NO131732B - - Google Patents

Description

Synthetic core-sheath type antistatic filament.

The use of a thinly insulated, electrically conductive thread with non-conductive, synthetic fibers for the production of carpets with low static electricity is described in US Patent No. 3639807" In carpets containing the conductive thread, this can be bent and pressed down and there -

by becoming less efficient. The use of electrically conductive carbon black dispersed in fibers for the production of antistatic textile materials is described in US patent documents No. 23^5962 and No. 3706195» However, these fibers have poor mechanical and physical properties,

e.g. brittleness and low tenacity (toughness), and may therefore prove to be not very durable with normal handling and use by consumers,

as recognized in US Patent No. 3582^8 in which conductive, carbon black-containing coatings (mantles) on synthetic filaments are described for anti-

static purposes.

In the U.S. patent documents no. 3<>>+75898 and no. 3558^19 describe synthetic, antistatic coating/core filaments, where polyethylene oxide is dispersed in the core or a special block copolymer of polyether and polyamide forms the core. Each of these solutions has, for certain purposes, been shown to provide an unsatisfactory reduction in the propensity of the filaments and textile materials produced from them to be charged with static electricity.

The invention provides a synthetic, antistatic filament consisting of a synthetic, thermoplastic polymer, preferably polyethylene, in which electrically conductive carbon black is dispersed so that the polymer is electrically conductive with an electrical resistance of less than 0.^ x 10<11> ohm/ cm when exposed to a direct current potential of 2 kV, and the filament is characterized by the fact that the polymer 'with the' electrically conductive carbon black forms the core of a bicomponent filament of the core-sheath type where the sheath consists of a synthetic, thermoplastic, fiber-forming polymer which is different from the core polymer, preferably polyamide.

The mantle must make up at least ^ 0% of the cross-sectional area of the filaments, i.e. at least 50 volume- of the cross-sectional area.

If they are to be used in low concentrations in a mixture with other filaments, the present filaments should preferably have a core with an electrical resistance of less than 0.<*>+ x 10^ ohm/cm at a direct current potential of 2 kV. It is preferred that the filaments have a molecularly oriented layer (mantle) as a result of an orientation obtained by spinning and/or stretching during the manufacture of the filaments.

Highly conductive core materials, i.e. "core materials that contain over 20% by weight of the aforementioned carbon black, are preferably used in filaments with a layer that makes up at least 80% of the filament's cross-sectional area"

By means of the present invention, antistatic filaments are provided which can be used in textile materials with a light colour. For such applications, the layer constitutes at least $0% of the filament, and the layer is made matte to partially shield the black core so that the filament is given a light reflectance as described below of over 20%. A preferred matte filament contains 2-7% by weight of titanium in oxy dpi gment in the layer.

With a suitable choice of the layer polymer, the antistatic filaments according to the invention can be colored as desired, made fuller under a number of different conditions and used for end purposes where the saleability of the layer is important.

It has surprisingly turned out that despite the fact that a main part

of the filament consists of the non-conductive layer which acts as electrical insulation, the filaments according to the invention can be used with very good results for antistatic protection (e.g. to prevent the accumulation of electrostatic charges) regardless of the relative humidity and in a very small portion of a weave, yarn or other textile material consisting mainly of other synthetic fibers or filaments that must be protected from the accumulation of electrostatic charges. In such textile materials, which may mainly consist of yarn and staple fibres, the main part is made up of non-conductive synthetic filaments and less than 20% by weight of a mixture of the present filaments. In such mixtures, the present filaments can provide excellent antistatic protection even when present in concentrations as low as less than 2% by weight, but the mixture preferably contains at least approx. 0.05% by weight of the present filaments» The layer polymer in such mixtures can be dyed at the same time as the non-conductive filaments, and more particularly the layer polymer can consist of the same type of polymer as the polymer in the non-conductive filaments.

The most preferred products according to the invention are conductive filaments which can especially be used for the production of carpets with a static tendency of less than 2.5 kV as measured by means of the below-described examination of the static tendency of carpets. The present filaments exhibit an excellent balance between electrical conductivity and antistatic properties while not leading to an unwanted color.

In the production of the present antistatic, synthetic filaments, an electrically conductive core material comprising an electrically conductive carbon black dispersed in a thermoplastic, synthetic polymer is spun in one operation into a layer/core filament, the core being surrounded by a non-conductive layer material of a synthetic, thermoplastic, fiber-forming polymer different from the core polymer, and the materials are spun in such relative amounts that the layer material will constitute at least $0% of the filament volume, after which the spun filaments are collected.

In the drawing, fig. 1 schematically shows a cross-section through a layer/core filament according to the invention and fig. 2 schematically a cross-section through an antistatic yarn comprising a mixture of filaments as shown in Fig. 1 and non-conductive, synthetic filaments"

According to that in fig. 1 shown filament cross-section 5, the core material 1 comprises a conductive material of carbon black 3 dispersed in a polymer matrix h which is surrounded by a layer material 2 comprising a non-conductive polymer.

