EP0305808B1 - Process for the preparation of unfinished stretched fibres - Google Patents

Description

The present invention relates to the preparation of preparation-free synthetic fibers from high polymers, with glass transition temperatures of over 100 ° C, by melt spinning and subsequent stretching via heated godets.

An indispensable procedural measure in the conventional manufacture of man-made fibers and a prerequisite for most further processing operations, e.g. the production of filament yarns staple fibers and staple fiber yarns is the application of a suitable preparation to the surface of the spun filaments. This preparation has very diverse and in some cases almost contradictory tasks to be carried out in the manufacturing and processing process and the experts have put a lot of effort into finding preparations that fulfill all of these tasks in an optimal, balanced degree.

The preparations are intended to prevent the formation of electrostatic charges on the filaments, to reduce the friction of the filaments on the thread guiding elements and also the thread / thread friction, but at the same time to ensure sufficient filament adhesion, which, however, e.g. in the production of staple fibers (staple fibers), must not prevent the filament packets from opening, and, last but not least, it must ensure a perfect stretching process.

Chemical fibers are therefore usually heated immediately after melt spinning and before any intermediate rinsing or stretching Godets are made, provided with a preparation. The substances and substance mixtures, which all have the properties required by preparations to a high degree, are generally applied to the filaments either as aqueous solutions or emulsions or anhydrous on the basis of mineral oil. The first application is usually carried out before or when the spun individual filaments are first brought together by means of preparation rollers or with so-called preparation thread guide members. After the evaporation of the water or the volatile parts of the mineral oil phase in the course of the production process, the preparation applied to the filaments forms a coating remaining on the filaments, which gives them the required running properties.

An inadequate preparation effect usually leads to difficulties already in the production stage immediately after the preparation stage, the stretching of the filaments. If a preparation order is completely dispensed with, fiber production is no longer possible according to the previously customary methods. Chemical fibers manufactured according to previous methods therefore always have a preparation application on their surface.

For special areas of application, contrary to the usual textile and non-textile uses, chemical fibers without a preparation order are desired (chemical fibers should be understood here as a generic term for filaments, staple fibers and yarns). It is therefore necessary to subsequently wash the man-made fibers, which have been produced in the usual way, with water (and detergent additives) or with solvents in order to free them from the superficial preparation application. The complete removal of the preparation from the fiber surface by such a post-treatment is not only complex, expensive and polluting, but often not even completely possible, because at the high temperatures to which the man-made fibers are exposed during their manufacture, preparation components can be firmly attached to the fiber surface or become insoluble.

An important area of application of man-made fibers, which is still becoming increasingly important, is their use for the production of fiber-reinforced plastics. However, preparation-free fiber surfaces are required especially for this application.

Even if prepared fibers are desired due to the requirements for further processing into yarns for the textile sector, it can be advantageous to keep the filaments free of prepregation even after the last heated godet, because the formation of preparation vapors and the deposition of preparation residues on the heated ones Godets is avoided. In this case, the preparation can be applied between the last hot godet and the winding.

The present invention now relates to a process for producing completely preparation-free synthetic fibers with a high molecular orientation and the usual textile technology characteristics, in which the filaments are produced from high polymers with a glass transition temperature of over 100 ° C. by melt spinning and subsequent stretching with a predetermined stretching ratio using heated godets.

The process according to the invention is characterized in that the filaments are subjected to a liquid before drawing, which can evaporate without residue during the drawing process and that the temperature of the preheating godet is chosen to be at least 40 ° C higher than in the conventional procedure with preparation.

Liquids which can evaporate without residue during the plugging process are those which have a boiling point in the range from about 80 to 220 ° C., preferably 90 to 180 ° C. If an organic liquid is to be used, it is advisable to choose one which has a high ignition temperature and can be easily and completely removed from the exhaust air and, if appropriate, recovered.

Examples of such substances are e.g. aliphatic compounds containing OH groups and / or ether groups with 2 to 8, preferably 3 to 6, carbon atoms, such as e.g. Alkanols, glycols, glycol monoethers or diglycol monoethers. Water is particularly preferred as a residue-free evaporable liquid.

