阅读说明：本技术 阴离子改性纤维素纳米纤维分散液和组合物 (Anionically modified cellulose nanofiber dispersions and compositions ) 是由 高市贤志 中山武史 佐藤伸治 于 2016-05-13 设计创作，主要内容包括：本发明提供在加热时不会着色的阴离子改性纤维素纳米纤维分散液和组合物。具体而言,该分散液含有阴离子改性纤维素纳米纤维；选自硼酸盐类、亚硫酸盐类和它们的组合中且相对于所述阴离子改性纤维素纳米纤维的绝对干燥质量为1～30质量％的防着色剂；以及,溶剂。(The invention provides an anionic modified cellulose nanofiber dispersion and a composition which are not colored when heated. Specifically, the dispersion liquid contains an anion-modified cellulose nanofiber; an anti-coloring agent selected from borate salts, sulfite salts, and a combination thereof, wherein the anti-coloring agent is 1 to 30 mass% relative to the absolute dry mass of the anion-modified cellulose nanofibers; and, a solvent.)

1. An anion-modified cellulose nanofiber dispersion liquid comprising an anion-modified cellulose nanofiber, a stain-proofing agent selected from sulfite salts and having an absolute dry mass of 1 to 30% by mass relative to the anion-modified cellulose nanofiber, and a solvent.

2. The dispersion liquid according to claim 1, wherein the sulfite salt is at least one selected from the group consisting of sodium hydrogen sulfite, potassium hydrogen sulfite, ammonium hydrogen sulfite, sodium sulfite, potassium sulfite, ammonium sulfite, sodium sulfite, potassium sulfite, calcium sulfite, sodium metabisulfite, potassium metabisulfite, magnesium metabisulfite, and calcium metabisulfite.

3. The dispersion according to claim 1 or 2, wherein the sulfite is sodium bisulfite.

4. The dispersion liquid according to claim 1 or 2, wherein the total amount of the stainblocker is 1 to 15% by mass relative to the absolute dry mass of the anion-modified cellulose nanofibers.

5. The dispersion liquid according to claim 1 or 2, wherein the pH is from 6.5 to 10.

6. The dispersion liquid according to claim 1 or 2, wherein the anionically modified cellulose nanofibers have carboxyl groups in an amount of 0.5 to 2.0mmol/g relative to the absolute dry mass of the anionically modified cellulose nanofibers.

7. The dispersion liquid according to claim 1 or 2, wherein the anion-modified cellulose nanofibers are carboxymethylated cellulose nanofibers having a degree of substitution of carboxymethyl group of 0.01 to 0.50 per glucose unit of the anion-modified cellulose nanofibers.

8. The dispersion liquid according to claim 1 or 2, wherein the anion-modified cellulose nanofibers have been subjected to a reduction treatment with a reducing agent.

9. The dispersion liquid according to claim 1 or 2, wherein the anion-modified cellulose nanofibers have an average fiber length of 50 to 2000nm and an average fiber diameter of 2 to 50 nm.

10. An anion-modified cellulose nanofiber composition obtained by removing a solvent from the anion-modified cellulose nanofiber dispersion liquid according to any one of claims 1 to 9.

11. A production method of the dispersion liquid according to any one of claims 1 to 9, comprising:

(i) a step for oxidizing a cellulose raw material in water with an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromides, iodides, and mixtures thereof to produce oxidized cellulose,

(ii) a step of obtaining an oxidized cellulose nanofiber dispersion by defibrating the oxidized cellulose, and

(iii) and a step of obtaining a cellulose nanofiber dispersion containing the oxidized cellulose nanofiber dispersion and the stainblocker.

12. A method for producing the composition according to claim 10, comprising the steps of:

(i) a step for oxidizing a cellulose raw material in water with an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromides, iodides, and mixtures thereof to produce oxidized cellulose,

(ii) a step for obtaining an oxidized cellulose nanofiber dispersion by defibrating the oxidized cellulose,

(iii) a step of obtaining a cellulose nanofiber dispersion containing the oxidized cellulose nanofiber dispersion and the stainblocker, and

(iv) and removing the water from the nanofiber dispersion.

