JP2005248341A - Crystalline cellulose ester fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide crystalline cellulose ester fiber having high heat resistance and giving soft touch feeling. <P>SOLUTION: The crystalline cellulose ester fiber is characterized by being made from a cellulose ester-based composition. The fiber has the following properties: number-average molecular weight is 15,000-150,000; melting point is 160-250°C; tenacity is 0.5-4.0 cN/dtex; elongation at break is 5-60%; Young's modulus is 10.0-30.0 cN/dtex; single filament fineness is 0.5-30.0 dtex; and fiber U% is ≤3.0%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a crystalline cellulose ester fiber having excellent heat resistance and a soft texture by having a melting peak of a crystal below the thermal decomposition temperature of a polymer.

  As cellulose ester fibers, fibers such as cellulose diacetate and cellulose triacetate are generally widely known. Since all of these fibers are derived from cellulose, they have very good characteristics for apparel such as good gloss, color developability and moisture absorption / release. However, these cellulose acetate fibers have the disadvantage that the hydroxyl group of the glucopyranose ring is modified only with an acetyl group having a small number of carbon atoms, and therefore the flexibility is poor, and the texture becomes stiff when made into a fabric. There was a problem of end.

  In order to solve this problem, a method has been proposed in which polyester polyol or polyether polyol having a molecular weight of 400 to 2000 is added to cellulose diacetate as a softening agent to give flexibility (see Patent Document 1). According to this method, the cellulose diacetate is softened by the low to medium molecular weight softening agent, and the texture becomes soft. However, with this method, the glass transition point of the polymer is lowered, and furthermore, since this polymer is amorphous, it is fused and measured by heating in a higher processing step, which is an essential step for clothing fibers. However, remarkable heat shrinkage occurred, and it was difficult to employ industrially.

  In order to increase the ratio of the cellulose diacetate component, a method has also been proposed in which the degree of polymerization of cellulose diacetate is lowered and fiberized (see Patent Document 2). However, since this method eventually contains a low to medium molecular weight softening agent, the glass transition point of the amorphous polymer is not lowered, and the above problem is not fundamentally solved. It was.

On the other hand, since cellulose triacetate has crystallinity, compatibility with a softening agent is remarkably low, and there is a problem that processing itself for softening the texture is difficult. For this reason, the cellulose ester fiber which was excellent in heat resistance by having crystallinity, but was soft was desired.
JP-A-9-78339 Japanese Patent Laid-Open No. 10-317228

  An object of the present invention is to overcome the above-described problems and provide crystalline cellulose ester fibers having excellent heat resistance and a soft texture.

  An object of the present invention described above is a crystalline cellulose ester fiber comprising a composition having a number average molecular weight of 15,000 to 150,000 and a cellulose ester having a melting point within a range of 160 to 250 ° C. as a main component. Can be solved.

  At that time, the strength of the crystalline cellulose ester fiber is 0.5 to 4.0 cN / dtex, the elongation is 5 to 60%, the Young's modulus is 10.0 to 30.0 cN / dtex, and the single fiber fineness is 0.5 to 30.0 dtex and U% of the fiber are preferably 3.0% or less. A cellulose ester having a total substitution degree of 2.85 to 3.00 can be suitably employed. Furthermore, it can be solved by crystalline cellulose ester fibers in which the cellulose ester is cellulose tripropionate or cellulose tributyrate.

  According to the present invention, a fiber having excellent heat resistance and a soft texture based on a cellulose derivative that has not been obtained in the past can be obtained. Thus, soft and supple that could not be expressed with conventional cellulose fibers, It is possible to obtain a fiber that does not cause heat shine or fusion, and also has good gloss, color developability, moisture absorption and desorption, etc. derived from cellulose. Thereby, it can use suitably for the clothing use whole.

