EP0976854B1 - Monofilamentary bicomponent core-sheath fibres - Google Patents

Abstract

Core-sheath bicomponent monofilaments have a core containing a liquid crystal polymer and a homogeneous sheath containing a polyester. An Independent claim is also included for the production of the monofilaments by melt extrusion and cooling in a gas stream or liquid below the spinneret to a temperature at least 0-30 degrees C below the glass transition temperature of the sheath material, such that the ratio of the spinning speed (in volume/area - time) to haul-off speed is 1:5-30, preferably 1:(8-15). The monofilament may then be wound up and conditioned.

Description

The invention relates to monofilaments in the form of bicomponent threads Core sheath types which comprise a core which is a liquid crystalline polymer contains, their production and their use in particular for Manufacture of paper machine fabrics.

A monofilament in the sense of the invention is to be understood as an endless yarn which consists of a single continuous fiber, which is made with or without twist and which have a diameter of at least 0.01 mm, preferably at least 0.08 mm, in particular 0.1 mm and more. It is different from Individual filaments in the form of core sheath threads, which are usually used for textiles Purposes are made, especially by the significantly higher Diameter.

Monofilaments are mainly used for the production of technical articles, in particular technically used fabrics, in contrast to Multifilament yarns that are made up of fine individual filaments and before used mainly in the textile industry.

Monofilaments in the form of bicomponent threads of the core sheath type are in themselves are already known and are described for example in EP 0 763 611 A1. The core component there is a polyester, whereas the sheath is a polyamide is. The polyester of the core can also be a liquid-crystalline polymer. Around To improve the adhesion between the core and the sheath component, the Coat a polymer that promotes adhesion.

Despite the use of an agent supporting liability, liability is waived still to be desired, so that it is, especially with strong mechanical Stress, to a separation of core and shell component, at least in part, which comes down to the mechanical properties of the products produced in such monofilaments. The strengths are too still in need of improvement.

According to the teaching of Japanese patent application JP-07 / 097,719-A Multi-component threads of the core sheath type are produced, in which the core is made of an aromatic polyester and the jacket is a semi-aromatic Contains polyamide. Notes on the production of monofilaments can be found in the abstract not to be inferred from this Japanese application; liability also leaves here between the core and the coat left something to be desired.

In Japanese patent application 1992/370 322 or the corresponding Japanese patent J 04 272 226 describes monofilaments which consist of a Core exist, the core component being an optically anisotropic in the Contains melt processable aromatic polyester material and Sheath component is an oriented crystallized flexible high polymer. Indications of a jacket component, which consists of mixtures of polymers, in particular from mixtures of polyester and 1-5% by weight of polycarbonate do not exist in this document.

Japanese patent application 1992/370 321 also describes monofilaments with an A Component as a core component and a B component as a sheath component described, wherein the B component consists of 80% polycarbonate. Bicomponent monofilaments in which the jacket component is made of polyester and 1 - 5% by weight Polycarbonate are not described in this document and are not suggested.

Finally, a core sheath filament is disclosed in Japanese patent application JP-07 / 243,128 described, which has a liquid-crystalline polyester core and a jacket thermoplastic polymer. This thermoplastic polymer of the shell forms a so-called Sea component and contains an anisotropic aromatic polyester as so-called island components. That is, the jacket is constructed from a matrix of a thermoplastic polymer, in which contains larger deposits that are not compatible with the matrix. Although a number of monofilaments of the core sheath type, in which the Core contains a liquid-crystalline polymer, are known, there is still one Need for improved monofilaments of this type.

The object of the invention is therefore to monofilament in the form of bicomponent threads of the core shell type, which fall over a core which contains a liquid-crystalline polymer and a surrounding this core Sheath, in which the cohesion between the core and The sheath component is very good and does not tend to fibrillate, a very high one Have abrasion resistance and good strength and where the jacket has a has an excellent protective effect on the core.

This object is achieved by monofilaments according to claim 1.

Particularly advantageous embodiments of the monofilaments according to the invention are given in claims 2 to 11.

