JP2009298972A - Cellulose fiber and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a cellulose fiber suitable as a gas barrier film material. <P>SOLUTION: The manufacturing method of a cellulose fiber comprises an oxidation process for oxidizing natural cellulose to obtain a dispersion liquid containing oxycellulose fibers wherein a carboxyl group content of cellulose constituting a cellulose fiber is 0.1-2.0 mmol/g, an enzyme treatment process for adding and holding an enzyme in the dispersion liquid, and a process for mechanically loosening the oxidized cellulose fibers in the dispersion liquid. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cellulose fiber that can be used as a gas barrier film material, a production method thereof, and a gas barrier molded article obtained from the cellulose fiber.

  Natural cellulose nanofibers obtained by using 2,2,6,6, -tetramethyl-1-piperidine-N-oxyl (TEMPO) as a catalyst are known (Non-patent Document 1) and are used in various fields. Application to is expected.

  As one of the uses of the natural cellulose nanofiber, a gas barrier film of oxygen or the like can be considered. In that case, for example, a method may be considered in which an aqueous dispersion of natural cellulose nanofibers is prepared and cast on the substrate surface to form a film.

When such a casting method is applied, if an aqueous dispersion having a concentration of 1% by mass or more is used, the time for evaporating water can be shortened, so that the subsequent process becomes easy. However, when the concentration of the natural cellulose nanofiber is 1% by mass or more, the viscosity becomes high, and film formation by casting becomes difficult.
JP 2008-1728

  The present invention provides a cellulose fiber production method that can be easily formed by applying a known film forming method such as casting, etc., even when the concentration of the dispersion is increased, and the cellulose obtained from the cellulose fiber production method. It is an object of the present invention to provide a gas barrier molded body of oxygen or the like using fibers. Here, the gas barrier refers to a function of shielding various gases such as oxygen, nitrogen, carbon dioxide, organic vapor, and water vapor, and aromatic substances such as limonene and menthol.

The present invention provides the following inventions as means for solving the problems.
1. An oxidation step of oxidizing natural cellulose to obtain a dispersion containing cellulose fibers having a carboxyl group content of 0.1 to 2.0 mmol / g of cellulose constituting the cellulose fibers;
An enzyme treatment step of adding and holding the enzyme in the dispersion;
The manufacturing method of a cellulose fiber which has the process of fibrillating the cellulose fiber in the said dispersion liquid mechanically.
2. The manufacturing method of the cellulose fiber of Claim 1 which makes the said oxidation process and the said enzyme treatment process parallel.
3. The manufacturing method of the cellulose fiber of Claim 1 which performs the said enzyme treatment process after the said oxidation process.
4). The manufacturing method of the cellulose fiber of Claims 1-3 which makes the said enzyme treatment process and the said defibration process parallel.
5. The manufacturing method of the cellulose fiber of Claims 1-3 which performs the said fibrillation process after the said enzyme treatment process.
6). The manufacturing method of the cellulose fiber of Claims 1-3 which performs the said fibrillation process before the said enzyme treatment process.
7). A gas barrier molded article using cellulose fibers obtained from the method for producing cellulose fibers according to claim 1.

  Since the viscosity of the aqueous dispersion of the cellulose fiber of the present invention when it is made into an aqueous dispersion having a concentration of 1% by mass or more does not become too high, a film or the like can be easily applied by applying a known molding method such as casting. It can be made into a molded body.

<Cellulose fiber>
The cellulose fiber 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, and still more preferably 1 to 50 nm. An average fiber diameter is calculated | required by the measuring method as described in an Example.

  The carboxyl group content of the cellulose constituting the cellulose fiber of the present invention is 0.1 to 2 mmol / g, preferably 0.4 to 2 mmol / g, more preferably 0, from the viewpoint that high gas barrier properties can be obtained. .6 to 1.8 mmol / g. Carboxyl group content is calculated | required by the measuring method as described in an Example.

  The cellulose fiber of the present invention has a viscosity (23 ° C.) of a 1% by mass dispersion of 5 to 3500 mPa · s, preferably 50 to 3000 mPa · s, more preferably 100 to 2000 mPa · s. A viscosity is calculated | required by the measuring method as described in an Example.