13. A sheet comprising the composition of claim 10.

Technical Field

The present invention relates to anionically modified cellulose nanofiber dispersions and compositions.

Background

It is known that when a cellulose raw material is treated in the presence of 2,2,6, 6-tetramethyl-1-piperidine-N-oxyl (hereinafter, also referred to as TEMPO) and an inexpensive oxidizing agent, sodium hypochlorite, carboxyl groups can be efficiently introduced onto the surface of cellulose microfibrils. The oxidized cellulose thus obtained can be made into a uniform and transparent aqueous dispersion of cellulose nanofibers by imparting a very small amount of defibering energy. Various studies have been made on the method for producing oxidized cellulose and the method for producing cellulose nanofibers (patent document 1).

Disclosure of Invention

However, the cellulose nanofibers disclosed in patent document 1 have a problem of coloring when heated. When such cellulose nanofibers are thermally processed to form a product, the obtained product is discolored, and therefore, there is a problem that industrial use thereof is difficult.

It is an object of the present invention to provide an anionic modified cellulose nanofiber dispersion and a composition which are not colored when heated.

The above problems are solved by the present invention described below.

(1) An anion-modified cellulose nanofiber dispersion liquid comprising an anion-modified cellulose nanofiber, a stain-proofing agent selected from borates, sulfites and combinations thereof, and a solvent, wherein the stain-proofing agent is 1 to 30% by mass relative to the absolute dry mass of the anion-modified cellulose nanofiber.

(2) The dispersion liquid according to (1), wherein the total amount of the stainblocker is 1 to 15% by mass based on the absolute dry mass of the anion-modified cellulose nanofibers.

(3) The dispersion liquid according to (1) or (2), wherein the pH is 6.5 to 10.

(4) The dispersion liquid according to any one of (1) to (3), wherein the anionically modified cellulose nanofibers have carboxyl groups in an amount of 0.5 to 2.0mmol/g relative to the absolute dry mass of the anionically modified cellulose nanofibers.

(5) The dispersion liquid according to any one of (1) to (3), wherein the anion-modified cellulose nanofibers are carboxymethylated cellulose nanofibers having a degree of substitution of carboxymethyl group of 0.01 to 0.50 per glucose unit of the anion-modified cellulose nanofibers.

(6) The dispersion liquid according to any one of (1) to (5), wherein the anion-modified cellulose nanofibers have been subjected to reduction treatment with a reducing agent.

(7) The dispersion liquid according to any one of (1) to (6), wherein the anion-modified cellulose nanofibers have an average fiber length of 50 to 2000nm and an average fiber diameter of 2 to 50 nm.

(8) An anion-modified cellulose nanofiber composition obtained by removing a solvent from the anion-modified cellulose nanofiber dispersion liquid according to any one of (1) to (7).

(9) A method for producing the dispersion liquid according to any one of (1) to (7), comprising:

(i) a step for oxidizing a cellulose raw material in water with an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromides, iodides, and mixtures thereof to produce oxidized cellulose,

(ii) a step of obtaining an oxidized cellulose nanofiber dispersion by defibrating the oxidized cellulose, and

(iii) and a step of obtaining a cellulose nanofiber dispersion containing the oxidized cellulose nanofiber dispersion and the stainblocker.

(10) A method for producing the composition according to (8), comprising the steps of:

(i) a step of oxidizing a cellulose raw material in water with an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromides, iodides, and mixtures thereof to obtain oxidized cellulose,

(ii) a step for obtaining an oxidized cellulose nanofiber dispersion by defibrating the oxidized cellulose,

(iii) a step of obtaining a cellulose nanofiber dispersion containing the oxidized cellulose nanofiber dispersion and the stainblocker, and

(iv) and removing the water from the nanofiber dispersion.

(11) A sheet comprising the composition according to (8) above.

According to the present invention, an anion-modified cellulose nanofiber dispersion and a composition which are not colored when heated can be provided.

Detailed Description

The present invention will be described in detail below. In the present invention, "X to Y" includes X and Y as their end values.

