JP2017071700A - Method for producing anion-modified cellulose nanofibers - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide cellulose nanofibers which are not colored during heating.SOLUTION: There is provided a method for producing anion-modified cellulose nanofibers, which comprises: (A) a step of chemically modifying a cellulose raw material to obtain an anion-modified cellulose; (B) a step (alkali-treatment step) of mixing water, an alkalization agent and the anion-modified cellulose obtained in (A) in a ratio of the water:the alkalization agent:the anion-modified cellulose=100:0.01 to 10:0.01 to 10 (pts.wt), followed by stirring for 10 minutes to 10 hours under a condition of 0 to 40°C; and (C) a step of fibrillating the anion-modified cellulose subjected to alkali treatment to obtain cellulose nanofibers.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing anion-modified cellulose nanofibers.

  When cellulose raw material is treated in the presence of 2,2,6,6-tetramethyl-1-piperidine-N-oxy radical (hereinafter also referred to as TEMPO) and an inexpensive oxidizing agent, sodium hypochlorite, cellulose micro It is known that a carboxyl group can be efficiently introduced into the fibril surface. The carboxylated cellulose thus obtained can be prepared into a uniform and transparent cellulose nanofiber aqueous dispersion by applying a slight fibrillation energy. Various studies have been conducted on a method for producing such carboxylated cellulose and a method for producing cellulose nanofiber (Patent Document 1).

JP 2008-001728 A

  However, the cellulose nanofiber disclosed in Cited Document 1 has a problem of coloring when heated. When coloring occurs during heating, there is a problem that when the cellulose nanofiber is used industrially, particularly when it is molded by thermal processing, the product is discolored.

  Then, an object of this invention is to provide the manufacturing method of the anion modified cellulose nanofiber which is not colored at the time of a heating.

The above problem is solved by means including the following [1] to [3].
[1] A method for producing anion-modified cellulose nanofibers,
(A) a step of chemically modifying a cellulose raw material to obtain an anion-modified cellulose;
(B) water, an alkalinizing agent, an anion-modified cellulose obtained in (A),
Step of stirring for 10 minutes to 10 hours under the condition of 0 to 40 ° C. after mixing at a ratio of water: alkalizing agent: anion-modified cellulose = 100: 0.01 to 10: 0.01 to 10 (parts by weight) (Step of alkali treatment), and (C) defibrating the alkali-treated anion-modified cellulose to obtain cellulose nanofibers,
A process for producing anion-modified cellulose nanofibers, comprising:
[2] The anion-modified cellulose nanofiber is characterized in that the amount of carboxyl groups is 0.6 mmol / g to 3.0 mmol / g with respect to the dry weight of the anion-modified cellulose nanofiber [1] ] The manufacturing method of the anion modified cellulose nanofiber of description.
[3] The anion-modified cellulose according to [1], wherein the anion-modified cellulose nanofiber has a degree of carboxymethyl substitution per glucose unit of the anion-modified cellulose nanofiber of 0.01 to 0.50. Manufacturing method of nanofiber.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the anion modified cellulose nanofiber which is not colored at the time of a heating can be provided.

  The dispersion and composition of the anion-modified cellulose nanofiber (hereinafter, sometimes referred to as “anion-modified CNF”) of the present invention are stirred for 10 minutes to 10 hours under the condition of 0 to 40 ° C. of anion-modified cellulose. It is characterized by performing an alkali treatment.

  In the present invention, the reason why the composition containing an anion-modified CNF obtained by heating and drying an anion-modified CNF dispersion produced by fibrillation after an anion-modified cellulose is treated with an alkali is presumed as follows. Is done.

  When anion-modified cellulose is produced to produce anion-modified cellulose, it is considered that a substance that is colored by heating is generated in an amorphous substance as a side reaction. It is presumed that the amorphous substance can be peeled from the anion-modified cellulose by alkali treatment, which makes it difficult to color.

  Furthermore, in the case of TEMPO-oxidized cellulose, it is considered that a large amount of the amorphous substance that becomes the coloring substance is included in association with the oxidation reaction using the N-oxyl compound. It is thought that the suppression effect can be expected further.

