CA1084696A - Insulated electrical conductors - Google Patents
Insulated electrical conductorsInfo
- Publication number
- CA1084696A CA1084696A CA248,307A CA248307A CA1084696A CA 1084696 A CA1084696 A CA 1084696A CA 248307 A CA248307 A CA 248307A CA 1084696 A CA1084696 A CA 1084696A
- Authority
- CA
- Canada
- Prior art keywords
- vinyl acetate
- ethylene
- conducting
- crosslinked
- insulation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/20—Conductive material dispersed in non-conductive organic material
- H01B1/24—Conductive material dispersed in non-conductive organic material the conductive material comprising carbon-silicon compounds, carbon or silicon
-
- 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
- H01B3/441—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 from alkenes
-
- 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
- H01B3/448—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 from other vinyl compounds
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B9/00—Power cables
- H01B9/02—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients
- H01B9/027—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients composed of semi-conducting layers
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Chemical & Material Sciences (AREA)
- Dispersion Chemistry (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Conductive Materials (AREA)
- Insulated Conductors (AREA)
- Organic Insulating Materials (AREA)
- Inorganic Insulating Materials (AREA)
Abstract
ABSTRACT
A vulcanizable semi-conducting insulation shielding composition comprising, based on the total weight of said composition, (A) about 55 to about 90 weight percent of an ethylene-vinyl acetate copolymer containing from about 27 to 45 weight percent of vinyl acetate based on the total weight of said copolymer, (B) about 10 to 45 weight percent of conducting carbon black and (C) as the only crosslinking agent in said composition from 0.2 to 5 weight percent of an agent selected from the group consisting of .alpha., .alpha.' bis-(tertiary-butylperoxy) diisopropyl benzene and 2,5-dimethyl-2', 5'-di(tertiary-butylperoxy) hexane and mix-tures thereof.
The composition can be used to provide stripp-able insulation shielding for electrical conductors.
Insulated electrical conductors containing the strippable insulation shielding compositions are also disclosed.
1.
A vulcanizable semi-conducting insulation shielding composition comprising, based on the total weight of said composition, (A) about 55 to about 90 weight percent of an ethylene-vinyl acetate copolymer containing from about 27 to 45 weight percent of vinyl acetate based on the total weight of said copolymer, (B) about 10 to 45 weight percent of conducting carbon black and (C) as the only crosslinking agent in said composition from 0.2 to 5 weight percent of an agent selected from the group consisting of .alpha., .alpha.' bis-(tertiary-butylperoxy) diisopropyl benzene and 2,5-dimethyl-2', 5'-di(tertiary-butylperoxy) hexane and mix-tures thereof.
The composition can be used to provide stripp-able insulation shielding for electrical conductors.
Insulated electrical conductors containing the strippable insulation shielding compositions are also disclosed.
1.
Description
~ 69 ~
This invention relates to vulcanizable semi-conducting compositions of ethylene-vinyl acetate co-polymers which provide strippable semi-conducting insulation shielding compositions for crosslinked polyethylene in-sulated conductors.
The construction of insulated electrical conductors, i.e. wires and cable, designed for medium to high voltage applications is well known in the art and commonly com-prises a core conductor which comprises one or more strands or a conducting metal or alloy such as copper or aluminum, a layer of semi-conducting conductor shielding, a layer of ; insulation, such as crosslinked polyethylene, and a layer of semi-conducting insulation shielding overlying said in-sulation. A plurality of neutral wires which are usually made of copper or aluminum may be embedded in or wrapped around the layer of semi-conducting insulation shielding, if desired, in the form o~ a concentric ring around the `~ insulated cable.
The insulation layer and its overlying semi-con-ducting shielding layer are usually formed by what is known ~ ~ ;
in the art as tandem extrusion whereby these layers are formed in sequence employing tandem extruders and cured simultaneously in a single operation to minimize manufactur-ing steps, However, the simultaneous curing of the two layers by heat and presRure results in apparent mixing at _ the interface and formation of crossl-,nking bonds across the interface. This appears true even in what is known in the art as a two pass operation where the insulation i5 cured in a previous operation and the semi-conducting shielding layer afterwards extruded and cured onto the insulation.
This invention relates to vulcanizable semi-conducting compositions of ethylene-vinyl acetate co-polymers which provide strippable semi-conducting insulation shielding compositions for crosslinked polyethylene in-sulated conductors.
The construction of insulated electrical conductors, i.e. wires and cable, designed for medium to high voltage applications is well known in the art and commonly com-prises a core conductor which comprises one or more strands or a conducting metal or alloy such as copper or aluminum, a layer of semi-conducting conductor shielding, a layer of ; insulation, such as crosslinked polyethylene, and a layer of semi-conducting insulation shielding overlying said in-sulation. A plurality of neutral wires which are usually made of copper or aluminum may be embedded in or wrapped around the layer of semi-conducting insulation shielding, if desired, in the form o~ a concentric ring around the `~ insulated cable.
The insulation layer and its overlying semi-con-ducting shielding layer are usually formed by what is known ~ ~ ;
in the art as tandem extrusion whereby these layers are formed in sequence employing tandem extruders and cured simultaneously in a single operation to minimize manufactur-ing steps, However, the simultaneous curing of the two layers by heat and presRure results in apparent mixing at _ the interface and formation of crossl-,nking bonds across the interface. This appears true even in what is known in the art as a two pass operation where the insulation i5 cured in a previous operation and the semi-conducting shielding layer afterwards extruded and cured onto the insulation.
2, , ~01~4~i~6 The formation of these crosslinking bonds between the insulation and shielding makes subsequent separation of the two layers (insula~ion and semi-conducting shielding) such as occurs in making splices or terminal connections, very difficult and time consuming. Such a strong bond also makes the semi-conductive layer prone to leave carbon residue on the insulation even when it is finally pealed off. A Strippable semi-conducting shielding which can be easily and cleanly stripped from the insulation of an insulated conductor is therefore very desirable in this art.
