JP7195126B2 - Cellulose fine fiber dehydrate and method for producing the same - Google Patents

Description

The present invention relates to a dehydrate of fine fibers made from cellulosic material.

Attention has been focused on a new material called nanocellulose, which is obtained by subdividing fibers constituting a plant-derived cellulose material to a fiber diameter of less than 1 μm. Among these materials, mainly materials with a fiber diameter of about 3 to 100 nm have a large specific surface area and have excellent properties as reinforcing fibers, and are therefore being manufactured and researched. Although various names have been proposed for this material, this application refers to this material as cellulose nanofibers. In addition, those having a size and aspect ratio similar to cellulose nanofibers are collectively called cellulose fine fibers together with cellulose nanofibers. In order to produce cellulose fine fibers, it is necessary to finely defibrate a cellulose material such as pulp, and even if the cellulose material itself is to be defibrated as it is, it is a strong material and requires a large amount of energy. For this reason, a technique has been proposed that makes it easier to obtain cellulose fine fibers by chemically modifying a cellulose material to make it easier to defibrate.

Cellulose fine fibers obtained by such chemical modification include, for example, the following. 2,2,6,6-tetramethyl-1-piperidine-N-oxy radical (hereinafter referred to as "TEMPO") is used as a catalyst to introduce carboxyl groups into cellulose and defibrate TEMPO-oxidized cellulose nanofibers. , xanthate cellulose fine fibers in which xanthate groups (-OCSS ^- M ⁺ ) are introduced by adding carbon disulfide to alkali-treated cellulose, and phosphate esterified cellulose nanofibers in which phosphate groups are introduced.

Dispersions of cellulose fine fibers, which are obtained by chemically modifying cellulose materials such as TEMPO-oxidized cellulose nanofibers and xanthate-modified cellulose fine fibers, and which are defibrated to single microfibril units maintain their dispersibility. Therefore, the weight of water several times to several hundred times that of cellulose fine fibers was required. At such a low concentration, there were various problems such as securing storage space and increasing transportation costs. Therefore, it is important to concentrate the cellulose fine fibers as much as possible before transporting and storing them.

However, when trying to simply concentrate a dispersion of cellulose fine fibers by filtration, etc., it is difficult to concentrate, and the dispersed cellulose fine fibers caused by defibration cause agglomeration, making it difficult to redisperse them at the delivery destination. However, there is a problem in that when they are mixed, they remain in an agglomerated state and cannot return to a suitable dispersion.

Patent Document 1 describes a method for producing a concentrate by adding an inorganic flocculant to anion-modified cellulose nanofibers to flocculate the cellulose nanofibers, and that redispersion is also possible.

In Patent Document 2, a nonionic surfactant is added to an aqueous dispersion of cellulose nanofibers to impart a clouding point or a thermal gelation point, and the temperature is raised to a temperature equal to or higher than the clouding point or the thermal gelation point. It describes a method for producing a concentrate obtained by filtering aggregates containing cellulose nanofibers while the temperature is elevated, and that redispersion is also possible.

However, in the production method described in Patent Document 1, an auxiliary agent (inorganic coagulant) is required for concentration, and there is a problem that the auxiliary agent is difficult to remove after concentration or re-dispersion. In addition, there is also a limitation that the pH of the dispersion medium must be adjusted to be alkaline during redispersion.

Also, in the production method described in Patent Document 2, it is essential to use a concentration aid, and it is necessary to keep the equipment used at the time of concentration at 65 to 80 ° C., so there is a problem that the operation becomes complicated. was there.

By the way, in Patent Document 3, a slurry in which cellulose fibers are phosphated to facilitate defibration (step (a)) is fibrillated with a homogenizer or the like to obtain phosphate esterified cellulose fine fibers (step (b) )) and then removing the phosphate groups (step (c)) to obtain cellulose fine fibers. In addition, it is disclosed that a cellulose fine fiber slurry obtained by removing phosphate groups is aggregated, washed, and then re-dispersed with a homodisper to obtain a slurry (Patent Document 3). [0058]).

JP 2016-186018 A JP 2018-48218 A Japanese Patent No. 5783253

However, in order to sufficiently remove the phosphoric acid groups from the phosphate-esterified cellulose fine fibers, a hydrolysis treatment in a heated environment over a long period of time is necessary, and a short-time removal treatment requires the substitution of the substituents. It has been found that desorption is insufficient. Even in Patent Document 3, the residual amount of substituents is large in Examples 1 and 2, and the conditions of Example 3 are necessary to sufficiently reduce the amount of substituents. was

On the other hand, since xanthate-modified cellulose fine fibers have a very high affinity for water due to the xanthate group, they cannot be sufficiently concentrated and dehydrated by simple filtration or the like. When the xanthate-modified cellulose fine fibers are detached from the xanthate groups and subjected to a regeneration treatment to return them to hydroxyl groups to obtain cellulose fine fibers, concentration and dehydration can be performed to some extent by filtration or the like, but the xanthate groups have been detached. When the dehydrated product was re-diluted, a cellulose fine fiber slurry in which the aggregates were not sufficiently dispersed was obtained.

Therefore, in handling cellulose fine fibers, the present invention makes it possible to easily concentrate high-quality cellulose fine fibers from which substituents have been sufficiently eliminated without using a concentration aid, and to easily concentrate after once concentrating. It is intended to improve the practicality of cellulose fine fibers by making it possible to dilute them to 100%, facilitating storage and transportation.

The present invention relates to a solid content concentration obtained by dehydrating and concentrating cellulose fine fibers obtained by regenerating cellulose xanthate after disentangling xanthate groups, followed by dispersion treatment. The above problem was solved by making the cellulose fine fiber dehydrated product of 2% by mass or more and 15% by mass or less.

Xanthate-modified cellulose fine fibers can be rapidly desorbed from xanthate groups by acid treatment or heat treatment, and high-quality cellulose fine fibers can be obtained. In addition, the cellulose fine fibers derived from xanthate-modified cellulose fine fibers are subjected to a regenerating treatment to return the chemically modified functional groups to hydroxyl groups after fibrillation, and then subjected to a dispersion treatment to prevent the cellulose fine fibers from aggregating. Concentration becomes possible, and a dispersion can be easily obtained when the concentrated dehydrated product is re-diluted.

The concentration of regenerated cellulose fine fibers at the time of production is approximately 0.1% by mass or more and 1.5% by mass or less, but a more concentrated cellulose fine fiber dehydrated product with a higher solid content concentration can be realized. In addition, the cellulose fine fibers are of high quality with almost no remaining substituents interposed for fibrillation.

The dehydrated cellulose fine fibers subjected to the dispersion treatment tend to have a smaller median diameter in the particle size distribution than those concentrated without the dispersion treatment. Specifically, it is preferable that the median diameter in the particle size distribution is 1/4 or less before and after the dispersion treatment.

When the dehydrated product once concentrated according to the present invention is then diluted to obtain a re-diluted product, it exhibits high dispersibility. As a result, it is possible to reduce the water content during storage and transportation, thereby saving space and weight, and at the same time, it is possible to save the trouble of re-fibrillating the fiber when using it at the customer's destination, and use it as a product. available in an easy-to-use format. Moreover, the rediluted product derived from xanthate-modified cellulose fine fibers exhibits higher dispersibility than the case of treating cellulose fine fibers derived from phosphate-esterified cellulose fine fibers in the same manner. As a result, the quality and convenience when used after once condensed, stored and transported are greatly improved.

Further, after regeneration, it may be subjected to hydrogen peroxide water treatment, followed by dispersion treatment, dehydration concentration, and re-dilution.

