JP6079039B2 - Fine fibrous cellulose and method for producing the same - Google Patents

Description

  The present invention relates to fine fibrous cellulose.

In recent years, materials using reproducible natural fibers have attracted attention due to the substitution of petroleum resources and the growing environmental awareness. Among natural fibers, cellulose fibers having a fiber diameter of 10 to 50 μm, especially wood-derived cellulose fibers (pulp) have been widely used as paper products so far.
As cellulose fibers, fine fibrous cellulose having a fiber diameter of nanometer order is also known (Patent Document 1). For example, Patent Document 1 describes fine fibrous cellulose having a degree of polymerization of 500 or more obtained by defibrating beaten pulp.
In recent years, the use of fine fibrous cellulose has been studied for various applications. For example, it has been studied to obtain a fiber-reinforced composite resin by mixing fine fibrous cellulose with an emulsion resin and then dehydrating it.

JP 2012-036529 A

Usually, the fine fibrous cellulose is obtained in the form of a slurry. However, the fine fibrous cellulose described in Patent Document 1 sometimes has a high viscosity when slurried.
Moreover, when the fine fibrous cellulose described in Patent Document 1 is mixed with the emulsion resin, it is easy to form an aggregate.
An object of the present invention is to provide fine fibrous cellulose that has a low viscosity when slurried and hardly forms an aggregate when mixed with an emulsion resin.

The fine fibrous cellulose of the present invention is a fine fibrous cellulose having an average fiber width of 2 to 20 nm and a polymerization degree of 150 to 400 , and is a polar group represented by the following formula (1) or the following formula (2). And the polar group content is 0.1 to 1.0 mmol / g.
Formula (1) (—O—PO ₃ ²⁻ ) · X ^{p +} _{2 / p}
Formula (2) (—OCO—R—COO ⁻ ) _q · Y ^{q +}
(Where p is 1 or 2. X ^{p +} _{p / 2} is at least selected from the group consisting of alkali metal cations, ammonium ions, aliphatic ammonium ions, and aromatic ammonium ions when p = 1. In addition, when p = 2, it is at least one selected from the group consisting of alkaline earth metal cations or polyvalent metal cations, ^q is a natural number of 1 to 3, and Y ^{q +} is , Q = 1, at least one selected from the group consisting of alkali metal cations, ammonium ions, aliphatic ammonium ions, and aromatic ammonium ions, and when q = 2 or 3, alkaline earths is at least one selected from a metal ion or the group consisting of polyvalent metal ions .R is unsaturated - a linear hydrocarbon group, the carbon constituting R There is two.)

When the fine fibrous cellulose of the present invention has a polar group represented by the formula (1), it is preferably produced by the following production method.
A decomposition step for decomposing cellulose, a polar group introduction step for forming a polar group (1) in cellulose by treating the cellulose after the decomposition step with an oxo acid or a salt thereof containing a phosphorus atom, and a polar group (1 A method for producing fine fibrous cellulose, comprising an alkali treatment step of treating the cellulose formed with an alkali solution with an alkali solution and a defibration step of refining the cellulose after the alkali treatment.
When the fine fibrous cellulose of the present invention has a polar group represented by the formula (2), it is preferably produced by the following production method.
Decomposing step for decomposing cellulose, treating the cellulose after the decomposing step with a carboxylic acid compound to form a polar group (2) in cellulose, and forming the polar group (2) in cellulose The manufacturing method of the fine fibrous cellulose which has an alkali treatment process which treats this with an alkaline solution, and a fibrillation process which refines | miniaturizes and fibrillates the cellulose after alkali treatment.
In these production methods, fine fibrous cellulose having an average fiber width, polymerization degree, and polar group content within the above ranges can be easily produced, and it is not necessary to use special chemicals, so that the cost is low.

  The fine fibrous cellulose of the present invention has a low viscosity when slurried, and hardly forms aggregates when mixed with an emulsion resin.

<First Embodiment>
The fine fibrous cellulose of this embodiment is a cellulose fiber or rod-like particle having an I-type crystal structure that is much finer and shorter than pulp fibers that are normally used in papermaking applications.
The fact that the fine fibrous cellulose has a type I crystal structure is that 2θ = 14 to 17 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 ° and 2θ = 22-23 °.
The degree of crystallinity of the fine fibrous cellulose determined by the X-ray diffraction method is preferably 60% or more, more preferably 65% or more, and further preferably 70% or more. If the degree of crystallinity is not less than the lower limit, further excellent performance can be expected in terms of heat resistance and low linear thermal expansion. The degree of crystallinity can be obtained by measuring an X-ray diffraction profile and using a conventional method (Segal et al., Textile Research Journal, 29, 786, 1959).

(Fiber width)
The fine fibrous cellulose of this embodiment is a cellulose having an average fiber width (average fiber diameter) of 200 nm or less determined by observation with an electron microscope. The average fiber width of the fine fibrous cellulose is preferably 100 nm or less, and more preferably 20 nm or less. When the average fiber width of the fine fibrous cellulose exceeds the upper limit, it becomes difficult to obtain characteristics (high strength, high rigidity, high dimensional stability) as the fine fibrous cellulose.
On the other hand, the average fiber width of the fine fibrous cellulose is 1 nm or more, and preferably 2 nm or more. When the average fiber width of the fine fibrous cellulose is less than the lower limit, the cellulose molecules are dissolved in water, so that the characteristics (high strength, high rigidity, high dimensional stability) as the fine fibrous cellulose are obtained. Becomes difficult.

Measurement of the average fiber width of the fine fibrous cellulose by observation with an electron microscope is performed as follows. A fine fibrous cellulose-containing slurry is prepared, and the slurry is cast on a carbon membrane-coated grid that has been subjected to a hydrophilization treatment to obtain a transmission electron microscope (TEM) observation sample. When wide fibers are included, an operation electron microscope (SEM) image of the surface cast on glass may be observed. Observation by an electron microscope image is performed at any magnification of 1000 times, 5000 times, 10000 times, 20000 times, 50000 times or 100,000 times depending on the width of the constituent fibers. However, the sample, observation conditions, and magnification are adjusted to satisfy the following conditions.
(1) One straight line X is drawn at an arbitrary location in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y perpendicularly intersecting the straight line X is drawn in the same image, and 20 or more fibers intersect the straight line Y.
For the electron microscope observation image as described above, the width (minor axis of the fiber) of at least 20 fibers (that is, at least 40 in total) is read for each of the fibers intersecting with the straight line X and the fibers intersecting with the straight line Y. . In this way, at least three or more sets of electron microscope images as described above are observed, and the fiber width of at least 40 × 3 sets (that is, at least 120 sets) is read. The fiber widths thus read are averaged to obtain the average fiber width.

