DE2419209A1 - Crosslinkable ethylene copolymer insulation cable - contg. a silane and a silanol condensation catalyst - Google Patents

Abstract

A process for the shaping of organic polymers, esp. in the prodn. of insulation sheathing for electric cables is claimed. The polymer is mixed and reacted with a silane and a compound able to produce free radicals in the polymers. Before or during the reaction a silanol condensation catalyst is added. Immediately after the reaction the polymer is extruded and shaped. Water or moisture is allowed to contact with the polymer to crosslink it. This process is more economic than prior art. The polymer is used esp. for sheathing electric cables.

Description

Process for processing crosslinkable organic polymers The increasing electrical, mechanical and thermal demands on electrical Cables and wires constantly lead to the development of new materials, in particular of insulating materials, efficient manufacturing processes for their economical processing need to be developed. More and more recently they are networkable Plastics, in particular crosslinkable polymerized olefins, olefin polymers or olefin copolymers, for sheathing electrical cables and lines, in particular used as insulating or jacket material. Such polymers include especially polyethylene, polypropylene and consisting of at least two olefin components Copolymers, which optionally contain a diene as a further component, For example, ethylene-propylene rubber (EPR) and ethylene-propylene terpolymer rubber (EPDR). These polymers, especially polyethylene, are usually based on chemical goat cross-linked by means of suitable peroxides. The networking usually takes place in a tube that has to be passed through continuously, the water vapor under high pressure contains.

In such a production process, the production speed, which depends on the crosslinking temperature, limited by the fact that the pressure of the water vapor rises sharply with increasing temperature. The ones in manufacturing Controllable temperatures are around 200 to 21,000.

Crosslinking at temperatures of 250 to 30,000 would be desirable and also permissible with regard to the crosslinkable material. So you already have provided, the sheaths of electrical cables and lines in a liquid bath, for example in a salt bath, to be crosslinked without pressure. Here, however, exists because of the lack of pressure, the risk of bubble formation in the crosslinked material. Such bubbles reduce the electrical strength of the respective envelope.

There are now organic polymers known that without a special heat treatment, only under the action of moisture or Let the water crosslink. This is, for example, polyethylene or a copolymer of ethylene and a small amount of propylene or butylene, that initially in a first processing stage in the presence of a compound that is able to generate free radical sites in the polymer, reacted with a silane is, º wherein the reaction is carried out at a temperature above 140 0; In a further processing stage, the polymer reacted with the silane is subjected to a shaping process and then in the presence of a silanol condensation catalyst exposed to moisture. The silanol condensation catalyst can incorporated into the mixture during or after the reaction of the polymer with the silane (DD-hS 1 963 571). For the processing of these substances it is essential that the reaction of the polymer with the silane is carried out under conditions in which the polymer is subjected to mechanical working through.

This mechanical working through can, for example, in one Extruder which is constructed in such a way that it has both a putty and a exerts a mixing effect, i.e. in a mixing extruder, or in a Banbury internal mixer or on a rolling mill.

It is therefore typical for this known processing method that the Polymer is reacted with a silane in a first processing stage and that then after the addition or with the addition of a silanol condensation catalyst In a further step, namely the shaping stage, the material is used for the final The product is shaped and then exposed to moisture.

For organic polymers that can be crosslinked in the presence of moisture such as polyethylene, herylatpolymerisate, polyvinyl chloride or e in Acrylni tril-buta an acrylonitrile-butadiene-styrene copolymer is also known a method in the case of which a silane is also initially grafted onto the polymers mentioned becomes, under mechanical working conditions, under which free radicals are formed in the polymer, and in which before, during or after mixing the Mixture a silanol condensation catalyst is added. Mechanical processing of the polymer and the silane, which lead to a reaction of the silane with the polymer can be done during any of the subsequent processing operations, for example take place during the niche stage, the extrusion stage or the shaping stage (DT-AS 1 794 028).