According to the present invention, for high-quality cellulose fine fibers with a small residual amount of substituents, the dehydrated cellulose fine fibers in which the water content is reduced to reduce the space and weight occupied during storage and transportation can be simply diluted. , it becomes available as a cellulose fine fiber redilution well dispersed to a state close to the original pre-dehydration. As a result, the production of the cellulose fine fibers can be performed at a place temporally and spatially separated from the site of use, and the convenience of the cellulose fine fibers can be greatly improved.

TEM image of xanthated cellulose microfiber slurry produced in the manufacturing process of Example 1 TEM image of regenerated cellulose fine fiber redispersion slurry produced in the manufacturing process of Example 1 Graph comparing the filtration time and final filtrate volume of Example 1 and Comparative Examples 1 and 2 Graph showing particle size distribution changed by redispersion treatment in Example 1 Photograph showing the difference in slurry depending on the presence or absence of redispersion in Reference Example 1 Photographs of dehydrated products of Examples 2-4 Photographs showing conditions after emulsification treatment in Comparative Examples 5 and 6, Examples 8a and 8b, Comparative Examples 7 and 8, and Examples 9a and 9b

The present invention will be described in detail below. The present invention provides a method for producing a dehydrated product concentrated so as to facilitate re-dilution using cellulose fine fibers produced via xanthate-modified cellulose fine fibers, and a re-diluted cellulose fine fiber using the same. is a manufacturing method.

The cellulose fine fibers used in the present invention refer to fine fibers obtained by chemically modifying a cellulose material and defibrating while maintaining the cellulose type I structure, and fine fibers chemically denatured again. . The latter includes those in which the functional groups introduced in the first chemical modification are returned to hydroxyl groups by a second chemical modification and returned to cellulose. Those that have been converted back to cellulose are specifically called regenerated cellulose fine fibers. Although the range to which the method according to the present invention can be applied is not strictly limited, it is preferable that fibers in a state called nanofibers having a fiber diameter of less than 1 μm account for 80% by mass or more of the solid content. , and more preferably accounts for 90% by mass or more of the solid content.

The cellulose material mentioned above refers to a material containing cellulose type I α-cellulose in a crystalline state. Even if it is α-cellulose, a material that has lost its crystalline state and completely converted to cellulose type II cannot be suitably used. Specific materials include, for example, wood-processed kraft pulp and sulfite pulp, wood powder, biomass-derived materials such as rice straw, paper-derived materials such as used paper, filter paper, and paper powder, powdered cellulose, and microfibers. Examples include processed cellulose products that retain crystallinity, such as meter-sized microcrystalline cellulose. However, it is not limited to these examples. Moreover, these cellulose materials do not need to be pure α-cellulose, and may contain other organic and inorganic substances such as β-cellulose, hemicellulose, and lignin within a removable range. In the following description, simply calling "cellulose" means "α-cellulose". Among these cellulose materials, it is preferable to use wood pulp because the length of the original cellulose fibers is easily maintained.

It is difficult to defibrate the cellulose material as it is. It takes a lot of time and effort to make fibers finer simply by mechanical fibrillation, which is inefficient. Although fibrillation can be performed in a high-temperature and high-pressure environment, there is a possibility that the fiber length of the cellulose fine fibers will be shortened and other damages will occur. Therefore, by introducing a functional group into the cellulose molecule through chemical modification and utilizing the electrostatic repulsion due to this functional group, defibration can be performed under relatively mild conditions. As a result, fine fibers are obtained which are fibrillated while maintaining the cellulose type I structure.

The fine fibers obtained by chemically modifying the cellulose material and then fibrillating it include xanthated cellulose fine fibers obtained by adding carbon disulfide to alkali-treated cellulose to introduce xanthate groups (-OCSS ^- M ⁺ ). is used. In addition to this, chemically modified cellulose fine fibers used for the same type of application include TEMPO-oxidized cellulose nanofibers, which are fibrillated by introducing carboxyl groups into cellulose by using TEMPO as a catalyst, and phosphate-esterified cellulose. phosphate-esterified cellulose nanofibers. However, it is not easy for TEMPO-oxidized cellulose nanofibers to convert carboxyl groups back to hydroxyl groups. Although it is possible to remove substituents from phosphate-esterified cellulose nanofibers, the reaction takes a long time, and the removal of substituents is insufficient and tends to remain, making it difficult to obtain pure cellulose fine fibers. In addition, residual substituents can affect the resulting dehydrates and redilutions. In contrast, xanthated cellulose fine fibers can be easily converted back to cellulose by chemical modification again. Specifically, xanthate-modified cellulose fine fibers can be regenerated by acid treatment or heat treatment to restore xanthate groups to hydroxyl groups, and regenerated cellulose fine fibers can be obtained. This process can proceed rapidly and readily yields pure regenerated cellulose microfibers.

Here, the regenerated cellulose fine fibers are desirably those in which all of the xanthate groups introduced by chemical modification are returned to hydroxyl groups, but even if some of the xanthate groups remain, they are sufficiently usable. be. Specifically, among the introduced xanthate groups, the residual xanthate group is preferably 1% or less, more preferably 0.2% or less. Basically, the lower the residual rate, the better. In the case of phosphate-esterified cellulose nanofibers, treatment over a long period of time is required to remove the substituents to this extent.

In most cases, the regenerated cellulose fine fibers are dispersed in an aqueous solvent. The water-based solvent refers to a polar solvent containing water, and may be water alone or a mixture of water and an organic solvent. Examples of organic solvents include ethanol, dimethylformamide, and dimethylacetamide. However, when returning to hydroxyl groups by acid treatment, it is preferable to use only water containing no organic solvent as the solvent because the risk of side reactions is reduced.

The solid content concentration of the regenerated cellulose fine fibers after regeneration is about 0.1% by mass or more and 1.5% by mass or less. The regenerated cellulose fine fibers can be concentrated and dehydrated by filtration or the like, but compared to the xanthate-modified cellulose fine fibers before regeneration, the xanthate group has been detached. It is in a partially aggregated state. It is desirable that the cellulose fine fibers account for 95% or more of the solid content. If other additives used for fibrillation or regeneration are contained, it is desirable to remove them by washing with distilled water or the like.

In the present invention, the slurry of cellulose fine fibers after regeneration is subjected to dispersion treatment. Hereinafter, this distribution processing performed after reproduction is referred to as "re-distribution processing". When the re-dispersion treatment is performed, general devices and methods used for dispersion treatment, such as rotary homogenizers, high-pressure homogenizers, and ultrasonic dispersers, can be employed.

The re-dispersion treatment is a treatment in which the regenerated cellulose fine fibers are deaggregated in the aqueous solvent and dispersed so as to prevent re-aggregation. Specifically, the median diameter of the aggregates of regenerated cellulose fine fibers after redispersion treatment is reduced to 1/4 or less of the median diameter of aggregates of regenerated cellulose fine fibers before redispersion treatment. It is desirable that the dispersion is advanced to such an extent that it is reduced to 1/8 or less, more preferably 1/10 or less. Unless the redispersion treatment reduces the median diameter of the aggregates to this extent, the aggregated state is not sufficiently removed, and after concentration and dehydration to obtain a dehydrated product, it is diluted again to obtain a rediluted product. It is considered that the distributed state cannot be maintained in this case.

In the re-dispersion treatment, the slurry after treatment maintains a dispersed state without sedimentation, and the slurry after treatment preferably has a transmittance of 45% or more, more preferably 55% or more.

The re-dispersion treatment does not have to be a one-time treatment, and may be achieved by repeating the treatment under appropriate conditions a plurality of times.

