obtain a dispersion of carboxyl-containing, low-aspect-ratio microfibrillated cellulose fibers (solid content: 1.0% by mass). The microfibrillated cellulose fibers had an average fiber diameter of 4.2 nm, an average fiber length of 325 nm, an average aspect ratio of 77, and a carboxyl group content of 1.1 mmol / g.

[0169] Preparation Example 11 of Fine Cellulose Fiber (Blending with Long Fiber) 0.145 g (solids 0.05 g) of the dehydrated oxidized pulp obtained in Preparation Example 1, 1.0 g (solids 0.41 g) of the washed oxidized pulp obtained in Preparation Example 5, and 42.1 g of ion-exchanged water were mixed and subjected to 10 rounds of micronization treatment at 150 MPa using a high-pressure homogenizer to obtain a dispersion of carboxyl-containing, low-aspect-ratio microfibrillated cellulose fibers (solids concentration 1.0% by mass). The microfibrillated cellulose fibers had an average fiber diameter of 7.0 nm, an average fiber length of 270 nm, an average aspect ratio of 38, and a carboxyl group content of 1.1 mmol / g.

[0170] Production example 1 of fine cellulose fiber composite (bonding type: ionic bond) A beaker equipped with a magnetic stirrer and a stirring bar was charged with 35 g of the dispersion of fine cellulose fibers (solid content concentration 5% by mass) obtained in the preparation examples shown in Tables 1, 2, and 4. Subsequently, compounds having the types of modifying groups shown in Tables 1, 2, and 4 were charged in an amount corresponding to 1 mol of amine groups per 1 mol of carboxyl groups of the fine cellulose fibers, and dissolved in 300 g of DMF. The reaction solution was reacted at room temperature (25°C) for 1 hour. After the reaction was completed, the mixture was filtered and washed with DMF to obtain a fine cellulose fiber composite in which amine groups were bonded to the fine cellulose fibers.

[0171] Production Example 2 of Fine Cellulose Fiber Composite (Bonding Type: Amide Bond) A beaker equipped with a magnetic stirrer and a stirring bar was charged with 40 g of the carboxyl group-containing fine cellulose fiber dispersion obtained in Preparation Example 1 or 3 of the fine cellulose fiber (solid content concentration 5.0% by mass). Subsequently, the types of amines shown in Table 3 (all commercially available products) were charged in an amount corresponding to 1.2 mol of amine groups per mol of carboxyl groups in the fine cellulose fiber, 0.34 g of 4-methylmorpholine, and 1.98 g of the condensing agent DMT-MM, and dissolved in 300 g of DMF. The reaction solution was reacted at room temperature (25 ° C) for 14 hours. After the reaction was completed, the mixture was filtered, washed with ethanol to remove the DMT-MM salt, and then washed and solvent-substituted with DMF to obtain a fine cellulose fiber composite in which aliphatic hydrocarbon groups, EOPO copolymers, and aromatic hydrocarbon groups were linked to the fine cellulose fibers via amide bonds.

[0172] Production Example 3 of Fine Cellulose Fiber Composite (Dual Graft) A beaker equipped with a magnetic stirrer and a stirring bar was charged with 35 g of the fine cellulose fiber dispersion obtained in Preparation Example 3 (solid content concentration 5% by mass). Subsequently, compounds having the types of modifying groups shown in Tables 5 to 6 were charged in amounts corresponding to 0.8 mol of primary amine groups (compound (1) in Tables 5 to 6) and 0.2 mol of secondary amine groups (compound (2) in Tables 5 to 6) per mol of carboxyl groups of the fine cellulose fibers, and dissolved in 300 g of DMF. The reaction solution was reacted at room temperature (25°C) for 1 hour. After the reaction was completed, the mixture was filtered and washed with DMF to obtain a fine cellulose fiber composite in which two types of amine groups were bonded to the fine cellulose fibers.

[0173] The fine cellulose fiber dispersion (solid content concentration 5.0% by mass) used in Preparation Examples 1 to 3 was specifically prepared as follows. 2000 g of the carboxy group-containing fine cellulose fiber dispersion (solid content concentration 1.0% by mass) obtained in Preparation Example 1 was stirred with a mechanical stirrer at room temperature (25°C) for 30 minutes. 245 g of 1 M aqueous hydrochloric acid solution was then added, and the mixture was stirred at room temperature for 1 hour to allow the reaction to proceed. After the reaction was completed, the mixture was filtered and washed with ion-exchanged water to remove the hydrochloric acid and salt. Subsequently, the solvent was replaced with DMF to obtain a fine cellulose fiber dispersion (solid content concentration 5.0% by mass) corresponding to Preparation Example 1, in which the carboxy group-containing fine cellulose fibers were swollen in DMF. The same treatment was performed for Preparation Examples 2 to 11 to obtain the respective fine cellulose fiber dispersions (solid content concentration 5.0% by mass).

