JP2013253200A - Fine fibrous cellulose, method for producing the same, fine fibrous cellulose dispersion, and non-woven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fine fibrous cellulose which can be produced at a high yield, can secure stability of a dispersion in a slurry state even at an acidic side and can reduce viscosity of the dispersion.SOLUTION: A fine fibrous cellulose includes a salt of a carboxyl group and a salt of a phosphoric acid group or a salt of a sulfonic acid salt. The fine fibrous cellulose preferably has a polymerization degree in the range from 50 to 500.

Description

  The present invention relates to a fine fibrous cellulose and a method for producing the same, a fine fibrous cellulose dispersion, and a nonwoven fabric.

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 1000 nm or less is also known. Various applications have been studied for the use of fine fibrous cellulose. For example, it is said that when fine fibrous cellulose is added to a resin or rubber as a reinforcing agent, the effect of improving mechanical properties is increased.
As a method for producing fine fibrous cellulose, a fiber raw material containing cellulose is oxidized with an N-oxyl compound and then dispersed (Patent Document 1). The fiber raw material is oxidized with ozone and then defibrated. A method for miniaturization (Patent Document 2) is known.
Further, as a method for producing fine fibrous cellulose, there is known a method (Patent Document 3) in which a fiber raw material is fibrillated and refined and then treated with phosphoric acid or sulfonic acid.

JP 2008-1728 A JP 2010-254726 A JP 9-509694 A

However, the methods described in Patent Documents 1 and 2 have insufficient yields of fine fibrous cellulose. Moreover, since the dispersion stability in the acidic side of the dispersion liquid which slurried the fine fibrous cellulose was inadequate, it was difficult to use for the use which makes a slurry acidic.
In the method described in Patent Document 3, the viscosity of the dispersion of fine fibrous cellulose tends to be high, and it is difficult to prepare a high concentration dispersion. Furthermore, the yield of fine fibrous cellulose may be insufficient.
An object of the present invention is to provide a fine fibrous cellulose that can be produced with a high yield, can ensure the stability of a slurry dispersion on the acidic side, and can reduce the viscosity of the dispersion. Another object of the present invention is to provide a method for producing fine fibrous cellulose, which can ensure the stability of the slurry dispersion in the acidic side and can produce fine fibrous cellulose that can reduce the viscosity of the dispersion with high yield. .

The present invention has the following aspects.
[1] A fine fibrous cellulose having a functional group represented by the following formula (1) and a functional group represented by the following formula (2).
(1) (—COO ⁻ ) _p · X ^{p +}
(2) (—O—PO ₃ ²⁻ ) · Y ^{q +} _3−q
(Where p is a natural number of 1 to 3. X ^{p +} is at least 1 selected from the group consisting of an alkali metal cation, ammonium ion, aliphatic ammonium ion, and aromatic ammonium ion when p = 1. In addition, when p = 2 or 3, it is at least one selected from the group consisting of alkaline earth metal ions or polyvalent metal ions, ^q is 1 or 2. Y ^{q +} _3-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, It is at least one selected from the group consisting of cations or cations of polyvalent metals.)
[2] A fine fibrous cellulose having a functional group represented by the following formula (1) and a functional group represented by the following formula (3).
(1) (—COO ⁻ ) _p · X ^{p +}
(3) (—SO ₃ ⁻ ) _r · Z ^{r +}
(Where p and r are each independently a natural number of 1 to 3. X ^{p +} and Z ^{r +} are alkali metal cations, ammonium ions, and aliphatic ammonium ions when p = 1 and r = 1. And at least one selected from the group consisting of aromatic ammonium ions, and when p = 2 or 3, r = 2 or 3, a group consisting of an alkaline earth metal cation or a polyvalent metal cation. At least one selected from
[3] The fine fibrous cellulose according to [1] or [2], wherein the degree of polymerization is in the range of 50 to 500.
[4] The fine fibrous cellulose according to any one of [1] to [3], wherein the average fiber width is 200 nm or less.

[5] An oxidation step in which a fiber raw material containing cellulose is oxidized to form a carboxy group, and after the oxidation step, the fiber raw material is treated with an oxo acid containing a phosphorus atom or a salt thereof to form a phosphate group. And an acid group forming step of forming acid group-forming cellulose to form a fine fibrous cellulose.
[6] An oxidation step of oxidizing a fiber raw material containing cellulose to form a carboxy group, and after the oxidation step, the fiber raw material is treated with an oxo acid containing a sulfur atom or a salt thereof to give a sulfonic acid group. And an acid group forming step of obtaining acid group-containing cellulose to form a fine fibrous cellulose.
[7] The method for producing fine fibrous cellulose according to [5] or [6], wherein in the oxidation step, the fiber raw material is subjected to at least ozone treatment to form a carboxy group.
[8] Any of [5] to [7], which includes an alkali treatment step for obtaining a cellulose salt by alkali treatment of the acid group-containing cellulose after the acid group formation step, and a defibration step for defibrating the cellulose salt. The manufacturing method of the fine fibrous cellulose as described in any one.
[9] The method for producing fine fibrous cellulose according to any one of [5] to [7], further comprising a defibrating step of defibrating the acid group-containing cellulose after the acid group forming step.

[10] A fine fibrous cellulose dispersion, wherein the cellulose fiber according to [1] or [2] is dispersed in a dispersion medium.
[11] A nonwoven fabric containing the fine fibrous cellulose according to [1] or [2].

The fine fibrous cellulose of the present invention can be produced in a high yield, can ensure the stability of the slurry dispersion in the acidic side, and can lower the viscosity of the dispersion.
According to the method for producing fine fibrous cellulose of the present invention, the stability of the slurry dispersion can be ensured even on the acidic side, and the fine fibrous cellulose capable of reducing the viscosity of the dispersion can be produced in a high yield.

“First Embodiment”
<Fine fibrous cellulose>
First, the fine fibrous cellulose of the first embodiment will be described.
The fine fibrous cellulose of the first embodiment has a functional group represented by the above formula (1) (hereinafter referred to as “functional group (1)”) and a functional group represented by the above formula (2) (hereinafter, referred to as “functional group (1)”). Cellulose fiber having “functional group (2)”.

The content of (—COO ⁻ ) of the functional group (1) in the fine fibrous cellulose of this embodiment is preferably 0.06 to 1.2 mmol / g, and is 0.1 to 0.9 mmol / g. It is more preferable. (-COO ^-) When the content of the above lower limit, can be prepared in a more high yield, whereas, (- COO ^-) content is equal to or less than the upper limit, dissolved in water as the cellulose molecule Therefore, the characteristics (high strength, high rigidity, and high dimensional stability) as fine fibrous cellulose can be easily obtained.