In fig. 2 the filaments are located with a cross section of it on

fig" 1, type 5 appeared among a far greater number of non-conductive synthetic filaments 6.

The "non-conductive layer" of the present filaments is made of a synthetic fiber-forming polymer. The filaments have a surface resistivity of over 0.5 x 10 12 ohm/cm as measured when the filament surfaces are brought into contact with a low DC voltage of e.g. 100 V or less. Homofibers of such layer materials would also have an electrical resistance of over 0.^+ x 10 12 ohm/cm in a corresponding measurement. The term "fiber-forming" as used herein is intended to denote linear polymers with a high molecular weight that can be formed into fibers with sufficient strength and toughness.

Compared to the non-conductive layer with high electrical resistance, the filament's core has low electrical resistance and high electrical conductivity as soon as it comes into electrical contact, e.g. with electrodes that penetrate the layer and into the core, or by using surface contact electrodes and applying a sufficiently high electrical voltage so that this will strike through the layer and thereby establish electrical contact with the core"

For the latter case, i.e. the use of surface contact electrodes, as an applied direct voltage increases to several hundred, especially several thousand, volts, a point will occur where a registered or sudden bending of the electric current will cause the electric current to be conducted as described in the for-sock method set out below. As soon as an electric wire has been created in this way, the electric current will as a rule continue to flow even if the applied voltage is reduced, provided that the filament contact with the electrode of the measuring device does not change."

The low electrical resistance of these filament grinders shows that the tar maintains its electrical continuity over the entire length of the measured filament. Breaks in the continuity of the core between the measuring electrodes are manifested by a much higher electrical resistivity that will approach the electrical resistivity of the layer." Any breaks in the continuity of the core have not been shown to significantly adversely affect the antistatic properties of the present filaments. However, the continuity of the core is preferably maintained over the entire length of the present filaments, regardless of whether these are present as staple filaments or continuous filaments. It is essential that the core retains its continuity over a sufficient length of the filament to provide an effective antistatic network In conjunction with other such antistatic filaments" Filaments having a core of the specified electrical conductivity when examined by means of the method described below has been shown to provide effective antistatic protection.

The filament layer can consist of any extrudable, synthetic, thermoplastic, fiber-forming polymer or copolymer" Of these, mention may be made of the polyolefins, such as the polyethylenes and polypropylenes, polyacrylic polymers, polyamides and polyesters with a molecular weight that allows them to be formed into fibers0 The condensation polyamides of diamines and dicarboxylic acids and of amino acids, condensation polyesters, especially of terphthalic or isophthalic acids and lower glycols such as ethylene glycol, tetramethylene glycol and hexahydro-p-xylyenediol, and polyacrylonitriles are particularly suitable as layer polymers. Such polymers can, in a known manner, be modified in terms of their ability to take up dyes, e.g. by means of copolymerization to provide sites receptive to basic or acid dyes and to facilitate the mixing of the polymers and the simultaneous dyeing thereof with other colored or dyeable synthetic fibers'

The tensile strength and other physical properties of the present filaments are mainly dependent on the layer polymer. For high-strength filaments, layered polymers with a higher molecular weight and layered polymers that enable higher stretch ratios are used. Although, according to the invention, unstretched filaments can provide a sufficient strength for certain applications, stretched filaments are preferred.

The thickness of the layer must be sufficient to provide the desired protection of the core, for example that it must have sufficient firmness and resistance to heat and wear, and it must also help to prevent the core from showing if this is important. is generally required that the layer has a thickness of at least

3 /^m, the greater thicknesses being determined by the filament denier or

-diameter that can be used» Suitable layer thicknesses for common textile material diameters are 8-22 tj, m0 For in certain applications, such as

for example, when the filaments are to be subjected to high-temperature treatment, such as by increasing the filaments' bulk volume by means of hot fluid jets or by texturing, it is of essential importance that the layer has a sufficiently high melting point so that an unwanted softening or melting will be avoided under these conditions . A layer polymer with a high melting point, such as polyhexamethylene adipamide, is preferred over polycaproamide for such applications0

The filament core consists of an electrically conductive carbon black dispersed in a base mass of a thermoplastic polymer material" The core material is selected mainly on the basis of its electrical conductivity and workability. Carbon black concentrations of 15-50% can be used in the core. It has been shown that with carbon black concentrations of 20-35%, a preferred high electrical conductivity is obtained while at the same time a reasonably good machinability is preserved" The core materials used to form the core preferably have a specific electrical resistance of less than 200 ohm/cm , preferably below 50 ohm/cm0 In order to reduce the required amount as much as possible, it is useful to use known, specially produced, highly electrically conductive carbon black qualities0

