WO1997048840A1

WO1997048840A1 - Polyamide yarn and integrated stretch spinning method for manufacturing same

Info

Publication number: WO1997048840A1
Application number: PCT/FR1997/001103
Authority: WO
Inventors: Bruno Colombo; François PINAUD
Original assignee: Nylstar S.A.
Priority date: 1996-06-19
Filing date: 1997-06-19
Publication date: 1997-12-24
Also published as: FR2750144A1; AU3446997A; FR2750144B1

Abstract

The invention discloses a stretch spinning method for manufacturing a multifilament yarn and a polyamide yarn with a high shrinkage force. It concerns more particularly a novel polyamide yarn obtained by an integrated stretch spinning method. Yarn stretching is effected by passing the yarn (1) over two rolls (7, 8) arranged in such manner that the yarn describes an S. The yarn forms an open loop on each roll. It is heated by the device (10) to its stretching temperature, then after stretching it is subjected to a relaxation treatment by being heated with the nozzle (11) before being coiled on a reel.

Description

POLYAMIDE YARN AND INTEGRATED SPREAD-DRAWING METHOD FOR THE

PRODUCTION OF THIS YARN

The invention relates to an integrated spinning-drawing process for the production of yarns. polyamide and a polyamide 66 multifilament yarn with a high withdrawal force.

Integrated spinning-drawing processes for the high speed production of polyamide yarns are known and described in numerous patents. Thus, German Application No. 2,435,009 describes a process for drawing a high-speed spun yarn by passing the unstretched yarn between two rollers having different peripheral speeds. Each of these rollers comprises an auxiliary roller which makes possible a multiple winding around the main roller. These auxiliary rollers are driven in rotation either by pneumatic motors or only by the wire which surrounds them. French patent Nos. 2,490,252 and 2,494,729 have also proposed methods for the manufacture of stabilized multifilament polyamide 6 yarns by high speed spinning and passing the yarn through a set of two unheated rollers, the first roller being a roll for drawing the thread under the die, the second roller being a drawing roller. The wire is stabilized at the outlet of the second roll by a hot gas before being returned to a reel. According to patent 2,494,729, the rollers can be heated rollers. It is also described that the wire can form an open loop on the first roll only.

In these different methods, the drawing of the wire requires the use of a roller associated with a loose roller, or duets of rollers to exert sufficient tension on the wire and thus be able to apply a drawing rate. With such systems, it is necessary to have a set of drawing rollers or duets per wire. Thus, the installations occupy a large floor area. For example, it is not possible to arrange the winders on several levels, in a substantially superimposed manner. Consequently, installations according to known methods require significant investments. Furthermore, these methods do not make it possible to obtain yarns having a high withdrawal force, in particular of the level obtained with yarns spun at low speed, that is to say at low orientation, then drawn in a second. step.

One of the aims of the present invention is to avoid these drawbacks by proposing a process for obtaining polyamide yarns by high-speed spinning-drawing allowing, moreover, a simplification of the spinning installation with a more compact arrangement. 2

devices, and a lower investment, and a polyamide 6.6 yarn obtained by this process and having a high withdrawal force.

The subject of the invention is a process for manufacturing multifilament yarns of polyamide which consists of a high speed spinning-stretching process. By high speed, it is necessary to understand wire winding speeds greater than 3500 m / min, preferably between 4000 m / min and 8000 m / min. By the term "polyamide", the applicant designates linear synthetic polymers which can be spun in the molten state comprising repeating amide functions. These polymers can be either homopolymers or copolymers, or mixtures of polymers. The term “polyamide” should also be understood to mean compositions comprising, as main component, the above homopolymers or copolymers and, as other components, additives such as, for example, pigments, matting agents, light and / or heat stabilizers , brighteners or the like. In other words, the name "polyamide" is used in the present description to designate all compositions which can be spun through a die and comprising as main component or matrix at least one linear synthetic polymeric compound conforming to the definition above, and as other components of the additives conventionally used for the manufacture of yarns.

As preferred linear synthetic polymeric compounds of the invention, mention may especially be made of polyhexamethylene adipamide, polycaprolactam, their copolymers or mixtures.

