JP2001049591A - Fiber raw material and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fiber raw material comprising a specific carboxyl group- containing polysaccharide, to obtain a method for producing the same, and to obtain a molded article which has a high additive-adsorbing effect. SOLUTION: This fiber raw material comprises a polysaccharide which is obtained by oxidizing a polysaccharide such as cellulose with an oxidizing agent in the coexistence of an N-oxyl compound (2,2,6,6-tetramethyl-1-piperidine N-oxide) and a bromide (sodium bromide or the like) or an iodide to oxidize the primary hydroxyl groups of the glucose residues into carboxyl groups. The fiber raw material has a tear index of >=35 N.m/g and a water retention value of <=200%. The molded article comprises the fiber raw material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fiber material composed of a polysaccharide containing a specific amount of a carboxyl group, a method for producing the same, and a molded article composed of the fiber material.

[0002]

2. Description of the Related Art Fiber materials composed of polysaccharides such as cellulose have been used in various fields taking advantage of their safety and strength. In recent years, as the field of use of these fiber materials has expanded, diversification and higher functionality have been required.

[0003] Cellulose is a linear polymer having a β-1,4-glucan structure, and it is difficult to impart functionality by ionic bonding. However, cellulose has a small amount of carboxyl groups contained in cellulose fibers. Has been reported to play an important role in fiber functioning. For example, in the papermaking field, it is known that the amount of adsorbed paper additives correlates with the amount of carboxyl groups in pulp (Isokai et al., Journal of the Textile Society of Japan, p. 649-654 (1992)). Furthermore, in the case of chemical pulp, the amount of carboxyl groups contained in the raw material is less than 0.1 mmol / g. However, if more carboxyl groups are introduced into this pulp, the effect of adsorbing additives is high. Pulp can be obtained.

As a method for introducing a carboxyl group into a polysaccharide such as cellulose, an alkali cellulose intermediate obtained by alkali treatment of raw cellulose is reacted with monochloroacetic acid in an organic solvent such as isopropyl alcohol to form carboxymethyl cellulose (CMC). It is known to get However, the introduction of a carboxymethyl group increases the water swellability (water retention) of the fiber material, and when a sheet is formed, the inter-fiber bonding area increases and the mechanical properties change significantly. Further, in this reaction, monochloroacetic acid reacts with water present in the reaction system to generate a large amount of by-products, and the reaction efficiency is generally low. Furthermore, it is necessary to use monochloroacetic acid which is a toxic reagent.

On the other hand, attempts have been made to introduce a carboxyl group by an oxidation reaction treatment of a polysaccharide such as cellulose. For example, it is known that by adding nitrogen dioxide N ₂ O ₄ to cellulose dispersed in chloroform, a primary hydroxyl group at the 6-position of glucose residue of cellulose is oxidized to a carboxyl group (Yackel) et al.,
Journal of American Chemical Society
(J. Am. Chem. Soc.), 64, p.121-127, (1942)).
However, in this method, a side reaction cannot be avoided and uniform oxidation cannot be achieved. Further, since highly toxic N ₂ O ₄ is used, it is not industrially practical.

There is also known a method in which an aldehyde group is introduced by cleaving between the C2 and C3 positions in a cellulose molecule by an oxidation reaction with periodic acid. However, this method cannot suppress a decrease in molecular weight and side reactions, and thus cannot be said to be a practical method.

[0007] As described above, in the oxidation reaction of cellulose using nitrogen dioxide or periodic acid, the mechanical strength of the formed sheet is deteriorated due to the cleavage of the cellulose main chain.

[0008] JP-A-10-251302 discloses that
2,2,6,6-tetramethyl-1-piperidine N-
There is disclosed a method of oxidizing alkali-treated cellulose or regenerated cellulose using an oxidizing agent in the presence of an oxyl compound (hereinafter sometimes simply referred to as “TEMPO”). This document discloses that a water-soluble cellulose in which primary hydroxyl groups of glucose residues are almost entirely oxidized to carboxyl groups can be obtained.

In the method of oxidizing cellulose using TEMPO, a large amount of a hydrophilic carboxyl group is introduced, resulting in an increase in the water swelling property of the material, and thus the mechanical properties may be reduced.

