JP6213961B2 - Method for producing fine cellulose fiber dispersion, method for producing fine cellulose fiber, and method for finely dispersing dried oxidized cellulose fiber - Google Patents

Description

  The present invention relates to a method for finely dispersing dried oxidized cellulose fibers, a method for producing fine cellulose fiber dispersions using dried oxidized cellulose fibers, and a method for producing fine cellulose fibers using the fine cellulose fiber dispersions. About.

  Fine cellulose fibers (hereinafter sometimes referred to as “cellulose nanofibers”), which are nano-sized materials, use cellulose, which is a large amount of naturally existing biomass, as an oxidation catalyst using N-oxyl compounds as an oxidation catalyst. And then finely dispersed (hereinafter referred to as “nanodispersion”) by mechanical fibrillation treatment that imparts a shearing force in water to the oxidized cellulose (hereinafter sometimes referred to as “oxidized cellulose fiber”). Sometimes obtained). The oxidized cellulose nanofiber dispersion in which the oxidized cellulose fibers are nano-dispersed (hereinafter sometimes referred to as “fine cellulose fiber dispersion”) is used as a thickening agent as it is or in a gel form combined with other materials. it can. In addition, a material such as a sheet, a film, a foam, and an airgel can be produced by drying the oxidized cellulose nanofiber dispersion as it is or by combining it with another material (for example, Patent Documents). 1). The oxidized cellulose nanofiber is a bio-based nanofiber with a uniform width and a high aspect ratio, and has an excellent nanodispersibility in water due to a large specific surface area, high strength, and introduced carboxyl groups. There are features. Therefore, it is expected to be used in various fields such as an oxygen barrier film, a general-purpose plastic reinforcing material, a medical material, a cell culture substrate, a catalyst carrier, an adsorbent, and a separating material.

  However, the aqueous dispersion of the oxidized cellulose nanofiber (hereinafter sometimes referred to as “oxidized cellulose nanofiber dispersion” or “cellulose nanofiber dispersion”) has a solid content concentration of 0.1% by mass to 5%. Mass% is very low. Therefore, when transporting the oxidized cellulose nanofiber dispersion used for producing a product using the oxidized cellulose nanofiber, there is a problem that a large amount of water is transported and the cost for transport is high. In addition, when the oxidized cellulose nanofiber dispersion is stored, there is a problem that it must be refrigerated or treated with a preservative as a countermeasure against microorganisms.

As a countermeasure to the above problem, it is conceivable to transport the oxidized cellulose fiber dried and having a solid content concentration increased to 90% or more. However, even when a gentle drying method such as freeze drying is used, once dried, there is a problem that a cellulose nanofiber dispersion cannot be produced even under severe dispersion treatment conditions. .
If the nano-dispersion is not possible, there is a problem that the characteristics of the oxidized cellulose nanofiber such as uniform ultra-fine width, high aspect ratio, gel and film transparency are not exhibited.

  As another countermeasure, fibrous oxidized cellulose before defibration and nano-dispersion treatment (width 0.01 mm to 0.06 mm, length 0.1 mm to 5 mm, wood cellulose fiber before oxidation treatment) Squeezed in the washing and filtration step, and the solid content concentration was raised to about 10% to 40% (that is, containing 90% to 60% water) in an undried state, It is conceivable to carry. If it is the said undried oxycellulose, a cellulose nanofiber dispersion can always be manufactured by the fibrillation process in water. However, there is still a problem that the amount of water is still large even in an undried state, and the cost for transportation is high, and that preservative measures during storage are necessary.

  In addition, as a method for producing a thickening cellulose fiber that can be easily redispersed in water, an aqueous cleaning solution containing 50 to 75% of a polar solvent other than water and cellulose after oxidation has been used, and a pH of 5. A method of drying after purification under conditions of 5 or more has been proposed (for example, see Patent Document 2). However, the thickening cellulose fiber obtained by the above proposal has low transparency of the dispersion and cannot be said to be sufficiently dispersed, and repeated washing and drying using a polar solvent is an environmental burden. From the viewpoint of cost and cost, there is a problem that it cannot be said that it is suitable for practical use.

  Therefore, the cost of transportation can be reduced, and dried oxidized cellulose fibers with excellent storage stability can be dispersed in a solvent in the same way as when prepared from an undried state with low environmental impact, easily and inexpensively. The current situation is that there is a strong demand for the rapid development of a method that can be applied.

Japanese Patent No. 4998981 JP 2013-104133 A

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, the present invention is capable of reducing transportation costs and is similar to the case where dried oxidized cellulose fibers having excellent storage stability are prepared from an undried state with low environmental impact, easily and inexpensively. It is an object to provide a method for finely dispersing dried oxidized cellulose fibers that can be finely dispersed in a solvent, a method for producing a fine cellulose fiber dispersion, and a method for producing fine cellulose fibers.

