JP2018095761A - Method for producing chemically modified pulp dry solid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chemically modified pulp dry solid that gives CNF having good dispersibility in a dispersion medium.SOLUTION: A method for producing a chemically modified pulp dry solid includes a step of drying a mixture of a chemically modified pulp produced by chemically modifying a cellulose raw material and a liquid medium at 20 to 80°C.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a chemically modified pulp dry solid.

  Chemically modified pulp is useful as a raw material for cellulose nanofibers (hereinafter also referred to as “CNF”) and the like. Cellulose nanofibers are fine fibers having a fiber diameter of about 2 to several hundred nanometers and are excellent in water-based dispersibility, and therefore are expected to be applied to fields such as foods, cosmetics, medical products, and paints. Specifically, it is expected to be applied to the viscosity maintenance of paints, the strengthening of food material dough, the maintenance of moisture, the improvement of food stability, the low calorie additive, the emulsion stabilization aid and the like.

  Although the chemically modified pulp is obtained in a state of being dispersed in water, it is preferably a dry product in consideration of the cost during transportation. However, since a hydrogen bond is formed between cellulose fibers in a chemically modified pulp dry solid, it is difficult to sufficiently defibrate even if water is added to the dry solid and subjected to a defibrating treatment. Therefore, the CNF obtained in this way has a problem that the dispersibility in the dispersion medium is worse than CNF obtained without being dried.

  In order to solve this problem, a method of reducing oxidized cellulose and drying it (Patent Document 1), a method of defibrating a dried product of oxidized cellulose using hot water (Patent Document 2), and the like have been proposed. .

JP2015-113376 JP2015-134870

  In the method described in Patent Document 1, reduction treatment is essential and the process becomes complicated. Moreover, the method described in Patent Document 2 requires hot water at the time of defibration, and the process is similarly complicated. In view of such circumstances, an object of the present invention is to provide a chemically modified pulp dry solid that gives CNF having good dispersibility by a simpler method.

The said subject is solved by the following this invention.
(1) A method for producing a chemically modified pulp dried solid, comprising a step of drying a mixture of a chemically modified pulp obtained by chemically modifying a cellulose raw material and a liquid medium at 20 to 80 ° C.
(2) The production method according to (1), wherein the liquid medium is water or a mixed solvent of water and a water-soluble organic solvent.
(3) The production method according to (2), wherein the amount of the water-soluble organic solvent in the mixed solvent is 10% by mass or more.
(4) The carboxyl group amount of the chemically modified pulp is 0.6 to 3.0 mmol / g with respect to the absolute dry mass of the cellulose nanofiber, according to any one of (1) to (3). Production method.
(5) The manufacturing method in any one of (1)-(3) whose carboxymethyl substitution degree per glucose unit of the said chemically modified pulp is 0.01-0.50.
(6) The manufacturing method in any one of (1)-(3) whose cation substitution degree per glucose unit of the said chemically modified pulp is 0.02-0.50.
(7) The production method according to any one of (1) to (6), wherein the water-soluble organic solvent is a lower alcohol.
(8) A method for producing a chemically modified pulp dispersion, comprising dispersing a dry solid of the chemically modified pulp obtained by the method according to any one of (1) to (7) in a dispersion medium.
(9) A method for producing cellulose nanofiber, comprising defibrating the chemically modified pulp in the chemically modified pulp dispersion according to (8).

  ADVANTAGE OF THE INVENTION By this invention, the chemically modified pulp dry solid which gives CNF which has the favorable dispersibility with respect to a dispersion medium can be provided.

  Hereinafter, the present invention will be described in detail. In the present invention, “X to Y” includes X and Y which are end values. “X or Y” means one or both of X and Y.

1. Method for producing chemically modified pulp dry solids Chemically modified pulp is a pulp obtained by chemically modifying a cellulose raw material. Chemically modified pulp is a raw material for CNF and is different from CNF. Preferably, the average fiber diameter of the chemically modified pulp is 10 μm or more. The method for producing a chemically modified pulp dry solid of the present invention includes a step of drying a mixture of a chemically modified pulp obtained by chemically modifying a cellulose raw material and a liquid medium at 20 to 80 ° C.

(1) Preparation of mixture of chemically modified pulp and liquid medium In the present invention, first, a mixture of chemically modified pulp obtained by chemically modifying a cellulose raw material and a liquid medium is prepared. The mixture may be a simple mixture of chemically modified pulp and a liquid medium, or may be a dispersion in which chemically modified pulp is dispersed in a liquid medium. It is more preferable to acidify the chemically modified pulp before preparing the mixture. By performing the acidification treatment, it is possible to improve workability when washing and dehydrating chemicals used in the chemical modification contained in the chemically modified pulp. In the present invention, acidification means that a chemically modified pulp is dispersed in water to form an aqueous dispersion, and the pH of the dispersion (water) is preferably 5 or less, more preferably 3 or less, using an acid such as mineral acid. That means. Chemically modified pulp acidified by a conventional method can be isolated and used for the preparation of the mixture. Even if the chemically modified pulp thus treated is subjected again to filtration and washing, the pH of the aqueous dispersion does not become 5 or more.

