RU2804166C1 - Electrical insulating compound based on ethylene propylene diene rubber - Google Patents

Abstract

FIELD: polymer chemistry.

SUBSTANCE: polymer compounds based on ethylene propylene diene rubber for the manufacture of insulation for power cable with extruded insulation for a rated voltage of 6 to 35 kV, inclusive. An electrical insulating compound based on ethylene propylene diene rubber is proposed, including (wt. parts): ethylene propylene diene rubber (100), organic peroxide (5-11), zinc oxide (2-8), kaolin (50-150), characterized in that it additionally contains a softener (paraffin (2-8), rosin (2-8), high-pressure polyethylene (8-18)), a filler (calcium oxide (3-9), titanium dioxide (5-12), barium sulphate (2-8), aluminium hydroxide (3-9)), as well as an antifatigue (polyethylene wax (1-6)) and an antioxidant (a condensation product of acetone with aniline (0.5-2)).

EFFECT: improvement in physical and mechanical properties, including elastic and strength characteristics, in combination with high resistance under alternating loads at elevated temperatures, high resistance to thermal aging, high tensile strength.

1 cl, 3 tbl

Description

1. Field of technology to which the invention relates

The invention relates to polymer compounds based on ethylene propylene diene rubber, used in the cable industry, in particular, as insulation in the manufacture of power cables with extruded insulation for rated voltages from 6 to 35 kV inclusive.

2. State of the art

A composition based on ethylene propylene rubber is known, used as an intercore filler in electrical cables and wires (RU 2 225651). The composition based on ethylene propylene rubber contains, wt.%: ethylene propylene rubber - 100.0, paraffin - 34.0-84.0, stearic acid - 4.0-6.0, dibutyl phthalate - 4.0-13.3, chalk - 328.0-751.7, talc - 27.0-45.0. The technical result of the proposed technical solution is to eliminate adhesion to insulation and ensure fire safety of the electrical cable.

The combination of the above ingredients in the stated range eliminates the adhesion of the composition to the cable insulation and sheath material, makes it possible to achieve fire safety of the electric cable, and also makes it possible to easily, without damaging the core insulation, cut the cable during installation.

The disadvantage of the known composition is that the composition based on ethylene-propylene rubber has low electrical and mechanical properties.

A known composition is based on ethylene propylene or ethylene propylene diene rubber and a copolymer of ethylene and octine, used as an intercore filler in electrical cables and wires. (RU 2 256 676). This rubber mixture is a composition comprising, parts by weight: rubber - 100, ethylene-octine copolymer - 25-55, paraffin - 50-170, stearic acid - 4-30, dibutyl phthalate - 4-25, chalk - 500- 1600. The composition may additionally contain aluminum trihydrate - 180-270 parts by weight. per 100 parts by weight rubber.

The combination of the above ingredients in the stated range eliminates the adhesion of the composition to the cable insulation and sheath material, and also solves the problem of improving the electrical, physical and technological characteristics of materials for filling cable products.

The disadvantage of the known composition is that the composition based on ethylene-propylene rubber has low electrical and mechanical properties.

There is a known method for producing a polymer material by preparing a composition including ethylene-propylene diene rubber for the manufacture of electrical cable insulation (RU 2 644 896). A polymer electrical insulating material is obtained by preparing a composition including ethylene propylene diene rubber containing, mol.%: ethylene - 60-77, ethylidene norbornene - 0.9-6, propylene - the rest, a vulcanizing system containing organic peroxide and vulcanization coagent - 1.2 -polybutadiene, filler - carbon black with a particle size of 250-403 nm, highly dispersed silicon dioxide, zinc oxide, red lead, bifunctional vinyl silane, paraffin oil, antioxidant, calcined kaolin with a moisture content of less than 0.4% and technological additives, mixing the components and its vulcanization.

The electrical insulating material obtained by the claimed method provides the necessary electrical strength of the current-carrying conductors, is heat-resistant, aggressively resistant, due to which there is no violation of the integrity of the insulation, no current leaks or breakdowns.

The insulation for an electric cable obtained from the specified polymer electrical insulating material has good physical and mechanical properties, however, the disadvantage of the specified composition, adopted as a prototype, is that the composition has low elasticity, characterized by the indicator “relative elongation at break”; the composition also has low resistance to thermal aging, characterized by the indicator “change in relative elongation after aging in air at 150°C for 168 hours.”

The closest to the claimed invention in technical essence is a polymer electrical insulating material (RU 2 644 896).

Power cables with extruded insulation are intended for the transmission and distribution of electrical energy in stationary installations at a rated alternating voltage of 6, 10, 20 and 35 kV with a nominal frequency of 50 Hz for networks with a grounded and insulated neutral, intended for use in distribution networks and when completing infrastructure facilities oil and gas and oil refining, chemical and mining industries, oil and gas transportation, metro facilities, including in explosive zones of all classes.

