DE1694268B2 - Curable molding compounds based on ethylene-propylene copolymers - Google Patents

Description

The present invention relates to curable molding compounds based on ethylene-propylene copolymers, from

a) an ethylene-propylene copolymer with a mineral filler or carbon black,

b) I to 10 percent by weight, based on the ethylene-propylene copolymer, one below Normal conditions liquid polybutadiene,

c) 0.25 to 8 percent by weight, based on the ethylene-propylene mixed polymer, of a vinylsilane,

d) 0.1 to 10 percent by weight, based on the Ätliylen-Propylen-Mischpoiymerisat, a customary organic peroxide hardener

exist.

According to a preferred embodiment, these curable molding compositions are further characterized by that the vinylsilane and the peroxide curing agent initially mixed separately and then added to the polymer compositions (a + b).

The invention also relates to a method for producing a curable ethylene-propylene elastomer, with which one

a) an ethylene-propylene elastomer with mineral Filler and mixed with polybutadiene which is liquid under normal conditions and

b) a vinylsilane and an organic peroxide curing agent, below the curing temperature, is added.

According to a preferred embodiment of this process is carried out in such a way that one as mineral Adding filler calcined aluminum silicate and vinyl-tris- (2-methoxyethoxy) -silane as vinylsilane.

Finally, the present invention also relates to the use of the ethylene-propylene copolymer produced according to the invention as insulating material for electrical lines. Thereby, after another

See the embodiment of this new ethylene-propylene copolymer used together with known conductive materials as insulating material.

In the case of electrical cables or the like, it has been considered necessary in the prior art to to provide one or more layers or plies of conductive or semiconductive material based on plastic. Conductive or semiconductive plastic-based material is simply a composition that of a discontinuous (i.e., composed of discrete particles) conductive substance in combination with a plastic or an elastomeric, non-conductive binder or a base material insists: while the conductive composition makes a relatively good electrical conductor, it still has a greater specific resistance than the metallic conductor. It is important that the conductor materials are mutually compatible with the insulation and adhere to this to a practically continuous and to create close contact surfaces for the purpose of avoiding any concentrations of electrical Fields and a possible breakdown at some discontinuous point, for example as a result of an air pocket in the contact area.

The state of the art includes conductive layers made of cross-linked polyethylene, which contains conductive carbon, such as carbon black. Such a conductor layer has been found to be very useful is in combination with an insulating layer made of a cross-linked polyethylene composition, both arising from extrusion and the hardening of each layer at the time of extrusion or where appropriate also takes place later. However, it has been found that the conductive compositions are based on of crosslinked polyethylene do not have the desired low resistivities to which it matters in high voltage applications. Furthermore, the hardened polyethylene compositions have which have electrical and thermal properties that are generally better than that of the prior art vulcanized elastomeric compositions, does not provide adequate stability under ionizing conditions or in the presence of ozone.

The closest prior art is the US Pat. No. 2,938,012 and the British Patent specification 898 264 should be mentioned, both of which are liquid polybutadiene as an ingredient of a curable ethylene-propylene-elastomer composition not suggest

3 4

) betw. suggest. There are certain ingredients of the 85 mole percent and the ethylene content in general

Elastomer produced according to the invention, for example, is at least 15 mol percent. To these

alternatively the organic peroxide hardener per se as defined copolymers also include the suitable ones

Such is known, however, is the combination of the normally solid elastomers that make up the state of the art

[Ingredients of the curable mold according to the invention - 5 of the technology as ethylene-propylene rubbers (EPR)

[wet also in the aforementioned literature references and as ethylene-propylene terpolymers (EPT and

not prescribed. EPDM) are known with Mooney viscosities

Specifically, the U.S. patent describes (8 minutes at 100 "C) of at least 25, the

2 938 012 a process for crosslinking normal-preferred viscosities about the value 80 or

wise solid polymer, namely of polyethylene and io achieve something about it.

Copolymers of ethylene and propylene, which is contained in the conductor composition according to the present invention, that the polymer is in the presence of a device based on an elastomeric ethylene bis (3,4-dichloro-a, a-dimethylbenzyl) peroxide in the case of propylene copolymers, this is crosslinked at a higher temperature. nuely arranged or distributed highly conductive

British Patent 898 264 describes a method of 15 mass blending. Among such discontinuous For the mixed vulcanization of amorphous, saturated, arranged highly conductive materials, elec-copolymers are used from ethylene and α-olefins, an Irish conductor understood, such as highly acidic fillers, sulfur and certain peroxides, conductive carbon black or metal particles, the the conductive ingredients, optionally substituted with halogen atoms, in any particle form, can also be present in fiber form, for example, by heating to the temperature range 110 20, up to 220 ° C. The continuous phase of the composition consists

In contrast, the present invention is based on the copolymer base. Preferably will

