WO2019176465A1

WO2019176465A1 - Method for producing cellulose nanofiber dispersion

Info

Publication number: WO2019176465A1
Application number: PCT/JP2019/006001
Authority: WO
Inventors: 利一村松; 啓吾渡部; 淳之重見
Original assignee: 日本製紙株式会社
Priority date: 2018-03-14
Filing date: 2019-02-19
Publication date: 2019-09-19
Also published as: JPWO2019176465A1; JP7402154B2

Abstract

This method for producing a high-transparency cellulose nanofiber dispersion has a preliminary defibration step for beating chemically modified cellulose using a single disk-type refiner, and a main defibration step for defibrating pulp obtained in the preliminary defibration step through treatment by a high-pressure disperser at a treatment pressure of 1-400 MPa.

Description

Method for producing cellulose nanofiber dispersion

The present invention relates to a method for producing a highly transparent cellulose nanofiber dispersion that is produced with low power consumption.

Cellulose nanofibers obtained by refining cellulose are fibers having a nano-level fiber diameter of about 1 to 100 nm, and the dispersion has high transparency. For this reason, application to transparency, for example, optical film, film coating agent, compounding to glass, etc. is expected. For this reason, various studies have been made on methods for producing cellulose nanofibers (see Patent Document 1).

JP 2008-1728 A

However, in the conventional method for producing cellulose nanofibers, a large amount of electric power is used for production because the finer treatment is generally performed several times by a dispersing machine having a strong shearing force such as an ultra-high pressure homogenizer. In addition, the ultra-high pressure homogenizer pushes the sample into a very narrow gap to make it high pressure, so when processing large fibers such as pulp, clogging may occur, resulting in extremely poor productivity and workability. It was a problem.

An object of the present invention is to provide a method for producing a cellulose nanofiber dispersion that efficiently produces a highly transparent cellulose nanofiber dispersion with low power consumption.

The present invention provides the following (1) to (7).

(1) A method for producing a cellulose nanofiber dispersion comprising producing a highly transparent cellulose nanofiber dispersion from chemically modified cellulose, comprising the following steps (A) and (B):
Step (A): preliminary defibrating step of beating the chemically modified cellulose using a single disc type refiner,
Step (B): This defibrating step of defibrating the cellulose obtained in the preliminary defibrating step (A) by treatment with a high-pressure disperser at a treatment pressure of 1 MPa to 400 MPa.

(2) In the preliminary defibrating step (A), the plate used in the refiner is a viscous beating plate, a fine bar type plate, a plate having a structure for closing the raw material flow path, a grindstone plate, a flat without a groove. The method for producing a cellulose nanofiber dispersion according to (1), which is any one of metal plates.

(3) Production of cellulose nanofiber dispersion according to (1) or (2), wherein in the preliminary defibrating step (A), the treatment rate of the chemically modified cellulose is 30 m ³ / hr or less. Method.

(4) In the preliminary defibrating step (A), the concentration of the chemically modified cellulose during treatment is 2.5 to 15% by mass, according to any one of (1) to (3) Of manufacturing cellulose nanofiber dispersion liquid.

(5) The cellulose nanofiber dispersion according to any one of (2) to (4), wherein in the preliminary defibrating step (A), the clearance of the plate is 0.01 to 0.4 mm. Manufacturing method.

(6) The cellulose nanofiber dispersion according to any one of (2) to (5), wherein the peripheral speed of the plate is 24.5 m / s or more in the preliminary defibrating step (A) Manufacturing method.

(7) The cellulose nanostructure according to any one of (2) to (6), wherein in the preliminary defibrating step (A), the shear rate of rotation of the plate is 100 (1 / ms) or more. A method for producing a fiber dispersion.

According to the present invention, it is possible to provide a method for efficiently producing a highly transparent cellulose nanofiber dispersion with low power consumption. Moreover, according to this invention, generation | occurrence | production of the blockage | clogging in the defibrating machine which deteriorates productivity can be suppressed in this defibrating process which converts the chemically modified cellulose into nanofibers.

The method for producing a cellulose nanofiber dispersion according to the present invention includes a step (A): a preliminary defibrating step of beating a chemically modified cellulose using a single disk type refiner, and a step (B): the preliminary defibrating step. And a main defibrating step of defibrating the cellulose obtained in (A) by treatment with a high-pressure disperser at a treatment pressure of 1 MPa to 400 MPa.

In the present invention, cellulose fibers are defibrated by different mechanisms by combining preliminary defibration by mechanical beating processing with a conventional beating device and main defibration, so that while reducing power consumption, transparency can be reduced. A high cellulose nanofiber dispersion can be produced.

The reason why a highly transparent cellulose nanofiber dispersion can be obtained by the present invention is presumed as follows. In preliminary defibration, the refinement of chemically modified cellulose as a raw material proceeds, and the outside of the cellulose fiber is loosened. Therefore, in this subsequent defibration, shear energy such as an ultra-high pressure homogenizer easily acts on the cellulose, and a cellulose nanofiber dispersion with high transparency can be produced efficiently.

