JP2022059589A - Method for producing modified cellulose fiber - Google Patents

Abstract

To provide a modified cellulose fiber that can suppress coloration and gives a high-yield dispersoid, and a method for producing a modified fine cellulose fiber.SOLUTION: A method for producing a modified cellulose fiber has a step A for reacting an anion-modified cellulose fiber having a cellulose I crystal structure with an amine compound to prepare a modified cellulose fiber. In the step A, the reaction is induced in the presence of an amine compound in an amount smaller than 0.3 mol eq. of anionic groups of the anion-modified cellulose fiber.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a modified cellulose fiber.

Conventionally, plastic materials derived from petroleum, which is a finite resource, have been widely used, but in recent years, technologies with less impact on the environment have come into the limelight, and under such technological background, it is a biomass that exists in large quantities in nature. Cellulose fibers, especially materials using fine cellulose fibers, are attracting attention because various mechanical properties are remarkably improved.

Normally, since the surface of the fine cellulose fiber is hydrophilic, it aggregates in a hydrophobic solvent or a hydrophobic resin. Therefore, when used in the above system, it is necessary to hydrophobically modify the fine cellulose fibers.

Patent Document 1 includes a step of micronizing a hydrophobically modified cellulose fiber having an average fiber length of 1 μm or more and 1,000 μm or less, which is formed by binding a modifying group to an anion-modified cellulose fiber, in an organic solvent. A method for producing a modified hydrophobic cellulose fiber is described.

Japanese Unexamined Patent Publication No. 2019-119983

However, in Patent Document 1, there is room for improvement in that the obtained dispersion is unintentionally colored. A dispersion of the modified cellulose fiber or the finely divided modified cellulose fiber in which the coloring is suppressed is preferable because the coloring of the member containing the same can be suppressed and the quality is improved.
Therefore, the present invention relates to a method for producing a modified cellulose fiber and a finely divided modified cellulose fiber, which can suppress coloring and obtain a dispersion having a high yield.

The present invention relates to the following [1] to [3].
[1] A method for producing a modified cellulose fiber, which comprises a step A of reacting an anion-modified cellulose fiber having a cellulose I-type crystal structure with an amine compound to obtain a modified cellulose fiber.
A method for producing a modified cellulose fiber, wherein in step A, the reaction is carried out in the presence of an amine compound in an amount less than 0.3 molar equivalent of the anionic group of the anionic modified cellulose fiber.
[2] A method for producing a miniaturized modified cellulose fiber, which comprises a step B of micronizing the modified cellulose fiber obtained by the production method according to the above [1] in a solvent.
[3] Modified cellulose by reacting a finely divided anion-modified cellulose fiber having a cellulose I-type crystal structure, an average fiber length of 1 μm or less, and an average fiber diameter of 0.5 nm or more and 50 nm or less with an amine compound. A method for producing a miniaturized modified cellulose fiber, which comprises step C for obtaining the fiber.
A method for producing a micronized modified cellulose fiber, wherein in step C, an amine compound in an amount less than 0.3 molar equivalent of the anionic group of the micronized anion-modified cellulose fiber is present and the reaction is carried out.

According to the present invention, it is possible to produce a modified cellulose fiber or a finely divided modified cellulose fiber that can suppress coloring even when blended in a resin in high yield.

The reason why the modified cellulose fiber and the finely divided modified cellulose fiber obtained by the production method of the present invention can exert the above-mentioned effect is not clear, but by reducing the amount of the amine compound, not only the coloring is suppressed but also the coloring is suppressed. It is presumed that the reason is that it also suppresses the miniaturization of the anion-modified cellulose fiber.

1. 1. Method for Producing Modified Cellulose Fiber The method for producing the modified cellulose fiber of the present invention is a production method including step A described later, and in step A, the amount of anionic groups of the anionic modified cellulose fiber is less than 0.3 mol equivalent. One of the characteristics is that the reaction is carried out in the presence of an amount of the amine compound.
Step A: A step of reacting an anion-modified cellulose fiber having a cellulose I-type crystal structure with an amine compound to obtain a modified cellulose fiber.

1-1. Anion-modified Cellulose Fiber The anion-modified cellulose fiber used in the present invention is a cellulose fiber that has been anion-modified so as to contain an anionic group in the cellulose fiber.

The anion-modified cellulose fiber has a cellulose type I crystal structure. The crystallinity of the anion-modified cellulose fiber is preferably 10% or more, more preferably 15% or more, still more preferably 20% or more, from the viewpoint of the mechanical strength of the resin molded product. Further, from the viewpoint of raw material availability, it is preferably 90% or less, more preferably 85% or less, still more preferably 80% or less, still more preferably 75% or less. In the present specification, the crystallinity of various cellulose fibers is the cellulose I-type crystallinity calculated from the diffraction intensity value by the X-ray diffraction method, and can be measured according to the method described in Examples described later. .. The cellulose type I is the crystal form of natural cellulose, and the cellulose type I crystallization degree means the ratio of the amount of the crystal region to the whole cellulose fiber. The presence or absence of the cellulose I-type crystal structure can be determined by the peak at 2θ = 22.6 ° in the X-ray diffraction measurement.

The average fiber length of the anion-modified cellulose fiber is preferably 1 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more, still more preferably 25 μm or more, from the viewpoint of exhibiting high transparency in the finely divided modified cellulose fiber. On the other hand, from the same viewpoint, it is preferably 1000 μm or less, more preferably 800 μm or less, still more preferably 500 μm or less, still more preferably 400 μm or less.

In the present invention, the raw material cellulose fiber or anion-modified cellulose fiber may be subjected to, for example, biochemical treatment and / or chemical treatment to adjust the length so as to have the above-mentioned average fiber length. The biochemical treatment is not particularly limited in the drug to be used, and examples thereof include treatment using an enzyme such as endoglucanase, exoglucanase, and beta-glucosidase. The chemical treatment is not particularly limited in the chemicals used, and examples thereof include acid hydrolysis treatment with hydrochloric acid and sulfuric acid, oxidation treatment with hydrogen peroxide and ozone, and alkali hydrolysis treatment with alkali such as sodium hydroxide. .. For the conditions of the alkaline hydrolysis treatment and the acid hydrolysis treatment, for example, paragraphs 0034 to 0035 of JP-A-2019-119983 can be referred to.

The average fiber diameter of the anion-modified cellulose fiber is preferably 1 μm or more, more preferably 5 μm or more, still more preferably 15 μm or more from the viewpoint of production efficiency, and from the viewpoint of exhibiting high transparency in the finely divided modified cellulose fiber. It is preferably 300 μm or less, more preferably 100 μm or less, still more preferably 60 μm or less.

The average aspect ratio of the anion-modified cellulose fiber is preferably 1 or more, more preferably 2 or more, still more preferably 3 or more, from the viewpoint of improving the strength of the member containing the miniaturized modified cellulose fiber. From the viewpoint of exhibiting high transparency in the quality cellulose fiber, it is preferably 100 or less, more preferably 50 or less, still more preferably 20 or less.
The average fiber length, average fiber diameter and average aspect ratio of the anion-modified cellulose fiber are measured by the methods described in Examples described later.

The content of anionic groups in the anion-modified cellulose fiber is preferably 0.1 mmol / g or more, more preferably 0.4 mmol / g or more, still more preferably 0, from the viewpoint of stable miniaturization and introduction of modifying groups. It is 6.6 mmol / g or more. From the same viewpoint, the upper limit is preferably 3.0 mmol / g or less, more preferably 2.5 mmol / g or less, still more preferably 2.0 mmol / g or less. The content of anionic groups can be measured by the method described in Examples below.

