CA1234649A - Water stabilized polymeric composition containing hydrated alumina - Google Patents

Abstract

ABSTRACT

A water stabilised polymeric composition incorporating a hydrated alumina filler, which is characterised by the presence of an effective amount of an antimony ? compound.
The compositions have a reduced tendency to absorb water and specific compositions find application as electrical insulation and in the production of dimensionally recoverable articles.

Description

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The presen-t invention concerns polymeric compositions and more specifi-cally such compositions which contain a particulate filler or fillers and is rela-ted to co-pending Canadian Applica-tion Serial No. 363,754 filed on October 31, 1980, inventors Richard Stuart Skipper and Richard John Penneck filed on even date and assigned to the same assignee.
Polymeric compositions incorporating hydrated alumina fillers, especia-lly of the formula A12O3. x H2O wherein x is 0.5 to 3, e.g. to impart flame ret-ardant properties or to enhance the anti-tracking properties in electrical appli-cations, frequently exhibit a tendency to absorb water particularly when the com-position comprises a polar polymer.
This tendency to absorb water is often directly or indirectly attribut-able to the particulate filler, i.e. to the hygroscopic nature of the filler per se or of the filler after incorporation into the polymeric composition. In the latter respect, it has been found that hydrated aluminas when incorporated into certain polymeric compositions can undergo, at least to a limited extent, a che-mical or physical transformation yielding a chemical species substantially more hygroscopic than the incorporated filler per se.

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The presence of such chemical species in a filled polymeric sys-tem may result in a very high water pick-up when exposed to wet environments, especially hot wet environments.
The tendency of polymeric compositions to absorb water may render the use thereof in cer-tain applications unsuitable, particularly in electrical insul-ation applications and especially flame retarded systems wherein reliance is pla-ced on hydrated alumina fillers to provide flame retardancy.
The present invention is concerned with reducing or elimina-ting -the tendency of hydrated alumina filled polymeric compositions to absorb water, here-inafter referred to as "water stabilisation" and the expression "water stabili-ser" is -to be construed accordingly.
A first aspect of the present invention provides a water stabilised polymeric composition, incorporating a hydrated alumina filler which is charac-terised by the presence of an effective amount of an antimony _ compound and com-prises less than 15 weight percent based on the composition of halogen atoms.
A second aspect of the present invention provides water stabilised hyd-rated alumina characterised in that it includes an effective amount of an anti-mony _ compound.
A third aspect of the present invention provides electrical equipment, for example a wire or cable, or a high voltage ~:3~19 insulator, incorporating as electrical insulation a polymeric composition in accordance with the first aspect of the invention. ~

A fourth aspect of the present invention provides a water stabilised dimensionally recoverable, and especially heat-recoverable, article comprising a polymeric composition in accordance with the first aspect of the invention, prefer-ably in cross-linked form.

A fifth aspect of the present invention provides a water stabilised adhesive composition or sealant composition comprising a polymeric composition in accordance with the first aspect of the present invention.

A sixth aspect of the present invention provides water stabilised panels and cladding especially reinforced, e.g.
glass reinforced, panels and cladding, for use e.g. in the construction industry and passenger transit vehicle industry comprising a polymeric composition in accordance with the first aspect of the invention.

The particulate fillers that may be employed in the composi-tions of the present invention are those which have a tendency to absorb ~ater at least after incorporation into the composition. Particularly important classes of fillers include hydrated al~minas used as inorganic flame retardants 4~

and electrical anti-tracking agents, especially halogen-free such Eillers. Pre-ferred fillers are hydrated aluminas of the formula A12O3. x H20 wherein x is 0.5 to 3, for example alumina mono-hydrates e.g. A1203.H20, but especially alumina trihydrate A12O3.3H20. In this specification the term hydrated alumina is also intended to include materials which are known as aluminium hydroxides e.g. Al(O~l)3 and aluminium oxyhydroxides e.g. AlO.OH. Other suitable hydrated alumina fillers include ammonium and sodium dawsonite. Mixtures of hydrated alumina fillers may be used if desired.
The hydrated alumina filler used is preferably selected from those hav-ing a surface area of at least 0.1m2/g, up -to 300mm2/g and most preferably having a surface area of from 0.lm /g to 100m /g, particularly 2 to 40m2/g, and especia-lly 4 to 16m /g, as measured by the well known B.E.T. method using nitrogen ad-sorption, as described by Brunauer, Emmett and Teller (B.E.T.). Outstanding imp-rovements in the electrical properties of filled polymer compositions containing high surface area alumina trihydrate fillers may be achieved using the present invention.
The amount of filler incorporated in the compositions of the invention will naturally depend inter alia on the nature thereof although in general, amounts in the range 5 to 80%, more preferably 20 to 70%, especially 30 to 70%, e.g. 40 to 70~ based on the weight of the composition, are preferred.