(1) Cellulose raw material In the present invention, the cellulose raw material refers to materials in various forms mainly composed of cellulose, and pulp (bleached or unbleached wood pulp, bleached or unbleached non-wood pulp, refined linter, jute, Manila hemp , Pulp derived from herbs such as kenaf), 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 Examples thereof include fine cellulose obtained by depolymerizing cellulose by subjecting the cellulose raw material to mechanical treatment such as hydrolysis, alkaline hydrolysis, enzymatic decomposition, explosion treatment, and vibration ball mill.

(2) Chemical modification process of cellulose (Oxidation)
In the present invention, the oxidation of the cellulose raw material can be performed using a known method, and is not particularly limited, but the amount of carboxyl groups is 0.5 mmol / g with respect to the absolute dry mass of the cellulose nanofiber. It is preferable to adjust so as to be ˜3.0 mmol / g.

For example, cellulose can be obtained by oxidizing cellulose in water in the presence of an N-oxyl compound and a compound selected from the group consisting of bromide, iodide, or a mixture thereof. By this oxidation reaction, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized, and a cellulose fiber having an aldehyde group and a carboxyl group or a carboxylate group 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. An N-oxyl compound refers to a compound capable of generating a nitroxy radical. As the N-oxyl compound, 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 oxidizing the cellulose as a raw material. For example, with respect to 1 g of absolutely dry cellulose, 0.01 to 10 mmol is preferable, 0.02 to 1 mmol is more preferable, and 0.05 to 0.5 mmol is more preferable. Further, it is preferably about 0.1 to 4 mmol / L with respect to the reaction system.

Bromide is a compound containing bromine, and examples thereof include alkali metal bromide that can be dissociated and ionized 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 further 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 0.7 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. . Further, for example, 1 to 40 mol is preferable with respect to 1 mol of the N-oxyl compound.

In the cellulose oxidation step, the reaction can 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 make the oxidation reaction proceed 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 progress of oxidation, and is usually 0.5 to 6 hours, for example, about 1 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. The ozone concentration in the gas containing ozone is preferably 50 to 250 g / m ³ , and more preferably 70 to 220 g / 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, preferably about 30 to 300 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, peracetic acid and the like. 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 the carboxyl group, carboxylate group, and aldehyde group of the cellulose fiber can be adjusted by controlling the amount of the oxidizing agent added and the reaction time. The carboxyl group content is measured, for example, by preparing 60 mL of a 0.5 mass% slurry (aqueous dispersion) of oxidized cellulose, adding 0.1 M hydrochloric acid aqueous solution to pH 2.5, and then adding 0.05 N sodium hydroxide. The electrical conductivity was measured by dropping the aqueous solution until the pH reached 11, and the amount was calculated from the amount of sodium hydroxide (a) consumed in the neutralization step of the weak acid where the change in electrical conductivity was slow, using the following formula: can do.
Amount of carboxyl group [mmol / g oxidized cellulose or cellulose nanofiber]
= A [mL] x 0.05 / oxidized cellulose mass [g]

(Carboxymethylation)
In the present invention, the carboxymethylation of the cellulose raw material can be performed using a known method, and is not particularly limited. However, the degree of carboxymethyl group substitution per anhydroglucose unit of cellulose is 0.01 to 0.00. It is preferable to adjust to 50. As an example, the following production method can be mentioned, but it may be synthesized by a conventionally known method or a commercially available product may be used. Cellulose is used as a starting material, and 3 to 20 times by weight water and / or lower alcohol as a solvent, specifically methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, tertiary butanol, etc. Or a mixed medium of two or more. The mixing ratio of the lower alcohol is 60 to 95% by mass. As the mercerizing agent, 0.5 to 20 times moles of alkali metal hydroxide, specifically sodium hydroxide or potassium hydroxide is used per anhydroglucose residue of the bottoming material. A bottoming raw material, a solvent, and a mercerizing agent are mixed, and a mercerization process is performed 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. The etherification reaction is performed for ˜4 hours.

As a method for measuring the degree of carboxymethyl substitution per glucose unit, for example, the following method can be used. That is, 1) About 2.0 g of carboxymethylated cellulose fiber (absolutely dry) is precisely weighed and put into a 300 mL conical stoppered Erlenmeyer flask. 2) Add 100 mL of a solution of 100 mL of special concentrated nitric acid to 1000 mL of nitric acid methanol and shake for 3 hours to convert the carboxymethyl cellulose salt (CM cellulose) into hydrogenated CM cellulose. 3) Weigh accurately 1.5 to 2.0 g of hydrogenated CM-modified cellulose (absolutely dry), and put into a 300 mL Erlenmeyer flask with a stopper. 4) Wet the hydrogenated CM cellulose with 15 mL of 80% methanol, add 100 mL of 0.1N NaOH, and shake at room temperature for 3 hours. 5) Back titrate excess NaOH with 0.1N H ₂ SO ₄ using phenolphthalein as indicator. 6) The degree of carboxymethyl substitution (DS) is 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

