WO2020020421A1

WO2020020421A1 - High-performance heating cable

Info

Publication number: WO2020020421A1
Application number: PCT/DE2019/200085
Authority: WO
Inventors: Thomas Damerow
Original assignee: Leoni Kabel Gmbh
Priority date: 2018-07-25
Filing date: 2019-07-23
Publication date: 2020-01-30
Also published as: DE102018117942B4; DE102018117942A1

Abstract

The invention relates to a heating cable as defined in the claims, said heating cable containing polymer-insulated wires made of a first metal alloy and a second metal alloy. The invention further relates to a process for manufacturing the heating cables as defined in the claims as well as to the use of the heating cables.

Description

High-performance heating cable The invention relates to a heating cable and a method for producing the heating cable. In addition, the invention relates to the use of the heating cable in a seat or seat element.

State of the art

Heating cables in car seats are exposed to heavy loads. Since they can hardly be felt from the outside, they must have very small dimensions (maximum diameter 2 mm). Despite high tensile loads and constant movement on the seat, the heating cables must not break. Should the breakage of single wires with age not ver ^¬ shun leave, the remaining current-carrying wires may not produce high current densities which could lead to a dangerous heating (hot spot).

Meeting these requirements is a major challenge. The change in the number of wires per cable to very small values (e.g. less than 40), in order to keep the diameter of the heating cable small, results in a deterioration in the resistance to bending. On the other hand, a change towards a very high number of wires (e.g.> 100) leads to a sharp increase in costs and does not allow the production of very small outer diameters.

The DE 10 2015 104 947 Al discloses the use of two different Le ^¬ alloys to produce a strand having a desired resistance of the heating cable. The individual wires are stranded together to form a strand. However, the individual wires stranded directly with one another do not have the desired mechanical properties that are necessary for use as heating cables.

DE 10137976 Al discloses strands for a seat heater, wherein the strands comprise a plurality of types of single wires, rule for setting the desired electrical properties of the strand ^¬ have the different types of individual wires have different electrical properties. The individual wires are preferably provided with a metallic coating. However, this does not allow the desired mechanical properties when the wires move against each other. In addition, the strands are also stranded directly together without a polymer coating separating the individual wires.

There was therefore a need to provide heating cables which have good heating properties and improved mechanical strength.

Summary of the invention

The various heating cable requirements mentioned above are met by the heating cables according to the invention. The underlying concept is based on polymer-insulated wires, the wires consisting of a first and a second metal alloy. However, it is not excluded that a third and further metal alloy is present.

The structure of the inner conductor is based on at least two different alloys, e.g. CuSnO, 3 (e.g. LEONI Histral® H72) and CuSn6 (e.g. LEONI Histral® R15). The different alloys should have different ohmic resistances. This has the advantage that the desired resistance can be set in a cost-effective manner to meet the requirements of the heating cable via the number of respective wires.

CuSnO, 3 and CuSnö alloys have good bending properties, but very different electrical conductivities. To prepare a 0.65 ohm / m heater cable ^¬ a total of 48 pieces 0.05 mm enamelled wires can for example be selected, to achieve the resistance in the ratio of 12 wires CuSnO, 3 (eg LEONI Histral® H72) and 36 wires CuSn6 (e.g. LEONI Histral® R15) can be mixed. The aim is to introduce as many individual wires as possible into the heating cable to improve the resistance to alternating bending, without exceeding the maximum outer diameter of 1.0 or 2.0 mm.

The cable is also equipped with tensile fibers, such as Vectran ™, to withstand forces in the longitudinal direction. Due to the hybrid structure with several alloys, the number of wires can be controlled independently of the resistance in order to achieve the highest possible fatigue strength by increasing the number of wires and the use of particularly resistant alloys. The flexural fatigue resistance was further increased according to the invention in particular increased that the wires are individually polymer-coated and have a lubricating lacquer layer.

