EP0455193B1 - Interlaced multifilament yarn made from high modulus single filaments and method of making such a yarn - Google Patents

Abstract

An entangled multifilament yarn made of high-modulus individual filaments, such as, for example, aramide, carbon or glass, and a method of making this yarn are described. Customary air entangling is virtually unusable in the case of high-modulus yarns, since, owing to their brittleness, they have a tendency to break, which leads in particular to a substantial decrease in the tenacity. The invention proposes to carry out the entangling at elevated temperature, either by preheating the yarn or by heating the entangling air. Surprisingly, it has been shown that this substantially avoids a lowering of the tenacity at relatively low entanglement spacings and in some cases even makes it possible to increase the tenacity. The multifilament yarn made by this process is distinguished in particular by a small number of breaks of the individual filaments. The invention is also applicable to so-called comingled yarns in which only a portion of the yarn consists of high-modulus filaments and the other portion of thermoplastic filaments. <IMAGE>

Description

The invention relates to a method for producing a multifilament yarn with a total denier of 500-4000 dtex, preferably 700-3000 dtex, in which at least part of the yarn consists of high-modulus individual filaments of an initial modulus of more than 50 GPa, preferably more than 80 GPa which method the yarn is swirled by a swirling medium, in particular air, and such a multifilament yarn.

Such high modulus yarns made from liquid crystalline or special high polymers with less flexible chains, e.g. Aramid, carbon and glass are generally very stiff. The conventional method of air interlacing, such as is used to increase the thread closure or to mix with other yarn components, leads to considerable difficulties, especially with a high degree of interlacing, because the individual filaments are difficult to intermingle due to their stiffness and tend to break due to their brittleness , which results in a significant reduction in the fineness-related maximum tensile strength (fineness strength). The thread closure of these yarns is then insufficient, and because of the large number of breaks in the individual filaments, it is not possible to produce a smooth, lint-free yarn. A strong air turbulence of such high modulus yarns therefore does not lead to results that are acceptable in practice.

The present invention is intended to create a method for producing a high-modulus multifilament yarn and such a multifilament yarn which has a high thread closure and is as smooth and lint-free as possible. In particular, a reduction in the fineness-related maximum tensile force due to the intermingling should be avoided as far as possible.

To achieve this object, a method with the features specified at the outset is characterized in that the intermingling is carried out at a temperature of (0.25-0.9) T _s , in which T _{s is} the melting or decomposition temperature of the high-modulus individual filaments , measured in ° C.

According to the invention, the multifilament yarn is characterized in that the average intermingling distance of the yarn, measured in the needle test (using the ROTHSCHILD ENTANGLEMENT TESTER 2050), is less than 150 mm and the number of breaks in the individual filaments, measured in the light barrier method on one side of the yarn, is less than 20 /damn.

The intermingling basic patent US 29 85 995 already contains the general information that the intermingling of yarns can be carried out at elevated temperature and that, in particular when the yarn tension is too high and / or the intermingling medium pressure is too low, a certain plasticization of the yarn by moistening and / or warming favors the vortex. This idea is taken up in US Pat. Nos. 30 69 836 and 30 83 523, in which yarns made of polyester or polyamide are interlaced with heated air in order to produce yarns with particularly low shrinkage. In EP-PS 01 64 624 a polyester yarn is swirled with heated air so that the yarn can be wound up in the heated state. Finally, DD-PS 240 032 describes the production of a yarn made of polyamide, polyester or polyolefin, in which the yarn is treated with steam or moist hot air in a thread-closing device in order to obtain a silk that can be wound up perfectly.

In contrast to this prior art, the present invention is based on the knowledge that, in the case of particularly high-modulus multifilament yarns, warm intermingling, in contrast to cold intermingling, has practically no reduction in the fineness-related maximum tensile force and can even lead to an increase in the maximum tensile force. In fact, the invention succeeded for the first time in producing a highly intermingled multifilament yarn with a starting modulus of more than 50 GPa, which has a high thread closure has, smooth and practically lint-free and its fineness-related maximum tensile strength is not or not significantly less than that of the unwired yarn.

The yarn is expediently interlaced so strongly that the average interlacing distance of the yarn, measured in the needle test, is less than 150 mm, preferably less than 70 mm or 50 mm.

Conventional swirl nozzles can be used for swirling. The swirl distance or swirl density is primarily determined by the pressure of the swirl medium and the special type of nozzle. Therefore, in order to achieve a desired swirl distance, an appropriate swirl pressure must be selected for a specific nozzle type. The working pressure is expediently in the range from 1 to 10 bar, preferably 1.5 to 8 bar and in particular 2 to 4 bar.

