WO2017057710A1

WO2017057710A1 - Cellulose nanofiber dispersion liquid and method for producing same

Info

Publication number: WO2017057710A1
Application number: PCT/JP2016/079089
Authority: WO
Inventors: 利一村松; 健嗣藤井; 金野　晴男; 伸治佐藤
Original assignee: 日本製紙株式会社
Priority date: 2015-09-30
Filing date: 2016-09-30
Publication date: 2017-04-06
Also published as: JP7033920B2; JPWO2017057710A1

Abstract

Provided is a method for efficiently producing a highly transparent cellulose nanofiber with a small power consumption level. The present invention pertains to a method for producing a cellulose nanofiber dispersion liquid having an average fiber width of 3-100 nm, the method comprising: a preliminary fibrillation step (A) for beating a raw material pulp until the type-B viscosity of a pulp slurry containing the raw material pulp at a concentration of 3% (v/w) in water, serving as a dispersion medium, becomes 50 mPa·s or higher; and a true fibrillation step (B) for fibrillating the pulp obtained at the preliminary fibrillation step (A) until the fiber width becomes 3-100 nm.

Description

Cellulose nanofiber dispersion and method for producing the same

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

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. Therefore, it is expected to be applied to applications requiring transparency, for example, optical films, film coating agents, compounding into glass, and the like. For this reason, various studies have been made on methods for producing cellulose nanofibers (Patent Document 1).

JP 2008-001728 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.

Therefore, an object of the present invention is to provide a method for efficiently producing highly transparent cellulose nanofibers with low power consumption.

Means for solving the problems are as follows.
[1] A method for producing a cellulose nanofiber dispersion having an average fiber width of 3 to 100 nm, comprising the following steps (A) to (B):
Step (A): Pre-defibration step of beating the raw material pulp until the B-type viscosity becomes 50 mPa · s or more when the concentration is 3% (v / w) pulp slurry using water as a dispersion medium. B): Main defibrating step of defibrating the pulp obtained in the preliminary defibrating step (A) until the fiber width becomes 3 to 100 nm [2] The pulp filter obtained in the preliminary defibrating step (A) The method for producing a cellulose nanofiber dispersion according to [1], wherein the water degree is 1 to 30 ml and the average fiber diameter is 30 to 1000 nm.
[3] The method for producing a cellulose nanofiber dispersion according to [1] or [2], wherein the mechanical beating process uses at least one defibrating apparatus selected from a refiner, a beater, or a disaggregator.
[4] The production of the cellulose nanofiber dispersion according to any one of [1] to [3], wherein the beating treatment uses at least one beating apparatus selected from a refiner, a beater, or a disaggregator. Method.
[5] The method for producing a cellulose nanofiber dispersion according to any one of [1] to [4], wherein the raw pulp is a chemically modified pulp.
[6] A cellulose nanofiber dispersion obtained by the production method according to any one of [1] to [5].

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

In the method for producing a cellulose nanofiber dispersion of the present invention, the B-type viscosity is 50 mPa · s or more in the step (A): a pulp slurry having a concentration of 3% (v / w) using water as a dispersion medium. A preliminary defibrating step in which the raw pulp is beaten, and step (B): a main defibrating step in which the pulp obtained in the preliminary defibrating step (A) is defibrated to an average fiber width of 3 to 100 nm, It is characterized by having. In the present invention, “X to Y” includes X and Y which are their end values.

In the present invention, cellulose fiber is defibrated by different mechanisms by combining preliminary defibration by mechanical beating processing using a conventional mechanical beating device and this defibration, thereby reducing power consumption. However, highly transparent cellulose nanofibers can be produced.