Examples of the anionic group contained in the anion-modified cellulose fiber include a carboxy group, a sulfonic acid group and a (phosphorous acid) group, and the carboxy group is preferable from the viewpoint of introduction efficiency into the cellulose fiber.
Examples of the ion (counter ion) paired with the anionic group in the anion-modified cellulose fiber include metal ions such as sodium ion, potassium ion, calcium ion and aluminum ion generated in the presence of an alkali during production, and these metals. Examples thereof include protons generated by substituting an ion with an acid.

1-2. Method for Preparing Anion-Modified Cellulose Fiber The anion-modified cellulose fiber used in the present invention is subjected to an oxidation treatment or an anionic group addition treatment to the raw material cellulose fiber, and at least one or more anionic groups are introduced to introduce the anion-modified cellulose fiber. It can be obtained by letting it.

[Raw material cellulose fiber]
As the cellulose fiber which is a raw material of the anion-modified cellulose fiber, it is preferable to use a natural cellulose fiber from the viewpoint of having a cellulose type I crystal structure and the environmental load. Examples of the natural cellulose fiber include wood pulp such as coniferous tree pulp and broadleaf tree pulp; cotton pulp such as cotton linter and cotton lint; non-wood pulp such as straw pulp and bagas pulp; and bacterial cellulose and the like. One of these can be used alone or in combination of two or more.

The average fiber diameter and the average fiber length of the raw material cellulose fiber are not particularly limited. The average fiber diameter is, for example, preferably 1 μm or more from the viewpoint of availability, and preferably 100 μm or less from the same viewpoint. The average fiber length is, for example, preferably 1000 μm or more from the viewpoint of availability, and preferably 10,000 μm or less from the same viewpoint. The average fiber diameter and the average fiber length of the raw material cellulose fiber can be measured by the method described in Examples described later.

[Method of introducing anionic groups]
(1) When introducing a carboxy group as an anionic group into a cellulose fiber As a method of introducing a carboxy group into a cellulose fiber, for example, a method of oxidizing a hydroxy group of a cellulose fiber to convert it into a carboxy group, or a method of converting a hydroxy group of a cellulose fiber into a carboxy group, or a method of introducing a hydroxy group of a cellulose fiber. Examples of the group include a method of reacting at least one selected from the group consisting of a compound having a carboxy group, an acid anhydride of the compound having a carboxy group and a derivative thereof.

As a method for oxidizing the hydroxy group of the cellulose fiber, for example, 2,2,6,6-tetramethyl-1-piperidin-N described in JP-A-2015-143336 or JP-A-2015-143337. -Examples include a method in which an oxidizing agent such as sodium hypochlorite and a bromide such as sodium bromide are reacted with the raw material cellulose fiber using oxyl (TEMPO) as a catalyst. By performing the oxidation treatment of the cellulose fiber using TEMPO as a catalyst, the hydroxymethyl group (-CH ₂ OH) at the C6 position of the cellulose constituent unit is selectively converted into a carboxy group. In particular, this method is advantageous in that the selectivity of the hydroxyl group at the C6 position to be oxidized on the surface of the raw material cellulose fiber is excellent, and the reaction conditions are mild. Therefore, a preferred embodiment of the anion-modified cellulose fiber in the present invention is a cellulose fiber in which the C6 position of the cellulose constituent unit is a carboxy group. In the present specification, such cellulose fibers may be referred to as "oxidized cellulose fibers".

The compound having a carboxy group for use in introducing the carboxy group into the cellulose fiber is not particularly limited, and specific examples thereof include acetic acid halide. Examples of the halogenated acetic acid include chloroacetic acid and the like.
The acid anhydride of the compound having a carboxy group and its derivatives for use in introducing the carboxy group into the cellulose fiber are not particularly limited, but are not particularly limited, such as maleic anhydride, succinic anhydride, phthalic anhydride and adipic acid anhydride. Examples thereof include acid anhydrides of dicarboxylic acid compounds, acid anhydrides of compounds having a carboxy group, and derivatives of acid anhydrides of compounds having a carboxyl group. These compounds may be substituted with hydrophobic groups.

(2) When introducing a sulfonic acid group or a (phosphorous acid group) as an anionic group into a cellulose fiber As a method for introducing a sulfonic acid group into a cellulose fiber, a method of adding sulfuric acid to the cellulose fiber and heating it can be mentioned. Be done.
As a method for introducing a (sub) phosphoric acid group into a cellulose fiber, a method of mixing a powder or an aqueous solution of (sub) phosphoric acid or a (sub) phosphoric acid derivative with a dry or wet state cellulose fiber, or a method of mixing a cellulose fiber. Examples thereof include a method of adding an aqueous solution of (sub) phosphoric acid or a (sub) phosphoric acid derivative to the dispersion liquid of. When these methods are adopted, in general, dehydration treatment, heat treatment and the like are performed after mixing or adding powder or aqueous solution of (sub) phosphorous acid or (sub) phosphorous acid derivative.

1-3. Amine Compounds As used herein, an amine compound is a compound having a modifying group and at least one amino group in the molecule.

[Modifying group]
Examples of the modifying group contained in the amine compound include (a) a hydrocarbon group and (b) a polymer group. These modifying groups may be attached to the anion-modified cellulose fiber by one type alone or in combination of two or more types.

(a) Hydrocarbon groups Examples of the hydrocarbon groups include monovalent hydrocarbon groups, for example, chain-type saturated hydrocarbon groups, chain-type unsaturated hydrocarbon groups, cyclic-type saturated hydrocarbon groups, and (heterocyclic) fragrances. Group hydrocarbon groups can be mentioned.
The hydrocarbon group has 1 or more carbon atoms, preferably 3 or more, more preferably 8 or more, still more preferably 10 or more, while preferably 30 or less, more preferably 22 or less, still more preferably 18 or less. Is. The hydrocarbon group may have a substituent described later, and a part of the hydrocarbon group may be substituted with a hydrogen nitride group.

Specific examples of the chain saturated hydrocarbon group include, for example, 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, and a tert-pentyl group. Examples thereof include 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.

Specific examples of the chain unsaturated hydrocarbon group include an ethylene group, a propylene group, a butene group, an isobutene group, an isoprene group, a pentene group, a hexene group, a heptene group, an octene group, a nonene group, a decene group, and a dodecene group. , Tridecene group, tetradecene group, octadecene group.

Specific examples of the cyclic saturated hydrocarbon group include, for example, a cyclopropane group, a cyclobutyl group, a cyclopentane group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, a cyclododecyl group, and a cyclotridecyl group. , Cyclotetradecyl group, cyclooctadecyl group and the like.

As the aromatic hydrocarbon group, for example, it is selected from the group consisting of an aryl group and an aralkyl group.

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 a group in which these groups are substituted with a substituent described later.

Examples of the aralkyl group include a benzyl group, a dibenzyl group, a trityl group, a phenethyl group, a phenylpropyl group, a phenylpentyl group, a phenylhexyl group, a phenylheptyl group, a phenyloctyl group, and an aromatic group of these groups as a substituent. Examples include groups further substituted with.

