US2711627A - Method of producing composite yarn - Google Patents

Description

fabric having substantial stretchability.

METHOD -OF PRODUCING CORIPOSITE YARN William I. Leath, Charlotte, N. C., and Frank E. Bobo, Jr., Gainesvilie, Ga, assignors, by mesne assignments, to 'Chadolon, Inc, Charlette, N. C., a corporation of North Carolina No Drawing. Original application August 3, 1954, Serial No. 447,600. Divided and this application September 2, 1954, Serial No. 453,761

'7 Claims. (01. 57-457 This invention relates to textile products and methods and more particularly to the production of yarns having different twists and tendencies to untwist in opposite directions and the knitting of these yarns separately and in opposing relationship to provide a balanced knitted This fabric may be knitted so as to form ladies full fashion or seamless hose, or may be knitted or woven to produce ladies" underwear or other garments where stretchability of the garment is desirable.

For illustrative purposes the invention will be described hereafter as applied to the production of ladies hose, a presently important commercial embodiment, but without limiting the scope of the invention thereto. Also forsake of brevity, the use of the yarn will be described hereafter in connection with knitting operations, but it is to be understood that thisis byway of illustration and not limitation, and that the yarn may be used in weaving or other textile operations.

One of the important features of the knitted fabric manufactured from this yarn is the balanced or rel'axed construction that avoids puckering or uneven contraction along the length or width of the fabric, thereby enabling it to lie flat and undistorted so that the hose or other garment made therefrom will assume its usual shape and desired appearance and will differ only in size and stretchability from the same garment knitted in conventional fashion.

An advantageous feature of the ladies hose made in accordance with this invention is the sheerness or dil'aphanous character of the hose that results from knitting of separate, unplied low denier yarn ends.

Prior attempts to produce ladies .lrose from yarn having substantial stretch characteristics have not provcn commercially successful because the hose were opaque, heavy and unattractive in appearance. The yarn used for producing these non-sheer hose was doubled, plied yarn having 'two yarn ends highly twisted in opposite directions and plied together. This type of highly twisted and plied yarn contains a multiplicity of small coils that give the yarn stretchability characteristics and which coils are pulled out or elongated when the yarn is stretched.

A characteristic feature of the yarn of the present invention is a wildness or liveliness, i. e., a tendency to twist or form loops, which is induced in the yarn by certain twisting and heat-setting operations. This liveli-ness or wildness in the yarn does not produce the multiplicity of small coils that characterize the abovementioned high twist yarn and which coils require doubling or plying with a similar high twist yarn. However, the liveliness does require temporary restraining of the yarn to permit knitting or weaving of the yarn in single ends to produce a sheer knitted fabric for ladies hosiery, panties, etc. This temporary control of ,the yarn, required for knitting or weaving operations, may be effected by temporarily plying with the twisted lively yarn, a different type of untwisted yarn that will exert a restraining efiect on the wildness of the twisted yarn,

2,711 ,627 Patented June 28, 1955 ICC so that it can be managed satisfactorily in the knitting machine or loom.

A presently preferred restraining type of yarn for temporarily holding the twisted yarn, is silk, particularly because of its adaptability for knitting with the same machines and equipment used for knitting the twisted, main yarn. Also the silk is further adapted for removal after the knitting operation by dissolving with a suitable chemical such as, for example, caustic soda. Another type of temporary restraining yarn that might be used for plying with the twisted yarn and which can be subsequently removed by dissolving with suitable chemicals, e. g., acetone or acetic acid, is cellulose acetate. Likewise, any other natural or synthetic fiber yarn that would serve the above purpose and could be removed thereafter is also contemplated for use in the method of this invention.

Regarding the main or permanent yarn to be used for forming the stretchable knitted fabric of this invention, including ladies hosiery, underwear, etc., the present commercially advantageous type of yarn is nylon, commonly used today for knitting such garments. Although nylon yarn is the logical choice at present because of its technical characteristics and commercial availability, other synthetic yarns, for example those known in the trade as DACRON (a condensation polymer of terephthalic acid and ethylene glycol) and dynel (a polymer of vinyl chloride and acrylonitrile), might be used, as well as other suitable synthetic or natural fiber yarns. The following description refers particularly to nylon yarn but by way of illustration only.

