JP2017133037A - Fine cellulose fiber production process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process that can produce a fine cellulose fiber in which a hydrophobic group and a cationic group or an anionic group are introduced into the cellulose at a high yield.SOLUTION: Provided is a process for producing a fine cellulose fiber in which a hydrophobic group and a cationic group or an anionic group are introduced to the cellulose, characterized in that: the step of introducing a hydrophobic group and a cationic group or an anionic group into a hydroxyl group of cellulose of a cellulose fiber raw material is carried out in the presence of alkali.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing fine cellulose fibers.

  In recent years, attention has been focused on the application of reproducible natural fibers due to the substitution of petroleum resources and the growing environmental awareness. Among natural fibers, cellulose fibers, particularly wood-derived cellulose fibers (pulp) are widely used mainly as paper products. Most cellulose fibers used for paper have a width of 10 to 50 μm. As cellulose fibers, fine cellulose fibers having a fiber diameter of 1000 nm or less are also known, and various uses of the fine cellulose fibers have been studied.

  Patent Document 1 includes a step of preparing a suspension containing plant fibers and water, and a step of putting the suspension and beads obtained by the above step into a bead mill and defibrating, characterized in that A method for producing plant fibers is described. Patent Document 1 further describes a microfibrillated plant fiber obtained by the above production method, a resin molding material containing the microfibrillated plant fiber and a resin, and the like. In addition, Patent Document 1 discloses, as a plant fiber, an esterification reaction with an acid halide, or a reaction to neutralize part or all of the carboxy group generated after half esterification with an alkyl or alkenyl succinic anhydride. It is described that the resulting hydrophobized modified plant fiber can be used.

JP 2011-213754 A

  This invention made it the subject which should be solved to provide the method which can manufacture the fine cellulose fiber by which the hydrophobic group and the cationic group or the anionic group were introduce | transduced into the cellulose with a high yield.

  As a result of intensive studies on the above problems, the present inventors have introduced a step of introducing a hydrophobic group into the hydroxyl group of cellulose and a step of introducing a cationic group or an anionic group, or a group of hydrophobic group and cation with respect to the hydroxyl group of cellulose. It has been found that the above problem can be solved by carrying out the step of introducing a compound having both an ionic group or an anionic group in the presence of an alkali, and the present invention has been completed.

That is, according to the present invention, the following inventions are provided.
(1) A step of introducing a hydrophobic group and a cationic group or an anionic group into a hydroxyl group of cellulose of a cellulose fiber raw material in the presence of an alkali, wherein the hydrophobic group and the cationic group or A method for producing fine cellulose fibers into which an anionic group is introduced.
(2) The method according to (1), wherein a compound having both a hydrophobic group and a cationic group or an anionic group is introduced to the hydroxyl group of cellulose of the cellulose fiber raw material in the presence of an alkali.

(3) (a) A cellulose half-esterification step in which a cellulose fiber raw material is treated with succinic anhydride substituted with a hydrophobic group in the presence of an alkali; and (b) a half-esterification obtained in the half-esterification step. The manufacturing method as described in (1) or (2) including the alkali treatment process which processes the obtained cellulose with the alkali solution, and the defibration process process which fibrillates the said (c) said alkali-treated cellulose.
(4) The production method according to any one of (1) to (3), wherein the pH of the reaction solution in the alkali treatment step is 9 or more.

(5) In the half esterification step of cellulose, the reaction is performed by heating and stirring and dehydrating a mixture of cellulose fiber raw material, alkali, and a succinic anhydride substituted with a hydrophobic group, (3) or (4) Manufacturing method.
(6) The manufacturing method in any one of (3) to (5) whose density | concentration of the cellulose fiber raw material in a reaction liquid is 10 mass%-90 mass% in the half esterification process of a cellulose.

(7) (a) a step of treating a cellulose fiber raw material with a cationizing agent or anionizing agent in the presence of an alkali, a step of treating with a chemical modifier for introducing a hydrophobic group in the presence of an alkali, and (b ) The production method according to (1), comprising a defibrating treatment step of defibrating the cellulose obtained above.
(8) The production method according to (7), wherein the pH of the reaction solution in the step of treating the cellulose fiber raw material with a cationizing agent or anionizing agent in the presence of an alkali is 9 or more.

  According to the present invention, fine cellulose fibers having both a hydrophobic group (preferably a hydrophobic bulky group) and a cationic group or an anionic group can be produced in high yield. In addition, the fine cellulose fiber produced by the method of the present invention has a cationic group or an anionic group, and thus can efficiently produce fine cellulose fiber that is stably dispersed in water by light mechanical treatment. Fine cellulose fibers can be easily recovered. In the case of an anionic group, fibrillation is facilitated by alkali treatment. In addition, the quaternization cation facilitates defibration. Moreover, the fine cellulose fiber manufactured with the method of this invention has surface active ability by having a hydrophobic group simultaneously with a hydrophilic group.

