US3224068A - Process for imparting improved latent crimp to filaments - Google Patents

Description

United States Patent 3,224,068 PROCESS FOR IMPARTING IMPROVED LATENT CRIMP TO FHLAMENTS Robert Alexander Edington, George Edward Barlow, and

Peter Bernard Checkland, Harrogate, England, assignors to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain No Drawing. Fiied May 15, 1963, Ser. No. 280,724 Claims priority, application Great Britain, May 24, 1962, 20,046/ 62 5 Claims. (Cl. 28-72) The present invention relates to an improved device for making potentially crimped or crimped synthetic linear polymer filaments.

In our British Patent 808,213 is described a process and apparatus for making potentially crimped continuous synthetic polymer filaments by heating the moving filaments non-uniformly while passing over a narrow surface heated to a temperature above the melting temperature of the filaments in such a way that the filaments are heated on one side only continuously along their length, while under a tension to give a stable stretch to the filaments of not more than The latent crimp in the potentially crimped filaments is brought out by relaxing the filaments by subjecting them to a heat treatment while they are under a free or controlled tension which permits free or controlled shrinkage.

The narrow surface disclosed in the specification of British Patent 808,213 was an electrically heated wire, pin or bar. The heating was affected by the resistance of the wire, pin or bar and was rather difiicult to control. The path over which each filament passed was cooled by the passage of the filament and when filament strayed slightly from its path it was subjected to uneven heat until the new path had been cooled. In the process described in the specification of British Patent 808,213 the wire was heated to red heat, and the filament paths cooled to black heat with the passage of the filaments.

We have now discovered that the process described in British Patent 808,213 is improved if the heated narrow surface is provided on an indirectly heated member. The yarn produced by the improved process is of the same character as the yarn produced by the earlier process, but is more uniform, having a greater regularity of bulk along its length.

According to the present invention, in a process for making potentially crimped continuous thermoplastic synthetic linear polymer filaments by heating moving continuous filaments non-uniformly while passing over a narrow surface heated to a temperature above the melting temperature of the filaments in such a way that the filaments are uniformly heated on one side only continuously along their length, wherein the heated narrow surface is provided on an indirectly heated member.

The latent crimp in the potentially crimped filaments is brought out when the filaments are heated and relaxed, preferably at a temperature above the second order transition temperature of the filaments and at least C. below the melt temperature of the filaments. This heat treatment may be carried out whilst the filaments are under a free or controlled tension which permits free or controlled shrinkage, and may be carried out by hot inert fluids, for example, or by contact with a heated surface.

Further according to the present invention we provide apparatus for carrying out the improved process.

The surface-providing member is preferably made of an abrasion-resistant heat-conducting material, such for example as tungsten, molybdenum tungsten carbide or ceramic material.

Alternatively, the member may be formed of softer metal, such as iron, brass or aluminium, having an outer layer of the abrasion-resistant material which provides the narrow surface.

The indirectly heated member may be in thermal contact with a heated body or may be heated indirectly by radiated heat. The heated body can be heated by a heating element, by electrical induction or resistance, by high frequency induction or by heat exchange with a heated fluid, which may be circulated from or may surround a suitable heat source.

A thermal sensing device may be arranged near or to in contact with the indirectly heated member, preferably on or close to the surface contacted by the moving filaments, in order to measure and/or control the temperature attained by the metal strip or bar.

In operation the yarn is preferably passed over a ribbon forming device which may take the form of a convex surface terminating near to, but not in contact with, the heated narrow surface. The etfect of this ribbon forming device is to spread the filaments of the yarn substantially into the form of a ribbon in which the filaments are continually reshufiiing and passing over one another. The ribbon forming guide may be made of mild steel provided with sand blasted and satin chromed finish, hardened steel or alloys, solid ceramics or metals with ceramic or other hardened coatings. It should be effectively heat insulated from the heated narrow surface so that the temperature of the ribbon forming guide never rises substantially, being limited to approximately C. in operation.