The elasticity of insulation of power cables for rated voltages from 6 to 35 kV and resistance to thermal aging are necessary properties that provide power cables with the ability to operate under conditions of alternating loads and elevated temperatures.

The objective of the claimed invention is the need to develop an electrical insulating compound based on ethylene propylene diene rubber (hereinafter referred to as the compound), providing high elasticity, higher resistance to thermal aging, resistance to low ambient temperatures down to minus 60°C, which will allow the use of the claimed compound as insulation in the manufacture of power cables.

The technical result of the claimed compound is an increase in physical and mechanical parameters, including elastic-strength indicators in combination with high resistance under conditions of alternating loads at elevated temperatures, high resistance to thermal aging, and high tensile strength.

3. Disclosure of the invention

The essence of the invention is to achieve the mentioned technical result by developing a compound for power cables with extruded insulation based on triple ethylene propylene rubber containing a small amount of ethylidene norbornene monomer (hereinafter referred to as ENB) (to impart unsaturation to the polymer). The selected rubber contains ethylene in the amount of (from 59 to 65)% propylene (from 35 to 41)% and 6% ENB with cross-linking organic peroxide containing 3.7-3.9% active oxygen, allowing the mixture to be in a viscous state during extrusion .

Moreover, the claimed compound contains a silicate filler, titanium dioxide, barium sulfate, which have good coloring ability, and aluminum hydroxide, which increases fire resistance.

To improve the manufacturability of the proposed compound, paraffin, high-density polyethylene, rosin, calcium oxide are used; unoxidized polyethylene wax and an antioxidant (condensation product of acetone with aniline) act as an anti-fatigue agent.

The technical result is achieved by the fact that the composition of the claimed compound includes ingredients that distinguish the claimed invention from the prototype:

- titanium dioxide, barium sulfate, aluminum hydroxide;

- polyethylene wax;

- paraffin;

- calcium oxide;

- high pressure polyethylene;

- rosin.

Vulcanization of samples in the form of plates of size (150x200) with a thickness of (2.0 ± 0.2) mm and (150x200) mm with a thickness of 6 mm to control the quality of the compound is carried out on a hydraulic vulcanization press 100-400 2E at a temperature of 180°C, a pressure of 10- 12 MPa for 10 min.

The production of the claimed compound occurs in one stage.

When implementing the claimed technical solution, the following quantitative composition of the claimed compound is used, parts by weight:

- ethylene propylene diene rubber - 100

- organic peroxide - 5-11

- kaolin -50-150

- titanium dioxide - 5-12

- zinc oxide - 2-8

- barium sulfate - 2-8

- antioxidant (condensation product of acetone with aniline) - 0.5-2

- aluminum hydroxide - 3-9

- polyethylene wax - 1-6

- paraffin -2-8

- calcium oxide - 3-9

- high pressure polyethylene - 8-18

- rosin - 2-8.

The selected composition of the claimed compound makes it possible to improve the physical and mechanical parameters, to ensure maximum elasticity, higher resistance to thermal aging, and resistance to low ambient temperatures down to minus 60°C.

Comparative characteristics of the prototype and the claimed compound are shown in Table 1.

Table 1 Indicator name Test results Test method Suggested compound Prototype Conditional strength at elongation, MPa 14.1 12.3-13.8 GOST 60811-501 Elongation at break, % 510 121 - 134 GOST 60811-501 Change in relative elongation after aging in air at 150 °C for 168 hours, % Minus 15.5 Minus 25.6 GOST 9.024-74 Temperature limit of brittleness, °C Minus 60 --- GOST 7912-74 Electric strength at alternating voltage, kV/mm 40.12 38.24 GOST 6433.3 Specific volumetric electrical resistance, 1000V, Ohm ₂ cm 7.2x10 ¹⁵ 6.3×10 ¹⁵ GOST 6433.3

4. Carrying out the invention

The essence of the proposed invention is confirmed by specific examples of implementation, which clearly demonstrate the possibility of achieving the required technical result.

Let us give an example of obtaining an electrical insulating compound based on ethylene propylene diene rubber in the stated ratio. The production of the compound is carried out in workshop conditions using installed domestic and foreign equipment.

All components included in the compound are products produced on an industrial scale.

Contents of the technological process for the production of the claimed compound.

Preparation of materials:

synthetic rubber is released from packaging, cut into pieces corresponding to the size of the loading hole of the rubber mixer, and transported to the dosing scales. The remaining materials are supplied in the supplier's packaging.

Materials are weighed and dosed.

The amount of prepared materials must correspond to the recipe of the declared compound, in mass parts:

- ethylene propylene diene rubber - 100

- organic peroxide - 11

- kaolin -150

- titanium dioxide - 12

- zinc oxide - 8

- barium sulfate - 8

- antioxidant (condensation product of acetone with aniline) - 2

- aluminum hydroxide - 9

- polyethylene wax - 6

- paraffin -8

- calcium oxide - 9

- high pressure polyethylene - 18

The preparation of the mixture occurs in one stage.