Hereinafter, the present invention will be described in more detail.
<Cellulose fiber raw material>
Cellulose fiber materials used as raw materials for fine cellulose fibers include paper pulp, cotton pulp such as cotton linter and cotton lint, non-wood pulp such as hemp, straw and bagasse, cellulose isolated from sea squirts and seaweeds, etc. Is mentioned. Among these, paper pulp is preferable in terms of availability. Paper pulp includes hardwood kraft pulp (bleached kraft pulp (LBKP), unbleached kraft pulp (LUKP), oxygen bleached kraft pulp (LOKP), etc.), softwood kraft pulp (bleached kraft pulp (NBKP), unbleached kraft pulp) (NUCKP, oxygen bleached kraft pulp (NOKP), etc.), sulfite pulp (SP), chemical pulp such as soda pulp (AP), semi-chemical pulp (SCP), semi-chemical pulp such as chemiground wood pulp (CGP) In addition, mechanical pulp such as groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP), non-wood pulp using raw material such as cocoon, sardine, hemp, kenaf and the like, and deinked pulp using raw paper as a raw material. Among these, kraft pulp, deinked pulp, and sulfite pulp are preferable because they are more easily available. A cellulose fiber raw material may be used individually by 1 type, and may be used in mixture of 2 or more types.

<Chemical treatment process>
In the present invention, the hydrophobic group and the cationic group or anion are introduced into the cellulose by performing the step of introducing a hydrophobic group and a cationic group or an anionic group into the cellulose hydroxyl group of the cellulose fiber raw material in the presence of an alkali. Fine cellulose fibers into which a functional group is introduced can be produced.

  Specifically, as a step of introducing a hydrophobic group and a cationic group or an anionic group to the hydroxyl group of cellulose, the cellulose fiber raw material is subjected to a hydrophobic group and a cationic group or an anionic group in the presence of an alkali. A method of treating with a compound (hereinafter, method A), or a step of treating a cellulose fiber raw material with a cationizing agent or anionizing agent in the presence of alkali, and chemical modification for introducing a hydrophobic group in the presence of alkali And a step of treating with an agent (hereinafter, method B). Method A is preferable because both a hydrophobic group (hydrophobic bulky group) and a carboxy group can be introduced simultaneously, the reaction becomes very simple, and the production process can be simplified. Hereinafter, method A and method B will be described.

(About Method A)
In one example of the present invention, the cellulose fiber raw material can be treated with a compound having both a hydrophobic group and a cationic group or an anionic group in the presence of alkali. As the compound having both a hydrophobic group and a cationic group or an anionic group, specifically, succinic anhydride substituted with a hydrophobic group can be used. As an example of Method A, a cellulose half-esterification process in which a cellulose fiber raw material is treated with succinic anhydride substituted with a hydrophobic group in the presence of an alkali; Fine cellulose fibers in which a hydrophobic group and a cationic group or an anionic group are introduced into cellulose can be produced by an alkali treatment step of treating with an alkaline solution.

  The kind of the hydrophobic group in the succinic anhydride substituted with the hydrophobic group is not particularly limited, and specific examples of the succinic anhydride substituted with the hydrophobic group include alkyl or alkenyl succinic anhydride. Specific examples of the alkyl or alkenyl succinic anhydride include, but are not particularly limited to, compounds having a skeleton derived from an olefin having 1 to 24 carbon atoms and a maleic anhydride skeleton. Specifically, 2-methyl succinic anhydride, 2,3-dimethyl succinic anhydride, itaconic anhydride, allyl succinic anhydride, (2-methyl-2-propynyl) succinic anhydride, octyl succinic anhydride, nonyl anhydride Alkyl succinic anhydrides such as succinic acid, decyl succinic anhydride, dodecyl succinic anhydride, tetradecyl succinic anhydride, hexadecyl succinic anhydride, octadecyl succinic anhydride, 2-hexen-1-yl succinic anhydride, pentenyl succinic anhydride, Hexenyl succinic anhydride, octenyl succinic anhydride, decenyl succinic anhydride, undecenyl succinic anhydride, dodecenyl succinic anhydride, tridecenyl succinic anhydride, hexadecenyl succinic anhydride, octadecenyl succinic anhydride, isoocta And alkenyl succinic anhydride such as decenyl succinic anhydride. However, it is not limited to these. These can be used alone or in combination of two or more.

  The amount of succinic anhydride substituted with a hydrophobic group is preferably about 0.1 to 1000 parts by weight, more preferably about 0.5 to 500 parts by weight, and 1 to 500 parts by weight with respect to 100 parts by weight of the cellulose fiber raw material. Is more preferable.

  The treatment temperature when treating with succinic anhydride substituted with a hydrophobic group is preferably 250 ° C. or less from the viewpoint of the thermal decomposition temperature of cellulose. Furthermore, when water is contained in the treatment, the temperature is preferably 80 to 200 ° C, more preferably 100 to 170 ° C.

  The reaction conditions of the cellulose fiber raw material and succinic anhydride substituted with a hydrophobic group are not particularly limited. For example, the cellulose fiber raw material, an aqueous alkali solution (for example, an aqueous sodium hydroxide solution), and anhydrous anhydrous substituted with a hydrophobic group Examples thereof include a method of mixing succinic acid, heating and stirring to evaporate and remove moisture.

  The concentration of the cellulose fiber raw material in the mixed solution is not particularly limited, but the dehydration process can be shortened, the fiber raw material and the succinic anhydride substituted with a hydrophobic group are easily contacted, and the reactivity is increased. Is preferably 10% by mass or more, and more preferably 20% by mass or more. On the other hand, 90 mass% or less is preferable, 80 mass% or less is more preferable, and 70 mass% or less is especially preferable in order not to impair the swelling property of the fiber raw material.

