CA1156405A - Process for treating fibrous structure - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A process for treating a fibrous structure which comprises at least two components at least one component of which is a polyester containing an SO3M group wherein M represents hydrogen or an alkali metal. The process is characterized in that the fibrous structure is treated with an agent which deteriorates the polyester prior to an alkali treatment for the removal of the polyester component.

Description

0 ~

The present inven-tion relates to a process for treatiny a fihrous structure con~aining polyester. It has been broadl~ known that the treatment of a polyester fibrous struc-ture with alkali develops soft handle of -the structure by partial dissolution and removal of the materials. Furthermore, it has also been known that the mixtures of readily soluble fibers and relatively insoluble fibers treated with alkali can be provided with excellent soft handle by dissolution and removal of the readily soluble fibers.
However, the treatment not only takes a considerable lenyth of time to completely dissolve the readily soluble fibers, but also the readily insoluble fibers are damaged to some extent by alkali which leads to unexpected deterioration of physical properties. On the other hand, if the readily soluble fibers become more soluble in alkali, the fibers cannot withstand mixing, blending, knitting and weaving processes due to deterioration of their physical properties.
The readily soluble fibers also suffer from difficulty of fiber spinning (extruding).
This method of alkali treatment, therefore, is not practi-cally applied at present, though outstanding soft handle can be obtained.
In the case of conjugated (composite) fibers which consist of an alkali-readily-soluble co~onent and a relatively insoluble component which are treated with alkali to obtain micro(super) fine and special shape fibers, the problem is more serious since fine fibers which must remain in the structure are simply dissolved.
As a result of intensive studies by the inventors to solve this problem, there has now been found a process to selectively dissolve the readily soluble polyester fibers in a shorter time.

~ ~5~05 According to the present invention thexefore, there is provi.ded a process for trea-ting a fibrous structur0 having a-t least two components at least on~ component of which ls a polyester containing an 503M grollp where:in ~ represen-ts hydrogen or a metaL, said process comprisiny re-moval o~ the S03M yroup-containing polyester, preceded by pre~treatment of the fibrous structure with a degrading agent for said S03M group-containing polyester which preferentially degrades said S03M group-containing polyester, there-by producing a fibrous structure capable of being treated in a subsequent alkal.i treat~ent step to produce a soft fibrous product.
Particular embodiments of ~he present invention will now be described, by way of exarnple only, with reference to the accompany-ing drawings, in which:
Figures 1 through 9 are cross sections of conjuyate fibers which may ~e treated by the process of the present invention.
Figures 10 through 12 are cross sections of the conjugate fiber shown in Figure 3 from which the sea component has been removed by various methods.
In the present invention the pre-treatment of the fibrous structure with a degrading agent for polyester takes place at the stage of removal of a partial polyester component by the alkali treatment.
The present invention can not only produce a soft and bonney polyester fibrous structure with suEficient resilience, but can also enhance efficiency of the alkali treatment. The fibrous structures herein involve while fibers and processed goods such as yarn, staple fiber, tow, top, woven fabric, knitted fabric, and non woven fabric and they may contain finishing agents such as silicone resin, ` . . , 1 156~0~

melamine resin and llrethcme resin.
The fibrous s-tructures treated in the present invention which comprise two components or more, at least one of which is polyester contain.ing an S03M group, are for example, rnixtures of these separately spun components by a subsequen-t mixing or blending process. Conjugated fibers consist oE the components, as illustrat-ed in Figure 1-9, though they are not limited to the above mentioned.
Thus, the treated fibrous structures have a polyester component containing an S03M group which can be removed by the alkali treatment with one or more other components, but are not limited to any particular arrangement of - 2a -1 lS6~S

