US3069837A - Twisting process - Google Patents

Description

Dec. 25, 1962 E. H. OLSON TWISTING PROCESS Filed June 30. 1959 FIG! INVENTOR EARL HERBERT OLSON ATTORNEY tent .a corporation of Delaware I Filed June 30, 1959, Ser. No. 824,025

8 Claims. (Cl. 57157) This invention relates to textured stretch yarns. More particularly, this invention has reference to the production of such structures from yarns composed of synthetic polyamides, polyesters, and the like by a process which obviates the usual irnprocess twisting operations.

Nylon filaments were the first therornplastic textile materials capable of being heat set to a degree sufiicient to permit preparation of textured crimp and stretch yarns, for example, of the Helanca variety. Initially, such yarns were prepared in a stepwise operation during which continuous multifilament yarn first was highly twisted, the twisted yarn, usually packaged, then heated to set the twist, and finally the twist-set yarn was backtwisted to produce a structure which, upon. subsequent exposure to conditions of relaxation, would coil, curl, or spontaneously crimp into a structure exhibiting greatly enhanced built. In addition to increased bulk, such yarns would exhibit increased elasticity. By suitable adjustment of processing conditions, yarns exhibiting a surprisingly high degree of elasticity could be prepared.

An essential step in the production of textured stretch yarn is that wherein a high level of twist is set in the yarn by exposure to plasticizing agents, for example, heat, steam, solvents. and/or the like. In the stepwise or batch process, yarn first is twisted to very high levels, e.g., on the order of 30 turns per inch or more with conventional twisting means, and then set in that configuration in a subsequent operation, which usually involves packaged yarn. In the continuous process, the yarn is subject to the action of a false twister, which serves to generate a segment of yarn in the running yarnline which contains a very high level of twist. The highly twisted segment of yarn upstream of the false twister is exposed to plasticizing conditions, permitting thereby continuous setting of the yarn in the highly twisted configuration. Upon passing the false twister, the yarn loses the temporary false twist, yet, by virtue of the setting treatment remembers its experience in the highly twisted state.

The most time-consuming operation in either the continuous or the batch procedure is twisting. Mechanical up-, down-, or falsetwisters depend on rotating mechanical parts. These components severely restrict processing speeds because of the limiting effects of friction, centrifugal force, and the like. Because of these and other limitations, presently practiced stretch yarn processing is a low-output time-consurning proposition. Moreover, the mechanics of those operations and the additional handling required thereby often result in yarn of reduced quality and uniformity. All of these factors combine to render the conventional textured stretch yarn a disproportionately expensive commodity.

An object of this invention is to provide a process and apparatus for preparing stretch-type yarns at high speeds. A further object is to provide an apparatus for producing stretch-type yarns, the essential twisting component of which is non-rotating. Another object of this invention is a process and apparatus whereby yarn may be colddrawn and converted into a textured stretch yarn in a single continuous operation. A still further object is such a process wherein yarn is twisted at an etfective rate approaching one million turns per minute. These and other objects, together with means for accomplishing them, will appear hereinafter.

According to this invention a continuous thermoplastic synthetic organic textile strand, hereinafter referred to as a yarn although it may be a single filament, tape, etc., is plasticized and then passed, while still plasticized, in about one or more helical wraps about a fine wire, followed by winding the yarn (e.g., to a package) in conventional manner. In a preferred embodiment, a stretch yarn is prepared during a conventional drawing operation by subjecting as-drawn yarn, prior to packaging, to the essential steps of this invention. In another preferred embodiment, the yarn is imparted additional twist upstream from the wire by over-end take-off of the feed yarn from the supply package, the total level of twist up stream from the wire, i.e., in the twist setting zone, being controlled by the wire. By this invention, there can be produced at very high speeds a yarn which, after exposure to relaxing conditions, exhibits a high and uniform level of developed twist, twist which serves to render the resulting structure highly elastic.

In the following description of the invention, the term latent twist refers to that twist which has been set in the yarn by the instant process. Such twist usually is not apparent from the overt characteristics of the product, but can be developed after suilicient exposure to conditions of relaxation, e.g., by steaming or heating the yarn under conditions of minimum restraint. The term twist setting" or simply setting refers to the two-step procedure involving plasticization, which permits (owing to reduced torsional modulus, etc.) the yarn to assume a highly twisted configuration, followed by quenching, which fixes sufiiciently the configuration assumed by the yarn while in the plastic condition so that the yarn retains a memory" for that configuration and tends to return to it whenever distorted, unless later reset in another configuration.

