Bleaching and dyeing; fluid treatment and chemical modification – Chemical modification of textiles or fibers or products thereof
Reexamination Certificate
2000-11-01
2004-05-18
Wilson, D. R. (Department: 1713)
Bleaching and dyeing; fluid treatment and chemical modification
Chemical modification of textiles or fibers or products thereof
C008S115680, C008S115690, C525S329100, C525S329200, C525S329300, C525S367000, C525S376000
Reexamination Certificate
active
06736856
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a crosslinked acrylic moisture absorbing fibers capable of reversibly and repeatedly carrying out moisture absorption and moisture releasing. More specifically, the invention relates to a method of efficiently obtaining crosslinked acrylic moisture absorbing fibers having a high quality by using acidic comonomer-containing acrylic fibers of at least 1% by weight as raw material acrylic fibers, and also to crosslinked acrylic moisture absorbing fibers obtained by the method.
BACKGROUND OF THE INVENTION
Acrylic fibers are one kind of synthetic fibers most widely used, and the moisture absorbing rate of usual commercially available acrylic fibers is from about 1 to 2%, which is lower than those of natural fibers such as cotton, sheep wool, etc. About such acrylic fibers, a fiber material which can be repeatedly carried out a moisture absorption and moisture releasing and also can be applied for the fields of clothes and nightdresses has been required.
For the purpose of imparting the moisture absorbing-moisture releasing property to acrylic fibers, it is proposed in Japanese Patent Laid-Open No. 91271/1990 or 132858/1993 that after applying a crosslinking treatment to acrylic fibers with hydrazine, the nitrile group remaining in the fibers are converted to a carboxyl group or the metal salt of a carboxyl group by hydrolyzing the nitrile group with an alkali metal hydroxide, whereby the crosslinked acrylic fibers imparted with the moisture absorbing-moisture releasing property.
In the above-described crosslinked acrylic moisture absorbing fibers of prior art, the saturated moisture absorbing rate and the degree of swelling by water under the standard condition of 20° and 65% RH show high values as from 25 to 50% and 150 to 300%, respectively.
Now, it is known that acrylic fibers are generally obtained by copolymerizing acrylonitrile as the main constituent and a neutral comonomer such as a vinyl monomer (such as vinyl acetate, a vinyl halide, a vinylidene halide, etc.), styrene, an acrylic acid ester, a methacrylic acid ester, (meth)acrylamide, etc.; an acidic comonomer such as sulfonic acid-containing comonomer (such as (meth)allylsulfonic acid, p-styrenesulfonic acid, etc., and the salts thereof), a carboxylic acid-containing comonomer (such as (meth)acrylic acid, itaconic acid, etc., and the salts thereof); or a basic comonomer such as vinylpyridine, methylvinylpyridine, etc., as other comonomer component.
Such a comonomer used for producing acrylic fibers is used for the purposes of improving the spinning property at the production of acrylic fibers and improving the characteristics of the products. In these comonomers, the acidic group-containing comonomer and the salts thereof, particularly, the sulfonic acid-containing comonomer and the salts thereof are generally used for improving the dyeing property, etc., of acrylic fibers, and usually the comonomer is copolymerized in a ratio of not more than 1% by weight.
Such an acidic group-containing comonomer has hitherto been used for improving the dyeing property of acrylic fibers even when the acrylic fibers contain more than 1% by weight the comonomer, the dyeing property is not further improved. Thus, for general acrylic fibers for clothing, a copolymer containing at least 80% by weight an acrylonitrile component and not more than 1% by weight a dyeing property-improving comonomer (that is, an acidic group-containing comonomer) and a neutral comonomer is used.
Because in the crosslinking treatment by the above-described method of prior art, the object of the treatment is ordinary acrylic fibers widely used, the content of the acidic group-containing comonomer in the acrylic fibers is usually small as less than 1% by weight. For applying the crosslinking treatment to such acrylic fibers widely used, it was necessary to carry out the treatment using an aqueous solution of a hydrazine concentration of from 0.5 to 3 times to the fibers to be treated, that is, an aqueous solution of from 5 to 30% by weight hydrazine (bath ratio of 1:10), under a high-temperature condition of, for example, a temperature of 98° C. for a long time of from 3 to 10 hours.
As described above, in the case of producing above-described crosslinked acrylic fibers of prior art imparted with the moisture absorbing-moisture releasing property, there was a problem of requiring severe reaction conditions for the crosslinking treatment and the hydrolytic treatment, that is, the severe reaction conditions of the long treatment time under the high treatment temperature, and also there were problems that the using amount of the chemical liquid (hydrazine and alkali metal oxide, etc.) was large, an excessive amount of the chemical liquid for reaction had to be supplied to the fibers, and the cost of the fibers obtained became high.
Also, in the above-described crosslinked acrylic moisture absorbing fibers of prior art imparted with the moisture absorbing-moisture releasing-property, the problem that the form-retentivity after absorbing moisture (or after absorbing water) was inferior because the degree of swelling by water was high (from 150 to 300%) as described above was severe and thus, the fibers had the problem that the application to the uses requiring the form stability was difficult.
On the other hand, it was known, for example, by Japanese Patent Laid-Open No. 91271/1990 that the treatment time for imparting the moisture absorbing-moisture releasing property could be shortened by simultaneously carrying out crosslinking and the hydrolytic reaction.
However, in the method of prior art of simultaneously carrying out crosslinking and the hydrolytic reaction, reaction rate of crosslinking is slow, whereby the crosslinking reaction becomes a rate-determining step. For example, to obtain the crosslinking degree of the increase in nitrogen content=0.6%, 5 hours (98° C.) was required for the crosslinking reaction at a hydrazine concentration of 2% (bath ratio 1:10).
As described above, when the hydrazine concentration used for the crosslinking treatment was allow concentration (for example, about 2%), a long time was required for making the crosslinking degree a desired range to advance the hydrolysis more than necessary. As the result thereof, the reaction of an alkali metal hydroxide was severe, whereby there were problems that the degree of swelling by water of the moisture absorbing fibers obtained was increased and the strength was also lowered.
For avoiding the occurrences of such problems, there is a method of increasing the degree of crosslinking by increasing the hydrazine concentration (for example 5% or higher) or increasing the treatment temperature (for example, 98° C. or higher) to shorten the crosslinking treatment time (about 2 hours). However, in the method, there was a problem that the amounts of the chemical liquids (hydrazine and sodium carbonate, etc.) for the crosslinking treatment and the hydrolytic treatment or the energy required for increasing the treatment temperature was increased.
Thus, an object of the present invention to provide a production method capable of reducing the amounts of the chemical liquids (hydrazine and sodium carbonate, etc.) for the crosslinking treatment and the hydrolytic treatment, capable of shortening the treatment time, and capable of obtaining crosslinked acrylic moisture absorbing fibers having a sufficient moisture absorbing-moisture releasing performance by using specific raw material fibers, and to provide the crosslinked acrylic moisture absorbing fibers at a low cost.
Furthermore, another object of the invention is to provide, in addition to the above-described object, crosslinked acrylic moisture absorbing fibers capable of repeatedly and reversibly carrying out a moisture absorption and moisture releasing, and also to provide crosslinked acrylic moisture absorbing fibers which has excellent form-stability after absorbing moisture and the production method.
DISCLOSURE OF THE INVENTION
The present invention is crosslinked acrylic moisture absorbing
Matsumoto Hideo
Takahashi Hayashi
Jordan and Hamburg LLP
Toho Tenax Co., Ltd.
Wilson D. R.
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