GB2433511A

GB2433511A - Cold-setting composition for filling electric cable joints

Info

Publication number: GB2433511A
Application number: GB0625440A
Authority: GB
Inventors: Paul Naylor; Peter Worrall
Original assignee: WT Henley Ltd
Current assignee: Sicame UK Ltd
Priority date: 2005-12-21
Filing date: 2006-12-20
Publication date: 2007-06-27
Anticipated expiration: 2026-12-20
Also published as: GB0625440D0; GB0525931D0; GB2433511B

Abstract

A cold-setting composition for use in filling electric cable joints, comprises as resin base monomer, at least one (meth)acrylic acid ester of an alkanol having 6-24 carbon atoms, such as isodecyl or tridecyl methacrylate, together with a di- or tri(meth)acrylate cross-linker in an amount of 0.2-5 parts by weight per hundred parts of resin base monomer, an initiator and at least one mineral filler: characterised in that the composition further comprises a reactive diene, such as 1,4-polybutadiene, in an amount of 0.1-10 parts by weight per hundred parts of resin base monomer, and the composition being substantially free from non-reactive solvent.

Description

RESIN COMPOSITIONS AND ELECTRIC CABLE JOINTS

The present invention relates to cold polymerising synthetic resin compositions suitable for use as the filling medium for joints in electric power cables, and to joints produced using these resins A variety of different resin types have been used in the preparation of joints in power cables, especially power cables for service at low and medium voltage. For example, polyurethane-based casting resins are widely used, but are potentially hazardous because of the highly reactive isocyanate ingredient. Epoxy-based systems are comparably hazardous. W098/25989 describes an alternative class of composition that is claimed to be relatively hazard-free, but this is a proprietary material whose longterm effects may not yet be fully understood. Acrylic resins are sometimes used, but these are mostly based wholly or in part on methyl methacrylate and/or iso-butyl methacrylate, usually with ethylene glycol dimethacrylate as cross-linking agent. Each of these ingredients is classed as "irritant", liable to cause sensitisation on skin contact, and suspected of being teratogenic. One example of this type of resin is described in EP1070730 (Pirelli cables (2000) Ltd) the entire text of which is hereby imported by reference and intended to form an integral part of this disclosure. The compositions described in EP1070730 include compositions that incorporate a non-reactive solvent to improve the adhesion of the cold polymerising resin compositions to various components (especially polyolefins) of the cable and/or joint. In the above invention the solvent types are specifically "non-reactive" i.e. they contain no functional groups or features that allow them to participate with the free radical polymerisation reaction However, the presence of a non-reactive solvent causes the properties of the polymerised resin to change over time, as the solvent migrates. We have unexpectedly discovered a range of resin compositions containing not non-reactive solvents but reactive dienes which improve the compatibility of cold polymerising resin compositions with common polymeric cable materials. These new compositions appear to be free of health hazards, of high enough flash point to avoid significant flammability risks, mobile enough to fill cavities reliably, and which adhere sufficiently to all the usual cable materials, including in particular polyethylenes that have been cross-linked by a silane grafting technique (the so-called Sioplas" or Monosil' process).

In summary, compatibility of polymeric insulation and polymeric jacketing materials with the cured resin composition is of great importance as there will be intimate chemical contact at potentially elevated temperatures for the service life of the cable accessory. The invention detailed in EP1 070730 uses a non-reactive solvent to improve the adhesion of the resin composition to Silane grafted cross-linked polyethylene. In contrast, we have found that by use of a reactive diene instead of a non-reactive solvent it is possible to produce a resin composition which exhibits improved long term compatibility with polymeric insulating and jacketing materials.

In accordance with a first aspect of the present invention there is provided a cold-setting composition for use in filling electric cable joints and which sets to form a resin having surface tack, the composition comprising, as resin base monomer, at least one acrylic acid ester of an alkanol, together with a di-or tri(meth)acrylate cross-linker present in an amount of between 0.2 and 5 parts by weight per hundred parts of resin base monomer, an initiator and at least one mineral filler; characterised in that the composition further comprises a reactive diene present in the composition in an amount of 0.1 to 10 parts by weight per hundred parts of resin base monomer, the composition being substantially free from non-reactive solvent.

Preferably the composition is a two-part composition with Part A comprising the base resin monomer, the cross-linker and the reactive diene, and Part B the filler and initiator.

Preferably the said alkanol has 9 -24 carbon atoms.

