DE102017222744A1 - Crosslinking of polyethylene-based insulation layers - Google Patents

Abstract

The present invention relates to a method of manufacturing a cable or cable core having one or more polyethylene-based insulation layers. Furthermore, the invention relates to cables or cable cores with polyethylene-based insulation layer, produced by this method.

Description

The present invention relates to a method of manufacturing a cable or cable core having one or more polyethylene-based insulation layers. Furthermore, the invention relates to cables or cable cores made with this method.

State of the art

An electrical cable usually comprises at least one metallic conductor, hereinafter also referred to as "cable core" or "conductor", which is sheathed. A conductor can also consist of several sheathed cable cores, which are combined into units and in turn are sheathed once or several times. As the material for the sheaths polyethylene-based materials can be used, wherein in a cable different shells of different materials may be present.

Polyethylene-based materials are applied to the substrate without cross-linking, for example to a cable core, and then crosslinked. This crosslinking has hitherto been crosslinked by introducing rays, especially β-radiation. This is particularly disadvantageous, since the Kabelbestandeile existing at the time of networking must be resistant to the action of radioactive radiation. Especially fluoropolymers are not suitable to be exposed to higher radiation doses.

It is also known that polyethylene poorly absorbs microwave radiation because it is non-polar and has a very small dielectric loss factor.

The use of dielectric inorganic additives to increase microwave absorption is believed to be the case for silicones US 4,980,384 . EP 0945916 A2 and EP 1655328 B1 described. Such additives are not needed in the context of the present invention.

DE 198 55 718 A1 describes the crosslinking of silicone rubbers, in particular by condensation crosslinking, by means of microwave radiation for the production of moldings, for example medium and high voltage fittings for plastic power cables. Moreover, those in the DE 19855718 required crosslinking times of eg 25 minutes (Example 1 of DE 19855718 ) not suitable for cable production.

EP1900767 B1 discloses a method of making silicone foams using microwave radiation. The synthesis method described requires the addition of magnetite to absorb the microwave radiation. In addition, blowing agents are used to produce foams. The production of cable sheathing is not proposed.

The DE2422914 describes a cable with polyethylene insulation, which is crosslinked peroxide, under the influence of microwaves. In this case, carbon black is used for absorbing the microwave radiation. The use of metal catalysts to crosslink grafted polyethylene with microwave radiation is not described.

In view of the above-mentioned problems, therefore, there has been a demand to provide an improved method for producing polyethylene sheaths for cables or cable cores.

Summary of the invention

In the context of the present invention, it has been found that polyethylene-based sheaths for cables or cable cores can be cross-linked by the use of microwave radiation. Here, for example, a silane-grafted polyethylene is crosslinked in the presence of a catalyst under the action of microwave radiation. The polyethylene or a polyethylene copolymer may, for example, be grafted with vinyl silanes.

According to the invention, a metal catalyst is used which is heated by the microwave radiation. The essence of the invention is that the energy required for crosslinking is transported by the microwaves to the places where the reactive components are and where it is used. As a result, the degree of crosslinking in the layer becomes higher. In principle, it is a silane crosslinking, which is additionally activated by the microwaves. This achieves a degree of crosslinking which is higher for normal silane crosslinking, since the metal catalysts and possibly present peroxides are directly excited by the microwaves. An additional advantage could be obtained if the materials, after reacted, have no polar or less polar properties. The energy supply through the microwaves is thus self-regulating. This is an improvement over conventional thermal crosslinking support. Another advantage is that a lesser amount of catalyst is sufficient because the reactivity is enhanced by the microwaves.

Another advantage of the present invention is that a metallic conductor is inserted into and / or performed in a microwave chamber. The microwave radiation couples into the conductor, the resulting "microwave field" spreads radially symmetrical and runs along the conductor, so that even different geometries can be fully networked (ie the microwave radiation is guided along the metallic conductor and the conductor serves as a kind of antenna). In the use of microwaves according to the invention, temperatures are not so high that the materials of the cable could outgas.

1. a) Aufbringen einer Masse, enthaltend
   • a1) Polyethylen und/oder Polyethylen-Copolymer, das/die mit Silan gepfropft ist/sind, und einen Metallkatalysator; oder
   • a2) Polyethylen und/oder Polyethylen-Copolymer, Silan, Peroxid, und einen Metallkatalysator,
   mittels eines Extrusionsverfahrens auf
   1. i) einen oder mehrere metallische(n) Kabeladerkern(e), oder
   2. ii) eine Kabelader, oder
   3. iii) mehrere zu einer Einheit zusammengefasste Kabeladern, wobei die Einheit bereits ein oder mehrere Isolationsschichten als Ummantelung der Kabeladern aufweisen kann,
   um eine Isolationsschicht zu bilden; und
2. b) Vernetzen der aufgebrachten Masse in einer Mono-Mode-Mikrowellenkammer mit kontinuierlicher Strahlung von 1,9-3,0 GHz.

The present invention thus relates to a method for producing a cable or a cable core, with one or more insulation layers based on polyethylene, comprising the steps:

1. a) applying a mass containing
   • a1) polyethylene and / or polyethylene copolymer grafted with silane, and a metal catalyst; or
   • a2) polyethylene and / or polyethylene copolymer, silane, peroxide, and a metal catalyst,
   by means of an extrusion process
   1. i) one or more metallic cable core (s), or
   2. ii) a cable core, or
   3. iii) a plurality of cable cores combined into one unit, wherein the unit may already have one or more insulation layers as a sheathing of the cable cores,
   to form an insulating layer; and
2. b) crosslinking of the applied mass in a mono-mode microwave chamber with 1.9-3.0 GHz continuous radiation.

In addition, the invention relates to a cable produced by the method according to the invention or a cable core, as well as products containing them.