The wires, which are more resistant to bending changes (e.g. CuSn6), are preferably arranged in the outer area of the stranded wire in order to absorb the major part of the acting forces. This protects the weaker wires (e.g. CuSnO, 3). The individual wires are insulated from one another by at least one lacquer layer, for example a polyurethane lacquer layer, in order not to generate high current densities in the event of a break. The coated wires are provided with an additional layer of lubricating varnish to largely avoid frictional wear between the wires when the cable moves. For this purpose, the lubricant is added to the lacquer and applied as a second lacquer layer (referred to herein as a “sliding lacquer layer”) of approximately 1 pm. However, it is also possible to apply further layers, the outer layer being a lubricating lacquer layer.

The hybrid heating cable of several alloys having a particularly high flexural fatigue strength cases reach a higher reliability in case of breakage caused from ^¬. The ever same dimension of the heating cable inside a resistance ^¬ range also allows for retaining the setting parameters in the further processing processes in spite of change in resistance.

The present invention thus relates to a heating cable as claimed in claims defi ^¬ defined, and processes for the preparation of the heating cable as defined in the claims and the use of the heating cable in a seat or seat element, preferably car seat, or as a heating cable in robot cables, or in heated wiper systems , or in heating elements.

Detailed description of the invention

The present invention relates to a heating cable, comprising:

- at least one, e.g. one, two or three, inner conductors, containing (preferably consisting of):

a) 3-50, preferably 6-18, each polymer-insulated wires of a first Metalllegie ^¬ tion,

b) 10-100, preferably 30-42, each polymer-insulated wires made of a second metal alloy, and

c) tensile fibers arranged in the longitudinal direction of the inner conductor; and

- at least one casing, the outer diameter of the heating cable is preferably less than 2 mm; and wherein the polymer insulated wires made of the first and second metal alloy have different electrical conductivity. The second metal alloy has a lower conductivity than the first metal alloy. Electrical conductivity can, for example, according to ASTM E

1004 can be measured.

The electrical conductivity of the first and second metal alloy is preferably 1-60 Siemens m / Omm ² at 20 ° C, preferably between 1-25 or 35-60 m / Qmm ² at 20 ° C, the range> 25 and <35 less is preferred. In particular, the first metal alloy preferably has an electrical conductivity in the range of 35-60 m / Qmm ² at 20 ° C and the second metal alloy has an electrical conductivity in the range of 1-25 m / Qmm ² at 20 ° C.

Preferably, the electrical conductivity of the first and second metal alloy, expressed as "IACS" (International Annealed Copper Standard), 10-90% IACS. More specifically, the first metal alloy preferably an electric Leitfä ^¬ ability in the range of 50-90% IACS and second metal alloy has an electrical conductivity in the range of 10-25% IACS.

In addition or as an alternative to the electrical conductivity specified above, the difference in electrical conductivity between the first metal alloy and the second metal alloy is at least 0.008 mm ² / m at 20 ° C., or at least 0.05 mm ² / m at 20 ° C. or at least 0.08 Qmm ² / m at 20 ° C, e.g. 0.008 to 0.74 Qmm ² / m at 20 ° C. The resistance of the heating cable can be 0.4-1.0 ohm / m, preferably about 0.65 ohm / m.

In one embodiment, the polymer-insulated wires made of the first and second metal alloy are not defined by a different electrical conductivity, but by a different ohmic resistance.

The heating cable according to the invention contains polymer-insulated wires of at least two types, ie the wires consist of either a first or a second metal alloy. In addition, the polymer-insulated wires can also differ in the type of coating and the cable diameter. By “type of coating” or “polymer insulation” is meant: number of layers, layer thicknesses, type of coating, in particular type of polymer / polymer composition. Self- understandably different polymers can be present in one coating / layer. However, it is not excluded to add a third or further type of polymer insulated wire with a different metal alloy and / or a different coating.