In a further preferred embodiment the said alkanol has 10 -22 carbon atoms.

Preferably the said (meth) acrylate is isodecyl rnethacrylate.

In an alternative preferred embodiment the said (meth)acrylate is tridecyl methacrylate.

In a further alternative preferred embodiment the (meth)acrylate is behenyl methacrylate.

It is intended that the above examples of methacrylate esters are not limiting, but rather serve to illustrate the wide range of esters which may be used in this context.

Preferably the cross-linker is derived from polyethylene glycol.

Preferably the cross-linker is derived from the grade of polyethylene glycol sold as "PEG200".

Preferably said mineral filler is selected from the group comprising chalk, sand, solid or hollow glass beads or fly ash.

Preferably said mineral filler comprises a sand filler of well rounded particle type with particle sizes in the range 130 -400 micro metres.

Preferably said mineral filler comprises solid or hollow glass microspheres.

In an alternative preferred embodiment said mineral filler comprises ground limestone with particle sizes predominantly in the range 2 -50 micro metres.

In a further alternative embodiment said mineral filler is selected from the group comprising alumina trihydrate, barium titanate, antimony trioxide, zinc borate, gypsum, wollastonite, clays, mica, quartz, silica, silicon carbide, Zirconium silicate, carbon black, synthetic zeolites and oxides of aluminium, zinc and titanium.

Preferably the reactive diene comprises a polybutadiene. More preferably the diene component comprises a polybutadiene with a preponderance of 1,4-cis double bonds such as Polyoil 110 or Polyoil 130 as sold by Degussa Corporation, Parsippany, NJ 07054-0677, USA.

In an alternatively preferred embodiment the reactive diene comprises a maleic anhydride adduct of a I,4-polybutadiene. Examples of such maleic anhydride adducts are Polyvest OC 800 S and Polyvest EP-OC 1200 S as sold by Degussa Corporation.

It will be appreciated that other butadienes may also be advantageously employed in this context, such as hydroxyl tipped butadienes, epoxy functional butadienes and carboxyl functional butadienes. Preferably the proportion of 1,4-cis double bonds in the butadiene is greater than 50% and more preferably in the region of It is intended that the above examples are not limiting, but rather serve to illustrate the wide range of butadienes which may be used in this context.

Preferably the initiator is a peroxide.

Preferably the composition further comprises a catalyst and preferably said catalyst comprises a condensation product of para-toluidine with ethylene oxide.

In a further preferred embodiment the composition further comprises one or more plasticisers. A wide variety of plasticisers for resins are already known and would be suitable candidates as selected by the materials specialist. In a particularly preferred embodiment the plasticiser may include a carbon -carbon double bond such that the plasticiser may also take part in the polymerisation process. An example of such a plasticiser is di-allyl phthalate.

The invention includes an electric cable joint filled with a cold-setting resin composition as claimed herein.

The compatibility of resin compositions containing low molecular weight polybutadiene oils consisting of 1,4 cis and 1,4 trans unsaturation have been compared with resin compositions containing di-methyl ester solvents (santosol DME-1) against silane cross-linked polyethylene and typical PVC material used in cable jacketing applications. Resin compositions containing polybutadiene oils exhibit better compatibility compared to dimethyl ester solvents such as Santosol DME-1.

Compatibility was assessed by soaking specimens of fixed geometry in the respective materials for a fixed period of time and measuring the resultant weight change. These results are shown in Table II below.

It is essential that a cable jointing resin remains a good electrical insulator whilst operating under damp conditions at elevated temperatures. A screening test has therefore been developed to measure this property of a cold polymerising resin composition. A sample of the resin composition is poured in to a suitable plastic cup, two electrodes are cast into the sample so they penetrate approx 25 mm into the bulk of the material, these are supported by an insulating disk thus maintaining a reproducible electrode separation. When polymerisation is complete the plastic cup is removed and the test sample placed in to a lidded bucket containing water. This is placed in a constant temperature enclosure and stored for a predetermined period of time. At the end of the period the electrical resistance between the electrodes is measured.

Compositions which still maintain good electrical insulation after 2 months at 50 deg C are deemed to have suitable hydrophobicity.

The use of a reactive diene allows the additive to be bound to the polymer matrix, which prevents migration over time. Polybutadiene oils as described above contain 1,4 unsaturation and are reactive and capable of participating in free radical polymerisation reactions. These materials have been used as co-agents in peroxide cured elastomers.

