JP2016069536A - Producing method of cellulose nano fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an effective producing method for large scale production of cellulose nano fiber.SOLUTION: A producing method of cellulose nano fiber includes: a reaction step introducing functional groups (carboxyl group, carboxylate group, carboxyl methyl group, quaternary ammonium) to surface of cellulose raw material; a step dehydrating and washing fluid dispersion of modified cellulose; a step preparing the fluid dispersion of the modified cellulose; and a defibrating step defibrating the fluid dispersion of the modified cellulose by applying mechanical shearing power.SELECTED DRAWING: None

Description

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

  It is expected that various useful new materials and devices will be born from nanotechnology, which is a technology that freely controls substances in the nanometer range, that is, atomic and molecular scales. In particular, nanofibers (nanofibers) have attracted a great deal of attention because, when the fibers are made as thin as possible, completely new physical properties that were not found in conventional fibers are born. By applying this nanofiber, for example, it is expected to develop a purification device with a high-performance filter that does not allow any fine foreign substances to pass through, increase the strength of chemical fibers and high-performance clothing, and increase the efficiency of fuel cells. ing.

  Cellulose nanofiber is a fiber having a nano-level fiber diameter of 1000 nm or less, and can be generally obtained by defibrating chemically modified cellulose fiber with mechanical shearing force (Patent Document 1). Moreover, regarding the manufacturing method of a cellulose nanofiber, various manufacturing methods including the manufacturing method described in patent document 1 are examined.

JP 2008-1728 A

  However, as for the production methods of various cellulose nanofibers including the production method described in Patent Document 1, only a production method at a laboratory level is disclosed, and efficient in large-scale production. The present situation is that the manufacturing method is not disclosed.

  Therefore, an object of the present invention is to provide an efficient manufacturing method for large-scale production of cellulose nanofibers.

The present invention provides the following [1] to [2].
[1] A method for producing cellulose nanofiber, comprising the following steps 1 to 4.
[Step 1] A step of introducing a carboxyl group, a carboxylate group, a carboxylmethyl group, or a quaternary ammonium group into a hydroxyl group on the raw material cellulose surface in a solution containing water as a main component.
[Step 2] A step of dehydrating and washing the dispersion of the modified cellulose obtained in Step 1 using any one of a centrifugal dehydration type, vacuum dehydration type, and pressure dehydration type dehydration apparatus.
[Step 3] A step of adjusting the modified cellulose obtained in Step 2 to a dispersion of 0.1 wt% to 10 wt%.
[Step 4] A step of defibrating the modified cellulose prepared in step 3 to 1 to 1000 nm using a high-speed shearing type, collision type, or bead mill type pulverizer.
[2] The method for producing cellulose nanofibers according to [1], including a step of crushing a sheet-like cellulose raw material before the step 1.

The present invention can provide an efficient production method for large-scale production of cellulose nanofibers.

1. Overall production flow The present invention includes a reaction step for introducing a functional group on the surface of a cellulose raw material, a step for dehydrating and washing the modified cellulose dispersion, a step for adjusting the modified cellulose dispersion, and a mechanical treatment for the modified cellulose dispersion. The present invention relates to a method for producing cellulose nanofibers having a defibrating step of defibrating by applying a shearing force.

2. Cellulose raw material In the present invention, the cellulose raw material refers to materials in various forms mainly composed of cellulose, such as pulp (bleached or unbleached wood pulp, bleached or unbleached non-wood pulp, refined linter, jute, Manila hemp, kenaf, etc. Natural cellulose such as cellulose produced by microorganisms such as acetic acid bacteria, regenerated cellulose spun after dissolving cellulose in some solvent such as copper ammonia solution, morpholine derivative, and the above cellulose raw material Examples thereof include fine cellulose obtained by depolymerizing cellulose by performing mechanical treatment such as hydrolysis, alkali hydrolysis, enzymatic decomposition, blasting treatment, and vibration ball mill.

In the present invention, when a sheet-like cellulose raw material is used, it is preferably crushed to a size of about 0.5 to 5 cm square. By roughly crushing to the size, the cellulose raw material can be modified efficiently and uniformly in the next reaction step. The method for coarse crushing is not particularly limited, and a uniaxial rotary shear pulverizer, a biaxial rotary shear pulverizer, a multi-screw screw pulverizer, a shredder, a guillotine cutter, or the like can be used. Among these, it is preferable from the viewpoint of coarse pulverization to use a uniaxial rotary shearing pulverizer and a shredder.