  The maximum fiber width of the fine fibrous cellulose is preferably 500 nm or less, and more preferably 200 nm or less. If the maximum fiber width of the fine fibrous cellulose is less than or equal to the above upper limit, the composite resin obtained by mixing with the emulsion resin has high strength, and it is easy to ensure the transparency of the composite resin. is there.

(Degree of polymerization)
The degree of polymerization of the fine fibrous cellulose is 50 or more and 500 or less, preferably 50 or more and less than 500, more preferably 100 or more and 460 or less, and further preferably 150 or more and 400 or less. If the degree of polymerization of the fine fibrous cellulose is less than the lower limit value, it cannot be said to be “fibrous” and is difficult to use as a reinforcing agent. On the other hand, when the polymerization degree of the fine fibrous cellulose is not less than the above upper limit value, the slurry viscosity becomes too high when the fine fibrous cellulose is slurried, and the dispersion stability is lowered. In addition, aggregates may be formed when mixed with the emulsion resin.
The degree of polymerization of fine fibrous cellulose is measured by the following method.
Fine fibrous cellulose (centrifugated supernatant, concentration about 0.5% by mass on a polytetrafluoroethylene petri dish and dried at 60 ° C. to obtain a dry sheet. The pulp viscosity is measured according to Tappi T230, the viscosity is measured only with the dispersion medium, the blank test is performed, and the blank viscosity is measured.Numerical value obtained by dividing the pulp viscosity by the blank viscosity 1 is subtracted to obtain the specific viscosity (ηsp), and the intrinsic viscosity ([η]) is calculated using the following formula.
[Η] = ηsp / (c (1 + 0.28 × ηsp))
C in a formula shows the cellulose concentration at the time of a viscosity measurement.
Then, the degree of polymerization (DP) in the present invention is calculated from the following formula.
DP = 1.75 × [η]
Since this degree of polymerization is an average degree of polymerization measured by a viscosity method, it may be referred to as “viscosity average degree of polymerization”.

(Average fiber length)
The average fiber length of the fine fibrous cellulose is preferably 0.03 to 5 μm, and more preferably 0.1 to 2 μm. If average fiber length is more than the said lower limit, the strength improvement effect at the time of mix | blending fine fibrous cellulose with resin is fully acquired. If average fiber length is below the said upper limit, the dispersibility at the time of mix | blending fine fibrous cellulose with resin will become more favorable. The fiber length can be determined by analyzing the electron microscope observation image used when measuring the average fiber width. That is, at least 20 fibers (that is, a total of at least 40 fibers) are read for each of the fibers intersecting with the straight line X and the fibers intersecting with the straight line Y with respect to the electron microscope observation image as described above. In this way, at least three or more sets of electron microscope images as described above are observed, and the fiber length of at least 40 × 3 sets (that is, at least 120 sets) is read. The average fiber length is obtained by averaging the fiber lengths thus read.

(Average aspect ratio)
The average aspect ratio of the fine fibrous cellulose is preferably in the range of 10 to 300, more preferably in the range of 25 to 250, and most preferably in the range of 50 to 200. If the average aspect ratio is equal to or greater than the lower limit, it is more suitable as a reinforcing agent for resins and rubbers. If the axial ratio is less than or equal to the above upper limit, the viscosity when slurried becomes lower.
The average aspect ratio is obtained by the following method.
That is, 40 fibers are randomly selected for each fiber observed from the electron microscope image, and each aspect ratio, that is, (fiber length) / (fiber width) is obtained. The average aspect ratio of the present invention is an average value of the 40 aspect ratios.

(Polar group represented by formula (1))
The fine fibrous cellulose of the first embodiment has a polar group represented by the above formula (1) (hereinafter referred to as “polar group (1)”).
The content of the polar group (1) in the fine fibrous cellulose of the first embodiment is 0.06 to 2.0 mmol / g, preferably 0.1 to 1.0 mmol / g, 0.2 to More preferably, it is 0.6 mmol / g. When the content of the polar group (1) is within the above range, the hydration property of the fine fibrous cellulose does not become too high, and the viscosity when slurried becomes low. If the content of the polar group (1) exceeds the above upper limit, the hydration property becomes too high and the fine fibrous cellulose may be dissolved.

The content of the polar group (1) is the content of the polar group (1) per 1 g of cellulose, and is measured by applying TAPPI T237 cm-08 (2008). Specifically, in order to make it possible to measure the introduction amount of acidic groups introduced into cellulose over a wider range, among the test solutions used in the test method, sodium bicarbonate (NaHCO ₃ ) / sodium chloride (NaCl) = The test solution prepared by dissolving 0.84 g / 5.85 g in 1000 ml with distilled water was changed to a test solution obtained by dissolving 1.60 g of sodium hydroxide in 1000 ml with distilled water, and before and after the introduction of polar group (1). The measurement is performed according to TAPPI T237 cm-08 (2008) except that the difference in the measured value of the cellulose fiber is the substantial polar group (1) content.
Moreover, since the acidic group content measurement method is basically a method for measuring the introduction amount of a monovalent acidic group (carboxy group), the introduction amount of the polar group (1) which is a polyvalent acidic group is The content of the polar group (1) obtained as the content of the monovalent acidic group is divided by the acid number 2 of the polar group (1).

In the polar group (1), p is 1 or 2.
X ^{p +} _{2 / p} is at least one selected from the group consisting of alkali metal cations, ammonium ions, aliphatic ammonium ions, and aromatic ammonium ions when p = 1. In addition, when p = 2, at least one selected from the group consisting of a cation of an alkaline earth metal (eg, magnesium, calcium, barium, etc.) or a cation of a polyvalent metal (eg, iron, aluminum, etc.) is there.
Among the above ^{Xp +} _{2 / p} , those with p = 1 are preferable, and further, the substance is general and inexpensive as an alkali, and the yield of fine fibrous cellulose is also improved. And ammonium ions are more preferred.

  The fine fibrous cellulose of this embodiment may have other polar groups other than the polar group (1) and the hydroxy group originally possessed by the cellulose as long as the effects of the present invention are not impaired.

(Method for producing fine fibrous cellulose)
Examples of the method for producing the fine fibrous cellulose include a production method having a decomposition step, a polar group introduction step, an alkali treatment step, and a defibration step.
Hereinafter, each step will be described in detail.

