JPH0770824A - Production of hollow acrylic fiber - Google Patents

Abstract

PURPOSE:To stably obtain a hollow acrylic fiber having a continuous hollow part in the fiber axis direction with a conventional sheath-core conjugate spinning spinneret in good producibility without using a special polymer. CONSTITUTION:Two kinds of acrylic polymers having a difference of >=3wt.% between the acrylonitrile contents of the acrylic polymers are melt-spun into a conjugate fiber in which one of the acrylic polymers is the sheath component and the other is the core component. Before drying and densifying, the spun fiber is dried into a water content of <=520wt.% at a temperature of >=580 deg.C to form a hollow part between the core part and the sheath part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing hollow acrylic fibers suitable for clothing and the like.

[0002]

2. Description of the Related Art Conventionally, many attempts have been made to make acrylic fibers have a hollow structure for the purpose of improving heat retention, bulkiness, and water absorption. For example, JP-A-54-68415.
No. 61-28014, 61-2961
No. 1, JP-B-60-18332, JP-B-62-728
No. 6 and Japanese Patent Laid-Open No. 3-249215. However, in these proposals, a continuous hollow structure cannot be obtained and becomes porous. In order to obtain a hollow structure, the copolymer composition that can be used is limited, and it is necessary to reduce the concentration of the core solution as a core solution. When the viscosity difference between the sheaths becomes large, it is difficult to obtain hollow fibers in a stable manner with a normal core-sheath composite spinneret. In order to maintain the stock solution of the core component at a low concentration and make it highly viscous, the molecular weight is very high. It has a problem that the use of highly specialized polymers is required.

[0003]

DISCLOSURE OF THE INVENTION The present invention has a hollow portion which is continuous in the fiber axial direction, is stable in a usual core-sheath composite spinneret, and can be produced without using a special polymer. Well in obtaining hollow acrylic fibers.

[0004]

According to the present invention, one of two acrylonitrile-based polymers having a difference in acrylonitrile amount of 3 wt% or more is used as a sheath component and the other is used as a core component, and after spinning by composite spinning. The method for producing a hollow acrylic fiber is characterized in that the spun yarn is dried to a moisture content of 20 wt% or less at a temperature of 80 ° C. or less to form a hollow portion between the core and the sheath before being dried and densified.

The acrylonitrile-based polymer that can be used in the present invention is a copolymer of polyacrylonitrile and acrylonitrile of 50 wt% or more with various vinyl monomers. Examples of the vinyl monomer as a copolymerization component include vinyl acetate. , Vinyl chloride, vinylidene chloride, vinyl bromide, acrylamide, acrylic acid, methyl acrylate,
Examples thereof include methyl methacrylate and sodium methacryl sulfonate.

In the present invention, one of two acrylonitrile polymers having a difference in acrylonitrile amount of 3 wt% or more is used as a sheath component and the other is used as a core component. One of them may be used as either the sheath component or the core component. In the present invention, in order to form a continuous hollow structure, it is necessary to previously provide the polymer between the core and the sheath components with a difference in the amount of acrylonitrile. If the difference in the amount of acrylonitrile is less than 3 wt%, the continuous hollow structure is obtained. I can't get the structure.

In the present invention, it is natural that one of the two acrylonitrile-based polymers having a difference in the amount of acrylonitrile of 3 wt% or more may be polyacrylonitrile, but both are copolymers. when,
One may be an acrylonitrile-based polymer which is different in the amount of acrylonitrile by 3 wt% or more from the other, regardless of the type of the copolymerization component and the number of the copolymerization components. Further, the molecular weight of the acrylonitrile polymer used is not limited at all.

The production of acrylic fiber in the present invention is
A method generally used in the acrylic fiber spinning process is applied, and spinning is carried out by a known core-sheath composite spinning using an ordinary core-sheath composite spinning spinneret using a spinning stock solution for the sheath component and a spinning stock solution for the core component. It is a thing. As the solvent in the spinning dope, those commonly used as a solvent for acrylonitrile polymers can be used, for example, dimethylacetamide, dimethylformamide, γ-butyrolactan, ethylene carbonate, sodium thiocyanate nitrate, aqueous zinc chloride solution, etc. Is mentioned. The concentration of the spinning dope is not particularly limited and is appropriately selected according to the spinning method. As the spinning method, wet spinning and dry wet spinning are preferably used.