Means for solving the problems are as follows. That is,
<1> a hot water treatment step of treating dried oxidized cellulose fibers with hot water;
A dispersion step of dispersing the oxidized cellulose fiber treated with hot water in a solvent,
The dried oxidized cellulose fiber is obtained by drying oxidized cellulose fiber obtained by oxidizing a cellulosic raw material in a reaction solution containing an N-oxyl compound and a co-oxidant. It is a manufacturing method of a cellulose fiber dispersion.
<2> A method for producing fine cellulose fibers, comprising a drying step of drying the fine cellulose fiber dispersion produced by the production method according to <1>.
<3> a hot water treatment step of treating the dried oxidized cellulose fiber with hot water;
A dispersion step of dispersing the oxidized cellulose fiber treated with hot water in a solvent,
Drying characterized in that the dried oxidized cellulose fiber is obtained by drying oxidized cellulose fiber obtained by oxidizing a cellulosic raw material in a reaction solution containing an N-oxyl compound and a co-oxidant. This is a method for finely dispersing used oxidized cellulose fibers.

  ADVANTAGE OF THE INVENTION According to this invention, the said problem in the past can be solved, the said objective can be achieved, the cost concerning transportation is possible, and the dry oxycellulose fiber excellent in preservability is reduced in environmental load. A method for finely dispersing dried oxidized cellulose fibers that can be finely dispersed in a solvent in the same manner as when prepared from an undried state easily and inexpensively, a method for producing a fine cellulose fiber dispersion, and fine A method for producing a cellulose fiber can be provided.

FIG. 1 is a graph showing the results of measuring the light transmittance of the fine cellulose dispersions of Examples 1 and 2. FIG. 2 is a graph showing the results of measuring the light transmittance of the dispersion liquid of Comparative Example 1.

(Production method of fine cellulose fiber dispersion)
The method for producing a fine cellulose fiber dispersion of the present invention includes at least a hydrothermal treatment step and a dispersion step, and further includes other steps as necessary.

<Hot water treatment process>
The hot water treatment step is a step of treating dried oxidized cellulose fibers with hot water.

-Dried oxidized cellulose fiber-
The dried oxidized cellulose fiber is obtained by drying oxidized cellulose fiber obtained by oxidizing a cellulosic material in a reaction solution containing an N-oxyl compound and a co-oxidant.

-Cellulose-based raw material-
The cellulose-based raw material is not particularly limited and may be appropriately selected depending on the intended purpose. For example, softwood pulp, hardwood pulp, cotton pulp such as cotton linter or cotton lint, straw pulp, bagasse pulp, etc. Non-wood pulp, bacterial cellulose, cellulose isolated from sea squirt, cellulose isolated from seaweed, and the like. These may be used individually by 1 type and may use 2 or more types together.
The cellulosic material may be subjected to a treatment for increasing the surface area such as beating.

There is no restriction | limiting in particular as the dispersion medium of the said cellulose raw material in the said reaction liquid, According to the objective, it can select suitably, For example, water etc. are mentioned.
There is no restriction | limiting in particular as a density | concentration of the said cellulose raw material in the said reaction liquid, According to the objective, it can select suitably.

--N-oxyl compound--
There is no restriction | limiting in particular as said N- oxyl compound, According to the objective, it can select suitably, For example, "" Cellulose "Vol. 10, 2003, pages 335-341. Shibata and A.I. Examples include the compounds described in “The Catalytic Oxidation of Cellulose Using TEMPO Derivatives: HPSEC and NMR Analysis of Oxidation Products” by Isogai. These may be used individually by 1 type and may use 2 or more types together.
Specific examples of the N-oxyl compound include 2,2,6,6-tetramethylpiperidine-N-oxyl (hereinafter sometimes referred to as “TEMPO”), 4-acetamido TEMPO, 4-carboxy-TEMPO, 4-phosphonooxy-TEMPO etc. are mentioned.
There is no restriction | limiting in particular as content of the said N- oxyl compound in the said reaction liquid, According to the objective, it can select suitably, For example, a catalyst amount etc. are mentioned.

--Co-oxidant--
The co-oxidant is not particularly limited and may be appropriately selected depending on the intended purpose. For example, hypohalous acid or a salt thereof, hypohalous acid or a salt thereof, perhalogen acid or a salt thereof, hydrogen peroxide And perorganic acids. These may be used individually by 1 type and may use 2 or more types together.
Specific examples of the co-oxidant include sodium hypochlorite and sodium hypobromite.
There is no restriction | limiting in particular as content of the said co-oxidant in the said reaction liquid, According to the objective, it can select suitably.

