EP0579558B1 - Continuous polyamide filament cords and method of making the same - Google Patents

Description

The present invention relates to a coherent and regular cable of continuous polyamide-based filaments intended for the preparation of short fibers.

It also relates to a method for obtaining such a cable.

Continuous filament cables intended to be cut and used for example for electrostatic projection are generally present, in packages, in the form of folded lengths regularly arranged side by side and on top of each other, so that the packages or cartons can be easily transported from one place to another, stored and stored for a long time until their later use.

When the cables are intended to be used for electrostatic projection, their presentation must be particularly careful, and in particular the continuous filaments constituting them must be kept perfectly parallel to each other and be free from any irregularity such as breaks, loops etc. .., so that they can then be handled.

Thus the filaments, at the outlet of their packaging are always taken up while keeping the strands parallel to each other and having good cohesion between them either to be brought to the cutter or to be widened and spread out without becoming entangled.

To maintain continuous filaments in the form of coherent and compact cables, one solution consists in carrying out a helical wrapping by means of one or more identical or different wires, according to a process described in FR 2 188 625. Such a solution, however, is expensive. and heavy in the context of industrial production.

Furthermore, modern cutters industrially used for the manufacture of short fibers are very large capacity machines requiring for optimized operation, a supply with a cable having a very large number of filaments. and suitable surface properties on the part of these filaments, so that the cables which can be used to supply industrial cutters must have a very large overall titer as well as particularly efficient frictional properties to facilitate cutting and subsequent treatments.

It has now been found that it is possible to prepare continuous filament cables based on polyamides, of overall bulk, without requiring covering and having good cohesion of the filaments with one another.

The present invention relates to continuous filament cables, generally intended to be cut in the form of short fibers, having an overall titer greater than 110 ktex, generally greater than 180 ktex, having a moisture content equal to or greater than 15% generally up to '' at 40% and a sizing ratio of between 0.05 and 0.20% by weight relative to the weight of the polyamide, preferably from 0.05 to 0.15%, the sizing ratio being measured according to the method described below. Preferably, the size is in the form of an aqueous emulsion of sulphited fatty amide.

The cable can be made up of filaments of very variable strand titer, which can range from very fine titer for example, 0.5 dtex or even less to high titer for example 40 dtex or even more depending on the desired applications (clothing, furniture, car seats, carpets) according to the process for obtaining continuous filaments. For example, in the case of use of carpet yarns, generally cooled in water, the strand titers can be much higher and go up to 100 dtex or more.

The cables according to the invention are more specifically intended for use in an electrostatic field but other uses can be envisaged.

The present invention also relates to a process for obtaining cables of continuous filaments defined above by spinning in the usual manner of polyamide, the filaments being converged then sized, wetted, and grouped in the form of wicks which are themselves combined in a regular tablecloth; this is essentially stretched by passing between at least two trains of rollers rotating at different speeds and again moistened by passing through one or more trays containing an aqueous sizing emulsion; after passage of the sheet between a last train of expressing rollers, it is taken up again to constitute the final cable which will be packed.

Preferably, the continuous filaments are air-cooled and drawn at a rate ≥ 2.5 x, depending on the titer of the individual filaments which it is desired to obtain. However, for very large strands, stretching is not necessary.

Depending on the subsequent use of the filaments and the precise nature of the polyamide, it may be desirable to carry out a heat treatment by any known means to reduce the final shrinkage of the filaments. For example, PA6-based filaments must necessarily be treated with heat to obtain a low shrinkage rate. The heat treatment is generally carried out at a variable temperature, for example between 150 ° C. and 220 ° C. depending on the strand count of the continuous filaments.

The heating means is generally placed after the train of recovery or drawing rollers, but before the expressing rollers; these are located at the end of treatment in order to precisely regulate the final humidity and sizing rates.

The final humidity level is generally continuously checked to ensure good humidity regularity. After pressing, the layer of filaments is taken up in a known manner on these rollers to form the final cable.

The continuous filament cables according to the invention have a large overall titer, greater than 110 ktex, generally greater than 180 ktex which can range up to 270 ktex or even more. They have a moisture content of more than 15%, up to 40% or even more; it has on the one hand, the advantage of giving both flexibility, cohesion and good parallelization of the strands between them without requiring covering or any other device capable of keeping the strands parallel, and on the other hand that of facilitate cutting in cutters by avoiding the use of a deposit of too large size, expensive and troublesome for the subsequent treatments, dyeing and / or deposit of electrolytes intended for the activation treatment.