[Cellulose raw material]
The raw materials for fine fibrous cellulose (hereinafter referred to as “cellulose raw material”) include paper pulp, cotton pulp such as cotton linter and cotton lint, non-wood pulp such as hemp, straw and bagasse, sea squirt and seaweed Cellulose isolated from Among these, paper pulp is preferable in terms of availability. Paper pulp includes hardwood kraft pulp (bleached kraft pulp (LBKP), unbleached kraft pulp (LUKP), oxygen bleached kraft pulp (LOKP), etc.), softwood kraft pulp (bleached kraft pulp (NBKP), unbleached kraft pulp) (NUCKP, oxygen bleached kraft pulp (NOKP), etc.), sulfite pulp (SP), chemical pulp such as soda pulp (AP), semi-chemical pulp (SCP), semi-chemical pulp such as chemiground wood pulp (CGP) In addition, mechanical pulp such as groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP), non-wood pulp using raw material such as cocoon, sardine, hemp, kenaf and the like, and deinked pulp using raw paper as a raw material. Among these, kraft pulp, deinked pulp, and sulfite pulp are preferable because they are more easily available.
A cellulose raw material may be used individually by 1 type, and may be used in mixture of 2 or more types.

[Disassembly process]
The decomposition step is a step of decomposing cellulose contained in the cellulose raw material. As the decomposing step, the desired degree of polymerization and polar group content can be easily obtained. Therefore, it is preferable to perform an enzyme treatment for decomposing cellulose using an enzyme or a sulfuric acid treatment for decomposing cellulose using sulfuric acid. In particular, the enzyme treatment is more preferable because the fine fibrous cellulose can be easily obtained. Cellulose may be decomposed by treatments other than enzyme treatment and sulfuric acid treatment. Examples of the treatment other than the enzyme treatment and the sulfuric acid treatment include a blasting treatment that instantaneously changes from a heat-pressed state to a non-pressurized state.

When enzyme treatment is performed in the decomposition step, it is preferable to perform mechanical crushing treatment before enzyme treatment in order to improve enzyme reaction efficiency. The pulverization method may be either dry or wet.
As the pulverizer used for the pulverization treatment, a shearing pulverizer such as a grinder, a pressure homogenizer, a shredder and a cutter mill, a compression pulverizer such as a jaw crusher and a cone crusher, an impact pulverizer such as an impact crusher, a roll mill, a stamp Examples thereof include a crusher such as a mill, an edge runner mill, a rod mill, and the like. From these, a final use and cost can be appropriately selected.
Further, as the pulverizer, a disintegrator that disaggregates pulp or a refiner that beats pulp can also be used.

  Moreover, before the enzyme treatment, it is preferable to dilute the cellulose raw material with a dispersion medium to obtain a dispersion having a cellulose concentration of 0.2 to 20% by mass. Either water or an organic solvent can be used as the dispersion medium, but water is preferred.

The cellulolytic enzyme used in the enzyme treatment is an enzyme collectively called cellulase having cellobiohydrolase activity, endoglucanase activity, and betaglucosidase activity.
The cellulolytic enzyme used in the enzyme treatment may be prepared by mixing various cellulolytic enzymes with appropriate amounts of enzymes having respective activities, but commercially available cellulase preparations may also be used. Many commercially available cellulase preparations have the above-mentioned various cellulase activities and also have hemicellulase activity.
Commercial cellulase preparations include Trichoderma, Acremonium, Aspergillus, Phanerocheet, Trametes, Humicola, and Humicola. There are cellulase preparations derived from the above. Commercially available products of such cellulase preparations are all trade names, for example, cellulosin T2 (manufactured by HIPI), mecerase (manufactured by Meiji Seika Co., Ltd.), Novozyme 188 (manufactured by Novozyme), multifect CX10L (manufactured by Genencor) ) And the like.

The ratio of the activity of endo-glucanase (hereinafter referred to as “EG activity”; degradation activity against amorphous part) to the activity of cellobiohydrolase (hereinafter referred to as “CBHI activity”; degradation activity against crystal part) of the enzyme or enzyme mixture ( (EG activity / CBHI activity) is preferably 0.06 or more, more preferably 0.1 or more, and even more preferably 1 or more. If the ratio of EG activity to CBHI activity is equal to or greater than the lower limit, the aspect ratio of the cellulose fiber after the enzyme treatment is increased, and the yield of fine fibrous cellulose is increased.
The ratio of EG activity to CBHI activity is preferably 20 or less, more preferably 10 or less, and even more preferably 6 or less.

The EG activity is measured as follows.
A substrate solution of carboxymethylcellulose (CMCNa High viscosity; Cat No 150561, MP Biomedicals, Inc.) at a concentration of 1% (W / V) (containing 100 mM, pH 5.0 acetate-sodium acetate buffer) is prepared. The enzyme for measurement is diluted in advance with a buffer solution (same as above) (dilution ratio is such that the absorbance of the enzyme solution below falls within a calibration curve obtained from the glucose standard solution below). 10 μl of the enzyme solution obtained by the dilution is added to 90 μl of the substrate solution and reacted at 37 ° C. for 30 minutes.
In order to prepare a calibration curve, ion-exchanged water (blank) and glucose standard solution (4 standard solutions having different concentrations from at least 0.5 to 5.6 mM) are selected, and 100 μl each is prepared, 37 ° C., Incubate for 30 minutes Into the enzyme-containing solution after the reaction, blank for calibration curve, and glucose standard solution, 300 μl of DNS coloring solution (1.6% by weight NaOH, 1% by weight 3,5-dinitrosalicylic acid, 30% by weight) % Sodium potassium tartrate) and boil for 5 minutes to develop color. Immediately after color development, cool with ice, add 2 ml of ion-exchanged water, and mix well. After standing for 30 minutes, the absorbance is measured within 1 hour.
Absorbance is measured by dispensing 200 μl into a 96-well microwell plate (269620, manufactured by NUNC), and measuring the absorbance at 540 nm using a microplate reader (infiniteM200, manufactured by TECAN).
A calibration curve is prepared using the absorbance and glucose concentration of each glucose standard solution obtained by subtracting the absorbance of the blank. The amount corresponding to glucose in the enzyme solution is calculated using the calibration curve after subtracting the blank absorbance from the absorbance of the enzyme solution (if the absorbance of the enzyme solution does not fall within the calibration curve, the enzyme is diluted with the above buffer. Measure again by changing the dilution ratio. The amount of enzyme that produces 1 μmole glucose equivalent of reducing sugar per minute is defined as 1 unit, and EG activity is obtained from the following formula.
EG activity = 1 ml of enzyme solution obtained by diluting with buffer solution (μmole) / 30 minutes x dilution factor
[See Fukui Sakuzo, “Biochemical Experimental Methods (Quantitative Determination of Reducing Sugars) Second Edition”, Academic Publishing Center, p23-24 (1990)]