The fluidization temperature is preferably (0.5-0.9) T _s , in particular (0.7-0.8) T _s . If, for example, the high modulus individual filaments are made of aramide, the fluidization temperature is expediently in the range of 200-360 ° C, preferably at 300 ° C. In the case of carbon, the fluidization temperature should be between 200 ° and 500 ° C, preferably between 300 ° and 500 ° C. If the high-modulus individual filaments are made of glass, the swirl temperature is 300 ° -600 ° C, preferably 300 ° -500 ° C.

The high-modulus individual filaments can be heated to the swirling temperature before intermingling, the heating being able to be carried out by means of godets, heating surfaces, heating tubes, radiant heating under pre-tensioning or hot air. If the entire yarn consists of the high modulus individual filaments, the intermingling medium can also be heated to the intermingling temperature.

The invention can be used not only with one-component yarns, but also with so-called commingled yarns, in which only part of the yarn is made of high-modulus individual filaments and the other part is made of thermoplastic Individual filaments of a lower initial module exist. The term "commingled yarn" is explained, for example, in chemical fibers / textile industry (industrial textiles), 39/91, T 185 (1989). In this case, only the high modulus individual filaments are preheated to the fluidization temperature, while the lower melting thermoplastic individual filaments are not preheated and the fluidization medium is not heated.

The thermoplastic single filaments with a lower initial module are e.g. PEEK (polyether ether ketone), PEI (polyether imide), PET (polyethylene terephthalate) and PPS (polyphenylene sulfide) in question.

As already mentioned, the multifilament yarn produced according to the invention is characterized in that the number of breaks in the individual filaments is less than 20 per meter. The number of breaks is preferably even less than 10 / m and can even be almost zero, in particular less than 3 / m and very particularly preferably less than 0.1 / m. The breaks of the individual filaments are measured by the usual light barrier method, which detects the broken ends of the individual filaments projecting on one side of the yarn (for example with a Shirley Hairiness Meter, Shirley Institute, Manchester).

An important feature of the multi-filament yarn designed in accordance with the invention is that the fineness-related maximum tensile force is significantly higher than in the case of a cold intermingling of the yarn. On the one hand, this may be due to the lower number of breaks in the individual filaments and, on the other hand, in a more advantageous alignment of the individual filaments. If it is a one-component yarn that consists of the high modulus single filaments, the fineness-related maximum tensile strength of the interlaced yarn should be at least 80% of that of the non-interlaced yarn. It is often possible to achieve a fineness-related maximum tensile strength of at least 90% and in certain cases more than 100% of that of the non-interlaced yarn.

Even in the case of commingled yarns, the invention leads to an increase in fineness-related maximum tensile force compared to cold-twisted yarns. In fact, the commingled yarns are also characterized by high thread closure and great smoothness, which can even make the yarns suitable for weaving.

Examples of the invention are explained on the basis of diagrams shown in the figures. Show it:

FIGS. 1-5 diagrams in which the relationship between the fineness-related maximum tensile strength (fineness strength) and the warm intermingling provided according to the invention is shown for aramid multifilament yarns;

FIGS. 6 and 7 are diagrams which, for glass and carbon multifilament yarns, show the relationship between the tenacity and the warm intermingling provided according to the invention;

FIG. 8 shows a diagram in which the tenacity of single-component yarns and commingled yarns according to the invention is shown.

The diagram shown in FIG. 1 shows the tenacity (in cN / tex) of a commercially available aramid yarn, the broken curve a for a yarn with a twist Z100 and the curve b for an unthreaded yarn examined for experimental purposes. The left ends of the two curves refer to the non-swirled feed yarn, while the middle of the curves apply to a cold-swirled yarn and the right ends of the curves apply to a yarn according to the invention, which was swirled after preheating to 300 ° C.

As the two curves make clear, the fineness of strength drops considerably in the case of cold swirling, while it is essentially retained in the case of the warm swirling provided according to the invention. Below the diagram, the intermingling distance (in mm) of the yarn is shown, which in the case of the cold-twisted yarn is 32 mm and in the case of warm-twisted yarn is 19 mm.

The diagram in FIG. 2 shows the relationship between the tenacity and the intermingling temperature, specifically for another commercial aramid yarn with twist Z100. In this case, as can be seen, the tenacity increases with the turbulence temperature. The intermingling distance is largely independent of the intermingling temperature.

The diagram in FIG. 3 shows the relationship between the tenacity and different types of heating for the aramid yarn used in FIG. For example, the yarn was preheated to 300 ° C with godet or preheated to 300 ° C or 400 ° C with hot air, and as a further possibility, the interlacing air was heated to 300 ° C. This diagram also makes it clear that the fineness of strength drops significantly in the case of cold swirling, while it remains practically the same or increases in the case of the warm swirling provided according to the invention.