The reason why a highly transparent cellulose nanofiber can be obtained by the present invention is presumed as follows. In the preliminary defibration, in the preliminary defibration process, the pulp as a raw material is first refined and the outside of the pulp fiber is loosened, so that a slight increase in viscosity occurs. When using a device with a relatively high shearing force, such as an ultra-high pressure homogenizer, during the subsequent final defibration, the viscosity increases due to preliminary defibration and acts on the pulp without losing the shear energy from the defibrator. Since this defibration can be performed, highly transparent cellulose nanofibers can be produced efficiently.

(1) Pulp raw materials In the present invention, the pulp raw materials include bleached or unbleached wood pulp, bleached or unbleached non-wood pulp, refined linters, jute, Manila hemp, pulp derived from herbs such as kenaf, and the above pulp raw materials. 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.

(2) Chemical modification treatment By subjecting the above cellulose raw material to chemical treatment, it is preferable that the load in the present defibrating step (B) for defibrating until the average fiber width becomes 3 to 100 nm is reduced. Further, the chemical modification treatment method is not limited, but examples thereof include oxidation, etherification, cationization, and esterification.

(2-1) Oxidation By oxidizing the above cellulose raw material in water using an oxidant in the presence of an N-oxyl compound and a compound selected from the group consisting of bromide, iodide or a mixture thereof. Oxidized cellulose having a carboxyl group introduced into cellulose can be obtained. Another method includes ozone oxidation.

The 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 catalyst amount capable of turning 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, 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 from 0.1 to 100 mmol, more preferably from 0.1 to 10 mmol, and even more preferably from 0.5 to 5 mmol, based on 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 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 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 the oxidation, and is usually 0.5 to 6 hours, preferably 2 to 6 hours, and 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.

Moreover, the oxidizing agent used for the oxidation reaction may be added at once or may be added sequentially. Sequential addition can efficiently introduce carboxyl groups into the cellulose raw material and promote the oxidation of the cellulose raw material. Although the end of the oxidation reaction can be confirmed by the disappearance of the color of the oxidizing agent, the reaction may be stopped by decomposing the oxidizing agent with sodium thiosulfate or the like. After completion of the oxidation reaction, the liquid removal treatment may be carried out as it is. However, it is desirable to carry out the liquid removal after neutralization with hydrochloric acid or the like because the oxidized cellulose is likely to be decomposed at a high pH.

The conditions are preferably set so that the carboxyl group amount of oxidized cellulose is 0.2 mmol / g or more based on 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.

The amount of carboxyl groups in the oxidized cellulose can be measured by the following procedure:
Prepare 60 ml of 0.5% by mass slurry of oxidized cellulose, 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. Is calculated from the amount of sodium hydroxide (a) consumed in the neutralization step of the weak acid with a gradual change in electrical conductivity, using the following formula:
Carboxyl group amount [mmol / g oxidized cellulose] = a [ml] × 0.05 / oxidized cellulose mass [g].

(2-2) Etherification Examples of the etherified product of cellulose include carboxymethylcellulose, methylcellulose, ethylcellulose, cyanoethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, ethylhydroxyethylcellulose, hydroxypropylmethylcellulose, and salts thereof. As follows, a method for producing carboxymethylation will be described.

<Carboxymethylation>
The above cellulose raw material is used as a bottoming raw material, and 3 to 20 times by weight of lower alcohol as a solvent, specifically methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, tertiary butanol, etc. A single or a mixture medium of two or more kinds and water is 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 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.

In the present invention, when the cellulose raw material is carboxymethylated, it is preferable that the degree of carboxymethyl substitution per glucose unit in the cellulose is 0.01 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 0.01, sufficient nano-fibrosis cannot be 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.

The carboxymethyl substitution degree can be measured by the following method.

