JP2016061002A - Cellulose nanofiber production process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cellulose nanofiber production process that improves the yield when producing cellulose nanofibers from cellulose material, and can produce cellulose nanofibers efficiently.SOLUTION: The cellulose nanofiber production process according to the present invention is characterized to include a treatment step for swelling-treating a cellulose material, and a treatment step for applying ultrasound to the cellulose material which has undergone the swelling-treatment step, to fibrillate the cellulose fiber. As a swelling-treatment of the cellulose material, a process in which Swollenin acts on the cellulose material, is effective.SELECTED DRAWING: Figure 2

Description

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

  Cellulose nanofibers are ultrafine fibrous materials obtained by fibrillating naturally occurring cellulose fibers to a size having an average width of about several to 100 nm and an average length of about 0.5 to several μm. Cellulose nanofibers are extremely lightweight and at the same time have a strength more than five times that of steel, and the development of utilization technology is being promoted as a natural renewable material obtained from plant cell walls.

Currently, cellulose nanofibers are produced by applying an enzyme agent containing cellulase to cellulose to partially fragment the cellulose fibers and then subjecting them to fibrillation with a blender or grinder.
As an example of using ultrasonic waves for the production of cellulose nanofibers, ultrasonic treatment is performed before enzymatic treatment of cellulose raw materials to facilitate the penetration of enzymes into highly crystalline cellulose raw materials (Patent Document 1), preliminary By applying ultrasonic waves to the defibrated fiber raw material to make fine fibers, a method of causing an enzyme to act (Patent Document 2), natural biomass such as pineapple and sugarcane bagasse, by enzymatic treatment and ultrasonic treatment There are methods for preparing nanofibers (Non-Patent Document 1) and the like.

JP 2008-150719 A JP 2008-169497 A

Adriana de Campos, Ana Carolina Correa, David Cannella, Eliangela de M Teixeira, Jose M. Marconcini, Alain Dufresne, Luiz HC Mattoso, Pierre Cassland, Anand R. ”Cellulose, 20, 1491-1500 (2013)

  In the method of producing cellulose nanofibers by causing the enzyme described above to act on cellulose raw materials, there is a problem that the yield of cellulose nanofibers is lowered because cellulose is decomposed to glucose or cellooligosaccharide, which is its constituent monosaccharide. . This is because natural cellulose fibers have a structure with very high crystallinity in which bundles of cellulose are associated, and when enzymes are allowed to act on cellulose fibers, the cellulose fibers are decomposed from the outside and the amount of nanofibers is reduced. . In addition, the enzyme is unlikely to act on the portion where the cellulose fiber crystallinity is high, and even if the enzyme is reacted, the original cellulose fiber remains, and it is difficult to obtain cellulose nanofiber, so the yield of cellulose nanofiber is reduced. There was also a problem.

  An object of this invention is to provide the manufacturing method of the cellulose nanofiber which can improve the yield at the time of manufacturing a cellulose nanofiber from a cellulose material, and can manufacture a cellulose nanofiber efficiently.

The method for producing cellulose nanofibers according to the present invention comprises a treatment step of swelling a cellulose material, and a treatment step of defibrating cellulose fibers by applying ultrasonic waves to the cellulose material that has undergone the swelling treatment step. Features.
The method for producing cellulose nanofibers according to the present invention is a method for obtaining cellulose fibers by swelling cellulose materials in advance and then applying ultrasonic waves as a method for obtaining cellulose nanofibers by defibrating cellulose materials. As a result, they were found to be extremely effective.

The swelling treatment performed as a pretreatment for applying ultrasonic waves to the cellulose material is a treatment that promotes the action of defibrating the cellulose material by ultrasonic treatment, and decomposes the cellulose material such as enzyme treatment into glucose, cellooligosaccharide, etc. It means not an action but an action of weakening the binding of cellulose fibers while maintaining the fiber form of the cellulose fibers.
By swelling the cellulose material, water molecules enter from the site where the crystallinity of the cellulose fiber has been loosened during the ultrasonic treatment, and the ultrasonic wave can be efficiently operated and separated into cellulose nanofibers.