The term "polymer-insulated" refers to an electrically insulating coating containing a polymer. The term "polymer-insulated wire", as used herein, refers to a wire with at least one polymer coating, in particular to a metal alloy in the shape of a single wire which is electrically insulated from the other polymer-insulated wires by means of at least one polymer layer, that is to say which is coated with an electrically insulating coating comprising a polymer and optionally further coatings, preferably a sliding layer.

The term “two polymer coatings” as used herein means that two distinguishable coatings are present, the coatings preferably differing in the type of polymer (or polymers) and / or the further constituents of the coating, for example by the presence of a lubricant in the outer coating.

The wires of the polymer-insulated wires are preferably constructed homogeneously from the or a metal alloy and in particular do not have a layer structure made of metallic wire and metallic sheathing or metallic coating.

The term “polymer-isolated” thus encompasses the use of a polymer of one type, for example polyurethane, and polymer compositions containing one or more different types of polymers, in particular homopolymers, copolymers, polymer blends and mixtures thereof (for example polyurethanes and polyamides) and optionally additives such as fillers, plasticizers, flame retardants, lubricants and dyes / color pigments. The polymers are preferably organic polymers. The polymer insulation thus preferably comprises organic polymers, but can also additionally include inorganic polymers, for example as flame retardants and non-polymers Components included.

The tensile fibers are arranged in the center of the inner conductor, ie the polymer-insulated wires are arranged around them. The polymer-insulated wires can be distributed symmetrically (C _n symmetry with n times the axis of rotation) or asymmetrically (without Cn symmetry with n times the axis of rotation). The sheath is applied around the inner conductor. Depending on the application, more than one jacket can also be used. According to the invention, the polymer-insulated wires are not embedded in a matrix so that they maintain the desired mobility.

The heating cable can

at least one, e.g. one, two or three, inner conductors, containing (preferably consisting of):

a) 6-18 each polymer-insulated wires made of CuSn (copper-tin) alloy, preferably CuSnO, 3 alloy,

b) 30-42 each polymer-insulated wires made of CuSn alloy, preferably CuSn6 alloy, and

at least one casing,

wherein the outer diameter of the heating cable is less than 2 mm.

In addition to CuSn alloys, other alloys are possible, which the radio tion ^¬ able to fulfill a heating cable, for example CuMg (copper-magnesium) alloys, CuNi (copper-nickel) alloys.

A CuSn6 alloy is defined according to DIN CEN / TS 13388 (DIN SPEC 9700) as follows:

Copper alloy with 5.5-7.0% by weight Sn, 0.01 to 0.4% by weight P, admixtures up to 2.0% by weight, the rest is Cu.

The admixtures are preferably up to 1.0% by weight or up to 0.5% by weight, more preferably up to 0.2% by weight.

In one embodiment, the admixtures are up to 0.2% by weight of Ni, up to 0.2% by weight of Zn, up to 0.1% by weight of Fe, up to 0.02% by weight of Pb and less than 0.1% by weight of other substances.

In a preferred embodiment, LEONI Histral® R15 (CuSnö) wire is used. It has the following characteristics. It is of course also possible to use other CuSn6 wires with the same or similar properties: Nominal values: soft hard

Specific resistance * (Ohm 0.1110 0.1330

mm ² / m)

Electrical conductivity * (% 15 13

IACS)

Tensile strength * (N / mm ² ) 380 690

Elongation * (%) 30 1

Temperature coefficient of resistance 0.00065 0.00065

Stand (1 / ° C)

Density (g / cm ³ ) 8.8 8.8

* Values depend on surface coating, degree of deformation and thermal treatment during the processing process

The values given above can be determined in accordance with EN 12166 and DIN CEN / TS 13388.

A CuSnO, 3 alloy is defined according to the "Unified Numbering System for Metals and Alloys (UNS) C14425" as follows:

Copper alloy with 0.1-1.5% by weight, preferably 0.2-0.4% by weight, or about 0.3% by weight of Sn, admixtures up to 2.0% by weight, the rest is Cu.

The admixture is preferably up to 1.0% by weight or up to 0.5% by weight, more preferably up to 0.2% by weight.