The filament cable according to the present invention also has the advantage of having a low sizing ratio of between 0.05 and 0.20% by weight of the cable, preferably 0.05 to 0.15% or even 0, 05 to 0.1%.

Sizing products are still used and necessary in the preparation of threads and fibers and textiles to facilitate their passage over the mechanical components and the sliding of the strands between them. In the context of the invention, the sizing agents, together with the moisture content contained in the wires, must also contribute to the flexibility and cohesion of the cable and facilitate passage through the cutters, thus avoiding excessively rapid wear. knives, wear which deteriorates the edge of the blade and causes the strands to stick together by pressing.

They must be able to be easily removed, for example during the dyeing treatment to avoid desensing the fibers before dyeing or to obstruct the dyeing and finishing treatments.

Consequently, if the size is necessary to improve the frictional properties of the filaments and the sliding of the knife, it must be present in the smallest amount possible, as is the case with the cables according to the present invention.

The products used for sizing the filaments according to the invention are preferably aqueous emulsions of the anionic type. Preferably, a sulfite fatty amide composition is used.

• des chaînes grasses contenant 12 à 30 atomes de carbone, de préférence 16 à 20, saturées ou non ;
• des groupes amides favorisant l'hydrophilie et l'adhésion ;
• des groupes apportant l'autoémulsionnabilité et/ou la solubilité, tels que des groupes SO₃, avec éventuellement des groupes COOH ou CH₂OH,

et possède un pH compris entre 5 et 7.Such a composition essentially comprises:

• fatty chains containing 12 to 30 carbon atoms, preferably 16 to 20, saturated or unsaturated;
• amide groups promoting hydrophilicity and adhesion;
• groups providing self-emulsibility and / or solubility, such as SO ₃ groups, with optionally COOH or CH ₂ OH groups,

and has a pH between 5 and 7.

Among the sizes which are particularly suitable, mention may be made of Sopromine 1686 sold by the company Rhône-Poulenc Spécialités Chimiques, but other sizes may also be suitable.

The term “polyamide” means all the spinnable and transformable polyamides for obtaining threads, for example polyamide 6, and preferably polyamide 66 or copolyamides containing at least 85% of hexamethylene adipamide units and up to 15% of other units obtained by replacing, for example, the starting adipic acid with caprolactam.

The starting polyamides may also contain additives such as matting agents, stabilizers with respect to light, or with respect to heat, and to oxidation, additives intended to reduce the accumulation of static charges or modifying the dyeing ability, etc.

Likewise, the cable thus prepared is preferably sterile and protected for the time of storage. This protection is carried out during the last stages of the process by known broad spectrum fungicides, compatible with the toxicity standards. It allows storage in a very humid environment at 40% water or more, for several months at high ambient temperatures.

The continuous filaments constituting the cable according to the invention can have any suitable shape depending on the aspects desired on the finished article, glossy, silky appearance, etc. The structure can be round, three-lobed or multi-lobed, hollow, etc. depending on the desired appearance and characteristics.

The relative viscosity of the starting polymer, measured on a 90% w / v solution in formic acid is a viscosity usually used for spinning polyamides. For polyamide 66 it is usually in a range between 35 and 40 or 45. But for filaments subjected to high stresses it must be increased to values which can go up to 60 or 80.

• taux d'humidité : il est réalisé dans une étuve ventilée à 105°C ; on mesure la perte de poids de la fibre après passage pendant 3 heures dans l'étuve. Le taux d'humidité s'exprime en % par rapport au poids sec.
• taux d'ensimage = on réalise une extraction à température ambiante par l'éther, de l'huile déposée sur le fil et l'on effectue la pesée du résidu huileux après évaporation du solvant. La mesure est exprimée en pourcentage par rapport à la masse du fil.

The humidity and sizing levels are controlled and evaluated using the following methods:

• humidity level: it is carried out in a ventilated oven at 105 ° C; the weight loss of the fiber is measured after passing for 3 hours in the oven. The humidity is expressed in% relative to the dry weight.
• sizing ratio = an extraction is carried out at ambient temperature with ether, of the oil deposited on the wire and the oily residue is weighed after evaporation of the solvent. The measurement is expressed as a percentage relative to the mass of the wire.