With the method according to the invention, polyethylene-based insulation layers can be produced on a substructure which contains temperature-sensitive materials, for example a cable or cable core covering, for the purpose of a multilayer construction. Heretofore, it has been difficult to apply and cross-link a radiation cross-linked polyethylene layer to fluoroethylene propylene or a layer of comparable fluoroplastic. The radiation doses used in the hitherto known methods for crosslinking polyethylene-based insulation layers were too high. However, processes based on purely chemical effects do not achieve the high crosslinking required. In the microwave technology based method of the present invention can be dispensed with a radioactive radiation, so that premature aging of fluoropolymers can be excluded. In addition, the selective introduction of energy only at reactive sites (i.e., by absorption of energy by the catalyst) of the crosslinkable material prevents melting of the materials already present prior to application of the polyethylene layer. In addition, due to the activation, a smaller amount of catalyst is sufficient.

Another advantage of the method according to the invention is that the microwave beams are coupled in an advantageous manner into the metallic conductor of the cable, the cable core and / or the sheathing and the crosslinking reaction is accelerated. The inventive method is thus more efficient and faster. In particular, the conductor in the microwave chamber has a positive effect on the heating. If a metallic conductor is introduced into the waveguide, a coaxial structure results. This has the advantage that the microwave is immediately coupled into the metallic part and the resulting "microwave field" propagates radially symmetrically and runs along the conductor. So the microwave does not run into the empty microwave chamber, where it is reflected by the housing, but can be coupled into the center of the line. Here are two effects. On the one hand, the microwave immediately inserts into the metallic conductor and, on the other hand, the microwave passes through the polyethylene insulation layer. As a result, a larger area is "irradiated".

As already described, microwave irradiation of the uncrosslinked polyethylene-containing composition takes place in a microwave chamber, wherein the microwave radiation is generated by means of a magnetron and irradiated by means of a waveguide.

The coupling of the microwave radiation in the conductor, however, leads to a disadvantage, namely that the radiation from the microwave chamber can escape through the conductor into the environment. According to the invention, this radiation is "captured" again by an absorber arrangement and at least partially reflected back into the microwave chamber. The absorbers according to the invention enable a construction with only one energy source, i. Irradiation of the energy exclusively into the microwave chamber. The absorbers also increase the safety of the microwave system, as they protect the workforce from radiation.

Moreover, the use of a microwave system results in less energy losses compared to conventional methods and the method is more environmentally friendly and less expensive. In particular, the use of the microwave system described herein enables very high energy efficiency and production speed. Also, by the Omitting previously required long sintering distances a space saving can be achieved. In addition, the microwave radiation used in the invention suffers no power loss in depth. The microwave penetrates completely into the material and heats it evenly. With IR, the heating is inhibited by the material thickness in the component.

Detailed description of the invention

For the purposes of the present invention, a "wire" is a single solid metallic conductor / strand. A "strand", e.g. Round strand, Zopflitze, or flat strand, consists of bundled wires. A core or cable core has a metallic cable core cored with one or more insulation layers. A "cable" contains cores which, optionally with fillers or other elements, are stranded together and encased in one or more layers. Cores can be twisted elemental to pairs or triples, the elements can again rum around one or more layers with fillers for gusset filling, be stranded and form a unit. The cable may also include a screen whereby coats can be networked outside the screen and layers that are underneath the screen and protected at the RF level can not be crosslinked.

For example, PTFE, glass silk, polyamide, polypropylene or cotton filler can be used for gusset filling. Preferably, the wires and strands are made of copper, or copper, which has a layer support such as e.g. Tin, nickel or silver.

Thus, according to the invention, a first polyethylene-based insulating layer may be applied to the metallic conductor, i. Wire / wires or stranded wire / strands are applied. However, it is also possible to use a subsequent layer, e.g. applying a second or third layer to one or more layers already on the conductor. Similarly, multiple pooled cable cores may be provided with a polyethylene based insulation layer. In this case, either cable cores can be stranded and optionally provided with further components and then surrounded with a polyethylene-based insulation layer. Alternatively, the unit of multiple cable cores may already be provided with one or more cladding (s) and a succeeding layer, e.g. a second or third layer applied to the layer (s) already on the unit. Of course, after the application of the polyethylene-based insulation layer, further layers can be applied to the cable core or the cable. It is also possible to apply a second or further polyethylene-based insulation layer directly to a polyethylene-based insulation layer or to a layer above the polyethylene-based insulation layer.

The present invention relates to the following embodiments:

1. a) Aufbringen einer Masse, enthaltend
   • a1) Polyethylen und/oder Polyethylen-Copolymer, das/die mit Silan gepfropft ist/sind, und einen Metallkatalysator; oder
   • a2) Polyethylen und/oder Polyethylen-Copolymer, Silan, Peroxid, und einen Metallkatalysator,
   mittels eines Extrusionsverfahrens auf
   1. i) einen oder mehrere metallische(n) Kabeladerkern(e), oder
   2. ii) eine Kabelader, oder
   3. iii) mehrere zu einer Einheit zusammengefasste Kabeladern, wobei die Einheit bereits ein oder mehrere Isolationsschichten als Ummantelung der Kabeladern aufweisen kann,
   um eine Isolationsschicht zu bilden; und
2. b) Vernetzen der aufgebrachten Masse in einer Mono-Mode-Mikrowellenkammer mit kontinuierlicher Strahlung von 1,9-3 GHz, bevorzugt 2450 MHz ± 100 MHz, bevorzugt unter kontinuierlicher Durchführung der aufgebrachten Masse durch die Mono-Mode-Mikrowellenkammer.

A method of making a cable or cable core comprising one or more polyethylene based insulation layers comprising the steps of:

1. a) applying a mass containing
   • a1) polyethylene and / or polyethylene copolymer grafted with silane, and a metal catalyst; or
   • a2) polyethylene and / or polyethylene copolymer, silane, peroxide, and a metal catalyst,
   by means of an extrusion process
   1. i) one or more metallic cable core (s), or
   2. ii) a cable core, or
   3. iii) a plurality of cable cores combined into one unit, wherein the unit may already have one or more insulation layers as a sheathing of the cable cores,
   to form an insulating layer; and
2. b) crosslinking of the applied mass in a monomode microwave chamber with continuous radiation of 1.9-3 GHz, preferably 2450 MHz ± 100 MHz, preferably with continuous application of the applied mass through the mono-mode microwave chamber.