In one embodiment, the admixtures are up to 0.01% by weight P, up to 0.01 0.02% by weight Ni, up to 0.10% by weight Zn, up to 0.02% by weight. % Fe, up to 0.10% by weight Pb and less than 0.1% by weight other substances.

In a preferred embodiment, LEONI Histral® H72 (CuSnO, 3) wire is used. It has the following characteristics. It is of course also possible to use other CuSnO, 3 wires with the same or similar properties: Nominal values: soft hard

Resistivity * (Ohm 0.0216 0.0240

mm ² / m)

Electrical conductivity * (% 80 72

IACS)

Tensile strength * (N / mm ² ) 250 600

Elongation * (%) 20 1

Temperature coefficient of resistance 0.00290 0.00290

Stand (1 / ° C)

Density (g / cm ³ ) 8.9 8.9

The values given above can be determined in accordance with LV112-4 and DIN CEN / TS 13388. The outer diameter of the heating cable is preferably less than 1 mm.

In a preferred embodiment, 10-14, preferably about 12, polymer-insulated wires made of a first metal alloy, preferably a CuSn alloy, more preferably a CuSnO, 3 alloy, are present. Additionally or alternatively, 34-40, preferably about 36, polymer-insulated wires made of a second metal alloy, preferably a CuSn alloy, more preferably a CuSn6 alloy, can be present.

The polymer-insulated wires are preferably insulated from one another by at least one lacquer layer, in particular a lacquer layer selected from the group consisting of polyurethanes, polyesterimides, polyamideimides and aromatic polyimides.

The varnish layer enables the wires to be insulated from each other. A lacquer layer of the polymer-insulated wires is preferably applied directly to the CuSnO, 3 alloy / CuSnö alloy. For example, a lacquer layer can be applied in accordance with IEC 60317-0-1 Gradl with a layer thickness of 2.5 pm to 5.0 pm. Lacquer layer thicknesses up to degree 3, ie up to (approximately) 11 pm, or 2.5 pm to 11 pm, or 5.0 pm to 11 pm, are also possible. These values are based on the core diameter of 0.05mm and change with the diameter according to IEC 60317-0-1.

In one embodiment (see exemplary embodiment), a polyurethane basecoat is used. The painting was carried out in accordance with IEC 60317-20. Based on the fact that the prevailing standards only speak of enamelled copper wire, however alloys are used in the present case and the values of these standards relating to copper must therefore be ignored.

The polymer-insulated wires preferably each have at least two polymer coatings, the inner layer serving for electrical insulation and the outer layer serving as a sliding layer. The term “polymer-isolated” thus means that the “polymer insulation” consists of the at least two polymer coatings.

Preferably, the inner layer is a lacquer layer, in particular the above ^¬ be required lacquer layer which CuSn6 alloy is brought to ^¬ on the CuSnO, 3-alloy /. The sliding layer can be produced, for example, by mixing a lacquer with a lubricant. For example, a polyurethane basecoat can be ver ^¬ turns, the polyethylene wax was added as a lubricant.

In one embodiment, each polymer insulated wire has two layers.

The polymer-insulated wires preferably each have at least two coatings (in one embodiment exactly two coatings), the inner layer being a lacquer layer, preferably a polyurethane lacquer layer, and the outer layer being a lubricating lacquer layer, the thickness of the lubricating lacquer layer preferably being 0. 5-3.0 pm, more preferably about 1 pm. If more than two coatings applied ^¬ to, the outermost layer should always be a bonded coating to allow the sliding of the wires.

The polymer insulated wires can have a diameter of less than 0.08 mm, preferably 0.04-0.06 mm, or about 0.05 mm. The wires have preferably a diameter of 0.03-0.07 mm, preferably about 0.05 mm, aufwei ^¬ sen. The total number of polymer insulated wires can be, for example, 36-60, preferably 42-54, or about 48. The CuSnO, 3 alloy can, for example, consist of 0.1-0.5% by weight of Sn, admixtures up to 2.0% by weight, and the rest is Cu. The admixture is preferably up to 1.0% by weight or up to 0.5% by weight, more preferably up to 0.2% by weight.

