Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
  • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
  • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
  • H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
  • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances

Definitions

• This invention relates to a filling compound for use in cables and connectors used for connecting corresponding electrical conductors of two cables at a splice location. More particularly, the invention relates to a filling compound which waterproofs, insulates and reduces contamination in cables and connectors caused by dirt, dust, fungus, water and other contaminants.
• Cable used in the telecommunications industry such as in telephone systems, generally requires a waterproofing filling material in the cable to protect the cable from water entry. This is true whether the cable is buried beneath the ground or laid under water. Waterproofing is also sometimes required in aerial applications. Attempts to waterproof cable, such as buried cable, began nearly 100 years ago and were unsuccessful in a practical sense until the introduction of plastic insulated cable during the 1950's. Since 1970, large quantities of cable have been filled with waterproofing compounds. This approach followed the recognition that in plastic insulated cable the localized intrusion of water into the cable sheath is not in itself a serious problem. Disruption or deterioration of service occurs when long lengths of cable become flooded.
• the Sabia filling material is a styrene-ethylene butylene-styrene triblock copolymer (SEBS) dissolved in mineral oil, with polyethylene added for consistency.
• SEBS styrene-ethylene butylene-styrene triblock copolymer
• An acceptable composition for this application ranges from about 5 - 7% SEBS, 87 - 91% mineral oil, and 2 - 6 % polyethylene.
• the composition disclosed contains no protective ingredients and thus if water or another contaminant penetrates the physical boundary created by the filling compound it will cause contamination of the filling compound and corrosion of the cable.
• this filling material would be more susceptible to fungal and other types of contamination and would tend to become contaminated.
• the filling compound taught has a tendency to flow out of above ground cables, especially where solar heating (up to 80°C) is a factor.
• each cable In the communications industry it is commonplace for two cables to be connected at one or more splice locations. Typically, each cable comprises a multitude of individual conductors which must be spliced to join the cables. It has been estimated that over two billion pair splice connections are made each year by the telephone industry. It is obviously important in the industry for these splice connections to be durable and, preferably, permanent connections.
• the individual conductor ends to be spliced are brought and held together in multiple contact connectors such as the one disclosed in United States Patent 3,858,158 of Henn et al., which disclosure is incorporated herein, by reference.
• the connector is commonly packed with a filling compound which is meant to prevent the conductors from contacting water and other contaminants, inasmuch as the exposure of spliced conductors to water and other contaminants lowers the life-time of the connections. Not only is the capacitance balance of transmission lines upset but also serious corrosion may occur. Telephone companies spend many hours and much expense repairing lines and restoring telephone service following such damage to conductors.
• a major problem is that once water or any other contaminant enters a cable or a multiple contact connector, it typically spreads through the filling compound to all of the conductors within the connector and, as a result, the entire connector must be replaced and each conductor re-spliced. Therefore, to prevent the above problems, these companies, for example, have developed filling compounds for use in connectors. Although the physical function of the connector filling material is straightforward the choice of the material is not. Among the many parameters or characteristics that have in the past been considered important for materials used in this application are the hydrophobic nature of the material, its stability on aging, low temperature properties, flow characteristics at elevated temperatures, processing characteristics, handling characteristics, dielectric properties, toxicity, and cost.
• the filling compounds for use with cables as described above are not suitable for use in connectors.
• a lower viscosity material is used for connectors so that the filling compound will disperse within the voids created by the electrical conductors and the structure of the connector.
• This problem has been solved in the industry by using a material having a higher amount of oil and/or different amounts of SEBS and polyethylene.
• such a filling compound suffers from the same problems as the above filling compounds for use in cables in that contamination of the filling compound may occur, which results in corrosion of the electrical conductors.
• Filling compounds of the types as above described have been used in the industry and have been the source of user complaints due to yellowing of the filling compound. This yellowing further has been seen to lead to corrosion and loss of telephone service. Therefore, if this filling compound is used in connectors, the filling compound and the spliced conductors still are susceptible to corrosion and contamination over time due to contact with various contaminants, such as fungus, dirt, water, etc. and telephone service may be interrupted.
