KR830001600B1 - How to continuously form coatings such as electric cables - Google Patents

Abstract

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Description

How to continuously form coatings such as electric cables

The figure is an explanatory diagram of an apparatus for carrying out the method according to the invention.

The present invention relates to a method of continuously producing a coating of long material, in particular an insulating layer of a medium or high voltage cable, from a peroxide-netically bondable olefin mixed polymer.

The demand for greater use of cable networks, greater use of higher voltages, and higher use voltages is linked to the need for higher quality cables. Particularly valuable is the cable insulation without impurities in order to eliminate the discharge of the cable and eventually the corona discharge of the cable insulation which leads to the breakage of the cable. In thermoplastic polyethylene, in order to remove foreign substances, such as a so-called polyethylene-tobacco, a metal, and the like, the filtering of the polymer material through a net is actually performed. In this net or filter process, the material temperature rises to 130 ° C., in particular by giving shearing stress to the material, and therefore, a thermoplastic material or elastomer containing a netting agent. When it was necessary to ensure the absence of impurities, it was impossible to guarantee insulation.

Due to the increase in pressure when the polymer material is sieved through the mesh and the increase in the shearing stress due to the increase in pressure, partial reticular bonding occurs when the retardant is incorporated in the melt of the retardable polyethylene. Since this so-called scorch formation considerably degrades the extruder, the material containing the netting agent has given up the filtering of the foreign matter in the tool, or a wooden net has been used.

However, it was very difficult to coat the conductors with a particularly pure insulating material, especially in order to use the reticulated material in the high voltage range. Purity can be guaranteed for a long time only by fine mesh or filter treatment. The reason for this is that this fine net can remove impurities contained in the granular material and generated during the treatment.

Accordingly, the present invention aims to explore the possibility of adapting the thermoplastic resin refining process to such a material that contains a netting agent and is likely to undergo a netting reaction due to the compounding temperature generated by the netting agent.

This problem is solved as follows by this invention. First, the polymer base material without peroxide is melt homogenized, and then molding is performed in a processing stage spatially separated from the melting process and homogeneous process in the same processing step. During the molding process, the polymer material is melted and homogenized. This is solved by introducing at least a network binder (peroxide).

The idea is that, for example, the netting agent given by the fluid reaches a homogeneous melt and then disperses rapidly and well in the melt, thus not disturbing the homogeneous and melting process and taking into account the peroxides that generate scorch. It is not necessary to, and therefore, this step can be performed satisfactorily.

The present invention, although having a specific purpose, departs from well-known devices. The apparatus consists of two extruders installed in an L shape, and the first extruder is used for melting and homogenizing, and the second extruder for molding. It is ensured that an impurity-free insulation is formed when carrying out the invention with this device.

When manufactured by the method of this invention, the problem of screw lining known practically is solved by the removal of the oxidation-resistant agent on the surface of a granular material. The screw itself may be provided with a stirring portion suitable for rapidly or homogeneously dispersing the network agent.

In order to further improve the present invention, the polymer material after melting and homogenization may be subjected to an impurity removal treatment before the molding stage. This is advantageous because it can pass through the net of detail and can be carried out without considering the risk of generating scotch due to high shearing stress. It is also advantageous to at least measure the introduction of the netting agent between the uniform process and the start of the molding process in time and space. In addition to the netting agent, other additives, that is, a stabilizer and an oxidation resistant agent, may be added here.

When degassing in the contact range from a 1st extruder to a 2nd extruder, it is suitable to supply at least a network agent during pressurization in a shaping | molding process.

The degassing treatment has no adverse effect on the distribution of the netting agent in the insulator. As the netting agent, a known compound such as an organic perproduct of the trade name "Trinox D 140" or a compound such as di-tert-butyl peroxide or the trade name "Pelcadox 14" or dicumylperoxide may be used. .

Since these additives are solid at room temperature except di-tert-butyl peroxide, what is necessary is just to apply a netting agent in a molten state at the time of implementing this invention. In this case, it is particularly advantageous if the solution containing the netting agent contains a solvent or a voltage stabilizer in solution state which simultaneously acts as a voltage stabilizer. In many cases, the solvent of the peroxide network agent, which is a hydrocarbon having an aromatic ring, contains an unsaturated group such as vinyl or propenyl, and thus graft bonds to the polyethylene-macromolecule in whole or in part during network bonding.

In addition to the peroxides or peroxide mixtures used in the preparation of network-bondable polymer materials and additives such as dicumylperoxide, for example, diisopropyl benzenemonohydro peroxide or tert-butyl hydroperoxide, etc. Peroxides having a high decomposition temperature may be used.

Next, the present invention will be described in detail by way of examples. For example, a polymer mixture such as polyethylene is supplied into the skin 1 of the extruder 2. The rotating screw first melts and homogenizes the mixing of the polymer materials. Corresponding to the pitch of the screw, the homogenized material is supplied to the extruder 5 via the connecting flange 4. This extruder 5 is formed as a so-called discharge extruder.

By this extruder 5, the material extruded in this way is provided in the head 6 in a conductor 7, for example, a high voltage cable. In order to ensure that there are no impurities to the extent that the material to be used is satisfied to a predetermined condition, a weakly shown network device is provided in the part 8, and the homogeneous material is filtered through the network device. The temperature rises due to shearing stress, but this elevated temperature does not interfere with the mixing of this material. The reason for this is that up to this point, the polymerized material thus treated does not contain a netting agent.

Unlike in the case of supplying the netting agent with the polymer material as in the prior art, a connector is provided in the part 9 of the discharge extruder 5 as shown in the drawing, and through this connector, a substance mixture containing no impurities during pressurization. Directly introduce the netting agent.

The reticulant is absorbed as desired, dispersed in the mixture, and discharged through the injection head 6 together with the polymer material without partial reticular bonding.

Claims (1)

A method for the continuous production of coatings of elongates, in particular electrical or high voltage cables, from peroxide-combinable olefin polymers or olefin copolymers, in which the olefin polymer or olefin copolymer is first melted and homogenized and then flowed In the method of adding a peroxide after melting, the polymer is melted and homogenized, and the impurities are filtered out, and the filtered material is homogenized again in the same process but in the next stage, and at least the netting agent (peroxide) is added during the homogenization. Measuring and distributing homogeneously, then coating the material and extruding.

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