JP5456269B2 - Method for producing cellulose dispersion - Google Patents

Description

  The present invention relates to a method for producing a highly transparent fine oxidized cellulose fiber dispersion containing fine oxidized cellulose fibers having an average fiber diameter of 200 nm or less.

  In industrial products, structural materials, cosmetics, foods, gas barrier materials, etc., production of biodegradable and fine cellulose dispersions has been studied.

  Patent Document 1 describes a method for preparing a cellulose dispersion, but does not describe the carboxyl group content of cellulose. In addition, since a super high pressure homogenizer and a medium mill are used in combination, it cannot be said to be a simple manufacturing method.

  Patent Document 2 does not describe the carboxyl group content of cellulose. Since the grinder and the high-pressure homogenizer are substantially used in combination, it is considered that the damage of the cellulose fiber is increased.

  Patent Document 3 does not describe the carboxyl group content of cellulose. Processing is performed with a high-pressure homogenizer, and the fiber width after the processing is 1 μm or more.

  Patent Document 4 describes that a carboxyl group is introduced into cellulose by using periodic acid or a salt thereof, but since a substantial grinder and a high-pressure homogenizer are used, the cellulose fiber is greatly damaged. The number average fiber length after the treatment is considerably large as 0.05 to 0.3 mm.

  Non-Patent Document 1 discloses that the surface of cellulose is oxidized using an oxidizing agent in the presence of bromide and 2,2,6,6-tetramethylhydroxy-1-hydroxy radical in water, and then transparent using Waring Blender. However, there is no description regarding the operating conditions, and the transmittance of light (λ: 550 nm) of the 0.1% dispersion is only 77%.

Non-Patent Document 2 describes that the light transmittance of a 0.1% dispersion is 90% or more, but it is very inefficient because it is stirred for 10 days with a magnetic stirrer.
Japanese Patent No. 3262917 JP 2004-411119 A Japanese Patent Laying-Open No. 2005-270891 JP 2002-194691 A Bio MACROMOLECULES Volume 7, Number 6, June 2006, Published by the American Chemical Society Bio MACROMOLECULES Volume 8, Number 8, August 2007, Published by the American Chemical Society

  This invention makes it a subject to provide the manufacturing method of the fine oxycellulose fiber dispersion liquid which can obtain the highly transparent dispersion liquid containing the oxycellulose fiber refined | miniaturized.

  The present invention provides the following inventions as means for solving the problems.

The invention of claim 1 oxidizes cellulose fiber using 2.0 mmol to 10 mmol of oxidizing agent with respect to 1 g of the cellulose fiber (absolute dry basis), and contains a carboxyl group of cellulose constituting the cellulose fiber. Obtaining an oxidized cellulose fiber having an amount of 0.1 to 2.0 mmol / g;
A process for producing an oxidized cellulose fiber dispersion comprising a step of obtaining an oxidized cellulose fiber having an average fiber diameter of 200 nm or less by mechanically treating the oxidized cellulose fiber,
The mechanical treatment is a method for producing an oxidized cellulose fiber dispersion in which a high-speed rotary disperser having a rotating body is used and the peripheral speed of the blade tip of the rotating body is processed at 15 m / s or more.

  According to the production method of the present invention, it is possible to obtain a highly transparent aqueous dispersion containing fine oxidized cellulose fibers, and it is also possible to control the transparency to a desired level.

  Hereinafter, the manufacturing method of this invention of a fine oxidization cellulose fiber dispersion is demonstrated for every process.

<Oxidation process>
First, as a pretreatment step before the oxidation treatment, about 10 to 1000 times the amount (mass basis) of water is added to the raw natural cellulose fiber (absolute dry basis), and treated with a mixer or the like. Make a slurry.

  As natural cellulose fibers used as raw materials, wood pulp, non-wood pulp, cotton, silk, wool, chitin, chitosan, alginic acid, collagen, regenerated cellulose, bacterial cellulose and the like can be used.

  Next, the cellulose fiber in the slurry is oxidized to obtain an oxidized cellulose fiber having a carboxyl group content of 0.1 to 2.0 mmol / g of cellulose constituting the cellulose fiber.

  As a method for oxidizing cellulose fibers, for example, 2,2,6,6, -tetramethyl-1-piperidine-N-oxyl (TEMPO) is used as a catalyst, and an oxidizing agent such as sodium hypochlorite, A method of oxidizing in combination with bromide such as sodium bromide can be applied.