[0010]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fiber material comprising a polysaccharide into which a specific amount of a carboxyl group has been introduced without increasing the water retention value (water retention ratio), and a process for producing the same. It is to provide a method.

[0011] It is another object of the present invention to provide a fiber material whose surface is composed of a selectively oxidized polysaccharide without deteriorating mechanical properties, and a method for producing the same.

It is still another object of the present invention to provide a molded article such as a fiber sheet in which the effect of adsorbing additives is greatly improved.

[0013]

Means for Solving the Problems In view of the above problems, the present inventors have conducted intensive studies. As a result, when the surface of a polysaccharide is oxidized by an oxidation reaction using TEMPO, a polysaccharide having a specific amount of a carboxyl group introduced therein is obtained. Was found to be obtained efficiently, and the present invention was completed.

That is, the fiber material of the present invention is composed of a polysaccharide (eg, cellulose or a derivative thereof) containing a carboxyl group in an amount of 0.1 to 1 mmol per gram of the material. In this fiber material, primary hydroxyl groups on the fiber surface are selectively oxidized. This fiber material has a high specific tensile index, for example, 35 N · m / g or more, and does not lower the mechanical properties. In addition, the water retention value (water retention ratio) is low (for example, 200% or less).

Such a fiber material is prepared by oxidizing the surface of a polysaccharide (eg, cellulose) fiber with an oxidizing agent in the presence of an N-oxyl compound (oxoammonium salt) represented by the following formula: Obtainable.

[0016]

Embedded image

(Wherein ring A is a non-aromatic group 5 which may have another hetero atom together with the nitrogen atom constituting the ring)
Or a ring composed of a 6-membered ring).
It includes 6,6-tetramethyl-1-piperidine N-oxyl and the like, but the N-oxyl compound may be present in the system as a reaction intermediate. Further, in the oxidation by the N-oxyl compound, it is considered that substantially the corresponding oxoammonium ion is a reaction intermediate, and if the reaction is mediated by this reaction intermediate, the reaction proceeds through the precursor of the oxoammonium ion. Is also good.

The oxidation reaction is carried out in an aqueous medium (particularly in water).
It is often carried out in the presence of the N-oxyl compound and a bromide or iodide. As the bromide or iodide, a compound which can be dissociated and ionized in water, for example, an alkali metal bromide or an alkali metal iodide can be used. Examples of the oxidizing agent include halogen, hypohalous acid, halogenous acid and perhalic acid or salts thereof, halogen oxides, nitrogen oxides, peroxides, and the like. Any oxidizing agent can be used.

The N-oxyl compound such as 2,2,6,6-tetramethyl-1-piperidine N-oxyl (TEMPO) is sometimes referred to as oxo ion, oxo cation or oxo radical. However, in the present specification, these compounds and the corresponding oxoammonium compounds are collectively referred to as “N-oxyl compounds”.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION [Polysaccharide] As a polysaccharide, it is only necessary to have a fiber-forming property and to have a primary hydroxyl group such as a hydroxymethyl group, and homoglycans and heteroglycans can be used. Or a derivative thereof, N-
Acetyl glucosamine polymer (chitin, chitosan, etc.)
And the like. Among these polysaccharides, cellulose or a derivative thereof is particularly preferred.

As the cellulose, as long as it is a polysaccharide having a β-1,4-glucan structure, cellulose derived from higher plants, cellulose derived from animals (such as sea squirt cellulose), cellulose derived from bacteria, etc., are exemplified. As regenerated cellulose (rayon,
Such as cellophane). In addition,
If necessary, cellulose chemically modified by esterification, etherification or the like (eg, cellulose ester such as cellulose acetate, cellulose ether, etc.) may be used. Usually, as the cellulose, cellulose derived from higher plants, for example, wood fibers (wood pulp such as conifers and hardwoods), seed hair fibers (cotton such as linters,
Bombax cotton, Kapok, etc.) are used. Preferred celluloses include wood pulp (sulfite method,
And wood linters obtained from conifers and hardwoods by conventional methods such as the craft method.
These celluloses may be further subjected to beating treatment by mechanical force to increase reactivity.

[0022] As cellulose, α-
High-purity cellulose having a high cellulose content (for example, α
Cellulose content 70-100% by weight, preferably 8
Cellulose (about 0 to 100% by weight) may be used.