-Other ingredients-
The said reaction liquid may contain other components other than the cellulose raw material mentioned above, a N-oxyl compound, and a co-oxidant.
There is no restriction | limiting in particular as said other component, According to the objective, it can select suitably, For example, a bromide, iodide, or a mixture thereof etc. are mentioned.

There is no restriction | limiting in particular as said bromide and iodide, According to the objective, it can select suitably, For example, an alkali metal bromide, an alkali metal iodide, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together.
There is no restriction | limiting in particular as content of the said bromide, iodide, or these mixtures in the said reaction liquid, According to the objective, it can select suitably.

The oxidized cellulose fiber has a carboxyl group content of 0.8 mmol / g to 2.2 mmol / g and an aldehyde group content of 0.8 mmol / g or less.
The amount of carboxyl groups and the amount of aldehyde groups in the oxidized cellulose fiber are T.P. Saito and A.A. Isogai, “TEMPO-mediated oxidation of native cellulose. The effect of oxidative conditions on chemical and molecular structures of the biofuels of the world. 5, pp. 1983-1989 (2004)), and can be measured by an additional oxidation treatment with sodium chlorite and conductivity titration.

Moreover, the oxidation cellulose fiber which does not contain an aldehyde group can be obtained by selecting the said oxidation conditions, without performing the post-oxidation process mentioned later.
The oxidation conditions for obtaining the oxidized cellulose fiber not containing the aldehyde group are not particularly limited and may be appropriately selected depending on the intended purpose. Saito, M .; Hirota, N .; Tamura, S .; Kimura, H .; Fukuzumi, L. Heux, A .; Isogai, “Individualization of nano-sized plant cellose fibrils by direct surface carboxylation using TEMPO catalyst numerators, biocondensations of biomolecules. 10, 1992-1996, 2009) can be selected as appropriate.

--- Oxidation treatment ---
The oxidized cellulose fiber may be subjected to additional oxidation treatment in addition to the oxidation.
The said additional oxidation process is a process which further oxidizes the oxidized cellulose fiber obtained by the said oxidation with sodium chlorite.
The conditions for the additional oxidation treatment are not particularly limited and may be appropriately selected depending on the purpose. Saito and A.A. Isogai, “TEMPO-mediated oxidation of native cellulose. The effect of oxidative conditions on chemical and molecular structures of the biofuels of the world. 5, pp. 1983 to 1989, 2004) can be selected as appropriate.
Oxidized cellulose fibers not containing an aldehyde group obtained by oxidizing a small amount of the aldehyde group generated at the C6 position to a carboxyl group by the additional oxidation treatment can be obtained.

The oxidized cellulose fiber may be dried as described later after suction filtration washing with water.
Since the oxidized cellulose fiber is not dispersed to the nanofiber unit at this stage, it can be washed by a normal water washing-suction filtration washing method.
Specific examples of the washing method include a method of washing and washing with at least one of suction filtration and centrifugation. The number of times of washing may be one time or a plurality of times. The unreacted cooxidant and various byproducts can be removed by the washing.

--Dry--
There is no restriction | limiting in particular as a method of drying the said oxidized cellulose fiber, According to the objective, it can select suitably, For example, the drying method using an oven dryer, the freeze-drying method, the spray-drying method etc. are mentioned.
There is no restriction | limiting in particular as said drying conditions, According to the objective, it can select suitably, For example, 105 hours and 3 hours etc. are mentioned.
The drying conditions at 105 ° C. for 3 hours are generally the absolutely dry conditions for cellulose fibers.

  The water content of the dried oxidized cellulose fiber is not particularly limited and can be appropriately selected depending on the purpose.However, the lower the water content, the lower the cost for transportation, Absolutely dry oxidized cellulose fibers are more preferred.

-Hot water treatment-
There is no restriction | limiting in particular as an aspect of the said hot water process, Although it can select suitably according to the objective, The aspect which immerses the said dried oxidized cellulose fiber in water and heats is preferable.

  There is no restriction | limiting in particular as the temperature of the said hot water, Although it can select suitably according to the objective, 70 degreeC or more is preferable, 75 degreeC or more is more preferable, and 80 to 100 degreeC is especially preferable. When the temperature of the hot water is less than 70 ° C., the oxidized cellulose fiber may not be finely dispersed. On the other hand, when it is in the preferable range, the oxidized cellulose fiber can be easily finely dispersed.

  There is no restriction | limiting in particular as time of the said hydrothermal treatment process, Although it can select suitably according to the objective, 15 minutes or more are preferable, 30 minutes or more are more preferable, and 1 to 4 hours are especially preferable. When the time of the hot water treatment step is less than 15 minutes, the oxidized cellulose fiber may not be finely dispersed. On the other hand, when it is in the preferable range, the oxidized cellulose fiber can be easily finely dispersed.

