DE1915892A1 - Method and device for wrapping strand-like goods with crosslinked thermoplastics - Google Patents

Description

^ SÜDDEUTSCHE KABELWERKE Frankfurt / M., March 19, 1969

Branch of the BbI / HGa ί η ι er ο η ο

United German Me «ι 3 I 0 ο ö I tallwerke AG, Mannheim

prov. No. 6176 V

Method and device for wrapping strand-shaped Good things with cross-linked thermoplastics

The invention relates to a method for wrapping strand « shaped material, in particular electrical conductors with a hardened thermoplastic material.

It has long been known to produce strand-like material by extrusion from a screw press using thermoplastics to envelop. In particular, it is known to use electrical conductors or cable cores or the like by this method to be provided with insulation or a jacket made of polyethylene. Such insulation, especially sheaths of high-voltage cables made of normal polyethylene, however, have certain disadvantages caused by the use of crosslinkable polyethylene can largely be avoided. The cross-linking of those produced in the usual way by extrusion However, insulation or sheathing is expensive or requires a considerable amount of technology if a large amount of space is required Expenditure.

It is known to have one made with an extruded insulation to lead normal polyethylene-sheathed electrical conductors through a system with an active radiation source, whereby the polyethylene passes into the crosslinked state. This method is so expensive that it is only used in exceptional cases will ο

Usually the polyethylene to be crosslinked is treated with a crosslinking agent, preferably an organic peroxide,

00 98 U / 1 7Λ 2 - 2 -

offset that at or above the extrusion temperature reacts with the polyethylene and cross-links the polyethylene chains causes. For this it is necessary to let the extruded polyethylene at the crosslinking temperature for some time and at the same time subjecting it to sufficient pressure to prevent the formation of bubbles or cavities from the to prevent gaseous or vaporous reaction products. For this purpose it can be coated with crosslinkable polyethylene Can easily be guided through a pipeline connected to the extruder head, in which steam and Water zones of suitable temperature for crosslinking and

fc subsequent cooling required physical conditions are made. The operation of such systems, in which the vulcanizing pipe is horizontal, along a Chain line or preferably arranged vertically, requires a large amount of space in addition to the considerable space required. wall on control and monitoring devices. Contact with the pipe wall leads to undesirable deformations of the thermoplastic material, which is also due to its relatively low viscosity at the crosslinking temperature can shift eccentrically with respect to the enveloped good. The monitoring of the product inside the pipe is difficult, so that any errors are often only noticed after running through the entire length of the pipe, which is too high

"Committee can lead.

More recently, there is an apparatus for a method for Manufacture of molded parts from crosslinked polyethylene has become known (DBGM 1 974 254), in which the disadvantages of the procedure outlined above are avoided. The mixed with a crosslinking agent becomes thermoplastic Plastic in a pressure chamber is subjected to momentary compression to a very high pressure, for example 10,000 atm, where he is heated to about plasticizing temperature and cross-linked and the cross-linking agent in the plastic is extremely fine

00Ö842 / 1742 - 3 -

is distributed. "Partly networked" is to be understood as a condition In which the crosslinking of the polymers has already started, but the plastic mixture is still its thermoplastic properties. The fully cross-linked material, on the other hand, is essentially thermoset Properties on. That becomes from the pressure chamber Heated and fully cross-linked material is fed into an injection or casting mold, where it is exposed to further heat is cross-linked.

The invention is based on the object, known per se, of high-voltage insulation from networked! Making polyethylene economical.

The invention therefore proposes a method for continuous Enveloping strand-like goods, for example electrical conductors, from a pressure chamber with a rushed one thermoplastic plastic, the plastic being under such high pressure during crosslinking that the Formation of macroscopic vesicles from the gaseous or vaporous ones Reaction products is prevented. The object is achieved in that the short-term in a chamber Under the influence of very high pressure, cross-linked thermoplastic material in a still deformable state, steadily through pressed a compression head with a mouthpiece designed as a heatable tube, formed in this around the material and during the passage through the mouthpiece is completely crosslinked under the action of heat, with high due to the structure Pressure from the open end of the mouthpiece, the formation of macroscopic gas or vapor in the cross-linked material vesicles from products of the crosslinking reaction are prevented. The said press head points to the introduction of the object a conically tapering quill; a heated mouthpiece with a bore whose conical entrance is the The shape of the quill end is adapted, is mounted on the press head so that it can be centered on the material passing through and is screwed tightly.

