JP2012012713A - Method of producing microfibrous cellulose - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing microfibrous cellulose comprising mechanically defibrating cellulose fiber so as to easily provide microfibrous cellulose with a fiber width of 2-1000 nm.SOLUTION: There is provided a method of producing microfibrous cellulose in which a cellulose fiber is treated at least through a degreasing process, a delignifying process, a hemicellulose-removing process and a refining process so as to produce the microfibrous cellulose with a fiber width of 2-1000 nm, and an acid aqueous solution treatment is performed in the delignifying process. In the delignifying process, the acid aqueous solution treatment is followed by an aqueous alkali solution treatment.

Description

  The present invention relates to a method for producing fine fibrous cellulose that can easily obtain fine fibrous cellulose having a fiber width of 2 to 1000 nm by mechanically defibrating cellulose fibers.

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 the cellulose fiber is treated (beating, pulverizing) with a refiner, kneader, sand grinder or the like, and the cellulose fiber is refined (microfibril), a 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 with a high modulus of elasticity and a low coefficient of thermal expansion, and heat resistant dimensional stability is improved by compositing cellulose fibers with polymers. Yes. However, normal cellulosic fibers are aggregates of crystals, and are fibers having cylindrical voids, so that dimensional stability is limited.
The aqueous dispersion of fine fibrous cellulose having mechanically pulverized cellulose fibers and having a fiber width of 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. However, when the fine fibrous cellulose sheet is impregnated with a resin, the voids are filled, so that a transparent sheet is obtained. Furthermore, the fibers of the fine fibrous cellulose sheet are an aggregate of cellulose crystals, very stiff, and because the fiber width is small, the number of fibers is dramatically increased at the same mass compared to ordinary cellulose sheets (paper). To be more. Therefore, when composited with a polymer, fine fibers are dispersed more uniformly and densely in the polymer, and the heat-resistant dimensional stability is dramatically improved. Moreover, since the fibers are thin, the transparency is high. A fine fibrous cellulose composite 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.

  There have been many disclosures on the fine fiber technology related to fine fibrous cellulose, but most of the technology related to pulp that can easily obtain fine fibrous cellulose having a diameter of 2 to 1000 nm by mechanically defibrating the pulp. The current situation is not disclosed.

Patent Document 1 discloses a technique of fine fibrous cellulose that defines water retention, but fine fibrous cellulose is obtained by high-pressure treatment of kraft pulp. However, the defibrating efficiency is poor, and a long time treatment is required to obtain a fiber having a small diameter.
Patent Document 2 discloses a technique for obtaining cellulose nanofibers in a high yield by allowing an endoglucanase to act on an amorphous portion having improved enzyme permeability on an aggregate of cellulose microfibrils. However, since cellulose aggregates that are in the form of fine fibers in advance are used as raw materials, there is a problem that the efficiency is low in consideration of the overall productivity.
Patent Document 3 describes a technique for efficiently producing nanofibers by preliminarily defibrating cellulosic fiber raw material that has been disaggregated in a wet manner, and allowing enzymes such as cellulase, xylanase, and hemicellulase to act during the ultrasonic treatment process. Is disclosed, however, an enzyme treatment step is required, and it cannot be said that the efficiency is sufficiently high. In addition, ordinary pulp for papermaking is used as a raw material.
Patent Document 4 discloses a technique in which fibers are oxidized using an oxidizing agent such as persulfuric acid, treated with an enzyme, and subjected to a reduction treatment to form a fibril. However, the fiber width is as large as 3 to 5 μm and fine. The process has not progressed sufficiently.
Patent Document 5 discloses a technique for beating a lignocellulose fiber using any one of ammonium oxalate, sodium hydroxide, chlorite, and hypochlorite. The width of is in a thick state, and the miniaturization efficiency has not been improved.
Patent Document 6 discloses a microporous cellulose sheet composed of cellulose fibers having a maximum fiber diameter of 1 μm or less, and normal pulp for papermaking or bacterial cellulose is used as a pulp raw material.

