EP1664405A1

EP1664405A1 - A method and a device for texturizing a yarn of thermoplastic material

Info

Publication number: EP1664405A1
Application number: EP04745233A
Authority: EP
Inventors: Paolo c/o Officine Meccaniche Riva S.r.l. CAPRA; Claudio c/o Officine BRUSADELLI
Original assignee: Officine Meccaniche Riva Srl
Current assignee: Officine Meccaniche Riva Srl
Priority date: 2003-09-16
Filing date: 2004-07-23
Publication date: 2006-06-07
Also published as: WO2005026422A1; ITMI20031770A1

Abstract

A device (10) for texturizing a yarn (12) of thermoplastic material comprises a first ambient-temperature feeder (16) for feeding the yarn (12) towards a texturizing zone (18). The texturizing zone (18) comprises a first, substantially rectilinear oven (20), a substantially rectilinear cooling track (22), and a false twisting device (24) suitable for imparting a twist to the yarn along the cooling track (22) and along the first oven (20). A thermal stabilization zone (26) is also provided and comprises a second rotary oven or hot godet (28), preceded by a second ambient-temperature feeder (30) disposed immediately downstream of the false twisting device (24) in the direction of movement of the yarn (12) through the texturizing device (10).

Description

DESCRIPTION A method and a device for texturizing a yarn of thermoplastic material [001] The subject of the present invention is a method of texturizing a yarn of thermoplastic material according to the preamble to Claim 1. A further subject of the present invention is a device for texturizing a yarn of thermoplastic material according to the preamble to Claim 5. [002] The present invention relates in particular to a texturizing device of the false twisting type, known as an FTF device, that is, the type in which there is a first oven, a false twisting device, and a second oven or stabilizing oven. Similarly, the respective method is also of the type comprising a step of twisting or torsion of the yarn. [003] With reference to FTF devices, it is known to produce a texturizing device comprising a feeder which brings the yarn to a texturizing zone. This zone generally comprises a first, substantially rectilinear oven, a cooling track, and a false twisting device. The texturizing zone terminates with a feeder for drafting the yarn and the fibres are interlaced by means of an interlacer device. [004] The second oven is of the substantially rectilinear type and is suitable for bringing the yarn to a stabilization temperature. The second oven is followed by a further feeder for sending the yarn to the collection zone. [005] Known devices are quite bulky, particularly because of the presence of the rectilinear ovens and the cooling track, and do not permit the provision of a structure which is ergonomic for the operators . [006] The yarn passes through the linear ovens, moving at a predetermined speed which is set by the characteristics of the yarn and by the drafting ratios. The length of the path followed by the yarn inside the ovens is predefined by the length of the oven and a change in temperature can be achieved only by modifying the oven setting. The final characteristics of the yarn, which depend substantially on the temperature reached in both the first and the second ovens, are consequently linked to a large extent to the structure of the device. The limited versatility, particularly of the thermal treatment system, leads to limited versatility in the characteristics of the finished product and often to the production of a product of mediocre quality owing to the rubbing of the texturized filaments on the hot surface of the second oven. [007] Attempts to limit the space occupied by the device and to improve the quality and versatility of the finished product have always been directed towards modification of the structure of the texturizing zone, since that was considered to be the portion which would most affect the characteristics of the yarn. [008] Modifications in the structure of the second oven, or stabilizing oven, have always been considered not to be applicable since they would be acting on a yarn which had already undergone a first thermal treatment and therefore had limited strength characteristics . Moreover, it has always been considered that the puckered filaments should not be stretched and that the yarn should be free to contract under the thermal effect of the oven. [009] An attempt to propose changes in the structure of the ovens and of the feeders was made in WO00/14313 in which two rotary ovens or hot godets were provided for performing preheating in two stages upstream of the texturizing zone and a third rotary oven or hot godet was provided immediately downstream of the false twisting device, in accordance with the direction of travel of the yarn in the texturizing device. The solution described in WOOO/14313 has disadvantages which considerably limit its propagation on the market. In particular, the limitations of this arrangement have been attributed to the fact that the yarn which passes through the third hot godet is unstable as a result of the false twisting, with the result that the heat is not transferred uniformly to the yarn and the final product is therefore not uniform. [0010] The problem underlying the present invention is that of proposing a