JPH0441707A - Production of acrylic fiber having high water retention ratio - Google Patents

Abstract

PURPOSE:To obtain the title fiber having high water retention, water absorption, excellent mechanical strength, and after-treatment by dissolving a high molecular acrylonitrile-based polymer containing a hydrophilic monomer as a copolymer component in an organic solvent and spinning the resultant dope. CONSTITUTION:An acrylonitrile-based polymer with >=300000 weight-average molecular weight containing >=80% acrylonitrile and a hydrophilic monomer [e.g. acrylamide, 2-hydroxyethyl (meth)acrylate sodium salt, or p- sulfophenylmethacryl ether] having >=5% solubility to water at 20 deg.C in an amount of >=3% as a copolymer component is dissolved in an organic solvent, and the resultant dope is spun to provide the objective fiber having <=0.1d single fiber fineness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing acrylic fibers whose water retention rate is significantly higher than that of conventional acrylic fibers.

[Conventional technology]

Acrylic fiber aiFi is widely used in the fields of clothing and interior design due to its excellent texture and dyeability, but in recent years, in addition to these properties, it has also been improved in terms of heat retention, flame retardancy, water absorption, liquid retention, etc. There is a demand for acrylic fibers that have added functions such as odor. In general, synthetic fibers are inferior to Xen@i fibers in terms of water absorption and liquid retention, and acrylic fibers are no exception.

Studies have been conducted to improve the water absorption and liquid retention properties of acrylic fibers, and various acrylic fibers with improved water retention and liquid retention properties and their manufacturing methods have been proposed (Tokuko Sho 6n-
No. 11124, Japanese Patent Publication No. 61-42005 1゜These are related to water-absorbing acrylic fibers due to the formation of fine voids, which provide fine voids in the fibers, which absorb water through capillary action and retain water by retaining voids. It has improved characteristics. However, in order to produce these acrylic fibers, it is necessary to mix additives to provide voids in the fibers during the raw solution process. For example, in Japanese Patent Publication No. 60-11124, cellulose acetate is added to the spinning stock solution to create voids in the fibers, but the spinning stock solution with cellulose vinegar added is of course better than the spinning stock solution containing only acrylonitrile polymer. The stability and spinnability of the stock solution are poor, and this method is not industrially satisfactory as a method for producing acrylic fibers with improved liquid retention and water absorption. Further, in Japanese Patent Publication No. 61-42005, voids are created in the fibers by adding a non-volatile solvent and extracting the hindlimb solvent from dry spinning.

In the manufacturing process of acrylic fibers, production costs are generally reduced by recovering the spinning solvent, but such a method adds a great deal to the solvent recovery process. Like the described technology, it is hard to say that it is an industrially completed technology.

Providing voids in the fibers is effective in improving liquid retention and water absorption, but tends to impair the mechanical strength that acrylic fibers inherently have, causing problems in post-processing properties such as spinnability.

As mentioned above, the demand for acrylic fibers with high liquid retention and water absorption has increased in recent years, but high water retention acrylic fibers and the abandoned industrial production methods for producing them have not yet been obtained. The current situation is that there is no such thing.

[Problem to be solved by the invention]

The purpose of the present invention is to provide an acrylic fiber that has high water retention and water absorption properties, maintains the mechanical strength of acrylic fiber, and has excellent post-processability such as spinning. An object of the present invention is to provide a method for producing highly water-retentive acrylic fibers that is advantageous for

[Means to solve the problem]

The gist of the present invention is that acrylonitrile is
An acrylonitrile polymer having a weight average molecular weight of 300,000 or more and containing 3% of a hydrophilic monomer having a solubility in water at 20°C of 5 or more as a copolymer component.
The object of the present invention is to produce acrylic fibers with a single fiber fineness of α1d or less and a high water retention rate by spinning a stock solution obtained by dissolving the acrylonitrile polymer containing the above in a solvent.

The present invention uses acrylonitrile fiber KJII with a single fiber fineness Q of 1 cL or less! It has macrovoids inside the fibers and
Hydrophilic groups have been introduced into the fibers.

By reducing the single fiber fineness of the acrylonitrile fiber to α11, KIIIll gaps are created between the fibers, which speeds up the diffusion of moisture through capillary action, and allows the macrovoids present inside Km fibers to retain moisture. By introducing a hydrophilic group inside, the retention capacity is increased.