  As a method of combining chemical treatment and mechanical pulverization treatment, pulp is slightly hydrolyzed, washed with filtered water, dried and pulverized to produce cellulose fine particles partially containing amorphous regions, and purified pulp is treated with hydrochloric acid. Alternatively, a technique of hydrolyzing with sulfuric acid and pulverizing leaving only the crystalline region is disclosed, but the level of refinement is not sufficient, and the transparency of the obtained aqueous suspension of fine fibrous cellulose is also Insufficient (Non-Patent Document 1). Here, hydrolysis is carried out with hydrochloric acid or sulfuric acid, but this method is a treatment after pulping, which is a technique completely different from the present invention, and the defibration property is insufficient.

  Utilizing the surface oxidation reaction of cellulose by N-oxyl compound, the maximum fiber diameter is 1000 nm or less and the number average fiber diameter is 2 to 150 nm, and some of hydroxyl groups of cellulose are selected from the group consisting of carboxyl group and aldehyde group A technique (Patent Document 7) that provides fine fibrous cellulose that is oxidized to at least one functional group and has a cellulose I-type crystal structure is disclosed. However, this method has a problem in practical use, such as impregnation with a hydrophobic resin, because a hydrophilic group is introduced by oxidation of the surface.

  A technique for wet-grinding fibrous cellulose pretreated by any of enzyme treatment, acid treatment, alkali treatment, and swelling chemical treatment with a vibration mill grinder is disclosed (Patent Document 8), but the efficiency is still low. The yield of fine fibrous cellulose is low and the practicality is poor. Moreover, although a part of cellulose fiber is defibrated to a width of 50 to 70 nm by the enzyme treatment, it is a part of the fiber and the efficiency is low. Moreover, there is no description that the width | variety of a cellulose fiber will be 1000 nm or less by acid treatment.

  Furthermore, a method has been proposed in which wood powder is defatted, delignified with sodium chlorite and acetic acid, washed, dehemicellulosed, and then refined to produce fine fibrous cellulose (Patent Document 9). Since the compound uses sodium chlorite, the lignin on the surface of the wood flour is removed, but the permeability is poor, so it is difficult to remove the lignin inside the wood flour, and as a result, fine fibers with a low YI value. In addition, organic chlorine compounds are contained in the wastewater after the reaction, which causes environmental problems.

Non-Patent Documents 2 to 4 disclose a technique for delignifying with an acidic aqueous solution and an alkaline aqueous solution, but this is a technique for improving the pulp yield by leaving hemicellulose, and mechanically using this pulp. There is no technical idea of defibrating to produce fine fibrous cellulose.
Patent Document 10 discloses that wood chips are hydrophilized with dilute caustic soda at room temperature, lignin is selectively partially oxidized in dilute nitric acid, denatured, and digested under atmospheric pressure using dilute caustic soda aqueous solution. Techniques for manufacturing are disclosed. Although it is a technique for producing pulp with a high yield and recovering lignin, there is no description of utilizing it as a pulp for fine fibrous cellulose.

  As described above, various techniques for refining fibrous cellulose have been disclosed. However, development of a technique for producing fine fibrous cellulose having a high yield on an industrial level is desired.

Akira Yamaguchi "Pulverization and Microfibrillation of Cellulose" Paper and Pulp Technology Times Vol. 28, No. 9, pp. 5 (1985) Wen Bang Ba “Research on nitrate pulp (Part 1) Behavior of wood polysaccharides” Journal of the Wood Society Vol. 26, No. 12, p. 12 (1980) Wen Bang Ba “Research on nitrate pulp (2nd report) Study on nitrate pulp (2nd method) Model experiment on behavior of carbohydrates” Journal of Wood Science, Vol. 26, No. 11, p. 738 (1980) Wen Bang Ba "Studies on nitrate pulp (Part 3) Reaction of Vanillyl Alcohol and dilute nitric acid" Journal of the Wood Society Vol. 28, No. 2, p. 129 (1982)

JP-A 56-1000080 JP 2008-150719 A JP 2008-169497 A Special table 2004-520494 gazette Japanese Patent No. 4306373 JP 2006-193858 A JP 2008-1728 A JP-A-6-10288 JP 2008-24788 A JP 2009-167554 A

  The present invention provides a method for producing fine fibrous cellulose, in which fine fibrous cellulose having a fiber width of 2 to 1000 nm can be easily obtained by mechanically defibrating cellulose fibers.