The CBHI activity is measured as follows.
Dispense 32 μl of 1.25 mM 4-methyl-umbelliferyl-cellulobioside (dissolved in acetic acid-sodium acetate buffer solution with a concentration of 125 mM, pH 5.0) into a 96-well microwell plate (269620, manufactured by NUNC). 4 μl of 100 mM glucono-1,5-lactone is then added. Furthermore, 4 μl of the enzyme solution for measurement diluted with the same buffer as above (dilution ratio should be within the calibration curve obtained from the following standard solution with the fluorescence emission degree of the enzyme solution below) is added and reacted at 37 ° C. for 30 minutes. After that, 200 μl of 500 mM glycine-NaOH buffer (pH 10.5) is added to stop the reaction.
Dispense 40 μl of 4-methyl-umbelliferone standard solution (4 standard solutions with different concentrations of 0 to 50 μM) as standard solutions for the calibration curve into the same 96-well microwell plate as above, at 37 ° C. for 30 minutes. After warming, 200 μl of 500 mM glycine-NaOH buffer (pH 10.5) is added.
Using a microplate reader (Fluoroskan Ascent FL, manufactured by Thermo-Labsystems), the fluorescence intensity at 350 nm (excitation light: 460 nm) is measured. Calculate the amount of 4-methyl-umbelliferone produced in the enzyme solution using the calibration curve created from the data of the standard solution. I do). CBHI activity is determined from the following formula, assuming that the amount of enzyme that produces 1 μmol of 4-methyl-umbelliferone per minute is 1 unit.
CBHI activity = diluted enzyme solution 1 ml 4-methyl-umbelliferone production (μmole) / 30 minutes × dilution ratio

When cellulose is decomposed by sulfuric acid treatment, specifically, a cellulose raw material is added to a sulfuric acid aqueous solution and heated.
As a density | concentration of sulfuric acid aqueous solution, it is preferable that it is 0.01-20 mass%, and it is more preferable that it is 0.1-10 mass%. If the concentration of the sulfuric acid aqueous solution is not less than the lower limit, cellulose can be sufficiently decomposed, and if it is not more than the upper limit, the handleability is excellent.
The heating temperature during the sulfuric acid treatment is preferably 10 to 120 ° C, and more preferably 20 to 80 ° C. If heating temperature is more than the said lower limit, the decomposition reaction of cellulose can be easily controlled. In heating, in order to prevent the disappearance of water in the sulfuric acid aqueous solution, it is preferable to condense and reflux the evaporated water.

[Polar group introduction step]
The polar group introduction step is a step of forming the polar group (1) in cellulose by treating the cellulose raw material after the decomposition step with an oxo acid containing a phosphorus atom (hereinafter referred to as “phosphoro oxo acid”) or a salt thereof. It is.
In the polar group introduction step, the hydroxy group of the cellulose molecule and the phosphorus oxoacid having at least (HPO ₄ ) ^2- or a salt thereof undergo a dehydration reaction, and the polar group (1) as shown in the following reaction formula (A) Form.
—OH + HPO ₄ ²⁻ → —O—PO ₃ ²⁻ + H ₂ O (A)

Examples of the phosphorus oxo acid include phosphoric acid, metaphosphoric acid, polyphosphoric acid and the like.
Examples of the salt of phosphorus oxo acid include phosphoric acid, metaphosphoric acid, lithium salt of polyphosphoric acid, sodium salt, potassium salt, calcium salt, ammonium salt, and organic alkali salt.
Phosphooxo acids or salts thereof may be used alone or in combination of two or more.
Among these, phosphoric acid and / or sodium salt and potassium salt of phosphoric acid are preferable because they are easy to handle at low cost and increase the introduction efficiency of phosphoric acid groups.

  The mass proportion of the phosphorus oxo acid or salt thereof relative to the cellulose raw material is preferably 0.2 to 500 parts by mass, more preferably 1 to 400 parts by mass as the phosphorus element amount of the phosphorus oxo acid or salt thereof relative to 100 parts by mass of the cellulose raw material. 2 to 200 parts by mass is most preferable. If the ratio of the phosphorus oxo acid or its salt is not less than the lower limit, the yield of fine fibrous cellulose can be further improved. However, even if the above upper limit is exceeded, the effect of improving the yield reaches its peak, and only the use of phosphorus oxoacid or its salt is uselessly.

The heat treatment temperature in the polar group introduction step is preferably 250 ° C. or less from the viewpoint of the thermal decomposition temperature of cellulose. Moreover, it is preferable that the heat processing temperature is 100-170 degreeC from a viewpoint of suppressing hydrolysis of a cellulose. Furthermore, regarding the heating while water is contained in the system to which the phosphorus oxoacid or its salt is added during the heat treatment, it is preferable to heat at 130 ° C. or less, more preferably 110 ° C. or less, and to sufficiently absorb the water in the slurry. It is good to remove and dry. After that, it is preferable to heat-process at 100-170 degreeC. Moreover, you may use a vacuum dryer when removing the water | moisture content in a slurry.
In the heat treatment, an organic compound that melts at a high temperature such as urea may coexist in the system. When an organic compound that melts at a high temperature coexists, the cellulose swells, and the organic compound melts to provide a solid-liquid reaction field, thereby improving the efficiency of phosphate group formation.

[Alkali treatment process]
An alkali treatment process is a process of processing the cellulose which formed the polar group with the alkaline solution containing the alkali compound represented by Xp ⁺ * (OH ^{< - >} ) _p . By the alkali treatment, the polar group (1) is formed in the cellulose.
Although it does not specifically limit as a method of an alkali treatment, For example, the method of immersing the cellulose in which the polar group was formed in an alkaline solution is mentioned.
The alkali compound contained in the alkali solution may be an inorganic alkali compound or an organic alkali compound. X ^{p +} in the alkali compound is at least one selected from the group consisting of alkali metal cations, ammonium ions, aliphatic ammonium ions, and aromatic ammonium ions when p = 1. Moreover, when p = 2 or 3, it is at least one selected from the group consisting of alkaline earth metal ions or polyvalent metal ions. X ^{p +} is an alkali metal cation, ammonium ion, alkaline earth metal cation or polyvalent metal cation is an inorganic alkali compound, and aliphatic ammonium ion or aromatic ammonium ion is It is an organic alkali compound.
Examples of the alkali compound containing an alkali metal cation include lithium hydroxide, sodium hydroxide, and potassium hydroxide.
Examples of the alkali compound containing an alkaline earth metal cation include magnesium hydroxide, calcium hydroxide, and barium hydroxide.
Examples of the alkali compound containing a polyvalent metal cation include an aqueous solution of aluminum hydroxide / sodium hydroxide.
Aqueous ammonia is mentioned as an alkali compound containing an ammonium ion.
Examples of the alkali compound containing an aliphatic ammonium ion include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.
Examples of the alkali compound containing an aromatic ammonium ion include aqueous solutions of phenylamine (aniline), diphenylamine, and triphenylamine.

The solvent in the alkaline solution may be either water or an organic solvent, but is preferably a polar solvent (polar organic solvent such as water or alcohol), and more preferably an aqueous solvent containing at least water.
Of the alkaline solutions, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution and ammonia aqueous solution are particularly preferred because of their high versatility.