Surprising knowledge is based on the fact that a carbon black is used as a conductor material, which corresponds to the prior art

normal conditions liquid polybutadiene one of the art known as extra high conductivity XCF carbon black

is very advanced curing aid. 35 is, and furnace soot is also excellent. A

It is therefore according to the present invention in the first extra highly conductive carbon black, which is also outstandingly suitable for the prak line an elastomeric conductor composition with low tables implementation of the present invention, excellent specific resistance and improved corona, has a dry resistance and ozone resistance created which a specific stand value of about 0.27 ohm-cm at a density usefulness in electrical high-voltage conductors 30 of 0.54 g / cm ³ . It can of course also be owned by others. Furthermore, according to the present invention, comparable or equivalent types of carbon black are used, an elastomeric insulating composition is found which, in general, the carbon black in the conductor composition also has an increased resistance to corona in proportions of at least 50 percent by weight, discharges and ozone, and which are also associated with the above on the ethylene-propylene-elastomer, on the other hand, said conductor compositions are well tolerated. 35 and not substantially the value of 100 weight

The present invention also lies in exceeding the recognition percentage.

nis based that electrical cables with advantage from A surprising advance that with the pre-practical sulfur-free, extruded and hardened lying invention is achieved, is that the Layers a. s conductive plastic material is made of conductor compositions with very low volume resistance, which consists of an elastomeric ethylene 40 values below 10 ohm-cm. Typical Propylene copolymer and a discontinuous resistance values are in the range of 1 ohm-cm highly conductive material present therein, such as at- to 10 ohm-cm, as determined by ASTM test D991-60 For example, from conductive soot or the like. Consists of; a was established. It also became surprisingly wider Part of this electrical cable is a way of saying that these resistance values too Non-conductive insulating layer in a continuous narrow 45 within a temperature range of 20 to 100 ° C Contact with the conductor layer just mentioned, remaining practically stable, with at most small the insulating layer from a practically sulfur-free variations occur.

elastomeric crosslinked ethylene-propylene copolymers Preferred I lärtemiUel for the elastomeric compo-

consists. Positions according to the present invention are organic

The system of conductor layer and insulating layer 50 peroxides, in particular of the general type

can be present several times or in combined R-O-O-H or R-O-O-R ', in which

Form are present to the desired ozone and formulas the organic radicals R and R 'alkyl,

Corona-resistant electrical conductors to create the cycloalkyl, aryl, aralkyl, acyl, alkenyl and

are suitable for many applications, such cycloalkenyl radicals and also those functional

represent multiple layers of conductor layers or insulating groups that neither contain the peroxide in

cables with layers are called multiaxial dangerous ways of making them unstable or making them very stable,

Cable. The conductor layers and the insulating layers do not exist under the preferred heat conditions

are preferably created or more reacted by extrusion. Furthermore, R or R 'can be halogen, the

applied, either individually or in hydroxyl, alkoxy, aryloxy, carboxy, peroxy and

Combination, where the extruded layers mean a nitro group. Organizations to be used with preference

neither individually nor together either at the time of the niche Peroxides are those in which R and R '

Extrusion or optionally to a certain extent each mean a hydrocarbon residue that is a

later hardened. having tertiary carbon atom, which in each case

According to the present invention to be used a peroxide-oxygen atom is bonded, whereby to-

Copolymers are materials that have at least one of the two symbols R and R 'at least

Technique well known per se, namely polymers having an aromatic radical. Preferred one

from ethylene and propylene with high density or clogging peroxides are those that are used in the USA.

with low density, the propylene content 15 being described in patent specification 3,079,370. A peroxide

5 6

which in the practical implementation of the percentage, based on the ethylene-propylene copoly-

Invention found to be particularly suitable is mer, versus icin

Di-Ä-cumyl peroxide, which will be used here in the following is called dicumyl peroxide. The permanent found, a ternary hardening composition Oxides are used in an amount of 0.1 to 10 weight- 5, which consists of an orp-inischen peroxide, percent, based on the copolymer and preferably a liquid polybutadiene and a vinylsilane used from about 1 to 10 percent by weight. consists. The products derived therefrom have,

Other Härtungsüiittcl, which in the production as well as other compositions according to the present

of the conductive compositions according to the present invention, an excellent corona discharge

Invention can be used with advantage, are io and ozone resistance and also an unexpected and

the dioximes and their derivatives including aliphatic leaps and bounds of advanced electrical water stability,

Roommate dioxime, for example Succinaldehyddioxim The preferred vinyl silanes, even where μ

2,5-hexanedione dioxime and glutaiaidehyddioxime, ier- lower alkoxyvinylsilanes, for example vinyltris-

aromatic dioximes. Preferred to be used (2-methoxyethoxyl) -silanes, include, can in amounts

