CH637569A5 - Device for producing a product with an inner part extruded from polymer material and a layer surrounding this - Google Patents

Description

The invention relates to a device according to the preamble of claim 1.

When manufacturing extruded products from polymer material, it is important to be able to interrupt an ongoing manufacturing process as soon as possible or to change the manufacturing conditions if the quality of the manufactured product is unsatisfactory. This largely prevents large quantities of the manufactured product from having to be disposed of as waste.

For example, if the product is a high-voltage cable in which the conductor is surrounded by an inner conductive layer (inner semiconductor), defects in the form of, for example, tips or edges or vulcanized hard particles in the interface between the inner can occur conductive layer and insulation occur. Since such defects increase the electrical stress in the layer and adversely affect the quality of the cable, it is important that the application of the polymer material as insulation for the cable on the layer mentioned is interrupted as soon as such defects occur or that the application of the inner conductive layer is corrected.

The inner conductive layer is normally applied by extrusion following extrusion of the insulation. In addition, an outer conductive layer (outer semiconductor) is applied to the insulation. The application of the outer conductive layer, which, like the inner conductive layer, normally consists of a polymer material which contains conductive carbon black and is therefore opaque, is often carried out by extruding the layer onto the insulation after the insulation has been extruded. If the materials in the conductive layers and in the insulation are crosslinkable, they can be subjected to crosslinking by heating the conductor with the conductive layer and the insulation under pressure in a vulcanization tube. If the materials cannot be cross-linked, the conductors with the applied materials go directly to a cooling device. If the outer conductive layer is extruded onto the insulation immediately after molding, i.e. Without the conductor with insulation being passed through any devices for crosslinking or cooling the insulation, defects in the inner conductive layer cannot be discovered before the cable is finished and even then only by a destructive sample. The invention is therefore based on the object to create a device of the type mentioned at the beginning which enables ongoing control during the manufacture of the product.

The object is achieved according to the invention by the features specified in the characterizing part of claim 1.

According to the present invention, it is possible during the manufacturing process in progress to continuously check the quality of the inner conductive layer as well as defects in the form of bubbles and impurities in the cable insulation, provided that this is done for the Insulation used material, as is the case with many known and often used materials for cable insulation, is transparent at the temperature at which the material is extruded. Taking into account the observations made during the control, the manufacturing process can be interrupted or corrected if necessary.

It follows from the characterizing part of claim 1 that the smallest inner diameter of the connecting piece must correspond to the outer diameter of the transparent inner part of the product to be manufactured. Such a connector also ensures that when manufacturing cables with cross-linked insulation, this maintains its outer diameter.

Furthermore, the connector can serve both in the manufacture of cables with cross-linked insulation and in the production of cables without cross-linked insulation as a control for the conductor with insulation, so that the outer conductive layer immediately after forming the insulation in a uniform Layer can be placed on the insulation 40. This can lead to a large saving in the space required for the production equipment. Furthermore, the connector can serve as a vulcanization pipe under special circumstances.

The invention can be used particularly advantageously in the production of tubes, hoses and other profiles by extrusion molding a polymer material that is transparent during molding and then extruding an opaque polymer material onto the first polymer material.

50 The transparent inner part of the product can, for example, be an insulation for a cable conductor provided with an electrically conductive layer (inner semiconductor). The opaque layer surrounding the inner part can be, for example, an electrically conductive layer (outer semiconductor) on a cable insulation.

Polyethylene and copolymer of ethylene and another unsaturated monomer such as ethyl acrylate, butyl acrylate and 60 vinyl acetate can be mentioned as examples of suitable materials for the inner part which is transparent at the molding temperature. In the copolymer, the weight of ethylene is preferably at least 60 percent of the combined weight of ethylene and another unsaturated compound. The polymeric material can be used 65 without the addition of a crosslinking substance. The insulation gets thermoplastic properties. The polymeric material may alternatively be mixed with a peroxide or other substance capable of causing crosslinking.

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Examples of suitable peroxides include Di-a-kumyl peroxide, di-tert-butyl peroxide and 2,5-dimethyl-2,5-di (t-butyl peroxy) -hexine-3 can be mentioned. The amount of peroxide is expediently 0.1-5 parts by weight per 100 parts by weight of polymer material. An antioxidant, such as, for example, polymerized trimethyldihydroquinoline or aldon-a-naphthylamine, is also usually added to the polymer material, advantageously in an amount of 0.5-5 parts by weight per 100 parts by weight of polymer.

