DE2803964A1 - Crosslinking silane on cable insulation - core with extruded covering passes through pressurised steam chamber before being cooled - Google Patents

Abstract

Long lengths of sheathing, e.g. on electric cables, conductors, tubes, profiles etc. are produced by grafting a silane cpd. on to the molecules of basic material such as olefin polymers/mixed polymers, elastomers or rubber, using a substance which crosslinks under the influence of moisture. The sheathings are extruded in >=1 layer, opt. separately, and then immediately passed through a tube containing a humid atmosphere under pressure. Process increases the output of a continuous vulcanising plant, giving rapid penetration of sheathing by moisture. Blister formation in extrusion is minimised and the sheathing can be cooled. High stability against mechanical distortion (e.g. in high voltage cables) is achieved and e.g. high density polyethylene can be used.

Description

Process for the continuous production of casings

for elongated goods made of crosslinkable materials The present The invention relates to a method for the continuous production of casings for elongated goods, for example electrical cables and wires, pipes, Profiles and the like, made from one by grafting a silane compound onto the molecules of the base material which can be crosslinked under the action of moisture. These materials can be olefin polymers or olefin copolymers, elastomers or thermoplastic rubbers.

For a long time, crosslinkable materials have been on the market because of the constantly increasing demands for better electrical, mechanical or thermal Properties to an increasing extent also for electrical cables, for sheathing of pipes and the like. Application. While processing this Materials are required to be manufactured continuously, that is, in the injection molding process Cross-linking sections must be connected by means of known extruders, which ensure a continuous influence on the material to be crosslinked.

The greatest technical importance in this context has so far it concerns electrical cables and wires, the networking of thermoplastic Materials such as polyethylene with the help of organic peroxides. At a higher temperature These peroxides break down into so-called alkoxy radicals. These split from the polymer chain Hydrogen and in this way create radical sites on the macromolecule. Two Such radical sites of various macromolecules can now be formed under training saturate a C-C bond, so that a spatial network arises, the density of which is through characterizes the distance between the individual network points or network nodes will. The crosslinking yield of polyethylene depends on the chemical constitution the peroxide and the degree of branching of the macromolecules. The primary radical generation on the macromolecule, however, in addition to peroxides, other radical initiators, z. B. high-energy radiation.

It is still used for chemical crosslinking by means of suitable peroxides It has long been known to use so-called CV systems, which are horizontally arranged or pipes installed at an angle or in the form of a chain line, which contain water vapor under high pressure and through which the extruded material, z. B. the sheathing of an electrical cable or with a plastic insulation jacketed pipe, is continuously passed through.

The production speed are limits in such known systems set by the fact that the pressure of the water vapor increases with increasing temperature increases and due to the necessary dwell time in the steam section the systems are necessary, especially in the case of casings with a larger cross-section have to take on larger dimensions. An improvement on this known crosslinking process one has tried to achieve that the extruded materials are not under Pressure, but have been crosslinked without pressure in a liquid bath. This technique has so far not been able to assert itself, as there are other difficulties such as B.

Blistering of the envelope.

A new and more economical type of networking could therefore in more recent times be those in which the materials, e.g. B.

organic polymers, now without any special heat treatment are only crosslinked under the action of moisture. Prerequisite for this is that so-called organo-functional silanes, such as trimethoxy-vinyl-silane, grafted onto the polyethylene macromolecules (DAS 17 94 028, DOS 2 439 513). These silane compounds are grafted on, for. B. in the course of an extrusion process under the influence of radical generating compounds, mainly peroxide and high temperature, roughly in the range of 1800 to 2400 C. Another possibility of Bringing in the crosslinking chemicals is that of making the individual particles of the free-flowing thermoplastic or elastomeric base material caused to move rapidly and during or before this movement the silane or the silane compound as well as the additives necessary for grafting and for crosslinking in liquid form can be added. Penetrate at temperatures below the crystallite melting range these materials then wholly or partially by diffusion into the surface of the Particles of the base material and lead to a homogeneous distribution there, see above that the silane or the silane compound distributed homogeneously in the base material then can be grafted onto the molecules of the base material. Through this, that actual grafting process upstream of the homogenization process used Let materials high-quality and high-quality extrudates Achieve degree of networking.

