EP0350626A2 - Process for the production of polybutyleneterephthalate carpet yarn - Google Patents

Abstract

Process for the production of high-quality carpet yarn from PBT with an intrinsic viscosity of 0.9 to 1.2 by means of an integrated spin stretch texturing process at a transport speed to the texturing unit of at least 1800 m / min.

Description

The invention relates to a process for the production of carpet yarn from polybutylene terephthalate (PBT) with an intrinsic viscosity of 0.9 to 1.2 by integrated spin stretch texturing at a feed speed to the texturing unit of at least 1800 m / min.

PBT carpet yarns are known. For example, DE-A 22 23 950 describes plush carpets based on staple fibers, which are melt spun by PBT with an intrinsic viscosity of about 0.8, winding up the threads at a speed of 610 m / min, subsequently stretching at a temperature of 80 ° C. Stuffer box crimping and finally heat setting at 150 ° C for 18 minutes were obtained.

The process of DE-A 20 11 813 is similar, the final stage of an 18-minute heat setting of the fiber strand ultimately also determining the processing speed and thus the economics of the process.

PBT staple fibers with a somewhat higher inherent viscosity (at least 0.76), which should also be suitable for carpets, are known from DE-B 20 37 217. Although referred to as crimped, they are non-textured, only stretched and subsequently fixed at 145 ° C. for 5 minutes. But here, too, the economy is largely determined by the time-consuming heat setting.

While the first two documents do not contain any information on the viscosity of the fibers, the inherent viscosity of the fibers in the majority of cases is considerably below that of the starting PBT, in the worst case 20% below. The associated polymer degradation leads, among other things, to the release of low, mostly cyclic oligomers and to corresponding pollution of the blown air, water vapor and indoor air. Any necessary cleaning of these media, for example with activated carbon, which is required by the newer environmental legislation means additional energy requirements and disposal of the cleaning compound. Furthermore, the partial PBT degradation causes a greater unevenness in the yarn quality.

It goes without saying that such multi-minute fixing stages are not compatible in time with modern spin-stretch texturing processes operating at 2000 or 3000 m / min. Accordingly, known integrated spin-draw texturing processes never refer to PBT.

Such an integrated method is described, for example, for polyamide-6 and -6.6 in US Pat. No. 4,096,226, wherein a texturing device in accordance with US Pat. No. 3,908,248 is preferably to be used. The latter is also said to be suitable for polyethylene terephthalate (PETP). Although a limitation of the speed is not specified, the exemplary data are quite low, generally 50 to 100 m / min and, based on nylon 6, 800 - 1200 m / min.

If one then tries to rework the example of US Pat. No. 4,096,226 given for polyamide 6 with PETP, one obtains, if at all, essentially amorphous filaments which, besides other defective properties, have none at all have permanent crimp. Obviously, the texturing device mentioned is only suitable for PETP if work is carried out at low and therefore less economical speeds of a few 100 m / min, as is already known from the PBT.

The object of the present invention is consequently to put the production of PBT carpet yarn on a more economical basis than is the case with the prior art described at the outset. The yarn quality should at least be equivalent to that which can be achieved with conventional processes comprising several separate stages, and the environmental impact should be as low as possible.

