JP3138756B2 - Cellulose fiber provided with shrink resistance and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shrink-proof cellulose fiber and a method for producing the same.

[0002]

BACKGROUND OF THE INVENTION Cellulose typified by cotton is widely used because of its many advantages such as moisture absorption and touch, but it has the disadvantage that it tends to shrink. Thus, various treating agents have been used to overcome such disadvantages. For example, a method of treating a cellulose fiber using a cellulose-reactive resin containing a urea formalin resin or a glyoxal resin as a derivative thereof as an active ingredient has been adopted.

However, the method of treating with such a cellulose-reactive resin has the following disadvantages. That is,
When cellulose fibers are treated with a cellulose-reactive resin containing a urea formalin resin or a glyoxal resin as a derivative thereof as an active ingredient, it is inevitable that formalin remains in the cellulose fibers even after the treatment. Formalin is known as a carcinogen, in addition to its peculiar odor, and adversely affects not only the working environment in the fiber treatment process but also consumers who use the final product. In recent years, safety orientation has been further increased, and the use of carcinogenic formalin tends to be strictly regulated and self-restraint is unavoidable.

[0004] Under the present circumstances, it has been desired that an epoch-making non-form processed cellulose fiber which does not use a urea formalin resin or a glyoxal resin appears.

[0005]

Means for Solving the Problems In view of such a situation, the present inventors have intensively studied to provide a cellulose fiber having the above-mentioned drawbacks and having a shrinkproof property. as a result,
By heat-treating an ester having at least two carboxyl groups of a polycarboxylic acid and an aliphatic or alicyclic polyol and a cellulose fiber, the ester can be firmly bonded to the cellulose fiber, and the cellulose fiber has a high durability. It has been found that excellent shrink resistance can be imparted. The present invention has been completed based on such findings.

That is, the present invention provides a method for heat-treating an ester having at least two carboxyl groups of a polycarboxylic acid and an aliphatic or alicyclic polyol and a cellulose fiber, thereby obtaining a carboxyl group in the ester and a cellulose fiber. The present invention relates to a cellulose fiber imparted with shrinkage resistance, which is obtained by subjecting the above ester to an esterification reaction with a hydroxyl group of the above and bonding the ester to the cellulose fiber through an ester bond.

The cellulosic fibers in the present invention include cotton, hemp, rayon and blended fibers containing these fibers, and also products such as woven, knitted and non-woven fabrics made of these fibers.

[0008] In the present invention, the ester acting on the cellulose fiber is an ester of a polycarboxylic acid and an aliphatic or alicyclic polyol and has at least two carboxyl groups in the molecule.

As the polycarboxylic acid which is one component constituting the ester of the present invention, conventionally known polycarboxylic acids can be widely used, and examples thereof include linear aliphatic polycarboxylic acids, branched aliphatic polycarboxylic acids, and alicyclic rings. Group polycarboxylic acids, aromatic polycarboxylic acids, and the like, and these acids may have a halogen atom, a carbonyl group, a carbon-carbon double bond, and the like. Specific examples of such polycarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid and the like, and their branched carboxylic acids, maleic acid and fumaric acid. Alicyclic dibasic acids such as saturated dibasic acid, cyclohexanedicarboxylic acid, tetrahydrophthalic acid and nadic acid; tribasic acids such as tricarballylic acid, aconitic acid and methylcyclohexentricarboxylic acid; butanetetracarboxylic acid; cyclopentanetetracarboxylic acid Acid, tetrahydrofurantetracarboxylic acid, tetrabasic acids such as ene adduct of methyltetrahydrophthalic acid and maleic acid, o-phthalic acid, m-phthalic acid,
Examples thereof include aromatic polycarboxylic acids such as p-phthalic acid, trimellitic acid, pyromellitic acid, biphenyltetracarboxylic acid, benzophenonetetracarboxylic acid, and diphenylsulfonetetracarboxylic acid. Among these polycarboxylic acids, water-soluble and tetrabasic acid butanetetracarboxylic acid is the most suitable because it can further exert the effect of the present invention that it can impart excellent durability and shrink-proof performance to cellulose fibers. .