Materials are loaded into a rubber mixer type RS 40/16-40, where mixing occurs

The initial temperature of the rubber mixer chamber is 20-25° C.

The temperature of the unloaded mixture is 50-165° C.

Total mixing time is 30 - 35 minutes.

The mixture unloaded from the rubber mixer is rolled for 0.5 - 1 minute on Sm 1500 660/660P rollers, cut into sheets, cooled in air for 20 minutes, aged for at least 2 hours, after which the material is processed into granules with a diameter of 6±1 mm with a height of no more than 7 mm. on a JYZ 2000-M granulator. The compound granules are treated with an anti-adhesive (zinc stearate or kaolin). After production, the compound in the form of granules is placed in prepared dry plastic barrels.

As a special case, let us consider the extreme values of the quantitative composition of the declared compound:

1) with the highest content of ethylene propylene diene rubber

wt.h:

- specified rubber - 100

- organic peroxide - 5

- kaolin -50

- titanium dioxide - 5

- zinc oxide - 2

- barium sulfate - 2

- antioxidant (condensation product of acetone with aniline) - 0.5

- aluminum hydroxide - 3

- polyethylene wax - 1

- paraffin -2

- calcium oxide - 3

- high pressure polyethylene - 8

- rosin - 2

The test results on the physical and mechanical properties of the specified compound are presented in Table 2.

table 2 Indicator name Test result Test method Conditional strength at elongation, MPa 14.3 GOST 60811-501 Elongation at break, % 610 GOST 60811-501 Change in relative elongation after aging in air at 150 °C for 168 hours, % Minus 5.3 GOST 9.024-74 Temperature limit of brittleness, °C Minus 60 GOST 7912-74 Electric strength at alternating voltage with a frequency of 50 Hz, kV/mm 39.9 GOST 6433.3 Specific volumetric electrical resistance, 1000 V, Ohm ² cm 7.0×10 ¹⁵ GOST 6433.3

2) with the lowest content of ethylene propylene diene rubber

wt.h:

- specified rubber - 100

- organic peroxide - 11

- kaolin -150

- titanium dioxide - 12

- zinc oxide - 8

- barium sulfate - 8

- antioxidant (condensation product of acetone with aniline) - 2

- aluminum hydroxide - 9

- polyethylene wax - 6

- paraffin -8

- calcium oxide - 9

- high pressure polyethylene - 18

- rosin - 8

The test results on the physical and mechanical properties of the specified compound are presented in Table 3.

Table 3 The name of indicators Test results Test method Conditional strength at elongation, MPa 13.8 GOST 60811-501 Elongation at break, % 580 GOST 60811-501 Change in relative elongation after aging in air at 150°C for 168 hours, % Minus 12.3 GOST 9.024-74 Temperature limit of brittleness, °C Minus 60 GOST 7912-74 Electric strength at alternating voltage with a frequency of 50 Hz, kV/mm 38.30 GOST 6433.3 Specific volumetric electrical resistance, 1000 V, Ohm ² cm 6.8×10 ¹⁵ GOST 6433.3

The data given in Tables 2 and 3 show that the claimed compound based on ethylene propylene diene rubber, containing organic peroxide, softeners, and fillers, has high elasticity of the material and is resistant to low ambient temperatures.

Combining the components in a certain ratio allows you to obtain the desired set of properties: elastic-strength properties combined with high resistance under conditions of alternating loads at elevated temperatures, high resistance to thermal aging, high tensile strength.

Thus, an electrical insulating compound based on ethylene propylene diene rubber provides a full range of properties: improved physical and mechanical parameters, the best elasticity of the material, high tensile strength, higher resistance to thermal aging and resistance to low ambient temperatures. The specified set of properties of the electrical insulating compound ultimately makes it possible to improve the characteristics of cable products.

Claims (2)

Electrical insulating compound based on ethylene propylene diene rubber, including ethylene propylene diene rubber, organic peroxide, zinc oxide, kaolin, characterized in that it additionally contains paraffin, rosin, high-density polyethylene as a softener, calcium oxide, titanium dioxide, barium sulfate as a filler, aluminum hydroxide, as well as an anti-fatigue agent - polyethylene wax, as an antioxidant - the condensation product of acetone with aniline in the following ratio of components, parts by weight: ethylene propylene diene rubber 100 organic peroxide 5-11 kaolin 50-150 titanium dioxide 5-12 zinc oxide 2-8 barium sulfate 2-8 antioxidant - acetone condensation product with aniline 0.5-2 aluminum hydroxide 3-9 polyethylene wax 1-6 paraffin 2-8 calcium oxide 3-9 high pressure polyethylene 8-18 rosin 2-8