JP2013185122A - Method for producing cellulose nano-fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a cellulose nano-fiber, nano-fibrillated to an unprecedented region using anion-modified cellulose as a raw material, concretely, a method for producing a highly transparent cellulose nano-fiber dispersion including the anion-modified cellulose nano-fiber.SOLUTION: A method for producing a cellulose nano-fiber comprises treating the anion-modified cellulose with a high pressure homogenizer.

Description

  The present invention relates to a method for producing cellulose nanofibers using anion-modified cellulose as a raw material.

It is expected that various useful new materials and devices will be born from nanotechnology, which is a technology that freely controls substances in the nanometer range, that is, atomic and molecular scales. In particular, nanofibers (nanofibers) have attracted a great deal of attention because, when the fibers are made as thin as possible, completely new physical properties that were not found in conventional fibers are born. By applying this nanofiber, for example, it is expected to develop a purification device with a high-performance filter that does not allow any fine foreign substances to pass through, increase the strength of chemical fibers and high-performance clothing, and increase the efficiency of fuel cells. ing.
Various developments and researches on this nanofiber have been carried out. For example, Patent Document 1 discloses a microfibrillated anion-modified cellulose (anion-modified microfibrillated plant fiber).

WO2011 / 115154

  However, the anion-modified microfibrillated plant fiber described in Patent Document 1 is insufficient in nano-defibration, and further improvement (especially transparency of a dispersion containing anion-modified microfibrillated plant fiber) is desired. It was rare.

  Therefore, an object of the present invention is to provide a method for producing cellulose nanofibers that have been nano-defibrated to an unprecedented region using anion-modified cellulose as a raw material. Specifically, it aims at providing the manufacturing method of the dispersion liquid of the cellulose nanofiber which has high transparency containing the cellulose nanofiber by which anion modification | denaturation was carried out.

The present invention provides the following [1] to [2].
[1] A method for producing cellulose nanofiber, wherein anion-modified cellulose is treated with a high-pressure homogenizer.
[2] The method for producing cellulose nanofiber according to [1], wherein the anion-modified cellulose has a degree of carboxymethyl substitution per glucose unit of 0.02 to 0.50.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the cellulose nanofiber nanofibrinated to the area | region which has not existed conventionally using the anion modified cellulose as a raw material can be provided. Specifically, it is possible to provide a method for producing a highly transparent dispersion of cellulose nanofibers containing anion-modified cellulose nanofibers.

  In the present invention, the anion-modified cellulose can be obtained by anion-modifying a cellulose raw material exemplified below using a known method. As an example, the following manufacturing method can be mentioned. Cellulose is used as a starting material, and 3 to 20 times by weight of a lower alcohol, specifically methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, tertiary butanol, etc. alone or in a solvent Use a mixture of two or more mixtures and water. The mixing ratio of the lower alcohol is 60 to 95% by weight. As the mercerizing agent, 0.5 to 20 times moles of alkali metal hydroxide, specifically sodium hydroxide or potassium hydroxide is used per glucose residue of the bottoming material. A bottoming raw material, a solvent, and a mercerizing agent are mixed and subjected to mercerization treatment at a reaction temperature of 0 to 70 ° C., preferably 10 to 60 ° C., and a reaction time of 15 minutes to 8 hours, preferably 30 minutes to 7 hours. Thereafter, a carboxymethylating agent is added in an amount of 0.05 to 10.0 times mol per glucose residue, a reaction temperature of 30 to 90 ° C., preferably 40 to 80 ° C., and a reaction time of 30 minutes to 10 hours, preferably 1 hour. Perform etherification reaction for ~ 4 hours.

  In the present invention, the degree of carboxymethyl substitution per glucose unit in the anion-modified cellulose is preferably 0.02 to 0.50. By introducing a carboxymethyl substituent into cellulose, the celluloses are electrically repelled. For this reason, the cellulose which introduce | transduced the carboxymethyl substituent can be nano-defibrated easily. In addition, when the carboxymethyl substituent per glucose unit is smaller than 0.02, nano-defibration cannot be sufficiently performed. On the other hand, if the carboxymethyl substituent per glucose unit is larger than 0.50, it may swell or dissolve, and may not be obtained as a nanofiber.