Preferred dienes are 1,4 polybutadienes manufactured by Degussa with the trade name "polyoil", the preferred material is polyoil 110. Maleic anhydride adducted polybutadienes may also be used as may hydroxyl functional butadienes or other functional butadienes, as described herein.

The resin base consists of at least one (meth)acrylic ester of an alkanol having 6 to 24 carbon atoms together with a di-or tn- functional acrylate or methacrylate cross-linker present in an amount of between 0.2 and 5 parts by weight per hundred parts of resin base an initiator, at least one mineral filler; provided that a reactive diene is present in the resin composition in an amount of 0.1 to 10 parts by weight per one hundred parts by weight of the resin base.

The most favourable presentation of the resin composition is in the form of a two-part resin system. Part A consists of the resin base, the cross-linker and reactive diene, and part B the filler and initiator. Known two compartment packaging can be used.

Preferably the resin base consists of one or more methacrylic esters of alkanols containing 9-24 carbon atoms and more preferably 10-22 carbon atoms. For example, isodecyl methacrylate is available in commercial quantities and is the preferred choice by way of its low volatility, low viscosity, flash point in excess of 100 Deg C, low density and the ability to retain a large quantity of filler material. Other methacrylates such as tridecyl, lauryl, stearyl and behenyl are also obtainable and would be suitable.

The resin base may contain one or more acrylic esters of an alkanol containing 6 to 24 carbon atoms, although use of these is less preferable than the corresponding methacrylic esters. The above examples are not intended to be limiting in any way and simply serves to illustrate that a wide range of such chemical entities can be used.

The di-or tn-functional (meth)acrylate cross-linker may be any di-or tn- (meth)acrylate that is miscible or soluble in the resin base, (meth)acrylic monomers or oligomers of higher functionality may used. The required quantities of these would decrease with increasing functionality. A range of (meth)acrylic monomers or oligomers are suitable including ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, diethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1, 4 butanediol dimethacrylate, 1,6 hexanediol dimethacrylate, 1,6 hexane diol dimethacrylate, and 1,3 butylene glycol dimethacrylate. Higher molecular weight (meth)acrylates are also suitable, these include (meth)acrylates derived from polyethylene glycol, such materials include PEG200 dimethacrylate, PEG400 dimethacrylate, and PEG 600 dimethacrylate.

It is also possible to use the diacrylate analogues of any of the above materials. Once again, the above examples are not intended to be limiting in any way and simply serves to illustrate that a wide range of such chemical entities can be used.

The term "reactive diene" is used in this context to indicate any diene which is miscible with (meth)acrylate and cross-linker components. This component of the mixture should feature chemical functionality which allows the diene to react with free radicals and therefore participate in the free radical polymerisation reaction.

A wide variety of low cost inorganic fillers of mineral origin can be used, such as can solid or hollow glass beads derived from fly ash. Sand fillers derived from glacial deposits where there has been considerable rounding of the grains have been found to be particularly suitable. Ground calcium carbonate fillers with a particle size distribution from I to 100 microns have been found to be suitable. Silica sands such as Chelford and Congleton CHST 50 have been found to be suitable in this invention.

Hollow or solid glass rnicrospheres can be used atone or preferably combined with a selection of other mineral fiHers examples such as sand and calcium carbonate.

The use of hollow glass microspheres leads to a mixed resin of lower density which allows lower consignment weights for a given volume and places less mechanical stress on primary packaging materials. We have found that fillite SG sold under the trade name FILLITE (RTM) to be a suitable material. Grades offering similar particle size distributions from this or other manufacturers would also be suitable.

Alumina trihydrate can be used to impart flame retardance with out the use of halogenated materials. Suitable high permittivity fillers may be used to obtain a resin composition of high permittivity. This feature of such a composition may be used in applications where electrical stresses are required to be controlled. A suitable example of such a filler are barium titanate. Other fillers which appear to be suitable for use in this invention would be assorted clays, quartz, silica, gypsum, carbon black, mica, silicon carbide, oxides of aluminium zinc and titanium or zirconium silicate It will be appreciated that the fillers described above may be used alone or in any combination as determined by a materials specialist The use of suitable wetting and dispersing agents allow an increase in the filler loading whilst maintaining a mixed resin with easy poring characteristics. We have found that materials such BYK 9010 which is solvent free are suitable for this purpose.