The method of the invention consists in spinning in the molten medium a polymer, as defined above, in the form of filaments to obtain at least one bundle of filaments, in cooling the filaments, in making the filaments of each bundle or of several bundles converge at a point of convergence to form at least one multifilament yarn, possibly to deposit on each yarn a size, to stretch each yarn in a drawing zone comprising two rollers arranged so that the path of the yarn passing through the drawing zone describes substantially an "S".

The first roller in the direction of advancement of the wire has a peripheral or linear speed of rotation lower than that of the second roller.

The thread (s) form on each roll an open loop with a winding angle of less than 360 ° C., the thread being heated, to a drawing temperature at least higher than the Tg of the polymer at a point or a zone located between the first point of contact of the wire on the first roller and the first point of contact of the wire on the second roller, said contact points forming part of said drawing zone. The wire is then subjected to a relaxation treatment by heating between the first point of contact of the wire on the second roller of the drawing zone and the reel for winding the drawn wire. The wire is then returned at a speed greater than 3500 m / min. According to a first embodiment of the method of the invention, the first and / or the second roller in the drawing zone comprise heating means, for example a double envelope with circulation of a heat-transfer fluid, or a peripheral surface heated by electrical resistors, infrared heating means, by electromagnetic induction or by ultrasound

In another embodiment of the invention, the wire is heated at a point located between the two rollers. As means of heating the wire, all the usual means of heating the wires can be used, such as convection, radiation heating, for example, hot plates, infrared radiation, or the like

According to a preferred embodiment, this heating means is a nozzle supplied with a hot gaseous fluid, preferably by superheated steam or hot air

Advantageously, this nozzle can also cause entanglement of the filaments, which improves the cohesion of the yarn However, and this without departing from the scope of the invention, the entanglement or a complementary entanglement of the filaments can be carried out before and / or after the arrival of the wire in the drawing area

According to the invention, it is advantageous to carry out the drawing of the wires heated to a temperature which is about 30 ° C. above the Tg of the polymer. The drawing rate applies between the first and the second roller of the drawing zone. is advantageously greater than 1.05, preferably between 1.1 and 2

The draw rate is adjusted by controlling the linear speeds of at least one of the rollers by any means known and customary in the technical field of the invention

The nature of the surfaces of the rollers can vary within wide limits. Thus, it is possible to use the usual surfaces of the rollers used in conventional processes for the manufacture of synthetic yarns or fibers and in particular the wire drawing devices, such as polished chrome surfaces. or matt Plasma coated surfaces can also be used to adjust the frictional forces of the wire on the surfaces of the rollers according to the tensions applied to the wire both at the first roller and at the second roller

According to another characteristic of the invention, the wire leaving the drawing zone is subjected to relaxation to reduce and limit the tension of the wire on the winding reel

This relaxation is obtained by heating the wire, for example, with steam, at a temperature greater than 100 ° C. and a rotational speed of rotation of the second roller greater than that of the winding reel. Advantageously, this treatment is carried out by a nozzle through which the wire to be treated passes. Water vapor is fed into the nozzle in a secant direction, advantageously perpendicular, or parallel with the wire path.

However, in a variant of the method of the invention, the relaxation of the wire can be carried out at the level of the second roller of the drawing zone, by heating the wire present on this roller. For this, a heating roller such as described above or any suitable heating means

It is also possible to provide a system for controlling the tension of the thread before rewinding on a reel. The use in the drawing area of two rollers on which the thread (s) are wound with an open loop and an angle of winding less than 360 ° and preferably less than 200 ° makes it possible to simultaneously treat several wires on said drawing rollers without using a roller associated with each wire. Thus the installation requires lower investments, also a smaller footprint and allows '' installing winding devices or coils on several levels or stages in a superimposed manner

The wire can be sized either before or after the stretching area. It is also possible to provide several sizing devices arranged before and after the drawing area if necessary. The suitable sizes are those used for the production of yarns or fibers in conventional and usual procedures, and are a function of the type of yarn and the use thereof

The threads obtained by the process of the invention can be used for the production of woven or knitted textile surfaces either alone or by combining with other threads such as for example natural threads, artificial threads or elastic threads such as by example elastane yarns