(1-1) Cellulose raw materials Cellulose raw materials are known to originate from plants, animals (for example, ascidians), algae, microorganisms (for example, acetic acid bacteria (Acetobacter)), microbial products, etc. Any of them can be used in the invention. Examples of plant-derived materials include wood, bamboo, hemp, jute, kenaf, farmland waste, cloth, pulp (conifer unbleached kraft pulp (NUKP), conifer bleach 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), recycled pulp, waste paper, etc.). In the present invention, plant or microorganism-derived cellulose fibers are preferred, and plant-derived cellulose fibers are more preferred. The cellulose raw material is chemically modified as described below.

(1-2) Chemical modification [Carboxymethylation]
Carboxymethylated cellulose can be used as the chemically modified pulp. Although the said cellulose raw material can use what carboxymethylated the above-mentioned cellulose raw material by the well-known method, you may use a commercial item. The following method can be raised as an example of a method for producing such carboxymethylated cellulose. First, the cellulose raw material is used as a bottoming raw material, a solvent and a mercerizing agent are mixed, and the reaction temperature is 0 to 70 ° C., preferably 10 to 60 ° C., and the reaction time is 15 minutes to 8 hours, preferably 30 minutes to 7 hours. Then, mercerization processing is performed. As the solvent, 3 to 20 times by mass of water or lower alcohol, specifically, water, methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, tertiary butanol, or a combination thereof is used. it can. When mixing lower alcohol, the mixing ratio is 60-95 mass%. As the mercerizing agent, 0.5 to 20-fold moles of alkali metal hydroxide, specifically sodium hydroxide or potassium hydroxide can be used per anhydroglucose residue of the bottoming material.

  Subsequently, a carboxymethylating agent is added in an amount of 0.05 to 10.0 times mol per glucose residue, a reaction temperature of 30 to 90 ° C., preferably 40 to 80 ° C., and a reaction time of 30 minutes to 10 hours, preferably 1 hour. The etherification reaction is performed for ˜4 hours to obtain carboxymethylated cellulose. As described above, the degree of carboxymethyl substitution per glucose unit is preferably 0.01 to 0.50, and more preferably 0.02 to 0.50. If the substituent is smaller than 0.01, nano-defibration may not be sufficiently achieved. On the other hand, if the carboxymethyl substituent per glucose unit is greater than 0.50, it may swell or dissolve, and may not be a nanofiber.

[Carboxylation]
As the chemically modified pulp, carboxylated (oxidized) cellulose (also referred to as “oxidized cellulose”) can be used. Carboxylated cellulose can be obtained by carboxylating (oxidizing) the above cellulose raw material by a known method. Although it does not specifically limit, 0.6-3.0 mmol / g is preferable with respect to the absolute dry mass of CNF, and, as for the quantity of a carboxyl group, 1.0-2.0 mmol / g is more preferable.

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 mass 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. Examples include 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) and its derivatives (for example, 4-hydroxy TEMPO).

  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 is preferable with respect to the reaction system.

  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 amount of the oxidizing agent used is preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, still more 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 oxidation of cellulose 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 2-position and 6-position hydroxyl groups 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 mass, and more preferably 5 to 30 parts by mass when the solid content of the cellulose raw material is 100 parts by mass. 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.

  The amount of carboxyl groups in the oxidized cellulose can be adjusted by controlling the reaction conditions such as the added amount of the oxidizing agent and the reaction time.

[Cationization]
As the chemically modified cellulose, cellulose obtained by further cationizing the carboxylated cellulose can be used. The cation-modified cellulose is prepared by adding a cationizing agent such as glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrialkylammonium hydride or a halohydrin type thereof to the carboxylated cellulose raw material, and an alkali hydroxide as a catalyst. A metal (sodium hydroxide, potassium hydroxide, etc.) can be obtained by reacting in the presence of water or an alcohol having 1 to 4 carbon atoms.

  The degree of cation substitution per glucose unit is preferably 0.02 to 0.50. By introducing a cationic substituent into cellulose, the celluloses repel each other electrically. For this reason, the cellulose which introduce | transduced the cation substituent can be nano-defibrated easily. If the degree of cation substitution per glucose unit is smaller than 0.02, nano-fibrosis cannot be sufficiently achieved. On the other hand, if the degree of cation substitution per glucose unit is more than 0.50, it may swell or dissolve, and may not be obtained as a nanofiber. In order to efficiently perform defibration, the cation-modified cellulose-based raw material obtained above is preferably washed. The degree of cation substitution can be adjusted by the amount of the cationizing agent to be reacted, the composition ratio of water or an alcohol having 1 to 4 carbon atoms.