  In addition, since the cellulose fiber of the present invention is very fine compared to the known cellulose fiber, the dispersion prepared under the following conditions is not an aqueous solution but is transparent by visual observation, and is an absorptiometer When the light transmittance is measured by (model name UV-2550 manufactured by Shimadzu Corporation), a light transmittance of 5% or more is shown. In the case of known biocellulose or cellulose prepared by mechanical shearing (for example, the product name Selish FD-200L manufactured by Daicel Chemical Industries, Ltd.) The light transmittance is 0%.

  The cellulose fiber of the present invention preferably has a light transmittance of 30% or more, more preferably 50% or more, still more preferably 60% or more, and particularly preferably 70% or more.

  Here, it describes about the analysis method of the enzyme and protein in a cellulose or a dispersion liquid. As an analysis method, for example, there is a proteome analysis method by a PMF (peptide mass fingerprinting) method or a two-dimensional electrophoresis method, and identification can be performed by these methods.

<Method for producing cellulose fiber>
As a manufacturing method of the cellulose fiber of the present invention,
(I) a production method having an oxidation step and an enzyme treatment step,
(II) a production method having an oxidation step, an enzyme treatment step and a mechanical defibration step,
Either method can be applied.

  The production method (I) includes two methods: a production method in which the oxidation step and the enzyme treatment step are performed together, and a production method in which the enzyme treatment step is performed after the oxidation step.

The manufacturing method of (II) is
(II-1) a production method in which the oxidation step and the enzyme treatment step are performed together;
(II-2) a production method for performing an enzyme treatment step after the oxidation step,
Of the two,
Furthermore, the production method of (II-1) is as follows:
(II-1-1) A manufacturing method in which an enzyme treatment step and a mechanical defibration step are performed together after the oxidation step,
(II-1-2) a production method for performing a mechanical defibration step after the enzyme treatment step after the oxidation step,
Is included.

  Hereafter, the manufacturing process included in the manufacturing method of this invention is demonstrated for every process.

<Oxidation process>
As a pretreatment step before the oxidation treatment, about 10 to 1000 times (mass basis) of water is added to the natural cellulose (absolute dry basis) as a raw material and treated with a mixer or the like to form a slurry. . The absolute dry standard here refers to calculating the absolute dry pulp amount from the moisture content of natural cellulose (pulp) naturally dried in an environment of 20 ° C. and 50% RH measured with a halogen moisture meter. .

  As natural cellulose used as a raw material, wood pulp, non-wood pulp, cotton, silk, wool, regenerated cellulose, bacterial cellulose and the like can be used.

  Next, natural cellulose in the slurry is oxidized to obtain oxidized cellulose fibers having a carboxyl group content of 0.1 to 2 mmol / g of cellulose constituting the cellulose fibers.

  As a method for oxidizing natural cellulose, 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 natural cellulose (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 and acts directly on the fiber to improve fiber dispersibility and transparency. Promoted.

  The amount of the oxidizing agent used is 0.1 mmol to 10 mmol, preferably 1 mmol to 8 mmol, more preferably 1.4 mmol to 6 mmol, more preferably 1.7 mmol with respect to 1 g of cellulose fiber (absolute dry basis) used as a raw material. ~ 5 mmol. If it is 0.1 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 step 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, more preferably 0.7 mmol to 5 mmol, based on 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 10 mmol or less, the removal burden in the subsequent process is reduced.

  The pH is preferably in the range of 9 to 12 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 cellulose constituting the cellulose fiber can be 0.1 to 2 mmol / g. The content is preferably 0.4 to 2 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 0.1 mmol / g or more, the average fiber diameter of the cellulose fibers becomes 200 nm or less when the fiber refining treatment described later is performed, and the solid content concentration is 0.1. A mass% aqueous dispersion becomes transparent. Further, 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 light transmittance described in the visual observation or examples) is obtained. It becomes easy to improve.

<Enzyme treatment process>
The enzyme treatment in this step is a treatment in which an enzyme is added to an aqueous dispersion of cellulose fibers or an aqueous dispersion containing oxidized cellulose fibers during the oxidation step and held for a certain period of time. The holding | maintenance process means making an enzyme adsorb | suck to a cellulose and making it act. At this time, it can also stir as needed.