Dioximes are also aromatic quinone dioximes, e.g. B, 15 from 0.25 to 8 percent by weight, based on the

para-quinone dioxime, para-benzoquinone dioxime, tetra-ethylene-prophen-fOpolymcr, be present.

chloro-para-benzoquinonedioxime and 2,5-dichloro-para-It was also made in accordance with the present invention

benzoquinonedioxime. Besides the aromatic quinone found that the properties of the hardened

dioximes, their tautomers can also be used, compositions and, in particular, their isolation properties

z. B. para-dinitrosobenzene, poly-paradinitrosobenzene. 20 shafts can be improved by one

The dioximes are in an amount of 0,: to small amount of polyethylene filler in the base

10 percent by weight, based on the ethylene mixture, from which the cured copolymer

pylene copolymer, used. A preferred shark arises. The polyethylenes used here are

management system for the conductive compositions consists of pohmere materials, which by the polymerization

from an organic peroxide and a dioxime. 25 originated from ethylene, for example after the

w -with the corresponding components in the above- teaching of the USA. Patent 2 153 io3 or according to the

Proportional quantities mentioned are available and reference Modem Plastics Encyclopedia. New

preferably in an amount of 1 to 10 york by weight. 1949, pp. 268-271. These polymeric materials

percent, based on the ethylene-propylene copolymer. are generally solids, albeit also

in organic peroxide, for example in such a liquid polyethylene, is not excluded; she

of the type R - Γ - υ - R ', in which ·, r formula <l ^% e are by polymerization of ethylene at high

Sjmboic κ and R 'each produced a hydrocarbon residue at temperatures and pressures. The molecule;

mean, which contains a tertiary cohieribofl ^ vum. weights of these polymers can largely

each bound to a peroxide-oxygen atom in the range of 2000 to 30,000 or more

is, with at least one of the two symbols R and R '35, the higher molecular weights relate to Contains at least one aromatic substance and also solid polyethylene. Other polyethylenes with

0.1 to 5 percent by weight, based on da «; Ethylene different molecular weights are in the literature

Propylene copolymer on a diox ^: m, preferably Lawtoi et al .. Industrial and Engineering

on a quinone dioxime. Chemistry. 46. pp. 1702-1709 (1954). described.

An ethylene-propylene copolymer is a practically 40 An excellent description of low pressure saturated elastomer, it is.i the prior art polyethylene, which according to the present invention well known that certain difficulties arise when used is found in Modem Plastics. Vol. 33. if one tries to crosslink with reagents No. 1 (September 1955), from p. S5. The polyethylene too cause that split off free radicals, for example additives should be added in amounts up to 25 by weight with dicumyl peroxide. The number was 45 percent, based on the ethylene-propylene copolymer mentioned curing aids described, but have to be present.

brought most of the disadvantages so that the blends of the present invention can

resulting crosslinked polymers often do not contain the further small amounts, d. H. up to a few percent,

possessed desired properties, for example, contain antioxidants, their selection according to the

this applies to extruded electrical conductor layers. 50 respective circumstances can take place. To the

In accordance with the present invention, there were now conventional antioxidants. found at the prak, that the curing of elastomeric ethylene tables carrying out the present invention is a propylene copolymer in the presence of a small settable belong hydroquinone ethers. ver-crowd a polydifferent substituted hydroquinones, which are liquid in normal conditions, with carbon butadiene with low molecular weight, arylamines substituted to form a hydrogen radical and verProdukt high degree of hardening, which leads to various aniline derivatives, waxy tolylamines probably superior heat aging properties as variously substituted naphthylamines, poly also has electrical properties. The preferred ter- rmerized hydroquinolines, substituted phenyls Measured polybutadienes to be used with lower diamine, variously substituted phenols Molecular weight at normal temperature are 60 phenol derivatives, all of which in themselves represent the state of the art Liquids and viscosities on a large scale are well known.

Order range from 500 to 5000 poise, preferably the compositions according to the present invention;

in the range of 900 to 1100 poise. A preferred one can also optionally fillers, dyes

Polybutadiene to be used in a reasonable manner is therefore pigments, plasticizers, stabilizers. Procedure

indicates that there is a ratio of 1.2 to 3.4 65 help. Contain dispersants, hardening aids and the like

Addition of about 3 to 1 possesses. The liquid PoIv- In general, these additives are supposed to be the most conductive!

butadienes, the compositions according to the present invention used in accordance with the present invention

can be selected in the range of 1 to 10 weight that they the conductor properties of the end

not adversely affecting cured polymers; apart from the added conductive carbon black, the fillers only roll in relatively small quantities be fair.

The insulating compositions according to the present Er-ί The invention may contain any suitable filler material, including those conventionally used fillers And their derivatives, the conventionally adhered to Quantities are also used here.