[0174] <Compounds with modifying groups> TBAH: Tetrabutylammonium hydroxide (Wako Pure Chemical Industries, Ltd.) Propylamine: Wako Pure Chemical Industries, Ltd. Dodecylamine: Wako Pure Chemical Industries, Ltd. Octadecylamine: Wako Pure Chemical Industries, Ltd. Dihexylamine: Wako Pure Chemical Industries, Ltd. Trioctylamine: Wako Pure Chemical Industries, Ltd. Dimethylbehenylamine: Kao Corporation, Farmin DM2285 Aniline: Wako Pure Chemical Industries, Ltd. EOPO amine: an amine obtained by Production Example 4 shown below

[0175] Production Example 4 of Amine Having EO / PO Copolymer Moiety (EOPO Copolymer Amine) 132 g (1 mole) of propylene glycol tert-butyl ether was placed in a 1-L autoclave and heated to 75°C. 1.2 g of flaky potassium hydroxide was added and stirred until dissolved. Next, 1541 g of ethylene oxide (EO) and 35 g of propylene oxide (PO) were reacted at 110°C and 0.34 MPa. 7.14 g of Magnesol 30 / 40 (magnesium silicate, manufactured by Dallas Group) was then added and neutralized at 95°C. 0.16 g of di-tert-butyl-p-cresol was added to the resulting product, which was then mixed and filtered to obtain a polyether EO / PO copolymer.

[0176] Separately, the polyether obtained above (8.4 mL / min), ammonia (12.6 mL / min), and hydrogen (0.8 mL / min) were fed into a 1.250 mL tubular reactor packed with a nickel oxide / copper oxide / chromium oxide (molar ratio: 75 / 23 / 2) catalyst (Wako Pure Chemical Industries, Ltd.). The temperature of the reactor was maintained at 190°C, and the pressure was maintained at 14 MPa. The crude effluent from the reactor was then distilled at 70°C and 3.5 mmHg for 30 minutes. 200 g of the resulting aminated polyether and 93.6 g of 15% aqueous hydrochloric acid were charged into a flask, and the reaction mixture was heated at 100°C for 3.75 hours to cleave the tert-butyl ether with the acid. The product was then neutralized with 144 g of 15% aqueous potassium hydroxide. The neutralized product was then distilled under reduced pressure at 112°C for 1 hour and filtered to obtain a monoamine having an EO / PO copolymer moiety represented by formula (i). In the obtained monoamine, the EO / PO copolymer moiety and the amine are directly bonded, and R1 in formula (i) is a hydrogen atom.

[0177] The molecular weight of the amine copolymerization portion is 1541 [EO molecular weight (44) × EO added moles (35)] + 464 [PO molecular weight (58) × PO added moles (8.0)] + 58 [PO portion molecular weight (propylene glycol) in the starting material] = 2063 was rounded up to 2000.

[0178] Examples 1 to 36 and Comparative Examples 1 to 7 <Thermosetting Resin> (However, Examples 2 to 5, 10 to 12, 17 and 20 are reference examples.) A predetermined amount of the microfibrillated cellulose fiber composite obtained in Production Examples 1 to 3 (i.e., 1.12 g in terms of microfibrillated cellulose fiber), 8.0 g of the epoxy resin jER828 (manufactured by Mitsubishi Chemical Corporation), and DMF were mixed and finely treated using a high-pressure homogenizer at 100 MPa for one pass and 150 MPa for two passes. To the resulting solution, 0.4 g of 2-ethyl-4-methylimidazole (manufactured by Wako Pure Chemical Industries, Ltd.) was added as a curing agent, and the mixture was stirred for 7 minutes using a planetary mixer called the Awatori Rentaro (manufactured by Thinky Corporation). The resulting varnish was applied to a thickness of 0.4 mm using a bar coater. After drying at 80°C for 1 hour to remove the solvent, the mixture was thermally cured at 150°C for 1 hour to produce a sheet-like molded product with a thickness of approximately 0.1 mm.

[0179] Reference example 1 A molded article was produced in the same manner as in Example 1, except that the fine cellulose fiber composite was not added and the coating thickness of the solution was changed to 0.1 mm.

[0180] The properties of the resulting resin composition (paint) and molded article (coating film) were evaluated according to the methods of the following Test Examples 1 to 3. The results are shown in Tables 1 to 6.

[0181] Test Example 1 (Storage Modulus) Using a dynamic viscoelasticity analyzer (manufactured by SII Corporation, product name "DMS6100"), measurements were taken in tension mode on a strip-shaped sample 5 mm wide and 20 mm long in a nitrogen atmosphere at a frequency of 1 Hz, with the temperature rising from 30°C to 300°C at a rate of 10°C per minute. The storage modulus values ​​used were those at 30°C and 200°C. A higher storage modulus at 30°C indicates superior mechanical strength, while a higher storage modulus at 200°C indicates superior heat resistance.