In contrast to the crosslinking reaction described above in the more recent cross-linking technology, reactive due to the action of moisture low molecular weight compounds, e.g. B. organo-silanes, grafted onto the macromolecules, which then lead to chain linking in the course of secondary reactions. The grafted ones Compounds are polyfunctional in terms of crosslinking; i.e., they can react with several macromolecules to form bundle-like cross-links. There are then no so-called networking nodes, as is the case with C-C networking only two macromolecules are fixed to each other, but three, four or more.

So that the action of moisture, which ultimately leads to crosslinking Silane-grafted materials can be extruded Materials, e.g. B. provided with a sheathed cables or lines, pipes and the like., subjected to water storage. The duration of the water storage depends on the essentially depends on the thickness of the selected envelope, but also on whether through special measures if moisture is not already present in the extrudate and subsequent water storage is only carried out as a precaution.

On the basis of this prior art, the object of the invention is to be found based on the so-called continuous ones already in use all over the world Adapt vulcanization systems (CV systems) to the increased performance requirements and to ensure that the continuous networking in the general manufacturing process no longer represents a bottleneck. In doing so, despite the increase in the actual Performance of the extruder adapted to throughput, speed1 to higher quality evaluating end products are produced.

This object is achieved according to the invention when using under the The action of moisture-crosslinkable materials is solved by the fact that the casing in one or more layers, possibly spatially separated from one another is extruded and the material immediately then containing a water atmosphere and runs through a pipe section under pressure. This combination of graftable and therefore under the action of moisture crosslinkable materials and with the continuous crosslinking of the process steps, some of which are common, leads to that normal CV systems with a much greater output than before can be operated, the profitability of such systems can be significantly improved will. The invention enables faster penetration of the envelope with Moisture reached, a separate operation to bring in the moisture is avoided. The pressurization during the run also has the significant advantage that the formation of bubbles in the extruded material is suppressed will. It is also possible for the casing to be cooled under pressure leave, which leads to a further improvement in the quality of the end product.

Any materials can be used in the practice of the invention be, d. H. thermoplastic materials, elastomeric materials or thermoplastic materials Rubbers, as well as polyblends made of EP crumb rubbers and polypropylene and the like., provided that they can be crosslinked under the influence of moisture.

But copolymers of the materials mentioned can also be one Find advantageous application, such as compounds that form the silicon hydride group tSi-H contained one or more times in the molecule and on double bonds of the thermoplastic or elastomeric materials are deposited.

Another major advantage of the method according to the invention it can be seen that through the crosslinking with simultaneous pressure treatment under the action of moisture networkable coverings by means of per se known continuous vulcanization systems one opposite the peroxidic crosslinking has better stability against mechanical deformations given is. This is particularly desirable when producing larger wall thicknesses, z. B. in electrical high-voltage cables that are used for voltages above 60 kV Find.

In addition to the high efficiency and economy of the process according to the invention is to be emphasized as a particular advantage that here crosslinkable Materials can be processed, their processing using conventional means is not possible without further ado. So is z. B. the networking of polyethylene higher Density, d. H. between 0.94 and 0.96, known as so-called hard PE or "high density" PE, because of the injection temperatures of 180 - 240 C required here 0 0 and only relatively low light-off temperatures of the peroxides available today of around 1300 - 1350 C not possible (scorch formation). However, these materials could be used without difficulty processed according to the method according to the invention, the opposite of polyethylene lower density of about 0.92 more favorable electrical properties could be in the cable position z. B.

can be used to the full.