Due to the fact that plastic materials tend to become reinforced or rigid if they contain large amounts of carbon black, it is preferred for the core to use the generally softer polymeric base materials with a low melting point (also with a lower transformation temperature of another order) instead of the stiffer polymeric matrix materials with a higher melting point. The polymer used in the core preferably has a lower melting point than the polymer used in the layer, and has a lower transformation temperature of a different order than the layer polymer" This facilitates the processing (e.g. prevents breakage in the core and disturbance of the distribution of carbon black particles) while the core and the finished filament retain their electrical conductivity. It is not of decisive importance that the core material as such can be spun into filaments, and the core polymer therefore need not be a fibre-forming polymer. The core polymer must be heat stable and extrudable under the conditions required for spinning the layer polymer. Suitable polymers for the core include the polyamides, polyesters, polyacrylic resins, polyethers, polycaprolactone and polyolefins (e.g. polypropylene and the LD and HD polyethylenes). The polymers can be mixed with other materials, such as oils and waxes, to facilitate processing" Copolymers can also be used, such as polyethylene/vinyl acetate copolymers"

The carbon black used can be dispersed in the core polymer using known mixing techniques. Care must be taken so that a sufficiently even dispersion of the carbon black used in the core polymer is obtained so that an extrusion can be carried out, without overmixing and the resulting possible reduction in the ability of the electrical conductor 0

In order to achieve satisfactory spinning, it is important that volatile material is removed from the polymers to which carbon black has been added, for the melt spinning. This can be done before or after the carbon black used has been incorporated into the polymeric base material. It can be useful to vacuum dry such polymers, e.g. for 16 hours under a weak vacuum at 68°C. Usual precautions are taken to prevent oxidative degradation during spinning, which is excluded by oxygen and the use of inert gas in the supply system for the polymer.etc„

In the composite filament, the conductive core only needs to have a cross-sectional area (which is directly proportional to the volume of the filament) so that the core will have the desired resistivities, and the cross-sectional area can be as low as Oi, 5 vol%0 The lower limit is mainly conditional on it being possible to produce layer/core filaments with a sufficiently uniform quality at the same time as maintaining sufficient core continuity at the low core volume.

The filaments according to the invention can be spun using ordinary spinning equipment for simultaneous spinning of the two polymers which make up the layer and the core respectively, taking into account the different properties of the two polymers. The filaments can be easily produced using known spinning techniques and by using such polymers as, for example, are described in US patent document no. 2936M320 In US patent document no. 2989793 further guidelines are given for such spinning of polyamides.

Normal stretching processes can be used for the filaments, but care must be taken to avoid sharp corners which are likely to break up or damage the core. It is generally preferred to use hot stretching, i.e. where some form of auxiliary heating of the filament is used during stretching. This makes the core material even softer, and the stretching of the filaments then becomes easier. These antistatic filaments can be twined with vanlj ^-3 , synthetic, unstretched filaments and stretched together with these»

The present filaments can easily be produced with a tenacity of at least 1.5 g/denier, which is fully sufficient when the filaments are included as a minor component in a mixture with other filaments. The present filaments preferably have an elongation at break of at least 10%, but less than 150%. The properties obtained as a result of the mixed textile materials are mainly dependent on the properties of the other filaments. For general applications, the filaments according to the invention have a denier per filament (dpf) of less than 50, preferably less than 25, dpf.

The filaments can be round or non-round and have eccentrically or concentrically arranged layers around the core or combinations thereof. The concentric design provides maximum protection and coverage of the core. The fineness of the core greatly contributes to its being covered, and filaments with small cores can be used in colored or patterned textile materials without the use of other core-covering agents. A further concealment of the core can be achieved by means of cavities or a matting agent, such as a white, solid, particulate matting agent1, such as a titanium dioxide pigment, in the layer. Filaments that are not round, e.g. that are multilobal, will also contribute to a further concealment of nuclear nc

Of the variables that will affect the concealment of the core, mention can be made of the thickness and colorability of the layer, the ratio between layer and core, the concentration of a oxidizing agent, such as titanium dioxide, in the layer and also cavities formed by separating the layer from the core and which occur in oriented filaments with different layers

and core polymers, such as filaments with a layer of nylon and a core of polyethylene.

If a covering layer to hide the blackness of the core does not

is present, the fibers filled with carbon black will usually have a light reflection of less than 5%. Light reflectance of over approx. 20%, which can be achieved according to the invention, provides a significantly improved avoidance of color problems when the present filaments are used in light-coloured products.

The filaments according to the invention can provide excellent antistatic protection for all types of textile end products, including knitted, tufted, woven and non-woven textile products. They can contain common additives and stabilizers, such as water-soluble organic dyes and antioxidants0 They can be subjected to all types of textile processing, including crimping, binding, washing and bleaching etc. They can be combined with staple or filament yarns and used as staple fibers or as continuous filaments .