Of course, prior to crosslinking, the applied mass must not be provided with a shield (e.g., metal shield) that keeps the RF radiation away from the deposited mass.

Unless explicitly referred to herein polyethylene copolymers, the term "polyethylene" also refers to "polyethylene copolymers", but in the preferred embodiment, only "polyethylene".

According to the invention, polyethylene, or a polyethylene copolymer, or mixtures of different polyethylenes, different polyethylene copolymers, or mixtures of polyethylene (s) with polyethylene copolymer (s) can be used.

In the polymer-containing composition, these polymers are preferably already grafted with silanes. For example, the polymers in the presence of peroxides and vinylsilanes or grafted to other silanes to obtain the starting material for step (a1).

The crosslinking of the grafted polyethylene requires the presence of water. Unless there is a particularly dry climate, the ambient humidity is sufficient. Preferably, the humidity during crosslinking is at least 40%, more preferably at least 50% or 60%, relative humidity at 20 ° C.

The melting points of the polyethylenes before crosslinking, e.g. determined by differential scanning calorimetry, for example, may be in the range of 80-150 ° C. For example, grafted PE (i.e., PE crosslinked according to the invention) may be between about 105 to about 135 ° C. Preferably, the melting point is 125-135 ° C for HDPE.

Preferably, the MFI is the polyethylene-containing composition 23 - 70 g / 10 min, measured according to EN ISO 1133, under conditions of 180 ° C and a load of 21,6kg.

As used herein, HDPE (or PE-HD) refers to PE with weakly branched polymer chains and therefore high density greater than 0.935 to 0.97 g / cm ^{3 as} determined by ISO 1183, where "HD" stands for "high density". stands.

As used herein, LDPE (or PE-LD) refers to PE having highly branched polymer chains and hence low density from 0.915 g / cm ³ to 0.935 g / cm ³ , where "LD" stands for "low density".

As used herein, refers VLDPE (or PE-VLD) on PE very low density of 0.85 g / cm ³ to less than 0.915 g / cm ^3, determined according to ISO 1183, wherein "VLD" for "very low density " stands. The VLDPE is especially linear VLDPE.

As used herein, LLDPE (or PE-LLD) refers to linear low density polyethylene whose polymer molecules have only short branches. These branches are prepared by copolymerization of ethene and higher alpha-olefins (typically butene, hexene or octene) ("LLD" stands for "linear low density").

As used herein, PE-HMW refers to high molecular weight polyethylene. The polymer chains are longer than in PE-HD, PE-LD or PE-LLD, the average molecular weight is 500-1000 kg / mol ("HMW" stands for "high molecular weight").

As used herein, PE-UHMW refers to ultrahigh molecular weight HDPE having an average molecular weight of up to 6000 kg / mol and a density of 0.93-0.94 g / cm ³ , as determined by ISO 1183, where "UHMW" represents "Ultra high molecular weight" stands.

According to the invention, the polyethylenes described herein can be used. Either these are grafted directly in the process according to the invention, or the grafting takes place beforehand. Preferably, LDPE and HDPE are used. For example, the commercially available vinyltrimethoxysilane-grafted polyethylene called SEG 11 / 337.8 the company Silon, CZ.

Polyethylene copolymers, by copolymerization of ethene and higher α-olefins (eg C ₄ -C ₁₂ α-olefins, typically butene, hexene or octene) may also be used herein. These can be used alone or in admixture with other polyethylenes.

For the purposes of the invention, a degree of grafting of 0.2 to 20 wt .-% (proportion of carboxyl-containing compounds), based on the polyethylene, has proven to be favorable, in particular Pfropfungsgrade from 0.5 to 15 wt .-% and in particular preferably from 1 to 10 wt .-%, come into question.

The size of the particles of the grafted polymer is preferably small, that is to say <0.5 μm, in particular <0.1 μm, and> 0.001 μm, in particular> 0.005 μm. The particle size can be determined, for example, using a volumetric dynamic refraction method, preferably using a measuring instrument from Malvern Instruments, Ltd., Malvern, Great Britain, preferably a mastersizer 2000 to be determined.

2. The method according to embodiment 1 wherein the polyethylene-containing composition contains, in addition to the catalyst substance (s) and optionally polar peroxides, no dielectric, inorganic additives. Preferably, less than 1.5% by weight of polar substances are present in the applied mass.

In principle, additives can be used, for example, in an amount of 0.1-5 wt .-%. Fumed silica or pyrogenic silica, as it is also called, consists entirely of amorphous silica particles (SiO ₂ ), which are aggregated into larger units. These have a very good dipole moment and are very well activated by microwaves. According to the invention therefore no microwave additives must be added. In addition, the presence of the electrical conductor causes the energy utilization is improved.

3. The method according to embodiment 1 or 2 wherein at least one absorber assembly is disposed on at least one of the apertures of the microwave chamber to direct microwave radiation along the passage of the same Polyethylene-containing mass through the mono-mode microwave chamber, to absorb and reflect.