  In the production process of the dispersion and composition of the anion-modified CNF of the present invention, it is important to include an alkali treatment process. At the time of alkali treatment, when 5 parts by weight of chemically modified pulp is added to 100 parts by weight of water, if the amount of alkali added is less than 0.01 parts by weight, the effect of peeling the amorphous substance is low, The coloring suppression effect does not appear.

  The alkali treatment step oxidizes cellulose to produce anion-modified cellulose, and is performed immediately after the washing / dehydration step, thereby exhibiting a coloring suppression effect. Moreover, even when the alkali treatment is performed, the transparency of the anion-modified CNF obtained by defibration may be lower than that obtained by defibration of the anion-modified pulp not including the alkali treatment step. Absent.

(Anion-modified cellulose nanofiber)
In the present invention, anion-modified CNF is a fine fiber having a fiber width of about 3 to 500 nm and an aspect ratio of 100 or more, and can be obtained by fibrillating anion-modified cellulose (also called oxidized cellulose).

(Cellulose raw material)
Examples of cellulose raw materials for producing anion-modified cellulose include plant materials (for example, wood, bamboo, hemp, jute, kenaf, farmland waste, cloth, pulp (coniferous unbleached kraft pulp (NUKP), coniferous bleaching). Kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP) thermomechanical pulp (TMP), regenerated pulp , Waste paper, etc.), animal materials (for example, ascidians), algae, microorganisms (for example, acetic acid bacteria (Acetobacter)), microbial products, etc., any of which can be used. Is a cellulose fiber derived from a plant or a microorganism, more preferably a plant Is a cellulose fiber of come.

(Carboxylation)
In the present invention, carboxylated cellulose (also referred to as oxidized cellulose) can be obtained by carboxylating (oxidizing) the above cellulose raw material by a known method. Although not particularly limited, at the time of carboxylation, the amount of carboxyl groups should be adjusted to 0.6 to 2.0 mmol / g with respect to the absolute dry weight of carboxylated cellulose nanofibers. Is preferable, and it is more preferable to adjust so that it may become 1.0 mmol / g-2.0 mmol / g.

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

  The N-oxyl compound refers to a compound that can generate a nitroxy radical. As the N-oxyl compound, any compound can be used as long as it promotes the target oxidation reaction. For example, 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) and its derivative (for example, 4-hydroxy TEMPO) are mentioned.

  The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount capable of oxidizing cellulose as a raw material. For example, 0.01 to 10 mmol is preferable, 0.01 to 1 mmol is more preferable, and 0.05 to 0.5 mmol is more preferable with respect to 1 g of absolutely dry cellulose. Moreover, about 0.1-4 mmol / L with respect to a reaction system is good.

  Bromide is a compound containing bromine, examples of which include alkali metal bromides that can dissociate and ionize in water. Further, an iodide is a compound containing iodine, and examples thereof include alkali metal iodide. The amount of bromide or iodide used can be selected as long as the oxidation reaction can be promoted. The total amount of bromide and iodide is, for example, preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, and still more preferably 0.5 to 5 mmol with respect to 1 g of absolutely dry cellulose.

  As the oxidizing agent, known ones can be used, and for example, halogen, hypohalous acid, halous acid, perhalogen acid or salts thereof, halogen oxide, peroxide and the like can be used. Of these, sodium hypochlorite is preferable because it is inexpensive and has a low environmental impact. The appropriate amount of the oxidizing agent used is, for example, preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, further preferably 1 to 25 mmol, and most preferably 3 to 10 mmol with respect to 1 g of absolutely dry cellulose. . For example, 1-40 mol is preferable with respect to 1 mol of N-oxyl compounds.

  The cellulose oxidation process allows the reaction to proceed efficiently even under relatively mild conditions. Therefore, the reaction temperature is preferably 4 to 40 ° C, and may be room temperature of about 15 to 30 ° C. As the reaction proceeds, a carboxyl group is generated in the cellulose, so that the pH of the reaction solution is reduced. In order to advance the oxidation reaction efficiently, an alkaline solution such as an aqueous sodium hydroxide solution is added to maintain the pH of the reaction solution at about 8 to 12, preferably about 10 to 11. The reaction medium is preferably water because it is easy to handle and hardly causes side reactions.

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

  The oxidation reaction may be performed in two stages. For example, by oxidizing the oxidized cellulose obtained by filtration after the completion of the first-stage reaction again under the same or different reaction conditions, the efficiency is not affected by the reaction inhibition by the salt generated as a by-product in the first-stage reaction. Can be oxidized well.