The following examples serve to further illustrate the conductive compositions herein Invention. All parts are parts by weight.

example 1

100 parts of ethylene propylene rubber, 8 parts of dicumyl peroxide, 1 part of para-quinone dioxime, 70 parts particularly good conductive carbon black, 5 parts of zinc oxide, 5 parts of a microcrystalline wax and 5 parts of a heavy oils were mixed in the conventional way and then cured.

The crosslinked elastomeric semiconducting composition produced according to this example had a tensile strength of 123.9 kg / cm ² , an extensibility of 354 ″, a 200 ° _o modulus of 1090, a Shore Α hardness of 72 a Mooney viscosity at 121 ° C. of 69, a specific gravity of 1.142, a surface resistance of 123 ohms per square / inch and a volume resistivity of 7 ohm-cm.

This composition also has outstanding aging properties, measured as a percentage Immutability, as shown in Table I below.

Table I.

35

Time temperature train
strength Extensibility ( ⁰ Q (%) <° ") 7 Taee 121 74 87 14 days 121 87 90 7 days 150 57 75 14 days 150 36 62

45

The mixture of Example 1 was further extruded after blending into a No. 12-19 strand, the consisted of a smooth, flexible and strong extrudate in the form of a wire with a thickness of 0.5 mm. A 90 cm long piece of this extrudate exhibited electrical resistance when immersed in water of 7000 ohms between the conductor and the water. The ozone resistance was found to be excellent, Another test piece of the extrudate showed after a 25% elongation at a temperature of 25 ° C in the presence of 0.03 percent by volume of ozone, no breakage symptoms even after 100 hours. In contrast showed a similarly produced styrene-butadiene rubber, which is also a conductor composition showed no ozone resistance under the same conditions. An extruded specimen from the latter material broke into several pieces under the same stress.

The conductive elastomeric composition of the present invention thus has an unusual, surprising one and valuable combination of properties such as good ozone resistance, flexibility, heat aging property and conductivity, making them ideal and unpredictable for high voltage applications.

Example 2

100 parts of an ethylene-propylene rubber, 70 parts of a particularly good conductive carbon black, 8 parts of dicumyl peroxide, 1 part of para-quinone dioxime, 1 part of N, N'-di- / 9-naphthyl-para-phenylenediamine, 5 parts of a microcrystalline wax , 5 parts of zinc oxide and 5 parts of a heavy oil were mixed and hardened in the conventional manner. The composition prepared according to the present example had the same desirable and exceptional properties as the composition of Example 1, including excellent processability into thin-walled extrudates. great economy, ozone resistance, heat aging properties (measuring temperature about 90 ^c C), good physical properties and great flexibility. Because of its surprisingly low volume resistance (7.0 ohm-cm) and the low surface resistance (123 ohms per square inch), this composition is ideally and unusually suitable as an electrical conductor composition in high-voltage cables.

The following examples serve to further illustrate the insulation compositions according to the present invention Invention. All parts are parts by weight.

Example 3

100 parts of an ethylene-propylene rubber, 3 parts liquid polybutadiene, 3.2 parts dicumyl peroxide, 1 part polymerized trimethyldihydroquinoline, 120 parts of an aluminum silicate treated with a liquid silicone, 5 parts of an electrical grade oil and 1 part of zinc stearate were mixed and hardened in a manner known per se. The composition of this The example is particularly valuable as an extrudable electrical insulation material due to its exceptional properties Corona resistance, their low specific inductive capacity, their low power factor, also because of their tracking resistance, their flexibility. Ozone resistance, excellent workability and lower prime costs.

Example 4

A preparation was first made which consisted of 90 parts of ethylene propylene rubber and 10 parts Polyethylene. Polymerized 2 parts of dicumyl peroxide, 0.5 part of vinyl tris (2-methoxyethoxy) silane, 0.5 part Trimethyldihydroquinoline, 100 parts of calcined clay, 3 parts of zinc oxide and 2 parts of lead dioxide consists. According to a preferred embodiment, the ingredients mentioned were physical mixed in a known manner and then physically with 3 parts by weight of liquid polybutadiene and then the mixture is heat-treated at 166 to 182 ° C for 3 minutes. The resulting The preparation, like that of Example 3, is an eminently suitable extrudable electrical; Insulating material.

Example 5

100 parts of ethylene propylene rubber, 5 parts of liquid polybutadiene, 8 parts of dicumyl peroxide, 60 parts Aluminum silicate treated with a liquid silicone and 5 parts of an oil for electrical goods (Sun XX oil) were mixed with one another and hardened in a manner known per se.

409520/41

Example 6

This example is identical to example 5, with the Exception that instead of the polybutadiene this time 0.25 part of sulfur, as a typical representative of a conventional curing aid were used.