  The present inventors mechanically defibrated pulp obtained by subjecting cellulose fibers (wood chips) to delignification treatment by acidic aqueous solution treatment and alkaline aqueous solution treatment, whereby fine fibrous cellulose having a fiber width of 2 to 1000 nm. Was easily obtained, and the present invention was completed.

The present invention includes the following inventions.
(1) A method of producing a fine fibrous cellulose having a fiber width of 2 to 1000 nm by treating cellulose fibers through at least a degreasing step, a delignification step, a dehemicellulose step, and a micronization step, in the delignification step It is a manufacturing method of the fine fibrous cellulose which performs acidic aqueous solution processing.

(2) The method for producing fine fibrous cellulose according to (1), wherein the alkaline aqueous solution treatment is performed after the acidic aqueous solution treatment is performed in the delignification step.

(3) Production of fine fibrous cellulose according to (1) or (2), wherein the acidic aqueous solution in the delignification step is at least one selected from sulfuric acid aqueous solution, hydrochloric acid aqueous solution, nitric acid aqueous solution, formic acid aqueous solution, and acetic acid aqueous solution. Is the method.

(4) The method for producing fine fibrous cellulose according to (2), wherein the alkaline aqueous solution in the delignification step is a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution.

(5) It is a manufacturing method of the fine fibrous cellulose of any one of (1)-(4) which processes a cellulose fiber sequentially through a degreasing process, a delignification process, a dehemicellulose process, and a refinement | miniaturization process.

The present inventors have studied various methods for improving the yield of fine fibrous cellulose. First, chemical pulp such as kraft pulp (NBKP or LBKP) or sulfite pulp (SP) was treated with an acidic aqueous solution, but the desired fibrillation could not be achieved by mechanical treatment, and fine fibrous cellulose could not be obtained. I understood that. When delignification methods such as kraft cooking and sulfite cooking are applied, lignin is removed, but at the same time, the bonding force between microfibrils constituting the crystalline region of cellulose is strengthened, and it is thought that it becomes difficult to defibrate. It is done.
Next, the present inventors selected wood flour as a raw material for cellulose fibers, degreased the wood flour, and delignified with an acidic aqueous solution. It has been found that the cellulose fibers thus obtained are very excellent in defibration properties and fine fibrous cellulose having a fiber width of 2 to 1000 nm can be easily obtained. This is because the lignin is effectively removed by applying an acidic aqueous solution treatment in the delignification step, and the bond between cellulose and lignin is weakened, thereby causing fine fibrils and even between microfibrils constituting the crystalline region. It is considered that the binding force is reduced and the pulp can be easily refined by mechanical treatment.

On the other hand, enzyme (xylanase, cellulase) treatment, chemical (alkali, zinc chloride, ethylenediamine, thiourea, benzenesulfonic acid) treatment and the like are known as methods for fibrillating cellulose fibers to obtain fine fibrous cellulose. The present invention is characterized in that delignification using an acidic aqueous solution, which is said to have no great merit as a delignification method, is employed.
According to the present invention, it is possible to provide a method for producing fine fibrous cellulose from which fine fibrous cellulose can be easily obtained.

Hereinafter, the present invention will be described in detail.
Plant-derived cellulose is preferred as a raw material for obtaining the fine fibrous cellulose of the present invention. More specifically, wood-based raw materials for conifers and broad-leaved trees, cotton-based raw materials such as cotton linter and cotton lint, non-wood such as hemp, rice straw, straw, bagasse (sugar cane squeezed rice cake), bamboo, kenaf, kouzo, and mitsumata System materials and the like. Among these, wood-based raw materials and non-wood-based raw materials are preferable because they can be easily made into fine fibers. Cotton-based materials are not preferred because they are difficult to make into fine fibers.
The raw material is preferably wood flour. The size of the wood powder is preferably 1 mm or less, more preferably 0.6 mm or less, and particularly preferably 0.3 mm or less. If the size of the wood powder exceeds 1 mm, it is difficult to form fine fibers, which is not preferable.
Furthermore, ground wood pulp such as SGP (Stone Ground Wood) or CGP (Chemical Groundwood Pulp), which is lightly chemically treated with sodium sulfite and then ground, can be used. Are preferably used.