The present filaments may be combined with other filaments or fibers at any suitable stage in the manufacture of yarn (for example, by spinning, drawing, binding, twisting, rewinding and yarn spinning) or in the manufacture of woven fabrics. as far as possible to reduce breakage in the antistatic filaments. During handling, for example, the relative lengths and shrinkages of the antistatic and other filaments must be adjusted so that a good workability of the desired filling, co-winding, twisting or binding properties is achieved.

Below is a description of the examination methods used to determine some of the properties of the present filaments.

Filament tk. the electrical resistivity of the iron

The electrical resistance of the filament core is determined from the electrical current that occurs, at an applied voltage of 2 kV on

a filament sample with a length of 5.08 cm" An apparatus suitable for carrying out this measurement is a 15 kV dielectric measuring apparatus of the Biddle type. A filament bundle with 3 filaments is clamped in a straight line between a pair of electrodes placed at a distance of 5.08 cm from each other, and a sufficiently high electrical voltage (e.g.

1-^ kV) is applied until an electric current will flow. When the electric current flows, the voltage is regulated to 2 kV, and the yarn's electrical resistance is calculated from the electric current in accordance with Ohm's law where R = E/I. If, for example, the current at an applied voltage of 2 kV is 10-^ for a filament sample with a length of 5.0 cm, the electrical resistance of the three filaments is

ability 0.<*>+ x 10 8 ohm/cm. The resistance, per filament is then 1.2 x 10 ohm/cm. In order to obtain an electric current as mentioned above, the voltage should be increased gradually to avoid a sudden surge of current which could burn out the filaments. A burnout can be easily observed visually,

(in the case of filaments "with broken or surface-melted or charred filaments), and such test pieces must be scrapped" The electrical resistance of filaments with lengths shorter than 5.08 cm can be measured by suitable adjustment of the distance between the electrodes"

Light reflection

Light reflection, which is an expression of the lightness or whiteness of the sample compared to a standard magnesium oxide, is measured using a photoelectric reflection measuring device. A suitable apparatus is a model 610 type apparatus with a green three-stimulus filter (catalog no. 6130), a model 610-Y type apparatus and a catalog no. 75%, all of which are marketed by Photovolt Corp., 95 Madison Avenue, New York, New York 10016. The electrically conductive filament sample to be measured is wound for approx. 6 layers of 5.08 cm x 7.62 cm black mirror cards, and the reflection from each card is measured (average of 10 measurements).

The percentage amount of carbon black in the core

Standard analytical methods can be used to determine the concentration of carbon black in the filament or in the core material. A suitable method for use in connection with ethylene plaster containing carbon black is described in or can be derived from ASTM Method DI603-68. This is a heat gravimetric method suitable for use in the absence of non-volatile pigments or fillers other than carbon black.

The percentage core volume in the filament

The percentage core volume can be most easily determined by comparing the cross-sectional area of the black core with the cross-sectional area of the overall filament using a microscope, It is advantageous that the set magnification is approx. ^00 X„ For round filaments, the percentage core volume can be easily calculated from the ratio of the square of the core diameter to the square of the total filament diameter. The average of 10 calculations is used to compensate for any unevenness in the measurement results0 For non-round cross-sections, the percentage core volume can be easily calculated from measurements of photographs taken of filament cross-sections at known magnification"

If the layer polymer has sufficiently different dissolution properties in relation to the core material, this can be removed by differential dissolution, and the percentage amount of chemicals can be determined gravimetrically by dissolving the layer and comparing the weight of the insoluble core with the weight of the original try. As an example of a suitable solvent, formic acid can be mentioned, which can be used to dissolve a layer of 66-nylon from a polyethylene core.

K. the specific electrical resistance of the ferrous material

The specific electrical resistivity of a core material containing carbon black is determined by measuring the resistance to direct current across a film strip of the sample with one length of 5.08 cm,

a width of 2.5V cm and a thickness of approx. 0.25 mm. Such films can be easily produced by pressing a powdered or pelletized sample of the core material between two sheets of aluminum foil in a press for 1-2 minutes at a temperature above the melting point of the core material and a pressure of 1^-07 kp/cm. After cooling, the foil is removed from the sample film, and strips with a width of 2.5<*>+ cm and a length of 6.35-7.62 cm are cut out of the sample. The thickness of the film is measured with a micrometer. A strip is clamped between two copper electrodes placed at a distance of 5.08 cm from each other, and the resistance to direct current is measured with an ohm meter. The specific electrical resistivity of the film in ohm-cm is calculated from the instrument reading in ohms, as the product of the measured electrical resistance multiplied by the width times the thickness and divided by the length of the sample, all dimensions in centimeters.