Comparative tests were carried out with regard to the physical and electrical properties of the products of Examples 5 and 6, and the results are summarized in Tables II and III below:

Table Il

Physical Properties

Original 200% modulus in kg / cm ²

Tensile strength in kg / cm ²

Extensibility in%

Properties after 7 days

Heat treatment
200% modulus in kg / cm ²

Tensile strength in kg / cm ²

Extensibility in%

Example 5 Example 6

15.8

34.7 555

31.1 45.4 415

11.8 45.6 889

10.1 21.1 939

Table III

Electrical properties at 100 ° C. Example 5

Power factor (° ₀ )

Specific inductive capacity
Volume resistance (10 ^ia ohms per cm ² )

0.76 2.42

959

Example 6

0.83 2.58

222

The use of liquid polybutadiene as a curing aid not only leads to a cured one Product with exceptional properties but also brings surprising progress regarding the workability of the uncured compositions. This advance is in the following Table IV set out in which the properties

* o of the products of Examples 7, 8 and 9 combined are, in which the hardening aids with otherwise the same composition of sulfur, liquid Polybutadiene and solid cis-1,4-polybutadiene consist.

Table IV

ingredients

Example 7 Example 8 Example 9

Ethylene-propylene terpolymer

Aluminum silicate clay treated with liquid silicone

Electrically puncture resistant oil

Zinc oxide filler

sulfur

Liquid polybutadiene

Solid cis-1,4-polybutadiene

Dicumyl peroxide

Curing 3 minutes at 18O ⁰ C.
Original physical properties

200% modulus in kg / cm ²

Tensile strength in kg / cm ²

Extensibility in%

Physical properties after 7 days aging at 150 ⁰ C

200% modulus in kg / cm ²

Tensile strength in kg / cm ²

Extensibility in %

Processability

100

100

100

60 60 60 5 5 5 1 1 1 0.25 - - 5 5 8th 8th 8th 16.0 15.8 13.2 52.6 34.7 36.0 933 555 668 10.1 31.1 25.1 21.1 44.8 43.1 939 415 548 to some extent very good bad

While conventional blending and curing processes generally are practically employed in the present invention, there are certain instances, such as in Example 4 above, where certain variations of the conventional processes result in even better products. Such procedural modifications can be determined by the average person skilled in the art to the extent of his knowledge and ability. It has also been found, in accordance with the present invention, however, that improved products can be obtained by a novel mix-curing process which is set out in Table V below.

This new mixed-hardening system makes it possible to use calcined clays while maintaining the good electrical properties and even improving the physical properties that are necessary for high-voltage cables. This mixing process requires two components, namely a base mix and a so-called acceleration mix. The basic mixture contains polybutadiene and all the ingredients of the composite

(Please see Table V) with the exception of vinylsilane and peroxide. The base mixture is blended 6 to 10 Minutei long in a Banbury mixer and shaped dam to a temperature of 160-177 ⁰ C So then the preparation is briefly ground in a two-roll mill and allowed to cool then after removal from the mill. The final mix can be prepared in a Banbury mixer, a Zweiwalzec mill or the like. First, di

Basic mixing of the grinder or the Banbury mixer ■ ucted and briefly mixed. The acceleration mixture is then added. The mixing process is continued for 1 to 2 minutes, during which it is taught that the temperature of the preparation is in the range from 93 to 107 ° C. The acceleration mixture is removed from the wiper, cooled and, for example, press cured for 5 minutes at a temperature of 180 ° C. or for 1 minute at a vapor pressure of 16.1 kg / cm ² .

Table V below describes the data and preparations from which to it can be seen how specific this mixed-hardening system is with respect to those filled with calcined clay Compositions is. The composition of Example 13 has been used successfully as 35 kV power cable insulation tested with great electrical water stability, d. H.,

this preparation perfectly fulfills the requirements of a power cable insulation the high demands to be made. A small modification of example 13 in which an ethylene-propylene terpolymer instead of the EPR copolymer (EPT) also gave good electrical properties including electrical water stability.

Terpolymers as used according to the present invention are, for example, the polymers

ίο which are described in the following references: Philadelphia Rubber Group Symposium, Jan. 24, 1964; The New York Rubber Group Symposium, October 18, 1963; Joint Meeting of the Divisions of Rubber Chemistry, American Chemical Society and

is Chemical Institute of Canada, Toronto, May 7-10 1963. A preferred terpolymer to be used is described in U.S. Patent 3,000,866.

Table V

Basic mixture 10

11th

12th

13th

Ethylene-propylene terpolymer

Polyethylene

Zinc oxide

Lead dioxide

Polymerized trimethyldihydroquinoline

Aluminum silicate clay treated with liquid silicone

volume

Vinyl tris (2-methoxyethoxy) silane

Liquid polybutadiene

Electrically dielectric oil

Acceleration mix

Liquid polybutadiene

Vinyl silane

Oicumyl Peroxide

Cure: 5 minutes at ISO ⁰ C

200% module (in kg / cm ^a )

Tensile strength in kg / cm ²

Extensibility in%

95
5
3
2
0.5

100 «>

70.1
203

100

3
2

1
3

60.7
68.3
266

95 5 3 2 0.5

100 < ⁴ > 1

49.8 260

100

3 2

100 *)

1.5 3

58.6 70.4 260

*) Optionally 50 to 190 parts (° / ₀ ), preferably 80 to 150 parts (° / ₀ ) per 100% weight percent of elastomer.

