US3365768A - Method for making stretch yarns and fabrics - Google Patents

Description

' Jan. 1968 J. E. BROWN ETAL 3,365,768

= METHOD FOR MAKING STRETCH YARNS AND FABRICS Filed April 28. 1964 5 Sheets-Sheet 1 PLIED YARN,

3'25/ THERMOPLASTlC BALANCE CELLULOSE TREATED WITHOUT TENSION WITH CELLULOSE SWELLING AGENT COILED PLIED YARN HEAT SET STRETCH YARN (Close Helix) i REVERSE TWIST I 1 STRETCH YARN pe l l /m/en/0r5 l v James E Brawn A [Ml/mm Fran/r Toy/0r By Ihe/r attorneys A44. MM.

1968 J. E. BROWN ETAL 3,365,76

METHOD FOR MAKING STRETCH YARNS AND FABRICS Filed April 28, 1964 3 Sheets-Sheet PLIED YARN,3-25/JHERMOPLASTIC,

BALA NCE CELLULOSE TREAT WITHOUT TENSION WITH CELLULOSE SWELLING AGENT COILED PLIED YARN HEAT SET SET STRETCH YARN REVERSE TWIST REVERSE TWISTED PULL OUT COILS- YARN PULL OUT TWIST STRETCHED,UNCOILED YARN WEAVING, KNTTTING, ETC.

FABRIC RELAX IN AQUEOUS FLUID STRETCH FABRIC /m/en/0rs F/ 2 James E Brown l Z /'///0m Frank Toy/0r By Meir aflorneys M My Jan; 30, 1968 J. E. BROWN ETAL METHOD FOR MAKING STRETCH YARNS AND FABRICS Filed April 28, 1964 3 Sheets-Sheet .1

PLIED YARN,

3 25% THERMOPLASTIC, BALANCE CELLULOSE CONVERT TO FABRIC FABRIC TREAT WITHOUT TENSION WITH CELLULOSE SWELLING AGEN T RAW STRETCH FABRIC HEAT SET STRETCH FABRIC James E. Brown l l ////0m Fran/r 7by/0/ 5y Meir oI/orneys United States Patent Patented Jan. 30, 1 968 ice This invention relates to stretch yarns and fabrics and to 1 method for their production.

g It is known to make stretchy yarns and threads from cellulosic materials by impregnating them with elastomeric materials such as rubber. However, such yarns are obviously limited in the uses to which they may be put. Moreover, it is 'found'that most stretch yarns are difficult to handle on conventional textile machinery simply be cause of their stretchiness.

The present invention provides a way to make stretch yarns which are predominantly cellulosic and which are therefore relatively inexpensive. Yarns according to the invention have the advantage of temporarily losing their stretch when wound on spools so that they can be woven or knitted as conventional. non-stretch yarns on ordinary textile machinery. The stretch can then be 'fully redeveloped merely by wetting the fabric.

in accordance with the invention, a stretch yarn is made by treating a plied yarn, comprising cellulose filaments and from about 3% to about 25% by weight thermoplastic filaments, in the absence of tension, with a cellulose swelling agent equivalent to an aqueous solution containing 5 to 40% NaOH, and heating the yarn to a'temperature sufficient to plasticize the thermoplastic filaments. I

Following heating the yarn may be back twisted, if desired.

Yarns made in accordance with the process just described. prior to back twisting, have the form of a close helix. The thermoplastic filaments have the shape re quired by the helix and have acquired a memory for that shape through heat setting. Upon back twisting, a three-dimensional irregular yarn is produced having a sequence of sections comprising closely Wound helices and uncoiled sections in which the individual plies are separated from one another and sprung outwardly from the main axis of the yarn.

In making stretch fabrics according to the invention, yarns made as described above may be pulled out and retained in an extended position until they fail to return to the contracted'form upon release. No special technique is required for this, since if the yarns are spooled under tension sufficient to pull the yarn out, by the time the spools have been transferred to a loom or knitting machine. the recovery will have been lost. The fabric may then be manufactured by any conventional technique, using the yarn as though it had never had stretch properties. After the fabric is made, it may be washed or steamed to redevelop the stretch propertiesi Alternatively, fabric may be mad fromi a plied yarn containing 3 to 25% thermoplastic filaments and the balance cellulose filaments, and thep treated slack with a swelling agent of the class described, followed by heat setting of the thermoplastic filaments. In general, however, it is more desirable to treat the yarn as yarn, prior to making it into fabric.

