Process For The Treatment Of Polyester Fiberous Materials

Abstract

A process for improving the handling of fibrous materials made of polyester by impregnating said fibrous materials with a solution containing an alkaline substance and a polymeric substance soluble or dispersible in said alkaline solution, and then treating said fibrous materials with dry heat at a temperature higher than 120.degree. C. and lower than the melting point of the polyester fiber.

Description

SUMMARY OF THE INVENTION

This invention relates to a process for improving the handling of polyester fibrous materials comprising polyester fibers, especially polyester long filaments. More particularly, this invention relates to a process for treating (with dry heat continuously and at high speed) polyester fibers and knitted goods or woven goods of polyester fibers impregnated with an aqueous solution containing an alkaline substance and a polymeric substance which is soluble or dispersible to form a hydrophilic colloid in an alkaline solution.

DESCRIPTION OF THE PRIOR ART

Improvement of the handling of knitted goods or woven goods made of polyester fiber by impregnating said goods with an aqueous solution of an alkaline metal hydroxide with warming is known. When polyester fibers, for example, polyethylene terephthalate fiber is treated with an aqueous solution of an alkali metal hydroxide, the outer layer of the fiber dissolves and the affected layer is hydrolyzed into terephthalic acid and ethylene glycol. A small amount or a considerable amount of the outer layer is hydrolyzed or dissolved, according to the condition of the treatment. The fineness of polyester fibers is reduced in proportion to the degree of hydrolysis of the outer layer and the fibers constituting the fabric move easily by application of external force. Thus, improvement perceptible as a more silky handling is effected. While the degree of hydrolysis is 2-4 percent by weight, the original hard touch of the product of polyester fibers is only slightly improved, but when the degree of hydrolysis is 10-20 percent by weight, the product has very good silky handling.

In treating polyester fibers for the above-mentioned purpose, it has heretofore been required to select the proper kind of alkali and to maintain the concentration of the alkali, temperature of the treating bath and period of treatment at proper values. However, there is substantial difficulty in choosing the condition of treatment, when the process is carried out on an industrial scale.

For example, in order to reduce the weight of woven fabric of polyethylene terephthalate fiber by 15 percent by weight, it has to be dipped in about 5 percent by weight aqueous solution of sodium hydroxide at 95.degree.-98.degree. C. for more than 2 hours in a jigger. This is a very inefficient process and in addition, it is very difficult to maintain the concentration of the alkali constant throughout. As a result, the effect of the treatment is not uniform. Various methods, for example, methods wherein a primary or secondary amine is used as a catalyst of hydrolysis (Japanese Pat. Publication Nos. 3946/1962 and 7393/1962 ) and a method wherein a quaternary ammonium salt is added to shorten the period of treatment (U.S. Pat. No. 3,135,577) in treating polyesters containing an aromatic dicarboxylic acid have been proposed in order to overcome the above-mentioned difficulties.

However, these methods are not satisfactory since they attach too much importance either to the uniformity of the treatment at the sacrifice of the efficiency or to the efficiency of the process at the sacrifice of the uniformity. Furthermore, the equipment used heretofore for such treatment, for example, equipment for processing textile such as a jigger have a drawback in that they structurally are not suitable for continuous alkali treatment.

DESCRIPTION OF THE INVENTION

The present invention provides a process for treating polyester fibrous materials, e.g., polyester filament, fiber, thread, strand, tow, silver, and knitted or woven goods made of polyester fibers, especially of polyester long filaments, and the like (hereinafter fibrous material for short) with dry heat at an elevated temperature after application of a liquid mixture of a highly concentrated solution of an alkali and a solution of a hydrophilic polymeric substance which is soluble or dispersible in the alkaline solution and can form a hydrophilic colloid.

According to this invention, the fibrous materials can be treated continuously and at high speed and at the same time, uniformly yielding the product having improved handling. Furthermore, the treatment can be accomplished in a very short time.