  The amount of TEMPO used is 0.1 to 10% by mass, preferably 0.2 to 8% by mass, more preferably 0.4 to 5% by mass, based on the cellulose fiber (absolute dry basis) used as a raw material. It is. If it is 0.1% by mass or more, the oxidation reaction proceeds smoothly, and if it is 10% by mass or less, the removal burden in the subsequent process is reduced.

  As the oxidizing agent, hypohalous acid or a salt thereof, or halogenous acid or a salt thereof can be used. Examples of hypohalites include sodium hypochlorite, potassium hypochlorite, and lithium hypochlorite. Examples of the halite include sodium chlorite, potassium chlorite, and lithium chlorite. The oxidizing agent is preferably sodium hypochlorite. When sodium hypochlorite is used, increasing the proportion of cellulose fiber used increases the amount of carboxyl groups introduced, increasing the electrostatic repulsion between the fibers or acting directly on the fibers. By doing so, the dispersibility of the fibers is improved and the transparency is promoted.

  The amount of the oxidizing agent used is 2.0 mmol to 10 mmol, preferably 2.3 mmol to 9 mmol, more preferably 2.5 mmol to 8 mmol, more preferably 3 to 1 g of cellulose fiber (absolute dry basis) used as a raw material. 0.0 mmol to 7.5 mmol. If it is 2.0 mmol or more, the oxidation reaction proceeds smoothly, and a transparent dispersion can be obtained. If it is 10 mmol or less, the removal burden in the subsequent process is reduced.

  Examples of the bromide include lithium bromide, potassium bromide, sodium bromide and the like, and sodium bromide is preferable.

  The amount of bromide used is 0.1 mmol to 10 mmol, preferably 0.5 mmol to 7 mmol, and more preferably 0.7 mmol to 5 mmol, with respect to 1 g of cellulose fiber (absolute dry basis) used as a raw material. If it is 0.1 mmol or more, the oxidation reaction proceeds smoothly, and if it is 5 mmol or less, the removal burden in the subsequent process is reduced.

  The pH is preferably in the range of 9.0 to 12.0 from the viewpoint of allowing the oxidation reaction to proceed efficiently. More preferably, the pH is 9.5 to 11.5.

  The temperature (temperature of the slurry) and time for the oxidation treatment are 1 to 50 ° C., and preferably 1 to 300 minutes.

  After the treatment in this step is completed, the used catalyst or the like may be removed by washing with water or the like, and a drying treatment may be performed as necessary.

  By the treatment in this step, the C6 position of the cellulose constituent unit can be selectively oxidized to a carboxyl group, and the carboxyl group content of the cellulose constituting the cellulose fiber can be 0.1 to 2.0 mmol / g. it can. The content is preferably 0.4 to 2.0 mmol / g, more preferably 0.5 to 1.7 mmol / g, and still more preferably 0.6 to 1.7 mmol / g. Said carboxyl group content is calculated | required by the measuring method as described in an Example. When the lower limit value of the carboxyl group content is less than 0.1 mmol / g, the average fiber diameter of the cellulose fibers does not become 200 nm or less even when the fiber refining treatment described later is performed, and the solid content concentration is 0. A 1% by weight aqueous dispersion does not become transparent. Furthermore, when the carboxyl group content is within the above range, the transparency of the aqueous dispersion having a solid content concentration of 0.1% by mass refinement (evaluated by the visual observation or the transmittance described in the examples) is improved. It becomes easy to make.

<Mechanical treatment process>
Next, the oxidized cellulose fiber obtained in the previous step is refined to a mean fiber diameter of 200 nm or less by mechanical treatment. As the mechanical treatment in this step, the following method can be applied. The oxidized cellulose fiber is preferably mechanically treated after it is made into an aqueous dispersion having a solid concentration of 0.01 to 10% by mass, preferably 0.05 to 5% by mass.

  As the mechanical treatment, a high-speed rotary disperser having one or more rotating bodies serving as stirring means is used, and the peripheral speed (hereinafter referred to as “peripheral speed”) of the blade tip of the rotating body is 15 m / s or more. It is a method of processing. The peripheral speed is 15 m / s or more, more preferably 20 m / s or more, and particularly preferably 22 m / s or more. The upper limit of the peripheral speed is not particularly present, but is preferably 100 m / s or less in view of economy and the mechanical strength of the disperser.