- 5 ~ RK102/128 Whilst we believe that insolubilisation of residual sodium in the filler plays a role in water stabilisation by anti-mony V compounds, the complete mechanism~of water stabili-sation is not fully understood and will vary depending on the nature of the insolubilising agent. It is conjectured that in addition to forming a water insoluble compound with any available sodium present, the antimony V compound may also function as a water stabiliser by forming a water barrier around the filler particles thereby inhibiting water access to any hygroscopic moieties in the hydrated alumina even when the antimony V compound is not pre-coated onto the filler. Furthermore, and depending on the nature of the filler and antimony V compound, we believe that such water barrier may be the result of complex formation between the antimony V compound and the surface of the filler particles.

Although not essential, it is preferred that the level of sodium impurity in the hydrated alumina should b'e reduced to a minimum. This may be achieved by pre-treatment, for example, washing with water or an aqueous medium particu-larly aqueous inorganic or organic acids, e.g. to a total sodium level less than 1000 ppm, more preferably less than 600 ppm of sodium measured as Na20, based on the weight of the hydrated alumina.

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Reduction of the sodium impurity level may also be achieved by pre-treatment of the filler with a sodium complexing or - 6 - ~3~ RK102/128 chelating agent such as particularly zinc or magnesium uranyl acetate, but also uranic acid, molybdic acid, orthophosphoric acid, hypophosphorous acid, and dodeca~olyb-dophosphoric acid. Such treatment is followed by washing o~
the filler to remove any water soluble compounds thus formed.

Many conventional polymer processing methods involve milling, internal mixing e.g. in a Banbury mixer, or other treatment stages likely to cause some break-up of the filler particles thereby exposing sodium ions previously trapped within the crystal lattice. It will be appreciated therefore that for many purposes merely reducing the soluble sodium content of the filler prior to blending with the polymer is not suffi-cient to water stabilise the filled polymer system.

The antimony V compound may be incorporated by distribution thereof throughout the composition or altern~atively the hydrated alumina may be treated by coating therewith as approprlate.

However, it has been found that greatly improved results are obtained if the hydrated alumina, an effective amount of the antimony V compound, and the polymer, are processed together, for example on a mill or in an internal mixer, for an extended period of time. Such processing is preferably .

~L23~ 9 carried out for at least 5 minutes, and preferably from 10 to 60 minutes. Alternatively, the hydrated alumina may be treated with the antimony V compound prior to blending with the polymer. Suitable antimon`y V compounds include, for example the hydratsd forms of àntimony V oxide, especially the monohydrate Sb2O5 H2O, antimony alkoxides, for example antimony V pentamethoxide, and antimony pentahalides, for example antimony pentachloride. The treatment step may require to be followed by a washing treatment with an aqueous or organic solvent depending upon the antimony V
compound used but at least in the case of the hydrated antimony V oxides this is not essential.

Whatever the mechanism of -the water stabilisation by the antimony V compound, it has been found in practice that further improved results may be obtained when the hydrated alumina is treated with a coupling agent.

Examples of such coupling agents include organo-silicon and titanium deri~atives such as silanes and titanates.

4~ 3 27065/~8 Examples of appropriate silanes are disclosed in UK Patent No.
1,284,082 and "Silane Coupling Agents", Additives for Plastics, Vol I pp 123 - 167, Academic Press 1978, and appropriate titanium compounds in S.J. Monte and G. Sugerman, J. Elastomers and Plastics, Volume 8 (1976) pages 30 - 49 and in Bulletins KR 0376-4 and 0278-7 "Ken React Titanate Coupling Agents for Filled Polymers" publi-shed by Kenrich Petro Chem Inc.

In some cases processing aids such as stearic acid and stearates, e.g. calcium stearate, and aluminium soaps such as aluminium di-isopropoxy diversatate or polyoxo carboxylates, such as polyoxo aluminium stearate, may be added during processing of the composition. Examples of appropriate aluminium soaps and polyoxo aluminium carboxylates are given in U.K. Patent No. 825,878, The amount of coupling agent employed preferably lies in the range 0.1 to 15 weight per cent, more preferably 1 to 10 weight per cent based on the weight of the filler.

_ g ~23~6~9 RK102/128 Of the:possible antimony V compounds, including antimony V
complexes, which may be employed in the compositions of the present invention particularly preferrgd are the hydrated forms of antimony V oxide, especially the monohydrate, i.e.
Sb2O5.H2O, and precursors thereof. Such precursors include compounds which during processing or by other chemic~l or physical treatment may be converted into a hydrated anti-mony V oxide. However good results may also be obtained using antimony V alkoxides, for example antimony V penta-methoxide.