As the aliphatic or alicyclic polyol which is another component constituting the ester of the present invention, conventionally known ones can be widely used. As the aliphatic polyol, specifically, ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, dodecanediol, neopentylglycol, methylpentanediol, trimethylpentane Diol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,2-
Polymers of butylene oxide, aliphatic diols such as polytetramethylene glycol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, diglycerin, triglycerin, polyglycerin, xylitol, sorbitol, mannitol , Reducing sugars such as erythritol,
Monosaccharides such as xylose, sorbose, arabinose, ribose, erythrose, and galactose; and disaccharides such as lactose, sucrose, and maltose. Specific examples of the alicyclic polyol include cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, spiroglycol, and the like, and geometric isomers thereof. Further, polyester polyols of the above polyols and polycarboxylic acids are also included in the polyol of the present invention. Among the above polyols, aliphatic to alicyclic diols are preferred. The polyester polyol is preferably not crosslinked and gelled, and is preferably at least soluble in a solvent, and if possible, water soluble. However, those which can be emulsified and solubilized by using a surfactant can be used even if they are insoluble in water.

[0011] Among the above aliphatic or alicyclic diols,
Water soluble and excellent in operability, molecular weight 200 to 20
Polyethylene glycol having a molecular weight of about 000 is preferred, and polyethylene glycol having a molecular weight of about 400 to 2,000 is most preferred. In such polyethylene glycol,
The fraction components such as ethylene glycol, diethylene glycol, triethylene glycol and tetraethylene glycol may be mixed. If the molecular weight of the ethylene glycol is too large, it is difficult to exhibit the effect of the present invention that it can impart shrinkage resistance with excellent durability to the cellulose fiber, while if the molecular weight is too small,
Although the effects of the present invention are exhibited, the production of esters becomes difficult, which is not practically preferable.

When an aliphatic or alicyclic diol is used as the aliphatic or alicyclic polyol, the most typical structure of an ester of a polycarboxylic acid and the diol is as follows.

(A)-(B)-(A) [A is a group derived from a polycarboxylic acid, and when the polycarboxylic acid is a dicarboxylic acid, (HO ₂ C) (R) CO
₂ , In the case of tricarboxylic acid, (HO ₂ C) ₂ (R) C
In the case of O ₂ or tetracarboxylic acid, (HO ₂ C) ₃ (R) C
O ₂ . B is a residue derived from an aliphatic or alicyclic diol. As the ester used in the present invention, a water-soluble ester is preferable from the viewpoint of workability. The most preferred of the esters are one mole of polyethylene glycol and 1,
An ester with 2,3,4-butanetetracarboxylic acid 2 mol, that is, an ester having the following structure.

[0014]

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The composition ratio of the aliphatic or alicyclic diol constituting the ester and the polycarboxylic acid is 2 mol of the polycarboxylic acid to 1 mol of the diol. But,
The ester of the present invention may contain a polyester or oligoester compound corresponding to a composition of 2 mol or less of polycarboxylic acid per 1 mol of diol mixed during ester production.

The cellulose fiber of the present invention is produced, for example, by impregnating the above-mentioned ester with the cellulose fiber and subjecting the cellulose fiber to heat treatment.

When impregnating the cellulose fibers with the ester, the cellulose fibers may be immersed in a treatment liquid containing the ester. The treatment liquid usually comprises the ester and a solvent. As the solvent, an organic solvent can be used, but it is preferable to use water as the solvent in consideration of safety and cost. When the ester does not dissolve in water, it is preferable to prepare a liquid in which the ester is emulsified or solubilized with a surfactant. Here, as the surfactant, conventionally known surfactants can be widely used as long as they are active in an acidic aqueous solution.Examples thereof include an ethylene oxide adduct of an alkylphenol, an ethylene oxide adduct of a higher alcohol, an alkylbenzene sulfonate, an alkyl sulfate, and an alkyl sulfate. Examples include betaines, sorbitan fatty acid esters and ethylene oxide adducts thereof, fatty acid monoglycerides and ethylene oxide adducts thereof, and the like. In the present invention, an ethylene oxide adduct of an alkylphenol and an ethylene oxide adduct of a higher alcohol, which are stable for a long time in an acidic aqueous solution and are not easily affected by an alkali for pH adjustment described below, are particularly preferable. The amount of the surfactant used is not particularly limited as long as the ester can be stably dispersed in water.
What is necessary is just to mix | blend about 10 weight%.

