JPH0291271A - Highly hygroscopic fiber - Google Patents

Abstract

PURPOSE:To obtain a highly hygroscopic fiber having a water-swelling degree suppressed below a specific level, resistant to permanent set and disfigurement and durable to repeated use between moisture-absorbed state and moisture- released state by subjecting an acrylic fiber to simultaneous crosslinking treatment and hydrolysis treatment and introducing a specific amount of a salt-type carboxyl group into the fiber. CONSTITUTION:A highly hygroscopic fiber having a tensile strength of >=1g/d (especially >=2g/d), an elognation of 15-60%, a water-swelling degree of <=300% and a water-content of >=20% (preferably >=30%) at 20 deg.C and 65% RH can be produced by subjecting an acrylic fiber to simultaneous crosslinking treatment and hydrolysis treatment and introducing >=2meq/g (especially >=4meq/g) of a salt-type carboxyl group into the fiber. A highly hygroscopic sheet can be produced by using said highly hygroscopic fiber in combination with a hot-melt fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a fiber that has high moisture absorption performance and also has practical performance that can withstand processing such as card hanging.

(Prior Art and Problems) Hygroscopic agents have traditionally been used as a means to remove moisture in a space.

Silica gel, synthetic zeolite, sodium sulfate, activated alumina, activated carbon, etc. are examples of moisture absorbing agents that retain their shape even after moisture absorption and can be reused. It has drawbacks such as requiring high temperatures for subsequent drying.

In addition, hygroscopic agents such as lithium chloride, calcium chloride, magnesium chloride, and phosphorus pentoxide absorb a large amount of moisture and have a fast rate of moisture absorption, but these hygroscopic agents are deliquescent and can liquefy after absorbing moisture, contaminating others. Shaping and straightening that is difficult to handle,
It has drawbacks such as difficulty in reproduction.

In order to solve this drawback, methods have been proposed in Japanese Patent Application Laid-open Nos. 52-107042 and 68-31522, in which a water-absorbing resin and a deliquescent salt are mixed together.

However, in order to use the moisture absorbent in the form of a sheet, nonwoven fabric, etc. by the above method, the moisture absorbent is sprinkled onto the sheet, nonwoven fabric, etc., and then the moisture absorbent is sandwiched or wrapped. There are problems such as the fact that it is easy to use, does not have sufficient moisture absorption ability, and requires complicated steps to process into the above-mentioned form.

It is also known that water-swellable fibers, of which the applicant's Japanese Patent Publication No. 58-10508i is a representative example, have a certain degree of hygroscopicity; Because of this, it has been difficult to apply it to applications that require morphological stability.

(Problems to be Solved by the Invention) The objects of the present invention are to absorb a large amount of moisture, have a fast moisture absorption rate, be easy to handle, be easily processed into various shapes, and have excellent shape retention after moisture absorption. It is an object of the present invention to provide a highly hygroscopic fiber that can be easily recycled.

(Means for Solving the Problems) A highly hygroscopic fiber capable of achieving the above-mentioned object of the present invention can be obtained by simultaneous crosslinking and hydrolysis treatment of acrylic fiber.
It does not have a salt type carboxyl group of q/9 or more introduced, and has a tensile strength of Lf/d or more and a moisture content of 20% or more at 20° C. and 65% relative humidity.

The present invention will be described in detail below.

First, the acrylonitrile (hereinafter referred to as AN) polymer that forms the acrylic fiber used as the starting fiber is preferably a polymer containing 40% by weight or more, preferably 50% by weight or more of AN, and may also be an AN homopolymer. . Copolymerization agents include vinyl halides and vinylidene halides such as vinyl chloride, vinyl bromide, and vinylidene chloride; ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid, and their salts. (meth)acrylic acid methyl, (methaneethyl acrylate, (methanebutyl acrylate, etc.); (metalacrylic acid entel m) such as (meth)acrylic ethyl acrylate; Ethylenically unsaturated sulfonic acids such as p-styrene sulfonic acid and their salts; (includes vinyl compounds such as methanacrylamide, vinylidene cyanide, methacrylonitrile, etc.; among them, ethylenically unsaturated carboxylic acids and their salts; (Methane acrylic acid esters, ethylenically unsaturated sulfonic acids, and their salts are preferable from the viewpoint of their hydrolysis promoting effect and moisture absorption performance, and vinyl esters are preferable from the viewpoint of the balance between practical performance and moisture absorption performance. .