If the mechanical processing within the shaping stage takes place with the help of an extruder, this must be a so-called mixer extruder act, which is a mixing part for intensive mixing and kneading of the Polymerisates contains Mixing extruders of this type have a relatively small output marked, so that with the simultaneous use of such extruders as a molding tool, for example for sheaths of electrical cables production speeds are accepted that are significantly below the production speed of extruders, with which a crosslinkable thermoplastic is merely plasticized, homogenized and is carried out.

The invention is based on the task of processing under Exposure to moisture or water to crosslinkable organic polymers finished products, in particular for sheathing electrical cables or lines, to make it more economical.

To solve this problem, the invention is based on a method for Processing of organic polymers in which the polymer with a Silane and with a chemical compound that is able to create free radical sites to produce in the polymer, mixed and reacted with the silane and at that of the converted polymer, that of a silanol condensation catalyst before or during the reaction was supplied, immediately afterwards by extrusion of the shaping, in particular the shaping for sheathing the cable or line, subjected and final is crosslinked by the action of moisture or water. According to the invention it is provided that for the processing of copolymers of ethylene, in which the comonomers are polar in character, first the silane and the chemical compound on a present in granulate, powder or grit form copolymer in liquid State or drummed up in solution and mixed with the copolymer will; the copolymer prepared in this way is then added after addition or with simultaneous addition of the silanol condensation catalyst by means of a the mixture of only plasticizing, homogenizing and discharging extruders formed into the finished product, in particular for wrapping.

For the processing method designed according to the invention are So two measures are essential: 1. On the polymer base substance, which is for example a copolymer of ethylene and vinyl acetate or of ethylene and acrylic acid ester can act, be the silane and the chemical compound just drummed up.

2. The mixture obtained with this reeling is then with processed in an extruder, which only plasticizes and homogenizes the mixture and unsubscribes. So there is no extruder used, which has a special mixing part contains; There is therefore no need to mechanically work through the basic polymer substance. This means that the reaction of the copolymer with the silane takes place at the same time takes place with the shaping of the mixture, on an extruder, as it is usually done for shaping thermoplastics, crosslinkable thermoplastics or elastomers is used, which therefore has a high output and thus high production speeds guaranteed.

In the case of the method designed according to the invention, there is therefore no need the previously necessary mechanical working through of the copolymer. This simplification the process is apparently based on the property of the copolymers, the silane and soak up the chemical compound. The silane and the chemical Compounds thus diffuse into the respective copolymer. It was surprising that the use of such polymeric base substances leads to a substantial simplification and thus more economical use of the known crosslinking under action from moisture or water.

The new method is also associated with the advantage that the products manufactured by this process even with a thin wall thickness of the extruded coating through a perfectly smooth surface and homogeneous Distinguish quality.

The diffusion that takes place when the new process is used in the copolymer can also be achieved in that the silane and the chemical Connection to the copolymer present in granulate, powder or grit form be drummed up only superficially and that the mixture produced in this way is stored in the extruder before further processing. The diffusion takes place then essentially during storage be increased when storage at elevated temperature, preferably at about 60 ° C.

In the case of the method provided within the scope of the invention, it can be expedient be, the silanol condensation catalyst simultaneously with the silane on the copolymer to drum up.

In this case, the catalytic converter is used simultaneously with the rest Additives added to the copolymer.

Sometimes it can also be useful to use the silanol condensation catalyst the mixture of the copolymer and the silane only when the mixture is poured in to be added to the extruder via a dosing device. In both cases it is appropriate to to add the silanol condensation catalyst as a batch, i.e. mixed with the copolymer used in granulate, powder or semolina form or else as a mixture with an olefin polymer present in powder or grit form.

The pulverulent copolymers which can be used in the context of the invention and olefin polymers expediently have a grain size of at most 300 / u. The mean grain size of gritty copolymers and olefin polymers is most suitable between 200 and 500 / u.

The invention is explained in more detail below using an example.