In practice of this invention, said fibrous materials (e.g., knitted or woven goods) composed of polyester fibers or containing at least 65 percent by weight of polyester fibers and less than 35 percent by weight of other filamentary materials are impregnated uniformly with a mixture of a solution of an alkaline substance and a hydrophilic polymeric substance (hereinafter referred to as substance A) which gives proper viscosity to the solution of the alkaline substance and which can at the same time form a hydrophilic colloid in the alkali solution (hereinafter this substance is referred to as substance A), treated with dry heat for a short time, for example 5-300 sec., at a temperature higher than 120.degree. C. and lower than the melting point of the polyester fiber to solubilize the surface of the fiber and then washed with water to remove the solubilized matter. Thus, the fibrous materials e.g., knitted or woven goods of polyester fibers may be processed continuously into a product which is soft to the touch, and in addition, the effect of the treatment is uniform.

Typical alkaline substances for use in the practice of this invention include alkali metal hydroxides and other alkaline salts such as alkali metal sulfides, alkali metal sulfites, alkali metal phosphates, alkali metal silicates and alkali metal carbonates. An alkaline solution is prepared by dissolving at least one such alkaline salt. Suitable concentrations of the alkaline solution differ with the fineness of the fiber or filament to be treated, thickness of the cloth, degree of the softness of the cloth desired, concentration of the substance A used therein, properties of the solvents for the alkaline substance and substance A, temperature of the treatment etc., and it is generally 1-80 percent by weight preferably 5-60 percent by weight, based on the total amount of the solution of the alkaline substance and the substance A.

The essential aspect of the process of the present invention is that a solution of substance A is used together with a solution of an alkaline substance, as mentioned above.

The substance A includes natural gums, for example, tragacanth gum, gum arabic, karaya gum, fine gum, kipro gum, and nafka crystal gum processed starches, for example, dextrin, corn starch, crystal gum, British gum and synthetic sizes, for example, polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose and ethyl cellulose. These substances may be used singly or in combination. These substances can form a highly viscous colloidal solution in an aqueous solution.

Suitable concentration of the solution of the above-mentioned substance A differs greatly with the concentration of the alkali solution used, degree of softness of the cloth desired, temperature of treatment, period of treatment and the kind of equipment used for heat treatment. For example, in the case of gum arabic, the use of 3-20 percent by weight is preferable, when the concentration of the alkali solution is 5-40 percent by weight, based on the amount of the whole solution.

As the solvent for the above-mentioned alkali substance and substance A, a solution of at least one heterocyclic organic nitrogen-containing compound such as pyridine or heterocyclic oxygen-containing compounds such as dioxane containing more than 50 percent by weight of water may be used. The use of water is preferable from the economic point of view.

The polyester fibrous materials impregnated with the above-mentioned alkaline solution is generally subjected to heat treatment at a temperature higher than 120.degree. C. and lower than the melting point of said polyester fibrous materials. As the equipment for use in the process, any equipment which presents continuous dry heat treatment may be used, such as a metal cylinder dryer, metal cylinder covered with an endless belt, pin tenter, clip tenter, nontouch dryer, short loop dryer, hot flue etc. The time required for heating is generally 5-300 seconds.

In this invention, the substance A is added to the alkaline solution in order to repress vaporization of water from the knitted or woven goods containing the alkaline solution at the time of dry heat treatment and as a result, to promote hydrolysis advantageously. The substance A itself does not catalytically promote the hydrolysis.

Accordingly, the process of this invention exhibits its characteristic aspect at the time of dry heat treatment at an elevated temperature, especially at the time of dry heat treatment at an elevated temperature higher than the boiling point of the solvent dissolving the alkaline substance and the substance A.

This invention is further illustrated by the following examples, although it will be understood that these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention.