State content of, the ^{X +} functional group (1) was ^{H +} above (-COO ^-) content is, per cellulose 1 g ^- a content, (-COO) (- ^- COO) Measure with That is, the content of the carboxy group is measured. The content of the carboxy group can be measured by the following method.
[Method for measuring content of carboxy group in cellulose fiber]
The carboxy group content is determined using the method of “Test Method T237 cm-08 (2008): Carboxyl Content of pulp” of TAPPI, USA. In order to make it possible to measure the introduction amount of the carboxy group to a wider range, among the test solutions used in the test method, sodium hydrogen carbonate (NaHCO ₃ ) / sodium chloride (NaCl) = 0.84 g / 5.85 g was distilled water. In the test solution dissolved and diluted in 1000 ml, the concentration of the test solution was changed to sodium bicarbonate / sodium chloride = 3.36 g / 23.40 g so that the concentration of the test solution was substantially 4 times. Except that the difference in the measured value in the cellulose fiber is a substantial substituent introduction amount, it conforms to TAPPI T237 cm-08 (2008). In addition, the absolutely dry cellulose fiber used as a measurement sample is one obtained by freeze-drying in order to avoid alteration of cellulose that may occur due to heating during heat drying.

The content of (—O—PO ₃ ²⁻ ) in the functional group (2) in the fine fibrous cellulose is preferably 0.1 to 2.0 mmol / g, and preferably 0.2 to 1.5 mmol / g. It is more preferable. If the content of (—O—PO ₃ ²⁻ ) is equal to or higher than the lower limit value, it can be produced with higher yield. However, when the content of (—O—PO ₃ ²⁻ ) exceeds the upper limit, fine fibrous cellulose is dissolved, and the yield may be lowered.

The content of (—PO ₃ ²⁻ ) in the functional group (2) is the content of (—PO ₃ ²⁻ ) per 1 g of cellulose, and was 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) = A 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 (-O-PO ₃ ^2- ) Measured according to TAPPI T237 cm-08 (2008), except that the difference in the measured values of the cellulose fibers before and after introduction was changed to a substantial (-O-PO ₃ ²⁻ ) content.
In addition, 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 a phosphate group which is a polyvalent acidic group is as described above. The (−O—PO ₃ ²⁻ ) content obtained as the monovalent acidic group content was divided by the (—O—PO ₃ ²⁻ ) acid number 2.

The total content (ie, anionic group content) of (—COO ⁻ ) and (—O—PO ₃ ²⁻ ) in the fine fibrous cellulose is preferably 0.2 to 3.0 mmol / g. More preferably, it is 5-2.5 mmol / g. If the total content of (—COO ⁻ ) and (—O—PO ₃ ²⁻ ) is equal to or higher than the lower limit, it can be produced with higher yield. Further, when the total content of (—COO ⁻ ) and (—O—PO ₃ ²⁻ ) is within the above range, the dispersion stability when the fine fibrous cellulose is slurried becomes higher.

In the functional group (1), p is a natural number of 1 to 3.
X ^{p +} 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 p = 1. When p = 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.
In the functional group (2), q is 1 or 2.
Y ^{q +} _3-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, it is at least one selected from the group consisting of an alkaline earth metal cation and a polyvalent metal cation.
Among the above ^{Xp +} , ^{Yq +} _3-q , those having p, 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 are more preferred.

The fine fibrous cellulose is a cellulose fiber or rod-like particle having an I-type crystal structure that is much finer and shorter than the pulp fiber usually used for papermaking.
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 from the pattern (Seagal et al., Textile Research Journal, 29, 786, 1959).

Fine fibrous cellulose is cellulose having an average fiber width of 1000 nm or less as observed with an electron microscope. The average fiber width of the fine fibrous cellulose is preferably 200 nm or less, and more preferably 100 nm or less. If the average fiber width of the fine fibrous cellulose is not more than the above upper limit, the characteristics (high strength, high rigidity, high dimensional stability) as the fine fibrous cellulose can be easily obtained.
On the other hand, the average fiber width of the fine fibrous cellulose is preferably 1 nm or more, and more preferably 2 nm or more. If the average fiber width of the fine fibrous cellulose is not less than the above lower limit value, it becomes difficult to dissolve in water as cellulose molecules, so the characteristics (high strength, high rigidity, high dimensional stability) as a fine fibrous cellulose are easily obtained. Can be obtained.
In applications where transparency is required for fine fibrous cellulose, when the average fiber width exceeds 30 nm, it approaches 1/10 of the wavelength of visible light, and when combined with a matrix material, visible light is refracted and scattered at the interface. The average fiber width is preferably 2 nm to 30 nm, and more preferably 2 to 20 nm.

Measurement of the average fiber width of the fine fibrous cellulose by observation with an electron microscope is performed as follows. A slurry containing fine fibrous cellulose having a concentration of 0.05 to 0.1% by mass is prepared, and the slurry is cast on a carbon film-coated grid subjected to a hydrophilization treatment to obtain a sample for TEM observation. When wide fibers are included, an 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 degree of polymerization of the fine fibrous cellulose is preferably 50 to 500, more preferably 100 to 400, and further preferably 150 to 300. When the degree of polymerization of the fine fibrous cellulose is less than the lower limit, it cannot be said to be “fibrous”, and it becomes difficult to use as a reinforcing agent, and when the upper limit is exceeded, when blended with a resin or rubber Further, the dispersibility becomes low, and the slurry viscosity becomes too high when the fine fibrous cellulose is slurried, so that the dispersion stability becomes low.
The degree of polymerization of fine fibrous cellulose is measured by the following method.
Fine fibrous cellulose (supernatant liquid after centrifugation, concentration of about 0.5% by mass) is reduced in pressure on a 500 mesh polyester mesh to prepare a wet sheet, and dried at 105 ° C. to obtain a dry sheet. . The pulp viscosity is measured according to Tappi T230 using the obtained dry sheet. Moreover, a blank test is performed without using a cellulose sample by the same method, and a blank viscosity is measured. By subtracting 1 from the value obtained by dividing the pulp viscosity by the blank viscosity, the specific viscosity (ηsp) is obtained, 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”.

  The average fiber length of the fine fibrous cellulose is preferably 0.1 to 5 μm. When the average fiber length is at least the lower limit, an effect of improving the strength when fine fibrous cellulose is blended with the resin can be obtained. If average fiber length is below an upper limit, the dispersibility at the time of mix | blending fine fibrous cellulose with resin is favorable. The fiber length can be obtained by image analysis of TEM, SEM, or AFM.

  The axial ratio (fiber length / average fiber width) of the fine fibrous cellulose is preferably in the range of 100 to 10,000. If the axial ratio is equal to or greater than the lower limit value, 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 and the dispersion stability becomes higher.