In the present invention, the anion-modified cellulose nanofiber dispersion liquid is a liquid containing the nanofibers, a stain-proofing agent selected from borate salts, sulfite salts and combinations thereof, and a solvent, and the anion-modified cellulose nanofibers are dispersed in the solvent. The anionically modified cellulose nanofiber composition is a composition containing the nanofibers and an anti-coloring agent. The composition may contain the above-mentioned solvent and the like. In compositions containing a solvent, the nanofibers need not be dispersed in the solvent.

1. Anionic modified cellulose nanofiber dispersion

(1) Stain blocking agent

The stainblocker is an additive for preventing coloring of the anion-modified cellulose nanofibers (hereinafter, also referred to as "anion-modified CNF") by heating. In the present invention, an anti-coloring agent selected from the group consisting of borates, sulfites and combinations thereof is used.

(1-1) salts of boric acid

In the present invention, borates are a generic name of borates (Boric acid) and monohydrocarbyl borates (Boronic acid). The term "borate" in the present invention means a compound derived from boric acid (B (OH)₃) And monovalent metal ions. The metal ion is preferably an alkali metal ion. As the anion derived from boric acid, there is borate ion [ BO₃]^3－Boric acid hydrogen radical ion [ HBO ]₃]^2－Or a dihydrogen borate ion [ H₂BO₃]^－. The term "monohydrocarbylborate" as used herein means a compound derived from the anion of monohydrocarbylborate [ R-BO₂H]^－、[R－BO₂]^2－And monovalent metal ions. R is a monovalent hydrocarbon group, preferably an alkyl group or an aryl group. Among them, R is preferably a phenyl group or an alkylphenyl group. The boronic acid with R as phenyl is phenylboronic acid. That is, in the present invention, the borate is M₃[BO₃]、M₂[HBO₃]、M[H₂BO₃]、M₂[R－BO₂]Or M [ R-BO₂H]Salts of (M is a monovalent metal ion, R is a monovalent hydrocarbon group) are shown. These borates can exist in the anion-modified CNF dispersion and composition as solids, ionized, or reacted with functional groups in the anion-modified CNF.

Examples of the preferable borate include sodium borate, lithium borate, potassium borate, rubidium borate, cesium borate, sodium monohydrocarbylborate, potassium monohydrocarbylborate, rubidium monohydrocarbylborate, and cesium monohydrocarbylborate. For example, the sodium borate is a mixture of Na and any one or combination of the above 3 kinds of anions derived from boric acid⁺A salt of (a). In the present invention, sodium borate is preferred from the viewpoint of cost and availability.

The amount of borate is preferably 1 to 30% by mass, more preferably 5 to 25% by mass, and still more preferably 10 to 15% by mass, based on the absolute dry mass of the anion-modified cellulose nanofiber. If the content of the borate is less than 1% by mass or exceeds 30% by mass, a sufficient coloring-suppressing effect is not exhibited.

The mechanism by which borates act as stain repellents is not limited but can be considered as follows: it is presumed that the anion-modified cellulose nanofibers are decomposed by heating and then undergo dehydration reaction and condensation reaction to form coloring matter. In this case, it is presumed that when the borate is added, the borate reacts with the hydroxyl group in the cellulose nanofibers to form a borate ester, and therefore, the decomposition product generated by heating is inhibited from further decomposing and dehydrating, and coloring is unlikely to occur. The evaluation of coloring is not particularly limited, and may be performed by visual evaluation, a spectral colorimeter, or the like.

(1-2) sulfites

In the present invention, the sulfite refers to sulfite (M)₂SO₃: m is a monovalent cationic site), bisulfite (MHSO)₃: m is a monovalent cation site), pyrosulfite (M)₂S₂O₅Or M' S₂O₅: m is a monovalent cationic site, M' is a divalent cationic site), hyposulfite (M)₂S₂O₄Or M' S₂O₄: m is a monovalent cationic site, M' is a divalent cationic site) or a hydrate thereof. Examples of M include alkali metal ions and ammonium ions, and examples of M' include alkaline earth metal ions. Preferred sulfite salts include sodium bisulfite, potassium bisulfite, ammonium bisulfite, sodium sulfite, potassium sulfite, ammonium sulfite, sodium sulfite, potassium bisulfite, calcium sulfite, sodium metabisulfite, potassium metabisulfite, magnesium metabisulfite, calcium metabisulfite, and the like, and among them, sodium bisulfite is particularly preferred.