In order to achieve strippability between the insulation layer and its semi-conducting shielding layer several methods have been herétofore attempted with varying degrees of success such as sulfonating the insulation or -Coating it with release agents prior to applying the semi- "
conducting shielding layer. Other methods include using a synthetic rubber made of chlorosulfonated polyethylene sold under the tradename of Hypalonas the base resin for the insulation shield or using a semi-conducting shield-ing composition such as qeen disclosed by U.S. Patents
In order to achieve strippability between the insulation layer and its semi-conducting shielding layer several methods have been herétofore attempted with varying degrees of success such as sulfonating the insulation or -Coating it with release agents prior to applying the semi- "
conducting shielding layer. Other methods include using a synthetic rubber made of chlorosulfonated polyethylene sold under the tradename of Hypalonas the base resin for the insulation shield or using a semi-conducting shield-ing composition such as qeen disclosed by U.S. Patents
3,719,769, and 3,769,085.
As considered herein an easily strippable semi-conducting insulation shielding composition is one in which the adhesion between the insulation and said shielding composition of an insulated electrical conductor is not greater than 16 pounds per half inch strip.
~' .
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It has now been discovered ~hat such types of easily strippable aemi-con~ucting shielding compositions for cross-linked polyethylene insulation can be obtained from the w lcanizable semi-conducting insulation shielding com- -positions of this invention as described more fully below.
Thus, it is an object of this invention to provide a vulcanizable semi-conducting insulation shielding com-position which is particularly useful for providing a strippable shielding for insulated electrical conductors, e.g. wires and cables, that contain, as the prlmary in-sula~ion, crosslinked polyethylene. Another object of this invention is to provide insulated electrical con-ductors, e.g. wires and cables, comprising, as the primary insulation, a crosslinked polyethylene, and as the shielding material for said insulation an easily strippable crosslinked semi-conducting shielding composition. Other objects and advantages of this invention will become rea~ily appar~nt from the following description and appended claims.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
More specifically, the instant invention may be described as a strippable w lcanizable semi-conducting insulation shielding composition comprising, based on the total weight of said compo~ltion, (A) about 55 to about 90 weight percent of an ethylene-vinyl acetate copolymer con- ;
taining from about 27 to 45 weight percent of vinyl acetate based on the total weight of said copolymer, (B) about 10 to 45 weight percent of conducting carbon black and (C) as the only crosslinking agent in said composition , .
~892 ~ 69 ~
from 0.2 to 5 weight percent of an agent selected from the group consisting of o~ , ~< ' bis(tertiary-butylperoxy) diisopropyl benzene and 2,5-dimethyl-2', 5'-di(tertiary-butylperoxy) hexane and mixtures thereof.
The vulcanizable ethylene-vinyl acetate copolymers and/or their methods of preparation, which can be employed in this invention are well known in the art. However, it has been discovered that in order to obtain a semi-conduct-ing insulation shielding that is easily strippable from crosslinked polyethylene insulated electrical conductors it is important to employ an ethylene-vinyl acetate co-polymer that is incompatible with the crosslinked poly-ethylene insulation. The term incompatible is used herein to mean that there is a lack of physiochemieal affinity between the polyethylene and ethylene-vinyl acetate resins during extrusion and curing conditions. This incompatibility , results in a mutual repulsion between said resins which in ; turn prevents mixing and bond formation between them.
Whether or not a particular w lcanizable semi-conducting composition will exhibit such incompatibility and will furnish a crosslinked polyethylene insulated electrical conductor with an easily strippable semi-conducting insulatlon shielding may be determined by , measuring the adhesion between a laminate of crosslinked polyethylene and the crosslinked product of the w lcanizable semi-conducting composition according to ASTM-D903. In order to be considered an easily strippable insulation shielding composition the laminate adhesion level of the semi-conducting composition for the crosslinked ~ 5 ~ 6~36 9~92 polyethylene should not be more than 16 pounds per half inch strip when measured accoxding to said test method.
Thus, the ethylene-vinyl acetatP copolymer employed herein should contain from 27 to 45, preferably from 29 to 35 weight percent of vinyl acetate based on the total weight of said copolymer for it is considered that copolymers containing less than 27 weight percent vinyl acetate will result in semi-conductive shieldings that are bonded too ~-strongly to an insulation of crosslinked polyethylene to be considered easily strippable; while copolymers having more than 45 weight percent of vinyl acetate may provide too weak an adhesion to crosslinked polyethylene. The amount of ethylene-vinyl acetate copolymer present in the ^ vulcanizable semi-conducting insulation shielding com-positions of this invention can range from about 55 to 90 weight percent, preferably from about 60 to 75 weight percent, based on the total weight of the w lcanizable composition. Such ethylene-vinyl acetate copolymers and/or ~ -methods for their preparation are well known in the art.
The employment o conducting carbon black in semi-conducting compositions is well ~nown in the art and ~ny conducting carbon black ln any suitable form can be employed in this lnvention including channel blacks, oil furnace blacks or ~cetylene blacks, providing they are conducting. The amount o~ conducting carbon black -~
present in the w lcanizable semi-conducting insulation~;
shielding compositions of this invention can range from about 10 to 45 welght percent, preferably ~rom about 30 to 40 weight percent, based on the total weight o the . . .
... ..
~ 9892 ; vulcanizable composition.
The only crosslinking agents employed in the ;emi-conducting compositions of this invention include :~ose selected from the group consisting of 9C ,o~ ' bis-(tertiary-butylperoxy) diisopropyl benzen~, (Vulcup*), ~ 2,5-dimethyl-2', 5'-di(tertiary-butylperoxy) hexane, ; (Varox*),and mixtures thereof. While the preferred amount of crosslinking agent employed may vary depending upon the particular e~hylene-vinyl acetate copolymer employed and other such obvious conditions, in general, it is ~
considered that said amount of crosslinking agent will ~ -;~ norn,ally fall within the range of about 0.2 to 5 preferably about 0.6 to 2, weight percent ~ased on the total weight of the w lcanizable semi-conducting composition.
Of course, it is to be understaod, that said amount ` ranges may not be suitable for every po~sible semi-conduc~ing composition of this invention and that for any given w lcanizable semi-conducting composition the use of amounts of crosslinking agents that may provide a cross-linked semi-conducting product that would have a~ adhesion of greater than 16 pounds per half inch when measured as defined above for crosslinked polyethylene should be avoided, and that such can be determined by routine experimentation.