Swollenin known as cellulose swelling protein can be preferably used for the swelling treatment of the cellulose material. Swollenin penetrates between highly crystalline cellulose fibers and has the effect of breaking or loosening hydrogen bonds. Swollenin can be easily cultured using a known genetic recombination method, and can be used by adjusting the amount of Swollenin according to the amount of cellulose material treated.
The swelling treatment of the cellulose material can be performed by a method of immersing in a buffer solution adjusted to pH 5.0 to pH 6.0. This is because when the pH is 5.0 or lower and 6.0 or higher, the stability of Swollenin decreases.

  When the cellulose material is swollen as a swelling treatment of the cellulose material, the cellulose fiber crystal structure has a (002) crystal plane characteristic of the cellulose I type fiber. (021) crystal structure having a crystal plane. That is, by applying a swelling treatment to the cellulose material, the crystal structure of the cellulose material can be changed, and it can be known from the characteristic change of the crystal structure that the swelling treatment has been performed.

  It is effective that the frequency of the ultrasonic wave to be applied in the treatment for defibrating the cellulose fiber is in the range of 28 kHz to 200 kHz. In defibrating treatment using ultrasonic waves, there are cases where effective defibration is performed depending on the frequency of ultrasonic waves, and effective defibration may not be performed. A frequency of 28 kHz to 200 kHz is effective for cellulose fiber defibrating treatment, and in particular, 200 kHz ultrasonic waves can be used effectively. In the defibrating process, it is necessary to completely defibrate the core part of the cellulose fiber. It is important to select a suitable frequency as the frequency of the ultrasonic wave to be applied in order to efficiently defibrate the core portion of the cellulose fiber.

  The target material used as the cellulose material in the method for producing cellulose nanofibers according to the present invention is not particularly limited, and commonly used cellulose materials, for example, grain waste such as rice, wheat, corn, sugarcane, Grass, wood, pulp, waste paper, various residues, etc. can be used. In use, these cellulose materials may be used after pretreatment as necessary.

  According to the method for producing cellulose nanofibers according to the present invention, cellulose nanofibers can be obtained from a cellulose material efficiently and by a simple method.

It is a SEM image of the surface of a cellulose sample which has not yet been treated and a cellulose sample treated with Swollenin. It is a SEM image of the surface of a cellulose sample when the frequency of the ultrasonic cleaner is 28, 200, and 950 kHz. It is a SEM image of the surface of a cellulose sample when the ultrasonic treatment time is 10 minutes, 20 minutes, and 30 minutes. It is a SEM image of the surface of a cellulose sample that has been subjected to ultrasonic treatment with the treatment days of Swollenin treatment being 4 days and 5 days. It is a graph which shows the XRD measurement result about each sample. It is a SEM image of the surface of a cellulose sample when a cellulose sample is treated with an enzyme (EG V) and swollenin. It is a graph which shows a XRD measurement result when a cellulose sample is processed with an enzyme (EG V).

In the method for producing cellulose nanofibers according to the present invention, cellulose nanofibers are produced by subjecting a cellulose material to a swelling treatment, and subjecting the cellulose material subjected to the swelling treatment to ultrasonic treatment and defibrating treatment.
In the following examples, specific examples of experimental production of cellulose nanofibers from cellulose materials will be described, and the results of actual fibrillation treatment of cellulose materials from preparation of cellulose materials and preparation of swollenin, which is a cellulose swelling protein, will be described. .