In the present invention, the amount of the sulfite is preferably 0.1 to 15% by mass, more preferably 1 to 15% by mass, even more preferably 1.0 to 12% by mass, and even more preferably 3.0 to 10% by mass, based on the absolute dry mass of the anion-modified CNF.

The mechanism by which the sulfite salt functions as a stain inhibitor can be considered, though not limited to, as follows: the anion-modified CNF has a ketone group and an aldehyde group due to oxidation of a hydroxyl group by anion modification. When such anion-modified CNF is heated, a β -dissociation reaction occurs using a ketone group and an aldehyde group as a scaffold, and a2, 3-diketone derived from the ketone group and an α, β -unsaturated aldehyde derived from the aldehyde group are produced at the non-reducing end of the cellulose newly produced by the reaction. Further, a peeling reaction (peeling reaction) occurs from the reducing end of the newly produced cellulose, and a coloring matter having 2, 3-diketone is accumulated. However, in the present invention, since the sulfite reduces the ketone group and the aldehyde group present in the anion-modified CNF, coloring due to heating can be suppressed.

This effect is particularly remarkable in a carboxyl group-modified CNF having a carboxyl group amount of 0.5 to 2.0mmol/g, which is produced by defibrating oxidized cellulose obtained by oxidation of a cellulose raw material using an oxidation catalyst such as an N-oxyl compound (TEMPO, TEMPO derivative, or the like) and an oxidizing agent, or oxidation of a cellulose raw material using ozone. In the production of oxidized cellulose using an N-oxyl compound as an oxidation catalyst, a carboxyl group is selectively produced at the C6 position, while oxidation of secondary alcohols at the C2 position and C3 position of cellulose by an N-oxyl compound and sodium hypochlorite occurs as a side reaction, and ketone groups are produced at the C2 position and C3 position. In addition, oxidation to a carboxyl group at the C6 position by the TEMPO catalyst is a two-step reaction via an aldehyde, and a part of aldehyde groups remain without being oxidized to a carboxyl group. By such a mechanism, the conventional carboxyl group-modified CNF has a problem of coloring when heated, but as described above, the present invention can solve the problem by using a sulfite salt. In addition, the sulfite salts also have the following advantages: the cellulose nanofibers are not damaged, have high safety as a substance, and are not the subject of the PRTR system. Therefore, the use of the sulfite salt can achieve both of suppression of coloring and safety. Sulfites can exist as solids, ionized or oxidized in anionically modified CNF dispersions and compositions.

When borate and sulfite are used in combination as the stainblocker, the above amounts are preferably used.

(1-3) anionically modified cellulose nanofibers

In the present invention, the length-average fiber diameter of the anion-modified CNF is 2 to 1000nm, the lower limit is preferably 2.5nm, more preferably 3nm, further preferably 4nm, and the upper limit is preferably 500nm, more preferably 100nm, further preferably about 10 nm. The average fiber length is preferably 100 to 3000nm, more preferably 150 to 1500nm, and further preferably 200 to 1000 nm. The aspect ratio (length-average fiber length/length-average fiber diameter) of the anion-modified CNF is preferably 10 to 1000, and more preferably 100 to 1000. The anion-modified CNF can be obtained by defibrating an anion-modified cellulose such as a carboxylated cellulose (also referred to as "oxidized cellulose") obtained by modifying a cellulose raw material, a carboxymethylated cellulose, and a cellulose having a phosphate group introduced thereto. The raw materials, modification method and the like will be explained below.