In addition, the fiber diameter is preferably as thin as possible from the surface area (or moisture absorption rate), but from the viewpoint of fiber physical properties etc., it is approximately 3 to 100, preferably 5 to 5.
0μ is recommended. In addition, the cross-sectional shape of the fibers is not limited to round, flat, triangular, etc., and any shape can be used such as short fibers, long fibers, threads, non-woven fabrics, knitted fabrics, etc. can.

In order to use the acrylic fiber as a starting fiber to produce the desired highly hygroscopic fiber, it is necessary to carry out simultaneous crosslinking and hydrolysis treatments.

In the present invention, known crosslinking agents such as formalin, hydrazine, and hydroxylamine can be used, except that it is important to perform crosslinking and hydrolysis at the same time. Although any method may be used, the following method is recommended for industrially advantageous production of the desired highly hygroscopic fiber.

That is, an aqueous solution in which hydrazine and alkali metal hydroxide coexist is mixed with alkali metal hydroxide (NaOH equivalent) of 10 to 50%, preferably 15 to 45%, hydrazine Adjust the attached fibers so that (N2 H4 pure content equivalent) is in the range of 1-10%, preferably [,5-9% 1. Heat the fibers at a temperature of 80°C or higher for 5-120 minutes. , preferably 100-150'
It is desirable to adopt a method of heating in a moist heat atmosphere for 10 to 80 minutes. Note that as the solvent for preparing the aqueous solution, water is preferred from an industrial perspective, but a mixed solvent of water and a water-miscible organic solvent such as alcohol, acetone, or dimethylformamide may also be used.

In this way, 2 m of the outer layer of the starting acrylic fiber was added.
Salt-type carboxyl groups of eq/9 or more, preferably 3 meq/9 or more, more preferably 4 meq/9 or more are introduced, and 11176 or more, preferably 1.5 f/d or more, even more preferably 2 f/d It has a tensile strength of 15% to 60% or more, and an elongation of 15% to 60%, preferably 4%
It is possible to provide a highly hygroscopic fiber having a degree of water swelling of 00% or less, more preferably 800% or less, and a moisture content of 20% or more, preferably 80% or more at 20° C. and 65% relative humidity. can.

Here, fA (meq/f/
) Accurately weigh approximately 0.25 f of a sufficiently dried sample (XI)
After adding 10(1+/) water and 0.5F sodium chloride to this, add IN hydrochloric acid aqueous solution to make the pH 2, then obtain a titration curve with 0.IN caustic soda aqueous solution according to a conventional method. The amount of caustic soda aqueous solution consumed by carboxyl groups (Ym/ ) was determined from the titration curve, and 1oos+ was added to the sample (XIF) in which approximately 0.25F was accurately weighed.
After adding / of water and 0.51 of sodium chloride, 0,
The amount of caustic soda aqueous solution consumed (Ylml) was determined by titration with an IN aqueous sodium hydroxide solution in the same manner as above, and calculated from the above measurement results using the following formula.

Salt type carboxyl All carboxyl (group m:
meq/g) = (Amount of group: meq/f/'-(Binana Yuz〉7) = 0.1Y/x-0, IYl/+Xt As for the type of salt-type carboxyl group, lithium ,sodium,
Alkali metals such as potassium; salts such as di- or triethylamine, di- or tripropylamine, and glutylamine; salts such as ammonium, tetramethifleammonium, and tetofbutylammonium; introduction of salt-type carboxyl groups; As a method, acid type carpoquin group-containing fibers are treated with an aqueous solution of an alkali metal hydroxide, a basic salt such as sodium bicarbonate or sodium carbonate, an amine, or ammonia, or a ganne such as ammonia or a lower amine. There are ways to do so. Note that acid type carboxyl groups may coexist as long as the amount of salt type carboxyl groups satisfies the above range.