About 2.0 g of sample is precisely weighed and placed in a 300 ml stoppered Erlenmeyer flask. Add 100 ml of methanol nitric acid (1 ml of anhydrous methanol plus 100 ml of concentrated concentrated nitric acid) and shake for 3 hours to convert sodium carboxymethylcellulose (Na-CMC) to carboxymethylcellulose (H-CMC). Weigh out 1.5-2.0 g of the absolutely dry H-CMC and place in a 300 ml stoppered Erlenmeyer flask. Wet H-CMC with 15 ml of 80% methanol, add 100 ml of 0.1N NaOH, and shake at room temperature for 3 hours. Excess NaOH is back titrated with 0.1 N H ₂ SO ₄ using phenolphthalein as an indicator. The following formula:
[{100 × F ′-(0.1N H ₂ SO ₄ (ml)) × F} / (absolute dry mass of H-CMC (g))] × 0.1 = A carboxyl methyl substitution degree = 0. 162A / (1-0.058A)
A: Amount of 1N NaOH required to neutralize 1 g H-CMC (ml)
F ′: Factor of 0.1N H ₂ SO ₄ F: Factor of 0.1N NaOH

(2-3) Cationization In the present invention, the cationization of the cellulose raw material can be performed using a known method, and is not particularly limited. As an example, glycidyltrimethylammonium chloride, 3-chloro-2 A cationizing agent such as hydroxypropyltrialkylammonium hydride or its halohydrin type and 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. By reacting, cation-modified 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.

In the present invention, the cation substitution degree per unit of glucose of the cationized cellulose is preferably 0.012 to 0.450. 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 0.012, nano-fibrosis cannot be sufficiently performed. On the other hand, if the degree of cation substitution per glucose unit is larger than 0.450, the fiber form cannot be maintained because it swells or dissolves, and may not be obtained as a nanofiber.

(2-4) Esterification Examples of esterification include thioesterification, phosphate esterification, sulfate esterification, nitrate esterification, and carbonate esterification.

In the present invention, the mechanical beating treatment is a general process such as refiner, beater, PFI mill, kneader, disperser, or the like that causes a metal or blade and pulp fibers to act around the rotation axis, or that is caused by friction between pulp fibers. Devices known in the art can be used.

In the present invention, a known device can be used as the refiner. For example, a single disc refiner, a conical disc refiner, a double disc refiner, a twin disc refiner, or the like can be used.

In the present invention, the beater is a device in which the raw material is drawn between the rotor and the stator by the rotation of the rotor and is struck by both blades to circulate in the circulation tank, and a known device can be used.

In the present invention, the PFI mill can use an apparatus defined in JIS P 8221.

In the present invention, a kneader or a disperser is a mechanical stirring device designed to give a compressive force to pulp or to receive moderate friction between fibers, and has a uniaxial or biaxial structure, and a rotor blade There is moderate biting between the stator blades, and sufficient shearing force is applied to the fibers even at low speed rotation, so that a known apparatus can be used.

(3) Preliminary fiber removal: Process (A)
In the present invention, it is important to perform preliminary defibration and beating the above-described raw material pulp. In the beating, when the treated pulp is dispersed in water to obtain a pulp slurry having a concentration of 3% (w / v), the B-type viscosity is 50 mPa · s or more, preferably 1000 mPa · s or more, more preferably 2000 mPa · s. Do as above. Since the raw pulp is beaten to the extent that it exhibits the B-type viscosity by the preliminary defibrating, the load in the next defibrating step can be greatly reduced. The upper limit of the B-type viscosity is not limited, but is preferably 100,000 mPa · s or less from the viewpoint of workability and the like.

The apparatus used for the beating process used in the preliminary defibration is not particularly limited, but when at least one beating apparatus selected from a refiner, a beater, or a disaggregator is used, the outer layer of the pulp fiber is loosened or the fibrils inside This is preferable because nanofibers can be easily obtained in this defibrating step and the load is reduced.

The pulp concentration in the preliminary defibrating step (A) is 0.5% (w / v) to 10% (w / v), more preferably 1% (w / v) to 5% (w / v). . If the concentration is lower than 0.5% (w / v), the concentration of the dispersion is too low and not efficient, and if it exceeds 10% (w / v), the viscosity becomes too high and the efficiency is not high.

