US3438105A - Process for crimping thermoplastic yarns - Google Patents

Description

April 15, 1969 J, JOLY ETAL 3,438,105

PROCESS FOR CRIMPING THERMOPLASTIC YARNS Filed Sept. 23, 1966 Inventor-1 B gm ,owm; r 72%;

United States Patent 0 Int. Cl. D04h N06 US. Cl. 28--72 3 Claims ABSTRACT OF THE DISCLOSURE The invention discloses a process for crimping thermoplastic yarns in which one or more yarns to be crimped are introduced, together with an auxiliary yarn, into an elongated space by means of a current of fluid which is under pressure and is at a temperature sutficient to set the yarn or yarns to be crimped, with the weight percentage and speed of introduction of the auxiliary yarn as compared with the yarn or yarns to be crimped being within specified limits, the fluid is controllably released laterally in a subsequent portion of the enclosed space, the yarns are allowed to pack in such space portion and then discharged freely therefrom, the together-packed yarns are subjected to a thermal treatment and the auxiliary yarn is then dissociated from the crimped yarn or yarns.

This invention relates to the crimping of thermoplastic yarns and has for its object the provision of a process providing crimped yarns of improved mechanical characteristics.

This application is a continuation-in-part of our c0- pending application Ser. No. 283,574 filed May 27, 1963, now abandoned.

In the process according to this invention, the yarn or yarns to be crimped is or are associated with an auxiliary yarn or filament during the crimping treatment and, subsequent to such treatment, said auxiliary yarn or filament is separated from said yarn or yarns to be crimped.

Several processes are known in which a filament to be crimped is temporalily associated with an auxiliary filament and separated therefrom when the crimp has been made permanent. One such process is described in US. Patent No. 3,222,859 to the same assignee. This process consists of submitting two filaments, travelling at different speeds, in a compressed filament feed jet to the action of a turbulent fluid thereby producing a composite mock boucle yarn in which one yarn constitute a peripheral yarn with individual filaments having a random, non periodic, crimp and the second yarn constitutes a core yarn and, after setting the crimp in the said peripheral yarn, removing the core yarn.

In these known processes, the proportion of auxiliary filament in relation to the crimped filament has always been fairly high and the operations necessary for its subsequent elimination or recovery detract fromthe industrial value of these techniques, which in any event have a poor efficiency.

In the process according to the invention, which permits operation at very high speeds, the proportion of the auxiliary filament is very low. This constitutes a clear economic advantage but also an important technical advantage for, after dissociation of this auxiliary yarn, it

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is not generally necessary to eliminate it from the crimped yarn, since it represents a very low percentage of impurities.

It is known, for example, according to US. Patent No, 3,142,147, that a heat treatment of an already crimped yarn carried out in a relaxed or substantally relaxed condition increases the bulkiness, crimpiness and stretchability of the yarn. However, the effectiveness of this treatment is particularly improved if, as is the case in the present process, the filament is maintained in the configuration which it had been given at the moment of crimping. The maintenance of this structure is assured by the auxiliary yarn, which permits the packing of yarn to remain intact with practically the same cohesion as in the packing zone, throughout the subsequent heat treatmentor any other processing.

It has already been proposed, e.g. in US. Patent No. 3,099,594, to pack a yarn by means of a fluid, but either the packing of yarn has been at least partially destroyed at the exit from the packing zone, or the cohesion has been assured by plasticising to an extent necessary for bonding the filaments between themselves to give a cylindrical filter element from which the yarn has not been recoverable for textile purposes.

According to the present invention, we provide, in a process for crimping thermoplastic yarns by introducing said yarns in an elongated confined space, by means of a current of fluid under pressure at a temperature sufiicient to set the yarn and then allowing said fluid to be controllably released laterally in a further portion of said enclosed elongated space, allowing said yarns to pack in said further portion of said enclosed elongated space, and to discharge freely from said elongated space, the improvement consisting of introducing in the elongated space together with at least one yarn to be crimped one auxiliary yarn, said auxiliary yarn being introduced by the same opening as the yarn to be crimped and by action of the same fluid, said auxiliary yarn being in a weight percentage of less than 0.05 of the yarn or the yarns to :be crimped, the speed of admission of said auxiliary yarn being comprised between 0.2 to 2 percent of the speed of the fastest yarn to be crimped, forcing the together-packed auxiliary yarn and yarn or yarns to be crimped through said enclosed space at a speed substantially equal to the speed of said auxiliary yarn, subjecting the together-packed yarns to a thermal treatment and thereafter dissociating the auxiliary yarn from the crimped yarn or yarns.