[Oxidation or Carboxylation Reaction] In the oxidation step of oxidizing a polysaccharide using an oxidizing agent, in the present invention, at least an N-oxyl compound represented by the following formula (1) is present as a catalyst component: To carry out an oxidation reaction.

[0024]

Embedded image

(Wherein ring A is a non-aromatic group 5 which may have another hetero atom together with the nitrogen atom constituting the ring)
In the present invention, a polysaccharide (eg, cellulose) can be smoothly oxidized without alkali treatment (particularly without producing alkali cellulose), and a carboxyl group is introduced. it can.

In a preferred embodiment, the polysaccharide fiber is oxidized using an oxidizing agent in the presence of a catalyst component obtained by combining the N-oxyl compound (oxoammonium salt) with a bromide or iodide. By such an oxidation reaction, primary hydroxyl groups on the surface of the polysaccharide fiber can be selectively and efficiently converted to carboxyl groups. In particular, in cellulose, a part of the primary hydroxyl group of the glucose unit (the hydroxymethyl group at the 6-position of the glucose residue) present on the fiber surface can be efficiently oxidized to convert the hydroxymethyl group into a carboxyl group.

In the above formula (1), the ring A may have a 5- or 6-membered ring which may have another hetero atom (nitrogen atom, oxygen atom, sulfur atom) together with a nitrogen atom. The 5- or 6-membered ring may be condensed with an aromatic ring or the like. Examples of such a ring A include a pyrrolidine ring,
Imidazolidine ring, indoline ring, isoindoline ring,
Examples thereof include a ring having a non-aromatic 5-membered ring such as a carbazole ring and a ring having a non-aromatic 6-membered ring such as a piperidine ring, a piperazine ring and a morpholine ring. Preferred ring A includes a piperidine ring.

Preferred compounds are oxoammonium compounds represented by the following formula (1a), particularly the following formula (1b) (N-
Oxyl compounds).

[0029]

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(Wherein R ¹ , R ² , R ³ and R ⁴ are the same or different and represent an alkyl group having about 1 to 4 carbon atoms;
In the oxidation reaction, the compounds represented by the formulas (1), (1a) and (1b) are converted into the following formulas (2), (2a) and (2a) by oxidation of polysaccharide. (2b)

[0031]

Embedded image

(Wherein R ¹ , R ² , R ³ , R ⁴ , and ring A are the same as described above).
The hydroxy compound is reduced in the reaction system to form the above-mentioned formula (1),
It seems to be converted to the compounds represented by formulas (1a) and (1b). Therefore, it is considered that the N-oxyl compound, the oxoammonium compound, and the N-hydroxy compound are substantially equivalent in the reaction system.

Examples of the alkyl group represented by R ¹ , R ² , R ³ and R ⁴ include methyl, ethyl, propyl, isopropyl, butyl and the like, and usually a methyl group.
The compound represented by the formula (1a) includes 2,2,6,6-
Tetra C _1-3 alkyl-1-piperidinyloxy cation (2,2,6,6-tetra C _1-3 alkyl-1-piperidine N-oxyl), especially TEMPO (2,2
6,6-tetramethyl-1-piperidine N-oxyl). The N-oxyl compound such as TEMPO seems to function as a cation radical such as 2,2,6,6-tetramethyl-1-piperidinyloxy cation in water.

The amount of the N-oxyl compound represented by the above formula (1) is not particularly limited as long as it is a catalyst that exhibits an activity with respect to the oxidation reaction. , 0.01 to 15 parts by weight, preferably 0.1
10 to 10 parts by weight, more preferably about 0.1 to 5 parts by weight, and may be about 0.2 to 8 parts by weight. The amount of the N-oxyl compound to be used relative to the glucose unit of cellulose is, for example, 0.0001 to 0.1 times mol, preferably 0.001 to 0.1 times mol, particularly 0.001 to 0.1 times mol.
It is about 05 times mol.

The oxidation reaction conditions using the N-oxyl compound are not particularly limited, and should be optimized depending on the properties of the polysaccharide, the equipment used, and the like. However, the oxidation reaction in the presence of bromide or iodide is necessary. Is performed, the oxidation reaction can proceed smoothly even under mild conditions, and the introduction efficiency of the carboxyl group can be greatly improved.