(Function and effect)
Since the fine fibrous cellulose of this embodiment has a functional group (1) and a functional group (2), it is manufactured with a high yield. That is, since the electric repulsion does not occur between simple celluloses, the defibration property is not high. However, between celluloses having a functional group (1) and a functional group (2), (—COO ⁻ ) and (—O— Since PO ₃ ²⁻ ) is likely to cause an electric repulsion, the defibration property is high. Therefore, the fine fibrous cellulose having the functional group (1) and the functional group (2) can be obtained with a high yield.
Moreover, the fine fibrous cellulose of this embodiment is excellent in dispersion stability regardless of whether the dispersion is alkaline or acidic. The dispersion containing the fine fibrous cellulose is excellent in dispersion stability even on the acidic side. Acid dissociation constant pK _a of the carboxylic acid is relatively large (about 4-5), are easily dissociated hydrogen ions in an alkaline under -COO ^- but is formed, the hydrogen ions is less likely to dissociate under acidic conditions, -COO ^- it is unlikely to be formed. Therefore, only the functional group (1) does not provide sufficient dispersion stability under acidic conditions. However, the phosphate group (of the order of 1 to 2) acid dissociation constant pK _a small, in the fine fibrous cellulose of the present embodiment having the functional group (2), in acidic condition (-O-PO ₃ Since H ⁻ ) and (—O—PO ₃ ²⁻ ) are formed, they are stabilized in the dispersion medium.
Moreover, since the fine fibrous cellulose of this embodiment has a slightly low degree of polymerization, it can reduce the viscosity when it is used as a dispersion. In particular, a low viscosity can be maintained even when the concentration of the dispersion is increased.

<Method for producing fine fibrous cellulose>
The manufacturing method of this embodiment which manufactures the said fine fibrous cellulose has an oxidation process, an acid group formation process, an alkali treatment process, and a defibration process.
Hereinafter, each step will be described in detail.

[Textile raw materials]
In the present invention, the fiber raw material containing cellulose, which is a raw material for fine fibrous cellulose, includes pulp for papermaking, cotton pulp such as cotton linter and cotton lint, non-wood pulp such as hemp, straw, bagasse, sea squirt and Examples include cellulose isolated from seaweed and the like. 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) (NUKKP, 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 fiber raw material may be used individually by 1 type, and may be used in mixture of 2 or more types.

(Oxidation process)
The oxidation step is a step of forming a carboxy group by oxidizing a fiber raw material containing cellulose. Specifically, as shown in the following reaction formula (A), it is a step of forming a carboxy group by oxidizing at least the 6-position hydroxy group of the glucopyranose ring constituting cellulose. In this step, not all of the 6-position hydroxy groups are oxidized, but only some of them are oxidized. Some hydroxy groups are not oxidized to carboxy groups, but become carbonyl groups.

Examples of the oxidation step include ozone treatment in which the fiber raw material is brought into contact with ozone and oxyl treatment in which the fiber raw material is brought into contact with the N-oxyl compound. However, ozone treatment is preferable in that the viscosity of the dispersion can be lowered.
Further, the oxidation step may be only ozone treatment or oxyl treatment, but since the yield of fine fibrous cellulose can be increased by oxidizing the carbonyl group to form a carboxy group, after the ozone treatment or oxyl treatment, The fiber raw material subjected to ozone treatment or oxyl treatment may be further oxidized (hereinafter referred to as “additional oxidation treatment”) with an oxidizing agent other than ozone and N-oxyl compound.

[Ozone treatment]
As a specific ozone treatment method, a method of leaving a fiber raw material in a gas containing ozone for a predetermined time, a method of passing a fiber raw material in a gas containing ozone, a method of applying a gas containing ozone to the fiber raw material, etc. are applied. can do.
The gas containing ozone can be generated using a known ozone generator using an oxygen-containing gas such as air, oxygen gas, or oxygen-added air as an ozone raw material.
When cellulose is treated with ozone, at least the 2-position and 6-position hydroxy groups of the glucopyranose ring are oxidized and the cellulose is decomposed to lower the molecular weight. In the oxidation step, the glucopyranose ring other than the 2nd and 6th positions may be oxidized.

In the ozone treatment, the ozone treatment conditions (the ozone concentration in the gas containing ozone, the amount of ozone added to the fiber raw material, the ozone treatment time, the ozone treatment temperature, etc.) are appropriately adjusted.
The higher the ozone concentration in the gas containing ozone, the greater the amount of ozone added to the fiber raw material, the longer the ozone treatment time, and the higher the ozone treatment temperature, the more the oxidation of hydroxy groups proceeds and the functional group ( The content of 1) increases, and the degree of polymerization decreases as the molecular weight of cellulose progresses.

Further, the ozone concentration in the ozone containing gas is preferably 50 to 1000 g / ^{m 3,} more preferably 100 to 500 g / ^{m 3.} If the ozone concentration is equal to or higher than the lower limit, cellulose can be sufficiently oxidized, and further, the cellulose fibers can be sufficiently decomposed and cut. Therefore, the yield of fine fibrous cellulose is further increased, and the fine fibrous cellulose is slurried. The dispersion stability can be further improved. On the other hand, if the ozone concentration is not more than the above upper limit value, excessive oxidation and decomposition of the cellulose fibers can be prevented, and the characteristics (high strength, high rigidity, high dimensional stability) as the fine fibrous cellulose can be easily obtained. be able to.

  As an ozone addition rate with respect to a fiber raw material, it is preferable that it is 0.1-80 mass%, and it is more preferable that it is 1-60 mass%. If the ozone addition rate is equal to or higher than the lower limit, cellulose can be sufficiently oxidized, and further, the cellulose fibers can be sufficiently decomposed and cut, so that the yield of fine fibrous cellulose is further increased. The dispersion stability when slurryed can be further improved. On the other hand, if the ozone addition rate is less than or equal to the above upper limit value, excessive oxidation and decomposition of cellulose fibers can be prevented, and the characteristics (high strength, high rigidity, high dimensional stability) as fine fibrous cellulose can be easily obtained. Can be obtained.

The ozone treatment time is preferably 1 minute or longer, and more preferably 30 minutes or longer. If the ozone treatment time is equal to or more than the lower limit, cellulose can be sufficiently oxidized, and further, the cellulose fibers can be sufficiently decomposed and cut, so that the yield of fine fibrous cellulose is further increased. The dispersion stability when slurryed can be further improved.
On the other hand, the ozone treatment time is preferably 600 minutes or less, and more preferably 360 minutes or less. If the ozone treatment time is less than or equal to the above upper limit value, excessive oxidation and decomposition of the cellulose fiber can be prevented, and characteristics (high strength, high rigidity, high dimensional stability) as a fine fibrous cellulose can be easily obtained. Can do.