A redispersed regenerated cellulose fine fiber used in the present invention is called a redispersed regenerated cellulose fine fiber. The size of the redispersed regenerated cellulose fine fibers is the size dispersed in the dispersion medium, and the average fiber diameter is generally 3 nm or more and 300 nm or less, which is easy to obtain and easy to use.

The slurry of the redispersed regenerated cellulose fine fibers subjected to the redispersion treatment can be easily dehydrated and concentrated by filtration or other treatment, similarly to the regenerated cellulose fine fibers before the redispersion treatment. Although it is in a dispersed state by the above-mentioned redispersion treatment, the xanthate group has been eliminated compared to the xanthate-modified cellulose fine fibers before the regeneration treatment, so the hydrophilicity is low. Therefore, it is presumed that the force of holding water between fibers is weakened.

The regenerated cellulose fine fiber dehydrate obtained by dehydrating and concentrating the redispersed regenerated cellulose fine fiber after the above redispersion treatment by filtration or a centrifugal dehydrator should have a solid content concentration of 2% by mass or more. can be easily made, and it is also possible to make it 5% by mass or more. If it is less than 2% by mass, the amount of water is too large, and the storage and transport efficiency of the dehydrated product is insufficient, and the effects of the present invention cannot be fully exhibited. When it is 2% by mass or more, the amount of weight reduction is large compared to the original slurry, and the advantages of storage and transportation are large. When it is 5% by mass or more, it can be handled as a paste-like mass instead of a slurry-like liquid. About 5% by mass of the dehydrated matter is in a state where some free water is released by pressing the mass strongly. It is also possible to increase the concentration by further squeezing water from this state. If it is 5% by mass or more, it can be easily stored and transported as a mass, which is preferable in terms of handling.

On the other hand, the regenerated cellulose fine fiber dehydrated product should have a solid content concentration of 15% by mass or less. Although dehydration itself is possible when the solid content concentration exceeds 15% by mass, the dehydrated product becomes too hard and it becomes difficult to dilute it again later. 12% by mass or less is preferable for operation, and if it is 10% by mass or less, re-dilution, which will be described later, can be easily performed. If dehydration is performed only by a centrifugal dehydrator, 10% by mass is almost the upper limit. Dehydrated regenerated cellulose fine fibers having a solid content concentration of about 10% by mass are plate-shaped and are in such a state that free water hardly leaks out even if the mass is pushed.

After being stored or transported, the regenerated cellulose fine fiber dehydrate can be diluted by adding an aqueous solvent and stirred to easily obtain a rediluted regenerated cellulose fine fiber. This regenerated cellulose fine fiber re-dilution material is less likely to aggregate to the same degree as the regenerated cellulose fine fiber re-dispersion material that has been subjected to re-dispersion treatment after regeneration treatment, and even after storage and transportation, immediately after re-dispersion before dehydration. A slurry of the regenerated cellulose fine fiber rediluted material in a state close to can be easily obtained. The solid content concentration of the re-diluted regenerated cellulose fine fibers, which is the slurry, can be adjusted to a suitable value depending on the site of use within a range lower than the solid content concentration of the regenerated cellulose fine fiber dehydrated product. Specifically, the regenerated cellulose fine fiber rediluted material can be practically used at a solid content concentration of about 0.1% by mass or more and 1.5% by mass or less.

The regenerated cellulose fine fibers may be treated with an aqueous hydrogen peroxide solution before the redispersion treatment, and then subjected to the redispersion treatment, followed by dehydration, concentration, and redilution.

In the treatment with the hydrogen peroxide solution, it is desirable to heat to 50° C. or higher, more preferably 60° C. or higher, in order to increase the reactivity of the added hydrogen peroxide. On the other hand, if the temperature is too high, the fibers constituting the regenerated cellulose fine fibers may be cut.

The amount of hydrogen peroxide added is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, in the entire slurry of regenerated cellulose fine fibers to be treated. On the other hand, if the concentration is too high, it not only increases the dispersibility of the regenerated cellulose fine fibers, but also may shorten the fiber length too much. preferable.

The regenerated cellulose fine fibers according to this invention can also be used as an emulsifier. Regenerated cellulose fine fibers containing few impurities through xanthate-modified cellulose fine fibers exhibit high dispersibility by redispersion treatment after regeneration. That is, the dehydrated regenerated cellulose fine fiber that has been dehydrated, concentrated and stored after production is easily diluted and exhibits high dispersibility when used as an emulsifier, and the regenerated cellulose The fine fibers form a weak network structure, incorporate hydrophobic substances into the network structure, and exhibit high emulsifying performance.

EXAMPLES Examples in which the present invention is specifically carried out are shown below. First, the following materials were used as cellulose materials.
- Kraft pulp (manufactured by Nippon Paper Industries Co., Ltd.: NBKP, α-cellulose content: 90% by mass, average polymerization degree of α-cellulose: 1000) Hereinafter referred to as “NBKP”.

(Example 1)
First, the procedure for producing xanthate-modified cellulose fine fibers obtained by defibrating chemically modified cellulose will be described.
<Alkaline treatment>
NBKP was weighed to 100 g of pulp solid content (referring to solid content including α-cellulose and impurities such as lignin, and modified products thereof; the same shall apply hereinafter). This was introduced into a 3 L beaker, 2500 g of an 8.5% by mass aqueous sodium hydroxide solution was added, and the mixture was stirred at room temperature for 3 hours for alkali treatment. The alkali-treated pulp was subjected to solid-liquid separation using a centrifugal dehydrator (H-110A manufactured by Kokusan Co., Ltd., filter cloth 400 mesh) to obtain a dehydrated alkali cellulose. The alkali cellulose dehydrated product had a sodium hydroxide content of about 7.5% by mass and a pulp solid content of 27.4% by mass.

<Xanthate treatment>
The dehydrated alkali cellulose prepared above was weighed so that the pulp solid content was 100 g, and introduced into an eggplant-shaped flask. 35 g of carbon disulfide (35% by mass based on the pulp solid content) was introduced into this eggplant-shaped flask, and a sulfurization reaction was allowed to proceed at room temperature for about 4.5 hours to perform a xanthate treatment to obtain cellulose xanthate.

<Measurement of degree of substitution of xanthate>
In addition, the average degree of xanthate substitution of the xanthated cellulose was 0.312 as measured by the Bredee method. The degree of xanthate substitution is a value relative to the degree of introduction of xanthate groups per glucose unit of cellulose. The procedure of the Bredee method was performed as follows. About 1.5 g of xanthated cellulose was precisely weighed in a 100 mL beaker, and 40 mL of a saturated ammonium chloride solution (5°C) was added. The sample was crushed with a glass rod and mixed well, allowed to stand for about 15 minutes, filtered through GFP filter paper (GS-25 manufactured by ADVANTEC), and thoroughly washed with a saturated ammonium chloride solution. The sample was placed in a 500 mL tall beaker together with the GFP filter paper, and 50 mL of 0.5 M sodium hydroxide solution (5°C) was added and stirred. After standing for 15 minutes, it was neutralized with 1.5 M acetic acid. (Phenolphthalein indicator) After neutralization, 250 mL of distilled water was added and well stirred, and 10 mL of 1.5 M acetic acid and 10 mL of 0.05 mol/L iodine solution were added with a whole pipette. This solution was titrated with a 0.05 mol/L sodium thiosulfate solution. (1% starch solution indicator) The degree of xanthate substitution was calculated from the following formula (1) from the titration amount of sodium thiosulfate and the cellulose content of the sample.

Degree of xanthate substitution = (0.05 x 10 x 2-0.05 x sodium thiosulfate titer (mL)) / 1000 / (cellulose amount in sample (g) / 162.1) (1)

<Confirmation of retention of crystallinity of xanthated cellulose>
As a result of IR measurement of the cellulose obtained during the measurement of the cellulose content in the xanthate-modified cellulose, a peak shape corresponding to cellulose type I was observed.