(B) Polymer group A polymer group is a functional group containing a polymer structure. The molecular weight of the polymer group is preferably 100 or more, more preferably 200 or more, still more preferably 300 or more, still more preferably 400 or more, still more preferably 600 or more, from the viewpoint of improving the transparency of the resin containing the modified cellulose fiber. , More preferably 1,000 or more, still more preferably 1,500 or more. From the same viewpoint, it is preferably 10,000 or less, more preferably 7,000 or less, still more preferably 5,000 or less, still more preferably 4,000 or less, still more preferably 3,500 or less, still more preferably 2,500. It is as follows.

The polymer group is preferably a functional group having a repeating structure linked by a structure having an oxygen atom, and more preferably a polysiloxane structure (silicone chain), from the viewpoint of improving the transparency of the resin containing the modified cellulose fiber. And a functional group having a repeating structure linked by oxygen atoms such as a polyoxyalkylene structure (alkylene oxide chain), more preferably a functional group having a polyoxyalkylene structure, and still more preferably an alkoxypolyoxyalkylene group.

(b-1) Polysiloxane structure (silicone chain)
The polysiloxane structure (silicone chain) is a structure having a siloxane bond as a main chain, and may be further accompanied by an alkylene group. The polysiloxane structure may have a substituent described later.

(b-2) Polyoxyalkylene structure (alkylene oxide chain)
The polyoxyalkylene structure (alkylene oxide chain) is preferably one kind or two or more kinds of oxy selected from oxyalkylenes having 2 or more and 8 or less carbon atoms from the viewpoint of improving the transparency of the resin containing the modified cellulose fiber. An alkylene (co) polymer structure, more preferably one or more oxyalkylene (co) polymer structures selected from oxyalkylenes having 2 or more and 4 or less carbon atoms, still more preferably ethylene oxide (EO). And a (co) polymer structure of one or two oxyalkylenes selected from propylene oxide (PO), more preferably a copolymer in which ethylene oxide (EO) and propylene oxide (PO) are polymerized at random or in a block shape. It is a structure (also referred to as a (EO / PO) structure).

As the polyoxyalkylene structure, for example, the following equation:

(In the formula, R ¹ represents a hydrogen atom, a hydrocarbon group having 1 or more and 6 or less carbon atoms, -CH ₂ CH ₂ NH ₂ groups, or -CH ₂ CH (CH ₃ ) NH ₂ groups. EO and PO are random. Or it exists in a block shape, where a is 0 or a positive number indicating the average number of added moles of EO, b is 0 or a positive number indicating the average number of added moles of PO, where a and b are 0 at the same time. The structure shown by) is mentioned.

When R ¹ is a linear or branched alkyl group having 1 or more and 6 or less carbon atoms, the alkyl group is preferably a methyl group, an ethyl group, an n-propyl group and a sec-propyl group. R ¹ may be a hydrogen atom.

From the viewpoint of improving dispersion stability, a is preferably 0 or more, more preferably 1 or more, still more preferably 3 or more, still more preferably 6 or more, still more preferably 11 or more, still more preferably 15 or more, still more preferably. It is 20 or more, more preferably 25 or more, still more preferably 30 or more. From the same viewpoint, it is preferably 100 or less, more preferably 70 or less, still more preferably 60 or less, still more preferably 50 or less, still more preferably 40 or less.

From the viewpoint of improving the dispersion stability, b is preferably 0 or more, more preferably 1 or more, still more preferably 3 or more, still more preferably 5 or more. From the same viewpoint, it is preferably 50 or less, more preferably 40 or less, still more preferably 30 or less, still more preferably 25 or less, still more preferably 20 or less, still more preferably 15 or less, still more preferably 10 or less.

In the above formula, a + b indicates the total number of added moles of EO and PO, and is preferably 4 or more, more preferably 6 or more, and more preferably 8 or more from the viewpoint of improving dispersion stability, and from the same viewpoint. It is preferably 100 or less, more preferably 70 or less.

The PO content (mol%) in the (EO / PO) structure can be calculated based on a and b, and can be specifically obtained from b × 100 / (a + b). From the viewpoint of further improving the dispersibility, the PO content is preferably 1 mol% or more, more preferably 5 mol% or more, still more preferably 7 mol% or more, still more preferably 10 mol% or more. From the same viewpoint, it is preferably 100 mol% or less, more preferably 90 mol% or less, still more preferably 85 mol% or less, still more preferably 75 mol% or less, still more preferably 60 mol% or less, still more preferably 50 mol%. Below, it is more preferably 40 mol% or less, still more preferably 30 mol% or less.

The formula weight (molecular weight) of the polyoxyalkylene structure is preferably 100 or more, more preferably 200 or more, still more preferably 300 or more, still more preferably 500 or more, still more preferably 1,000 or more, from the viewpoint of improving dispersion stability. , More preferably 1,500 or more. From the same viewpoint, it is preferably 10,000 or less, more preferably 7,000 or less, still more preferably 5,000 or less, still more preferably 4,000 or less, still more preferably 3,500 or less, still more preferably 2,500. It is as follows.

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

[Specific examples of amine compounds]
The amine compound may be any of a primary amine, a secondary amine, a tertiary amine and a quaternary ammonium compound. As the anion component of the quaternary ammonium compound, from the viewpoint of reactivity, halogen ions such as chlorine ion and bromine ion, hydrogen sulfate ion, perchlorate ion, tetrafluoroborate ion and hexafluorophosphate ion are preferable. , Trifluoromethanesulfonate ion, hydroxy ion and the like.

(a) Amine compound having a hydrocarbon group As a specific example of an amine compound having a hydrocarbon group, examples of the primary to tertiary amines include ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, butylamine and di. Butylamine, hexylamine, 2-ethylhexylamine, dihexylamine, trihexylamine, octylamine, dioctylamine, trioctylamine, dodecylamine, diddecylamine, stearylamine, distearylamine, monoethanolamine, diethanolamine, triethanolamine , Oleylamine, aniline, octadecylamine, dimethylbehenylamine, benzylamine, dibenzylamine, tritylamine, naphthylamine, imidazole, 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, Examples thereof include 2-phenyl-4-methylimidazole and 1- (3-aminopropyl) imidazole.

Examples of the quaternary ammonium compound include tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetraethylammonium chloride, tetrapropylammonium hydroxide (TPAH), tetrabutylammonium hydroxide (TBAH), and tetra. Examples thereof include butylammonium chloride, lauryltrimethylammonium chloride, dilauryldimethylchloride, stearyltrimethylammonium chloride, distearyldimethylammonium chloride, cetyltrimethylammonium chloride, and alkylbenzyldimethylammonium chloride.

The amine compound having a hydrocarbon group can be prepared by using a commercially available product or by a known method.

(b-1) Amine Compounds Having a Polysiloxane Structure Examples of the amine compounds include those having a structure in which an amino group is bonded to a skeleton of a polysiloxane structure via an alkylene group or the like. As used herein, such amine compounds may be referred to as "amino-modified silicones". The amino-modified silicone can be prepared by using a commercially available product or by a known method. Only one kind of amino-modified silicone may be used, or two or more kinds may be used.