The invention further relates to a method for producing this Monofilaments according to claim 12 and the use of the monofilaments according to of the invention according to claims 13 to 15.

The production of the monofilaments according to the invention can be carried out in the following way happened:

The core and the sheath component are melted separately in the extruder and spun in a one-step process in a bicomponent spin pack. After leaving the spinneret, the emerging monofilaments are below the Spinneret in a shaft, for example with a tempered gas flow cooled. It is also possible to cool the threads with the help of a liquid. The threads are cooled down to a temperature which is preferably at least 0 to 30 ° C below the Glass conversion of the cladding material lies. Spray speed and trigger (the so-called spinning speed) are coordinated so that a Delay of at least 1: 5 to 1:30, preferably 1: 8 to 1:15, is reached.

As the final spinning and also through the quenching process Properties of the monofilament can already be determined is not one Post-stretching still reduces shrinkage via thermal Fixing process with shrinkage approval required. It is not one either Post-stretching required. By coordinating the deduction conditions it is possible to give the monofilaments a partial orientation, it can be pure amorphous or partially crystalline states can be achieved.

In general, the monofilaments are wound up after the spinning take-off.

It is possible to anneal the monofilaments in a further step. It did turned out to be advantageous if one allowed the annealing within a certain Temperature range. For example, tempering is possible to start at 200 ° C and then continuously up to, for example, 270 ° C increase. The tempering conditions naturally depend in particular on the jacket material used. The maximum temperature should be 20 to 30 ° C are below the melting temperature of the jacket polymer.

A conventional liquid-crystalline polymer can be used as the core component become. A single polymer can be used, but it is also possible to mix several liquid-crystalline polymers. there the mixture should be spun as homogeneously as possible. Instead of mixtures of purely liquid-crystalline polymers can also be mixtures one or more liquid crystalline and one or more not liquid-crystalline polymers are used.

Polycondensation products are preferred as liquid-crystalline polymers Base of p-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid, in particular those which are composed of 70 to 80, preferably 72 to 74 mol% of p-hydroxybenzoic acid and 20 to 30, preferably 26 to 28 mole% 2,6-hydroxynaphthoic acid.

Usual polyesters such as Polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, but also polyethylene 2,6-naphthalate or poly (1,4-bis (hydroxymethyl) cyclohexane terephthalate are used.

These polyesters can be used alone or as a mixture.

The polycarbonates used as a further component are commercially available available; this has proven to be very suitable under the Makrolon trade name distributed product proven. Polycarbonates are suitable in the context of Invention as a sheath component, especially when mixed with other polyesters.

In a particularly advantageous embodiment of the invention, the Sheath one or more elastomeric polyesters. These are in particular Copolyesters based on dicarboxylic acids such as terephthalic acid or their Derivatives and a diol such as 1,4-butanediol or ethylene glycol and one Polyglycol, in particular for example the polyglycol based on Tetrahydrofuran.

Polytetrahydrofuran butylene terephthalate is preferred. This elastomeric polyester can be built up, for example, by polycondensation of dimethyl terephthalate, butanediol and polytetrahydrofuran of the formula HO (CH ₂ CH ₂ CH ₂ CH ₂ O) _n H.

n is an average and can take different values, correspondingly high then the molecular weight is in the order of about 600 to about 2,000, especially in the order of 1,000, is advantageous. a average molecular weight of about 1,000 corresponds to an average of n 17th

The sheath of the monofilament bicomponent thread should be essentially homogeneous be, i.e. have no macroscopically detectable heterogeneous structure, such as for example a matrix with embedded discrete islands. With mixtures single-phase mixtures are preferred. For components that are used in the Extrusion temperature itself in two phases side by side is through vigorous mixing, for example intensive stirring, for a corresponding To ensure homogenization.

Suitable temperature control conditions can be selected by simple preliminary tests in order to obtain optimal properties. It is convenient to temper over a period of time, preferably over several hours, perform.