• a) Schmelzspinnen von Polybutylenterephthalat mit einer Intrinsic-Viskosität von 0,9 bis 1,2 und einem Wassergehalt von maximal 50 Gewichts-ppm bei einer Temperatur von 245 bis 270 °C und einem Spinnverzug von 1 : 20 bis 1 : 100,
• b) Abkühlen der Filamente in einem Blasschacht mittels senkrecht zur Fadenlaufrichtung mit einer Geschwindigkeit von 0,4 bis 0,8 m/sec einströmender, turbulenzfreier Luft,
• c) Präparieren der abgekühlten Filamente mittels einer Öl-Wasser-Mischung bei einer Ölauflage relativ zum Fadengewicht von mindestens 0,5 %,
• d) Verstrecken der Filamente zwischen zwei beheizten Galettensystemen, wobei die Temperatur des ersten Systems im Bereich Glasumwandlungstemperatur ± 30 °C liegt und diejenige des zweiten Systems um mindestens 100 °C höher, und wobei das Verstreckverhältnis so hoch gewählt wird, daß die Reißdehnung des fertigen Fadens maximal 45 % beträgt,
• e) Zuführen der verstreckten Filamente bei einer Transportgeschwindigkeit des zweiten Galettensystems von mindestens 1800 m/min zu einer Texturiereinheit, in der sie mit Luft mit einer mindestens gleichhohen Temperatur wie die des zweiten Galettensystems dreidimensional verblasen und gestaucht werden,
• f) Ausstoßen der Filamente aus der Texturiereinheit und Ablegen in einer Kühleinheit mit einer zur Abkühlung unter Glastemperatur ausreichenden Verweilzeit,
• g) Abziehen der Filamente mittels eines unbeheizten, dritten Galettensystems, dessen Geschwindigkeit mindestens 10 % unter der des zweiten Galettensystems liegt,
• h) Regeln der Prozeßbedingungen der Stufen a) bis g) derart, daß die Intrinsic-Viskosität in Stufe j) maximal 5 % niedriger liegt als in Stufe a),
• i) Verwirbeln der Filamente mittels einer Luftblasdüse bei einem zur Erzielung einer Entangling-Knotenzahl von mindestens 12 Pro Meter ausreichenden Luftdruck,
• j) und Aufspulen der Filamente.

According to the invention, this object is achieved by using an integrated spin-draw texturing process consisting of

• a) melt spinning polybutylene terephthalate with an intrinsic viscosity of 0.9 to 1.2 and a water content of at most 50 ppm by weight at a temperature of 245 to 270 ° C. and a spin delay of 1:20 to 1: 100,
• b) cooling the filaments in a blow chute by means of turbulence-free air flowing in perpendicular to the direction of the thread at a speed of 0.4 to 0.8 m / sec,
• c) preparing the cooled filaments using an oil-water mixture with an oil layer relative to the thread weight of at least 0.5%,
• d) stretching the filaments between two heated godet systems, the temperature of the first system being in the glass transition temperature range ± 30 ° C. and that of the second system being at least 100 ° C. higher, and the stretching ratio being chosen so high that the elongation at break of the finished one Thread is a maximum of 45%,
• e) feeding the drawn filaments at a transport speed of the second godet system of at least 1800 m / min to a texturing unit in which they are blown and compressed three-dimensionally with air at a temperature at least as high as that of the second godet system,
• f) ejecting the filaments from the texturing unit and depositing them in a cooling unit with a dwell time sufficient for cooling under glass temperature,
• g) pulling off the filaments using an unheated third godet system, the speed of which is at least 10% below that of the second godet system,
• h) regulating the process conditions of stages a) to g) such that the intrinsic viscosity in stage j) is at most 5% lower than in stage a),
• i) intermingling the filaments by means of an air blowing nozzle at an air pressure sufficient to achieve an entangling knot number of at least 12 per meter,
• j) and winding the filaments.

The spooled PBT carpet yarns obtained by the process according to the invention are characterized by
- an intrinsic viscosity of at least 0.86,
- a single capillary titer of at least 16 dtex,
a capillary cross-sectional ratio based on a trilobal profile of at least 2.2,
- a cooking shrinkage of less than 1.0%,
- a degree of crimp of at least 15%, with thread development at 120 ° C,
a bulkiness of at least 9% absolute, defined as the difference between the degree of crimp during thread development at 120 ° C and that at room temperature,
- a dyeability with disperse dyes at a maximum of 100 ° C without carrier,
- excellent anti-soiling behavior
as well as when processing into a carpet
- a positive look,
- excellent coverage
- and high elasticity and recovery.