0~ course, it is to be also understood that the vulcanizable semi-conducting insulation shielding compositions of this invention, if desired, can contain other conventional additives in the conventional used quantities commonly employed in semi-conducting compositions.
* tradename .~,"", .
~ 6~ 6 989~
Examples of such additives include e.g. age resistors proces~ing aids, stabilizers, antioxidants, crosslinking boosters and retarders, pigments, fillers, lubricants, ultraviolet stabilizers, anti-block agents and the like.
The total amount of such additives which are commonly used normally amounts to no more than about 0.05 to 3 percent by weight based on the total weight of the insu-lation shielding compositionA
As pointed out above, another aspect of this invention may be more specifically described as an in-sulated electrical conductor, e.g. electrical wire, elec-trical cable, etc., containing as the primary insulation, crosslinked polyethylene and as the external semi-conductins shielding for said insulation, a crosslinked ethylene-vinyl acetate copolymer obtained upon crosslinking the vulcanizabl-~
semi-conducting insulation shielding composition of this ;
invention which has been already previously defined above. -~
; Of course, it is to be understood that the term "crosslinked polyethylene" as used herein includes and encompasses insulation compositions derived from a cross-linkable polyethylene homopolymer or a crosslinkable polyethylene copolymer having a comonomer content that will not adversely affect the desired result of the in-~tant invention. Normally the preferred crosslinked poly-ethylene insulation is derived from a crosslinkable polyethylene homopol~mer. The use of polyethylene i~sulation compositions and semi-conducting compositions, '', ~ 696 9892 the manner of cheir preparation, and the preparation of insulated conductors are so well known that no further discussion is required here to enable one skilled in the art to understand how the polymer components are produced and used in the preparation of insulated conductors.
For instance, the use of low densi~y polye~hylene com-positions, which if desired, may contain conventional additives such as fillers, age resistors, talc, clay, calcium carbonate and other processing aides, along with a conventional crosslinking agent is well known in the art as are the conventional semi-conducting conductor shielding compositions. The insulated electrical con- - -ductors o~ this invention can also be prepared by con- --ventional procedures, e.g. such as by tandem extrusion whereby thè insulating layer is extruded over the con-ductor, which has been previously covered with an ordinary extruded semi-conductive conductor s~ielding, followed by extruding the vulcanizable layer and then simultaneously curing (crosslinking) both the insulation and insulation shielding layer under pressure. Another conventional ; method involves curing the insulation layer prior to contact with the vulcanizable semi-conducting insulation shielding composition which is then itsel~ cured while in contact under pressure with said cured insulation layer.
However, it is considered desirable to prevent any pre-mixing o~ the ins~lation cornposition and vulcanizable semi-conducting insulation ~hielding composition prior to curing said compositions slnce such can allow the cross-linking agents employed to assert their in1uence on adhesion between the two layers through intercrosslinking .
' . ' - ,'' ,,, : ' , ~ 6~ 6 9892 across the interface of the two layers. The other particular attributes of the insulated electrical conductors of this - invention may also conform to con~entional insulated electrical conductors and are not- ,~ritical for they depend for the most part merely upon the desired end use of the insulated electrical conductors.
The insulated electrical conductors of the instant invention are indeed unique in view of the fact that the crosslinked insulation shi~lding composition can be easily and cleanly stripped> generally in one piece, ; from the crosslinked polyethylene insulation. -The following examples are illustrative of the present invention and are not to be regarded as limitative.
~`~ It is to be understood that all parts> percentages and proportions referred to herein and in the appended claims are by wei.ght unless otherwise indicated.
GLOSSARY
EVA = ethylene vinyl acetate copolymer VA = weight percent of vinyl acetate in copolymer MI s melt index Dicup* -di-~C-cumyl perox~de ~ Lupersol*-130 =2,5-dimethyl-2', 5'-di(tertiary-butyl-; peroxy)-hexyne-3 Vulcup*= c~ '-bis-(tertiary butylperoxy~ diisopropyl-benzene Varox* ~2,5-dimethyl, 2',5'-di(tertiary-butylperoxy)-hexane EXAMPLES 1 to 16 A series of w lcanizable semi-conducting com-positions were prepared wherein the weight percent of .
*tradename ~-10.
, ~
'~;'' ~. i ~ 6~ 6 9892 vinyl acetate in the ethylene-vinyl acetate copolymer was varied as were the crosslinking agents employed. The components of each composition are listed below in Table I and each composition contained in addition to the com-ponen~s listed 40 weight percent of conducting carbon black and 0.4 weight percent of polymerized 1,2-dihydro-2, 2,4-trimethyl quinoline, an antioxidant, the amounts of all the ingredients in each composition being based on the total weight of each composition unless otherwise indica~ed.
The compositions were formed by uniformly ad-mixing the components thereof in a laboratory size Banbury mixer and about 1300 grams of each composition were pre-pared.
In order to evaluate the strippability properties of these compositions as semi-conducting insulation sheild-ings, each composition was respectively used to prepare a polyethylene/ethylene-vinyl ace~ate laminate. Said ~` laminates were prepared from laboratory test plaques, the polyethylene plaque in each instance was derived from a crosslinkable polyethylene homopolymer composition con-sisting of polyethylene homopolymer (98%), di-~-cumyl peroxide (2a/o) and bis(2-methyl,5-tertiary butyl,4-hydroxy-phenyl) sulfide (0.2%), an antloxidant.
In Examples 1 to 9 the polyethylene/ethylene-vinyl acetate laminates were made by first molding the - polyethylene plaques (measuring 8" by 8" and 250 mils thick) at 175C. for 15 minutes and crosslinking same, then the w lcanizable ethylene-vinyl acetate plaques (measuring 8" by 8" and 125 mils thick) were separately .. .. .
, ~ . . .
~ 6 molded, but not crosslinked, and the laminates made by pressing each vulcanizable ethyl~ne-vinyl acetate plaque together with one of the crosslinked polyethylene plaques at 200C. and 200 psi. pressure for 20 minutes during which time the w lcanizable ethylene-vinyl acetate com-position became crosslinked.