In the alkali treatment step, the alkali compound concentration of the alkali solution is adjusted so as to neutralize all phosphate groups formed in the polar group introduction step.
When the alkali compound is an inorganic alkali compound, the concentration of the inorganic alkali compound in the alkali solution is preferably 0.01 to 5% by mass, and more preferably 0.05 to 3% by mass. If the concentration of the inorganic alkali compound is not less than the lower limit, the yield of fine fibrous cellulose can be further improved, and if it is not more than the upper limit, the pH can be suppressed from being excessively high, and the alkali solution can be handled. Will be better.
When the alkali compound is an organic alkali compound, the concentration of the organic alkali compound in the alkali solution is preferably 0.01 to 5% by mass, and more preferably 0.05 to 3% by mass. If the concentration of the organic alkali compound is not less than the above lower limit, the yield of fine fibrous cellulose can be further improved, and if it is not more than the above upper limit, the pH can be suppressed from becoming excessively high, and the alkali solution can be handled. Will be better.

  The pH of the alkaline solution at 25 ° C. is preferably 9 or more, more preferably 10 or more, and even more preferably 11-14. If the pH of the alkaline solution is not less than the lower limit, the yield of fine fibrous cellulose will be higher, and if the pH is 14 or less, the handleability of the alkaline solution will be good.

[Defibration process]
The defibrating step is a step of refining cellulose after the alkali treatment.
The cellulose before being refined is preferably diluted with water to form a dispersion having a cellulose concentration of 0.1 to 1.0% by mass. The cellulose concentration is more preferably 0.2 to 5% by mass, and further preferably 0.3 to 3% by mass. If the cellulose concentration is equal to or higher than the lower limit value, the defibrating efficiency is increased. If the cellulose concentration is equal to or lower than the upper limit value, an increase in viscosity during the defibrating process can be prevented.

  Examples of the miniaturization method include a method using various pulverizers. High-speed defibrator, grinder (stone mortar-type pulverizer), high-pressure homogenizer and ultra-high-pressure homogenizer, high-pressure collision type pulverizer, ball mill, bead mill, disk type refiner, conical refiner, twin-screw kneader, vibration mill, high speed A wet milling apparatus such as a homomixer under rotation, an ultrasonic disperser, or a beater can be used as appropriate. Among these, a high-pressure homogenizer, a high-speed rotation type defibrator, or a combination of both is particularly preferable.

A high-pressure homogenizer is a device that pressurizes an enzyme-treated dispersion and refines it by rapidly depressurizing the pressurized dispersion. The high-pressure homogenizer treatment may be performed once, but by repeating a plurality of times, the degree of refinement can be further increased and fine fibers having a desired fiber width can be easily obtained. As the number of repetitions increases, the degree of miniaturization can be increased. However, when the number of repetitions is too large, the cost increases.
Specific examples of the high-pressure homogenizer include “Starburst” manufactured by Sugino Machine, “High-Pressure Homogenizer” manufactured by Izumi Food Machinery, and a homovalve-type high-pressure homogenizer typified by “Minilab 8.3H type” manufactured by Rannie, "Microfluidizer" manufactured by Microfluidics, "Nanomizer" manufactured by Yoshida Kikai Kogyo Co., Ltd., "Ultimizer" manufactured by Sugino Machine Co., Ltd., "Genus PY" manufactured by Shiramizu Chemical Co., Ltd., "DeBEE2000" manufactured by BB Japan, NiroSoavi Chamber type high-pressure homogenizers such as “Ariete series” of the company are listed.

The high-speed rotating defibrator is a device that generates a high shear rate by passing a narrow gap while rotating the enzyme-treated dispersion at high speed. Examples of the high-speed rotation type defibrator include a type that allows the dispersion liquid to be processed to pass through the gap between the rotating body and the fixed part. The high-speed rotation type defibrator includes an inner rotating body that rotates in a fixed direction, and an outer rotating body that rotates the outer side of the inner rotating body opposite to the inner rotating body, and the inner rotating body and the outer rotating body. The pulp fiber to be treated is passed through and dispersed in the gaps between them.
Examples of high-speed defibrating machines include “Clairemix” manufactured by M Technique, “TK Robotics” and “Filmix” manufactured by Primics, “Milder”, “Cabitron” and “Cabitron” manufactured by Taihei Koki. Sharp flow mill ".

  After the defibrating treatment, fine fibrous cellulose having a small average fiber diameter and a maximum fiber diameter can be easily obtained. Therefore, it is preferable to centrifuge the defibrated dispersion liquid.

(Function and effect)
The fine fibrous cellulose of this embodiment has a low degree of polymerization and a low viscosity when slurried because the polar group (1) content is in the above range and has hydration properties that are not too high. Become. Therefore, it is possible to easily increase the concentration of the slurry and improve the handleability.
The fine fibrous cellulose described in Patent Document 1 has a high degree of polymerization, does not have a polar group, and is low in hydratability, so it seems that the viscosity when slurried is high.
Conventionally, it has been considered that the higher the degree of polymerization of fine fibrous cellulose, the higher the mechanical properties of the fiber-reinforced composite resin obtained by mixing with the emulsion resin. However, as a result of investigations by the present inventors, when the degree of polymerization of the fine fibrous cellulose is large, there is a case where aggregates are easily formed when mixed with the emulsion resin, and the effect of improving the mechanical strength is not fully exhibited. There was found. Since the fine fibrous cellulose of this embodiment has a small degree of polymerization, it is difficult to form aggregates when mixed with an emulsion resin. Therefore, the mechanical properties of the obtained fiber reinforced composite resin can be sufficiently improved, and a good appearance can be easily obtained.

Second Embodiment
The fine fibrous cellulose of the second embodiment is the first except that it has a polar group represented by the following formula (2) instead of the polar group (1) (hereinafter referred to as “polar group (2)”). It is the same as the fine fibrous cellulose of the embodiment.

  The content of the polar group (2) in the fine fibrous cellulose of the second embodiment is 0.06 to 2.0 mmol / g, preferably 0.1 to 1.0 mmol / g, 0.2 to More preferably, it is 1.0 mmol / g. When the content of the polar group (2) is within the above range, the hydration property of the fine fibrous cellulose does not become too high, and the viscosity when slurried becomes low. When the content of the polar group (2) exceeds the upper limit, the fine fibrous cellulose is dissolved and the viscosity tends to increase.

The content of the polar group (2) is the content of the polar group (2) per 1 g of cellulose, and is measured by applying TAPPI T237 cm-08 (2008). Specifically, in order to make it possible to measure the introduction amount of acidic groups introduced into cellulose over a wider range, among the test solutions used in the test method, sodium bicarbonate (NaHCO ₃ ) / sodium chloride (NaCl) = The test solution prepared by dissolving 0.84 g / 5.85 g in 1000 ml with distilled water was changed to a test solution obtained by dissolving 1.60 g of sodium hydroxide in 1000 ml with distilled water, and before and after the introduction of polar group (2). Measured according to TAPPI T237 cm-08 (2008) except that the difference in the measured value of the cellulose fiber is the substantial polar group (2) content.