Another example of the carboxylation (oxidation) method is a method of oxidizing by contacting a gas containing ozone and a cellulose raw material. By this oxidation reaction, at least the hydroxyl groups at the 2nd and 6th positions of the glucopyranose ring are oxidized and the cellulose chain is decomposed. Ozone concentration in the ozone containing gas is preferably 50 to 250 g / ^{m 3,} more preferably 50~220g / ^{m 3.} The amount of ozone added to the cellulose raw material is preferably 0.1 to 30 parts by weight and more preferably 5 to 30 parts by weight when the solid content of the cellulose raw material is 100 parts by weight. The ozone treatment temperature is preferably 0 to 50 ° C, and more preferably 20 to 50 ° C. The ozone treatment time is not particularly limited, but is about 1 to 360 minutes, and preferably about 30 to 360 minutes. When the conditions for the ozone treatment are within these ranges, the cellulose can be prevented from being excessively oxidized and decomposed, and the yield of oxidized cellulose is improved. After the ozone treatment, an additional oxidation treatment may be performed using an oxidizing agent. The oxidizing agent used for the additional 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, these oxidizing agents can be dissolved in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and a cellulose raw material can be immersed in the solution for additional oxidation treatment.

(Carboxymethylation)
As an example of the carboxymethylation method, cellulose is used as a starting material, and after mixing with a mercerizing agent and performing a mercerization treatment, an anion-modified cellulose is obtained by performing an etherification treatment using an etherifying agent. Can do. As the solvent, water alone, or 3 to 20 times by weight of lower alcohol, specifically, methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, tertiary butanol and the like alone or two kinds Use a mixture of the above mixture and water. The mixing ratio of the lower alcohol is 60 to 95% by weight. As the mercerizing agent, 0.5 to 20 times mol of alkali metal hydroxide, specifically sodium hydroxide or potassium hydroxide is used per glucose residue of the bottoming material. The mercerizing agent is an aqueous solution of 5 to 70% by weight, more preferably 30 to 60% by weight. Examples of the etherifying agent include monochloroacetic acid, sodium monochloroacetate, methyl monochloroacetate, ethyl monochloroacetate and isopropyl monochloroacetate. Of these, monochloroacetic acid and sodium monochloroacetate are preferable from the viewpoint of easy availability of raw materials. An aqueous solution of 5-70% by weight, preferably 30-60% by weight of an etherifying agent, is used in an amount of 0.05-10.0 moles of the etherifying agent per glucose residue of the bottoming material. At this time, the total weight of the cellulose dry solids and water with respect to the cellulose dry solids (liquid) Ratio) is adjusted to 1.0 to 4.0.

  In the mercerization treatment, the reactor is adjusted to a reaction temperature of 0 to 50 ° C., preferably 10 to 40 ° C., an aqueous solution of mercerizing agent is added while mixing cellulose, and the reaction time is 15 minutes to 8 hours, preferably 30. It is carried out by stirring for 3 to 3 hours. Thereby, alkali cellulose is obtained. Thereafter, an aqueous solution of an etherifying agent is added to the alkali cellulose in the reactor and stirred for 15 minutes to 4 hours while keeping the temperature constant. Thereafter, the reaction temperature is 30 to 90 ° C, preferably 40 to 80 ° C, and The etherification reaction is performed for a reaction time of 30 minutes to 10 hours, preferably 1 hour to 4 hours to obtain carboxymethylated cellulose.

(Alkali treatment)
In the present invention, it is preferable from the viewpoint of coloring suppression that an anion-modified CNF is produced using an anion-modified cellulose subjected to alkali treatment. The alkalinizing agent is an alkaline compound and is not particularly limited, but is preferably 0.01 parts by weight of alkali metal hydroxide, specifically sodium hydroxide, potassium hydroxide, or both with respect to 100 parts by weight of water. -10 parts by weight, preferably 0.5-8 parts by weight. For alkali treatment of anion-modified cellulose, 0.01 to 10 parts by weight, preferably 0.5 to 8 parts by weight of anion-modified cellulose is added to the aqueous alkali solution, and the treatment temperature is 0 to 40 ° C. Preferably, the alkali treatment is performed at 20 to 38 ° C. and a stirring time of 10 minutes to 10 hours, preferably 30 minutes to 2 hours. When the processing temperature is higher than 40 ° C., coloring due to heating proceeds, and when the processing temperature is lower than 0 ° C., a sufficient coloring suppression effect cannot be obtained.