As amino-modified silicones, from the viewpoint of performance, TSF4703 (kinematic viscosity: 1000, amino equivalent: 1600), TSF4708 (kinematic viscosity: 1000, amino equivalent: 2800), Toray Dow Corning manufactured by Momentive Performance Materials Co., Ltd. SS-3551 (Dynamic Viscosity: 1000, Amino Equivalent: 1600), SF8457C (Dynamic Viscosity: 1200, Amino Equivalent: 1800), SF8417 (Dynamic Viscosity: 1200, Amino Equivalent: 1700), BY16- 209 (Dynamic Viscosity: 500, Amino Equivalent: 1800), BY16-892 (Dynamic Viscosity: 1500, Amino Equivalent: 2000), BY16-898 (Dynamic Viscosity: 2000, Amino Equivalent: 2900), FZ-3760 (Dynamic Viscosity: 220, Amino Equivalent: 1600), KF8002 (Dynamic Viscosity: 1100, Amino Equivalent: 1700), KF867 (Dynamic Viscosity: 1300, Amino Equivalent: 1700), KF-864 (Dynamic Viscosity: 1700) manufactured by Shin-Etsu Chemical Industry Co., Ltd. , Amino equivalent: 3800), BY16-213 (kinematic viscosity: 55, amino equivalent: 2700), BY16-853U (kinematic viscosity: 14, amino equivalent: 450) are preferable. In (), the kinematic viscosity shows a measured value (unit: mm ² / s) at 25 ° C., and the unit of amino equivalent is g / mol.

(b-2) Amine Compound Having a Polyoxyalkylene Structure In an amine compound, the polyoxyalkylene structure and the nitrogen atom of the amine compound are preferably bonded directly or via a linking group. As the linking group, a hydrocarbon group is preferable, and an alkylene group having a carbon number of preferably 1 or more and 6 or less, more preferably 1 or more and 3 or less can be mentioned. As such an alkylene group, for example, an ethylene group and a propylene group are preferable.

Examples of the amine compound having a polyoxyalkylene structure include the following formula (i):

Examples thereof include the compounds indicated by. ^R1 , a and b in the formula (i) are the same as ^R1 , a and b in the formula showing an example of the above-mentioned polyoxyalkylene structure.

The amine compound having a polyoxyalkylene structure is a compound for introducing a modifying group represented by the polyoxyalkylene structure, and can be prepared according to a known method. For example, after adding ethylene oxide or propylene oxide in a desired amount to propylene glycol alkyl ether, the hydroxy group terminal may be aminated. If necessary, the alkyl ether can be cleaved with an acid to form a hydrogen atom at the end. For these production methods, Japanese Patent Application Laid-Open No. 3-181448 can be referred to, and details of such amine compounds are described in, for example, Japanese Patent No. 6105139.

As the amine compound having a polyoxyalkylene structure, for example, a commercially available product can be preferably used.
Specific examples of the amine compound having a hydrocarbon group and having the polymer structure of EO or the polymer structure of PO include SUNBRIGHT MEPA-10H, SUNBRIGHT MEPA-20H, and SUNBRIGHT manufactured by NOF CORPORATION. Examples thereof include MEPA-50H, SUNBRIGHT MEPA-10T, SUNBRIGHT MEPA-12T, SUNBRIGHT MEPA-20T, SUNBRIGHT MEPA-30T, and SUNBRIGHT MEPA-40T.
Specific examples of the amine compound having an EO / PO copolymer structure and which may have a hydrocarbon group include Jeffamine M-2070, Jeffamine M-2005, Jeffamine M-2095 and Jeffamine manufactured by HUNTSMAN. M-1000, Jeffamine M-600, Surfoamine B200, Surfoamine L100, Surfoamine L200, Surfoamine L207, Surfoamine L300, Surfoamine B-100, XTJ-501, XTJ-506, XTJ-507, XTJ-508, M3000, Jeffamine ED- 600, Jeffamine ED-900, Jeffamine ED-2003, Jeffamine D-230, Jeffamine D-400, Jeffamine D-2000, Jeffamine D-4000, XTJ-510, Jeffamine T-3000, Jeffamine T-5000, XTJ-502, Examples include XTJ-509 and XTJ-510. These may be used alone or in combination of two or more.

1-4. Process A
The anion-modified cellulose fiber used in step A is an anion-modified cellulose fiber having a cellulose I-type crystal structure. In step A, the anionic-modified cellulose fiber is reacted with the amine compound to bond the anionic group of the anionic-modified cellulose fiber with the amine compound, and the modifying group of the amine compound is introduced into the anionic group. To obtain modified cellulose fibers.

Specific examples of the bonding mode between the amine compound and the anionic group include an ionic bond and / or an amide bond with an amine salt or the like from the viewpoint of dispersibility of the finely divided modified cellulose fiber. For example, (1) JP-A-2015-143336 can be referred to when introducing via an ionic bond, and JP-A-2015-143337 can be referred to when introducing via an amide bond. Can be.
After the completion of the binding step, post-treatment may be appropriately performed in order to remove unreacted compounds and the like. As the post-treatment method, for example, filtration, centrifugation, dialysis and the like can be used.

(1) Mode of introduction via ionic bond When introducing a modifying group via an ionic bond, the anionic-modified cellulose fiber and the amine compound may be mixed, whereby the anionic property contained in the anionic-modified cellulose fiber is contained. An ionic bond is formed between the group and the amino group of the amine compound.
For example, when an oxidized cellulose fiber is used as the anion-modified cellulose fiber and a primary amine having the above-mentioned modifying group is used as the amine compound, as shown in the following formula, the C6 position of glucose constituting the cellulose fiber is used. The above-mentioned modifying group can be introduced into the carboxy group via an ionic bond (in the formula, C ⁶ is the carbon atom at the 6-position of glucose constituting the cellulose fiber, and R is the modifying group). ..

The abundance of the amine compound in this embodiment is less than 0.3 molar equivalent of the anionic group of the anionic modified cellulose fiber from the viewpoint of exhibiting high transparency in the finely divided modified cellulose fiber. In the present specification, the "amino compound having an equivalent of 0.3 mol of the anionic group of the anion-modified cellulose fiber" means that "the amino group of the amino compound is 0. It means "an amount of amino compound corresponding to 3 mol". The abundance of the amino compound is preferably 0.01 molar equivalent or more, more preferably 0.02 molar equivalent, from the viewpoint of improving the dispersibility when the modified cellulose fiber or the finely divided modified cellulose fiber is blended into the member. The above is more preferably 0.03 molar equivalent or more. On the other hand, from the viewpoint of suppressing the coloring of the obtained dispersion and improving the yield, the abundance of the amino compound is less than 0.3 molar equivalent, preferably 0.2 molar equivalent or less, more preferably 0.15. It is less than or equal to the molar equivalent. When the amine compound has a plurality of amino groups, the total number of moles of the amino groups is made to be the said number of moles.

It is preferable to use a solvent for mixing. As the solvent, it is preferable to select a solvent in which the compound to be used is dissolved, and for example, methanol, ethanol, isopropanol (IPA), N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N, N-dimethylacetamide. , Tetrahydrofuran (THF), acetone, methyl ethyl ketone (MEK), cyclohexanone, ethyl acetate, acetonitrile, dichloromethane, chloroform, toluene, acetic acid, 1-methoxy-2-propanol (PGME), water and the like. It can be used alone or in combination of two or more.

The temperature at the time of mixing is preferably 0 ° C. or higher, more preferably 5 ° C. or higher, still more preferably 10 ° C. or higher, from the viewpoint of the reactivity of the compound. Further, from the viewpoint of suppressing the coloring of the modified cellulose fiber, the temperature is preferably 200 ° C. or lower, more preferably 180 ° C. or lower, and further preferably 150 ° C. or lower. The mixing time can be appropriately set depending on the type of the compound and the solvent used, but from the viewpoint of the reactivity of the compound, it is preferably 0.01 hours or more, more preferably 0.1 hours or more, and the productivity. From the viewpoint of the above, it is preferably 48 hours or less, more preferably 24 hours or less.