In one embodiment, the admixtures are up to 0.01% by weight of P, up to 0.01% by weight of Ni, up to 0.01% by weight of Zn, up to 0.01% by weight of Fe, up to 0.005% by weight of Pb and less than 0.1% by weight of other substances. The CuSn6 alloy can consist of 5.5-7.0 wt% Sn, 0.01-0.4 wt% P, admixtures up to 2.0 wt%, and the rest is Cu ,

The admixtures are preferably up to 1.0% by weight or up to 0.5% by weight, more preferably up to 0.2% by weight. In one embodiment, the admixtures are up to 0.2% by weight of Ni, up to 0.2% by weight of Zn, up to 0.1% by weight of Fe, up to 0.02% by weight of Pb and less than 0.1% by weight of other substances.

The tensile fibers can consist, for example, of aromatic polyesters and are preferably produced by condensation of 4-hydroxybenzoic acid and 6-hydroxynaphthalene-2-carboxylic acid.

For example, 200 dtex Vectran ™ multifilament fiber can be used. The fiber material can, for example, be introduced into the core of the inner conductor during the stranding process. The inner conductor is encased in the extruder ^¬ to.

The tensile fibers can, based on the cross section of the inner conductor, be arranged radially in the middle as a strand. In one embodiment, the heating cable has an elongation at break of less than 5%, preferably 3% or less, or about 3%.

The sheath is applied directly to the stranded polymer-insulated wires, which means that no matrix or filler layer is used. The polymer ^¬ insulated wires themselves are therefore not embedded in a matrix, because they should remain movable by the anti-friction varnish. The sheath can consist of a thermoplastic elastomer, for example. The casing can be made of, for example TPE-U (thermoplastic elastomer based on urethane), polyamide (e.g. PA12) or ETFE (ethylene-tetrafluoroethylene copolymer),

The polymer-insulated wires made of the second metallic alloy with lower conductivity, preferably a CuSn6 alloy, can be arranged more radially on the outside, based on the cross section of the inner conductor, and the polymer-insulated wires made of the first metallic alloy with higher conductivity , preferably made of CuSnO, 3 alloy, based on the cross section of the inner conductor, are increasingly arranged radially on the inside.

The wires can be arranged in parallel or intertwined / twisted. In one embodiment, the inner conductor, based on the cross section, can have an outermost layer consisting of polymer-insulated wires made of CuSn6 alloy. The present invention relates to the use of the heating cable according to the invention as a heating cable, preferably as a heating cable in a seat or seat element, preferably car seat, or systems as heating in robot cables, or in heated wiper ^¬, or heating elements (for example, blanket, heating pads, flexible heating element for Vessels, and steering wheel heating).

The present invention also relates to a method for producing a heating cable according to the invention, the method comprising the following steps:

(a) coating a wire made of a first metal alloy with lacquer,

(b) coating the coated wire from step (a) with a lubricating varnish and obtaining a polymer-insulated wire from a first metal alloy and optionally coating the wire with further coatings,

(c) coating a wire made of a second metal alloy with lacquer,

(d) coating the coated wire from step (c) with a lubricating varnish and obtaining a polymer-insulated wire from a second metal alloy and optionally coating the wire with further coatings,

(e) stranding of the tensile fibers and the predetermined number of polymer ^¬ insulated wires of step (b) and (d) to form a strand; and

(f) wrapping the strand of step (e) in an extrusion line with the Umman ^¬ telungsmaterial and obtaining the heating cable.

