JP2012046848A - Method for producing microfibrous cellulose - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a microfibrous cellulose in which a microfibrous cellulose having a fiber width of 2 to 1000 nm can be easily obtained by mechanically defibrating cellulose fibers.SOLUTION: A method for producing a microfibrous cellulose having a maximum fiber width of 1000 nm or less includes the steps of: processing wood chips into wood flour; chemically treating the wood flour; and pulverizing the resultant. The shape of wood flour that is subjected to the chemical treatment process is processed such that it has a major radius of 10 to 40 μm and a minor radius of 5 to 20 μm at the point where number accumulation in a particle size and shape distribution measurement is 50%. After that, degreasing treatment, delignifying treatment, and hemicellulose removing treatment are carried out in this order in the chemical treatment process. The delignifying treatment is carried out in a temperature range of 70 to 99°C and in a pH range of more than 3 and 7 or less.

Description

  An object of the present invention is to provide a method for producing fine fibrous cellulose having a maximum fiber width of 1000 nm or less with high yield.

In recent years, nanotechnology aimed at obtaining physical properties different from the bulk and molecular levels by making a material a nanometer size has attracted attention. On the other hand, attention is also focused on the application of natural fibers that can be regenerated due to the substitution of petroleum resources and the growing environmental awareness.
Among natural fibers, cellulose fibers, particularly wood-derived cellulose fibers (pulp) are widely used mainly as paper products. Most cellulose fibers used for paper have a width of 10 to 50 μm. Paper (sheet) obtained from such cellulose fibers is opaque and is widely used as printing paper because it is opaque. On the other hand, when cellulose fibers are processed (beating, pulverizing) with a refiner, kneader, sand grinder, etc., and the cellulose fibers are refined, transparent paper (glassine paper or the like) is obtained. However, the transparency of the transparent paper is at a semi-transparent level, the light transmittance is lower than that of the polymer film, and the haze level (haze value) is large.

Cellulose fibers are aggregates of cellulose crystals having a high modulus of elasticity and a low coefficient of thermal expansion. Since dimensional stability is increased by combining cellulose fibers with a resin, they are used for laminates and the like. However, a normal cellulose fiber is an aggregate of a crystalline part and an amorphous part, and has a limit in dimensional stability because of a fiber having a cylindrical void.
The aqueous dispersion of fine fibrous cellulose obtained by treating cellulose fibers by various methods and setting the fiber width to 50 nm or less is transparent. On the other hand, since the fine fibrous cellulose sheet contains voids, it is diffusely reflected white and becomes highly opaque, but when the fine fibrous cellulose sheet is impregnated with a resin, the voids are filled, so that a transparent sheet is obtained. The fibers of the microfibrous cellulose sheet are very stiff and have a narrow fiber width, so the number of fibers is dramatically increased at the same mass compared to ordinary cellulose sheets (paper). Inside, fine fibers are more uniformly and densely dispersed, and the heat-resistant dimensional stability and strength are dramatically improved. Furthermore, since the fibers are thin, transparency is high. The composite of fine fibrous cellulose having such characteristics is expected to be very large as a flexible transparent substrate (a transparent substrate that can be bent or folded) for organic EL or liquid crystal displays.

  However, even if it is compounded with a resin using fine fibrous cellulose and a transparent substrate is obtained, several heat treatments are essential in the actual device forming step. When heat treatment is performed, there is a problem that a small amount of lignin remaining in the fine fibrous cellulose, hemicellulose, or a reducing end group of cellulose or coloring components react with each other, and a YI value (Yellowing Index) is determined as an index. ing. In order to prevent the coloration, in the process of producing fine fibrous cellulose in advance, the trace amount of residual lignin, hemicellulose, or reducing end groups of cellulose or extracted components should be removed as much as possible, or a raw material with few of them should be selected. However, there is a demand for manufacturing.

  Cellulose has a layered structure inside the wood and is chemically bonded to components such as lignin and hemicellulose. Therefore, it is a final product that is combined with resin and subjected to heat treatment for several hours only by mechanical grinding. It is difficult to obtain fine fibrous cellulose having a low YI value and a maximum fiber width of 1000 nm or less. A method combining chemical or biological treatment and mechanical grinding is generally used.