In the present invention, it is desirable to further blend a polycarboxylic acid in the above-mentioned treating solution. By using the above-mentioned ester and polycarboxylic acid in combination, the shrinkage-preventing effect of the present invention is further enhanced. The polycarboxylic acid used in combination with the ester may be the same carboxylic acid as the polycarboxylic acid constituting the ester or a different polycarboxylic acid. When the polycarboxylic acid does not dissolve in a solvent such as water, the above surfactant may be used.

The concentration of the ester or the concentration of the polycarboxylic acid in the treatment liquid may be set to a concentration calculated from the squeezing rate of the treatment liquid and the required impregnation amount. The amount of the ester to be impregnated into the cellulose fiber is usually about 1 to 100% by weight, preferably about 5 to 50% by weight based on the cellulose fiber. If the impregnated amount of the ester is too small, it is difficult to exhibit the effect of the present invention that it is possible to impart excellent shrinkage resistance with excellent durability to the cellulose fiber, while the effect corresponding to the impregnated amount even when impregnated in a large amount becomes difficult. Not effective and not economical. The amount of the polycarboxylic acid to be impregnated into the cellulose fiber varies depending on the type of the polycarboxylic acid used and cannot be unconditionally determined, but is usually 0.1 to 50% by weight based on the cellulose fiber.
Level, preferably about 0.5 to 20% by weight. If the amount of polycarboxylic acid impregnated is too small, the combined effect with the above ester is insufficient, and even if impregnated in a large amount, the effect corresponding to the impregnated amount is not exhibited, and it is not economical.

It is desirable that the pH of the solution is previously adjusted by adding a pH adjuster to the aqueous solution in which the ester or the ester and the polycarboxylic acid are dissolved. The pH range is usually in the range of 1 to 6, preferably 2 to 5. When the pH of the liquid is higher than the above range, the shrinkage-preventing effect tends to be difficult to be exhibited, while when the pH of the liquid is lower than the above range, a decrease in fiber strength due to hydrolysis of cellulose tends to be unavoidable. Is not preferred. As the pH adjuster, an alkali or a salt thereof is usually used. Specific examples of the pH adjuster include, for example, sodium hydroxide, sodium bicarbonate, sodium borate, sodium metaborate, sodium silicate, sodium metasilicate, sodium phosphate, sodium metaphosphate, sodium polyphosphate, sodium pyrophosphate ,
Examples include sodium phosphite, sodium hypophosphite, sodium formate, sodium acetate and the like. The above pH
Instead of sodium as a modifier, potassium, ammonium and the like, and salts of volatile lower amines such as methylamine, dimethylamine, trimethylamine and triethylamine can also be used. These may be used alone or in combination of two or more. The amount of these pH adjusters varies depending on the amounts and types of the above-mentioned esters and polycarboxylic acids, and cannot be determined unconditionally. However, it is generally preferable to add about 0.1 to 10% by weight in the treatment solution.

In the present invention, the cellulose fibers to be treated are immersed in the treatment liquid prepared as described above, squeezed according to the required impregnation amount, and then dried.

The rate of penetration of the treatment liquid of the present invention into cellulose fibers is sufficiently high, and there is no particular limitation on the immersion time and bath temperature. Usually, the immersion time is 0.5 to 300 seconds and the bath temperature is 10
Performed at ４０40 ° C. The drawing differs depending on the cellulose fiber product to be processed, and an appropriate drawing method and a drawing ratio can be adopted for each. Usually, it is preferable to set the aperture ratio at 40 to 200%. The temperature for the subsequent drying is 40 ~
The temperature is preferably about 150 ° C., and the drying time may be appropriately set according to the temperature.

When heat-treating the cellulose fiber impregnated as described above, the temperature of the heat treatment is usually 100 to 250 ° C., preferably 120 to 200 ° C., and the heat treatment time is about 30 seconds to 1 hour. Is good. By this heat treatment, the hydroxyl group in the cellulose fiber and the carboxyl group in the ester undergo an esterification reaction, and the ester is firmly bonded on the cellulose fiber by an ester bond. If the conditions of the heat treatment are milder than the above, the shrinkage-preventing effect of the cellulose fibers tends to be hardly exhibited, while if the conditions are too severe, the cellulose fibers tend to deteriorate, and the strength decreases and the fiber yellows. Are not preferred.