(2) Mode of introduction via amide bond When introducing a modifying group via an amide bond, the anion-modified cellulose fiber and the amine compound may be mixed in the presence of a known condensing agent. , An amide bond is formed between the anionic group and the amino group of the amine compound.
For example, when an oxidized cellulose fiber is used as the anion-modified cellulose fiber and a primary amine having the above-mentioned modifying group is used as the amine compound, the C6 position of glucose constituting the cellulose fiber is as shown in the following formula. The above-mentioned modifying group can be introduced into the carboxy group of the above via an amide bond (in the formula, C ⁶ is a carbon atom at the 6-position of glucose constituting the cellulose fiber, and R is a modifying group. ).

The abundance of the amine compound in this embodiment is preferably 0.01 molar equivalent or more, more preferably 0, from the viewpoint of improving the dispersibility when the modified cellulose fiber or the finely divided modified cellulose fiber is blended into the member. It is 0.02 molar equivalent or more, more preferably 0.03 molar equivalent or more. On the other hand, from the viewpoint of suppressing the coloring of the obtained dispersion and improving the yield, the abundance of the amino compound is less than 0.3 molar equivalent, preferably 0.2 molar equivalent or less, more preferably 0.15. It is less than or equal to the molar equivalent. When the amine compound has a plurality of amino groups, the total number of moles of the amino groups is made to be the said number of moles.

The condensing agent is not particularly limited, and examples thereof include the condensing agent described in Synthetic Chemistry Series Peptide Synthesis (Maruzen Co., Ltd.) P116 or Tetrahedron, 57, 1551 (2001). Dimethoxy-1,3,5-triazine-2-yl) -4-methylmorpholinium chloride (hereinafter, may be referred to as "DMT-MM") and the like can be mentioned. It is also possible to carry out the reaction only by heat treatment without using a condensing agent.

A solvent may or may not be used in the amidation reaction. When a solvent is used, it is preferable to select a solvent in which the compound to be used dissolves, and specific examples of the solvent include the solvent exemplified in the above-mentioned "(1) Aspects of introduction via an ionic bond".

The reaction time and reaction temperature in 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 the reaction rate. be. The reaction temperature is preferably 0 ° C. or higher, more preferably 5 ° C. or higher, still more preferably 10 ° C. or higher, from the viewpoint of reactivity. Further, from the viewpoint of product quality such as coloring, it is preferably 200 ° C. or lower, more preferably 180 ° C. or lower, and further preferably 150 ° C. or lower.

1-5. Modified Cellulose Fiber The average fiber length of the modified cellulose fiber obtained by the above-mentioned "(1) mode of introduction via ionic bond" or "(2) mode of introduction via amide bond" is from the viewpoint of dispersibility. Therefore, it is 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, still more preferably 25 μm or more, and from the same viewpoint, 1,000 μm or less, preferably 800 μm or less. It is more preferably 500 μm or less, still more preferably 400 μm or less.

The average fiber diameter of the modified cellulose fiber is not particularly limited, and is, for example, preferably 1 μm or more, more preferably 5 μm or more, still more preferably 15 μm or more, while preferably 300 μm or less, more preferably 100 μm or less, still more preferable. Is 60 μm or less. The average fiber diameter and the average fiber length of the modified cellulose fiber can be measured according to the method described in Examples described later.
The preferable ranges of the average fiber length, the average fiber diameter and the average aspect ratio of the modified cellulose fiber are the same as the preferable ranges of the average fiber length, the average fiber diameter and the average aspect ratio of the above-mentioned anion-modified cellulose fiber.

The modified cellulose fiber has a cellulose I-type crystal structure due to the fact that natural cellulose fiber is used as a raw material thereof. The cellulose type I is the crystal form of natural cellulose, and the cellulose type I crystallization degree means the ratio of the amount of the cellulose type I crystal region to the whole cellulose. The presence or absence of the cellulose I-type crystal structure can be determined by the peak at 2θ = 22.6 ° in the X-ray diffraction measurement.

From the viewpoint of dispersibility, the degree of cellulose I-type crystallinity of the modified cellulose fiber is preferably 30% or more, more preferably 35% or more, still more preferably 40% or more, still more preferably 45% or more. Further, from the viewpoint of the cost of the cellulose raw material used, it is preferably 95% or less, more preferably 90% or less, still more preferably 85% or less, still more preferably 80% or less. In this specification, the degree of cellulose I-type crystallinity in cellulose fibers, modified cellulose fibers, etc. is specifically measured by the method described in Examples described later.

The average aspect ratio of the modified cellulose fiber is preferably 1 or more, more preferably 5 or more, still more preferably 8 or more from the viewpoint of production efficiency, and preferably 100 or less, more preferably 80 or more from the viewpoint of dispersibility. Below, it is more preferably 50 or less. The average aspect ratio of the modified cellulose fiber can be measured by the method described in Examples described later.

The average bond amount of the modifying group in the modified cellulose fiber is preferably 0.01 mmol / g or more from the viewpoint of dispersibility, and preferably 3.0 mmol / g or less from the same viewpoint. When any two or more kinds of modifying groups are simultaneously introduced into the modified cellulose as modifying groups, the amount of the modifying group bonded is preferably within the above range.

From the viewpoint of dispersibility, the introduction rate of the modifying group in the modified cellulose fiber is preferably 10 mol% or more, and the higher the value, the more preferably 100 mol%. When any two or more kinds of modifying groups are introduced at the same time as the modifying group, it is preferable that the total introduction rate is within the above range within the range not exceeding the upper limit of 100 mol%.

The average bond amount and introduction rate of the modifying group can be adjusted depending on the type and addition amount of the modifying compound, reaction temperature, reaction time, type of solvent and the like. The average bond amount (mmol / g) and introduction rate (mol%) of the modifying group are the amount and ratio of the modifying group introduced (bonded) to the anionic group in the modified cellulose fiber.

2. 2. Method for Producing Miniaturized Modified Cellulose Fiber As the method for producing the miniaturized modified cellulose fiber of the present invention, for example, the following two embodiments can be exemplified depending on the difference in the manufacturing process. That is, the method including step B in which the modified cellulose fiber produced by the above-mentioned "1. Method for producing modified cellulose fiber" is micronized in a solvent, and the average fiber length having a cellulose I type crystal structure This method comprises a step C of reacting a finely divided anion-modified cellulose fiber having an average fiber diameter of 0.5 nm or more and 50 nm or less with an amine compound to obtain a modified cellulose fiber of 1 μm or less.
Hereinafter, each method will be described separately.

2-1. Method including step B In step B, the modified cellulose fibers obtained as described above are finely dispersed in a solvent, and those in which the solvent is removed are finer than those newly dispersed in a solvent. It is possible to carry out the conversion process. For example, it can be carried out with reference to the description of the miniaturization step of Japanese Patent Application Laid-Open No. 2013-151661.