These excellent fiber properties, which even outperform conventionally produced PBT fibers in terms of crimp and recovery, were completely surprising and, in view of the negative course of the previously described experiment with the closely related PETP, also unexpected.

This surprising success is probably due to an exact and optimized coordination of the numerous process parameters both with one another and with a single defined polymer with relatively narrow viscosity limits.

The starting material used is PBT with an intrinsic viscosity of 0.9 to 1.2, preferably 0.9 to 1.1, measured in a mixture of 3 parts by weight of phenol and 2 parts of 1,2-dichlorobenzene at 25 ° C. and a concentration of 0.5 g / 100 ml. The water content of the PBT should be as low as possible, at most 50 ppm, preferably at most 30 ppm, since otherwise a partial hydrolytic degradation of the polymer cannot be ruled out. The usual additives, such as matting agents, are permissible, but otherwise pure PBT should be used. In principle, the method according to the invention is also suitable for PBT with a slightly different viscosity or low comonomer content, but the limits to lower yarn quality are fluid here.

Depending on the local conditions, granulate or a melt flow coming directly from the polycondensation is assumed. The direct route should be preferred, since the underwater pelletizing of the PBT is not necessary, and the polymer melt is practically water-free. The polymerization itself can be carried out by any method, for example as described in US Pat. Nos. 4,680,376 and 4,499,261.

Melt spinning is carried out at a temperature in the range from 245 to 270 ° C. and a spinning delay of 1:20 to 1:100, preferably at 258 to 265 ° C. and 1:30 to 1:50. The residence time in the melt state must be limited and should, in the case of PBT granules, from melting to for the spinneret exit not more than 8 min, preferably about 4 min. Since this first stage makes a significant contribution to the ratio of the intrinsic viscosity of the starting PBT to that of the filaments to be produced, particularly careful regulation of the process conditions is of particular importance here.

According to their determination as carpet yarn, the individual filaments with a preferably trilobal cross section should have a final titer of at least 16 dtex, preferably 20 to 30 dtex, with a total titer of 600 to 6000 dtex.

The cooling in the blow chute takes place at least to such an extent that the individual filaments cannot stick together. Immediately afterwards, the filaments are prepared and drawn. For the preparation, an at least 20% oil in water mixture is preferably used with an oil layer relative to the thread weight of at least 0.5%. The temperature of the stretch godet systems depends on the glass transition temperature which is dependent on the molecular structure of the polymer. The temperature of the first godet system is preferably in the range from 20 to 60 ° C. and that of the second system in the range from 120 to 200 ° C. The draw ratio is adjusted by regulating the relative speeds of the two godet systems so that the elongation at break of the finished thread is at most 45%, preferably 25 to 35%. Generally the ratio is in the range of 3.0 to 4.5.

The second godet system also serves as a feed element to the texturing unit at a transport speed of at least 1800 m / min, preferably 2000 to 2800 m / min. The temperature of the texturing air should be at least as high as that of the second godet system, preferably in the range from 170 to 220 ° C.

The subsequent cooling of the textured filaments takes place by means of any cooling unit, preferably by means of a perforated, rotating drum, through which room air is drawn in with the aid of a connected vacuum system. The residence time of the filaments on the drum should be sufficient to ensure cooling below the glass temperature and is generally 1 to 6 seconds.

The filaments are then drawn off using a third godet system and transported further at a speed of at least 1500 m / min, preferably 1700 to 2500 m / min.

The final swirling is done in a conventional manner, usually prior to spooling, with air pressure sufficient to ensure an entangling knot number of at least 12, preferably at least 20 per meter. At higher winding speeds of more than about 2500 m / min, for example 3000 or 4000 m / min, however, it can be advantageous to wind up the filaments before the intermingling, and the intermingling later, before the further processing.

The inventive integration of spinning, drawing and texturing in a single process results in a particularly uniform and reproducible yarn quality in addition to high economy. In particular, errors and damage caused by intermediate winding are eliminated.