Thus, as has been pointed out, the elastomeric insulation compositions are effective in terms of strength reduced corona discharge, especially in combination with the conductive compositions Ethylene-propylene copolymer; they continue to be unusually and unexpectedly resistant to Degradation and deterioration under conditions of corona discharge and similar ionization phenomena.

In a series of tests, corona resistance was determined in the usual manner by placing hardened specimens 0.62 mm thick of the insulating composition between flat circular electrodes. The lower electrode is 2.5 cm in diameter and has rounded edges of a radius 1.6 mm, the top electrode 1.25 cm in diameter and rounded edges with a 0.16 mm radius; the test temperature was 80 ⁰ C. The Isolierkompositionen of ethylene-propylene rubber, which according to the present invention were prepared under the conditions of this test had a service life of 1300 minutes. In contrast, the high voltage cable | State-of-the-art insulation under the same test conditions only lasts between 25 and 40% of the value just mentioned. In addition, determination of the corona resistance test pieces that were extruded according to the invention with the unc | hardened insulation made of ethylene-propylene copolyl mer were provided in water (so-called ground electrode) under extreme corona conditions ge

tests with no action taken, ur | to moderate the discharge; the specimens was loaded in this way for up to 500 hours without showing any failure. With the same conditions the high-voltage insulations of the prior art fail within a few minutes.

All compositions according to the present invention. H. both the conductive and the insulating " Compositions possess this unusual coron

Resistance. Since ozone is formed by corona discharges as a result of atmospheric ionization, a generally recognized, definitive way of measuring resistance to corona discharges is to measure the stability of the compositions to be tested or the electrical cables made from them in relation to a so-called ozonolytic environment. It has been found in this case that all the cured compositions according to the invention against degradation or deterioration are resistant to ozone when they are located in an atmosphere containing 0.03 volume percent ozone under a 25% elongation stress for 10 hours at 25 ⁰ C. Another type of measurement of stability under ionizing conditions, the so-called "Coast Guard Corrosion Test," in which a spiral specimen of copper wire 7 days at 7O ⁰ C in an atmosphere with 100% relative humidity is maintained. Samples of the compositions according to this invention tested in this way surprisingly showed a change in resistance of 0%. Under the same test conditions, on the other hand, test pieces made of elastomeric insulation from the prior art always show considerable signs of corrosion on the copper wire and significant changes in resistance.

The drawings, which illustrate preferred embodiments of the invention, serve for further purposes Explanation.

F i g. 1 is a radial cross-section through a high savings cable;

F i g. 2 is a radial cross section through another Embodiment of the high tension cable;

F i g. 3 is a radial cross section through a power cable, and

F i g. 4 is a cross section through an X-ray cable.

One embodiment of this invention relates to new high voltage and low voltage direct current cables Currents, especially for electronic applications. Such cables require a lower one Simm transport capacity in combination with a high dielectric strength and high corona resistance values. In general, under a high voltage cable for low currents in the In the context of this description, understood as such, which for voltage values above 15 kilovolts and is generally not determined above 100 kilovolts. Such cables are also generally available for maximum A current of 50 amperes is determined, the conductive capacitance generally being the value of Does not exceed 5 amps.

A fundamentally simpler design of the cable according to the invention is shown in FIG. 1, in which a direct current high-voltage cable for electronic applications is disclosed, which has an electrical potential E and also consists of a linear metallic conductor 1, a plastic conductor 2, which lies concentrically in layer form with close contact on the metallic conductor As can be seen in FIG , the cable has a diameter Du I n, measured across the dielectric 3, and a diameter d, measured over the plastic inner conductor. 2

In the cable of FIG. 1 is made up of the plastic ladder

preferably of a hardened, preferably sulfur-free, substantially homogeneous, electrically conductive, extruded elastomeric material with a volume resistance of at most 10 ohm-cm, generally in the range from 1 to 10 ohm-cm, the volume resistance practically in the range from 20 to 100 ⁰ C is independent of temperature.

This elastomeric conductive composition is preferably an ethylene copolymer rubber and consists of a copolymer of ethylene and a CC ₁ olefin, e.g. B. propylene or butylene. Such a composition is most practically produced by a conventional extrusion and curing technique from the compositions given in the above examples and consists of an elastomeric copolymer of ethylene and propylene, a particularly good conductive carbon black, which is based in an amount of at least 50 percent by weight on the copolymer is present, as well as a peroxide curing agent. The plastic conductor not 4 of FIG. 1 preferably consists of the same composition.