  There is no restriction | limiting in particular as solid content concentration of the said oxidation cellulose fiber in the said hot water, According to the objective, it can select suitably, For example, 0.01 mass%-5 mass% etc. are mentioned.

The hot water may contain other components other than the oxidized cellulose fiber.
There is no restriction | limiting in particular as said other component, According to the objective, it can select suitably.

  There is no restriction | limiting in particular as pH of the hot water containing the said oxidized cellulose fiber, According to the objective, it can select suitably.

The hot water treatment is preferably performed with stirring.
There is no restriction | limiting in particular as said stirring means, According to the objective, a well-known means can be selected suitably.
There is no restriction | limiting in particular as conditions of the said stirring, According to the objective, it can select suitably, For example, when stirring with a magnetic stirrer, it is set as the gentle stirring of about 300 rpm-400 rpm.

<Dispersing process>
The dispersion step is a step of dispersing oxidized cellulose fibers treated with hot water in a solvent. The oxidized cellulose fiber can be finely dispersed by the dispersing step.

-Solvent-
The solvent is not particularly limited and may be appropriately selected depending on the intended purpose. For example, water, alcohols, ethers, ketones, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfone Examples include killide. These may be used individually by 1 type and may use 2 or more types together.
Specific examples of the alcohols include methanol, ethanol, isopropanol, isobutanol, sec-butanol, tert-butanol, methyl cellosolve, ethyl cellosolve, ethylene glycol, and glycerin.
Specific examples of the ethers include ethylene glycol dimethyl ether, 1,4-dioxane, tetrahydrofuran and the like.
Specific examples of the ketones include acetone and methyl ethyl ketone.
Among the solvents, water is preferable.

-Dispersion-
The dispersion means used in the dispersion step (hereinafter also referred to as “defibration means”) is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a screw mixer, paddle mixer, disperser Type mixer, turbine type mixer, homomixer under high speed rotation, high pressure homogenizer, super high pressure homogenizer, double cylinder type homogenizer, ultrasonic homogenizer, water flow collision type disperser, beater, disk type refiner, conical type refiner, double Examples thereof include a disk type refiner, a grinder, and a twin-screw kneader.

The conditions for the dispersion step are not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include conditions for preparing the dispersion described in the item “light transmittance” described later.
By the dispersion step, the oxidized cellulose fiber is finely dispersed, and a fine cellulose fiber dispersion is obtained.

The fine cellulose fibers in the fine cellulose fiber dispersion are cellulose single microfibrils having a width of about 2 nm to 5 nm and a length of about 0.2 μm to 5 μm.
The solid content concentration of the fine cellulose fiber in the fine cellulose fiber dispersion is not particularly limited as long as it is finely dispersed, and can be appropriately selected according to the purpose. For example, 0.01% by mass to 5% by mass Etc.

  Whether or not the fine cellulose fiber dispersion has been obtained can be determined, for example, by measuring light transmittance, observing birefringence, or the like.

-Light transmittance-
When determining whether or not the fine cellulose fiber dispersion is obtained by measuring the light transmittance, for example, a dispersion having a dried oxidized cellulose fiber concentration of 0.1% by mass prepared as follows: Light transmittance (hereinafter referred to as “transmittance”) at a wavelength of 600 nm of the liquid (dispersion liquid that remains unremoved even when there is undefibrated material. May be determined to be finely dispersed (nanodispersed). When the light transmittance does not reach 80%, it can be determined that the fiber contains undefibrated components that are not finely dispersed.

The dispersion can be prepared as follows.
The dried oxidized cellulose fiber dried at 105 ° C. for 3 hours is diluted with water to a concentration of 0.1% by mass to obtain a 40 mL dispersion. The dispersion was placed in a 50 mL centrifuge tube (polypropylene; manufactured by Corning), and directly used with a double-cylindrical homogenizer (blade diameter 1.5 cm, Microtech Nichion NS-56). Defibration treatment is performed at 500 rpm for 2 minutes. Next, after the defibrating treatment with the double cylinder type homogenizer, the surroundings of the container are immediately cooled with ice water as they are, and the ultrasonic homogenizer (US-300T, manufactured by Nippon Seiki Co., Ltd., probe tip 7 mm, output 300 W, 19.5 kHz) is used for 8 minutes. Perform defibrating treatment.
In the treatment with the ultrasonic homogenizer, in order to avoid the temperature rise of the dispersion due to the ultrasonic treatment, a cycle of ultrasonic treatment for 2 minutes and standing and cooling for 1 minute is repeated, and the total ultrasonic treatment time is reached. For 8 minutes.