The invention may be better understood by referring to the attached drawing, wherein:

FIGURE 1 is a schematic view of a preferred apparatus arrangement for processing yarn in accordance with the invention and FIGURE 2 is an end view of the hot plate 12 shown in plan view in FIGURE 1.

Referring to the drawing, there is shown an apparatus assembly whereby this invention may be utilized to pre' pare stretch yarn immediately after drawing a supply yarn, prior to packaging. According to this embodiment, undrawn yarn 1 is removed over the end of package 2 by way of guide means 3, then passes guide 4 onto and around cot S thence about driven feed roll 6. The yarn is thereby supplied at predetermined speed by feed roll 6 to draw pin 7, takes one or more wraps thereabout then passes to and around draw roll 8 and its associated canted separator roll 9. The yarn is drawn at pin 7 due to the urging of draw roll 8 which, of course, has a higher peripheral speed than the speed at which the yarn is supplied from feed roll 6. From draw roll 8 theyarn is passed over pin guides 10 and H and then through the slot in hot plate 12, then passes in at least about one helical wrap about the fine wire 13. From the wire, the yarn again encounters draw roll 8. If desired, draw roll 8 may be of stepped construction, in order to permit the yarn a metered amount of relaxation while it is in the vicinity of hot plate 12. From draw roll 8, the yarn passes pigtail guide 14 and is wound up in conventional manner by ring 16 and traveler 15 onto package 17 driven through spindle 13 1 drive means not shown).

The yarn path between the feed roll and the draw roll (initial contact) can be considered as the drawing zone." The yarn path between the draw roll and the windup can be considered as the stretch processing zone. In this embodiment, freshly drawn yarn passes from the draw e into the stretch processing zone. Surprisingly, as yarn passes the wire, downstream from the hot plate, s twisted by the wire. The direction of such twist or 2) depends on the disposition of the wire with root to the yarn path. In general, the wire should be lted in the direction of the yarn travel in order to oh- 1 unidirectional, i.e., non-alternating, twist in the yarn. There exists a second and equally important source of st. Since, in the preferred embodiment shown, the n is taken off over'end from the supply package 2, one 1 of twist is generated for each convolution of the yarn ut the supply-package. The magnitudeof such, twist )f course, of a very low order, and is further dispersed m extent proportional to the amount of drawing which as place. Such twist normally proceeds evenly to the dup package. However, the wrap of yarn on the wire res to limit the passage of such twist, thereby causing igh yet uniform concentration of twist to accumulate ve the wire in the vicinity of the hot plate. Such twist onfined mainly in the zone between the pin guides 11 and the wire 13, that is, in the vicinity of the plate. If it is desired to confine further the upstream it accumulation, more acute snubbing means should employed, e.g., meshing gears. The hot plate (or ivalent plasticizing means) functions to plasticize the tted segment of yarn upstream from the wire. Ob- Jsly, the twist resulting from over-end take-off should in the same direction as the twist generated by the e in order to obtain maximum benefit from each source. or being set in the highly twisted configuration, the n is efiectively backtwisted" after passing the wire, l can be wound up in an essentially untwisted state, luding, of course, the generally low level of twist gented at the windup and that which passes the wire. The various factors which determine the potential reliability, i.e., the amount of latent twist in the prodof this invention (in addition to the nature and identity the yarn per se), include the nature, mode, and durarof the plasticizing step, the amount of quenching Ech occurs between the setting means and the wire, the ree of compliance of the yarn about the wire, the :ction of twisting at the windup, and so on. in important facet of the process of this invention is step whereby the twist which accumulates in the sticized yarn upstream of the twisting wire i set 4 he running yarn by cooling, forming thereby the latent st on which the ultimate character of the product is dicated. Plasticizing may be accomplished in a numof ways, the preferred method utilizing dry heat. table sources of heat include hot plates, radiant heatinfrared lamps, ovens, and the like. Also useful as sticizing agents are high temperature liquid baths, pro- :d that such liquids are reasonably inert towards the :1. Mineral oil, molten metal, or the like may be used :uch baths. Setting may be facilitated by treating the n with mild swelling agents, such as those disclosed in I. 2,157,119 (Miles), viz., hydroxylated non-solvents nylon. The etfectiveness of any setting treatment ends on the degree of plasticizing achieved, i.e., by the ation and efficacy of the particular treatment employed r to cooling. It has been determined that the most :ctive setting operation involves the use of the highest sible plasticizing temperature which still avoids fusion degradation of the yarn. In general, the yarn temature during plasticization should be above the so- [ed second-order transition temperature but below the lting point of the polymer. Temperatures lower than second-order transition temperature of the yarn mate- 1 are usually not employed because, under these condi 15, any crimping of the filaments is not permanent and ity of the product is reduced. The preferred temperae is that which results in plasticization without fusion degradation of the yarn. Moreover, the higher the n speed, the longer should be the path of exposure to setting means, in order to achieve a similar effective 4 treatment. At very high yarn speeds, the temperature of the plasticizing means may even exceed the melting point of the yarn composition, owing to the abbreviated exposure. High denier yarn usually requires longer exposure and/or higher temperatures during plasticizing to compensate for the greater mass of the filaments.