Example 1

Concentric ply/core filaments were made with a ply of ^5 RV 66 nylon and a polyethylene core containing 20% electrically conductive carbon black. The carbon black used was an oil furnace carbon black of the extra conductive "Vulcan" XC-72 type (bonded carbon 98%, volatile constituents 2%, particle size 30 nm, electrical resistivity torr-lowest). The carbon black dispersion was prepared by mixing this carbon black at a temperature of approx. 120°C with a LD (o.9l6) polyethylene resin with a melt index of 23 and which is marketed under the trademark "Alathon" 2821, by painting—4_j3t dough mixing apparatus The carbon black used was slowly added, and the landing was plugged for 10 minutes after the addition was finished. This polyethylene resin was chosen because of its softness (other resins used are an LD (0.916) polyethylene with a melt index of \ 11.9 and marketed under the trademark "Alathon" 20, used alone \ or mixed with 15- ^0% of an oil or wax)0 The molten carbon black-containing mixture was filtered through a 100 x 100 mesh screen and extruded. Pressed films of this mixture exhibited excellent dispersion and electrical conductivity and had a specific electrical resistivity of 12.7 ohm-cm. From this material as a core material, continuous ply/core filaments (three 65/ denier monofilaments) were spun at a speed of 389 m/min. , the overall denier being kept constant and the core volume reduced by changing the pump speeds so that the products shown in table h were obtained. The core volume was determined by the pumping speed and was confirmed by cross-sectional analyzes of the filaments at a magnification of 200x. A stainless steel spinneret with 3 holes was used in which the layer and core polymers were fed concentrically and separately until they came out through the front of the spinneret. A capillary tube was inserted to guide the core polymer material towards the front of the spinneret, where it exited the spinneret surrounded by the layer polymer. The filaments were spun to a thickness of approx. 65 dpf.. They were then stretched 3506 times at a speed of approx. 183 m/min. on a curved, heated plate which was maintained at a temperature of 150°C. The yarn's physical and electrical properties are shown in table 1.

The test carpets according to Table 1 were made from a commercially available 3700 denier/20^ filament carpet yarn of fluffed, trilobal, continuous filaments of 66-nylon and with a tuft height of 1.27 cm„ One yarn end of the conductive fiber (about 0.56 weight %) was twisted together with the carpet yarn by cross-poling and tufted. The visibility of the conducting filaments decreased considerably in the carpet with reduction of the core volume.

Example 2

Production of layered polymer

A 317.5 kg aqueous solution containing 50% by weight hexamethylenediammonium adipate (66-nylon salt) was filled into a stainless steel container to which was added 721 g of an aqueous solution containing 10% by weight manganese hypophosphite [Mn(H"2P02)2] . provided with an agitator. The autoclave was purged of air with inert gas and heated to about 200°C and a pressure of 17 atmospheres. 1^.83 kg of an aqueous slurry containing h9% by weight titanium dioxide marketed under the trade name "Ti- pure Rutile", was filled with stirring into the pressurized autoclave. The heating was continued until a temperature of 273°C, and the pressure was gradually reduced to atmospheric pressure. The polymerization cycle was continued as described in Example 1 of US Pat. ft. No. 2I63636. After completion of polymerization, the molten polymer was extruded in the form of strands with a diameter of approx. 6.3 mm. After quenching in water, the strands were divided into pieces of 6.3 x <*>+.7 mm which were suitable for melting in a spinning apparatus. The small pieces had the following properties: Relative viscosity ^3.5, (NH2) M-6.0 eg/10^g, Ti02 5.0^% and Mn(H2P02)2 0.0<*>4-8$ .

K. iron polymer

Composition in % by weight:

Polyethylene: 70%

Electrically conductive carbon according to example 1: 30%

The polyethylene used is marketed under the trademark "Alathon" PE-^318 and was an LD polyethylene (specific gravity 0.916, melt index 23 ASTM-D-1238)„ It contained 50 parts of antioxidant per million to improve its stability to heat and storage. The core polymer was prepared by filling 1905 g of polyethylene and 816.5 g of carbon black in a dough mixer with a capacity of 3.7 1 and equipped with double stirrer arms. The mixture was mixed for 30 minutes at 10-0°C, extruded, filtered through a 100 x 100 mesh screen and pelletized.

The product had the following properties: Specific electrical resistivity of a film stopped at a temperature of approx. 180°C, 2.9-!+.2 ohm-cm, % carbon black by analysis 30.2% and moisture 0.0^-%.

If the moisture content is above 0.1%, the pellets should be dried for 2 hours at 70°C and under vacuum for spinning.

The layer and core polymers were simultaneously spun on a single-spinning machine of the screw melt type using a spinning die assembly so that concentric layer/core filaments were spun using the technique described in US Patent No. 2936^82.