In addition to the tenacity (curve I), the diagram in FIG. 4 also shows the elongation (in%, curve II) for the aramid yarn used in FIG. The four breakpoints of the two curves apply to the non-swirled feed yarn without twist, the non-swirled feed yarn with twist Z100 and the warm-twirled yarn with and without twist. With this yarn too, the warm interlacing leads to a certain increase in the tenacity, while the elongation remains almost constant.

The diagram in FIG. 5 shows a series of measurements corresponding to curve I in FIG. 4 in the form of a bar diagram for another commercially available aramid yarn. It can be seen in the diagram that the swirling according to the invention does not lead to a decrease in strength. It can also be seen that when the yarns are twisted (non-intermingled and intermingled) there is an increase in strength occurs, which is larger in the interlaced yarn than in the non-interlaced yarn.

The diagram in FIG. 6 shows the tenacity of a multi-filament yarn made of glass, which was present once as an untreated master yarn, then as a cold-twisted yarn and finally as a warm-twisted yarn. In the case of warm intermingling, the yarn was preheated with hot air, once to 300 ° C and the other to 600 ° C. The swirl pressure was 1.0 bar in each case.

As can be seen from the diagram, in the case of glass yarn too, the cold interlacing leads to a significant reduction in the tenacity, while it is retained or increased during the warm interlacing.

The same relationship is shown in the diagram in FIG. 7, in which the lower curve applies to a type E glass yarn and the upper curve applies to a carbon yarn.

The diagram of FIG. 8 shows the tenacity for intermingled and non-intermingled single-component yarns of different materials as well as for different commingled yarns. The cross-hatched columns apply to non-interlaced yarns made of aramid, carbon, glass or PEEK. The cross-hatched columns apply to warm-twisted yarns of the same materials. Finally, the columns hatched with dashed lines apply to commingled yarns made of aramid, carbon or glass, to which PEEK has been added.

It applies to all diagrams that the swirl temperature was 300 ° C. during hot swirling, unless otherwise stated in the diagrams.

Claims (12)

1. A process for producing a multifilament yarn having a total linear density of 500-4000 dtex, preferably 700-3000 dtex, and consisting at least in part of high modulus monofilaments having an initial modulus of more than 50 GPa, preferably more than 80 GPa, by intermingling the yarn using an intermingling medium, in particular air, which comprises intermingling at a temperature of (0.25-0.9)T_m, preferably (0.5-0.9)T_m, where T_m is the melting temperature or decomposition temperature of the high modulus monofilaments, measured in °C.
2. The process of claim 1, wherein the yarn is intermingled using a jet and an intermingling medium at a pressure of 1-10 bar.
3. The process of either of claims 1 and 2, wherein the high modulus monofilaments are made of aramid and the intermingling temperature is 200-360°C, preferably 300°C.
4. The process of either of claims 1 and 2, wherein the high modulus monofilaments are made of carbon and the intermingling temperature is 200°-500°C, preferably 300°-500°C.
5. The process of either of claims 1 and 2, wherein the high modulus monofilaments are made of glass and the intermingling temperature is 300°-600°C, preferably 300°-500°C.
6. The process of any one of the preceding claims, wherein, prior to being intermingled, the high modulus monofilaments are heated to the intermingling temperature, which may be done by preheating in particular with a godet, heating panel, heating pipe, radiative heating under pretension or hot air.
7. The process of any one of the preceding claims, wherein the entire yarn consists of high modulus monofilaments and the intermingling medium is heated to the intermingling temperature.
8. The process of any one of claims 1 to 6, wherein the yarn only partly comprises high modulus monofilaments, the remainder comprising thermoplastic monofilaments of a lower initial modulus, preferably made of PEEK, PEI, PET or PPS, and only the high modulus monofilaments are preheated to the intermingling temperature and the intermingling of the two parts is carried out with an intermingling medium which is not being heated.
9. A multifilament yarn of a total linear density of 500-4000 dtex, preferably 700-3000 dtex, which consists at least in part of high modulus monofilaments having an initial modulus of more than 50 GPa, preferably more than 80 GPa, and has been intermingled, wherein the average entanglement spacing of the yarn, measured in the pin count test using the Rothschild Entanglement Tester 2050, is less than 150 mm, preferably less than 70 mm, and the number of broken monofilament ends, measured by the light barrier method on one side of the yarn, is less than 20/m, preferably less than 0.1/m.
10. The multifilament yarn of claim 9 which consists of high modulus monofilaments only and whose tenacity is at least 80%, preferably more than 100%, of that of the unintermingled yarn.
11. The multifilament yarn of either of claims 9 and 10, wherein the high modulus monofilaments are made of aramid, carbon or glass.
12. The multifilament yarn of any one of claims 9 to 11, wherein only part of the yarn comprises high modulus monofilaments while the other part comprises thermoplastic monofilaments of a lower initial modulus which are made in particular of PEEK, PEI, PET or PPS.

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