The acrylonitrile polymer used to produce such acrylonitrile aIm has a weight average molecular weight of 30.
The number must be 10,000 or more. Single lil fiber fineness α1a
In order to produce the following acrylic fibers, it is necessary to reduce the concentration of the acrylonitrile yarn polymer in the spinning dope, and to reduce the ratio of the linear velocity of the spinning dope from the spinning nozzle to the speed of the undrawn yarn, the so-called spinning draft, as much as possible. need to be higher. Therefore, it is preferable to set the concentration of the acrylonitrile polymer in the spinning dope to 100,000 or less, but if the weight average molecular weight of the polymer used is less than 300,000,
Even if such a low-concentration spinning stock solution is prepared, its viscosity is low (and spinnability is no longer expressed), making it impossible to continue spinning stably.

It is essential for the acrylonitrile fiber of the present invention to have macrovoids inside, but in order to generate macrovoids inside the fiber, it is preferable that the concentration of K in the spinning dope is low. The molecular weight of the polymer needs to be 300,000 or more.

Examples of the hydrophilic salts used in the present invention include acrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, sodium salt of p-sulfophenyl methacrylic ether, and sodium methallylsulfonate. It is necessary that the content of these hydrophilic 7-mers is 5 or more.

By copolymerizing such a hydrophilic monomer with acrylonitrile, firstly, hydrophilicity is introduced into the fibers, which has the effect of improving water retention. The second point is that coagulation progresses slowly, so even if conditions are selected that cause macro voids to occur during the coagulation process, polymer aggregation will not occur due to the reprecipitation phenomenon, and the mechanical Acrylonitrile fibers with high mechanical strength can be obtained. In other words, in order to increase the water retention rate of acrylonitrile fibers, it is necessary to have voids or surface wrinkles to retain water. If an attempt is made to generate macrovoids by spinning, the coagulation conditions that produce macrovoids will cause polyacrylonitrile, a hydrophobic polymer, to aggregate, forming a skin layer on the fiber surface, and further forming a skin layer inside the fiber. However, polymer particles with aggregated polymer molecules are produced, and only acrylic fibers with low mechanical strength can be obtained. However, in the method of the present invention, since hydrophilic monomers are copolymerized in the polymer, even if coagulation is performed under conditions where macrovoids are formed and coagulation is rapid, water associates with the hydrophilic groups, resulting in polymer aggregation. As the force weakens and coagulation progresses slowly, an acrylonitrile yarn 1l111 having a homogeneous structure except for macrovoids can be obtained.

Furthermore, as monomers other than the above-mentioned hydrophilic monomers that can be copolymerized with acrylonitrile, any monomer that can be copolymerized with acrylonitrile may be used, such as methacrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n -iso- or t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, α-chloroacrylonitrile, vinyl chloride, vinylidene chloride, vinyl bromide, vinyl acetate, and the like. These hydrophilic heptamers and other copolymerizable monomers can be copolymerized with acrylonitrile in the range of less than 20%. If the copolymerization ratio is 20 or more, the physical properties of the resulting acrylonitrile fiber will deteriorate, and it will not be possible to maintain sufficient physical properties for practical use.

Next, when carrying out the present invention, first, the above-mentioned acrylonitrile polymer is dissolved in an organic solvent such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, etc. to prepare a spinning stock solution.

Subsequently, such a spinning stock solution is filtered through a T material with a filtration accuracy of 10 μm or less, and is discharged from a spinning nozzle. The diameter of the spinning nozzle is preferably in the range of 30 to 50 microns. When it exceeds 50μ, the spinning draft becomes thick in the coagulation bath and yarn breakage increases, and when it is less than 30μ, the nozzle tends to become clogged, making it impossible to continue spinning stably for a long time. Furthermore, wet spinning is preferable as the spinning method. The coagulation bath uses a mixture of the solvent of the acrylonitrile polymer used and water, and the mixing ratio is preferably in the range of organic solvent/water = 5795 to 15/85 (weight ratio) to facilitate the generation of macro voids. .