The above-mentioned prior art types of ladies" stretchable hose are produced from multifilament nylon yarns, and this is considered essential in view of the high twist to which those yarns are subjected, i. e., approximately turns. This high order of twist in one direction, followed by an equal or greater number of twists in the opposite direction, produces the above-mentioned multiplicity of small coils in the multifilament yarn. This coiled structure, as well as the extreme wildness of the yarn so produced, requires plying of two ends of this yarn having opposite twists, so that the series of coils in one yarn end meshes or entwines with the series of coils in the other yarn end of opposite twist. By this arrangement one twist neutralizes or offsets the other twist and thereby produces a relaxed, double, plied yarn having stretchability but nevertheless being subject to the disadvantages of causing puckering, deformation, and non-Sheerness in the knitted fabric.

The yarn and twisting methods of the present invention are not limited to multifilament yarns, but employ equally as well the monofilament types of yarns. Thus, ladies sheer nylon hose of the most popular type today can be knitted from 15 denier monofilament nylon yarn that has been subjected to the desired twisting and setting operations and plied with a silk or other temporary restraining yarn. These operations comprise, generally, a first twisting of one end of the nylon yarn, multifilament or monofilament, in one direction, say to the right, so as to provide an S twist, then heating to a temperature sufficient to set the yarn and which temperature will be higher than all subsequently encountered temperatures in the treatment of the yarn or product made therefrom, followed by twisting the yarn in the opposite direction, that is to the left, and providing therein a Z twist. This reverse or backtwisting operation will determine principally the amount of liveliness or wildness in the yarn and the extent of twist will depend upon the degree of this property desired in the yarn.

The first twist applied to the yarn as described just above may vary substantially in extent, or number of twists applied, a typical range being 20 to 50 turns twist. At the end of this first twisting operation, especially if as many as 40 or 50 or more turns are applied, the twisted yarn will possess a substantial liveliness or wildness sufiicient to form a stretchable fabric, upon plying with a temporary restraining yarn and knitting or weaving. However, subsequent high temperature treatments of the twisted yarn or fabric produced therefrom, such as normally occur in the manufacture of full fashioned hosiery, would substantially remove the lively characteristics and stretchability of the yarn or fabric because of the fact that the yarn at this stage, immediately after the first twisting, has not been set with heat. Thus it is important in carrying out the method of this invention, to incorporate a heat-setting of the nylon yarn at an appropriate point and to have this heat-setting operation carried out at a temperature appreciably higher than any subsequently encountered temperature.

As above indicated, it is important, and in fact essential, to heat-set the yarn at the proper time and at an adequate temperature to avoid losing the lively effects induced in the yarn by the twisting operation when the hose knitted therefrom are subjected to subsequent higher temperature treatments. In the method of this invention, this heat-setting treatment may be carried out after the first twisting operation and prior to the second or backtwisting operation and, in fact, this is the presently preferred procedure. However, worth-while benefits may be obtained from the method of this invention when carried out as described above except for changing the time or point in the process of the heat-setting operation. For example, we have produced yarn having substantial stretchability and produced ladies full fashioned hose therefrom, in which the heat treating operation was applied to the yarn prior to twisting of the yarn. In this modification, no second or reverse twisting of the yarn is required; only the initial heat treating, followed by twisting the desired number of turns such as, for example, about 50 turns.

In the manufacture of nylon full fashioned hosiery, the twisted yarn would usually be heat-set at a temperature of about 270 F. for a sufiicient length of time, c. g., one half hour, to effect the desired heat-setting. This heatsetting temperature could be higher if desired, but the important point is the use of a temperature sufficiently higher than the subsequent processing temperatures to avoid damaging effects of the latter. In the manufacture of full fashioned hosiery, the subsequent processing temperatures encountered in the dyeing and finishing operations are in the order of 250 F. or about 20 lower than the above-mentioned 270 F. heatsetting temperature, which is found to be a safe margin. If the subsequent temperature equals or exceeds the previous heat-setting temperature, the twist effect in the yarn will be substantially completely lost.

