WO2000012798A1

WO2000012798A1 - Process for producing elastic textile fabrics

Info

Publication number: WO2000012798A1
Application number: PCT/EP1998/005543
Authority: WO
Inventors: Klaus Uhlmann
Original assignee: Boehme Chem Fab Kg; Klaus Uhlmann
Priority date: 1998-09-01
Filing date: 1998-09-01
Publication date: 2000-03-09

Abstract

A process for the production of textile fabrics from threads or yarns which are manufactured from natural fibers and/or cellulose fibers and/or protein fibers is characterized in that inelastic threads are knitted, machine-knitted or woven together, wherein one of the threads has been spun in a S-twist and the other thread has been spun in a Z-twist and these two threads are processed together in opposing directions, wherein the twist of the S-twisted thread is 10-percent greater than the twist of the Z-twist thread, and it is ensured in the case of knitting or machine-knitting that the S-twisted and Z-twisted threads are processed with a stitch size and, in the case of woven textile fabrics, that the S-twisted and Z-twisted threads in their arrangement as warp or weft, retain a spacing between them such that the S-twisted and Z-twisted threads can change in length sufficiently between their points of contact.

Description

Process for producing elastic textile fabrics

Description

The invention is directed to a process for producing textile fabrics from inelastic fibers which are manufactured from natural fibers and/or cellulose fibers and/or protein fibers, possibly accompanied by the use of a synthetic fiber, wherein two threads are knitted, machine-knitted or woven together, wherein one of the two threads has been spun in an S-twist and the other thread has been spun in a Z- twist.

It is generally known that of all the known fibers or threads used for the manufacture of textile fabrics, that is, especially materials for the garment industry, natural fibers such as cotton, wool, silk or other cellulose or protein fibers as well as mixtures of the above-mentioned fibers are preferred by those wearing these materials, since they are extremely comfortable to wear next to the skin. In particular, they have good breathing properties and are capable of absorbing body moisture. The fibers mentioned above are especially suitable for the manufacture of textiles that are worn directly on the skin such as underclothes, and it is a declared aim in this type of goods to impart a stretching effect so that the textile article always has a perfect, close fit even after frequent washing.

With the advent of synthetic fibers, it was possible to solve the formerly acute problem of permanent elasticity of textile fabrics because, due to their thermoplastic characteristic, fibers of this kind could deform when heated and therefore become elastic, namely through the texturing process, crinkle process, stuffer box process, or the like. The elastic to highly-elastic fabrics produced by means of such processes are also known in particular from the hosiery industry. However, there are also known disadvantages to all of these thermoplastic, synthetic fibers with respect to skin compatibility, breathing properties, moisture absorption, etc. For this reason, efforts have also been made to develop corresponding elasticizing methods also for natural fibers with their known skin-friendly properties, wherein, in particular, the wearing comfort and fitting shape with respect to elasticity known from purely synthetic articles are goals to be met. In this respect, as was described in DE-AS 1 088 892 and DE-GM 1 727 603, the inelastic natural fibers are processed together with elastic, synthetic fibers and threads, wherein substantial results have been achieved particularly through joint use of highly elastic polyurethane-based threads.

However, the processing of inelastic natural fibers together with highly elastic polyurethane threads causes major problems in production, especially in knitting, machine-knitting and weaving. These problems are of a mechanical nature and are caused by the different characteristics of these threads which are processed directly together on one and the same machine and cause interference in the operating process.

Apart from these technical problems, however, such mixed formations of the kind mentioned above still have the severe disadvantage that the synthetic fiber components cause a noticeable deterioration in skin compatibility, breathing properties and moisture absorption compared with pure natural fibers.

As a result, it is necessary to find a method for elasticizing natural fibers that do not naturally possess high elasticity.