In the polar group (2), q is a natural number of 1 to 3.
Y ^{q +} is at least one selected from the group consisting of alkali metal (for example, sodium, potassium, lithium, etc.) cations, ammonium ions, aliphatic ammonium ions, and aromatic ammonium ions when q = 1. When q = 2 or 3, at least one selected from the group consisting of a cation of an alkaline earth metal (eg, magnesium, calcium, barium, etc.) or a cation of a polyvalent metal (eg, iron, aluminum, etc.). It is a seed.
Among the Y ^{q +} , those with q = 1 are preferable, and further, since the substance is general and inexpensive as an alkali and the yield of fine fibrous cellulose is improved, sodium ion, potassium ion and ammonium ion Is more preferable.

R in the polar group (2) is a group connecting between two carboxy groups of the carboxylic acid compound used in the polar group introduction step described later, and is a group derived from each carboxylic acid compound. Specifically, a saturated-linear hydrocarbon group (for example, derived from malonic acid, succinic acid, etc.), a saturated-branched hydrocarbon group (for example, 2-methylpropanedioic acid, 2-methylbutanedioic acid, etc.) ), Saturated-cyclic hydrocarbon group (eg, derived from 1,2-cyclohexanedicarboxylic acid, etc.), unsaturated-linear hydrocarbon group (eg, derived from maleic acid, fumaric acid, etc.), unsaturated-branched carbonization Hydrogen groups (eg, derived from 2-methyl-2-butenedioic acid, itaconic acid, etc.), aromatic groups (eg, derived from phthalic acid, isophthalic acid, etc.), and functional groups such as carboxy group and hydroxyl group for them The derivative group (for example, derived from citric acid, pyromellitic acid, etc.) or a single bond (for example, derived from oxalic acid, etc.) is added.
The number of carbon atoms constituting R in the polar group (2) is preferably 20 or less, and more preferably 10 or less. When the number of carbon atoms constituting R exceeds 20, the carboxylic acid compound molecule may be too large to penetrate into the cellulose raw material. In addition, when the carbon atom number which comprises R is 0, it is a single bond, and the ester group and carboxy group of the both sides of R are couple | bonded directly.

The fine fibrous cellulose of this embodiment may have other polar groups other than the polar group (2) and the hydroxy group originally possessed by the cellulose as long as the effects of the present invention are not impaired. Examples of other polar groups include a carboxy group and an aldehyde group. The content of other polar groups is preferably 0.1 mmol / g or less.
Cellulose has a small amount (specifically, less than 0.1 mmol / g) of carboxy groups even without a treatment for introducing carboxy groups. When the content of all polar groups increases, the viscosity when slurrying fine fibrous cellulose increases. Therefore, it is preferable that the polar group of the fine fibrous cellulose of the present embodiment has no other polar group, and is only the polar group (2), the hydroxy group originally contained in the cellulose, and the carboxy group.

(Method for producing fine fibrous cellulose)
Examples of the method for producing the fine fibrous cellulose of the present embodiment include a production method having a polar group introduction step, an alkali treatment step, and a defibration step.
The cellulose raw material used in the production method of the present embodiment is the same as the cellulose raw material used in the production method of the first embodiment. The alkali treatment process and the defibration process in the present embodiment are the same as the alkali treatment process and the defibration process in producing the fine fibrous cellulose of the first embodiment. However, in the alkali treatment step, all carboxylic acid groups formed in the polar group introduction step are neutralized.
Note that, unlike the manufacturing method in the first embodiment, the manufacturing method in the present embodiment does not have to have a decomposition step. When the degree of polymerization does not become 50 or more and 500 or less only by the polar group introduction step, the alkali treatment step, and the defibration step, a decomposition step may be included.

[Polar group introduction step]
The polar group introduction step is a step of forming a polar group (2) in cellulose by treating a cellulose raw material with a carboxylic acid compound.
Examples of the method of treating the cellulose raw material with the carboxylic acid compound include a method of mixing the gasified carboxylic acid compound with the cellulose raw material, and a method of adding the carboxylic acid compound to the slurry of the cellulose raw material. Among these, a method of mixing a gasified carboxylic acid compound with a cellulose raw material is preferable because the process is simple and the efficiency of introducing a carboxy group is high. Examples of the method for gasifying the carboxylic acid compound include a method for heating the carboxylic acid compound.

The carboxylic acid compound used in the polar group introduction step is at least one selected from the group consisting of a compound having two carboxy groups, an acid anhydride of a compound having two carboxy groups, and derivatives thereof. Of the compounds having two carboxy groups, compounds having two carboxy groups (dicarboxylic acid compounds) are preferred.
The compounds having two carboxy groups include propanedioic acid (malonic acid), butanedioic acid (succinic acid), pentanedioic acid (glutaric acid), hexanedioic acid (adipic acid), 2-methylpropanedioic acid, 2 -Methylbutanedioic acid, 2methylpentanedioic acid, 1,2-cyclohexanedicarboxylic acid, 2-butenedioic acid (maleic acid, fumaric acid), 2-pentenedioic acid, 2,4-hexadienedioic acid, 2-methyl- 2-butenedioic acid, 2-methyl-2-pentenedioic acid, 2-methylidenebutanedioic acid (itaconic acid), benzene-1,2-dicarboxylic acid (phthalic acid), benzene-1,3-dicarboxylic acid (isophthalic acid) And dicarboxylic acid compounds such as benzene-1,4-dicarboxylic acid (terephthalic acid) and ethanedioic acid (oxalic acid).
Acid anhydrides of compounds having two carboxy groups include maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, itaconic anhydride, pyromellitic anhydride, 1,2-cyclohexanedicarboxylic anhydride Examples thereof include acid anhydrides of dicarboxylic acid compounds such as acids and compounds containing a plurality of carboxy groups.
The acid anhydride derivative of the compound having two carboxy groups includes at least a part of the acid anhydride of the compound having a carboxy group, such as dimethylmaleic anhydride, diethylmaleic anhydride, and diphenylmaleic anhydride. The hydrogen atom is substituted with a substituent (for example, an alkyl group, a phenyl group, etc.).
Of these, maleic anhydride, succinic anhydride, and phthalic anhydride are preferred because they are industrially applicable and easily gasified.

  The mass ratio of the carboxylic acid compound to the cellulose raw material is preferably 0.1 to 500 parts by mass, and more preferably 10 to 200 parts by mass with respect to 100 parts by mass of the cellulose raw material. . If the ratio of a carboxylic acid type compound is more than the said lower limit, the yield of a fine fibrous cellulose can be improved more. However, even if the upper limit is exceeded, the effect of improving the yield reaches its peak, and the carboxylic acid compound is merely used in vain.