In this invention, it is preferable that the cellulose content of the said raw material is 40 mass%-70 mass%, and 45 mass%-65 mass% are especially preferable. When the cellulose content is less than 40% by mass, the yield of the obtained pulp is lowered, which is not preferable. When the cellulose content exceeds 70% by mass, it is difficult to make fine fibers, which is not preferable.
The content of lignin as the raw material is preferably 10% by mass to 40% by mass, and particularly preferably 15% by mass to 35% by mass. When the lignin content is less than 10% by mass, it becomes difficult to make fine fibers. If the lignin content exceeds 40% by mass, the yield of the pulp decreases, which is not preferable.
The content of hemicellulose (pentosan such as xylan and araban) as the raw material is preferably 2% by mass to 35% by mass, and particularly preferably 5% by mass to 30% by mass. If the hemicellulose content is less than 2% by mass, it is difficult to make fine fibers, which is not preferable. When the content of hemicellulose exceeds 35% by mass, the yield of the pulp decreases, which is not preferable.
The crystallinity of the raw material is preferably 30% to 45%, particularly preferably 33% to 42%. A crystallinity of less than 30% is not preferable because the yield of fine fibrous cellulose decreases. If the crystallinity exceeds 45%, it is difficult to form fine fibers, which is not preferable.

In the present invention, in order to obtain fine fibrous cellulose, the raw material is processed through at least a degreasing process, a delignification process, a dehemicellulose process, and a refinement process.
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 is preferred.

Sodium carbonate in the degreasing step is used as an aqueous solution, and the concentration of the sodium carbonate aqueous solution is preferably 0.1% by mass to 10% by mass, preferably 0.3% by mass to 7% by mass, and 0.5% by mass to 4% by mass. % Is particularly preferred. When the concentration of the sodium carbonate aqueous solution is less than 0.1% by mass, the degreasing efficiency is lowered, which is not preferable. When the concentration of the sodium carbonate aqueous solution exceeds 10%, the degreasing effect is saturated and the necessity is economically low.
The addition ratio of the raw material with respect to the sodium carbonate aqueous solution is preferably 1% by mass to 10% by mass. When it exceeds 10 mass%, degreasing efficiency falls and it is not preferable.
The temperature of the sodium carbonate aqueous solution is preferably 40 ° C to 99 ° C, more preferably 60 ° C to 96 ° C, and particularly preferably 80 ° C to 93 ° C. When the temperature is lower than 40 ° C., the degreasing efficiency is extremely deteriorated, which is not preferable. If the temperature exceeds 100 ° C., it is difficult to make fine fibers, which is not preferable.

As a delignification method, it is necessary to perform an acidic aqueous solution treatment. Furthermore, it is preferable to perform the alkaline aqueous solution treatment after the acidic aqueous solution treatment because the yield of fine fibrous cellulose is improved. This is the principle that lignin is reduced in molecular weight by treatment with an acidic aqueous solution, and the reduced molecular weight lignin is removed with an alkaline aqueous solution.
Examples of the acidic aqueous solution in the delignification step include aqueous solutions of acetic acid, sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, acetic acid, benzoic acid, metachlorobenzoic acid, formic acid, propionic acid, and the like. It is preferable to use at least one selected from hydrochloric acid aqueous solution, nitric acid aqueous solution, formic acid aqueous solution and acetic acid aqueous solution.
The acid concentration of the acidic aqueous solution is not particularly limited, but when the acid is a strong acid such as sulfuric acid, hydrochloric acid, phosphoric acid or nitric acid, 1% by mass to 40% by mass is preferable, and 5% by mass to 20% by mass is particularly preferable. Good. If the concentration of the strong acid is less than 1% by mass, it is difficult to make fine fibers, which is not preferable. If the concentration of the strong acid exceeds 40% by mass, the cellulose fibers contained in the raw material are decomposed and the yield is lowered, or the fiber width of the obtained fine fibrous cellulose is not preferable. When the acid is a weak acid such as acetic acid, benzoic acid, metachlorobenzoic acid, formic acid or propionic acid, 70% by mass to 100% by mass is preferable, and 80% by mass to 95% by mass is particularly preferable. When the concentration of the weak acid is less than 70% by mass, it is difficult to make fine fibers, which is not preferable.
0.5 mass%-10 mass% of the addition ratio (solid mass of the pulp with respect to acidic aqueous solution) of the raw material with respect to acidic aqueous solution (The raw material after the degreasing process was preferable) is preferable. When the addition ratio of the raw material is less than 0.5% by mass, productivity is lowered, which is not preferable. When the addition ratio of the raw material exceeds 10% by mass, the efficiency of delignification decreases, which is not preferable.
The temperature of the acidic aqueous solution when the raw material is treated with the acidic aqueous solution is preferably 40 ° C to 99 ° C, more preferably 50 ° C to 98 ° C, and particularly preferably 60 ° C to 97 ° C. When the temperature is lower than 40 ° C., the efficiency of delignification is deteriorated, and the color becomes unfavorable. If it exceeds 99 ° C, it is difficult to make fine fibers, which is not preferable.