It is known, for example, from DE-OS 2 321 852, in a process for producing a yarn with a permanent stretch effect particularly from protein-containing fibers such as silk, to overtwist one or more threads in one twisting direction until close to the critical twisting point, to fix or set the twist by heat, hydrolytically active agents or the like, and then to twist the twisted yarn obtained in this way back to roughly the zero point or beyond. After carrying out this known process, the threads in the finished yarn are present as helical windings. While such yarns exhibit the desired elastic characteristic, it has also proved within the framework of further processing to form textile fabrics, for example, by knitting, machine-knitting or weaving, that the process steps on the highly complicated machinery are relatively prone to interference. Therefore, it is the object of the present invention to process threads of natural fibers, and also other fibers which have not been subjected to a prior elasticizing process, on the machine-knitting, knitting and/or weaving machine, wherein the textile fabric that is produced on the machines while taking into account precise thread spacings has the desired elastic characteristic following further process steps. This object is met in the process mentioned above in that these two threads are processed together in opposing directions, in that the S-twisted and Z- twisted threads are processed by knitting and machine-knitting with a stitch size, wherein, between their points of contact between the S-twisted and Z-twisted threads or, in the case of woven textile fabrics, in their arrangement as warps or wefts, they retain a spacing between them such that the S-twisted and Z-twisted threads can change in length sufficiently between their points of contact, and in that the fabric is subjected to a shrinking and fixing process to be carried out depending on the type of fiber that is used.

In this connection, it should be noted at the outset that it is and was known in general, as can also be seen from DE-AS 1 088 892, to produce threads from natural fibers or other cellulose or protein fibers in that the individual fibers of these materials are spun to form a thread or yarn by twisting them together. A Z- twist is preferably carried out; but a thread could just as well also have an opposite twist, that is, an S-twist, depending oh the setting of the spinning machine. Defined spinning twists are required in order to achieve a good elastic pull or elastic recovery of the thread or yarn. Inelastic natural-fiber threads or yarns, e.g., cotton with a yarn count of Nm 100/1 with conventional twist for processing of tricot articles as ladies' and men's undergarments, are spun in the Z-direction, namely with 1100 T/m, and are knitted on tricot knitting machines. A conventional tricot-knit article, e.g., in single-jersey knits or rib knits with the so-called rib elasticity given by the rib and alternating plain stitch and reverse stitch, is achieved in only one direction, for example, the width. In the present process according to the invention, exactly defined spinning twists beginning over the above-mentioned tricot twisting are required. It is also no longer necessary to use very high twists or even to twist to the so-called critical twist point. Also, it is never necessary to twist these threads back again and therefore to elasticize the thread itself. However, it is important that the inelastic threads with the above-defined spinning twists are spun in opposite twisting directions, namely in S-twists and Z-twists, respectively.

The invention described above achieves its effect in that two threads that have been twisted in opposite directions are deliberately processed together in the production of textile fabric, wherein it is also essential that these threads, starting from the S-twist or Z-twist on which they are based, are then processed together in opposite directions, wherein the selected stitch size and the selected spacing of the warp and weft are also essential. An advantageously selected stitch size of this type promotes the desired elastic characteristics of the textile fabric, i.e., the S-threads and Z-threads which are processed together in opposite directions in a fabric of this type retain sufficient room in a stitch size of this kind to allow them to exercise their elastic properties within the stitch formation. This means that the elongation in knits and machine-knits based on the process according to the invention depends above all on the stitch length. The longitudinal elongation or longitudinal elasticity of a knitted or machine-knitted article of this kind increases with the length of the stitch.

In woven fabrics, the spacing of the weft threads is decisive for the longitudinal elongation and the spacing of the warp threads is decisive for the width elongation.

According to the known prior art, it did not occur to the person skilled in the art to process in the S- and Z-twisting direction because it was believed that a twisted, uneven and distorted knit would result, which was the case in previous known crepe articles, wherein this special effect was also desired in this case, although only yarn with one twist direction was processed in such crepe articles. For this reason, the person skilled in the art declined to process in the S-direction and Z-direction for smooth, normal tricot articles. Of course, higher spinning twists than those mentioned above can also be used; this results in excellent elastic recovery of the elastic articles. The higher these twists, the greater the elastic recovery. In order to achieve the above-described effect, according to the invention, in knits, machine-knits and wovens, namely a two-dimensional elasticity of up to 100% and thus a stretchability and elastic recovery in the length and width directions in this order of magnitude of 100% which has not previously been achieved, it is necessary to adjust the parameters of the knitting machine, for example, in a precise manner and to select the required stitch length in such a way that the yarn thickness agrees with the machine gauge - needle spacing, sinking depth and stitch length - in such a way that sufficient elongation is possible without resulting in a limp, unattractive effect in the knitted article with overlarge stitches whose marketable appearance and practical wearability have been forfeited.