The degree of water swelling (%) was determined by immersing approximately 0.5y of the sample in 800g of pure water at 25'C for 80 minutes, followed by centrifugal dehydration (800g).
00G /) and calculated by the following formula.

Wl - W2 (Water swelling degree: %) = X100 Also, water content (
% sample of approximately 2V, 20'C, predetermined (DJ'lt
i degrees (inner volume 51 adjusted to 82, 45, 65, 951
After leaving it in a glass desiccator for 3 weeks, it was weighed (W3
f) L. Next, the sample was dried at 105° C. until it reached a constant weight, and then weighed (W4f) L. Calculated using the following formula.

Wa - W4 (moisture content 2%) = -X100 In order to further improve sagging and clogging during use, as well as processability for card hanging, etc., crimped fibers are used as starting acrylic fibers. It is desirable to use the fibers to form highly hygroscopic fibers having crimp characteristics in the range of approximately 5 to 15 crimps and a crimp degree of 5 to 25%.

In addition, in order to provide the fiber of the present invention that simultaneously satisfies the contradictory objectives of maintaining fiber properties that are free from practical problems and imparting high moisture absorption performance while suppressing water swelling as much as possible, in particular, the following needs to be achieved: It is desirable to adopt starting acrylic fibers with specific properties.

That is, the AN polymer molecules forming the fibers are sufficiently oriented and the Congo Red lt lower cR,! : It is desirable to use acrylic fibers with a dichroic ratio of 0.45 or more, more preferably 0.5 or more. In addition, CR dichroism ratio is calculated from Polymer Science 2B (252) 193 (1966)
It was determined according to the method described.

Note that there are no limitations to the method for producing such acrylic fibers.
As long as the above CR dichroic ratio is satisfied, known means can be used as appropriate, but among them, the total stretching ratio is 6 times or more,
Desired acrylic fibers can be produced industrially advantageously by employing means to preferably increase the shrinkage rate to 8 times or more and to reduce the shrinkage rate in the process to 30% or less, preferably 20% or less.

In addition, when short fibers are used as the starting fibers, the obtained highly hygroscopic fibers can be processed into threads, nonwoven fabrics, N-woven fabrics, etc., as appropriate depending on the final use form. In particular, in applications where dimensional stability is required, the highly hygroscopic fiber of the present invention and the heat-adhesive fiber (preferably 10 to 80%
A non-woven fabric with a blending rate of 1.5% is recommended. The heat-adhesive fiber can be used as long as it has heat-adhesive properties. For example, the low-melting point-high melting point component may be polyethylene (PE).
)-polypropylene (PP), PE-polyester tv
(PES), PES-PES, and the like.

(Effects of the Invention) The highly hygroscopic fiber of the present invention thus obtained maintains fiber physical properties that pose no problem in practical use, and also suppresses water swelling to a certain level or less. It has advantages such as high moisture absorption rate and flexibility in shape, and does not cause deformation or deformation during use, so it can be used repeatedly for moisture absorption and moisture release. Garuujj,
, m is a noteworthy effect of the present invention.

Such highly hygroscopic fibers can be used in any form of use in fields where dehumidification or humidity control is required, such as storage of foods such as confectionery, seaweed, and coffee beans, and medicines, and daily necessities such as closets and shoe cabinets. It is widely used in a wide variety of fields, such as preventing dew condensation in houses.

(Examples) Hereinafter, the present invention will be specifically explained with reference to Examples. Parts or percentages in the examples are expressed on a weight basis unless otherwise specified.

