CA1111175A - Electrical conductor with an irradiation crosslinked insulation - Google Patents

Abstract

Abstract of the Disclosure An electrical conductor has an irradiation crosslinked insulation with improved blocking and abrasion characteristics while maintaining elongation and flexibility characteristics. The insulation is composed of a blend of PVC
and CPE with difunctional and trifunctional acrylic monomers, the PVC/CPE network having a PVC content over 50X and less than 79X, by weight, of the total composition and CPE being between 30% and 9X by weight.

Description

~1111175 This invention relates to an electrical conductor having an irradiation crosslinked insulation and is particularly concerned with improved characteristics.
- It has been proposed to use an irradiation cross-linkable PVC formation, of which 80% is PVC (polyvinyl chloride), using a crosslinkable medium which is between lO and 50 phr (parts per hundred) of the total composition. Such medium itself must contain at least 50% difunctional monomer. A further inclusion in the crosslinkable medium has been proposed of at least one cyclic lO ether to stabilize against development of colour centres, this further inclusion of about 20% of the total medium. Such formulation$ are disclosed in United States Patent No. 3,623,940 issued November 30, l97l and Canadian Patent No. 97l,694 issued July 22, l975.
Compounds using existing formulating procedures do not adequately deal wi th the problem of maintaining acceptable wire elongation and flexibility together with high abrasion and low blocking characteristics.
The present invention provides an irradiation 20 crosslinkable formulation using a blend of PVC and CPE (chlorinated polyethylene) to maintain elongation and flexibility of the insulation while significantly improving the blocking and abrasion characteristics. The formulation is sensitized for irradiation by using a blend of difunctional and trifunctional monomers, with suitable stabilizers. No permanent plasticizer is necessary.
The invention will be readily understood by the following description of certain embodiments, by way of example, in conjunction with the accompanying drawing which is a transverse cross-section through an insulated conductor in accordance with 30 the invention.

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, . . ., .. . . . , . . - . . . . . . - -` 1111175 The invention is generally utilized to provide a conductor having a single layer of insulation, the insulation being of the particular formation, as illustrated in the drawing, the conductor core indicated at 10 and the particular insulation at 11.
The material of the conductor core 10 is not critical, for example copper or aluminum, or alloys of either of these materials. The conductor may be tinned.
The particular insulation, layer 11, is a compound having a base polymer which is a blend of PVC and CPE, with CPE ~ -comprising about 20% of the blend. Also included is a crosslinking medium which is a blend of difunctional and trifunctional acrylic monomers of about equal proportions. Lead salts, for example tetrabasic lead fumarate, is included as a stabilizer, when desired, and finely divided calcium carbonate is used as a filler, also when desired. A fire retardant material, such as antimony trioxide, can be included.
Conventional manufacture processes are used, for example dry blending, pellet manufacture, extrusion and then irradiation - up to 10 MRad dose level.
Two typical compounds are as follows:-#1 #2 (phr) % (phr) %
PVC 100 63.57 100 53.97 CPE 30 19.07 30 16.19 TEGDM 10 6.36 10 5.40 TMPTM 10 6.36 10 5.40 Stabilizer 7 4.45 7 3.78 Calcium Carbonate - - 25 13.49 Antioxidant .3 .19 .3 .16 Antimony Trioxide - - 1.61 where TEGDM = Tetraethylene Glycol Dimethacrylate - -- a difunctional monomer TMPTM = Trimethylopropane Trimethacrylate - a trifunctional monomer.
No permanent plasticizer is required.
Possible ranges of the various constituents of the compound are as follows, in parts per hundred:- PVC 70-91;
CPE 30-9, TEGDM 5-14; TMPTM 5-14, stabilizer 5, antimony trioxide 0-3, antioxidant up to .5. The PVC/CPE network provides for a PVC
content always over 50% by weight of the total composition but which is less than 79%, and in many cases is less than about 65%.
The use of CPE resin (42% ch10rine) provides great improvement in flexibility and antiblocking, with a very large improvement being obtained with the use of 30 parts of CPE.
The use of CPE, in place of more traditional plasticizers provides improvements in aging characteristics and fire retardant performance. The insulation meets all the requirements of solder iron resistance, low blocking, high abrasion resistance and high elongation. The insulated conductor is particularly suitable for freme wfring in d telecommunications sys~em.

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Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN
EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS
FOLLOWS:-

1. An electrical conductor with an irradiation crosslinked insulation comprising an electrically conducting core and an insulating layer formed from a compound composed of a blend of polyvinyl chloride and chlorinated polyethylene and a mixture of monomers which are tetraethylene glycol dimethacrylate and trimethylopropane trimethacrylate in substantially equal proportions in the mixture, each of the monomers being present in a proportion between 5 and 14 parts by weight per 100 parts of the compound, the polyvinyl chloride/chlorinated polyethylene network having a polyvinyl chloride content being over 50% and less than 79%, by weight, of the total composition, and chlorinated polyethylene being between 30% and 9% by weight.

2. A conductor as claimed in claim 1, said polyvinyl chloride content over 50% and less than about 65%.

3. A conductor as claimed in claim 1, the chlorinated polyethylene content a maximum of 30 parts per hundred.

4. A conductor as claimed in claim 1, said insulating layer including a stabilizer.

5. A conductor as claimed in claim 1, said insulating layer including a fire retardant material.

6. A conductor as claimed in claim 1, said insulating material including a filler.