EXAMPLE 1

A polyhexamethylene adipamide of relative viscosity 41 measured on a 90% solution in formic acid containing approximately 0.5% of titanium oxide is usually spun, the filaments being cooled in air at room temperature, then converged and moistened with an aqueous emulsion of a sizing agent known under the brand name Sopromine 1686 from the company Rhône-Poulenc Spécialités Chimiques (CAS No. 94-200-336) to produce a coherent wick which is returned in a known manner.

60 strands of total titer 144,000 dtex produced in an identical manner are combined in the form of a sheet and pass through a drawing device composed of several trains of rollers rotating at different speeds to obtain a drawing rate of 3.2 X.

Before passing over the last train of stretching rollers, the sheet is again moistened by passing through a tank containing the same aqueous sizing emulsion as that indicated above, then expressed to adjust the final humidity level to 19 % w / w dry matter and the sizing rate at 0.05% w / w. The sheet is taken up by rollers to form the final cable with a total title of 270 ktex, composed of title filaments with a strand of 1.7 dtex having the humidity and sizing rate indicated above.

Such a cable has practically parallel, coherent and manipulable filaments. It is directly placed in a waterproof bag to prevent moisture loss; itself is placed in a suitable packaging that can be handled and stacked.

It can be taken back and handled without any difficulty. In particular, this cable can either be brought to a rotary industrial cutter (for example a MATSUSHITA® or PIERRET® or OMT ® cut) to make a cut of desired length, or spread out to be dyed, then treated electrostatically on the surface (treatment of activation) in order to carry out an electrostatic projection in a known manner.

EXAMPLE 2

A wick with a total titer of 144,000 dtex is prepared according to the process indicated in Example 1, and 40 of these wicks are combined in the form of a sheet, the sheet being treated in the manner indicated above, that is to say say stretched at a rate of 3.2 X, sized with the same aqueous emulsion as that used in Example 1, and expressed in the manner indicated above to obtain a humidity rate of 30% and a rate of 0.15% size.

The final cable also has an overall titer of 180 ktex and the filaments a strand titer of 0.9 dtex. It is directly packed, can be stored without problems and used for cutting or dyeing.

EXAMPLE 3

A lock was prepared as indicated in Example 1, with a total titer of 95,000 dtex (after drawing).

20 of these locks are combined in a sheet treated in accordance with the above examples to obtain a final cable with a global title of 190 ktex, having a humidity rate of 38%, a sizing rate of 0.15%, consisting of continuous filaments of title to strand 17 dtex.

Claims (14)

1. Tow of continuous filaments based on polyamide, having an overall denier greater than 110 ktex, a moisture content greater than 15 % and a sizing agent content of between 0.05 and 0.20 % by weight of the tow.
2. Tow according to Claim 1, characterised in that it has an overall denier greater than 180 ktex.
3. Tow according to Claim 1, characterised in that the sizing product is an anionic aqueous emulsion based on a sulphited fatty amide composition.
4. Tow according to Claim 1, characterised in that it has a moisture content of between 15 and 40 %.
5. Tow according to Claim 1, characterised in that it has a sizing agent content of between 0.05 and 0.15 %.
6. Tow according to Claim 1, characterised in that the denier per strand of the filaments is between 0.5 and 40 dtex.
7. Tow according to Claim 1, characterised in that the denier per strand is between 0.6 and 10 dtex.
8. Tow according to Claim 1, characterised in that it is intended for the preparation of short fibres for electrostatic spraying.
9. Tow according to Claim 1, characterised in that the polyamide used is polyamide 66.
10. Tow according to Claim 1, characterised in that the polyamide used is polyamide 66.
11. Process for obtaining tows according to Claim 1, comprising the following stages:

    - melt spinning of the polyamide, the filaments being chilled and then brought together and moistened with an aqueous emulsion of a sizing agent and brought back into the form of a strand,

    - regrouping of a plurality of identical strands to form a web which is moistened with an aqueous emulsion of a sizing agent and then squeezed off to give the desired moisture and sizing agent contents, and

    - taking up the web to form the tow of continuous filaments.
12. Process according to Claim 11, characterised in that the sizing agent is an anionic compound based on a sulphited fatty amide composition.
13. Process according to Claim 11, characterised in that the filaments are chilled with air.
14. Process according to Claim 11, characterised in that the web consisting of strands is drawn to a ratio of ≥ 2.5 x.