EXAMPLE 1

20 g. of 2/1 -twill fabric composed of 75-denier filament of polyethylene terephthalate (semidull) was desized, scoured, dried, dipped in one liter of an aqueous solution containing 430 g. of sodium hydroxide and 80 g. of gum arabic and then squeezed with a mangle to a squeeze rate of 40 percent. The cloth was then treated with dry heat for 70 seconds in a clip tenter, the temperature of which was maintained at 180.degree. C. After this dry heat treatment, the cloth was washed in running water for one minute, in 5 percent aqueous solution of acetic acid for 2 minutes and again in running water for 2minutes, squeezed with a mangle and dried for 30 minutes in an air bath at 100.degree. C. After standing for 24 hours and a day at 20.degree. C. and at a relative humidity of 65 percent, the cloth had a constant weight 21 percent less than the weight before the treatment and had a very good silky touch.

On the other hand, when the same cloth was treated in the same manner except that gum arabic was added to the aqueous solution of the alkaline substance, the decrease of weight of the cloth after the treatment was 9 percent.

EXAMPLE 2

Plain fabrics of warp and woof densities of 110/inch composed of 75-denier filament of polyethylene terephthalate (semidull) were desized, scoured, dried, dipped in an aqueous solution containing 240 g. of sodium hydroxide, 50 g. of gum arabic, and 30 g. of carboxymethyl cellulose in one liter of solution and then squeezed with a mangle to a squeeze rate of 50 percent. The cloth was then treated with dry heat for 85 seconds in a pin tenter, the temperature of which was maintained at 200.degree. C. The cloth was washed and subjected to aftertreatment in the same manner as in Example 1. Decrease of the weight of the fabric produced by the treatment was 25 percent and the produced polyester cloth had a very soft and silky handling.

On the other hand, when the same cloth was treated in the same manner except that an aqueous solution containing only 240 g. of sodium hydroxide and no gum arabic and no carboxymethyl cellulose in one liter was used, the decrease of the weight of the cloth was 4 percent.

EXAMPLE 3

In one liter of a 1:1 liquid mixture of a 50 percent aqueous pyridine solution containing 600 g. of potassium hydroxide per liter and an aqueous solution containing 40 g. of crystal gum per liter, 30 g. of the same cloth as used in Example 1 was dipped, squeezed to a squeeze rate of 50 percent in the same manner as in Example 1 and then treated at 180.degree. C. in the same manner as in Example 1. The decrease of the weight of the thus produced cloth was 25 percent.

When the cloth was treated by the use of a liquid mixture prepared by mixing only water instead of an aqueous solution of crystal gum with the solution of potassium hydroxide, the decrease of the weight of the cloth by the treatment was 12 percent.

EXAMPLE 4

In a 2:1 mixture of a solution of 20 percent by weight of sodium hydroxide in 10 percent aqueous dioxane and an aqueous solution containing 5 percent by weight of methyl cellulose and 3 percent by weight of British gum, the same cloth as used in Example 2 was dipped. It was then squeezed to a squeeze rate of 55 percent, treated with dry heat for 60 seconds on the surface of a metal cylinder dryer the temperature of which was maintained at 130.degree. C., and aftertreated and dried in the same manner as in Example 1. Decrease of the weight of the cloth after this treatment was 23 percent.

When the same cloth was treated with a solution prepared by diluting a solution of 20 percent by weight of sodium hydroxide in 10 percent aqueous dioxane with the same amount of water, decrease of the weight of the cloth was 13 percent.

EXAMPLE 5

The same polyester fabrics as were used in Example 2 were dipped in one liter of aqueous solution containing 300 g. of caustic soda, 50 g. of sodium carbonate and 10 g. of fine gum and then squeezed with a mangle to a squeeze rate of 50 percent. The cloth was then treated with dry heat for 45 seconds at 160.degree. C. in a nontouch dryer. The cloth was washed in water, neutralized, washed in water and dried in the same manner as in Example 1.

The decrease of the weight of the cloth was 15 percent and the produced cloth had a desirable, silky handling.

On the other hand, when the cloth was treated in the same manner except that fine gum was not used, the decrease of the weight of the cloth was only 6 percent.

EXAMPLE 6

A tricot cloth composed of 50 denier/24 filaments of polyethylene terephthalate (full dull) was dipped in one liter of aqueous solution containing 350 g. of caustic soda, 20 g. of sodium silicate and 10 g. of Kipro-gum and then squeezed with a mangle to a squeeze rate of 50 percent. The cloth was then treated with dry heat for 200 seconds at 125.degree. C. in a short loop dryer. The cloth was, thereafter, washed in water, neutralized, washed in water and dried in the same manner as in Example 1.