  The means for measuring the light transmittance of the fine cellulose fiber dispersion is not particularly limited, and a known means can be appropriately selected. For example, an ultraviolet-visible near-infrared spectrophotometer (manufactured by JASCO Corporation) V-670).

-Birefringence-
When judging whether or not the fine cellulose fiber dispersion was obtained by observation of the birefringence, for example, if there is undefibrated residue, except for removing by light separation, the light transmittance A dispersion having a dried oxidized cellulose fiber concentration of 0.1% by mass prepared in the same manner as the dispersion prepared in the above measurement was placed between crossed polarizing plates, and when birefringence was observed, it was finely dispersed. (Nano-dispersed).

The centrifugation process can be carried out in a centrifuge for 10 minutes at 12,000 G with the centrifuge tube in the 50 mL container. This removes undefined cellulose fibers and obtains a supernatant that does not contain undefined cellulose fibers.
In addition, when the weight ratio of the undefibrated portion removed by the centrifugation treatment is 10% or more, it is determined that the fine cellulose fiber dispersion is “not nanodispersed in water”.

<Other processes>
The other steps are not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected according to the purpose. For example, a cooling step, a fine cellulose fiber dispersion drying step, a redispersion step, and the like. Can be mentioned.

-Cooling process-
The cooling step is a step of cooling the oxidized cellulose fiber obtained in the hot water treatment step.
The cooling step is preferably performed between the hot water treatment step and the dispersion step.
The cooling rate is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include rapid cooling and cooling.
There is no restriction | limiting in particular as temperature after the said cooling process, According to the objective, it can select suitably, For example, room temperature etc. are mentioned.

-Fine cellulose fiber dispersion drying process-
The fine cellulose fiber dispersion drying step is a step of drying the fine cellulose fiber dispersion obtained in the dispersion step. The fine cellulose fiber dried in the fine cellulose fiber dispersion drying step can be made into a fine cellulose fiber dispersion by a redispersion step described later.
There is no restriction | limiting in particular as a method of the said fine cellulose fiber dispersion drying process, According to the objective, it can select suitably, For example, a freeze-drying method, a spray-drying method, etc. are mentioned.
The drying conditions are not particularly limited and may be appropriately selected depending on the purpose.

-Redispersion process-
The redispersion step is a step of dispersing a dried product of the fine cellulose fiber dispersion obtained in the fine cellulose fiber dispersion drying step in a solvent.
There is no restriction | limiting in particular as a solvent in the said re-dispersion process, According to the objective, it can select suitably, The thing similar to the solvent in the above-mentioned dispersion | distribution process is mentioned.
There is no restriction | limiting in particular as a dispersion | distribution means used at the said re-dispersion process, According to the objective, it can select suitably, For example, a vortex mixer etc. are mentioned.

According to the method for producing a fine cellulose fiber dispersion of the present invention, dried oxidized cellulose fibers that could not be finely dispersed in the past were prepared from an undried state with low environmental impact, easily and inexpensively. As in the case, it can be finely dispersed in a solvent. According to the method for producing a fine cellulose fiber dispersion of the present invention, an absolutely dry oxidized cellulose fiber is also finely dispersed in a solvent in the same manner as when it is prepared from an undried state with a small environmental load, easily and inexpensively. be able to.
In the present invention, since the dried oxidized cellulose fiber is used, the cost for transporting the oxidized cellulose fiber can be reduced, and the storage stability of the oxidized cellulose fiber can be improved.

(Method for producing fine cellulose fiber)
The manufacturing method of the fine cellulose fiber of this invention includes a drying process at least, and also includes another process as needed.

<Drying process>
The said drying process is a process of drying the fine cellulose fiber dispersion manufactured by the manufacturing method of the fine cellulose fiber dispersion of this invention mentioned above.
The drying method can be performed in the same manner as the drying in the item of dried oxidized cellulose fiber in the above-described method for producing a fine cellulose fiber dispersion of the present invention.
Fine cellulose fibers can be obtained by the drying step.

<Other processes>
The other steps are not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected according to the purpose.

  The fine cellulose fiber can be suitably used in various fields such as an oxygen-preventing membrane, a general-purpose plastic reinforcing material, a medical material, a cell culture substrate, a catalyst carrier, an adsorbent, and a separating material.

(Method for finely dispersing dried oxidized cellulose fibers)
The method for finely dispersing dried oxidized cellulose fibers of the present invention includes at least a hydrothermal treatment step and a dispersion step, and further includes other steps as necessary.

<Hot water treatment process>
The hot water treatment step is a step of treating dried oxidized cellulose fibers with hot water, and can be performed in the same manner as the hot water treatment step in the method for producing a fine cellulose fiber dispersion of the present invention described above.