The antimony V compound is present in an amount ef~ective to improve the water stability of the composition, said amount being preferably in the range 0.1 to 60 weight per cent based on the composition, more preferably 0.1 to 25 weight per cent, although for water stabilisation purposes only, it has been found that amounts in the range 0.1 to 10 weight per cent e.g. 0.5 to 10 weight per cent are quite satisfactory. However, it has also surprisingly been found that whilst lower amounts have no substantial positive effect on flame retardancy of the composition and indeed, in some instances a depression of flame retardance is observed, in higher amounts, e.g. above 5 weight per cent, preferably from 10 to 25 weight per cent, especially 10 to 15 weight per cent based on the composition, a substantial increase in flame retardance is observed at elevated temperatures, i.e. as measured by the British Ministry of ~:3~6~1~

Defence specification NES 715 (based on ASTM-D-2863) whilst still providing satisfactory water stabilisation.
Polymeric compositions wherein the water stabilisers have been found to exhibit notable efficacy in reducing water absorption include non-cross-linked and cross-linked thermo~
plastic or elastomeric substituted or unsubstituted polyalkenes or alkene copolymers, such as alkene/alkene copolymers, vinyl ester homo- or copolymers and (meth) acrylate homo- or copolymers.
The term "copolymer" as used herein is employed in a broad sense to mean any polymer containing at least 2 different monomeric species and includes terpolymers and the like.
Unsubstitued polyalkenes and alkene copolymers of interest include polyethylenes and alkene/alXene copolymers such as ethylene/alkene copolymers, especially those disclosed in UK
Patent Application No. 2019412A and Canadian Patent No.
873,828 and elastomers such as EPDM (ethylene/propylene/ diene monomer) and SBR (Styrene/butadiene rubber).
The Vinyl ester homo - or copolymers of intrest are those derived from vinyl ester monomers of formula I, Z3~L6~1~
~ RK102/128 f = C ~

o wherein R1, R2 and R3 are each, independently ` hydrogen or a substituted or unsubstituted hydrocarbon group having up to 20 carbon atoms, e.g. C1 ~ C6 allcyl, and R4 is a substituted or unsubstituted hydro-carbon group having up to 20 carbon atoms, which may optionally include one or more hetero atoms, especially where R1, R2 and R3 are each indepen-dently hydrogen or C1 ~ C6 alkyl, and one-of R1, R2 and R3 may also signify .
- phenyl or benzyl, and R4 is an alkyl, alkenyl, alkoxyalkyl or alkoxy-alkenyl, aryl or aralkyl group having up to 20 carbon atoms e.g.. phenyl, naphthyl or benzyl, or C1 - C4, alkyl - or alkoxy-phenyl or benzyl, and particularly when R4 is C1 ~ C15 alkyl, phenyl or benzyl.

1~ - RK102/128 Examples of specific vinyl ester monomers useful in the polymers of interest are vinyl acetate, vinyl propionate, vinyl hexanoate, vinyl octanoate, vin~l versatate, vinyl stearate, vinyl laurate, vinyl methoxy-acetate, vinyl trimethylacetate, vinyl isobutyrate, vinyl tert. pentoate, vinyl lactate, vinyl caprylate, vinyl pelargonate, vinyl myristate, vinyl oleate, vinyl linoleate, vinyl benzoate, vinyl (C1 ~ C4) alkoxy benæoate, vinyl octylphthalate, vinyl ~-phenyl butyrate, vinyl ~-naphthoate, vinyl ethyl phthalate and vinyl phenyl acetate.

Vinyl ester copolymers of interest include mixed vinyl ester copolymers e.g. copolymers of vinyl acetate with higher vinyl esters, e.g. vinyl laurate as well as copolymers with comonomers other than vinyl esters. Other such comonomers include unsaturated hydrocarbons such as olefins e.g.
ethylene, propylene, particularly C4 - C12 ~unsaturated olefins, e.g. but-l-ene, hex-l-ene and oct-i-ene, styrene and unsubstituted or substituted esters, e.g. C1 ~ C12 (meth)acrylates and other vinyl monomers, e.g. vinyl chloride.

When copolymers with comonomers other than vinyl esters are employed, then preferably the vinyl ester monomer(s) is present in at least 5 mole %, preferably at least 10 mole %, e.g. 20 - 95 mole %, more preferably at least 30 mole %, e.g. 40 - 95 mole %.

~;~3D~
- - 13 - RK102~128 The (me`th)acrylate homo - or copolymers of interest are those derived from (meth)acrylate monomers of formula ~ 5 CH2 = C II
: - O - R6 n wherein R5 is H or CH3 ancl R6 is a substituted or unsubstituted hydrocarbon group having up to 20 carbon atoms, which may optionally include one or more hetero atoms, preferably an alkyl, alkenyl, alkoxyalkyl or alkoxy-alkenyl.aryl or aralkyl group having up to 20 carbon atoms, e.~. phenyl~
naphthyl or benzyl, and particularly C1 ~ C15 alkyl, phenyl or benzyl.

