Continuous Spinning And Stretching Process Of The Production Of Polyamide-6 Filaments

Abstract

A stretched polyamide-6-filament consisting of a polyamide-6, having a monoclinic structure, a Cu-K -X-ray reflection width -- measured in the half height of the equator reflection -- of at least 2.35.degree. corresponding to an angular distance of the (200) and (020) reflex of 0.8.degree. and an infra-red extinction ratio E.sub.833 /E.sub.1075 of = 13. The polyamide-6-filament is prepared by a continuous spinning and stretching process which comprises the following steps : (a) dressing the filaments spun from the polyamide-6 melt immediately after they have been cooled with a non-ionic, high temperature resistant dressing agent, (b) drawing off under transposition, (c) stretching the filaments over stretching rollers, and (d) winding up the stretched filaments under tension.

Parent Case Text

This application is a continuation of Ser. No. 4,350, filed Jan. 20, 1970, now abandoned.

Description

The invention relates to a continuous spinning and stretching process for the production of polyamide-6 filaments in which the spun mono- or multi-filaments are treated with a temperature resistant dressing after they have been cooled and are immediately stretched after they have been drawn off.

When stretched orientated polyamide-6 filaments are produced by the conventional process, they are first wound on to a spinning spool and, after being exposed for some time to moisture in which they undergo preliminary crystallisation in the hexagonal .gamma.-modification, they are orientated by stretching. The stretching process at the same time induces in the filaments the .alpha. -monoclinic crystal modification, which is regarded as thermodynamically the most stable, and rise in the proportion of crystalline material from 5 to 10 to 25 to 30 percent.

The structural modifications can be characterised by X-ray or infrared-analysis. The non-stable hexagonal .gamma.-modification shows a distinct 002-meridian-- and a 200-/020 -- equator-reflection in the Cu-K.sub..alpha.-X-ray spectrum and "amorpheous" bands (p.i. 1170,1075 and 974 cm.sup.-.sup.1) in the infra-red spectrum, (measured at a parallel fibre band with polarised light. The reonoclinic.beta. -- and .alpha. -modifications show a widened equator-reflection with the separated 200-- and 020 X-ray bands and "cristalline" absorption bands (1027,960 and 833 cm.sup.-.sup.1) in the infra-red spectrum.

The production of polyamide filaments would be rendered more economical by a continuous spinning and stretching process, but this continuous process would have to be simple to carry out and would have to deliver filaments of a quality at least as good as those produced by the conventional two-stage process with the same end breakage rate and without loss in spinning capacity.

A continuous spinning and stretching process for the production of stretched polyamide-6 filaments has now been found which is characterised in that melt-spun filaments are treated with a temperature resistant dressing immediately after they have been cooled and are then drawn off and then stretched to 2.5 to 5.5 times their length, using one or two hot rollers at 170 to 220.degree.C, after which the stretched filaments are immediately wound under a tension of 0.02 to 0.08 g/dtex.

The resulting polyamide-6 filament shows a Cu-K.sub..alpha.-X-ray reflection width -- measured in the half height of equator reflection -- of at least 2.35.degree. followed by the separated 200 to 020 X-ray bands -- in an angular distance of 0.8.degree. -- and an infra-red extinction ratio of E.sub.833 /E.sub.1075 .gtoreq. 0.13, determined according to the basal lines method of infra-red spectrum analysis and the equation

E = (2E + E )3.

In application in textile technique (sharing and knitting) the filaments show less than 0.05 faults/10.sup.5 m.

In contrast to both the known processes and to the accepted ideas about residence times, end breakage rate or conditioning before stretching, this simple process provides the properties of which are consistently better than those filaments which have been produced in batches. Furthermore, the process involves no loss in spinning capacity, no special measures are taken to ensure induction of precrystallisation and no additional residence times are needed. Mono- and multi- filaments produced according to the invention show the following improvements in properties compared with filaments produced by conventional, i.e. batchwise, processes as known by the following patents: Belgian Pat. Nos. 666 681, 646 636, French Pat. Nos. 1409952, 1 533 457 and U.S. Pat. No. 3,002,804:

increased breaking strength with the same elongation at break, increased dyeability (with acid dyes), transparency (water clear) of unpigmented compositions and lustre gloss of unpigmented or only slightly pigmented compositions, reduced shrinkage on boiling, .alpha.-monoclinic modification of maximum stability undergoing no further crystallisation on boiling in water, increased uniformity of filaments and reduced longitudinal swelling.

