US3196602A - Crimping synthetic thermoplastic yarns - Google Patents

Description

y 1965 D. ca. JENKINS ETAL 3,196,602

GRIMPING SYNTHETIC THERMOPLASTIC YARNS Original Filed May 11, 1962 2 Sheets-Sheet 1 9 Izqentora fl/u aa/ 414 14 4 M Attorney.

July 27, 1965 D. s. JENKINS ETAL 3,

CRIMPING SYNTHETIC THERMOPLASTIC YARNS Original Filed May 11, 1962 2 Sheets-Sheet 2 p I gnugnjo s United States Patent 3,106,602 CRIMPING SYNTHETIC THERMOPLASTIC YARNS Donald Glyn Jenkins, Ahersychan, Pontypool, and Brian Edward Clapson, Cwmbran, England, assignors to British Nylon Spinners Limited, Pontypool, England Qriginal application May 11, 1962, Ser. No. 194,108. Divided and this application Sept. 6, 1%3, Ser. No. 311,275 Claims priority, application Great Britain, May 19, 1961, 18,251/61 7 Claims. (Cl. 57-157) This application is a division of our copending application, Serial No. 194,108, filed May 11, 1962, now abandoned.

The present invention concerns improvements in or relating to crimping synthetic thermo-pastic yarns, and to crimped yarns of syntehtic thermo-plastic materials.

Continuous filaments of the various man-made varieties, such as those of nylon, are produced in substanially smooth straight condition; and they may be, and often are, used in the construction of fabrics in that condition, usually after having been twisted together as multifilament yarns.

It is sometimes desirable, however, that such yarns should be given a crimped configuration, in order that the handleof fabrics made therein-om should not be so smooth as is normally the case, and in order that these fabrics should be moreb ulky, or fuller, than fabrics made from the ordinary yarns, and that their covering power should be greater. Also, crimping of the yarns can introduce added stretchability thereto, if desired.

At the present time, a considerable number of processes for imparting crimp to normally smooth straight continuous filament yarns are known and practised. Some of these processes depend on twisting and untwisting, some on bending a yarn around a sharp edge, and others on compressing continuous lengths of yarn in a chamber so that the yarn assumes a zig-zag formation. In the case of the synthetic thermoplastic multifilament yarns, such as those of nylon and Terylene (Registered Trademark), heat is applied in all these processes prior to or concurrently with the application of the deforming force, so that the yarns are in a plastic condition at some period whilst the deforming force is being applied.

We have now found that such synthetic thermoplastic multifilament yarns can very simply be crimped at a high rate of production if they are squeezed between the nip of two co-acting rollers, whilst the yarns are twisted to a low degree and are at an elevated temperature, i.e. 100 C. or above, and provided that the conditions of the process are as defined hereinafter, and that the yarns are subsequently tensioned and some or all of the twist in them removed or even some small amount of residual twist in the reverse sense imparted. The invention, therefore, comprises a process for crimping a synthetic thermoplastic multifilament yarn wherein said yarn is squeezed between the nip of two hard, smooth-surfaced rollers, at least one of which is driven, whilst the yarn is in a lowtwisted state and at an elevated temperature i.e. above about 100 C., and the yarn is then back-twisted.

The invention also comprises a crimped multifilament yarn of synthetic thermoplastic material wherein the crimp of the filaments is of a regular zig-zag nature having rounded apices, said crimp being planar over short lengths, with adjacent short lengths difiering in respect of their planar orientation. Such a crimped yarn is essentially free from torque and has a relatively low extensibility.

The amount of low twist in the supply yarn will be selected mainly on economic grounds, but it will depend 3,195,602 Patented July 27, 1965 on the denier and on the denier-per-filament of the yarn, and it may be of the order of 4 turns per inch. The yarn may be pre-heated by dry heat, e.g. in the form of contact, radiation or hot air heating, and the temperature to which the yarn may be heated may be within the range between C. and a temperature 300 C. below the melting point of the thermoplastic material concerned.

The rollers, which may be mounted as in a mangle one on top of the other with their axis horizontal or which may be mounted side-by-side with their axis in the horizontal or the vertical plane, should be made of, or at least have a surface composed of, a smooth hard material, such as brass. It is not necessary that the mating surfaces of the rollers should actually be polished, however; and a slightly matt surface may be suitable. It is not absolutely essential that the surface material of the two rollers should be identical; but one roller should not have a surface which is significantly more resiliently compressible than the other. In general, it may be said that the surfaces of the rollers should be of material which, for a given stress, is harder than the material of the yarn.