At high yarn speeds, high temperatures and/or longer exposure distances are necessary to provide temperatures at the desired plasticizing level. These higher yarn temperatures may be achieved by means of an auxiliary heating device or pre-heater in the threadline, but a simple means for achieving this same effect is to have the yarn pass twice over a single heated plate so that yarn is preheated as it passes up along one face of the hot plate to a snubbing point and then is plasticized as the yarn progresses down across the reverse face of the hot plate to the wire.

After the setting step, the yarn should be quenched to an appreciable extent prior to its encountering the wire. As indicated hereinabove and understood in the art, quenching is the process step whereby the yarn is fixed in the highly twisted state it assumed while plastic. The greater the extent of quenching, the greater the amount of latent twist which is set in the yarn. Quenching may be accomplished by rapidly cooling of the filaments, removal of plasticizing or swelling agents, or the like, whichever is applicable. On the other hand, it is preferred that quenching not be completed until the yarn has passed the wire. Otherwise, the yarn assumes a rod-like character, i.e., a stifiness which can detract from its compliance at the wire. This, in turn, reduces the total level of twist in the yarn. Accordingly, the quenching step should be a compromise on the basis of the twist level desired in the product. The optimum amount of quenching can be determined by routine experimentation.

In its simplest embodiment, the apparatus of this invention comprises in serial relationship, yarn forwarding means, plasticizing means, the angularly disposed wire or its equivalent, and yarn takeup means. The yarn forwarding means are conveniently driven rolls or the like whereby yarn can be forwarded from a previous processing step or supplied from a package at predetermined speed to the twist setting means. The twist setting means, as discussed hereinabove, may be a hot plate, a hot bath, or the like, suitably disposed along the yarn path so as to provide adequate exposure of the yarn to the plasticizing conditions. The wire, about which the yarn makes at least about one helical wrap, is located a predetermined distance along the yarn path from the setting means, in order to allow the optimum amount of quenching of the plasticized yarn. The wire ordinarily makes an angle of between about 30 to about 60 to the yarn path. The single helical wrap of the yarn seems to be optimum for the purposes of this invention; very little additional benefit derives from increasing the an. ber of wraps. However, twisting starts to iaii oi the wrap is reduced to substantially less than u Preferably, the diameter of the wire is as smali as is practical. Experimental results indicate that the amount of twist obtainable depends in an inverse manner upon the diameter of the wire; Wire of a diameter of about 0.003 inch or less is preferred for the practice of this invention.

The yarn takeup means may be any of the conventional windup assemblies, including an uptwister, downtwister, or reciprocating traverse windup. Alternatively, the takeup means merely may forward the yarn to a subsequent operation or process step without an intervening packaging step. In the case where the takeup means is a twisting windup, the direction of twist imparted to the yarn at the windup should be in the same direction as that being developed upstream from the wire. Otherwise, the existence of opposite-hand twist immediately downstream from the wire may detract from its value both as a twist generator and as a twist valve.

s a es? In most of the above apparatus assemblies, yarn stringup is most simply accomplished by passing the wire about the yarn, then tautening the wire which results in the yarn being wrapped around the wire. The above assemblies, with relatively straight-forward modification, can 5 be utilized in multiple-end applications, including those whereby two or more yarns are imparted opposite-hand latent twist and plied at the windup to form balancedtwist products.