[Distributor]
In step B, for example, a miniaturization process can be carried out using a disperser. As a device that can be used in the miniaturization process, a known disperser can be mentioned as a suitable device. For example, a stirrer equipped with a stirrer, a breaker, a beater, a low pressure homogenizer, a high pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a roll mill, a short shaft kneader, a twin shaft kneader, a short shaft extruder, etc. A twin-screw extruder, an ultrasonic stirrer, a household juicer mixer, or the like can be used. The operating conditions of the device may be appropriately set with reference to the attached instruction manual.

〔solvent〕
Examples of the solvent that can be used in the miniaturization treatment include an aqueous solvent such as water and an organic solvent. An organic solvent is preferable from the viewpoint of dispersibility. When an organic solvent having solubility in water is used as a solvent, a mixture of water and the organic solvent may be used as the solvent.
The organic solvent is preferably N, N-dimethylformamide, dimethyl sulfoxide, N, N-dimethylacetamide, N-methylpyrrolidone, tetrahydrofuran (THF), succinic acid and triethylene glycol monomethyl ether from the viewpoint of dispersibility. Diester, dichloromethane, chloroform, toluene, acetic acid, methanol, ethanol, benzyl alcohol, n-propanol, 2-propanol, ethylene glycol, propylene glycol, t-butyl alcohol, cyclohexanone, acetonitrile, silicone oil, 1,3-dioxolane, acetic acid. It contains one or more organic solvents selected from the group consisting of methyl, ethyl acetate, butyl acetate, acetone and methyl ethyl ketone, more preferably N, N-dimethylformamide, dimethyl sulfoxide, N, N-dimethylacetamide. , N-Methylpyrrolidone, methanol, ethanol, benzyl alcohol, n-propanol, ethyl acetate and ethylene glycol, and more preferably N, N-dimethyl. It contains one or more organic solvents selected from the group consisting of formamide, dimethyl sulfoxide, N, N-dimethylacetamide, and N-methylpyrrolidone.

Further, as the organic solvent other than the above, an organic solvent having a reactive functional group can also be used. Examples of the organic solvent having a reactive functional group include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, n-hexyl acrylate, and n-methacrylate. Acrylates such as xyl, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, phenylglycidyl ether acrylate; urethane prepolymers such as hexamethylene diisocyanate urethane prepolymer, phenylglycidyl ether acrylate toluene diisocyanate urethane prepolymer; n-butyl Glycyzyl ether, 2-ethylhexyl glycidyl ether, glycidyl stearate ether, styrene oxide, phenyl glycidyl ether, nonylphenyl glycidyl ether, butylphenyl glycidyl ether, 1,6-hexanediol diglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl Glycidyl ethers such as ether; chlorostyrene, methoxystyrene, butoxystyrene, vinyl benzoic acid and the like can be mentioned.

Since such an organic solvent is presumed to have a high affinity with the modified cellulose fiber, the dispersibility of the cellulose fiber can be improved by using the organic solvent used in the preparation and the micronization treatment of the modified cellulose fiber. As a result, it is presumed that the finely divided modified cellulose fibers also exhibit high dispersibility.

The organic solvent used for the miniaturization treatment has a dielectric constant at 25 ° C. of preferably 75 or less, more preferably 55 or less, still more preferably 45 or less, from the viewpoint of better exerting the effect of the present invention. On the other hand, it is preferably 1 or more, more preferably 2 or more, and further preferably 3 or more. The dielectric constant of the organic solvent can be measured at 25 ° C. using a liquid dielectric constant meter Model871 (manufactured by Nihon Rufuto Co., Ltd.).

The amount of the solvent used in the micronization treatment may be such that the dispersed state of the modified cellulose fibers can be maintained, and is not particularly limited, but is preferable as the solid content content in the treatment target such as a suspension. Is an amount of 0.01% by mass or more, preferably 50% by mass or less.

2-2. Method including Step C In this method, as the anion-modified cellulose fiber to be reacted with the amine compound, "having a cellulose I-type crystal structure, an average fiber length of 1 μm or less, and an average fiber diameter of 0.5 nm or more and 50 nm or less. "Miniaturized anion-modified cellulose fiber" is used.

The refined anion-modified cellulose fiber has a cellulose type I crystal structure. The crystallinity of the anion-modified cellulose fiber is preferably 10% or more, more preferably 15% or more, still more preferably 20% or more, from the viewpoint of the mechanical strength of the resin molded product. Further, from the viewpoint of raw material availability, it is preferably 90% or less, more preferably 85% or less, still more preferably 80% or less, still more preferably 75% or less.

The average fiber length of the refined anion-modified cellulose fiber is 1 μm or less, preferably 500 nm or less, more preferably 300 nm or less, from the viewpoint of exhibiting high transparency in the refined modified cellulose fiber, while the handleability and the machine. From the viewpoint of the target strength, it is preferably 50 nm or more, more preferably 80 nm or more, and further preferably 100 nm or more.

The average fiber diameter of the micronized anion-modified cellulose fiber is 0.5 nm or more, preferably 1 nm or more, more preferably 2 nm or more from the viewpoint of mechanical strength, while the finely modified cellulose fiber has high transparency. From the viewpoint of exerting it, it is 50 nm or less, preferably 10 nm or less, and more preferably 6 nm or less.

Preferred properties other than the cellulose type I crystal structure, average fiber length and average fiber diameter of the finely divided anion-modified cellulose fiber are the same as those of the above-mentioned preferred properties of the anion-modified cellulose fiber.

The micronized anion-modified cellulose fiber is obtained by, for example, subjecting the raw material cellulose fiber to the same miniaturization treatment as in the step B to prepare a micronized cellulose fiber having a predetermined size. However, it can be prepared by carrying out the above-mentioned method for introducing an anionic group.

[Step C]
Step C is the same as the above-mentioned step A except that the micronized anion-modified cellulose fiber is used instead of the anion-modified cellulose fiber.
Therefore, as one embodiment of the preferred miniaturized modified cellulose fiber in the method including step C, the amine compound is bonded to the anionic group of the micronized anion-modified cellulose fiber via an ionic bond and / or an amide bond. Is. Here, the amine compound preferably has one or more modifying groups selected from the group consisting of the above-mentioned (a) hydrocarbon group and (b) polymer group.

The abundance of the amine compound in the step C is preferably 0.01 molar equivalent or more, more preferably 0, from the viewpoint of improving the dispersibility when the modified cellulose fiber or the finely divided modified cellulose fiber is blended into the member. It is 0.02 molar equivalent or more, more preferably 0.03 molar equivalent or more. On the other hand, from the viewpoint of suppressing the coloring of the obtained dispersion and improving the yield, the abundance of the amino compound is less than 0.3 molar equivalent, preferably 0.2 molar equivalent or less, more preferably 0.15. It is less than or equal to the molar equivalent. When the amine compound has a plurality of amino groups, it is present so that the total number of moles of the amino groups is the said number of moles.

2-3. Miniaturized Modified Cellulose Fiber The average fiber diameter of the miniaturized modified cellulose fiber obtained by the production method of the present invention is nano-order regardless of the type of modifying group. The average fiber diameter of the finely divided modified cellulose fiber is preferably 0.5 nm or more, more preferably 1 nm or more, still more preferably 2 nm or more from the viewpoint of handleability, availability, and cost, and is easy to handle and mechanical. From the viewpoint of strength, it is preferably 50 nm or less, more preferably 10 nm or less, still more preferably 6 nm or less.

