EP0934439A1

EP0934439A1 - Polyamide filament dyeing method

Info

Publication number: EP0934439A1
Application number: EP97903420A
Authority: EP
Inventors: Umberto Brenna; Olivier Chaubet
Original assignee: Novalis Fibres
Current assignee: Novalis Fibres
Priority date: 1996-02-09
Filing date: 1997-02-06
Publication date: 1999-08-11
Also published as: FR2744734A1; WO1997029235A1; AU1798597A; FR2744734B1

Abstract

A method for dyeing filaments produced by melt spinning a polyamide composition is disclosed. In particular, the method comprises a step of dyeing the filaments during the filament stretching step. Apart from the stretching step, the method comprises the steps of (i) gathering the filaments produced by spinning a polyamide composition and advantageously collected in the form of a yarn, web, cable or roving, (ii) applying at least one dissolved dye to the collection of filaments, (iii) heating said filaments to at least the glass transition temperature of the polyamide composition, (iv) washing the filaments before or after stretching, and (v) storing the resulting filaments in a suitable form. The resulting filaments are particularly suitable for making short or long fibres or for making bulk continuous filaments or flock cables.

Description

PROCESS FOR DYEING POLYAMIDE FILAMENTS

The present invention relates to a process for dyeing filaments obtained by spinning in a molten medium a composition based on polyamide. It relates more particularly to a process comprising the step of dyeing the filaments integrated into the stretching process thereof.

Polyamide filaments are generally obtained by spinning in a molten medium a composition comprising, as main polymeric material, a polyamide. The filaments obtained are cooled to a temperature below the glass transition temperature (Tg) of the polymer and then collected in the form of multifilament yarns or rovings. To improve the mechanical properties of these filaments, it is often necessary to subject them to stretching which causes the crystallization of the polymer and the orientation of the chains. The filaments thus obtained are either used for the manufacture of articles such as carpets, fabrics, etc., or for the manufacture of fibers by cutting multi-filament wicks.

Generally, the filaments are dyed either by incorporating pigments into the polyamide composition before spinning, or by impregnating the already drawn filaments or fibers with dyes which are dispersed or in solution in a solvent. Polyamide filaments are generally dyed with soluble dyes. The dyeing step can be carried out on the finished article, for example the carpet.

The dyeing processes require several stages such as washing the article beforehand, dyeing and then washing again. Thus, the dyeing processes generate large quantities of liquid effluents. In addition, these steps are long and can take several hours. To reduce these drawbacks, processes have been proposed for dyeing the filaments used before drawing them. Thus, US Pat. Nos. 3,241,906, EP 0 631 007 describe a process comprising a step of dyeing the filaments before the drawing step. These methods consist in applying to the filaments a dye dispersed in a solvent such as water or an organic solvent. The filaments are then drawn according to the desired drawing ratio. The penetration and fixing of the dye are obtained either by application of the dye at high temperature, or by heat treatment of the stretched filaments to allow diffusion of the dye in the mass of the filament. These methods apply to disperse dyes and more particularly to dye polyester filaments. These methods do not make it possible to dye filaments with soluble dyes such as those used for dyeing polyamide filaments. British patent 1,094,725 also describes a process consisting in applying a disperse dye to a filament before or after the drawing step. To penetrate the dye into the mass of the filament, the latter is then heat treated to obtain a shrinkage of at least 10%. This process is difficult to apply industrially because it requires modifying the installations for drawing the filaments and does not make it possible to obtain high mechanical properties. Indeed, to obtain the shrinkage rate necessary for the diffusion of the dye, the stretching tensions must be limited.

To remedy these drawbacks, the Applicant proposes a process comprising the dyeing of the polyamide filaments integrated into the stretching process thereof. The process of the invention makes it possible to dye the filaments without reducing the productivity of the existing drawing processes and without modifying them.

To this end, the invention provides a process for the manufacture of filaments obtained by spinning in a molten medium a composition based on polyamide, and drawing of these comprising a dyeing step integrated into the drawing step.