The yarns of the invention have better regularity of properties over the length of the yarn and in particular good regularity of the tension on the winding spool Consequently, when these spools are used on weaving or knitting machines, the tension of the thread in the loom will be regular and therefore will allow to obtain a regular textile surface

In the case of a polyhexamethylene adipamide yarn, it has special properties of withdrawal force and withdrawal with boiling water, different from those obtained in conventional integrated spinning-stretching processes. Thus a multifilament yarn made of polyhexamethylene adipamide obtained by an integrated spinning-stretching process has a shrinkage in boiling water greater than 6% and a shrinkage force greater than 1.3 cN / tex By polyhexamethylene adipamide, it is necessary to understand the polyamide obtained by polycondensation between hexamethylene diamine and adipic acid. However, this term also designates, for the interpretation of the invention, the polyhexamethylene adipamide copolyamides with, for example up to 5% by weight of units derived from caprolactam

According to another preferred characteristic of the invention, the withdrawal force of the wire satisfies the following inequalities:

0.1241 χ R _EB + 0.594 <F _R (1)

0.1241 x R _EB + 1.073> F _R (2) In which:

- R _EB is the percentage of withdrawal with boiling water, and

- F _R is the withdrawal force of the wire in cN / tex.

Other advantages, details and object of the invention will appear more clearly from the description of embodiments of the invention made with reference to the appended figure in which:

- Figure 1 is a single schematic view of a wire production installation according to a first embodiment of the method according to the invention. According to a first embodiment of the invention illustrated in FIG. 1, a multifilament yarn 1 is obtained by spinning a polymer through a die 2 comprising a multitude of holes to obtain a bundle 3 of filaments 4.

These filaments 4 converge at a point 5 called a point of convergence, thereby forming the wire 1.

In the illustrated embodiment, a device 6 for depositing size on the wire 1 is present at the point of convergence. This device 6 can be installed at any one or more points on the wire path.

The filaments 4 are, at the outlet of the die, cooled by a device advantageously forming a chimney into which cold air is injected. This conventional cooling device in melt spinning processes has not been shown in the figure for clarity.

The sized wire 1 is brought to a first roller 7 and forms thereon an open loop with a winding angle of less than 360 °, advantageously of the order of 180 °.

The wire 1 then passes over a second roller 8 of substantially identical size on which it also forms an open loop with a winding angle less than 360 °.

The rollers 7, 8 are arranged in such a way that the path of the wire 1 describes an S. The wire 1 is then wound on a winding reel 9. According to the embodiment illustrated in Figure 1, a heating nozzle 10 is disposed on the path of the wire 1 between the two rollers 7 and 8. This nozzle 10 is supplied with superheated steam (supply not shown) . An example of a nozzle suitable for the invention is described in French patent 2,490,252.

As the roller 8 has a higher peripheral or linear speed than that of the roller 7, the wire 1 is subjected to drawing.

The heating nozzle 10 also causes entanglement of the filaments to obtain cohesion of the wire. The installation illustrated in FIG. 1 comprises a second heating nozzle 11 arranged on the path of the wire 1 after the second roller 8. This nozzle is also supplied with superheated steam. This nozzle only allows the wire to be brought to a temperature sufficient to obtain a relaxation thereof, before being returned to a reel 9. The peripheral speed of the winding reel 9 is advantageously lower than the peripheral speed of the roller 8 to allow relaxation of the wire and thus reduce the tension thereof before winding on the coil 9.

The rollers 7 and 8 are advantageously driven in rotation by inverter devices (not shown) which also make it possible to control their speed of rotation.

As the thread 1 only describes an incomplete turn or winding on the rollers 7 and 8, it is possible to bring several threads 1 onto them and return them to the reels 9 arranged in a substantially superimposed manner or on several levels . Such an arrangement allows a reduction in the area occupied on the ground necessary compared to known methods.

