JPH10273821A - Water absorbing acrylic fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water absorbing acrylic fiber, good in heat resistance, shape retention properties and crimp stability and capable of performing the post processing in the same manner as that of a conventional acrylic fiber. SOLUTION: This water absorbing acrylic fiber is obtained by dissolving an acrylonitrile-based polymer containing at least 85 wt.% acrylonitrile units and cellulose in an aqueous solution of a thiocyanate, blending 80-95 wt.% acrylonitrile-based polymer with 20-5 wt.% cellulose and carrying out the wet spinning and further including macrovoids without disappearing by heat treatment such as drying or crimp setting therein. The heat treatment such as drying or crimp setting of the resultant acrylic fiber can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-absorbing acrylic fiber used for clothing, interior, and industrial materials.

[0002]

2. Description of the Related Art Natural fibers such as cotton and wool have a water absorption of 20%.
Although it shows a high water absorption of up to 40% by weight, general synthetic fibers are poor in water absorption and have a low commercial value as compared with natural fibers. Many studies have been made to improve the water absorption performance of synthetic fibers. Above all, a large number of fibers utilizing the capillary phenomenon by making the fibers have a porous structure have been proposed.

[0003] For example, Japanese Patent Application Laid-Open No. 47-25418,
JP-B-47-15901, JP-B-48-6649
And JP-B-48-6650 produce porous acrylic fibers by selecting mild drying conditions that leave microvoids or microvoids in the swollen gel tow during the acrylic fiber production process. A method is described. JP-A-47-25416, JP-B-48-8285, JP-B-48-828
No. 6 describes that a water-soluble compound is filled into a swollen gel tow in a process for producing an acrylic fiber, and the filler is eluted after drying and post-treatment to regenerate voids.

[0004] The common feature of the above methods is that it is a technique for producing a porous acrylic fiber in which microvoids originally contained in swollen gel tow in a process of producing an acrylic fiber are left in a final product.

[0005]

However, since the microvoids contained in the swollen gel tow are extremely unstable thermally, it is difficult to carry out drying, especially in the fiber production process, and high temperature treatment in the crimp set. However, the heat resistance, shape retention, and crimp stability of the final product are poor, which causes a significant decrease in the commercial value of the product. However, it is a reality that a water-absorbing acrylic fiber excluding such causes has not yet been achieved.

[0006]

Means for Solving the Problems Under such circumstances, the present inventors have made intensive studies to solve the above problems, and as a result, both acrylonitrile-based polymer and cellulose were dissolved in an aqueous thiocyanate solution to obtain a spinning solution. It has been found that this can be achieved by performing wet spinning and retaining macrovoids generated due to the difference in coagulation properties in acrylic fibers. That is, the present invention relates to an acrylonitrile-based polymer containing at least 85% by weight of acrylonitrile units and 80 to 95% by weight of cellulose and 20 to 5% by weight of cellulose.
% Of a polymer having a water absorption of 2% by weight.
Water-absorbent acrylic fiber characterized by being at least 0% by weight. Hereinafter, the present invention will be described in detail.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The acrylonitrile-based polymer which is the raw material of the acrylic fiber used in the present invention is not particularly limited as long as the acrylonitrile ratio is 85% by weight or more, and may be a homopolymer or a copolymer with a known monomer. Can be used. When the acrylonitrile (hereinafter, also referred to as AN) ratio is less than 85% by weight, the thermal stability of the acrylic fiber is significantly reduced, and the acrylic fiber is easily colored, so that the quality of the final product may be reduced.

The comonomer used in the copolymerization is not particularly limited as long as it can be copolymerized with acrylonitrile, such as another polymerizable unsaturated vinyl compound. Examples thereof include alkyl acrylate, alkyl methacrylate, acrylic acid, methacrylic acid, and methacryloyl. Nitrile, acrylamide, vinyl acetate, vinyl chloride, vinyl bromide, vinyl fluoride, vinyl alkylate, vinylidene chloride, vinylidene bromide, styrene, styrene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonate, allyl Sulfonates, methallylsulfonates, ethylene, propylene and the like can be used.

[0009] The cellulose used in the present invention is not particularly limited.
Amorphous cellulose which has been subjected to a pretreatment for disturbing the crystal structure in the cellulose in advance, and preferably has an average degree of polymerization of 50 to 500.

The AN polymer and cellulose thus prepared are dissolved in a thiocyanate aqueous solution as a solvent to form a spinning dope, and are wet-spun with a known nozzle. As thiocyanate, calcium thiocyanate,
Magnesium thiocyanate, lithium thiocyanate, strontium thiocyanate, and sodium thiocyanate are preferably used.