  In the present invention, the cellulose fiber raw material can be treated with succinic anhydride substituted with a hydrophobic group in the presence of alkali to half-esterify the cellulose. The alkali may be an inorganic alkali compound or an organic alkali compound. Examples of the inorganic alkali compound include alkali metal hydroxides and alkaline earth metal hydroxides. Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide, and examples of the alkaline earth metal hydroxide include calcium hydroxide. Examples of the organic alkali compound include ammonia, aliphatic amines, and aromatic amines. The solvent in the alkaline solution may be either water or an organic solvent, but a polar solvent (polar organic solvent such as water or alcohol) is preferred, and an aqueous solvent containing at least water is more preferred.

  In the reaction, a quaternary ammonium salt such as quaternary ammonium hydroxide or quaternary ammonium chloride can be used to improve the reactivity. The types of quaternary ammonium hydroxide include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, trimethylethylammonium hydroxide, trimethylbenzylammonium hydroxide, dimethyldibenzylammonium Examples include hydroxide. Examples of the quaternary ammonium chloride include tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetrabutylammonium chloride, trimethylethylammonium chloride, trimethylbenzylammonium chloride, dimethyldibenzylammonium chloride and the like. . These act as phase transfer catalysts that facilitate the reaction of succinic anhydride substituted with hydrophobic groups with hydrophilic cellulose. The amount of catalyst used is preferably 0.01 to 100 moles per mole of cellulose glucose units.

  In addition, by using an organic solvent in which succinic anhydride substituted with a hydrophobic group is dissolved, succinic anhydride substituted with a hydrophobic group penetrates into the inside of the cellulose to facilitate the reaction. As the organic solvent, water is preferable because it is easily mixed with water, such as ketone solvents such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran, ethylene glycol, propylene glycol, polyethylene glycol, and other ethers such as dimethyl and diethylated compounds. Amide solvents such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone; dimethyl sulfoxide and the like. Moreover, you may use 2 or more types of mixed solvents chosen from these. Although there will be no restriction | limiting in particular if the usage-amount will have sufficient quantity which can dissolve the succinic anhydride substituted by the hydrophobic group, 5-90 mass% of the total amount of solvent is preferable.

  The alkali concentration at 25 ° C. of the mixed solution consisting of alkali solution / cellulose fiber raw material / succinic anhydride substituted with a hydrophobic group is preferably 0.1% by mass or more, and preferably 0.5 to 12% by mass. Further preferred.

  The reaction apparatus is not particularly limited as long as it can be heated and stirred, but examples thereof include a reaction vessel equipped with stirring blades, a reaction vessel having a stirring bar, a kneader, a twin screw extruder, a lab plast mill, a bead mill, a ball mill, and the like. It is done. Since the reaction is basically a solid-liquid reaction, a stirrer with high stirring efficiency is preferable in order to increase the reaction efficiency. Specific examples include a kneader, a twin screw extruder, a lab plast mill, a bead mill, and a ball mill. Is done.

The cellulose half-esterified with succinic anhydride substituted with hydrophobic groups is then treated with an alkaline solution.
Although it does not specifically limit as a method of an alkali treatment, For example, the method of immersing the cellulose half-esterified with the succinic anhydride substituted by the hydrophobic group in an alkaline solution is mentioned. The alkali compound contained in the alkali solution may be an inorganic alkali compound or an organic alkali compound. Examples of inorganic alkali compounds include alkali metal hydroxides or alkaline earth metal hydroxides, alkali metal carbonates or alkaline earth metal carbonates, alkali metal phosphates or alkaline earth metal phosphoric acids. Salt. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide, and examples of the alkaline earth metal hydroxide include calcium hydroxide.

Examples of the alkali metal carbonate include lithium carbonate, lithium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, sodium carbonate, and sodium hydrogen carbonate. Examples of the alkaline earth metal carbonate include calcium carbonate.
Examples of the alkali metal phosphate include lithium phosphate, potassium phosphate, trisodium phosphate, and disodium hydrogen phosphate. Examples of alkaline earth metal phosphates include calcium phosphate and calcium hydrogen phosphate.

Examples of the organic alkali compounds include ammonia, aliphatic amines, aromatic amines, aliphatic ammoniums, aromatic ammoniums, heterocyclic compounds and their hydroxides, carbonates, and phosphates.
For example, ammonia, hydrazine, methylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, butylamine, diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, cyclohexylamine, aniline, tetramethylammonium hydroxide, Tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, pyridine, N, N-dimethyl-4-aminopyridine, ammonium carbonate, ammonium hydrogen carbonate, diammonium hydrogen phosphate, etc. Can be mentioned.

  The pH of the reaction solution at 25 ° C. in the alkali treatment step is preferably 9 or more, more preferably 10 or more, and still more preferably 11-14. If the pH of the reaction solution is at least the lower limit, the yield of fine cellulose fibers will be higher. However, when pH exceeds 14, the handleability of an alkaline solution will fall.

  After the alkali treatment, in order to improve the handleability, it is preferable to wash the alkali-treated cellulose with water or an organic solvent before the defibrating treatment step.

