EP3136402A1 - Cable, especially data transmission cable, conductor and method for manufacturing such a conductor - Google Patents

Abstract

The invention relates to a cable, in particular a data transmission cable, comprising at least one core (2), an inner conductor (4) and a core sheath (6) applied directly thereon, which comprises a dielectric layer (10) made of a foamed, uncrosslinked thermoplastic material, preferably polyethylene or polypropylene, wherein an outer skins layer (12) of non-foamed, chemically cross-linked polyethylene is arranged around the dielectric layer (10). The special core coating (6) leads to significantly improved soldering properties. Furthermore, a corresponding wire (2) is given and a manufacturing method for this.

Description

The invention relates to a cable, in particular data transmission cable, a wire for such a cable and a method for producing such a wire.

Basically, cable assemblies are known which contain several layers of cross-linked polyethylene. In a so-called foam-skin-PE cable for data transmission is used as an insulating layer, a foamed polyethylene, which is coated with a thin layer, which is also referred to as Aussenskin or Aussenskin layer, as an outer jacket, the entire structure is irradiated. The initially uncrosslinked cable as a whole is exposed to a typically complex electron beam crosslinking. The result is that all layers of polyethylene are at least partially physically crosslinked. Physically crosslinked polyethylene is referred to as PE-Xc according to general nomenclature.

Other cable assemblies all forego crosslinking due to the high cost of electron beam crosslinking. For example, in the US 2013/0180752 A1 describes a cable which has a dielectric layer made of foamed polyethylene around a plurality of inner conductors as a dielectric and as outer layer, ie as outer skin, a high-density polyethylene, PE HD for short. This layer construction is widespread and sufficient for many applications.

However, in cases where the inner conductor is to be connected to other conductors or contact elements by soldering, it has been found that a conventional Structure melts very quickly due to the heat input during the soldering process. This applies both to a soldering of the inner conductor of a single wire and, in particular, also to a soldering of a possibly additional outer conductor, for example a screen layer in the case of a data cable or an outer conductor in the case of a coaxial cable. In the case of a heat input, the foamed dielectric layer usually collapses, resulting in an impedance defect, which in turn usually disturbs the data transmission. With large disturbances in the dielectric even a short circuit can arise. Conventional cable assemblies are therefore suitable only for manual soldering, which depends significantly on the skill and speed of the soldering person, whether the cable is damaged or not. For industrial soldering such a cable construction is therefore unsuitable due to the low capabilities.

Against this background, it is an object of the invention to provide a cable and a wire therefor, having a conductor and a foamed dielectric, wherein the conductor can be connected by automatic soldering with other components. Here, the cable should survive a heat input as possible without damage during soldering. Furthermore, a manufacturing method for the wire is to be specified.

The object is achieved by a cable with the features of claim 1 and by a wire having the features of claim 11. Furthermore, the object is achieved by a method for producing an electrical wire with the features of claim 12. Vorteilhafte Ausgestaltungen, Weiterbildungen und Variants are the subject of the dependent claims. The advantages and configurations mentioned in connection with the cable also apply analogously to the wire as well as the method and vice versa.

The cable is designed in particular as a data transmission cable, for example as a symmetrical data cable or coaxial cable. The cable has at least one core, with an inner conductor and a core jacket applied directly to it, which has a foamed, dielectric layer, comprising uncrosslinked thermoplastic material, wherein an outer skin layer of non-foamed, chemically crosslinked polyethylene is arranged around the dielectric layer. The vein sheath is applied directly to an outer circumference, ie a lateral surface of the conductor. The thermoplastic material from which the dielectric layer is made is in particular an olefin, preferably a polyethylene or a polypropylene.