• a filling compound in accordance with the present invention which includes an ingredient which imparts protective properties to the filling compound. More particularly, the inventors of the present invention have discovered that the above discussed yellowing and contamination problems can be eliminated by including an anti-fungal ingredient in the filling compound. Surprisingly, the inventors discovered that the anti-fungal ingredient additionally provides significant anti-corrosive protection for the electrical conductors, when present in the compound in a particular range.
• the filling compound comprises a mixture of a styrene-ethylene butylene-styrene triblock copolymer (SEBS), oil such as mineral oil, a low molecular weight polyethylene, and an antifungal and anti-corrosive ingredient.
• SEBS styrene-ethylene butylene-styrene triblock copolymer
• the filling compound may comprise a copper deactivator, a styrene-ethylene-butylene (SEB) diblock copolymer and/or polybutene oil.
• SEB styrene-ethylene-butylene
• an anti-fungal compound which has been demonstrated to be effective in connectors is 2-(4-thiazolyl)-benzimidazole.
• the filling compounds of the invention have suitable temperature flow, capacitance stability, and processing characteristics equivalent to those of prior art materials and, further, significant anti-corrosive properties.
• a cable or connector filled with the filling compounds of the invention experiences essentially no growth of fungus.
• the filling compound of the present invention is an improvement over the filling compounds disclosed in U.S. Patents 4,176,240, 4,259,540 and 4,870,117 in that it retains all of the positive attributes of the filling compounds disclosed therein and, in addition, has resistance to contamination and protects the conductors from becoming corroded due to exposure to fungus, dirt, and other contaminants.
• the inventors have found that the addition of an anti-fungal ingredient substantially improves the ability of the filling compound to resist corrosion and contamination.
• a preferred embodiment of the invention incorporates 2-(4-thiazolyl)-benzimidazole which is known in the art to be a preservative which effectively controls mold and mildew on paint films and on natural and synthetic fibers but has not, insofar as applicants are aware, heretofore been used in a cable filling compound.
• the preservative is sold specifically for use in protecting natural and synthetic carpet fibers, surface coating films and canvas textiles by Calgon Corporation under the trade name "TK-100".
• TK-100 trade name
• the inventors have found that, surprisingly, the chemical also imparts significant anti-corrosive properties to the filling compound when present in the amount specified herein, properties which are not anticipated in the prior art.
• Table 1 One formulation of the filling compound of the invention is set forth in Table 1.
• the formulation is prepared as described hereinafter. Preheat the oil with the Irganox 1035 and Irganox 1024 to 130 ⁇ 5°C and add the other components while stirring. Stir until a homogeneous mixture free of agglomerates is obtained. Increase the blend mixture to 150°C for a minimum of 1 hour and a maximum of 2 hours. Maintain an inert gas blanket such as N 2 or CO 2 over the mixing vessel during the 150°C portion of the mixing cycle.
• an inert gas blanket such as N 2 or CO 2
• the amount of fungal and corrosion inhibitor is variable as long as the characteristics of the final compound are acceptable. Amounts from about 0.01 to 0.25 parts by weight are sufficient to impart desired qualities to the filling compounds of the invention. While this range is the preferable range it is apparent that amounts above 0.25 parts by weight may be used if the other properties of the filling compound are not negatively affected. However, amounts greater than 0.25 parts by weight of the compound 2-(4-thiazolyl)-benzimidazole would generally be considered economically unfeasible.
• composition prepared as in Table 1 should have the properties as in Table 2.
• the composition of Table I has been evaluated in terms of anti-fungal activity as well as anti-corrosive activity.
• the anti-fungal test was done in accordance with the specifications of the ASTM G-21 and FOTP-56 tests for fungal growth.
• the samples numbered as follows were 1) a specimen of the filling compound prepared as in the foregoing; 2) a specimen of the filling compound prepared as in the foregoing without the fungal and corrosion inhibitor; and 3) a strip of cotton duck. Each sample was placed in a petriplate and the petriplates were then inoculated with a mixed spore suspension by means of a fine mist atomizer.
• the following fungi were used: Fungus ATCC Number Aspergillus niger 9642 Penicillium funiculosum 11797 Chaetomium globosum 6205 Gliocladium virens 9645 Aureobasidium pullulans 15233 Aspergillus flavus 9643 Aspergillus versicolor 11730
• test results were as follows: TABLE 4 Sample Inspection at 7 Days Inspection at 14 Days Inspection at 21 Days 1 0 0 0 2 0 0 1 3 4 4 4
• the filling compound of the present invention substantially prevents contamination of the filling compound by fungus and prevents corrosion of copper wire.
• the filling compound prepared as in Table 1 is designed to be used in plural conductor connectors such as that disclosed in U.S. Patent 3,772,635 of Frey et al. , which patent is incorporated herein by reference. It is anticipated that the invention in other embodiments is also suitable for use as a filling compound for cables, whether underground or aerial, and for other applications.
• the anti-fungal/anti-oxidant ingredient can be used in an amount ranging from about 0.025 to 0.25 parts by weight in compositions such as those disclosed in U.S. Patents 4,176,240, 4,259,540 and 4,870,117.

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• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Compositions Of Macromolecular Compounds (AREA)

Applications Claiming Priority (2)

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Cited By (6)

• 1996
  • 1996-06-04 EP EP19960304042 patent/EP0749128A2/de not_active Withdrawn

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