(cellulose Material)

Examples of the cellulose raw material for producing the anion-modified cellulose include a regenerated cellulose obtained by spinning a cellulose dissolved in an arbitrary solvent such as a cuprammonium solution or a morpholine derivative, a regenerated cellulose obtained by hydrolyzing a plant material (for example, wood, bamboo, hemp, jute, kenaf, agricultural waste, cloth, pulp (needle unbleached kraft pulp (NUKP), Needle Bleached Kraft Pulp (NBKP), Leaf Unbleached Kraft Pulp (LUKP), Leaf Bleached Kraft Pulp (LBKP), Needle Unbleached Sulfite Pulp (NUSP), Needle Bleached Sulfite Pulp (NBSP), thermomechanical pulp (TMP), regenerated pulp, waste paper, etc.), an animal material (for example, ascidians), algae, a microorganism (for example, acetic acid bacteria (acetobacter)), a microorganism product, etc., a regenerated cellulose obtained by dissolving a cellulose in an arbitrary solvent such as a cuprammonium solution or a morpholine derivative, etc., a regenerated cellulose obtained by hydrolyzing the cellulose raw material, a cellulose obtained by spinning a cellulose, Any of the fine celluloses that are obtained by depolymerizing cellulose by mechanical treatment such as alkali hydrolysis, enzymatic decomposition, sand blasting, and vibration ball mill can be used. Among these, cellulose fibers derived from plants or microorganisms are preferable, and cellulose fibers derived from plants are more preferable.

(carboxymethylation)

Carboxymethylated cellulose can be obtained by carboxymethylating the above-mentioned cellulose raw material by a known method, and a commercially available product can be used. In either case, the degree of substitution of carboxymethyl groups per anhydroglucose unit of cellulose is preferably 0.01 to 0.50. As an example of a method for producing such carboxymethylated cellulose, the following method can be given.

Cellulose is used as a starting material, and a solvent is used in an amount of 3 to 20 times by mass. The solvent is water, lower alcohol or their mixture. Examples of the lower alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, and a combination thereof. The mixing ratio of the lower alcohol in the mixed solvent of water and the lower alcohol is 60 to 95 mass%. As the alkalinizing agent, alkali metal hydroxide, specifically sodium hydroxide and potassium hydroxide is used in an amount of 0.5 to 20 times by mole with respect to the anhydroglucose residue of the starting material. Mixing the starting raw materials with a solvent and an alkalizer, and carrying out alkalization treatment under the conditions of reaction temperature of 0-70 ℃, preferably 10-60 ℃ and reaction time of 15 minutes-8 hours, preferably 30 minutes-7 hours. Then, a carboxymethylating agent is added in an amount of 0.05 to 10.0 times by mole relative to the glucose residue, and the etherification reaction is carried out at a reaction temperature of 30 to 90 ℃, preferably 40 to 80 ℃, and a reaction time of 30 minutes to 10 hours, preferably 1 hour to 4 hours.

The "carboxymethylated cellulose" used in the present invention is a cellulose which can maintain at least a part of a fibrous shape even when dispersed in water. Therefore, carboxymethylated cellulose is distinguished from carboxymethyl cellulose, which is one of water-soluble polymers described later. When an aqueous dispersion of carboxymethylated cellulose is observed with an electron microscope, fibrous substances can be observed. On the other hand, even when an aqueous dispersion of carboxymethyl cellulose, which is one of water-soluble polymers, was observed, fibrous substances were not observed. In addition, although a peak of cellulose I-type crystals is observed in carboxymethylated cellulose when measured by X-ray diffraction, a peak of cellulose I-type crystals is not observed in carboxymethylated cellulose of a water-soluble polymer.

(carboxylation)

The carboxylated cellulose (oxidized cellulose) can be obtained by carboxylating (oxidizing) the above-mentioned cellulose raw material by a known method. Although not particularly limited, the amount of carboxyl groups is adjusted so that the amount of carboxyl groups is preferably 0.2mmol/g or more, more preferably 0.5 to 2.0mmol/g, still more preferably 0.6 to 2.0mmol/g, still more preferably 1.0 to 2.0mmol/g, and particularly preferably 1.0 to 1.8mmol/g, based on the absolute dry mass of the anion-modified cellulose nanofibers during carboxylation. The amount of the carboxyl group can be adjusted by the oxidation reaction time, the oxidation reaction temperature, the pH at the time of the oxidation reaction, the amount of the N-oxyl compound, the bromide, the iodide, and the oxidizing agent.