  A method of removing lignin bundled with cellulose or hemicellulose as a binder during chemical treatment is known as delignification treatment. For example, in Patent Document 1, wood chips are immersed in dilute caustic soda at room temperature. Thereafter, a technique is disclosed in which lignin is selectively partially oxidized and denatured in dilute nitric acid, and digested under atmospheric pressure using a dilute caustic soda aqueous solution to produce pulp. However, this method is a technique for producing pulp with a high yield and recovering lignin, and there is no description that it is used for fine fibrous cellulose.

  The pulp is lightly hydrolyzed, washed with filtered water, dried and pulverized to produce cellulose fine particles containing some amorphous regions, and the purified pulp is hydrolyzed with hydrochloric acid or sulfuric acid to leave only the crystalline regions and pulverize them. A technique (Non-Patent Document 1) is also disclosed. However, the treatment with hydrochloric acid or sulfuric acid is intended to hydrolyze the amorphous part of cellulose and is not intended for delignification treatment. Furthermore, the level of refinement is not sufficient and the transparency of the resulting aqueous suspension of fine fibrous cellulose is also insufficient.

  For the purpose of obtaining fine fibrous cellulose, there is also a technology in which fibrous cellulose such as pulp is pretreated by combining enzyme treatment, acid treatment, alkali treatment, and swelling chemical treatment, and then wet pulverized with a vibration mill pulverizer. It is disclosed (Patent Document 2). However, these chemical treatments are intended for pretreatment of wet pulverization treatment, there is no description of treatment conditions, and the fiber width of the obtained fine fibrous cellulose is several tens of microns, The level is not enough.

  A method (Patent Document 3) is disclosed in which pulp, linter, etc. are impregnated in water, treated at 100 to 150 ° C., beaten, and then refined (Patent Document 3). In addition to reducing the load in the refinement stage, lignin and hemicellulose are disclosed. However, it is not a delignification treatment of wood powder containing a large amount of lignin, the temperature is high, and there is no description of pH.

  Pulp and linter at pH 8-11, temperature 4-40 ° C., 2,2,6,6-tetramethyl-1-piperidine-N-oxyl (hereinafter abbreviated as TEMPO) and hydrogen peroxide as a co-oxidant Alternatively, a method of treating together with a perorganic acid or the like is disclosed (Patent Document 4), which is intended to separate fibers by introducing carboxyl groups into cellulose and is intended to remove lignin. is not.

  Furthermore, Patent Document 5 discloses a method of TEMPO oxidation of pulp treated with an inorganic acid at a pH of 2 to 6, 30 to 120 ° C. and a time of 80 ° C. for 1.5 to 6 hours. However, this acid treatment is intended to remove heavy metals in order to increase the efficiency of TEMPO oxidation as described in the [0014] stage of this document. That is, it is not a technique for removing lignin in wood flour as in the present invention, and there is no suggestion of application to wood flour.

  Disclosed is a method for treating lignin from lignocellulosic material having fiber bundles with sodium hypochlorite, further treating with sodium oxalate for pectin treatment, and then dehemicellulose treatment with caustic soda (Patent Document 6). ing. This method is advantageous in that it is a normal pressure treatment as described in the [0033] stage of the specification, but this method is suitable for non-wood fibers such as kenaf as described in the examples. However, it is not suitable for delignification treatment of raw materials containing a large amount of lignin such as wood powder, and there is no description of temperature and pH conditions in the delignification step.

  On the other hand, a method has been proposed in which wood powder is used as a raw material, degreased, and delignified with sodium chlorite and acetic acid, washed and dehemicellulose treated, and then refined to produce fine fibrous cellulose. (Patent Document 7). However, there is no description of what particle size or shape of wood flour is good.

  As described above, various techniques for refining fibrous cellulose have been disclosed, but a method for obtaining fine fibrous cellulose having a high yield on an industrial level, that is, fine fibers for performing a refining treatment after chemical treatment Of a method for producing such a wood flour and a method for producing such a wood flour in a method for producing a cellular cellulose, which suppresses the deterioration of the cellulose and performs delignification treatment under relatively mild conditions. Is desired.