The layer polymer was added at a rate of 19.8 g/min (calculated from the pump's capacity and speed) and the core polymer at a rate of 0.7 g/min. (calculated from the pump's capacity and speed). A concentric layer/core product was thereby obtained, of which the layer made up 96% by volume and the core h% by volume. During the spinning of the layer polymer and the core polymer, the temperatures in the screw melter were set to:

The spinning block temperature was 293°C. The feed funnels for layer polymer and core polymer were both flushed with inert gas"

The layer polymer's relative viscosity when it came out of the spinning die (free fall) was approx. 56, the increased relative viscosity being due to further polymerization of the dried 66 nylon in the screw melter. The spinning speed was approx. 81*4- m/min. The collected spun yarn was gray in color and had the following properties: Yarn finish approx. 1, 0%, ..percent core volume h%, percent layer volume 96%, denier for spun filament bundle 60, number of filaments per bundle 3 and light reflex ion 37-1+0%,

The electrically conductive 60-3 denier spun yarn was drawn on a stretch twister with a draw ratio of 2.7 times, a winding speed of 366 m/min. and a ground temperature of 180°C. The properties of the drawn yarn were: Number of filaments 3, tenacity 3.8 gpd, elongation 35%, modulus 13 gpd at 10% elongation, electrical resistivity of the core (in bundle) 1.8 ohm/cm and reflection 3<1>+%.

One end of an approx. 3^00 denier, 160 filament hollow filament yarn of nylon k of the type described in British Patent No. 1292388 was simultaneously fluffed with one end of the electrically conductive yarn in a position of the spinning machine for the hollow filament. The yarns were combined by hot chesting under a stretch of 10-20 g on the last calender roller medloper before they entered the up-fluffing jet. The calender roll was maintained at a temperature of 195°C, and the yarn speed was 108^ m/min. The simultaneous fluffing was carried out by passing the yarn through an air jet with an excess pressure of 8.M+- kp/cm^ and a temperature of 2<1>f0°C, as described in Belgian patent document No. 573230, for the production of filaments with arbitrary, three-dimensional, arcuate creping with alternating regions of S- and Z-filament winding. The yarn was then cooled and wound.

The tensile properties of the manufactured bulk yarn were essentially the same as the unmodified product. Carpets with piles and colors so that they had a surface with imitation monster and with a tuft height of 1.27 cm, which weighed 0.996 kg/m 2 , which had a thread distance of •+ mm and 7 stitches per 2.5^ cm and which was produced from yarns containing the conductive filaments (sample) and from yarns that did not contain conductive filaments (control) with a commercially available, non-woven backing of polypropylene marketed under the trademark "Typar", and provided with a commercially available latex gave the following electrostatic tendencies at a relative humidity of 20% and a temperature of 21°C.

The electrostatic examination was performed in accordance with AATCC Test Method 13M--I969 with the modifications adopted by the Carpet and Rug Institute, September, 1971.

In untreated or imitation dyed carpets, the 20-3 denier conductive filaments produced a very faint bluish tint. Dyed carpets of continuous bulk filaments and containing conductive filaments showed no difference between most of the solid color shades and only slight differences between certain solid light colors, e.g. yellow, orange and pink, compared to the control carpet.

If desired, the present filaments can be used in staple

shape, e.g. in an amount of 0.5-5% by weight together with non-conductive staple filaments in carpet yarn.

Example

It appears from this example that care must be taken when stretching the present filaments to avoid loss of electrical conductivity.

Filaments were spun where the layer was eccentrically arranged around the core, the layer consisting of nylon-66 with a relative viscosity of hh and containing 0.3% TiOpj while the core consisted of nylon-6 (with a relative viscosity of ^5, 31.8 equivalent -NR^ end groups 10^ g) and contained 20% carbon black of the type described in example 1. In the filaments, the core made up k- 0% by volume. The yarn of 3 filaments had a denier of approx. 79 in the spun state. The yarn was cold stretched with a stretching needle. It appears from table 2 that the resistance of the yarn after cold drawing increased as a function of the drawing ratio. When the yarn was "hot drawn" without a pin and using a curved, heated plate with a temperature of approx. 160°C, essentially no increase in resistance occurred. It has been suggested that when the yarn is heated in a heated JflØB stretching zone, upon stretching, a sufficient softening of the core **M^ could occur to prevent core breakage or displacement of the distribution of the carbon particles necessary for electrical conductivity.

Example h

Layer polymer

Polyethylene terephthalate flakes with a relative viscosity of 23 + 2 measured for 0.8 g of polymer in 20 ml of hexafluoroisopropanol at 25°C.

K. iernepolvmer

Nylon-6 - 22% conductive carbon black according to example 1.