Due to the combination, in the process of this invention, of several factors, namely (a) rebonding of the filaments by means of fluid, (b) packing of the yarn by fluid pressure, (c) combination of two heat treatments, one effected by the packing fluid, the other performed on the packed yarn, (d) maintenance of the cohesion of packing between the two heat treatments, and (e) a low percentage of auxiliary yarn, there is obtained a crimped yarn having remarkable properties, particularly with regard to resilience.

The apparatus for effecting the crimping step may be similar to that disclosed in US. patent application Ser. No. 355,379 filed Mar. 27, 1964, now US. Patent 3,373,470, granted Mar. 19, 1968, by Jean Joly, co-applicant hereof. In one embodiment, this apparatus comprises an injector formed by a nozzle screwed into a pipe which has an outlet surrounding the outlet from the nozzle, a conduit into which the outlet from the nozzle leads, enclosed axial extension to said conduit at the end thereof remote from said nozzle, such extension having a fluid permeable 3 wall, and a helical metal spring having gaps between its convolutions, such spring being fitted axially into said extension and having its free or outlet end projecting outwardly form said extension and eventually curved to arcuate form.

Such apparatus is shown in the accompanying drawings, wherein a yarn F to be crimped is introduced into injector tube 1, which comprises a nozzle 2 having therethrough a passage 2' and a pipe 3 into the end of which the nozzle 2 is screwed, the pipe 3 having an outlet 3 surrounding the outlet of the nozzle passage 2.

Fluid V is supplied through the tube 3. At the outlet of the pipe 3 is located a conduit 4 having a passage 4 and an enlarged portion 7, the wall of which is permeable. Within this extension is fitted a metal spring 5 having gaps 6 between the convolutions thereof.

In carrying out the crimping step of the process according to this invention, the yarn F is delivered by the supply roller 9 and the drive roller 10, while the auxiliary filament F is delivered by the roller 11, to the injector nozzle 2 being entrained therein in fluid V. The thus entrained yarn and filament are propelled by the fluid through the tubular passage 4 in the conduit 4, into the interior of the spring 5. The fluid escapes from the spring, the greater part escaping through the gaps 6, the permeable wall 7 canalizing the escaping fluid through the convolutions of the inlet end of the spring thus contributing to an increase in their temperature. The yarn is tightly packed in the spring 5 into a compact mass which leaves the outlet end of the spring in the form of a wad 8 which is collected on the conveyor 12 or other suitable means.

Because of the lateral flow of the fluid the yarns become tightly packed in the spring into a compact mass whose cohesion exists when this mass leaves the con tainer. The dimensions of the orifices through which the fluid laterally escapes may be adjusted by varying the extension of the spring. Variation of the bending of the spring may be made to adjust the packing of the yarns in the spring.

The filament to be crimped may be fed at speeds reaching 1,000 metres per minute and more. The speed at which the auxiliary yarn is supplied is between 0.2 and 2%, and generally 0.5 and 1% of the speed of the yarn to be crimped. When a number of yarns to be crimped are fed into the injector, the speed at which these various yarns are supplied may be equal. In this case, there is obtained after separation from the auxiliary filament a crimped tow, the number of filaments of which is the sum of the number of filaments of the yarns which were introduced into the chamber in order to be crimped.

It is thus possible to obtain with a plurality of yarns crimped tows of coarse count without any necessity for preassembly of the yarns.

It is also possible to separate the tow obtained into its various constituents. In contrast to what might have been expected, this separation takes place Without difficulty. It is therefore possible to prepare crimped yarns of different counts with one adjustment of the apparatus.

If the various yarns to be crimped are supplied at different speeds, a fancy yarn of chenille type is obtained after dissociation from the auxiliary yarn, the yarn to be crimped which has been introduced at the lowest speed constituting the core yarn, while the other yarn or yarns constitute the effect yarn or yarns.

On leaving the crimping space, after the crimping step, the yarns, which have been packed together, are either twisted or collected in their present state, for example, in a rotating pot, for subjection to the thermal treatment.

Since the auxiliary yarn is not permanent, it is preferable to reduce the percentage thereof. This percentage may be as low as 0.01% by weight. Above 0.02% it is necessary in certain cases to consider elimination of the auxiliary yarn after dissociation from the crimped yarn, but generally for present applications the percentage of the auxiliary yarn may reach 0.05% without this complementary operation of elimination being necessary.

The thermal treatment of the composite yarn may be effected by any appropriate technique. It is possible, for example to effect a treatment by hot air or steam at atmospheric pressure, but it is preferable to use steam under pressure, this leading to better quality of the filaments.

When it is desired to prepare dyed crimped yarns, it is preferable to dye the yarns, in their packed form, and to effect the heat treatment during the dyeing operation.