In the present invention, in order to make the acrylic fiber have a hollow structure, the spun yarn spun from the spinneret is dried at a temperature of 80 ° C. or less before the treatment step of densifying. It is essential to dry to 20 wt% or less. By this drying treatment at a low temperature, a hollow portion which is continuous in the fiber axis direction is formed between the core and the sheath. If the drying temperature exceeds 80 ° C. or if the water content exceeds 20 wt%, continuous hollow portions cannot be formed stably.

The method for drying the spun yarn at a low temperature is not particularly limited, but a method such as applying a heating roller, spraying room temperature or heated air is preferably used. This low-temperature drying treatment may be carried out before or after the stretching step, as long as it is before the treatment step for drying and densifying the spun yarn, but it is carried out before the stretching step, and then wet heat stretching at a high ratio, etc. It is preferable to stretch in order to develop a hollow structure. The dry densification treatment is carried out with a heating roller at a temperature of 100 ° C. or higher, but if this low temperature drying treatment is carried out after the dry densification treatment step, the hollow portion is no longer formed and the hollow fiber is not formed. Can't get

By the low temperature drying treatment of the present invention,
Interfacial delamination between core-sheath portions caused by a decrease in compatibility between core-sheath components and suppression of deformation of the sheath portion forms a crescent-shaped or ring-shaped hollow portion continuous in the fiber axial direction between the core and sheath. . This hollow portion is fixed by the subsequent dry densification treatment and does not disappear even in various post-processes in the yarn making process.

[0012]

EXAMPLES The present invention will be specifically described below with reference to examples.

(Example 1) 89 wt of acrylonitrile
%, Vinyl acetate 11 wt% acrylonitrile copolymer 24 wt% dimethylacetamide solution was used as the spinning solution for the sheath component, and acrylonitrile 92 wt% and vinyl acetate 8
A 20 wt% acrylonitrile copolymer 20 wt% dimethylacetamide solution was used as the spinning solution for the core component, and the sheath / core discharge ratio was set to 5/1. Dry-wet spinning was conducted. Coagulation bath is 50 wt.
% Aqueous solution was used. The spun yarn was washed with boiling water, blown with air at about 30 ° C. and dried at a low temperature, and the water content was set to 5 wt%. After that, the dry yarn is subjected to 5 times wet heat drawing in boiling water,
Then, a dry densification treatment was performed with a heating roller at 150 ° C. to obtain an acrylic fiber. The spinning condition was very stable, and the obtained acrylic fiber had a crescent-shaped hollow portion in its fiber cross section, and the hollow portion was continuous in the fiber axial direction.

(Example 2) 92 wt of acrylonitrile
%, Vinyl acetate 8 wt% acrylonitrile copolymer 24 wt% dimethylacetamide solution as a sheath component spinning stock solution, acrylonitrile 60 wt%, vinylidene chloride 40 wt% acrylonitrile copolymer 24 wt% dimethylacetamide solution core component spinning stock solution As a result, wet spinning was performed in which the sheath / core discharge amount ratio was 3/1 and the core / sheath composite spinneret was used to discharge into a coagulation bath. 50 ° C for coagulation bath
A 55 wt% aqueous solution of dimethylacetamide was used. After washing the spun yarn with boiling water and drawing 5 times wet heat in boiling water, about 3
Blow air at 0 ° C to dry at low temperature, the water content is 5w
It was set to t%. Then, a dry densification treatment was performed with a heating roller at 150 ° C. to obtain an acrylic fiber. The spinning condition was very stable, and the obtained acrylic fiber had a crescent-shaped hollow portion in its fiber cross section, and the hollow portion was continuous in the fiber axial direction.

(Example 3) The same procedure as in Example 1 was repeated except that the sheath component spinning dope was replaced with the core component spinning dope and the core component spinning dope was replaced with the sheath component spinning dope. Acrylic fiber was obtained. The spinning condition was very stable, and the obtained acrylic fiber had a crescent-shaped hollow portion in its fiber cross section, and the hollow portion was continuous in the fiber axial direction.

(Example 4) An acrylic fiber was obtained in the same manner as in Example 1 except that heated air at 80 ° C was used for low temperature drying after washing with boiling water in Example 1. The spinning condition was very stable, and the obtained acrylic fiber had a crescent-shaped hollow portion in its fiber cross section, and the hollow portion was continuous in the fiber axial direction.