A pre-dispersed slurry of 22.68 kg of conductive carbon marketed under the trade name "Cabot XC-72", 86.18 kg of caprolactam and 83.91 kg of distilled water was prepared in an agitator mixing tank at a temperature of 50-55° C. The slurry was then filled into a 226.8 kg capacity stainless steel autoclave fitted with an agitator. The autoclave was purged of air and filled with inert gas, and heating was started. The temperature of the autoclave was increased to 2?8°C and the pressure to 17.6 kp/cm<2> overpressure to effect the first opening of the caprolactam ring and to initiate prepolymerization reactions. After this heating cycle, which lasted approx. 6-7 hours, the pressure was reduced gradually over the course of 1.5 hours from 17.6 .kp/cm overpressure to atmospheric pressure (reducing cycle). The polymer was then extruded at 278°C into a continuous ribbon which was quenched with water and divided into flakes with a 3.2 mm diameter. While stirring, the flake was washed with water for approx. h hours in a boiler which was heated to 95°C, to remove monomer. This operation was repeated 3 times, and at the end of this,

about. 6.3% caprolactam extracted. The polymer was then dried under vacuum (635 nm Hg) until its moisture content was below 0.3%. The flake was melted, extruded and filtered through a filter screen of increasing mesh size (30 to 200 mesh) and pelletized, after which it was vacuum dried until it contained below 0.03% moisture.

The specific electrical resistivity of films stopped from this polymer varied between 10 and 60 ohm-cm.

The layer and core polymers were simultaneously spun and stretched

an associated spinning-stretching machine at a take-up speed of 1372 m/min (calculated on the basis of take-up roll speed expressed in revolutions per minute).

The layer polymer was added in an amount of 29.7 g/min (calcd

on the basis of the denier in the spun state and the winding speed)

and the core polymer in an amount of 6.7 g/min (calculated on the basis of the denier in the spun state and the winding speed) so that the

a material consisting of a concentric layer around a core was obtained, the layer being 8% by weight (calculated on the basis of the amount added) and the core 19% by weight (calculated on the basis of the amount added). During spinning, the temperatures in the screw melting machine were set as follows:

The spinneret temperature was 290°C. The yarn was stretched at a draw ratio of 3:1 using a water vapor drawing jet and electrically heated rollers maintained at a temperature of 180°C (16 co-rollers).

The stretched yarn was black and had the following properties:

Number of filaments per skein 1, denier 19.02 overall yarn finish 1.83%, core resistivity 1.3 x 10 9 ohm/cm, tenacity 2.5 gpd, elongation 39.9% and modulus 13.6 gpd at 10% elongation.

Example 5

Layer polymer

Polyethylene terephthalate flakes with a relative viscosity of 30.

Core polymer

Prepared as in example 2.

The layer polymer and the core polymer were simultaneously spun as in Example 2 at a speed of 787 m/min. The layer polymer was added in an amount of 36.3 g/min (calculated on the basis of pump speed and capacity) and the core polymer in an amount of 1.38 g/min (calculated on the basis of pump speed and capacity) to form a material with a concentric layer around a core, the layer being 96% by volume and the core h volume% of the material, determined on the basis of cross-sectional magnification.

During spinning, the temperature in the screw melting machine was set to:

The spinning bed temperature was 292°C.

The yarn was spun to 60 denier and consisted of 3 filaments (60-3).

The produced 60-3 denier ply/core yarn was stretched at a speed of h±5 m/min and with a stretch ratio of 3.8:1, the hot bed having a temperature of 97°C.

The drawn yarn had the following properties: denier 17.2, number of filaments 3, core resistivity 2.66 x 10^ ohm/cm/fil., tenacity 5.3 gpd, elongation 21.5% and modulus (Mi) <*>+ 3.2 gpd at 10% extension.

The ply/core test yarn was bound with a commercially available 150-3^ polyester yarn on a "Leesona 570" false twist binding machine. The bonded yarn (1 end 17.2-3 ply core with 1 end 150-3*4- polyester) was woven into a "Suisse Pique" double knit weave. This fabric was dyed and finished using usual methods. After 30 washings, the fabric was examined on a static testing device, a so-called "electrometer", and compared with the control fabric made from the same polyester yarn alone and further treated under identical conditions.

It appears from the above results that the test tissue was well electrostatically protected.

Example 6

A 60-3 yarn was produced from the nylon-66 layer polymer according to example 2 and from a nylon'-6 core polymer containing 28% carbon black prepared as described in example h. Filaments of which the layer constituted 96% by volume and the core h volume% were stretched with a stretch ratio of 3:1 over a curved hot plate (6 cm) at a temperature of l80°C. The yarn properties were as follows: denier for filament bundle 20.2 tenacity 3.18 gpd elongation *+9.1%, modulus (M ) 2k, k

Q

gpd, core resistivity 1.77'x 10 ohm/cm/filc and reflection 32%.