In carrying out the invention, one can proceed in such a way that for extrusion the layer or layers of crosslinkable under the action of moisture Materials ungrafted materials are used. Then it is necessary that the grafting in the formed state of the material in passage through the Pipe section takes place. This method has the advantage that in terms of cost cheaper materials can be used, with the mixing of the components z. B. can be done in the extruder. In this case it is also necessary to use the silane or the silane compound e.g. B. together with the usual crosslinking chemicals to mix in the extruder. Here you can continue the invention thank you proceed in such a way that the material, which is still ungrafted per se, is brought to temperatures in the extruder is heated by at least 1800 C, so that here a grafting of the silane compounds takes place on the macromolecules of the base material. However, at times it can also be beneficial be, especially if existing extruders are used, their Temperature control is generally around 1200 to 1500 C, the material is ungrafted to extrude and to ensure the grafting that as subsequent Water vapor heated to over 1800 C is used. That has z. B. the advantage that the water vapor present in the heating zone for the same time the necessary penetration of the insulation with water.

Instead of using ungrafted material in the extrusion of the casings, it can sometimes also be advantageous for the extrusion of the layer or layers to use grafted materials. Then it will be advantageous to proceed in such a way that at the extrusion of the material has an extruder melt temperature of not more than 1800 C, preferably 1200 to 1400 C, is selected.

The advantage here is that existing extruders are used, with a simple pressurized water temperature control of the individual zones is possible. Of the The efficiency in the regulation can be significantly improved. Will the mass temperature Chosen as low as possible and it is, for example, 800 to 1100 C and the for the subsequent cooling, selected pressure 1 to 2 bar, is an all-round suppression Avoided expressions of bubbles on the coating. For a use of lower Temperatures during the extrusion of moisture-crosslinkable mixtures also speak that hose tools can be used for the extrusion process, which of Allow better centering at home. On the other hand, there may be a choice higher temperatures for the extrusion process also achieve a higher output will.

Is, as provided in a continuation of the invention, the extruder melt temperature at most 1800 C, preferably 1200 to 1400 C and has the water atmosphere that connects to the spray device in the pipe section, at least 1800 C, then the selected large pressure difference prevents evaporation highly volatile substances.

An improvement of the manufacturing method proposed according to the invention can sometimes result from the moisture required for crosslinking is fed in the extruder barrel or in the extruder head. As an extruder you can use here also those with a so-called shaving head can be used.

These are facilities in which the warming is wholly or partially takes place by shearing the flowing mass. For this purpose spray heads with rotating or tools that hit with a certain frequency are used as well as those, in which the mass is pressed through narrow gaps and thereby the heating necessary shear forces are generated.

Bringing in the moisture required for crosslinking in the barrel or head of the extruder means a tuition or a sole Measure for the introduction of moisture. It is advantageous that now a lower Moisture penetration from the outside is necessary, so that the residence time in the subsequent pipe section can be further reduced or vice versa that the Manufacturing speed is further increased.

If, as expediently provided in a continuation of the invention, the The pressure in the pipe section is at least equal to the water vapor pressure in the material chosen before the extrusion of introduced water, then is with the smallest possible technical Expenditure prevents the material from foaming in whole or in part. Advantageous it can also be if the good that is a cable, a line or even a with a Plastic sheathed pipe can be, after leaving the pressurized Water atmosphere also below Pressure in a water bath to at least 800 C is cooled.

In this way they are also in the pressureless state through an internal Evaporation, no bubbles in the extrudate detectable.

The manufacturing method selected according to the invention can be further improved when stepwise cooling is used to cool the extruded layers the final value is made. This has the advantage of moisture penetration used when the cooling water is warmer. In addition, with an exclusive No or negligible cooling in the pipe section following the extruder Microvoids occur. This would have particular advantages in the manufacture of electrical Cable for use at higher voltages, especially for manufacturing too This is because the cable itself is round due to the buoyancy of the insulation is held. In this context it could be useful, e.g. B.

a stretch after the injection mold filled with steam under pressure set up. For example, a steam section of 1 to 3 m in length, a water section, approx. 30 m long, with a water temperature of 180 C with the corresponding pressure and a subsequent remaining stretch with a water temperature of 20 to 0 40 C. This ensures full utilization of the so-called CV system given.