Further, the cellulose fiber of the present invention is obtained by impregnating the cellulose fiber with a polycarboxylic acid and an aliphatic or alicyclic polyol instead of the above-mentioned ester.
It is also produced by heat-treating the cellulose fiber. The polycarboxylic acid impregnated in the cellulose fibers and the aliphatic or alicyclic polyol react by the heat treatment to produce an ester, and the produced ester has a carboxyl group in the cellulose fibers and a carboxyl group in the cellulose fibers. The hydroxyl group causes an esterification reaction, and the ester bonds to the cellulose fiber.

As the polycarboxylic acid and the aliphatic or alicyclic polyol used in this method, any of the polycarboxylic acid and the aliphatic or alicyclic polyol constituting the above ester can be used. Further, as the polycarboxylic acid, various carboxylic acids having a hydroxyl group in a molecule such as hydroxy fatty acids such as malic acid, tartaric acid and citric acid can be used. As the polycarboxylic acid used here, a water-soluble, tetrabasic acid butanetetracarboxylic acid is particularly preferred. Water-soluble carboxylic acids such as tricarballylic acid, aconitic acid, and citric acid are compounds that have good workability and are preferably used. The aliphatic or alicyclic polyol has a molecular weight of 200 to 2,000.
Polyethylene glycol of about 0 is particularly preferred. The impregnation amount of the polycarboxylic acid varies depending on the type of the polycarboxylic acid used and cannot be unconditionally determined, but is usually about 0.1 to 50% by weight, preferably 0.5 to 20% by weight based on the cellulose fiber to be usually treated. It is good to be about weight%. If the impregnated amount of the polycarboxylic acid is too small, the shrinkage-preventing effect is insufficient, and even if impregnated in a large amount, the effect corresponding to the impregnated amount is not exhibited and it is not economical. The amount of the impregnated polyol is different depending on the kind of the polyol used and cannot be unconditionally determined, but is usually about 0.1 to 100% by weight, preferably 1 to 50% by weight based on the usually treated cellulose fiber.
It is good to be about. If the impregnated amount of the polyol is too small, the shrinkage-preventing effect is insufficient, and even if impregnated in a large amount, the effect corresponding to the impregnated amount is not exhibited and it is not economical.

The means for impregnating cellulose fibers with the polycarboxylic acid and the aliphatic or alicyclic polyol, the means for heating the impregnated cellulose, and the like can be performed in the same manner as described above.

The cellulose fibers processed as described above are further subjected to conventional means such as washing with water, soaping, and application of a fiber softener to obtain a desired product.

[0028]

According to the present invention, there is provided a cellulose fiber having excellent durability and imparted shrink resistance.

[0029]

EXAMPLES The present invention will be further clarified with reference to Reference Examples, Examples and Comparative Examples. Hereinafter, "%" means "% by weight".

Reference Example 1 Polyethylene glycol # 600 (hydroxyl value: 181) 6
2 g (0.1 mol), 46.8 g (0.2 mol) of 1,2,3,4-butanetetracarboxylic acid and 8 g of water
The reactor was charged into a reactor having a stirrer, the pressure of the reaction system was reduced, and the temperature was raised to 150 ° C. The reaction was continued while removing the produced water, and after 3 hours, a viscous liquid was obtained. The hydroxyl value of this product was trace and the neutralization value was 336 (mg KOH
/ G). This ester is hereinafter referred to as “ester A”.

Reference Example 2 Polyethylene glycol # 1000 (hydroxyl value 107)
Reference Example 1 except that 104 g (0.1 mol) was used.
A viscous liquid was obtained in the same manner as described above. The hydroxyl value of the product was a trace amount, and the neutralization value was 246 (mgKOH / g). This ester is hereinafter referred to as "ester B".