Any grid spinning heads and extruders used practically may be used for spinning polymide-6 filaments. These filaments are spun under substantially the usual condition for the various titres in an ordinary blowshaft where they are cooled by an air blast. Below the blow shaft, the filaments are treated with a dressing which can withstand a temperature of up to 220.degree.C at least for a short time and which does not produce any additional deposits on rollers heated to 220.degree.C. A dressing which is temperature resistant up to 200.degree.C may, for example, consist of an aqueous emulsion of non-ionic melting agents such as oleic acid triglyceride, a phosphoric acid ester and a non-ionic emulsifier. The amount of the dressing agent applied to the filament is in the range of between 0.4 to 0.8 percent by weight.

The dressed filaments are drawn off using a draw-off roller with transposition device such as a ceramic rod or auxiliary roller which are looped round once or several times. It is advantageous to use a fixed ceramic rod and one or two loops round rod and roller. The draw-off roller rotates at 200 to 1500 m/min which is the usual spinning velocity for the various titres. The filaments drawn off with the more slowly rotating draw-off roller are then carried by means of an injector nozzle at least four times round a stretching roller heated to 170.degree. to 220.degree.C with an auxiliary roller placed at a slight distance from the stretching roller. Alternatively, the filaments can be passed round two similar or different stretching rollers both heated to about the same temperature, and rotating at a rate which is 2.5 to 5.5 times the draw-off velocity, which depends on titre and spinning velocity. The filaments which have been stretched in this way and orientated by a continuous process are wound on to a winding spool or laid off in a storage device. This continuous process operating without times of stay enables the filament to be wound on friction driven spools with a very good package development. In this particular embodiment of the process, in which the winding rate is usually about 1 to 5 percent below the stretching rate, the relaxation of filament due to stretching is anticipated to such an extent that the filament is rendered stable to heat to such an extent that inspite of its negative water balance it runs on to the spool with the necessary pretension for the buildup of a good package, and neither in an extremely dry nor in an extremely moist atmosphere will it undergo changes which would impair the build-up of package and subsequent processing.

An embodiment of the process of the invention is illustrated in the drawing.

The filaments 2 extruded from the spinning dies 1 are cooled in the blow-shaft 3 by a blast of air, collected by a guide 4 and guided so that they meet the dressing rollers 5 rotating in dressing vats tangentially before they are drawn off by the draw-roller 6 with auxiliary roller or ceramic rods 7, being looped once or several times round these rollers. The auxiliary roller may free-wheel or be driven. From the draw-off roller 6, the filaments are stretched between 6 and 8a by a pair of stretching rollers 8a and 8b which rotate 2.5 to 5 times faster than the draw-off roller and are heated to 170.degree. to 220.degree.C or by an equally hot stretching roller 8a and an undriven unheated auxiliary roller 9, and by passing at least three times round the pairs 8a, 8b or 8a, 9 they are fixed by heat so that they run with a sufficient pretension for satisfactory build-up of the package on the winding spool 10 which rotates more slowly by 1 to 5 percent.

Polyamide-6 melts obtained from autoclave shavings or from fully continuously operating condensation plants or obtained directly by fully continuous melting can be worked up by the process of the invention to produce filaments of high quality. The customary air conditioning in the draw-off room (winding room) is not necessary.

The following examples illustrate more particularly the invention.

EXAMPLE 1

Polycaprolactam autoclave shavings pigmented with 1.2 percent by weight of TiO.sub.2 and having a relative solution viscosity of 2.76 in 1 percent m-cresol solution are melted in a grid spinning plant and extruded at 280.degree.C through 9-aperture dies having an aperture diameter of 0.25 mm, cooled in a blow-shaft with an air blast at 22.degree.C, dressed with an aquous emulsion of oleic acid triglyceride, a phosphoric acid ester and a non-ionic emulsifier, carried once round a draw-off roller rotating at 1,400 m/min with ceramic rod arranged at a small distance from the roller, looped 5 times round a pair of stretching rollers rotating at 4000 m/min and heated to 205.degree.C, and conveyed to a friction driven winding spool which rotates 1.5 percent more slowly. The quantity of oil applied to the filaments should be between 0.4 and 0.8 percent. The stretching and winding apparatus is situated in a room which is air conditioned at 22.degree.C and 50 percent relative humidity. The extrusion of the melt is adjusted so that the 9-filament yarn running on to the winding spool has a titre of 50 dtex. Application of the yarn is carried out using an air injector nozzle. The spun zero twist threads can be warped directly from the spinning spools with a very low defect count and worked up into knitted samples which can be dyed without streakiness. They have the following technical properties:

Tensile strength 5,5 g/dtex Elongation at break 35% Angular distance of sharp CuK.sub..alpha.- radiation interferences (200) and (020) 1.55 degrees Intensity ratio of (002) and (200) interferences 0.19 E.sub.833 /E.sub.1075 0.33

EXAMPLE 2

Polycaprolactam shavings obtained from a fully continuously operating condensating plant and containing 0.3 percent of TiO.sub.2 and 0.2 percent of constituents which can be extracted with methanol and having a relative solution viscosity of 2.8 in m-cresol are spun and dressed as in Example 1, but at an extrusion rate which is 25 percent less than in Example 1. The draw-off roller is adjusted to 1,000 m/min and the stretching roller which is heated to 210.degree.C is adjusted to 3,000 m/min. The thread is guided once round the draw-off roller and ceramic rod and 6 times round the stretching roller and the air mounted auxiliary roller which rotates at a slight distance from the stretching roller, and is wound on a friction driven winding spool rotating at a 1 percent lower rate. The stretching and winding room is not air conditioned. The finished threads have the same properties as the threads in Example 1. The properties of the thread are practically unchanged when hot dry air is used in the auxiliary roller. When these threads are worked up, again only very low defect counts of the order of less than 0.1 for 1 kg are registered.

______________________________________ Tensile strength 5,4 g/dtex Elongation at break 37% Angular distance of the (200) and (020) equator reflection 1,45 degrees Intensity ratio of (002) and (200) interferences 0,22 E = E.sub.833 /E.sub.1075 0,30 ______________________________________

EXAMPLE 3

A polycaprolactam melt taken directly from a fully continuously operating condensation plant is spun from a 4-aperture die with apertures of 0.6 mm diameter at a total outflow rate from an extruder of 27 g/min. The melt is not pigmented. The mass has a relative solution viscosity of 3.1 in m-cresol and contains 2.5 percent of constituents which can be extracted with methanol. The temperature of the die is 290.degree.C. The four filaments are wetted with an anhydrous preparation based on fatty acid ester, fatty acid ethanolamide and non-ionic emulsifier, looped three times round the draw-off roller rotating at 254 m/min and auxiliary roller rotating with it, and stretched in the ratio of 1:4.5 by which they are looped 5 times. These filaments are wound using a winding apparatus which operates at a constant winding tension. The filaments are water-clear and glossy. Their tensile strength is 7.3 g/dtex at 24 percent elongation at break. Their relative loop and knot strengths are distinctly above 80 percent.

______________________________________ Angular distance of the (020) and (200) reflection 1,6 degrees Intensity ratio of (002) and (200) X-ray interferences 0,08 E = 0,36 ______________________________________

Claims

We claim:

1. A continuous process for the production of stretched polyamide-6 filament consisting of the sequential steps of

1. spinning polyamide-6 filament from a melt;

2. cooling the spun filament;

3. dressing the filament immediately after cooling with 0.4 to 0.8 percent by weight of a non-ionic dressing agent which is temperature resistant up to 220.degree.C;

4. drawing off the filament over a draw-off roller with a transposition device;

5. stretching the filament to 2.5 to 5.5 times its length using stretching rollers heated to 170.degree. to 220.degree.C; and

6. winding up the stretched filament under a tension of between 0.02 to 0.08 g/dtex.

2. The process of claim 1, wherein the stretching step (5) is carried out using a heated pair of stretching rollers.

3. The process of claim 1, wherein the stretching step (5) is carried out using a heated stretching roller with auxillary roller.

4. The process of claim 1 in which step (4), drawing off, is conducted at a speed of 200 to 1500 m/min.

5. The process of claim 1 in which step (6), winding-up, is conducted at a rate 1-5 percent below the stretching rate, step (5).