Akira Yamaguchi "Pulverization and Microfibrillation of Cellulose" Paper and Pulp Technology Times Vol. 28, No. 9, pp. 5 (1985)

JP 2009-167554 A JP-A-6-10288 JP 2010-115574 A JP 2008-1728 A JP 2009-243014 A Japanese Patent No. 4306373 JP 2008-24788 A

  An object of the present invention is to provide a method for producing fine fibrous cellulose for producing a fine fibrous cellulose having a maximum fiber width of 1000 nm or less in a simple method and producing a high yield by a method with little cellulose deterioration. is there.

  There is no patent document that describes or specifies the relationship between the shape of wood flour as a raw material and delignification of wood flour. The inventors of the present application have examined this point from various perspectives, and have found that the optimum shape of the wood flour varies depending on what conditions are adopted as the method for delignification of the wood flour.

  That is, in the chemical treatment step, when delignification treatment is performed at a temperature of 100 ° C. or less and a pH of more than 3 and 7 or less, hydrolysis of the cellulose chain is suppressed as compared with treatment at pH of 3 or less. The delignification property is somewhat inferior. Therefore, it is understood that various problems can be solved by studying wood flour of various shapes under the above conditions and controlling the wood flour shape (major axis, minor axis, aspect ratio) within a specific range. It came to complete.

The present invention includes the following inventions.
(1) A method for producing a fine fibrous cellulose having a maximum fiber width of 1000 nm or less after making a wood chip into a wood powder, chemically treating it, and then subjecting it to a chemical treatment step. After processing the shape to have a major axis of 10 to 40 μm and a minor axis of 5 to 20 μm at a point where the cumulative number of particles in the particle size / shape distribution measurement is 50%, degreasing treatment, delignification treatment, and dehemicellulose treatment are performed. A method for producing fine fibrous cellulose, in which chemical treatment is sequentially performed, and delignification treatment is performed at a temperature of 70 to 99 ° C. and a pH of more than 3 and 7 or less.

(2) The manufacturing method of the fine fibrous cellulose as described in (1) processed so that the aspect-ratio of the said wood flour may be 1-3.

(3) The wood fiber finely pulverized by an impact method without using a pulverizing medium without coarsely pulverizing the wood chip and then classified, and then subjected to the chemical treatment. (1) or (2) Production method.

(4) The method for producing fine fibrous cellulose according to any one of (1) to (3), wherein the moisture content of the wood chips used for producing the wood powder is 7% or less.

(5) In the delignification treatment, at least one selected from acetic anhydride and hydrogen peroxide, acetic acid, hydrogen peroxide and a catalytic amount of sulfuric acid, or a combination of chlorous acid and acetic acid is used (1) to (4) The manufacturing method of the fine fibrous cellulose of any one of (4).

The present invention provides a method capable of efficiently producing fine fibrous cellulose even under relatively mild conditions.
That is, in the method of obtaining fine fibrous cellulose in high yield by chemical treatment and refinement treatment of wood flour, the shape of wood flour is smaller and longer than in the case of acidic conditions at high temperature and low pH. Even at temperatures not exceeding 100 ° C, the delignification reaction proceeds as effectively as under acidic conditions, and the bond between cellulose and lignin is weakened, thereby forming fine fibrils and even crystalline regions. It is considered that the yield increases because the bonding force between the microfibrils is reduced and the pulp can be easily refined by subsequent mechanical treatment. Moreover, under these conditions, the cellulose molecules in the wood flour are less susceptible to hydrolysis, so that fine fibrous cellulose with little deterioration can be obtained.

Hereinafter, the present invention will be described in detail.
In the present invention, when the cellulose fibers are refined, examples of fiber raw materials include plant-derived cellulose, animal-derived cellulose, and bacterial-derived cellulose. Among them, wood-based raw materials that are easily available and inexpensive are used as wood flour. To use. The wood flour includes coniferous trees (domestic bay pine, spruce pine, todo pine, red pine, larch, etc., foreign black spruce, white spruce, Douglas fir, western hemlock, southern pine, jack pine, etc.) (For example, Japanese cypress, linden, sen, poplar, hippopotamus, foreign aspen, cottonwood, black willow, yellow poplar, yellow birch, eucalyptus, etc.), and pine and eucalyptus are preferred. In particular, a raw material derived from a plantation tree of eucalyptus is a preferred embodiment because of the high uniformity of the material.

  Eucalyptus derived from planted trees that can be used in the present invention includes at least one material selected from globulas, grandis, camaldrensis, perita, saligna, danai, nightens, a hybrid of camaldrensis and eurofila, and the like. It is done.