009842/1742 _ 4 -

A line system, for example one or more ducts connected to the pressure chamber, is used for the uniform Distribution of the cross-linked thermoplastic around the product. The channels expediently open into the conical Space between the quill end and the entrance to the bore of the mouthpiece. The bore of the mouthpiece can be cylindrical or slightly conical, such that its inside width towards the open end of the mouthpiece decreases slightly.

The latter embodiment is particularly useful in order to build up high pressure in the press head from the open end of the mouthpiece to force forth.

The mode of operation of the method is that the in. Thermoplastic synthetic material, which is cross-linked to the pressure chamber, is fed into the press head under very high pressure and gradually cross-linked on the way through the mouthpiece as a result of the sustained supply of energy through external heating becomes, whereby it goes into the thermosetting state.

When the cross-linked covering is used as insulation for electrical conductors, in particular as high-voltage insulation is to be avoided, the formation of bubbles or cavities must be avoided. This is achieved in that the material while going through the actual ver ™ wetting zone, i.e. the heated mouthpiece, is kept under high pressure, this being built up from the open end of the mouthpiece. This pressure build-up in turn will achieved in that the mass during the passage of the mouthpiece from a more or less viscous state in passes the thermoset state, i.e. almost non-deformable and forms a plug which tightly closes the open end of the mouthpiece. Without this change of state would be predominantly linear in the viscous liquid from entry into the mouthpiece to exit from it

009842/1742

There is a pressure drop down to zero pressure »The gaseous reaction products could therefore expand and form macroscopic vesicles and cavities. Since the transition ' from the thermoplastic (crystalline) state to the thermoset (amorphous) state with disordered interlinking between the macromolecules is usually associated with a slight increase in volume, the thermoset Plug held in the end of the mouthpiece with very great force. When processing fabrics without or with insufficient volume increase during crosslinking, according to a development of the invention, the bore of the Mouthpiece be designed slightly conical, so that its clear width decreases slightly towards the open end. The almost non-deformable thermosetting plug can only with the application of considerable forces through the end of the Mouthpiece are driven through, with a large pressure built up in the entire material in the area of the mouthpiece will. The force to force the thermosetting plug through the end of the mouthpiece is provided by the lower very high pressure delivered from the pressure chamber pressed material. The one flowing through the press head under large Compressed mass exerts such great forces on the goods it encases that they generally do not slip takes away. Accordingly, there is often no need to provide a conveying device for the goods to be wrapped. From the The way in which the press head works is that the outer diameter of the casing is clearly determined by the opening of the mouthpiece will. In contrast to the extrusion process, it does not depend on the pull-off speed of the goods. As is well known hot, viscous plastic compounds tend to adhere to hot metal surfaces. To prevent this, one suggests Further development of the invention, all surfaces of the press head coming into contact with the crosslinked material to be covered with a coating that prevents adhesion.

■ - 6 009842/1742

The light emerging from the mouthpiece cross-linked (thermoset) material although not clear, but as far as throughput ..- cautiously that any macroscopic bubbles or other imperfections can be detected immediately. By this way direct observation method of the invention is advantageously different from the conventional method of cross-linking in the vulcanising tube, where & thereto expensive equipment are required.

The strand emerging from the mouthpiece of the press head with cross-linked! Plastic surrounding goods can be in a pressureless Cooling device, preferably a tub filled with water, cooled and then a winding device are fed.

Another suggests to increase the delivery rate Further development of the invention to connect more than one, for example three pressure chambers to the press head, wherein the compression head is designed so that the connections of all pressure chambers in the same system for uniform Distribution of the material around the property flow into it.

It is known to coat multi-wire conductors of cable cores with a smoothing layer of thermoplastic material, preferably made semiconducting. In order to avoid air inclusions, this plastic should fuse as seamlessly as possible with the material of the insulating sleeve applied over it. It is customary to produce the said smoothing layer from crosslinkable polyethylene under an insulating cover made of crosslinkable plastic, for example crosslinkable polyethylene. ,

The invention therefore proposes two methods according to which a smoothing layer is applied to an electrical conductor cross-linked semiconducting plastic and above A series of insulating sleeves made of cross-linked thermoplastic material is applied.