  The processing time can be appropriately set in relation to the peripheral speed, the capacity of the processing tank, the amount of processing performed once, and the like. For example, when the peripheral speed of the rotating body is 20 m / s, the capacity of the treatment tank is 1 L, and 500 g of an aqueous dispersion having a solid content concentration of 1% by mass is used, the treatment time is about 1 to 120 minutes.

  The high-speed rotating disperser is miniaturized by shearing force, impact force, and cavitation generated in the vicinity of a rotating body that rotates at high speed. The rotating body is a known one such as a stirring blade of various shapes, or one in which the tank itself rotates.

  The high-speed rotary disperser is a type in which the oxidized cellulose fiber to be processed is passed through the gap between the rotating body and the fixed part to disperse the inner rotating body rotating in a certain direction and the outside of the inner rotating body reversed. And an outer rotator rotating around the outer rotator, and the oxycellulose fiber to be treated is passed through and dispersed in the gap between the inner rotator and the outer rotator. High-speed rotary dispersers include, for example, M Technique's Claremix, Taihei Koki Co., Ltd. Milder, Primics Co., Ltd. TK Robotics, and Taihei Kiko Co., Ltd. Machine (Cabitron), high-speed rotating disperser (Sharp Flow Mill) manufactured by Taihei Koki Co., Ltd., and thin film swirl type high-speed rotating disperser (Filmix) manufactured by PRIMIX Corporation.

Since a high shear rate (unit s ⁻¹ ) can be generated by passing through a narrow gap while rotating at a high speed in this way, compared with a case where it is simply rotated at a high speed (that is, like a domestic juicer mixer). In addition, compared with the case where mechanical means having a large gap and a low shear rate are used, the refinement process can be effectively performed. The size of the gap is preferably 5 mm or less, more preferably 3 mm or less, and still more preferably 2 mm or less.

  In addition, what was processed once with the high-speed rotating disperser can be processed again. In the present invention, the first processing is one pass, the first processing is followed by the second processing is two passes, Similarly, processing three times is referred to as three passes. The number of passes is preferably 1 to 20 passes and more preferably 1 to 10 passes from the viewpoint of productivity.

  As the mechanical treatment in the mechanical treatment step, a medium stirring type disperser (media mill) can also be applied. The media mill is a method of dispersing the processing liquid by flowing the media filled in the mill by stirring or the like. For example, the following processing methods can be applied.

As a processing method,
(I) a batch processing method of injecting a processing liquid into a mill filled with media, processing for a predetermined time, and extracting the processing liquid;
(Ii) In a state where the inside of the mill filled with the medium is stirred with a stirrer, the liquid to be processed in another tank is continuously supplied into the mill by a pump or the like, and the dispersed processing liquid is supplied to the original tank. Circulation method method to return in,
(Iii) A dispersion treatment method by a pass method or the like in which all of the treatment liquid is received in a separate tank can be mentioned. The dispersion speed at the time of the dispersion treatment can be adjusted by the particle size and filling rate of the media, the stirring peripheral speed of the media mill, the supply speed, and the like.

  Examples of the media mill include a bead mill, a sand mill, a ball mill, and the like. Specifically, a visco mill (manufactured by AIMEX Co., Ltd.), a tower mill, a DCP super flow, a Cosmo (manufactured by Nihon Eirich Co., Ltd.), a star mill (Ashizawa).・ Finetech Co., Ltd.), Ultra Apex Mill (manufactured by Kotobuki Industries Co., Ltd.), Pico Mill (manufactured by Asada Iron Works Co., Ltd.), SC Mill, MSC Mill, Attritor (Mitsui Mine Co., Ltd.) And other known media mills.

  Examples of the material of the medium include high-hardness metals such as steel and chromium alloy, high-hardness ceramics such as alumina, zirconia, zircon, and titania, and polymer materials such as glass, ultrahigh molecular weight polyethylene, and nylon.

  The fine oxidized cellulose fiber obtained by the production method of the present invention has an average fiber diameter of 200 nm or less, preferably 1 to 200 nm, more preferably 1 to 100 nm, from the viewpoint of increasing the transparency of the aqueous dispersion. Preferably it is 1-50 nm. An average fiber diameter is calculated | required by the measuring method as described in an Example.

  The fine oxidized cellulose fiber obtained by the production method of the present invention preferably has an average fiber length of 40 μm or less from the viewpoint of increasing the transparency of the aqueous dispersion.