Example l ANg □% and methyl acrylate (hereinafter referred to as MA)
48% of 10 parts of AN-based polymer (intrinsic viscosity [η]: 1.2 in dimethylformamide at 30°C) consisting of 10%
After spinning and stretching (total stretching ratio: 10 times) a spinning stock solution dissolved in 90 parts of Rodan soda aqueous solution according to a conventional method,
Soft bulb/wet bulb = 120°'C/6 Q'c No. 3, 9, dry the bottom (shrinkage rate 14%), mechanically crimp, cut (fiber length 51H), and cut the raw material. Fiber t(CR
A dichroic ratio of 0.58) was obtained.

Next, raw fiber 1 was added with 25% caustic soda and 7 hydrazine.
After adhering 100% of the aqueous solution containing
y) was produced.

Table 1 shows the results of evaluating the fiber characteristics.

As is clear from Table 1, it is understood that the fiber 1 according to the present invention has excellent moisture absorbing performance while maintaining m retention that is free from practical problems.

On the other hand, as a comparative example, raw fiber l was immersed in a 3% hydrazine aqueous solution, treated at 100'C for 3 hours, and then boiled for 30 minutes in 5% and 25% caustic soda aqueous solutions R1j. Fiber 1 could hardly maintain its fiber morphology.

Example 2 Raw material fiber 2 (process shrinkage rate 16%, CR dichroism ratio 0) was prepared in the same manner as in Example 1 except that vinyl acetate was used instead of MA.
．． 56) was obtained, and then a test fiber (1) (fiber diameter 32μ) was produced according to the same recipe as in Example 1.

Table 2 shows the evaluation results of the fiber characteristics.

Table 2 Three types of m-fibers 1-1 were produced in the same manner as above.

The evaluation results are also listed in Table 3.

Table 3 From Table 2, it is understood that the present invention can provide highly hygroscopic fibers with excellent overall properties.

Example 3 From Table 3 of Example 2, the desired moisture content was obtained by changing the amount of caustic soda or hydrazine attached (purity) as shown in Table 3. It is understood that R fibers with water swelling degree and fiber physical properties can be produced.

Example 4 Four types of fibers W~ ■
was created.

The evaluation results are also listed in Table 4.

From the table above in Table 4, it is understood that by controlling the CR dichroic ratio, high moisture absorption performance can be imparted without impairing the fiber properties.

Example 5 The Ra170% produced in Example 1 and 80% of heat-welding Mable fiber (low density PE, crystalline PP-1,1, single fiber fineness 3d1 fiber length 51m) were carded to form a 100y/- A web was formed and then treated with hot air at 145c for 5 seconds to produce a nonwoven fabric.

A nonwoven fabric could be produced without any problems such as carding, water swelling degree was 185%, moisture content was 82% at RH 65%, and it had good dimensional stability.

Example 6 The fiber a1 produced in Example 1 was immersed in an aqueous solution of hydrochloric acid at pH 2 for 30 minutes at room temperature to change the Na salt type carboxyl group to the acid type to form the fiber X. R fiber X was treated with a lithium hydroxide aqueous solution to change the acid type carboxyl group to Li salt type to produce fiber aX.

The evaluation results are shown in Table 5.

Table 5 Example 7 Fiber 1 of Example 1 and commercially available dried silica gel (diameter 2 to 5 MM) each 5y were left in a room at a temperature of 20°C and RH 75%, and the moisture content was measured after a predetermined period of time had passed. .

The results are shown in Table 6.

From Table 6, it can be seen that the product of the present invention has a much higher water absorption rate and water content than silica gel.

Claims (2)

[Claims] 1. 2 meq/g or more of salt-type carboxyl groups are introduced through simultaneous crosslinking and hydrolysis treatment of acrylic fibers, and it has a tensile strength of 1 g/d or more and a moisture content of 20% or more at 20°C and 65% relative humidity. Highly hygroscopic fiber with 2. A highly hygroscopic sheet comprising the highly hygroscopic fiber according to claim 1 and heat-adhesive fiber.