Another important feature of the twisting and heatsetting operations of this invention is that of twisting the yarn adequately following the first twisting and heatsetting operations, because the heat-setting operation substantially removes or neutralizes the liveliness imparted to the yarn by the first twisting operation. This being so, the yarn, after heat-setting, requires further twisting to etfect the desired liveliness. The amount of twisting employed after heat-settin will depend upon the desired degree of liveliness or stretchability desired in the yarn or fabric made therefrom. This twisting after heat-setting may vary substantially as to the number of twists and may be of the order of the first twisting operation described above prior to heat-setting. In other words, a typical number of twists for this second twisting operation would be 30 to 50 turns or higher. Usually it is desirable to employ a somewhat higher number of twists in the second twisting operation than in the original twisting operation. For example, if the yarn is originally twisted about 40 to 50 turns, the second twisting operation, after heatsetting, might be in the order of 50 to turns.

Also, it is usually of advantage to employ in this second twisting operation, a twist that is opposite in direction to the original twist, i. e., a Z twist for the second twistmg operation where an S twist has been employed in the original twisting operation. A reverse or back twist of this type, after heat-setting, will increase desirably the liveliness in the yarn as compared to a continuation of twist in the same direction as the original twist. Furthermore, the strength and other physical properties of the yarn will be better maintained by use of a reverse or back twist for the second twisting operation.

When multifilament yarns are used in these twisting operations, it is important to extend the reverse or back twisting operation at least some few turns more than the twist in the original twisting operation, so that the several filaments comprising the yarn will be integrated more completely by the additional turns twist than would be the case if the back twist equaled the forward twist and left the filaments in substantially untwisted or parallel position. This filament difficulty does not arise, of course, when monofilament yarns are used, but even with such yarns it has been found desirable to utilize a somewhat more extensive reverse twist than the original twist and thereby obtain a greater liveliness in the yarn. Following the above-described three steps of first twistmg about 40 to 50 turns in one direction, then heat-setting and twisting about 50 to 60 turns in the reverse direction, the yarn will possess such liveliness that it could not be handled practically in the knitting or weaving operation. At this point, it is then necessary to ply the yarn temporarily with silk or other restraining yarn, as above mentioned.

In carrying out this plying operation, the twisted nylon yarn is plied with the restraining yarn by twisting the two yarns together for a relatively few turns, such as, for example, 5 to 20 turns. A higher number of turns twist for this plying operation could be employed if it is desired, although it is not usually necessary. The plying twist 1s usually in the direction of the original twist and therefore opposite to the direction of the twist after heatsetting. More specific but non-limiting examples of the twistmg and heat-setting operations described generally above, WhICh we have employed satisfactorily in the production of yarn for knitting ladies sheer nylon stretchable hose, are as follows:

One end of monofilament nylon yarn is twisted 30 turns per inch in a Z or left twist direction. Another end of the same nylon yarn is twisted 30 turns per inch in an S or right twist direction. These two separately twisted nylon yarns are subjected to treatment with live steam in suitable equipment such as a pressure or vacuum retort and at a temperature of approximately 265 F.270 F. for a sufficient length of time to effect proper penetration. After this treatment with live steam, the yarn is transferred to twister bobbins and twisted 37 turns in the opposite direction of the original twist. As a consequence of this twisting operation, the yarn is very lively or wild and could not be satisfactorily knitted in this condition, and it is therefore plied with the silk yarn as above mentioned, the details of which are as follows:

The yarn that was twisted originally 30 turns to the left, Z twist, then backtwisted 37 turns to the right, S twist, is plied with one end of silk of either 13/ 15 or 20/22 size, and the plied yarns given a total of approximately 14 turns to the left, Z twist. The other yarn, which was originally first twisted 30 turns to the right, 8 twist, then backtwisted 37 turns to the left, Z twist, is now plied with one end of the silk yarn and the plied construction given a total of 14 turns twist to the right, S twist. This plying of the nylon and silk yarns may be carried out in one or more stages on conventional twisting machines. This silk will usually be treated prior tion.

to plying with conventional silk soaking treatment, followed by drying and skein winding. Also, it is not necessary to impart any twist to the silk yarn.