The amount of cellulose added is 5 to 5 of the total amount of the polymer.
It is 20% by weight, preferably 7 to 15% by weight.
When the amount of cellulose added is less than 5% by weight, the water absorption is low, and when it exceeds 20% by weight, the water absorption increases,
The yarn breakage during spinning increases and the mechanical properties of the yarn decrease.

The water-absorbing acrylic fiber of the present invention is obtained by blending the above-mentioned polymer in a state where the spun fiber has a multilayer structure of an acrylonitrile polymer and cellulose in a single fiber, followed by wet spinning. can get. As the spinning method, any of ordinary wet spinning and dry-wet spinning can be suitably employed. It is spun into a thiocyanate / water-based solution as a coagulating liquid, is subjected to stepwise desolvation and water washing, is stretched 7 to 12 times, is dried and densified, and is then crimped and crimped. Do.

[0013] The crimp set is 120-150 ° C, 10
This is carried out under the conditions of seconds to 15 minutes, more preferably 12 minutes.
5-140 degreeC is good. The water absorption increases rapidly from 125 ° C., but if the treatment temperature is too high the fibers may stick. The processing time may be shorter at higher temperatures,
It is preferably 15 seconds or more to avoid staining spots. The water absorption was measured by the following method. After opening 10 g of fiber, wrap it in gauze and surfactant (Neugen HC 1 ml / 1 l)
After washing at 60 ° C. for 30 minutes in running water, it was washed with running water and dehydrated. Subsequently, the mixture was boiled in ion-exchanged water for 30 minutes, washed with running water, and then dehydrated. After drying at 110 ° C for 20 minutes,
It was immersed in ion-exchanged water adjusted to 30 ° C. and allowed to stand for 3 hours. Centrifugal dehydrator (Type H- manufactured by Domestic Centrifuge Co., Ltd.)
The scale of 770A) was adjusted to 3 and dehydrated for 3 minutes. The fiber was taken out of the gauze and weighed. Then at 90 ° C 3
After drying for 0 minutes, the weight was measured. The water absorption refers to a value calculated by the equation 1.

[0014]

(Equation 1)

[0015]

According to the present invention, a blend polymer solution obtained by dissolving two kinds of polymers, an acrylonitrile-based polymer and a cellulose, having essentially different coagulation properties in an aqueous solution of thiocyanate, which is a common solvent, is wet-spun to obtain fibers. The macro voids are generated due to the difference in coagulation properties, and the voids disappeared by drying or crimp setting with the acrylonitrile polymer alone, due to the heat resistance of water and cellulose held in the voids due to the hydrophilicity of the cellulose,
It remains even after the heat treatment and imparts water absorption by capillary action.

[0016]

The following examples are provided to facilitate understanding of the present invention, but are merely illustrative, and the gist of the present invention is not limited thereto. In the examples, parts and percentages are shown on a weight basis unless otherwise specified.

Example 1 Acrylonitrile and methyl acrylate were added in an amount of 90% by weight to 1%.
The ratio of the acrylonitrile polymer polymerized at a ratio of 0% by weight to the cellulose having a polymerization degree of 200 was adjusted to 96/4 to 65.
The mixture was dissolved in a 60% by weight aqueous solution of calcium thiocyanate to prepare a stock solution for spinning having a polymer concentration of 15%. This was wet-spun using a 15% by weight aqueous solution of calcium thiocyanate at 25 ° C. as a coagulating liquid, washed with water, stretched 10 times, dried at 130 ° C. with a heater roller under tension, and densified. For 5 minutes, five kinds of acrylic fiber samples were obtained.
(Sample Nos. 1 to 5) Table 1 shows the water absorption and the tensile strength and elongation.

[0018]

[Table 1]

Fibers having a cellulose content of 4% by weight or less have a water absorption of 20% by weight or less when subjected to a heat treatment corresponding to drying and crimp setting. In the case where the content was not less than 10% by weight, the balance of the strength and elongation was maintained even after performing the same treatment, and a high water absorption of not less than 20% by weight was exhibited. Experiment N
o. After drying and densifying the fibers of No. 2
When crimp setting was performed at 0 ° C., a heat-resistant and stable crimp that did not disappear even after boiling could be provided. If the cellulose content was 20% by weight or less, spinning and stretching could be performed stably, but if it exceeded 20% by weight, thread breakage during stretching frequently occurred. Further, at 35% by weight, stretching could not be performed, so that the tensile strength was reduced to 0.9 g / d.