3. Process 1: Reaction process In this invention, the fibrillation efficiency in the process 4 improves significantly by introduce | transducing a carboxyl group, a carboxylate group, a carboxyl methyl group, and a quaternary ammonium group into a cellulose raw material.

(1) Anion-modified (1-1) Carboxymethylation Using the above cellulose raw material as a starting raw material, the solvent is 3 to 20 times by weight lower alcohol, specifically methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, tertiary butanol or the like alone or a mixture of two or more and water are used. The mixing ratio of the lower alcohol is 60 to 95% by weight. As the mercerizing agent, 0.5 to 20 times moles of alkali metal hydroxide, specifically sodium hydroxide or potassium hydroxide is used per glucose residue of the bottoming material. A bottoming raw material, a solvent, and a mercerizing agent are mixed and subjected to mercerization treatment at a reaction temperature of 0 to 70 ° C., preferably 10 to 60 ° C., and a reaction time of 15 minutes to 8 hours, preferably 30 minutes to 7 hours. Thereafter, 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. Perform etherification reaction for ~ 4 hours.

In the present invention, the degree of carboxymethyl substitution per glucose unit in the anion-modified cellulose is preferably 0.02 to 0.50. By introducing a carboxymethyl substituent into cellulose, the celluloses are electrically repelled. For this reason, the cellulose which introduce | transduced the carboxymethyl substituent can be nano-defibrated easily. In addition, when the carboxymethyl substituent per glucose unit is smaller than 0.02, nano-defibration cannot be sufficiently performed. On the other hand, if the carboxymethyl substituent per glucose unit is larger than 0.50, it may swell or dissolve, and may not be obtained as a nanofiber.
(1-2) Oxidation By oxidizing the above cellulose raw material in water using an oxidizing agent in the presence of a compound selected from the group consisting of N-oxyl compounds and bromides, iodides or mixtures thereof. Oxidized cellulose having a carboxyl group introduced into cellulose can be obtained.

  An N-oxyl compound is a compound capable of generating a nitroxy radical. As the N-oxyl compound used in the present invention, any compound can be used as long as it promotes the target oxidation reaction.

The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount capable of forming cellulose into nanofibers. 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 the absolutely dry cellulose raw material.

  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 from 0.1 to 100 mmol, more preferably from 0.1 to 10 mmol, and even more preferably from 0.5 to 5 mmol, with respect to 1 g of an absolutely dry cellulose raw material.

  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. Among these, from the viewpoint of cost, sodium hypochlorite, which is the most widely used in industrial processes and has a low environmental load, is particularly preferable. The appropriate amount of the oxidizing agent used is, for example, 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 the absolutely dry cellulose raw material. preferable.

  The cellulose oxidation process allows the reaction to proceed efficiently even under relatively mild conditions. Therefore, the reaction temperature may be a room temperature of about 15 to 30 ° C. As the reaction proceeds, a carboxyl group is generated in the cellulose constituting the pulp, so that the pH of the reaction solution is reduced. In order to advance the oxidation reaction efficiently, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution at about 9 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 progress of oxidation, and is usually 0.5 to 6 hours, preferably 2 to 6 hours, more preferably about 4 to 6 hours. However, in the present invention, since the oxidation time can be reduced as described above, the reaction time is preferably 30 minutes to 120 minutes, more preferably 30 to 100 minutes, and even more preferably 30 to 70 minutes.

  The oxidation reaction may be performed in two stages. For example, oxidized cellulose obtained by filtration after the completion of the first stage reaction is oxidized again under the same or different reaction conditions, so that the cellulose is not subject to reaction inhibition by the salt produced as a by-product in the first stage reaction. A carboxyl group can be efficiently introduced into the raw material, and oxidation of the cellulose raw material can be promoted.

  The conditions are preferably set so that the amount of carboxyl groups of oxidized cellulose is 0.2 mmol / g or more with respect to the absolute dry mass of cellulose. In this case, the carboxyl group amount is more preferably 0.6 mmol / g to 2.0 mmol / g, and still more preferably 1.0 mmol / g to 1.8 mmol / g. The amount of the carboxyl group can be adjusted by adjusting the oxidation reaction time, adjusting the oxidation reaction temperature, adjusting the pH during the oxidation reaction, adjusting the addition amount of the N-oxyl compound, bromide, iodide, or oxidizing agent.