In Examples 10 to 16 the polyethylene/ethylene-vinyl acetate laminates were prepared in the same manner as described above except that the polyethylene plaques were molded at 110C. so as not to crosslink them. Cross~
linking of both types of plaques took place simultaneously when the laminate was made.
The adhesion between the test laminates (cut to 8" by 1"~ were then determined according to ASTM Test Method D903 which measures the peel strength between the two plaques of the laminate in terms of pounds per half-inch strip and which is employed herein as a measure of thestriPpability of a semi-conducting ethylene-vinyl acetate insulation sheilding from a crosslinked poly-ethylene insulation. The test results of each laminate of polyethylene/ethylene-vinyl acetate sheilding prepared as di~cussed above are also listed in said Table I.
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~ 6~ 6 9892 Examples 5, 7, 9 and 12 to 15 which represent the present inven~ion demonstrate the excellent stripp-ability of the insulation shielding compositions, the insulation shielding layer in each example having been stripped clean and in one piece from the insulation.
This example illustrates the preparation of an insulated electrical cable.
A standard aluminum conductor was se~uentially covered with an ordinary semiconducting strand shielding layer (0.025" thick), a polyethylene insulating layer (0.267" thick), and a semiconducting insulation shielding layer (0.055" thick) consisting of polyethylene/vinyl acetate (2~/o vinyl acetate, MI = 20) and 0.6% Vulcup-In preparing the cable the extruded strand shielding layer and insulation layer were cured in a steam w lcanization tube t250 lbs./sq. in. of steam) prior to extruding the insulation shielding layer over the insulation, said insulation shielding layer then being cured during a second pass through the steam vulcanization tube. This process procedure is conventionally known in the art as a two pass extrusion.
Iwo parallel incisions in the insulation shield-ing of the insulated cable so prepared were mad~ one-half inch apart running in the axial direction of the cable -; and said insulation shielding was subjected to a tensile ; peeling test to determine the adhesion of the insulation.
- The insulation shielding wa~ stripped clean and in one . .
piece from the insulation and exhibited an adhesion level of 6-8 pounds per half-inch strip, thus demonstrating the ', ' ~
1~. .
~ 6 9892 excellent strippability of the insulation shielding composition of this invention.
A comparative insulated electrical cable pre-pared and tested in the same manner, but using an insu-lation shielding composition consisting of vinyl acetate and 2% Dicup resulted in a cable having an insulation shielding that exhibited an adhesion level of 20-25 pounds per half-inch strip and which did not strip clean butbroke off in pieces from the insulation.
This example illustrates the preparation of an insulated electrical cable.
A standard aluminum conductor was sequentially covered with an ordinary semiconducting strand shielding ; layer (0.025" thick), a polyethylene insulating layer . .
(0.267" thick), and a semi~onducting insulation shielding layer (0.055" thick) consisting of polyethylene/
vinyl acetate (29% vinyl acatate, MI = 20) and 0.6%
Vulcup.
In preparing the cable, all three layers of strand shielding, insulation and insulation shielding were extruded sequentially and simultaneously cured in a steam vulcanization tube (250 lbs./sq. in. of steam).
This process procedure is conventionally known in the art as a single pass triple extrusion.
The adhesion o~ the insulation shielding to the insulation of the insulated cable was determined by the same method described in Example 17. The insulation shielding was stripped clean and in one piece from the insulation and exhibi.ted an adhesion level o 14-16 .
~ 69 6 poun~ pcr h~lf-inch strlp, thus demonstratlng the excellent strippabllity of the insulation sheilding com-position of ~his invention.
A comparative insulated electrical cable pre-pared and tested in the same manner, but using the insu-lation shielding composition consisting of vinyl acetate and 2% Dicup resulted in a cable having an insulation shielding that exhibited such a strong adhesion to the insulation that its strippability could not be measured by the peel test, the two layers being intimately fused at the interface.
Various modifications and variations of this invention will be obvious to a worker skilled in the art and it is to be understood that such modifications and -- :
variations are to be included within the purview of this appllcation and the spirit and scope of the appended , . .
claims.
, ' .
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16.
As considered herein an easily strippable semi-conducting insulation shielding composition is one in which the adhesion between the insulation and said shielding composition of an insulated electrical conductor is not greater than 16 pounds per half inch strip.
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It has now been discovered ~hat such types of easily strippable aemi-con~ucting shielding compositions for cross-linked polyethylene insulation can be obtained from the w lcanizable semi-conducting insulation shielding com- -positions of this invention as described more fully below.
Thus, it is an object of this invention to provide a vulcanizable semi-conducting insulation shielding com-position which is particularly useful for providing a strippable shielding for insulated electrical conductors, e.g. wires and cables, that contain, as the prlmary in-sula~ion, crosslinked polyethylene. Another object of this invention is to provide insulated electrical con-ductors, e.g. wires and cables, comprising, as the primary insulation, a crosslinked polyethylene, and as the shielding material for said insulation an easily strippable crosslinked semi-conducting shielding composition. Other objects and advantages of this invention will become rea~ily appar~nt from the following description and appended claims.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
More specifically, the instant invention may be described as a strippable w lcanizable semi-conducting insulation shielding composition comprising, based on the total weight of said compo~ltion, (A) about 55 to about 90 weight percent of an ethylene-vinyl acetate copolymer con- ;
taining from about 27 to 45 weight percent of vinyl acetate based on the total weight of said copolymer, (B) about 10 to 45 weight percent of conducting carbon black and (C) as the only crosslinking agent in said composition , .
~892 ~ 69 ~
from 0.2 to 5 weight percent of an agent selected from the group consisting of o~ , ~< ' bis(tertiary-butylperoxy) diisopropyl benzene and 2,5-dimethyl-2', 5'-di(tertiary-butylperoxy) hexane and mixtures thereof.
The vulcanizable ethylene-vinyl acetate copolymers and/or their methods of preparation, which can be employed in this invention are well known in the art. However, it has been discovered that in order to obtain a semi-conduct-ing insulation shielding that is easily strippable from crosslinked polyethylene insulated electrical conductors it is important to employ an ethylene-vinyl acetate co-polymer that is incompatible with the crosslinked poly-ethylene insulation. The term incompatible is used herein to mean that there is a lack of physiochemieal affinity between the polyethylene and ethylene-vinyl acetate resins during extrusion and curing conditions. This incompatibility , results in a mutual repulsion between said resins which in ; turn prevents mixing and bond formation between them.