[Esterification]
As chemically modified cellulose, esterified cellulose can be used. The said cellulose is obtained by the method of mixing the powder and aqueous solution of phosphoric acid compound A with the above-mentioned cellulose raw material, and the method of adding the aqueous solution of phosphoric acid compound A to the slurry of a cellulose raw material.

  Examples of the phosphoric acid compound A include phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid, and esters thereof. These may be in the form of salts. Among these, a compound having a phosphate group is preferable because it is low in cost, easy to handle, and can improve the fibrillation efficiency by introducing a phosphate group into cellulose of the pulp fiber. Compounds having a phosphate group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, phosphorus Examples include tripotassium acid, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium metaphosphate, and the like. These can be used alone or in combination of two or more. Among these, phosphoric acid, phosphoric acid sodium salt, phosphoric acid potassium salt, phosphoric acid, from the viewpoint that phosphoric acid group introduction efficiency is high, is easy to be defibrated in the following defibrating process and is industrially applicable. The ammonium salt is more preferred. In particular, sodium dihydrogen phosphate and disodium hydrogen phosphate are preferred. In addition, the phosphoric acid compound A is preferably used as an aqueous solution because the uniformity of the reaction is enhanced and the efficiency of introduction of phosphate groups is increased. The pH of the aqueous solution of the phosphoric acid compound A is preferably 7 or less because the efficiency of introducing phosphoric acid groups is high, but is preferably pH 3 to 7 from the viewpoint of suppressing hydrolysis of pulp fibers.

  The following method can be mentioned as an example of the manufacturing method of phosphate esterified cellulose. Phosphoric acid compound A is added to a dispersion of a cellulose-based raw material having a solid content concentration of 0.1 to 10% by mass with stirring to introduce phosphate groups into the cellulose. When the cellulose-based raw material is 100 parts by mass, the addition amount of the phosphoric acid compound A is preferably 0.2 to 500 parts by mass, and more preferably 1 to 400 parts by mass as the amount of phosphorus element. . If the ratio of the phosphoric acid type compound A is more than the said lower limit, the yield of a fine fibrous cellulose can be improved more. However, if the upper limit is exceeded, the effect of improving the yield reaches its peak, which is not preferable from the viewpoint of cost.

  At this time, in addition to the cellulose raw material and the phosphoric acid compound A, powders or aqueous solutions of other compounds B may be mixed. Compound B is not particularly limited, but a nitrogen-containing compound showing basicity is preferable. “Basic” as used herein is defined as an aqueous solution exhibiting a pink to red color in the presence of a phenolphthalein indicator, or an aqueous solution having a pH greater than 7. Although the nitrogen-containing compound which shows the basicity used by this invention is not specifically limited as long as there exists an effect of this invention, the compound which has an amino group is preferable. For example, urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine and the like can be mentioned, but not particularly limited. Among these, urea which is easy to handle at low cost is preferable. The amount of compound B added is preferably 2 to 1000 parts by weight, more preferably 100 to 700 parts by weight, based on 100 parts by weight of the solid content of the cellulose raw material. The reaction temperature is preferably 0 to 95 ° C, more preferably 30 to 90 ° C. The reaction time is not particularly limited, but is about 1 to 600 minutes, and more preferably 30 to 480 minutes. When the conditions for the esterification reaction are within these ranges, the cellulose can be prevented from being excessively esterified and easily dissolved, and the yield of phosphorylated esterified cellulose is improved. After dehydrating the obtained phosphate esterified cellulose suspension, it is preferable to heat-treat at 100 to 170 ° C. from the viewpoint of suppressing hydrolysis of cellulose. Furthermore, while water is contained during the heat treatment, it is preferably heated at 130 ° C. or less, preferably 110 ° C. or less, and after removing water, heat treatment is preferably performed at 100 to 170 ° C.

  It is preferable that the phosphate group substitution degree per glucose unit of phosphorylated cellulose is 0.001 to 0.40. By introducing a phosphate group substituent into cellulose, the celluloses are electrically repelled. For this reason, the cellulose which introduce | transduced the phosphate group can be nano-defibrated easily. In addition, when the phosphate group substitution degree per glucose unit is smaller than 0.001, nano-defibration cannot be sufficiently performed. On the other hand, if the degree of phosphate group substitution per glucose unit is greater than 0.40, it may swell or dissolve, and may not be obtained as a nanofiber. In order to perform defibration efficiently, it is preferable that the phosphoric esterified cellulose raw material obtained above is washed by boiling water and then washing with cold water.

(1-3) Liquid medium The liquid medium is preferably water, a water-soluble organic solvent, or a mixed solvent thereof. Considering the dispersibility of the chemically modified pulp, the liquid medium is preferably water or a mixed solvent of water and a water-soluble organic solvent. When the liquid medium is water, the aqueous dispersion of chemically modified pulp prepared as described above can be directly subjected to drying. Alternatively, the aqueous dispersion may be concentrated by subjecting the aqueous dispersion to drying or filtration.