1. (i) 60-99 Gew.-%, bevorzugt 90-98 Gew.-%, weiter bevorzugt 95-98 Gew.-%, Polyethylen-Moleküle oder gepfropfte Polyethylen-Moleküle enthält, und/oder
2. (ii) 1-10%, bevorzugt 1-7%, Katalysatorsubstanzen und Hilfsstoffe, z.B. in der Form eines Masterbatches zugesetzt (enthaltend z.B. Stabilisatoren, Metalldesaktivatoren und Katalysatorsubstanzen, bevorzugt enthaltend Metallkatalysator(en), beispielsweise in einer Menge von 0,5-2%), und gegebenenfalls Peroxid(e) enthält, und/oder
3. (iii) hochtemperaturvernetzend, bevorzugt bei einer Temperatur von oberhalb 95°C vernetzbar, ist. Die Menge an Katalysator beträgt bevorzugt 0,5 - 2 Gew.-%. Besonders bevorzugt enthält die Polyethylen-enthaltenden Masse nur gepfropftes Polyethylen (oder Mischungen von verschiedenen Polyethylenen) und Metallkatalysator(en).

4. The process of any one of the preceding embodiments, wherein the uncrosslinked polyethylene-containing composition comprises:

1. (i) 60-99 wt%, preferably 90-98 wt%, more preferably 95-98 wt%, polyethylene molecules or grafted polyethylene molecules, and / or
2. (ii) 1-10%, preferably 1-7%, of catalyst substances and auxiliaries, for example in the form of a masterbatch (containing, for example, stabilizers, metal deactivators and catalyst substances, preferably containing metal catalyst (s), for example in an amount of 0.5- 2%), and optionally contains peroxide (s), and / or
3. (iii) high temperature crosslinking, preferably crosslinkable at a temperature above 95 ° C. The amount of catalyst is preferably 0.5-2% by weight. Most preferably, the polyethylene-containing composition contains only grafted polyethylene (or mixtures of different polyethylenes) and metal catalyst (s).

5. The method according to any one of the preceding embodiments, wherein the metal catalyst is selected from inorganic and organic metal catalysts, preferably organic metal catalysts, more preferably organotin compounds.

According to the invention, metal catalysts are used which, due to their dielectric properties, can be heated by microwave radiation.

6. The process according to any one of the preceding embodiments, wherein the organotin compound is an alkyl tin compound or dialkyltin compound, preferably dibutyltin oxide, monobutyltin oxide, dimethyloxybutyltin, dialkyltin dicarboxylate, e.g. Dibutyltin dilaurate (DBTL), dioctyltin maleate, or dibutyltin diacetate, preferably dibutyltin dilaurate.

7. The process according to any one of the preceding embodiments, wherein the peroxides are selected from the group consisting of: hydrogen peroxide, hydroperoxides of the formula ROOH, dialkyl or diaryl peroxides of the formula ROO-R ', potassium peroxodisulfate K ₂ S ₂ O ₈ , percarbonates RO- CO-OO-CO-OR, dibenzoyl peroxides R-Ph-CO-OO-CO-Ph-R, di-tert-butyl peroxide (CH ₃ ) ₃ -C-CO-OO-CO-C- (CH ₃ ) ₃ , Bis- (2,4-dichlorobenzoyl peroxide (DCLBP) and tert-butyl hydroperoxide (CH ₃ ) 3-COOH, acyl peroxides of the formula R-CO-OH, (aromatic) diacyl peroxides of the formula R-CO-OO-CO-R and inorganic peroxide compounds, wherein R and R 'independently represent, for example, a C _1-5 alkyl group, a C _1-5 aryl group, or a C _1-10 alkylaryl group.

1. i) der eine oder die mehrere metallische(n) Kabeladerkern(e), oder
2. ii) die Kabelader, oder
3. iii) mehrere zu einer Einheit zusammengefasste Kabeladern, nur Abschnittsweise vernetzt werden und zwischen den vernetzten Abschnitten unvernetzte Abschnitte verbleiben. Diese kann mit Hilfe eines Mikrowelleninjektors erreicht werden. Derartige Geräte können beispielsweise von der Firma Fricke und Mallah Microwave Technology GmbH, DE, bezogen werden (http://www.microwaveheating.net/generatoren.html). Die breite der vernetzten Abschnitte kann durch die Breite des Mikrowelleninjektors bestimmt werden.

8. The method according to one of the preceding embodiments, wherein

1. i) the one or more metallic cable core (s), or
2. ii) the cable core, or
3. (iii) multiple cable cores aggregated into a single unit are cross-linked only in sections and non-cross-linked sections remain between the cross-linked sections. This can be achieved with the help of a microwave injector. Such devices can be obtained, for example, from the company Fricke and Mallah Microwave Technology GmbH, DE (http://www.microwaveheating.net/generatoren.html). The width of the crosslinked sections can be determined by the width of the microwave injector.

9. The process according to any of the preceding embodiments, wherein the silane is selected from the group consisting of vinyltrimethoxysilane, vinyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3 Glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N -2- (aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N- (vinylbenzyl) -2 -aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyltrialkoxysilane, 3-isocyanate prop yltriethoxysilane, tris (trimethoxysilylpropyl) isocyanurate, and 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropyltrimethoxysilane.

10. The method of any one of the preceding embodiments, wherein the polyethylene is selected from LDPE and HDPE.

1. (i) als einzige Wärmequelle verwendet wird; und/oder
2. (ii) mit einer Leistung von mindestens 900 W, eingestrahlt wird.

11. The method according to any one of the preceding embodiments, wherein the microwave radiation

1. (i) is used as sole heat source; and or
2. (ii) with a power of at least 900 W, is radiated.

12. The process according to any one of the preceding embodiments, wherein the crosslinking of the ungrafted polyethylene is carried out in one or two stages, wherein the polyethylene is crosslinked in the one-step process in the presence of peroxide, silanes and metal catalyst and the polyethylene in the two-stage process in the first stages Silanes in the presence of peroxide is treated, and is crosslinked in a subsequent second stage.

1. (i) zwei oder mehr Polyethylen-Isolierungsschichten vorhanden sind und diese entweder nacheinander oder gleichzeitig aufgebracht werden, und/oder
2. (ii) die Kabelader, oder die mehreren zu einer Einheit zusammengefassten Kabeladern, bereits eine Fluorethylenpropylen-Schicht oder eine Schicht aus vergleichbarem Fluorkunststoff aufweist.