(2) Cationic modification A cationizing agent such as glycidyltrimethylammonium chloride, 3-chloro-2hydroxypropyltrialkylammonium hydride or its halohydrin type and an alkali metal hydroxide (sodium hydroxide, water) as a catalyst. Cation-modified cellulose can be obtained by reacting potassium oxide and the like in the presence of water and / or alcohol having 1 to 4 carbon atoms. In this method, the cation substitution degree per glucose unit of the cation-modified cellulose obtained is controlled by the amount of the cationizing agent to be reacted, the composition ratio of water and / or alcohol having 1 to 4 carbon atoms. Can be adjusted.

In the present invention, the cation substitution degree per glucose unit of the cation-modified cellulose 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. In addition, when the cation substitution degree per glucose unit is smaller than 0.02, nano-fibrosis cannot be sufficiently performed. 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 the next defibration, the oxidized cellulose raw material obtained above is preferably washed.

The reaction tank used in Step 1 for modifying the cellulose raw material to obtain modified cellulose is not particularly limited, but a tank provided with stirring blades, a pulper, a kneader, a ribbon type mixing device, a screw type mixing An apparatus etc. can be illustrated. Among these, when the reaction proceeds at a raw material concentration of about 3% or less, it is preferable to use a tank or a pulper provided with a stirring blade capable of stirring a liquid or liquid slurry. In addition, when the reaction is carried out under conditions where the raw material concentration exceeds 3%, since the reactants are solid and not in liquid form, a kneader, ribbon type mixer, screw type mixer that can mix and agitate them is used. It is preferable to do.

4). Step 2: Washing step In the present invention, the dispersion of the modified cellulose obtained in Step 1 is a step of washing with water after the dehydration treatment, and this step is an essential step for obtaining cellulose nanofibers with less impurities. It is.

  In this step, centrifugal dehydration type, vacuum dehydration type and pressure dehydration type dehydration devices can be used. Specifically, centrifugal separation type: (Tanabe Wiltech centrifugal separator, Kokusan centrifugal separator Vacuum dehydration type: drum type vacuum dehydrator, Tsukishima machine horizontal belt filter, pressure dehydration type: filter press, tube press, screw press, belt press horizontal belt filter, poly disc filter, vibrating screen, etc. Can do. 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.

5. Adjustment process In this invention, in order to perform the following defibration process efficiently, it is essential to adjust the density | concentration of the dispersion liquid of a modified cellulose to 0.1 to 10 weight%. If it is less than 0.1% by weight, the presence of the modified pulp is too small to sufficiently defibrate. On the other hand, when the amount exceeds 10% by weight, as the defibration progresses, the viscosity of the modified pulp dispersion increases, and a sufficient force cannot be applied to the modified pulp.

6). Step 4: Defibration Step In the present invention, it is essential to defibrate the modified cellulose. The pulverizer used in this step can be any type of high-speed shear type, collision type, bead mill type, high-speed rotation type, colloid mill type, high-pressure type, roll mill type, and ultrasonic type. Specifically, high-speed rotation type: stone mill grinder Super Mass Colloider (made by Masuko Sangyo), colloid mill type: emulsifier (made by Iwaki), roll mill type: 3-roll mill (made by Amex), ultrasonic type: air purge type Ultrasonic disperser (manufactured by SMT) High-speed shear type: Nano manufacturer (manufactured by Advanced Nano Technology), Collision type: Wet atomizer Starburst (manufactured by Sugino Machine), Bead mill type wet bead mill MSC mill (Japan) Coke Industries). A plurality of these can also be used in combination. Among these, it is preferable to use a high-speed shearing type, collision type, and high-speed rotation type defibrating device from the viewpoint of processing a stronger shearing force under a condition where the risk of contamination by media is low.

Hereinafter, the manufacturing method and manufacturing system of the nanofiber of Example 1 provided with the reaction process, the washing | cleaning dehydration process, and the disaggregation process are demonstrated.

