CN115379948A

CN115379948A - Cable protective sleeve

Info

Publication number: CN115379948A
Application number: CN202180026054.3A
Authority: CN
Inventors: T·利尔曼
Original assignee: Certoplast Technische Klebebander GmbH
Current assignee: Certoplast Technische Klebebander GmbH
Priority date: 2020-04-01
Filing date: 2021-03-09
Publication date: 2022-11-22
Also published as: WO2021197771A1; DE202020101774U1

Abstract

Protective sheath for cables (1), in particular cable ties for cable harnesses in motor vehicles, having a carrier (2,3), which carrier (2,3) has in its entirety or in part at least one textile carrier layer (2), characterized in that the textile carrier layer (2) has in its entirety or in part carbon nanotubes.

Description

Cable protective sleeve

Technical Field

The invention relates to a protective sheath for cables, in particular a cable wrap for a cable bundle in a motor vehicle, comprising a carrier which is provided in whole or in part with at least one textile carrier layer.

Background

For example, as described in US 2002/0098311 A1, the jacketing of electrical cables has long been used to mechanically protect the cables. Supports having a plurality of layers are generally used for this purpose. The protective sheath here, corresponding to fig. 6 of the aforementioned U.S. document, can surround the cable to be protected as a longitudinal jacket or sheath. However, it is also possible to wrap the protective sheath in the form of a spiral around the cable to be bundled and protected (see fig. 5 and 6 in US 2002/0098311 A1).

For this purpose, the known carrier consists of two separately needle-stitched (vernadelten) nonwoven layers which are connected to one another by means of an interposed adhesive layer.

A similar vector construction is described in WO2005/085379 A1. In this case, the whole relates to a highly wear-resistant and noise-reducing strap for cable harnesses, in particular in automobiles. For this purpose, the carrier has a first top layer a, which is bonded to a second layer C over the entire surface of the top layer a. The top layer a may be velour (Velours), scrim (Gelege), woven (Gewebe) or knitted (Gewirke). The C layer consists of a porous planar structure, for example a textile fabric made of foam or a foam film, having an open but stable three-dimensional structure. Furthermore, the layer C is joined on its open side to a second top layer B over the entire face of the top layer B. The top layer B consists of velour, scrim, woven or knitted fabric.

The cables equipped therewith (in particular in motor vehicles) should therefore be protected against abrasion, rubbing and wear, in particular against sharp corners and sharp edges. In addition, a high wear protection is sought. For this reason, the attrition resistance of the support is typically at least 150% by weight of the sum of the attrition resistances of the individual layers.

The known protective sheath ensures that the cables assembled and wrapped in this way are protected from mechanical influences, in particular in the engine compartment or in the motor vehicle in general during normal operation. Recently, other requirements have been added to the use of such mechanical protection in automobiles in addition to the temperature and chemical resistance typically required for such protective covers (especially for gasoline and diesel). These are exhibited particularly in hybrid and electric vehicles, and due to the large current flowing in this case, a plurality of 100A's are sometimes generated in a voltage range of up to 400V and a strong alternating magnetic field range of up to 800V. These not only generate interference currents in the on-board electronics, but in principle they are also a possible source of interference to the human body. To date there is no relevant standard and no reliable solution. Attempts have been made to provide at least partial electromagnetic shielding in the interior of motor vehicles, for example by means of shielding plates, which, however, are generally inadequate. This is the place of employment of the present invention.

Disclosure of Invention

The invention is based on the technical problem of further developing such a protective sheath for cables in order to provide an effective shielding against electromagnetic radiation.

In order to solve this problem, the invention proposes that, in the case of a universal protective sleeve, the textile support layer is provided with carbon nanotubes in its entirety or in part.

Typically, the carbon nanotubes in the woven support layer are generally present at a minimum concentration of 0.01 wt% based on the mass of the support. A maximum grammage of up to 30% by weight of the carbon nanotubes in the woven carrier layer is generally observed compared to the mass based on the carrier. However, a significantly lower concentration of carbon nanotubes in the woven carrier layer is often sufficient to provide an effective shielding against electromagnetic radiation. It has been found that a maximum grammage of 10% by weight, based on the mass of the support, is advantageous. In principle, it is even possible to use only 5% by weight of grammage in the textile carrier layer, based on the mass of the carrier. Furthermore, the lower limit may be about 0.01% by weight of the carbon nanotubes in the woven carrier layer, again based on the mass of the carrier.