  When the liquid medium is the mixed solvent, a water-soluble organic solvent is added to the aqueous dispersion of the chemically modified pulp prepared as described above or the aqueous dispersion of the chemically modified pulp that has been acidified, or the aqueous dispersion A part may be replaced with a water-soluble organic solvent. In the substitution, water is removed from the aqueous dispersion of the chemically modified pulp by drying or filtration to obtain a concentrated aqueous dispersion or a wet cake of the chemically modified pulp, and a water-soluble organic solvent is added thereto. Can be prepared. The amount of the liquid medium is preferably such an amount that the concentration of the chemically modified pulp in the mixture is 10 to 40% by mass, and more preferably 20 to 30% by mass.

  The water-soluble organic solvent is an organic solvent that dissolves in water. Examples thereof include methanol, ethanol, 2-propanol, butanol, glycerin, acetone, methyl ethyl ketone, 1,4-dioxane, N-methyl-2-pyrrolidone, tetrahydrofuran, N, N-dimethylformamide, N, N-dimethylacetamide, Dimethyl sulfoxide, acetonitrile, and combinations thereof. Of these, lower alcohols having 1 to 4 carbon atoms such as methanol, ethanol and 2-propanol are preferable. From the viewpoint of safety and availability, methanol and ethanol are more preferable, and ethanol is more preferable. The amount of the water-soluble organic solvent in the mixed solvent is preferably 10% by mass or more, more preferably 50% by mass or more, and further preferably 70% by mass or more. The upper limit of the amount is not limited, but is preferably 95% by mass or less, and more preferably 90% by mass or less. In addition, the liquid medium may contain a water-insoluble organic solvent as long as the effects of the invention are not impaired.

(2) Drying In this step, the mixture is dried at a relatively low temperature of 20 to 80 ° C. to obtain a dry solid of chemically modified pulp. Drying may be performed as known. When the drying temperature is high, the cellulose is colored or damaged, and when the drying temperature is low, the production efficiency is lowered. Therefore, the drying temperature is preferably 20 to 70 ° C, more preferably 30 to 60 ° C. Drying is preferably carried out at atmospheric pressure or lower.

  Examples of the drying method include known methods such as spray drying, pressing, air drying, hot air drying, and vacuum drying. In the present invention, continuous tunnel dryer, band dryer, vertical dryer, vertical turbo dryer, multi-stage disk dryer, aeration dryer, rotary dryer, air dryer, spray dryer dryer, sprayer Drying device, cylindrical drying device, drum drying device, screw conveyor drying device, rotary drying device with heating tube, vibration transport drying device, batch box drying device, aeration drying device, vacuum box drying device, or stirring drying Devices or the like can be used alone or in combination. As described above, the amount of liquid medium in the mixture may be reduced before drying. A means for reducing the amount of the liquid medium is not limited, and examples thereof include a separation means such as filtration.

2. Chemically modified pulp dry solid The dry solid means a dry solid (liquid medium amount 0% by mass) or a wet state in which the liquid medium amount is 20% by mass or less. From the viewpoint of reducing transportation costs, the amount of the liquid medium is preferably 0 to 20% by mass, and more preferably 0 to 15% by mass.

  Conventionally, when a dispersion obtained by once dispersing a chemically modified pulp once dried in a dispersion medium is defibrated, a certain degree of nano defibration is possible and a CNF dispersion can be obtained, but the nano defibration is not sufficiently performed. There was a problem that foreign matter remained. However, according to the present invention, it is possible to obtain a CNF dispersion having almost no foreign matter, that is, having good dispersibility even when the dispersion dispersed again is used. The reason for this is not limited, but by drying chemically modified pulp at a relatively low temperature of 20 to 80 ° C., generation of hydrogen bonds between fibers, which is considered to be a factor that reduces electrical repulsion suitable for defibration, This is presumably because entanglement between fibers can be suppressed. When the liquid medium contains a water-soluble organic solvent, the production of hydrogen bonds can be more effectively suppressed, and this effect becomes even more remarkable.

  An apparatus for re-dispersing the dried solid in a dispersion medium to obtain a dispersion liquid is not particularly limited, and examples thereof include a disperser such as a homomixer. As a dispersion medium used at the time of redispersion, water, the water-soluble organic solvent, and a mixed solvent thereof can be used, and water is most preferable. The solid content concentration in the dispersion again dispersed is not particularly limited, but is preferably 0.1 to 10% by mass, and more preferably 1 to 5% by mass. Cellulose nanofibers (CNF) can be produced by defibrating the redispersed liquid. Defibration can be carried out using a known apparatus such as a high-pressure homogenizer.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to these.
<Production of aqueous dispersion of carboxylated (TEMPO oxidized) pulp>
5 g (absolutely dry) of bleached unbeaten kraft pulp derived from conifers (whiteness 85%) was added to 500 mL of an aqueous solution in which 39 mg of TEMPO (Sigma Aldrich) and 514 mg of sodium bromide were dissolved, and the mixture was stirred until the pulp was evenly dispersed. . An aqueous sodium hypochlorite solution was added to the reaction system so as to be 5.5 mmol / g, and the oxidation reaction was started. 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 is acidified with hydrochloric acid, filtered through a glass filter to separate the pulp, and the pulp is thoroughly washed with water (hereinafter referred to as “carboxylated cellulose”, “carboxylated”). Pulp "or" TEMPO oxidized pulp "). The pulp yield was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.6 mmol / g.