009842/1742

According to the first method, a compression head is used which two distribution systems to produce two concentric ones Has sheaths around the electrical conductor. Such devices are known from extrusion heads in extruder technology. The distribution system for the production of the inner shell (the smoothing layer) consists of a first pressure chamber fed with semiconducting crosslinked material and the distribution system for the production of the outer The (insulating) shell is fed with cross-linked material from a second or, expediently, from several pressure chambers. According to the second method, two according to the invention Devices for wrapping strand-like goods with cross-linked thermoplastic material arranged in tandem. The first of these facilities is fed with crosslinkable material made semiconducting. From this facility the electrical connection, which is provided with a smoothing layer made of semiconducting cross-linked plastic, occurs Head into the second device, in which it is covered with a concentric insulating sleeve made of cross-linked plastic will.

After a further development of this method, instead of the first device arranged in tandem for wrapping the Conductor with a smoothing layer of semiconducting crosslinked plastic a device, preferably a Extruder, used, in which the conductor is covered with a semiconducting, crosslinkable plastic. The networking This relatively thin plastic layer then takes place in the second "device together with that in this one Device applied insulating sheath, the two shells fuse together.

The invention has compared to the known method for wrapping strand-like goods, in particular the head of High voltage cables with crosslinked thermoplastics essential technological and economical

009842/1742

. 1915893

Benefits on. It avoids building extensive and costly networking facilities, especially the preferred towers for hanging the vulcanizing tubes as well in the pressure pipe the transition from the steam or hot water zone to the cooling zone with pressurized water. There is no handling with high-tension steam and the associated safety measures »deformation of the casing as a result of uncontrolled behavior in the vulcanizing tube can not occur; the casing leaves the mouthpiece in an almost non-deformable state. She has a completely smooth, high-gloss surface. Forced cooling of the product emerging from the mouthpiece can be appropriate, but can be dispensed with in principle. P The investment costs of a complete according to the invention Plants are at least an order of magnitude smaller than those for a conventional plant for manufacturing of high voltage cables with insulation made of cross-linked polyethylene. The lower conveyor speed can be in an economic comparison by setting up several operated by a single person at the same time inventive systems are more than compensated.

The invention is explained in more detail below with reference to the drawings,

Fig. 1 shows a system in a schematic representation

»For wrapping elongated goods according to the invention.

Fig. 2 shows a section through a press head with

a distribution system and a feed point.

Fig. 3 shows a section through a press head with

two distribution systems and two feed points.

Fig. 4 shows the schematic view of two devices arranged in tandem.

In Fig. 1, the reference numeral 10 designates the pressure chamber in which the with a crosslinking agent

- 9 009842/174 2

offset thermoplastic material is crosslinked and from which it is ejected into the press head 20. The cross-linked plastic is in the press head around the item to be wrapped 31 and then completely crosslinked in the mouthpiece 21 by the action of heat. The good 31 is of the ■ Cross-linked plastic running through the compression head without slipping taken and withdrawn from the unwinder 30. The one emerging from the mouthpiece of the press head, with crosslinked Material 32 encased in plastic is guided through the pressureless cooling device 40 and from that with a drive 51 provided winder 50th added without tension.

The press head 20 according to Pig. 2 consists of the pressure-resistant housing 23, which by means of the flange 231 with the pressure chamber 10 is connected. The discharge tube 11 of the pressure chamber opens into the line system 24 at the feed point 241 uniform distribution of the cross-linked plastic around the item 31. The centerable by means of a device 25 The mouthpiece 21 is firmly connected to the housing 23, for example by means of a pressure screwing 26. In the housing 23 the quill 27 is arranged to be exchangeable; its rear end is formed by the conically tapering nipple 271. With 28 and 29 heating devices for the housing or denotes the mouthpiece 21.

The pressing head 20 * shown in FIG. 3 is suitable for the simultaneous sheathing of electrical conductors with a semiconducting smoothing layer 33 and an insulating sheath 34. It has two flanges 231 ^r and 231 ^! * for connecting pressure chambers 1Ό and two essentially concentric line systems 24 * and 24 **.

Fig. 4 shows another arrangement for encasing electrical Conductor with a semiconducting smoothing layer and a concentric insulating sleeve in one operation.

Two examples of the sheathing of electrical conductors that have been carried out may serve to further explain the invention.