In any case, it has been found within the scope of the invention that even a relatively low concentration of carbon nanotubes in the textile carrier layer is sufficient to achieve a significant shielding of electromagnetic radiation. In this connection, an attenuation of the electromagnetic radiation in the frequency range from about 100MHz to about 10GHz is actually observed, which is generally higher than 5dB, mostly more than 10dB, preferably more than 20dB and in particular 30dB and more. The frequency range in question from about 100MHz to about 10GHz is relevant in this respect, for example the standard DIN EN 50147-1 96 is relevant here for shielding attenuation and is based on the electromagnetic compatibility test (EMV). In this connection, DE 10 2017 603 A1 merely illustrates an exemplary illustration of a shielding element for an electrical or electronic functional element, wherein the shielding element is used in a vehicle to discharge charge and/or to attenuate electromagnetic fields according to the above criteria.

Carbon nanotubes embedded in a textile carrier layer herein refers to tubes or tubules having a diameter typically <100 nm. Typically, values of a few nanometers in diameter are observed for this. The term nanotubes has indicated that the length of the tubes exceeds their diameter. Lengths of a few micrometers are typical here.

Technically, such carbon nanotubes or CNTs (carbon nanotubes) can be prepared by means of laser ablation of graphite, arc discharge between carbon electrodes or by Chemical Vapor Deposition (CVD). The individual carbon nanotubes can be formed as single-walled or multi-walled. Their walls are composed of carbon, wherein the carbon atoms form a 6-cornered honeycomb structure.

The mechanical properties of the carbon nanotubes are very excellent. Since their density is from 1.3 to 1.4g/cm ³ And the tensile strength of the single-wall embodiment is 30GPa, and the tensile strength of the multi-wall embodiment is up to 63GPa. In contrast, the density of the steel is about 7.85g/cm ³ And the maximum tensile strength is 2GPa.

For this reason, the prior art according to EP 2 079 816 B1 already discloses solutions in which the adhesive tape used as a packaging tape has a carrier which has carbon nanotubes in at least one of its carrier films. In this case, high modulus values (e.g. as stress at 10% elongation) and tensile strengths are observed in the longitudinal direction in the case of packaging tapes of this type. This means that the known teaching is limited to the mechanical reinforcement of adhesive tapes as packaging adhesive tapes by means of carbon nanotubes. The problem of electromagnetic resistance is rather irrelevant.

The present invention is, however, specifically directed to cable jackets for significant electromagnetic shielding. This is measured in the relevant frequency range of about 100MHz to 10GHz according to attenuation values that have been explained previously. In particular, such protective sheaths are used as cable ties for automobile cable harnesses and preferably for automobiles with hybrid or electric drive.

The invention also proceeds from the recognition that protective sheaths of this type are usually equipped with a carrier which has, in whole or in part, at least one textile carrier layer. Since such a woven carrier layer offers various advantages in the described field of application. A protective sheath equipped in this way can thus be mounted particularly easily on the cable to be wrapped. Furthermore, a certain degree of noise attenuation can already be achieved by means of the textile carrier layer, since cables wound in this way, in particular cable harnesses in motor vehicles, would otherwise generate rattling noise. Finally, the woven carrier layer already provides the required mechanical stability and in particular abrasion resistance, as described in detail in the context of already acknowledged WO2005/085379 A1.

The embedding of the carbon nanotubes in the textile carrier layer according to the invention promotes and strengthens the aforementioned positive properties of the textile carrier layer with regard to the realization of a protective sheath, i.e. the textile carrier layer also obtains a shielding effect against electromagnetic radiation in this way. In this connection, even low concentrations of carbon nanotubes in the textile carrier layer of only a few percent by weight are sufficient to achieve a significant attenuation of the electromagnetic radiation. Overall, this means that the positive properties of the textile carrier layer and thus the carrier are not actually influenced or at most only slightly influenced during processing as a cable protective sheath. This means that the processing and the mechanical properties of the carrier of the protective casing modified in this way are designed such that little compromise is observed in terms of mechanical strength, wear resistance, noise attenuation or bending properties. This is where the main advantage can be seen.