components.
~ In l'igurcs 1-9, componcrlt ~ is the readily soluble component to be removed by the alkali tre.LttlleJIt. I~ conj~Jga-te ~lbers o~ islands-in-sea type, the soa component is general.ly the read:ily soluble component. rhe readily soluble polyester component to be removed by the alkali treatment is a polyester containing a S03M group wherein M represents a metal~ particularly, an alkali metal or an alkaline earth metal or hydrogen atom. In consideration of both the spinnability and accessibility to alkali treatment after the treatment for degradation of the polyester, the polyester should be poly-ethylene terephthalate copolymerized with preferably 1-15 molar %, particularly preferably 3-S molar %~ of 5-(sodium sulfo) isophthalic acid ~he other one or more components a.re preferably synthetic fibers such as polyester, polyamide and polyacryl fibers, semi-synthetic fibers such as acetate fibers, regenerated fibers such as rayon fibers and natural fibers such as cotton, wool and silk fibers all of which are rather less soluble than the readily soluble polyester component to be removed by the alkali treatment.
The effects of the present invention are particularly remarkable for polyester fibers which are less soluble but not highly resistant to the alkali..
The terms "readily soluble" and "less soluble or relatively insol-uble" used herein are expressed depending upon their solubility but not in-dicated prior to the treatment with the degrading agent. The alkali treatment comprises hydrolysis of polyester with an alkaline substance. In general the treatment of polyester is effected in boiling aqueous solution of an alkaline substance such as sodium hydroxide for 30-120 minutes~ or in saturated steam at 100-130C for 1-5 minutes, after impregnation with alkali substance, or dry heat or superheated steam at 130-200C for 1-5 minutes, otherwise aging at 40_60C for 10-30 hours. In the process of the present invention, any tech-nique can be applied provided stable treatMent can ~e achieved. Alkaline metal or alkaline earth metal hydroxides such as sodium hydroxide and potassium hy-droxide, and basic salts such as sodium carbonate and potassium carbonate, can be applied as the alkali substance. The degradation agents ~or polyester in the present inven~ion lower average molecular weights of the polyesters They include, for example, amines such as ethylenediamine, ethylenetriamine and monoethanolamine, zinc salts such as zinc chloride, zinc sulfa~e and zinc ni-trate, oxidizing agents such as hydrogen peroxide, sodiurn hypochlorite and sodium chlorite, and acids such as hydrochloric acid, sulfuric acid, nitric acid, phos-phoric acid and oxalic acid. The acids are particularly appropriate, since they degradate selectiveJy the S03M group-containing polyester. The treatment is effected, for example, by the following processes:
a) The fibrous structure is treated in a boiling aqueous solution containing degrading agent for about 10-120 minutes;
b) The degrading agent is added to the fibrous strwcture and sub sequently treated with saturated ~apor at 100-130C for about 1-30 minutes;
c) Dry heat or superheated steam treatment is effected at 130-220C for about 1-10 minutes;and d) The fibrous structure is aged at 40-60C for 10-30 hours.
However, the possible processes are not limited to ~hose listed above but any process can be applied provided the average molecular weight can be lowered by degrading agents. Particwlarly desirable i.s thc tr0atment with acid in boiling aqeous solution at below PH2 ~or 60 minutes or 110-140C at below PH3 for 30 minutes. The addition of carrier, surfactant or quaternary ammonium salt in the treating bath can improve results.
The characteristic features of the process of the present invention are listed below in comparison with çonventional processes:

) 5 (1) tn the treatment of a ~iblous structure cvrnpris:ing blendcd yarn or mixed filament yarn, substarlti.ll de~ra~atiorl o~ ro~;iducll fibe-rs can be effected by long-term treatnletlt witll alkali in a convontional process. Ilowevcr the fibrous structures can achieve an-l maintain better handle without loss of physical propert:ies in the present lnve~tio~ because of short-term treatment. Although stable spinning or weaving calmot usually be expected for fi.bers which can be removed rapidly with alkali, the process of the present invention provides this stability since the treatment with degrading agent for the polyester promotes the hydrolysis rate in alkali.

(2) The process of the present invention is particularly effective in the case of polyester in both components of an islands-in-sea type conjugated fiber as shown in Figure 3. Only the :fiber shown in Pigure 11 can be obtained if the readily soluble component (A~ is removed by the conventional process, because a part of the less soluble component (e) is also dissolved. ~lowever, the pro-cess of the present invention provides complete removal of component A prior to the hydrolysis of component B, and finally can produce the fiber shown in Figure 10. The process of the present invention actually maintains the original ; shape o the island component through the removal of the sea component. There-fore, if an islands-in-sea fiber as shown in Figure 1 is treated by the process of the present invention, the respective independent islands can be left sep-arately with minimum damage of the islands component on the outside. In the conventional process~ the outer island components will sometimes disappear before the inner island component have been separated.

(3) The alkali reduction rate of the polyester increases by the process of the present invention. The alkali reduction rate can also be increased by the con~
ventional process if quaternary ammonium salt is used in the alkali treatment.
llowever~ the alkali reduction rate of only one component is increased selectively ll~B~V5 in tlle process of the present invcntion, while the reduction rates o the two components are -incre~lsel in the convcntional process. Iherefore, the conven-tional process cilnnot ~roviclo thc sarnc cffect as the proccss of tho present invent i.on .
The Eollowing examples further illustrate the process of the present invention, but they by no means limit the present invention.
Example 1.
Fabric in taffeta construction is woven with islands-in-sea fibers ~75 denier, 36 filaments) as shown in ~igure 3 for both warp and weft. The specifications of used fibers are as follows:
Component A: Polyethylene terephthalate copolymerized with ~ molar % of 5-(sodium sulfo) isophthalic acid.
Component B: Polyethylene terephthalate.
A/B ratio : 30/70 The fabric was treated in boiling I % aqueous sulfuric acid solution for 60 minutes and then in boiling 1,5 % aqueous sodium hydroxide sol-ution for 4 minutes to completely remove component A. Reduction in the amount of weight was 30.5 % at th.is time. Thereafter, the fabric was dyed by an or-dinary method. Thus dyed fabric had a mild color tone, high water absorption, excellent handling and was free from the problems of yarn slippage and tenacity.
In the cross section of the fiber, the edges were sharp as sholm in Figure 10.
In comparative Example 1, the fabric was treated directly in boil-ing 1.5 % aqueous sodium hydroxide solution omitting the sulfuric acid treatment. The complete removal of component A took 110 minutes with ~8 %
reduction in weight. This fact indicates that component B had also been reduced considerably in weight~
In comparative Example 2, the fabric was treated in the boiling 1.5 %