<Dispersing process>
The said dispersion | distribution process is a process of disperse | distributing the oxidized cellulose fiber processed with the hot water to a solvent, and can be performed like the dispersion | distribution process in the manufacturing method of the fine cellulose fiber dispersion of this invention mentioned above.

<Other processes>
The other steps are not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected according to the purpose. For example, the other steps in the method for producing a fine cellulose fiber dispersion of the present invention described above can be used. It can be performed in the same manner as the process.

(Manufacturing method of fine cellulose fiber molding)
The method for producing a fine cellulose fiber molded body includes at least a step of removing a liquid component while holding the fine cellulose fiber dispersion produced by the method for producing a fine cellulose fiber dispersion of the present invention in a predetermined shape, If necessary, other steps are further included.

The method for removing the liquid component while holding the fine cellulose fiber dispersion in a predetermined shape is not particularly limited and may be appropriately selected depending on the purpose. For example, the fine cellulose fiber dispersion may be selected on a substrate such as a glass plate. Examples include a method of forming a film by removing the liquid component of the dispersion by a drying method such as natural drying, air blowing drying, or vacuum drying after casting the cellulose fiber dispersion.
A fine cellulose fiber molded body can be obtained by peeling the film from the substrate.

Moreover, it is good also as a fine cellulose fiber molded object by forming a fine cellulose fiber layer on the molded object using the said fine cellulose fiber dispersion.
There is no restriction | limiting in particular as said molded object, According to the objective, it can select suitably, For example, foil shape, desired shape, A three-dimensional container such as a box or a bottle can be used.
There is no restriction | limiting in particular as a material of the said molded object, According to the objective, it can select suitably, For example, paper, paperboard, a plastics, a metal, these composites etc. are mentioned.
The structure of the molded product may be a single layer or multiple layers.

There is no restriction | limiting in particular as a method to provide the said fine cellulose fiber dispersion on the said molded object, According to the objective, it can select suitably, For example, the apply | coating method, the spraying method, the immersion method etc. are mentioned.
Further, a fine cellulose fiber molded body formed in a film shape may be bonded to the surface of the molded product. There is no restriction | limiting in particular as the said bonding method, According to the objective, it can select suitably, For example, the method of using an adhesive agent, the heat sealing | fusion method, etc. are mentioned.

<Other processes>
There is no restriction | limiting in particular as said other process, According to the objective, it can select suitably.

(Production method of fine cellulose fiber composite)
The method for producing the fine cellulose fiber composite is a dispersion obtained by mixing the fine cellulose fiber dispersion produced by the above-described method for producing the fine cellulose fiber dispersion of the present invention and a liquid material containing the composite material. It includes at least a step of preparing a liquid, and further includes other steps as necessary.

The material of the composite is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include synthetic polymers such as polyvinyl alcohol, nylon (registered trademark), polypropylene, polyethylene terephthalate, and polyester. .
The synthetic polymer can be dissolved in an organic solvent and spun (solution spinning) or formed into a film.
Therefore, by using a dispersion obtained by mixing the fine cellulose fiber dispersion and a liquid material containing the synthetic polymer, it is possible to obtain a fibrous molded article or a film-like molded article that is the fine cellulose fiber composite. it can.
Also, a monomer and the fine cellulose fiber dispersion are mixed in an organic solvent, and the monomer is polymerized to synthesize a polymer, thereby forming a composite of the fine cellulose fiber and the synthetic polymer. You can also.

<Other processes>
There is no restriction | limiting in particular as said other process, According to the objective, it can select suitably.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
As the oxidized cellulose fiber, undried TEMPO oxidized cellulose (manufactured by Nippon Paper Industries Co., Ltd., carboxyl group amount; 1.45 mmol / g, aldehyde group amount; 0.05 mmol / g, solid content rate: 15.95%) was prepared. .
The undried TEMPO oxidized cellulose is dried in an oven at 105 ° C. for 3 hours, and is then referred to as dried oxidized cellulose fiber having a solid content of 100% by mass (hereinafter referred to as “absolutely dried TEMPO oxidized cellulose”). )

<Hot water treatment process>
A 100 mL eggplant flask was charged with 40 mL of distilled water containing 0.4 g of the above-mentioned absolutely dry TEMPO-oxidized cellulose and stirred at 80 ° C. for 30 minutes without sealing.
The stirring was performed with a magnetic stirrer, and a stirrer bar having a diameter of 7 mm and a length of 20 mm was used. The strength of stirring was gentle stirring of about 300 rpm to 400 rpm.

<Cooling process>
After the hot water treatment step, the absolutely dry TEMPO oxidized cellulose-containing liquid was rapidly cooled in ice water. Thereafter, the volatilized water was replenished to obtain an absolutely dry TEMPO oxidized cellulose aqueous dispersion (0.1 mass / volume%).