13. The method according to one of the preceding embodiments, wherein

1. (i) two or more polyethylene insulation layers are present and these are applied either sequentially or simultaneously, and / or
2. (ii) the cable core, or the plurality of cable cores integrated into a unit, already has a fluoroethylene propylene layer or a layer of comparable fluoroplastic.

1. (i) der Kabelkern einen Durchmesser von ≥1 mm aufweist, und/oder
2. (ii) die Polyethylenschicht eine Schichtdicke von 0,5 mm - 4,0 mm aufweist.

14. The method according to one of the preceding embodiments, wherein

1. (i) the cable core has a diameter of ≥1 mm, and / or
2. (ii) the polyethylene layer has a layer thickness of 0.5 mm - 4.0 mm.

15. The method of any preceding embodiment, wherein the polyethylene-containing composition contains no additive selected from the group consisting of: silicon carbide, silicon carbonitride, carbon nanotubes, iron compounds, carbon black, and metal oxides, especially no carbon black.

16. The method according to any one of the preceding embodiments, wherein the uncrosslinked polyethylene-containing composition is high temperature crosslinking, and preferably at a temperature of above 95 ° C, preferably in a range of 110 ° C to 220 ° C, crosslinkable. The residence time, based on 1 cm irradiation section, in the process according to the invention is preferably between 0.012 s and 0.006 s. The production rate is thus preferably between 50 and 100 m per minute.

17. The method according to one of the preceding embodiments, wherein the microwave radiation (generated by a magnetron) is used as the sole energy source. In particular, the method is performed using the microwave system described herein.

18. The method according to one of the preceding embodiments, wherein the microwave radiation with a power of at least 900 W, preferably 900 W to 6 kW or 900 W to 2500 W, is irradiated. In general, 900 W of power is sufficient for the crosslinking reaction. However, to achieve the production speed, the performance can be increased.

19. The method of any preceding embodiment, wherein the polyethylene-containing composition does not contain carbon black. Soot absorbs microwave radiation at sites that are not chemically active for crosslinking. Therefore, the use of carbon black is not advantageous.

20. The method according to any one of the preceding embodiments, wherein the extrusion is carried out with a mixture of two components. One component contains the grafted base polymer and the other is a masterbatch containing a metal catalyst.

21. The method of any preceding embodiment, wherein the polyethylene-containing composition does not contain ferrites, e.g. Magnetite, and / or propellant contains. Propellants are gases or chemical compounds that release gases or water under crosslinking conditions, e.g. Carbonate.

22. The method according to any one of the preceding embodiments, wherein the polyethylene-containing composition except catalysts, no dielectric and / or conductive, inorganic additives such as silicon carbide, silicon carbonitride, Kohlenstoffnanotubes; Iron compounds (e.g., iron carbonyls), carbon black, and metal oxides, especially iron oxide or iron oxide-containing metal oxides.

23. The method of any one of the preceding embodiments, wherein the polyethylene-containing composition contains pigments.

24. The method of any preceding embodiment, wherein a plurality of polyethylene insulation layers are applied to the cable or the cable core and these are applied either sequentially or simultaneously.

25. The method according to one of the preceding embodiments, wherein the cable comprises or consists of one or more wires running parallel in the longitudinal direction of the cable.

26. The method according to any one of the preceding embodiments, wherein the insulation materials of the stranded cables (the sheathing of the stranded cores) may consist of high-performance plastics such as fluoropolymers, PEEK, PTFE. According to the invention, for example, the wires can be isolated with polyethylene, then the wires are stranded and encased again with polyethylene. Polyethylene can also be used for gusseting to make the cable round. The polyethylene can in principle be applied directly to the metal, or over another polymer layer. Thus, the polyethylene sheath can be used as a core insulation and / or as a sheath material and / or as a filler.

27. The method according to any one of the preceding embodiments, wherein the substructure may consist of or coated materials that tend to degas at high temperatures, which may be in the form of bubbles on the polyethylene insulation. In the use of microwaves according to the invention, temperatures are not so high that the materials could outgas. The term "substructure" refers to the substrate to which the polyethylene-based insulation layer is applied.

28. The method according to one of the preceding embodiments, wherein the cable comprises a current-carrying element or signal-carrying element, for example a current-carrying wire or a current-carrying conductor and / or a conductor element and / or signal transmission element.

29. The method of any one of the preceding embodiments, wherein the cable core is made of one wire (s), e.g. Flat wire, a wire bundle, a wire mesh, e.g. Braided hose, or consists of a strand / multiple strands.

30. The method according to one of the preceding embodiments, wherein the cable is an endless cable, or the conductor is an endless conductor, or the cable core is an endless cable core, and preferably has a length of at least 500 meters.

31. The method according to one of the preceding embodiments, wherein the cable core has a diameter of ≥1 mm.

32. The method of any preceding embodiment, wherein the polyethylene layer is applied directly to the metal-containing cable core, preferably uninsulated, coated or uncoated wires or strands.

The metal in the core of the cable has a positive influence on the cross-linking of the polyethylene-containing mass. On the one hand, the metallic conductor acts like an antenna. The microwave couples into the ladder. With the housing of the microwave chamber creates a coaxial structure, which means a homogeneous field propagation between the conductor and the microwave chamber.

33. The method according to any of the preceding embodiments, wherein the polyethylene insulation layer has a layer thickness of 0.5 mm - 4.0 mm.