The short total dwell time of the integrated process, in conjunction with the low water content of the starting polymer and optimized temperature conditions, enables the PBT to be processed very gently and therefore minimizes the environmental impact of PBT degradation products.

example

251 g / min PBT with an intrinsic viscosity of 0.93 and a water content of 29 ppm are spun at 260 ° C. at a speed of 650 m / min and a spinning delay of 1:38 through a spinneret with 64 holes with a trilobal cross section .

After the filaments had solidified in a blow chute with air flowing in perpendicularly to the direction of the thread at a speed of 0.55 m / sec, the filaments were prepared with an oil layer of 0.8% relative to the thread weight, the 64 filaments being combined into one strand will.

Immediately afterwards, the drawing is carried out with the aid of two godet systems, the temperature of the first system being 55 ° C., that of the second system 160 ° C. and the drawing ratio 1: 3.3.

The filaments are fed to a jet texturing unit at a transport speed of the second godet system of 2145 m / min, and are blown and compressed three-dimensionally by means of 210 ° C. hot air.

The filaments ejected from the texturing unit are continuously deposited on a cooling drum and cooled to a temperature below 40 ° C. with a residence time of about 1.5 seconds.

With the help of a third, unheated godet system, the cooled filaments are drawn off and transported on at 1888 m / min. Before the final winding, the yarn is fed an entangling knot number of 22 per meter using an air blowing nozzle.

The resulting wound yarn has the following property values: Intrinsic viscosity 0.90 Tensile strength 25 cN / tex Elongation at break 28% Boiling shrink 0.4% Single capillary titer 21 dtex Capillary cross-section ratio 2.8 Degree of crimp (120 ° C) 18% Bulkiness 9% and results in carpets of excellent quality, which can be excellently dyed with disperse dyes at a maximum of 100 ° C without the addition of a carrier.

Claims (4)

1. A process for the production of polybutylene terephthalate carpet yarn with a degree of crimp of at least 15% in the case of thread development at 120 ° C. and with a bulkiness defined as a difference in the bulkiness in the case of thread development at 120 ° C. to that at room temperature of at least 9% in absolute terms by an integrated spin stretch texturing -Process consisting of: a) melt spinning polybutylene terephthalate with an intrinsic viscosity of 0.9 to 1.2 and a water content of at most 50 ppm by weight at a temperature of 245 to 270 ° C. and a spin delay of 1:20 to 1: 100, b) cooling the filaments in a blow chute by means of turbulence-free air flowing in perpendicular to the direction of the thread at a speed of 0.4 to 0.8 m / sec, c) preparing the cooled filaments using an oil-water mixture with an oil layer relative to the thread weight of at least 0.5%, d) stretching the filaments between two heated godet systems, the temperature of the first system being in the glass transition temperature range ± 30 ° C. and that of the second system being at least 100 ° C. higher, and the stretching ratio being chosen so high that the elongation at break of the finished one Thread is a maximum of 45%, e) feeding the drawn filaments at a transport speed of the second godet system of at least 1800 m / min to a texturing unit in which they are blown and compressed three-dimensionally with air at a temperature at least as high as that of the second godet system, f) ejecting the filaments from the texturing unit and depositing them in a cooling unit with a dwell time sufficient for cooling under glass temperature, g) pulling off the filaments using an unheated third godet system, the speed of which is at least 10% below that of the second godet system, h) regulating the process conditions of stages a) to g) such that the intrinsic viscosity in stage j) is at most 5% lower than in stage a), i) intermingling the filaments by means of an air blowing nozzle at an air pressure sufficient to achieve an entangling knot number of at least 12 per meter, j) and winding the filaments. 2. The method according to claim 1, characterized in that the intermingling of the filaments according to stage i) takes place after the winding according to stage j). 3. The method according to claim 1, characterized in that step a) follows without intermediate granulation of the polybutylene terephthalate production. 4. The method according to claim 1, characterized in that in step a) polybutylene terephthalate granules are used.