As an example of the carboxylation (oxidation) method, there is a method of oxidizing a cellulose raw material in water using an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromides, iodides, and mixtures thereof. By this oxidation reaction, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized, and an aldehyde group and a carboxyl group (-COOH) or a carboxylate group (-COO) can be obtained on the surface^－) The cellulose fiber of (1). The concentration of cellulose during the reaction is not particularly limited, but is preferably 5% by mass or less.

N-oxyl compounds are compounds which generate nitroxide radicals. Any compound may be used as the N-oxyl compound as long as it promotes the desired oxidation reaction. Examples thereof include 2,2,6, 6-tetramethylpiperidine-1-oxyl (TEMPO) and derivatives thereof (e.g., 4-hydroxy TEMPO).

The amount of the N-oxyl compound used is not particularly limited as long as it is an amount of a catalyst capable of oxidizing the cellulose as a raw material. For example, the amount of the surfactant is preferably 0.01 to 10mmol, more preferably 0.01 to 1mmol, and still more preferably 0.05 to 0.5mmol based on 1g of the absolutely dry cellulose. Further, the concentration of the catalyst may be about 0.1 to 4mmol/L relative to the reaction system.

Bromides are bromine-containing compounds, examples of which include alkali metal bromides that dissociate in water to become ionized. In addition, the iodide is an iodine-containing compound, and examples thereof include alkali metal iodides. The amount of bromide or iodide used may be selected within a range capable of promoting the oxidation reaction. The total amount of the bromide and the iodide is, for example, preferably 0.1 to 100mmol, more preferably 0.1 to 10mmol, and still more preferably 0.5 to 5mmol, per 1g of absolutely dry cellulose.

As the oxidizing agent, known oxidizing agents can be used, and examples thereof include halogen, hypohalous acid, perhalogenic acid, salts thereof, halogen oxides, and peroxides. Among them, sodium hypochlorite is preferred which is inexpensive and has little environmental load. The amount of the oxidizing agent is, for example, preferably 0.5 to 500mmol, more preferably 0.5 to 50mmol, still more preferably 1 to 25mmol, and most preferably 3 to 10mmol, per 1g of absolutely dry cellulose. Further, for example, 1mol to 40mol is preferable to 1mol of the N-oxyl compound.

The oxidation step of cellulose enables the reaction to proceed efficiently even under relatively mild conditions. Therefore, the reaction temperature is preferably 4 to 40 ℃ and may be about 15 to 30 ℃. As the reaction proceeded, carboxyl groups were formed in the cellulose, and thus, it was confirmed that the pH of the reaction solution decreased. In order to efficiently perform the oxidation reaction, an alkaline solution such as an aqueous sodium hydroxide solution is added to maintain the pH of the reaction solution at preferably about 8 to 12, more preferably about 10 to 11. The reaction medium is preferably water from the viewpoint of ease of handling, difficulty in causing side reactions, and the like.

The reaction time in the oxidation reaction may be appropriately set according to the degree of progress of the oxidation, and is usually about 0.5 to 6 hours, preferably about 2 to 4 hours.

The oxidation reaction can be carried out in 2 stages. For example, by oxidizing the oxidized cellulose obtained by filtration separation after the completion of the reaction in the 1 st stage again under the same or different reaction conditions, the oxidation can be efficiently performed without being inhibited by the reaction due to the common salt produced as a by-product in the reaction in the 1 st stage.