To prepare the nylon yarn which is to be plied with the silk yarn, it will be understood from the foregoing that bobbins, spools, p'irns or other suitable carriers of the nylon yarn will be used and one or more of these carriers will contain the nylon yarn twisted in one direction and another carrier will contain a supply of the yarn twisted in the opposite direction.

The plying of the twisted lively nylon yarn with silk or other suitable yarn restrains the liveliness as described above and thereby enables the yarn to be handled satisfactorily in knitting ladies hose. However, once the silk or other restraining yarn is removed from the knitted structure, the yarn will again become lively and this requires knitting of the yarn in a manner suitable to restrain somewhat this lively characteristic in the knitted structure. For that purpose, yarns of opposite twist, prepared as described above, are used in counteracting relationship while at the same time avoiding plying of the yarns and the adverse effects thereof. Instead of plying these yarns of opposite twist as has been done heretofore, they are knitted singly in alternating courses or groups of courses, as above mentioned. In other words, the yarn which has a final S twist is used for knitting one or several courses and the yarn that has the opposite or Z twist is used for knitting the next adjacent course or several courses. In this manner, the courses of yarn that tend to untwist to the left are counterbalanced to some extent by the adjacent courses of yarn that tend to untwist to the right, and this results in the balanced knitted fabric or structure mentioned above when these alternating courses recur throughout the length of the fabric, such as the length of a knitted full fashioned ladies hose.

The knitting operation may be carried out on conventional knitting machines of the full fashioned hosiery type, and the separate left and right twisted yarns (plied with silk) are knitted in an alternating pattern; for example, two courses of the nylon and silk plied yarn containing an S twist are first knitted, followed by two courses of nylon and silk plied yarn containing the Z twist. 7

We have found in commercial practice that knitting of these oppositely twisted yarns may advantageously be carried out in alternating pairs of courses, that is, two courses knitted with left twist yarns and the next two courses knitted with right twist yarns and this alternation repeated throughout the length of the fabric. This paired arrangement is best suited for the usual types of full fashioned knitting machines, but it is to be understood that the courses may be alternated singly instead of in pairs. On the other hand, a greater number of courses, such as 4 or 6 courses, of yarn of one twist may be alternated with a similar number of courses of yarn of the opposite twist.

Although this alternation of courses of opposite twist yarns sufficiently counteracts the torsional forces of these two yarns to prevent puckering or distortion of the fabric generally, the fabric formed in this manner has sufiicient distortion or liveliness in the individual stitches or loops to impart substantial stretchability. As an illustrative example of this stretchability, a ladies hose composed of the fabric of this invention can be stretched as much as 50% to 100% or more of its original length without permanent deformation of the stitches or loops, and has the property of contracting to substantially its original length when the stretching tension is removed.

The present-day sheer type of ladies hose normally uses nylon yarn of not greater than 30 denier and the yarn most commonly used is 15 denier nylon yarn, although 12 denier and denier nylon yarns are available and these yarns or even lower denier yarns may be employed in producing ladies sheer hosiery in accordance with this inven- Ladies hose made with nylon yarn as high as degree of sheerness.

30 denier, in accordance with this invention, possess a Similarly, .hose knitted with substantially higher denier yarns, such as 70 denier or higher, and which are known in the trade as service weight" hose, may likewise be knitted fom the stretchable yarn of this invention.

One of the attractive features of ladies hose produced from this yarn, irrespective of the denier used, is that the hose have substantially the same appearance as hose knitted from conventional yarn of the various deniers, which is in distinct contrast to hose knitted from the abovementioned highly twisted and plied yarns, such as yarn composed of two plies of 20 denier each.