In the drawings:

FIG. 1 is allow diagram illustrating the process for making stretch yarn according to the invention.

FIG. 2 is a flow diagram illustrating the preferred process for making stretch fabric in accordance with the invention.

FIG. 3 is a flow diagram illustrating another method for making stretch fabric according to the invention.

FIG. 4 shows a stretch yarn made in accordance with .the invention without reverse twisting.

FIG. 5 shows the yarn of FIG. 4 after reverse twisting. Referring first to FIG. 1, the first stage in making stretch yarns according to the invention is to obtain a plied yarn containing 3 to 25% thermoplastic filaments and the balance cellulose'filaments.

The thermoplastic filaments useful in the present invention may be any of those available on the market. They need only be capable of softening or plasticization by heat, at temperatures which will'not adversely affect cellulose, say at less than 200 C. Among the substances that may be used as the thermoplastic component there may be mentioned cellulose esters, polyesters such as olyethylene terephthal. te, acrylic polymers, for example olyacrylonitrile and polyolefins such as polyethylene or polypropylene.

The cellulose filaments may be'natura-l cellulose fibers such as cotton, ramie, jute or linen, or rgenerated cellulose fibers whether made by the viscose, cuprammonium, nitrate, or other conventional processes such as the saponification of cellulose acetate. Preferably, however, if

regenerated cellulose fibers are used, they will be thesecalled polynosique or high wet modulus fibers. This is a comparatively recent type of viscose rayon fiber characterized by a generally circular cross-section (in a direction perpendicular to its axis), a substantially smooth, non-crenulated skin, with no apparent skin-core structure, and a fine microfibrillar structure. As a class polynosique fibers are characterized by a much higher resistance to swelling in water or caustic soda than is conventional viscose rayon. They are often referred to as high wet modulus fibers because the wet modulus, i.e., the stress required to cause an elongation of a specified amount when the fiber is wet, is much greater than is the case with conventional rayon, amounting to greater than 1 gram per denier stress for a 5% elongation.

Fibers of this type may be made by extruding unripened viscose into a coagulating bath Weak in regenerative power and stretching the filaments to a very high degree prior to or simultaneously with regeneration. See Tachikawa 2,732,279 and Cox 2,937,070.

Conventional rayon is preferably not used as the cellu lose component in the yarns of the invention in'proportions greater than 90% of the weight of the yarn. The reason for this is that with treating solutions of the type described, conventional rayon tends to become gelatinized, so. that when'proportions of more than 90% are present the final product tends to be stiff, brittle and inflexible.

The thermoplastic and cellulose filaments may be assembled in various ways. In the preferred embodiment the singles yarns are made up of a blend of cellulose staple and thermoplastic staple and these single yarns are then plied. Alternatively, continuous individual thermoplastic filaments may be twisted with individual continuous filaments of rayon to make up the singles yarn. Again, in plying the yarn, a yarn of thermoplastic filaments, which may be continuous or staple, may be plied with a yarn or yarns of cellulose fibers, either continuous or staple. Regardless of how the components are selected or assembled, the weight proportion of thermoplastic filaments in the plied yarn should be between about 3% and about 25% based on the weight of the combined yarn.

The individual singles yarns which are plied'preferably have from about 10 to about 40 twists per inch. The plied yarn itself must have at least two plies and may have up to say 6 plies. The plied yarn is preferably twisted to the opposite hand from the singles yarns, and the singles yarns are preferably all twisted to the same hand. The plied yarnwill have from say to 40 twists per inch.

As will be seen from FIG. 1, the first step in the novel process is subjecting the plied yarn to a swelling treatment. The preferred swelling agent is caustic soda of 5 to say 40% concentration. The precise concentration employed will vary with the cellulosic fiber being treated, since even among cellulose fibers of the same general class, there is some variation in the effect of different caustic concentration. In place of caustic soda, otheralkali metal hydroxides, e.g., KOH, maybe used, as well as such materials as zinc chloride and sodium zincatc. Where swelling agents other than sodium hydroxide are used their concentrations are selected to give a swelling effect equivalent to that of sodium hydroxide in concentrations of 5 to 40%.