Another example of the carboxylation (oxidation) method is a method in whichA method for oxidizing a cellulose raw material by bringing an ozone-containing gas into contact with the cellulose raw material. By this oxidation reaction, hydroxyl groups at least at the 2-and 6-positions of the glucopyranose ring are oxidized, and decomposition of the cellulose chain occurs. The concentration of ozone in the ozone-containing gas is preferably 50 to 250g/m³More preferably 50 to 220g/m³. The amount of ozone added to the cellulose raw material is preferably 0.1 to 30 parts by mass, more preferably 5 to 30 parts by mass, per 100 parts by mass of the solid content (absolute dry mass) of the cellulose raw material. The ozone treatment temperature is preferably 0 to 50 ℃, and more preferably 20 to 50 ℃. The ozone treatment time is not particularly limited, and is about 1 to 360 minutes, preferably about 30 to 360 minutes. When the conditions of the ozone treatment are within these ranges, the cellulose can be prevented from being excessively oxidized and decomposed, and the yield of the oxidized cellulose becomes good. After the ozone treatment, an additional oxidation treatment using an oxidizing agent may be performed. The oxidizing agent used in the post-oxidation treatment is not particularly limited, and examples thereof include chlorine compounds such as chlorine dioxide and sodium chlorite, oxygen, hydrogen peroxide, persulfuric acid, and peracetic acid. For example, the post-oxidation treatment can be performed by dissolving the oxidizing agent in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and immersing the cellulose raw material in the solution.

In the present invention, it is preferable to use carboxylated CNF subjected to reduction treatment from the viewpoint of suppressing coloring. Particularly high effects are obtained by reduction treatment when borates are used as stainblocker. The reduction treatment is preferably performed on the oxidized cellulose raw material before defibration. Any reducing agent can be used as long as it can reduce a part of the aldehyde groups and ketone groups formed to alcohols, and examples thereof include thiourea, dithionite, sodium bisulfite, sodium borohydride, sodium cyanoborohydride, and lithium borohydride. The amount of the reducing agent used is 0.1 to 150 parts by mass, preferably 0.5 to 100 parts by mass, and more preferably about 1 to 50 parts by mass, per 100 parts by mass of the oxidized cellulose raw material. In addition, the reduction treatment temperature is preferably about 10 to 90 ℃, and more preferably 20 to 70 ℃ from the viewpoint of the reduction treatment efficiency and the suppression of the deterioration of the fibers. The pH in the reduction treatment may be appropriately selected depending on the reducing agent used, and is usually 2 to 12, preferably 3 to 10. The reaction time in the reduction reaction is not particularly limited, and may be appropriately set according to the degree of progress of the reduction, and is usually 0.5 to 6 hours, preferably 1 to 5 hours, and more preferably 1 to 4 hours.

(defibering)

Cellulose nanofibers are obtained by defibrating anionically modified cellulose. The apparatus used for the defibration is not particularly limited, and a high-speed rotation type, a colloid mill type, a high-pressure type, a roll mill type, an ultrasonic type, or the like can be used. It is preferred to apply strong shear force to the aqueous dispersion of the anionically modified cellulose during defibration. In particular, in order to efficiently perform defibration, a wet high-pressure or ultra-high-pressure homogenizer capable of applying a pressure of 50MPa or more and a strong shearing force to the aqueous dispersion is preferably used. The pressure is more preferably 100MPa or more, and still more preferably 140MPa or more. Before the defibration and dispersion treatment by the high-pressure homogenizer, the aqueous dispersion may be subjected to a pretreatment using a known mixing, stirring, emulsifying, and dispersing apparatus such as a high-speed shear mixer, if necessary.

(1-4) anion-modified CNF Dispersion

This can provide the anionically modified CNF dispersion of the present invention. The stainblocker may be added before the anion-modified cellulose is defibrated, or may be added to the anion-modified CNF dispersion obtained by defibration. However, from the viewpoint of further improving the defibration efficiency, it is preferably added to the anion-modified CNF dispersion after the defibration. The temperature at which the stainblocker is added is not particularly limited, but is preferably 0 to 50 ℃ and more preferably 10 to 40 ℃. The pH of the anion-modified CNF dispersion is not limited, but is preferably 6.5 to 10, and more preferably 8 to 9.5. When the pH of the dispersion is in this range, a high effect of suppressing coloring is exhibited. The solvent is preferably water from the viewpoint of the solubility of the stain-proofing agent, but an organic solvent such as alcohol may be contained within a range not impairing the solubility. The concentration of the anion-modified CNF in the dispersion is preferably 0.1 to 10% (w/v).

