JPH09143819A - Cellulose acetate conjugated fiber and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a cellulose acetate conjugated fiber, having a definite two-layer structure comprising a sheath part which is substantially unacetylated sheath layer and capable of producing a touch feeling having wetness. SOLUTION: This cellulose acetate conjugated fiber has a core part comprising cellulose triacetate having >=56.2 and <=62.5% average acetyl content and a sheath part, comprising a substantially unacetylated cellulose and having >=2μm thickness thereof. The conjugated fiber is obtained by dissolving cellulose triacetate having >=56.2 and <=62.5% average acetyl content in an organic solvent, using the resultant spinning solution as a core component, dissolving cellulose diacetate having >=48.8 but <56.2% average acetyl content in an organic solvent, using the prepared spinning solution as a sheath component, carrying out the dry spinning of the spinning solutions into a core-sheath type, performing the saponification treatment of the resultant precursor fiber with an alkali and converting all the cellulose diacetate in the sheath part into cellulose.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel cellulose acetate composite fiber and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, cellulose triacetate fibers are subjected to an alkali saponification treatment such as a dipping method or a dry heating method to make the surface of the fibers cellulosic and impart the same antistatic property and wet feeling as rayon. It has been known. However, since the saponification proceeds from the surface of the fiber, the fiber obtained by such a technique has an intermediate layer in which different levels of saponification are mixed between the cellulose layer on the surface of the fiber and the cellulose triacetate inside the fiber. Adversely affects the dyeability of.

Further, when an aqueous alkali solution is adhered to the surface of cellulose triacetate fiber and subjected to high temperature steam treatment or high temperature dry heat treatment, it is also disclosed in JP-A-5-140865.
When the cellulose triacetate fiber is immersed in an alkaline aqueous solution as described in Japanese Patent Laid-Open, and pre-dried and then steam-treated, a cellulose layer containing a small amount of an intermediate layer of cellulose acetate mixed in the surface layer of the cellulose triacetate fiber is obtained, but saponification is performed. Flecking is prone to occur and treatment at high temperatures damages the fibers. Furthermore, in the method of directly saponifying cellulose triacetate from such a fiber surface, it is difficult to obtain a cellulose layer without the presence of an intermediate layer mixed with cellulose acetate only by a saponification reaction, and at high temperature, for a long time, at a high concentration. Need
There are problems in safety and control.

[0004]

DISCLOSURE OF THE INVENTION The present invention utilizes the difference in alkali properties between cellulose triacetate and cellulose diacetate, so long as cellulose diacetate easily alkali-saponified is preliminarily placed on the surface layer of the cellulose triacetate fiber. It is based on the finding that the cellulose layer can be obtained by the alkali saponification treatment under mild conditions without the presence of the intermediate layer containing the cellulose acetate. It is an object of the present invention to provide a clear 2 that the sheath part is a cellulose layer which is not substantially acetylated.
An object of the present invention is to provide a cellulose acetate composite fiber having a layered structure and giving a wet feeling.

[0005]

According to the present invention, the core part is made of cellulose triacetate having an average degree of acetylation of 56.2% or more and 62.5% or less, and the sheath part is made of cellulose which is not substantially acetylated. , A cellulose acetate composite fiber characterized in that the thickness of the sheath portion is 2 microns or more,

And, as the core component, the average degree of acetylation is 56.2%.
Above 62.5% of cellulose triacetate is dissolved in an organic solvent to prepare a spinning dope, which has an average acetylation degree of 4 as a sheath component.
Using a spinning dope in which 8.8% or more and less than 56.2% of cellulose diacetate is dissolved in an organic solvent, dry spinning is performed into a core-sheath type, and the obtained core-sheath type composite fiber is subjected to an alkali saponification treatment to a sheath portion. 2. A method for producing a cellulose acetate composite fiber, which comprises converting all of the cellulose diacetate into cellulose.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The cellulose acetate conjugate fiber of the present invention has an average acetylation degree of 56.2% or more and 62.5% at the core.
It consists of the following cellulose triacetate, the sheath consists only of cellulose, and the thickness of the sheath is 2 microns or more. Therefore, between the cellulose of the sheath and the cellulose triacetate of the core, there is an intermediate of cellulose diacetate or cellulose monoacetate. It has a clear two-layer structure with no layers.

Therefore, the cellulose acetate conjugate fiber of the present invention has hygroscopicity and texture based on the cellulose of the sheath portion, and this hygroscopicity is accompanied by improvement of antistatic property.
Further, the cellulose acetate conjugate fiber of the present invention has good dyeability without causing spots even when dyed.

The method for producing the cellulose acetate conjugate fiber of the present invention is as follows. Acetation degree of 5 as core component
Dissolve 6.2% or more and 62.5% or less of cellulose triacetate and 48.8% or more and less than 56.2% of cellulose diacetate as a sheath component in a solvent such as methylene chloride or a mixed solvent such as methylene chloride and methanol. Then, a spinning dope is prepared with each solution having a concentration of 15 to 30% by weight, preferably 18 to 27% by weight.