(Method B)
In another example of the present invention, a step of treating a cellulose fiber raw material with a cationizing agent or anionizing agent in the presence of an alkali, and a step of treating with a chemical modifier for introducing a hydrophobic group in the presence of an alkali To produce a fine cellulose fiber in which a part of the hydrogen atoms of the hydroxyl group of cellulose is substituted with a hydrophobic group and a part of the hydrogen atoms of another hydroxyl group of cellulose is substituted with a cationic group or an anionic group. be able to. The order of the step of treating the cellulose fiber raw material with a cationizing agent or anionizing agent in the presence of alkali and the step of treating with a chemical modifier for introducing a hydrophobic group in the presence of alkali is not particularly limited. After the step of treating the fiber raw material with a cationizing agent or anionizing agent in the presence of alkali, a step of treating with a chemical modifier for introducing a hydrophobic group in the presence of alkali may be carried out. Alternatively, the cellulose fiber raw material may be treated with a chemical modifier for introducing a hydrophobic group in the presence of an alkali and then treated with a cationizing agent or an anionic agent in the presence of an alkali. Good.

  Examples of the anionic group include a carboxy group, a phosphoric acid group, and a sulfonic acid group.

As a method of introducing a carboxy group into a cellulose fiber raw material, a method of oxidizing a part of the hydroxyl group of cellulose to a carboxy group using an oxidizing agent can be mentioned.
Oxidizing agents include ozone, chlorine dioxide, hydrogen peroxide, peracetic acid, persulfuric acid, permanganic acid, chlorine, hypochlorous acid, chlorous acid, chloric acid, perchloric acid or an aqueous solution thereof such as six salts. Chromic acid sulfuric acid mixture, Jones reagent (acidic sulfuric acid solution of chromic anhydride), chromic acid oxidizing reagent such as pyridilinium chlorochromate (PCC reagent), activated dimethyl sulfoxide reagent used for Swern oxidation, etc., and catalytic oxidation And N-oxyl compounds such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and the like. Of these, ozone, TEMPO, hydrogen peroxide, and chlorine dioxide are preferred, and ozone and TEMPO are more preferred because of the high efficiency of introducing carboxy groups into cellulose fibers.

As a method for introducing a carboxy group into a cellulose fiber raw material, a method using a carboxylic acid compound having two or more carboxy groups in the molecule is also preferred.
In the treatment with the carboxylic acid compound, the hydroxy group of the cellulose molecule and the carboxylic acid compound undergo a dehydration reaction to form a polar group (—COO ⁻ ). Thereby, the bond strength between cellulose fibers becomes weak and defibration improves.

  Specific methods for treating the cellulose fiber raw material with the carboxylic acid compound include a method of mixing the gasified carboxylic acid compound with the cellulose fiber raw material, a method of adding the carboxylic acid compound to the dispersion of the cellulose fiber raw material, and the like. Can be mentioned. Among these, since the process is simple and the efficiency of introducing a carboxy group is high, a method of mixing a gasified carboxylic acid compound with a cellulose fiber raw material is preferable. Examples of the method for gasifying the carboxylic acid compound include a method for heating the carboxylic acid compound.

The carboxylic acid compound used in this treatment is at least one selected from the group consisting of a compound having two carboxy groups, an acid anhydride of a compound having two carboxy groups, and derivatives thereof. Of the compounds having two carboxy groups, compounds having two carboxy groups (dicarboxylic acid compounds) are preferred.
The compounds having two carboxy groups include propanedioic acid (malonic acid), butanedioic acid (succinic acid), pentanedioic acid (glutaric acid), hexanedioic acid (adipic acid), 2-methylpropanedioic acid, 2 -Methylbutanedioic acid, 2-methylpentanedioic acid, 1,2-cyclohexanedicarboxylic acid, 2-butenedioic acid (maleic acid, fumaric acid), 2-pentenedioic acid, 2,4-hexadienedioic acid, 2-methyl 2-butenedioic acid, 2-methyl-2-pentenedioic acid, 2-methylidenebutanedioic acid (itaconic acid), benzene-1,2-dicarboxylic acid (phthalic acid), benzene-1,3-dicarboxylic acid (isophthalic acid) ), Benzene-1,4-dicarboxylic acid (terephthalic acid), ethanedioic acid (oxalic acid), and the like.

Acid anhydrides of compounds having two carboxy groups include maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, itaconic anhydride, pyromellitic anhydride, 1,2-cyclohexanedicarboxylic anhydride Examples thereof include acid anhydrides of dicarboxylic acid compounds such as acids and compounds containing a plurality of carboxy groups.
The acid anhydride derivative of the compound having two carboxy groups includes at least a part of the acid anhydride of the compound having a carboxy group, such as dimethylmaleic anhydride, diethylmaleic anhydride, and diphenylmaleic anhydride. The hydrogen atom is substituted with a substituent (for example, an alkyl group, a phenyl group, etc.).
Of these, maleic anhydride, succinic anhydride, and phthalic anhydride are preferred because they are industrially applicable and easily gasified.

  As a method for introducing a phosphate group into a cellulose fiber raw material, a method of mixing a powder or an aqueous solution of phosphoric acid or a phosphoric acid derivative with a dry or wet cellulose fiber raw material, phosphoric acid or Examples thereof include a method of adding an aqueous solution of a phosphoric acid derivative. In these methods, dehydration treatment, heat treatment, and the like are usually performed after mixing or adding a powder or aqueous solution of phosphoric acid or phosphoric acid derivative.