Thus, the method of the invention further comprises the drawing step, the following steps: i) taking up of the filaments obtained by spinning a composition based on polyamide, advantageously gathered in the form of threads, web, cable or wick. ii) Application of at least one dye in solution to said collection of filaments, iii) Heating of said filaments to a temperature at least higher than the Tg of the polyamide composition. iv) Washing the filaments, before or after stretching them, and v) Storage of the filaments produced in an appropriate form. The appropriate storage depends on the type of collection of the filaments. Thus, when the filaments are gathered together in the form of threads, this thread is advantageously returned to spools or beams after having been possibly subjected to a crimping or texturing process. The filaments collected in the form of cables or wicks can be, after having been possibly subjected to a crimping process, stored in containers to be used as supply cables in the flocking processes or in the short fiber manufacturing processes or long. It is also possible to produce these fibers by feeding cables, dyed sheets according to the method of the invention in a cutting device without storage or intermediate recovery. The method of the invention therefore makes it possible to obtain dyed filaments during the drawing process, with the application of dyes, advantageously before the effective drawing of the filaments, in other words before the structural rearrangement of the macromolecular chains together. a preferred characteristic of the invention, the filaments are, before storage, fixed by a heat treatment, carried out for example with water vapor at a temperature above 100 ° C., for a duration greater than one minute

This thermal fixing makes it possible in particular to fix the mechanical properties such as shrinkage and also the deformations imposed on the filaments such as the fnsures or twists in the case where a fnsage step is provided for in the process.

This thermal fixing also makes it possible to obtain a diffusion of the dye in the heart of the filament

In fact, step m) of heating the filaments at the outlet of step n) of dyeing allows fixing of at least part of the dye on the surface of the filament, and penetration of the latter onto a penpale crown. thin The diffusion of the dye into the core of the filament can advantageously be carried out during the thermal fixing step

According to the invention, the dyes are dyes soluble in a solvent, advantageously water. As dyes, mention may be made, for example, of the "Acid Yellow" dyes No. 246. 219, 240, 236, 242, 137, "Acid Orange" n ° 43, 67, 108, 127, "Acid brown" n ° 298, "Acid red" n ° 277, 299, 361, "Acid Blue" n ° 113, 286, 277, 350, "Acid Black" n ^β 60, 132. 218 It is also possible to use mixtures of dyes To improve the fixing of the dye on the filament, additives such as benzyl alcohol can be added to the solution at concentrations of a few grams per liter to several tens of grams per liter

Other additives usually added in dye baths, such as "anti-frosting" agents, wetting agents, natural or synthetic thickeners, acid generators may also be present in the dye solution suitable for the process. of invention

The dyeing solution is applied to the filaments gathered advantageously in the form of sheets, threads, rovings or cables by passing them through a dye bath, or by spraying the dye bath on the assemblies of filaments, called α-apres cables for clarity. Other application techniques can be used without departing from the scope of the invention The cables are then expnmes by the usual techniques such as padding, for example According to the invention, the filaments at the outlet of step ii) of dyeing are heated to a temperature higher than the glass transition temperature (Tg) of the polyamide composition, for a brief period of duration greater than 5 seconds and advantageously between 5 and 60 seconds. This heating can be achieved by any means. However, in a preferred embodiment of the invention, this heating is carried out by treatment with an atmosphere saturated with water vapor. The temperature of this vapor is usually 100 ° C. However, higher temperature water vapor can be used at pressures above atmospheric pressure. This heat treatment makes it possible to fix a certain quantity of dye on the surface of the filaments without fixing the structure of the latter.

To remove excess dye or dye bath which is not fixed and retained in the cable, it is washed or rinsed by passage through a solvent, or spraying with a washing or rinsing liquid.

This solvent or washing or rinsing liquid is advantageously water. This washing can be carried out by several successive sprays of washing liquid alternating with a wringing of the cable obtained for example by compression

The filaments obtained are generally subjected to drawing which can be carried out cold or at a higher temperature. This drawing is carried out by means of conventional drawing benches and known in the art. The stretching rate applied is generally between 2 and 5.

The filaments can also be subjected to crimping or texturing according to known techniques.

The filaments obtained by the invention are filaments obtained by spinning in a molten medium a composition based on polyamide. As preferred polyamides of the invention, there may be mentioned aliphatic polyamides such as hexamethylene polyadipamide, also called PA 66, polycaproamide called PA 6, their copolymers or their mixtures. These polyamides may also include other repeating units such as aromatic sulfonate units such as the repeating unit derived from 5-isophthalic acid or the like, or units derived from other dicarboxylic acids such as iso or terephthalic acids or d 'other diamines.

Of course, any polyamide which can be spun and dyed with soluble dyes can be used for the manufacture of filaments according to the invention. By way of example, mention may be made of aliphatic polyamides of type PA 4-6, semi-aromatic polyamides. The process of the invention applies more particularly to the manufacture of multifilament cables intended for use in the manufacture of short or long fibers, whether or not crimped, or of "BCF" (Bulk Continuous Filaments) yarns in the manufacture of carpets, or finally cables for flock. Short or long fibers, crimped or not, are used in particular for the manufacture of fiber yarns, or for textile and nonwovens uses.