The physical properties of the monofilament according to the invention, such as Strength, modulus, shrinkage, shrinkage force and creep behavior under load and temperature, are largely due to the physical Properties of the core determined. The main task of the coat is to create the core protect against fibrillation, abrasion and soiling. Furthermore, the Coat the processing and improve the usage behavior.

The monofilaments of the invention can be advantageous for a whole Use a number of uses, such as manufacturing Fabrics for papermaking, for example for screen fabrics, such as those used in the Sheet forming section, the press section and the drying section of Paper machines are desired, filter fabrics can also be produced Conveyor belt fabric, coated or uncoated. The Monofilaments, for example, can only be used as weft material but it is also possible to completely remove the tissue from the invention To produce monofilaments. Another intended use Fabric is the reinforcement in car tires; made accordingly Fabrics can also be used for screen printing.

It was particularly surprising that the monofilaments according to the invention were considerable are better protected against fibrillation that they can easily be rewound and both as warp and as weft when used for the production of Fabrics can be used. The monofilaments are characterized by a particularly low tendency to creep.

By adding carbodiimide, especially in the jacket component, can the already good resistance to hydrolysis is still considerable improve. This increases the residual strength after 85 hours at 135 ° C Saturated steam treatment from 85% to over 90%.

The invention is illustrated by the following examples:

example 1

The product Vectra A 910 was used as the fully aromatic polyester for the core (LCP) selected, a blend consisting of 96.4% of the Polyethylene naphthalate Polyclear N 100 (PEN), 3% from Vectra A 910 as it is also used in the core, and 0.6% from the carbodiimide Stabaxol 1.

Both materials were melted in an extruder and over Gear pumps pressed into a bicomponent spin pack. The melt temperature in the pack was 330 ° C. The Vectra A 910 formed the core current, the blend the rotationally symmetrical sheath flow.

A spinneret with 40 holes was used, each spinning orifice with one Fine bore of 0.80 mm. The promotion per nozzle hole was 5.79 g / min for the core flow and 2.48 g / min for the sheath flow. So the core takes about 70% of the cross-sectional area, the jacket about 30% of the cross-sectional area of the monofilament under the nozzle.

Below the nozzle, the monofilaments were placed in a water bath with a pulley guided. The water temperature was 95 ° C, the distance between the spinneret and the water surface 20 cm. There was a behind the water bath Deduction drafting system.

The calculated spraying speed was 11.82 m / min Take-off speed of the drafting system 130 m / min. This results in a Spin delay of 1:11. This condition was frozen in a water bath. Behind the drafting system, the monofilaments were wound on metal spools.

• Aufheizen von Raumtemperatur auf 160°C in 70 min
• Temperung bei 160°C für 24 h
• Aufheizen von 160°C auf 180°C in 30 min
• Temperung bei 180°C für 24 h, anschließend Abkühlung auf Raumtemperatur (ca. 2 h)

In a second step, the wound monofilaments were subjected to the following thermal aftertreatment in a forced air oven:

• Heating from room temperature to 160 ° C in 70 min
• Annealing at 160 ° C for 24 h
• Heating from 160 ° C to 180 ° C in 30 min
• Annealing at 180 ° C for 24 h, then cooling to room temperature (approx. 2 h)

The following textile values resulted after this thermal treatment: diameter 0.50 mm module > 60 GPa spec. strength 85 cN / tex Elongation at break 2.2% to 2.5% free thermal shrinkage at 180 ° C <0.1%

Example 2

An LCP (Vectra A 910) for the core was used as a fully aromatic polyester selected, as a sheath material a blend of 10% isophthalic acid modified polyethylene terephthalate, the proportion of which is 40% of the mixture makes up, and 40% of an elastomeric copolyester (Riteflex 655).

Both materials were melted in an extruder and over Gear pumps pressed into a bicomponent spin pack. The melt temperature in the pack was 285 ° C. The Vectra A 910 formed the core stream, the copolyester blend the rotationally symmetrical sheath flow.

A 40-hole spinneret was used, each spinning orifice with one Fine bore of 0.80 mm. The delivery was 319.6 g / min, of which 147.3 g / min for the core flow and 172.3 g / min for the sheath flow. The core takes about 45%, the jacket about 55% of the cross-sectional area of the under the nozzle resulting monofilament.