The conductive yarn was bulked as described in Example 2 along with a 1225-68 nylon-66 blanket yarn of hollow, continuous

filaments which are marketed under the trademark "Antron" type 85<*>+ and which can be dyed with a basic, water-soluble, organic dye, and from the obtained yarn carpets with surface loops and with a tuft width of o 6.35 mm and a basis weight of 0.<!>+75 kg/m 2 , as described in example 2. The reflection from and the electrostatic susceptibility of the imitation dyed carpet were compared with a control carpet made without electrically conductive yarn.

The visual measurements of the carpets agreed with the measured reflectance from the carpets.

Example 7

Filaments (<>>+ ends of 60 denier in the spun state, 3 filaments) with a nylon layer and a polyethylene core which were essentially the same as described in Example 2 were prepared for use as staple fibers and had the following properties: Yarn finish 0, ^3%, the core's share 3.5% by weight, the layer's share 96.5% by weight, carbon content in the core 32.3%, reflection 39% and the resistance of the core in the filament bundle (12 filaments) 2.0 x IO<7> ohm/ cm.

The spun yarn was drawn, by combining 8 ends, on a pre-sbx drawing machine with a draw ratio of 3.0:1, a winding speed of 210 m/min and a bed temperature of 180°C.

The drawn yarn had the following properties: Denier for filament bundle 690, number of filaments 96, tenacity h, 72 gpd and elongation 18.5%.

This conductive yarn bundle was divided into pieces with a length of

about. 16.5 cm and mixed with commercially available nylon-66 carpet staple yarn during carding in amounts of 0.6, 2 and 5%. The blends were processed under normal staple conditions to produce spun yarns with a cotton thread count of 2.<*>+, 2 components and a twist of 3.5 Z/3.5 S. The yarns were heat-set in one autoclave and then tufted into carpets with cut locks and with a flat

weight of 1.19 kg/m , a filament spacing of 3.96 mm, a tuft height of 1.9 cm and the Sa.chse type, in that the carpets had a backing of polypropylene which is marketed under the trademark "Typar" and includes a commercially available latex . The carpets were washed and dyed in the usual way with a mixture of 3 commercially available yellow, red and blue acid dyes.

The dyed carpets gave the following electrostatic tendencies after they had been subjected to a rubbing test at a relative humidity of 20% and a temperature of 21°C.

Example 8

In this example, a further number of applications of the present filaments are shown. Each product contained 3 filaments per end, and the carbon black used was the same as that used in example 1.

Product A was essentially the same as that produced according to example 2, but with the exception that the cross-sections of the filaments were rib-shaped. The core contained 0.25% by weight of the sterically hindered phenolic antioxidant 1,3,5-trimethyl-2,6-tris-(3,5-di-tert-butyl-*+-hydroxybenzyl)-benzene.

Product B was essentially the same as product A, but with the change that it had a trilobal cross-section with a modification ratio of 2.5.

Products C-H had filaments with a round cross-section.

Product C comprised filaments with a layer of nylon 66 containing 5% titanium dioxide, and a core containing 30% carbon black in a polyolefin base material consisting of 0% polypropylene, 20% polyethylene and 10% of an elastomer sold under the trademark "Nordel " 1500 and which is based on a terpolymer of ethylene, propylene and a non-conjugated diene.

Product D comprised filaments with a layer of a commercially available polypropylene resin marketed under the designation "PWD-I52" and a core of the same composition as for product A.

In product E, the same layer as in product D occurred, and the core material consisted of a polycaprolactone resin which is marketed under the designation "PCL-700" and which contains 30% carbon black.

In product F, the layer consisted of nylon-66 containing 5% titanium dioxide pigment, and the core consisted of a polypropylene resin which is marketed under the designation "8 MSR" and which contains 25% carbon black.

In product G, the layer consisted in the same way as in product D of polypropylene, and the core consisted of a polyethylene ether resin which is marketed under the name "TLF 168 IS" and which contains 26% carbon black.

Product H was a non-antistatic control product with a nylon layer as for product A and with the same polyethylene resin core that did not contain carbon black.

The filament properties for these products are reproduced in table 3c

Claims (2)

1. Synthetic, antistatic filament consisting of a synthetic, thermoplastic polymer, preferably polyethylene (k), in which electrically conductive carbon black (3) is dispersed so that the polymer is electrically conductive with an electrical resistivity of less than 0.<*>+ x 10^ ohm/cm when exposed to a direct current potential of 2 kV, characterized in that the polymer (k) with the electrically conductive carbon black (3) forms the core (l) of a bicomponent filament (5) of the core-sheath type where the sheath (2) consists of a synthetic^ thermoplastic fiber-forming polymer different from the core polymer (*+), preferably polyamide. 2. Filament according to claim 1, characterized in that the mantle (2) is matted so that the filament (5) has a light reflectance of over 20%.