1. (i) ein Magnetron zur Erzeugung einer ungepulsten, elektromagnetischen Strahlung,
2. (ii) eine Mono-Mode-Mikrowellenkammer mit zwei sich gegenüberliegenden Öffnungen,
3. (iii) einen Hohlleiter, welcher das Magnetron mit der Mono-Mode-Mikrowellenkammer verbindet,
4. (iv) mindestens eine Absorberanordnung an zumindest einer der Öffnungen der Mikrowellenkammer, wobei die Absorberanordnung eine oder mehrere Kammern, aufweist, und
5. (v) ein System zur Impedanzanpassung des Mikrowellensystems,

für die Mikrowellenvernetzung von Isolationschichten auf Polyethylen-Basis, bevorzugt zu einer Mikrowellenvernetzung gemäß einem Verfahren nach einer der vorangegangenen Ausführungsformen.34. Use of a microwave system, comprising

1. (i) a magnetron for generating an unpulsed, electromagnetic radiation,
2. (ii) a mono mode microwave chamber with two opposing openings,
3. (iii) a waveguide connecting the magnetron to the mono-mode microwave chamber,
4. (iv) at least one absorber arrangement on at least one of the openings of the microwave chamber, the absorber arrangement having one or more chambers, and
5. (v) a system for impedance matching the microwave system,

for the microwave crosslinking of polyethylene-based insulation layers, preferably for microwave crosslinking according to a method according to one of the preceding embodiments.

35. Cable or cable core with insulation layer, which is preferably bubble-free, polyethylene-based, prepared or prepared using the method according to any one of the preceding embodiments, wherein the wall thickness of the insulating layer based on polyethylene preferably 0.5 mm - 4.0 mm is.

36. The cable or cable core according to the previous embodiment, wherein there is a temperature-sensitive sheath under the polyethylene-based insulation layer.

37. A thermal sensor or indicator containing the cable or the cable core according to one of the preceding embodiments, wherein the cable or the cable core is only partially cross-linked and remain uncrosslinked sections between the cross-linked sections.

According to the invention, at least one absorber arrangement is preferably arranged on at least one of the openings of the microwave chamber in order to absorb the microwave radiation and at least partially reflect. Since the microwave radiation couples into the conductor, ie the metallic cable core, there is a certain loss of power without the absorber arrangement according to the invention, as a result of radiation emerging from the microwave chamber, so that the radiation is at least partially reflected back.

The implementation of the method will be further described below, in particular in the examples. Basically, the starting material, i. the metallic cable core, a cable core, or a plurality of combined into one unit cable cores, which may already be covered, to be wound on a winding device. The starting material is then unwound and, optionally after further treatment, passed to an extruder where it is coated with the uncrosslinked polyethylene-containing composition.

Subsequently, it is passed through for crosslinking through the microwave chamber, that is, the starting material enters through an opening in the microwave chamber and through an opposite opening back out of the microwave chamber again. After complete or desired curing, the coated product or intermediate product can optionally be rewound onto a winding device. It is of course possible at any point of the process to perform additional, additional process steps, e.g. the application of release agents against the sticking of the cable on the winding device (coil).

In one embodiment, therefore, a polyethylene-based sheath is applied to a cable core or unit of cable cores, the unit already having one or more sheaths. In this multi-layered construction too, the coupling of the microwave radiation into the conductor has a positive effect, since the radially symmetric microwave field is well suited for the irradiation of the multi-layer structure.

For networking, a microwave system is used. The microwave system may be configured according to the following embodiments:

1. (i) ein Magnetron zur Erzeugung einer ungepulsten, elektromagnetischen Strahlung,
2. (ii) eine Mono-Mode-Mikrowellenkammer mit zwei sich gegenüberliegenden Öffnungen,
3. (iii) einen Hohlleiter, welcher das Magnetron mit der Mono-Mode-Mikrowellenkammer verbindet,
4. (iv) mindestens eine Absorberanordnung an zumindest einer der Öffnungen der Mikrowellenkammer, wobei die Absorberanordnung eine oder mehrere Kammern, bevorzugt 2-8, oder 3-6, insbesondere bevorzugt 3-4 Kammern, aufweist, und
5. (v) ein System zur Impedanzanpassung des Mikrowellensystems.

M1. Microwave system comprising

1. (i) a magnetron for generating an unpulsed, electromagnetic radiation,
2. (ii) a mono mode microwave chamber with two opposing openings,
3. (iii) a waveguide connecting the magnetron to the mono-mode microwave chamber,
4. (iv) at least one absorber arrangement on at least one of the openings of the microwave chamber, the absorber arrangement having one or more chambers, preferably 2-8 or 3-6, particularly preferably 3-4, chambers, and
5. (v) a system for impedance matching the microwave system.

The opposing apertures of the mono-mode microwave chamber are configured to pass products, in particular, with uncrosslinked polyethylene-containing compound-provided cables / cable conductors / conductors during microwave heating. In particular, the openings of the microwave chamber and absorber for cables are adapted with a cross section of 0.5 mm ² to 125.0 mm ² . Here, the distance between the cable and the microwave chamber or the absorber is at least 1.0 cm. The chambers of the absorber assembly (hereinafter also the "absorber") are also equipped with opposing openings so that the products can also be performed through these chambers. The chambers of the absorber and the mono-mode microwave chamber are arranged in a row. For example, in the manufacture of continuous cable cable coatings, a cable transport system is used that continuously passes the cable product through all of the chambers, including the mono-mode microwave chamber. Subsequently, further treatment steps or the cable product is produced as a finished product.

The number of chambers and the length of the absorber are dependent on the line to be crosslinked and the overall structure of the microwave system. In particular, by increasing the reflection of the radiation by appropriate design of the absorber or by increasing the number of absorber chambers, a higher performance can be achieved on the product to be processed. This is particularly important if the part of the product to be heated is poorly absorbing microwave radiation.

In one embodiment, a polyethylene-based sheath is applied to a cable core or unit of cable cores, the unit already having one or more sheaths.

The geometric design has been adapted so that the energy maximum lies in the microwave chamber. A person skilled in the field of high-frequency technology can make such an adaptation, in particular a necessary impedance adaptation of the structure.

1. (i) die eine oder die mehreren Kammern, oder die Wände der Kammern, Aluminium enthalten oder daraus bestehen, und/oder
2. (ii) die Innenwände der Kammern mit Mikrowellen-absorbierenden Additiven, bevorzugt Siliziumcarbid oder ein Polymer, enthaltend ein Mikrowellenabsorbierendes Additiv, beschichtet sind.