method and a device for texturizing a yarn of thermoplastic material which has structural and functional characteristics such as to overcome the above-mentioned disadvantages discussed with reference to the prior art and the widespread prejudice which has led to the avoidance of modifications in the structure of the second oven, or to the attribution of the lack of success of the device to such modifications. [0011] This problem is solved by means of a method of texturizing a yarn of thermoplastic material according to Claim 1 and by a device for texturizing a yarn of thermoplastic material according to Claim 5. [0012] Further characteristics and the advantages of the method and of the device for texturizing a yarn of thermoplastic material according to the invention will become clear from the following description of a preferred embodiment thereof which is given by way of non-limiting example with reference to the appended drawing. [0013] With reference to the said drawing, a device for texturizing a yarn 12 of thermoplastic material is generally indicated 10. [0014] The appended view corresponds to a section through the device, along the path of the yarn 12 inside the device. [0015] The extruded yarn (continuous, parallel and non-stretched multi-filament yarn) is wound in a cop, not shown, disposed in a creel 14 for cops to be processed. [0016] The yarn to be processed is withdrawn from the creel by a first ambient-temperature feeder 16. The sectioned view shows a linear feeder but an ambient- temperature godet feeder, also known as a cold godet, or feeders of other types may be used. [0017] A texturizing zone to which the yarn is sent by means of the first feeder 16 is indicated 18. [0018] The texturizing zone 18 comprises a first, substantially rectilinear oven 20 suitable for heating the yarn to a texturizing temperature T_t. Next, in the direction of movement of the yarn through the device 10, there is a cooling track 22, which is also substantially rectilinear and can bring the yarn to a fixing temperature T_f. Finally, still in the direction of movement of the yarn through the device 10, there is a false twisting device 24 suitable for imparting a twist to the yarn which extends along the cooling track 22 and through the first oven 20. [0019] Downstream of the texturizing zone 18 there is a thermal stabilization zone 26 comprising a second oven 28 of the rotary or hot godet type, preceded by a second ambient-temperature feeder 30, preferably formed by a non-heated or cold godet. The second feeder 30 is disposed immediately downstream of the false twisting device 24 in the direction of movement of the yarn 12 through the texturizing device 10. [0020] An interlacer device 32 is advantageously provided between the second ambient-temperature feeder 30 and the second oven 28. [0021] The extruded yarn withdrawn from the creel enters the texturizing zone directly. The yarn passes through the texturizing zone, pulled by the second cold feeder which is disposed immediately downstream of the false twisting device, in the direction of movement of the yarn through the device 10. The second feeder thus brings about drafting of the yarn in the texturizing zone so as to achieve the desired count of the texturized yarn. [0022] In the section between the false twisting device and the second feeder, the yarn untwists at relatively low temperature (often below 70°C) , retaining the puckered shape of the continuous filaments which was imparted by the twisting in the hot texturizing zone. The yarn is thus formed by filaments which are not twisted but are puckered. The yarn then optionally enters a short zone for the interlacing of the filaments. The interlacing preferably takes place by means of an air-jet and the yarn is supplied to the interlacer device with a controlled tension, preferably with an overfeed, to ensure low air consumption and a good interlacing effect as provided for, for example, in patent IT 1226460 which is incorporated herein by reference. [0023] Downstream of the interlacing device, if there is one, the second rotary oven or hot godet feeds and stabilizes the yarn, replacing, by a single element, both the second rectilinear oven and the subsequent feeder which supplies the yarn to the collecting device for the formation of the cop. [0024] Downstream of the second oven, the yarn can be collected directly since the hot godet performs the feeder function which ensures the precision of the collection tension. [0025] In accordance with the foregoing description, the present invention also relates to a method of texturizing a yarn 12 of thermoplastic material, comprising the steps of : - feeding the yarn, at ambient temperature, towards a texturizing zone 18 by means of a first ambient-temperature feeder 16, - heating the yarn along a first, substantially rectilinear oven 20 to a texturizing temperature T_t, - cooling the yarn along a substantially rectilinear cooling track 22 to a fixing temperature T_f, - applying a false twist to the yarn 12, the false twist being imparted to the yarn during the step of heating to the texturizing temperature and during the step of cooling to the fixing temperature, - thermal stabilization by means of a second rotary oven or hot godet 28, the stabilization step being preceded by a step