<Fibrillation treatment>
The xanthated cellulose prepared by the above xanthate treatment was weighed into a 5 L beaker with a handle so that the pulp solid content was 100 g, and distilled water was added to obtain a slurry concentration of about 5% for dispersion. Centrifugal dehydration was performed using a centrifugal dehydrator (H-110A manufactured by Kokusan Co., Ltd., filter cloth 400 mesh), followed by thorough washing while adding distilled water to remove impurities, alkali, carbon disulfide, etc. . All of the washed cellulose xanthate was recovered, and distilled water was added to make 20 kg of slurry having a cellulose solid content of 0.5% by mass. Using a high-pressure homogenizer (Sanwa Engineering Co., Ltd. H20 type), the slurry was defibrated by passing it a total of 5 times at a flow rate of 2.5 L/min and a pressure of 40 MPa to obtain xanthate-modified cellulose fine fibers. .

<Degree of defibration of fine fibers>
Distilled water was added to the slurry of the xanthate-modified cellulose fine fibers (cellulose solid content: 0.5% by mass) that had been defibrated as described above to adjust the slurry concentration to 0.1% by mass. This slurry was centrifuged (12000 G, 10 minutes) to sediment the unfibrillated matter. The supernatant was separated as a nanofiber slurry and transferred to an Erlenmeyer flask. Distilled water was added to the sedimented unfibrillated matter and centrifuged again to wash the unfibrillated matter. The unfibrillated material was transferred to a crucible and absolutely dried, and the mass of the unfibrillated material was measured. Based on the mass of the unfibrillated material and the content of cellulose in the defibrated cellulose xanthate, the yield of xanthate-modified cellulose nanofibers was obtained from the following equation (2). Hereinafter, xanthate-modified cellulose fine fibers that did not settle in the centrifugal separation operation are defined as xanthate-modified cellulose nanofibers. The nanofiber production rate of the xanthate-modified cellulose fine fibers obtained by the defibration treatment was 99.0%.

Production rate of cellulose xanthate nanofibers (% by mass) = (cellulose content in cellulose xanthate - mass of undisentangled matter) ÷ (cellulose content in cellulose xanthate) x 100 (2)

A portion of the supernatant of the xanthate-modified cellulose fine fibers transferred to the Erlenmeyer flask was sampled and placed in a 500 mL tall beaker. 50 mL of 0.5 M sodium hydroxide solution (5° C.) was added thereto and stirred, and the average degree of xanthate substitution was measured by the Bredee method and found to be 0.263.

A slurry of xanthate-modified cellulose fine fibers diluted to about 0.1% by mass with water was placed in a centrifuge tube and centrifuged at 12000 G for 10 minutes to collect the centrifugal supernatant. This centrifugal supernatant was subjected to concentration adjustment, dyeing, and dried on a supporting membrane to obtain a dry specimen. Observation was performed using a transmission electron microscope (TEM, JEM-1400, manufactured by JEOL Ltd.) at an accelerating voltage of 120 kV. The photograph is shown in FIG. 50 nanofibers were selected from the observed 50,000-fold image, the fiber diameter was measured, and the average value was obtained. , the number average fiber diameter was 6.1 nm.

<Regeneration treatment and re-dispersion treatment>
360 ml of 1 M sulfuric acid (sulfuric acid amount 4.4 mmol/g-cellulose solid content) was added to 16.4 kg of the xanthate-modified cellulose fine fiber slurry (0.5% by mass of cellulose solid content) obtained by the above procedure, and the mixture was stirred with an agitator. The mixture was stirred for about 1 hour for regeneration treatment. After completion of the treatment, the slurry was neutralized to pH 7 with a 1M sodium hydroxide solution to obtain a regenerated cellulose fine fiber slurry. When the average degree of xanthate substitution was measured, it was less than the lower limit of measurement of 0.001, so it was confirmed that the xanthate groups were almost completely eliminated by the acid treatment and returned to hydroxyl groups.

The regenerated cellulose fine fiber slurry obtained above was centrifugally dehydrated using a centrifugal dehydrator (H-130C manufactured by Kokusan Co., Ltd., filter cloth 400 mesh), and thoroughly washed while adding distilled water. All the regenerated cellulose fine fibers after washing were collected, and distilled water was added to make 10 kg of slurry having a cellulose solid content of 0.5% by mass. This slurry was re-dispersed by passing it three times in total at a flow rate of 2.5 L/min and a pressure of 40 MPa using a high-pressure homogenizer (Sanwa Engineering Co., Ltd. H20 type). Particle size distribution and transmittance were measured at the end of each pass. The transition of the particle size distribution is shown in FIG. 4, the median diameter of the particle size distribution is shown in Table 1, and the transmittance is shown in Table 2. Compared with the regenerated cellulose fine fibers before redispersion treatment, it can be confirmed that the median diameter of the particle size distribution of the redispersed redispersed regenerated cellulose fine fibers is smaller, and the transmittance increases as the number of passes increases. became. From these results, it was found that nano-dispersion was further advanced by subjecting the regenerated cellulose fine fiber slurry to re-dispersion treatment. Furthermore, when the average fiber diameter of the regenerated cellulose fine fiber redispersion slurry was calculated in the same manner as the xanthate cellulose fine fiber slurry, the fiber diameter of the regenerated cellulose fine fiber redispersion was 3.0 nm to 7.4 nm, and the number average The fiber diameter was 6.0 nm. As shown in FIG. 2, which is a TEM photograph of the redispersed regenerated cellulose fine fibers, it was confirmed that the fiber diameter was maintained at the same level as before the regeneration treatment. The concentration of the slurry of the redispersed regenerated cellulose fine fibers was 0.5% by mass, which was the same as the concentration of 0.5% by mass of the xanthate-modified cellulose fine fiber slurry before the regeneration treatment.

In addition, in measuring the particle size distribution shown in Table 1, a laser diffraction particle size distribution analyzer (manufactured by Microtrack Bell Co., Ltd.: MT3300EXII) was used. The measurement method was a flow cell, particle refractive index 1.53, solvent refractive index 1.333, measurement range 0.02 to 2000 μm, concentration of measurement sample 0.5% by mass. The median diameter is the particle diameter when 50% of the total particles are integrated from the smallest particle diameter.

In addition, in measuring the transmittance, the redispersed regenerated cellulose fine fibers were diluted to 0.1% by mass. After that, the sample was allowed to stand for 5 minutes and no sedimentation was observed. Using an ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation: UV-2450), the diluted slurry was placed in a quartz cell, and the transmittance at an optical path length of 10 mm and a wavelength of 660 nm was measured.

(Reference example 1)
Redispersion was performed under the same conditions except that the concentration of the regenerated cellulose fine fibers during the redispersion treatment was changed from 0.5% by mass to 1.0% by mass. Fig. 5 shows photographs of the slurry before redispersion (left photo) and the slurry after redispersion (right photo). In the slurry before redispersion (left photo), the particles have become large due to agglomeration, and solid sedimentation has occurred near the bottom. On the other hand, in the slurry after re-dispersion (right photo), the aggregation is almost eliminated and the individual particles are small, so no sedimentation occurs and the particles are dispersed throughout the slurry.

<Dehydration concentration treatment>
Furthermore, 30 g of the regenerated cellulose fine fiber redispersion slurry was filtered with a pressure filter (KST-47 manufactured by Advantech Co., Ltd.) (5C filter paper with a pore size of 1.0 μm, pressure of 3 kgf / cm ² ). When the filtration time was measured when it stopped changing for a minute, it was 26 minutes. In addition, when the solid content concentration of the slurry after filtration was calculated from the amount of the final filtrate (28.4 mL), it was 9.6% by mass, and a regenerated cellulose fine fiber dehydrate with a high solid content concentration was easily obtained. rice field.