(Cationization)
In the present invention, the cationization of the cellulose raw material can be performed using a known method, and for example, ammonium, phosphonium, sulfonium, or a group having ammonium, phosphonium or sulfonium can be contained in the cellulose molecule by cationization. A group containing ammonium is preferred, and a group containing quaternary ammonium is particularly preferred. A specific cationization method is not particularly limited, but as an example, a cationizing agent such as glycidyltrimethylammonium chloride, 3-chloro-2hydroxypropyltrimethylammonium chloride or a halohydrin type thereof is used as a cellulose raw material. Cationic modification having a group containing a quaternary ammonium by reacting a catalyst alkali metal hydroxide (sodium hydroxide, potassium hydroxide, etc.) in the presence of water and / or an alcohol having 1 to 4 carbon atoms. Cellulose can be obtained.

In this method, the degree of cation substitution per glucose unit of the cation-modified cellulose obtained is controlled by the addition 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. The degree of substitution herein refers to the number of substituents introduced per unit structure (glucopyranose ring) constituting cellulose. In other words, it is defined as “a value obtained by dividing the number of moles of the introduced substituent by the total number of moles of hydroxyl groups of the glucopyranose ring”. Since pure cellulose has three substitutable hydroxyl groups per unit structure (glucopyranose ring), the theoretical maximum value of the degree of substitution of the cellulose fiber of the present invention is 3 (minimum value is 0).

In the present invention, the degree of cation substitution per glucose unit of cationized cellulose is preferably 0.01 to 0.40. 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 0.01, nano-defibration cannot be sufficiently performed. On the other hand, if the degree of cation substitution per glucose unit is larger than 0.40, the fiber form cannot be maintained because it swells or dissolves and may not be obtained as a nanofiber.

The degree of cation substitution per glucose unit can be calculated from the following equation by measuring the nitrogen content with a total nitrogen analyzer TN-10 (Mitsubishi Chemical) after drying the sample (cation-modified cellulose). . The degree of substitution referred to 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

(Esterification)
A method for obtaining an esterified cellulose fiber or an esterified cellulose nanofiber by esterifying a cellulose raw material or a defibrated cellulose fiber is not particularly limited, and examples thereof include a method of reacting compound A with a cellulose raw material or a defibrated cellulose fiber. It is done. Compound A will be described later.

Examples of the method of reacting compound A with cellulose raw material or defibrated cellulose fiber include a method of mixing powder or aqueous solution of compound A with cellulose raw material or defibrated cellulose fiber, and compound A into a slurry of cellulose raw material or defibrated cellulose fiber. The method of adding the aqueous solution of this is mentioned. Among these, since the uniformity of the reaction is enhanced and the esterification efficiency is increased, a method in which an aqueous solution of Compound A is mixed with a cellulose raw material, a defibrated cellulose fiber or a slurry thereof is preferable.

Examples of compound A include phosphoric acid compounds (eg, phosphoric acid, polyphosphoric acid), phosphorous acid, phosphonic acid, polyphosphonic acid, and esters thereof. Compound A may be in the form of a salt. Among them, a phosphoric acid compound 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 a cellulose raw material (eg, pulp fiber). . The phosphate compound may be any compound having a phosphate group. For example, phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, diphosphate Examples include potassium hydrogen, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, and ammonium metaphosphate. . The phosphoric acid compound used may be one type or a combination of two or more types. 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. Ammonium salt is preferable, sodium salt of phosphoric acid is more preferable, and sodium dihydrogen phosphate and disodium hydrogen phosphate are more preferable. In addition, it is preferable to use an aqueous solution of a phosphoric acid compound in the esterification because the uniformity of the reaction is enhanced and the efficiency of introduction of phosphoric acid groups is increased. The pH of the aqueous solution of the phosphoric acid compound is preferably 7 or less because the efficiency of introduction of phosphate groups is increased. From the viewpoint of suppressing the hydrolysis of pulp fibers, a pH of 3 to 7 is more preferable.

Examples of the esterification method include the following methods. Compound A is added to a cellulose raw material or a suspension of defibrated cellulose fibers (for example, a solid content concentration of 0.1 to 10% by mass) with stirring to introduce phosphate groups into the cellulose. When the cellulose raw material or defibrated cellulose fiber is 100 parts by mass, when the compound A is a phosphoric acid compound, the addition amount of the compound A is preferably 0.2 parts by mass or more, preferably 1 part by mass or more as the amount of phosphorus element. Is more preferable. Thereby, the yield of esterified cellulose fiber or esterified cellulose nanofiber can be further improved. The upper limit is preferably 500 parts by mass or less, and more preferably 400 parts by mass or less. Thereby, the yield corresponding to the usage-amount of the compound A can be obtained efficiently. Therefore, 0.2 to 500 parts by mass is preferable, and 1 to 400 parts by mass is more preferable.