<Method for measuring the amount of carboxyl group>
Prepare 60 mL of a 0.5% by mass slurry (aqueous dispersion) of carboxylated cellulose, add 0.1 M aqueous hydrochloric acid solution to pH 2.5, then add 0.05 N aqueous sodium hydroxide solution 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].

<Production of aqueous dispersion of carboxymethylated pulp>
To a stirrer capable of mixing pulp, 200 g dry pulp (NBKP (conifer bleached kraft pulp), manufactured by Nippon Paper Industries Co., Ltd.) and 111 g sodium hydroxide by dry mass are added, and the pulp solid content is 20 mass%. Water was added so that Thereafter, after stirring at 30 ° C. for 30 minutes, 216 g (as an active ingredient) of sodium monochloroacetate was added. After stirring for 30 minutes, the temperature was raised to 70 ° C. and stirred for 1 hour. Thereafter, the reaction product was taken out, neutralized, acidified with hydrochloric acid, and then washed to obtain a carboxymethylated pulp having a carboxymethyl substitution degree of 0.25 per glucose unit.

<Measurement method of carboxymethyl substitution degree per glucose unit>
About 2.0 g of carboxymethylated cellulose fiber (absolutely dry) was precisely weighed and placed in a 300 mL Erlenmeyer flask with a stopper. 100 mL of a solution prepared by adding 10 mL of special grade concentrated nitric acid to 90 mL of methanol was added, and the mixture was shaken for 3 hours to convert the carboxymethylated cellulose salt (CM-converted cellulose) into hydrogenated CM-converted cellulose. 1.5-2.0 g of hydrogenated CM-modified cellulose (absolutely dry) was precisely weighed and placed in a 300 mL conical flask with a stopper. Hydrogenated CM-modified cellulose was moistened with 15 mL of 80% methanol, 100 mL of 0.1 N NaOH was added, and shaken at room temperature for 3 hours. Excess NaOH was back titrated with 0.1 N H ₂ SO ₄ using phenolphthalein as an indicator. The degree of carboxymethyl substitution (DS) was calculated by the following formula:
A = [(100 × F ′ − (0.1 N H ₂ SO ₄ ) (mL) × F) × 0.1] / (absolute dry mass of hydrogenated CM-modified cellulose (g))
DS = 0.162 × A / (1-0.058 × A)
A: 1N NaOH amount (mL) required for neutralizing 1 g of hydrogenated CM-modified cellulose
F: Factor of 0.1N H ₂ SO ₄ F ′: Factor of 0.1N NaOH

<Manufacture of aqueous dispersion of cationized pulp>
To a stirrer that can stir the pulp, add 200 g of dry pulp (LBKP, Nippon Paper Industries Co., Ltd.) and 24 g of sodium hydroxide by dry weight, and add water so that the pulp solid concentration is 15% by mass. added. Then, after stirring for 30 minutes at 30 ° C., the temperature was raised to 70 ° C., and 190 g (in terms of active ingredient) of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added as a cationizing agent. After the reaction for 1 hour, the reaction product was taken out, neutralized and washed to obtain a cation-modified cellulose having a cation substitution degree of 0.04 per glucose unit.

<Measurement method of degree of cation substitution per glucose unit>
The degree of substitution of the cationic group was calculated by the following equation after drying the sample (cation-modified cellulose), measuring the nitrogen content with a total nitrogen analyzer TN-10 (manufactured by Mitsubishi Chemical Corporation). The degree of substitution here represents the average value of the number of moles of substituents per mole of anhydroglucose unit.
Degree of cation substitution = (162 × N) / (1-151.6 × N)
N: Nitrogen content

<Measurement of average fiber diameter, average fiber length, and aspect ratio of CNF>
The average fiber diameter and average fiber length of the cellulose nanofiber (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

<Measurement of B-type viscosity>
The viscosity of the CNF aqueous dispersion (solid content: 1.0% by mass, 25 ° C.) was measured using a B-type viscosity system. The measurement conditions were a rotation speed of 60 rpm and 3 minutes.

<Measurement of transparency>
The transparency (660 nm light transmittance) of the CNF aqueous dispersion (solid content: 1.0% by mass) was measured using a UV spectrophotometer U-3000 (manufactured by Hitachi High-Tech).