  The ozone treatment temperature is preferably 0 to 100 ° C, and more preferably 20 to 50 ° C. If the ozone treatment temperature is equal to or higher than the lower limit value, a device for ozone treatment can be simplified, and if the ozone treatment temperature is equal to or lower than the upper limit value, decomposition of ozone can be suppressed and the fiber raw material can be efficiently ozone treated. .

[Oxyl treatment]
The N-oxyl compound used in the oxyl treatment generates 2,2,6,6-tetramethylpiperidinooxy radical (hereinafter referred to as “TEMPO”). Therefore, in the oxyl treatment, the fiber raw material is treated by TEMPO.
The amount of the N-oxyl compound used is not particularly limited, and is preferably 1 to 80 parts by mass with respect to 100 parts by mass of the fiber raw material.

In the oxyl treatment, a co-oxidant is usually reacted with a fiber raw material together with an N-oxyl compound. Examples of the co-oxidant include sodium hypochlorite, sodium chlorite, sodium hypobromite, sodium bromite, etc. The amount of the co-oxidant used is not particularly limited, and is 100 parts by mass of the fiber raw material. On the other hand, 1-80 mass parts is preferable.

Further, the oxyl treatment is usually performed in the presence of an alkali halide. Examples of the alkali halide include alkali iodide, alkali bromide, alkali chloride, alkali fluoride and the like.
The amount of alkali halide used is not particularly limited, and is preferably 0.1 to 15 parts by mass with respect to 100 parts by mass of the fiber raw material.

The treatment temperature during the oxyl treatment is preferably in the range of 20 to 100 ° C., and the treatment time is preferably 0.5 to 4 hours.
Moreover, in order to perform an oxyl process uniformly, it is preferable to process, stirring with various stirring apparatuses.

[Additional oxidation treatment]
Although it does not specifically limit as a method of an additional oxidation process, For example, the method of immersing the fiber raw material which carried out ozone treatment in the oxidizing agent solution is mentioned.
As the oxidizing agent other than ozone used for the additional oxidation treatment, a known oxidizing agent (for example, chlorine-based compounds such as chlorine dioxide and sodium chlorite) is used. The oxidizing agent may be used alone or in combination of two or more.
The solvent in the oxidant solution may be either water or an organic solvent, but a polar solvent (polar organic solvent such as water or alcohol) is preferable, and an aqueous solvent containing at least water is more preferable.

  As an oxidizing agent addition rate with respect to a fiber raw material, it is preferable that it is 0.1-100 mass%, and it is more preferable that it is 1-30 mass%. If the oxidant addition rate is equal to or greater than the lower limit, cellulose can be further oxidized, and further, the cellulose fibers can be further decomposed and cut, so that the yield of fine fibrous cellulose is further increased, and the fine fibrous cellulose is slurried. The dispersion stability can be further improved. On the other hand, if the oxidant addition rate is less than or equal to the above upper limit value, excessive oxidation and decomposition of the cellulose fibers can be prevented, and the characteristics as fine fibrous cellulose can be easily obtained.

  The oxidant treatment time is preferably 10 to 360 minutes, and more preferably 60 to 180 minutes. If the oxidizing agent treatment time is equal to or more than the lower limit, cellulose can be further oxidized, and further, the cellulose fibers can be further decomposed and cut. Therefore, the yield of fine fibrous cellulose is further increased, and the fine fibrous cellulose is slurried. The dispersion stability can be further improved. On the other hand, if the oxidizing agent treatment time is less than or equal to the above upper limit value, excessive oxidation and decomposition of the cellulose fibers can be prevented, and the characteristics as fine fibrous cellulose can be easily obtained.

  The oxidizing agent treatment temperature is preferably 5 to 90 ° C, and more preferably 10 to 70 ° C. If the oxidant treatment temperature is equal to or higher than the lower limit value, the oxidation treatment can be promoted. If the oxidant treatment temperature is equal to or lower than the upper limit value, decomposition of the oxidant can be suppressed and the fiber raw material can be efficiently treated with the oxidant.

(Acid group forming step)
In the acid group forming step in the present embodiment, after the oxidation step, the fiber raw material is treated with an oxo acid containing a phosphorus atom (hereinafter referred to as “phosphoroxo acid”) or a salt thereof, whereby the acid group-containing cellulose is treated. It is a process to obtain.
In the acid group formation step, for example, when a hydroxy group remaining in the cellulose molecule after the oxidation step and a phosphorus oxo acid having at least (HPO ₄ ) ^2- or a salt thereof undergo a dehydration reaction, the following reaction formula (B) Thus, the phosphate group of the functional group (2) is formed.

—OH + HPO ₄ ²⁻ → —O—PO ₃ ²⁻ + H ₂ O (B)

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 fiber 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 fiber 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.

It is preferable that the heat processing temperature in an acid group formation process is 250 degrees C or less from the point of the thermal decomposition temperature of a 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 acid group formation.

(Alkali treatment process)
The alkali treatment step is a step of treating the acid group-containing cellulose with an alkali solution containing an alkali compound represented by X ^{p +} · (OH ⁻ ) _p or Y ^{q +} · (OH ⁻ ) _q . By the alkali treatment, the functional group (1) and the functional group (2) are formed in the cellulose. X ^{p +} · (OH ⁻ ) _p and Y ^{q +} · (OH ⁻ ) _q may be the same or different.
Although it does not specifically limit as a method of an alkali treatment, For example, the method of immersing an acid group containing cellulose 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.
Y ^{q +} 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 q = 1. Further, when q = 2, it is at least one selected from the group consisting of an alkaline earth metal cation and a polyvalent metal cation.
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 in the alkali solution is adjusted so as to neutralize all carboxy groups formed in the oxidation step and all phosphate groups formed in the acid group formation 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 defibrating an alkali-treated fiber obtained by alkali-treating oxidized cellulose after the alkali treatment step.
In the defibrating process, a defibrating apparatus is usually used. Defibration treatment equipment includes high-speed defibrator, grinder (stone mortar grinder), high-pressure homogenizer and ultra-high pressure homogenizer, high-pressure collision grinder, ball mill, bead mill, disk refiner, conical refiner, twin-screw kneader, vibration mill A wet milling device such as a homomixer under high-speed rotation, an ultrasonic disperser, or a beater can be used as appropriate.

  In the defibrating process, it is preferable to dilute the alkali-treated fiber with water and an organic solvent alone or in combination to form a slurry. The diluted solid content concentration of the alkali-treated fiber is preferably 0.1 to 20% by mass, and more preferably 0.5 to 10% by mass. If the solid content concentration of the alkali-treated fiber after dilution is equal to or higher than the lower limit, the efficiency of the defibrating treatment is improved, and if it is equal to or lower than the upper limit, blockage in the defibrating apparatus can be prevented.