When reacting Compound A with cellulose raw material or defibrated cellulose fiber, Compound B may be further added to the reaction system. Examples of the method of adding Compound B to the reaction system include a method of adding Compound B to a slurry of cellulose raw material or defibrated cellulose fiber, an aqueous solution of Compound A, or a slurry of cellulose raw material or defibrated cellulose fiber and Compound A. It is done.

Compound B is not particularly limited, but preferably exhibits basicity, more preferably a nitrogen-containing compound exhibiting basicity. “Show basic” usually means that the aqueous solution of Compound B is pink to red in the presence of a phenolphthalein indicator, or / and the pH of the aqueous solution of Compound B is greater than 7. The nitrogen-containing compound showing basicity is not particularly limited as long as the effects of the present invention are exhibited, but a compound having an amino group is preferable. Examples of the compound having an amino group include urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine and the like. Of these, urea is preferable because it is easy to handle at low cost. The amount of compound B added is preferably 2 to 1000 parts by mass, and more preferably 100 to 700 parts by mass. The reaction temperature is preferably 0 to 95 ° C, more preferably 30 to 90 ° C. The reaction time is not particularly limited, but is usually about 1 to 600 minutes, preferably 30 to 480 minutes. If the conditions for the esterification reaction are in any of these ranges, cellulose can be prevented from being excessively esterified and easily dissolved, and the yield of phosphorylated esterified cellulose can be improved. it can.

After reacting compound A with cellulose raw material or defibrated cellulose fiber, a suspension of esterified cellulose fiber or esterified cellulose nanofiber is usually obtained. The suspension of esterified cellulose fiber or esterified cellulose nanofiber is dehydrated as necessary. Heat treatment is preferably performed after dehydration. Thereby, hydrolysis of a cellulose raw material or a defibrated cellulose fiber can be suppressed. The heating temperature is preferably 100 to 170 ° C. While water is included in the heat treatment, heating is performed at 130 ° C or less (more preferably 110 ° C or less), and after removing water, heating is performed at 100 to 170 ° C. More preferably, it is processed.

In phosphate esterified cellulose, a phosphate group substituent is introduced into the cellulose, and the cellulose repels electrically. Therefore, the phosphate esterified cellulose fiber can be easily defibrated up to cellulose nanofibers (the defibration performed until the cellulose nanofibers are thus formed is also referred to as nano-defibration). The phosphate group substitution degree per glucose unit of the phosphate esterified cellulose fiber is preferably 0.001 or more. Thereby, sufficient defibration (for example, nano defibration) can be implemented. The upper limit of the degree of phosphate group substitution per glucose unit of the phosphate esterified cellulose fiber is preferably 0.40 or less. Thereby, swelling or melt | dissolution of phosphate esterified cellulose fiber can be suppressed, and generation | occurrence | production of the situation where a cellulose nanofiber cannot be obtained can be suppressed. Accordingly, the phosphate group substitution degree per glucose unit of the phosphate esterified cellulose fiber is preferably 0.001 to 0.40. Further, the degree of phosphate group substitution per glucose unit of cellulose nanofibers (phosphate esterified cellulose nanofibers) modified by phosphoric esterification is preferably 0.001 or more. The upper limit is preferably 0.40 or less. Therefore, the phosphate group substitution degree per glucose unit of the phosphate esterified cellulose nanofiber is preferably 0.001 to 0.40. It is preferable that the phosphorylated cellulose fiber is subjected to a washing treatment such as washing with cold water after boiling. Thereby, defibration can be performed efficiently.

The reaction tank used in the step of chemically modifying this cellulose raw material to obtain modified cellulose is not particularly limited, but a tank provided with a stirring blade, 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.

(3) Dehydration / washing step In the present invention, the dispersion of chemically modified cellulose obtained in the chemical modification step of cellulose is a step of washing with water after the dehydration treatment. A fiber dispersion can be obtained.

In this step, a centrifugal, vacuum dehydration or pressure dehydration type dehydration apparatus can be used. Specifically, basket-type centrifuges, decanter-type centrifuges, etc. as centrifugal separation types, drum-type vacuum dehydrators as vacuum dehydration types, horizontal belt filters, etc., filter presses, tube presses, screw presses as pressure dehydration types Belt press horizontal belt filter, poly disk filter, vibrating screen and the like. Among these, since dehydration can be performed without applying strong shearing force to the dehydrated raw material, pressure dehydration type (filter press, tube press, screw press), centrifugal separation type (basket type, decanter type), vacuum dehydration type (Drum type vacuum dehydrator, horizontal belt filter) is preferable. A plurality of these can also be used in combination.

(4) Chemically modified cellulose concentration adjusting step In the present invention, the concentration of the chemically modified cellulose dispersion is 2.5% by mass to 15% by mass, more preferably 3% by mass in order to efficiently perform the preliminary defibrating step. Adjust to ˜10% by mass. When the amount is less than 0.5% by mass, the presence of the modified pulp is too small to efficiently defibrate. On the other hand, if it exceeds 15% by mass, the viscosity of the chemically modified cellulose dispersion is too high to efficiently defibrate.