  The wood chips used in the present invention are usually used in pulp production. For example, bay pine or eucalyptus chips are sun-dried or forcibly dried with a drier so that the moisture content is 7% or less, and then in a pulverization treatment step. Chips are crushed to produce wood flour. The particle size distribution of the chip is not particularly limited, but those having a thickness of 2 mm to 8 mm are preferably used because they are easily powdered into wood. If the moisture content of the chip exceeds 7%, the crystallinity of the finally obtained fine fibrous cellulose is greatly reduced, which is not preferable.

  In the production of wood flour in the present invention, the coarse pulverizer includes a shearing pulverizer such as a shredder and a cutter mill, a compression pulverizer such as a juicer crusher and a cone crusher, an impact pulverizer such as an impact crusher, or a roll mill and a stamp. It can be appropriately selected from among milling machines such as mills, edge runners, and rod mills in view of final use and cost. Here, it is not particularly necessary to adjust the particle diameter and shape, and therefore there is no problem even if pulverization is performed without using a screen.

  After coarse pulverization, the wood powder is finely pulverized without classification. For the fine pulverization, an autogenous pulverizer, a vertical roller mill, a high-speed rotary mill, a high-speed rotary mill with a built-in classifier, a container-driven medium mill, a medium There are stirring mills, airflow crushers, compaction shear mills, colloid mills, etc., but the impact method of pulverizing without using a medium such as a ball or rod made of SUS is preferable. It is preferable to use a manufactured DD mill. In the DD mill, wood powder of various shapes can be obtained by selecting appropriate screen diameters in the primary and secondary pulverization and changing the pulverization time. A screen having a diameter of 2 mmφ is preferably used. If sampling is performed at the exit of the crusher and the particle size / shape is not within the range specified by the present invention, it is necessary to increase the residence time by selecting a finer screen diameter. It is. Further, the fine pulverization process may be performed in two stages. If the desired particle size / shape cannot still be obtained, a coarse component or an excessively fine component may be removed by screening or sieving.

  The shape (particle size distribution) of the wood flour in the present invention can be prepared by appropriately changing the grinding conditions such as grinding time, wood flour concentration, medium type (material, shape, size) as described above. The shape of the wood flour is measured using a particle size / shape distribution measuring device (manufactured by Seishin Enterprise Co., Ltd .: trade name “PITA-1”), and the major axis, minor axis, and aspect ratio (= major axis / minor axis) of the wood powder using water as a dispersion medium. And the number of them is measured.

  In the particle size distribution of the wood flour used in the present invention, the major axis is 10 to 40 μm, more preferably 17 to 35 μm, and the minor axis is 5 to 20 μm, more preferably 10 to 10% in terms of the cumulative number. 15 μm. When the major axis and the minor axis are larger than this, an acidic aqueous solution having a pH of 3 or less is not so high in delignification, so that the delignification reaction does not proceed, so that the yield is greatly reduced. Conversely, when the major axis and minor axis are smaller than this, the delignification reaction proceeds, but at the same time, the hydrolysis of cellulose also proceeds, so that the viscosity and strength also decrease due to a decrease in the degree of polymerization of cellulose molecules.

  Moreover, it is preferable to process so that the aspect-ratio represented by ratio of a major axis and a minor axis may be 1-3, More preferably, it is 1.5-2.1. Since the same can be said for the aspect ratio, there is an appropriate range.

In the present invention, in order to obtain fine fibrous cellulose, it is necessary to treat the wood flour through at least a degreasing step, a delignification step, and a dehemicellulose step.
In the degreasing step of the present invention, carbene, alcohol, lipase, which is an enzyme that decomposes triglycerides of fatty acids, and the like, which are 1: 2 mixed solutions of carbonate, alcohol, and alcohol-benzene, can be used as appropriate. However, there is a method of treating at high temperature and high pressure, etc., but sodium carbonate is used because it is inexpensive as an agent, is not an organic solvent, can be used easily without using a pressure vessel, and has high degreasing efficiency. The method using is preferable.