Examples of the phosphoric acid or phosphoric acid derivative used here include at least one compound selected from an oxo acid, a polyoxo acid or a derivative thereof containing a phosphorus atom.
Specifically, phosphoric acid; sodium salt of phosphoric acid such as sodium dihydrogen phosphate, disodium hydrogen phosphate and trisodium phosphate; sodium salt of polyphosphoric acid such as sodium pyrophosphate and sodium metaphosphate; Potassium salts of phosphoric acid such as potassium hydrogen, dipotassium hydrogen phosphate and tripotassium phosphate; potassium salts of polyphosphoric acid such as potassium pyrophosphate and potassium metaphosphate; ammonium dihydrogen phosphate, diammonium hydrogen phosphate and phosphoric acid Examples thereof include ammonium salts of phosphoric acid such as triammonium; ammonium salts of polyphosphoric acid such as ammonium pyrophosphate and ammonium metaphosphate. These may be used alone or in combination of two or more. Among the above, sodium dihydrogen phosphate and disodium hydrogen phosphate are preferable.

  The cationic group is a group having an onium such as ammonium, phosphonium or sulfonium in the group, and is usually a group having a molecular weight of 1000 or less. Specific examples include ammonium such as primary ammonium, secondary ammonium, tertiary ammonium and quaternary ammonium, phosphonium, sulfonium, and groups having these ammonium, phosphonium or sulfonium. Examples of the cationizing agent that can be used in the present invention include glycidyltrialkylammonium halides such as glycidyltrimethylammonium chloride and 3-chloro-2-hydroxypropyltrimethylammonium chloride or halohydrin type compounds thereof.

  The hydrophobic group in the present invention is not limited as long as it is a functional group exhibiting hydrophobicity, but is preferably a hydrophobic bulky group. Hydrophobic group is not particularly limited, but is a hydrocarbon group or acyl having 2 to 50 carbon atoms, saturated or unsaturated, linear or branched, containing an aromatic ring, or containing a saturated or unsaturated ring Groups and the like. Specific examples of hydrophobic groups include acetyl, acryloyl, methacryloyl, propionyl, propioyl, butyryl, 2-butyryl, pentanoyl, hexanoyl, heptanoyl, octanoyl, nonanoyl, decanoyl, undecanoyl. Group, dodecanoyl group, myristoyl group, palmitoyl group, stearoyl group, pivaloyl group and other acyl groups, methyl group, ethyl group, propyl group, 2-propyl group, butyl group, 2-butyl group, tert-butyl group, pentyl group , Hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, alkyl group such as dodecyl group, myristyl group, palmityl group, stearyl group, and aromatic rings such as benzyl group, benzoyl group, naphthoyl group, etc. Functional groups etc. are mentioned, but these Not a constant.

  Reaction conditions of cellulose and a chemical modifier for introducing a hydrophobic group are not particularly limited, but a solvent, a catalyst, or the like can be used, heating, decompression, or the like can be performed as necessary.

  The type of chemical modifier for introducing a hydrophobic group is one or two selected from the group consisting of cyclic ethers such as acids, acid anhydrides, alcohols, halogenating reagents, isocyanates, alkoxysilanes, and oxiranes (epoxies). More than species.

  The alkali used in each of the step of treating the cellulose fiber raw material with a cationizing agent or anionizing agent and the step of treating with a chemical modifier for introducing a hydrophobic group may be an inorganic alkali compound or an organic alkali compound. Examples of the inorganic alkali compound include alkali metal hydroxides and alkaline earth metal hydroxides. Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide, and examples of the alkaline earth metal hydroxide include calcium hydroxide. Examples of the organic alkali compound include ammonia, aliphatic amines, and aromatic amines. The solvent in the alkaline solution may be either water or an organic solvent, but a polar solvent (polar organic solvent such as water or alcohol) is preferred, and an aqueous solvent containing at least water is more preferred.

  The pH at 25 ° C. of each reaction solution in the step of treating the cellulose fiber raw material with a cationizing agent or anionizing agent and the step of treating with a chemical modifier for introducing a hydrophobic group is preferably 9 or more, More preferably, it is 10 or more, and it is still more preferable that it is 11-14.

(Content of anionic group or cationic group and hydrophobic group in cellulose)
The content of an anionic group or cationic group in cellulose is preferably 0.1 to 2.0 mmol / g, more preferably 0.1 to 1.5 mmol / g, and 0.2 to 1. More preferably, it is 2 mmol / g. If content of an anionic group or a cationic group is the said range, the hydration property of a fine cellulose fiber will not become high too much, but the viscosity at the time of making a slurry will become low. If the content of the anionic group or the cationic group exceeds the above upper limit, the hydration property becomes too high, and the fine cellulose fibers may be dissolved, which is not preferable.

  The content of an anionic group can be determined using a method of “Test Method T237 cm-08 (2008): Carboxyl Content of pull” of TAPPI, USA. In order to make it possible to measure the content of anionic groups in a wider range, among the test solutions used in the test method, sodium hydrogen carbonate (NaHCO 3) / sodium chloride (NaCl) = 0.84 g / 5.85 g was distilled water. According to TAPPI T237 cm-08 (2008), except that the test solution dissolved and diluted in 1000 ml was changed to 1.60 g of sodium hydroxide so that the concentration of the test solution was substantially 4-fold. In addition, when an anionic group is introduced, the difference in measured values in the cellulose fiber before and after the introduction of the anionic group is regarded as a substantial anionic group content. In addition, the absolutely dry cellulose fiber used as a measurement sample is one obtained by freeze-drying in order to avoid alteration of cellulose that may occur due to heating during heat drying.