Preferably, the ribbon of filaments approach the leading edge of the heated narrow surface at an angle between 1 and 20 to the surface. Similarly, the potentially crimped yarn leaves the heated narrow surface at an angle between 1 and 20, not necessarily the same as the angle of incidence.

In a preferred form, the indirectly heated member is provided as a metal strip and the heated narrow surface provided on it is substantially flat, although the entry to the surface may be modified in the interests of operating efficiency. For example, modifying the approach edge of the strip and adjusting the angle of incidence of the yarn to the narrow surface and the angle of leaving can give increased production rates when using the process.

After a period of operation, the passage of filaments can wear grooves in the narrow surface parallel to the mean filament path but these, far from having a deleterious effect, may assist the uniformity of the product and such grooves may be produced advantageously in the virgin narrow surface.

Crimped yarn when produced by our invention consists of a bundle of individual filaments, each of which is crimped along its length, but crimped in such a way that examination of a length of a single filament reveals a range of crimp amplitude and frequency; this range is such that over intermittent lengths the filaments may be substantially uncrimped. The yarn itself consists of a bundle of such filaments in which the ditferent crimp amplitudes and frequencies in the individual filaments are substantially out of phase from one filament to another. Thus, if the yarn bundle is examined at any point along its length it will consist of filaments which, at the point of examination, show from one filament to another, a range of crimp amplitude and frequency, some perhaps showing substantially no crimp at all. Individual filaments may equally show a variation in crimp along their lengths, parts having greater or lesser crimp or even no crimp at all. The maximum frequency will depend on the temperature of the narrow surface, the polymer forming the filaments, the rate of passage over the heated narrow surface, i.e. the effective dwell time, and the denier of the filaments. Crunodal loops are rare and there is no tendency for the crimps to exist preferentially in the yarn surface.

The improved process of the present invention is subject to the same variation of modifications of details as the invention described and claimed in the specification of British Patent 808,213.

The filaments are preferably passed over the heated narrow surface at a speed between 100 and 1,000 metres per minute. The process of the invention may be preceded by a drawing process, preferably to extend the asspun length of the filaments at least three times, and followed by winding-up. The improved process may be incorporated in a spin-draw process, after drawing, when the filaments are under a small tension to stretch them not more than 10% The process of the present invention can be carried out when the filaments are wetted, for example with a lubricant spin finished solution.

The filaments produced by the present invention may be cut into the staple fibres and this can be done before or after the latent crimp is brought out by heating and relaxing. Equally, the heating and relaxing treatment may be carried out after the potentially crimped filaments have been woven or knitted into textile articles.

Preferred embodiments of the invention will now be described in further detail by way of examples:

Example I A sample of #144 filament polyethylene terephthalate yarn is melt spun and after being lubricated with a finish consisting of an aqueous dispersion of an oil, is wound up as undrawn yarn of 810 denier. It is drawn to 3.6 times its original length at a speed of 450 yds./min. and passed over the heated surface of a strip of tungsten 0030 wide which is maintained at 370 C. by contact with a metal block containing a 50 watt electrical heating element. Also clamped to the block is a ribbon forming guide in the shape of a 90 segment of a cylinder which assists in spreading the filaments into a ribbon. The ribbon forming guide is thermally insulated from the metal block so that its temperature does not rise above 100 C. The filaments when passing over the strip of tungsten are deflected by about 5 and are under sufficient tension to ensure good contact, but the tension causes a stretch of less than The yarn is then allowed to relax in a hot air system in which the air is at a temperature of 200 C. In this hot air Zone the yarn suffers a contractlon of 24%. The product is a bulky yarn similar to yarns made by the process described in British Patent 808,213, consisting of a bundle of filaments in which diiferent crimp amplitudes and crimp frequencies in individual filaments are substantially out of phase from one filament to another. The denier 0f the yarn remains substantially unchanged under loads up to 50 gms. and the single or plied yarn is suitable for end uses where bulky fabrics are required. It can be made into acceptable knitted and woven fabrics.