In addition, since the wires are drawn simultaneously on the same drawing device, the properties of the wires will be more homogeneous. This homogeneity coupled with the homogeneity of the properties over the length of a thread will make it possible to obtain textile surfaces with uniform appearance and therefore improved. According to another embodiment not illustrated, the method of the invention is implemented in an installation similar to that of the embodiment illustrated in the single figure. However, the relaxation of the wire 1 is carried out at the level of the second roller 8 which comprises, in this second embodiment, means for heating the wire (means not shown), the heating nozzle 11 being omitted. This second roller is of conventional design and may be identical in structure to the rollers of the "heating roller" type used in conventional methods of drawing synthetic threads. However, the heating of the wire passing over the second roller can be produced by any heating means known as infrared radiation, electromagnetic induction heating for example.

Thus, the yarn is brought to a relaxation temperature allowing a reduction in the winding tension and therefore obtaining coils which can be used in the processes for manufacturing textile surfaces.

Furthermore, without departing from the scope of the invention, sizing deposits on the wire 1 can be provided after the relaxation zone of the wire. The nature of the sizing compositions are not critical and are generally those usually used in the processes for manufacturing synthetic yarns. In addition, to improve the cohesion of the wires, it is possible to provide entanglement and or interlacing nozzles before or after the stretching zone, or as indicated above, use as heating nozzle 10 for stretching, a nozzle generating an entanglement of the filaments.

Yarns were obtained according to the method of the invention by spinning polyhexamethylene adipamide or polycaprolactam, either by using the first embodiment illustrated in the single figure, or according to the second embodiment described above.

The properties of shrinkage in boiling water and of shrinkage force are measured according to the following methods: - Shrinking in boiling water: (method derived from standard DIN 53 866)

The shrinkage of the wires in boiling water is determined by drawing the wire under a tension of 0.05 cN / dtex, and marking the wire in two places spaced from each other by a predetermined distance L- _| . After removing the tension, the wire is immersed in boiling water for 15 minutes, then the wire is wound up. After drying the wire at 80 ° C for 10 minutes and then reconditioning at room temperature for 10 minutes, the wire is again subjected to a tension of 0.05 cN / dtex. The distance L2 between the two previous marks is again measured. The shrinkage (R _EB ) of the wire is determined by the formula:

L ₁ - L ₂ R _EB (%) = x 100

The

1

- Withdrawal force:

This force is measured dynamically on a DYNAFIL brand device with a wire feed speed of 50 m / min. The length of the wire tested is 1000 m. The wire is brought to 180 ° C in the air between the two scroll rollers which rotate at equal speed. The force exerted on one of the rollers is measured. Examples according to the embodiment illustrated in Figure 1

The operating conditions of the process are as follows:

- Polymer: Polyamide 66 of relative viscosity 37 (measured in formic acid)

- Spinning temperature: 292 ° C

- Winding speed: 5200 m / min

- Winding tension: 0.8 g / tex

- Vapor pressure in the drawing nozzle 10: 6 bars

- Vapor pressure in the relaxation nozzle 11: 2 bars

- Relaxation rate between stretching rollers and winding reel: around 10%

- Thread title: 78/20

The yarns obtained have the following characteristics:

(1) Vapor pressure in the relaxation nozzle equal to 3.7 bars

Other tests were carried out with different vapor pressures in the drawing nozzle and the relaxation nozzle. The results are shown in the table below:

Examples produced according to the second embodiment

In this embodiment, the relaxation of the wire is brought about at the level of the second roller of the drawing zone equipped with heating means, for example a double envelope in which a heat transfer fluid circulates.

The operating conditions of the process are as follows:

- Polyamide 66 polymer of relative viscosity 42 (measured in formic acid) - Spinning temperature: 292 ° C

- Winding speed ^• 4500 m / min

- Winding tension. 2.7 g / tex

- Air heating at 200 ° C for stretching

- Relaxation rate between stretching rollers and winding reel around S% - Thread title: 22/6 10

The yarns obtained have the following characteristics

The yarns of the invention have characteristics of shrinkage and of withdrawal force superior to those of the yarns obtained by the "FE I" process (Spinning - Drawing - Integrated) Indeed, for a comparable drawing rate and a yarn of similarly, the withdrawal with boiling water of a FEI wire is of the order of 7% for a withdrawal force of 1.2 cN / tex

Manufacture of polycaprolactam yarn according to the second embodiment

Yarns with titles 44/20 and 44/12 were produced by spinning a polycaprolactam composition of viscosity 2.61 (relative viscosity measured in H2SO4, solution at 1.0% of polymer in H2SO4 at 96%) The composition also contains 1.70% titanium oxide as a matting agent

The spinning conditions are

- Spinning temperature. 270 ° C

- Winding speed ^• 4500 m / min - Heating temperature of the second roll 180 ° C

- Draw rate: 1, 3

- Relaxation rate ^• 10% 11

The characteristics of the wires obtained are

These yarns are used, for example, in knitting processes to produce textile-resistant surfaces.