The average fiber length of the finely divided modified cellulose fiber is preferably 50 nm or more, more preferably 80 nm or more, and further preferably 100 nm or more from the viewpoint of dispersibility. From the same viewpoint, it is preferably 1 μm or less, more preferably 500 nm or less, still more preferably 300 nm or less. The average fiber diameter and the average fiber length of the refined modified cellulose fiber are measured by the methods described in Examples described later.

3. 3. Resin molded body The modified cellulose fiber or micronized modified cellulose fiber obtained by the production method of the present invention is mixed with an organic solvent and / or various resins or resin precursors, and the modified cellulose fiber or micronized modified cellulose fiber is used. Various resins or resin precursors are mixed in the process of manufacturing cellulose fibers, or various resins or resin precursors are mixed in the process of refining anion-modified cellulose or modified cellulose fibers to modify the modified cellulose fibers or refined cellulose fibers. Dispersions containing quality cellulose fibers and various resins or resin precursors can be prepared. Examples of the resin contained in the resin molded body used in the present invention include thermoplastic resins, curable resins, cellulosic resins, rubber resins and the like. When such a dispersion contains a resin precursor, the resin precursor or the like is reacted to obtain a dispersion containing the target resin. For example, after removing the solvent in the resin dispersion, extrusion molding, injection molding, press molding, casting molding, etc., after removing the solvent or substituting with another suitable solvent, a known molding method such as a solvent casting method is appropriately used. By applying, a resin molded product can be manufactured. Such a resin molded product is not only excellent in dispersibility of cellulose fibers but also excellent in transparency, so that it can be suitably used for various purposes.

Specifically, for example, transparent resin materials, three-dimensional modeling materials, cushioning materials, repair materials, adhesives, adhesives, sealing materials, heat insulating materials, sound absorbing materials, artificial leather materials, paints, electronic materials, packaging materials, automobile parts. , Can be used for fiber composite materials. The shape of the resin molded body may be a sheet shape or a film shape such as a coating film.

Such a resin molded product can be produced by a known method, for example, the method described in paragraphs 0092 to 0114 of JP-A-2019-119983.

Hereinafter, the present invention will be specifically described with reference to examples. It should be noted that this embodiment is merely an example of the present invention and does not mean any limitation. The part in the example is a mass part unless otherwise specified. The "normal pressure" indicates 101.3 kPa, and the "normal temperature" indicates 25 ° C.

[Average fiber diameter and average fiber length of cellulose fiber, anion-modified cellulose fiber and modified cellulose fiber]
Deionized water is added to the cellulose fibers to be measured to prepare a dispersion having a content of 0.01% by mass. Using a wet dispersion type image analysis particle size distribution meter (manufactured by Jasco International, trade name: IF-3200), the dispersion is used for front lens: 2x, telecentric zoom lens: 1x, image resolution: 0.835 μm / pixel. , Syringe inner diameter: 6515 μm, spacer thickness: 500 μm, image recognition mode: ghost, threshold value: 8, analytical sample volume: 1 mL, sampling: 15%. 100 cellulose fibers are measured, and the average ISO fiber diameter thereof is used as the average fiber diameter, and the average ISO fiber length is calculated as the average fiber length.

[Average fiber diameter and average fiber length of miniaturized anion-modified cellulose fiber and miniaturized modified cellulose fiber]
Deionized water is added to the target cellulose fiber to prepare a dispersion having a concentration of 0.0001% by mass, and the dispersion is dropped onto a mica (mica) and dried, and the atom is used as an observation sample. Using an atomic force microscope (AFM, Nanoscopy III Tapping mode AFM, Digital instrument, probe used Point Probe (NCH) manufactured by Nanosensors), the fiber height of the cellulose fibers in the observation sample (fibers). Measure the difference in height between the presence and absence). At that time, in a microscope image in which the cellulose fibers can be confirmed, 100 of the cellulose fibers are randomly extracted, and the number average fiber diameter is calculated from the fiber heights thereof. 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.

[Anionic group content of anionic-modified cellulose fibers and modified cellulose fibers]
Take the cellulose fiber to be measured with a dry mass of 0.5 g in a beaker, add deionized water or a mixed solvent of methanol / deionized water = 2/1 (volume ratio) to make a total of 55 mL, and 0.01 M sodium chloride. Add 5 mL of aqueous solution to prepare a dispersion. The dispersion is stirred until the cellulose fibers to be measured are sufficiently dispersed. Add 0.1 M hydrochloric acid to this dispersion to adjust the pH to 2.5 to 3, and use an automatic titrator (manufactured by Toa DKK, trade name "AUT-701") to add a 0.05 M aqueous sodium hydroxide solution. Then, the solution is added dropwise to the dispersion under the condition of a waiting time of 60 seconds, and the electric conductivity and pH values are measured every minute. Continue the measurement until the pH reaches about 11, and obtain an electric conductivity curve. From this conductivity curve, the quantification of sodium hydroxide titration is obtained, and the anionic group content of the cellulose fiber to be measured is calculated by the following formula.
Anionic group content (mmol / g) = [Titration of aqueous sodium hydroxide solution (mL) x concentration of aqueous sodium hydroxide solution (0.05M)] / [Mass of cellulose fiber to be measured (0.5g)]

[Confirmation of crystal structure in various cellulose fibers]
The crystal structure of various celluloses such as cellulose raw materials, anion-modified cellulose fibers and modified cellulose fibers is confirmed by measuring under the following conditions using a diffractometer (manufactured by Rigaku Co., Ltd., trade name: MiniFlexII).
Measurement pellet preparation conditions: Smooth pellets with an area of 320 mm ² x thickness of 1 mm are prepared by applying pressure to the target cellulose in the range of 10 to 20 MPa with a tablet molding machine.
X-ray diffraction analysis conditions: Step angle 0.01 °, scan speed 10 ° / min, measurement range: diffraction angle 2θ = 5-40 °
X-ray source: Cu / Kα-radiation, tube voltage: 15 kv, tube current: 30 mA
Peak division condition: After removing the background noise, fitting is performed by a Gaussian function so that the error between 2θ = 13-23 ° is within 5%.

The crystal structure of various celluloses is confirmed by measuring under the above-mentioned conditions using the above-mentioned diffractometer.
The crystallinity of the cellulose I-type crystal structure is calculated based on the following formula (A) using the area of the X-ray diffraction peak obtained by the above-mentioned peak division.
Cellulose type I crystallinity (%) = [I _cr / (I _cr + I _am )] × 100 (A)
[In the formula, I _cr is the area of the diffraction peak of the lattice plane (002 plane) (diffraction angle 2θ = 22-23 °) in X-ray diffraction, and I _am is the area of the amorphous part (diffraction angle 2θ = 18.5 °). The area of the diffraction peak is shown. ]

[Solid content in dispersion or dispersion]
This is performed using a halogen moisture meter (manufactured by Shimadzu Corporation, trade name: MOC-120H). Measurement is performed every 30 seconds at a constant temperature of 150 ° C. for 1 g of a sample, and the value at which the mass loss is 0.1% or less is defined as the solid content.

Preparation Example 1
Bleached kraft pulp of coniferous tree (Fletcher Challenge Canada, trade name "Mackenzie", CSF 650 ml) was used as a natural cellulose fiber. As the TEMPO, a commercially available product (manufactured by ALDRICH, Free radical, 98% by mass) was used. As the sodium hypochlorite, a commercially available product (manufactured by Wako Pure Chemical Industries, Ltd.) was used. As sodium bromide, a commercially available product (manufactured by Wako Pure Chemical Industries, Ltd.) was used.