  Since the anionic group content measuring method is a measuring method for a monovalent anionic group (carboxy group), when the anionic group to be quantified is multivalent, the monovalent anionic group is contained. A value obtained by dividing the value obtained as a quantity by the acid value is defined as an anionic group content.

  When the cationic group is ammonium, the content of the cationic group is the amount of nitrogen contained in the cellulose fiber, using a nitrogen measuring device (manufactured by Mitsubishi Chemical Analytech, TN-10) according to JIS-K2609. It can be determined by measuring the amount. In this case, the cation group substance amount (mmol / g) per unit mass is obtained by dividing the nitrogen content (g / g) by the number of nitrogen atoms contained in the cation group and the atomic weight of nitrogen. When the cationic group is other than ammonium, it can be determined according to the above.

  The content of hydrophobic groups in cellulose is preferably 0.1 to 2.0 mmol / g, more preferably 0.1 to 1.5 mmol / g, and 0.2 to 1.2 mmol / g. More preferably. If the content of the hydrophobic group exceeds the upper limit, the fine cellulose fibers may be dissolved, which is not preferable.

<Defibration process>
In the present invention, cellulose fibers into which a hydrophobic group and a cationic group or an anionic group have been introduced are defibrated. In the defibrating process, the alkali-treated cellulose is usually defibrated using a defibrating apparatus to obtain a fine cellulose fiber suspension.

  High-speed defibrator, grinder (stone mill type crusher), high-pressure homogenizer and ultra-high pressure homogenizer, high-pressure collision type crusher, ball mill, disk type refiner, conical refiner, twin-screw kneader, vibration mill, high speed A wet milling apparatus such as a homomixer under rotation, an ultrasonic disperser, or a beater can be used as appropriate.

  In the defibrating treatment, it is preferable to dilute the alkali-treated cellulose in a slurry form by diluting water and an organic solvent alone or in combination. The solid content concentration of the alkali-treated cellulose after dilution is preferably 0.1 to 20% by mass, and more preferably 0.2 to 10% by mass. If the solid content concentration of the alkali-treated cellulose after dilution is equal to or higher than the lower limit, the efficiency of the defibrating process is improved, and if it is equal to or lower than the upper limit, blockage in the defibrating apparatus can be prevented.

<Fine cellulose fiber>
The fine cellulose fiber is preferably a cellulose fiber or rod-like particle having an I-type crystal structure that is much thinner and shorter than the pulp fiber usually used for papermaking.
The fact that the fine cellulose fiber has a type I crystal structure is that 2θ = 14 to 17 ° in a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418４) monochromatized with graphite. It can be identified by having typical peaks in the vicinity and two positions near 2θ = 22 to 23 °.

  The degree of crystallinity of fine cellulose fibers determined by the X-ray diffraction method is preferably 60% or more, more preferably 65% or more, and further preferably 70% or more. If the degree of crystallinity is not less than the lower limit, further excellent performance can be expected in terms of heat resistance and low linear thermal expansion. The degree of crystallinity can be obtained by measuring an X-ray diffraction profile and using a conventional method (Segal et al., Textile Research Journal, 29, 786, 1959).

<Fiber width>
The fine cellulose fiber is preferably cellulose having an average fiber width of 2 to 1000 nm determined by observation with an electron microscope. The average fiber width of the fine cellulose fibers is more preferably 2 to 100 nm, further preferably 2 to 50 nm, particularly preferably 2 to 30 nm, and most preferably 2 to 15 nm. When the average fiber width of the fine cellulose fibers exceeds the above upper limit, the characteristics as the fine cellulose fibers (high strength, high rigidity, high dimensional stability, high dispersibility when combined with resin, transparency) are obtained. Becomes difficult. If the average fiber width of the fine cellulose fibers is less than the lower limit value, the cellulose molecules are dissolved in the dispersion medium, so that characteristics (high strength, high rigidity, high dimensional stability) as fine cellulose fibers can be obtained. It becomes difficult.

Measurement of the average fiber width by observation with an electron microscope of fine cellulose fibers is performed as follows. A slurry containing fine cellulose fibers is prepared, and the slurry is cast on a carbon film-coated grid that has been subjected to a hydrophilization treatment to obtain a transmission electron microscope (TEM) observation sample. When wide fibers are included, an operation electron microscope (SEM) image of the surface cast on glass may be observed. Observation by an electron microscope image is performed at any magnification of 1000 times, 5000 times, 10000 times, 20000 times, 40000 times, 50000 times, or 100000 times depending on the width of the constituent fibers. However, the sample, observation conditions, and magnification are adjusted to satisfy the following conditions.
(1) One straight line X is drawn at an arbitrary location in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y perpendicularly intersecting the straight line X is drawn in the same image, and 20 or more fibers intersect the straight line Y.

  For the electron microscope observation image as described above, the width (minor axis of the fiber) of at least 20 fibers (that is, at least 40 in total) is read for each of the fibers intersecting with the straight line X and the fibers intersecting with the straight line Y. . In this way, at least three or more sets of electron microscope images as described above are observed, and the fiber width of at least 40 × 3 sets (that is, at least 120 sets) is read. The fiber widths thus read are averaged to obtain the average fiber width. This average fiber width is equal to the number average fiber diameter.

  The maximum fiber width of the fine cellulose fibers is preferably 500 nm or less, and more preferably 300 nm or less.