If the opaque layer is an electrically conductive layer, i.e. If the device is used to manufacture high-voltage cables, the polymer material in the layer can include of chlorosulfonated polyethylene, which contains mineral oil as a softening agent, conductive carbon black and possibly powdered filler such as talc, and also copolymers of ethylene and vinyl acetate, which contain carbon black and possibly powdered filler such as talc or chalk. If the layer is crosslinked, a peroxide, for example of the aforementioned type and in the aforementioned amount, is also added.

If the opaque layer is a protective layer on a pipe, hose or other profile such as a jacket that protects against the influence of ultraviolet rays, it can consist of a polymer material that contains a few percent soot. The type of polymer material can be of very different types. Suitable materials include Polyethylene, polypropylene, polyvinyl chloride, chlorosulfonated polyethylene, chloroprene, nitrile rubber, polyamide and polyurethane. When the layer is crosslinked, a peroxide is added, for example, of the type and amount as described above for the polymeric material in the inner part.

The material in the transparent part of the connecting piece can be glass or quartz, for example.

The invention will be described below by the description of exemplary embodiments and with reference to the accompanying drawings, in which

1 shows a device according to the invention for producing a high-voltage cable,

Fig. 2 shows a device according to the invention for producing a tube which is provided with a jacket for protection against ultraviolet rays, and

Fig. 3 shows another device according to the invention for producing a high voltage cable.

In the figures, the extrusion for forming the inner part is designated by 1, the extrusion press for forming the opaque layer by 2 and the connecting piece by a transparent part for checking the product provided with the inner part by 3. 1 and 2, both the connector 3 and the extruder 2 are located so that the extruded material in the extruder 1 is not cross-linked or has been subjected to another treatment when it passes through the connector 3 and into the Extrusion press 2 goes in.

In the device according to FIG. 3, the connecting piece 3 serves as a vulcanization tube, which is why the material extruded in the extrusion press 1 is cross-linked when it goes into the extrusion press 2. The connector 3 in the examples shown in FIGS. 1 and 2 consists of a cylindrical glass tube with a width of approximately 5 cm and an inner diameter which is the same size as the outer diameter of the inner part in the product to be manufactured. The connector is entirely transparent in the cases shown.

1, a cable conductor 4, which is conventional and can be made of copper or aluminum, is passed through the extrusion presses 1 and 2. The same is provided with an extruded inner conductive layer 5 when it enters the extrusion press 1. In the case described, this consists of a copolymer of ethylene and ethyl acrylate (weight ratio 80:20), which contains 40 parts by weight of conductive carbon black and 2 parts by weight of di-t-butyl peroxide pfo 100 parts by weight of copolymer. For the inner conductive layer, i.a. the materials mentioned in the above text as examples of materials for the outer conductive layer can also be used.

The insulation 6 of the cable is attached to the extruder 1. In the case described, it consists of LD-polyethylene with a melt index of 0.2-20, which contains 2 parts by weight of di-a-kumyl peroxide and 0.2 parts by weight of polymerized trimethyldihydroquinoline per 100 parts by weight of polyethylene. The polyethylene has an extrusion temperature of 125 ° C. In the extruder 2, an outer conductive layer 7 is applied, which in the described case consists of a copolymer of ethylene and vinyl acetate (weight ratio 60:40), the 30 parts by weight of conductive carbon black and 2 parts by weight of di-t-butyl peroxide per 100 parts by weight of the copolymer contains. The cable conductor 4 with the layers 5, 6 and 7 then goes into the only partially shown vulcanization tube 8, where the layers 5, 6 and 7 are crosslinked by heating to approximately 220 ° C. by being subjected to a pressure of 1 MPa. When the polyethylene passes through the glass tube 3, the polyethylene has a temperature of 125 ° C., as can be seen from the above, and is then transparent. One can therefore continuously check the quality of the inner conductive layer 5 and the insulation 6 and interrupt or adjust the production conditions if it should turn out that defects occur in the inner conductive layer or in the insulation itself.