  In the case of alkali treatment, an oxidizing agent, a reducing agent, a surfactant, a plasticizer, a dispersing agent, an ultraviolet absorber, an antioxidant, a storage stabilizer, and a thickening agent as long as they do not inhibit the effects of the present invention. Various known substances such as these can be added. The reducing agent is not particularly limited, and can be appropriately selected depending on the purpose. For example, sodium borohydride, thiourea, hydrosulfite, sodium bisulfite, sodium cyanoborohydride, borohydride Examples include lithium. These may be used individually by 1 type and may use 2 or more types together. The amount of the reducing agent used is about 0.1 to 150 parts by weight, preferably about 0.5 to 100 parts by weight, and more preferably about 1 to 50 parts by weight with respect to 100 parts by weight of the oxidized cellulose raw material. Among the reducing agents, sodium borohydride is preferable because it promotes a specific reaction.

  When the treatment time is shorter than 10 minutes, a sufficient coloring suppression effect cannot be obtained, and when the treatment time is longer than 2 hours, the coloring proceeds, so that good cellulose nanofibers cannot be obtained / coloring deteriorates.

(Washing)
It is preferable to remove the coloring substance after the alkali treatment from the viewpoint of inhibiting re-adsorption of the coloring substance peeled off by the alkali treatment during the production of the dry solid of CNF to the CNF fiber.

  The step of removing the coloring substance may be decomposition by irradiation with ultraviolet rays or radiation, addition of chemicals, filtration, washing with water or a solvent, and washing is preferably performed from the viewpoint of simplicity of the process and cost. Although it does not specifically limit as a washing | cleaning solvent, For example, water, methanol, ethanol, n-propyl alcohol, IPA, n-butyl alcohol, C1-C4 alcohols, such as isobutyl alcohol, acetone, diethyl ketone, methyl ethyl ketone, etc. Ketones, dioxane, diethyl ether and the like can be mentioned. These can use 1 type (s) or 2 or more types. Moreover, you may mix and use like a water-containing organic solvent, and the weight ratio of the water of a water-containing organic solvent and an organic solvent is not specifically limited. Among these, water is preferable from the viewpoint of availability and low cost.

 There are no particular limitations on the temperature and pressure when washing is performed, and the temperature is preferably selected in the range of 0 ° C. or higher and 100 ° C. or lower.

  The addition amount of the washing solvent is not particularly limited, but is preferably 10 times to 100,000 times, more preferably 100 times to 10,000 times the absolute dry weight of the anion-modified cellulose to be washed. The washing time is preferably 5 minutes to 24 hours, more preferably 10 minutes to 3 hours. If it is in these ranges, the detachment of the colored substance is good and the workability is also suitable. Moreover, a washing | cleaning process can be performed once or several times, and may be repeated 3-5 times.

  The method for separating the washing solvent is not particularly limited as long as it is a known method. For example, a centrifugal dehydration type, vacuum dehydration type, or pressure dehydration type separation device can be used. Specifically, centrifugal type: (Tanabe Wiltech centrifugal separator, Kokusan centrifugal separator, etc.), vacuum dehydration type: drum type vacuum dehydrator, Tsukishima Kikai horizontal belt filter, pressure dehydration type: filter press Tube press, screw press, belt press, horizontal belt filter, polydisc filter, vibrating screen and the like. Among these, since dehydration can be performed without applying a strong shearing force to the dehydrated raw material, pressurized dehydration type: (filter press, tube press), centrifugal type (Tanabe Wiltech centrifuge, Kokusan centrifuge Vacuum dehydration type: (drum type vacuum dehydrator, Tsukishima Kikai horizontal belt filter) is preferable. A plurality of these can also be used in combination. The anion-modified cellulose after separation of the washing solvent is preferably separated until the solid content becomes 1% to 90%, preferably 5% to 80%, more preferably 10% to 70%.