(Function and effect)
In the manufacturing method of the fine fibrous cellulose of the said embodiment, since the electrical repulsion between cellulose becomes large by forming a functional group (1) and a functional group (2) in a cellulose, fibrillation property becomes high. From the fiber raw material, fine fibrous cellulose can be produced in a high yield.
Further, the fine fibrous cellulose obtained by the production method of this embodiment has a pK _a less functional group (2), hydrogen ions under acidic conditions not only alkalinity under is readily dissociated -PO ₃ H ^- and for forming a _-PO ^{3 2-,} can be stabilized by dispersion medium. Therefore, the dispersion of fine fibrous cellulose is excellent in dispersion stability regardless of whether it is alkaline or acidic.
Moreover, in the fine fibrous cellulose obtained by the manufacturing method of this embodiment, since a polymerization degree becomes a little small by an oxidation process, the viscosity at the time of setting it as a dispersion liquid can be made low.
Moreover, since the said manufacturing method has an alkali treatment process, the fibrillation property of a cellulose becomes higher and can manufacture a fine fibrous cellulose from a fiber raw material with a higher yield.
Moreover, since the said manufacturing method has a fibrillation process, the acid group containing cellulose which carried out the alkali treatment can be refined | miniaturized reliably, and it can be set as a fine fibrous cellulose.

“Second Embodiment”
<Fine fibrous cellulose>
Next, the fine fibrous cellulose of the second embodiment will be described.
The fine fibrous cellulose of the second embodiment is a cellulose fiber having a functional group (1) and a functional group represented by the above formula (3) (hereinafter referred to as “functional group (3)”).
In addition, the polymerization degree, average fiber width, fiber length, and axial ratio of the fine fibrous cellulose of the present embodiment are the same as those of the fine fibrous cellulose of the first embodiment.

The content of (—COO ⁻ ) of the functional group (1) in the fine fibrous cellulose of this embodiment is preferably 0.06 to 1.2 mmol / g, and is 0.1 to 0.9 mmol / g. It is more preferable. (-COO ^-) When the content of the above lower limit, can be prepared in a more high yield, whereas, (- COO ^-) content is equal to or less than the upper limit, dissolved in water as the cellulose molecule Therefore, the characteristics (high strength, high rigidity, and high dimensional stability) as fine fibrous cellulose can be easily obtained.

The (—SO ₃ ⁻ ) content of the functional group (3) in the fine fibrous cellulose is preferably 0.01 to 2.0 mmol / g, more preferably 0.05 to 1.5 mmol / g. preferable. If the content of (—SO ₃ ⁻ ) is not less than the lower limit, it can be produced with higher yield. However, when the content of (—SO ₃ ⁻ ) exceeds the upper limit, the yield may be lowered.
The content of (—SO ₃ ⁻ ) in the functional group (3) is the content of (—SO ₃ ⁻ ) per 1 g of cellulose, and was 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 in which 0.84 g / 5.85 g was dissolved and diluted in 1000 ml with distilled water was changed to a test solution in which 1.60 g of sodium hydroxide was dissolved and diluted in 1000 ml with distilled water, and before and after (-SO ₃ ⁻ ) introduction. of substantially the difference between the measured value in the cellulose fibers (-SO ₃ ^-) except for using content was measured according to TAPPI T237 cm-08 (2008) .
In addition, 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 a sulfonic acid group that is a polyvalent acidic group is The (−SO ₃ ⁻ ) content obtained as the content of the monovalent acidic group was divided by the (—SO ₃ ⁻ ) acid value number 2.

The total content (ie, anion group content) of (—COO ⁻ ) and (—SO ₃ ⁻ ) in the fine fibrous cellulose is preferably 0.1 to 3.0 mmol / g, 0.5 to 2 More preferably, it is 5 mmol / g. If the total content of (—COO ⁻ ) and (—SO ₃ ⁻ ) is not less than the lower limit, it can be produced with higher yield. Further, when the total content of (—COO ⁻ ) and (—SO ₃ ⁻ ) is within the above range, the dispersion stability when the fine fibrous cellulose is slurried becomes higher.

In the functional group (3), r is a natural number of 1 to 3.
Z ^{r +} is at least one selected from the group consisting of alkali metal (eg, sodium, potassium, lithium, etc.) cations, ammonium ions, aliphatic ammonium ions, and aromatic ammonium ions when r = 1. When r = 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 above ^{Zr +} , those having r = 1 are preferable, and further, the substance is general and inexpensive as an alkali, and the yield of fine fibrous cellulose is improved, so that sodium ion, potassium ion and ammonium ion are improved. Is more preferable.

(Function and effect)
Since the fine fibrous cellulose of this embodiment has a functional group (1) and a functional group (3), it is manufactured with a high yield. That is, since an electrical repulsion does not occur between mere celluloses, the fibrillation property is not high. However, between celluloses having a functional group (1) and a functional group (2), (—COO ⁻ ) and (—SO ₃ ^- ) It is easy to cause electric repulsion due to (), so that the defibration property is high. Therefore, the fine fibrous cellulose having the functional group (1) and the functional group (3) can be obtained with a high yield.
Moreover, the fine fibrous cellulose of this embodiment is excellent in dispersion stability regardless of whether the dispersion is alkaline or acidic. The dispersion containing the fine fibrous cellulose is excellent in dispersion stability even on the acidic side. Acid dissociation constant pK _a of the carboxylic acid is relatively large (about 4-5), are easily dissociated hydrogen ions in an alkaline under -COO ^- but is formed, the hydrogen ions is less likely to dissociate under acidic conditions, -COO ^- it is unlikely to be formed. Therefore, only the functional group (1) does not provide sufficient dispersion stability under acidic conditions. However, since the sulfonic acid group has _a small acid dissociation constant pKa (about 1 to 2), in the fine fibrous cellulose of this embodiment having the functional group (3), —SO ₃ ^— is formed under acidity. Therefore, it is stabilized in the dispersion medium.
Moreover, in the fine fibrous cellulose of this embodiment, since the degree of polymerization is slightly small, the viscosity when used as a dispersion can be lowered. In particular, a low viscosity can be maintained even when the concentration of the dispersion is increased.

<Method for producing fine fibrous cellulose>
The manufacturing method of this embodiment which manufactures the said fine fibrous cellulose has an oxidation process, an acid group formation process, an alkali treatment process, and a defibration process.
The manufacturing method of this embodiment differs in the acid group formation process from the manufacturing method of 1st Embodiment. The oxidation process, alkali treatment process, and defibration process in the present embodiment are the same as the oxidation process, alkali treatment process, and defibration process in the first embodiment, and a description thereof is omitted.