The swelling treatment is preferably carried out at room temperature C.), but other temperatures ranging from 0 C. to 80 C. may be employed if desired. In accordance with well known principles lower temperatures enhance the swelling effect.

The time of treatment depends on many factors, including the concentration of swelling agent, the temperature,'the physical size of the yarn and mechanical details of the impregnating apparatus. In general the contact time of the yarn and swelling solution will range from say .1 to 120 minutes.

The swelling treatment is carried out in the substantial absence of tension. This may be done by passing the yarn, hanging in a catenary, through a bath of the swelling agent, laying the yarn in plaited form on a conveyor passing through a bath or under a spray, suspending skeins of the yarn in a bath, or in any other convenient way. In any event, the yarn must be free to contract, for in this swelling treatment the yarn assumes the form shown in FIG. 4. As shown in that figure, the yarn coils upon itself to form a tightly wound helix, the succeeding coils of which are substantially contiguous and the helix angle approaches 90 (say 45 or more).

Following the swelling treatment, the yarn may be neutralized, for example with a dilute solution of acetic acid, washed and dried.

In accordance with the invention, the yarn is next heated to a temperature suflicient to plasticize or soften the thermoplastic filaments. This temperature must not be so high as to melt the thermoplastic but it must be sufiiciently high so that, after cooling, the thermoplastic filaments develop a memory for the form they assumed by virtue of the coiling of the yarn, and will therefore tend to return to that configuration. This temperature will, of course, vary with the particular thermoplastic filament being used. Generally it will be between about 120 and about 200 C. The heating is also carried out with the yarn slack, i.e., in the substantial absence of tension. Conveniently it may be done by passing the yarn in air through a conventional drier or oven in a loop or catenary.

The yarn which is obtained as a product after the heat setting treatment will have the bulky, coiled form described above. The yarn in the close helix form may now be wound on spools and used to make fabric, as outlined below. Preferably, however, the yarn is reverse twisted, i.e., it is twisted to a direction opposite to that in which it was plied. The degree of reverse twist may range from say 80 to 200%, preferably from 135 to 160% of the twist applied during plying.

The effect of the reverse twist is shown in FIG. 5. As may be seen from that figure, the yarn is an irregular three dimensional sequence of helical sections, the helix angle of succeeding sections varying in an arbitrary and random manner.

If the yarn, whether in the close helix form of FIG. 4 or the open form of FIG. 5, is pulled out to its full length and released promptly, will return to its coiled form. If kept in an extended form under tension, it will gradually assume a more extended form so that after a matter of say 30 minutes it will apparently lose all of its stretch iness. However, upon relaxation in an aqueous fluid, e.g., water or moist steam, it readily returns to the coiled form.

The last property can be taken advantage of in making fabrics from the novel yarn. Thus, referring to FIG. 2 0f the drawing, plied yarn comprising cellulose fibers and 3 to 25% thermoplastic fibers are processed as described above and are then wrapped on a spool under tension. In accordance with normal procedures in the textile industry, considerable time elapses between the time when the yarn is spooled and the time when it is actually used on fabric making machinery, e.g., looms or knitting machines. In this time, the yarn, being under tension, has lost its stretchiness, so that it can be used on textile machinery as though it were conventional, non-stretch yarn. This is a very important practical advantage because the extreme extensibility of many stretch yarns makes them difiicult to handle on conventional machinery. Once the fabric has been formed, it can be washed cfr steamed and the yarns tend to reacquire their shape prior to winding, imparting stretchability to the fabric itself.

As indicated in FIG. 3, it is also possible to make a stretch fabric by weaving or knitting plied yarns containing cellulosic filaments and 3 to 25% thermoplastic filaments, then treating the fabric with 5 to 40% caustic soda or its equivalent and finally heating to set the thermoplastic filaments. In such processes the details of concentration, time, temperature and the like are the same as discussed above in connection with the treatment of yarn as such.

The invention is illustrated by the following specific examples.