The advantages achieved by the invention are, in particular, that the cable, hereinafter also referred to without restriction as a data transmission cable, can be soldered particularly easily, i. in particular, that after a soldering operation, the cable has no impedance defect and no short circuit. The essential core idea here is in particular the special combination of an uncrosslinked plastic as a dielectric layer and a chemically crosslinked plastic as an outer skins layer. Compared to physically crosslinked, i. in particular radiation crosslinked polyethylene, the technical advantage is achieved in particular that only the outer skin layer crosslinks. All other layers, however, remain uncrosslinked. In this way, a complex beam crosslinking is dispensed with and advantageously only the outer skins layer is crosslinked, while the dielectric layer remains uncrosslinked, i. The core coating is, so to speak, only locally crosslinked, namely in the area of the outer skin layer. An uncrosslinked plastic for the formation of the dielectric layer now has the advantage that overall better mechanical properties are achieved, whereby the wire with uncrosslinked plastic as a dielectric over a vein with crosslinked plastic survives a higher number of bending cycles without failure. In particular, local crosslinking also prevents cohesive bonding, such that upon collapse of the foamed dielectric layer, the outer skins layer remains intact, i. their structure is preserved.

The core consists of an inner conductor, for example a solid conductor or a stranded conductor, as well as an artery casing, which is applied directly to the outer circumference of the conductor. In particular, the core sheath has a plurality of layers, but at least the dielectric layer and the outer skin layer. The dielectric layer serves to electrically insulate the wire and preferably additionally ensures a certain distance between the inner conductor and adjacent components in the cable. In this case, the core sheath has a total thickness and the dielectric layer has a thickness which makes up a substantial part of the total thickness, preferably about 65 to 95%.

In a symmetrical data transmission cable with multiple wires, such as a paired data transmission cable or a star quad cable, in particular a defined distance between the wires, in particular the inner wires of the wires is achieved by the thickness of the dielectric layer. In a non-symmetrical data transmission cable, such as a coaxial cable, a defined distance between the inner conductor and a shield or outer conductor is defined by the dielectric layer. Such a defined spacing between different components effectively avoids impedance variations which would otherwise interfere with data transmission, e.g. through reflections, which ultimately reduces the possible maximum data transfer rate.

The dielectric layer of the core rubber coating has a layer of a foamed, uncrosslinked thermoplastic, in particular based on olefin. The foaming has the advantageous effect that the relative primitivity, which is also called the dielectric constant, is reduced compared to a similar plastic in unfoamed form, which ultimately affects the impedance, dimension, capacitance and damping in a conventional manner and thereby again a higher data transmission speed can be achieved.

Around the dielectric layer, ie in particular at an outer edge of the dielectric layer of uncrosslinked, foamed thermoplastic, the outer skins layer, also called thin layer or outer skins, is made of non-foamed, chemically cross-linked polyethylene, which is also known as PE-Xa, PE. Xb, PEX-d is called. In this case, PE xa is a peroxidic Crosslinking, with PE Xb a Silanvernetzung and with PE Xd an Az networking in the salt bath. The outer skin layer advantageously forms a stable tube which surrounds the dielectric layer, ie a layer of soft, foamed, uncrosslinked thermoplastic material. If the amount of heat should result in a partial melting of the dielectric layer at one end of the wire, the outer skin layer, due to its stability, provides adequate protection at least against a short circuit of the inner conductor to other conductive components of the cable.

Experiments also showed that such an outer skin improves the solderability of the wire. This is attributed in particular to the fact that the cross-linked polyethylene on the one hand even has a higher continuous service temperature of up to 150 ° C in particular over a non-chemically cross-linked polyethylene having a continuous service temperature of in particular about 85 ° C. Due to the low thermal conductivity of the layers, the foamed dielectric layer is advantageously less heated.

In a preferred variant, the thermoplastic of the dielectric layer is a foamed polyethylene, in short PE-LD, i. in particular the dielectric layer consists of PE-LD. This has the advantage that due to the similar materials, a good connection with the outer skin layer is achieved.

In a preferred variant, the thermoplastic of the dielectric layer is a foamed polypropylene, PP-E for short, i. in particular the dielectric layer consists of PP-E. This has the advantage that when using PP-E up to 20 ° C higher continuous use temperature is achieved, whereby the solderability is further improved.

The outer skin layer has a thickness which is preferably in the range of 70 to 150 μm, ie micrometers, and more preferably in the range of 80 to 120 μm. At lower thicknesses, it was found that the heat capacity of the outer skin layer is insufficient, so that in a soldering of about 10 seconds already caused damage to the cable regularly. The upper limit of the preferred range is in particular due to the necessary flexibility of the cable.