(1-5) anion-modified CNF composition

The anion-modified CNF composition is a composition containing an anion-modified CNF and the stain inhibitor, and as the composition, a composition obtained by drying the anion-modified CNF dispersion is preferable. Drying is the removal of the solvent from the dispersion. The composition may be in an absolutely dry state without a solvent, but may contain about 10 to 100000 mass% of a solvent based on the absolutely dry mass of the anion-modified CNF. As described above, in the anion-modified CNF composition obtained in this way, the stain inhibitor may be present by reacting with a functional group such as a hydroxyl group in the anion-modified CNF. However, it is not practical to identify the reaction morphology and determine the amount.

The removal of the solvent containing water can be performed using, for example, a centrifugal dehydration type, a vacuum dehydration type, a pressure dehydration type, or a combination thereof. Alternatively, the solvent may be removed by, for example, spray drying, pressing, air drying, hot air drying, vacuum drying, or the like. The drying apparatus is not particularly limited, and examples thereof include a continuous tunnel drying apparatus, a Belt drying apparatus (Band drying apparatus), a vertical drying apparatus, a vertical turbo drying apparatus, a multistage circular plate drying apparatus, an aeration drying apparatus, a rotary drying apparatus, an air flow drying apparatus, a spray dryer drying apparatus, a spray drying apparatus, a cylinder drying apparatus, a drum drying apparatus, a Belt drying apparatus (Belt drying apparatus), a screw conveyor drying apparatus, a rotary drying apparatus with a heating pipe, a vibration conveying drying apparatus, a batch type box drying apparatus, an aeration drying apparatus, a vacuum box drying apparatus, an agitation drying apparatus, and the like, and combinations thereof.

The anion-modified CNF composition of the present invention can be used as an additive and the like in various fields. Examples of the fields include fields such as food, beverages, personal care products, cosmetics, pharmaceuticals, various chemical products, paper manufacture, civil engineering, paints, inks, coating compositions, agricultural chemicals, construction, automobiles, anti-epidemic agents, electronic materials, batteries, flame retardants, heat insulators, household sundries, detergents, water treatment, drilling fluids, neutral functional substances, shale gas, and outflow control or recovery of oil. Specifically, the composition is useful as a thickener, a gelling agent, a paste, a food additive, an excipient, a reinforcing material for rubber and plastic, an additive for coating material, an additive for adhesive, an additive for paper making, a polishing agent, a water absorbing material, an odor inhibitor, an antirust agent, a water retaining agent, a humectant, a cold retaining agent, a shape retaining agent, a sludge regulator, a filter aid, a sludge overflow preventing agent, etc., and is applicable to rubber and plastic materials, coating materials, adhesives, coating agents for coated paper, adhesives, cosmetics, lubricating compositions, polishing compositions, wrinkle reducing agents for clothing, ironing lubricants, etc., containing these as a constituent.

In particular, the CNF composition of the present invention obtained by TEMPO oxidation is suitable as a material for film members such as films and sheets, or molded articles.

2. Method for producing anion-modified CNF dispersion and composition

The anion-modified CNF dispersion liquid is not particularly limited, but is preferably produced by a method including the following steps (i) to (iii).

(i) A step for oxidizing a cellulose raw material in water with an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromides, iodides, and mixtures thereof to produce oxidized cellulose,

(ii) a step of obtaining an oxidized cellulose nanofiber dispersion by defibrating the oxidized cellulose,

(iii) and a step of obtaining a cellulose nanofiber dispersion containing the oxidized cellulose nanofiber dispersion and the stainblocker.

In the step (iii), a coloring inhibitor is added to the oxidized cellulose nanofiber dispersion and mixed. The temperature at this time is not particularly limited, but is preferably 0 to 50 ℃, and more preferably 10 to 40 ℃. The pH of the dispersion after addition is preferably 4 to 10, more preferably 5 to 9. The pH can be adjusted by an aqueous sodium hydroxide solution or the like at the time of addition. The mixing conditions are not particularly limited, and for example, a propeller stirrer of 600 revolutions may be used for 0.5 to 6 hours.

By removing the water from the dispersion thus obtained (step (iv)), an anion-modified CNF composition can be obtained. The conditions for removing water and the like are as described above.