(Defibration)
The apparatus used for defibrating carboxylated cellulose is not particularly limited, and apparatuses such as a high-speed rotation type, a colloid mill type, a high-pressure type, a roll mill type, and an ultrasonic type can be used. In defibration, it is preferable to apply a strong shearing force to the aqueous dispersion of anion-modified cellulose. In particular, for efficient defibration, it is preferable to use a wet high-pressure or ultrahigh-pressure homogenizer that can apply a pressure of 50 MPa or more to the aqueous dispersion and can apply a strong shearing force. The pressure is more preferably 100 MPa or more, and further preferably 140 MPa or more. In addition, prior to defibration and dispersion treatment with a high-pressure homogenizer, if necessary, the aqueous dispersion may be pretreated using a known mixing, stirring, emulsifying, and dispersing device such as a high-speed shear mixer. Good.

  As the dehydration method, known methods can be used, for example, centrifugal dehydration type, vacuum dehydration type, pressure dehydration type dehydration apparatus can be used, and a plurality of these can be used in combination. it can.

  As a drying method, a known method can be used, and examples thereof include spray drying, pressing, air drying, hot air drying, and vacuum drying. The drying device is not particularly limited, but is a continuous tunnel drying device, a band drying device, a vertical drying device, a vertical turbo drying device, a multi-stage disk drying device, an aeration drying device, a rotary drying device, an air flow drying device, a spray. Dryer dryer, spray dryer, cylindrical dryer, drum dryer, belt dryer, screw conveyor dryer, rotary dryer with heating tube, vibration transport dryer, batch-type box dryer, aerated dryer, vacuum A box-type drying device, a stirring drying device, or the like can be used alone or in combination of two or more.

(Use of anion-modified CNF)
The anion-modified CNF of the present invention is generally used in various fields in which additives are used, such as foods, beverages, personal care products, cosmetics, pharmaceuticals, various chemicals, papermaking, civil engineering, paints, inks, coating compositions, Agricultural chemicals, construction, automobiles, epidemiological drugs, electronic materials, batteries, flame retardants, heat insulating materials, household goods, cleaning agents, water treatment, drill fluid, neutral functional substances, shale gas and oil spill control and / or recovery Can be used as an additive. Specifically, thickeners, gelling agents, glues, food additives, excipients, rubber / plastic reinforcing materials, paint additives, adhesive additives, papermaking additives, abrasives, Rubber that can be used as a water-absorbing material, deodorant, rust preventive, water retention agent, moisturizing agent, cold insulation agent, shape retention agent, mud adjuster, filter aid, overflow prevention agent, etc. -It can be applied to plastic materials, paints, adhesives, coated paper coatings, coated papers, binders, cosmetics, lubricating compositions, polishing compositions, clothing wrinkle reducing agents, ironing slip agents, and the like.

  Hereinafter, although an example is given and the present invention is explained still in detail, the present invention is not limited to these.

<Production of alkali-treated carboxylated (TEMPO oxidized) pulp>
Add 500 g of bleached unbeaten kraft pulp (whiteness 85%) derived from coniferous trees (absolutely dry) to 500 ml of an aqueous solution in which 780 mg of TEMPO (Sigma Aldrich) and 75.5 g of sodium bromide are dissolved, until the pulp is uniformly dispersed Stir. An aqueous sodium hypochlorite solution was added to the reaction system to 6.0 mmol / g to initiate the oxidation reaction. During the reaction, the pH in the system was lowered, but a 3M sodium hydroxide aqueous solution was sequentially added to adjust the pH to 10. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system no longer changed. The reaction mixture was filtered through a glass filter to separate the pulp, and the pulp was sufficiently washed with water to obtain oxidized pulp (carboxylated cellulose, carboxylated pulp, TEMPO oxidized pulp). The pulp yield at this time was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.6 mmol / g.

<Production of alkali-treated carboxymethylated (CM) pulp>
To a reactor capable of stirring the pulp, 112 g of a 50 wt% aqueous sodium hydroxide solution and 67 g of water were added while stirring 250 g of pulp (LBKP, manufactured by Nippon Paper Industries Co., Ltd.) in dry weight. After stirring at 30 ° C. for 30 minutes, 364 g of 35 wt% aqueous sodium monochloroacetate solution was added with stirring. Then, it stirred at 30 degreeC for 30 minutes, heated up to 70 degreeC over 30 minutes, and reacted at 70 degreeC for 1 hour. Thereafter, the reaction product was taken out, neutralized and washed to obtain carboxymethylated cellulose (carboxymethylated pulp) having a carboxymethyl substitution degree of 0.25 per glucose unit.

