GB1581828A - Heat transfer to and from yarns - Google Patents

Description

(54) HEAT TRANSFER TO AND FROM YARNS (71) We, IMPERIAL CHEMICAL INDUSTRIES LIMITED, Imperial Chemical House, Millbank, London SW1P 3JF, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: The present invention relates to a process for transferring heat between an advancing filamentary yarn which is rotating about its longitudinal axis, as for example in a false twist crimping (texturing) process, and a fluid.

In a process where heat is to be transferred between an advancing filamentary yarn which is rotating about its longitudinal axis, e.g. as when twisting, and a fluid, such as air, in which the yarn is passed through a vortex in the fluid substantially along or parallel to the longitudinal axis of the vortex, it has been found particularly beneficial, in terms of yarn quality, if the direction of rotation of the yarn is opposite to the direction of rotation of the vortex in the fluid.

Thus, according to the invention there is provided a process for transferring heat between an advancing filamentary yarn which is rotating about its longitudinal axis and a fluid in which the yarn is passed through a counter-rotating vortex in the fluid substantially parallel to the longitudinal axis of the vortex.

Thus, heat may be transferred to and/or from an advancing filamentary yarn by the process of the invention.

Preferably the advancing yarn is rotated about its longitudinal axis by conventional twisting means but desirably twist is inserted by false twisting the yarn. Thus, the yarn after passing through one or more devices for generating fluid vortices may be advanced to false twisting means. Advantageously, two fluid vortice generating devices may be employed in a yarn false twist texturing process so that the yarn may be successively heated and cooled before it reaches the false twisting means.

Devices suitable for generating fluid vortices in the present invention are described in U.K.

patent specification no. 1,529,674.

In particular the fluid vortice inducing means comprises a chamber having tangential fluid entry channels arranged symmetrically around the chamber circumference. Yarn entry and exit tubes are also arranged co-axially one on either side of the chamber to contain the two vortices induced in the chamber. These tubes are long in comparison with the size of the chamber so that the vortices may be maintained in contact with an advancing yarn for a relatively long period. The ends of the tubes remote from the chamber may also be restricted as described in copending UK application 15023/76 (Serial No. 1581827).

Any fluid, gaseous or liquid, which is substantially inert to the yarn may be used but preferably the fluid is gaseous at the temperature of the process. In addition to air mentioned above, carbon dioxide, nitrogen or steam may also be employed.

The following comparative examples are intended only to illustrate the present invention.

The various measurements referred to in the examples were taken by conventional means well known to those skilled in the art, unless otherwise indicated.

EXAMPLE 1 In this example a heat transfer device similar to that shown in Figures 2A, 2B and 2C of copending cognate UK applications 45206/74 and 47974/74 (Serial No. 1,529,674) was used. The vortex "chamber" had a maximum internal diameter of 2.38 mm and the four air entry jets a diameter of 0.51 mm. The continuous yarn entry and exit tube had an overall length of about 380 mm.

The device was employed as a yarn heater in a simultaneous drawing and false twist crimping (texturing) process, in which a partially oriented or drawn 350 decitex 30 filament polyester yarn derived from polyethylene terephthalate (birefringence 27 x 10-3) was advanced by feed rolls, first through the heating device and then over and in contact with a 0.95 metre long metal cooling plate (located 12 cm downstream of the device) to a friction twisting bush (single pass and similarly in Example 2) and then to draw rolls. The draw roll sped was 600 metres/minute and the bush was rotated in two separate processes A and B at 18,500 r.p.m.: Process A in which the yarn was rotated in the same direction as that of the vortices in the fluid, and Process B in which the yarn was rotated in the opposite direction to that of the vortices in the fluid. (counter - rotating vortices).The draw ratio was 2.1. The results from processesA and B are tabulated on Page 5.

* ** A Mean air Air Airflow Mean yarn Mean twist temperature pressure (Ambient temp. on level in in chamber Temp) exit from yarn below cubic feet/ device device hour (yam snatch) (cfh) turns/metre "C psi C (tpm) 225 80 110 152 2270 247 80 110 166 2345 257 80 110 173 2222 268 80 110 189 2237 279 80 110 198 2250 285 80 110 200 2252 290 80 110 202 2305 300 80 110 208 2257 305 80 110 210 2272 322 80 110 217 2220 332 80 110 220 2240 B * ** ** Mean air Air Airflow Mean yarn Mean twist temperature pressure (ambient temp. on level in in chamber temp) exit from yarn below device device (yarn snatch) "C psi cfh cc tpm snatch) 225 80 110 145 2365 247 80 110 165 2335 257 80 110 170 2405 268 80 110 185 2265 279 80 110 190 2400 285 80 110 196 2330 290 80 110 200 2365 300 80 110 207 2440 305 80 110 209 2420 322 80 110 215 2330 332 80 110 219 2325 * Using an infra-red scanning pyrometer available from Cambridge Consultants Ltd., Cambridge, England.