Increased filler loadings lead to a lower polymerisation exotherm which is a desirable property of resin utilised for cable jointing applications.

The free radical polymerisation reaction is initiated by a source of free radicals.

These can be generated by the decomposition of a suitable organic peroxide or originate from another suitable source. We have found that di-benzoyl peroxide supported on an inorganic filler is a suitable initiator. For curing at ambient or lower temperatures, an accelerator is required. This accelerator is a substance which causes the peroxide to decompose and generate free radicals, which initiate the polymerisation. Similarly a di-acyl peroxide could be used with an amine initiator.

Ketone peroxides are also suitable when used with alternative accelerators such as cobalt napthenate. Peroxides present in the form of powder would be incorporated with the inorganic filler materials.

Tertiary amines are effective accelerators and a range of tertiary amines suitable for this purpose are commercially available. Adducted materials offer sufficient reactivity with lower toxicity and potential irritancy compared no non-adducted materials. Bisomer PTE (ethoxylated para-toluidine) is a preferred material as it is of lower toxicity and potential irritancy compared to other materials. Use of such accelerators give fast cure at temperatures encountered in Northern European climatic zones. Unmodified tertiary amines which are encapsulated or micro-encapsulated are also suitable. Where the accelerator is in a solid encapsulated form it may be added to the inorganic filler and peroxide. Where the accelerator is in liquid form it would be incorporated into the liquid monomer component.

In one embodiment the diene component comprises a polybutadiene with a preponderance of 1,4-cis double bonds such as Polyoil 110 or Polyoll 130 as sold by Degussa Corporation, Parsippany, NJ 07054-0677, USA. Polyoil and derivatives are stereospecific, low viscosity, unsaponifiable liquid polybutadienes with a high 1,4-cis double bond content. Their high reactivity results in excellent water and chemical resistance, in addition to good electrical insulating properties. Polyoil 110 is a stereospecific, low-viscosity, unsaponifiable, aliphatic-, aromatic-and ether-soluble, liquid polybutadiene having the following composition:-Approx 75% of 1,4-cis double bonds Approx 24% of 1,4-trans double bonds Approx 1% of vinyl double bonds.

It has a mean molar mass of approximately 2200 g/mol when measured using GPC and approximately 1800 g/mol when measured using vapour pressure osmometry. In contrast, Polyoii 130 has a mean molar mass of approximately 3800 or 3000 when measured under the same conditions.

In an alternative embodiment the reactive diene comprises a maleic anhydride adduct of a 1,4-polybutadiene. Examples of such maleic anhydride adducts are Polyvest OC 800 S and Polyvest EP-OC 1200 S as sold by Degussa Corporation.

Polyvest OC 800 S is a maleic anhydride adduct of a low molecular weight 1,4-cis-polybutadiene. The succinic anhydride groups randomly distributed along the polymer chain leads to higher polarity and various chemical reactions.

Polyvest OC 800 S is soluble in aliphatics, aromatics, ethers, and compatible with long-oil alkyds, rosins, resins esters, and zinc resonates.

Polyvest DC 800 S has good electrical insulation properties and low-temperature stability.

Polyvest EP-OC 1200 S is a maleic anhydride adduct of a low molecular weight cis-1,4 polybutadiene. It contains a higher percentage of succinic arihydride groups distributed randomly along the polymer chains. This makes the originally apolar polybutadiene more polar and thus accessible for various chemical reactions.

Polyvest OC 800 S has a mean molecular mass of 2200-2600 g/mol measured by GPC and 1800-2400 g/mol measured by vapour pressure osmometry. The respective value for Polyvest EP-OC 1200 S measured using GPC is approximately 2500.

A plasticiser may be added to the composition as necessary to prevent the resultant resin from becoming brittle over time. Whilst there are a wide number of plasticisers known it is advantageous if the plasticiser also takes part in the polymerisation process, such that it is bound within the resin matrix. One suitable material is di-allyl phthalate.

In the monomeric form, di-allyl phthalate is a colourless liquid ester widely used as a cross-linking monomer for unsaturated polyester resins, and as a polymerisable plasticiser for many resins. It polymerises easily, increasing in viscosity until it finally becomes a clear, infusible solid. The name DAP is used for both the monomeric and polymeric forms. In the partially polymerised form, DAP is used in the production of thermosetting moulding powders, casting resins and laminates. Used in many electronic applications where high arc resistance and dielectric strength, low dielectric loss, and good mechanical properties must be maintained under high humidity and temperature conditions.