M2. Microwave system according to embodiment M1 , in which

1. (i) the one or more chambers, or the walls of the chambers, contain or consist of aluminum, and / or
2. (ii) the inner walls of the chambers are coated with microwave-absorbing additives, preferably silicon carbide or a polymer containing a microwave-absorbing additive.

Preferably, the walls of the chambers are made of aluminum, which walls may be coated and may also include additional components, for example, additional metal plates or chamber walls of aluminum or other material to enhance absorber performance. For example, the chamber could be equipped with a double wall or a lining of ferrite elements.

1. (i) mindestens eine Absorberanordnung mit mehreren Kammern im Querschnitt an die Öffnung der Mono-Mode-Mikrowellenkammer angepasst ist, um die austretende Mikrowellenstrahlung absorbieren zu können, und/oder
2. (ii) die Kammern der Absorberanordnung mit zwei sich gegenüberliegenden Öffnungen ausgestattet sind.

M3. Microwave system according to embodiment M1 or M2 , in which

1. (i) at least one absorber arrangement with a plurality of chambers is adapted in cross-section to the opening of the mono-mode microwave chamber in order to be able to absorb the exiting microwave radiation, and / or
2. (ii) the chambers of the absorber assembly are provided with two opposing openings.

M4. Microwave system according to one of the embodiments M1 - M3 wherein the magnetron produces microwaves at a frequency of 2450 MHz ± 100 MHz.

1. (i) mindestens eine Absorberanordnung derart nach der Mikrowellenkammer angeordnet ist, dass ein Kabel nach dem Hindurchführen durch die Mikrowellenkammer durch diese Absorberanordnung hindurchgeführt werden kann; und/oder
2. (ii) mindestens eine Absorberanordnung derart vor der Mikrowellenkammer angeordnet ist, dass ein Kabel vor dem Hindurchführen durch die Mikrowellenkammer durch diese Absorberanordnung hindurchgeführt werden kann.

M5. Microwave system according to one of the embodiments M1 - M4 , in which

1. (i) at least one absorber arrangement is arranged after the microwave chamber in such a way that a cable can be passed through this absorber arrangement after passing through the microwave chamber; and or
2. (ii) at least one absorber arrangement is arranged in front of the microwave chamber in such a way that a cable can be led through this absorber arrangement before passing through the microwave chamber.

M6. Microwave system according to one of the embodiments M1 - M5 wherein at least one absorber arrangement is present, which has two or more chambers and a round and / or concentric geometry.

M7. Microwave system according to embodiment M6 wherein the two or more chambers of the at least one absorber assembly are spaced from each other.

M8. Microwave system according to one of the embodiments M1 - M7 , wherein the chambers of the absorber arrangement have openings with a diameter of ≥ 1 mm.

M9. Microwave system according to one of the embodiments M1 - M8 , wherein the impedance matching system is adjusted by the mechanical displacement of the short circuit (open circuit) in the waveguide.

This adaptation can be carried out semi-automatically or preferably fully automatically by software-assisted evaluation of the scattering parameters, which are known to the person skilled in the art, e.g. is known by stepless screws.

The openings of the absorber arrangement are dependent on the line to be crosslinked. Preferably, a cable core has a diameter of ≥1 mm.

M10. Microwave system according to one of the embodiments M1 - M9 wherein the mono-mode microwave chamber and the chambers of the absorber assembly are configured to transport an endless cable through the chambers for irradiation purposes.

M11. Microwave system according to one of the embodiments M1 - M10 , where the magnetron has a power consumption of up to 6 kilowatts.

• i) einen metallischen Kabeladerkern, oder
• ii) eine Kabelader, oder
• i) mehrere zu einer Einheit zusammengefasste Kabeladern, wobei die Einheit bereits ein oder mehrere Isolationsschichten als Ummantelung der Kabeladern aufweisen kann,

aufgebracht ist, durchgeführt werden kann.M12. Microwave system according to one of the embodiments M1 - M11 wherein the mono-mode microwave chamber has a cylindrical or rectangular shape, the mono-mode microwave chamber and the chambers of the absorber assembly having two opposing openings through which by means of an existing cable transport system, a polyethylene-containing mass on

• i) a metallic cable core, or
• ii) a cable core, or
• i) a plurality of cable cores combined into one unit, wherein the unit may already have one or more insulation layers as a sheathing of the cable cores,

is applied, can be performed.

The microwave chamber may be cylindrical or rectangular. The geometry depends on which local point the field maximum for polyethylene crosslinking builds up. The mechanical length of the waveguide is on adapted the electrical length of the transmission path, so that the field maximum shifts into the microwave chamber.

The cable transport system consists of a cable reel unwinder and rewinder (as detailed in relation to cable manufacture elsewhere).

Hereinafter, a suitable absorber arrangement and multiple uses of the devices disclosed herein will be described.

M13. Absorber arrangement as defined in one of the embodiments M1-M8.

M14. Use of an absorber arrangement as defined in one of the embodiments M1-M8 for absorption and at least partial reflection, preferably for absorption, of microwave radiation.

M15. Use according to embodiment M14, wherein the microwave radiation is generated for curing a polyethylene-based insulation layer of a cable.

M16. Use of a microwave system according to one of the preceding embodiments for crosslinking a polydimethylsiloxane-based polyethylene insulation layer as a cable sheathing or sheath of a metallic cable core.

M17. Use of a system consisting of a magnetron and a waveguide connecting the magnetron to the mono-mode microwave chamber for microwave crosslinking of polyethylene-based insulating layers, preferably to microwave crosslinking according to the method of embodiment 1.

M18. Use of an impedance matching system in a method according to any one of Embodiments 1-32. The impedance matching can be carried out by mechanical displacement of the short circuit or idle in the waveguide or an adjustment semi-automatic or preferably fully automatically by software-based evaluation of the scatter parameters by vectorial network analysis.