(Comparative example 1)
A regenerated cellulose fine fiber slurry was obtained in the same manner as in Example 1 above, except that the re-dispersion treatment was not performed. When this regenerated cellulose fine fiber slurry (solid content concentration 0.5% by mass) was similarly dehydrated and concentrated, the filtration time was 20 minutes, the final filtrate volume was 26.8 mL, and the solid content concentration of the dehydrated regenerated cellulose fine fiber was was 4.7% by mass. Compared with Example 1, the filtration time was fast, but the solid content concentration was low. This is presumably because the regenerated cellulose fine fibers are agglomerates, making it difficult to remove water in the gaps between the agglomerates during filtration.

(Comparative example 2)
Cellulose nanofibers (BiNFi-s manufactured by Sugino Machine Co., Ltd.) obtained by mechanical fibrillation were dispersed in water to prepare a slurry having a solid content concentration of 0.5% by mass. When this slurry was dehydrated and concentrated in the same manner as in Example 1, the filtration time was 33 minutes and the final filtrate volume was 28.8 mL. Such a result was obtained.

FIG. 3 shows a graph comparing the filtration time and final filtrate volume in Example 1 and Comparative Examples 1 and 2. In FIG. Example 1, which was re-dispersed after regeneration, shows a similar filtration amount in about half the time of Comparative Example 2 as a whole, and the time required for concentration is significantly greater than that of mechanically defibrated cellulose nanofibers. It was shown that it can be shortened to In addition, compared to Comparative Example 1, the filtration time was slightly delayed, but the amount of filtrate was increased, indicating that the solid content concentration of the regenerated cellulose fine fiber dehydrated product after concentration could be increased.

<Verification of re-dilution>
(Examples 2-5)
A regenerated cellulose fine fiber slurry was obtained in the same procedure as in Example 1. This regenerated cellulose fine fiber slurry was subjected to re-dispersion treatment in the same manner as in Example 1. 2.0 kg of the redispersed regenerated cellulose fine fiber redispersion slurry was weighed in a 2 L beaker with a handle, and centrifuged using a centrifugal dehydrator (H-110A manufactured by Kokusan Co., Ltd., filter cloth 400 mesh). , all the dehydrated regenerated cellulose fine fibers remaining in the filter cloth were recovered. The recovered regenerated cellulose fine fiber dehydrated matter was 333 g, and the cellulose solid content of the dehydrated matter was 3.0% by mass (Example 2).

In the same operation with the centrifugal dehydration conditions changed, the centrifugal dehydration time was adjusted so that the solid content concentration was about 5% by mass, about 10% by mass, and about 15% by mass. Dehydrated products were obtained respectively. Specifically, when the target solid content concentration was about 5% by mass, the amount of dehydrated matter was 222 g and the cellulose solid content was 4.5% by mass (Example 3). When the target solid content concentration was about 10% by mass, the amount of dehydrated matter was 102 g and the cellulose solid content was 9.8% by mass (Example 4). When the target solid content concentration was about 15% by mass, the amount of dehydrated matter was 68 g and the cellulose solid content was 14.6% by mass (Example 5).

Photographs of these dehydrated products are shown in FIGS. 6(a) to 6(c). In Example 2 (solid content 3.0% by mass, FIG. 6(a)), it is a paste with a high water content, and in Example 3 (solid content 4.5% by mass, FIG. 6(b)), it is almost water. It becomes a paste-like form that has been removed. In Example 4 (solid content 9.8% by mass, FIG. 6(c)), plate-like lumps were obtained. In addition, in Example 5, a plate-like mass almost similar to that in Example 4 was obtained.

(Example 2a, Example 2b)
In Example 2, 167 g of the regenerated cellulose fine fiber dehydrate obtained above (containing 5 g of cellulose solid matter) was weighed into a 2 L beaker, 167 g of water was added, and the dehydrate was thoroughly kneaded with a glass rod. After that, water was further added to make 1000 g of a 0.5% by mass slurry. This slurry was re-diluted by stirring at 1000 rpm for 5 minutes (Example 2a) or 10 minutes (Example 2b) using a stirrer (HEIDON three-one motor 1200G manufactured by Shinto Kagaku Co., Ltd.). . Table 3 shows the median diameter and transmittance of the re-diluted regenerated cellulose fine fibers after re-dilution. When compared with the redispersed regenerated cellulose fine fiber slurry (Example 1) before the dehydration treatment, the regenerated cellulose fine fiber rediluted slurry obtained by rediluting the dehydrated product had approximately the same median diameter and transmittance. From this, it was found that the dehydrated matter dewatered after the redispersion treatment can be dispersed in a state substantially similar to that of the redispersion before dehydration by the redilution treatment.

Further, when the time required for the redilution treatment was doubled (Example 2a→Example 2b), the median diameter decreased slightly and the transmittance increased to approach the median size and transmittance before dehydration. From this, it was confirmed that although dehydration and concentration caused aggregation to progress slightly, progressing with re-dilution could easily approach the situation before dehydration and concentration.

(Example 3)
As Example 3, the dehydrated regenerated cellulose fine fiber having a cellulose solid content of 4.5% by mass obtained above was also subjected to re-dilution treatment. As for the method of adding water for re-dilution, stepwise dilution and kneading were carried out until the solid content concentration became 2% by mass or less. That is, the same mass of water was added to a dehydrated product (111 g) having a cellulose solid content of 4.5% by mass, and the mixture was sufficiently kneaded with a glass rod, diluted to 2.25% by mass, and further diluted to 1.13% by mass. It was diluted and kneaded in the same manner, and finally diluted to 0.5% by mass to obtain a regenerated cellulose fine fiber slurry. Other than that, redilution was performed in the same manner as in Example 2b. Table 3 shows the results.

(Example 4a)
As Example 4, 51 g of the regenerated cellulose fine fiber dehydrate obtained above (9.8% by mass, containing 5 g of cellulose solids) was added with water so that the concentration was halved in the same manner as in Example 3. Repeat the kneading operation (9.8% by mass → 4.9% by mass → 2.45% by mass → 1.23% by mass), and finally add water to make a 0.5% by mass regenerated cellulose fine fiber slurry. got The regenerated cellulose fine fiber slurry was rediluted as in Examples 2b and 3. When this rediluted product was allowed to stand for 1 hour, the solid content settled. Table 3 shows the median diameter and transmittance of the re-diluted regenerated cellulose fine fibers after re-dilution. Aggregation due to dehydration progressed as compared with Example 3, and it was found that the energy required for re-dilution increased.

(Example 4b)
As Example 4, 51 g of the dehydrated regenerated cellulose fine fiber obtained above (9.8% by mass, containing 5 g of cellulose solid matter) was weighed into a 2 L beaker, 51 g of water was added, and the dehydrated matter was sufficiently removed with a glass rod. kneaded to In the same manner, water is added and kneaded so that the concentration is halved (9.8% by mass → 4.9% by mass → 2.45% by mass → 1.23% by mass). .23% by mass of kneaded material. Finally, water was added to make 1000 g of 0.5% by weight slurry. This slurry was re-diluted using a rotary homogenizer (manufactured by Nippon Seiki Seisakusho: AM-7) at 10,000 rpm for 5 minutes, and was able to be dispersed. Table 3 shows the median diameter and transmittance of the re-diluted regenerated cellulose fine fibers after re-dilution. Compared with the redispersed regenerated cellulose fine fibers before the dehydration treatment (Example 1), the regenerated cellulose fine fiber rediluted product obtained by rediluting the dehydrated regenerated cellulose fine fibers has the same median diameter and transmittance. Therefore, it was found that this regenerated cellulose fine fiber dehydrated product can also be sufficiently dispersed by redilution treatment.