The outer skin layer expediently has a degree of crosslinking G of greater than 50%, preferably greater than 60%. At low degree of crosslinking, the continuous use temperature is usually too low. When crosslinking, individual polymer chains form crosslinking sites with one another. The degree of crosslinking is determined in particular by the number of crosslinking sites relative to the total number of polymer chains. In particular, the degree of crosslinking is proportional to the so-called entanglement density.

The outer skin layer preferably consists of unfoamed, silane-crosslinked polyethylene. According to the nomenclature, this form of crosslinked polyethylene is referred to as PE-Xb. By a silane-crosslinked outer skin layer a particularly good temperature resistance is achieved during soldering.

In a preferred development, in particular as part or further layer of the core sheathing, an additional innerskin layer, in short innerskin, is formed. This is conveniently located directly on the outer circumference of the inner conductor, i. between the inner conductor and the dielectric layer. The innerskin layer then consists in particular of unfoamed polyethylene. In particular, the heat transfer between the inner conductor and the dielectric layer is reduced by such an innerskin layer, so that the soldering properties during soldering of the inner conductor are substantially improved.

Particularly advantageous in this case is the formation of the innerskin layer of a particularly chemically crosslinked polyethylene, whereby the wire is particularly effectively shielded against heat input during soldering.

Particularly preferred is a variant with a non-foamed and chemically crosslinked polyethylene, whereby the soldering behavior is further improved, since in particular by the higher continuous service temperature of the innerskin layer a much longer soldering time compared to a non-foamed, uncrosslinked polyethylene is made possible.

The innerskin layer preferably has a thickness of 25 to 100 .mu.m, preferably 50 to 80 .mu.m. With this thickness range, the best soldering results were achieved in tests.

The wire is particularly suitable for forming the cable as a coaxial cable. This then expediently has an outer conductor, which surrounds the inner conductor and also the dielectric layer, and an outer jacket, which surrounds the outer conductor. The outer conductor then forms in particular a screen for the inner conductor, so it is a shielding layer. Due to the above-mentioned advantageous soldering properties, in particular the structure of the coaxial cable is advantageously retained during soldering, in particular the distance between the inner and outer conductor predetermined by the dielectric layer. In particular, both a soldering of the inner we and the outer conductor with the advantages mentioned is possible.

In a suitable variant, the coaxial cable consists of a core with an inner conductor, preferably an inner skinned layer applied directly to the inner conductor, a dielectric layer applied thereto and an outer skim layer located on the outer edge of the dielectric layer, as well as a shield and a jacket. The jacket is preferably an outer jacket of the cable.

In a suitable variant, the cable is a symmetrical data cable, with at least two wires, each having an inner conductor and a core coating applied directly to it, which has a dielectric layer made of a foamed, uncrosslinked thermoplastic material, wherein an outer skin layer is provided around the respective dielectric layer. Layer of non-foamed, chemically crosslinked polyethylene is arranged.

The symmetrical data cable consists in a suitable variant of at least two wires, or even four, six, or a higher even number of wires, each with an inner conductor, preferably an innerskin layer applied directly to the inner conductor, a dielectric layer applied thereon, and a outer skin layer located on the outer edge of the dielectric layer, and a single screen applied around all the cores, ie a common shielding layer, or about two cores applied umbrellas and a jacket which surrounds the individual screen or all umbrellas. The jacket is then in particular an outer jacket of the cable.

In an advantageous development, the cable has a shielding layer, which surrounds the wires. In other words, around the outer skin layers of the wires is a screen applied or arranged, i. the screen surrounds at least the outer skin layers of two wires. The cores of such a cable are usually stranded together and then in particular are twisted together. The shield layer is formed, for example, as a D-screen, i. as a wire, which is spun around the veins.

The screen, i. the shield layer is particularly preferably a C-screen, i.e., the coaxial cable and the symmetrical data cable, generally the cable. a braid shield, alternatively a D-shield, i. Helical or spiral screen, or a St screen, i. static screen, such as foil screen, which is also called B-screen. In further layers, further shieldings can be arranged beyond.

In an expedient embodiment, at least one shielding layer is applied or arranged directly on the outer skin layer, ie in particular in contact with the outer skin layer. This achieves in particular that when soldering the shield layer, the outer skin layer absorbs the heat generated during soldering and protects the underlying layers. It has been found that an outer skin layer of non-foamed, chemically cross-linked polyethylene disposed directly under the shield layer drastically reduces the time of exposure to heat during soldering before adversely affecting the foamed dielectric layer increases, so that an automatic soldering process can be used without problems in such a structure.