As the bromide or iodide, various compounds (particularly, inorganic salts and metal halides) which are water-soluble and can be dissociated and ionized in water can be used. Bromide and iodide are oxidized by the oxidizing agent and OX in water.
^- anion (wherein, X represents a bromine atom or an iodine atom) generates, this anion appears to be involved in regeneration of the N- oxyl compound from the N- hydroxy compound.

Examples of the bromide or iodide include ammonium salts (ammonium bromide, ammonium iodide), alkali metal bromides or iodides (bromides such as lithium bromide, potassium bromide and sodium bromide, and lithium iodide). , Potassium iodide, iodide such as sodium iodide), alkaline earth metal bromide or bromide such as calcium bromide, magnesium bromide, strontium bromide, calcium iodide, magnesium iodide, strontium iodide And the like). These bromides and iodides can be used alone or in combination of two or more.

Preferred compounds include an alkali metal bromide (such as sodium bromide) or an alkali metal iodide (such as sodium iodide).

The amount of bromide and / or iodide used can be selected within a range capable of accelerating the oxidation reaction.
The amount is 0.1 to 100 parts by weight, preferably 1 to 80 parts by weight, more preferably about 5 to 60 parts by weight, or about 2 to 75 parts by weight with respect to 00 parts by weight. The amount of bromide and / or iodide used per glucose unit of cellulose is, for example, about 0.1 to 2 times, preferably about 0.2 to 1.5 times, and about 0.5 to 1 time. There may be.

When oxidized with an oxidizing agent in the presence of the catalyst component, even under mild conditions (for example, normal temperature and normal pressure),
Carboxyl groups can be efficiently introduced onto the surface of the polysaccharide fiber.

As the oxidizing agent, halogen (chlorine, bromine,
Iodine), a halogen-containing oxyacid or a salt thereof [hypoxia
Logenic acid or its salt (hypochlorous acid or its salt, hypobromite
Acid or its salt, hypoiodic acid or its salt),
Genic acid or its salt (chlorous acid or its salt, bromic acid or
Salt, iodic acid or its salt), perhalic acid or
Is a salt thereof (perchloric acid or a salt thereof, perbronic acid or a salt thereof,
Periodic acid or a salt thereof), halogen oxide
(For example, ClO, ClO_Two, Cl_TwoO₆, BrO_Two, Br
_ThreeO₇And nitrogen oxides (eg, N2
O, NO_Two, N_TwoO _ThreeEtc.), peroxides (hydrogen peroxide, peroxide
Acetic acid). These oxidants can be used alone or
Can be used in combination of two or more.

Examples of the hypohalite include hypochlorites [eg, ammonium hypochlorite, alkali metal salts (lithium hypochlorite, potassium hypochlorite, sodium hypochlorite, etc.), alkali hypochlorite, and the like. Earth metal salts (calcium hypochlorite, magnesium hypochlorite, strontium hypochlorite, etc.), and the corresponding hypobromite (lithium hypobromite, potassium hypobromite, And sodium hypoiodate (eg, lithium hypoiodite, potassium hypoiodite, sodium hypoiodite).

Examples of the halogenite include chlorites [eg, ammonium chlorite, alkali metal salts (lithium chlorite, potassium chlorite, sodium chlorite, etc.), and alkaline earth metal salts (eg, Calcium chlorate, magnesium chlorite, strontium chlorite, etc.), and the corresponding bromates and iodates.

Examples of perhalates include perchlorates [eg, ammonium perchlorate, alkali metal salts (such as lithium perchlorate, potassium perchlorate, sodium perchlorate, etc.), and alkaline earth metal salts (eg, perchlorate). Calcium chlorate, magnesium perchlorate, strontium perchlorate, barium perchlorate, etc.), and the corresponding periodates (lithium periodate, potassium periodate, sodium periodate, etc.), etc. Can be illustrated.

Preferred oxidizing agents include halogen-containing oxyacids or salts thereof, particularly hypohalites (preferably hypochlorites), especially alkali metal hypochlorites.

The amount of the oxidizing agent to be used can be selected according to the amount of carboxyl group introduced into the polysaccharide.
It can be selected from a range of about 1 to 10 moles, preferably about 0.01 to 5 moles, and more preferably about 0.01 to 1 mole.