Examples of the alkaline aqueous solution in the delignification step include sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and magnesium hydroxide. From the viewpoint of yield and efficiency of delignification, sodium hydroxide and potassium hydroxide. Is preferred.
The concentration of the alkaline aqueous solution in the delignification step is preferably 0.1% by mass to 10% by mass, more preferably 0.3% by mass to 7% by mass, and particularly preferably 0.5% by mass to 4% by mass. If the concentration of the alkaline aqueous solution is less than 0.1% by mass, the efficiency of delignification is not preferred. When the concentration of the alkaline aqueous solution exceeds 10%, the effect of delignification is saturated and the necessity is economically low.
As for the addition ratio of the raw material with respect to aqueous alkali solution, 1 mass%-10 mass% are preferable. When the addition ratio of the raw material is less than 1% by mass, the productivity is undesirably lowered. If it exceeds 10% by mass, the effect of delignification decreases, which is not preferable.
The temperature of the alkaline aqueous solution is preferably 40 ° C to 99 ° C, more preferably 60 ° C to 96 ° C, and particularly preferably 80 ° C to 93 ° C. If the temperature is less than 40 ° C., the efficiency of delignification deteriorates, which is not preferable. When the temperature exceeds 100 ° C., the effect of delignification is saturated, and it is not necessary economically.

In the present invention, a dehemicellulose step may be added after the delignification step. As a method for dehemicellulose formation, an immersion treatment at room temperature overnight using an aqueous solution of an alkali metal hydroxide, a short treatment at a high temperature while stirring in the aqueous solution, or a pressure in the aqueous solution under pressure. The method of processing under high temperature and high pressure, stirring, etc. are mentioned. Among them, potassium hydroxide is most preferable because it is inexpensive, can be used at room temperature and normal pressure, and the efficiency of dehemicellulose is high.
The concentration of potassium hydroxide is preferably 1% by mass to 20% by mass, preferably 2% by mass to 15% by mass, and particularly preferably 3% by mass to 10% by mass. When the concentration of potassium hydroxide is less than 1% by mass, the efficiency of dehemicellulose is undesirably lowered. If the concentration of potassium hydroxide exceeds 20%, the cellulose becomes mercerized, and as a result, the yield of fine fibrous cellulose is lowered, which is not preferable.
As for the addition ratio of the raw material with respect to potassium hydroxide aqueous solution, 1 mass%-10 mass% are preferable. When the addition ratio of the raw material is less than 1% by mass, the productivity is undesirably lowered. 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 make fine fibers, which is not preferable.

  The cellulose fibers subjected to the dehemicellulose treatment are 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. When the concentration is less than 0.1% by mass, the productivity is undesirably lowered. 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 in the present invention is a cellulose fiber or rod-like particle that is much narrower than the pulp fiber usually used in papermaking. Fine fibrous cellulose is an aggregate of crystalline cellulose molecules, and its crystal structure is type I (parallel chain). The width of the fine fibrous cellulose is preferably 2 nm to 1000 nm as observed with an electron microscope, more preferably 2 nm to 500 nm, still more preferably 4 nm to 100 nm. When the width of the fiber is less than 2 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. Moreover, when it is a use by which transparency is required for the composite of fine fibrous cellulose, the width of the fine fibers is preferably 50 nm or less. Composite materials obtained from these fine fibrous celluloses have high density and high density because they become dense structures, and in addition to obtaining high elastic modulus derived from cellulose crystals, there is little scattering of visible light High transparency is also obtained.