The method according to the invention is suitable in principle for the production of man-made fibers from all known and conceivable melt-spinnable high polymers with a glass transition temperature of> 100 ° C.

Known melt-spinnable high polymers, which have a glass transition temperature of over 100 ° C (over 373 ° K) and which can thus be spun into size-free chemical fibers by the process according to the invention, can be found in many groups of polymeric substances and condensation polymers, which are known from the relevant literature ( e.g. Encyclopedia of Polymer Science and Engineering, Verlag John Wiley & Sons (1986), Vol. 6, pp. 707 to 725; Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley & Sons, 3rd edition, Vol. 18, S. 595 to 611; Ullmann's Encyclopedia of Industrial Chemistry, Verlag Chemie, Weinheim / Bergstr., 4th edition, vol. 11 pp. 206/207, 291 ff.) Are known, for example in the groups of polyesters and polyamides with predominantly aromatic Building blocks, the fully aromatic polyethers, the aromatic polyurethanes, the polyarylene sulfides, the polybenzimidazoles, the polyether ketones, the polyether sulfones and the polyetherimides.

Highly technically particularly valuable high polymers which can be processed into size-free chemical fibers by the process according to the invention are those of the series of polyether ketones, polyether sulfones and polyether imides.

Based on the available literature (e.g. J. Brandrup, EH Immergut, Polymer Handbook, Verlag John Wiley & Sons (1975), Tab. Pp. III-139 to III-179) or by simple known analytical analysis, it is possible to select from the above-mentioned groups of melt-spinnable high polymers , those are selected whose glass transition temperature is greater than 100 ° C. In the same way, the person skilled in the art can determine whether a melt-spinnable high polymer selected by him from other points of view has a glass transition temperature of> 100 ° C. and can therefore advantageously be processed into size-free chemical fibers by the process according to the invention.

It was extremely surprising that it is technically so simple to prepare synthetic fibers without the need for a complex washing and cleaning process.

This is not only apparent from the fact that despite the obvious economic senselessness of first applying a sophisticated preparation to the fibers, laboriously washing off this preparation after the fiber material has been finished and finally also treating the washing water in an ecologically harmless manner for the preparation of preparation-free chemical fibers no easier path has been taken, but it also becomes clear if one looks at the previous man-made fiber production process and observes its reaction to changes in the process conditions.

If in the usual way prepared synthetic fibers from melt-spinnable high polymers with the help of If godet pairs (or individual godets with laying rollers) are to be stretched, they are normally passed over a heated pair of godets before stretching and then over at least one further pair of godets, the surface speed of which is above the surface speed of the first pair of godets by the desired stretching ratio and which may be heated can. The person skilled in the art knows that for a low-interference stretching, the surface temperature of the first pair of godets must be set approximately in the order of magnitude of the glass transition temperature (T _g ) of the polymer and must not deviate strongly from this temperature. The setting of significantly higher surface temperatures leads to the drawing process being disturbed because the yarn or individual filaments stick to the godet surface. Also, at a surface temperature that is more than about 30 ° C above the glass transition temperature of the polymer, the orientation is no longer as high for a given stretching ratio as when a surface temperature between T _g and T _g + 30 ° C is selected.

The temperature of the preheating godet, at which there is a perfect stretching of the prepared fibers, still depends to a certain extent on the other process conditions and the mechanical conditions. The godet temperature for stretching prepared fibers is therefore routinely optimized in individual cases.

If, for the preparation of preparation-free chemical fibers, in particular from high polymers with glass transition temperatures above 100 ° C, the commonly used preparation (either water-based or water-free on the basis of mineral oils) is replaced by a liquid that can evaporate without residue at the stretching temperature, e.g. by pure Water, one observes a strong one with unchanged adjustment of the stretching device Deterioration in running properties. The stretching force rises sharply and begins to fluctuate very much and there are many breaks in individual filaments or the entire yarn breaks.

This deterioration in running behavior is also due to a moderate change in the temperature of the preheating godet, e.g. by 10 to 20 ° C up or down, not to be fixed.