  The apparatus used in the polar group introduction step is not particularly limited. For example, a heating reaction vessel having a stirring blade, a rotary heating reaction vessel, a pressure vessel having a heating jacket, a rotary pressure vessel, or a uniaxial mixer having a heating jacket. Alternatively, a twin-screw mixer, or a kneader having a heating device such as a twin-screw extruder, a multi-screw kneading extruder, a pressure kneader, or a double arm kneader may be used.

  The treatment temperature is preferably 250 ° C. or less from the viewpoint of the thermal decomposition temperature of cellulose. Furthermore, when water is contained in the treatment, the temperature is preferably 80 to 200 ° C, more preferably 100 to 170 ° C.

  In the polar group introduction step, a catalyst can be used as necessary. As the catalyst, it is preferable to use a basic catalyst such as pyridine, triethylamine, sodium hydroxide or sodium acetate, or an acidic catalyst such as acetic acid, sulfuric acid or perchloric acid.

(Function and effect)
The fine fibrous cellulose of this embodiment has a low degree of polymerization and a low viscosity when slurried because the content of the polar group (2) is in the above range and has hydration properties that are not too high. Become. Therefore, it is possible to easily increase the concentration of the slurry and improve the handleability.
Moreover, since the fine fibrous cellulose of this embodiment has a small degree of polymerization, it is difficult to form aggregates when mixed with an emulsion resin. Therefore, the mechanical properties of the obtained fiber reinforced composite resin can be sufficiently improved, and a good appearance can be easily obtained.

  Examples of the present invention are shown below, but the present invention is not limited to the examples. In the following examples, “%” means “mass%” and “part” means “part by mass”.

Example 1
1.69 g of sodium dihydrogen phosphate dihydrate and 1.21 g of disodium hydrogen phosphate are dissolved in 3.39 g of water to obtain an aqueous solution of a phosphoric acid compound (hereinafter referred to as “phosphorylation reagent”). It was. The pH of this phosphorylating reagent was 6.0 at 25 ° C.
Softwood bleached kraft pulp (manufactured by Oji Paper Co., Ltd., moisture 50%, Canadian standard freeness (CSF) 700 ml measured according to JIS P8121) is refluxed in a 0.3 mol / L sulfuric acid aqueous solution at 100 ° C. for 15 minutes. Then, the mixture was heated while being sufficiently washed with ion exchange water to obtain a sulfuric acid-treated pulp. The obtained sulfuric acid-treated pulp was diluted with ion-exchanged water so that the water content was 80% to obtain a pulp slurry. 6.15 g of the phosphorylating reagent (20 parts as the amount of phosphorus element with respect to 100 parts of dry pulp) is added to 15 g of this pulp slurry, and a fan dryer (Yamato Scientific Co., Ltd. DKM400) at 105 ° C. is used every 15 minutes. It was dried until the mass became constant while kneading. Subsequently, it heat-processed with the 150 degreeC ventilation drying machine for 1 hour, and introduce | transduced the phosphate group into the cellulose.
Next, 300 ml of ion-exchanged water was added to the cellulose into which phosphate groups had been introduced, followed by stirring and washing, followed by dehydration. The dehydrated pulp was diluted with 300 ml of ion-exchanged water, and 5 ml of 1N sodium hydroxide aqueous solution was added little by little with stirring to obtain an alkali-treated pulp dispersion having a pH of 12 to 13. The alkali-treated pulp dispersion was dehydrated and washed by adding 300 ml of ion exchange water. This dehydration washing was repeated two more times.
Ion-exchanged water was added to the pulp obtained after washing and dehydration, followed by stirring to obtain a 0.5% slurry. The pulp slurry was defibrated for 30 minutes under a condition of 21,500 rpm, using a defibrating apparatus (Cleamix-2.2S, manufactured by M Technique Co., Ltd.) to obtain a fine fibrous cellulose dispersion. .

(Example 2)
Softwood bleached kraft pulp (manufactured by Oji Paper Co., Ltd., moisture 50%, Canadian standard freeness (CSF) 700 ml measured according to JIS P8121) was added to ion-exchanged water to make a slurry with an absolute dry solid content of 1%. . To the slurry, endoglucanase (GenExor GCExtra) was added in an amount corresponding to 1% of the absolute dry solid content, treated with stirring at pH 5 and 50 ° C. for 6 hours, and then thoroughly washed with ion-exchanged water. Enzyme-treated pulp was obtained.
The obtained enzyme-treated pulp was diluted with ion-exchanged water so that the water content was 80% to obtain an enzyme-treated pulp dispersion. To the enzyme-treated pulp dispersion 15 g, 6.29 g of a phosphorylating reagent similar to that used in Example 1 (20 parts as the amount of phosphorus element with respect to 100 parts of dried pulp) was added, and a blow dryer at 105 ° C. ( Yamato Scientific Co., Ltd. DKM400) was dried until the mass became constant while kneading every 15 minutes. Subsequently, it heat-processed with the 150 degreeC ventilation drying machine for 1 hour, and introduce | transduced the phosphate group into the cellulose.
Next, 300 ml of ion-exchanged water was added to the cellulose into which phosphate groups had been introduced, followed by stirring and washing, followed by dehydration. The dehydrated pulp was diluted with 300 ml of ion-exchanged water, and 5 ml of 1N sodium hydroxide aqueous solution was added little by little with stirring to obtain an alkali-treated pulp dispersion having a pH of 12 to 13. The alkali-treated pulp dispersion was dehydrated and washed by adding 300 ml of ion exchange water. This dehydration washing was repeated two more times.
Ion-exchanged water was added to the pulp obtained after washing and dehydration, followed by stirring to obtain a 0.5% slurry. The pulp slurry was defibrated for 30 minutes under a condition of 21,500 rpm, using a defibrating apparatus (Cleamix-2.2S, manufactured by M Technique Co., Ltd.) to obtain a fine fibrous cellulose dispersion. .

(Example 3)
Hardwood kraft pulp (manufactured by Oji Paper Co., Ltd., moisture 50%, Canadian standard freeness (CSF) 600 ml measured according to JIS P8121) is dried at 105 ° C. for 3 hours to obtain a dried pulp having a moisture content of 3% or less. It was. Next, a maleic anhydride solution obtained by dissolving 2 g of maleic anhydride in 4 g of acetone was added dropwise to 4 g of the dried pulp and stirred to soak the maleic anhydride solution in the dried pulp. Subsequently, acetone was volatilized by drying at 40 ° C. for 30 minutes, and then the autoclave was filled. The autoclave was placed in an oven at 100 ° C. and treated for 2 hours. This introduced a carboxy group into the cellulose.
Next, the dried pulp treated with maleic anhydride was dispersed in 250 mL of 0.8% sodium hydroxide aqueous solution to form a slurry, and the resulting slurry was stirred to alkali-treat the pulp. The pH of the slurry was about 12.5. Thereafter, the pulp after alkali treatment was washed with water until the pH became 8 or less.
Subsequently, ion exchange water was added to the pulp after washing with water to prepare a slurry having a solid content concentration of 0.5%. The slurry was defibrated for 30 minutes at 21500 rpm using a defibrating apparatus (Cleamix-2.2S, manufactured by M Technique Co., Ltd.). And after centrifuging at 12000G for 10 minutes using the cooling high-speed centrifuge (the Kokusan company make, H-2000B), the supernatant liquid was collect | recovered and the fine fibrous cellulose dispersion liquid was obtained.