Whether or not a particular w lcanizable semi-conducting composition will exhibit such incompatibility and will furnish a crosslinked polyethylene insulated electrical conductor with an easily strippable semi-conducting insulatlon shielding may be determined by , measuring the adhesion between a laminate of crosslinked polyethylene and the crosslinked product of the w lcanizable semi-conducting composition according to ASTM-D903. In order to be considered an easily strippable insulation shielding composition the laminate adhesion level of the semi-conducting composition for the crosslinked ~ 5 ~ 6~36 9~92 polyethylene should not be more than 16 pounds per half inch strip when measured accoxding to said test method.
Thus, the ethylene-vinyl acetatP copolymer employed herein should contain from 27 to 45, preferably from 29 to 35 weight percent of vinyl acetate based on the total weight of said copolymer for it is considered that copolymers containing less than 27 weight percent vinyl acetate will result in semi-conductive shieldings that are bonded too ~-strongly to an insulation of crosslinked polyethylene to be considered easily strippable; while copolymers having more than 45 weight percent of vinyl acetate may provide too weak an adhesion to crosslinked polyethylene. The amount of ethylene-vinyl acetate copolymer present in the ^ vulcanizable semi-conducting insulation shielding com-positions of this invention can range from about 55 to 90 weight percent, preferably from about 60 to 75 weight percent, based on the total weight of the w lcanizable composition. Such ethylene-vinyl acetate copolymers and/or ~ -methods for their preparation are well known in the art.
The employment o conducting carbon black in semi-conducting compositions is well ~nown in the art and ~ny conducting carbon black ln any suitable form can be employed in this lnvention including channel blacks, oil furnace blacks or ~cetylene blacks, providing they are conducting. The amount o~ conducting carbon black -~
present in the w lcanizable semi-conducting insulation~;
shielding compositions of this invention can range from about 10 to 45 welght percent, preferably ~rom about 30 to 40 weight percent, based on the total weight o the . . .
... ..
~ 9892 ; vulcanizable composition.
The only crosslinking agents employed in the ;emi-conducting compositions of this invention include :~ose selected from the group consisting of 9C ,o~ ' bis-(tertiary-butylperoxy) diisopropyl benzen~, (Vulcup*), ~ 2,5-dimethyl-2', 5'-di(tertiary-butylperoxy) hexane, ; (Varox*),and mixtures thereof. While the preferred amount of crosslinking agent employed may vary depending upon the particular e~hylene-vinyl acetate copolymer employed and other such obvious conditions, in general, it is ~
considered that said amount of crosslinking agent will ~ -;~ norn,ally fall within the range of about 0.2 to 5 preferably about 0.6 to 2, weight percent ~ased on the total weight of the w lcanizable semi-conducting composition.
Of course, it is to be understaod, that said amount ` ranges may not be suitable for every po~sible semi-conduc~ing composition of this invention and that for any given w lcanizable semi-conducting composition the use of amounts of crosslinking agents that may provide a cross-linked semi-conducting product that would have a~ adhesion of greater than 16 pounds per half inch when measured as defined above for crosslinked polyethylene should be avoided, and that such can be determined by routine experimentation.
0~ course, it is to be also understood that the vulcanizable semi-conducting insulation shielding compositions of this invention, if desired, can contain other conventional additives in the conventional used quantities commonly employed in semi-conducting compositions.
* tradename .~,"", .
~ 6~ 6 989~
Examples of such additives include e.g. age resistors proces~ing aids, stabilizers, antioxidants, crosslinking boosters and retarders, pigments, fillers, lubricants, ultraviolet stabilizers, anti-block agents and the like.
The total amount of such additives which are commonly used normally amounts to no more than about 0.05 to 3 percent by weight based on the total weight of the insu-lation shielding compositionA
As pointed out above, another aspect of this invention may be more specifically described as an in-sulated electrical conductor, e.g. electrical wire, elec-trical cable, etc., containing as the primary insulation, crosslinked polyethylene and as the external semi-conductins shielding for said insulation, a crosslinked ethylene-vinyl acetate copolymer obtained upon crosslinking the vulcanizabl-~
semi-conducting insulation shielding composition of this ;
invention which has been already previously defined above. -~
; Of course, it is to be understood that the term "crosslinked polyethylene" as used herein includes and encompasses insulation compositions derived from a cross-linkable polyethylene homopolymer or a crosslinkable polyethylene copolymer having a comonomer content that will not adversely affect the desired result of the in-~tant invention. Normally the preferred crosslinked poly-ethylene insulation is derived from a crosslinkable polyethylene homopol~mer. The use of polyethylene i~sulation compositions and semi-conducting compositions, '', ~ 696 9892 the manner of cheir preparation, and the preparation of insulated conductors are so well known that no further discussion is required here to enable one skilled in the art to understand how the polymer components are produced and used in the preparation of insulated conductors.
For instance, the use of low densi~y polye~hylene com-positions, which if desired, may contain conventional additives such as fillers, age resistors, talc, clay, calcium carbonate and other processing aides, along with a conventional crosslinking agent is well known in the art as are the conventional semi-conducting conductor shielding compositions. The insulated electrical con- - -ductors o~ this invention can also be prepared by con- --ventional procedures, e.g. such as by tandem extrusion whereby thè insulating layer is extruded over the con-ductor, which has been previously covered with an ordinary extruded semi-conductive conductor s~ielding, followed by extruding the vulcanizable layer and then simultaneously curing (crosslinking) both the insulation and insulation shielding layer under pressure. Another conventional ; method involves curing the insulation layer prior to contact with the vulcanizable semi-conducting insulation shielding composition which is then itsel~ cured while in contact under pressure with said cured insulation layer.
However, it is considered desirable to prevent any pre-mixing o~ the ins~lation cornposition and vulcanizable semi-conducting insulation ~hielding composition prior to curing said compositions slnce such can allow the cross-linking agents employed to assert their in1uence on adhesion between the two layers through intercrosslinking .