When using a refiner in the preliminary defibrating step (A), the plate clearance is 0.01 mm to 3 mm, more preferably 0.1 mm to 1 mm. If it is 0.01 mm or less, the plate will be abruptly worn, and if it is 3 mm or more, the clearance will be too wide to proceed the process.

In the preliminary defibrating step (A), when a refiner is used, a general plate can be used without any problem, but a plate suitable for viscous beating is preferred.

In this step, the raw material pulp is subjected to a beating process so that the B-type viscosity is 50 mPa · s or more when the pulp slurry has a concentration of 3% (v / w) using water as a dispersion medium. As the pulp beating progresses, the viscosity of the pulp slurry increases, and the viscosity is a measure of the beating state of the pulp. The B type viscosity is measured at a rotation speed of 60 rpm and a temperature of 25 ° C. by selecting a rotor suitable for the viscosity. When the concentration of the pulp slurry obtained in the step (A) exceeds 3% (w / v), the viscosity is measured after dilution with water to adjust the concentration to 3% (w / v). On the other hand, when the concentration of the pulp slurry obtained in the step (A) is less than 3% (w / v), the viscosity is measured after removing with water and adjusting the concentration to 3% (w / v). . Alternatively, the pulp subjected to the beating treatment may be once isolated and then redispersed in water to prepare a slurry having a concentration of 3% (w / v), and the viscosity may be measured. However, when redispersed in water, it is necessary to prevent the actual defibration performed in the step (B) from occurring.

(4) Main defibration: Process (B)
In the present invention, this defibration refers to applying a strong shearing force to the pulp obtained by preliminary defibration using a high-speed rotation type, a colloid mill type, a high pressure type, a roll mill type, an ultrasonic type, or the like. This means that the fiber is defibrated to an average fiber width of 3 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 50 MPa or more to the dispersion and can apply a strong shearing force. The pressure is more preferably 100 MPa or more, and further preferably 140 MPa or more. By this treatment, the oxidized pulp is defibrated to form cellulose nanofibers, and the cellulose nanofibers are dispersed in the medium. As the medium, water is preferably used from the viewpoint of easy handling.

The cellulose nanofiber of the present invention preferably has an average fiber length of about 0.1 to 5 μm, and more preferably about 0.5 to 5 μm. The fiber length can be adjusted in the step (B), or the fiber length may be adjusted by providing another step.

<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 content of oxidized pulp was measured by the following method:
Prepare 60 ml of 0.5% by weight 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 is 11 Was calculated from the amount of sodium hydroxide (a) consumed in the neutralization step of the weak acid with a gradual change in electrical conductivity using the following formula:
Amount of carboxyl group [mmol / g oxidized pulp] = a [ml] × 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 having a concentration of 3% (w / v) that had undergone the above oxidation treatment was subjected to beating treatment with Niagara Beata (manufactured by Kumagaya Riki Kogyo Co., Ltd.). In addition, the power consumption per 1 kg of pulp in this beating process was 0.5 Kwh. Moreover, B type viscosity was 2000 mPa * s on the conditions of 25 degreeC and 60 rpm of the obtained pulp slurry (concentration 3% (w / v)).
Moreover, the freeness of the obtained pulp slurry was 10 mL.

(This defibration of oxidized pulp)
After the pulp slurry subjected to the preliminary defibrating treatment was diluted to a concentration of 1% (w / v), the treatment with an ultrahigh pressure homogenizer was performed at a treatment pressure of 140 MPa. The power consumption of 1 kg of pulp at this time was 7.5 Kwh. The clogging of the dispersion nozzle did not occur. Further, after defoaming the obtained cellulose nanofiber dispersion with an ultrasonic device, the transparency (%) measured at a wavelength of 660 nm of an ultraviolet-visible spectrophotometer (UV-1800, manufactured by Shimadzu Corporation) is used as the transparency. Was 60%. Moreover, when the obtained cellulose dispersion was observed using an atomic force microscope (AFM), the average fiber length of 50 randomly selected fibers was 2 μm, and the average fiber width was 10 nm.