Other advantages, details and aims of the invention will appear more clearly in the light of the examples given below solely for illustrative purposes and having no limiting character. Polyamide filaments obtained by spinning a composition of PA 6 with a titer of 13 dtex are collected in the form of a cable with a titer of 11 ktex. These titles are measured after drawing and crimping the filaments.

This cable made up of unstretched filaments is fed into a process comprising a dyeing step. This dyeing is carried out, in the example illustrated, by padding in a dye bath.

This dye bath includes a dye such as "LANASYNE Navy Blue SBL, and / or LANASYNE Brown SGL" sold by the company CLARIANT.

It can also include benzyl alcohol as a promoter for fixing the dye on the filament and also anti-icing additives ("antifrosting") such as TANAPRINT PN "sold by the company TANATEX.

The bath temperature is from 15 to 50 ° C, preferably 20 ° C, while its pH is between 4 and 8, preferably equal to 7.

The duration of passage of the cable in the dye bath is not critical, and is of the order of 1 to 10 seconds, preferably 5 seconds.

The cable impregnated with dye is taken up by driving rollers, and compressed between two rollers to remove the excess dye bath entrained with the cable, according to the padding technique.

The cable is then drawn into a dye fixing area. This step consists in heating for a short period, of the order of 5 to 60 seconds, the filaments to allow the dye to fix and penetrate into a peripheral ring of the filament. This heating is carried out in the example illustrated by steam at a temperature of 100 ° C.

The cable is then taken up by rollers in a washing or rinsing zone which is carried out by passing the wick through one or more water tanks mounted in series. Advantageously, a flow of water is ensured in the tanks, against the current with respect to the direction of travel of the cable. The cable can be wrung out before being drawn into a drawing bench, when the latter is carried out in air, as in the example illustrated.

The drawing bench is a conventional device comprising several pairs of rollers driven at different speeds and capable of applying a drawing rate of the order of 2 to 5 to the wick. In the examples illustrated, the draw ratio is equal to 3.

The drawn cable can then be subjected to a finishing step such as crimping. After drying it can either be stored in pots or fed into a cutting device to make short or long fibers.

In one embodiment of the invention, the fibers, rovings, cables or windings thus produced are subjected to a heat fixing treatment for a relatively long period. This heat treatment is advantageously carried out with water vapor at 120 ° C for a period equal to 10 min. During this heat treatment, the dye diffuses throughout the thickness of the filament.

The dyeing quality of the products obtained is assessed by determining the following characteristics:

- Resistance to dry or wet friction, according to ISO 105 X12 standard.

- Color fastness after washing with water, determined according to ISO 105 E 01

The conditions of the cable dyeing tests described above according to a method in accordance with the invention are collated in Table I below:

Table I

Comparative tests were also carried out by dyeing a wick identical to that used for tests 1 to 9. The conditions for these tests are collated in Table II below.

Table II

The dyeing properties of the dyed cables were determined according to the methods described above. They are collated in Table III below:

Board

Claims

1 - Process for the production of dyed synthetic filaments obtained by spinning in the molten state of a polyamide-based composition comprising the following steps: i) taking up of the filaments obtained by spinning a polyamide-based composition, collected in the form of yarns, web, cable or wick, ii) Application of at least one dye in solution to said collection of filaments, iii) Heating of said filaments to a temperature at least higher than the Tg of the polyamide composition. iv) Washing or rinsing the filaments, before or after stretching them, and v) Storage of the filaments produced in an appropriate form.

2 • Method according to claim 1, characterized in that the filaments are subjected to a fixing by heat treatment before step v) of storage.

3 - Process according to claim 1 or 2, characterized in that the dyes are soluble in water.

4 - Method according to one of claims 1 to 3, characterized in that the application of dyes is carried out by spraying or quenching.

5 - Method according to one of the preceding claims, characterized in that step iii) of heating the filaments is carried out by an atmosphere saturated with water vapor.

6 - Method according to claim 1 or 5, characterized in that the heating of the filaments (step iii) has a duration between 5 seconds and 60 seconds.

7 • Method according to one of claims 2 to 6, characterized in that your thermal fixation is carried out by a treatment with water vapor for a period greater than 1 minute and a temperature greater than 100 ° C.

8 - Method according to one of the preceding claims, characterized in that step iv) of washing or rinsing is carried out by quenching or spraying with a solvent for the dyes, preferably the solvent is water. 9 - Method according to one of the preceding claims, characterized in that ies washed filaments are wrung by compression before or after the stretching step.

10 - Method according to one of the preceding claims, characterized in that the filaments are combined in the form of a wick before the application of dyes.

11 - Process according to claim 10, characterized in that the collection of filaments is subjected before or after thermal fixing to a cutting operation of the fiber filaments.