EXAMPLE I A singles yarn-comprising 10% Dacron (polyethylene terephthalate) staple and of a high wet modulus rayon staple, and having 30 turns per inch twist, in the Z direction, is plied to give a two ply yarn with 22 turns per inch twist in the S direction. The plied yarn is then wound into meter skeins which are treated with an aqueous 16% NaOH at 20 C. for 1 minute. The skeins are then washed in water at 66 C. for 3 minutes, neutralized in 1% acetic acid for 3 minutes, again washed, extracted and dried at 121 C ,for 5 minutes, followed by heating at C. for 5 minutes. The resultant yarn has the appearance of FIG. 4.

The yarn is stretched to its maximum length, held for 10 seconds and then released. For maximum stretch,

stretched lengthoriginal length original length This is repeated ten times. The length of the yarn after final release is measured and the growth is calculated as original length final length original length x log The recovery of the yarn is then calculated as percent stretch -pereent, growth 100 percent stretch and determined to be 50%.

EXAMPLE-II 1 The rayon has a dry tenacity of 5 grams per denier, a wet tenacity of 4 grams per denier and a. stress or 2 grams per Y denier at 5% elongation when wet.

EXAMPLE III A lain weave fabric is made from the yarn described in Example I. The yarn is wound on spools, pulling out all stretch. Approximately 6 hours later yarn is drawn from the spools and fed to a single shuttle loom. After it is removed from the loom, the fabric is wet out with water at 80 C. for 10 minutes. It has a 200% stretch, and when held for 30 seconds and then released, has an 85% recovery. After being stretched for 40% and held for 5 minutes, it has a 95% recovery. This recovery increases upon standing, so that after 5 hours 99% recovery is Obtained.

EXAMPLE IV A plain weave fabric is made from the reverse twist yarn described in Example 11. The yarn is wound on spools and in this operation all stretch is pulled out. Approximately 24 hours after winding, the yarn is Woven, on a loom. After removal from the loom, the fabric is steamed, without tension, with saturated steam at atmosphcric pressure. The fabric shrinks and becomes stretchy. it has a maximum stretch of 90%. Fabric samples are stretched 40%, held for various times and the percent recovery is recorded. Results are indicated below:

Recovery percent Time Held Extended i Immo- After After After diate 1 Hr. 3 Hrs. 5 Hrs.

I V 30 econds 91 98 98 98 5Hllllti!ti. 90' 90 i 98 93 EXAMPLE V A two-ply yarn, 10% Dacron and 90% high wet modulus rayon staple fiber is woven into a loose fabric. It is then treated, without tension, with an aqueous slution containing 16% NaOH at 20 C. for 3 minutes. After removal from'the bath the fabric is neutralized, washed, dried and then heated at 176 C. for 2 minutes. A Sli'cltlli fabric results.

EXAMPLE v1 v Yarns made in accordance with Example II are knit into stockings on an 18-gauge circular knitting machine. After knitting. the stockings are placed in water at 66: C. for minutes. After relaxation, one inch strips are cut from one of the stockings. Five inch reference marks are placed on one of the strips. It is then stretched along a calibrated scale to determine maximum stretch. A value of 200% is obtained.

EXAMPLE VII EXAMPLE VIII A 24/2 yarn is spun from 90% conventional textile grade rayon staple fiber and Dacron staple with 5.5 twist multiplier in the singles in the Z direction and with a ply twist of22.5 turns per inch in the S directionyThe yarn is treated in the skein without tension, in 25% aqueous NaOH C. for 2 minutes, rinsed in 65 C. water for 3 minutes, neutralized with 5% acetic acid,

6 rinsed with 20 C. water and dried relaxed. It is heated, relaxed, at 175 C. for 4 minutes and reverse twisted 31.8 turns per inch in the Z direction. The yarn has a maximum stretch of 206%, a recovery from maximum stretch after a 5 minute hold of 7 and a recovery after 25 maximum stretches, with immediate release, of 84%.

What is claimed is:

1. A method for making a stretch yarn which comprises treating a multi-ply yarn comprising between about 3% and about 25% by weight thermoplastic filaments and between about and about 97% cellulose filaments, under substantially zero tension, with a swelling agent for cellulose equivalent to an aqueous solution containing between about 5% and about 40% NaOH and heating the treated yarn to set the thermoplastic filaments.