' . ' - ,'' ,,, : ' , ~ 6~ 6 9892 across the interface of the two layers. The other particular attributes of the insulated electrical conductors of this - invention may also conform to con~entional insulated electrical conductors and are not- ,~ritical for they depend for the most part merely upon the desired end use of the insulated electrical conductors.
The insulated electrical conductors of the instant invention are indeed unique in view of the fact that the crosslinked insulation shi~lding composition can be easily and cleanly stripped> generally in one piece, ; from the crosslinked polyethylene insulation. -The following examples are illustrative of the present invention and are not to be regarded as limitative.
~`~ It is to be understood that all parts> percentages and proportions referred to herein and in the appended claims are by wei.ght unless otherwise indicated.
GLOSSARY
EVA = ethylene vinyl acetate copolymer VA = weight percent of vinyl acetate in copolymer MI s melt index Dicup* -di-~C-cumyl perox~de ~ Lupersol*-130 =2,5-dimethyl-2', 5'-di(tertiary-butyl-; peroxy)-hexyne-3 Vulcup*= c~ '-bis-(tertiary butylperoxy~ diisopropyl-benzene Varox* ~2,5-dimethyl, 2',5'-di(tertiary-butylperoxy)-hexane EXAMPLES 1 to 16 A series of w lcanizable semi-conducting com-positions were prepared wherein the weight percent of .
*tradename ~-10.
, ~
'~;'' ~. i ~ 6~ 6 9892 vinyl acetate in the ethylene-vinyl acetate copolymer was varied as were the crosslinking agents employed. The components of each composition are listed below in Table I and each composition contained in addition to the com-ponen~s listed 40 weight percent of conducting carbon black and 0.4 weight percent of polymerized 1,2-dihydro-2, 2,4-trimethyl quinoline, an antioxidant, the amounts of all the ingredients in each composition being based on the total weight of each composition unless otherwise indica~ed.
The compositions were formed by uniformly ad-mixing the components thereof in a laboratory size Banbury mixer and about 1300 grams of each composition were pre-pared.
In order to evaluate the strippability properties of these compositions as semi-conducting insulation sheild-ings, each composition was respectively used to prepare a polyethylene/ethylene-vinyl ace~ate laminate. Said ~` laminates were prepared from laboratory test plaques, the polyethylene plaque in each instance was derived from a crosslinkable polyethylene homopolymer composition con-sisting of polyethylene homopolymer (98%), di-~-cumyl peroxide (2a/o) and bis(2-methyl,5-tertiary butyl,4-hydroxy-phenyl) sulfide (0.2%), an antloxidant.
In Examples 1 to 9 the polyethylene/ethylene-vinyl acetate laminates were made by first molding the - polyethylene plaques (measuring 8" by 8" and 250 mils thick) at 175C. for 15 minutes and crosslinking same, then the w lcanizable ethylene-vinyl acetate plaques (measuring 8" by 8" and 125 mils thick) were separately .. .. .
, ~ . . .
~ 6 molded, but not crosslinked, and the laminates made by pressing each vulcanizable ethyl~ne-vinyl acetate plaque together with one of the crosslinked polyethylene plaques at 200C. and 200 psi. pressure for 20 minutes during which time the w lcanizable ethylene-vinyl acetate com-position became crosslinked.
In Examples 10 to 16 the polyethylene/ethylene-vinyl acetate laminates were prepared in the same manner as described above except that the polyethylene plaques were molded at 110C. so as not to crosslink them. Cross~
linking of both types of plaques took place simultaneously when the laminate was made.
The adhesion between the test laminates (cut to 8" by 1"~ were then determined according to ASTM Test Method D903 which measures the peel strength between the two plaques of the laminate in terms of pounds per half-inch strip and which is employed herein as a measure of thestriPpability of a semi-conducting ethylene-vinyl acetate insulation sheilding from a crosslinked poly-ethylene insulation. The test results of each laminate of polyethylene/ethylene-vinyl acetate sheilding prepared as di~cussed above are also listed in said Table I.
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/J
~ 6~ 6 9892 Examples 5, 7, 9 and 12 to 15 which represent the present inven~ion demonstrate the excellent stripp-ability of the insulation shielding compositions, the insulation shielding layer in each example having been stripped clean and in one piece from the insulation.
This example illustrates the preparation of an insulated electrical cable.
A standard aluminum conductor was se~uentially covered with an ordinary semiconducting strand shielding layer (0.025" thick), a polyethylene insulating layer (0.267" thick), and a semiconducting insulation shielding layer (0.055" thick) consisting of polyethylene/vinyl acetate (2~/o vinyl acetate, MI = 20) and 0.6% Vulcup-In preparing the cable the extruded strand shielding layer and insulation layer were cured in a steam w lcanization tube t250 lbs./sq. in. of steam) prior to extruding the insulation shielding layer over the insulation, said insulation shielding layer then being cured during a second pass through the steam vulcanization tube. This process procedure is conventionally known in the art as a two pass extrusion.
Iwo parallel incisions in the insulation shield-ing of the insulated cable so prepared were mad~ one-half inch apart running in the axial direction of the cable -; and said insulation shielding was subjected to a tensile ; peeling test to determine the adhesion of the insulation.
- The insulation shielding wa~ stripped clean and in one . .
piece from the insulation and exhibited an adhesion level of 6-8 pounds per half-inch strip, thus demonstrating the ', ' ~
1~. .
~ 6 9892 excellent strippability of the insulation shielding composition of this invention.
A comparative insulated electrical cable pre-pared and tested in the same manner, but using an insu-lation shielding composition consisting of vinyl acetate and 2% Dicup resulted in a cable having an insulation shielding that exhibited an adhesion level of 20-25 pounds per half-inch strip and which did not strip clean butbroke off in pieces from the insulation.
This example illustrates the preparation of an insulated electrical cable.
A standard aluminum conductor was sequentially covered with an ordinary semiconducting strand shielding ; layer (0.025" thick), a polyethylene insulating layer . .
(0.267" thick), and a semi~onducting insulation shielding layer (0.055" thick) consisting of polyethylene/
vinyl acetate (29% vinyl acatate, MI = 20) and 0.6%
Vulcup.