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 nm. 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.

  In the present invention, the yield of fine fibrous cellulose in the refinement step is preferably 30% or more. If the yield is less than 30%, there are many components that do not refine cellulose, which is not preferable from the viewpoint of economy.

  In the present invention, it is a preferred embodiment in terms of yield that the cellulose fiber raw material is processed in the order of a degreasing step, a delignification step, a dehemicellulose step, and a refinement step.

  Examples are given below to describe the present invention in more detail, but it goes without saying that the present invention is not limited thereto. Moreover, unless otherwise indicated, the part and% in an example show a mass part and mass%, respectively.

<Example 1>
Using bay pine wood flour (average particle size 0.2 mm, crystallinity 55%) as a raw material, as a degreasing process, wood flour (BD 30 g) was stirred at 90 ° C. in a 2% sodium carbonate aqueous solution (1800 g). Treated for 2 hours. The raw material after the treatment was washed with 10 times the amount of distilled water and dehydrated with a Buchner.
Next, as the delignification step, the degreased wood flour was added to a 10% nitric acid aqueous solution (1500 g) and treated at 80 ° C. for 2 hours. The raw material after the treatment was washed with 10 times the amount of distilled water and dehydrated with a Buchner. Distilled water was added to prepare a 0.5% pulp suspension to obtain a fine fibrous cellulose pulp.
The resulting fine fiber cellulose pulp is defibrated (refined) for 21500 rotations for 30 minutes with a high-speed defibrator ("CLEAMIX CLM-2.2S" manufactured by M Technique Co., Ltd.), and the fine fibrous cellulose aqueous suspension A liquid was obtained, and the supernatant concentration was measured. The obtained fine fibrous cellulose suspension was treated at about 12000 G for 10 minutes using a centrifuge (“H-200NR” manufactured by Kokusan Co., Ltd.), the supernatant concentration was measured, and the yield was calculated from the following calculation. Asked.
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, and it was confirmed that it could be formed into a sheet.

<Example 2>
Using bay pine wood flour (0.2 mm, crystallinity 55%) as a raw material, as a degreasing process, wood flour (BD 30 g) was treated in a 2% aqueous sodium carbonate solution (1800 g) at 90 ° C. for 2 hours. did. The raw material after the treatment was washed with 10 times the amount of distilled water and dehydrated with a Buchner.
Next, as the delignification step, the degreased wood flour was added to a 10% nitric acid aqueous solution (1500 g) and treated at 80 ° C. for 2 hours. The raw material after the treatment was washed with 10 times the amount of distilled water and dehydrated with a Buchner. Next, the treated wood flour was added to a 1% aqueous sodium hydroxide solution (600 g) and treated at 95 ° C. for 1 hour.
The raw material after the treatment was washed with 10 times the amount of distilled water and dehydrated with a Buchner. Distilled water was added to prepare a 0.5% pulp suspension to obtain a fine fibrous cellulose pulp.
The resulting fine fiber cellulose pulp is defibrated (refined) for 21500 rotations for 30 minutes with a high-speed defibrator ("CLEAMIX CLM-2.2S" manufactured by M Technique Co., Ltd.), and the fine fibrous cellulose aqueous suspension A liquid was obtained, and the supernatant concentration was measured. The obtained fine fibrous cellulose suspension was treated at about 12000 G for 10 minutes using a centrifuge (“H-200NR” manufactured by Kokusan Co., Ltd.), the supernatant concentration was measured, and the yield was calculated from the following calculation. Asked.
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, and it was confirmed that it could be formed into a sheet.