[Example 2]
Cellulose nanofibers were produced in the same manner as in Example 1 except that the preliminary defibration was changed to a refiner (manufactured by Kumagai Riki Kogyo Co., Ltd.) and two-pass treatment was performed. The power consumption per 1 kg of pulp in this beating treatment was 0.5 Kwh, and the B-type viscosity of the obtained pulp slurry (concentration 3% (w / v)) was 2900 mPa · s. The freeness was 3 mL. Moreover, the transparency after this defibration was 58%, the average fiber length was 1.9 μm, and the average fiber width was 5 nm. The clogging of the dispersion nozzle did not occur.

[Example 3]
Cellulose nanofibers were produced in the same manner as in Example 1, except that the preliminary defibration was changed to a refiner 1-pass treatment. The power consumption per 1 kg of pulp in this beating treatment was 0.3 Kwh, and the B-type viscosity of the obtained pulp slurry (concentration 3% (w / v)) was 1500 mPa · s. The freeness was 25 mL. Further, the transparency of this defibration was 55%, the average fiber length was 2 μm, and the average fiber width was 10 nm. The clogging of the dispersion nozzle did not occur.

[Comparative Example 1]
Only preliminary defibration was carried out in the same manner as in Example 1 except that only the actual defibration was processed using an ultra-high pressure homogenizer so that the power consumption of 1 kg of pulp was 8.0 Kwh. As a result, the B-type viscosity of the pulp slurry (concentration 3% (w / v)) before this defibration was 40 mPa · s. The freeness was 500 mL. The transparency after this defibration was 34%, the average fiber length was 3 μm, the average fiber width was 110 nm, and the clogging of the dispersion nozzle occurred 5 times.

Compared with Comparative Example 1, in Examples 1 to 3, high-quality cellulose nanofibers with high transparency could be produced. Moreover, the operability of this defibration was good, and the clogging of the dispersion nozzle did not occur.

Table 1 shows the measurement results of power consumption and transparency of the nanofibers obtained in Examples 1 to 3 and Comparative Example 1.

From Table 1, the total power consumption required for preliminary defibration and this defibration is the same in Examples 1 to 3 and Comparative Example 1, and in Examples 1 to 3, cellulose cellulose nanometers with high efficiency and high brightness are obtained. It can be seen that fibers can be produced.

Further, in Comparative Example 1, it can be seen that the nozzle of the defibrating machine is clogged during the defibrating, so that the operability is inferior.

Claims

A method for producing a cellulose nanofiber dispersion having an average fiber width of 3 to 100 nm, comprising the following steps (A) to (B):
Step (A): Pre-defibration step of beating the raw material pulp until the B-type viscosity becomes 50 mPa · s or more when the concentration is 3% (v / w) pulp slurry using water as a dispersion medium. B): This defibrating step of defibrating the pulp obtained in the preliminary defibrating step (A) until the fiber width becomes 3 to 100 nm.
2. The method for producing a cellulose nanofiber dispersion according to claim 1, wherein the pulp obtained in the preliminary defibrating step (A) has a freeness of 1 to 30 ml and an average fiber diameter of 30 to 1000 nm.
The method for producing a cellulose nanofiber dispersion according to claim 1 or 2, wherein the beating process uses at least one defibrating device selected from a refiner, a beater, or a disaggregator.
The method for producing a cellulose nanofiber dispersion according to any one of claims 1 to 3, wherein the beating process uses at least one beating apparatus selected from a refiner, a beater, or a disaggregator.
The method for producing a cellulose nanofiber dispersion according to any one of claims 1 to 4, wherein the raw material pulp is a chemically modified pulp.
A cellulose nanofiber dispersion obtained by the production method according to any one of claims 1 to 5.