CA1045917A - Copper conductors in contact with a polyethylene composition - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Copper conductors in contact with polyethylene insulation containing between 0.2 to 0.8% by weight of an antioxidant such as 2:2'-methylene bis 6(.alpha.-methyl cyclohexyl)-4-methyl phenol or similar dihydroxy phenols.

Description

Po 26415 ~ 4 S ~ ~7 This invention relates to copper conductors in contact with a polyethylene compo~ition.
~ver since the di~co~ery of polyethyle~e, it has been u~ed as insulation for copper conductors used in telephone cable~ and rad~r installati~ns.
Polyethylene u~ed as insulation normally contains small amounts of an antioxidant co~pound which le3sens the degradative effects o~ oxygen on the polyethyle~e and polyethylene insulation which is in contact with copper frequently co~tains a ~o-called copper stabiliser such as N,N'diacetyl(adipoyl dihydrazide) or nickel bis-(3:5-ditertiarybutyl-4-hydroxy be~zyl phosphonic acid monoethylate) which lessen~ the embrittlement which occurs in the presence of copper~ ~hese so-called copper ~tabilisers tend to be expensive materials.
Antioxidants such as 2:2'-methylene bis[6-(a~methyl cyclohexyl)-4-methyl phenoll and the similar compounds described in British patent specification 744 875 have been commercially available ~or over fifteen years and have been used in non-irradiated polyethylene insulation in amounts of up to 0.1% though as much as 1%~by weight of the antioxidants have been proposed ~or use in thermoplastic rubbers where the loss of antioxidant by "blooming" (i.e. exuding of the - ~ . .: .. .. .: - . . . . : .. . . . . : .

Po 26415 ~ S~3~7 antioxidant from the thermopla~tic) i8 a le~s serious problem and where it i~ believed the ~ntioxidant~
al~o retard the onset of copper catalysed oxidation of rubber.
It has now been discovered that the presence of certain ~pecified amounts of 2:2'-methylene bi~[6-(a-methyl cyclohexyl)-4-methyl phenol] and similar antioxidants in polyethylene which is in contact with copper does not lead to excessive amounts of bloomi~g and it reduces the embrittlement of the polyethylene by the copper.
Accordingly by thi~ invention we provide a copper conductor in contact with a polyeth~lene composition wherein the polyethylene composition comprises between 0.2 to 0.8% by weight of an antioxidant which is a dihydroxy phenol or a normal or basic aluminium, barium, calcium, magnesium, strontium or zinc salt thereof, the dihydroxy phenol having the general formula ~< ~ :
~ _ ~5_ y ~

Po 26415 J
~f~45 ~ 17 in which R1 and R~ are alkyl radisals, preferably primary alkyl radicals containing from 1 to 3 carbo~
atoms, ~ and R3 are alkyl, cycloalkyl or alkyl substituted cycloalk~l radicals and R5 is an alkylene radical which may contai~ side-chain alkyl groups.
The radicals R1 and R4 may be the same or different but are pre~erably both m~th~l groups. Tha radicals ~ and R3 may also be the same or differe~t. ~5,may be ~or example a methylene, ethylene, isoprop~lene or 4-methyl pent~lene radical. A preferred a~tioxidant ~-i~ 2:2'-methylene bi~6-(a-methyl c~clohex~ 4-methyl phenol].
Preferably the polyethylene compositio~ comprises from 0~3 to 0.5% by weight of the antioxidant.
It is particularly preferred tha~ the polyethylene composition be foamed. The polyethylene composition may be foamed by means of blowing agents such as a~odicarbonamide or diphenyl oxide-4,4'-disulphohydrazide.
Other blowing agents are described in an article by Dr A H Scheurlen in ~unststoffe Volume 47 No. 8 of 1957 pages 446 to 455.
~he invention is illustrated by the following -example.
:E~AMPIæ
A polyethylene composition having a melt flow Po 26415 1~59~7 index of 0.3 (when mea~ured according to Briti~h Standard 2782: Part 1/105C/1970 using a 2.16 Kg load) and a density of 0.932 Kg/cm2 (when measured according to British Standard ~412 of 1966) and containing 0.3~ by weight o~ 2,2'-methylene bi~t6(~-methyl cyclohexyl)-4-methyl phenol] and 0.~/o by weight of azodicarbonamide was extrusion coated onto copper :~
wire 90 as to produce a foamed polyethylene covering which wac 0.1 mm thick. Samples of the covered conductor were then suspended in an oven maintained ~: .
at 105C for 1,000 hours. ~he sample~ were then removed and it was found that they could all be bent through 360 without crack~ forming. Hence it wa~
concluded that no serious embrittlement of the polyethylene had occurred.

~.

Claims (4)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A copper conductor in contact with a polyethylene composition wherein the polyethylene composition comprises between 0.2 to 0.8% by weight of an antioxidant which is a di-hydroxy phenol or a normal or basic salt of a member selected from the group consisting of aluminium barium, calcium, magne-sium, strontium and zinc, the dihydroxy phenol having the general formula in which R1 and R4 are alkyl radicals, preferably primary alkyl radical s containing from 1 to 3 carbon atoms, R2 and R3 are alkyl, cycloalkyl or alkyl substituted cycloalkyl radicals and R5 is an alkylene radical which may contain side-chain alkyl groups.

2. A copper conductor in contact with a polyethylene composition as claimed in Claim 1 wherein the antioxidant in the polyethylene composition is 2:2'-methylene bis[6-(.alpha.-methyl cyclohexyl)-4-methyl phenol].

3. A copper conductor in contact with a polyethylene composition as claimed in Claim 1 wherein the polyethylene composition comprises from 0.3 to 0.5% by weight of the anti-oxidant.

4. A copper conductor in contact with a polyethylene composition as claimed in Claim 1 wherein the polyethylene composition is foamed.