The carbon nanotubes may be present in powder form. This can be achieved without problems, since carbon nanotubes with a diameter of less than 100mm and a length of only a few micrometers have a powdery structure anyway. The carbon nanotubes as powder can thus be present as a constituent of the process material for producing the textile support layer. In this case, the processing mass consists partly of carbon nanotubes and optionally at least one additive. The additive in the process mass is advantageously polymer particles.

In principle, the processing material for producing the textile support layer can also consist entirely of carbon nanotubes. In this case, no additional polymer particles are required for processing. Either way, the carbon nanotubes in the process mass are generally present in a minimum concentration of 0.01 wt.%, and preferably at least 1 wt.%, in particular at least 5 wt.%. In most cases, a minimum concentration of carbon nanotubes was observed even in 10 wt% of the processed material. The maximum concentration of carbon nanotubes in the process mass is typically 100% by weight.

The processing material is advantageously an extrusion material for producing textile carbon fibers or carbon threads from carbon nanotubes and/or textile composite fibers or composite threads from carbon nanotubes and additives. That is, if the processing mass is entirely composed of carbon nanotubes (100 wt%), then in achieving an extruded mass, the textile carbon fibers or carbon threads are prepared and extruded from the carbon nanotubes. This is possible in principle. Furthermore, the processing material can also have carbon nanotubes and, for example, polymer particles as additives. In this case, the corresponding extrusion materials for the production of textile fibers are used for the production of textile composite fibers or composite threads from carbon nanotubes and additives. Both the carbon fibers and the composite fibers can be prepared as finite length or continuous filaments.

With the aid of such carbon fibers or carbon threads or composite fibers or composite threads, all textile carrier layers can thus be produced, for example, from woven fabrics, non-woven fabrics, knitted fabrics, scrims, velours, alone or in combination, or from which they consist. That is, within the scope of this variant, the woven carbon fibers or carbon threads and/or composite fibers or composite threads form such a woven carrier layer in whole or in part.

In connection with this, it can be embodied in that the textile carrierThe body layer is made of sewn non-woven fabric

And (4) forming. Here, the non-woven fabric support may be made of plastic fibers, particularly PET fibers, which are not embedded in the carbon nanotubes, so that a conventional manufacturing process may be used. In contrast, the sewing thread of the nonwoven fabric carrier for sewing the sewn nonwoven fabric is made of woven carbon fibers or carbon threads or composite fibers or composite threads of composite threads. In this way, a particularly simple and functionally conventional production method can be realized and implemented.

As an alternative to this, the textile carrier layer can also consist of a woven fabric, the weft threads being made wholly or partially of carbon fibers or carbon threads and/or composite fibers or composite threads. This means that in this case the warp threads are made of conventional plastic fibres without embedded carbon nanotubes, while the weft threads use wholly or partly carbon fibres or carbon threads and/or composite fibres or composite threads. In this case, it is further possible to do so such that the weft threads are thicker than the warp threads.

In this way, the protective sleeve can be designed to be particularly wear-resistant, since the wear resistance of the protective sleeve is given and determined primarily by the weft threads. In addition, the weft threads, which are thicker than the warp threads, easily contain therein plastic nano-tubes required for the electromagnetic shielding effect. In fact, the weaving loom can be designed, for example, such that the thread strength of the warp threads is between 20dtex and 100 dtex. In contrast, the thread strength of the weft thread can be between 150dtex and 400dtex or even greater. Further, the number of warp threads may be specified to be 20 per centimeter to 50 per centimeter. The number of weft threads can be designed similarly. In this way, approximately 50g/m is observed ² And 300g/m ² Woven fabric basis weight in between.

Furthermore, an abrasion resistance according to standard LV 312 (standard 2009/10) of at least class B or class C can be achieved (if such a fabric is additionally provided with an adhesive coating). The possibility of making the weft threads thicker than the warp threads thus not only increases the wear resistance but also makes the production overall easier, according to the invention, since mainly the weft threads are equipped with embedded carbon nanotubes, while other woven fabric components can be manufactured and processed conventionally. It is of course also possible in principle for the woven carrier layer to be formed by a woven fabric, the warp threads being made wholly or partly of carbon fibres or carbon threads and/or composite fibres or composite threads. In this case, the weft threads can be those made of conventional plastic fibers or threads. Furthermore, it is of course also possible to realize and implement hybrid forms in which the warp and weft threads are made wholly or partly of woven carbon fibers or carbon threads and/or composite fibers or composite threads.