The diameter of the rollers is not critical, although it will have some elfect on the crimp produced. For instance, rollers of 1 inch diameter have proved satisfactory, but larger or smaller diameter rollers than this may be used. Normally, the two rollers will be of similar diameter, and both will be driven.

The force to be applied to press the rollers together to squeeze the yarn therebetween will depend on the ma terial of the yarn to be crimped, and on the diameter and width of the rollers; and the value to be selected will involve a compromise between the degree of crimp desired and the tenacity of the crimped yarn that is required at any given twist value.

The ettects of the amount of low twist in the supply yarn, and of the load applied to the nip-rollers, are demonstrated in the following Tables 1 and 2. Table 1 shows the effect of varying twist with a constant load; and Table 2 shows the effect of varying load with a constant twist. In both cases the yarn is 950 denier/ 68 filament yarn of polyhexamethylene adipamide.

TABLE 1 Effect of varying twist with constant load of 164 lbs.

Crimp Brealn'ng Twist, turns per inch Frequency, load in Remarks on rimps grams per Crimp per inch denier 1 03 No crimp. 2 3.18 Poor crimp. 7 3.15 Good crimp. l0 3. 04 Very good crimp.

TABLE 2 Eflect of varying load with constant twist of 4 turns per inch Crimp Breaking Load in 1b. frequency load in Remarks on Remarks on in crimps grams per Crimp Tenacity per inch denier 5% 3.42 Poor erimp Good tenacity.

7 3. 30 Fair crimp. Do. 7 3.15 Good crimp Fair tenacity. 7 2.80 do Poor tenacity. 7% 1.05 do Useless tenacity.

The crimp produced in the process is not apparent on egress of the yarn from the rollers; and it a concurrent post-setting treatment is applied, as by heating the yarn to an elevated temperature for a short period, the yarn will be set in the flat ribbon form which it is in on emer gence from the rollers and this will lead to an enhanced crimp after some or all of the twist has been removed. Thus, a concurrent setting treatment after crimping is preferred, and can conveniently be carried out on the yarn while it is passing from the rollers to a wind-up mechanism. In the case of nylon yarns, for instance, this post-setting may be accomplished by passing them through a radiant heater or in contact with a heated metal plate, and the same heating device may be employed for both pre -heating and post-setting. The yarn should then be tensioned and all, or most, of the twist removed. This can conveniently be achieved at the time of wind-up by the use of a ring-spindle wind-up. It is possible, however, for the post-setting treatment to be carried out on the yarns after they have been tensioned and de-twisted, rather than before. In that case, post-setting may be performed whilst the yarns are in hanks or whilst they are loosely wound in a soft package; and steam is then the preferred setting agent.

The rollers may be cold, or they may be at an elevated temperature compared with the room temperature.

In a convenient embodiment of the process of the invention, rnultifilament yarn of e.g. polyhexamethylene adipamide having a low degree of twist is withdrawn at e.g. 200 feet/minute, from a cheese-type supply package by a pairof brass nip-rollers, both of which are driven and through whose nip the yarn is passed after having passed in contact with a metal strip heater to raise its temperature to, e.g. 120 C., and the yarn is then passed through a guide to a ring-spindle wind-up which removes all, or substantially all, of the twist. The tension in the yarn, either before or after the nip-rollers, should not exceed more than about 0.4 gram per denier. The total load on the rollers forcing them together'may be of the order of /2 lb. per denier, but the relationship between load and denier is not linear.-

In such an embodiment of the process, the yarn may be of a wide range of deniers, e.g. from 70 to 950, and the denier per filament may be from 1 to 15, for instance. In general terms, the finer the denier per filament, the less amount of twist need be present in the yarn: for instance, about 2 turns per inch only will sufiice for a 70 denier/75 filament polyhexamethylene adipamide yarn. It is advantageous to use a yarn having low molecular orientation; and if the supply yarn is actually undrawn, suflicient drawing (orientation) can be arranged to take place at the nip of the rollers for most textile purposes.