  The crystalline cellulose ester fiber in the present invention comprises a cellulose ester composition, and the cellulose ester as the main component thereof has a number average molecular weight of 15,000 to 150,000. If the number average molecular weight is 15000 or more, the high elongation as a fiber can be maintained. Moreover, if it is 150,000 or less, it can be set as the soft texture of a fiber. The number average molecular weight is preferably 17,000 to 100,000, more preferably 20,000 to 75,000.

  Moreover, the cellulose ester in this invention has melting | fusing point in the range of 160-250 degreeC. Having a melting point means having a crystal part in the polymer, and means that it is difficult to be thermally deformed by heating below that temperature, that is, it has good heat resistance. The melting point in the present invention is obtained by DSC measurement using DSC-7 manufactured by PerkinElmer, Inc., once melted and cooled the polymer in a nitrogen atmosphere, and then heated again at 10 ° C./min. It is the peak temperature of the endothermic peak on the thermogram. However, the peak temperature of a weak peak whose peak width is wider than 50 ° C. or whose endotherm is less than 5 J / g is not recognized as the melting point. The lower the melting point, the more preferable because the fibers have a softer texture. Moreover, if it has melting | fusing point of 160 degreeC or more, it can endure the heating in a high-order processing process. Preferably it is 165-245 degreeC, More preferably, it is 170-240 degreeC.

  The crystalline cellulose ester fiber of the present invention has a strength of 0.5 to 4.0 cN / dtex, an elongation of 5 to 60%, a Young's modulus of 10.0 to 30.0 cN / dtex, and a single fiber fineness. It is preferable that 0.5 to 30.0 dtex and U% of the fiber is 3.0% or less. This can be achieved by using a composition whose main component is a cellulose ester having a number average molecular weight of 15,000 to 150,000 and having a melting point in the range of 160 to 250 ° C.

  A strength of 0.5 cN / dtex or more is preferable because it can be used as a fiber for clothing. The strength of the crystalline cellulose ester fiber of the present invention is more preferably 0.7 to 4.0 cN / dtex, and most preferably 1.0 to 4.0 cN / dtex.

  If the elongation is 5% or more, yarn breakage is difficult in high-order processing steps such as weaving and knitting. In addition, when the elongation is 60% or less, the fiber is not deformed if the stress is low, and a dyeing defect of the final product due to wetting marks at the time of weaving does not occur. The elongation is more preferably 10 to 45%, and most preferably 20 to 40%.

  A Young's modulus of 30.0 cN / dtex or less is preferable because the texture becomes soft. In addition, it is preferable that the Young's modulus is 10.0 cN / dtex or more because generation of wrinkles when made into a fabric can be suppressed. More preferably, it is 12.5-27.5 cN / dtex, Most preferably, it is 15.0-25.0 cN / dtex.

  When used as a clothing application, the single fiber fineness is preferably 0.5 to 30.0 dtex. More preferably, it is 1.0-20 dtex, Most preferably, it is 1.5-15 dtex. U% (Worster normal%) is the fineness unevenness in the length direction of the fiber, and the closer to 0, the better the fineness uniformity. It is a fiber excellent in the uniformity of the fineness that U% of the fiber is 3.0% or less, more preferably 2.5% or less, and most preferably 2.0% or less. Further, since the fiber fluctuation during spinning cannot be substantially eliminated, the lower limit of U% of the fiber is 0.1% or more.

  The crystalline cellulose ester fiber in the present invention is composed of a cellulose ester composition, and the total substitution degree of the cellulose ester as the main component is preferably 2.85 to 3.00. The total degree of substitution is the sum of the degree of substitution of each ester group. A high degree of substitution is preferred to produce crystals in the fiber. In addition, since the number of hydroxyl groups contained in the repeating unit of cellulose is 3, the upper limit of the total substitution degree is 3.00. The total degree of substitution is more preferably 2.87 to 3.00, and most preferably 2.90 to 3.00. The ester substituent may be one kind or two or more kinds. In that case, the substitution degree of each ester group can use arbitrary things.