(5) Pre-defibration process (A)
In the present invention, the apparatus used in the preliminary defibrating beating process is a single disk type refiner. The single disc type refiner has high plate surface accuracy and can be operated with a narrow plate clearance. Carrying out the preliminary defibrating step (A) leads to loosening the outer layer of the cellulose fibers and fibrillation inside, so that cellulose nanofibers can be easily obtained in this defibrating step (B) and the load is reduced.

In the preliminary defibrating step (A), the treatment rate of chemically modified cellulose in a single disc type refiner is 30 m ³ / hr or less. By setting the treatment rate to 30 m ³ / hr or less, a highly transparent cellulose nanofiber dispersion can be produced.

In the preliminary defibrating process (A), the single disk type refiner includes a papermaking plate (viscous beating plate, fine bar type plate), a plate (plate with a dam) that closes the raw material flow path, and a grindstone plate. Any flat metal plate without grooves is used.

The plate clearance of the refiner used in the preliminary defibrating step (A) is 0.01 mm to 0.4 mm, more preferably 0.1 mm to 0.3 mm. If the thickness is less than 0.01 mm, the plate will be abruptly worn. If the thickness exceeds 0.4 mm, the clearance is too wide and the processing is difficult to proceed. In the preliminary defibrating step (A), a conventional refiner that adjusts the clearance by moving the rotor side plate using a hydraulic or pneumatic jack may be used, but a ball screw type clearance adjustment mechanism is more preferable. The use of a refiner with a squeezer and further precise control of the clearance between the plates by means of a laser position measurement mechanism or the like enables efficient pre-defibration.

In the preliminary defibrating step (A), the peripheral speed of the plate is preferably 24.5 m / s or more, more preferably 30 m / s or more. By setting the peripheral speed of the plate to 24.5 m / s or more, preliminary defibration can be performed efficiently. In the preliminary defibrating step (A), the rotational shear rate of the refiner plate is 100 (1 / ms) or more, more preferably 150 (1 / ms) or more.

Here, the rotational shear rate of the plate = (the peripheral speed of the plate / plate clearance). When the rotational shear rate of the plate is less than 100 (1 / ms), preliminary defibration cannot be performed efficiently. In the preliminary defibrating step (A), a normal head case-shaped refiner may be used, but in order to prevent heat generation due to stirring of the raw material staying inside the head case, the space inside the head case is 10 L or less. It is better to do. More preferably, a cooling water jacket for cooling the pulp is installed in the space inside the head case so that the treatment is performed while suppressing the influence of heat on the pulp.

(6) This defibrating process (B)
In the present invention, the present defibration means that cellulose obtained by preliminary defibration is applied with a strong shearing force using a high-pressure disperser, and an average fiber length of 0.5 to 5 μm and an average fiber width of 3 to Defibration up to 100 nm. In particular, in order to efficiently obtain cellulose nanofibers, it is preferable to use a wet high-pressure or ultrahigh-pressure homogenizer that can apply a pressure of 1 MPa to 400 MPa to the chemically modified cellulose dispersion and can apply a strong shearing force. More preferably, a wet high-pressure or ultrahigh-pressure homogenizer that can apply a pressure of 10 MPa to 400 MPa and a strong shear force to the chemically modified cellulose dispersion is preferably used. By this treatment, the chemically modified cellulose is defibrated to form cellulose nanofibers, and the cellulose nanofibers are dispersed in the medium to produce a cellulose nanofiber dispersion. In addition, it is preferable to use water as a medium from the ease of handling.
<Measuring method of average fiber length and average fiber width>
The average fiber length and average fiber width of the cellulose nanofiber can be measured by observing the cellulose nanofiber using an atomic force microscope (AFM).

Next, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples.

[Example 1]
(Pulp raw material adjustment: oxidized pulp)
Bleached unbeaten pulp (Nippon Paper Co., Ltd.) 5 g (absolutely dried) derived from coniferous trees, TEMPO (Tokyo Kasei Co., Ltd.) 78 mg (0.5 mmol) and sodium bromide (Wako Pure Chemical Industries, Ltd.) 756 mg (7.35 mmol) ) Was dissolved in 500 mL of the dissolved aqueous solution and stirred until the pulp was uniformly dispersed. To this, 2.3 mmol of sodium hypochlorite (manufactured by Wako Pure Chemical Industries, Ltd.) was added in the form of an aqueous solution, and then a liquid feed pump was added so that sodium hypochlorite was added at a rate of 0.23 mmol / min per gram of pulp. Was added gradually to oxidize the pulp. The addition was continued until the total amount of sodium hypochlorite added was 22.5 mmol. During the reaction, the pH in the system was lowered, but a 3N sodium hydroxide aqueous solution was successively added to adjust the pH to 10. From the start of the addition of the aqueous sodium hydroxide solution (that is, from the time when the oxidation reaction is started and a decrease in pH is observed) until the addition is completed (that is, the oxidation reaction is completed and no decrease in pH is observed) The reaction time was taken as the reaction time. The reaction solution was neutralized with hydrochloric acid until neutral, and then the reaction solution was filtered through a glass filter and sufficiently washed with water to obtain an oxidized pulp.