[Reference Example 1]
Water was added to the carboxylated pulp to prepare an aqueous dispersion having a solid content of 1.0% by mass, neutralized with sodium hydroxide, and then treated twice with a high-pressure homogenizer (20 ° C., 150 MPa) to obtain carboxyl. A CNF aqueous dispersion (average fiber diameter: 4 nm, aspect ratio: 150) derived from modified pulp was obtained.

[Reference Example 2]
Water was added to the carboxymethylated pulp to prepare an aqueous dispersion having a solid content of 1.0% by mass, neutralized with sodium hydroxide, and then treated twice with a high-pressure homogenizer (20 ° C., 150 MPa). A CNF aqueous dispersion derived from carboxymethylated pulp (average fiber length of 12 nm, aspect ratio: 130) was obtained.

[Reference Example 3]
Water was added to the cationized pulp to prepare an aqueous dispersion having a solid content of 1.0% by mass, neutralized with sodium hydroxide, and then treated twice with a high-pressure homogenizer (20 ° C., 150 MPa) to obtain a cation. A CNF aqueous dispersion (average fiber length 20 nm, aspect ratio: 110) derived from a modified pulp was obtained.

[Example 1]
A dispersion having a solid content of 1.0% by mass in which the carboxylated pulp was dispersed in 50 mL of a liquid medium was prepared. However, the composition of the liquid medium was water: ethanol = 25 mass%: 75 mass%. A Buchner funnel was used to prepare a wet cake-like mixture with a reduced amount of liquid medium and dried with a blow dryer at 50 ° C. until the mass became constant, and a carboxylated pulp having a solid content concentration of 96% by mass was dried. A dry solid was obtained.

  Next, water was added to the dried solid of the carboxylated pulp thus obtained to obtain an aqueous dispersion having a solid content concentration of 1.0% by mass, and the mixture was stirred for 60 minutes using a disper (1,000 rpm). The aqueous dispersion was neutralized with sodium hydroxide and then treated twice with a high-pressure homogenizer (20 ° C., 150 MPa) to obtain a CNF aqueous dispersion derived from carboxylated pulp (average fiber diameter: 4 nm, aspect ratio: 150). Got.

[Example 2]
A mixed solvent dispersion of carboxylated pulp (solid content concentration: 1.0% by mass) was obtained in the same manner as in Example 1 except that the composition of the liquid medium was changed to water: ethanol = 10% by mass: 90% by mass. A Buchner funnel was used to prepare a concentrated wet cake-like mixture with a reduced amount of liquid medium, and this was dried with a blow dryer at 50 ° C. until the mass reached a constant weight. A dry solid was obtained.

  Next, water was added to the dried solid of the carboxylated pulp thus obtained to obtain an aqueous dispersion having a solid content concentration of 1.0% by mass, and the mixture was stirred for 60 minutes using a disper (1,000 rpm). The aqueous dispersion was neutralized with sodium hydroxide and then treated twice with a high-pressure homogenizer (20 ° C., 150 MPa) to obtain a CNF aqueous dispersion derived from carboxylated pulp (average fiber diameter: 4 nm, aspect ratio: 150). Got.

[Example 3]
Except that the drying temperature was set to 30 ° C., in the same manner as in Example 1, a carboxylated pulp dry solid having a solid content concentration of 95% by mass was obtained. Next, water was added to the dried solid of the carboxylated pulp to obtain an aqueous dispersion having a solid content concentration of 1.0% by mass, and the mixture was stirred for 60 minutes using a disper (1,000 rpm). The aqueous dispersion was neutralized with sodium hydroxide and then treated twice with a high-pressure homogenizer (20 ° C., 150 MPa) to obtain a CNF aqueous dispersion derived from carboxylated pulp (average fiber diameter: 4 nm, aspect ratio: 150). Got.

[Example 4]
A dry solid of carboxylated pulp having a solid content of 97% by mass was obtained in the same manner as in Example 1 except that methanol was used instead of ethanol. Next, water was added to the dry solid of the carboxylated pulp to obtain an aqueous dispersion having a solid concentration of 1.0% by mass, and the mixture was stirred for 60 minutes using a disper (1,000 rpm). The aqueous dispersion was neutralized with sodium hydroxide and then treated twice with a high-pressure homogenizer (20 ° C., 150 MPa) to obtain a CNF aqueous dispersion derived from carboxylated pulp (average fiber diameter: 4 nm, aspect ratio: 150). Got.

[Example 5]
A dispersion having a solid content concentration of 1.0% by mass in which the carboxylmethylated pulp was dispersed in 50 mL of a dispersion medium was prepared. The composition of the liquid medium was water: ethanol = 25% by mass: 75% by mass. Prepare a wet cake-like mixture by reducing the amount of liquid medium using a Buchner funnel and drying it with a blow dryer at 50 ° C. until the mass reaches a constant weight. Carboxymethylated pulp having a solid content of 96% by mass A dry solid was obtained.