The entire coaxial cable or the symmetrical data cable expediently has an outer sheath, also referred to as a cable sheath, which is arranged around the wire and in particular the shielding layer, and thus forms an outer layer. The outer jacket is therefore exposed directly to environmental influences in particular and protects all internal layers and components against such environmental influences.

For the production of an electrical wire, an electrical conductor is first provided. This is passed through an extrusion head. The extrusion head is connected to several extruders. In this case, a material is provided by each extruder.

The dielectric layer is applied by a dielectric extruder providing a foamed, uncrosslinked thermoplastic and applying this material around the conductor via a dielectric region in the extrusion head. In a suitable variant, the dielectric layer is extruded directly onto the conductor. The material for the dielectric layer is foamed physically or chemically. Chemical foaming is accomplished, for example, by incorporation of a propellant, e.g. Azodicarbonamide, short ADCA. Physical foaming takes place, for example, by introducing an inert gas, such as e.g. Carbon dioxide or nitrogen.

In the dielectric extruder, the material polyethylene or polypropylene is preferably provided.

The outer skins layer is applied by providing an outdoor skins extruder with a non-foamed chemically crosslinked polyethylene and applying this material directly over the dielectric layer over an outer skins area in the extrusion head. Preferably, the chemically crosslinked polyethylene is in this case by extrusion of in particular immediately before the extrusion mixed components obtained from a silane-crosslinkable compound and a crosslinking activator in the extrinsic skin extruder. In other words, the components required to produce cross-linked polyethylene, which in particular are initially provided as granules, are mixed before extrusion. The mixing takes place either manually, but preferably directly at a feed zone of the outer skins extruder with the aid of a dosing station. An automatic mixing using a dosing station is particularly process-reliable. In the outer skins extruder, the molten compound and molten crosslinking activator are then mixed. By immediate is then understood in particular that the residence time of the components in the extruder outer-extruder is less than about 30 minutes, since in this mixing in Außenskin extruder already uses the crosslinking and in particular is not yet complete.

In this case, in a preferred variant, an innerskin layer is additionally applied to the inner conductor by providing a particularly unfoamed polyethylene through an innerskin extruder and extruding directly onto the electrical conductor via an innerskin region in the extrusion head. In addition, the innerskin layer is preferably produced in particular similar to the outer skins layer as a chemically crosslinked innerskin layer of polyethylene.

The extrusion head is conveniently a coextrusion head for extruding multiple layers around the inner conductor. The extrusion head then has several stages, namely the innerskin area as the first area, the dielectric area as the second area, and the outer skink area as the third area. In one variant, the extrusion head has only the two last-mentioned regions and, accordingly, no innerskin layer is extruded.

In this case, the extrusion of the outer skin layer, the dielectric layer and, in the case of an additional innerskin layer, also the extrusion thereof, in particular in a multi-layer process, ie a two- or three-layer process. Here are the outer skin layer, the dielectric layer and in the presence also the innerskin layer in a common extrusion head and applied at the same time over the various areas of the extrusion head.

Fig. 1

eine elektrische Ader,

Fig. 2

ein als Koaxialkabel ausgebildetes Kabel,

Fig. 3

ein als symmetrisches Datenkabel ausgebildetes Kabel.

Embodiments of the invention will be explained in more detail with reference to a drawing. In each case show schematically and in cross section:

Fig. 1

an electrical wire,

Fig. 2

a cable designed as a coaxial cable,

Fig. 3

a cable designed as a symmetrical data cable.

In the figures, like-acting parts are provided with the same reference numerals.

In Fig. 1 In the embodiment shown here, this has an innerskin layer 8 and a dielectric layer 10. In a variant which is not shown, the innerskin layer 8 is omitted and the dielectric layer 10 is applied directly to the conductor 4. The wire 2 further comprises an outer skin layer 12 disposed around the dielectric layer 10. The dielectric layer 10 is here made of a foamed, uncrosslinked thermoplastic polymer based on olefin.