In preparing the cable, all three layers of strand shielding, insulation and insulation shielding were extruded sequentially and simultaneously cured in a steam vulcanization tube (250 lbs./sq. in. of steam).
This process procedure is conventionally known in the art as a single pass triple extrusion.
The adhesion o~ the insulation shielding to the insulation of the insulated cable was determined by the same method described in Example 17. The insulation shielding was stripped clean and in one piece from the insulation and exhibi.ted an adhesion level o 14-16 .
~ 69 6 poun~ pcr h~lf-inch strlp, thus demonstratlng the excellent strippabllity of the insulation sheilding com-position of ~his invention.
A comparative insulated electrical cable pre-pared and tested in the same manner, but using the insu-lation shielding composition consisting of vinyl acetate and 2% Dicup resulted in a cable having an insulation shielding that exhibited such a strong adhesion to the insulation that its strippability could not be measured by the peel test, the two layers being intimately fused at the interface.
Various modifications and variations of this invention will be obvious to a worker skilled in the art and it is to be understood that such modifications and -- :
variations are to be included within the purview of this appllcation and the spirit and scope of the appended , . .
claims.
, ' .
' ~.,' ' :,'~ ' :
.' ' ' .
~:
; .
~'' '.
16.
Claims (16)
1. A vulcanizable semi-conducting insulation shielding composition comprising,based on the total weight of said composition,(A) about 55 to about 90 weight percent of an ethylene-vinyl acetate copolymer containing from about 27 to 45 weight percent of vinyl acetate based on the total weight of said copolymer, (B) about 10 to 45 weight percent of conducting carbon black and (C) as the only crosslinking agent in said composition from 0.2 to 5 weight percent of an agent selected from the group consisting of .alpha.,.alpha.' bis-(tertiary-butylperoxy) diisopropyl benzene and 2,5-dimethyl-2', 5'-di(tertiary-butylperoxy) hexane and mixtures thereof.
2. A vulcanizable semi-conducting insulation shield-ing composition as defined in claim 1, wherein said composition comprises about 60 to 75 weight percent of an ethylene-vinyl acetate copolymer containing from about 29 to 35 weight percent of vinyl acetate based on the total weight percent of said copolymer, about 30 to 40 weight percent of conducting carbon black and about 0.6 to 2 weight percent of said crosslinking agent.
3. A vulcamizable semi-conducting insulation shield-ing composition as defined in claim 2 wherein said cross-linking agent is .alpha.,.alpha.' bis-(tertiary-butylperoxy) diisopropyl benzene.
4. A vulcanizable semi-conducting insulation shielding composition as defined in claim 2 wherein said crosslinking agent is 2,5-dimethyl-2', 5'-di(tertiary_ butylperoxy) hexane.
17.
17.
5. A vulcanizable semi-conducting insulation shielding composition as defined in claim 3 wherein said ethylene-vinyl acetate copolymer contains about 29 weight percent of vinyl acetate based upon the total weight of said copolymer.
6. A vulcanizable semi-conducting insulation shielding composition as defined in claim 3 wherein said ethylene-vinyl acetate copolymer contains about 33 weight percent of vinyl acetate based upon the total weight of said copolymer.
7. A vulcanizable semi-conducting insulation shielding composition as defined in claim 4 wherein said ethylene-vinyl acetate copolymer contains about 29 weight percent of vinyl acetate based upon the total weight of said copolymer.
8. A vulcanizable semi-conducting insulation shielding composition as defined in claim 4 wherein said ethylene-vinyl acetate copolymer contains about 33 weight percent of vinyl acetate based upon the total weight of said copolymer.
9. An insulated electrical conductor containing as the primary insulation, crosslinked polyethylene and as the external semi-conducting shielding for said in-sulation, a crosslinked ethylene-vinyl acetate copolymer obtained upon crosslinking the vulcanizable semi-conducting insulation shielding composition as defined in 18.
claim 1, with the proviso that the adhesion between a laminate of said crosslinked polyethylene and said crosslinked ethylene-vinyl acetate copolymer is not greater than 16 pounds per half inch strip when measured according to ASTM Test Method D903.
claim 1, with the proviso that the adhesion between a laminate of said crosslinked polyethylene and said crosslinked ethylene-vinyl acetate copolymer is not greater than 16 pounds per half inch strip when measured according to ASTM Test Method D903.
10. An insulated electrical conductor con-taining as the primary insulation, crosslinked poly-ethylene and as the external semi-conducting shielding for said insulation, a crosslinked ethylene-vinyl acetate copolymer obtained upon crosslinking the vulcanizable semi-conducting insulation shielding compo-sition as defined in claim 2, with the proviso that the adhesion between a laminate of said crosslinked poly-ethylene and said crosslinked ethylene-vinyl acetate copolymer is not greater than 16 pounds per half inch strip when measured according to ASTM Test Method D903.
11. An insulated electrical conductor containing as the primary insulation, crosslinked polyethylene derived from a polyethylene homopolymer and as the external semi-conducting shielding for said insulation, a crosslinked ethylene-vinyl acetate copoly-mer obtained upon crosslinking the vulcanizable semi-con-ducting insulation shielding composition as defined in claim 3, with the proviso that the adhesion between a laminate of said crosslinked polyethylene and said crosslinked ethylene-vinyl acetate copolymer is not greater than 16 pounds per half inch strip when 19.
measured according to ASTM Test Method D903.
measured according to ASTM Test Method D903.
12. An insulated electrical conductor containing as the primary insulation, crosslinked poly-ethylene derived from a polyethylene homopolymer and as the external semi-conducting shielding for said insul-ation, a crosslinked ethylene-vinyl acetate copolymer obtained upon crosslinking the vulcanizable semi-conducting insulation shielding composition as defined in claim 4, with the proviso that the adhesion between a laminate of said crosslinked polyethylene and said crosslinked ethylene-vinyl acetate copolymer is not greater than 16 pounds per half inch strip when measured according to ASTM Test Method D903.