<Method for measuring the amount of carboxyl group>
After preparing 60 ml of a 0.5 wt% slurry (aqueous dispersion) of carboxylated cellulose and adding 0.1 M hydrochloric acid aqueous solution to pH 2.5, 0.05 N sodium hydroxide aqueous solution was added dropwise to adjust the pH to 11 The electrical conductivity was measured until the amount of sodium hydroxide consumed in the neutralization stage of the weak acid with a slow change in electrical conductivity (a) was calculated using the following formula: g carboxylated cellulose] = a [ml] × 0.05 / carboxylated cellulose mass [g].

<Measurement method of carboxymethyl substitution degree per glucose unit>
The degree of substitution of the carboxymethyl group was determined by preparing a sample in 0.6% by weight slurry, adding 0.1 M aqueous hydrochloric acid solution to pH 2.4, then dropping 0.05 N aqueous sodium hydroxide solution dropwise to adjust the pH to 11 Then, the electric conductivity was measured until the amount of carboxylic acid group was determined, and the amount of carboxyl groups was measured from the amount of sodium hydroxide consumed in the neutralization step of the weak acid where the change in electric conductivity was slow. The degree of substitution referred to here represents the average value of the number of moles of substituents per mole of anhydroglucose unit.
Carboxymethyl substitution degree = (162 × C) / (1-58 × C)

<Measuring method of average fiber diameter and aspect ratio>
The average fiber diameter and average fiber length of anion-modified CNF were analyzed for 200 fibers selected at random using a field emission scanning electron microscope (FE-SEM). The aspect ratio was calculated by the following formula: aspect ratio = average fiber length / average fiber diameter.

<Coloring evaluation>
The degree of coloration inhibition of anion-modified CNF was evaluated by visual observation according to the following criteria by heat-treating a 50 μm thick CNF film prepared from an anion-modified CNF aqueous dispersion at 150 ° C. for 30 minutes. The CNF film was prepared by drying an aqueous dispersion of anion-modified CNF at 40 ° C. for 24 hours on a petri dish made of polystyrene. Not colored: ++>+>±>-(no alkali treatment)> ― ―: Colored

Example 1
5 parts by weight of TEMPO oxidized pulp obtained in the above step was added to a sodium hydroxide aqueous solution in which 5 parts by weight of sodium hydroxide was dissolved in 100 parts by weight of water, and the mixture was stirred at 30 ° C. for 30 minutes for alkali treatment. . Washing was performed at 30 ° C. for 30 minutes using 100 times the amount of water of the TEMPO oxidized pulp absolutely dry after the alkali treatment, and dehydration was performed using a centrifugal separator manufactured by Tanabe Wiltech. At this time, the solid content of the alkali-treated TEMPO oxidized pulp was 40%.

  The alkali-treated TEMPO oxidized pulp obtained in the above process is adjusted to 1.0% (w / v) with water, treated 5 times with an ultrahigh pressure homogenizer (20 ° C., 150 MPa), and a TEMPO oxidized CNF dispersion. Got. The obtained fiber had an average fiber diameter of 4 nm and an aspect ratio of 150.

The TEMPO oxidized CNF dispersion obtained in the above step was dried on a petri dish made of polystyrene at 40 ° C. for 24 hours to obtain a TEMPO oxidized CNF film having a thickness of 50 μm.
(Example 2)
In Example 1, a TEMPO-oxidized CNF film was obtained in the same manner as in Example 1 except that the amount of sodium hydroxide used in the alkali treatment was changed from 5 parts by weight to 0.5 parts by weight.

(Example 3)
In Example 1, a TEMPO-oxidized CNF film was obtained in the same manner as in Example 1 except that the amount of sodium hydroxide used in the alkali treatment was changed from 5 parts by weight to 8 parts by weight.

Example 4
In Example 1, a TEMPO oxidized CNF film was obtained in the same manner as in Example 1 except that the temperature of the alkali treatment was changed from 30 ° C. to 10 ° C.