(Measurement of carboxyl group content of oxidized pulp)
The carboxyl group amount of oxidized pulp was measured by the following method. Prepare 60 mL of 0.5% by mass slurry of oxidized pulp, add 0.1 M hydrochloric acid aqueous solution to pH 2.5, then add 0.05 N aqueous sodium hydroxide solution dropwise until the pH reaches 11 Was calculated from the amount (a) of sodium hydroxide consumed in the neutralization step of the weak acid where the change in electrical conductivity was gradual, using the following equation.
Amount of carboxyl group [mmol / g oxidized pulp]
= A [mL] x 0.05 / oxidized pulp mass [g]
As a result of this measurement, the carboxyl group content of the obtained oxidized pulp was 1.60 mmol / g.

(Preliminary defibration of oxidized pulp)
The slurry of oxidized pulp that had undergone the above oxidation treatment was subjected to a preliminary defibration treatment using a single disk type refiner made by Aikawa Tekko. As the refiner, a fine bar type plate was used, and the shape of the plate blade was a blade width of 0.8 mm, a groove width of 1.5 mm, a blade length of 90 mm, a blade angle of 15 °, and a plate clearance of 0.1 mm. The processing speed of the preliminary defibrating by the refiner is 1 m ³ / hr, the raw material concentration of the oxidized pulp slurry used for the preliminary defibrating processing is 3% (w / v), and the peripheral speed of the refiner plate is 40.2 m / s. The rotational shear rate of the plate was 402.0 (1 / ms), and the number of refiner passes was 1. As a result, the preliminary defibrating treatment could be operated without any problems. The power consumption of preliminary defibration was 0.76 kWh / kg.

(This defibration of oxidized pulp)
The pulp slurry subjected to the preliminary defibrating treatment was treated with an ultrahigh pressure homogenizer at a concentration of 3% (w / v) at a treatment pressure of 140 MPa. As a result, the defibrating treatment could be operated without any problems. The power consumption at this time was 1.8 kWh / kg. Further, the obtained cellulose nanofiber dispersion was diluted to 1% (w / v) and then defoamed with an ultrasonic device to obtain a wavelength of 660 nm of an ultraviolet-visible spectrophotometer (UV-1800, manufactured by Shimadzu Corporation). The transmittance (%) measured in this manner, that is, the transparency was 71.0%.

[Example 2]
Among the experimental conditions of Example 1, the plate is a dam formed on the outer periphery of a fine bar type plate, and the shape of the plate blade is a blade width of 0.8 mm, a groove width of 1.0 mm, a blade length of 80 mm, The experiment was performed under the same conditions as those of Example 1 except that the blade angle was changed to 15 ° and the treatment speed was changed to 3 m ³ / hr. In this case, both the preliminary defibration and the main defibration processes could be operated without any problems. The power consumption of preliminary defibration was 0.17 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. The transparency of the obtained cellulose nanofiber dispersion was 44.5%.

[Example 3]
Of the experimental conditions of Example 1, the experiment was performed under the same conditions as those of Example 1 except that the plate was changed to a grindstone plate (no blade) and the processing speed was changed to 3 m ³ / hr. In this case, both the preliminary defibration and the main defibration processes could be operated without any problems. The power consumption of preliminary defibration was 0.18 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. Moreover, the transparency of the obtained cellulose nanofiber dispersion was 44.1%.

[Example 4]
Of the experimental conditions of Example 1, the plate is a viscous beating plate, and the shape of the plate blade is a blade width of 4.5 mm, a groove width of 3.5-4.5 mm, a blade length of 95 mm, and a blade angle of 10 °. The plate clearance is 0.13 mm, the processing speed is 19.2 m ³ / hr, the plate peripheral speed is 24.6 m / s, the rotational shear rate of the plate is 189.2 (1 / ms), by the refiner The experiment was performed under the same conditions as in Example 1 except that the number of treatments was set to 3. In this case, both the preliminary defibration and the main defibration processes could be operated without any problems. The power consumption of preliminary defibration was 0.03 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. Moreover, the transparency of the obtained cellulose nanofiber dispersion was 52.3%.

[Example 5]
Of the experimental conditions of Example 1, the plate is of the dam type (3-stage dam), and the shape of the plate blade is 4.0 mm blade width, 4.0 mm groove width, 75-85 mm blade length, and 0 ° blade angle. The processing speed was 9.0 m ³ / hr, the peripheral speed of the plate was 24.6 m / s, the rotational shear rate of the plate was 246.0 (1 / ms), and the number of processing by the refiner was 2. The experiment was performed under the same conditions as in Example 1 except for the above. In this case, both the preliminary defibration and the main defibration processes could be operated without any problems. The power consumption of preliminary defibration was 0.05 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. Moreover, the transparency of the obtained cellulose nanofiber dispersion was 51.6%.