As already mentioned, the method according to the invention is applicable to any Applicable products that are manufactured continuously and with a cross-linkable coating should be provided.

The use of the method according to the invention has particular advantages but for the manufacture of electrical cables. Because this is where it all comes down to indicate that the thermoplastic used in the layer structure of an electrical cable or elastomeric materials are optimally processed and achieve properties in the process, which guarantee reliable use even at high and extremely high voltages. It therefore has particular advantages if the insulation and / or the adjacent Conductive layers due to the action of moisture in the Pass through the pipe section is fully or partially networked A partial network has the Advantage that at least the known grooves on the surface, external deformations Envelopes etc. should be avoided. To insist solely on a partially networked pipe section, would also have the advantage that the production speed because of the lower Dwell time of the pipe section is increased.

As far as possible, the casing should be fully networked in the pipe section or be guaranteed for a foreseeable period after leaving the facility. However, a complete network can also be achieved with a view to increased production speeds be waived if z. B. by controlling the networking mechanism and choice suitable boundary conditions ensure that if the predominant and finally full networking takes place within the next few days, this networking too takes place independently of the respective environmental influences, that is, is certainly repeatable.

Each electrical cable has a plurality of extrudable in its construction Layers made of materials. In carrying out the invention, for. B. the outer protective sheath can be crosslinked by the action of moisture. Because of the relatively large surface with small wall thickness of this material is a relatively little moisture exposure required, resulting in a high deduction allowed in the manufacturing process.

Another advantageous application of the method according to the invention in the manufacture of electrical cables and wires is when one or more the extrudable layers provided in the cable structure, such as insulation, conductive layers, Coat, made of a crosslinked under the action of moisture and peroxide Material. This combination of one or more layers different Networking mechanism allows further optimization and fit to the respective requirements in the manufacture of electrical cables. That is true also for the manufacturing process of such cable types. In this context can it will be further advantageous if each of the above-mentioned layers consists of at least two further layers with materials with different crosslinking mechanisms consists. This enables better utilization of the various material properties, resulting from the different networking systems are possible. Also should there is an increase in the dielectric strength in all cases where the layers should have an increased dielectric strength. E.g. growing into the insulation Trees could migrate onwards due to the change in the networking mechanism be prevented at least for a shorter or longer period of time.

The structure of several layers can bring further advantages, that at the seams an accumulation in the insulating material of migrating chemicals occurs, so that a kind of voltage-stabilizing effect occurs here. By different cooling processes, different contracting materials, e.g. B. filled or unfilled materials, diffusion of the materials used, etc. can also affect the structure of the material at the seams Layers occur, which also lead to an increase in electrical strength leads if the material used is such. B. to the isolation of electrical High or extra high voltage cables are involved.

It is known that cleavage products due to the peroxide crosslinking system have a tension-stabilizing effect in the insulation after the crosslinking has been completed. These substances migrate out of the insulation through heat and vacuum from the outside. Due to the layered structure of the insulation proposed according to the invention or other layers provided in the cable structure become barriers at the interfaces built in, so that the volatility of the cleavage products is entirely or predominantly prevented will.

In continuation of this idea, the respective "barrier layers" Different thicknesses can be selected, but individual layers can also be used be especially designed as bump layers. For example, the insulation of an electrical Cable from an inner layer made of a moisture crosslinkable by grafting silanes Material are made to which a further layer of a filled peroxidic crosslinkable material adjoins.

Above that as the outer layer then follows again the one layer of one moisture-crosslinkable material.