(Example 5)
In Example 1, a TEMPO oxidized CNF film was obtained in the same manner as in Example 1 except that the alkali treatment temperature was changed from 30 ° C. to 38 ° C.

(Example 6)
In Example 1, a TEMPO oxidized CNF film was obtained in the same manner as in the above operation except that the alkali treatment time was changed from 30 minutes to 10 minutes.

(Example 7)
In Example 1, a TEMPO oxidized CNF film was obtained in the same manner as in Example 1 except that the alkali treatment time was changed from 30 minutes to 120 minutes.

(Example 8)
In Example 1, a TEMPO-oxidized CNF film was obtained in the same manner as in Example 1 except that dehydration was performed without washing after alkali treatment.

Example 9
5 parts by weight of the carboxymethylated pulp obtained in the above step is added to an aqueous sodium hydroxide solution in which 5 parts by weight of sodium hydroxide is dissolved in 100 parts by weight of water, and the mixture is stirred at 30 ° C. for 30 minutes for alkali treatment. did. Washing was performed at 30 ° C. for 30 minutes using 100 times the amount of water of the TEMPO oxidized pulp absolutely dry after the alkali treatment, and dehydration was performed using a centrifugal separator manufactured by Tanabe Wiltech. At this time, the solid content of the alkali-treated carboxymethylated pulp was 40%.

  The alkali-treated carboxymethylated pulp obtained in the above step is adjusted to 1.0% (w / v) with water, treated five times with an ultrahigh pressure homogenizer (20 ° C., 150 Mpa), and carboxymethylated CNF. A dispersion was obtained. The obtained fiber had an average fiber diameter of 12 nm and an aspect ratio of 150.

  The carboxymethylated CNF dispersion obtained in the above step was dried on a petri dish made of polystyrene at 40 ° C. for 24 hours to obtain a carboxymethylated CNF film having a thickness of 50 μm.

(Example 10)
In Example 9, a carboxymethylated CNF film was obtained in the same manner as in Example 9 except that the amount of sodium hydroxide used in the alkali treatment was changed from 5 parts by weight to 0.5 parts by weight.

(Example 11)
In Example 9, a carboxymethylated CNF film was obtained in the same manner as in Example 9 except that the amount of sodium hydroxide used in the alkali treatment was changed from 5 parts by weight to 8 parts by weight.

(Example 12)
In Example 9, a carboxymethylated CNF film was obtained in the same manner as in Example 9 except that the alkali treatment temperature was changed from 30 ° C to 10 ° C.

(Example 13)
In Example 9, a carboxymethylated CNF film was obtained in the same manner as in Example 9 except that the alkali treatment temperature was changed from 30 ° C to 38 ° C.

(Example 14)
In Example 9, a carboxymethylated CNF film was obtained in the same manner as in Example 9 except that the alkali treatment time was changed from 30 minutes to 10 minutes.

(Example 15)
In Example 9, a carboxymethylated CNF film was obtained in the same manner as in Example 9 except that the alkali treatment time was changed from 30 minutes to 120 minutes.

(Example 16)
In Example 9, a carboxymethylated CNF film was obtained in the same manner as in Example 9 except that after alkali treatment, dehydration was performed without washing.

(Comparative Example 1)
The TEMPO oxidized pulp obtained in the above step was adjusted to 1.0% (w / v) with water and treated 5 times with an ultrahigh pressure homogenizer (20 ° C., 150 Mpa) to obtain a TEMPO oxidized CNF dispersion. . The obtained fiber had an average fiber diameter of 4 nm and an aspect ratio of 150.
The TEMPO oxidized CNF dispersion obtained in the above step was dried on a petri dish made of polystyrene at 40 ° C. for 24 hours to obtain a TEMPO oxidized CNF film having a thickness of 50 μm.

(Comparative Example 2)
In Example 1, a TEMPO-oxidized CNF film was obtained in the same manner as in Example 1 except that the amount of sodium hydroxide used in the alkali treatment was changed from 5 parts by weight to 0 parts by weight.

(Comparative Example 3)
To a sodium hydroxide aqueous solution in which 5 parts of sodium hydroxide is dissolved in 100 parts of water, 5 parts of TEMPO oxidized pulp obtained in the above step and 1 ml of 30% hydrogen peroxide water are added and stirred at 80 ° C. for 120 minutes. did. The TEMPO oxidized pulp after the alkali-hydrogen peroxide treatment was treated five times with an ultra-high pressure homogenizer (20 ° C., 150 Mpa) to obtain a TEMPO oxidized CNF dispersion. The obtained fiber had an average fiber diameter of 4 nm and an aspect ratio of 150.