(Preparation of cellulose material)
Various cellulose materials can be used for the cellulose material for producing the cellulose nanofiber. In the examples, cotton linter pulp (manufactured by Nippon Paper Industries Co., Ltd.) was used as the cellulose sample. Since this cellulose sample was in the form of a sheet, it was cut into strips with a shredder (MS shredder, C-38S, MEIKO) and then dry-pulverized using a small pulverizer (Wonder Blender WB-1: Osaka Chemical). A thing was used. The grinding treatment conditions are: electric capacity: 700 W, rotation speed: 25,000 rpm.

(Preparation of Swollenin)
In this example, Swollenin was used as the cellulose swelling protein. Swollenin is known to have a function of breaking hydrogen bonds between cellulose and matrix.
A genetic recombination procedure was used to prepare Swollenin. For expression of the genetically modified swollenin, yeast Pichia pastoris KM71 (Invitorogen) transformed with the expression vector pPIC9K incorporating cDNA encoding swollenin derived from Trichoderma reesei was used.

  Subsequently, the spores of the transformant P. pastoris were inoculated in the RBD / geneticin medium, and then statically cultured at 30 ° C. for 5 days to form colonies. After sterilizing the prepared BMGY medium, one colony was inoculated per 60 ml and cultured at 30 ° C. and 120 rpm for 4 days. Thereafter, the mixture was centrifuged at 4000 rpm for 5 minutes, the precipitate was suspended in 400 ml of BMMY medium, cultured at 30 ° C. and 120 rpm for 7 days, and methanol was added to make up 1% of the whole culture solution every 24 hours. After the culture, the obtained culture solution was centrifuged at 8000 rpm for 10 minutes, and the resulting supernatant was used as a crude enzyme solution. Ammonium sulfate was added to the crude enzyme solution to a final concentration of 1 M, and proteins were precipitated while gently rotating at 4 ° C. The precipitate was centrifuged at 10,000 rpm for 15 minutes, and the resulting precipitate was suspended in 100 ml of 50 mM sodium acetate buffer (pH 5.5).

Next, in order to purify Swolelinin, 12 g of microcrystalline cellulose powder (Merck) was suspended in 50 mM sodium acetate buffer (pH 5.5) containing 1 M ammonium sulfate, and this was added to an Econocolumn (φ2.8 cm × 12.8 cm, Bio-Rad), and two affinity columns were prepared.
About 50 mL of the protein solution after the ammonium sulfate precipitation described above was applied to these two columns. After washing away the protein not adsorbed on the cellulose by flowing a sufficient amount of the same buffer, the protein adsorbed on the cellulose was eluted by flowing deionized water. The solution obtained by this operation was stored as a Swollenin solution at 4 ° C. and used for the swelling operation of the cellulose sample.

  The amount of protein in the Swollenin solution obtained by the method described above was measured by the Lowry method. That is, 150 μL of a reaction solution prepared with a composition of 2 wt% sodium carbonate-sodium hydroxide: 1 wt% calcium tartrate: 1 wt% copper sulfate (II) pentahydrate = 100: 1: 1 (vol / vol / vol) 300 μL of the original enzyme solution was mixed. Thereafter, the mixture was allowed to stand at room temperature for 15 minutes, and 20 μL of 1 N folinthiocartol phenol reagent was added, and the mixture was further allowed to stand for 30 minutes. Then, the absorbance at 620 nm was measured using an absorptiometer. A calibration curve was prepared in the range of 0 μg / mL to 200 μg / mL using bovine serum albumin (Bio-Rad) as the standard substance.

(Swelling treatment)
Add 10 ml of the Swollenin solution with a protein amount of 0.15 mg / ml obtained by the above-mentioned gene recombination method to 5 mg of the cellulose sample obtained by the above-mentioned method, and further add ammonium sulfate powder so that the final concentration becomes 1 M. , Reacted at 40 ° C. The reaction time was 3 conditions of 3, 4, and 5 days.