The process of this invention is relatively insensitive to yarn tension or speed. This behavior is quite unlike thatof the prior art processes, where very low yarn speeds are required and tensions of a low order are necessary to permit eflicient twisting. The instant process may be I operated with or without relaxation, based on relative 5 yam lengths, in the setting zone. By operating at relatively high tensions in the setting zone, yarn tenacities and moduli are not diminished in that step, as is the case with inert prior art procedures. Therefore, in most procedures or operations carried out in accordance with this invention, yarn is processed without overfeed into the setting zone. In general, this invention is applicable to yarns composed of thermoplastic materials capable of being twist-set by plasticization and quenching. It is particularly applicable to yarn or the like structures composed either partially or entirely of synthetic polymeric materials such as the polyamides (nylon), e.g., poly(ecaproamide) and poly(hexamethylene adipamide); polyesters, e.g., poly(ethylene terephthalate), poly(trans-phexahydroxylylene terephthalate); vinyl polymers, e.g., poly(vinyl chloride), poly(vinylidene chloride); the numerous copolymers of the above compositions; cellulose triacetate, and the like. These yarns may contain any of the conventional yarn additives, such as delusterants, pigments, and the like. Where heat is employed as tions of relaxation. The developed twist" (t.p.i.), which includes both twist due to inherent yarn liveliness and latent twist which develops upon steaming, was determined by steaming (atmospheric steam) the yarn while under a tension of 0.0012 gram per denier. The tension was applied by fastening a piece of aluminum foil at the free end of a suspended measured length of yarn. A beam of light was directed so that its reflection from the foil would illume a photocell, twice per each complete revolution of the test yarn. An electronic counter suitably connected to the photocell counted the number of revolutions made by the yarn during the steaming step, enabling the determination of the extent of twist development during such steaming. Results are expressed on a turns-per-inch basis. Even though the foil rotated quite rapidly during steaming, often in excess of 100 r.p.rn. this method gave entirely accurate results. The results show the affect or" varying important process and yarn conditions on the amount of developed twist in the product.

The apparatus employed in all of the examples is shown diagrammatically in FIGURE 1. The draw pin, composed-of Alsimag," is 1 inch in diameter, and the yarn makes one wrap (360) thereabout. The draw roll is of polished chrome, 2 inches in diameter. The hot plate is made of aluminum, extends 10 inches along the yarn path, and contains a width x depth slot in which the yarn runs during processing. The hot plate is electrically heated; thetemperature is controlled by the amount of current to the plate. The wire is composed of high tensile steel and has the diameters indicated in Table I. The process speed reported is based on the yarn speed, in yards per minute, in the stretch processing zone. The wire is located 2 inches from the hot plate, at an angle of 45 to the yarn line.

Table I Yarn, as-drawn Filament Draw Processing Hot late Wire Devolo ed Run count (den/til.) cross section ratio speed ter! 1 p., diameter, twist (y.p.rn.) C. in (t.p.i.)

15/1 nylon l Round 4. 54 424 250 0. 003 11-15 -do--- 4. 47 424 250 0.003 20-25 d0- 4. 41 424 250 0. 003 38-40 15/2 nylon 1 3. 88 424.- 250 0. 003 82-4-1 15/5 nylon L 3. 17 424 250 0. 003 18-20 20 7 nylon l 3. 17 424 250 0. 003 15-lS 30/10 nylon 1 3. 17 424 250 0. 003 14-18 30/4 nylon l 3. 88 4.24 260 0. 003 25-27 /14 nylon 3. 17 424 250 0.003 S-l0 /0 nylon 3. 83 424 250 0. 003 10-17 15/2 nylon -.---d0. 3. B8 780 250 0. 003 20455 15/l-nylon 1 Cruetiorm 4. 47 780 250 0. 003 18-24 15/2 polytethylene Round 3. 12 424 225 0. 005 20. 33

terephthalatc) 1 Poly(hexarnethylone adipamide) the setting agent, it is desirable that the yarn contain a r suitable antioxidant. Suitable antioxidants for nylon are d disclosed by Stamatoff in US. Patents 2,705,227; 2,640,044; and 2,630,421. Other useful antioxidants are disclosed by Gray in US. Patent 2,510,777, and Dreyfus in US. Patent 2,345,700.