  Examples of the cellulose ester used in the present invention include cellulose tripropionate, cellulose tributyrate, cellulose trivalerate, cellulose tricaprylate, cellulose trilaurate, cellulose tripalmitate, cellulose tristearate, cellulose triphthalate, Cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate valerate, cellulose acetate caprylate, cellulose acetate laurate, cellulose acetate palmitate, cellulose acetate stearate, cellulose acetate phthalate, cellulose propionate butyrate, etc. However, those that form crystals when fiberized are preferred, most preferably cellulose A Ropioneto or cellulose tributyrate.

  The fiberization method of the present invention is not particularly limited, and the dry spinning method employed in the current cellulose acetate or the like, the wet spinning method employed in rayon or the like, the melting employed in nylon or the like. Any known production method such as a spinning method may be employed. Moreover, in order to raise the crystallinity degree of the obtained fiber, after fiberizing, you may pass through an extending | stretching process using a well-known apparatus.

  The fiber cross-sectional shape is not particularly limited, and may be a perfect circular circular cross-section, and may be a multilobal, flat, elliptical, W-shaped, S-shaped, X-shaped, H-shaped, C-shaped, Different cross-section yarns such as a square shape, a cross beam shape, and a hollow shape may be used. Further, there may be some distortion of the fiber cross-sectional shape that occurs slightly when the wet spinning method or the dry spinning method is adopted.

  In the present invention, a weak organic acid, a phosphite, a thiophosphite, or the like is used alone or in combination of two or more kinds as a stabilizer for preventing thermal deterioration and preventing coloring, as long as the required performance is not impaired. A mixture may be added. In addition, additives such as lubricants, antistatic agents, dyes, pigments, lubricants, matting agents and the like may be blended.

  Hereinafter, the present invention will be described in detail by way of examples. In addition, the physical property in an Example was calculated | required with the following method.

A. Number average molecular weight Waters 2690 manufactured by Waters Co., Ltd. was used, polystyrene was used as an internal standard, measurement was performed at a column temperature of 40 ° C., a moving bed tetrahydrofuran, and a flow rate of 1 ml / min. The sample was completely dried, and the sample concentration was adjusted to 0.1% (w / v). The measurement was performed once per sample.

B. Melting point About 10 mg of a sample was precisely weighed, and obtained using DSC (DSC-7 manufactured by Perkin Elmer Co., Ltd.), once melted and cooled in a nitrogen atmosphere, and then heated again at 10 ° C./min. The peak temperature of the endothermic peak on the thermogram was taken as the melting point. However, the peak temperature of a weak peak with a peak width wider than 50 ° C. or an endothermic amount of less than 5 J / g is not recognized as a melting point, and the measurement was performed once per sample.

C. Strength, elongation and Young's modulus Tensilon UCT-100 manufactured by Orientec Co., Ltd. was used to conduct a tensile test under the conditions of a sample length of 20 cm and a tensile speed of 20 cm / min, and the stress at the point indicated by the maximum load was determined as the fiber strength (cN / Dtex), the elongation at break was defined as the elongation (%) of the fiber. The initial tensile resistance was defined as the fiber Young's modulus (cN / dtex). The measurement was performed 5 times per sample, and the average value was adopted.

D. Single fiber fineness The value obtained by dividing the fineness of the obtained fiber by the number of cap holes was defined as the single fiber fineness. The measurement was performed once per sample.

E. U%
The measurement was performed once with a Worcester tester 4-CX manufactured by Zerbegger Worcester at a yarn feeding speed of 200 m / min, and the obtained Worcester normal% was defined as U% of the fiber.

F. Degree of substitution and total degree of substitution ¹ H NMR of cellulose ester was measured using a JEOL nuclear magnetic resonance apparatus (JNM-EX-270). The degree of substitution of each ester group was measured by the integral ratio of protons derived from the pyranose ring of cellulose and protons derived from each ester group. The measurement was performed once per sample, and the total degree of substitution was the sum of the degree of substitution of each ester group.