  Next, water was added to the dry solid of the carboxymethylated pulp thus obtained to obtain an aqueous dispersion having a solid concentration of 1.0% by mass, and the mixture was stirred for 60 minutes using a disper (1,000 rpm). The aqueous dispersion was neutralized with sodium hydroxide and then treated twice with a high-pressure homogenizer (20 ° C., 150 MPa) to obtain a CNF aqueous dispersion derived from carboxymethylated pulp (average fiber length of 12 nm, aspect ratio: 130). Got.

[Example 6]
A dispersion of carboxymethylated pulp (solid content concentration: 1.0% by mass) was obtained in the same manner as in Example 5 except that the composition of the liquid medium was changed to water: ethanol = 10% by mass: 90% by mass. Prepare a wet cake-like mixture by reducing the amount of the liquid medium using a Buchner funnel, dry it with a blow dryer at 50 ° C. until the mass becomes constant, and dry the carboxymethylated pulp having a solid content of 98% by mass A solid was obtained.

  Next, water was added to the dry solid of the carboxymethylated pulp thus obtained to obtain an aqueous dispersion having a solid concentration of 1.0% by mass, and the mixture was stirred for 60 minutes using a disper (1,000 rpm). The aqueous dispersion was neutralized with sodium hydroxide and then treated twice with a high-pressure homogenizer (20 ° C., 150 MPa) to obtain a CNF aqueous dispersion derived from carboxymethylated pulp (average fiber length of 12 nm, aspect ratio: 130). Got.

[Example 7]
A dispersion having a solid content concentration of 1.0% by mass in which cationized pulp was dispersed in 50 mL of a dispersion medium was prepared. However, the composition of the liquid medium was water: ethanol = 25 mass%: 75 mass%. Prepare a wet cake-like mixture by reducing the amount of liquid medium using a Buchner funnel, dry with a blow dryer at 50 ° C. until the mass reaches a constant weight, and dry solid of cationized pulp having a solid content of 96% by mass I got a thing.

  Next, water was added to the dry solid of the cationized pulp thus obtained to obtain an aqueous dispersion having a solid content concentration of 1.0% by mass, and the mixture was stirred for 60 minutes using a disper (1,000 rpm). The aqueous dispersion was neutralized with sodium hydroxide and then treated twice with a high-pressure homogenizer (20 ° C., 150 MPa) to obtain a CNF aqueous dispersion derived from cationized pulp (average fiber length 20 nm, aspect ratio: 110). Obtained.

[Example 8]
A cationized pulp dispersion (solid content concentration: 1.0% by mass) was obtained in the same manner as in Example 7 except that the composition of the liquid medium was changed to water: ethanol = 10% by mass: 90% by mass. Prepare a wet cake-like mixture by reducing the amount of liquid medium using a Buchner funnel, dry it with a blow dryer at 50 ° C. until the mass becomes constant, and dry solid of cationized pulp with a solid content of 99% by mass I got a thing.

  Next, water was added to the dry solid of the cationized pulp thus obtained to obtain an aqueous dispersion having a solid content concentration of 1.0% by mass, and the mixture was stirred for 60 minutes using a disper (1,000 rpm). The aqueous dispersion was neutralized with sodium hydroxide and then treated twice with a high-pressure homogenizer (20 ° C., 150 MPa) to obtain a CNF aqueous dispersion derived from cationized pulp (average fiber length 20 nm, aspect ratio: 110). Obtained.

[Comparative Example 1]
An aqueous dispersion having a solid content concentration of 1.0% by mass in which carboxylated pulp was dispersed in 50 mL of water was prepared. A wet cake-like mixture is prepared by reducing the amount of water using a Buchner funnel and dried to a constant weight for 3 hours with an air dryer at 105 ° C. to obtain a dry solid of carboxylated pulp having a solid content concentration of 95% by mass. It was.

  Next, water was added to the solid matter of the carboxylated pulp thus obtained to obtain an aqueous dispersion having a solid content concentration of 1.0% by mass, and the mixture was stirred for 60 minutes using a disper (1,000 rpm). The aqueous dispersion was neutralized with sodium hydroxide and then treated twice with a high-pressure homogenizer (20 ° C., 150 MPa) to obtain a CNF aqueous dispersion derived from carboxylated pulp (average fiber diameter: 4 nm, aspect ratio: 150). Got.

[Example 9]
An aqueous dispersion having a solid content concentration of 1.0% by mass in which carboxylated pulp was dispersed in 50 mL of water was prepared. Prepare a wet cake-like mixture by reducing the amount of water using a Buchner funnel and drying it with a blow dryer at 50 ° C. until the mass reaches a constant weight to obtain a dried product of carboxylated pulp having a solid content of 94% by mass. It was.