Consequently, in order to achieve the desired results according to the invention, it is also absolutely necessary to adhere to accurate production parameters in the processing, i.e., manufacture, of textile articles.

The production parameters with respect to knitting are the following: Defined yarn thicknesses for the respective machine gauges, defined stitch settings with respect to thread tension cN, stitch length ML, density factor DF, and sinking depth K, as will be seen from the examples shown hereinafter.

By means of the process steps according to the invention which were described in detail above, two-dimensionally elastic textile articles are provided within the framework of the spinning, according to the invention, of the threads to be processed as well as within the framework of the knitting, machine-knitting and weaving of same, according to the invention; however, this elasticity is not yet optimum and, in particular, not yet permanent.

In order to achieve an optimum elastic fabric, the above-described textile fabric is subjected to a shrinking and fixing process to be carried out depending on the respective fiber type. This aftertreatment of the textile fabric obtained in accordance with the invention ensures that this textile fabric will not lose its desired elastic property even after long use and frequent washing. In carrying out this aftertreatment, it must be ensured that products suited to the selected fibers are used to compact, i.e., shrink, the goods as far as possible and that the goods are then fixed in this state such that they always return to this basic state after stretching. The elastic properties, in full, and the permanence and resistance to washing required for wearability of finished articles produced therefrom are obtained only after this shrinking and fixing process.

Surprisingly, as a result of the production process characterized by the above-described features, a textile fabric is obtained which has the desired highly elastic characteristics and, further, a very uniform appearance.

It has turned out that the appearance of the desired textile fabric is further improved when the twist of the S-twisted thread is 10-percent greater than the twist of the Z-twisted thread. The reason for this higher number of twists in an S-twisted thread compared with the Z-twisted thread is that the opposite twisting direction of the knitting machine is accordingly compensated or balanced resulting in a completely smooth stitch formation, that is, a uniform knitted article, without distortion in one direction or curling up of stitches.

The processes and products vary for different types of natural fiber. For the group of cellulosic fibers including cotton, rayon staple, viscose staple, Tencel® and Lyocell, suitable wetting agents and detergents with alkaline treatments can be used by themselves or can be applied with subsequent fixing treatment with products suitable for this purpose, for example, high-grade finishing, or the like. In order to reinforce the shrinking and fixing process, this process can be followed immediately by a bleaching process which can be immediately followed by a dyeing process, if required.

Bleaching or dyeing, or both in succession, additionally reinforces this shrinking and fixing process. All bleaching and dyeing methods suitable for cellulose fibers can be applied. For the group of protein fibers, namely wool, silk etc., processes and products suitable for this group are applied. For example, products based on ammonium alkanol sulfonate (Siroset® FW and the like), carbamides and the like, steaming and hydrolytically active agents are used for splitting cysteine bridges and disulfide bridges and for fixation. The following processes have proven effective for the shrinking and fixing treatment of cotton: Prior to normal bleaching, pre-bleaching and dyeing according to the processes applicable for cotton, namely substantive or direct dyeing, reactive dyeing, etc., the goods are treated in a dyeing apparatus with the following products: Wetting agents and detergents based on sulfo-dicarboxylic acid esters, quick-wetting agents (Perenin® AS), washing agents for removing natural cotton wax and impurities based on alkyl polyglycol ether or fatty alcohol polyglycoi ether (Perenin®G 392, Solpon® 4488 DA) and sodium hydroxide solution, approximately 3-5 ml per liter NaOH, 50-%, depending on density and weight of the article, at boiling temperature for 30-60 minutes, in combination with a suitable product which counteracts the hardening and rigidity of the cellulose fibers because fiber stiffness does not allow for any elastic properties in the fabric.

