US2952964A

US2952964A - False twist device for curling thermoplastic yarn

Info

Publication number: US2952964A
Application number: US442166A
Authority: US
Inventors: Gonsalves Conrad Joseph; Cloux Henri Du
Original assignee: American Enka Corp
Current assignee: Akzona Inc
Priority date: 1953-07-14
Filing date: 1954-07-08
Publication date: 1960-09-20
Anticipated expiration: 1977-09-20

Description

Sept 1960 c. J. GONSALVES ETAL 2,952,964

FALSE TWIST DEVICE FOR CURLING THERMOPLASTIC YARN Filed July 8, 1954 INVENTORS CONRAD JOSEPH GONSALVES HENRI DU BY wwwam ATTORNEYS FALSE TWIST DEVICE FOR CURLING THERMOPLASTIC YARN Conrad Joseph Gonsalves and Henri Du Cloux, Am-

hem, Netherlands, assignors, by mesne assignments, to American Enka Corporation, Enka, N.C., a corporation of Delaware Filed July 8, 1954, Ser. No. 442,166 Claims priority, application Netherlands July 14, 1953 1 Claim. (Cl. 57-34) This invention relates to a method and apparatus for the production of curled yarns or threads from thermoplastic materials and more particularly to a method and apparatus for the continuous production of curled untwisted multi-filament thermoplastic yarns.

In the production of curled yarns or threads from parallel filament yarns of the thermoplastic type it has been heretofore customary to soften the yarn with a swelling agent such as caustic alkali, a zinc chloride solution, xylene, phenol, chlorohydrin or the like, to twist the yam while it is soft, to fix curl as with a steam treatment or with formaldehyde or by drying, and to untwist the fixed product. These operations have resulted in the production of satisfactory curled products but the cost is high due to the fact that the process is discontinuous and quite slow.

In an elfort to mitigate the foregoing disadvantages, false twisters were introduced so that a separate untwisting step could be avoided. However, the simple twisting tube proved to be unreliable and special false twisters were designed. Even these specially designed false twisters offer a good deal of friction to the tender threads and they tend to impose too much stretch.

It is therefore an object of this invention to overcome the foregoing disadvantages and to provide a method and apparatus for the economical, continuous production of curled thermoplastic yarn of high quality.

According to the present invention it is proposed that smooth, straight, thermoplastic yarns be false twisted and drawn at a uniform speed successively through -a heating zone and a cooling zone with maintenance of low but uniform tension during heating and cooling whereby no softening or fixing agents are required.

Other objects and advantages of invention will be apparent upon consideration of the following detailed description of a preferred embodiment'thereof in conjunction -with the annexed drawings wherein;

Figure l is a schematic view of the entire apparatus employed in imparting curl to thermoplastic yarn according to the present invention; and

Figure 2 is a view in section to an enlarged scale of the false twisting device employed as a part of the assembly of Figure 1.

Referring now to the drawings in greater detail the numeral 1 indicates the thermoplastic yarn. It is withdrawn from a package 2 over a guide roller 3 and through a thread brake 4 or other friction-imparting device. The propulsion of the thread is accomplished entirely by a triple roller draw-01f device 8 which is shown at the right extremity of Figure 1. After leaving the thread brake 4 the yarn 1 passes through a heating tube 5, a cooling zone 6 and a false twisting device 7.

Hot air is supplied to the heating tube through a conduit 9 and this air, being centrally supplied, issues from the ends '10 and 11 of the tube 5. The yarn 1 issuing from the end 11 of the tube 5 passes through a cooling zone 6 during which it is exposed to the cooling Patented Sept. 20, 1960 drag imparting device or thread brake 4 and the point 17a of the false twisting device 7, the yarn 1 is in a twisted condition, while between the point 17a and the draw-01f device 8 the yarn is untwisted. The draw-ofl? device 8 lies on the extended axis of false twisting device 7, and is remote therefrom, as shown in Figure 1. I

The false twisting device 7 comprises a fixed supporting arm 13 having a sleeve 12 integral therewith. Bearings 15 and 16 support the spindle 17 for rotation within the sleeve 12. The spindle 17, storare wheel 18 and discharge disc or body 19 are integral and are provided with a sheave 14 which overlies the sleeve 12 and which receives a driving belt 20 by which the false twisting device is rotated.

An appreciation of the use of the present invention can be had upon consideration of the following examples:

Example I A polyamide thread of 60 denier and consisting of 10 filaments was treated. This thread was produced by polymerization of caprolactam and spinning of the molten polyamide.

Hot air was fed into the tube 5 which had a length of cm., so that in the tube the temperature was C. The air zone 6 had a length of 100 cm. The speed of the false twisting device was 20,000 rpm. The triple roller device took off the thread at a speed of 5.6 in per minute. The thread brake 4 was so adjusted that the tension of the thread 1 before the hollow spindle 17 of the twisting device amounted to 2.5 g.

Example 11 a denier of 50 and consisted of 10 filaments. The heating tube had a length of 250 cm, while the temperature in the tube amounted to C. In the air cooling zone which had a length of 90 cm. a blower was placed, which was provided with a slot from which atmospheric air was blown from below against the passing thread. The speed of the twisting device amounted to 50,000 rpm. and the triple roller device made the thread travel at a speed of 12.5 in. per minute, the thread tension before the twisting device being adjusted at 5 g.

In the same way threads from polyvinyl chloride and from polyethylene glycol terephthalate were curled with a favorable result, the temperature being 80 C. in the case of polyvinyl chloride, and 170 C. in the case of polyethylene glycol terephthalate.