[Example 6]
Among the experimental conditions of Example 1, the experiment was performed under the same conditions as those of Example 1 except that the raw material concentration was changed to 5 percent. As a result, it was possible to operate without problems in both the preliminary defibrating process and the main defibrating process. The power consumption of preliminary defibration was 0.65 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. Moreover, the transparency of the obtained cellulose nanofiber dispersion was 69.0%.

[Example 7]
Among the experimental conditions of Example 1, the experiment was performed under the same conditions as those of Example 1 except that the treatment speed was changed to ³ m ³ / hr. In this case, both the preliminary defibration and the main defibration processes could be operated without any problems. The power consumption of preliminary defibration was 0.25 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. Moreover, the transparency of the obtained cellulose nanofiber dispersion was 54.6%.

[Example 8]
Of the experimental conditions of Example 1, the experiment was performed under the same conditions as those of Example 1 except that the treatment speed was changed to 3 m ³ / hr and the raw material concentration was changed to 5%. In this case, both the preliminary defibration and the main defibration processes could be operated without any problems. The power consumption of preliminary defibration was 0.28 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. Moreover, the transparency of the obtained cellulose nanofiber dispersion was 63.3%.

[Example 9]
Of the experimental conditions of Example 1, the experiment was performed under the same conditions as those of Example 1 except that the treatment speed was changed to 9 m ³ / hr. In this case, both the preliminary defibration and the main defibration processes could be operated without any problems. The power consumption of preliminary defibration was 0.07 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. Moreover, the transparency of the obtained cellulose nanofiber dispersion was 52.7%.

[Example 10]
Of the experimental conditions of Example 1, the experiment was performed under the same conditions as those of Example 1 except that the treatment speed was changed to 9 m ³ / hr and the raw material concentration was changed to 5%. In this case, both the preliminary defibration and the main defibration processes could be operated without any problems. The power consumption of preliminary defibration was 0.08 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. Moreover, the transparency of the obtained cellulose nanofiber dispersion was 63.5%.

[Example 11]
Of the experimental conditions of Example 1, the processing speed was 15 m ³ / hr, the plate peripheral speed was 24.6 m / s, the rotational shear rate of the plate was 246.0 (1 / ms), and the number of processing by the refiner was 3. The experiment was performed under the same conditions as in Example 1 except that. In this case, both the preliminary defibration and the main defibration processes could be operated without any problems. The power consumption of preliminary defibration was 0.03 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. Moreover, the transparency of the obtained cellulose nanofiber dispersion was 57.3%.

[Example 12]
Of the experimental conditions of Example 1, the plate clearance was 0.08 mm, the processing speed was 23.4 m ³ / hr, the plate peripheral speed was 30.7 m / s, and the rotational shear rate of the plate was 383.8 (1 / ms). The experiment was performed under the same conditions as in Example 1 except that the number of treatments by the refiner was set to 8. In this case, both the preliminary defibration and the main defibration processes could be operated without any problems. The power consumption of preliminary defibration was 0.03 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. Moreover, the transparency of the obtained cellulose nanofiber dispersion was 63.3%.

[Example 13]
Among the experimental conditions of Example 1, the experiment was performed under the same conditions as those of Example 1 except that the raw material concentration was changed to 7%. In this case, both the preliminary defibration and the main defibration processes could be operated without any problems. The power consumption of preliminary defibration was 0.45 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. Moreover, the transparency of the obtained cellulose nanofiber dispersion was 70.0%.

[Example 14]
Of the experimental conditions of Example 1, the processing speed was 3 m ³ / hr, the plate peripheral speed was 55.8 m / s, and the rotational shear rate of the plate was changed to 558.0 (1 / ms). The experiment was performed under the same conditions as the experimental conditions. In this case, both the preliminary defibration and the main defibration processes could be operated without any problems. The power consumption of preliminary defibration was 0.57 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. Moreover, the transparency of the obtained cellulose nanofiber dispersion was 67.3%.

[Example 15]
Of the experimental conditions of Example 1, the experiment was performed under the same conditions as those of Example 1 except that the treatment speed was 9 m ³ / hr, the raw material concentration was 10%, and the number of treatments by the refiner was 3. In this case, both the preliminary defibration and the main defibration processes could be operated without any problems. The power consumption of preliminary defibration was 0.12 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. Moreover, the transparency of the obtained cellulose nanofiber dispersion was 60.2%.

[Example 16]
Of the experimental conditions of Example 1, the plate clearance was 0.22 mm, the processing speed was 11.6 m ³ / hr, the raw material concentration was 5%, the plate peripheral speed was 30.7 m / s, and the rotational shear rate of the plate was 139. The experiment was performed under the same conditions as those of Example 1 except that 5 (1 / ms) and the number of treatments by the refiner were set to 4. In this case, both the preliminary defibration and the main defibration processes could be operated without any problems. The power consumption of preliminary defibration was 0.29 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. Moreover, the transparency of the obtained cellulose nanofiber dispersion was 68.0%.

Table 1 shows refiner conditions, power consumption, and experimental results of Examples 1 to 16.