In addition to the aforementioned possibility of designing the processing material as an extrusion material for producing textile carbon fibers or carbon threads from carbon nanotubes and/or for producing textile composite fibers or composite threads from carbon nanotubes and additives, the invention proposes, additionally or alternatively, the option of applying a coating solution and/or a coating dispersion in which carbon nanotubes are dispersed, for example for brushing (strichaftrag) onto the textile carrier layer. In this case, the carbon nanotubes are advantageously dispersed in this application solution in a concentration of 0.01% to 30% by weight. The solution can then be applied as an application solution and/or application dispersion to the textile support layer in connection with, for example, the brushing already mentioned. In this case, it is even conceivable to produce the textile support layer in a conventional manner, i.e. the carbon nanotubes are only applied to the textile support layer by means of the application solution and/or the application dispersion.

The above-described brush application can be applied, for example, in the sense of a doctor blade application and represents a particularly simple and easy-to-implement possibility of designing the carrier of the protective sleeve according to the invention as an electromagnetic shield. Of course, the application solution or dispersion can also be applied to the textile support not by brushing but by other means, for example by spraying (Aufspr. U hen), rolling (Aufrollen), roller application (Walzenauftrag) and the like. In principle, the application solution can also be applied entirely generally to the support instead of to the textile support layer, and for example in the case of supports which, in addition to the textile support layer, also have one or more further layers, for example foam layers or film coatings.

In this case, the carbon nanotubes are mostly dispersed in the application solution or dispersion at a concentration of 0.1% by weight to a maximum of 30% by weight. As possible solvents, in addition to water in principle, the use of organic solvents such as alcohols and in particular ethanol, propanol, ethylene glycol and the like is typically considered. Toluene or, for example, ethyl acetate are the same.

Another alternative or additional possibility is that the carbon nanotubes in powder form together with the polymer particles form a processing mass which serves as an extrusion mass for producing at least one additional film layer and/or foam layer of the carrier. This means that, in addition to the necessary textile carrier layer, a film layer or foam layer of this kind is also used supplementarily. In this particular case, this means that not only the textile carrier layer is provided with embedded carbon nanotubes, but additionally also a film layer or a foam layer. A particularly effective electromagnetic shielding can be achieved thereby. Furthermore, it is possible in principle to set the concentration of carbon nanotubes particularly low in the textile carrier layer on the one hand and in the film or foam layer on the other, since these two layers cumulatively provide the desired electromagnetic shielding in this variant.

The polymer particles can be polyethylene particles, polypropylene particles, PET particles, polyamide particles, PUR particles, or particles, generally thermoplastics, which are melted as a compound in an extruder after the introduction of the carbon nanotubes and are extruded, for example, to form a film layer. In principle, the compounds in question can also be foamed to form a foam layer. The film or foam layer in question can also be partially joined in the molten state to a textile carrier layer to form a carrier. In principle, the connection can also be made with an adhesive layer interposed between. The carbon nanotubes in the polymer particles discussed herein are present at a concentration of about 0.01% to 30% by weight.

It has proven to be useful if the carrier as a whole is constructed as a multilayer carrier. In fact, the multi-layer carrier has at least one film layer and/or foam layer in addition to at least one textile carrier layer. The support can furthermore be provided with an adhesive coating, at least in regions, to improve the application on the cable to be coated. Of course, other measures of application of the protective sheath are also conceivable, for example, by means of additional fixing measures to hold the protective sheath in the wrapped state on the cable.

The invention also explicitly encompasses variant embodiments constructed in a comparable manner to WO2005/085379 A1. This means that the carrier may for example consist of two woven fabrics coupled to each other by an adhesive layer. If only one of these woven fabrics of the carrier is provided with embedded carbon nanotubes, it is sufficient to achieve the desired electromagnetic shielding. Therefore, abrasion resistances comparable to those required in LV 312 or in ISO 6722 specified in WO2005/085379A1 can be achieved and implemented.

Furthermore, the invention naturally includes the construction of a carrier, wherein the textile carrier layer consists of a woven fabric connected to a non-woven fabric, two non-woven fabric carriers, a woven fabric plus a foam layer, etc., with or without additional film layers. In all these cases, conventional manufacturing methods can be used, so that on the one hand the desired mechanical properties are achieved, and on the other hand the protective sleeve achieved in this way provides special effects in terms of its electromagnetic shielding. This is where the main advantage can be seen.