(Example 5)
As Example 5, the regenerated cellulose fine fiber dehydrated product (14.6% by mass, 34 g) obtained above was weighed in a 2 L beaker, 34 g of water was added, and the dehydrated product was thoroughly kneaded with a glass rod. In the same manner as in Example 4b, the operation of adding water and kneading is repeated so that the concentration is halved (14.6% by mass → 7.3% by mass → 3.65% by mass → 1.83% by mass %) and 1.83 mass % kneaded product. Finally, water was added to make 1000 g of 0.5% by weight slurry. Next, a redilution treatment was performed by the same procedure as in Example 4b. However, the dilution time was extended from 5 minutes to 10 minutes. Table 3 shows the median diameter and transmittance of the re-diluted regenerated cellulose fine fibers after re-dilution. Compared with the redispersed regenerated cellulose fine fibers before the dehydration treatment (Example 1), the regenerated cellulose fine fiber rediluted product obtained by rediluting the dehydrated regenerated cellulose fine fibers has the same median diameter and transmittance. Therefore, it was found that this regenerated cellulose fine fiber dehydrated product can also be dispersed by redilution treatment.

<Difficulty in re-dilution without re-dispersion treatment>
(Comparative Example 3)
By the same procedure as in Comparative Example 1, a regenerated cellulose fine fiber slurry was obtained without redispersion treatment. 2.0 kg of this regenerated cellulose fine fiber slurry was weighed in a 2 L beaker with a handle, centrifuged using a centrifugal dehydrator (H-110A manufactured by Kokusan Co., Ltd., filter cloth 400 mesh), and distilled water was added. was washed thoroughly. All the regenerated cellulose fine fiber washing dehydrated matter remaining in the filter cloth was recovered. The recovered regenerated cellulose fine fiber washed dehydrated matter was 333 g, and the cellulose solid content of the dehydrated matter was 3.0% by mass. 167 g of this regenerated cellulose fine fiber washed dehydrated product (3.0% by mass, containing 5 g of cellulose solids) was added with water and kneaded in the same manner as in Example 2 so that the concentration was halved. A regenerated cellulose fine fiber slurry of 0.5% by mass was typically prepared. Next, when it was re-diluted in the same procedure as in Examples 2b and 3, it sedimented without dispersing. Table 3 shows the median diameter of this rediluted product. Since the redispersion treatment was not performed after the regeneration treatment, the median diameter was not reduced even by the redilution treatment, and it was found that the regenerated cellulose fine fibers in the rediluted product aggregated.

<Difference in re-dilution process>
(Comparative Example 4)
By the same procedure as in Comparative Example 1, a regenerated cellulose fine fiber slurry was obtained without redispersion treatment. 2.0 kg of this regenerated cellulose fine fiber slurry was weighed in a 2 L beaker with a handle, centrifuged using a centrifugal dehydrator (H-110A manufactured by Kokusan Co., Ltd., filter cloth 400 mesh), and distilled water was added. was washed thoroughly. All the regenerated cellulose fine fiber washing dehydrated matter remaining in the filter cloth after washing was recovered. The recovered regenerated cellulose fine fiber washed dehydrated matter was 333 g, and the cellulose solid content of the dehydrated matter was 3.0% by mass. Distilled water was added to 50 g of this regenerated cellulose fine fiber washed dehydrated product (3.0 mass %, containing 1.5 g of cellulose solid matter) to prepare 300 g of slurry having a cellulose solid content of 0.5 mass %. This slurry was subjected to a re-dilution treatment using a rotary homogenizer (manufactured by Nippon Seiki Seisakusho: AM-7) at 15000 rpm for 5 minutes. Table 3 shows the median diameter and transmittance of this rediluted regenerated cellulose fine fiber rediluted product. When the slurry of this regenerated cellulose fine fiber rediluted product was allowed to stand still for 1 hour, the solid content settled down, resulting in a rediluted product in which aggregates were not sufficiently dispersed. From this, it was confirmed that even if the redilution process was changed, the redilution was difficult unless the redispersion process was performed before the dehydration and concentration.

<Hydrogen peroxide water treatment of regenerated cellulose fine fibers>
(Example 6)
Among the procedures of Example 1, the regeneration treatment and neutralization were performed to obtain a slurry (A) of regenerated cellulose fine fibers. 10 kg of this regenerated cellulose fine fiber slurry (A) is weighed into a bucket with a capacity of 20 L, centrifuged using a centrifugal dehydrator (H-130C manufactured by Kokusan Co., Ltd., filter cloth 400 mesh), and distilled water. was thoroughly washed while adding All the washed dehydrated regenerated cellulose fine fibers (B) remaining in the filter cloth after washing were recovered, and distilled water was added to make 10 kg of concentration-adjusted slurry of regenerated cellulose fine fibers having a cellulose solid content of 0.5% by mass. . 34 mL of a 10 M sodium hydroxide solution was added to this regenerated cellulose fine fiber concentration-adjusted slurry (C), and the mixture was stirred in a hot water bath at 70°C. After the slurry temperature reaches 60° C. or higher, hydrogen peroxide solution (manufactured by Santoku Chemical Industry Co., Ltd., hydrogen peroxide concentration 31% by mass) is added so that the hydrogen peroxide concentration of the entire slurry becomes 0.7%. 225.8 g was added and stirred for 1 hour. After cooling, it was neutralized with 1M sulfuric acid to obtain regenerated cellulose fine fibers (D) treated with hydrogen peroxide water. The regenerated cellulose fine fibers (D) treated with hydrogen peroxide water are centrifuged and dehydrated using a centrifugal dehydrator (H-130C manufactured by Kokusan Co., Ltd., filter cloth 400 mesh) to rewash and dehydrate the regenerated cellulose fine fibers. A product (E) was obtained. This regenerated cellulose fine fiber rewashed dehydrated product (E) was thoroughly washed while adding distilled water. All the washed regenerated cellulose fine fiber rewashed dehydrated matter (E) after washing was collected, and distilled water was added to make 10 kg of slurry having a cellulose solid content of 0.5% by mass. This slurry was re-dispersed by passing it once at a flow rate of 2.5 L/min and a pressure of 40 MPa using a high-pressure homogenizer (Sanwa Engineering Co., Ltd. H20 type). This regenerated cellulose fine fiber redispersion (F) had a median diameter of 13.98 μm and a transmittance of 96.1%.

In the description of Examples 6 to 9 and Comparative Examples 5 to 8, the respective regenerated cellulose fine fiber slurries, dehydrated products, etc. are indicated by the following symbols.
・Regenerated cellulose fine fiber slurry neutralized after regeneration treatment (A)
・Regenerated cellulose fine fiber washed dehydrated product obtained by centrifugally dewatering (A) … (B)
・Concentration-adjusted regenerated cellulose fine fiber slurry obtained by adding distilled water to (B) to adjust the concentration … (C)
・ After heating (C), add hydrogen peroxide water, stir and neutralize with acid (hydrogen peroxide water treatment) regenerated cellulose fine fiber slurry … (D)
<(D) and after are all treated with hydrogen peroxide>
・ Re-washed dehydrated regenerated cellulose fine fibers obtained by centrifugally dewatering (D) ...... (E)
・Regenerated cellulose fine fiber redispersion, which is a slurry obtained by adding distilled water to (E) and redispersing with a homogenizer ... (F)
・Regenerated cellulose fine fiber dehydrate obtained by centrifugally dehydrating (F) and concentrating it (G)
・ Regenerated cellulose fine fiber redilution product obtained by rediluting (G) ...... (H)

2.0 kg of this hydrogen peroxide water-treated regenerated cellulose fine fiber redispersion (F) (0.5% by mass) was weighed in a 2 L beaker with a handle, and a centrifugal dehydrator (H-110A manufactured by Kokusan Co., Ltd., Centrifugal dehydration was performed using a filter cloth (400 mesh), and all the dehydrated regenerated cellulose fine fibers (G) remaining in the filter cloth were recovered. The recovered regenerated cellulose fine fiber dehydrated product (G) was 250 g, and the cellulose solid content in the dehydrated product was 4.0% by mass.