The invention will be further described by way of the following examples:-Resin compositions were prepared according to compositions set out in Table

Table I

Formulation A B C Isodecyl methacrylate 100 100 100 PEG 200 dimethacrylate 0.6 0.6 1 Bisomer PTE 1 1 1 Dibenzoyl peroxide (50 % active on 10 10 10 mineral filler) by weight.

Superfine Calcium carbonate 100 150 100 Silica Sand 450 450 450 Hollow microspheres (fullite SG) ---Polyoilllo 2.5 3 3 Polyvest 0C800 BYK 9011 (wetting and dispersing agent) -1.5 -All formulations resulted in a cured resin that had good thermal stability and sufficient surface tack to provide good adhesion of the resin to the cable joint.

All of the examples provide resin compositions which have good flow properties and stable insulation resistance values in the order of 2.5x io M) in a typical 3-core 185 mm2 copper waveform straight joint with cross-linked polyethylene (XLPE) insulation and using about 20 litres of resin to fill the joint enclosure. The suitability of the compositions to provide good electrical insulation was determined by casting samples into plastic coffee cups with suitable electrodes embedded into the composition. Cured resin samples were stored in a closed bucket containing water at 50 C for one month.

The resistance between the electrodes was measured at the end if this period and found to be in excess of i04 Meg Ohms. This result indicates suitability for use in cable jointing applications.

The compatibility of the solvent and diene in their pure forms with cable materials was assessed by soaking weighed test pieces of polymeric materials in Santosol DME-1 and Polyoil 110 for 72 hours at room temperature. At the end of the test period, the samples were removed from the solvents, wiped and weighed.

Changes in weight for the various materials and solvents are detailed in the table below. This indicates that polyoil 110 offers better compatibility with Silane grafted cross-linked polyethylene and PVC compared to Santosol DME-1.

Test samples of PVC oversheath were also surrounded with mixed resin that was allowed to cure; these were aged at a temperature of 50 C for 7 Days. After this test the specimens were removed, cleaned and mechanically tested for tensile strength and elongation at break. This exercise was carried out using the composition C as this contained the greatest concentration of liquid materials in the uncured state and was more likely to have detrimental effects on the PVC Jacket material.

Results after encapsulation in resin at 50 C for 7days for PVC oversheath Control Sample (unaged) -Tensile strength -21.47 MPa, elongation at break = 214.6% After encapsulation and ageing -Tensile strength = 20.8 Mpa, elongation at break = 163.7% These results indicate good compatibility of the composition with PVC.

Resistance to foaming at elevated temperatures was checked by taking the formulations listed and subjecting them to 2 hours at 100 deg C. None of the compositions A, B or C exhibited any indication of foaming.

Table II

Weight change of samples soaked in pure DME-1 and Polyoil 110 Material weight change (%) Weight change (%) polyoil SANTOSOLDME-1 110 Si XLPE +0.22 +0.06 PVC + 47.0 -1.0

Notes on Table II

The XLPE and PVC used in this exercise were obtained from a piece of AEI Cables 300 Square mm waveform cable.

Santosol DME is solvent consisting of the mixed dimethyl esters of adipic, glutaric and succinic acids.

Polyoil 110 is a 1,4 polybutadiene oil exhibiting high reactivity, available from Degussa.

Results in Table II indicate that a resin incorporating the reactive diene polyoil 110 (RTM) exhibits much better compatibility with common cable materials than DME -1.

This is a desirable property of any material that contacts polymeric cable components.

The adhesion properties of Formulation C were measures. Adhesion to Silane cross-linked polyethylene and aluminium was assessed by casting resin around a sample of XLPE material or Aluminium, allowing the resin to cure and measuring the force required to pull the material out of the resin block.

Four XLPE measurements were made using strips of width 25 mm and thickness 2.3 mm which were cast into resin to a depth of 25 mm. After curing for 24 hours at room temperature the pull out force was measured using a tensiometer.

Result -Pull out force was greater than the force required to initiate cold drawing of the XLPE -this result indicates there is good adhesion to XLPE.

Four Aluminium measurements were made on strips with dimensions 25 mm x 1.5 mm which were cast into resin to a depth of 25 mm. after curing for 24 hours at room temperature the pull out force was measured with a tensiometer.

Result -average force of 883 Newtons was required to remove samples from the cured resin. This indicates good adhesion of the resin to Aluminium.