Claims

1 - Polyhexamethylene adipamide multifilament yarn, characterized in that it has a boiling water shrinkage greater than 6% and a shrinkage force greater than 1, 3 cN / tex.

2 - Wire according to claim 1, characterized in that the withdrawal force (F _R ) of the wire satisfies the following inequalities:

0.1241 χ R _EB + 0.594 <F _R (1) 0.1241 χ R _EB + 1.073> F _R (2)

In which :

- R _EB is the percentage of withdrawal with boiling water, and

- F _R is the withdrawal force of the wire in cN / tex.

3 - Process for manufacturing polyamide multifilament yarns by spinning, in a molten medium, a polymer and drawing the yarn before rewinding, characterized in that it consists in i) spinning the molten polymer through at least one die having several holes of a die to produce at least one bundle of filaments, ii) to cool said filaments, iii) to converge the filaments of a bundle or of several bundles at at least one point of convergence to form at least one multifilament film, iv) stretching each wire in a drawing zone comprising two rollers arranged so that the path of the wire or wires describes an S, the first roller in the direction of advancement of the wire having a peripheral speed of rotation lower than that of the second roller , the wire or wires forming an open loop less than 360 ° on each roller, the wire being heated to a drawing temperature at least higher than the Tg of the polymer in a point or an area located between the first point of contact between the wire and the first roller, and the first point of contact between the wire and the second roller in the direction of advancement of the wire, said contact points being part of the drawing area, v) causing relaxation of the wire between the first point of contact between the wire and the second roller of the drawing area and the spool for winding the drawn wire, vi) returning the wire to a speed greater than 3500 m / min. 4 - Method according to claim 3, characterized in that the heating of the wire in step iv) is carried out by using as a first roller or as a second roller of the drawing zone, a roller equipped with heating means.

5 - Method according to claim 3, characterized in that the heating of the wire in step iv) of drawing is carried out by a heating means of the wire disposed between the first and the second roller of the drawing zone

6 - Method according to claim 4 or 5, characterized in that the heating means are constituted by convection heating, by radiation

Infrared, by electromagnetic induction, by ultrasound, or by a circulation of heat transfer fluid disposed in said rollers

7 - Method according to claim 5, characterized in that the heating means is a nozzle supplied with a hot fluid

8 - Process according to claim 7, characterized in that the hot fluid is superheated steam or hot air.

9 - Method according to one of claims 3 to 8, characterized in that the drawing temperature is at least higher than the glass transition temperature (Tg) of the polymer, preferably higher than Tg + 30 ° C

10 - Method according to one of claims 3 to 9, characterized in that the stretching rate applied in the stretching zone is at least greater than 1.05, preferably between 1, 1 and 2.

11 - Method according to one of claims 3 to 10, characterized in that step v) of relaxation of the wire is carried out by heating the wire between the second roller of the drawing zone and the winding reel.

12 - Method according to claim 11, characterized in that the heating is provided by a hot fluid.

13 - Method according to one of claims 3 to 10, characterized in that the step of relaxation of the wire is implemented by heating the wire on the second roller of the drawing zone 14 - Method according to claim 13, characterized in that the heating means of the wire on the second roller are constituted by heating by convection, by infrared radiation, by electromagnetic induction, by ultrasound, or by a circulation of heat transfer fluid disposed in said second roller.

15 - Method according to one of claims 3 to 14, characterized in that the winding speed is greater than 3500 m / min.

16 - Method according to one of claims 3 to 15, characterized in that the polymer is a thermoplastic polyamide chosen from the group comprising PA6,

PA66, their copolymers and mixtures.