Compositions for filling electrical connectors of mineral oil,polyethylene,petroleum resin and dioctyl sebacate

BACKGROUND OF THE INVENTION

Our invention relates to dielectric compositions useful ₂o for filling electrical connectors, principally for the purpose of excluding moisture. The connectors containing the present composition have particular application for splicing the conductors of telephone cables. In use, the ends of telephone conductors are inserted into a plastic tube containing our composition. An example of a connector of the type for which our composition is useful is described in D’Ascoli Pat. 2,906,810, issued in 1959. This patent describes a splice where the conductors are bared and twisted together. More recently, however, connectors have been developed, such as that described in Smith Pat. 3,265,807, where the ends of the conductors are not stripped and twisted together, but merely inserted into the connector tube and electrical connection is made by compressing a pronged metal sleeve over both conductors. The prongs pierce the insulation of both conductors when the entire connector is pressed between the jaws of an appropriate tool.

In Pat. 2,914,501, D’Ascoli, one of the inventors of the present composition, described a composition suitable for filling connectors of the type where the conductors are twisted together. This composition, which is described in the patent as having the body of chewed chewing gum, has the deficiency that, when it is attempted to insert small telephone conductors, such as number 26 AWG copper telephone conductors into a connector, the conductors buckle rather than penetrate the stiff composition. This is particularly troublesome where the conductors are inserted parallel, rather than being twisted together, since the twisted conductors for which the stiffer composition was intended, have, of course, a much greater rigidity than two conductors laid parallel. In the practical use of our invention many hundreds of splices are required to be made by high-cost labor within 'a short time and any delays caused by difficulties in inserting conductors into the connectors will be fatal to the commercial success of a splice or splicing method. At the same time it is required that the connector composition should wet the surface of metal conductors, particularly copper and aluminum and also wet the surface of polyethylene and other plastics such as polyvinyl chloride. Polyethylene, particularly, has been hard to wet with compounds of known composition.

It was, therefore, required to discover a softer composition with excellent moisture resistance and wetting properties, but at the same time it was necessary that this compound should not flow from the connectors in which it was used even at temperatures of 140° F. and as high as 158° F. On the other hand the composition was required to flow freely into the connectors at temperatures lower than the softening point of the compound from which the connector, itself, was fabricated.

SUMMARY

We have invented a new composition for filling electrical connectors consisting essentially of 30 to 55, and preferably 42 to 46, parts by weight of mineral oil with a viscosity at 210° F. of 50-150 seconds; 5 to 20, and preferably 12 to 16, parts by weight of polyethylene having a molecular weight of 5,000 to 10,000; and 20 to 40, and preferably 28 to 33, parts by weight of a resinous polymerization product obtained by the catalytic polymerization of a mixture of unsaturated monomers derived from deep cracking petroleum. This resinous product has a ball and ring softening point of about 100° C., a specific gravity at 25° C. of .970 to .975, a refractive index at 20° C. of about 1.5116, an acid number less than 1.0, a Wijs iodine value of about 120, a bromine number of about 73 and a molecular weight of about 1100. In addition, it is essential that our composition contain 5 to 15, and preferably 8 to 12, parts by weight of dioctyl sebacate, and that it shall pour freely at 190° F. but be free from flow at 140° F.

EXAMPLE

Description of preferred embodiments

A composition was prepared by heating 45 parts of Sun XX mineral oil, which is available from the Sun Oil Company, to 250° F. Sun XX oil has a specific gravity, at 60° F., of .922 to .934, a flash point of 460° to 470° F., an SU viscosity, at 210° F., of 104 to 132 seconds, a maximum pour point of 15° F.; and an aromatic content of 38 to 51%. The mineral oil in our composition is used as a solvent for the polyethylene moiety and its selection is not critical so long as it has a Saybolt Universal (SU) viscosity at 210° F. between 55 and 135 seconds and a pour point between —5° and 20° F., and is present to a weight percent between 30 and 55 and preferably between 42 and 46, of the composition.

In the further preparation of the composition of the Example 15 parts of Union Carbide DYGT polyethylene was added and dissolved in the hot oil. The molecular weight of this polyethylene is about 7,000 but we believe that polyethylene with molecular weight between 5,000 and 10,000 can be employed for the preparation of our composition. Following the dissolution of the polyethylene, 10 parts of dioctyl sebacate and 30 parts of Piccopale 100 were added to the warm solution. We prefer to maintain the dioctyl sebacate content between 8 and 12 parts but additions as low as 5 parts and as great as 15 parts can be useful for making connector filling composition according to our invention.

The Piccopale 100 is available from Pennsylvania Industrial Chemical Corporation and is obtained by the Catalytic polymerization of a mixture of monomers derived from deep cracking petroleum. The monomers have a molecular weight of approximating 90, and are composed essentially of dienes and reactive olefins. The resin has a ball and ring softening point of about 100° C., a specific gravity at 25° C. of .970 to .975, a refractive index at 20° C. of 1.5116, an acid number less than 1.0, a Wijs iodine value of about 120, a bromine number of about 7.3, and a molecular weight of about 1100. Although we prefer to keep the weight percent of Piccopale between 28 and 33 useful compositions may include as few as 20 and as many as 40 parts of this resin.

The above-formulated composition of the example was found to have a Gardner viscosity, at 212° F., of 312 centipoises and was tested as follows:

Environmental stress test.—Polyethylene and polypropylene insulated telephone wires, size 24 AWG, were wrapped around their own diameters, coated with our composition, and maintained for 14 days at 140° F. Polyethylene connector sleeves were coated with composition

3,536,626 and also held for 14 days at 140° F. Examination under magnification failed to disclose any stress cracking or other deleterious effect on either the conductors or the sleeves.

Corrosion test.—Copper and aluminum conductors and brass and tinned bronze connector parts were coated with the composition of the example and maintained at 150° F. for 14 days. Thereafter the metal parts were examined and found to be free from any signs of corrosion.

Flow tests.—A one-gram globule of composition was set on a 45° inclined plane, and connectors, filled with composition, were inverted and all held for 72 hours at 158° F. No flow of the composition from the connectors or on the inclined plane was found to have occurred.

Penetration tests.—A commercial B-connector was filled with the composition of the example and held for 4 hours at 20° F. Without warming, an AWG 26 insulated telephone wire was inserted into the compound. No buckling of the wire occurred whereas when the same test was made with the composition of Pat. 2,914,501 the same type and size of wire buckled upon attempted insertion.

Water immersion test at room temperature.—96 2- or 3-conductor splices in AWG 22 and 24 were made with compression type B-connectors filled with the composition of the example. These were immersed in water and tested for resistance between the conductors and water with a standard 600 volt megger. After 48 hours 96% of the specimens showed infinite resistance and after 72 hours 70% of the specimens showed infinite resistance. These results qualify connectors employing our composition for use where water-resistant connectors are required.

We have invented a new and useful composition of which the foregoing description has been exemplary rather than definitive and for which we desire an award of Letters Patent as defined in the following claims.