The compact form of the packed yarns, due to the great difference in the supply into the injector of the auxiliary yarn and of the yarn to be crimped, does not impair good penetration of the dyestuif. The crimped yarn wound after separation exhibits a good level effect, and the articles made up from this yarn show no dyeing irregularity.

This variant of the process is particularly economical since it enables two treatments to be performed in a single operation.

In order to minimise the number of necessary manipulations, it is advantageous to collect the packed yarns as they leave the crimping apparatus, directly in a perforated unoxidizable cage of the type currently employed in dyeing.

The separation of the packed yarns, i.e. the recovery of the crimped yarn may be carried out by various methods, such as:

Dissolution of the auxiliary yarn, when the latter is readily soluble in a suitable solvent, e.g. when the auxiliary yarn is cellulose acetate or polyvinyl alcohol;

Melting of the auxiliary yarn, when the latter possesses a relatively low melting point, e.g. when the yarn is polyethylene;

Mechanical methods producing, by traction, breakage of the auxiliary yarn into short lengths which can be separated or eliminated, but not necessarily, because of the very low content of the auxiliary yarn.

The process of this invention is applicable to all thermoplastic yarns regardless of their nature, and more especially to those based upon polyamides, polyesters, polyolefines, polyacryl or polyvinyl derivatives, or cellulose acetate or cellulose triacetate.

In addition to the advantage of a high-bulk crimp having no loops and undulations in phase between the various filaments, the yarns obtained in accordance with this invention possess mechanical characteristics (notably high resilience) which render them very suitable for the manufacture of carpets.

The following tables summarise the results obtained in a series of tests carried out with the aid of the apparatus referred to above. The abbreviations appearing in these tables have the following meanings:

P=pressure in kg./cm. of the fluid passed into the injector t=temperature V speed of supply of the yarns in m./rnin. PA=polyhexamethylene adipamide PP polypropylene PE=ethylene polyterephthalate Ac=cellulose acetate Vis=viscose (The figures appearing after these symbols indicate in each instance the count of the yarn in deniers and the number of filaments in the yarn.)

The twist of the yarns employed is in each instance lower than or equal to 20 turns per metre. The speed at which the packed yarns are collected is substantially equal to the speed of passage of the auxiliary yarn.

The separation of the packed yarns is effected in all cases by subjecting it to sufficient tension to break the auxiliary yarn.

In the examples grouped together in Table I a single yarn to be crimped was fed into the injector.

TABLE I Yarn To Be Crimped Auxiliary Yam Fluid Setting Results Example No. Steam Chamber Percentage of Production, Nature V Nature V Nature P t auxiliary yarn g./hour per 11 Duration before separation injector 1 PA 520/30 800 PA 15/1 3. 2 3. 147 145 0. 01 2, 770 2-. PA 1,040/60 400 PA /1 3.2 8. 5 147 145 0.01 2, 770 3. P 468/78 3. 4 3. 5 147 130 0. 02 1, 540 4 4. 2 3. 7 149 130 0. 015 2, 640 5 4. 7 4. l 151 130 0. 015 3, 080 6- 3. 2 3. 5 147 130 0. 015 2, 180 7 3. 4 3. 7 140 130 0. 011 3, 080 8- PE 1,000/ 3. 3 3. 5 147 130 0.05 1, 330 9 PE 1,000/20 4. 2 3. 5 147 130 0. 03 2, 660 10 PE 1,000/20 4. 6 3. 5 147 130 O. 02 3, 990 11 PA 1,040/60-. 4. 2 3. 5 147 145 0. 04 2, 770

TABLE II Example Auxiliary Yarn Yarns To Be Crirnped Fluid ho- Nature V Nature V Nature P t" 12 PA 20/7 5.8 2 ends PP 450/30 300 Steam 5 158 In Example 12, which is given in Table II, the various yarns to be crimped were fed into the injector at the same speed; after steam treatment and separation, the crimped tow was wound.

In Example 13, which is given in Table III, the yarns to be crimped were fed at the same speed into the injector, but after steam treatment and separation the crimped yarns were wound onto two separate bobbins.

Example 14 In this example, the thermal setting and the dyeing were carried out in a single operation.

Packed yarns were prepared from a polyhexamethylene adipamide yarn, 1040 deniers, 60 filaments, and a cellulose In one hour, the temperature was brought to 130 C. and then maintained at this value for one hour.

After rinsing and drying, the packed yarns are unravelled and then submitted, by passage between two pairs of rollers rotating at diflerent speeds, to a tension suflicient to break the auxiliary yarn.

A moss-green dyed yarn with stable crimp was obtained, in which the broken strands of auxiliary yarn were not apparent.