The method can in particular comprise the following steps:

(a) coating a CuSnO, 3-wire with lacquer, (b) coating the coated wire from step (a) with a lubricant and obtaining a polymer-insulated wire made of CuSnO, 3 alloy and optionally coating the wire with further coatings,

(c) coating a CuSnö wire with lacquer,

(d) coating the coated wire from step (c) with a lubricating varnish and obtaining a polymer-insulated wire made of CuSn6 alloy and optionally coating the wire with further coatings,

(e) stranding the tensile fibers and the predetermined number of polymer insulated wires from steps (b) and (d) into a strand; and

(f) sheathing the strand from step (e) in an extrusion line with the sheathing material and obtaining the heating cable.

In each step, the preliminary products can run from a spool and can be rewound on a spool after processing.

One or more of the following steps can further the applied ^¬ to:

Pulling the CuSnO, 3-wire, prior to step (a) to a predetermined end ^¬ the diameter, for example 0.05 mm.

Recrystallize (soft anneal) the drawn CuSnO, 3-wire before step (a) at elevated temperature, in particular the drawn CuSnO, 3 wire with a diameter of 0.03-0.07 mm, preferably about 0.05 mm.

CuSn6 pulling the wire prior to step (a) to a predetermined end ^¬ the diameter, for example 0.05 mm.

Recrystallization (annealing) of the drawn CuSnö wire prior to step (c) at elevated temperature, in particular of the drawn CuSnO, 3 wire egg ^¬ nem diameter of 0.03-0.07 mm, preferably about 0.05 mm.

The step (e) of stranding the tensile fibers and the desired number of polymer-insulated wires can be carried out in a conventional stranding / stranding machine.

The Verlitzprozess can be divided itzsch rode it into several Verl, if, for example, individual layers of the strand have a different impact direction sol ^¬ len.

Even if some of the aspects and details described above have been described with reference to the heating cable so these aspects / details of the way can be realized in the method for manufacturing of the heating cable in corresponding ^¬. The present invention will be further explained with reference to FIG. 1:

Figure 1 shows schematically the cross section of an embodiment of a heating cable.

Specific details are set forth below, without limitation, to provide a full understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be used in other embodiments that may differ from the details set forth below. The figure also serves only for the purpose of clarifying exemplary embodiments. You are not to scale and are intended to reflect my concept of the invention by way of example only the general ^¬. For example, features contained in the figure should by no means be considered a necessary component.

FIG. 1 shows an exemplary embodiment of a heating cable 1. The inner conductor 2 comprises the polymer-insulated wires made of a first metal alloy (4), the polymer-insulated wires made of a second metal alloy (5) and a sheath (6). The polymer-insulated wires have two coatings (only one of these is indicated in FIG. 1).

According to a variant of the exemplary embodiment, the polymer-insulated wires (4) consist of LEONI Histral® H72 (a CuSnO, 3 alloy). The polymer-insulated wires (5) consist of LEONI Histral® R15 (a CuSn6 alloy).

The exemplary embodiment shown has the following characteristic values:

The exemplary embodiment has 12 wires CuSnO, 3 and 36 wires CuSn6. The following values result from this combination:

Metallic conductor cross section: 0.09mm ²

Resistance: 0.65 ohm / m

Insulation wall thickness: 0.25mm

Outer diameter of the line: 1.0 mm

With the exemplary embodiment,> 20,000 bending changes were achieved in one test. With earlier designs (without lubricating varnish and with only one alloy), only> 10,000 bending cycles were achieved. The heating cable 1 can be manufactured, for example, by a method as defined in the claims.

The exemplary embodiment shown was produced as follows:

In a first step, the LEONI Histral® H72 was drawn to a final diameter of 0.05 mm. The wire obtained was recrystallized or annealed at a temperature of 300 ° C to 700 ° C for 0.15 to 30 seconds. Temperature and time are difficult to determine because the downstream wire coating machine continues to recrystallize due to the high temperature. The wire obtained was coated with Elantas Wire Enamel 1342 in a wire enamelling machine with polyurethane enamel at a temperature of 400 ° C to 600 ° C. The layer thickness was 2.5-5.0 pm. The wire coated with polyurethane lacquer was coated with a mixture of polyurethane and polyethylene wax in a wire coating machine with polyurethane lacquer at a temperature of 400 ° C. to 600 ° C. This layer is a lubricating varnish. The layer thickness was approximately 1 pm. The same procedure was carried out for the LEONI Histral® R15 wires.