The cellulose triacetate spinning dope and the cellulose diacetate spinning dope are preferably distributed in a core-sheath type in a cellulose triacetate / cellulose diacetate ratio, that is, a core-sheath weight ratio of 5/95 to 95/5. Cellulose triacetate having an average acetylation degree of not less than 56.2% and not more than 62.5% by spinning into a core-sheath type by a dry spinning method of supplying to a core-sheath composite spinning nozzle device and discharging in a high temperature atmosphere, sheath part Is an average acetylation degree of 48.8% or more 5
A core-sheath composite precursor fiber of less than 6.2% cellulose diacetate is produced.

Next, the core-sheath type composite precursor fiber is subjected to alkali saponification treatment. The conditions for the alkali saponification treatment are determined by the difference in the alkaline properties of cellulose triacetate and cellulose diacetate, and it is necessary to select the conditions under which cellulose triacetate does not react and only cellulose diacetate easily reacts. As the alkali, sodium hydroxide, calcium carbonate or the like is used. The treatment conditions should be such that reaction to cellulose triacetate or insufficient reaction of cellulose diacetate should be avoided, and preferable treatment conditions include sodium hydroxide concentration of 0.5 to 5% by weight, more preferably 1 to
2% by weight aqueous solution, temperature 30 to 90 ° C., more preferably 3
0 to 60 ° C, time 5 to 25 minutes, more preferably 8 to 15
Minutes are used.

According to the invention, the thickness of the cellulose layer is 2
The thickness of the cellulose layer can be set to be not less than micron, and the thickness of the cellulose layer can be arbitrarily set by the ratio of the core portion and the sheath portion, that is, the core-sheath weight ratio, when the core-sheath type composite precursor fiber is manufactured. It is possible to obtain a cellulose acetate composite fiber having an antistatic property and a wet feeling according to the above.

[0013]

The present invention will be described below in more detail with reference to examples. The acetylation degree, the weight loss rate, and the water content in the examples were measured by the following methods.

<Acetification degree> About 2 g of a sample is put in a weighing bottle,
After drying at 105 ° C. for 2 hours, the sample is cooled in a desiccator for 1 hour and weighed to measure the weight of the sample. Then sample 50
In a 0 ml Erlenmeyer flask, 100 ml of acetone and 300 ml of dimethyl sulfoxide were added and left for 20 hours, then 30 ml of 1N-sodium hydroxide aqueous solution was added and stirred for 2 hours, and a few drops of phenolphthalein solution was added as an indicator, Excess sodium hydroxide was titrated with a 1N-sulfuric acid solution to calculate the average degree of acetylation.

<Reduction rate> A dry sample (Wb) before the alkali saponification treatment and a dry sample (Wa) after the alkali saponification treatment were measured and calculated by the following formula. Weight loss rate (%) = [(Wb-Wa) / Wa] × 100

<Moisture Content> About 10 g of a sample is put in a weighing bottle, dried at 105 ° C. for 2 hours, cooled in a desiccator for 1 hour, and weighed to measure the dry weight (Wa) of the sample.
Then, the sample was allowed to stand in a constant temperature and constant humidity chamber adjusted to 20 ° C. and 65% RH for 24 hours, and then the moisture absorption weight (Wc) was measured and calculated by the following formula. Moisture content (%) = [(Wc-Wa) / Wa] × 100

Examples 1 to 3 Cellulose triacetate having an average acetylation degree of 61.6% and cellulose diacetate having an average acetylation degree of 55.2% were dissolved in a mixed solvent of methylene chloride / methanol = 91/1. Then, a cellulose triacetate spinning stock solution having a solution concentration of 22% by weight and a cellulose diacetate spinning stock solution having a solution concentration of 22% by weight were prepared. Using both spinning stock solutions, a core-sheath composite spinning nozzle was dry-spun at a core-sheath weight ratio shown in Table 1 to obtain a precursor fiber of 75 denier / 20 filaments. The precursor fiber thus obtained was subjected to alkali saponification treatment under the following conditions to obtain a cellulose acetate conjugate fiber having a cellulose layer with a sheath portion having a thickness of 2 μm or more. The weight loss rate, acetylation degree and water content of the obtained cellulose acetate conjugate fiber were measured, and the results are shown in Table 1. Further, the cross section of the fiber after dyeing with the direct dye was observed to check whether or not a two-layer structure was formed.

Alkaline aqueous solution: 1% by weight aqueous solution of sodium hydroxide Treatment temperature: 60 ° C. Treatment time: 10 minutes Bath ratio: 1: 100

Comparative Example 1 The precursor fiber obtained in Example 2 was subjected to alkali saponification treatment under the following conditions. The obtained cellulose acetate fiber was a cellulose layer having a sheath portion with a thickness of less than 2 microns, and cellulose diacetate or cellulose monoacetate in the sheath portion of the precursor fiber remained. The weight loss rate, acetylation degree, and water content of the obtained cellulose acetate fiber were measured, and the results are shown in Table 1.