Such an embodiment of the process of the invention is illustrated in the accompanying drawings, in which:

FIGURE 1 is a diagrammatic representation of the threadline of such embodiment; 7

FIGURE 2 is a perspective side view of a modified form of a roller arrangement for use in such embodiment; and 7 FIGURE 3 is a side view, on an enlarged scale, of a length of yarn produced by the apparatus of FIGURES l and 2.

In PEGURE 1, yarn 1 is shown being withdrawn over the top end of yarn supply package 3, through guide 5 and thence around tensioner 7 which imparts to it a substantially constant tension for the subsequent heat treatment. Such takes place by contact of the yarn with the curved surface of electrical heater plate 9, the tempera: ture of which is automatically maintained constant by controller 11. The yarn whilst at the required elevated temperature is squeezed between nip-rollers 15 of the roller assembly 13, both rollers being driven by means not shown in the figure. The loading of top roller is effected by the presslfi'. After emerging from the nip of the rollers, the yarn, which will be in substantially fiat ribbon form, is led through a guide 1?, thence downwardly to balloon guide 21 of the ring-spindle wind-up.

4 In the balloon, the yarn is tensioned and de-twisted; and finally it is wound into package 23 rotated on its spindle by spindle-whorl 25, the yarn passing through traveller 29 which rotates around the vertically recipro cating ring 31.

Another method of loading the top roller of a pair of nip-rollers is shown in perspective in FIGURE 2. Rollers 35 and 37 are mounted one above the other in mounting 33. The axle of the top roller 37 is urged downwardly by hearing blocks, one of which is shown by reference numeral 39. The load to be applied to these blocks is conveniently provided by a balanced tray arrangement, which comprises a tray mounted at the end of long arms 43 and adapted to carry the required small weight 47, which tray (when unweighted) is balanced by counterweight 4-9 on the other side of pivotal points 51. The eifective load applied by the arms 43 to bifurcated rods 41, and thence to blocks 3% is many times the weight 47 owing to the length of the arms 43 and to the closeness of the rods 41 to the pivotal point of the system. Hook 53, which is one of a pair, is for holding top roller 37 in place when the lower roller is removed. Again, both rollers are driven in this case also, but for simplicity the driving means have not been shown.

Referring to FIGURE 3 there is shown, on an enlarged scale, a length of yarn 1 after it has been crimped by the method of the present invention. The crimp in the yarn is of a regular zig-z'ag nature having rounded apices 55. The crimps'are planar over short lengths, with adjacent short lengths 57 differing in respect of their planar orientation.

The invention will now be further illustrated by the following examples, which show the conditions for crimping a number of different yarns of polyhexamethylene adipamide.

EXAMPLE 1 950 denier/68 filament drawn yarn of polyhexamethylene adipamide was twisted to 4 turns per inch. Such twisted yarn was used as the supply yarn for crimping, and was withdrawn from itspackage at 150 feet per minute at a tension of grams. The yarn was heated to a temperature within the range 180-200 C., and whilst at that temperature it was squeezed between the nip-rollers, with a load thereon of 164 lb. The yarn emerged from the nip as a fiat ribbon, the filaments being lightly stuck together and slightly deformed in cross-section. When tensioned and dc-twisted to zero turns per inch the crimp was produced, the frequency in each filament thereof being about 7 crimps per inch.

The denier or" the crimped yarn was 1200 at wind-up; and the crimp of the filaments was of a regular zig-zag nature, the apiees, or knees, of the crirnps being rounded rather than saw-tooth (as in stufifenbox crimped yarn), and the crimp-s lying in one plane over short lengths of yarn but such planes alternating in their orientation. The crimped yarn was of low extensibility and was essentially non-torque; and as such, it was sutiable for knitting, weaving or for use in the pile of carpets.

EXAMPLE 2 70 denier/ filament drawn yarn of polyhexamethylene adipamide was twisted to 2 /2 turns per inch. Such twisted yarn was used as the supply yarn for crimping, and was withdrawn from its package at feet per minute at a tension of 3 grams. The yarn was heated to a temperature within the range 2GG C., and whilst at that temperature it was squeezed between the nip-rollers with a load thereon of 128 lb. After tensioning and de-twisting, the yarn was crimped, each filament thereof containing some 24 crimps per inch. The crimp was of the same essential nature as that of the yarn of Example 1.