FIG. 1 is an SEM image of an untreated cellulose sample and a cellulose sample treated with a swollenin solution.
In FIG. 1, untreated means pulverized using a pulverizer, and swollennin treated means reacted for 3 days using a swollenin solution. SEM images of low magnification and high magnification are shown respectively.
When the cellulose sample is treated with Swollenin, the fissure is generated in the cellulose fiber. Such tears are not seen in the untreated cellulose sample. It is thought that the swollenin treatment loosened the bond between the cellulose fibers and caused a tear.

The surface of the fiber was observed with a scanning electron microscope as follows.
A cellulose sample freeze-dried overnight with a freeze dryer FDU-1200 (Tokyo Science) was fixed on a carbon tape (Nisshin EM) affixed to the sample stage. Place the sample stage on which the cellulose sample is placed in the vacuum evaporation system Twin Coater JEC-550 (JEOL), perform sputtering at 1.5 kVA for 2 minutes 30 seconds, deposit platinum, and then use FE-SEM SU-8000 (Hitachi). The fiber surface was observed.
Hereinafter, the fiber surface of the cellulose sample is observed with a scanning electron microscope in the same manner.

(Defibration processing)
After the cellulose sample was reacted with the swollenin solution by the above-described method, the cellulose sample was subjected to a treatment for applying ultrasonic waves as a defibrating treatment without deactivating swollenin. Sonication is performed in a 15 ml Erlenmeyer flask with a stopper, and once every 5 minutes, the Erlenmeyer flask is removed from the ultrasonic cleaner and stirred by pipetting, and then the Erlenmeyer flask is placed in the ultrasonic cleaner. Then, ultrasonic waves were further applied.
Model used: Mitsui Electric bath type ultrasonic cleaner, frequency: 28, 200, 950 kHz, power: 300 W, processing time: 10, 20, 30 minutes, processing temperature: 20-30 ° C.

FIG. 2 shows the results of examining how the frequency of ultrasonic waves acting on the cellulose sample acts on the defibration of the cellulose sample. The SEM images of the cellulose sample surface when the frequency of ultrasonic waves is 28, 200, and 950 kHz, respectively, for those not subjected to swollenin treatment and those subjected to swollenin treatment are shown.
In the same figure, “Swo” → “sonic” means that a solution obtained by adding a swollenin solution (including ammonium sulfate) to a cellulose suspension is subjected to ultrasonic treatment. Swollenin processing days are 3 days. “Swo no → sonic” means that the water sample and the cellulose sample after the pulverization treatment were put into an Erlenmeyer flask and sonicated without the treatment of Swollennin. Both sonication times are 30 minutes.

In FIG. 2, when looking at the cellulose sample that has not been swollenin-treated, there is almost no change even when sonication is performed and when it is not sonicated. That is, it can be seen that the cellulose sample is not refined (not defibrated) by simply ultrasonication.
On the other hand, when the cellulose sample treated with swollenin is subjected to ultrasonic treatment, it can be seen that the cellulose sample is clearly refined (defibrated). However, regarding the frequency of sonication, when the frequency is 28 kHz, the surface portion of the cellulose sample is refined, but the core portion of the cellulose sample remains without being refined, and when the frequency is 200 kHz, the core of the cellulose sample. On the other hand, when the frequency is 950 kHz, the effect of miniaturization is hardly obtained.
This experimental result shows that it is preferable to set the frequency of the ultrasonic wave to 200 kHz when the cellulose sample subjected to the swollenin treatment is subjected to an ultrasonic wave for defibrating treatment.

Fig. 3 shows the results of investigating how the sonication time affects the defibration of cellulose samples. The sonication time is 10 minutes, 20 minutes, and 30 minutes, respectively. The SEM image of the surface of a cellulose sample is shown.
In FIG. 3, the upper SEM image is obtained when ultrasonic waves are applied to a cellulose sample that has not been swollennin-treated, and the lower SEM image is obtained when ultrasonic waves are applied to a cellulose sample that has been swollennin-treated. The number of days for the Swollenin treatment was 3 days, and the frequency of the ultrasonic treatment was 200 kHz.