The oxidation reaction is usually performed in an aqueous reaction system (in an aqueous medium) using water as a solvent. That is, when water-insoluble cellulose is used, the oxidation reaction is often performed in a heterogeneous reaction system in which fibers are suspended, and can be performed with stirring as necessary.

The method of the present invention is characterized in that the oxidation reaction can proceed smoothly even under mild conditions. Therefore, the reaction temperature is in an appropriate range, for example, 0 ° C.
It can be appropriately selected from the range of about 100 ° C. The reaction temperature is, for example, 0 ° C. to 50 ° C., preferably room temperature (10 to 3 ° C.).
The cellulose can be efficiently oxidized even at a low temperature of about 0 to about 25 ° C. The reaction may be carried out under pressure, but it is advantageous to carry out the reaction at normal pressure in terms of the reaction operation.

A carboxyl group is generated as the reaction proceeds, and a decrease in the pH of the reaction solution is observed. for that reason,
In order for the oxidation reaction to proceed efficiently, the reaction system must be in an alkaline region, for example, pH 9 to 12 (for example, 10 to 10).
12), and is preferably maintained at about 10 to 11. The pH of the reaction system can be adjusted by appropriately adding an alkali (such as an aqueous solution containing an alkali metal component such as an aqueous sodium hydroxide solution or ammonia) to the reaction system.

In a typical oxidation reaction, a polysaccharide fiber is suspended in water, and a predetermined amount of an N-oxyl compound (eg, TEMPO), an alkali metal bromide (eg, sodium bromide) or an alkali metal iodide (eg, sodium iodide, etc.) ) And an oxidizing agent (e.g., hypochlorite such as sodium hypochlorite, etc.),
It can be performed at room temperature (15-35 ° C.).

When the oxidation reaction is performed excessively for a long time,
An excessive carboxyl group may be introduced into the polysaccharide, and the mechanical strength of the fiber may decrease. Therefore, it is preferable that the oxidation reaction is terminated without water-solubilization while maintaining the water-insoluble form (non-uniform and suspended state). More specifically, a polysaccharide fiber (eg, 10 g of cellulose fiber) is mixed with an N-oxyl compound (eg, 0.025 g of TEMPO) and a bromide (eg, 0.25 g of sodium bromide) in an aqueous medium (750 ml of water). In the coexistence of an oxidizing agent (for example, a 10.5% aqueous solution of sodium hypochlorite 2.5-40m
When oxidizing using L), maintain the pH of the system at room temperature in the alkaline region (about 10.5), and add water-insoluble Fiber can be obtained.

After completion of the reaction, a poor solvent (for example, alcohols such as methanol and ethanol) is added to the reaction mixture to stop the reaction, and the product can be isolated by filtration. Since the product does not dissolve in water, it can be washed with a washing solution (water, a mixed solvent of ethanol / water, etc.).

The fiber material of the present invention may be variously derivatized (for example, acylation such as acetylation, carboxymethylation, methylation, ethylation, hydroxyethylation, hydroxypropylation, etc.), if necessary. May be performed.

The fiber material of the present invention comprises:
The carboxyl group is 0.07 to 1 mmol (for example, 0.1 to 1 mmol).
1-1 mmol), preferably 0.1-0.5 mmol (e.g., 0.12-0.5 mmol), more preferably 0.12-0.45 mmol (e.g., 0.12-mmol).
0.3 mmol), and the carboxyl group content may be about 0.1 to 0.2 mmol per 1 g of the raw material. For quantification of carboxyl groups, for example, TA
The method described in PPI test method T237 om-93 can be used. When the amount of carboxyl groups per gram of the material is in the above range, a sufficient effect is exerted on the adsorption efficiency of the wet end additive (anionic, cationic or nonionic wet end additive). Also, 1.0
If an attempt is made to introduce more than millimoles, many reaction reagents are required, which is not preferable in terms of production cost. When more carboxyl groups are introduced, the hydrophilicity of the material is developed, and the mechanical properties decrease,
Problems may arise depending on the application. In the fiber material of the present invention, polysaccharide fibers (for example, pulp for papermaking) may be treated with monochloroacetic acid to introduce carboxyl groups on the fiber surface.