It has been found that by the instant process, the highest level of latent twist can be set in yarn which is freshly drawn, as compared with aged or lagged yarn. Also, highest levels of latent twist result when the yarn being processed has other than circular cross section filaments, e.g., yarns of filaments having ribbon, cruciform, or the 60 similar non-round cross sections. It is believed that such yarns are more compliant in the wrap about the twisting wire. Finally, the level of latent twist usually increases as the total denier of the yarn is decreased, at constant denier-per-filament, or as the number of filaments is decreased, at constant total denier.

The following examples illustrate various embodiments of the process of this invention. The results, listed in Table I, are reported on the basis of the amount of twist which develops in the product during controlled condi- It is apparent from inspection of Table i that quite high levels of latent twist can be imparted at hi' h i a running yarn. In experiment ll, for ex receives up to about 980,000 turns of d per minute. The various factors Cfiflilib amount of latent twist are apparent from ins--- the table and from the discussion hereinabove. For best results, the relaxing conditions employed to develop latent twist approximate the original plasticizing conditions. Where heat is used, the yarn temperature during plasticizing and subsequent relaxing should be above the secondorder transistion temperature of the yarn but below the melting point of the yarn.

The process of this invention can he carried out at any practical yarn-processing speed during any convenient stage of yarn handling, but it is preferably carried out during the drawing operation. Yarn tension during stretch processing need not be maintained at any extremely high or low level in order to insure opcrability, rather it should be relatively constant when product uniformity is desired. The product does not incur a tenacity loss during stretch processing in accordance with this invention. The ap assess! us of this invention is compact and inexpensive, and res little or no maintenance due to the absence of mg or rotating parts. The stretch product is fully alent in performance to the comparable yarns prel via the cumbersome and expensive prior art proce- The many other advantages inherent in the pracaf this invention will be readily apparent to those rtaking its practice.

18 claimed invention:

In the process for producing stretch yarn wherein a ling yarn of thermoplastic organic polymer filaments tsticized by heating to a temperature below the melttoint during passage through a heating zone, is subsetly deplasticized by cooling during passage through a lag zone, is twist-set during passage through said heatand cooling zones by application of a false twist to up twist into the heating zone and then remove the ied false twist after a high level of latent twist has me set in the cooling zone, and the twist-set yarn is ad into a package, the improvement of applying said t by passing the yarn, in said cooling zone while still tally plasticized, in at least about one 360 helical around a fine stationary wire positioned slarttwise ss the yarns path at an angle thereto in the range of it 30 to about 60 to accomplish a false twisting :t and thereby cause twist to be built up in the heating The process of claim 1 in which the yarn being processed is "as drawn" yarn which has been freshly drawn but not packaged.

3. The process of claim 1 in which the yarn being processed is removed from a supply package by over-end take-off.

4. The process of claim 1 in which the yarn is poly (hexamethylene adipamide).

5. The process of claim 1 in which the wire is round and has a diameter of less than about 0.003 inch and lies at an angle of between 30 and 60 of the yarn path.

6. The process of claim 1 in which the yarn is poly (ethylene terephthalate).

7. The process of claim 1 in which the yarn being processed has an cut-of-round cross section.

8. The process of claim 1 in which the yarn is poly (e-CZPIO amide) References fitted in the file of this patent UNITED STATES PATENTS 2,451,919 Clarkson Oct. 19, 1948 2,875,502 Matthews et al Mar. 3, 1959 2,919,534 Bolinger et al Ian. 5, 1960 2,943,433 Van Dijk luly 5, 1960 FOREIGN PATENTS 200,740 Australia Feb. 9, 1956 210,620 Australia Oct. 9, 1957 802,689 Great Britain Oct. 8, 1958 808,213 Great Britain Ian. 28, 1959

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