Example 15 The object of this example is to illustrate the advantages of the process according to the present invention over known processes using an auxiliary yarn and heat treatment.

In order to establish as complete a comparison as possible, a prior process has been chosen in which an auxiliary yarn and yarn to be crimped are associated by pneumatic means. In this process, described in United States Patent No. 3,222,859, the two yarns are combined by passage through a fluid current the turbulence of which is sutficient to entangle the strands of the filament to be crimped with the strands of the auxiliary yarn, this entanglement causing undulations in the yarn to be crimped, this being fed at a higher speed.

The results of these comparative experiments are given acetate yarn, 43 deniers, 13 filaments. in the following table:

Auxiliary Yarn Yarn To Be Crirnped Fluid Proportion by Processes weight of fluid Heat Composition V Composition V Delivery Composition 1? Delivery to yarn to be treatment (gin/mill.) (gm./min.) crimped Known process PA 20/7"... 15 PA 1,040/ 250 28. 9 Air 7. 5 700 24. 2 Steam, 2 hrs.

PA 20/7- 15 PA 520/30 300 17. 3 Air 7. 5 700 40 145 C.

Inventive process"-.. PA 20/7 6 PA 1,040/60 400 46. 2 Steam 3. 5 90 1.95 Do. PA 20/7..." 11. 4 PA 1,040/60. 800 92. 4 106 l. 1 Do. PA 20/7"-.. 15 PA 1,040/60 1,000 115. 5 126 1. 1 Do.

The speed of supply of the polyamide yarns to the injector was 400 m./min., and that of the cellulose acetate yarn 4 m./min.

The fluid sent into the injector Was steam heated at 147 C. under a pressure of 3.5 kg./cm.

The packed yarns were collected in a perforated unoxidisable cage.

Desizing was efiected at 90 C. by means of an aqueous solution comprising, per litre, 5 cc. of NaOH at 36 B and 2 cc. of non-ionic detergent of a standard type.

After rinsing, followed by neutralisation with acetic acid, the cage containing the yarn was introduced into a pressure dyeing apparatus of standard tpye, i.e. an autoclave machine with circulation of solution.

The dyeing solution, brought to a pH of 4 by the addition of acetic acid comprised:

Clearly, as can be seen from these experiments, the speed of crimping in the process of the present invention is far superior to that of the known process when using the same fluid pressure and feed speed of auxiliary yarns, the qualities of the crimped yarns obtained after separation of the auxiliary yarn being comparable.

Indeed, in the known process, the entanglement of the yarns built up undulations, which must be important and which necessitate the increased fluid delivery assuring severe turbulence. In the present process the undulations are due to the packing of the yarns, which may be effected at extremely high speed with relatively low fluid delivery speeds.

The cohesion of this packing of the yarn remains intact at the exit of the crimping zone and is preserved during the heat treatment as is evident in the crimped yarn obtained, by a swelling and a remarkable stability of crimp.

We claim:

1. In a process for crimping thermoplastic yarns by introducing said yarns in an elongated confined space, by means of a current of fluid under pressure at a temperature sutficient to set the yarn and then allowing said fluid to be controllably released laterally in a further portion of said enclosed elongated space, allowing said yarns to pack in said further portion of said enclosed elongated space, and to discharge freely from said elongated space, the improvement consisting of introducing into the elongated space together with at least one yarn to be crimped one auxiliary yarn, said auxiliary yarn being introduced by the same opening as the yarn to be crimped and by action of the same fluid, said auxiliary yarn being in a weight percentage of less than 0.05 of the yarn to be crimped, the speed of admission of said auxiliary yarn being between 0.2 and 2 percent of the speed of the fastest yarn to be crimped, forcing the together-packed yarns through said enclosed space at a speed substantially equal to the speed of said auxiliary yarn, subjecting the t0- gether-packed yarns to a thremal treatment and thereafter dissociating the auxiliary yarn from the crimped yarn.

2. A process according to claim 1, wherein the speed of feed of the auxiliary yarn is between 0.5 and 1% of the speed of the fastest yarn to be crimped.

3. A process according to claim 1, wherein the auxiliary filament is dissociated from the crimped yarn by breaking the auxiliary yarn into short lengths.

References Cited UNITED STATES PATENTS LOUIS K. RIMRODT, Primary Examiner.

@2 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,438, 105 Dated April 15, 1969 I Inventon's) Jean Joly et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading, insert Claims priority, applications France, No. 899,096, May 29, 1962, Nos. 930, 949 and 930,950, April 9, 1963 swam; mi SEALED m a (SEAL) Attest:

WILLIAM E- 5mm, 33. Edwud fiomia'sionor of Patents Anestingoffioer

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