[0182] Test Example 2 (Coefficient of Linear Thermal Expansion) Using a thermal stress-strain measuring device (Hitachi High-Tech Science Corporation, product name "EXSTAR TMA / SS6100"), a rectangular sample 5 mm wide and 20 mm long was measured in a nitrogen atmosphere in tension mode with a load of 30 mN, while the temperature was increased at a rate of 5°C per minute. The linear thermal expansion coefficient was calculated by averaging the linear thermal expansion coefficient over a temperature range from room temperature (30°C) to 100°C. A lower linear thermal expansion coefficient indicates better dimensional stability.

[0183] Test Example 3 (Weight Loss) Using a thermal analyzer (Hitachi High-Tech Science Corporation, product name "STA7200"), approximately 1 mg of sample was placed on an aluminum pan, and the temperature was raised from 30°C to 200°C at a rate of 40°C per minute in a nitrogen atmosphere, and then the weight loss was measured after holding at 200°C for 60 minutes. Although the difference in weight loss may be difficult to discern, a smaller weight loss indicates better heat resistance.

[0184] [Table 1]

[0185] [Table 2]

[0186] [Table 3]

[0187] [Table 4]

[0188] [Table 5]

[0189] [Table 6]

[0190] From the above, it can be seen that the resin composition containing the fine cellulose fiber composite of the present invention has excellent heat resistance, and that the molded body of such a resin composition has excellent mechanical strength at room temperature, high strength at high temperatures, excellent heat resistance, and good dimensional stability. [Industrial Applicability]

[0191] The resin composition containing the fine cellulose fiber composite of the present invention has excellent heat resistance, and molded articles of this resin composition have excellent mechanical strength, heat resistance, and dimensional stability. Therefore, the present invention can be suitably used for various industrial applications such as daily necessities, home appliance parts, packaging materials for home appliance parts, and automobile parts.

Claims

1. A fine cellulose fiber composite having a carboxy group content of 0.1 mmol / g or more, in which modifying groups are bonded to the carboxy groups of fine cellulose fibers having a carboxy group at the C6 position of a cellulose constituent unit, an average aspect ratio of more than 50 and less than 100, and an average fiber diameter of 20 nm or less, a compound having a modifying group is bound to the carboxy group via an ionic bond; the compound having a modifying group is at least one selected from the group consisting of a primary amine, a secondary amine, a tertiary amine, and a quaternary ammonium compound each having a chain saturated hydrocarbon group having from 1 to 30 carbon atoms, aniline, and a compound represented by formula (i): Fine cellulose fiber composite. 【Chemistry 1】 [wherein R 1 represents a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a —CH 2 CH(CH 3 )NH 2 group, or a group represented by the following formula (ii), ethylene oxide (EO) and propylene oxide (PO) are present in a random or block form, a is a positive number indicating the average number of moles of EO added, and b is a positive number indicating the average number of moles of PO added] 【Chemistry 2】 [wherein n is 0 or 1; R 2 is a phenyl group, a hydrogen atom, or a linear or branched alkyl group having 1 to 3 carbon atoms; EO and PO are present randomly or in a block form; c and e are the average number of moles of EO added and are independently numbers from 0 to 50; and d and f are the average number of moles of PO added and are independently numbers from 1 to 50]

2. 2. The fine cellulose fiber composite according to claim 1, wherein the standard deviation of the average aspect ratio is 4 or more and 60 or less.

3. 2. The fine cellulose fiber composite according to claim 1, wherein the length of the fine cellulose fiber composite is 500 nm or less.

4. The fine cellulose fiber composite according to any one of claims 1 to 3, wherein the number of modifying groups bonded to the carboxy groups of the fine cellulose fibers is two or more.

5. The fine cellulose fiber composite according to any one of claims 1 to 3, wherein the carboxyl group content of the fine cellulose fibers is 3 mmol / g or less.

6. A resin composition comprising a resin and the fine cellulose fiber composite according to any one of claims 1 to 3.

7. The resin composition according to claim 6, wherein the content of the resin in the resin composition is 50% by mass or more and 99% by mass or less.

8. The resin composition according to claim 6, wherein the content of the fine cellulose fiber composite in the resin composition is 0.1% by mass or more and 50% by mass or less.

9. A resin molded article obtained by extrusion molding, injection molding, press molding, cast molding or solvent casting of the resin composition according to claim 6.

10. 10. The resin molded article according to claim 9, which is in the form of a sheet having a thickness of 0.01 mm or more and 1.5 mm or less.

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