From FIG. 3, it can be seen that in the method of subjecting a cellulose sample not treated with swollenin to ultrasonic treatment, the cellulose fibers are not defibrated even if the treatment time is increased.
On the other hand, in the case of a cellulose sample treated with swollenin, cellulose fibers are effectively defibrated by ultrasonic treatment. However, since the defibrating action proceeds from the surface of the cellulose sample, thick fibers remain in the center after 10 minutes of ultrasonic treatment. In the treatment for 20 minutes, defibration progresses, but the central fiber partially remains. After 30 minutes of treatment, most of the fibers were in a defibrated state. This experimental result shows that 30 minutes is appropriate as the ultrasonic treatment time under the present experimental conditions.

FIG. 4 shows how the number of days of treatment with Swollenin affects the defibrating effect by ultrasonic treatment. FIG. 4 shows an SEM image of the surface of a cellulose sample subjected to ultrasonic treatment with the treatment days of the swollenin treatment being 4 days and 5 days. The ultrasonic frequency is 200 kHz, and the ultrasonic treatment time is 30 minutes.
The measurement results shown in FIG. 4 are almost the same as the cellulose sample shown in FIG. Therefore, it can be said that 3 days is sufficient as the swollenin treatment days.

(Measurement of crystallinity of cellulose nanofiber)
In order to examine the fiber morphology of the cellulose sample subjected to ultrasonic treatment after the above-mentioned swollenin treatment, the crystallinity of the fiber was examined by XRD measurement.
Figure 5 shows an untreated cellulose sample (untreated), a cellulose sample subjected to ultrasonic treatment (Sonic only), a cellulose sample subjected to Swollenin treatment (Swo only), and a cellulose sample subjected to Swollennin treatment and supertreatment. It is the XRD graph of what added sonication (Swo-> sonic). In addition, the result measured about serish (trademark: Daicel Corporation) which is a commercially available cellulose nanofiber is also shown for a comparison.

  In the XRD graph shown in FIG. 5, the peak of the (002) crystal plane showing the crystallinity characteristic of cellulose type I fiber appears in any sample. That is, it can be seen that each of the cellulose samples has crystallinity characteristic of cellulose I-type fibers. In addition, it is characteristic that the peak of (021) crystal plane appears for the sample subjected to the swollenin treatment (only swo) and the sample subjected to swollenin treatment and ultrasonic treatment (swoe → sonic). (021) The crystal plane is a plane inclined with respect to the longitudinal direction (fiber direction) of the cellulose fiber. The presence of the (021) crystal face in the cellulose sample subjected to the Swollenin treatment indicates that the bonding between the cellulose fibers is loosened by the Swollenin treatment, and the crystallinity is lowered as compared with that before the treatment.

The crystallinity of the cellulose sample was measured using an XRD measuring machine (XRD-6000: manufactured by Shimadzu Corporation) using a freeze-dried cellulose sample as a measurement sample.
The crystallinity (CrI) of cellulose fiber is given by the following equation by the Segal method.
Iam / I002 × 100 = CrI (%)
The relative crystallinity was obtained by dividing the value of 2θ = 18.5 (Iam: amorphous part of cellulose fiber) by the value of 2θ = 22.6 (I002: crystalline part of cellulose fiber).
Table 1 shows the crystallinity obtained based on the XRD measurement results.

  When the crystallinity of the untreated sample and the sample (Swo → sonic) subjected to the swollenin treatment and the ultrasonic treatment are compared, the crystallinity is hardly changed. In addition, the degree of crystallinity is comparable even when compared with Celish (registered trademark), which is an existing cellulose nanofiber. That is, cellulose nanofibers obtained by applying ultrasonic treatment after swollenin treatment are expected to have the same degree of crystallinity as natural cellulose and to have high strength equivalent to that of natural cellulose.