[Comparative Example 1]
The preliminary defibrating treatment was not performed, and the treatment with the ultrahigh pressure homogenizer of this defibration was performed once at a treatment pressure of 140 MPa. As a result, in the defibrating process, clogging occurred in the dispersion nozzle. The power consumption of this defibration was 1.8 kWh / kg. Moreover, the transparency of the obtained cellulose nanofiber dispersion was 30.0%.

[Comparative Example 2]
As a refiner plate, a cut type plate with a blade width of 2.2 mm, a groove width of 3.8 to 4.8 mm, a blade length of 95 mm, and a blade angle of 0 ° is used as the refiner plate, and the plate clearance is set to 0.1 mm. An attempt was made to defibrate, but a metal touch occurred and preliminary defibration was not possible.

[Comparative Example 3]
Of the experimental conditions of Example 1, the experiment was performed under the same conditions as those of Example 1 except that the treatment speed was 40 m ³ / hr and the number of treatments by the refiner was 3. In this case, both the preliminary defibration and the main defibration processes could be operated without any problems. The power consumption of preliminary defibration was 0.07 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. Moreover, the transparency of the obtained cellulose nanofiber dispersion was 33%, which was low.

[Comparative Example 4]
Among the experimental conditions of Example 1, the preliminary defibration was performed under the same conditions as the experimental conditions of Example 1 except that the raw material concentration was 16% and the number of treatments by the refiner was 3, but the viscosity of the sample was high. The operability was poor and the preliminary defibration was not possible.

[Comparative Example 5]
Of the experimental conditions of Example 1, the plate peripheral speed is 15 m / s, the rotational shear rate of the plate is 150.0 (1 / ms), and the number of treatments by the refiner is 3, and the same as the experimental conditions of Example 1. The experiment was conducted under conditions. In this case, both the preliminary defibration and the main defibration processes could be operated without any problems. The power consumption of preliminary defibration was 1.8 kWh / kg, and the power consumption of this defibration was 1.8 kWh / kg. Further, the transparency of the obtained cellulose nanofiber dispersion was 35.2%, which was low.

Table 2 shows the refiner conditions, power consumption, and experimental results of Comparative Examples 1 to 5.

In Examples 1 to 16, high-quality cellulose nanofiber dispersions with low power consumption and high transparency could be produced. Further, the operability of the preliminary defibration and the main defibration was good, and the clogging of the dispersion nozzle did not occur. Furthermore, the number of preliminary defibration and the number of passes of ultrahigh pressure homo may be appropriately adjusted according to the required transparency.

On the other hand, in Comparative Example 1, clogging occurred in the dispersion nozzle in this defibrating process, resulting in poor operability. Further, the transparency of the obtained cellulose nanofiber dispersion was lower than that of Examples 1 to 16. In Comparative Example 2, a metal touch occurred and preliminary defibration could not be performed. In Comparative Example 3, the transparency of the obtained cellulose nanofiber dispersion was lower than that in Examples 1-16. In Comparative Example 4, the viscosity of the sample was too high, the operability was poor, and preliminary defibration could not be performed. In Comparative Example 5, the transparency of the obtained cellulose nanofiber dispersion was lower than that in Examples 1-16.

Claims

The manufacturing method of the cellulose nanofiber dispersion which manufactures a highly transparent cellulose nanofiber dispersion liquid from the chemically modified cellulose characterized by having the process of following (A) and (B).
Step (A): preliminary defibrating step of beating the chemically modified cellulose using a single disc type refiner,
Step (B): This defibrating step of defibrating the cellulose obtained in the preliminary defibrating step (A) by treatment with a high-pressure disperser at a treatment pressure of 1 MPa to 400 MPa.
In the preliminary defibrating step (A), the plate used in the refiner is a viscous beating plate, a fine bar type plate, a plate having a structure for closing the raw material flow path, a grindstone plate, a flat metal plate without grooves. It is either, The manufacturing method of the cellulose nanofiber dispersion liquid of Claim 1 characterized by the above-mentioned.
The method for producing a cellulose nanofiber dispersion according to claim 1 or 2, wherein, in the preliminary defibrating step (A), a processing rate of the chemically modified cellulose is 30 m 3 / hr or less.
The cellulose nanoparticle according to any one of claims 1 to 3, wherein, in the preliminary defibrating step (A), a concentration of the chemically modified cellulose during treatment is 2.5 to 15% by mass. A method for producing a fiber dispersion.
The method for producing a cellulose nanofiber dispersion according to any one of claims 2 to 4, wherein, in the preliminary defibrating step (A), the clearance of the plate is 0.01 to 0.4 mm. .
6. The method for producing a cellulose nanofiber dispersion according to claim 2, wherein in the preliminary defibrating step (A), the peripheral speed of the plate is 24.5 m / s or more. .
The cellulose nanofiber dispersion according to any one of claims 2 to 6, wherein, in the preliminary defibrating step (A), a shear rate of rotation of the plate is 100 (1 / ms) or more. Manufacturing method.