In the exemplary embodiment shown here, the innerskin layer 8 has a thickness D1 of approximately 60 μm, the dielectric layer 10 has a thickness D2 of approximately 1.35 mm and the outer skins layer 12 has a thickness D3 of approximately 90 μm. Thus, the thickness D2 of the dielectric layer makes up about 90% of a total thickness of the core sheath 6.

Fig. 2 shows a cable 14, which is designed as a coaxial cable. The cable 14 has a wire 2 according to Fig. 1 on, which is surrounded by an outer conductor 16. The inner conductor 4 and the outer conductor 16 thus form two concentric conductors of the coaxial cable, between which the dielectric layer 10 as a dielectric is arranged with a certain thickness D2. Around the outer conductor 16 around an outer sheath 18 is arranged. The outer conductor 16 also forms a shield layer 20.

Fig. 3 shows a variant of the cable 14, which is designed here as a symmetrical data cable, with two wires 2, each according to Fig. 1 are formed. The two wires 2 are jointly surrounded by a shield layer 20, which in turn is surrounded by an outer sheath 18.

The following Table 1 shows results from comparison test of the respective Löwendenung compared to conventional cables from very bad (-) to very good (++). As a comparison, ie as a reference here serves a conventional core 2, which has only a conductor 4 made of copper with a foamed dielectric layer 10 applied thereon as a core sheath 6. Table 1 No. inner conductor Innenskin layer dielectric Außenskin layer outer conductor outer sheath soldering suitability Ref. Cu - PE-LD or PP-X / EPP - - - - 1 Cu - LDPE PE-Xb - - + 2 Cu PE-Xb LDPE PE-Xb - - ++ 3 Cu PE-Xb LDPE PE-Xb D wing PVC inner conductor ++
outer conductor ++ 4 Cu PE-Xb PP-X / EPP PE-Xb D wing PVC inner conductor ++
Screen orientation ++

In test series 1, a core 2 with an inner conductor 4 made of copper, without innerskin layer 8, a dielectric layer 10 made of foamed, uncrosslinked polyethylene, short PE-LD, an outer skin layer 12 made of non-foamed, silanvernetztem polyethylene, PE short Xb, without outer conductor 16 or shield layer 20 and without outer jacket 18 tested. This wire 2 already shows good soldering behavior (+) when soldering the inner conductor 4 to cores according to the prior art.

In the experimental series 2, a vein, as in Fig. 1 shown, tested. The core 2 consists of an inner conductor 4 made of copper, an innerskin layer 8 made of non-foamed, silane-crosslinked polyethylene, short PE-Xb, a dielectric layer 10 made of foamed, uncrosslinked polyethylene, short PE-LD, an outer skin layer 12 made of non-foamed, silane cross-linked polyethylene, short PE-Xb, no outer conductor 16, no shield layer 20 and no outer sheath 18. Due to the innerskin layer 8, this core 2 shows a significantly improved soldering behavior (++) compared to the experimental series 1 when soldering the inner conductor 4.

In Experimental Series 3, a cable 14 formed as a coaxial cable was used as shown in FIG Fig. 2 shown, tested. The coaxial cable consists of a core 2 with an inner conductor 4 made of copper, an innerskin layer 8 made of non-foamed, silane-crosslinked polyethylene, short PE-Xb, a dielectric layer 10 made of foamed, uncrosslinked polyethylene, short PE-LD, an outer skin layer 12 of unfoamed, silane-crosslinked polyethylene, PE-Xb for short, an outer conductor 16, which here is a D-shield, and an outer jacket 18 made of PVC. Due to the innerskin layer 8, both the inner conductor 4 and the outer conductor 16, and thus the cable 14 as a whole, show a significantly improved soldering behavior (++).

In the test series 4, a symmetrical, ie paired data cable cable 14 was formed, as in Fig. 3 shown, tested. The data cable consists of two stranded cores 2, each with an inner conductor 4 made of copper, a Innenskin layer 8 made of non-foamed, silanvernetztem polyethylene, short PE-Xb, a dielectric layer 10 made of foamed, uncrosslinked polyethylene, short PE-LD, an outer skin layer 12 made of non-foamed, silanvernetztem polyethylene, short PE-Xb, and a both wires 2 surrounding shield layer 20, which is a D-screen here and a surrounding the shield layer 20 outer sheath 18 made of PVC. Due to the inner skin layer 8, the cores 2 and the shielding layer 20 and thus the cable 14 as a whole show a significantly improved soldering behavior (++).