  By the treatment in this step, hydrolysis of the oxidized cellulose fiber is promoted, and the viscosity of the aqueous dispersion of oxidized cellulose fiber is reduced. This is presumed to be based on a decrease in the width or length or aspect ratio of the oxidized cellulose fiber.

  In addition, an enzyme treatment process can also make a difference in a process condition with the case where it does not perform a mechanical defibration process. In addition, it heats to about 50-100 degreeC after an enzyme treatment as needed, and inactivates an enzyme.

  The enzyme used in this step is mainly cellulase and may be a single component or a mixture. Preferred cellulases belong to families 5, 6, 7, 12, and 45 in the family classification “Biochem. J. 280p. 309-16 (1991)” based on amino acid sequence similarities devised by Henrissat et al. It is.

  Although the source of such cellulase is not particularly limited, the cellulase of family 5 is obtained from Bacillus sp. KSM-S237 strain (FERM P-16067) disclosed in JP-A-10-313859. And alkaline cellulase.

Examples of the family 7 cellulase include endoglucanase EGI obtained from Humicola insolens DSM1800 strain disclosed in International Patent Application Publication 91-17244.

Family 6 cellulases include endoglucanases obtained from Cellulomonas fimi strains described in “Gene vol. 44 (2-3) p. 315-324, 1986” by Wong et al.

Examples of the family 12 cellulase include endoglucanase EG III obtained from a Trichoderma reesei strain disclosed in International Patent Application Publication 92-06184.

Family 45 cellulases include endoglucanase EG V obtained from the Humicola insolens strain described in “FEBS Letters vol. 376 p. 49-52” by Biosset et al.

  The amount of enzyme used should be selected according to the characteristics of the cellulase used. From the viewpoint of bringing the viscosity of the cellulose fiber water-decomposed solution into an appropriate range, the enzyme is used in an amount of 0. 0001-10 mass parts is preferable, 0.0005-5 mass parts is more preferable, 0.001-2.5 mass parts is still more preferable.

  The temperature during the enzyme treatment should be selected according to the characteristics of the cellulase used, but is preferably 10 to 70 ° C, more preferably 20 to 60 ° C, from the viewpoint of improving the activity of the enzyme and promoting the enzyme reaction. 30-50 degreeC is still more preferable.

  The pH at the time of enzyme treatment should be selected according to the characteristics of the cellulase used. From the viewpoint of improving the enzyme activity and promoting the enzyme reaction, the pH is preferably from 3.5 to 11.5, and the pH is preferably from 4.5 to 10 0.5 is more preferable, and pH 5.0 to 9.5 is still more preferable.

  The treatment time is preferably 10 minutes to 1 month when no mechanical defibrating treatment is performed, and preferably 24 hours or less when the mechanical defibrating treatment is performed.

<Mechanical fibrillation process>
In the mechanical defibration process, it is used as a disaggregator, a beater, a low pressure homogenizer, a high pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a short shaft extruder, a twin screw extruder, an ultrasonic stirrer, and a domestic juicer mixer. Then, the desired fiber width and length are adjusted by defibrating the cellulose fiber that has been or has been subjected to the enzyme treatment.

  After the above enzyme treatment or fibrillation treatment, the used catalyst can be removed by washing with water or the like to obtain cellulose fibers as described above.

<Oxygen gas barrier film>
The barrier molded article of the present invention includes a single-layer molded article composed only of the above-described cellulose fibers, and a composite molded article in which one layer or a plurality of layers composed of the cellulose fibers are formed on a suitable base material. Examples of molded articles for oxygen barrier applications are given below.

(Single layer molded product)
A single-layer molded body that does not use a substrate can be produced, for example, as follows. A cellulose fiber is cast-coated on a substrate such as a glass plate and then dried by a drying method such as natural drying or air drying to form a film. Thereafter, the film is peeled off from the substrate to obtain an oxygen barrier film.