Example The following mixture components were used for the mixture to be produced used: a) 100 parts of a copolymer of ethylene and vinyl acetate in granular form, Melt index MFI2 / 190 = 1.5, proportion of vinyl acetate 15%.

b) 3.5 parts of a silane c) 0.15 parts of dicumyl peroxide d) 0.3 parts phenolic antioxidant e) 0.3 part metal deactivator On 95 Parts of a mixture provided from components a) to e) continued to be used f) 5 parts of a batch are provided, which consists of 100 parts of a commercially available polyethylene low density in powder form and 1.0 part of dibutyltin dilaurate as a silanol condensation accelerator duration.

To process these components, components b) to f) drummed onto component a) in a fluid mixer and then 24 stored at 60 ° C. for h. In particular, components b and d diffused into the copolymer, the mixture was then dry.

This mixture was then used for the extrusion of cable insulation conventional extruder used; in this extruder the mixture did not become any subjected to a special mixing process, but merely plasticized, homogenized and then discharged. Here a cable core was manufactured, which consists of a There was a conductor with a cross section of 1.5 mm2 and insulation with a wall thickness of 0.7 mm. The core insulation produced was perfectly smooth and homogeneous. After the crosslinking process has been carried out under the effect of moisture (effect of boiling water over a period of 3 min) was the so-called "hot set Test "with which the sufficient crosslinking of the core insulation produced is tested will be passed with certainty.

Comparative example In a comparative experiment, according to example 1 proceeded, however, a commercially available polymeric base material was used Polyethylene high density used in granular form. The produced vein showed in irregular Intervals unevenness that can be attributed to a gel particle content.

After the crosslinking carried out subsequently (5 minutes residence time in boiling water) the "hot set test" was not passed.

O Figures 8 claims

Claims (8)

Claims methods for processing organic polymers, in particular for the production of a casing such as insulation or a jacket an electrical cable or an electrical line in which the polymer with a silane and with a chemical compound capable of creating free radical sites to produce in the polymer, mixed and reacted with the silane and at that of the converted polymer, that of a silanol condensation catalyst before or during the reaction is added, immediately thereafter by extrusion of the shaping, in particular the shape for sheathing an electrical cable or line, subject and finally crosslinked by the action of moisture or water is, characterized in that for processing copolymers of ethylene, in which the comonomers are polar in character, first the silane and the chemical Compound to a copolymer present in granulate, powder or grit form drummed up in the liquid state or in solution and here with the copolymer are mixed, and that then the copolymer prepared in this way after Addition or with simultaneous addition of the silanol condensation catalyst by means of one is the mixture of the prepared copolymer and the silanol condensation catalyst only plasticizing, homogenizing and discharging extruder to manufacture Product, in particular for wrapping, is formed. 2. The method according to claim 1, characterized in that the silane and the chemical compound to that present in granular, powder or semolina form Copolymer can only be sufgentrummelt superficially and that the produced in this way Mixture is stored in the extruder before further processing. 3. The method according to claim 2, characterized in that the storage the mixture at an elevated temperature, preferably at a temperature of about 60 ° C. 4. The method according to any one of claims 1 to 3, characterized in that that the silanol condensation catalyst simultaneously with the silane on the polymer is drummed up. 5. The method according to any one of claims 1 to 3, characterized in, that the silanol condensation catalyst when pouring the mixture of the copolymer and the silane is added to the mixture via a metering device in the extruder. 6. The method according to any one of claims 1 to 5, characterized in that that the silanol condensation catalyst as a batch, i.e. in a mixture with the in Granulate, powder or semolina form used copolymer or as a mixture with is added to an olefin polymer present in powder or grit form. 7. The method according to any one of claims 1 to 6, characterized in that that the powdery copolymer and / or olefin polymer has a grain size of has less than or at most equal to 300 / u. 8. The method according to any one of claims 1 to 5, characterized in, that the gritty copolymer and / or olefin polymer has an average grain size from 200 to 500 / u.