JPH07330990A - Rubber material for equipment related to power cable - Google Patents

Abstract

PURPOSE:To obtain the subject material not suffering from the bleeding and migration of plasticizer and stabilized in mechanical and electrical properties for a long time by mixing an EPDM rubber having a Mooney viscosity of a specified value with a plasticizer having a viscosity index of a specified value. CONSTITUTION:This rubber material is obtained by mixing a base rubber comprising an ethylene/propylene/nonconjugated terpolymer (EPDM) having a Mooney viscosity (ML1+4; 100 deg.C) of 50 or below with a plasticizer having a viscosity index of 100cP or above. In general, plasticizers such as process oil are apt to suffer from bleeding which is a phenomenon in which the plasticizer migrates and bleeds to the surface and from migration which is a phenomenon in which the plasticizer stains another material in contact with the material because it is not present in a state immobilized among the molecules of the rubber after crosslinking. By using the above base rubber having a low viscosity and the plasticizer having a high viscosity index, the amount of the plasticizer used is reduced, resulting in the reduction in the bleeding and migration of the plasticizer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber material for power cable equipment used in a connecting portion or a terminal portion of a power cable.

[0002]

2. Description of the Related Art EPDM is superior to natural rubber, butyl rubber and styrene-butadiene copolymer rubber in electrical resistance, heat resistance and weather resistance. It is generally used as an insulating material and a conductive material for necessary parts.

Since power cable equipment made of EPDM is usually manufactured by injection molding, petroleum-based process oil having a high affinity with EPDM is added in order to improve moldability, that is, plasticity. Since this process oil has little addition of physical properties even if it is blended in a large amount, conventionally, a low viscosity one is used in a high blending ratio to reduce the viscosity of the compound and improve the plasticity.

[0004]

Generally, a plasticizer such as a process oil exists in a state where it is not fixed between the molecules of the rubber after molding and crosslinking of the rubber, so that it easily moves inside the rubber. . Therefore, the low-viscosity process oil, which has been frequently used in the past, moves from the inside of the rubber to the outside, and a bleeding phenomenon that oozes out on the surface and a migration phenomenon that contaminates other materials in contact easily occur, and a large amount of bleeding and bleeding occur. There has been a problem that the migration deteriorates long-term electrical and mechanical properties of power cable equipment.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and provides a rubber material for electric power cable equipment, which has stable electrical and mechanical properties for a long term without bleeding or migration of the plasticizer. The feature is that EPD with a Mooney viscosity (ML _{1 + 4} , 100 ° C) of 50 or less as the base rubber.
This is because M rubber was used and a plasticizer having a viscosity index of 100 cp or more was used.

As the plasticizer, paraffinic process oil, polyolefin or a mixture thereof is effective, and 35 parts by weight or less of the plasticizer is sufficient for 100 parts by weight of EPDM to maintain moldability.

[0007]

Function In both paraffin type process oil and polyolefin, it is considered that movement in rubber after crosslinking behaves as a normal fluid, and the ease of movement, that is, the ease of movement, is greatly affected by viscosity. For this reason, in order to prevent bleeding and migration that would degrade long-term electrical and mechanical properties to the extent that they pose practical problems,
A plasticizer having a high viscosity may be used.

On the other hand, it is important for the moldability and processability that the viscosity of the rubber material itself before cross-linking is sufficiently low, which depends on the viscosity of the additive itself including the base rubber and the plasticizer and the compounding ratio thereof. Depends on. Therefore, when a plasticizer having a high viscosity is used, moldability and workability are significantly deteriorated. However, the viscosity of the rubber material itself before crosslinking is not only the plasticizer,
It is also greatly affected by the viscosity of the base rubber itself, and by lowering the viscosity of the base rubber, it is possible to reduce the viscosity of the rubber material itself before crosslinking. It is possible to further reduce the bleeding phenomenon and migration by reducing the viscosity of the base rubber itself and reducing the compounding amount of the plasticizer to the extent that it does not impair the moldability and processability of the rubber material before crosslinking. is there.

Therefore, in the present invention, EP having a low viscosity is used.
By blending DM with high-viscosity paraffinic process oil or polyolefin as a plasticizer, bleeding phenomenon and migration do not occur without impairing moldability and processability, and long-term deterioration of electrical and mechanical properties. Can be suppressed.

[0010]

EXAMPLES Table 1 shows examples of the present invention and comparative examples. The sample of the example has a viscosity index of 105 cp as a plasticizer.
Highly refined paraffinic process oil, viscosity index 108cp
Of ethylene-propylene copolymer and an equal amount mixture of these plasticizers were used to prepare EPDs having a Mooney viscosity of 40.
A mixture of 35 parts by weight with respect to 100 parts by weight of M is 180 ° C,
Heat press molding was performed for 30 minutes to obtain a sheet. The sample of the comparative example uses a highly purified paraffinic process oil of 80 cp and a paraffinic process oil of viscosity index 70 cp as a plasticizer, and 35 parts by weight of these are added to 100 parts by weight of EPDM having a Mooney viscosity of 65 to obtain an example sample. It was molded into a sheet under the same conditions. In each of Examples and Comparative Examples, 5 parts by weight of dicumyl peroxide was added as a crosslinking agent to 100 parts by weight of the base rubber.

To evaluate these samples, filter paper made of Toyo Roshi was adhered to the front and back of each sample, and 3.0 kgf / cm ^{2 of} each filter paper was attached.
Was applied, and the weight increase of the filter paper was examined after 50 hours at 70 ° C. Before press molding, the Mooney viscosity (ML _{1 + 4} , 100 ° C.) was measured for each sample to evaluate the moldability.

[0012]

[Table 1]

[0013]

As described above, according to the rubber material for electric power cable equipment of the present invention, the bleeding phenomenon and migration of the plasticizer do not occur, and the electric power cable equipment using the rubber material is electrically long-term. It is possible to realize a highly reliable device with stable mechanical characteristics and mechanical characteristics.

Claims (2)

[Claims] 1. A Mooney viscosity (ML) as a base rubber
_{1 + 4} , 100 ° C) 50 or less ethylene-propylene-non-conjugated diene terpolymer (EPDM) rubber is used, and a plasticizer having a viscosity index of 100 cp or more is used. Rubber material. 2. A rubber material for power cable equipment, wherein the plasticizer is a paraffinic process oil having a viscosity index of 100 cp or more.