<Dispersing process>
40 mL of the above-mentioned absolutely dry TEMPO oxycellulose aqueous dispersion was put into a 50 mL container centrifuge tube (made of polypropylene; manufactured by Corning), and a double-cylindrical homogenizer (blade diameter 1.5 cm, Microtech Nichion NS-) 56) was defibrated for 2 minutes at 7,500 rpm. After the defibrating treatment with the double cylindrical homogenizer, defibration with an ultrasonic homogenizer (Nippon Seiki US-300T, probe tip 7 mm, output 300 W, 19.5 kHz) for 8 minutes while immediately cooling the periphery of the container with ice water. Processed. In the sonication, in order to avoid the temperature rise of the dispersion, a cycle of sonicating for 2 minutes and allowing to cool for 1 minute is repeated so that the total sonication time becomes 8 minutes. went. Through the above treatment, a dispersion having a cellulose concentration of 0.1% by mass (hereinafter sometimes referred to as “fine cellulose fiber dispersion”) was obtained (yield 90%).

<Light transmission>
The light transmittance of the fine cellulose fiber dispersion (dispersion liquid that remains unremoved even if there is undefibrated material, which may be completely nanodispersed and may not have undefibrated material) The results of measurement using a spectrophotometer (V-670 manufactured by JASCO Corporation) are shown in FIG. 1 (“solid line” in FIG. 1). The light transmittance of the fine cellulose fiber dispersion at a wavelength of 600 nm was 83.9%.

<Birefringence>
As a result of confirming whether or not birefringence is observed by placing the fine cellulose fiber dispersion (if there is undefibrated residue, removed by centrifugation) between orthogonal polarizing plates, birefringence is observed. It was done.

(Example 2)
An absolutely dry TEMPO oxidized cellulose aqueous dispersion was obtained in the same manner as in Example 1 except that the hot water treatment time was changed from 30 minutes to 60 minutes.
About the said absolute dry TEMPO oxidation cellulose aqueous dispersion, the dispersion | distribution process was performed like the said Example 1, and the fine cellulose fiber dispersion was obtained (yield 90%).

<Light transmittance>
The result of measuring the light transmittance of the fine cellulose fiber dispersion in the same manner as in Example 1 is shown in FIG. 1 (“dotted line” in FIG. 1). The light transmittance of the fine cellulose fiber dispersion at a wavelength of 600 nm was 87.3%.

<Birefringence>
Birefringence was observed as a result of confirming whether or not the fine cellulose fiber dispersion showed birefringence in the same manner as in Example 1.

(Comparative Example 1)
<Preparation of dried oxidized cellulose>
Undried TEMPO oxidized cellulose (manufactured by Nippon Paper Industries Co., Ltd., carboxyl group amount; 1.45 mmol / g, aldehyde group amount; 0.05 mmol / g, solid content rate: 15.95%) was measured for an absolute dry weight of 2 g. And dispersed in 150 mL of distilled water. 2N sulfuric acid was added to this dispersion to adjust the pH to 7.0. Thereafter, the reaction solution was filtered using a glass filter.
Cellulose fibers obtained by this filtration were added to a water-containing solvent (acetone: water = 50: 50 [volume ratio]) as a washing liquid, and the mixture was stirred and dispersed uniformly while maintaining pH 7.0. This was again filtered using a glass filter. This operation was further repeated 4 times to purify the cellulose fiber.
After purification, this sample was allowed to stand at room temperature for 2 days and dried to obtain a dried product. The dried product had a loss on drying of 16%.

<Dispersing process>
The dried product was diluted with water to prepare 40 mL of a dispersion having a cellulose concentration of 0.1% by mass.
About the said dispersion liquid, the dispersion | distribution process was performed like the said Example 1, and the dispersion liquid (an undefibrated part is included) whose cellulose concentration is 0.1 mass% was obtained.

<Light transmission>
The result of measuring the light transmittance of the dispersion (including the undefibrated portion) in the same manner as in Example 1 is shown in FIG. The light transmittance at a wavelength of 600 nm of the dispersion liquid (including the undefibrated portion) was 68.7%.

<Birefringence>
In the same manner as in Example 1, it was confirmed whether or not birefringence was observed in the dispersion. As a result, although the birefringence was confirmed for the supernatant, the weight ratio of the undefibrated portion removed by centrifugation Was 31%, and the nanodispersion in water was not possible.
In addition, the said centrifugation was performed with the centrifuge for 10 minutes at 12,000 G with the centrifuge tube of the said 50 mL container.