Notwithstanding a version in which in the case of an electrical Cable uses different layers with different networking mechanisms it can sometimes also be advantageous to remove the individual layers, such as insulation, Conductive layers, jacket and the like. Made of a mixture of materials with different Build networking mechanism. In this way, the cross-section of the Layer a control of the crosslinking density, so that an opposite known Superstructures completely new structure construction is achievable. The thermal dimensional stability this can increase the volatility of certain chemicals, such as anti-aging agents, Stabilizers and the like. Contained to a low level of wetness. After choosing the mixing ratio the materials with different cross-linking mechanisms that z. E.g.

30 parts of silane-grafted: 70 parts of peroxidically crosslinkable material or vice versa, is also a control of the adhesion, gluing or welding possible with the adjacent materials. Such a mixed network, which with the Method according to the invention can be achieved by bringing about the statistical Distribution of the types of cross-linking with material-side advantages. That applies to in the event that the mixture contains ungrafted material upon extrusion.

In the case of a mixture of materials with different cross-linking systems different cross-linking chemicals are also brought in by these. By diffusing Residues of organosilanes or peroxide cleavage products, such as Acetophenone and cumyl alcohol can work synergistically in the respective layer Resulting effects that lead to a further improvement of the insulation.

Another possibility, through a layer structure in implementation the method according to the invention improved electrical values on cable or line insulation to obtain is z. B. also the combinations of individual layers of a core coating system with such mixed networking systems to choose. So can from the total insulation wall thickness a cable z. B. 2/3 from cross-linked polyethylene and 1/3 from a VPE / silane-grafted PE-Qemisch exist.

Such a construction can only be achieved with that according to the invention the proposed method.

In carrying out the method according to the invention are devices suitable for a wide variety of structures. It is advantageous, for. B. if the under Pressure standing pipe section is arranged horizontally or inclined. Here can one on the use of a known, simpler and tried and tested for many years and resort to widespread facilities without the need for new investment, at least larger scale, are required.

The same applies in the event that the pipe section is under pressure runs in the form of a known chain line. Also in this case you can Cheap economic facilities already on the market for the medium-sized and smaller dimensions can be used.

The application of the invention to such systems known per se means In addition, a significant increase in the previous production speed, which can be increased to at least double. So are increases of the previous 150 to 200 kg / h of polyethylene ejected from the extruder to 300 to 450 kg / h possible because the bottleneck CV system is no longer given.

The invention is based on the known systems in the case of pipe sections running in the form of a chain line, the system is useful in three To divide zones, e.g. B. in a steam zone from 200 to 2100 C, a short hot water zone from 200 to 800 C, the z. B. can be 20 m long, and the usual cold water zone. This three-way division makes the existing heating and cooling capacities better known Facilities fully exploited without the risk of being due to a strong thermal Difference in the area of the water level, bending or damage of pipes must be feared. The system can be operated more gently, they is less prone to repair and testing.

Another possibility of using systems known per se is nor the fact that the pipe section which is under pressure and containing water atmosphere is arranged vertically.

These so-called tower systems are used in high-voltage cable technology already known, they were built primarily for the purpose, even with larger ones Insulating wall thicknesses to ensure a circular shape of the extruded product.

In this context it should also be mentioned that to achieve a water atmosphere not only water alone or with additives in the pressurized pipe section, but also suitable other media containing water can be used.

So are z. B. polyhydric alcohols as a transport medium for moisture suitable, but it can also be, for. B. water-glycol mixtures used advantageously will. The glycerine can also be used for this, as it is already a moisture carrier itself is.

The invention is based on the exemplary embodiments shown in FIGS explained in more detail.

In Fig. 1, a so-called vertical G-system is described, in particular in the production of z. B. elec- tric high voltage cable with thicker insulation wall thicknesses, undesirable deformation after the extrusion process avoided by the weight of the material. This system consists z. B. from a the cable core 1 enclosing the cable preheating 2, a tower pedestal 3 for receiving of the extruder 4 with the funnel 5, a deflection wheel 6 and the one on the extruder head 7 adjoining telescopic tube 8. The latter serves to make an immediate transition without pressure loss to the total pipe section 9 to ensure that in a diversion tank 10 ends, from which the insulated cable core through a cooling zone 11 by means of a Pulled off the caterpillar haul-off 12 and, if necessary, wound up or for further processing is continued.