[Composite molded body]
The composite film using the base material has a layer made of the above-described cellulose fibers on the surface of the formed body that becomes the base material, and the molded body that becomes the base material is more than the above-described layer made of cellulose fibers. Also, the oxygen barrier property is low. (This means that the oxygen permeability by the predetermined method is high. As the predetermined method, the sample is evacuated for 24 hours using a gas permeation measuring device (model M-C3, manufactured by Toyo Seiki Seisakusho Co., Ltd.). Later, there is a measurement method based on the ASTM D-1434-75M method under the condition of 23 ° C.)
As the molded body serving as the base material, a thin film such as a film, a sheet, a woven fabric, and a non-woven fabric having a desired shape and size, and a three-dimensional container such as a box or bottle having various shapes and sizes can be used. These molded products may be made of paper, paperboard, plastic, metal (a material having a large number of holes or a wire mesh, which is mainly used as a reinforcing material), or a composite of these. it can. The molded body serving as the base material can also have a multilayer structure composed of a combination of the same or different materials.

  The plastic can be appropriately selected according to the use, but polyolefins such as polyethylene and polypropylene, polyamides such as nylon 6, 66, 6/10, and 6/12, polyethylene terephthalate, polybutylene terephthalate, aliphatic polyester, etc. One or more selected from polyester, polylactic acid, polycaprolactone, polybutylene succinate, cellophane such as cellulose, cellulose acetate and the like can be used.

  A composite molded body using a substrate can be produced, for example, as follows. When the substrate is a plastic sheet, an oxygen barrier material is attached to one or both surfaces of the sheet by a known method such as a coating method, a spray method, or a dipping method, and an oxygen barrier (permeate oxygen). A layer that can be suppressed). Then, it dries by methods, such as natural drying and ventilation drying.

  In the case where the substrate is a plastic sheet, a method of laminating a film or sheet made of an oxygen barrier material prepared in advance on the plastic sheet serving as the substrate can be applied. As a method for bonding, a known method such as a method using an adhesive or a heat fusion method can be applied.

  When the base material is a three-dimensional container such as a plastic bottle container or a paper box container, a known method such as a coating method, a spraying method, or a dipping method is applied to one or both of the outer surface and the inner surface of the container. The oxygen barrier material is deposited by combining methods as necessary to form an oxygen barrier (a layer capable of suppressing oxygen permeation). Then, it dries by methods, such as natural drying and ventilation drying.

  Cellulose fibers used in the production of the film may be made of known fillers, colorants such as pigments, ultraviolet absorbers, antistatic agents, water-resistant agents (silane cups) within the range of types and amounts that can solve the problems of the present invention. Ring agents, etc.), clay minerals (montmorillonite, etc.), colloidal silica, alumina sol, titanium oxide, etc. can be blended.

The oxygen barrier molded article of the present invention has an oxygen permeability of 0.2 cm ³ / m ² · day · hPa or less, preferably 0.05 cm ³ / m ² · day · hPa or less, more preferably 0.01 cm. ³ / m ² · day · hPa or less. The lower limit value of the oxygen permeability is 0 cm ³ / m ² · day · hPa.

  Since the cellulose fiber of the present invention has a low viscosity when the concentration is 1% by mass or more, it can be easily formed by applying a known film forming method such as a casting method. This also facilitates the production of the oxygen barrier molded article.

(1) Average fiber diameter In the image which can confirm the diameter of the cellulose fiber image | photographed with the atomic force microscope (Veeco Dimension 3100 Tapping mode), five or more points | pieces were extracted, the fiber diameter was measured, and the average fiber diameter was computed.

(2) Carboxyl group content (mmol / g)
About 0.5 g of absolutely dry pulp is put into a 100 ml beaker, and ion exchange water is added to make a total of 55 ml, and 5 ml of 0.01 M sodium chloride aqueous solution is added to make a 0.83% by weight 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 DK Corporation), a 0.05M sodium hydroxide aqueous solution is waited for 60 seconds. The electrical conductivity and the 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) Viscosity After preparing the cellulose fiber dispersion to a concentration of 1.0 to 1.1% by mass, the mixture was allowed to stand for 24 hours or more in an environment at 23 ° C., and then an E-type rotational viscometer (manufactured by Tokimec) Viscosity measurement was performed. The representative value was a value at a rotational speed of 5 rpm.