Sodium carbonate in the degreasing step is used as an aqueous solution, and the concentration of sodium carbonate in the aqueous solution is preferably 0.1% by mass to 10% by mass. If the concentration of sodium carbonate is less than 0.1% by mass, the degreasing efficiency is undesirably lowered. On the other hand, when the concentration exceeds 10% by mass, the degreasing effect is saturated and the necessity is also low economically.
As for the addition amount (solid content) of the sodium carbonate aqueous solution with respect to 100 mass parts of wood flour, 1 mass part-10 mass parts are preferable. When the addition amount is less than 1 part by mass, productivity is lowered, which is not preferable. If it exceeds 10 parts by mass, the degreasing efficiency decreases, which is not preferable.
The temperature is preferably 40 ° C to 99 ° C, and if it is less than 40 ° C, the degreasing efficiency is extremely deteriorated, which is not preferable. On the other hand, if it exceeds 100 ° C., it is difficult to make fine fibers, which is not preferable.

  The delignification solution used in the delignification process includes peracetic acid solution with acetic anhydride and hydrogen peroxide, peracetic acid solution with acetic acid, hydrogen peroxide and catalytic amount of sulfuric acid (equilibrium peracetic acid solution), or chlorous acid and acetic acid ( It is preferable to carry out using any one of Wise method solutions. Among them, the system using peracetic anhydride and hydrogen peroxide is preferably used in the treatment of an actual machine because peracetic acid is rapidly generated. When using chlorous acid and acetic acid, measures are required for the generation of chlorine during the reaction and organic chlorine compounds are discharged into the wastewater. There is a need to.

  The ratio of the delignification solution to the defatted wood flour is preferably 0.1% to 50%. The temperature when treating the wood flour is preferably 70 ° C. or higher and 99 ° C. or lower, more preferably 85 ° C. to 98 ° C., and particularly preferably 90 ° C. to 95 ° C. When the temperature is lower than 70 ° C., the efficiency of the delignification treatment is lowered, and a colored state is obtained. On the other hand, if it exceeds 99 ° C., it becomes difficult to make fine fibers, which is not preferable.

  In the present invention, the pH of the delignification solution needs to be more than 3 and 7 or less. In order to satisfy this condition, at least one of the alkali metal salt or alkaline earth metal salt is added to the delignification solution. Various basic aqueous solutions may be added. In particular, when the equilibrium peracetic acid is used, care must be taken because the reaction pH may be 3 or less due to a catalytic amount of sulfuric acid. As specific basic chemicals to be used, sodium hydroxide, potassium hydroxide, sodium carbonate or potassium carbonate is preferable because it can be used relatively easily. If the pH is 3 or less, the delignification reaction proceeds and at the same time the cellulose deteriorates. On the contrary, if the pH is 7 or more, the efficiency of the delignification reaction is lowered, which is not preferable.

  In the present invention, dehemicellulose treatment is performed after delignification treatment. Since alkali is used in this treatment, it is convenient to remove delignified fragments. As a method for dehemicellulose formation, an aqueous solution of an alkali metal hydroxide is used for immersion treatment at room temperature overnight, or a short time treatment at high temperature with stirring in the aqueous solution, or under pressure in the aqueous solution. And a method of treating under high temperature and high pressure while stirring. As the chemical used, potassium hydroxide is most preferable because it is inexpensive, can be used at normal temperature and pressure, and the efficiency of dehemicellulose is high.

The concentration of the potassium hydroxide solution is preferably 1% by mass to 20% by mass. If the concentration is less than 1% by mass, the efficiency of the dehemicellulose reaction is lowered, which is not preferable. On the other hand, if the concentration exceeds 20% by mass, the cellulose becomes mercerized, and as a result, the yield of the fine fibrous cellulose decreases, which is not preferable. The addition ratio of the potassium hydroxide solution to the delignified wood flour is preferably 1% by mass to 10% by mass. When the addition rate is less than 1% by mass, productivity is lowered, which is not preferable. When it exceeds 10 mass%, degreasing efficiency falls and it is not preferable.
The temperature of the potassium hydroxide aqueous solution is preferably 1 ° C to 40 ° C, more preferably 4 ° C to 36 ° C, and particularly preferably 8 ° C to 32 ° C. If the temperature is less than 1 ° C., the efficiency of dehemicellulose deteriorates, which is not preferable. If the temperature exceeds 40 ° C., it is difficult to form fine fibers, which is not preferable.