It is now essential for the invention that for processing z. B. the insulation of an electrical cable ungrafted or grafted insulation material can be used, which is extruded onto the cable core in the usual way and then for further treatment in the one containing a water atmosphere pipe section 13 under pressure is introduced. In the event that in the extruder 4 ungrafted material is used, it is advisable to proceed so that the base material, z. B. polyethylene or one of its copolymers, into the hopper 5 of the extruder 4 is entered and also the additives such as stabilizers, activators, crosslinking agents as well as the silane or the silane compounds also in the base material with the help of the extruder. The material prepared in this way is then transferred to the Spray head 7 applied to the cable core and then enters the pipe section 13, which in this case z. B. a water atmosphere in the form of a warmed over 1800 C. Has water vapor. Due to the sudden heating of the syringes Wrapping, the already extruded material is grafted, i. H.

the silane or the silane compounds are on the macromolecules grafted onto the base material used. Due to the simultaneous If water or water vapor is absorbed under pressure, the grafted material is crosslinked Materials, being through the compaction effect of the pressure at the same time any blistering that can lead to glow discharges in high-voltage cables, is avoided. The moisture introduced in the pipe section is sufficient for to ensure thorough networking at least in the further production section. To the Pipe section 13, which is heated in the present case, closes part 14 which is separated from the pipe section 13 by the steam-water transition 15. in the Area 14, the z. B. is designed as a cooling pressure zone, the heated under pressure and then subjected to a cooling before the material acted upon with water it is deflected in the deflection 10 and introduced into a post-cooling zone 11. Advantageous it can be the transition between heating zone 13 and cooling pressure zone 14 with a possible form low temperature coefficient, so that the cooling to the desired Value is achieved through gradual cooling in zone 14 and zone 11.

The extruder is here and also in the following exemplary embodiments shown schematically. Because in the event that several layers on top of each other in the run must be applied, it is of course necessary to have a corresponding To arrange the number of extruders in tandem one behind the other or the number of required To increase spray heads accordingly. (Double or triple spray head) In the event that that an already grafted material is used in carrying out the invention, this material is also introduced into the hopper 5 of the extruder 4. in the In contrast to the embodiment with still ungrafted material, in which this is already heated to temperatures of 1800 C and more in the extruder, are sufficient in In this case, existing extruders with a melt temperature of at most 180 ° C, 0 0 preferably from 120 to 140 C. Since there is no grafting in the adjoining pipe is necessary, the appropriate ones are no longer proportionate required high temperatures. One can therefore rely entirely on a temperature treatment under Refrain from pressure and moisture exposure by the pipe section 13 already as Pressure cooling zone is used because it only has the task of networking to bring the necessary water into the insulation. But there it is in special cases A temperature treatment after the extrusion can also be advantageous and there also often by applying a temperature-controlled moisture the rate of penetration of moisture into the insulation can be promoted can, you will in the pipe-0 stretch 13 to a maximum of 180 C heated water or Use water vapor, so that the moisture quickly under the prevailing pressure penetrates the insulation and requires short dwell times in the pipe section are.

To ensure that, in particular, with immediate pressure cooling Sufficient water is available after the extrusion when the crosslinking is initiated, it can sometimes also be advantageous to use the necessary networking Introduce moisture in the extruder barrel or in the extruder head directly. the The extruder screw is then used for an even distribution of moisture care for.