(Acid group forming step)
In the acid group formation step in this embodiment, after the oxidation step, the fiber raw material is treated with an oxo acid containing a sulfur atom (hereinafter referred to as “sulfur oxo acid”) or a salt thereof to form a sulfonic acid group. In this step, acid group-containing cellulose is obtained.
In the acid group formation step, for example, when a carbonyl group remaining in the cellulose molecule after the oxidation step reacts with a sulfur oxo acid having at least (HSO ₃ ) ⁻ or a salt thereof, the following reaction formula (C) In addition, a sulfonic acid group of the functional group (3) is formed.

^{_{-CHO + HSO 3 - → -CHOH-}} SO 3 - (C)

Examples of sulfur oxo acids include sulfurous acid and dithionic acid. Examples of the salt of sulfur oxo acid include sulfurous acid, lithium salt of dithionite, sodium salt, potassium salt, calcium salt, ammonium salt, organic alkali salt and the like. Sulfur oxo acid or a salt thereof may be used alone or in combination of two or more.
Of these, sodium sulfate and potassium salts of sulfurous acid are preferred because they are easy to handle at low cost and increase the introduction efficiency.
The amount of sulfur oxo acid or salt thereof added to 100 parts by mass of the fiber raw material is preferably 1 to 500 parts by mass, more preferably 5 to 100 parts by mass, and still more preferably 10 to 40 parts by mass. If the amount of sulfur oxo acid or its salt added is equal to or greater than the lower limit, the yield of fine fibrous cellulose can be further improved. However, even if the addition amount exceeds the above upper limit, the effect of improving the yield reaches its peak, and only the sulfur oxo acid is used in vain.

  The treatment temperature in the acid group forming step is preferably 10 to 90 ° C, and more preferably 20 to 70 ° C. If processing temperature is more than the said lower limit, a sulfonic acid group can be formed easily and if it is below the said upper limit, thermal decomposition of a cellulose can be suppressed.

  In addition, in the acid group formation step in the present embodiment, sulfur oxo acid or a salt thereof is added and phosphorus oxo acid or a salt thereof is added to treat the fiber raw material with sulfur oxo acid or a salt thereof to form a sulfonic acid group. In addition to the formation, it may be treated with a phosphorus oxoacid or salt thereof to form a phosphate group. Alternatively, before or after adding the sulfur oxo acid or salt thereof, the phosphorus oxo acid or salt thereof is added to treat the fiber raw material with the sulfur oxo acid or salt thereof to form a sulfonic acid group. Treatment with a salt may form a phosphate group.

(Function and effect)
In the manufacturing method of the fine fibrous cellulose of the said embodiment, since the electrical repulsion between cellulose becomes large by forming a functional group (1) and a functional group (3) in a cellulose, defibration property becomes high. From the fiber raw material, fine fibrous cellulose can be produced in a high yield.
Further, the fine fibrous cellulose obtained by the production method of this embodiment has a pK _a less functional group (3), -SO ₃ are easily dissociated hydrogen ions under acidic conditions not only alkaline under ^- Can be stabilized in the dispersion medium. Therefore, the dispersion of fine fibrous cellulose is excellent in dispersion stability regardless of whether it is alkaline or acidic.
Moreover, in the fine fibrous cellulose obtained by the manufacturing method of this embodiment, since a polymerization degree becomes a little small by an oxidation process, the viscosity at the time of setting it as a dispersion liquid can be made low.
Moreover, since the said manufacturing method has an alkali treatment process, the fibrillation property of a cellulose becomes higher and can manufacture a fine fibrous cellulose from a fiber raw material with a higher yield.
Moreover, since the said manufacturing method has a fibrillation process, the acid group containing cellulose which carried out the alkali treatment can be refined | miniaturized reliably, and it can be set as a fine fibrous cellulose.

<Fine fibrous cellulose dispersion>
The fine fibrous cellulose dispersion of the present invention is obtained by dispersing fine fibrous cellulose in a dispersion medium.
As the dispersion medium, water or a polar organic solvent can be used. Preferred polar organic solvents include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, t-butyl alcohol, ketones such as acetone and methyl ethyl ketone (MEK), diethyl ether, tetrahydrofuran (THF) and the like. Examples include ethers, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), and the like. These may be one type or two or more types. Further, a nonpolar organic solvent may be used in addition to the water and the polar organic solvent as long as the dispersion stability of the fine fibrous cellulose dispersion is not hindered.

  The content of fine fibrous cellulose in the fine fibrous cellulose dispersion is preferably 0.05 to 20% by mass, and more preferably 0.1 to 10% by mass. When the content of the fine fibrous cellulose is equal to or more than the lower limit, the production efficiency when producing a nonwoven fabric using the fine fibrous cellulose or a composite material containing the fine fibrous cellulose in a resin or the like is excellent. On the other hand, if the content of fine fibrous cellulose is not more than the above upper limit value, the dispersion stability of the dispersion is excellent.

The viscosity of the fine fibrous cellulose dispersion is preferably 400 mPa · s or less, and more preferably 200 mPa · s or less, because the handleability of the dispersion becomes high. On the other hand, the viscosity of the fine fibrous cellulose dispersion is preferably 1 mPa · s or more, and more preferably 5 mPa · s or more, from the viewpoint of ease of preparation.
Here, the viscosity is a value measured at 25 ° C. using a B-type viscometer using a dispersion containing 0.5% by mass of fine fibrous cellulose as a measurement sample.

<Nonwoven fabric>
Below, one Embodiment of the nonwoven fabric of this invention is described.
The nonwoven fabric of the present invention contains the fine fibrous cellulose.

  The thickness of the nonwoven fabric of the present invention is not particularly limited, but is preferably 10 μm or more, more preferably 50 μm or more, particularly preferably 80 μm or more, preferably 10 cm or less, more preferably 1 cm or less, more preferably 1 mm. Hereinafter, it is particularly preferably 250 μm or less. The thickness of the nonwoven fabric is preferably thicker than the above lower limit from the viewpoint of production stability and strength, and is preferably thinner than the upper limit from the viewpoint of productivity, uniformity and resin impregnation.

  The nonwoven fabric of the present invention preferably has a porosity of 35% by volume or more, and more preferably 35 to 60% by volume. If the nonwoven fabric has a low porosity, the resin is difficult to impregnate when a matrix material such as a resin is blended to obtain a composite material, and an unimpregnated portion remains, which may cause scattering at the interface and increase haze. . Moreover, when the porosity of a nonwoven fabric is high, in the composite material which mix | blended resin, the sufficient reinforcement effect by a cellulose fiber is not acquired, but it exists in the tendency for a linear thermal expansion coefficient to become large.