G. Texture Circular knitting was made using the obtained fibers, and the softness of the texture was evaluated by sensory test. The texture was evaluated by combining sensory tests with 10 subjects. Those that felt very good were marked with ◎, those that felt good with ○, normal with Δ, and inferior with ×. In this evaluation, it was determined that “O” or higher was acceptable.

H. Hot press A circular knitting was made using the obtained fiber, and it was pressed for 10 seconds using a Hashima fabric press (Harrilon transfer HT-130SG) set at 150 ° C. Sensory tests by 10 subjects were combined to evaluate the surface shine. The case where there was no change on the surface was rated as ◎, the case where there was no change as ◯, the case where it was slightly △ as the case, and the case where it was good as ×. In this evaluation, it was determined that “O” or higher was acceptable.

Synthesis example 1
Cellulose (dissolved pulp manufactured by Nippon Paper Industries Co., Ltd.) is dissolved in N, N-dimethylacetamide (DMAc) (manufactured by Wako Pure Chemical Industries, Ltd.) containing lithium chloride (LiCl) (manufactured by Wako Pure Chemical Industries, Ltd.). After that, the cellulose-containing DMAc / LiCl solution was heated to 40 ° C., and triethylamine (manufactured by Wako Pure Chemical Industries, Ltd.) was added 5 times the number of moles of cellulose hydroxyl group, propionic acid chloride (manufactured by Wako Pure Chemical Industries, Ltd.). After adding 7 times the number of moles, the reaction was carried out for 18 hours. After the reaction, the reaction solution was centrifuged, and the supernatant was reprecipitated with a large amount of water, filtered, and the collected filtrate was dried at 80 ° C. for 24 hours to obtain cellulose tripropionate. The number average molecular weight of the obtained cellulose tripropionate was 60,000, the total degree of substitution was 2.95, and the melting point was 240 ° C.

Example 1
Cellulose tripropionate obtained in Synthesis Example 1 is melted at a melter temperature of 260 ° C. using a short shaft type melt spinning machine, and a pack having 12 holes in a die hole at a discharge rate of 1.5 g / min. Spinning from a die with a part temperature of 260 ° C. The spun yarn is cooled by chimney wind, applied with an oil agent, converged, taken up by a first godet roller rotating at 500 m / min, and a second godet rotating at the same speed as the first godet roller It wound up with the winder through the roller. The obtained fiber had a strength of 1.5 cN / dtex, an elongation of 35%, a Young's modulus of 21.0 cN / dtex, a single fiber fineness of 2.5 dtex, and a fiber U% of 1.5%. Moreover, when the circular knitting was created with the obtained fiber and the softness of the texture was evaluated by a sensory test, it was very good. Further, when hot pressing was performed, the surface did not change at all.

Synthesis example 2
Cellulose tripropionate was obtained in the same manner as in Synthesis Example 1 except that 6 times mol of triethylamine, 6 times mol of propionic acid chloride and 25 hours of reaction time were used. The number average molecular weight of the obtained cellulose tripropionate was 90000, the total degree of substitution was 2.95, and the melting point was 240 ° C.

Example 2
The cellulose tripropionate obtained in Synthesis Example 2 was spun in the same manner as in Example 1 to obtain a fiber. The obtained fiber had a strength of 1.5 cN / dtex, an elongation of 30%, a Young's modulus of 22.0 cN / dtex, a single fiber fineness of 2.5 dtex, and a fiber U% of 1.8%. Moreover, when the circular knitting was created with the obtained fiber and the softness of the texture was evaluated by a sensory test, it was very good. Further, when hot pressing was performed, the surface did not change at all.

Synthesis example 3
Cellulose tripropionate was obtained in the same manner as in Synthesis Example 1 except that 7 times mole of triethylamine, 5 times mole of propionic acid chloride and 25 hours of reaction time were used. The number average molecular weight of the obtained cellulose tripropionate was 110,000, the total substitution degree was 2.95, and the melting point was 240 ° C.