  From the results of Examples 1 and 2 and Comparative Example 1, it was not possible to finely disperse dried oxidized cellulose fibers in Comparative Example 1 in which the hydrothermal treatment process of the present invention was not performed. On the other hand, the fine cellulose fiber dispersions of Examples 1 and 2 had a light transmittance of 80% or more at a wavelength of 600 nm, and birefringence was observed. It was shown that even a fiber can be finely dispersed in the same manner as when prepared from an undried state.

Examples of the aspect of the present invention include the following.
<1> a hot water treatment step of treating dried oxidized cellulose fibers with hot water;
A dispersion step of dispersing the oxidized cellulose fiber treated with hot water in a solvent,
The dried oxidized cellulose fiber is obtained by drying oxidized cellulose fiber obtained by oxidizing a cellulosic raw material in a reaction solution containing an N-oxyl compound and a co-oxidant. It is a manufacturing method of a cellulose fiber dispersion.
<2> The method for producing a fine cellulose fiber dispersion according to <1>, wherein the temperature of hot water is 70 ° C. or higher.
<3> The method for producing a fine cellulose fiber dispersion according to any one of <1> to <2>, wherein the time of the hydrothermal treatment step is 15 minutes or more.
<4> The fine cellulose fiber according to any one of <1> to <3>, further including a cooling step for cooling the oxidized cellulose fiber obtained in the hydrothermal treatment step between the hydrothermal treatment step and the dispersion step. It is a manufacturing method of a dispersion.
<5> A fine cellulose fiber comprising a drying step of drying the fine cellulose fiber dispersion produced by the method for producing a fine cellulose fiber dispersion according to any one of <1> to <4>. It is a manufacturing method.
<6> a hot water treatment step of treating the dried oxidized cellulose fiber with hot water;
A dispersion step of dispersing the oxidized cellulose fiber treated with hot water in a solvent,
Drying characterized in that the dried oxidized cellulose fiber is obtained by drying oxidized cellulose fiber obtained by oxidizing a cellulosic raw material in a reaction solution containing an N-oxyl compound and a co-oxidant. This is a method for finely dispersing used oxidized cellulose fibers.
<7> The method for finely dispersing dried oxidized cellulose fibers according to <6>, wherein the temperature of hot water is 70 ° C. or higher.
<8> The method for finely dispersing dried oxidized cellulose fibers according to any one of <6> to <7>, wherein the time of the hydrothermal treatment step is 15 minutes or more.
<9> The dried product according to any one of <6> to <8>, further including a cooling step for cooling the oxidized cellulose fiber obtained in the hydrothermal treatment step between the hydrothermal treatment step and the dispersion step. This is a method for finely dispersing oxidized cellulose fibers.
<10> The liquid component is removed while the fine cellulose fiber dispersion produced by the method for producing a fine cellulose fiber dispersion according to any one of <1> to <4> is held in a predetermined shape. It is the manufacturing method of the fine cellulose fiber molded object to do.
<11> A fine cellulose fiber dispersion produced by the method for producing a fine cellulose fiber dispersion according to any one of <1> to <4>, and a liquid material including a composite material. A method for producing a fine cellulose fiber composite comprising using a dispersion.

Claims (7)

A hydrothermal treatment step of treating the dried oxidized cellulose fiber with hot water;
A dispersion step of dispersing the oxidized cellulose fiber treated with hot water in a solvent,
The dried oxidized cellulose fiber is obtained by drying oxidized cellulose fiber obtained by oxidizing a cellulosic raw material in a reaction solution containing an N-oxyl compound and a co-oxidant. A method for producing a cellulose fiber dispersion.   The method for producing a fine cellulose fiber dispersion according to claim 1, wherein the temperature of the hot water is 70 ° C or higher.   The method for producing a fine cellulose fiber dispersion according to any one of claims 1 to 2, wherein the time of the hydrothermal treatment step is 15 minutes or more.   The manufacturing method of the fine cellulose fiber characterized by including the drying process which dries the fine cellulose fiber dispersion manufactured by the manufacturing method of the fine cellulose fiber dispersion in any one of Claim 1 to 3. A hydrothermal treatment step of treating the dried oxidized cellulose fiber with hot water;
A dispersion step of dispersing the oxidized cellulose fiber treated with hot water in a solvent,
Drying characterized in that the dried oxidized cellulose fiber is obtained by drying oxidized cellulose fiber obtained by oxidizing a cellulosic raw material in a reaction solution containing an N-oxyl compound and a co-oxidant. A method for finely dispersing used oxidized cellulose fibers.   The method for finely dispersing dried oxidized cellulose fibers according to claim 5, wherein the temperature of the hot water is 70 ° C or higher.   The method for finely dispersing dried oxidized cellulose fibers according to any one of claims 5 to 6, wherein the time of the hydrothermal treatment step is 15 minutes or more.