Below the nozzle, the monofilaments were placed in a water bath with a pulley guided. The water temperature was 92 ° C, the distance between the spinneret and the water surface 8 cm. There was a behind the water bath Deduction drafting system.

The calculated spraying speed was 11.82 m / min Take-off speed of the drafting system 130 m / min. The spinning delay was 1:11. This condition was frozen in a water bath.

The monofilaments were wound up on disc spools behind the drafting system. A thermal aftertreatment (as in Example 1) did not take place.

The following textile values were obtained for the monofilaments: diameter 0.60 mm titres 3,803 dtex module 28 GPa spec. strength 40 cN / tex Elongation at break 2.5% to 2.8% Thermal shrink at 180 ° C <0.2%

Claims (15)

1. Monofilaments in the form of bicomponent core-sheath-type threads having a core which contains a liquid-crystalline polymer and a substantially homogeneous sheath which consists of a mixture of 1 to 5% by weight of polycarbonate, the remainder to 100% consisting of one or several polyesters which are not polycarbonates.
2. Monofilaments according to claim 1, characterised in that the sheath contains polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate or poly-(1,4-bis-hydroxymethyl)-cyclohexaneterephthalate.
3. Monofilaments according to claim 1, characterised in that the sheath contains an elastomeric polyester.
4. Monofilaments according to claim 3, characterised in that the sheath contains polytetrahydrofuran-butylene-terephthalate as an elastomeric polyester.
5. Monofilaments according to at least one of claims 1 to 4, characterised in that the sheath contains 1 to 15% by weight of the liquid-crystalline polymer of which the core is made.
6. Monofilaments according to at least one of claims 1 to 5, characterised in that the sheath consists of a mixture containing 1 to 20% by weight of a fluorine-containing polyolefin and the remainder to 100% by weight of polyester together with 1 -5 % by weight of polycarbonate.
7. Monofilaments according to at least one of claims 1 to 6, characterised in that the cross-sectional-area of the core is 40- 90% of the entire cross-section area of the filament and the cross-sectional area of the sheath is 10 - 60% of that entire area.
8. Monofilaments according to at least one of claims 1 to 7, characterised in that the monofilament has a round, oval, rectangular or n-comered cross-section configuration, where n≥3.
9. Monofilaments according to at least one of claims I to 8, characterised in that the core is located centrally.
10. Monofilaments according to at least one of claims I to 9, characterised in that the core is located asymmetrically.
11. Monofilaments according to at least one of claims I to 10, characterised in that the core and / or sheath comprises 0.1 to 3 % by weight of mono- and or polycarbodi-imide as an end-sealing agent.
12. Procedure for the production of monofilaments in the form of bicomponent core-sheath-type threads, characterised in that a core material which contains a liquid-crystalline polymer and a substantially homogeneous sheath material comprising a mixture of 1 to 5 % by weight of polycarbonate and the remainder to 100% of one or several polyesters which are not polycarbonates are melt extruded through a die for the production of core-sheath-type threads and the emerging monofilaments are cooled by a temperature-controlled gas stream or liquid below the spinneret to a temperature which is at least 0 -30 °C below the glass-transition temperature of the sheath material, whereby the ratio of the emerging speed (spinning speed) expressed in volume per area and time and the drawing speed is so controlled that a spinning draw of 1:5 to 1:30, preferably 1: 8 to 1: 1.15 is obtained and whereby the monofilaments are optionally wound up and optionally heat-treated.
13. Use of the monofilaments according to at least one of claims 1 to 11 or produced in accordance with a method in accordance with claim 12 for the production of sieves and filters.
14. Use of the monofilaments according to at least one of claims 1 to 11 or produced in accordance with a method in accordance with claim 12 for the production of paper-machine clothing and, in particular, for the forming section, the press section and the drier section.
15. Use of the monofilaments according to at least one of claims 1 to 11 or produced in accordance with a method in accordance with claim 12 for the reinforcement of elastomers.