Example 3
The cellulose tripropionate obtained in Synthesis Example 3 was spun in the same manner as in Example 1 to obtain a fiber. The obtained fiber had a strength of 1.5 cN / dtex, an elongation of 30%, a Young's modulus of 22.5 cN / dtex, a single fiber fineness of 2.5 dtex, and a fiber U% of 1.8%. Moreover, when the circular knitting was created with the obtained fiber and the softness of the texture was evaluated by a sensory test, it was very good. Further, when hot pressing was performed, the surface did not change at all.

Synthesis example 4
Cellulose tripropionate was obtained in the same manner as in Synthesis Example 1 except that triethylamine was 3 times mol, propionate chloride was 5 times mol and the reaction time was 16 hours. The number average molecular weight of the obtained cellulose tripropionate was 24,000, the total substitution degree was 2.90, and the melting point was 220 ° C.

Example 4
The cellulose tripropionate obtained in Synthesis Example 4 was spun in the same manner as in Example 1 to obtain a fiber. The obtained fiber had a strength of 1.0 cN / dtex, an elongation of 35%, a Young's modulus of 20.5 cN / dtex, a single fiber fineness of 2.5 dtex, and a fiber U% of 1.3%. Moreover, when the circular knitting was created with the obtained fiber and the softness of the texture was evaluated by a sensory test, it was very good. Further, when hot pressing was performed, the surface did not change at all.

Synthesis example 5
Cellulose tripropionate was obtained in the same manner as in Synthesis Example 1 except that triethylamine was 3 times mol, propionate chloride was 6 times mol and the reaction time was 16 hours. The number average molecular weight of the obtained cellulose tripropionate was 18000, the total degree of substitution was 2.90, and the melting point was 220 ° C.

Example 5
The cellulose tripropionate obtained in Synthesis Example 5 was spun in the same manner as in Example 1 to obtain a fiber. The obtained fiber had a strength of 0.8 cN / dtex, an elongation of 25%, a Young's modulus of 20.0 cN / dtex, a single fiber fineness of 2.5 dtex, and a fiber U% of 0.8%. Moreover, when the circular knitting was created with the obtained fiber and the softness of the texture was evaluated by a sensory test, it was very good. Further, when hot pressing was performed, the surface did not change at all.

Synthesis Example 6
Cellulose tripropionate was obtained in the same manner as in Synthesis Example 1 except that triethylamine was 3 times mol, propionate chloride was 7 times mol and the reaction time was 16 hours. The number average molecular weight of the obtained cellulose tripropionate was 16000, the total degree of substitution was 2.90, and the melting point was 220 ° C.

Example 6
The cellulose tripropionate obtained in Synthesis Example 6 was spun in the same manner as in Example 1 to obtain a fiber. The obtained fiber had a strength of 0.6 cN / dtex, an elongation of 25%, a Young's modulus of 20.0 cN / dtex, a single fiber fineness of 2.5 dtex, and a fiber U% of 0.7%. Moreover, when the circular knitting was created with the obtained fiber and the softness of the texture was evaluated by a sensory test, it was very good. Further, when hot pressing was performed, the surface did not change at all.

Synthesis example 7
Cellulose tripropionate was obtained in the same manner as in Synthesis Example 1 except that triethylamine was 3 times mol, propionyl chloride was 5 times mol and the reaction time was 13 hours. The obtained cellulose tripropionate had a number average molecular weight of 30,000, a total degree of substitution of 2.87, and a melting point of 240 ° C.

Example 7
The cellulose tripropionate obtained in Synthesis Example 7 was spun in the same manner as in Example 1 to obtain a fiber. The obtained fiber had a strength of 1.4 cN / dtex, an elongation of 35%, a Young's modulus of 20.5 cN / dtex, a single fiber fineness of 2.5 dtex, and a fiber U% of 1.3%. Moreover, when the circular knitting was created with the obtained fiber and the softness of the texture was evaluated by a sensory test, it was very good. Further, when hot pressing was performed, the surface did not change.