The porosity here refers to the volume ratio of voids in the nonwoven fabric, and the porosity can be determined from the area, thickness, and mass of the nonwoven fabric according to the following formula.
Porosity (volume%) = {(1-B / (M × A × t)} × 100
Here, A is the area (cm ² ) of the nonwoven fabric, t (cm) is the thickness, B is the mass (g) of the nonwoven fabric, M is the density of cellulose, and M = 1.5 g / cm ³ is assumed in the present invention. To do. The film thickness of the nonwoven fabric is measured at 10 points with respect to various positions of the nonwoven fabric using a film thickness meter (PDN-20 manufactured by PEACOK), and the average value is adopted.

  Moreover, when calculating | requiring the porosity of the nonwoven fabric in a composite material, a porosity can also be calculated | required by carrying out image analysis of the spectral analysis and SEM observation of the cross section of a composite material.

The air permeability of the nonwoven fabric of the present invention is not particularly limited because it depends on the basis weight. For example, in the case of a sheet having a basis weight of 50 g / m ² , it is preferably 100 to 20000 seconds / 100 cc.

In addition, this invention is not limited to the said embodiment.
For example, the alkali treatment process may be omitted, and the defibration process may be performed after the acid group formation process.

Example 1
As a fiber raw material containing cellulose, a hardwood bleached kraft pulp (LBKP) having a carboxyl group content of 0.05 mmol / g, a solid content concentration of 30% by mass (water content of 70% by mass), and an absolute dry mass conversion was prepared.
The LBKP was placed in a container, and 2 L of an ozone / oxygen mixed gas having an ozone concentration of 200 g / m ³ was introduced into the container and shaken at 25 ° C. for 2 minutes. The ozone addition rate at this time was 2 mass% with respect to the pulp dry mass. After standing for 6 hours, ozone and air in the container were removed, and the ozone oxidation treatment was completed.
After the treatment, the suspension was washed with ion-exchanged water, and the washing was repeated until the pH of the washing water reached 6 or higher. Then, it filtered under reduced pressure using the filter paper, and obtained the oxidation process pulp with a solid content concentration of 20 mass%.
Next, 11.27 g of sodium dihydrogen phosphate dihydrate and 8.07 g of disodium hydrogen phosphate are dissolved in 22.60 g of water, and an aqueous solution of a phosphate compound (hereinafter referred to as “phosphorylation reagent”). Got. The pH of this phosphorylating reagent was 6.0 at 25 ° C.
41.94 g of the phosphorylating reagent (20 parts by mass as the amount of phosphorus element with respect to 100 parts by mass of dry pulp) is added to 100 g of the oxidized pulp having a solid content of 20% by mass, and an air dryer at 105 ° C. It was dried until the mass became constant while being kneaded once every 15 minutes with a company DKM400). Subsequently, it heat-processed with the 150 degreeC ventilation drying machine for 1 hour, and introduce | transduced the phosphate group into the cellulose.
Subsequently, ion-exchange water was added to the pulp into which the phosphate group was introduced to prepare a slurry having a solid content concentration of 2% by mass. Sodium hydroxide was added to the slurry so that the sodium hydroxide concentration was 0.3% by mass, and the mixture was stirred for 5 minutes and then allowed to stand at room temperature for 30 minutes. Subsequently, the suspension was washed with ion-exchanged water, and washing was repeated until the pH of the washing water became 8 or less to obtain a slurry containing alkali-treated pulp.
Next, ion-exchanged water was added to the slurry to prepare a cellulose fiber aqueous dispersion having a cellulose fiber concentration of 0.5% by mass. The cellulose fiber aqueous dispersion was defibrated for 30 minutes using a defibrating apparatus (Cleamix-2.2S, manufactured by M Technique Co., Ltd.) at 21500 rpm. Thereafter, using a centrifuge (“H-200NR” manufactured by Kokusan Co., Ltd.), the mixture was treated at about 12000 G for 10 minutes, and the supernatant thus separated was recovered as an aqueous dispersion of fine fibrous cellulose.

(Example 2)
An aqueous dispersion of fine fibrous cellulose was obtained in the same manner as in Example 1 except that the amount of the ozone / oxygen mixed gas introduced was 5 L (ozone addition rate 5 mass%).

(Example 3)
An aqueous dispersion of fine fibrous cellulose was obtained in the same manner as in Example 1 except that the amount of ozone / oxygen mixed gas introduced was 10 L (ozone addition rate 10 mass%).

Example 4
An aqueous dispersion of fine fibrous cellulose was obtained in the same manner as in Example 1 except that the amount of ozone / oxygen mixed gas introduced was 20 L (ozone addition rate 20 mass%).

(Example 5)
An aqueous dispersion of fine fibrous cellulose was obtained in the same manner as in Example 1 except that the amount of ozone / oxygen mixed gas introduced was 30 L (ozone addition rate: 30 mass%).

(Example 6)
The same LBKP as in Example 5 was placed in a container, and 30 L of an ozone / oxygen mixed gas having an ozone concentration of 200 g / m ³ was introduced into the container and shaken at 25 ° C. for 2 minutes. The ozone addition rate at this time was 30 mass% with respect to the pulp dry mass. After standing for 6 hours, ozone and air in the container were removed, and the ozone oxidation treatment was completed.
After the treatment, the suspension was washed with ion-exchanged water, and the washing was repeated until the pH of the washing water reached 6 or higher. Then, it filtered under reduced pressure using the filter paper, and obtained the ozone oxidation process pulp with a solid content concentration of 20 mass%.
Next, 400 g of 2 mass% sodium bisulfite (corresponding to 40 mass% as sodium bisulfite with respect to the absolute dry mass of the cellulose fiber) was added to 100 g of the oxidized pulp having a solid content of 20 mass%. The mixture was reacted at 70 ° C. for 3 hours to introduce sulfonic acid groups into the cellulose. After the treatment, the suspension was washed with ion-exchanged water, and the washing was repeated until the pH of the washing water reached 6 or higher.
In the same manner as in Example 1, the above oxidized pulp (20 g in terms of absolute dry mass) was subjected to alkali treatment, fibrillation treatment, and centrifugal separation treatment with sodium hydroxide to obtain an aqueous dispersion of fine fibrous cellulose. .

(Comparative Example 1)
An aqueous dispersion of fine fibrous cellulose was obtained in the same manner as in Example 1 except that the amount of ozone / oxygen mixed gas introduced was 30 L (ozone addition rate: 30 mass%), and the formation of phosphate groups was omitted. It was.

(Comparative Example 2)
An aqueous dispersion of fine fibrous cellulose was obtained in the same manner as in Example 1 except that phosphoric acid groups were formed without subjecting LBKP to ozone oxidation.

(Comparative Example 3)
An aqueous dispersion of fine fibrous cellulose was obtained in the same manner as in Example 1 except that sulfonic acid groups were formed without subjecting LBKP to ozone oxidation treatment.