In all cases, however, where there is a need for high production speeds arrives and where products with not extremely thick walls are to be transported the chain line-shaped pipe section shown in FIG proven beneficial. This also shown schematically again consists of the pusher wheel 17, which is expediently arranged on a pedestal 16, via the the cable core 18 guided, deflected and also arranged on the pedestal 16 Extruder 19 is fed. The extruder funnel is denoted by 20, the following one Telescopic tube bears the number 21. Finally, it joins without loss of pressure the telescopic tube 21, the pipe section 22, the z. B. designed as a heating section and merges into the pipe section 24 after a water-vapor transition 23. The attached Deflection wheel is denoted by 25, this deflection wheel is followed by another in the withdrawal direction Cool- zone 26. The labyrinth seals are used for sealing to the outside 27, which lead the wrapped soul outside, where it is removed from the caterpillar 28 is detected and transported on.

With regard to the implementation of the method according to the invention, the following applies the same as for the embodiment according to FIG. 1. Depending on the choice of material, d. i.e., whether grafted or ungrafted material is used, the extruder melt temperature becomes brought to a maximum of 1800 C or above 1800 C.

The subsequent pipe section 22, which is exposed to moisture and is always under pressure, can in turn be heated when it comes down to to graft the ungrafted and extruded material. In this case then takes place the first cooling after passing through the steam-water transition 23 in the area 24 and is then preferably in the form of gradual cooling in the cooling zone 26 continued.

However, in the event that material that has already been grafted is used, can dispense with heating the pipe section 22 at all and instead already do so this pipe section can be pulled out for the first pressure cooling. The following Cooling sections 24 and 26 can then be used for further gradual cooling down to the Final state can be used.

3 and 4 are exemplary embodiments of single-conductor high-voltage electrical cables described, the insulation of which has a special structure. According to FIG. 3 is the conductor 30 of the electrical cable, which consists of a large number of stranded individual wires may exist, covered by the inner conductive layer 31. Isolation follows 32, which are constructed from sublayers 33, 34 and 35 in carrying out the invention is. This consists, for. B. the layers 33 and 35 from one by grafting the base molecules of polyethylene can be crosslinked under the action of moisture Material, while the layer 34 consists of a peroxidically crosslinked polyethylene. At 36 is the outer conductive layer designated, 37 is the reinforcement of the electrical cable and 38 the outer sheath increased mechanical strength. Instead of the layer structure of the insulation shown, one can also proceed as follows: that one or both of the layers 33 and 35 are made of a peroxidically crosslinked material consist, while the intermediate layer 34 consists of one under the action is composed of moisture crosslinked material. By choosing the layer thickness the individual sub-layers can be adapted to the respective manufacturing conditions can also be adapted to the required properties, such as electrical Strength, mechanical stability and the like.

can be achieved.

A structure that differs from that of FIG. 3 is shown in FIG. 4.

Here, the inner conductor 39 consists of a large number of twisted together Single wires to avoid irregularities on the surface and thus Formation of field strength peaks are covered by the inner conductive layer 40. The subsequent insulation is denoted by 41. In carrying out the invention it does not consist of individual layers arranged one on top of the other Fig. 3, but the insulation consists of areas of different networking mechanisms. So are z. B. the areas 42 and 43 facing the conductive layers 40 and 45 made of a material which is peroxidically crosslinked, while the region 44 made of a material which is essentially crosslinked under the action of moisture consists. With 46 the armouring of the electrical cable is again referred to while 47 represents the outer mechanically resistant jacket.

Conversely, areas 42 and 43 can of course also be selected consist of a crosslinkable material under the action of moisture, while the area 44 is made up of a peroxidically crosslinked material. If the latter Area is still filled, there is a particularly favorable formation of a bump layer against ~ mater treeingt. Notwithstanding this, however, it is also possible To do without individual areas at all and a mixture of a peroxidic and to produce crosslinkable material under the action of moisture and to extrude, so that the different types of crosslinking are largely uniform Distribute over the entire cross-section. The distribution can then still be done through it control that the proportion of one and the other type of crosslinking by adding the required crosslinking chemicals is brought into a certain ratio. In In this case, but also in the previous ones, it can be advantageous to use the for the moisture crosslinking required silanol condensation catalyst in the To bring in the layer or the area of peroxidically crosslinkable material, see above that this diffuses only after the extrusion process to the point where it is needed will.