Claims

Claims: 1. A cold-setting composition for use in filling electric cable

joints and which sets to form a resin having surface tack, the composition comprising, as resin base monomer, at least one acrylic acid ester of an alkanol, together with a di-or tri(meth)acrylate cross-Unker present in an amount of between 0.2 and 5 parts by weight per hundred parts of resin base monomer, an initiator and at least one mineral filler; characterised that the composition further comprises a reactive diene is present in the composition in an amount of 0.1 to 10 parts by weight per hundred parts of resin base monomer, the composition being substantially free from non-reactive solvent.

2. A cold-setting composition as claimed in claim 1 wherein the acrylic acid ester is a (meth)acrylic acid ester.

3. A two part composition in accordance with claim 1 or claim 2, part A comprising the resin base monomer, the cross-linker and the diene, and part B the filler and initiator.

4. A resin composition as claimed in any preceding claim in which the said alkanol has 9 -24 carbon atoms.

5. A resin composition as claimed in any of claims 1, 2 or 3 in which the said alkanol has 10 -13 carbon atoms 6. A resin composition as claimed in any of claims 1, 2 or 3 in which the said acrylic acid ester comprises isodecyl methacrylate.

7. A resin composition as claimed in any of claims 1, 2 or 3 in which the said acrylic acid ester comprises tridecyl methacrylate.

8. A resin composition as claimed in any of claims 1, 2 or 3 in which said acrylic acid ester comprises behenyl methacrylate.

9. A resin composition as claimed in any one of the claims 1 to 8 in which the cross-linker is derived from polyethylene glycol.

10. A resin composition as claimed in any one of the claims 1 to 8 in which the cross-linker is derived from the grade of polyethylene glycol sold as "PEG200".

11. A resin composition claimed in any one of the claims 1 to 10 inclusive wherein said mineral filler is selected from the group comprising chalk, sand, solid or hollow glass beads or fly ash.

12. A resin composition as claimed in claim 11 wherein said mineral filler comprises a sand filler of well rounded particle type with particle sizes in the range 130 -400 micro metres.

13. A resin composition as claimed in claim 11 wherein said mineral filler comprises solid or hollow glass microspheres.

14. A resin composition as claimed in any one of claims 1 to 10 inclusive wherein said mineral filler comprises ground limestone with particle sizes predominantly in the range 2 -50 micro metres.

15. A resin composition as claimed in any one of claims 1 to 10 inclusive wherein said mineral filler is selected from the group comprising alumina trihydrate, barium titanate, antimony trioxide, zinc borate, gypsum, wollastonite, clays, mica, quartz, silica, silicon carbide, Zirconium silicate, carbon black, synthetic zeolites and oxides of aluminium, zinc and titanium.

16. A resin composition as claimed in any one of claims 1 to 15 inclusive wherein the initiator is a peroxide.

17. A resin composition as claimed in any one of claims 1 to 16 inclusive wherein the composition further comprises a catalyst 18. A resin composition as claimed in claim 17 in which said catalyst comprises a condensation product of para toluidine with ethylene oxide.

19. A resin composition as claimed in any of claims 1 to 18 inclusive wherein said reactive diene comprises a 1,4-polybutadiene.

20. A resin composition as claimed in claim 19 wherein the polybutadiene contains a preponderance of I,4-cis double bonds.

21. A resin composition as claimed in claim 20 wherein the proportion of 1,4-cis double bonds is 75% 5%.

22. A resin composition as claimed in claim 19 wherein the diene comprises a maleic anhydride adduct of a 1,4-poiybutadiene.

23. A resin composition as claimed in claim 19 wherein the diene comprises a hydroxyl tipped butadiene.

24. A resin composition as claimed in claim 19 wherein the diene comprises an epoxy functional diene or a carboxyl functional diene.

25. A resin composition as claimed in claim 19 wherein the 1,3-polybutadiene is selected from the group comprising:-Polyoil 110 Polyoil 130 Polyvest OC 800 S Polyvest EP-OC 1200 S where Polyoil and Polyvest are trade marks of Degussa Corporation.

26. A resin composition substantially free from a non-reactive solvent substantially as herein described.

27. An electric cable joint filled with a cold-setting resin composition as claimed in any one of the claims 1 to 26 inclusive.

28. An electric cable joint filled with a cold-setting resin composition substantially free from a non-reactive solvent substantially as herein described.