  The fine oxidized cellulose fiber obtained by the production method of the present invention preferably has an average aspect ratio (average fiber length / average fiber diameter) of 10 to 5,000, more preferably 10 to 2,000, still more preferably 10. ~ 1,000, more preferably 10-500.

  The aqueous dispersion obtained by the production method of the present invention has high transparency, and the transmittance measured by the method described in Examples can be 80% or more, preferably 85% or more, more preferably 90% or more. Can be.

  The transparency can be controlled to a desired level by appropriately selecting conditions in the oxidation treatment and the mechanical treatment. For example, in the oxidation treatment, the oxidation conditions are selected so that the carboxyl group content of the cellulose constituting the cellulose fiber is in a more preferable range. The transmittance can be maximized by setting the processing amount and the number of passes optimally. Then, by relaxing the oxidation treatment and the mechanical treatment conditions, the transmittance can be reduced from the maximum value to a desired level.

  The aqueous dispersion containing the refined oxidized cellulose fiber obtained by the production method of the present invention is used, if necessary, by removing the used catalyst by washing or the like, and in the form of a suspension (visually colorless and transparent or opaque Liquid) or, if necessary, dried powder (however, it is fibrous and does not mean grains). In addition, when making into suspension, what used only water may be used, and the mixed solvent of water, other organic solvents (for example, alcohol, such as ethanol), surfactant, an acid, a base, etc. was used. It may be a thing.

  The aqueous dispersion containing refined oxidized cellulose fibers obtained by the production method of the present invention can be used, for example, as a material for producing an oxygen barrier film or a water vapor barrier film.

  The measuring method of each item shown in Table 1 is as follows.

(1) Average fiber diameter As a pretreatment, the sample dispersion was diluted to 0.01 to 0.005% cellulose with ion-exchanged water. Next, after dropping one drop on the wall surface of the mica, water drops were blown off with air or the like and allowed to dry naturally. The measurement was performed on an image of cellulose fibers taken with an atomic force microscope (Veeco Dimension 3000 Tapping mode). Ten or more fiber diameters were extracted, measured from the height profile of the cross section of each fiber, and the average value was taken.

(2) Carboxyl group content (mmol / g)
About 0.5 g of absolutely dry pulp is put into a 100 ml beaker, and ion-exchanged water is added to make a total of 55 ml, and 5 ml of 0.01 M sodium chloride aqueous solution is added thereto to obtain a 0.83% by mass pulp suspension. Stir with a stirrer until dispersed. Then, 0.1M hydrochloric acid is added to adjust the pH to 2.5 to 3.0, and then using an automatic titrator (AUT-501, manufactured by Toa DKK Co., Ltd.), a 0.05M sodium hydroxide aqueous solution is waited for 60 seconds. The electric conductivity and pH value of the pulp suspension every minute were measured, and the measurement was continued until the pH reached about 11. And the sodium hydroxide titration amount was calculated | required from the obtained electrical conductivity curve, and carboxyl group content was computed.

(3) Transmittance (%)
The obtained aqueous dispersion of cellulose is diluted with pure water to obtain a 0.1% by mass aqueous dispersion. The obtained dispersion was put into a measurement cell, and the transmittance at a light wavelength of 550 nm was measured with a spectrophotometer (UVmini 1240, manufactured by Shimadzu Corporation).

Example 1
As a cellulose fiber raw material, bleached kraft pulp of coniferous tree (manufacturer: Fletcher Challenge Canada, trade name “Machenzie”, CSF 650 ml) was used.

<Pretreatment process>
First, 3 g of the bleached kraft pulp fiber of the above-mentioned conifer was sufficiently stirred with 297 g of ion-exchanged water and defibrated to some extent.

<Oxidation process>
Thereafter, the amount of TEMPO (manufacturer: ALDRICH, Free radical 98% by mass) becomes 1.25% by mass, sodium hypochlorite (Wako Pure Chemical Industries, Ltd., Cl concentration 5% by mass with respect to 3 g of pulp mass. ) 2.5 mmol / g-half sodium bromide (Wako Pure Chemical Industries, Ltd.) 3.6 mmol / g-half pH was added in this order. Then, it was dropped with 0.5M sodium hydroxide using a pH stud, the pH was maintained at 10.5 and the temperature was 25 ° C., and an oxidation reaction was performed for 60 minutes to obtain oxidized pulp. The oxidized pulp was sufficiently washed with ion-exchanged water and dehydrated.