Synthesis example 8
Cellulose tripropionate was obtained in the same manner as in Synthesis Example 1 except that 3 times mole of triethylamine, 5 times mole of propionic acid chloride and 10 hours of reaction time were used. The number average molecular weight of the obtained cellulose tripropionate was 30000, the total degree of substitution was 2.85, and the melting point was 240 ° C.

Example 8
The cellulose tripropionate obtained in Synthesis Example 8 was spun in the same manner as in Example 1 to obtain a fiber. The obtained fiber had a strength of 1.4 cN / dtex, an elongation of 35%, a Young's modulus of 20.5 cN / dtex, a single fiber fineness of 2.5 dtex, and a fiber U% of 1.3%. Moreover, when the circular knitting was created with the obtained fiber and the softness of the texture was evaluated by a sensory test, it was very good. Further, when hot pressing was performed, the surface did not change.

Synthesis Example 9
Cellulose tripropionate was obtained in the same manner as in Synthesis Example 1 except that 3 times mole of triethylamine, 5 times mole of propionic acid chloride and 20 hours of reaction time were used. The obtained cellulose tripropionate had a number average molecular weight of 30,000, a total degree of substitution of 2.95, and a melting point of 240 ° C.

Example 9
The cellulose tripropionate obtained in Synthesis Example 9 was spun in the same manner as in Example 1 except that the discharge rate was 10.8 g / min to obtain a fiber. The obtained fiber had a strength of 1.5 cN / dtex, an elongation of 30%, a Young's modulus of 20.5 cN / dtex, a single fiber fineness of 18 dtex, and a fiber U% of 1.3%. Moreover, when the circular knitting was created with the obtained fiber and the softness of the texture was evaluated by a sensory test, it was good. Further, when hot pressing was performed, the surface did not change at all.

Synthesis Example 10
Cellulose tributyrate was obtained in the same manner as in Synthesis Example 1 except that triethylamine was 3 times mol, butyric acid chloride was 5 times mol and the reaction time was 25 hours. The number average molecular weight of the obtained cellulose tributyrate was 50000, the total degree of substitution was 2.98, and the melting point was 180 ° C.

Example 10
The cellulose tributyrate obtained in Synthesis Example 10 was spun in the same manner as in Example 1 to obtain a fiber. The obtained fiber had a strength of 1.0 cN / dtex, an elongation of 40%, a Young's modulus of 17.5 cN / dtex, a single fiber fineness of 2.5 dtex, and a fiber U% of 0.9%. Moreover, when the circular knitting was created with the obtained fiber and the softness of the texture was evaluated by a sensory test, it was very good. Further, when hot pressing was performed, the surface did not change at all.

Synthesis Example 11
Cellulose acetate propionate was obtained in the same manner as in Synthesis Example 1 except that triethylamine was 3-fold mol, acetic acid chloride was 1-fold mol, propionic acid chloride was 4-fold mol, and the reaction time was 13 hours. The obtained cellulose acetate propionate had a number average molecular weight of 30,000, a total degree of substitution of 2.90, and a melting point of 245 ° C.

Example 11
The cellulose acetate propionate obtained in Synthesis Example 11 was spun in the same manner as in Example 1 except that the discharge rate was 1.8 g / min to obtain a fiber. The obtained fiber had a strength of 0.8 cN / dtex, an elongation of 25%, a Young's modulus of 25.5 cN / dtex, a single fiber fineness of 3.0 dtex, and a fiber U% of 1.8%. Moreover, when the circular knitting was created with the obtained fiber and the softness of the texture was evaluated by a sensory test, it was good. Further, when hot pressing was performed, the surface did not change at all.

Synthesis Example 12
Cellulose acetate propionate was obtained in the same manner as in Synthesis Example 1 except that triethylamine was tripled, acetic acid chloride was doubled, propionic acid chloride was tripled, and reaction time was 13 hours. The obtained cellulose acetate propionate had a number average molecular weight of 30,000, a total degree of substitution of 2.90, and a melting point of 250 ° C.