The TEMPO oxidized CNF dispersion obtained in the above step was dried on a petri dish made of polystyrene at 40 ° C. for 24 hours to obtain a TEMPO oxidized CNF film having a thickness of 50 μm.
(Comparative Example 4)
In Example 1, a TEMPO oxidized CNF film was obtained in the same manner as in Example 1 except that the temperature of the alkali treatment was changed from 30 ° C to 70 ° C.

(Comparative Example 5)
In Example 1, a TEMPO oxidized CNF film was obtained in the same manner as in Example 1 except that the alkali treatment time was changed from 30 minutes to 5 minutes.

(Comparative Example 6)
The carboxymethylated pulp obtained in the above step is adjusted to 1.0% (w / v) with water, treated 5 times with an ultrahigh pressure homogenizer (20 ° C., 150 Mpa), and a carboxymethylated CNF dispersion is obtained. Obtained. The obtained fiber had an average fiber diameter of 12 nm and an aspect ratio of 150. The carboxymethylated CNF dispersion obtained in the above step was dried on a petri dish made of polystyrene at 40 ° C. for 24 hours to obtain a carboxymethylated CNF film having a thickness of 50 μm.

(Comparative Example 7)
In Example 9, a carboxymethylated CNF film was obtained in the same manner as in Example 9 except that the amount of sodium hydroxide used in the alkali treatment was changed from 5 parts by weight to 0 parts by weight.

(Comparative Example 8)
To a sodium hydroxide aqueous solution in which 5 parts by weight of sodium hydroxide is dissolved in 100 parts by weight of water, 5 parts by weight of the carboxymethylated pulp obtained in the above step and 1 ml of 30% hydrogen peroxide water are added, For 120 minutes. The carboxymethylated pulp after the alkali-hydrogen peroxide treatment was treated five times with an ultrahigh pressure homogenizer (20 ° C., 150 Mpa) to obtain a TEMPO oxidized CNF dispersion. The obtained fiber had an average fiber diameter of 4 nm and an aspect ratio of 150.

  The carboxymethylated CNF dispersion obtained in the above step was dried on a petri dish made of polystyrene at 40 ° C. for 24 hours to obtain a carboxymethylated CNF film having a thickness of 50 μm.

(Comparative Example 9)
In Example 9, a carboxymethylated CNF film was obtained in the same manner as in Example 9 except that the alkali treatment temperature was changed from 30 ° C to 70 ° C.

(Comparative Example 10)
In Example 9, a carboxymethylated CNF film was obtained in the same manner as in Example 9 except that the alkali treatment time was changed from 30 minutes to 5 minutes.

  As for the anion modified CNF of Examples 1-16, the coloring after a heating is suppressed compared with the anion modified CNF of Comparative Examples 1-10. It can be said that the fact that coloring after heating does not occur is advantageous in that it is not affected by heat treatment in industrial use of CNF.

Claims (3)

A method for producing an anion-modified cellulose nanofiber,
(A) a step of chemically modifying a cellulose raw material to obtain an anion-modified cellulose;
(B) water, an alkalinizing agent, an anion-modified cellulose obtained in (A),
Step of stirring for 10 minutes to 10 hours under the condition of 0 to 40 ° C. after mixing at a ratio of water: alkalizing agent: anion-modified cellulose = 100: 0.01 to 10: 0.01 to 10 (parts by weight) (Step of alkali treatment), and (C) defibrating the alkali-treated anion-modified cellulose to obtain cellulose nanofibers,
A process for producing anion-modified cellulose nanofibers, comprising:   The amount of carboxyl groups in the anion-modified cellulose nanofiber is 0.6 mmol / g to 3.0 mmol / g based on the absolute dry weight of the anion-modified cellulose nanofiber. A method for producing anion-modified cellulose nanofibers.   The anion-modified cellulose nanofiber according to claim 1, wherein the anion-modified cellulose nanofiber has a degree of carboxymethyl substitution per glucose unit of 0.01 to 0.50. Method.