  In the present invention, as the cellulose raw material, natural cellulose such as cellulose produced by microorganisms such as bleached or unbleached wood pulp, refined linter, acetic acid bacteria, etc., cellulose is dissolved in some solvent such as copper ammonia solution, morpholine derivative, etc. Examples include regenerated cellulose re-spun, and fine cellulose that has been depolymerized or mechanically treated by hydrolysis, alkali hydrolysis, enzymatic decomposition, explosion treatment, vibration ball milling, or the like of the above cellulose-based material. .

  In the present invention, the high-pressure homogenizer is a total energy such as a collision between particles and a shearing force due to a pressure difference by pressurizing (high-pressure) the fluid with a pump and ejecting it from a very delicate gap provided in the flow path. It is a device that emulsifies, disperses, disintegrates, grinds, and makes ultrafine.

  In the present invention, the treatment condition by the homogenizer is not particularly limited, but the pressure condition is 30 MPa or more, preferably 100 MPa or more, more preferably 140 MPa or more. In addition, prior to defibration / dispersion treatment with a high-pressure homogenizer, if necessary, pretreatment of anion-modified cellulose is performed using a known mixing, stirring, emulsifying, and dispersing device such as a high-speed shear mixer. Is also possible.

  Hereinafter, the embodiments of the present invention will be described by way of examples, but the present invention is not limited thereto. Moreover, various physical properties of the substance according to the present invention were evaluated by the following methods.

<Measurement method of carboxymethyl substitution degree per glucose unit>
The degree of substitution of the carboxymethyl group was determined by preparing a sample in a 0.6% by mass slurry, adding 0.1 M aqueous hydrochloric acid solution to pH 2.4, and then dropping 0.05 N aqueous sodium hydroxide solution dropwise to adjust the pH to 11 Then, the electric conductivity was measured until the amount of carboxylic acid group was determined, and the amount of carboxyl groups was measured from the amount of sodium hydroxide consumed in the neutralization step of the weak acid where the change in electric conductivity was slow. The degree of substitution referred to here represents the average value of the number of moles of substituents per mole of anhydroglucose unit.
Carboxymethyl substitution degree = (162 × C) / (1-58 × C)
C: Amount of carboxyl group

<Measurement of transparency of cellulose dispersion>
The transparency of the cellulose dispersion (660 nm light transmittance) was measured using a UV-VIS spectrophotometer UV-265FS (Shimadzu Corporation).

Example 1
To a stirrer capable of mixing pulp, add 200 g of dry pulp (LBKP, Nippon Paper Industries Co., Ltd.) and 88 g of sodium hydroxide by dry weight, and add water so that the pulp solid concentration is 15%. It was. Then, after stirring for 30 minutes at 30 ° C., the temperature was raised to 70 ° C., and 117 g of sodium monochloroacetate (in terms of active ingredient) was added. After reacting for 1 hour, the reaction product was taken out, neutralized, and washed to obtain anion-modified cellulose having a carboxymethyl substitution degree of 0.05 per glucose unit. Thereafter, the anion-modified pulp was adjusted to a solid concentration of 1% and treated with a high-pressure homogenizer five times at 20 ° C. and a pressure of 140 MPa to obtain a cellulose dispersion.

(Example 2)
A cellulose dispersion was obtained in the same manner as in Example 1 except that 264 g of sodium hydroxide and 351 g of sodium monochloroacetate (active ingredient equivalent) were changed. In addition, the carboxymethyl substitution degree per glucose unit of the obtained cellulose was 0.15.

(Comparative Example 1)
A cellulose dispersion was obtained in the same manner as in Example 1 except that no anion modification was performed.

  In Examples 1 and 2, since the cellulose was sufficiently nano-sized, the dispersion was highly transparent. On the other hand, in Comparative Example 1, the nano-ization of cellulose was not sufficient and the transparency was low.

Claims (2)

A method for producing cellulose nanofibers, wherein anion-modified cellulose is treated with a high-pressure homogenizer. The method for producing cellulose nanofiber according to claim 1, wherein the degree of carboxymethyl substitution per glucose unit of the anion-modified cellulose is 0.02 to 0.50.