(Comparative Example 1)
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 1 except that the treatment step with the sulfuric acid aqueous solution was omitted.

<Evaluation>
[Transmission electron microscope observation, confirmation of crystal form]
After adding ion-exchanged water to the fine fibrous cellulose dispersion in each example to adjust the solid content concentration to 0.2%, using a cooling high-speed centrifuge (Kokusan Co., Ltd., H-2000B), conditions of 12000 G × 10 minutes And the resulting supernatant was recovered. The supernatant was diluted with water and dropped onto a carbon grid membrane that had been subjected to a hydrophilic treatment. After drying, it was stained with uranyl acetate and observed with a transmission electron microscope (JEOL-2000EX, manufactured by JEOL Ltd.). As a result, it was confirmed that the fine fibrous cellulose in each example was a fine fibrous cellulose having a width of about 4 nm.
Moreover, it was confirmed that the fine fibrous cellulose of each example maintained the cellulose I type crystal | crystallization by X-ray diffraction.

About the fine fibrous cellulose obtained in each Example and each comparative example, average fiber width, polymerization degree, and content of polar group were measured. The measurement results are shown in Table 1.
Moreover, about the sheet | seat obtained in each Example and each comparative example, the tensile strength of the sheet | seat and the viscosity of the dispersion liquid were measured. The measurement results are shown in Table 1.

[Average fiber width]
The average fiber width was measured by the method described in the above paragraph [0010].
[Degree of polymerization]
The degree of polymerization was measured by the method described in paragraph [0012] above.
[Polar group content]
The polar group content was measured by the method described in the above paragraph [0016] for the polar group (1) and by the method described in the above paragraph [0045] for the polar group (2).

[Viscosity of dispersion]
The viscosity of the dispersion liquid adjusted to a concentration of 0.5% was measured. In the measurement of the viscosity, it was measured according to JIS K7117-1 by using a B-type viscometer.

In Examples 1 to 3, the average fiber width is 200 nm or less, the degree of polymerization is 50 or more and 500 or less, and the content of the polar group (1) or the polar group (2) is 0.06 to 2.0 mmol / g. The viscosity of the dispersion was low.
In Comparative Example 1 having a degree of polymerization of 722, the viscosity of the dispersion when slurryed was high.

Claims (4)

A fine fibrous cellulose having an average fiber width of 2 to 20 nm and a polymerization degree of 150 to 400 , wherein the polar group represented by the following formula (1) or the polar group represented by the following formula (2) Fine fibrous cellulose having an ester substituent and a content of the polar group of 0.1 to 1.0 mmol / g.
Formula (1) (—O—PO ₃ ²⁻ ) · X ^{p +} _{2 / p}
Formula (2) (—OCO—R—COO ⁻ ) _q · Y ^{q +}
(Where p is 1 or 2. X ^{p +} _{p / 2} is at least selected from the group consisting of alkali metal cations, ammonium ions, aliphatic ammonium ions, and aromatic ammonium ions when p = 1. In addition, when p = 2, it is at least one selected from the group consisting of alkaline earth metal cations or polyvalent metal cations, ^q is a natural number of 1 to 3, and Y ^{q +} is , Q = 1, at least one selected from the group consisting of alkali metal cations, ammonium ions, aliphatic ammonium ions, and aromatic ammonium ions, and when q = 2 or 3, alkaline earths is at least one selected from a metal ion or the group consisting of polyvalent metal ions .R is unsaturated - a linear hydrocarbon group, the carbon constituting R There is two.) A decomposition step of decomposing cellulose such that the degree of polymerization is 150 to 400 ;
By treating the cellulose after the decomposition step with an oxo acid containing a phosphorus atom or a salt thereof, the polar group represented by the formula (3) is added to the cellulose, and the content of the polar group is 0.1 to 1.0. a polar group introduction step formed to have a mmol / g;
An alkali treatment step of treating the cellulose having the polar group represented by the formula (3) with an alkaline solution to form the polar group represented by the formula (1);
A method for producing fine fibrous cellulose, comprising a step of defibrating cellulose after alkali treatment so that the average fiber width becomes 2 to 20 nm .
Formula (3) -O-PO ₃ ^2-
Formula (1) (—O—PO ₃ ²⁻ ) · X ^{p +} _{2 / p}
(Where p is 1 or 2. X ^{p +} _{p / 2} is at least selected from the group consisting of alkali metal cations, ammonium ions, aliphatic ammonium ions, and aromatic ammonium ions when p = 1. In addition, when p = 2, it is at least one selected from the group consisting of alkaline earth metal cations or polyvalent metal cations.) A decomposition step of decomposing cellulose such that the degree of polymerization is 150 to 400 ;
By treating the cellulose after the decomposition step with a carboxylic acid compound, the polar group represented by the formula (4) is added to the cellulose, and the content of the polar group becomes 0.1 to 1.0 mmol / g. A polar group introduction step to be formed as follows:
An alkali treatment step of treating the cellulose having the polar group represented by the formula (4) with an alkaline solution to form the polar group represented by the formula (2);
A defibrating step of refining cellulose after alkali treatment so that the average fiber width is 2 to 20 nm or less and defibrating,
The method for producing fine fibrous cellulose, wherein the carboxylic acid compound is at least one selected from the group consisting of a compound having two carboxy groups, an acid anhydride of a compound having two carboxy groups, and derivatives thereof. .
Equation (4) -OCO-R-COO -
Formula (2) (—OCO—R—COO ⁻ ) _q · Y ^{q +}
(Where q is a natural number of 1 to 3. Y ^{q +} is at least one selected from the group consisting of alkali metal cations, ammonium ions, aliphatic ammonium ions, and aromatic ammonium ions when q = 1. Further, when q = 2 or 3, it is at least one selected from the group consisting of alkaline earth metal ions or polyvalent metal ions, R is an unsaturated-linear hydrocarbon group , R The number of carbon atoms constituting is 2. )   The manufacturing method of the fine fibrous cellulose of Claim 2 or 3 which decomposes | disassembles a cellulose using a sulfuric acid or an enzyme in the said decomposition | disassembly process.