2. The method claimed in claim 1 and comprising twisting the yarn in a direction opposite to its ply beyond the point where there is no twist in the original plied yarn, after heat setting.

3 The method claimed in claim 1 wherein the cellulose filaments are selected from the group consisting of natural cellulose filaments and rayon filaments having a wet modulus of greater than about 1 gram per denier at 5% extension.

4. A method for making a stretch fabric which comprises treating a multi-ply yarn containing between about 3% and about 25 /0 by weight thermoplastic filaments and the balance cellulose filaments, under substantially zero tension, with a swelling agent for cellulose equivalent in swelling effect to an aqueous solution containing 5 to 40% by weight NaOH, heating the treated yarn to set the thermoplastic filaments, subjecting the resulting yarn to tension until the stretch properties of the yarn are removed, converting the yarn to fabric and relaxing the fabric in an aqueous lluid to restore the stretch properties of the yarn.

5. The method claimed in claim 4 and comprising twisting the yarn in a direction opposite to its ply beyond the point where there is no twist in the original plied yarn, after heat setting.

6. The method claimed in claim 4 wherein the cellulose filaments are selected from the group consisting of natural cellulose filaments and rayon filaments having a wet modulus greater than about 1 gram per denier at 5% extension.

7. A method for making a stretch fabric which comprises converting a multi-ply yarn comprising cellulose filaments and between about 3 and about 25% by weight thermoplastic filaments, into a fabric, treating the fabric, in the substantial absence of tension, with a cellulose swelling agent equivalent in swelling power to an aqueous solution containing between about 5 and about 40% NaOH and then heat treating the fabric to set the thermoplastic filaments.

8. The method claimed in claim 7 wherein the cellulose filaments are selected from the group consisiing of natural cellulose filaments and rayon filaments having a wet modulus greater than about 1 gram per denier at 5% extension.

9. A multi-ply stretch yarn produced according to the method of claim 1.

10. A stretch fabric produced according to the method of claim 4.

11. A stretch fabric produced according to the method of claim 7.

References Cited UNITED STATES PATENTS 2,463,618 3/1949 Heberlein et al 57157 2,919,534 1/1960 Bolinger et a1. 57157 XR 3,025,659 3/1962 Stoddard et al 2872 XR JOHN PETRAKES, Primary Examiner.

Claims (2)

1. A METHOD FOR MAKING A STRETCH YARN WHICH COMPRISES TREATING A MULTI-PLY YARN COMPRISING BETWEEN ABOUT 3% AND ABOUT 25% BY WEIGHT THERMOPLASTIC FILAMENTS AND BETWEEN ABOUT 75% AND ABOUT 97% CELLULOSE FILAMENTS, UNDER SUBSTANTIALLY ZERO TENSION, WITH A SWELLING AGENT FOR CELLULOSE EQUIVALENT TO AN AQUEOUS SOLUTION CONTAINING BETWEEN ABOUT 5% AND ABOUT 40% NAOH AND HEATING THE TREATED YARN TO SET THE THERMOPLASTIC FILAMENTS.

4. A METHOD FOR MAKING A STRETCH FABRIC WHICH COMPRISES TREATING A MULTI-PLY YARN CONTAINING BETWEEN ABOUT 3% AND ABOUT 25% BY WEIGHT THERMOPLASTIC FILAMENTS AND THE BALANCE CELLULOSE FILAMENTS, UNDER SUBSTANTIALLY ZERO TENSION, WITH A SWELLING AGENT FOR CELLULOSE EQUIVALENT IN SWELLING EFFECT TO AN AQUEOUS SOLUTION CONTAINING 5 TO 40% BY WEIGHT NAOH, HEATING THE TREATED YARN TO SET THE THERMOPLASTIC FILAMENTS, SUBJECTING THE RESULTING YARN TO TENSION UNTIL THE STRETCH PROPERTIES OF THE YARN ARE REMOVED, CONVERTING THE YARN TO FABRIC AND RELAXING THE FABRIC IN AN AQUEOUS FLUID TO RESTORE THE STRETCH PROPERTIES OF THE YARN.

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