  Next, water was added to the dried product of the carboxylated pulp thus obtained to obtain an aqueous dispersion having a solid concentration of 1.0% by mass, and the mixture was stirred for 60 minutes using a disper (1,000 rpm). The aqueous dispersion was neutralized with sodium hydroxide and then treated twice with a high-pressure homogenizer (20 ° C., 150 MPa) to obtain a CNF aqueous dispersion derived from carboxylated pulp (average fiber diameter: 4 nm, aspect ratio: 150). Got.

[Example 10]
50 mL of carboxymethylated pulp aqueous dispersion having a solid content concentration of 1.0% by mass in which carboxymethylated pulp was dispersed in 50 mL of water was obtained. Prepare a wet cake-like mixture by reducing the amount of the liquid medium using a Buchner funnel, dry it with a blow dryer at 50 ° C. until the mass becomes constant, and dry the carboxymethylated pulp having a solid content of 94% by mass I got a thing.

  Next, water was added to the dried carboxymethylated pulp thus obtained to obtain an aqueous dispersion having a solid concentration of 1.0% by mass, and the mixture was stirred for 60 minutes using a disper (1,000 rpm). The aqueous dispersion was neutralized with sodium hydroxide and then treated twice with a high-pressure homogenizer (20 ° C., 150 MPa) to obtain a CNF aqueous dispersion derived from carboxymethylated pulp (average fiber length of 12 nm, aspect ratio: 130). Got.

[Example 11]
50 mL of a cationized pulp aqueous dispersion having a solid content concentration of 1.0% by mass in which cationized pulp was dispersed in 50 mL of water was obtained. Prepare a wet cake-like mixture by reducing the amount of liquid medium using a Buchner funnel, dry it with a blow dryer at 50 ° C. until the mass becomes constant, and dry product of cationized pulp having a solid content of 96% by mass Got.

  Next, water was added to the dried product of the cationized pulp thus obtained to obtain an aqueous dispersion having a solid concentration of 1.0% by mass, and the mixture was stirred for 60 minutes using a disper (1,000 rpm). The aqueous dispersion was neutralized with sodium hydroxide and then treated twice with a high-pressure homogenizer (20 ° C., 150 MPa) to obtain a CNF aqueous dispersion derived from cationized pulp (average fiber length 20 nm, aspect ratio: 110). Obtained.

[Comparative Example 2]
A dispersion having a solid content concentration of 1.0 mass% in which NBKP (conifer bleached kraft pulp, manufactured by Nippon Paper Industries Co., Ltd.) was dispersed in a 50 mL dispersion medium was prepared. However, the composition of the liquid medium was water: ethanol = 25 mass%: 75 mass%. A Buchner funnel was used to prepare a wet cake-like mixture with a reduced amount of liquid medium and concentrated to a constant weight by drying with a blow dryer at 50 ° C. for 3 hours to obtain a dry solid of NBKP having a solid content of 96% by mass. .

  Next, water was added to the dry solid of NBKP thus obtained to obtain an aqueous dispersion having a solid content concentration of 1.0% by mass, and the mixture was stirred for 60 minutes using a disper (1,000 rpm). The aqueous dispersion was neutralized with sodium hydroxide and then treated 5 times with a high-pressure homogenizer (20 ° C., 150 MPa) to obtain an NBKP-derived CNF aqueous dispersion (average fiber length 630 nm, aspect ratio: 30). . These results are shown in Table 1.

It is clear that CNF obtained from the dry solid of the chemically modified pulp of the present invention has the same physical properties as CNF obtained without drying from the chemically modified pulp dispersion.

Claims (9)

  A method for producing a chemically modified pulp dry solid, comprising a step of drying a mixture of a chemically modified pulp obtained by chemically modifying a cellulose raw material and a liquid medium at 20 to 80 ° C.   The production method according to claim 1, wherein the liquid medium is water or a mixed solvent of water and a water-soluble organic solvent.   The manufacturing method of Claim 2 whose quantity of the water-soluble organic solvent in the said mixed solvent is 10 mass% or more.   The manufacturing method in any one of Claims 1-3 whose carboxyl group amount of the said chemically modified pulp is 0.6-3.0 mmol / g with respect to the absolute dry mass of the said cellulose nanofiber.   The manufacturing method in any one of Claims 1-3 whose carboxymethyl substitution degree per glucose unit of the said chemically modified pulp is 0.01-0.50.   The manufacturing method in any one of Claims 1-3 whose cation substitution degree per glucose unit of the said chemically modified pulp is 0.02-0.50.   The manufacturing method in any one of Claims 1-6 whose said water-soluble organic solvent is a lower alcohol.   The manufacturing method of the chemically modified pulp dispersion liquid which disperse | distributes the dry solid substance of the chemically modified pulp obtained by the manufacturing method in any one of Claims 1-7 to a dispersion medium. The manufacturing method of a cellulose nanofiber including defibrating the chemically modified pulp in the chemically modified pulp dispersion liquid obtained with the manufacturing method of Claim 8.