  The wood powder subjected to the dehemicellulose treatment is dispersed in water and subjected to a finer treatment as an aqueous suspension. The concentration of the aqueous suspension is preferably 0.1% by mass to 7% by mass, and more preferably 0.3-5% by mass. If the concentration is less than 0.1% by mass, productivity is lowered, which is not preferable. On the other hand, if the concentration exceeds 7% by mass, the viscosity may increase excessively during the pulverization process, and handling may become very difficult.

  In the present invention, the method for refining fibrous cellulose is not particularly limited, but a high-speed fibrillator, a grinder (stone mill type pulverizer), a high-pressure homogenizer or an ultra-high pressure homogenizer, a high-pressure collision type pulverizer, a ball mill, a disk type refiner, A method of thinning cellulosic fibers by wet grinding using mechanical action such as conical refiner, twin-screw kneader (double-screw extruder), vibration mill, homomixer under high-speed rotation, ultrasonic disperser, beater, etc. Is preferred. Among these, a high-speed defibrator, a stone mill, a high-pressure homogenizer, or a ball mill treatment is particularly preferable because fine fibers can be obtained efficiently. Further, it may be refined after chemical treatment such as TEMPO oxidation, ozone treatment, enzyme treatment or the like.

  The fine fibrous cellulose obtained by the present invention is a cellulose fiber or rod-like particle that is much thinner than the pulp fiber usually used for papermaking. The fine fibrous cellulose is an aggregate of cellulose molecules including a crystal part, and its crystal structure is type I (parallel chain). The width of the fine fibrous cellulose is preferably 1 nm to 1000 nm as observed with an electron microscope, more preferably 2 nm to 500 nm, and still more preferably 4 nm to 100 nm. When the width of the fiber is less than 1 nm, since the cellulose molecule is dissolved in water, the physical properties (strength, rigidity, dimensional stability) as the fine fiber are not expressed. If it exceeds 1000 nm, it cannot be said that it is a fine fiber, and is merely a fiber contained in ordinary pulp, and physical properties (strength, rigidity, dimensional stability) as a fine fiber cannot be obtained. In particular, when the fine fibrous cellulose is used for transparency, the fine fiber width is preferably 50 nm or less. The composite material obtained by blending these fine fibrous celluloses with a polymer resin has a high density, a high strength because it becomes a dense structure, and a high elastic modulus derived from cellulose crystals is obtained. High transparency can be obtained because of less visible light scattering.

Here, the fact that the fine fibrous cellulose has a type I crystal structure is that 2θ = 14 in a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418４) monochromatized with graphite. It can be identified by having typical peaks at two positions near -17 ° and 2θ = 22-23 °. Moreover, the measurement of the fiber width by electron microscope observation of fine fibrous cellulose is performed as follows. An aqueous suspension of fine fibrous cellulose having a concentration of 0.05 to 0.1% by mass is prepared, and the suspension is cast on a carbon film-coated grid subjected to a hydrophilic treatment to obtain a sample for TEM observation. When a wide fiber is included, an SEM image of the surface cast on glass may be observed. Observation with an electron microscope image is performed at a magnification of 5000 times, 10000 times, or 50000 times depending on the width of the constituent fibers. At this time, when an axis of arbitrary vertical and horizontal image width is assumed in the obtained image, a sample and observation conditions (magnification, etc.) are set so that at least 20 fibers intersect the axis at least with respect to the axis. With respect to the observation image satisfying this condition, two random axes are drawn vertically and horizontally for each image, and the fiber width of the fiber intersecting with the axis is visually read. In this way, images of at least three non-overlapping surface portions are observed with an electron microscope, and the fiber width values of the fibers where two axes intersect each other are read (at least 20 × 2 × 3 = 120 fiber widths).
The fiber length of the fine fibers is preferably 1 μm to 1000 μm, more preferably 5 μm to 800 μm, and particularly preferably 10 μm to 600 μm. When the fiber length is less than 1 μm, it is difficult to form a fine fiber sheet. If it exceeds 1000 μm, the slurry viscosity of the fine fibers becomes very high and it becomes difficult to handle.
The fiber length can be obtained by image analysis of TEM, SEM, or AFM. The fiber length referred to in the present invention is a fiber length that occupies 30% or more of the fiber.
The axial ratio of the fine fibers according to the present invention is preferably in the range of 100 to 10,000. If the axial ratio is less than 100, it may be difficult to form a fine fiber sheet. Moreover, there is a possibility that the width becomes thick and the characteristics of the fine fiber are not expressed. When the axial ratio exceeds 10,000, the slurry viscosity becomes high, which is not preferable.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to these Examples. Moreover, unless otherwise indicated, the part and% in an example show a mass part and mass%, respectively.