It is important for the practice of the present invention that the conductive layers 2 and / or 4 be in continuous and close contact with the insulating layer 3. The presence of any air pockets or voids or any other air pockets, in the form of bubbles or the like, represent a potential source of failure for a high-voltage cable. may be any gas entrapment to Ionisierungserscheinun _t .n perform, possibly by means of which a breakdown of the cable is caused due to a Materialzerstorung. g in the cable of F i. 1, a virtually void-free and substantially continuous intimate contact most simply by grazing accomplished by an extruded, hardened and essentially sulfur-free composition of the ethylene copolymer rubber described above is used as the insulating layer 3. Such a rubber composition of the insulating materials described in the above examples is a surprisingly suitable electrical insulating material, and still owns both "ine u Ordinary compatibility as well as a very high level of adhesion / u the conductor compositions that make up the conductors 2 and 4 of the I i g. 1 order.

The metallic conductor 1 of FIG. 1 can simply be made from a single strand of a suitable metallic Conductor material or also mis a plurality of such Strands that are twisted or twisted in any way, or in other configurations with respect to one another arranged * ind. exist. The diameter of the linear metallic conductor becomes generally depend on the current density prevailing in it and, more precisely, on the purely physical stresses, to which the cable may be subjected. The specific conductor material that is selected will generally consist of a common conductive metal, which reflects its electrical and tensile strength properties Maintains up to a temperature of 100 C. For example, the head can be made out Copper, aluminum. Steel and the corresponding alloys exist, in fact thinner in shape metallic strands or layers and spatial shapes derived from them. Choosing the metallic Conductor material is generally the

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■ s η η

Follow conventional rules used by the industry are set up and which are known to the average person skilled in the art, taking into account the specific Purpose, in particular the current charge to be transported, taking into account the tensile loads and other requirements that may be placed on the cable.

In Fig. 2 shows a more specific embodiment of the high-voltage cable, in particular for electronic applications according to the present invention; this is the cross-section of a triaxial 40 kilovolt cable, which is intended to transport a current of approximately 20 amperes. In this cable embodiment of FIG. 2, the conductor 10 from a so-called 12 AWG 7 copper-clad steel strand, which is surrounded by an extruded conductor layer 11, which consists of a conductor composition of Example. 2 An extruded insulating layer, which is described in Example 3, is arranged around the conductor layer 11 in continuous and close contact. Then a second concentric conductor layer 13 is extruded onto the insulating layer 12 in continuous and close contact, with a second metallic conductor arranged around this layer 13, for example a tinned copper shielding layer 14. The 40 kilovolt DC potential is applied to the cable between the conductor 10 and given up to head 14. Above the shielding layer 14 there is a second layer of ethylene copolymer rubber insulation, which consists of the same material as the layer 12 and is extruded. A second metallic conductor 16, for example a tinned copper shielding layer, is located above the concentric layer 12. The electrical potential between conductors 16 and 14 can be up to 600 volts. The entire cable according to FIG. 2 can then be surrounded or sheathed with any conventional material, preferably with a plastic sheath. The corresponding concentrically arranged plastic layers U, 12, 13 and 15 are applied in a conventional manner by extrusion and then likewise hardened in a manner known per se, either individually or optionally together. The cable of FIG. 2 shows, as already stated above, no corona discharge whatsoever when tested with a display device which responds to 5 micro-coulombs with a passage of 40 kilovolts alternating current. The test with regard to the corona discharge was carried out in accordance with the IPCEA-NEM A publication “Standards for Rubber Insulated Wires and Cables”, Part 6; January 24, 1964.

The outer metallic layers 14 and 16 of the embodiment of FIGS. 3 neither in a positive nor in a negative sense has an influence on the freedom from corona discharge of the cable exercise; long cable cuts became successful tested using the hardened conductor layer 13 as a base layer, without any use any structures or layers that would have been arranged concentrically around them.

While the triaxial high voltage cable has mainly been discussed so far, a coaxial cable can be made according to the teachings of this invention, such cable being made from the Structural elements that are shown in FIG. 2 is shown, this time the first metallic layer 14 per se is the outer layer, which is only covered with a conventional top layer. A 40 kilovolt coaxial cables of this type are also free when loaded with 40 kilovolt alternating current of corona discharge.