(Measurement of specific surface area of cellulose nanofiber)
It was measured how much the specific surface area of the cellulose nanofibers was increased by the defibrating process.
In normal lyophilization, even if the fibers are swollen in water, the fibers may be aggregated again after the treatment. Therefore, in order to maintain the swollen shape of the fiber, the specific surface area was measured by performing a t-butyl alcohol substitution treatment. Specifically, first, the dispersion of the cellulose sample was centrifuged (8000 rpm, 25 ° C., 10 minutes), and the supernatant was removed. Next, t-butyl alcohol (Wako) was mixed well with the fiber, centrifuged again under the same conditions, and the supernatant was removed. By performing this operation 4 or 5 times, the dispersion of the cellulose sample was replaced with t-butyl alcohol. Thereafter, freeze-drying treatment was performed, and the specific surface area was measured by nitrogen adsorption.
Model used: BELSORP-mini made by Nippon Bell Co., Ltd., measurement principle: constant volume gas adsorption method (free space continuous measurement method), adsorption gas: nitrogen, sample cell: approx. 1.8 cm ³ , measurement program: adsorption / desorption isotherm measurement .

Table 2 shows measurement results for an untreated cellulose sample, an untreated cellulose sample added with ultrasonic waves, and a cellulose sample subjected to swollenin treatment and further subjected to ultrasonic treatment.
The measurement results of specific surface area showed almost no difference between the untreated cellulose sample and the sample treated with sonication only, but the swollenin-treated and further sonicated compared with the untreated sample. About 8 times larger. It shows that the specific surface area was increased by making nanofibers by swelling treatment and defibration treatment, but not by sonication.

(Comparison between enzyme treatment and swollenin treatment)
The difference between the swollenin treatment and the enzyme treatment on the cellulose sample was examined.
Fig. 6 shows the case where an enzyme (EG V) is allowed to act on a cellulose sample, and the SEM image of the surface of the cellulose sample when the enzyme treatment is performed and further subjected to the ultrasonic treatment. The SEM image of a cellulose sample is shown. The treatment days of EG V and Swollenin treatment are 3 days, the ultrasonic treatment frequency is 200 kHz, and the ultrasonic treatment time is 30 minutes.
The treatment with EG V was the same as the treatment with Swollenin, and the reaction was performed by adding 10 mL of an EG V stock solution (0.15 mg / ml) to 5 mg of a cellulose sample.
From FIG. 6, the cellulose sample is not defibrated at all even if an enzyme (EG V) is allowed to act on the cellulose sample or further subjected to sonication, whereas swollenin treatment and sonication are performed. It can be seen that the cellulose sample is refined and effectively defibrated.

FIG. 7 shows the results of XRD measurement of a sample obtained by allowing an enzyme (EG V) to act on a cellulose sample and further subjecting it to ultrasonic treatment. In FIG. 7, an untreated cellulose sample (untreated), an untreated cellulose sample subjected to ultrasonic treatment (ultrasonic), a cellulose sample subjected to swollenin treatment (Swollenin), and a cellulose sample treated with swollenin And sonication (Swollenin + ultrasound) and serisch (registered trademark).
FIG. 7 shows the peak of the (002) plane, which is characteristic of cellulose I-type fibers, both in the case of enzyme (EG V) treatment and in the case of enzyme (EG V) treatment and ultrasonic treatment. On the other hand, it shows that the peak due to the (021) plane that appears characteristically when swollenin treatment is applied does not appear at all. This measurement result suggests that the swelling treatment using Swollenin has a different action from the enzyme (EG V) treatment.

Next, in order to investigate the influence of the enzyme treatment and the swollenin treatment on the cellulose chain length, an average polymerization molecular weight was measured by gel permeation chromatography.
A measurement sample was prepared by freeze-drying a suspension of each cellulose sample. 10 mg of cellulose powder was added to a screw test tube, and 1 mL of dimethyl sulfoxide and 400 μL of phenyl isocyanate were added. The test tube containing this solution was derivatized with cellulose at 90 ° C. for 48 hours with occasional stirring. After heating, 10 mL of 50 v% methanol was added to precipitate and recover the derivatized cellulose, washed with 50 v% ethanol, and dried while sucking in a desiccator containing diphosphorus pentoxide. The derivatized cellulose (cellulose tricarbanilate) was dissolved in tetrahydrofuran to a concentration of 1 mg / mL, and passed through a 0.2 μm filter as a sample for gel permeation chromatography.