<Example 1>
[Chip processing]
After classifying bay pine chips to be used for pulp production into chips of 2 mm on with a chip thickness classification device, the moisture content of the chips (the amount of moisture / the total amount of chips including moisture) in the sun The sample was adjusted to about 7% and used as a wood powder sample.

[Wood powdering (coarse and fine)]
The chip was coarsely pulverized using a coarse pulverizer (hammer crusher: “HC-400”) manufactured by Hadano Sangyo Co., Ltd. Without classifying it, primary fine pulverization with a DD mill (screen 0.8 mmφ, DD-3 type) manufactured by Hadano Sangyo Co., Ltd., followed by secondary fine grinding with a DD mill (screen 0.2 mmφ, DD-3 type). It grind | pulverized and grind | pulverized so that it might become a predetermined particle size and shape.

[Measurement of the shape of wood flour]
After suspending 0.02-0.03 g of the above wood powder in 20 ml of distilled water at room temperature, a product name: “PITA-1” which is a particle size / shape distribution measuring instrument manufactured by Seishin Enterprise Co., Ltd. is used. Using a CCD camera, 5,000 images were taken in one sample (required time 15 to 30 minutes), and the major axis, minor axis, and aspect ratio were determined at a point where the cumulative number reached 50%.

[Degreasing]
The wood flour (BD 30 g) was treated at 90 ° C. for 5 hours with stirring in a 2% aqueous sodium carbonate solution. The treated wood flour was washed with 10 times the amount of distilled water, dehydrated with a Buchner, and distilled water was added to adjust the concentration.

[Delignin treatment]
The degreased wood flour was suspended in 1.8 L of water, 2.4 mL of acetic acid was added with stirring, 12 g of sodium chlorite was added, and the mixture was treated at 80 ° C. for 1 hour. The pH at that time was 4.0. After this operation was repeated 5 times, the treated wood flour was washed with about 10 times the amount of distilled water, dehydrated with Buchner, and the concentration was adjusted by adding distilled water.

[Dehemicellulose treatment]
The slurry was delignified and treated with wood powder (BD 30 g) using a 5% aqueous potassium hydroxide solution at room temperature for 24 hours. It was washed with 10 times the amount of distilled water, dehydrated with a Buchner, and distilled water was added to prepare a 0.5% pulp suspension.

[Refining treatment and yield measurement]
The above suspension is defibrated with a high-speed defibrator ("CLEAMIX" manufactured by MTechnic Co., Ltd.) for 21,500 rotations for 30 minutes (refining treatment) to obtain a fine fibrous cellulose aqueous suspension. The liquid concentration was measured. The obtained fine fibrous cellulose suspension was treated at about 12,000 G for 10 minutes using a centrifuge (“H-200NR” manufactured by Kokusan Co., Ltd.), the supernatant concentration was measured, and the following calculation was performed. The yield was determined.
Yield (%) = (Concentration of supernatant after centrifugation) ÷ (Slurry concentration after refinement) × 100
The fibers in the supernatant obtained by centrifugation were observed with an electron microscope, and the fiber width was measured. Further, the supernatant obtained by centrifugation was suction filtered on a membrane filter having a pore diameter of 0.45 μm to prepare a sheet of 80 g / m ² . The results are shown in Table 1.

[Measurement of polymerization degree from sample viscosity]
A sample of about 0.04 g is collected from a part of the sheet, sufficiently dried at 105 ° C., weighed, and suspended by adding water. Then, the viscosity was measured according to TAPPI T230om-99 using copper ethylenediamine, and converted into the degree of polymerization.

<Example 2>
In the delignification step, acetic anhydride and 30% hydrogen peroxide were mixed at a volume ratio of 1: 1, and this delignification solution was adjusted to a hydrogen peroxide equivalent to degreased wood flour (BD 30 g). The same procedure as in Example 1 was performed except that 1.5 L corresponding to 4.5% was added and the treatment was performed at 90 ° C. for 1 hour. The results are shown in Table 1.