<Example 3>
A fine fibrous pulp was obtained in the same manner as in Example 2 except that a 10% hydrochloric acid aqueous solution was used instead of the 10% nitric acid aqueous solution which was an acidic aqueous solution in the delignification step.
In the same manner as in Example 2, the fiber was defibrated using a high-speed defibrator, and the yield and fiber width of the fine fibrous cellulose were measured. It was also confirmed that it could be made into a sheet.

<Example 4>
A fine fibrous pulp was obtained in the same manner as in Example 2 except that a 10% sulfuric acid aqueous solution was used instead of the 10% nitric acid aqueous solution which was an acidic aqueous solution in the delignification step.
In the same manner as in Example 2, the fiber was defibrated using a high-speed defibrator, and the yield and fiber width of the fine fibrous cellulose were measured. It was also confirmed that it could be made into a sheet.

<Example 5>
A fine fibrous pulp was obtained in the same manner as in Example 2 except that a 90% formic acid aqueous solution was used instead of the 10% nitric acid aqueous solution which was an acidic aqueous solution in the delignification step.
In the same manner as in Example 2, the fiber was defibrated using a high-speed defibrator, and the yield and fiber width of the fine fibrous cellulose were measured. It was also confirmed that it could be made into a sheet.

<Example 6>
A fine fibrous pulp was obtained in the same manner as in Example 1 except that a 90% acetic acid aqueous solution was used instead of the 10% nitric acid aqueous solution which was an acidic aqueous solution in the delignification step.
In the same manner as in Example 2, the fiber was defibrated using a high-speed defibrator, and the yield and fiber width of the fine fibrous cellulose were measured. It was also confirmed that it could be made into a sheet.

<Comparative Example 1>
Oji Paper's NBKP (made by Kasugai Factory, raw material is pine, freeness 550ml csf.) Is defibrated (refined) for 30 minutes at 21500 rpm with a high-speed defibrator ("CLEARMIX CLM-2.2S" manufactured by MTechnic Co., Ltd.). Then, a fine fibrous cellulose aqueous suspension was obtained, and the supernatant concentration was measured. The obtained fine fibrous cellulose suspension was treated at about 12000 G for 10 minutes using a centrifuge (“H-200NR” manufactured by Kokusan Co., Ltd.), the supernatant concentration was measured, and the yield was calculated from the following calculation. Asked.
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 an attempt was made to measure the fiber width, but the yield was too low to measure. Further, the supernatant obtained by centrifugation was suction filtered on a membrane filter having a pore diameter of 0.45 μm. However, since the yield was low, only a very thin sheet could be formed.

<Comparative example 2>
Using bay pine wood flour (average particle size 0.2 mm, crystallinity 55%) as a raw material, as a degreasing process, wood flour (BD 30 g) was stirred at 90 ° C. in a 2% sodium carbonate aqueous solution (1800 g). Treated for 2 hours. The raw material after the treatment was washed with 10 times the amount of distilled water and dehydrated with a Buchner.
Next, as a delignification step, the degreased wood flour was added to a 1% aqueous sodium hydroxide solution (600 g) and treated at 95 ° C. for 1 hour. The raw material after the treatment was washed with 10 times the amount of distilled water and dehydrated with a Buchner. Distilled water was added to prepare a 0.5% pulp suspension to obtain a fine fibrous cellulose pulp.
The resulting fine fiber cellulose pulp is defibrated (refined) for 21500 rotations for 30 minutes with a high-speed defibrator ("CLEAMIX CLM-2.2S" manufactured by M Technique Co., Ltd.), and the fine fibrous cellulose aqueous suspension A liquid was obtained, and the supernatant concentration was measured. The obtained fine fibrous cellulose suspension was treated at about 12000 G for 10 minutes using a centrifuge (“H-200NR” manufactured by Kokusan Co., Ltd.), the supernatant concentration was measured, and the yield was calculated from the following calculation. Asked.
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 an attempt was made to measure the fiber width, but the yield was too low to measure. Further, the supernatant obtained by centrifugation was suction filtered on a membrane filter having a pore diameter of 0.45 μm. However, since the yield was low, only a very thin sheet could be formed.