** Mean yarn temprature on entry into device 200C (ambient) *** For the purpose of the Example the twist level in the yarns has been taken as an indication of the potential bulk in the yarns.

It will be seen that the main twist levels achieved m process B (twist in opposite direction) are consistently higher than those achieved in process A (twist in the same direction), on average of the order of 100 tpm, which is a significant difference in terms of potential bulk in the yarn, at such high twist levels.

EXAMPLE 2 Employing the same device and process as described in Example 1, a further comparison of processes A and B was made in terms of the relative number of unwanted broken filaments and loops produced in the yarns. These were detected and counted by passing 500 metres of the yarn at 335 metres/min under a tension of 8 gms through an optical device in which a significant proportion of the broken filaments or loops projecting from the yarn intersected a light beam producing pulses from a photo-electric cell which could be counted. The device was adjusted so that only those filaments/loops which projected from the yarn by at least 0.76 mm produced a signal.

The results are tabulated below: Mean air Air Airflow Mean yarn Yarn Yarn Yarn Relative No.

temp. in pressure (Ambient temp. on tension tension tension of broken chamber psi. Temp) exit from above before after filaments! device device friction friction loops!500 bush bush metres of "C cfh "C gms gms gms yarn A 290 80 110 202 38 54 98 916 B 290 80 110 202 33 51 90 48 Thus process B provides a clear and distinct improvement in terms of yarn quality and processing tensions.

In neither of the Examples did the fluid vortices cause significant filament interlacing or false twist in the advancing yarns and in this respect the present process differs markedly from similar processes which are known to induce considerable yarn interlacing and false twist.

The present'process is also applicable to the heating and/or cooling of twisted filamentary yarns though such a process does not form part of the present invention.

Though the present invention has been exemplified with respect to filamentary polyester yarns, the invention is equally applicable to a large variety of other filamentary yarns, for example, as may be derived from other synthetic materials, such as polyamides, polyacrylics or polyolefines; regenerated material polymers such as cellulose acetate or viscose rayon, or inorganic materials such as glass.

WHAT WE CLAIM IS: 1. A process for transferring heat between a filamentary yarn which is rotating about its longitudinal axis and a fluid which is at a different temperature to that of the yarn in which the yarn is advanced in the direction of its longitudinal axis through two counter-rotating (with respect to the rotation of the yarn) substantially non-false twisting and non-interlacing vortices in the fluid substantially along or parallel to the longitudinal axes thereof, the vortices decaying freely in opposite co-axial directions from their point of generation to their escape into the atmosphere.

2. A process according to claim 1 in which heat is transferred to the advancing yarn.

3. A process according to claim 1 in which heat is transferred from the advancing yarn.

4. A process according to any one of claims 1 to 3 in which the yarn is twisting while passing through the fluid vortices.

5. A process according to claim 4 in which the yarn is twisted by false twisting means.

6. A process according to claim 5 in which the yarn passes through separate fluid vortices which successively transfer heat to and from the yarn before it reaches the false twisting means.

7. A process for transferring heat between a filamentary yarn and a fluid substantially as hereinbefore described with reference to the Examples of the present invention.

8. Filamentary yarn when treated according to any one of the preceeding claims.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. In neither of the Examples did the fluid vortices cause significant filament interlacing or false twist in the advancing yarns and in this respect the present process differs markedly from similar processes which are known to induce considerable yarn interlacing and false twist. The present'process is also applicable to the heating and/or cooling of twisted filamentary yarns though such a process does not form part of the present invention. Though the present invention has been exemplified with respect to filamentary polyester yarns, the invention is equally applicable to a large variety of other filamentary yarns, for example, as may be derived from other synthetic materials, such as polyamides, polyacrylics or polyolefines; regenerated material polymers such as cellulose acetate or viscose rayon, or inorganic materials such as glass. WHAT WE CLAIM IS:

1. A process for transferring heat between a filamentary yarn which is rotating about its longitudinal axis and a fluid which is at a different temperature to that of the yarn in which the yarn is advanced in the direction of its longitudinal axis through two counter-rotating (with respect to the rotation of the yarn) substantially non-false twisting and non-interlacing vortices in the fluid substantially along or parallel to the longitudinal axes thereof, the vortices decaying freely in opposite co-axial directions from their point of generation to their escape into the atmosphere.

2. A process according to claim 1 in which heat is transferred to the advancing yarn.

3. A process according to claim 1 in which heat is transferred from the advancing yarn.

4. A process according to any one of claims 1 to 3 in which the yarn is twisting while passing through the fluid vortices.

5. A process according to claim 4 in which the yarn is twisted by false twisting means.

6. A process according to claim 5 in which the yarn passes through separate fluid vortices which successively transfer heat to and from the yarn before it reaches the false twisting means.

7. A process for transferring heat between a filamentary yarn and a fluid substantially as hereinbefore described with reference to the Examples of the present invention.

8. Filamentary yarn when treated according to any one of the preceeding claims.