Examples 1 and 2
(1) Raw material Natural fiber: Bleached kraft pulp of conifers (Manufacturer: Fletcher Challenge Canada, trade name “Machenzie”, CSF 650 ml)
TEMPO: Commercial product (Manufacturer: ALDRICH, Free radical, 98%)
Sodium hypochlorite: Commercial product (Manufacturer: Wako Pure Chemical Industries, Ltd. Cl: 5%)
Sodium bromide: Commercial product (manufacturer: Wako Pure Chemical Industries, Ltd.).

(2) Manufacturing procedure [Oxidation process]
First, 100 g of the bleached kraft pulp fiber of the above-mentioned coniferous tree was sufficiently stirred with 9900 g of ion-exchanged water, and then 1.24% by mass of TEMPO, 28.1% by mass of sodium hypochlorite, and 12.1% of sodium bromide with respect to 100 g of pulp. 4 mass% was added in this order, it was dropped with 0.5 M sodium hydroxide using a pH stud, the pH was maintained at 10.5 and the temperature was 20 ° C., and an oxidation reaction was performed to obtain oxidized pulp.

  Thereafter, the oxidized pulp was sufficiently washed with ion-exchanged water and filtered using a stainless steel sieve having an opening of 90 μm to obtain a wet pulp mat of 3 to 4% by mass.

[Defibration process]
10 g of oxidized pulp (solid content) was added to 990 g of ion-exchanged water, and 10 minutes with a mixer (trade name, ABSOLUTE (Vita-Mix Blender), manufactured by Osaka Chemical Co., Ltd., rotational speed 37,000 rpm, peripheral speed 140 m / sec). The fibrillation treatment was performed by stirring.

[Enzyme treatment process]
Cellulase (end type) (WKAC1500 POW (W)) was added to the aqueous dispersion (1% by mass, 23 ° C., pH 6.5) of the fibrillated oxidized pulp so as to have the concentration shown in Table 1. Then, using the mixer (trade name, ABSOLUTE (Vita-Mix Blender), manufactured by Osaka Chemical Co., Ltd., rotation speed: 37,000 rpm, peripheral speed: 140 m / sec), the mixture was further stirred for 10 minutes to carry out the enzyme treatment. went. The temperature of the aqueous dispersion after stirring for 10 minutes was about 72 ° C. Thereafter, the cellulase was inactivated by heating to about 90 ° C.

[Film forming process]
On one side of a polyethylene terephthalate sheet (trade name: Lumirror, manufactured by Toray Industries, Inc., sheet thickness: 7 μm) as a base sheet, a fine cellulose fiber dispersion obtained in Examples 1 and 2 (carboxyl group amount: 1.23 mmol / g, oxidized pulp amount: 1% by mass) and 30% by mass of isopropyl alcohol blended, coated with a bar coat (R, D, S webster, N, Y # 50) and then dried at 23 ° C. for 120 minutes. To form a composite sheet.

Comparative Examples 1 and 2
Films were obtained in the same manner as in Examples 1 and 2 under the production conditions shown in Table 1.

Claims (7)

An oxidation step of oxidizing natural cellulose to obtain a dispersion containing cellulose fibers having a carboxyl group content of 0.1 to 2.0 mmol / g of cellulose constituting the cellulose fibers;
An enzyme treatment step of adding and holding the enzyme in the dispersion;
The manufacturing method of a cellulose fiber which has the process of fibrillating the cellulose fiber in the said dispersion liquid mechanically.   The manufacturing method of the cellulose fiber of Claim 1 which makes the said oxidation process and the said enzyme treatment process parallel.   The manufacturing method of the cellulose fiber of Claim 1 which performs the said enzyme treatment process after the said oxidation process.   The manufacturing method of the cellulose fiber of Claims 1-3 which makes the said enzyme treatment process and the said defibration process parallel.   The manufacturing method of the cellulose fiber of Claims 1-3 which performs the said fibrillation process after the said enzyme treatment process.   The manufacturing method of the cellulose fiber of Claims 1-3 which performs the said fibrillation process before the said enzyme treatment process.   A gas barrier molded article using cellulose fibers obtained from the method for producing cellulose fibers according to claim 1.