(Example 5) An acrylic fiber was obtained in the same manner as in Example 1 except that the water content of the spun yarn was 18 wt% by low temperature drying after washing with boiling water. The spinning condition was very stable, and the obtained acrylic fiber had a crescent-shaped hollow portion in its fiber cross section, and the hollow portion was continuous in the fiber axial direction.

(Comparative Example 1) 89 wt of acrylonitrile
%, Vinyl acetate 11 wt% acrylonitrile copolymer 24 wt% dimethylacetamide solution was used as the spinning solution for the sheath component, and acrylonitrile 92 wt% and vinyl acetate 8
Wet spinning was performed by using a 24 wt% dimethylacetamide solution of a wt% acrylonitrile copolymer as a spinning stock solution of the core component, with a sheath / core discharge ratio of 5/1, and discharging into a coagulation bath using a core-sheath composite spinneret. It was As the coagulation bath, a 55 wt% aqueous solution of dimethylacetamide at 50 ° C. was used. The spun yarn was washed with boiling water, wet-heat stretched 5 times in boiling water, and then dried and densified with a heating roller at 150 ° C. to obtain an acrylic fiber. The obtained acrylic fiber was a solid yarn having no hollow portion in its fiber cross section.

(Comparative Example 2) 89 wt of acrylonitrile
%, Vinyl acetate 11 wt% acrylonitrile copolymer 24 wt% dimethylacetamide solution was used as the spinning solution for the sheath component, and acrylonitrile 92 wt% and vinyl acetate 8
Wet spinning was performed by using a 24 wt% dimethylacetamide solution of a wt% acrylonitrile copolymer as a spinning stock solution of the core component, with a sheath / core discharge ratio of 5/1, and discharging into a coagulation bath using a core-sheath composite spinneret. It was As the coagulation bath, a 55 wt% aqueous solution of dimethylacetamide at 50 ° C. was used. The spun yarn was washed with boiling water, blown with air at about 30 ° C., and dried at a low temperature to give a water content of 40 wt%. Then, the dried yarn was subjected to a wet heat draw of 5 times in boiling water, and then dried and densified with a heating roller at 150 ° C. to obtain an acrylic fiber. The obtained acrylic fiber was a mixture of those having a hollow portion and those not having a hollow portion in the fiber cross section.

(Comparative Example 3) 89 wt of acrylonitrile
%, Vinyl acetate 11 wt% acrylonitrile copolymer 24 wt% dimethylacetamide solution was used as the spinning solution for the sheath component, and acrylonitrile 90 wt%, vinyl acetate 1
A 24 wt% dimethylacetamide solution of 0 wt% acrylonitrile copolymer was used as a stock solution for spinning the core component
Wet spinning was performed using a core-sheath composite spinneret with a core discharge amount ratio of 5/1 and discharging into a coagulation bath. As the coagulation bath, a 55 wt% aqueous solution of dimethylacetamide at 50 ° C. was used. The spun yarn was washed with boiling water, blown with air at about 30 ° C., and dried at a low temperature to give a water content of 5 wt%. Then, the dried yarn was subjected to a wet heat draw of 5 times in boiling water, and then dried and densified with a heating roller at 150 ° C. to obtain an acrylic fiber. The obtained acrylic fiber was a mixture of those having a hollow portion and those not having a hollow portion in the fiber cross section.

[0021]

EFFECTS OF THE INVENTION According to the present invention, it has a hollow portion continuous in the fiber axis direction, is stable in an ordinary core-sheath composite spinneret, and has good spinnability without using a special polymer. It is possible to obtain a hollow fiber excellent in cost performance, and it is possible to provide an acrylic fiber which is excellent in heat retention and bulkiness and which can improve water absorption and which is suitable for bedding applications including clothing applications. It is a thing.

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Claims (1)

[Claims] 1. A spin-drying and densifying process after spinning by composite spinning using one of two acrylonitrile-based polymers having a difference in acrylonitrile amount of 3 wt% or more as a sheath component and the other as a core component, and before drying and densifying. A method for producing a hollow acrylic fiber, characterized in that the spun yarn is dried at a temperature of 80 ° C. or less to a water content of 20 wt% or less to form a hollow portion between the core and the sheath.