Example 2 95% by weight of acrylonitrile and methyl acrylate to 5%
An acrylonitrile polymer polymerized at a ratio of 90% by weight and a cellulose having a degree of polymerization of 200 are blended at a ratio of 90/10, and this is dissolved in a 60% by weight aqueous solution of calcium thiocyanate to obtain a stock solution for spinning having a polymer concentration of 15%. Was prepared. This was wet-spun at 25 ° C. using a 15% by weight aqueous solution of calcium thiocyanate as a coagulating liquid, washed with water, stretched by 10 times, dried at 130 ° C. with a heater roller under tension, and densified, and subjected to 120 to 150 ° C. For 3 minutes to obtain five types of acrylic fiber samples. (Sample Nos. 6 to 10) Table 2 shows the water absorption and the presence or absence of agglutination.

[0021]

[Table 2]

When the wet heat treatment temperature is 150 ° C. or higher, water becomes a plasticizer and acrylonitrile begins to melt, causing sticking. At 140 ° C. or lower, a fiber without sticking was obtained.

EXAMPLE 3 An acrylonitrile polymer having acrylonitrile and vinyl acetate in a ratio of 84% by weight to 16% by weight and a ratio of 85% by weight to 15% by weight, and immersed in a 20% by weight aqueous sodium hydroxide solution for 5 hours. After that, the mixture was neutralized with dilute sulfuric acid, washed with water, and dried.
/ 10 and 80/20 in a ratio of 6
It was dissolved in a 0% by weight aqueous solution of sodium thiocyanate to prepare a stock solution for spinning having a polymer concentration of 15%. This is 25 ° C,
After wet spinning with a 15% by weight aqueous solution of sodium thiocyanate as a coagulating liquid, washing with water, 10-fold hot stretching, drying at 130 ° C. with a heater roller under tension, and densification,
A wet heat treatment at 130 ° C. for 3 minutes was performed to obtain five types of acrylic fiber samples. (Sample Nos. 11 to 14) Table 3 shows the water absorption and the fiber whiteness.

[0024]

[Table 3]

When the acrylonitrile content of the acrylonitrile-based polymer is less than 84% by weight, the acrylonitrile-based polymer has low heat resistance, so that the acrylonitrile-based polymer is colored by drying, densification, and moist heat treatment at 130.degree. Degree decreased. On the other hand, with an acrylonitrile polymer of 85% by weight or more, almost no coloring was obtained, and good fibers were obtained.

Example 4 An acrylonitrile-based polymer having acrylonitrile and vinyl acetate in a ratio of 84% by weight to 16% by weight and a ratio of 85% by weight to 15% by weight, and immersed in a 20% by weight aqueous sodium hydroxide solution for 5 hours. Then, Table 4 shows the results obtained by dissolving cellulose having a polymerization degree of 200, which was neutralized with dilute sulfuric acid, washed with water and dried, with various solvents.

[0027]

[Table 4]

In an aqueous solution of nitric acid and zinc chloride, the acrylonitrile-based polymer was dissolved but the cellulose was not dissolved. In the copper ammonia solution and NMMO, the cellulose was dissolved but the acrylonitrile-based polymer was not dissolved. On the other hand, both the acrylonitrile polymer and the cellulose could be dissolved in the aqueous solution of calcium and sodium thiocyanate.

[0029]

As described above, conventionally, microvoids originally contained in a swollen gel tow in the process of producing an acrylic fiber are left in a final product to produce a water-absorbing acrylic fiber. Are extremely unstable thermally, cannot be dried especially in the fiber manufacturing process, and cannot be subjected to high-temperature treatment in the crimp set, and the heat resistance, shape retention and crimp stability of the final product It was poor in property and markedly reduced the commercial value of the product. The present invention relates to an acrylonitrile-based polymer having essentially different coagulability and cellulose.
Wet spinning of a blended polymer solution in which a type of polymer is dissolved in an aqueous solution of thiocyanate, a common solvent, generates macrovoids due to the difference in coagulation properties and provides water absorption by capillary action based on this. It provides water-absorbent acrylic fibers which have good heat resistance, shape retention and crimp stability and can be post-processed in the same manner as conventional acrylic fibers, and have great industrial significance.

Claims (2)

[Claims] An acrylonitrile-based polymer containing at least 85% by weight of an acrylonitrile unit and a polymer comprising 20 to 5% by weight of cellulose and having a water absorption of not less than 20% by weight. Characteristic water-absorbing acrylic fiber. 2. The water-absorbing acrylic fiber according to claim 1, wherein an aqueous solution of thiocyanate is used as a solvent when the acrylonitrile polymer and cellulose are dissolved to form a spinning solution.