<Mechanical treatment process>
Next, 600 g of an aqueous dispersion in which the solid content concentration of the obtained oxidized pulp was adjusted to 0.5% by mass was used, and a high-speed rotary disperser (CLEAMIX, model number: CLM-1.5S, manufactured by M Technique Co., Ltd.) The rotational speed was 17500 rpm, the peripheral speed of the rotating blade was 26 m / s, the capacity of the treatment tank was 1 L, and the gap between the rotating body and the fixed part was 0.2 mm. The transmittance of the aqueous dispersion treated for 60 minutes was 92%. The average fiber diameter was 2.7 nm. The transmittance of the aqueous dispersion before the mechanical treatment process was 60%.

Example 2
An oxidized pulp was obtained in the same manner as in Example 1 except that the sodium hypochlorite concentration was changed to the concentration shown in Table 1. Next, 2500 g of an aqueous dispersion in which the solid content concentration of the obtained oxidized pulp was adjusted to 0.5% by mass was used, and a high-speed rotary disperser (milder, model number: MDN303V, manufactured by Taihei Kiko Co., Ltd., rotational speed) 15000 rpm, rotary blade peripheral speed 24 m / s, treatment tank capacity 4 L, and the gap between the rotating body and the fixed part was 0.5 mm). The transmittance of the aqueous dispersion treated for 10 minutes was 81%. The average fiber diameter was 2.9 nm.

Example 3
It was produced in the same manner as in Example 2 except that the processing time by the high-speed rotary disperser was 60 minutes. The transmittance of the aqueous dispersion was 91%. The average fiber diameter was 2.6 nm.

Example 4
An oxidized pulp was obtained in the same manner as in Example 1 except that the sodium hypochlorite concentration was changed to the concentration shown in Table 1. Next, using an aqueous dispersion 5000 g in which the solid content concentration of the obtained oxidized pulp was adjusted to 0.5 mass%, a comb-type high-speed rotary disperser (Cabitron, manufactured by Taiyo Kiko Co., Ltd., rotation speed 11200 rpm) The rotor blade was processed at a peripheral speed of 40 m / s and a processing tank capacity of 20 L). The transmittance of the aqueous dispersion subjected to the 10-pass treatment was 98%. The average fiber diameter was 3.5 nm.

Example 5
An oxidized pulp was obtained in the same manner as in Example 1 except that the sodium hypochlorite concentration was changed to the concentration shown in Table 1. Next, 3000 g of an aqueous dispersion in which the solid content concentration of the obtained oxidized pulp was adjusted to 1.0% by mass was used, and a high-speed rotary disperser (Sharp Flow Mill, manufactured by Taiheiyo Kiko Co., Ltd., rotational speed 10,000 rpm, The rotor blade was processed at a peripheral speed of 68 m / s and a processing tank capacity of 5 L). The transmittance of the aqueous dispersion subjected to one pass was 98%. The average fiber diameter was 4.8 nm.

Example 6
An oxidized pulp was obtained in the same manner as in Example 1 except that the sodium hypochlorite concentration was changed to the concentration shown in Table 1. Next, 250 g of an aqueous dispersion in which the solid content concentration of the obtained oxidized pulp was adjusted to 0.5% by mass was used, and a thin-film swirl type high-speed rotary disperser (Filmix, manufactured by Primix Co., Ltd. The rotor blade was processed at a peripheral speed of 50 m / s and a processing tank capacity of 0.6 L). The transmittance of the aqueous dispersion treated for 3 minutes was 98%. The average fiber diameter was 6.2 nm.

Example 7
Oxidized pulp was obtained in the same manner as in Example 1 except that the sodium hypochlorite concentration was changed to 3.8 mmol / g-half halves in the oxidation treatment step (carboxy group content 1.51 mmol / g).

  Next, in the mechanical treatment step, 3000 g of an aqueous dispersion in which the solid content concentration of the obtained oxidized pulp was adjusted to 0.5% by mass was used, and a medium stirring type disperser (SC Mill, manufactured by Mitsui Mining Co., Ltd.) , Rotation speed rpm, rotating blade peripheral speed 13 m / s, used beads: 800 μmφ zirconia beads, treatment tank capacity 5 L). The transmittance of the aqueous dispersion treated for 10 minutes was 88%. The average fiber diameter was 4.7 nm.

Comparative Example 1
In Example 1, it manufactured similarly to Example 1 except having processed for 30 minutes with the high-speed rotary disperser (TK Robotics, Primix Co., Ltd. rotation speed 10000rpm, blade peripheral speed 13m / s). The transmittance of the aqueous dispersion after treatment was 68%. The average fiber diameter was 3.6 nm.