The weight average molecular weight was calculated from the following formula, where t is the retention time at the detection peak of the target substance and Mt is the height from the baseline at the detection peak.
Mw = (ΣtiMti) / (Σti)
The weight average molecular weight calculated from this formula was divided by the derivatized cellulose (cellulose tricarbanilate) monomer value (519.42) to determine the weight average molecular weight.

Table 3 shows the weight average molecular weight (Mw) and the degree of polymerization (DP) for the samples obtained by each treatment.
From Table 3, it can be seen that, when compared to the untreated cellulose sample, the chain length decreases to the same extent as when the swollenin treatment is performed, and the degree of polymerization (DP) is the same as when the enzyme (EG V) treatment is performed As a result, it is shown that the degree of polymerization is reduced to about half in both the case of the swollenin treatment and the case of the enzyme treatment as compared with the untreated one.

Next, in order to compare the yield of cellulose nanofibers obtained by enzyme treatment and swollenin treatment, the amount of reducing sugar was measured by the DNS method from the reaction solution after each treatment.
200 μl of the sample solution was dispensed into a test tube, and 600 μl of DNS reagent was added and mixed. Next, it was boiled for 5 minutes and cooled with ice for 5 minutes. Thereafter, 4 ml of distilled water was added, mixed, and allowed to stand for 10 minutes. Finally, the absorbance was measured at 540 nm using a spectrophotometer.
Table 4 shows the results of measuring the amount of reducing sugar for each treatment content.

In Table 4, “sonic only” means that an untreated cellulose sample was subjected to ultrasonic treatment, “Swo” only means that a cellulose sample was swollenin-treated, and “Swo → sonic” means a cellulose sample. Swollenin treatment and further sonication, EG V is treatment using the enzyme EG V, and EG V → sonic is sonication after the enzyme treatment.
The Swollenin treatment is 3 days, and the ultrasonic treatment is a frequency of 200 kHz and 30 minutes.

From Table 4, it can be seen that the cellulose sample treated with Swollenin has a smaller amount of reducing sugar produced than the enzyme treated with enzyme (EG V). As shown in Table 3, although the average degree of polymerization does not change significantly between swollenin treatment and enzyme (EG V) treatment, the amount of reducing sugar is greater than that of enzyme treatment in Table 4 when swollennin treatment is used. The reason for the decrease is that the production of cellobiose (disaccharide) and soluble cellooligosaccharide is less in the case of swollenin treatment than in the enzyme treatment. That is, it can be said that the effect of fragmenting the cellulose sample is lower in the case of the swollenin treatment than in the case of the enzyme (EG V) treatment, and thus the yield of producing the cellulose nanofiber is good.

Claims (4)

A treatment step of swelling the cellulose material;
Ultrasonic wave action is applied to the cellulose material that has undergone the swelling treatment process, and the cellulose fiber is defibrated,
A method for producing cellulose nanofibers, comprising:   The cellulose nanofiber production method according to claim 1, wherein swollenin is allowed to act on the cellulose material as the swelling treatment of the cellulose material.   The swollen treatment of the cellulose material is performed by causing swollenin to act on the cellulose material, and adding the crystal structure of the cellulose fiber to the (002) crystal plane to have a (021) crystal plane. A method for producing cellulose nanofibers. The method for producing cellulose nanofiber according to any one of claims 1 to 3, wherein the frequency of ultrasonic waves to be applied in the treatment for defibrating the cellulose fiber is 28 kHz to 200 kHz.