Surprisingly, however, it has now been shown that a very strong increase in this temperature, namely by 40 to 70 ° C., beyond the temperature which is optimal for stretching with preparation, can improve the stretching behavior again in such a way that there is no longer any difference to the driving style Preparation exists.

In the method according to the invention, the optimal godet temperature can be selected by observing the stretching process, which should run smoothly over long periods, or by measuring the fluff numbers with the aid of commercially available measuring devices. However, the godet temperature is preferably and more precisely set so that the drawing tension at the same drawing ratio is as high as it was when drawing with a preparation application.

The method according to the invention thus allows the production of preparation-free fibers without complex washing processes and shows a way of avoiding the generation of undesirable preparation vapors and deposits when stretching over heated godets.

The following exemplary embodiments illustrate the implementation of the method according to the invention in comparison to the conventional one.

Example 1 (comparison)

This comparative example describes the drawing of threads from an aromatic polyether ketone, which were provided with a preparation in the usual way after spinning: A commercially available aromatic polyether ketone (®Victrex PEEK from ICI) was spun into a multifilament with 50 individual filaments and immediately after Spinning in the usual way wetted with a preparation which consists of an emulsion of 6% by weight of mineral oil and 9% by weight of non-ionic and anionic emulsifiers in 85% by weight of water, such that about 1% (based on the fiber weight) non-aqueous preparation components were present on the spinning thread.

The thread prepared in this way was stretched over a drafting system comprising 4 pairs of godets. They had the peripheral speeds, temperatures and wrap numbers shown in Table 1: Table 1 Speed (m / min) Temperature (° C) Wraps 1st pair of godets 317.7 25th 5 2. " 322.0 160 3rd 3. " 618.3 25th 5 4. " 615.5 25th 5
Under these conditions, perfect stretching was possible. The drawn thread had about 27 cN / tex tensile strength and 40% elongation at break.

Example 2 (comparison)

Comparative example 1 was repeated with the difference that instead of the preparation used there, only demineralized water was applied to the filaments.

With the setting of the drafting system unchanged, so many thread breaks occurred that continuous drawing was not possible. A change in the temperature of the second pair of godets of up to 20 ° C up or down did not noticeably improve the course of the stretch.

Example 3

Example 2 was repeated with the difference that the temperature of the second pair of godets was increased from 160 ° C. to 220 ° C. All other settings have been retained.

Under these conditions, perfect stretching was again possible. The drawn thread had 28 cN / tex tensile strength and 41% elongation at break.

Example 4 (comparison)

In this comparative example, the machine setting of example 3 was retained, but the spinning thread was again prepared using the preparation described in example 1. Continuous stretching was again not possible under these conditions because the thread lengthened on the second pair of godets, adhered to the surface and tore off.

Table 2 summarizes the essential statements of the examples. Table 2 example preparation Temperature d. 2. Galette Stretching 1 (comparison) conventional 160 ° C Good 2 (comparison) water 160 ± 20 ° C impossible 3 (invention) water 220 ° C Good 4 (comparison) conventional 220 ± 20 ° C impossible

Claims (5)

1. A process for producing spin-finish-free manmade fibers by melt spinning high polymers having a glass transition temperature of above 100°C and subsequently drawing the filaments by means of preheater godets to a preset draw ratio, which comprises impingeing the filaments prior to drawing with a liquid which can evaporate residuelessly during drawing and selecting the temperature of the preheater godet not less than 40°C higher than in the customary procedure involving spin finish.
2. The process as claimed in claim 1, wherein the residuelessly evaporating liquid used comprises an aliphatic compound of 2 to 8 carbon atoms containing OH groups and/or ether groups, or water.
3. The process as claimed in at least one of claims 1 and 2, wherein the residuelessly evaporating liquid used is pure water.
4. The process as claimed in at least one of claims 1-3, wherein the temperature of the preheater godet is set not less than 50°C above the glass transition temperature.
5. The process as claimed in at least one of claims 1-4, wherein the temperature of the preheater godet is set sufficiently high that the drawing tension for a given draw ratio corresponds to that for spin-finished filaments.