It is also possible to adapt for the individual areas and / or layers to meet the requirements, different thicknesses can be selected. The structure the areas and / or layers can, however, also advantageously consist of a combination consist of mixed layers, e.g. B. inside 2/3 cross-linked polyethylene, outside 1/3 cross-linked polyethylene mixed with silane-grafted polyethylene. Networking with such a mixed material can be with other known methods and Devices cannot be reached.

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Claims (22)

Claims N r method for the continuous production of Coverings for elongated goods, for example electrical cables and wires, Pipes, profiles and the like., Made of one by grafting on a silane compound the molecules of the base material, such as olefin polymers or olefin copolymers, Elastomers or thermoplastic rubbers, under the action of moisture crosslinkable material, characterized in that the sheaths in one or several layers, possibly spatially separated from one another, are extruded and the material immediately afterwards containing a water atmosphere and below Pipe section under pressure runs through. 2. The method according to claim 1, characterized in that for the Extrusion of the layer (s) ungrafted materials are used. 3. The method according to claim i, characterized in that for the Extrusion of the layer (s) of grafted materials are used. 4. The method according to claim 2, characterized in that the grafting takes place in the formed state of the material as it passes through the pipe section. 5. The method according to claim 2 and 4, characterized in that as Water vapor heated to over 1800 C is used. 6. The method according to claim 2 and 4, characterized in that the ungrafted material already in the extruder to temperatures of at least 1800 C is heated and at least partially grafts. 7. The method according to claim 3, characterized in that the water atmosphere Water or steam heated to a maximum of 1800 C is used. 8. The method according to claim 3 or 7, characterized in that the Extruder wet temperature is at most 1800 C, preferably 1200 C to 1400 C. 9. The method according to claim 3, 7 or 8, characterized in that the extruder melt temperature is not more than 1800 ° C., preferably 1200 ° C. to 140 ° C., and the water atmosphere is at least 1800 C. 10. The method according to claim 1 or one of the following, characterized in, that the moisture required for crosslinking in the extruder barrel or head is fed. 11. The method according to claim 10, characterized in that the pressure in the pipe section at least equal to the water vapor pressure in the material the extrusion introduced water is. 12. The method according to claim 1 or one of the following, characterized in, that the good after leaving the pressurized water atmosphere also is cooled to at least 800 ° C. under pressure in a water bath. 13. The method according to claim 12, characterized in that for cooling the extruded layers are gradually cooled to the final value. 14. According to the method according to one or more of claims 1 to 13 manufactured electrical cable, characterized in that the insulation and / or the adjoining conductive layers due to the action of moisture in the flow are fully or partially networked through the pipe section. 15. Electrical cable according to claim 14, characterized in that the outer protective sheath is cross-linked by the action of moisture. 16. Electrical cable according to claim 14 or 15, characterized in that that one or more of the extruded layers provided in the cable structure, such as Insulation, conductive layers, jacket, from under the action of moisture and Peroxidically crosslinked materials exist. 17. Electrical cable according to claim 16, characterized in that each of the layers consists of at least two further layers with different materials Networking mechanism exist. 18. Electrical cable according to claim 16, characterized in that the layers made of a mixture of materials with different cross-linking mechanisms exist. 19. Electrical cable according to claim 18, characterized in that the mixing ratio of the materials with different cross-linking mechanisms 30:70. 20. Apparatus for performing the method according to claim 1 or one of the following, characterized in that the pipe section which is under pressure is arranged horizontally or inclined. 21. Apparatus for performing the method according to claim 1 or one of the following, characterized in that the pipe section under pressure runs in the form of a known chain line. 22. Device for performing the method according to claim 1 or one of the following, characterized in that the pipe section under pressure is arranged vertically.