Chemistry of inorganic compounds – Carbon or compound thereof – Elemental carbon
Reexamination Certificate
2000-12-01
2002-11-19
Silverman, Stanley S. (Department: 1754)
Chemistry of inorganic compounds
Carbon or compound thereof
Elemental carbon
C106S472000, C106S476000
Reexamination Certificate
active
06482386
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to carbon blacks and further relates to their use in wire and cable compounds, such as shielding compositions. The present invention farther relates to methods of incorporating these carbon blacks into wire and cable compounds and certain properties which can be achieved using the carbon blacks of the present invention.
Insulated cable is used extensively for transmission and distribution of electrical power. Two components of the power cable contain conductive carbon black the strand shield and insulation shield. These carbon black filled semi-conductive materials are used to create an equipotential surface between the conductor and the insulation and to orientate the field in the insulation parallel to the conductor.
Carbon blacks are incorporated into the polymer composition through variety of mixing techniques. They are used extensively in the industry to render resistive polymers electrically conductive. The degree of electrical conductivity imparted by a specific carbon black is related to its physical and chemical properties. For carbon blacks with desired conductivity, it is generally desirable to utilize those carbon blacks that will provide as low viscosity as possible, and thus improve the processability of carbon black-polymer composition of the mixture. For cable applications, another important factor affecting extended cable life is smoothness at the shield interfaces. Any defect at the interfaces can increase the stress levels and may lead to premature cable failure. These defects are generally found to be caused by contaminants, degraded polymer gels, and/or poorly dispersed carbon black.
The power cables designed for medium to high voltage applications have a copper or aluminum core conductor, a layer of semi-conductive shielding, a layer of insulation, and a layer of semi-conductive insulation shielding. The insulation layer is predominantly either crosslinked polyethylene or crosslinked ethylene propylene rubber (EPR). During the installation of the cable it is often necessary to make splices and terminal connections, this requires the clean delamination of the insulation shield layer from the insulation layer. Therefore, a strippable semi-conductive insulation shielding which can be easily stripped from the insulation layer will be desirable. However, a minimum strip force is required to maintain the mechanical integrity between the insulation layer and the semi-conductive insulation; if the force is too low then loss of adhesion may result in water diffusing along the interface causing electrical breakdown.
Accordingly, it will be advantageous to produce novel carbon black that can impair at the same time higher compound conductivity at a comparatively lower viscosity and high level of smoothness and a low adhesion in strippable formulations. These and other advantages are achieved by the carbon black and polymer compositions of the present invention.
SUMMARY OF THE INVENTION
A feature of the present invention is to provide novel carbon blacks which preferably provide one or more improved properties to the wire and/or cable compounds.
The present invention also relates to polymeric compositions, such as wire and cable compounds, containing the carbon blacks of the present invention.
Another feature of the present invention is to provide carbon blacks, which when incorporated into wire and cable compounds, provide a low viscosity.
In addition, a feature of the present invention is to provide carbon blacks, which when incorporated into wire and cable compounds, lead to an acceptable and higher conductivity ranges.
A further feature of the present invention is to provide carbon blacks which when incorporated into wire and cable compounds promote a very high smoothness of the formed compound.
An additional feature of the present invention is to provide carbon blacks, which when incorporated into wire and cable compounds, promote a very good stripability of the layer containing the carbon black.
Also, a feature of the present invention is to provide carbon blacks, which when incorporated into wire and cable compounds, provides a combination of all of the above-described properties.
Additional features and advantages of the present invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention will be realized and obtained by means of the elements and combinations particularly pointed out in the written description and appended claims.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, the present invention relates to a conductive carbon black having a nitrogen surface area of from 65 to 95 m
2
/g; an Iodine number without additive of from 64 to 120 mg/g; a tinting strength of about 90% or less; and a ASTM particle size of from 22 nm to 39 nm.
The present invention further relates to polymer compositions, such as cable and wire compounds, containing the above-described carbon black.
In addition, the present invention relates to a polymer composition containing the above-described carbon black, an ethylene containing polymer, and a crosslinking agent. This polymer composition can further contain an acrylonitrile butadiene type polymer and/or other conventional additives.
Furthermore, the above-described carbon black can be further treated with a variety of one or more treating agents such as a polymer comprising an acrylonitrile and at least one other monomer; ethoxylated esters or polyethers; compounds containing at least one long chain alkenyl or alkyl group and at least one amine group; alkylene type compounds such as polyethylene glycol, and the like.
In addition, the present invention relates to methods to lower viscosity, improve conductivity, improve smoothness, and/or improve stripability of the wire and cable compound using the carbon blacks of the present invention.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide a further explanation of the present invention, as claimed.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
The present invention relates to novel carbon blacks and their use in polymeric compositions such as wire and cable compounds. Preferably, the use of the carbon blacks in the wire and cable compounds leads to improved properties such as one or more of the following: a lowered viscosity of the wire and cable compounds; an improved conductivity range; an improved smoothness of the formed wire and/or cable compound; and/or an improved stripability of the formed wire and/or cable compound.
The carbon black of the present invention preferably has a nitrogen surface area of from about 65 to about 95 m
2
/g as measured by ASTM D4820. The carbon black further has an Iodine number without additive of from about 64 to 120 mg/g as measured by ASTM D1510. The carbon black further has a tinting strength of 90% or less as measured by ASTM D3265; and a ASTM particle size of from about 22 nm to about 39 nm as measured by ASTM D3849-89.
The carbon black of the present invention can further have one or more of the following additional characteristics which are preferred: a DBPA of from about 119 to about 128 cc/100 g as measured by ASTM D2414 and preferably a DBPA of from about 120 to about 124 cc/100 g and even more preferably 123 cc/100 g.
Preferably, the carbon blacks of the present invention have a nitrogen surface area of from about 65 to about 75 m
2
/g, more preferably 66 m
2
/g to 75 m
2
/g, and even more preferably 68 m
2
/g to 72 m
2
/g, and most preferably 70 m
2
/g; an Iodine number without additive of from 78 to 85 mg/g and more preferably 80 to 85 mg/g, and even more preferably 83 mg/g; a tinting strength of from about 75% to about 90% and more preferably about 81%; an ASTM particle size of from about 30 to
Atchetee Michael J.
Bhatt Sandeep
Tomme Marcel G.
Cabot Corporation
Johnson Edward M.
Silverman Stanley S.
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