Reference Example 3 Polytetramethylene glycol # 650 (having a hydroxyl value of 17)
2) A viscous liquid was obtained in the same manner as in Reference Example 1 except that 65 g (0.1 mol) was used. The hydroxyl value of the product was a trace amount, and the neutralization value was 322 (mg KOH / g). This ester is hereinafter referred to as "ester C".

Reference Example 4 Hydroxyl value of 1 consisting of succinic acid and triethylene glycol
Except for using 79 g of the polyester polyol of No. 42,
A viscous liquid was obtained in the same manner as in Reference Example 1 above. The hydroxyl value of this product was trace and the neutralization value was 286 (mg KO).
H / g). This ester is hereinafter referred to as “ester D”
That.

Example 1 As a test cloth, a cotton knit cloth (Kanoko) (30 cm × 30 c) on which a marking of 20 cm × 20 cm was made in advance.
m) was used.

An aqueous solution was prepared by dissolving 10% of the ester A obtained in Reference Example 1 and 4% of monobasic sodium phosphate. The test cloth was immersed in the aqueous solution at 25 ° C. for 5 minutes and squeezed at a squeezing ratio of 80%. After drying at 100 ° C. for 10 minutes, heat treatment was performed at 180 ° C. for 3 minutes to obtain a heat-treated test cloth.

Example 2 A heat treatment test was conducted in the same manner as in Example 1 except that an aqueous solution in which 10% of the ester B obtained in Reference Example 2 and 4% of monosodium pyrophosphate were dissolved was used. Got the cloth.

Example 3 Ester A obtained in Reference Example 1 was 5%, 1,2,3,4
Heat treatment test cloth in the same manner as in Example 1 except that an aqueous solution in which 6% of butanetetracarboxylic acid, 4% of monosodium phosphate and 4% of sodium hypophosphite are used is used. I got

Example 4 13% of ester B obtained in Reference Example 2, 1,2,3
A heat treatment test was performed in the same manner as in Example 1 except that an aqueous solution in which 4-butanetetracarboxylic acid was dissolved at a ratio of 6%, monobasic sodium phosphate at 4% and sodium hypophosphite at a ratio of 4% was used. Got the cloth.

Example 5 An isopropanol solution in which the ester C obtained in Reference Example 3 was dissolved at a ratio of 10% was prepared. The test cloth used in Example 1 was immersed in the solution at 25 ° C. for 5 minutes, and the squeezing ratio was 12
After squeezing to 0%, it was dried at 80 ° C. for 5 minutes. Then 1,
An aqueous solution in which 2,3,4-butanetetracarboxylic acid was dissolved at a ratio of 6% and monosodium phosphate at a ratio of 8% was prepared, and the test cloth was immersed in the aqueous solution at 25 ° C. for 5 minutes. We stopped down at 80%. After drying at 100 ° C. for 10 minutes, heat treatment was performed at 180 ° C. for 3 minutes to obtain a heat-treated test cloth.

Example 6 10% of the ester D obtained in Reference Example 4 was 1,2,3,3
A heat-treated test cloth was obtained in the same manner as in Example 1 except that an aqueous solution in which 4-butanetetracarboxylic acid was dissolved at a ratio of 6% and sodium carbonate was dissolved at a ratio of 2% was used.

Example 7 A water solution in which 1,2,3,4-butanetetracarboxylic acid was dissolved at a ratio of 4%, polyethylene glycol # 600 at a ratio of 2% and sodium phosphate monobasic at a ratio of 4% was used. A heat-treated test cloth was obtained in the same manner as in Example 1 above.

Example 8 1,2,3,4-butanetetracarboxylic acid at a ratio of 4%, polyethylene glycol # 1000 at 2%, sodium phosphate monobasic at 2% and sodium hypophosphite at a ratio of 2% A heat-treated test cloth was obtained in the same manner as in Example 1 except that the dissolved aqueous solution was used.

Example 9 4% 1,2,3,4-butanetetracarboxylic acid, 2% polymethylenetetramethylene glycol # 650, 2% monosodium phosphate, 2% sodium hypophosphite
%, And a heat-treated test cloth was obtained in the same manner as in Example 1 except that an aqueous dispersion obtained by emulsifying a 10% adduct of coconut alcohol and ethylene oxide at a rate of 4% was used.