009842/1742

Example 1:

A round aluminum conductor cable with a cross-section of 150 mm was passed through a press head according to Fig. 2 and with a 6 mm thick insulation made of cross-linked polyethylene high density (density 0.95 to 0.96). The mixture was heated to 110 ° C in the pressure chamber The temperature of the crosslinked material was 150 ° C. in the quill. 290 ° C. were reached in the mouthpiece. The length of the Mouthpiece was 250 mm. The throughput speed of the coated material was 20 m / hour.

Example 2;

On a round aluminum conductor with a cross-section

2
From 95 mm, a 1.3 mm thick smoothing layer was first extruded from a crosslinkable, carbon black-filled copolymer of ethylene. This rope was then passed through a press head according to FIG. 2 and sheathed with a 6 mm thick insulation made of crosslinked low density polyethylene (density 0.918 to 0.920). 0.8 part by weight of dicumyl peroxide was added to the polyethylene as a crosslinking agent. The mixture • was in the pressure chamber. 110 ° C heated. In the area of the quill, the temperature of the anynetwork material was 140 ° C. In the mouthpiece, 260 ° C were reached. The length of the mouthpiece was 250 mm. The throughput speed of the coated material was 28 m / hour.

- 11 claims

0Ό9842 / 1742

Claims (17)

Claims A method for wrapping strand-like material, in particular electrical conductors, with a cross-linked thermoplastic material, characterized in that the thermoplastic material which is cross-linked in a chamber by brief exposure to very high pressure, while still deformable, is continuously pressed into a press head with a mouthpiece designed as a heatable tube , is formed in this around the material and is completely crosslinked while passing through the mouthpiece under the action of heat, whereby the formation of macroscopic gas or vapor bubbles from products of the crosslinking reaction is prevented by the build-up of high pressure from the open end of the mouthpiece in the crosslinked material . 2. Compression head for performing the method according to claim 1, characterized by a conically tapering quill for introducing the strand-like material, a heated mouthpiece mounted so that it can be centered on the material and having a bore whose conical entrance is adapted to the shape of the finder, as well as a line system for uniform Distribution of the cross-linked thermoplastic material around the material, for example one or more channels connected to the outlet of the pressure chamber, which run out into the conical inlet of the mouthpiece. 3. Compression head according to claim 2, characterized in that «the bore of the mouthpiece is cylindrical. 4. Press head according to claim 2, characterized in that the bore of the mouthpiece is slightly conical and that its inside width decreases slightly towards the open end of the mouthpiece. - 12 QQ9842 / 1742 ' 5. Press head according to claim 3 or 4, characterized in that the mouthpiece is at least 200 mm long. 6. Press head according to claim 2, characterized in that all surfaces coming into contact with pre-crosslinked material are coated with a coating which prevents the crosslinked material from adhering. 7. The method according to claim 1, characterized in that the press head is fed from more than one pressure chamber with crosslinked material. 8. Compression head for performing the method according to claim 7 J ^ and claims 2 to 6, characterized in that all connections of pressure chambers for feeding cross-linked material open into the same line system for even distribution of the material around the material. 9. Press head for performing the method according to claim 7, characterized in that at least two line systems for the production of at least two concentric shells from networked! Material are provided and that each of these systems has at least one connection for feeding crosslinked material from a pressure chamber. 10. The method according to claim 7, characterized in that crosslinked material made semiconducting is fed into the innermost of the line systems according to claim 9. 11. The method according to claim 1, characterized in that two devices for wrapping strand-like goods with crosslinked thermoplastic material are arranged in tandem. , - 13 009842/1742 12. The method according to claim 11, characterized in that the first of the devices arranged in tandem is fed with a crosslinkable material made semiconducting. 13. The method according to claim 1, characterized in that the device for wrapping strand-like goods with crosslinked thermoplastic material is preceded by a device for wrapping the goods with crosslinkable material, for example an extruder. 14. The method according to claim 13, characterized in that the input into the upstream device crosslinkable material is made semiconducting. 15. The method according to any one of the preceding claims 1 to 14, characterized in that the exiting from the press head covered with crosslinked thermoplastic object in a pressureless cooling device, preferably a water-filled tub, enters and is then fed to a winding device. 16. The method according to one or more of the preceding claims 1 to 15, characterized in that polyethylene is used as the crosslinkable or crosslinkable and semiconducting thermoplastic material. 17. According to one or more of the preceding claims 1 to 16 produced electrical line or electrical cable, with a covered object Solid wire or a rope or a pipe or a cable core consisting of several insulated conductors is used. 009842/1742