<Example 3>
In the delignification step, the commercially available equilibrium peracetic acid (mixed acetic acid and hydrogen peroxide and added with a catalytic amount of sulfuric acid) is reduced to 4.5% in terms of hydrogen peroxide equivalent to the raw material after degreasing (BD 30 g). The same procedure as in Example 1 was performed except that 1.5 L of the corresponding delignification solution was added and treated at 90 ° C. for 1 hour. The results are shown in Table 1.

<Example 4>
It was performed in the same manner as in Example 1 except that planted tree eucalyptus (water content 6.5%) having an age of 8 years was used as the material type. The results are shown in Table 1.

<Example 5>
The same method as in Example 2 was used, except that eucalyptus planted tree 8 years old was used as the material type. The results are shown in Table 1.

<Comparative Example 1>
A fine fibrous cellulose aqueous suspension was obtained in the same manner as in Example 1 except that the shape of the bay pine wood flour was 60 μm for the major axis, 15 μm for the minor axis, and 4.0 for the aspect ratio. The results are shown in Table 1.

<Comparative example 2>
A fine fibrous cellulosic aqueous suspension was obtained in the same manner as in Example 2, except that an 8 year old planted tree eucalyptus having a moisture content of 30% was powdered with a CD mill manufactured by Chuo Kakoki Co., Ltd. . The results are shown in Table 1.

<Comparative Example 3>
A fine fibrous cellulose aqueous suspension was obtained in the same manner as in Example 3 except that sulfuric acid was added to adjust the pH to 1.5 in the delignification step. The results are shown in Table 1.

<Comparative example 4>
A fine fibrous cellulose aqueous suspension was obtained in the same manner as in Example 5 except that the temperature of the delignification treatment was 120 ° C. using an afforested eucalyptus tree of 8 years old. The results are shown in Table 1.

  As is clear from Table 1, by selecting the water content and the fine pulverizer so that the shape of the pine or eucalyptus wood flour is in the optimum range, the pH is changed at a subsequent temperature of 70 ° C. to 99 ° C. After performing chemical treatment including delignification treatment under conditions of more than 3 and 7 or less, the maximum fiber width is 1000 nm or less and the yield in the refinement treatment step is 80% or more by passing through the refinement treatment. It can be seen that fibrous cellulose can be obtained regardless of the difference between two different grades, has a high degree of polymerization, and has little cellulose degradation. On the other hand, it can be seen that, in both types of materials, when the shape of the wood powder falls outside the scope of the claims, the yield in this system decreases and the degree of polymerization also decreases.

  According to the present invention, it becomes possible to efficiently produce fine fibrous cellulose having a high yield in the refinement treatment step and a maximum fiber width of 1000 nm or less by a simple method. By impregnating this fine fibrous cellulose with a polymer resin, a transparent composite material is obtained, which is useful as a flexible transparent substrate for organic EL and liquid crystal displays.

Claims (5)

  A method for producing fine fibrous cellulose having a maximum fiber width of 1000 nm or less after finely treating a wood chip after converting the wood chip into wood powder, and the shape of the wood powder subjected to the chemical treatment step, At the point where the cumulative number of particles in the particle size / shape distribution measurement is 50%, after treating the major axis to be 10 to 40 μm and the minor axis to 5 to 20 μm, the chemistry is performed in the order of degreasing treatment, delignification treatment, and dehemicellulose treatment. A process for producing fine fibrous cellulose, wherein the treatment is performed, and the delignification treatment is performed at a temperature of 70 to 99 ° C. and a pH of more than 3 and 7 or less.   It processes so that the aspect-ratio of the said wood flour may be 1-3, The manufacturing method of the fine fibrous cellulose of Claim 1 characterized by the above-mentioned.   3. The fine fiber according to claim 1, wherein the wood fiber is subjected to the chemical treatment without coarsely pulverizing and then classifying the wood chip and then pulverized by an impact method without using a pulverization medium. A method for producing cellular cellulose.   The method for producing fine fibrous cellulose according to any one of claims 1 to 3, wherein the moisture content of the wood chips used for the production of the wood flour is 7% or less.   2. The delignification treatment uses at least one selected from acetic anhydride and hydrogen peroxide, acetic acid, hydrogen peroxide and a catalytic amount of sulfuric acid, or a combination of chlorous acid and acetic acid. The manufacturing method of the fine fibrous cellulose of any one of -4.