Example 10 Hydroxyl value of succinic acid and triethylene glycol 1
42% of polyester polyol 4%, 1,2,3,4
-4% of butanetetracarboxylic acid, 4% of monosodium pyrophosphate and 10% of coconut alcohol ethylene oxide
A heat-treated test cloth was obtained in the same manner as in Example 1 except that an aqueous dispersion in which the molar addition product was emulsified at a ratio of 4% was used.

Example 11 3% tricarballylic acid, polyethylene glycol # 6
A heat-treated test cloth was obtained in the same manner as in Example 1 except that an aqueous solution in which 00 was dissolved in a ratio of 2% and sodium monophosphate was dissolved in a ratio of 4% was used.

Example 12 Except that an aqueous solution containing 10% of citric acid, 2% of polyethylene glycol # 600 and 4% of sodium phosphate monobasic was used, and heat treatment was performed at 200 ° C. for 3 minutes. In the same manner as in Example 1, a heat-treated test cloth was obtained.

Comparative Example 1 The procedure of Example 1 was repeated except that soft water was used instead of the aqueous solution in which 10% of the ester A obtained in Reference Example 1 and 4% of sodium phosphate monobasic were dissolved. Thus, a heat-treated test cloth was obtained.

Comparative Example 2 A dried test cloth was obtained in the same manner as in Example 1 except that the heat treatment was not performed.

Comparative Example 3 A dry-treated test cloth was obtained in the same manner as in Example 7 except that the heat treatment was not performed.

Comparative Example 4 A heat-treated test cloth was obtained in the same manner as in Example 7 except that an aqueous solution in which 2% of polyethylene glycol # 600 and 4% of monosodium phosphate were dissolved was used.

Comparative Example 5 The procedure of Example 7 was repeated except that an aqueous solution in which 1,2,3,4-butanetetracarboxylic acid was dissolved at a ratio of 4% and sodium phosphate monobasic at a ratio of 4% was used. A heat-treated test cloth was obtained.

The operation of washing each of the treated test cloths obtained in Examples 1 to 12 and Comparative Examples 1 to 5 and drying with a tumbler was repeated 10 times, 20 times and 30 times. The marking distance of the test cloth after the above-mentioned operation was measured, and the ratio to the distance immediately after the heating or drying treatment was determined to be the shrinkage ratio. Table 1 shows the results.

[0053]

[Table 1]

Continued on the front page (72) Inventor Koichi Murai 4-6-6 Tenjin, Nagaokakyo-shi, Kyoto (72) Inventor Yoshiaki Sakai 1-23-6, Shirakashi-cho, Kashihara-shi, Nara Prefecture (72) Inventor Hiroyuki Miura Aichi Prefecture 175 Shinkai, Gohibo-cho, Konan-shi (72) Inventor Hiroshi Tsujimoto 1-1-1, Takasu-cho, Nishinomiya-shi, Hyogo Prefecture Mukogawa Danchi No.2 Building 918 (56) References JP-A-3-287864 (JP, A) JP-A Heihei 2-307974 (JP, A) Table 3-3-503072 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D06M 13/00-15/72

Claims (3)

(57) [Claims] 1. A heat treatment of a cellulose fiber and an ester having at least two carboxyl groups of a polycarboxylic acid and an aliphatic or alicyclic polyol, whereby a carboxyl group in the ester and a hydroxyl group in the cellulose fiber are converted. A cellulose fiber which has been subjected to an esterification reaction and has a shrinkproof property obtained by bonding the above ester to the cellulose fiber through an ester bond. 2. A cellulose fiber is impregnated with an ester having at least two carboxyl groups of a polycarboxylic acid and an aliphatic or alicyclic polyol, and then the cellulose fiber is subjected to a heat treatment, whereby the ester is added to the cellulose fiber. The method for producing cellulose fibers according to claim 1, wherein the cellulose fibers are bonded by an ester bond. 3. A cellulose fiber is impregnated with a polycarboxylic acid and an aliphatic or alicyclic polyol, and then the cellulose fiber is heated to esterify the polycarboxylic acid and the aliphatic polyol to form an ester. The method for producing cellulose fibers according to claim 1, wherein the ester produced is bonded to the cellulose fibers by an ester bond.