Following the knitting, seaming with a yarn constructed so as to give a comparable stretch to that of the stocking yarn, and other usual grey goods operations before dyeing of the knitted hose, they are subjected to a treatment with caustic soda which removes the silk from the hose, leaving the nylon unharmed. Although subject to variations, details of a typical caustic stripping operation of this type are as follows:

The stockings in the greige are placed in nets such as are normally used in processing and subjected to treatment in 0.75% to 1.0% solution of sodium hydroxide in water for approximately one hour at 210 F., or until the silk is dissolved. The dissolved silk is removed by washing with water, following which the hose are dyed and the excess moisture removed. The hose are then pulled over a boarding form of restricted size to straighten but not to stretch the hose. Subsequent finishing operations, including inspection and packaging of the hose for sale, are carried out in the regular manner.

This application is a division of our copending application Serial No. 447,600, filed August 3, 1954, and claims only the method of producing the composite yarn, the composite yarn product being claimed in our application Serial No. 453,783, filed concurrently herewith, .and the textile products utilizing the composite yarn being claimed in our application Serial No. 447,600, filed August 3, 1954.

Throughout the specification and claims herein in each instance where reference is made to turns in the twisted yarn, it is to be understood that this is based upon turns per inch, as already stated in one instance herein above.

Various modifications and changes may be made in the above-described materials, products and methods without departing from the scope of this invention as defined in the appended claims.

We claim:

1. A method of producing lively yarn adapted for the production therefrom of knitted and woven textile products, comprising first twisting nylon yarn about 20 to 50 turns per inch sufficient to induce a substantial liveliness in the yarn, subjecting the twisted yarn to an elevated temperature to heat-set the yarn and stabilize it against subsequently encountered elevated temperatures, then twisting the heat-set yarn in a direction opposite to that of the first twist, about 30 to 60 turns per inch without further heat setting, and then plying the twisted yarn with a temporary restraining yarn in a direction opposite to the direction of the said last twist that subdues the liveliness of the twisted yarn and enables practical handling thereof in knitting and weaving operations.

2. The method of claim 1 in which said nylon yarn is a monofilament yarn.

3. The method of claim 1 in which said elevated temperature is approximately 270 F.

4. The method of claim 3 in which said twisted yarn is subjected to said elevated temperature for approximately /2 hour.

5. The method of claim 1 in which said yarn is twisted a higher number of turns per inch by the second twist than by the first twist.

6. The method of claim 1 in which said yarn is twisted 7 40 to 50 turns per inch by the first twist and 50 to 60 turns per inch by the second twist.

7. The method of claim 1 in which said plying of said twisted yarn with said temporary restraining yarn consists of 5 to 20 turns per inch. 5

References Cited in the file of this patent UNITED STATES PATENTS 2,295,593 Miles Sept. 15, 1942 10 8 Meade Oct. 26, 1943 Hathorne et a1. July 18, 1944 Dorgin Nov. 13, 1951 Neumager June 16, 1953 Brooks June 1, 1954 FOREIGN PATENTS Great Britain Ian, 2, 1945 Great Britain Feb. 2, 1948

Claims (1)

1. A METHOD OF PRODUCING LIVELY YARN ADAPTED FOR THE PRODUCTION THEREFROM OF KNITTED AND WOVEN TEXTILE PRODUCTS, COMPRISING FIRST TWISTING NYLON YARN ABOUT 20 TO 50 TURNS PER INCH SUFFICIENT TO INDUCE A SUBSTANTIAL LIVELINESS IN THE YARN, SUBJECTING THE TWISTED YARN TO AN ELEVATED TEMPERATURE TO HEAT-SET THE YARN AND STABILIZED IT AGAINST SUBSEQUENTLY ENCOUNTERED ELEVATED TEMPERATURES, THEN TWISTING THE HEAT-SET YARN IN A DIRECTION OPPOSITE TO THAT OF THE FIRST TWIST, ABOUT 30 TO 60 TURNS PER INCH WITHOUT FURTHER HEAT SETTING, AND THEN PLYING THE TWISTED YARN WITH A TEMPORARY RESTRAINING YARN IN A DIRECTION OPPOSITE TO THE DIRECTION OF THE SAID LAST TWIST THAT PRACTICAL THE LIVELINESS OF THE TWISTED YARN AND ENABLES PRACTICAL HANDLING THEREOF IN KNITTING AND WEAVING OPERATIONS.