(Comparative Example 4)
An aqueous dispersion of fine fibrous cellulose was obtained in the same manner as in Example 1 except that the amount of ozone / oxygen mixed gas introduced was 60 L (ozone addition rate 60 mass%) and the formation of phosphate groups was omitted. It was.

  In each Example and each Comparative Example, the defibration yield was measured using an aqueous dispersion containing fine fibrous cellulose. That is, the centrifugal recovery rate of the aqueous dispersion containing fine fibrous cellulose was determined from the following formula, and the centrifugal recovery rate was defined as the fibrillation yield. The results of the defibration yield are shown in Table 1.

Moreover, in each Example and each comparative example, about the oxidized pulp after completion | finish of an oxidation process, content of the carboxy group was measured by the method as described in the said paragraph [0011]. Table 1 shows the results of the content of carboxy groups.
Further, the phosphoric acid group or sulfonic acid group content of the obtained fine fibrous cellulose was measured by the method described in Paragraph [0013] or Paragraph [0056]. The measurement results are shown in Table 1.
Moreover, the polymerization degree of the obtained fine fibrous cellulose was measured. In the measurement of the degree of polymerization, first, a fine fibrous cellulose (concentration of about 0.5% by mass) was reduced in pressure on a 500 mesh polyester mesh to prepare a wet sheet, dried at 105 ° C., and a dry sheet was obtained. Obtained. Next, the obtained dry sheet was dissolved in a 0.5 M copper ethylenediamine solution, and the degree of polymerization was determined by a viscosity method. Table 1 shows the measurement results of the degree of polymerization.

Moreover, the viscosity and dispersion stability of the aqueous dispersion containing each fine fibrous cellulose were measured.
The viscosity was measured at 25 ° C. using a B-type viscometer (manufactured by BROOKFIELD) using a dispersion containing 0.5% by mass of fine fibrous cellulose as a measurement sample.
In the dispersion stability, first, in the obtained aqueous dispersion of fine fibrous cellulose itself, a gel is formed and the fluidity is lost, and the dispersion is unstable (denoted as “x” in the table). The gel was not formed and the fluidity was maintained, and the dispersion was stable (denoted as “◯” in the table). Since the aqueous dispersion of fine fibrous cellulose is alkaline, this dispersion stability is evaluated on the alkaline side.
Next, the degree of gelation when 1N hydrochloric acid was dropped into a fine fibrous cellulose dispersion (concentration 0.2% by mass) was evaluated. Specifically, first, 100 ml of the dispersion containing the fine fibrous cellulose was stirred with a magnetic stirrer set at a rotation speed of 200 rpm. A 1N hydrochloric acid solution was slowly added dropwise to the stirred dispersion to adjust the pH to 3. At that time, the gel formed and lost the fluidity was determined as a dispersible unstable state (denoted as “x” in the table), and the gel was not formed and the fluidity was maintained. It was judged as a dispersion stable state (indicated as “◯” in the table). This dispersion stability is evaluated on the acidic side.

In Examples 1 to 6 in which (—COO ⁻ ) and (—O—PO ₃ ²⁻ ) or (—SO ₃ ⁻ ) were formed, the defibration yield was high. That is, a fine fibrous cellulose could be obtained with a high yield. Further, the degree of polymerization was small to some extent, and the viscosity was small. Moreover, the dispersion stability on the acidic side and the dispersion stability on the alkaline side were both high in the aqueous dispersion.
In Comparative Examples 1 and 4 where the ozone oxidation treatment was performed but the formation of phosphoric acid groups or sulfonic acid groups was omitted, the dispersion stability on the acidic side in the aqueous dispersion was insufficient.
Comparative Examples 2 and 3 which were not subjected to ozone oxidation treatment had a high degree of polymerization and a high viscosity.

Claims (11)

A fine fibrous cellulose having a functional group represented by the following formula (1) and a functional group represented by the following formula (2).
(1) (—COO ⁻ ) _p · X ^{p +}
(2) (—O—PO ₃ ²⁻ ) · Y ^{q +} _3−q
(Where p is a natural number of 1 to 3. X ^{p +} is at least 1 selected from the group consisting of an alkali metal cation, ammonium ion, aliphatic ammonium ion, and aromatic ammonium ion when p = 1. In addition, when p = 2 or 3, it is at least one selected from the group consisting of alkaline earth metal ions or polyvalent metal ions, ^q is 1 or 2. Y ^{q +} _3-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, It is at least one selected from the group consisting of cations or cations of polyvalent metals.) A fine fibrous cellulose having a functional group represented by the following formula (1) and a functional group represented by the following formula (3).
(1) (—COO ⁻ ) _p · X ^{p +}
(3) (—SO ₃ ⁻ ) _r · Z ^{r +}
(Where p and r are each independently a natural number of 1 to 3. X ^{p +} and Z ^{r +} are alkali metal cations, ammonium ions, and aliphatic ammonium ions when p = 1 and r = 1. And at least one selected from the group consisting of aromatic ammonium ions, and when p = 2 or 3, r = 2 or 3, a group consisting of an alkaline earth metal cation or a polyvalent metal cation. At least one selected from   The fine fibrous cellulose according to claim 1 or 2, wherein the degree of polymerization is in the range of 50 to 500.   The fine fibrous cellulose according to any one of claims 1 to 3, wherein the average fiber width is 200 nm or less.   An oxidation step of oxidizing a fiber raw material containing cellulose to form a carboxy group, and after the oxidation step, forming the phosphate group by treating the fiber raw material with an oxo acid containing a phosphorus atom or a salt thereof. And an acid group forming step of obtaining acid group-forming cellulose.   An oxidation step of oxidizing a fiber raw material containing cellulose to form a carboxy group, and after the oxidation step, forming the sulfonic acid group by treating the fiber raw material with an oxo acid containing a sulfur atom or a salt thereof. And an acid group forming step for obtaining acid group-containing cellulose.   The method for producing fine fibrous cellulose according to claim 5 or 6, wherein in the oxidation step, at least ozone treatment is applied to the fiber raw material to form a carboxy group.   The acid treatment is performed according to any one of claims 5 to 7, which comprises an alkali treatment step for obtaining a cellulose salt by subjecting the acid group-containing cellulose to an alkali treatment and a defibration step for defibrating the cellulose salt after the acid group formation step. Of producing fine fibrous cellulose.   The manufacturing method of the fine fibrous cellulose as described in any one of Claims 5-7 which has the fibrillation process which fibrillates an acid group containing cellulose after an acid group formation process.   A fine fibrous cellulose dispersion, wherein the cellulose fibers according to claim 1 or 2 are dispersed in a dispersion medium.   A nonwoven fabric comprising the fine fibrous cellulose according to claim 1 or 2.