The invention is explained in more detail below with reference to the drawings, which represent only exemplary embodiments; the display is as follows:

figure 1 shows a protective sheath for use according to the invention in a schematic longitudinal section,

fig. 2A and 2B show a protective sheath in connection with the wrapping and bundling of cables and

fig. 3 relates to the achieved attenuation of electromagnetic radiation in the frequency range between 100MHz and 10 GHz.

The figure shows the protective sheath of a cable 1. In the exemplary embodiment, and without limitation, cable 1 is a cable 1 that is a component of a cable harness in an automobile. As shown in fig. 2B, the protective sheath may be wound longitudinally around the cable 1 as a longitudinal sheath on the cable 1 in question. As an alternative to this, the protective sheath may also be wound helically around the cable 1 in question in the form of a cable wrap, as shown in fig. 2A.

To this end, as shown in the sectional view in fig. 1, the protective sleeve has carriers 2,3, which are configured as a multilayer carrier according to an exemplary embodiment. In fact, the supports 2,3 have, in whole or in part, at least one textile carrier layer 2. The woven carrier layer 2 is a woven fabric consisting of warp threads 2a extending in the longitudinal direction and weft threads 2b extending in the transverse direction.

In addition to the woven carrier layer 2, a film layer 3 is also implemented according to an exemplary embodiment. The sectional view according to fig. 1 furthermore shows an adhesive coating 4, which adhesive coating 4 is applied to the film layer 3 over the entire surface or over a part of the surface.

The woven carrier layer 2 can in principle also be a not shown layer made of nonwoven, knitted, scrim or also velour, alone or in combination. A combination of two woven fabrics bonded to one another is also conceivable as the woven carrier layer 2, for example a combination of woven fabric/nonwoven, nonwoven fabric/nonwoven or the like. In this connection, it may of course also be a stitched nonwoven.

In the context of the present invention, the textile carrier layer 2 is provided with embedded carbon nanotubes, the concentration of which is typically greater than 0.01% by weight. The concentration of carbon nanotubes in the woven carrier layer 2 was a maximum of 30 wt.%. A significantly lower concentration is generally sufficient to provide the electromagnetic shielding effectiveness of the protective casing particularly achievable and desired in accordance with the present invention.

In an exemplary embodiment, the carbon nanotubes are in powder form and present as a component of the processing mass. In the exemplary embodiment, the processing material is an extruded material, with the aid of which textile plastic fibers are prepared, which are processed further into plastic threads and thus into warp threads 2a and weft threads 2b. According to the invention, the carbon nanotubes may be present in the warp 2a in whole or in part. It is also possible that the weft threads 2b also have carbon nanotubes located therein.

According to an exemplary embodiment, the warp threads 2a and the weft threads 2b have the same yarn fineness. However, within the scope of a preferred variant, the weft threads 2b are significantly thicker than the warp threads 2a and can generally have a fineness of at least twice that of the warp threads 2 a. Furthermore, the design is such that only the weft threads 2b are completely or partially equipped with embedded carbon nanotubes.

However, in principle, carbon nanotubes can also be dispersed in the application solution. Such an application solution can be applied to the textile carrier layer 2, for example, by brushing, not shown here. In addition to the woven support layer 2, the film layer 3 can in principle also be provided with embedded carbon nanotubes. In this case, the grammage of the carbon nanotubes in the film layer 3 is also between 0.01% and 30% by weight.

From fig. 3 one can now understand the effect achieved in terms of shielding electromagnetic radiation with the aid of the protective sheath according to the invention. In fact, only the shielding effect of the woven carrier layer 2 is shown in fig. 3. The woven carrier layer 2 relates to a basis weight of 150g/m ² The woven fabric of (2). In the case of the example studied, the woven fabric of the above basis weight has warp threads 2a and weft threads 2b of respectively the same fineness. The wires 2a, 2b are each provided here with embedded carbon nanotubes. The concentration of carbon nanotubes in the textile support layer 2 under consideration is varied here. In fact, the respective weight specifications for the different and investigated example cases are based on the mass of the carrier layer 2, respectively.