This regenerated cellulose fine fiber dehydrated product (G) (4.0% by mass) was subjected to re-dilution treatment. As for the method of adding water for re-dilution, stepwise dilution and kneading were carried out until the solid content concentration became 2% by mass or less. That is, the same mass of water was added to regenerated cellulose fine fiber dehydrate (G) (250 g) having a cellulose solid content of 4.0% by mass, and the mixture was sufficiently kneaded with a glass rod, diluted to 2.0% by mass, The mixture was diluted to 1.0% by mass, kneaded in the same manner, and finally diluted to 0.5% by mass to obtain a rediluted regenerated cellulose fine fiber (H). Other conditions were the same as in Example 4b except that the dehydrated product used and the starting concentration were different. This regenerated cellulose fine fiber rediluted product (H) had a median diameter of 15.38 μm and a transmittance of 94.6%. was found to be sufficiently dispersible by

<Confirmation of the emulsification effect of re-diluted regenerated cellulose fine fibers>
(Example 7)
Re-dispersion, dehydration concentration, and re-dilution were performed under the same conditions as in Example 6, except that the concentration of hydrogen peroxide during the hydrogen peroxide water treatment was changed from 0.7% to 0.1%. The regenerated cellulose fine fiber redispersion (F) had a median diameter of 16.63 μm and a transmittance of 91.7%. The cellulose solid content of the regenerated cellulose fine fiber dehydrate (G) was 5.7% by mass. The regenerated cellulose fine fiber rediluted product (H) had a median diameter of 18.29 μm and a transmittance of 90.3%.

(Example 8a: Olive oil emulsification: regenerated cellulose fine fiber redispersion (F))
In Example 7, 14.4 g of regenerated cellulose fine fiber redispersion (F) was collected before dehydration concentration and redilution, and 9.6 g of distilled water was added to obtain 0.3% by mass of regenerated cellulose fines. A fiber slurry was prepared. 6 g of olive oil (manufactured by Nacalai Tesque Co., Ltd.: olive oil) was added to this slurry and emulsified using a homogenizer (manufactured by Nippon Seiki Seisakusho: AM-7) at 8000 rpm for 5 minutes. The obtained emulsion was collected in a 15 g sample bottle and allowed to stand. After standing for 7 days, the emulsified state was maintained.

(Example 8b: Olive oil emulsification: Regenerated cellulose fine fiber redilution (H))
Further, in Example 8a, the slurry of regenerated cellulose fine fibers used for emulsification treatment was redispersed with hydrogen peroxide water and the regenerated cellulose fine fibers treated with hydrogen peroxide water (F) was changed to the regenerated cellulose fine fibers treated with hydrogen peroxide water in Example 7. Emulsification treatment was carried out in the same manner except for changing to the re-diluted product (H). The obtained emulsion was collected in a 15 g sample bottle and allowed to stand. After standing for 7 days, the emulsified state was maintained.

(Comparative Examples 5 and 6: Olive oil emulsification)
As a comparison with Examples 8a and 8b, an emulsification treatment was performed using only water and olive oil without using a slurry of regenerated cellulose fine fibers (Comparative Example 5). In addition, in Example 8b, instead of the rediluted regenerated cellulose fine fiber (H), cellulose nanofiber (BiNFi-manufactured by Sugino Machine Co., Ltd.) mechanically defibrated without going through chemical modification such as xanthate s) was used for emulsification (Comparative Example 6).

(Example 9a: Squalane emulsification: regenerated cellulose fine fiber redispersion (F))
The same operation as in Example 8a was performed except that the olive oil was changed to squalane (manufactured by Nacalai Tesque Co., Ltd.: squalane). That is, emulsification was performed with the regenerated cellulose fine fiber redispersion (F) interposed before the dehydration concentration and redilution of Example 7 were performed. Similarly, when left to stand for 7 days, the emulsified state was maintained.

(Example 9b: Squalane emulsification: Regenerated cellulose fine fiber redilution (H))
Further, in Example 9a, the same is true except that the regenerated cellulose fine fiber slurry used in the emulsification treatment was changed from the regenerated cellulose fine fiber redispersion (F) to the regenerated cellulose fine fiber redilution (H) of Example 7. The emulsification treatment was performed by the operation of .

(Comparative Examples 7 and 8: Squalane emulsification)
As a comparison with Examples 9a and 9b, an emulsification treatment was performed using only water and squalane without using a slurry of regenerated cellulose fine fibers (Comparative Example 7). In Example 9b, instead of the regenerated cellulose fine fiber redilution (H), cellulose nanofibers (BiNFi manufactured by Sugino Machine Co., Ltd.) mechanically defibrated without undergoing chemical modification such as xanthate -s) was used to emulsify (Comparative Example 8).

FIG. 7 shows a photograph of each of the above emulsions left standing for 7 days. The example group of olive oil is shown on the left side of the photograph, and the example group of squalane is shown on the right side. The sample bottles are, from the left, water and olive oil only (Comparative Example 5), emulsification with olive oil and BiNFi-s (Comparative Example 6), emulsification with olive oil and regenerated cellulose fine fiber redispersion (F) (Example 8a), and olive oil. and regenerated cellulose fine fiber redilution (H) (Example 8b), water and squalane only (Comparative Example 7), squalane and BiNFi-s emulsification (Comparative Example 8), squalane and regenerated cellulose fine fiber redispersion emulsification with body (F) (Example 9a), followed by emulsification with squalane and regenerated cellulose fine fiber redilution body (H) (Example 9b). When the cellulose fine fibers were not added (Comparative Examples 5 and 7), layer separation was confirmed after about 1 hour of standing. When BiNFi-s was added (Comparative Examples 6 and 8), an emulsified portion was observed after one day of standing, but a layer-separated portion was confirmed. When the regenerated cellulose fine fiber redispersion (F) was added (Example 8a, Example 9a), or when the regenerated cellulose fine fiber redilution (H) was added (Example 8b, Example 9b), the separation layer was not identified. From this, it can be seen that the redispersed regenerated cellulose fine fibers can maintain an emulsified state, and the regenerated cellulose fine fiber rediluted, which is obtained by re-diluting the dehydrated and concentrated material after performing re-dispersion treatment, is also in an emulsified state. was found to hold Furthermore, it was found that the regenerated cellulose fine fibers according to the present invention exhibit higher emulsifying performance than mechanically defibrated cellulose nanofibers.

<Comparison with cellulose fine fibers defibrated by phosphate esterification>
(Comparative Example 9)
A portion of the cellulose fibers was phosphated to facilitate defibration, and then defibrated to obtain phosphate-esterified cellulose fine fibers. Then, after removing the substituents, re-dispersion treatment was carried out, and the substances remaining after the treatment for removing the substituents were removed using an ion-exchange resin. After dehydrating and concentrating the obtained cellulose fine fibers, the re-diluted product was used for comparison with the present invention. Specific detailed procedures are as follows.