Comparative Example 2
In Comparative Example 1, the production was performed in the same manner except that the treatment was performed for 120 minutes. The transmittance of the aqueous dispersion after treatment was 76%. The average fiber diameter was 3.4 nm.

Comparative Example 3
It was produced in the same manner as in Example 1 except that a pulp slurry having a concentration of 0.25% by mass that did not undergo oxidation reaction in Example 1 was prepared. The transmittance of the aqueous dispersion after treatment was 31%. Since the average fiber diameter was very large, it was observed by optical microscope observation. The average fiber diameter was 20 μm.

Comparative Example 4
In Example 1, after preparing a pulp slurry having a concentration of 0.25% by mass that does not undergo an oxidation reaction, a high-pressure disperser (Nanomizer, model number: YSNM-1500AR, manufactured by Yoshida Kikai Kogyo Co., Ltd.) at a pressure of 50 MPa. I tried processing, but it was clogged and could not be processed.

Comparative Example 5
An oxidized pulp was obtained in the same manner as in Example 1 except that the sodium hypochlorite concentration was changed to the concentration shown in Table 1. Next, using an aqueous dispersion 5000 g in which the solid content concentration of the obtained oxidized pulp was adjusted to 0.5 mass%, a comb-type high-speed rotary disperser (Cabitron, manufactured by Taiyo Kiko Co., Ltd., rotation speed 11200 rpm) The rotor blade was processed at a peripheral speed of 40 m / s and a processing tank capacity of 20 L). The transmittance of the aqueous dispersion subjected to 10-pass treatment was 52%. The average fiber diameter was 4.0 nm.

Comparative Example 6
An oxidized pulp was obtained in the same manner as in Example 1 except that the sodium hypochlorite concentration was changed to the concentration shown in Table 1. Next, 3000 g of an aqueous dispersion in which the solid content concentration of the obtained oxidized pulp was adjusted to 1.0% by mass was used, and a high-speed rotary disperser (Sharp Flow Mill, manufactured by Taiheiyo Kiko Co., Ltd., rotational speed 10,000 rpm, The rotor blade was processed at a peripheral speed of 68 m / s and a processing tank capacity of 5 L). The transmittance of the aqueous dispersion subjected to one pass was 40%. The average fiber diameter was 5.2 nm.

Comparative Example 7
An oxidized pulp was obtained in the same manner as in Example 1 except that the sodium hypochlorite concentration was changed to the concentration shown in Table 1. Next, 250 g of an aqueous dispersion in which the solid content concentration of the obtained oxidized pulp was adjusted to 0.5% by mass was used, and a thin-film swirl type high-speed rotary disperser (Filmix, manufactured by Primix Co., Ltd. The rotor blade was processed at a peripheral speed of 50 m / s and a processing tank capacity of 0.6 L). The transmittance of the aqueous dispersion treated for 3 minutes was 38%. The average fiber diameter was 6.8 nm.

Claims (3)

Cellulose fibers are oxidized with respect to 1 g of the cellulose fibers (absolute dry standard) using an oxidizing agent of 2.0 mmol to 10 mmol, and the carboxyl group content of cellulose constituting the cellulose fibers is 0.1 to 2. Obtaining an oxidized cellulose fiber that is 0.0 mmol / g;
A process for producing an oxidized cellulose fiber dispersion comprising a step of obtaining an oxidized cellulose fiber having an average fiber diameter of 200 nm or less by mechanically treating the oxidized cellulose fiber,
The method for producing an oxidized cellulose fiber dispersion, wherein the mechanical treatment uses a high-speed rotary disperser having a rotating body and the peripheral speed of the blade tip of the rotating body is 15 m / s or more. 2. The oxidized cellulose fiber dispersion according to claim 1, wherein the high-speed rotary disperser having the rotating body is of a type in which the oxidized cellulose fibers to be treated are passed through and dispersed in the gap between the rotating body and the fixed portion. Liquid manufacturing method. The high-speed rotary disperser having the rotating body has an inner rotating body that rotates in a fixed direction and an outer rotating body that rotates in reverse to the outside of the inner rotating body, and a gap between the inner rotating body and the outer rotating body. The method for producing an oxidized cellulose fiber dispersion according to claim 1, wherein the oxidized cellulose fiber to be treated is passed through and dispersed.