Example II A sample of 540 denier, 48 filament, polyethylene terephthalate melt spun yarn is drawn as in Example I, but at a speed of 750 ft./min. and passed over a tungsten strip 0.025" wide, heated to a temperature of 365 C. indirectly by contact with a metal block containing a 50 watt heater. The yarn is then relaxed in hot air at 205 C. by being overfed into a tube through which hot air circulates, the ratio of feed speed to final wind-up speed being 1.43: 1. The product, which is wound up on a cheese, is a crimped yarn containing filaments exhibiting a range of crimp amplitude and frequency and whose denier is unaffected by loads up to 45 gms. Examination of the yarn shows that crunodal loops are rare and there is no tendency for the crimps to exist preferentially in the yarn surface. The yarn may be knitted or woven into fabrics having considerably greater bulk than fabrics made from normal filament yarns.

4 Example III A sample of 36 filament polyethylene terephthalate yarn is melt spun and after being lubricated with a finish consisting of an aqueous dispersion of an oil is wound up as undrawn yarn of 360 denier. It is drawn to 3.2 times its original length at a speed of 1250' ft./min. and passed over the heated surface of a strip of tungsten carbide containing 6% cobalt, the strip being 0.030 wide and having a rectangular profile with the approach edge ground back at an angle of 30 to the surface :over which the filaments run for a depth of 0.0 20". The strip is maintained at 370 C. by contact with a metal block containing a thermostatted 50 watt electrical heating element. Clamped adjacent to the block is a ribbon forming guide in the shape of a 160 segment of a cylinder over of which the yarn passes to be spread substantially into the form of a ribbon. The ribbon forming guide is thermally insulated from the metal block so that its temperature does not rise above C. in operation. The filaments when passing over the strip of tungsten are deflected by about 10 and are under sufficient tension to ensure good contact. The yarn leaving the strip is then allowed to relax in a hot air system in which the air is at a temperature of 210 C. In this hot air zone the yarn suifers a contraction of 28%. The product is a bulky yarn similar to those made by the process described in British Patent 808,213 consisting of a bundle of filaments in which different crimp amplitudes and crimp frequencies in individual filaments are substantially out of phase from one filament to another The denier of the yarn remains substantially unchanged under loads up to 40 gms. and the single or plied yarn is suitable for end uses where bulky fabrics are required.

Example IV Undrawn nylon 66 yarn of 210 denier was triple plied and cold drawn through a draw ratio of 3.0 to 1 at a speed of 800 ft./min. and passed over the heated surface of a strip of tungsten 0.030" wide which was maintained at a temperature of 350 C. by contact with a metal block containing a thermostatted 50 watt electric heater. The yarn was then overfed into a tube through which hot air at a temperature of 205 C. was circulating. The ratio of feed speed to final wind-up speed was 1.2 to 1. The product, which was wound on a cheese package, was a crimped yarn containing filaments exhibiting a range of crimp amplitude and frequency in individual filaments and substantially out of phase from one filament to another. The product was suitable for knitting or weaving and showed a resistance to tension in excess of that normally exhibited in bulked yarns manufactured by false twist methods.

Example V A sample of 72 filament 360 denier polyethylene terephthalate melt spun yarn is drawn as in Example III at a speed of 1250 ft./min. and passed over satin-chrome plated curved guide having an arc of contact of 90 which spreads the filaments of the yarn substantially into the form of a ribbon. The yarn then passes over a tungsten strip spread 4" from the end of the curved guide, approaching the strip at an angle of 10 to the surface of the strip over which the yarn passes and leaving at an angle of 5 to said surface so that the yarn is held against said surface. The approach edge of the strip is shaped to a radius of 0.005" and the surface over which the yarn passes is grooved parallel to the yarn path, the grooves being spaced at 1500 per inch and 0.0005 in depth. The strip is heated indirectly and maintained at a temperature of 375 C. by contact with a metal block containing a 50 watt cartridge heating element which is thermostatically controlled. The curved guide is insulated from the tungsten strip and the heated block and maintains a temperature of 60 C. when the yarn is running.

The yarn leaving the tungsten strip is allowed to relax in hot air at 205 C. and the relaxation causes the yarn to suffer a 25% contraction.