The above-described shrinking and fixing process, followed by finishing processes, bleaching, pre-bleaching, dyeing and finishing treatment, is carried out economically in a dyeing apparatus providing for the possibility of producing inexpensive, marketable articles. In this way, it is possible for the first time to produce natural fiber articles that have been produced according to the present process according to the invention in marketable price ranges. In comparison to a cotton tricot produced, for example, from cotton and spandex or elastane (polyurethane-based), the cotton tricot according to the invention ranges between normal inelastic cotton and the above-mentioned cotton/elastane quality in terms of its production cost. Particularly when taking into consideration the known difficulties, also mentioned above, in the production of cotton/elastane mixtures and the high percentage of waste due to the elastane component, a considerable price advantage results for fabric produced by the process according to the invention. As was already mentioned, hardening and stiffness occurring in the fibers in conventional finishing processes in aqueous medium must be prevented in order to achieve elasticity in the natural fiber articles. In order to keep the goods flexible in all of the wet finishing processes, it is necessary to add suitable products, e.g., polycarboxylic acid derivatives (Tebolan® UFN). Further, additional process steps such as gradual cooling after thermal treatment can also be included. An increase in the elastic properties after the finishing processes can be achieved by a finishing arrangement which imparts flexibility and smoothness to the threads and fibers. The surface smoothness of the threads, in particular, allows the stitches to slide and noticeably increases the elasticity effect. This elasticity effect is achieved, for example, in cotton, through the use of two different fatty substances. The natural cotton fats and wax that are leached out through the shrinking and fixing process and subsequent finishing processes, dyeing, etc. are replaced by products such as quaternary fatty cycloammonium compounds (Bethamin® GFL) and the surface smoothness of the cotton fibers is achieved by outfitting with smoothing products such as emulsion-modified polysiloxanes (Viscosil® CSI). These treatments are likewise carried out in the dyeing apparatus as subsequent softening treatments.

Although the process according to the invention concerns exclusively natural fibers, cellulose fibers and/or protein fibers, a synthetic fiber can also be included when this is desirable for particular reasons.

The production of a highly elastic single-jersey, smooth type and highly-elastic knit hose will be shown hereinafter with reference to two examples.

1 st Example:

Production of a cotton knitted article:

a) Spinning:

Cotton, Nm 60/1 PP extra long staple, combed, (Egyptian maco) is spun on the ring spinning machine with

1200 T/m Z-twist = 1 thread 1260 T/m S-twist = 1 thread

b) Knitting:

The yarns produced in this way are knitted on a tricot knitting machine - knit type: smooth single-jersey. Manufacturer: Mayer & Cie Type MV 411 Diameter: 26-inch Needle number: 2268 needles Gauge: 0.99 mm

Machine setting:

T-tex T-Nm T-Ne ML DF K Qual.

16.7 60 36 0.284 14.4 1.8 200

wherein:

T-tex = yarn count in tex; T-Nm = yarn count in Nm; T-Ne = yarn count in Ne; ML = machine length in mm; DF = density factor in tex^1/2/cm; K = sinking depth in mm.

C) Shrinking and Fixing process:

In the dyeing apparatus - Then overflow dye machine - the produced knitted article is subjected to a shrinking and fixing process.

Bath-to-fiber ratio FV 1 :15 :

Recipe:

1 g/l Perenin® G 392 05 g/l Perenin® AS 1 g/I Delinol® VB 1 g/l Tebolan® WF.

The knitted article is treated for ten minutes in this bath at a temperature of 30° -40° . Subsequently, 3 ml/l NaOH, 50-percent, are added, the bath is heated to 98° , and the knitted article is treated therein for about 30 minutes, followed by hot rinsing and subsequent warm rinsing. Acidified with acetic acid pH 7.

This is followed by pre-bleaching and reactive dyeing in a known manner.

Subsequently, a softening treatment is carried out, namely with:

3% of fabric weight Bethamin® GFL

1 % of fabric weight Viscosil® CSI pH 5.5 (acetic acid),

the knitted article is treated therein for 15 minutes at 30° -40° , hydroextracted and dried. All of these wet processes should be carried out in the most tension- free manner possible.

A knitted article with a longitudinal and transverse elasticity of 80- 100% elongation with very good stretch recovery is obtained.

2nd Example: Production of a knit hose, for example, for the production of stockings or pantyhose:

a) Spinning:

Cotton yarn, Nm 60/1 , is spun with 1200 T/m Z-twist and 1320 T/m S-twist. b) Knitting:

This yarn is two-thread knitted on a ring knitting machine, 3 3/4 inch, 15-feed, smooth-knitted, without ribs.