A number of 12 LEONI Histral® H72 wires were stranded with a number of 36 LEONI Histral® R15 wires and 220 dtex Vectran ™ multifilament fibers. The strand was then sheathed in an extrusion line with the sheathing material (TPE-U, PA12 or ETFE). The layer thickness was 0.25 mm. The get ^¬ ne heating cable corresponded in construction the figure first

In each step, the preliminary products ran from a spool and were rewound on a spool after processing.

Claims

claims

1. heating cable (1), comprising:

- At least one inner conductor (2), containing:

a) 6-18 each polymer-insulated wires made of a first metal alloy (4),

b) 30-42 each polymer-insulated wires made of a second metal alloy (5), and

c) tensile fibers (3) arranged in the longitudinal direction of the inner conductor (2); and

- at least one casing (6),

the outer diameter of the heating cable (1) being less than 2 mm; and wherein the polymer insulated wires made of the first and second metal alloy have different electrical conductivity.

2. The heating cable (1) according to claim 1, wherein said polymer-insulated comprise wires per ^¬ weils at least two polymer coatings to the metal alloy, wherein the inner / is an inner layer for electrical insulation and top of the outer ^¬ re / outermost layer as Sliding layer serves.

3. The heating cable (1) according to claim 1 or 2, wherein said polymer-insulated wires are insulated from each other by at least one lacquer layer, especially min ^¬ least a paint layer, selected from the group consisting of polyurethanes, polyesterimides, polyamideimides and aromatic polyimides.

4. The heating cable (1) according to any preceding claim, wherein the poly-mer ^¬ insulated wires each having at least two coatings, wherein the inherent ^¬ re / an inner layer is a lacquer layer and the outer / outermost layer is a bonded coating.

5. The heating cable (1) according to claim 4, wherein the lubricating lacquer layer consists of a lacquer containing a lubricant.

6. heating cable (1) according to any preceding claim, comprising:

- at least one inner conductor, containing:

a) 6-18 each polymer-insulated wires made of a first CuSn alloy (4), preferably CuSnO, 3 alloy,

b) 30-42 each polymer-insulated wires from a second CuSn

Alloy (5), preferably CuSnö alloy, and

- at least one casing (6),

wherein the outer diameter of the heating cable (1) is less than 2 mm.

7. The heating cable (1) according to any preceding claim, wherein the polymer-insulated wires have a diameter of less than 0.08 mm.

8. The heating cable (1) according to one of the preceding claims, wherein the resistance of the heating cable is 0.4-1.0 ohm / m.

9. The heating cable (1) according to any preceding claim, wherein the tensile fibers consist of aromatic polyesters.

10. The heating cable (1) according to any preceding claim, wherein the poly ^¬ mer insulated wires from CuSnö alloy (5), based on the cross-section of the inner conductor increases, are arranged radially outwardly and the polymer isolated Dräh ^¬ th from CuSn0 , 3-alloy (4), based on the cross section of the inner conductor, are increasingly arranged radially on the inside.

11. Use of the heating cable (1) according to any one of claims 1-10 as a heating cable in a seat or seat element, or as a heating line in robot cables, or in heated wiper systems, or in heating elements.

12. A method for producing a heating cable (1) according to any one of claims 1-10, the method comprising the following steps:

(a) coating a wire made of a first metal alloy with lacquer,

(b) coating the coated wire with a lubricating varnish and obtaining a polymer-insulated wire from a first metal alloy,

(c) coating a wire made of a second metal alloy with lacquer,

(d) coating the coated wire with a lubricating varnish and obtaining a polymer-insulated wire from a second metal alloy, (e) entangling the tensile fibers and the predetermined number of polymer insulated wires from steps (b) and (d) into a strand; and