Alkaline aqueous solution: 1% by weight aqueous solution of sodium hydroxide Treatment temperature: 25 ° C. Treatment time: 1 minute Bath ratio: 1: 100

Comparative Example 2 The precursor fiber obtained in Example 2 was subjected to alkali saponification treatment under the following conditions. Although the obtained cellulose acetate fiber had a cellulose layer with a thickness of 2 μm or more, the cellulose diacetate or cellulose monoacetate formed by saponifying a part of the cellulose triacetate in the core of the precursor fiber was used. It was something that existed. The weight loss rate, acetylation degree, and water content of the obtained cellulose acetate fiber were measured, and the results are shown in Table 1.

Alkaline aqueous solution: 1% by weight aqueous solution of sodium hydroxide Treatment temperature: 100 ° C. Treatment time: 30 minutes Bath ratio: 1: 100

Reference Example Cellulose triacetate having an average acetylation degree of 61.6% was methylene chloride / methanol = 91.
A cellulose triacetate spinning stock solution having a solution concentration of 22% by weight was prepared by dissolving in a mixed solvent of / 9. Using this spinning dope, dry spinning was carried out using an ordinary spinning nozzle to obtain cellulose triacetate fibers of 75 denier / 20 filaments. The water content of the obtained cellulose triacetate fiber was measured, and the results are shown in Table 1 for reference.

[0024]

[Table 1]

As is clear from Table 1, the weight loss rate and acetylation degree of the cellulose acetate composite fiber of the present invention are irrespective of the core-sheath composite ratio of cellulose triacetate and cellulose diacetate before the alkali saponification treatment, regardless of the cellulose in the sheath. It was almost the same as the value calculated on the assumption that only diacetate was completely saponified to be cellulose and that the cellulose triacetate in the core was not saponified at all. Further, the cellulose acetate conjugate fiber of the present invention had a clear two-layer structure with no intermediate layer between the cellulose layer of the fiber surface layer and the cellulose triacetate of the core portion.

[0026]

According to the present invention, a cellulose acetate composite fiber having a clear two-layer structure in which the fiber surface layer is a cellulose layer without an intermediate layer and the core portion is cellulose triacetate can be obtained. Compared with the dry texture of cellulose triacetate fiber,
It is possible to obtain a cellulose acetate conjugate fiber having a rayon-like texture with a damp and wet feeling, hygroscopicity, and good dyeability under mild conditions.

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[Procedure amendment]

[Submission date] March 6, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

Examples 1 to 3 Cellulose triacetate having an average acetylation degree of 61.6% and cellulose diacetate having an average acetylation degree of 55.2% were each dissolved in a mixed solvent of methylene chloride / methanol = 91/9. Then, a cellulose triacetate spinning stock solution having a solution concentration of 22% by weight and a cellulose diacetate spinning stock solution having a solution concentration of 22% by weight were prepared. Using both spinning stock solutions, a core-sheath composite spinning nozzle was dry-spun at a core-sheath weight ratio shown in Table 1 to obtain a precursor fiber of 75 denier / 20 filaments. The precursor fiber thus obtained was subjected to alkali saponification treatment under the following conditions to obtain a cellulose acetate conjugate fiber having a cellulose layer with a sheath portion having a thickness of 2 μm or more. The weight loss rate, acetylation degree and water content of the obtained cellulose acetate conjugate fiber were measured, and the results are shown in Table 1. Further, the cross section of the fiber after dyeing with the direct dye was observed to check whether or not a two-layer structure was formed.

[Procedure amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction contents]

[0024]

[Table 1]

Claims (3)

[Claims] 1. The core part has an average acetylation degree of 56.2% or more 62.
A cellulose acetate conjugate fiber comprising 5% or less of cellulose triacetate, a sheath portion of cellulose which is not substantially acetylated, and a sheath portion having a thickness of 2 microns or more. 2. A spinning dope prepared by dissolving cellulose triacetate having an average acetylation degree of 56.2% to 62.5% in an organic solvent as a core component, and an average acetylation degree of 48.8 as a sheath component.
% Or more and less than 56.2% of cellulose diacetate is dissolved in an organic solvent to prepare a core-sheath type, which is dry-spun.
A method for producing a cellulose acetate conjugate fiber, which comprises subjecting the obtained core-sheath type conjugate fiber to alkali saponification treatment to make all of the cellulose diacetate in the sheath portion cellulose. 3. A sodium hydroxide concentration of 0.5 to 5% by weight
The method for producing a cellulose acetate conjugate fiber according to claim 1, wherein the alkali saponification treatment is carried out in an aqueous solution at a temperature of 30 to 90 ° C for a time of 5 to 25 minutes.