[Example 1]
Bleached kraft pulp pulverized to about 20mm square using an oriental pulverizer, which is a uniaxial rotary shearing pulverizer, is mixed and stirred with caustic soda and monochloroacetic acid soda into a ribbon-type mixing device, and gradually heated to 80 ° C for commercialization. After proceeding with the reaction, the slurry was diluted to 0.5% solids in a tank with an agitator to give a slurry of 5 m ³ . Next, the slurry was dehydrated to a solid content of 15% with a filter press (manufactured by Kurita Machine Seisakusho), diluted to 0.5% with a tank with an agitator, and made into a 5 m ³ slurry. The slurry was again dehydrated to 10% with a filter press, and diluted with a tank with an agitator to 0.5%, and the washing was repeated three times. The process of defibrating 0.5% slurry with a stone mill grinder Super Mass Colloid (manufactured by Masuko Sangyo), immediately cooling by heat exchange, and storing the slurry in a stock tank was repeated 5 times. 5% was obtained CM cellulose nanofiber slurry 4.5 m ^3.

[Example 2]
Bleached kraft pulp was added to a pulper (manufactured by Aikawa Tekko) together with water to prepare 5 m ^{3 of} 5% pulp slurry. After that, it was sent to a tank with an agitator, TEMPO and sodium bromide were added and diluted about 10 times to make 0.5% slurry 5 m ³ , then at a temperature of 23 ° C., caustic soda and sodium hypochlorite at pH 10.5. The reaction was advanced. During the reaction, additional caustic soda was added so as to keep pH 10.5 in accordance with the consumption of caustic soda. After confirming that sodium hypochlorite was consumed to less than 5 ppm, the reaction was terminated. Next, the slurry was dehydrated to a solid content of 15% with a filter press (manufactured by Kurita Machinery Co., Ltd.) and diluted to 0.5% with a tank with an agitator to give a 5 m ³ slurry. The slurry was again dehydrated to 10% with a filter press, and diluted with a tank with an agitator to 0.5%, and the washing was repeated three times. After the final cleaning, the slurry solid content is set to 1%, the fiber is defibrated by a nano maker (manufactured by Advanced Nano Technology) of a high-speed shearing defibrating device, immediately cooled by heat exchange, and the slurry is stored in a stock tank. The operation was repeated 10 times to obtain 4.5 m ³ of a TEMPO oxidized cellulose nanofiber slurry having a solid content of 1%.

[Example 3]
Bleached kraft pulp was added to a pulper (manufactured by Aikawa Tekko) together with water to prepare 5 m ^{3 of} 5% pulp slurry. After that, it was sent to a tank with an agitator, TEMPO and sodium bromide were added and diluted about 10 times to make 0.5% slurry 5 m ³ , then at a temperature of 23 ° C., caustic soda and sodium hypochlorite at pH 10.5. The reaction was advanced. During the reaction, additional caustic soda was added so as to keep pH 10.5 in accordance with the consumption of caustic soda. After confirming that sodium hypochlorite was consumed to less than 5 ppm, the reaction was terminated. Next, the slurry was dewatered to a solid content of 15% with a centrifuge (manufactured by Tanabe Wiltech), diluted to 0.5% with a tank with an agitator, and made into a 5 m ³ slurry. The slurry was again dehydrated to 10% with a centrifuge and the operation of diluting to 0.5% with an agitator tank was repeated three times to proceed with washing. After the final washing, the slurry solid content is 1%, defibration is performed with the impact type defibration device Starburst (manufactured by Sugino Machine), immediately after cooling by heat exchange, and the slurry is stored in the stock tank 10 times. Repeatedly, 4.5 m ³ of TEMPO-oxidized cellulose nanofiber slurry having a solid content of 1% was obtained.

Claims (2)

The manufacturing method of the cellulose nanofiber containing the following processes 1-4.
[Step 1] A step of introducing a carboxyl group, a carboxylate group, a carboxylmethyl group, or a quaternary ammonium group into a hydroxyl group on the raw material cellulose surface in a solution containing water as a main component.
[Step 2] A step of dehydrating and washing the dispersion of the modified cellulose obtained in Step 1 using any one of a centrifugal dehydration type, vacuum dehydration type, and pressure dehydration type dehydration apparatus.
[Step 3] A step of adjusting the modified cellulose obtained in Step 2 to a dispersion of 0.1 wt% to 10 wt%.
[Step 4] A step of defibrating the modified cellulose prepared in step 3 to 1 to 1000 nm using a high-speed shearing type, collision type, or bead mill type pulverizer. The method for producing cellulose nanofiber according to claim 1, comprising a step of crushing a sheet-like cellulose raw material before the step 1.