LIST OF REFERENCE NUMBERS

2

Vein

4

inner conductor

6

wire insulation

8th

Innenskin layer

10

dielectric

12

Außenskin layer

14

electric wire

16

outer conductor

18

outer sheath

20

screen orientation

D1, D2, D3

thickness

Claims (15)

Cable (14), in particular data transmission cable, with at least one core (2), with an inner conductor (4) and a core coating (6) applied directly thereon, which has a dielectric layer (10) of a foamed, uncrosslinked thermoplastic resin,
characterized,
that the dielectric layer (10) has a Außenskin layer (12) of non-cellular, chemically cross-linked polyethylene is arranged. Cable (14) according to claim 1,
characterized,
that the thermoplastic material of the dielectric layer (10) is a foamed polyethylene or polypropylene. Cable (14) according to one of the preceding claims,
characterized,
in that the outer skin layer (12) has a thickness (D3) in the range of 70 to 150 μm, preferably 80 to 120 μm. Cable (14) according to one of the preceding claims,
characterized,
Außenskin that the layer (12) has a cross-linking degree G of greater than 50%, preferably greater than 60% has. Cable (14) according to one of the preceding claims,
characterized,
Außenskin that the layer (12) consists of non-foamed, silane cross-linked polyethylene. Cable (14) according to one of the preceding claims,
characterized,
in that the core sheathing (6) has an innerskin layer (8) which is produced in particular from unfoamed polyethylene, in particular from a cross-linked polyethylene. Cable (14) according to one of the two preceding claims,
characterized
the innerskin layer (8) has a thickness (D1) in the range of 25 to 100 μm, preferably 50 to 80 μm. Cable (14) according to one of the preceding claims,
characterized,
that this is designed as a coaxial cable, with an outer conductor (16), which surrounds the inner conductor (4) and is spaced therefrom by the dielectric layer (10), and with an outer jacket (18), which the outer conductor (16) surrounds. Cable (14) according to one of claims 1 to 8,
characterized,
that this is designed as a symmetrical data cable, with at least two wires (2), each having an inner conductor (4) and an applied directly to this Aderummantelung (6), which has a dielectric layer (10) made of a foamed, uncrosslinked thermoplastic , wherein an outer skin layer (12) made of non-foamed, chemically cross-linked polyethylene is arranged around the respective dielectric layer (10). Cable (14) according to the preceding claim,
characterized,
that this has a shielding layer (20) surrounding the wires (2). A wire (2) for a cable (14) according to any one of the preceding claims, comprising an inner conductor (4) and a wire sheath (6) applied directly thereon, which comprises a foamed, dielectric layer (10). uncrosslinked thermoplastic material, wherein around the dielectric layer (10) an outer skins layer (12) of non-foamed, chemically crosslinked polyethylene is arranged, wherein the vein sheath (6) additionally preferably a Innenskin layer (8) of non-foamed and uncrosslinked or chemically crosslinked Polyethylene, which is surrounded in front of the dielectric layer (10). Method for producing an electrical wire (2) according to claim 11, comprising the steps: Providing an inner conductor (4), Passing the inner conductor (4) through a dielectric region and through an outer skin region of an extrusion head of an extrusion machine, - Applying a dielectric layer (10) made of a foamed thermoplastic material in the dielectric region of the extrusion head and - Applying a Außenskin layer (12) of non-foamed, chemically crosslinked polyethylene in the outer skins area of the extrusion head. The method of claim 12, wherein the thermoplastic of the dielectric layer (10) is foamed polyethylene or foamed polypropylene. A method according to any one of claims 12 or 13, wherein the chemically crosslinked polyethylene of the outer skins layer (12) is formed by mixing a silane crosslinkable compound with a crosslinking activator into a mixture and then extruding the mixture after mixing. The method of any one of claims 12 to 14, wherein prior to passing the inner conductor (4) through the dielectric region the inner conductor (4) is additionally passed through an innerskin area of the extrusion head, - An inner skins layer (8) is applied in particular of non-foamed polyethylene in the innerskin area of the extrusion head.

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