M19. Use of microwave absorbers in a method according to any of the embodiments described herein, attached to the openings of the microwave chamber to reflect back or absorb leakage radiation into the chamber. In this case, the absorbers are so spaced from the openings or the microwave chamber, that the maxima of the radiation can be adjusted so that they fall into the chambers of the absorber.

• 1a zeigt ein bekanntes Verfahren zum Vernetzen von Polyethylenummantelungen durch Erhitzen in Infrarot-Heizöfen.
• 1b zeigt das erfindungsgemäße Verfahren zum Vernetzen von Polyethylenummantelungen unter Verwendung von Mikrowellenstrahlen.
• 2 zeigt eine in Reihe geschaltete Anordnung von 4 Absorberkammern, durch die ein Leiter mit Beschichtung aus Polyethylen-enthaltender Masse geführt wird.

The present disclosure will be further explained with reference to figures:

• 1a shows a known method for crosslinking polyethylene sheaths by heating in infrared heaters.
• 1b shows the process of the invention for crosslinking polyethylene sheaths using microwave radiation.
• 2 shows a series arrangement of 4 absorber chambers through which a conductor is coated with polyethylene-containing compound.

example

The absorber arrangement and the magnetron are in 1b Not shown. 1b shows a cable 14 which via wire guides (coils) 13 through the extruder 12 for cold extrusion (about 25 ° C) and then in the microwave chamber 11 is heated.

2 shows an absorber arrangement 15 with a series arrangement of four absorber chambers 16 through which a ladder 14 is conducted with coating of polyethylene-containing mass.

The production of cables or cable cores according to the invention can be carried out as described below.

First, the system must be cleaned and assembled. First, the screw and the cylinder are cleaned and the extrusion head is assembled including tools. The coil with the conductor is installed in the unwinder and the conductor itself is passed through the extrusion head. The microwave system is then positioned and aligned so that the conductor passes centrally through the microwave chamber.

The uncrosslinked polyethylene-containing composition is charged in the form of granules, with the catalyst added via a gravimetric dosing device.

Once the polyethylene blend and equipment have been prepared, the extruder is started. First, it must be completely filled with the material. Once this is done and comes out of the nozzle polyethylene, a program is started. This program regulates the power of the magnetron depending on the extrusion speed. First, it is started slowly and the microwave is switched on, after a few seconds the microwave has started up and still has to be adjusted. This means that the impedance must be set to the cross section of the conductor. But this happens automatically via a software or should be stored as a recipe in the system. Shortly thereafter, the speed is adjusted to production conditions, at the same time the performance of the magnetron is adjusted. The start should be within a few seconds. The networked cable is then wound up on a spool. It may even have to be talcum-treated beforehand or treated with another release agent, but that is independent of the crosslinking process.

Quoted pamphlets

EP1655328B1 . DE19855718 . EP1900767 B1 . US 4,980,384 . EP0945916 . DE2422914

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 4980384 [0005, 0122]
• EP 0945916 A2
• EP 1655328 B1 [0005, 0122]
• DE 19855718 A1 [0006]
• DE 19855718 [0006, 0122]
• EP 1900767 B1 [0007, 0122]
• DE 2422914 [0008, 0122]
• EP 0945916 [0122]

Claims (11)

A method of making a cable or cable core having one or more polyethylene based insulation layers comprising the steps of: a) applying a mass containing a1) polyethylene and / or polyethylene copolymer grafted with silane, and a metal catalyst; or a2) polyethylene and / or polyethylene copolymer, silane, peroxide, and a metal catalyst, by means of an extrusion process i) one or more metallic cable core (s), or ii) a cable core, or iii) a plurality of cable cores combined into a unit, wherein the unit may already have one or more insulation layers as a sheathing of the cable cores to form an insulation layer; and b) crosslinking of the applied mass in a mono-mode microwave chamber with 1.9-3.0 GHz continuous radiation. The procedure according to Claim 1 wherein the polyethylene-containing composition contains, in addition to the catalyst substance (s), no dielectric, inorganic additives. The process of any one of the preceding claims, wherein the metal catalyst is selected from inorganic and organic metal catalysts. The process of any one of the preceding claims wherein the metal catalyst is an organotin compound selected from alkyl tin compounds and dialkyltin compound, preferably dibutyltin dilaurate. The method according to one of the preceding claims, wherein i) the one or more metallic cable core (s), or ii) the cable core, or (iii) multiple cable cores aggregated into a single unit are cross-linked only in sections and non-cross-linked sections remain between the cross-linked sections. The method of any one of the preceding claims, wherein the silane is selected from the group consisting of vinyltrimethoxysilane, vinyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, 2- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane , 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2 - (aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N- (vinylbenzyl) -2-aminoethyl 3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyltrialkoxysilane, 3-isocyanatopropyltriethoxy silane, tris (trimethoxysilylpropyl) isocyanurate, and 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropyltrimethoxysilane. The method of any one of the preceding claims, wherein the polyethylene is selected from LDPE and HDPE. The method according to one of the preceding claims, wherein the microwave radiation (i) is used as sole heat source; and or (ii) with a power of at least 900 W, is radiated. The process of any one of the preceding claims wherein the cross-linking of the ungrafted polyethylene is carried out in one or two stages wherein the polyethylene is cross-linked in the one-step process in the presence of peroxide, silanes and metal catalyst and the polyethylene is cross-linked with silanes in the two-stage process in the first stages Presence of peroxide is treated, and is crosslinked in a subsequent second stage in the presence of a metal catalyst. The method of any one of the preceding claims, wherein the polyethylene-containing composition contains no additive selected from the group consisting of: silicon carbide, silicon carbonitride, carbon nanotubes, iron compounds, carbon black, and metal oxides. Cable made using the method according to any one of Claims 1 - 10 ,

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