First, 100 g of coniferous bleached kraft pulp fiber is sufficiently stirred with 9900 g of deionized water, and then 1.6 g of TEMPO, 10 g of sodium bromide, and 28.4 g of sodium hypochlorite are added in this order to 100 g of the pulp mass. Was added in. Using pH stat titration with an automatic titrator (manufactured by DKK-TOA CORPORATION, trade name: AUT-701), 0.5 M sodium hydroxide was added dropwise to maintain the pH at 10.5 under sufficient stirring. After the reaction was carried out for 120 minutes (20 ° C.), the dropping of sodium hydroxide was stopped to obtain an oxidized cellulose fiber. The obtained cellulose oxide fiber was thoroughly washed with deionized water until it became 200 μs / cm or less in the conductivity measurement of the filtrate by a compact electric conductivity meter (LAQUAtwin EC-33B, manufactured by HORIBA, Ltd.), and then dehydrated. Was carried out to obtain an oxidized cellulose fiber having a solid content of 34.6%. The average fiber diameter of the oxidized cellulose fiber was 40 μm, the average fiber length was 2022 μm, the average aspect ratio was 51, the carboxy group content was 1.56 mmol / g, and the cellulose had a cellulose I-type crystal structure.

144.5 g of the dehydrated cellulose oxide obtained above is diluted with 1000 g of deionized water, and 1.4 g of 35% hydrogen peroxide solution is added thereto (relative to 100 parts by mass of the absolute dry mass of the raw material cellulose fiber). 1 part by mass of hydrogen peroxide) was added, and the pH was adjusted to 12 with 1 M sodium hydroxide. Then, it was subjected to alkaline hydrolysis treatment at 80 ° C. for 2 hours (solid content of cellulose oxide fiber 4.3% by mass). The obtained cellulose oxide fibers were thoroughly washed to obtain short fiberized cellulose oxide fibers having a solid content of 28.6%. The stapled oxidized cellulose fibers had an average fiber diameter of 39 μm, an average fiber length of 387 μm, an average aspect ratio of 10, and a carboxy group content of 1.29 mmol / g.

Example 1
(Step A)
In a beaker equipped with a magnetic stirrer and a stirrer, 0.15 g of the shortened cellulose oxide fibers obtained in Preparation Example 1 was charged in an absolute dry mass. Subsequently, octylamine in an amount corresponding to 0.1 mol of amino groups (that is, 0.1 mol equivalent) was charged with respect to 1 mol of the carboxy group of the oxidized cellulose fiber, and N, N-dimethylformamide (DMF) as a solvent was charged. ) Was dissolved in 30 g. By reacting the reaction solution at 80 ° C. for 1 hour, a DMF suspension of the modified cellulose fiber in which an octyl group as a modifying group was bonded to the carboxy group of the oxidized cellulose fiber via an ionic bond was obtained (solid content contained). Amount 0.5% by mass).

(Step B)
The DMF suspension of the obtained modified cellulose fiber was treated with a high-pressure homogenizer (manufactured by Yoshida Machinery Co., Ltd., trade name: NanoVeta L-ES) at 150 MPa for 5 passes, and the finely divided modified cellulose fiber was dispersed in DMF. A body (solid content content: 0.5% by mass) was obtained.

Comparative Example 1
In Example 1, the same treatment as in Example 1 was carried out except that an amount of octylamine corresponding to 0.3 mol of amino group (that is, 0.3 mol equivalent) was charged to 1 mol of carboxy group. , A dispersion (solid content content: 0.5% by mass) in which finely divided modified cellulose fibers were dispersed in DMF was obtained.

Test Example 1 (degree of coloring)
Using an ultraviolet-visible spectrophotometer (UV-VISIBLE SPECTROMETER UV-2550, manufactured by Shimadzu Corporation), the absorbance of the dispersions obtained in each Example and Comparative Example at 400 nm was measured. The transmittance in Example 1 was relatively determined, assuming that the absorbance in Comparative Example 1 was 100 (%). The lower the value, the more the coloration was suppressed in the dispersion.

Test Example 2 (Yield of refined modified cellulose fiber)
Using a high-speed cooling centrifuge (CR21G III, manufactured by Koki Holdings Co., Ltd.), 15 g (solid content: 0.075 g) of the dispersion obtained in each Example and Comparative Example was used at 25 ° C., 10000 G, for 1 minute. Centrifugation was performed under the conditions of. The yield (%) was calculated from the following formula.
Yield = 100- (precipitated solid content (g) /0.075 g) x 100 (%)
The transmittance in Example 1 was relatively determined, assuming that the yield obtained in Comparative Example 1 was 100 (%).

The results are summarized in Table 1.

It was found that the dispersion containing the micronized modified cellulose fiber obtained by the production method of the present invention had a lower absorbance and a higher yield than the dispersion in Comparative Example 1.

Since the modified cellulose fiber and the finely divided modified cellulose fiber obtained by the production method of the present invention are suppressed from being colored when they are made into a dispersion, even when they are made into a resin molded body mixed with various resins. Coloring is suppressed. Therefore, it can be suitably used for various industrial applications such as daily miscellaneous goods, home electric appliances parts, packaging materials for home electric appliances parts, and automobile parts.

Claims (10)

A method for producing a modified cellulose fiber, which comprises a step A of reacting an anion-modified cellulose fiber having a cellulose I-type crystal structure with an amine compound to obtain a modified cellulose fiber.
A method for producing a modified cellulose fiber, wherein in step A, the reaction is carried out in the presence of an amine compound in an amount less than 0.3 molar equivalent of the anionic group of the anionic modified cellulose fiber. The production method according to claim 1, wherein the average fiber length of the modified cellulose fiber is 1 μm or more and 1000 μm or less. The production method according to claim 1 or 2, wherein the modified cellulose fiber is formed by binding an amine compound to the anionic group of the anion-modified cellulose fiber via an ionic bond and / or an amide bond. The production method according to any one of claims 1 to 3, wherein the anion-modified cellulose fiber has an average fiber length of 1 μm or more and 1000 μm or less. The production method according to any one of claims 1 to 4, wherein the anion-modified cellulose fiber has an average aspect ratio of 100 or less. The production method according to any one of claims 1 to 5, wherein the amine compound has one or more modifying groups selected from the group consisting of (a) a hydrocarbon group and (b) a polymer group. A method for producing a refined modified cellulose fiber, which comprises a step B of subjecting the modified cellulose fiber obtained by the production method according to any one of claims 1 to 6 to a micronization treatment in a solvent. A modified cellulose fiber is obtained by reacting a finely divided anion-modified cellulose fiber having a cellulose I-type crystal structure, an average fiber length of 1 μm or less, and an average fiber diameter of 0.5 nm or more and 50 nm or less with an amine compound. A method for producing a miniaturized modified cellulose fiber, which comprises step C.
A method for producing a micronized modified cellulose fiber, wherein in step C, an amine compound in an amount less than 0.3 molar equivalent of the anionic group of the micronized anion-modified cellulose fiber is present and the reaction is carried out. The production method according to claim 8, wherein the refined modified cellulose fiber is formed by binding an amine compound to an anionic group of the refined anion-modified cellulose fiber via an ionic bond and / or an amide bond. The production method according to claim 8 or 9, wherein the amine compound has one or more modifying groups selected from the group consisting of (a) a hydrocarbon group and (b) a polymer group.