EXAMPLE 3 840 denier/140 filament undrawn yarn of polyhexamethylene adiparnide was twisted to 4 turns per inch. Such twisted, undrawn yarn was used as the supply yarn for crimping, and was withdrawn from its supply package, and tensioned by the tensioning device to 300 grams tension, by the nip-rollers which were rotating at a surface speed of 150 feet per minute. Before entering the nip of the nip-rollers, the yarn was heated to a temperature within the range 180-200 C. The load applied to the nip-rollers was 98 lb. The resultant yarn, after de-twisting to zero turns per inch, was a crimped yarn of low orientation, drawing to a ratio of 2121 having occurred at the nip-rollers. The filaments of the yarn contained 20 crimps per inch; and the crimp was of the same essential nature as that of the yarn of Example 1.

Instead of a single supply package and single wind-up, a plurality of supply packages may feed the one pair of nip-rollers, and the yarns crimped thereby be wound up either separately or together on one package. Instead of winding-up the crimped yarn on a bobbin, it may be coiled within a container. After wind-up, three or more such yarns may be plied, e.g. some 2 or 3 turns per inch in the direction opposite to the original twist in the singles yarns. Such plied yarns may then be hankdyed and used for the pile of tufted carpet. The filaments comprising the multifilament supply yarn may be other than circular in cross-section; and, after being squeezed by the rollers, the cross-section of originally circular cross-section filaments is likely to be deformed.

The process of the invention may be utilized to crimp all synthetic thermoplastic continuous filament yarns, including all nylons, Terylene (Registered Trademark) polyester fibre, Acrilan (Registered Trademark) polyacrylonitrile fibre, isotactic polypropylene and linear polyethylene. The conditions of the process and the nature of the crimp imparted will naturally differ as between the various kinds of fibres; but useful results are obtainable in all cases.

What we claim is:

1. A process for crimping a synthetic thermoplastic multifilament yarn consisting of the steps of:

(a) imparting a low degree of twist to said yarn;

(b) heating said twisted yarn to a temperature of at least C. but not greater than 30 C. below the melting point of the material of the yarn whilst the yarn is under tension;

(0) squeezing the twisted yarn between the surfaces of a pair of driven nip-rollers whilst it is at the said temperature; and

(d) back-twisting the yarn.

2. A process according to claim 1 in which the yarn is initially undrawn.

3. A process according to claim 1 in which the yarn is of polyhexamethylene adipamide and is heated to between -200 C.

4. A process according to claim 1 in which the backtwisted yarn is further heated whilst under low or zero tension.

5. A process according to claim 1 in which the surface, at least, of each of the rollers is composed of a material which, for a given stress, is harder than the material of the yarn.

6. A process according to claim 1 in which said low degree of twist is imparted by twisting the yarn up to about five turns per inch.

7. A crimped multifilament yarn of synthetic thermoplastic material made by the process of claim 1.

References Cited by the Examiner UNITED STATES PATENTS 2,089,193 8/37 Dreyfus 2872 2,451,919 10/48 Clarkson 2872 2,818,630 1/58 Le Boeuf 2872 2,917,779 12/59 Kurzke et a1. 2872 2,938,258 5/60 Starkie 2872 2,972,795 2/ 61 Backer et al. 19-66 3,001,355 9/61 Evans 57-34 3,052,009 9/62 Epstein et al. 2872 MERVIN STEIN, Primary Examiner.

Claims (2)

1. A PROCESS FOR CRIMPING A SYNTHETIC THERMOPLASTIC MULTIFILAMENT YARN CONSISTING OF THE STEPS OF: (A) IMPARTING A LOW DEGREE OF TWIST TO SAID YARN; (B) HEATING SAID TWISTED YARN TO A TEMPERATURE OF AT LEAST 100*C. BUT NOT GREATER THAN 30*C. BELOW THE MELTING POINT OF THE MATERIAL OF THE YARN WHILST THE YARN IS UNDER TENSION; (C) SQUEEZING THE TWISTED YARN BETWEEN THE SURFACES OF A PAIR OF DRIVEN NIP-ROLLERS WHILST IT IS AT THE SAID TEMPERATURE; AND (D) BACK-TWISTING THE YARN.

7. A CRIMPED MULTIFILAMENT YARN OF SYNTHETIC THERMOPLASTIC MATERIAL MADE BY THE PROCESS OF CLAIM 1.

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