<Fiber length>
As for the average fiber length of a fine cellulose fiber, 0.1-5.0 micrometers is preferable. If average fiber length is more than the said lower limit, the strength improvement effect at the time of mix | blending a fine cellulose fiber with resin will fully be acquired. If average fiber length is below the said upper limit, the mixability at the time of mix | blending a fine cellulose fiber with resin will become more favorable. The fiber length can be determined by analyzing the electron microscope observation image used when measuring the average fiber width. That is, at least 20 fibers (that is, a total of at least 40 fibers) are read for each of the fibers intersecting with the straight line X and the fibers intersecting with the straight line Y with respect to the electron microscope observation image as described above. In this way, at least three or more sets of electron microscope images as described above are observed, and the fiber length of at least 40 × 3 sets (that is, at least 120 sets) is read. The average fiber length is obtained by averaging the fiber lengths thus read.

When the fine cellulose fiber is applied to an application where strength such as a transparent substrate is required, the fiber length is preferably long (specifically, 500 nm to 4 μm), and when blended in a resin, the fiber length Is preferably shorter (specifically, 200 nm to 2 μm).
The following examples illustrate the invention, but the invention is not limited by the examples.

Example 1
Hardwood kraft pulp (LBKP) with a solid content of 30% is thoroughly mixed with 4 g of dry weight, 8 g of 4N sodium hydroxide, and 2 g of octenyl succinic anhydride (50 parts by mass with respect to 100 parts by mass of dry pulp). The mixture was heated and stirred for 2 hours. Next, the pulp treated with octenyl succinic anhydride was washed with 500 mL of water three times, and then ion-exchanged water was added to prepare 490 mL of a slurry. Then, while stirring the slurry, 10 mL of 4N aqueous sodium hydroxide solution was added little by little to adjust the pH of the slurry to 12 to 13, and the pulp was alkali treated. Thereafter, the pulp after alkali treatment was washed with water until the pH became 8 or less. When the amount of substituents (carboxy group amount) was measured, it was 0.44 mmol / g.

Next, ion exchange water was added to the pulp after the alkali treatment to prepare a slurry having a solid content concentration of 0.5% by mass. The slurry was defibrated for 30 minutes using a defibrating apparatus (Cleamix-2.2S, manufactured by MTechnic Co., Ltd.) under a condition of 21500 rotations / min to obtain a defibrated pulp slurry.
Ion exchanged water is added to the defibrated pulp slurry to adjust the slurry solid content concentration to 0.2% by mass, and the mixture is obtained by centrifuging at 12000G using a cooling high-speed centrifuge (Kokusan Co., Ltd., H-2000B). The resulting supernatant was collected.

(Example 2)
A defatted pulp slurry supernatant was obtained in the same manner as in Example 1 except that isooctadecenyl succinic anhydride was used instead of octenyl succinic anhydride. When the amount of substituents (carboxy group amount) was measured, it was 0.23 mmol / g.

(Example 3)
A sheet made of softwood bleached kraft pulp (NBKP) (solid content concentration of 90% by mass) is taken in an amount corresponding to 4.0 g in an absolutely dry mass, and using a hand mixer (manufactured by Osaka Chemical Co., Ltd., Lab Miller PLUS), the number of revolutions is 20 It was processed at 1,000 rpm for 15 seconds to make a fluffy pulp (pulverized solid concentration: 90% by mass).
Next, 4 g of cationizing agent (Kachio Master G, manufactured by Yokkaichi Chemical Co., Ltd., glycidyltrimethylammonium chloride, pure content: 73.1% by mass, moisture content: 20.2% by mass) (4.9 mmol with respect to 1 g of pulp absolute dry mass) ) And 1.5N aqueous sodium hydroxide solution (2.8 g) mixed with a cationizing agent solution using a spray, added to the fluffing pulp, and placed in a polyvinylidene chloride bag. By mixing by hand, the mixed solution was uniformly permeated into the pulp to prepare a sample for reaction (amount of solvent substance of 56 mmol per 1 g of pulp dry mass). The pH of this reaction sample was 13 at 25 ° C.

  Then, the air in a bag was removed and it was made to react at 80 degreeC for 1 hour, and the cationized pulp was obtained. 400 ml of ion-exchanged water was added to the resulting cationized pulp, washed with stirring, and then dehydrated. The washing / dehydration process was repeated four times. When the amount of substituents was measured, it was 0.71 mmol / g.

  In addition, content of a cation group measured the amount of nitrogen according to JIS-K2609 using the nitrogen measuring device (the Mitsubishi Chemical Analytech company make, TN-10) about the amount of nitrogen contained in a fine cellulose fiber. In this case, the cation group substance amount (mmol / g) per unit mass is obtained by dividing the nitrogen content (g / g) by the number of nitrogen atoms contained in the cation group and the atomic weight of nitrogen.

  Washed cationized pulp (solid content concentration: 12%) was collected in an absolute dry mass equivalent to 4.0 g, and 8 g of sodium hydroxide 8 g and benzyl chloride (39.1 parts by mass with respect to 100 parts by mass of dry pulp) The mixture was stirred and heated at 130 ° C. for 2 hours. 400 ml of ion-exchanged water was added, washed with stirring, and then dehydrated. The washing / dehydration process was repeated four times. As a result of measurement of infrared absorption spectrum by FT-IR, absorption based on a benzyl group was observed at 1607, 1498, 1456, 741, and 700 cm −1, and substitution of the benzyl group was confirmed.