The final product is a bulky yarn similar to that made in the .process described in British Patent 808,213 but of improved quality in that it has a better handle and the crimp is in general more uniform.

Example VI A sample of 48 filament 480 denier polyethylene terephthalate yarn is spun and drawn as in Example III but at a speed of 825 feet per minute. After passing through an arc of contact of 90 C. over a curved ribbon-forming guide it passes over a tungsten strip located from the end of the curved guide and heated indirectly to 365 C. by contact with a metal block containing a 50 watt cartridge heating element. The surface of the tungsten strip over which the yarn passes is inclined at 15 so that the angle of the approach edge is 105 and the angle of the leaving edge is 75. The yarn approaches the surface of the tungsten strip at an angle of 5 to the surface and leaves at an angle of to the surface, giving a deflection of by which the yarn is held against the surface.

The curved guide, which is insulated, maintains a temperature of 62 C. when the yarn is running.

The yarn leaving the tungsten strip is overfed at a ratio of 1.4 to 1 into a hot air system in which the air is at a temperature of 205 C.

The final product is a bulky yarn, similar to the products of British Patent 808,213, having crimp frequencies ranging from zero to a highest local value of 140 crimps per inch, but having an improved uniformity and a more pleasing handle.

In general, the products of the present invention, when compared with the products of British Patent 808,2113 show the same essential characteristics in that the crimp has the random nature described in the above examples, but is generally more uniform, has a greater regularity of bulk along its length, and, when woven or knitted,

6 produces fabrics of more uniform appearance and better handle.

What we claim is:

1. A process for improving imparting of a latent crimp to continuous synthetic linear polymer filaments which on relaxing will have more uniformity and will have a greater regularity of bulk along the length of said filaments comprising passing continuous synthetic linear polymer filaments over a narrow surface indirectly heated to a temperature above the melting temperature of said filaments in such a manner that said filaments are uniformly heated on one side only continuously along their length.

2. The process of claim 1 wherein the filaments after passing over the narrow surface are relaxed to bring out the latent crimp of said filaments.

3. The process of claim 2 wherein the filaments after passing over the narrow surface are heated and relaxed at under controlled tension at a temperature above the second order transition temperature of the filaments and below the melt temperature of the filaments whereby the latent crimp is brought out.

4. The process of claim 3 wherein the filaments are made of polyethylene terephthalate.

5. The process of claim 3 wherein the filaments are made of nylon.

References Cited by the Examiner UNITED STATES PATENTS 1,330,534 2/1920 Hertel et a1. 28-72 2,919,534 1/1960 Boliuger et al 28-72 3,017,684 1/1962 Pittman 28-72 3,025,584 3/1962 Evans 28-72 3,112,551 12/1963 Schmieder et al. 28-72 FOREIGN PATENTS 600,877 6/ 1960 Canada. 808,213 1/ 1959 Great Britain.

DONALD W. PARKER, Primary Examiner.

RUSSELL C. MADER, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,224,068 December 21, 1965 Robert Alexander Edington et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line 12, for "0.020 read 0.002 column 6, line 18, for "a under" read under a Signed and sealed this 18th day of October 1966.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims (1)

1. A PROCESS FOR IMPROVING IMPARTING OF A LATENT CRIMP TO CONTINUOUS SYNTHETIC LINEAR POLYMER FILAMENTS WHICH ON RELAXING WILL HAVE MORE UNIFORMITY AND WILL HAVE A GREATER REGULARITY OF BULK ALONG THE LENGTH OF SAID FILAMENTS COMPRISING PASSING CONTINUOUS SYNTHETIC LINEAR POLYMER FILAMENTS OVER A NARROW SURFACE INDIRECTLY HEATED TO A TEMPERATURE ABOVE THE MELTING TEMPERATURE OF SAID FILAMENTS IN SUCH A MANNER THAT SAID FILAMENTS ARE UNIFORMLY HEATED ON ONE SIDE CONTINUOUSLY ALONG THEIR LENGTH.