Since the fiber material of the present invention has an oxidized fiber surface, the degree of polymerization does not decrease due to cleavage of the main chain. Therefore, when the carboxyl group content of the fiber material is in the above range, fluctuations in mechanical properties and water retention can be suppressed regardless of the amount of carboxyl groups introduced. Further, mechanical strength (specific tensile index, tear strength, Young's modulus, elongation at break, etc.) can be maintained at a high level. The specific tensile index is 35 N · m / g or more (for example, 35 to 50 N · m / g).
g), preferably about 35 to 40 Nm / g. Young's modulus is 1 to 4 GPa, preferably 1.5 to 3.5 G
Pa, more preferably about 2.5 to 3.2 GPa. Further, the elongation at break tends to decrease as the amount of carboxyl group introduced increases. The water retention value is, for example, 200% or less (for example, 10 to 200%), preferably 50 to 200%, and more preferably 100 to 200%.
%, Especially about 150 to 190%.

After the introduction of the carboxyl group, the fiber material of the present invention is subjected to various derivatizations (eg, alkylation such as acetylation, carboxylation, methylation, and ethylation, hydroxymethylation, hydroxypropylation, etc.). , Etc.).

[Molded Article] The fiber material of the present invention can be processed into a molded article such as a woven fabric or a paper sheet. As a method for producing a paper sheet, for example, TAPPI Test Method T205
The method described in sp-95 can be used. These processed products may contain additives such as, for example, wet end additives and sizing agents.

Since the paper sheet obtained from the fiber material of the present invention has a specific amount of carboxyl groups, it is excellent in the effect of adsorbing additives (for example, polyamidoamine-epichlorohydrin resin). The adsorbing effect of the additive is remarkable when the introduced amount of the carboxyl group is about 0.1 to 1.0 mmol per 1 g of the raw material, and is remarkable when the introduced amount is 0.1 to 0.2 mmol, The fixing of the additive to the fiber can be greatly improved. In particular, the addition of a polyamidoamine-epichlorohydrin resin significantly improves the mechanical strength of the paper. Therefore, the molded article of the present invention may be used alone or in combination with other pulp. The proportion of the fiber material of the present invention in the whole molded article can be selected from the range of about 10 to 100% by weight, preferably about 30 to 100% by weight.

The molded article of the present invention (particularly, a sheet-shaped molded article)
Since it can suppress fluctuations in water retention and mechanical properties, it can be used in various fields (for example, papermaking, wallpaper, etc.).

[0060]

According to the present invention, a primary hydroxyl group on the surface of a polysaccharide fiber can be selectively oxidized by an oxidation reaction, and a specific amount of a carboxyl group can be introduced. Therefore, since the fiber material composed of the polysaccharide contains a specific amount of carboxyl group without affecting the water retention and mechanical properties, the molded article composed of the fiber material is an additive. Excellent adsorption effect.

[0061]

EXAMPLES The present invention will be described below in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 10 g of beaten bleached hardwood kraft pulp (carboxyl group content 0.06 mmol / g) was added to TEMPO.
The suspension was suspended in 750 ml of ion-exchanged water containing 0.025 g and 0.25 g of sodium bromide, and the pH of the system was adjusted to 10.5 using a 0.5N aqueous sodium hydroxide solution. Using an aqueous solution of 10.5% by weight of sodium hypochlorite,
The reaction was carried out at 20 ° C. for 2 hours while maintaining the pH of the system at about 10.5. After stopping the reaction by adding ethanol to the system, the product was recovered by filtration and washed with ion-exchanged water. As a result, a cellulose fiber containing up to 0.47 mmol / g of carboxyl groups was obtained.

Example 2 Using tap water having a calcium concentration of 0.6 mmol / L,
A pulp suspension containing 0.15% by weight of the cellulose fiber was prepared, and a handsheet sheet of about 60 g / m ² was prepared according to the method of TAPPI Test Method T205sp-95. The paper sheet is dried at a temperature of 20 ° C. and a humidity of 65% for one day or more, and further dried at 105 ° C. for 30 minutes.
It was left at a temperature of 65 ° C. and a humidity of 65% for one day or more.

The water retention value, specific tensile index, elongation at break and Young's modulus of the obtained cellulose fiber or paper sheet with respect to the carboxyl group content were measured.