<Comparative Example 3>
Using bay pine wood flour (average particle size 0.2 mm, crystallinity 55%) as a raw material, as a degreasing process, wood flour (BD 30 g) was stirred at 90 ° C. in a 2% sodium carbonate aqueous solution (1800 g). Treated for 2 hours. The treated raw material was washed with 10 times the amount of distilled water and dehydrated with a Buchner to obtain a pulp for fine fibrous cellulose.
The resulting fine fiber cellulose pulp is defibrated (refined) for 21500 rotations for 30 minutes with a high-speed defibrator ("CLEAMIX CLM-2.2S" manufactured by M Technique Co., Ltd.), and the fine fibrous cellulose aqueous suspension A liquid was obtained, and the supernatant concentration was measured. The obtained fine fibrous cellulose suspension was treated at about 12000 G for 10 minutes using a centrifuge (“H-200NR” manufactured by Kokusan Co., Ltd.), the supernatant concentration was measured, and the yield was calculated from the following calculation. Asked.
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 an attempt was made to measure the fiber width, but the yield was too low to measure. Further, the supernatant obtained by centrifugation was suction filtered on a membrane filter having a pore diameter of 0.45 μm. However, since the yield was low, only a very thin sheet could be formed.

<Comparative example 4>
Oji Paper NBKP (made by Kasugai Factory, raw material is bay pine, freeness 550 ml csf.) Was used as a raw material, and wood powder (BD 30 g) was stirred at 2O 0 C at 2O 0 C while stirring in 2% aqueous sodium carbonate solution (1800 g) as a degreasing treatment step. Time processed. The raw material after the treatment was washed with 10 times the amount of distilled water and dehydrated with a Buchner.
Next, as the delignification step, the degreased wood flour was added to a 10% nitric acid aqueous solution (1500 g) and treated at 80 ° C. for 2 hours. The raw material after the treatment was washed with 10 times the amount of distilled water and dehydrated with a Buchner. Distilled water was added to prepare a 0.5% pulp suspension to obtain a fine fibrous cellulose pulp.
The resulting fine fiber cellulose pulp is defibrated (refined) for 21500 rotations for 30 minutes with a high-speed defibrator ("CLEAMIX CLM-2.2S" manufactured by M Technique Co., Ltd.), and the fine fibrous cellulose aqueous suspension A liquid was obtained, and the supernatant concentration was measured. The obtained fine fibrous cellulose suspension was treated at about 12000 G for 10 minutes using a centrifuge (“H-200NR” manufactured by Kokusan Co., Ltd.), the supernatant concentration was measured, and the yield was calculated from the following calculation. Asked.
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 an attempt was made to measure the fiber width, but the yield was too low to measure. Further, the supernatant obtained by centrifugation was suction filtered on a membrane filter having a pore diameter of 0.45 μm. However, since the yield was low, only a very thin sheet could be formed.

  As is apparent from Table 1, fine fibrous pulp can be obtained with high yield by the method of the present invention, and it can be fibrillated to form a sheet.

  By mechanically defibrating the pulp obtained by the method of the present invention, fine fibrous cellulose having a fiber width of 2 to 1000 nm can be easily obtained, and further can be formed into a sheet.

Claims (5)

  A method for producing a fine fibrous cellulose having a fiber width of 2 to 1000 nm by treating cellulose fibers through at least a degreasing step, a delignification step, a dehemicellulose step, and a micronization step, wherein an acidic aqueous solution treatment is performed in the delignification step. The manufacturing method of the fine fibrous cellulose characterized by performing.   The method for producing fine fibrous cellulose according to claim 1, wherein the aqueous alkaline solution treatment is performed after the acidic aqueous solution treatment is performed in the delignification step.   The fine fibrous cellulose according to claim 1 or 2, wherein the acidic aqueous solution in the delignification step is at least one selected from sulfuric acid aqueous solution, hydrochloric acid aqueous solution, nitric acid aqueous solution, formic acid aqueous solution, and acetic acid aqueous solution. Manufacturing method.   The method for producing fine fibrous cellulose according to claim 2, wherein the alkaline aqueous solution in the delignification step is a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution.   The manufacturing method of the fine fibrous cellulose of any one of Claims 1-4 which processes a cellulose fiber through a degreasing process, a delignification process, a dehemicellulose process, and a refinement | purification process one by one.