An insulated electrical power cable for 15 kilovolts, which is manufactured according to the teaching of the present invention is is in FIG. 3 shown. In one embodiment of the cable according to FIG. 3 consists of this Cable made from a copper strand 21 of the type no. 2 AWG, an extruded cross-linked polyethylene (Vulkene) insulation layer 22, an extruded conductive shielding layer 23 made according to Example 2 and a conductive sheath 24. It can be readily seen that the cable of FIG. 3 one Standard embodiment corresponds, with the exception

is the arrangement of an extruded conductor layer 23, which fulfills the function which the general in the prior art so far spirally wound exercising semiconducting tape materials. The cable according to FIG. 3 is not only resistant to the

* o driving an oxidative and ozonolytic degradation, rather, it has the extruded conductor layer 23 due to the tight and continuous bond the insulating layer 22 even under such conditions that normally lead to a separation of the corresponding Laying apart from each other and, as a result, would lead to a breakdown of the cable, one increased stability by leaps and bounds,

According to another embodiment of the power cable of FIG. 3 is used as a composition of the insulating

layer 22 selected one of the preferred) insulating compositions of the aforementioned examples, namely because of the unusual compatibility of the compositions according to the present invention, with the success, that no zones of high electrical stress and resulting ionization available.

An X-ray cable, which after the teaching Can be produced according to the present invention is shown in FIG. 4 shown. In one embodiment of the X-ray

* o ray cable of the F i g. 4, this consists of a core composed of 2 insulated conductors 30, the conductors in turn consisting of twisted, tinned copper wires with a diameter of 0.22 mm; on the cores there are two non-insulated conductors 31, which are also made of twisted, tinned Copper wires with a diameter of 0.15 mm, from an extruded hardened conductor composition 32, which was produced according to Example 2, an extruded and hardened ethylene-propylene copolymer insulating composition 33, which was produced according to the present invention, a 0.15 mm thick tinned Copper shield skewed winding (with the angle of the skewed winding preferably being 65 ° ^C or more) and an outer cover layer 35, which preferably consists of a woven, diagonally wound fiber layer, which in turn is provided with a varnish coating was prepared, was subjected to a test that be i 50 kilovolt RMS 60 alternating current was carried out within 10 minutes and at 135 kilovolt direct current within 15 minutes; this test is a measure of the stability of the cable under extreme operating conditions; it turned out.

that no major damage or degradation of the cable could be discovered. Other cable coupons were subjected to a staged tension test using those shown in FIG

409 520/419

The following table summarized results were obtained:

60 changes Versaeen mm VI sample I. 660 sample current Maximum Versace Gradient piece A piece B Tabel RMS Volts per 0.025 Length of Test piece Isolation Composition 50 Kilovolt core to basic 60.1 22.5 m 11.7 m Wrapping 63.7 Time Time 60 changes 67.1 15 minutes. 10 min. current 70.6 5 min. 5 min. top 74.2 5 min. 5 min. 70.5 77.8 5 min. 5 min. 85 81.2 3 min. 5 min. 90 84.8 5 min. 5 min. 95 5 min. 5 min. 100 Wall thickness at failure 5 min. 5 min. 105 Medium voltage per 4.4 min. 2.8 min. 110 3.025 mm at fail fail 115 0.46 cm 0.47 cm 120 453 446 703

Samples of x-ray cables that like described above were subjected to extremely severe corona discharge conditions. These conditions included a sequence of 50 kiIovolt RMS with a 10 minute "hi-pot" followed by one 50 kilovolt (peak) increase within 5 minutes, starting at a 60 kilovolt RMS level became. No failure symptoms were found up to the 75 kilovolt RMS region. To the

ίο To determine cable capacity, a cable length was used made such that the electrode length was 90 cm using covered electrodes; it was room temperature. The following test data were obtained:

Table VII

VoIt- Power factor S. I. C. Beanspmchuns in% 60 changes per 0.025 mm 0.31 3.35 20th 0.30 40 0.30 60 0.30 75

(capacity - 100 micro-micro farads at 90 cm).

Hiei.'ii 1 sheet of drawings

Claims (5)

Patent claims: 1. Curable molding compounds based on ethylene-propylene copolymers the end: a) an ethylene-propylene copolymer with a mineral filler or carbon black, b) 1 to 10 percent by weight, based on the ethylene-propylene copolymer, one below Normal conditions liquid polybutadienes, c) 0.25 to 8 percent by weight, based on the ethylene-propylene copolymer, of a vinylsilane, d) 0.1 to 10 percent by weight, based on the ethylene · propylene copolymer, of a conventional one organic peroxide hardener. 2. Curable molding compositions according to claim 1, characterized in that the vinylsilane and the peroxide hardener are initially mixed for themselves and then given to the polymer compositions (ajb) according to claim 1. 3. A method for producing a curable ethylene-propylene elastomer, characterized in that that a) an ethylene-propylene elastomer with mineral filler and with under normal Conditions added to liquid polybutadiene, b) a vinylsilane and an organic peroxide curing agent, below the curing temperature is admitted. 4. Use of the ethylene-propylene copolymer prepared according to claim 1 or 2 as Insulating material for electrical conductors. 5. Use of the ethylene-propylene copolymer prepared according to claim i or 2 as Insulating material for electrical letters together with known conductive materials.