While the examples refer to polycaprolactam, polyvinyl chloride and polyethylene glycol terephthalate, the in vention is generally applicable to thermoplastic threads from synthetic polymerization and polycondensation products including also polyethlene, polyacrylonitrile, polyamide, polyesters or corresponding copolymers.

It is important to observe that in the present invention the heating and cooling of the yarns are both accomplished before the detwisting begins. In this regard it has been found that if detwisting commences before cooling is complete the stability or fixation of the curl those produced from oxygen-sensitive polymers. In the case of polyamide threads, such as nylon, atures of 140-170 air temper- C. are possible. For polyvinyl chloride threads, lower temperatures, for instance between 70 and 85 C., may be used and for threads from polyesters, such as polyethylene glycol terephthalate high er temperatures are recommended, for instance tem-' peratures between 145 and 175 C. 7 i In order to prevent the damage which results from feeding hot thread to the false twisting device, the path of the cooling zone 6 is quite long, it being necessary that the cooling take place before the twist is relieved. The length of the cooling zone 6 can be somewhat reducedif cool air is supplied, or if the air is circulated as by a fan or the like. It has been found, however,- that a free air path without forced circulation is entirely satisfactory if it is long enough.

It has been discovered that it is desirable to heat the thread practically without tension and for that reason thread brake 4 is employed immediately ahead of the heating zone. As a thread brake, one preferably uses a disc brake or pressure shoe brake which increases the tension additively according to the formula In the formula P represents the tension in the thread leaving the tensioning device. 7 the thread before it has been tensioned in the thread brake. n is the coefiicient of friction and N, of course, is the load of the brake. It is also desirable that the supply device be one which 'does not impose too much tension on the thread and to draw overhead from a cone-type package as illustrated in Figure 1 is satis factory. In order to avoid an agglutination of the filaments and to obtain a good open curling it has been found to'be of importance to keep the thread portion being twisted and'situated between the thread'brake and the false twisting device at the slightest possible uniform tension. It is also desirable to propel the thread at a uniform speed by means of a conveyor mechanism situated beyond the said air treatment zones.

Tests have shown that particularly good results are achieved if one uses a tension on the thread in the said 7 air treatment zones not exceeding about 6 g. per 100 denier.

It has further been found that the design and the operation of the false twisting device greatly influence the properties of the products obtained. It appears that those false twisting devices are most satisfactory which do not increase the tension towards the side of the cooling and heating zones and at the same. time open up the curled thread towards the opposite side. Both effects may be obtained by using the false twisting devices in which the thread enters the twisting device without ballooning but is delivered in a ballooning manner towards the discharge end, i.e., towards the side of the conveyor device arranged after the twisting device.

In the path between false twisting device and conveyor device the cooled thread loses its twist and is thenled further on by the conveyor mechanism whereupon the thread can be delivered to a collecting device.

' The twisted thread which loses its twist after the false twisting device but before reaching the conveyor mechanism now keeps the twist fixed in the cooling zone'in the form of curling. However, the detwisting ofthe thread causes bends and crinkles giving thethread' a tendency to twirl which later on shows its effect.

These false twisting devices may be very well balanced,- may have small dimensions, 6 and, as an almost ideal.

With these rotating body, they require little power.

devices it is possible to obtain, without appreciable difii- 20,000-60,000 r.p.m. while using a culties, speeds of p i 7 v 2,952,96;

the twisting device is preferably a triple roller with a detachable upper roller in order to facilitate threading 1n.

Finally, the confined space for heating the thread may be made suitable for treating arientire sheet of threads lying m.one plane and being twisted, the threads being conducted transversely'through the said confined space V ture of the air but also'on the nature of the thread, the

denier, and the speed of the thread.

0 The thread produced according to the present inventron shows a stable twist curling under atmospheric influences. Due to the tendency to enclose air pockets itis possible to produce fabrics therefrom which have good insulating properties. Tl1'e threads are extraordinarily P equals the tension of elastic so that they can be stretched out to four times their length. This elasticity manifests itself also in knit and woven fabrics made from these threads. It is also 7 possible to give these fabrics a thermal af-tertreatment belt or rope drive so thatrone may obtain with the whole device rather high drawing 01f speeds and consequently 7 high capacity. The thread conveyor device placed after without unfavorably affecting them provided the temperature of this aftertreatment does not exceed the temperature used when fixing the twist.

What is claimed is? In a thermoplastic yarn curling apparatus including a false twist device 'for imparting temporary twist to yarn passing therethrough and a heater for setting the false twist in the temporarily twisted yarn, the improvement residingin the false twist'device which comprises a rotatable spindle, a cylindricalyarn storage wheel formed integral with said'rotatablespindle, a'discharge disk formed integral with said yarn storage wheel, means defining a longitudinal yarn passageway in said rotatable spindle, means defining a connecting passageway between the outer surface of said yarn storage wheel and said longitudinal passageway, meansfor imparting rotation to said spindle'and to yarn passing therethrough, and means remote from said discharge disk and lying on the extendedaxis of said' rotatable spindle for withdrawing thermoplastic yarn throughsaidlongitudinal passageway, through said connectingpassageway, at least partially around said yarn storage wheel, over said discharge dish and laterally outwardly away from said rotatable spindle, said yarn ballooning between said yarn storage wheel and said withdrawing means and being twisted by said rotatable spindle in a first direction on the entrance side thereof while being twisted in a second direction equal to but opposite from said firstdirection on the discharge side thereof.

References. Cited in the file of this patent UNITED "STATES PATENTS 7 836,762 Germany Apr. 17, 1952