Fig. 2 shows a device for producing a tube which is provided with a protective layer against ultraviolet radiation. A mandrel 9 extends through the extruders 1 and 2. The tube 10, which is extruded in the extruder 1, consists of HD polyethylene with a melt index of 0.1, which contains 0.2 parts by weight of polymerized trimethyldihydroquinoline per 100 parts by weight of polyethylene . The polyethylene has an extrusion temperature of 240 ° C. In the extruder 2, a protective layer 11 made of HD polyethylene is applied, which contains 3 parts by weight of soot and 0.2 parts by weight of polymerized trimethyldihydroquinoline per 100 parts by weight of polyethylene. The tube constructed from layers 10 and 11, after molding, goes into a water bath, not shown, at a temperature of nearly 100 ° C, where it is cooled. When the polyethylene 10 passes through the glass tube 3, it has, as can be seen from the above, a temperature of 240 ° C. and is then transparent. The quality of the layer 10 can thus be checked continuously and the necessary changes made in the production process.

The connecting piece 3 in the devices according to FIG. 1 and FIG. 2 can also be conical or consist of a conical and a cylindrical part. The same has a smallest inside diameter that is the same size as the outside diameter of the inner part 6 or 10 in the product that is to be manufactured. The connecting piece can of course be made of metal, to a greater or lesser extent, and otherwise a transparent part. For example, the connector can consist of a cylindrical or conical metal tube into which a glass window is embedded.

3, the connector 3 between the extruders 1 and 2 is a glass tube, which also

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serves as a vulcanization pipe. The vulcanization tube is surrounded by a radiation source 12, which consists of a plurality of infrared lamps with tungsten filaments arranged around the tube, which work at a temperature of 2100 ° C. and thereby give off a radiation whose intensity maximum is at a wavelength of 1.2 [x . The conductor is first provided in the extrusion press 1 with an inner conductive layer 5 and then with an insulation 6. The materials in layers 5 and 6 can be the same as those mentioned for the corresponding layers in the production of the high-voltage cable described with reference to FIG. 1. The polyethylene in layer 6 has a temperature of approximately 125 ° C during extrusion. When the conductor 4 with the layers 5 and 6 passes the radiation source 12, the polymers in the layers 5 and 6 are crosslinked and then cooled with water or gas under pressure in a cooling tube, not shown, connected to the left end of the vulcanization tube 3. The polymers are exposed to pressure in the vulcanization tube. The pressure is generated by utilizing the thermal expansion of the polymer together with pressure from the die of the extruder 1 at one end of the vulcanization tube and pressure from the coolant at the other end of the vulcanization tube. The fact that the vulcanization tube and the polyethylene let the short-wave infrared radiation through at the forming temperature results in rapid heating of the conductor and the inner conductive layer of the cable, which leads to rapid heating and rapid cross-linking of the polymer in the entire cross section.

The outer conductive layer 7, which is applied in the extruder 2, can consist of a copolymer of ethylene io and vinyl acetate (weight ratio 60:40), which contains 20 parts by weight of conductive carbon black per 100 parts by weight of copolymer. If the layer is to be crosslinked, it must be mixed with a peroxide and subjected to heating in a heating device which is arranged behind the extruder 2 and in front of the cooling device in the direction of travel of the cable. By having the vulcanization pipe and also the insulation 6 while they. located in the vulcanization tube, is transparent, the quality of the inner conductive layer 5 and the insulation 6 can be continuously checked and the production conditions interrupted or adjusted if it should turn out that defects occur in one of these layers.

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1 sheet of drawings

Claims (3)

637 569 1. Apparatus for producing an inner part and a product having an opaque layer surrounding it, the inner part and layer being extruded from polymer material, with a first extrusion press (1) for forming the inner part (6, 10), which is transparent at the molding temperature, and a second one Extrusion press (2) for forming the opaque layer (7, 11) surrounding the inner part, characterized in that the two extrusion presses (1, 2) are connected to one another by a connecting piece (3), the inner wall of which is intended to abut the transparent inner part during extrusion and which is transparent or has a transparent part in order to be able to control the nature of the inner part and, if appropriate, of the parts lying within the inner part. 2. Device according to claim 1, characterized in that the connecting piece (3) is a cylindrical or conical, transparent tube. 2nd PATENT CLAIMS 3. Device according to claim 1 or 2, characterized in that the connecting piece (3) is a vulcanization tube for the transparent inner part (6, 10).