of feeding by means of a second ambient-temperature feeder 30 so that the yarn 12 undergoes an untwisting stage between the texturizing zone 18 and the second feeder 30. [0026] Optionally, the step of feeding by means of a second ambient-temperature feeder 30 is performed by means of a non-heated or cold godet. [0027] According to one possible embodiment, an interlacing step is provided between the step of feeding at ambient temperature by means of a second feeder 30 and the thermal stabilization step. [0028] According to one possible embodiment, the step of feeding the yarn, at ambient temperature, towards the texturizing zone 18 is performed by means of a godet which is kept at ambient temperature, or cold godet. [0029] The idea of using a hot godet as the second oven, which is novel in comparison with a conventional device, overcomes the prejudices in the field, producing a texturized and stabilized yarn with optimal characteristics. In particular, the arrangement of the second rotary oven preceded by the second "cold" feeder and optionally by the interlacer device, is particularly advantageous. When the yarn enters the hot godet which operates as the second oven or stabilizing oven, it is thus already untwisted by virtue of the advantageous presence of the cold feeder disposed at the output of the false twisting device. This arrangement stabilizes the yarn dynamically and prevents the skidding on the hot godet which is caused by rotation due to untwisting. Moreover, when the interlacer device is provided, the yarn enters the hot godet already fully interlaced, which contributes to its stability. [0030] The dynamic stability achieved in the yarn input to the second oven ensures the stability of the transfer of heat to the yarn and thus enables an improved uniformity of result to be achieved in the thermal treatment . [0031] In addition to the above-mentioned advantages, the texturizing device occupies less space than a conventional device owing to the elimination of both the rectilinear oven and the subsequent feeder for sending the yarn for collection. [0032] In particular situations, to facilitate free contraction of the yarn under the thermal stabilization effect, the hot godet may be formed with a slightly tapered shape (from 1% to 4%) . The output speed is thus reduced in accordance with the shortening of the yarn, preventing the contracting yarn from being forced to stretch as it is tightened on the cylindrical surface and then to contract resiliently only after it has been output from the godet . The percentage of shrinkage can be controlled by changing the pitch of the turns by variation of the adjustable inclination of the idle pin associated with each godet. [0033] The novel idea upon which the present invention is based lies in the unusual combination of a conventional texturizing zone, in particular having a linear oven, and of a second, rotary oven or hot godet, preceded by a "cold" feeder at the output from the texturizing zone. Previous efforts to improve the quality of the yarn and to limit the space occupied by known texturizing devices were always directed towards modification of the texturizing zone, since it was considered impossible to alter the downstream stabilization zone where the heated yarn does not have the necessary strength characteristics and where its behaviour is critical with regard to the qualitative result, or towards modification of the entire structure of the device, but without obtaining the results hoped for. [0034] The retention of a first linear oven along which the twist imparted to the yarn extends achieves both optimal spread of the heat in the yarn and optimal formation of continuous puckered filaments. The novel provision of a second cold feeder immediately downstream of the false twisting device and preceding the second oven ensures untwisting of the yarn whilst maintaining the puckered shape of the filaments prior to contact with the hot stabilization surface. [0035] The second oven thus receives a yarn which is stable from the point of view of the twist previously imparted, which has puckered, optionally fully-interlaced filaments, and which can be wound several times onto the hot godet which constitutes the second oven, without worries about further deterioration. [0036] The presence of the hot godet also allows for great versatility in the characteristics of the finished product, since the number of windings of the yarn can be modified in order to modify its thermal stabilization treatment . [0037] Naturally, variations and/or additions may be provided for the embodiment described and illustrated. [0038] For example, the cooling track 22 may be either passive or active and its length may vary. [0039] The first feeder may be of various types, for example, linear, of the godet type, etc. [0040] The length and type of the first rectilinear oven may be those available on the market. [0041] In order to satisfy contingent and specific requirements, a person skilled in the art may apply to the above-described preferred embodiment of the method and of the device for texturizing a yarn of thermoplastic material, many modifications, adaptations and replacements of elements with other functionally equivalent elements without, however, departing from the scope of the appended claims.