The three different reproduction curves relate to the solid line with a basis weight of 150g/m ² The woven fabric of (1), wherein the grammage or concentration of the carbon nanotubes is 4.1 wt%. A further and dashed variant is again equipped with 150g/m ² And has a carbon nanotube grammage of 7.5 wt%. The same and finally reproduced third line point curve again relates to a basis weight of 150g/m ² And in this case a woven fabric having a grammage or concentration of 10.5% by weight carbon nanotubes.

It can be seen that the attenuation of electromagnetic radiation in the relevant frequency range from about 100MHz to about 10GHz always amounts to more than 30dB, even with a minimum concentration of carbon nanotubes of 4.1 wt.% in the textile carrier layer 2. This attenuation can be increased with increasing concentration of carbon nanotubes to values of almost 50dB or even higher with the third embodiment having 10.5 wt%. It is therefore clear that with increasing concentration of carbon nanotubes in the textile carrier layer 2, the attenuation effect on electromagnetic radiation increases in the frequency range considered from 100Hz to 10 GHz.

Claims

1. Cable protective sheath (1), in particular a cable wrapping tape for cable harnesses in motor vehicles, having a carrier (2,3), which carrier (2,3) has in its entirety or in part at least one textile carrier layer (2), characterized in that the textile carrier layer (2) has in its entirety or in part carbon nanotubes.

2. Protective casing according to claim 1, characterized in that the carbon nanotubes are present in a concentration of 0.01 to 30 wt. -%, preferably 0.01 to 10 wt. -%, particularly preferably 0.01 to 5 wt. -%, each based on the mass of the support (2,3).

3. Protective casing according to claim 1 or 2, characterized in that a processing mass for producing the textile carrier layer (2) is provided, wherein the processing mass consists wholly or partially of carbon nanotubes and optionally at least one additive.

4. The protective sheath according to claim 3, characterized in that the carbon nanotubes in the processing mass are present in a minimum concentration of 0.01% by weight, preferably in a maximum concentration of at least 1% by weight, at least 5% by weight and in particular 10% by weight and 100% by weight.

5. The protective cover of claim 3 or 4, wherein the additive in the processing material is a polymer particle.

6. The protective sheath according to any of claims 3 to 5, characterized in that the processing mass is used as an extrusion mass for producing textile carbon fibers or carbon threads from the carbon nanotubes and/or for producing textile composite fibers or composite threads from the carbon nanotubes and possible additives.

7. Protective sheath according to any of claims 1 to 6, characterised in that the woven carbon fibres or threads and/or the composite fibres or threads form a woven carrier layer (2) in whole or in part.

8. Protective casing according to any of claims 1 to 7, characterized in that the woven carrier layer (2) consists of woven, non-woven, knitted, scrim, velour, alone or in combination.

9. Protective sleeve according to claim 8, characterized in that the textile carrier layer (2) consists of a stitched nonwoven, wherein the nonwoven carrier is made of plastic fibers, in particular PET fibers, and the sewing threads are made of textile carbon fibers or carbon threads and/or composite fibers or composite threads.

10. Protective sheath according to any of claims 1 to 9, characterised in that the woven carrier layer (2) consists of a woven fabric, wherein the weft threads (2 b) are made wholly or partly of woven carbon fibres or carbon threads and/or composite fibres or composite threads.

11. Protective sleeve according to claim 10, characterized in that the weft threads (2 b) are thicker than the warp threads (2 a).

12. Protective sheath according to any of claims 1 to 11, characterised in that the woven carrier layer (2) consists of a woven fabric, wherein the warp threads (2 a) are wholly or partly made of woven carbon fibres or carbon threads and/or composite fibres or composite threads.

13. Protective sheath according to one of claims 1 to 12, characterised in that an application solution and/or an application dispersion with carbon nanotubes dispersed therein in a concentration of 0.01 to 30 wt. -% is provided as a brush-on mass on the textile carrier layer (2).

14. Protective casing according to one of claims 3 to 13, characterized in that the processing mass is used as an extrusion mass for the additional film layer (3) and/or foam layer constituting the carrier (2,3).

15. Protective sheath according to one of claims 1 to 14, characterized in that the carrier (2,3) is constructed as a multilayer carrier which, in addition to the at least one textile carrier layer (2), also has at least one film layer (3) and/or foam layer and is additionally optionally provided with an adhesive coating (4) at least in regions.