The decrease of the weight of the tricot cloth produced by the treatment was 17 percent and the produced cloth had a soft and silky handling compared with that before the treatment.

On the other hand, when the cloth was treated in the same manner except that Kipro-gum was not used, the decrease of the weight of the tricot cloth was only 6 percent.

EXAMPLE 7

The same polyester tricot cloth as was used in Example 6 was dipped in one liter of aqueous solution containing 320 g. of caustic soda, 30 g. of potassium phosphate and 20 g. of Nafka Crystal Gum and then squeezed with a mangle to a squeeze rate of 50 percent.

The tricot was then subjected to a treatment for 30 seconds in a metal drum covered with an endless belt and having the surface temperature regulated at 140.degree. C.

The cloth was washed in water, neutralized, washed in water, and dried in the same manner as in Example 1.

The decrease of the weight of the tricot cloth was 18 percent. The tricot cloth thus produced had a very soft and silky handling compared with the original cloth.

On the other hand, when the tricot cloth was treated in the same manner except that Nafka Crystal Gum was not used, the decrease of the weight of the tricot cloth was 9 percent.

EXAMPLE 8

The same polyester tricot cloth as was used in Example 6 was dipped in one liter of aqueous solution containing 400g. of caustic soda, 50 g. of potassium sulfate and 25 g. of gum tragacanth and then squeezed with a mangle to a squeeze rate of 50 percent.

The tricot cloth was then made to contact with the surface of a metal cylinder dryer normally used for drying fabrics to be given a dry heat treatment for 70 seconds at 130.degree. C. Then the cloth was washed in water, neutralized, washed in water and dried in the same manner as in Example 1.

The decrease of the weight of the tricot cloth was 24 percent and the thus produced cloth had a very soft and silky handling, compared with that of the original cloth.

On the other hand, when the cloth was treated in the same manner except that gum tragacanth was not used, the decrease of the weight of the tricot cloth was 6 percent.

EXAMPLE 9

The same polyester fabrics as were used in Example 2 were dipped in one liter of an aqueous solution containing 310 g. of caustic potash and 50 g. of sodium sulfate and 20 g. of Karaya gum and squeezed with a mangle to a squeeze rate of 50 percent. The cloth was then subjected to a dry heat treatment for 40 seconds at 180.degree. C. in a hot flue. The cloth was, thereafter, washed in water, neutralized, washed in water and dried in the same manner as in Example 1.

The decrease of the weight of the cloth was 19 percent and the thus produced cloth had a very soft and silky handling, compared with that before the treatment.

On the other hand, when the fabrics were treated in the same manner except that Karaya gum was not used, the decrease of the weigh of the fabrics was 4 percent.

Claims

What is claimed is:

1. In the process for improving the handling of a fibrous material containing at least 65 percent aromatic polyester fibers by hydrolysis of said polyester fiber, the improvement comprising:

a. uniformly impregnating said material with an aqueous solution consisting essentially of an inorganic alkaline salt and a hydrophilic colloid selected from the group consisting of natural gum, processed starches, polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, and ethyl cellulose, the concentration of polymeric substance being 0.5 to 20 percent based on the total weight of the solution; and

b. heating by a dry heat treatment the impregnated material at a temperature higher than 120.degree. C. up to the melting point of the polyester, said heating being conducted from about 5 to about 300 seconds.

2. A process according to claim 1 wherein the concentration of the alkaline substance in solution is 1-80 percent by weight based on the total weight of the solution.

3. A process according to claim 1 wherein said polyester fiber is polyethylene terephthalate.

4. A process according to claim 1 wherein said inorganic alkaline salt comprises a hydroxide, sulfide, sulfite, phosphate, silicate or carbonate of an alkali metal.

5. A process according to claim 1 wherein the polyester fiber is in the form of a filamentous yarn.