aqueous sodium hy~roxide solution in the presence of 0.8 % DYK-1125 (a quaternary ammonium salt; a trade3narked prodwct of Cppo Co., Ltd). Cor~ponent A could be completcly removed in a short period of 15 minutes but the amownt of reduction in weight was large, 65 %. Tllis fact also indicates that component B had been re-duced considerably in weight.
The fabric in comparati-ve Example 1 and 2 were then dyed by an or-dinary method. Thus dyed fabric showed considerable yarn slippage and poor tenacity, effects not realized by the process of ~he present inven~ion. In the cross sections of the fibers, the original shapes of component B were deformed in some extent as shown in Figure 11 and Figure 12.
These strengths are shown in tha following table:

Process of the present invention lS00 (g) llO0 ~g) Comparative Example l 800 500 Comparative Example 2 400 200 An elemendorf tearing tester was used.
Example 2 Blended yarn of 20 % staple fiber of polyethylene terephthate co-polymerized with 4 molar % of 5-~sodium sulfo) isophthalic acid with 80 % wool was prepared. They were woven into a twill structure and then the fabric was passed through conventional twilling process.
The fabric was treated in boiling 0.5 % aqueous hydrochloric acid solution for 60 minutes and then in boiling 0.1 % aqueous sodium hydroxido solution for 35 minutes to completely remove the polyester component. Thereafter, the fabric was dyed by an ordinary method. Thus the wool fabric showed out-standing drapability with excellent handle.
In comparative Example 1, the fabric was treated directly in boiling ~1 56~

0.1 % aqueous socliurn hydroxide solution for 60 minutcs omitting the hydro-chloric acid treatMent. 'I'he l)olycster componerlt had hardly been removed frorm the fabric and thc resLIltillg dyod textilo was not c~arclcteriscd like the product by the process oP tilC` preSellt inVOllt:i.Oll.
In Comparativc Example 2, the fabric was treated in boiling 1.5 %
aqueous sodium hydroxide solution omitting the hydrochloric acid treatment. A
reduction in weight started in the wool component and the result was cornpletelydifferent from the process of the present invention.
Example 3 Islands-in-sea fibers (225 denier, 24 -filaments) as shown in Figure 1 were knitted into a sample hosiery. The fibers have the following specification:
Component A: Polyethylene terephthalate copolymerized with 4 molar % of 5-~sodium sulfo) isophthalic acid.
; Component B: Polyethylene terephthalate A/B Ratio : 22/78 Denier of component B in monofilament : 0.2 denier Component B: 36/filament The treatment of the sample hosiery in 10 % aqueous phosphoric acid solution at 130~C for 30 minutes and in boiling 1.5 % aqueous sodium hydroxide solution for

4 minutes resulted in complete removal of Component A, and made up beàutiful hosiery knit comprising the micro fine fibers. The reduction in weight was 22.2 %, but micro fine fibers from the island portions were substantially not reduced and their tenacity was, 730 g/filament.
I'n a comparative example, the sample hosiery was treated in the boil-ing 1.5 % aqueous sodium hydroxide solution omittin~ the treatment with phosphoric acid. A period of 150 minutes was required for completely removing component A.

The redwction in weight amounted to ~4.0 % at this time. The micro ~ine f'ibers in the island portions were reduced in weight approximately 30 % on average.
Accordingly, tenacity was also down as low as 330 g/filament.
The micro fine fibers obtained by the process of the presen~ invention nad wniform thickness of 0.2 denier, while those obtained in the cornparative sample had showed large fluctuation of 0.1-0.2 denier.

Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for treating a fibrous structure having at least two components at least one component of which is a polyester containing an SO3M group wherein M represents hydrogen or a metal, said process comprising removal of the SO3M group-containing polyester, preceded by pre-treatment of the fibrous structure with a degrading agent for said SO3M group-containing polyester which preferentially degrades said SO3M group-containing polyester, thereby producing a fibrous structure capable of being treated in a subsequent alkali treatment step to produce a soft fibrous product.

2. A process for treating a fibrous structure according to claim 1 wherein said agent is acid.

3. A process for treating a fibrous structure according to claim 1 characterized in that the fibrous structure is a mixture of two or more polyester fiber at least said two polyester fibers having different compositions.

4. A process for treating a fibrous structure according to claim 3 wherein the fibrous structure is formed of multi-component fibers having a plurality of cores in the cross section thereof with the SO3M group-containing polyester interposed between the cores.

5. A process for treating a fibrous structure according to claim 4 characterized in that the fibers have at least five cores in the cross section thereof.

6. A process for treating a fibrous structure according to claim 4 characterized in that the fibers have at least ten cores in the cross section thereof.