If the water content is higher than this range, the amount of pure water injected in order to dilute the organic solvent flowing out from the spinning dope into the coagulation bath and keep the concentration of the coagulation bath constant will become very large, resulting in an industrial problem. It cannot be said that it is an appropriate method. On the other hand, when the water content is low, the amount of macrovoids for retaining water is reduced, resulting in a decrease in the water retention rate of the resulting contact and separation.

The coagulated thread thus obtained is then stretched while washing the remaining solvent with warm water.

In order to reduce the single fiber fineness to 11d or less, it is preferable to combine stretching in warm water with stretching in a dry heat atmosphere using a hot roll, hot plate, heated tube, etc. The stretching ratio is preferably in the range of 6 times or more and less than 15 times. If it is less than 6 times, the obtained Il! Since the strength of the fibers is low, it is not practical, and at the same time, it is difficult to reduce the single fiber fineness to 01d or less. Moreover, if it is 15 times or more, thread breakage is likely to occur during spinning, making the process unstable.

After that, relaxation treatment is performed to suppress the shrinkage rate of the fibers, if necessary. Examples of the relaxation treatment method include a hot plate contact method and a Tsunoda steam method, but are not particularly limited.

The acrylic am obtained by the above method has a single fiber m fineness [
The acrylic compound of the present invention has Ll(1 or less, has sufficient mechanical strength for practical use, has a fine fineness, has macro voids, and has a hydrophilic group in 1!l#). Fiber products obtained using fibers have a high water absorption rate, and have a water retention ψ of 304 or more according to the evaluation method shown later, and because they absorb water in the macro voids, they do not feel sticky at all after use. It is a stutter that always has a dry touch texture.

Therefore, it can be used in fields where it is desirable to absorb a large amount of moisture, such as T-shirts, bath towels, and sports towels.

〔Example〕

Hereinafter, the present invention will be specifically explained using examples.

(1) f-IJ represents weight factor.

(2) "The weight average molecular weight (My) J was calculated by the following formula by measuring the intrinsic viscosity of the polymer at 25° C. using dimethylformamide as a solvent.

[wa] = 555X10''''4 (y v ) g) 72 (
3) The content of copolymerized monomers was determined by high-resolution nuclear magnetic resonance.

(4) "Water retention rate" was measured by the following method.

The obtained acrylic fibers were cut into lengths of 50 cm, scraped, scoured and dyed. After the dyed raw cotton was immersed in pure water for 24 hours, it was dehydrated for 10 minutes at an acceleration of 11]00 ().

Let the weight at that time be V. Thereafter, the raw cotton was dried in a dryer at 110° C. for 3 hours, and the weight at that time was designated as W2. Calculate the water retention rate using the following formula.

Vl-W water retention ratio C width) = ×100 Reference Example 1 The polymers used in the examples had the compositions shown in Table 1 and were produced by a suspension polymerization method.

Table 1! ! 2 5 N = Acrylonitrile HmMA = Hydroxy V Ethyl Methacrylate M =
Methyl acrylate AAm = Acrylamide Example 1 The polymer shown in Table 1 was dissolved in dimethylacetamide and passed through a [105φ/1000[]H spinning nozzle to obtain 1
Dimethylacetamide/water (15/85) at 40°C
wet spinning and stretching machine relaxation conditions t S k & 10 + w”
・It was made into fiber by steam treatment with G. The results are shown in Table 2.

The following items became clear from Table 2.

1. When the single fiber Jl11 degree exceeds [Ll (l), the water retention rate was 304 or less.In order to reduce the single fiber fineness to Qld or less, it is effective to increase the molecular weight of the polymer and lower the concentration of the stock solution. .

When λ acrylonitrile is not copolymerized with a hydrophilic heptamer, the water retention rate is 3 even if the single fiber fineness is 111 (L or less).
0 Yushi was small.

Patent originator: Mitsubishi Ray N Co., Ltd.

Claims (1)

[Claims] An acrylonitrile polymer having a weight average molecular weight of 300,000 or more and containing 80% or more of acrylonitrile, and containing 3% or more of a hydrophilic monomer having a solubility in water at 20°C of 5% or more as a copolymer component. A method for producing acrylic fibers with a single fiber fineness of 0.1 d or less and a high water retention rate, which comprises spinning a stock solution obtained by dissolving acrylic fibers in an organic solvent.