・Introduction of Substituents into Fiber Materials 66.43 g of sodium dihydrogen phosphate dihydrate and 124.81 g of disodium hydrogen phosphate dodecahydrate were dissolved in 60.22 g of distilled water to obtain a phosphorylation reagent. . 20 g of kraft pulp (manufactured by Nippon Paper Industries Co., Ltd.: NBKP) in absolute dry weight was collected in a 1 L beaker and uniformly impregnated with a mixture of 42 g of a phosphorylating reagent and 40 g of distilled water by spraying. The mixture was placed in a 105° C. blower dryer (manufactured by Isuzu Manufacturing Co., Ltd.: VTR-115), kneaded once every 15 minutes, and dried until the mass became constant. Then, it was heat-treated for 1 hour in a blower dryer at 150° C. to obtain a phosphate group-introduced cellulose fiber.

Next, all of the phosphate group-introduced cellulose fibers are added to 2 L of distilled water, stirred and dispersed, and centrifugally dehydrated using a centrifugal dehydrator (H-110A manufactured by Kokusan Co., Ltd., filter cloth 400 mesh), It was thoroughly washed while adding distilled water. All the washed phosphate group-introduced cellulose fibers remaining in the filter cloth were recovered, and 2 kg of distilled water was added to prepare a slurry having a solid content of 1% by mass. 62.6 mL of 1 M sodium hydroxide solution was added to this slurry to obtain a cellulose fiber-containing slurry having a pH of 12.1. Thereafter, this slurry was dehydrated, and 2 kg of distilled water was added to perform dehydration and washing again. This dehydration wash was repeated once more.

- Refinement of fiber raw material The cellulose fibers obtained after the above dehydration and washing were weighed in a 2 L beaker with a handle, and distilled water was added to make 1 kg of a slurry having a solid content of 0.5% by mass. This slurry is passed through a high-pressure homogenizer (Sanwa Engineering Co., Ltd. L-01 type) at a flow rate of 160 mL/min and a pressure of 60 MPa for a total of 7 passes for fibrillation, and then distilled water is added to solidify the slurry. The content was adjusted to 0.2% by mass, centrifuged (12000 G, 10 minutes), and the resulting supernatant was collected to obtain a fine cellulose fiber-containing slurry. The resulting slurry containing fine cellulose fibers is desalted according to the following "Desalting treatment of slurry containing fine cellulose fibers using an ion exchange resin", and substituted by the method "Measurement of the amount of substituents on the surface of cellulose". As a result of measuring the base amount, it was 0.512 mmol/g.

- Elimination of Substituent from Fine Fiber Raw Material 500 g of the resulting fine cellulose fiber-containing slurry was placed in a pressure-resistant glass container, and subjected to heat hydrolysis treatment at 120°C for 10 hours in an autoclave. After cooling, aggregates were collected by filtration and thoroughly washed with distilled water. All aggregates on the filter paper are collected, distilled water is added to prepare 200 g of 0.5% by mass slurry, and a homogenizer (manufactured by Nippon Seiki Seisakusho: AM-7) is used for 3 minutes at 8000 rpm. Then, a slurry containing fine cellulose fibers having desubstituted groups was obtained. The obtained slurry containing substituent-eliminated fine cellulose fibers was subjected to desalting treatment in the following "Desalting treatment of fine cellulose fiber-containing slurry using ion exchange resin", and the following "Measurement of the amount of substituents on the cellulose surface" was performed. As a result of measuring the amount of substituents by the method, it was 0.01 mmol/g. Moreover, the slurry containing the substituent-eliminated fine cellulose fibers maintained a dispersed state, and Table 4 shows the results of measuring the median diameter and transmittance.

- Desalination treatment of fine cellulose fiber-containing slurry using ion exchange resin In the treatment of fine cellulose fiber containing slurry using ion exchange resin, 1/10 by volume of ion exchange resin is added to fine cellulose fiber containing slurry, After shaking for 1 hour, the mixture was poured onto a sieve with an opening of 90 μm to separate the resin from the slurry, which was repeated three times. The first time was performed using a conditioned strongly acidic ion exchange resin (for example, Diaion SK110 manufactured by Mitsubishi Chemical Corporation). The second time was carried out using a conditioned strongly basic ion exchange resin (eg, Diaion SA12A, manufactured by Mitsubishi Chemical Corporation). The third time was treated in the same manner as the first time.

- Measurement of Substituent Group Amount on Cellulose Surface A fine cellulose fiber-containing slurry containing 0.04 g of absolute dry mass of the fine cellulose fibers obtained by the above treatment was fractionated and diluted to about 50 g with deionized water. While stirring this solution, measure the change in the value of the electrical conductivity when adding 0.01 M sodium hydroxide aqueous solution, and drop the 0.01 M sodium hydroxide aqueous solution when the value becomes minimum. The amount was taken as the drop amount at the end point of titration. At this time, the amount of substituents on the cellulose surface is represented by the following formula.

Amount of substituents on the surface of cellulose (mmol/g) = 0.01 (mol/L x 0.01M sodium hydroxide drop amount (mL) ÷ fine cellulose fiber-containing slurry solid content (g)

- Dehydration step of slurry containing desubstituted fine cellulose fibers 500 g of slurry containing desubstituted fine cellulose fibers was weighed in a 1 L beaker with a handle, and centrifuged (H-110A manufactured by Kokusan Co., Ltd., filter cloth 400 mesh). ) to collect all the substitutable dehydrated fine cellulose fiber remaining in the filter cloth. The collected dehydrated substance of desubstituted fine cellulose fibers was 67.6 g, and the solid content of the dehydrated substance was 5.2% by mass.

・Re-dilution treatment of dehydrated matter 67.6 g of dehydrated matter of desubstituted fine cellulose fibers (containing 2.5 g of solid matter) was weighed into a 1 L beaker, 67.6 g of water was added, and the dehydrated matter was sufficiently diluted with a glass rod. kneaded to After that, water was further added to make 500 g of a 0.5% by mass slurry. This slurry was subjected to re-dilution treatment using a rotary homogenizer (manufactured by Nippon Seiki Seisakusho: AM-7) at 10000 rpm for 5 minutes. Table 4 shows the median diameter and transmittance of the rediluted substituting group-eliminated fine cellulose fibers after redilution. Compared with the dehydrated fine cellulose fiber without dehydration treatment, the rediluted dehydrated fine cellulose fiber without dehydration treatment has a smaller median diameter and a lower transmittance. are at the same level. However, the regenerated cellulose fine fibers made from xanthate-modified cellulose fine fibers have a larger median diameter than the rediluted product obtained by re-diluting the dehydrated regenerated cellulose fine fibers made from xanthate-modified cellulose fine fibers. I found out that

Claims (5)

A cellulose fine fiber dehydrate in which the solid content concentration of regenerated cellulose fine fibers is 2% by mass or more and 15% by mass or less. After defibrating the xanthate cellulose material, for the cellulose fine fibers that have been regenerated back to cellulose by performing a regeneration treatment,
A method for producing a dehydrated product of cellulose fine fibers, wherein the dehydrated product of cellulose fine fibers according to claim 1 is obtained by carrying out a dehydration concentration treatment after performing a dispersion treatment. 3. The method for producing a dehydrated product of cellulose fine fibers according to claim 2, wherein a hydrogen peroxide solution treatment is performed after the regeneration treatment and before the dispersion treatment. 4. The method for producing dehydrated cellulose fine fibers according to claim 2 or 3, wherein the median diameter is reduced to 1/4 or less in the dispersion treatment. A method for producing a rediluted cellulose fine fiber, comprising diluting a dehydrated cellulose fine fiber produced by the production method according to any one of claims 2 to 4 in an aqueous solvent to obtain a rediluted cellulose fine fiber.

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