Example 4
A defatted pulp slurry supernatant was obtained in the same manner as in Example 1 except that allyl succinic anhydride was used instead of octenyl succinic anhydride. When the amount of substituents (carboxy group amount) was measured, it was 1.02 mmol / g.
(Example 5)
A supernatant of defibrated pulp slurry was obtained in the same manner as in Example 1 except that (2-methyl-2-propynyl) succinic anhydride was used instead of octenyl succinic anhydride. When the amount of substituents (carboxy group amount) was measured, it was 0.63 mmol / g.

(Example 6)
A supernatant of defibrated pulp slurry was obtained in the same manner as in Example 1 except that 2-hexen-1-yl) succinic anhydride was used instead of octenyl succinic anhydride. When the amount of substituents (carboxy group amount) was measured, it was 0.51 mmol / g.
(Example 7)
A defibrated pulp slurry supernatant was obtained in the same manner as in Example 1 except that n-octyl succinic anhydride was used instead of octenyl succinic anhydride. When the amount of substituents (carboxy group amount) was measured, it was 0.39 mmol / g.

(Example 8)
A defibrated pulp slurry supernatant was obtained in the same manner as in Example 1 except that 4 g of n-methylpyrrolidone was added. When the amount of substituents (carboxy group amount) was measured, it was 0.52 mmol / g.
Example 9
A supernatant of defibrated pulp slurry was obtained in the same manner as in Example 1 except that 0.32 g of a 25% aqueous solution of tetramethylammonium hydroxide was added. When the amount of substituents (carboxy group amount) was measured, it was 0.53 mmol / g.

(Comparative Example 1)
A defibrated pulp slurry supernatant was obtained in the same manner as in Example 1 except that sodium hydroxide was not added during the reaction. When the amount of substituents was measured, it was 0.11 mmol / g.

(Comparative Example 2)
A defibrated pulp slurry supernatant was obtained in the same manner as in Example 2 except that sodium hydroxide was not added during the reaction. When the amount of substituents was measured, it was 0.07 mmol / g.

(Comparative Example 3)
A defibrated pulp slurry supernatant was obtained in the same manner as in Example 3 except that sodium hydroxide was not added during the cationization reaction and the benzylation reaction. The amount of the substituent of the cationic group was measured and found to be 0.01 mmol / g. From the measurement of the infrared absorption spectrum by FT-IR, the peak derived from the benzyl group was not confirmed.

(Comparative Example 4)
A defatted pulp slurry supernatant was obtained in the same manner as in Example 1 except that the pulp after the reaction was not alkali-treated. When the amount of substituents was measured, it was 0.44 mmol / g.

(Evaluation)
About the defibrated pulp slurry of the said Examples 1-9 and Comparative Examples 1-4, the supernatant yield after centrifuging was measured by the method as described below. The measurement results are shown in Table 1. The supernatant yield after centrifugation is an indicator of the yield of fine cellulose fibers, and the higher the supernatant yield, the higher the yield of fine cellulose fibers. The supernatant yields of Examples 1 to 9 of the present invention were higher than those of Comparative Examples 1 to 4, and it was proved that fine cellulose fibers can be produced with a high yield by the method of the present invention.

[Measurement of supernatant yield after centrifugation]
Ion exchanged water is added to the defibrated pulp slurry to adjust the slurry solid content concentration to 0.2% by mass, and the mixture is obtained by centrifuging at 12000G using a cooling high-speed centrifuge (Kokusan Co., Ltd., H-2000B). The obtained supernatant was collected, and the solid content concentration of the supernatant was measured. And the yield of supernatant liquid was calculated | required from the type | formula of solid content concentration / 0.2 mass% of supernatant liquid.

Claims (5)

Including cellulose fibers into which a hydrophobic group and a cationic group or an anionic group are introduced,
Pulp having a yield calculated by the following calculation method of 60% or more.
[Calculation method]
After adding ion-exchanged water to the cellulose fiber to prepare a dispersion having a solid content concentration of 0.5% by mass, the cellulose fiber is defibrated for 30 minutes at 21500 rpm with a high-speed rotating defibrating apparatus. A slurry containing fine cellulose fibers is obtained. After adding ion-exchanged water to the fine cellulose fiber-containing slurry to adjust the solid content concentration to 0.2% by mass, the slurry is centrifuged under a condition of 12000 G using a cooling high-speed centrifuge. The supernatant thus obtained is recovered, and the yield is calculated from the following formula.
Formula: Yield = [Solid content concentration of supernatant] /0.2% by mass   The pulp according to claim 1, wherein the hydrophobic group includes one or more selected from an alkyl group and an alkenyl group.   The pulp according to claim 1, wherein the hydrophobic group includes one or more selected from a hydrocarbon group and an acyl group.   The pulp according to any one of claims 1 to 3, wherein the hydrophobic group has 3 or more carbon atoms. Including cellulose fibers into which a hydrophobic group and a cationic group or an anionic group are introduced,
A cellulose fiber-containing slurry having a yield calculated by the following calculation method of 60% or more.
[Calculation method]
Ion exchange water is added to the cellulose fiber-containing slurry to prepare a solid content concentration of 0.2% by mass, and then centrifuged under a condition of 12000 G using a cooling high-speed centrifuge. The supernatant thus obtained is recovered, and the yield is calculated from the following formula.
Formula: Yield = [Solid content concentration of supernatant] /0.2% by mass