C) Shrinking and Fixing process:

In a dyeing apparatus, the knit hose is subjected to a shrinking and fixing process, namely in a steeping water bath with:

1 g/l Perenin® G 392 1 g/l Tebolan® UFN 1 g/l Delinol® 9208.

The knit hose is treated therein at 30° -40° for ten minutes.

Subsequently, 3 ml/l NaOH, 50-percent, are added, the bath is heated to 98° , and the knit hose are treated therein at 98° for 30 minutes.

This is followed by bleaching with 2 g/l Cerafil® BFA, 1 g/l Tebolan® UFN and 3 ml/l H₂0₂, 35-percent. The knit hose are treated therein at 98° for 30 minutes. After 30 minutes, 1.5 ml/l H₂0₂, 35-percent, are added and the knit hose are treated therein for 20 minutes at 98° . This is followed by a hot and warm rinse at pH 7 (acetic acid).

Finally, an exhaust process is carried out with Bethamin® GFL, 3% of fabric weight, and Viscosil® CSI, 1 % of fabric weight. Further, a pH 5.5 is adjusted (acetic acid) and the knit hose are treated for 15 minutes at 30° -40° and subsequently hydroextracted and dried.

Tubular knits having a longitudinal elasticity of 120% and a transverse elasticity of 90% with very good stretch recovery are obtained. The products mentioned in the preceding description and examples and identified by the symbol ® are tradenames of products manufactured by the following companies:

Tradename Manufacturer Chemical characterization

Perenin AS Dr.Th. Bόhme KG Chem. sulfodicarboxylic acid ester Fabrik GmbH & Co.

Perenin G 392 Dr.Th. Bόhme KG Chem. alkyl polyglycol ether Fabrik GmbH & Co.

Solpon 4488 BA Dr.Th. Bόhme KG Chem. fatty alcohol polyglycol ether

Fabrik GmbH & Co.

Delinol VB Dr.Th. Bόhme KG Chem. salt of polyacrylic acid Fabrik GmbH & Co.

Delinol 9208 Dr.Th. Bόhme KG Chem. organic polymer compound Fabrik GmbH & Co.

Tebolan UFN Dr.Th. Bόhme KG Chem. polycarboxylic acid derivative Fabrik GmbH & Co.

Cerafil BFA Dr.Th. Bόhme KG Chem. combination of phosphoric acid ester Fabrik GmbH & Co. and alkylarylsulfonate

Bethamin GFL Dr.Th. Bόhme KG Chem. quaternary fatty cycloammonium Fabrik GmbH & Co. compounds Viscosil CSI Dr.Th. Bόhme KG Chem. emulsion of modified polysiloxanes Fabrik GmbH & Co.

Siroset FW Dr.Th. Bόhme KG Chem. substituted ammonium alkanol Fabrik GmbH & Co. sulfonates

Tencel Courtaulds a cellulosic fiber

Claims

Patent Claims

1. Process for the production of textile fabrics from inelastic fibers which are manufactured from natural fibers and/or cellulose fibers and/or protein fibers, possibly accompanied by the use of a synthetic fiber, wherein two threads are knitted, machine-knitted or woven together, wherein one of the two threads has been spun in an S-twist and the other thread has been spun in a Z-twist, characterized in that these two threads are processed together in opposing directions, in that the S-twisted and Z-twisted threads are processed by knitting and machine-knitting with a stitch size, wherein, between their points of contact between the S-twisted and Z-twisted threads or, in the case of woven textile fabrics, in their arrangement as warp or weft, they retain a spacing between them such that the S- twisted and Z-twisted threads can change in length sufficiently between their points of contact, and in that the fabric is subjected to a shrinking and fixing process to be carried out depending on the type of fiber that is used.

2. Process according to claim 1 , characterized in that the twist of the S-twisted thread is 10-percent greater than the twist of the Z-twisted thread.

3. Process according to one of the previous claims, characterized in that the shrinking and fixing process is followed immediately by a bleaching process in order to reinforce this shrinking and fixing process.

4. Process according to claim 3, characterized in that the shrinking and fixing process is followed immediately by a dyeing process in order to further reinforce this shrinking and fixing process.