Claims

1. A method of texturizing a yarn (12) of thermoplastic material, comprising the steps of: feeding the yarn, at ambient temperature, towards a texturizing zone (18) by means of a first ambient- temperature feeder (16) , heating the yarn (12) along a first, substantially rectilinear oven (20) to a texturizing temperature (T_t) , cooling the yarn (12) along a substantially rectilinear cooling track (22) to a fixing temperature (T_f) , applying a false twist to the yarn, the false twist being imparted to the yarn during the step of heating to the texturizing temperature (T_t) and during the step of cooling to the fixing temperature (T_f) , characterized in that it comprises a thermal stabilization step carried out by means of a second, rotary oven or hot godet (28) , preceded by a step of feeding by means of a second ambient-temperature feeder (30) , so that the yarn (12) undergoes an untwisting stage between the texturizing zone (18) and the second feeder (30) .

2. A method of texturizing a yarn of thermoplastic material according to Claim 1 in which the step of feeding by means of a second ambient-temperature feeder (30) is performed by means of a non-heated or cold godet.

3. A method of texturizing a yarn of thermoplastic material according to Claim 1 or Claim 3 in which an interlacing step is provided between the step of feeding at ambient temperature by means of a second feeder (30) and the thermal stabilization step.

4. A method of texturizing a yarn of thermoplastic material according to any one of the preceding claims, in which the step of feeding the yarn, at ambient temperature, towards the texturizing zone by means of a first feeder (16) is performed by means of a godet which is kept at ambient temperature, or cold godet.

5. A device (10) for texturizing a yarn (12) of thermoplastic material, comprising: a first ambient-temperature feeder (16) for feeding the yarn (12) towards a texturizing zone (18) , the texturizing zone (18) comprising a first, substantially rectilinear oven (20) suitable for heating the yarn to a texturizing temperature (T) , a substantially rectilinear cooling track (22) suitable for bringing the yarn (12) to a fixing temperature (T_f) , and a false twisting device (24) suitable for imparting a twist to the yarn along the cooling track (22) and along the first oven (20) , characterized in that the device comprises a thermal stabilization zone (26) comprising a second rotary oven or hot godet (28) , preceded by a second ambient- temperature feeder (30) disposed immediately downstream of the false twisting device (24) in the direction of movement of the yarn (12) through the texturizing device (10) .

6. A device (10) for texturizing a yarn of thermoplastic material according to Claim 5 in which the second ambient-temperature feeder (30) is a non-heated godet or cold godet.

7. A device (10) for texturizing a yarn of thermoplastic material according to Claim 5 or Claim 6, in which an interlacer device (32) is provided between the second ambient-temperature feeder (30) and the second oven (28) .

8. A device (10) for texturizing a yarn of thermoplastic material according to any one of Claims 5 to 7, in which the first feeder (16) for feeding the yarn (12) towards the texturizing zone (18) is a godet which is kept at ambient temperature, or cold godet.

9. A device for texturizing a yarn of thermoplastic material according to any one of Claims 5 to 8, in which the hot godet (28) is a hot godet with a slightly tapered surface.

10. A device for texturizing a yarn of thermoplastic material according to Claim 9 in which the taper of the hot godet (28) is between 1% and 4%.