Example 12
The cellulose acetate propionate obtained in Synthesis Example 12 was spun in the same manner as in Example 1 except that the discharge rate was 1.8 g / min to obtain a fiber. The obtained fiber had a strength of 0.7 cN / dtex, an elongation of 25%, a Young's modulus of 25.5 cN / dtex, a single fiber fineness of 3.0 dtex, and a fiber U% of 1.8%. Moreover, when the circular knitting was created with the obtained fiber and the softness of the texture was evaluated by a sensory test, it was good. Further, when hot pressing was performed, the surface did not change at all.

Comparative Example 1
Cellulose acetate propionate CAP482-20 (manufactured by Eastman Chemical Co., Ltd., number average molecular weight 75000, total substitution degree 2.70, no melting point) was dissolved in acetone, and 167 decitex 48 filament fibers were obtained by dry spinning. The obtained fiber had a strength of 0.8 cN / dtex, an elongation of 25%, a Young's modulus of 25.5 cN / dtex, a single fiber fineness of 3.5 dtex, and a fiber U% of 1.8%. Moreover, when the circular knitting was created with the obtained fiber and the softness of the texture was evaluated by a sensory test, it was good. Moreover, when the hot press was performed, the surface was crushed and the shine was produced.

Comparative Example 2
Cellulose triacetate LT-15 (manufactured by Daicel Chemical Industries, Ltd., number average molecular weight 75000, total substitution degree 2.90, melting point 295 ° C.) is dissolved in a mixed solvent of methylene chloride and methanol, and 167 decitex 48 filaments by dry spinning. Fiber. The obtained fiber had a strength of 1.1 cN / dtex, an elongation of 25%, a Young's modulus of 36.0 cN / dtex, a single fiber fineness of 3.5 dtex, and a fiber U% of 1.8%. Moreover, when the circular knitting was created with the obtained fiber and the softness of the texture was evaluated by a sensory test, it was inferior because it was crunchy and lacked smoothness. Further, when hot pressing was performed, the surface did not change at all.

Comparative Example 3
Cellulose diacetate L-30 (manufactured by Daicel Chemical Industries, Ltd., number average molecular weight 40000, total substitution degree 2.50, no melting point) was dissolved in acetone, and 167 decitex 48 filament fibers were obtained by dry spinning. The obtained fiber had a strength of 0.7 cN / dtex, an elongation of 25%, a Young's modulus of 34.0 cN / dtex, a single fiber fineness of 3.5 dtex, and a fiber U% of 1.8%. Moreover, when the circular knitting was created with the obtained fiber and the softness of the texture was evaluated by a sensory test, it was inferior because it was crunchy and lacked smoothness. Further, when hot pressing was performed, the surface did not change at all.

  A fiber with excellent heat resistance and soft texture, which is based on cellulose derivatives, can be obtained, so it is soft and supple that could not be expressed with conventional cellulosic fibers. In addition, it is possible to obtain a fiber having good gloss, color developability and moisture absorption / release properties derived from cellulose. Thereby, it can use suitably for the clothing use whole.

Claims (4)

  A crystalline cellulose ester fiber comprising a composition having a number average molecular weight of 15,000 to 150,000 and a cellulose ester having a melting point within a range of 160 to 250 ° C. as a main component.   The strength of the crystalline cellulose ester fiber is 0.5 to 4.0 cN / dtex, the elongation is 5 to 60%, the Young's modulus is 10.0 to 30.0 cN / dtex, and the single fiber fineness is 0.5 to 30.0 dtex. The crystalline cellulose ester fiber according to claim 1, wherein U% of the fiber is 3.0% or less.   The crystalline cellulose ester fiber according to claim 1 or 2, wherein the total degree of substitution of the cellulose ester is 2.85 to 3.00.   The crystalline cellulose ester fiber according to any one of claims 1 to 3, wherein the cellulose ester is cellulose tripropionate or cellulose tributyrate.