13. An insulated electrical conductor containing as the primary insulation, crosslinked poly-ethylene derived from a polyethylene homopolymer and as the external semi-conducting shielding for said insula-tion, a crosslinking the vulcanizable semi-conducting insulation shielding composition as defined in claim 5, with the proviso that the adhesion between a laminate of said crosslinked polyethylene and said crosslinked ethylene-vinyl acetate copolymer is not greater than 16 pounds per half inch strip when measured according to ASTM Test Method D903.
14. An insulated electrical conductor con-taining as the primary insulation, crosslinked poly-ethylene derived from a polyethylene homopolymer and as the external semi-conducting shielding for said insulation, a crosslinked ethylene-vinyl acetate copolymer obtained upon crosslinking the vulcanizable 20.
semi-conducting insulation shielding composition as defined in claim 6, with the proviso that the adhesion between a laminate of said crosslinked polyethylene and said crosslinked ethylene-vinyl acetate copolymer is not greater than 16 pounds per half inch strip when measured according to ASTM Test Method D903.
semi-conducting insulation shielding composition as defined in claim 6, with the proviso that the adhesion between a laminate of said crosslinked polyethylene and said crosslinked ethylene-vinyl acetate copolymer is not greater than 16 pounds per half inch strip when measured according to ASTM Test Method D903.
15. An insulated electrical conductor containing as the primary insulation, crosslinked poly-ethylene derived from a polyethylene homopolymer and as the external semi-conducting shielding for said insula-tion, a crosslinked ethylene-vinyl acetate copolymer obtained upon crosslinking the vulcanizable semi-conducting insulation shielding composition as defined in claim 7, with the proviso that the adhesion between a laminate of said crosslinked polyethylene and said crosslinked ethylene-vinyl acetate copolymer is not greater than 16 pounds per half inch strip when measured according to ASTM Test Method D903.
16. An insulated electrical conductor containing as the primary insulation crosslinked poly-ethylene derived from a polyethylene homopolymer and as the external semi-conducting shielding for said insulation, a crosslinked ethylene-vinyl acetate copolymer obtained upon crosslinking the vulcanizable semi-conducting insulation shielding composition as defined in claim 8, with the proviso that the adhesion between a laminate of said crosslinked polyethylene and said crosslinked 21.
ethylene-vinyl acetate copolymer is not greater than 16 pounds per half inch strip when measured according to ASTM Test Method D903.
22.
ethylene-vinyl acetate copolymer is not greater than 16 pounds per half inch strip when measured according to ASTM Test Method D903.
22.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US57519375A | 1975-05-07 | 1975-05-07 | |
| US575,193 | 1975-05-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1084696A true CA1084696A (en) | 1980-09-02 |
Family
ID=24299310
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA248,307A Expired CA1084696A (en) | 1975-05-07 | 1976-03-19 | Insulated electrical conductors |
Country Status (10)
| Country | Link |
|---|---|
| JP (1) | JPS51138894A (en) |
| AU (1) | AU510947B2 (en) |
| BE (1) | BE841518A (en) |
| CA (1) | CA1084696A (en) |
| DE (1) | DE2620105B2 (en) |
| FR (1) | FR2310618A1 (en) |
| GB (1) | GB1543212A (en) |
| IT (1) | IT1061028B (en) |
| NO (1) | NO141871C (en) |
| SE (1) | SE7605205L (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4990231A (en) * | 1981-06-12 | 1991-02-05 | Raychem Corporation | Corrosion protection system |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5325886A (en) * | 1976-08-21 | 1978-03-10 | Sumitomo Electric Ind Ltd | Brid ged polyolefine insulating hightension cable having outer semiconductor layers which can be treated off easily |
| EP0129617B1 (en) * | 1983-06-13 | 1988-02-03 | Du Pont-Mitsui Polychemicals Co., Ltd. | Semiconducting compositions and wires and cables using the same |
| US5575965A (en) * | 1995-05-19 | 1996-11-19 | Union Carbide Chemicals & Plastics Technology Corporation | Process for extrusion |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4210587Y1 (en) * | 1965-02-15 | 1967-06-12 | ||
| DE2051268B2 (en) * | 1970-06-13 | 1972-09-14 | Sumitomo Electric Industries Ltd., Osaka (Japan) | INSULATED CABLE |
| US3719769A (en) * | 1970-10-05 | 1973-03-06 | Sumitomo Electric Industries | Insulated electric cable having an external semiconductive layer |
| JPS4827111A (en) * | 1971-08-13 | 1973-04-10 |
-
1976
- 1976-03-19 CA CA248,307A patent/CA1084696A/en not_active Expired
- 1976-05-04 AU AU13598/76A patent/AU510947B2/en not_active Expired
- 1976-05-06 JP JP51050973A patent/JPS51138894A/en active Granted
- 1976-05-06 FR FR7613582A patent/FR2310618A1/en active Granted
- 1976-05-06 BE BE166780A patent/BE841518A/en not_active IP Right Cessation
- 1976-05-06 DE DE2620105A patent/DE2620105B2/en active Pending
- 1976-05-06 NO NO761574A patent/NO141871C/en unknown
- 1976-05-06 SE SE7605205A patent/SE7605205L/en unknown
- 1976-05-06 IT IT23036/76A patent/IT1061028B/en active
- 1976-05-06 GB GB18618/76A patent/GB1543212A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4990231A (en) * | 1981-06-12 | 1991-02-05 | Raychem Corporation | Corrosion protection system |
Also Published As
| Publication number | Publication date |
|---|---|
| NO141871B (en) | 1980-02-11 |
| AU1359876A (en) | 1977-11-10 |
| SE7605205L (en) | 1976-11-08 |
| NO761574L (en) | 1976-11-09 |
| DE2620105A1 (en) | 1976-11-18 |
| BE841518A (en) | 1976-11-08 |
| AU510947B2 (en) | 1980-07-24 |
| JPS51138894A (en) | 1976-11-30 |
| GB1543212A (en) | 1979-03-28 |
| IT1061028B (en) | 1982-10-20 |
| DE2620105B2 (en) | 1978-04-06 |
| FR2310618A1 (en) | 1976-12-03 |
| FR2310618B1 (en) | 1982-04-16 |
| NO141871C (en) | 1980-05-21 |
| JPS5619939B2 (en) | 1981-05-11 |
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