Each value was measured as follows. [Water retention value] A wet sample of cellulose fibers having a different carboxyl group content (corresponding to 0.1 g by absolute drying) in Example 1 was set in a 1G2 glass centrifuge tube with a glass filter, and centrifuged at 3000 rpm (about 2500 G) for 15 minutes. Dehydrated. Assuming that the weight of the dehydrated sample is W and the weight of the dehydrated sample after absolute drying is W ₀ , the water retention value (%) is obtained from the following equation
I asked.

Water retention value (%) = (W−W ₀ ) / W ₀ [Specific tensile index, elongation at break and Young's modulus] JIS P8
The sheet having a different carboxyl group content of Example 2 was prepared at 20 ° C. and 6 ° C. in accordance with No. 113 (TAPPI Test Method T404).
The humidity was adjusted to 0% relative humidity. Each sheet was cut into a strip having a width of 15 mm, and the sheet was pulled with a tensile tester (Tensilon), and the breaking load and breaking elongation were measured. The specific tensile index, elongation at break and Young's modulus were determined from the following formulas. Incidentally, absolute dry density was calculated based on the absolute dry weight W ₀ and the sheet volume obtained by the measurement of the water retention value.

(I) Specific tensile index (N · m / g) = (maximum stress (N / m^Two) / (Absolute dry density of sheet (g / m^Three)) = ((Maximum load (kg)) x 9.8) / (Sheet cross-sectional area (m^Two) X sheet dry density (g / m^Three)) (ii) Elongation at break (%) = [(L−L₀) / L₀] × 100 (where L is the sheet length at break, L₀Is the sheet before measurement
(Iii) The static Young's modulus (GPa) = [((_Two− (₁) / (Ε_Two−
ε₁)] × 10^-9 (Where ε_nIs ε_n= (L_n-L₀) / L₀(L_nIs a certain time
Length of sheet at n, L ₀Indicates the length of the sheet before measurement
) Indicates the strain represented by_nIs the strain ε_nAt
The measured stress (Pa) is shown. (n represents 1 or 2) The results are shown in FIGS. 1 and 2.

[Brief description of the drawings]

FIG. 1 is a graph showing the water retention value of the cellulose fibers obtained in Example 1.

FIG. 2 is a graph showing specific tensile index, Young's modulus and elongation at break of the paper sheet obtained in Example 2.

Claims (15)

[Claims] 1. A fiber material comprising a polysaccharide containing a carboxyl group in an amount of 0.1 to 1 mmol per gram of the material. 2. The fiber material according to claim 1, which has a specific tensile index of 35 N · m / g or more. 3. The fiber material according to claim 1, wherein the water retention value is 200% or less. 4. The fiber material according to claim 1, wherein the polysaccharide is cellulose or a derivative thereof. 5. The fiber material according to claim 4, wherein part of the 6-position of the glucose residue of cellulose or a derivative thereof is a carboxyl group. 6. The fiber material according to claim 1, comprising 0.1 to 0.5 mmol of carboxyl groups per gram of the material and comprising water-insoluble cellulose or a derivative thereof. 7. The following formula: (Wherein, ring A represents a ring composed of a non-aromatic 5- or 6-membered ring which may have another hetero atom together with a nitrogen atom constituting the ring) The method according to claim 1, wherein the surface of the polysaccharide fiber is oxidized using an oxidizing agent in the presence of the compound. 8. The method according to claim 8, wherein the N-oxyl compound is 2,2,6,6
The method for producing a fiber material according to claim 7, which is -tetramethyl-1-piperidine N-oxyl. 9. The method according to claim 7, wherein the fiber material is oxidized in an aqueous medium. 10. The method according to claim 7, wherein cellulose is oxidized with an oxidizing agent in the presence of an N-oxyl compound and a bromide or iodide ionizable in water. 11. The method according to claim 10, wherein the bromide or iodide is an alkali metal bromide or an alkali metal iodide. 12. The oxidizing agent is at least one selected from halogen, hypohalous acid, halogenous acid, perhalic acid or a salt thereof, halogen oxide, nitrogen oxide and peroxide. The method for producing the fiber material described in the above. 13. The method for producing a fiber material according to claim 7, wherein the fiber material is oxidized without being made water-soluble. 14. A molded article made of the fiber material according to claim 1. 15. The molded article according to claim 14, which is in the form of a sheet.