Preferred homo polymers include polyethyl acrylate, poly-butyl acrylate. Particularly preferred (meth)acrylate copolymers are ethylene/ethyl acrylate (18 weight per cent), ethylene/ethyl methacrylate ~20 weight per cent) and ter-polymers of ethylene, methyl acrylate and a cure-site ~'~3~6~
~14- 27065-48 carboxyl-containing monomer such as the terpolymer commer-cially available from DuPont under the trade name "Vamac*"
and analogous polymers described in UK Patent No. 1,548,232.
Other copolymers suitable for use in the present invention include those derived from any of the above mentioned monomers and a cure site monomer such as 2-chloroethyl vinyl ether or 2-chloroethyl acrylate.
Other polymers of interest which may be employed in the compositions of the invention include epoxy resins especially cycloaliphatic epoxy resins such as those employed for high voltage insulation applications, e.g. Araldite* CY175 and Bakelite* FRC 4221 especially when cured with cycloaliphatic acid anhydrides e.g. hexa-hydro phthallic anhydride, unsaturated polyesters especially glass filled polyesters, and polyamides especially aliphatic polyamides such as nylons.
Furthermore, such polymers may be employed as a blend system containing other polymers. Preferred polymer blends are those comprising vinyl ester homo- or copolymers, (meth) acrylate homo or copolymers, and/or substituted or unsub stituted polyalkenes or alkene copolymers. Blend polymers of interest are those which are preferably compatible, either alone or in association with compatabilising agents, with the aforedescribed polymers and which do not render the compositions unsuitable for the purpose for which they are intended. Such blends may include blends of two or more of *T~

3.23~ 9 the aforedescribed polymers or blends wi-th other polymers including thermoplastic and elastomeric polymers, examples of which are polyesters and polyethers including segmented polyether ester copolymers of the type available form DuPont under the trade name Hytrel* and described in Polymer Engin-eering and Science _ volume 12, 848-852 1974 "Segmented Polyether Ester copolymers - a new generation of high performance elastomers", silicone resins and elastomers and acrylic elastomers. Some preferred polymer blends are described and claimed in UK Patent No. 1,284,082 and in German Offenlegenschrift No. 2815520.
In the case of vinyl ester or (meth) acrylate polymers, when blends are employed such polymers are preferably present in the blend in at least 20 weight per cent, e.g. 30 - 99 weight per cent, more preferably at least 40 weight per cent, e.g. 5G - 99 weight per cent.
The polymer composition may also contain other additives such as organic halogen containing or inorganic flame retardants, or organo-phosphorous compounds, anti-tracking agents, high voltage erosion suppressan~s, stabilisers, e.g.

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antioxidants and ultra-violet stabilisers, fillers, pig-ments, colourants and the like. In yeneral it is preferred that the composition contain little or ~o halogen, e.g. less than 15 weight per cent based on the composition, more preferably less than 10 weight per cent, especially less than 5 weight per cent of halogen atoms.

For most purposes, it is preferred that the compositions of the invention are substantially cross-linked.

The degree of cross-linking of the compositions may be expressed in terms of the gel content (ANSI/ASTM D2765-68) of the cross-linked polymeric composition, i.e. excluding non-polymeric additives that may be present. Preferably the gel content of the cross-linked composition is at least 10%
more preferably at least 20%, eOg. at least 30~, more preferably at least 40%.

I

The compositions of the invention are produced in conven-tional manner, for example by blendiny together the compo-nents of the composition in a Banbury mixer.

They may then be processed into shaped articles, for example by extrusion or moulding, and when desired simultaneously or subsequently cross-linked.` Shaped articles so produced also form part of the present lnvention.

-17- ~3~6~ 27065-48 When desired the polymeric components of the composition may be cross-linked either by the incoporation of a cross-linking agent or by exposure to high energy radiation.
Examples of suitable cross-linking agents are free radical initiators such as peroxides for example, dicumyl peroxide,

2,5-bis-(_-buty peroxy)-2,5-dimethylhexane, 2,5-bis-(t-butyl-peroxy)-2, 5-dimethylhexhyne-3, and ~,~-bis(t-butyl-peroxy)-di-iso propylbenzene. Other examples of appropriate cross-linking agents are disclosed in C.S. Sheppard & V.R.
Kamath Polymer Engineering & Science 19 No. 9 597-606,1979 "The Selection and Use of Free Radical Initiators". In a typical chemically cross-linked composition there will be about 0.5 to 5 weight per cent of peroxide based on the weight of the polymeric composition. The cross-linking agents may be employed alone or in association with a cocuring agent such as a poly-functional vinyl or allyl compound, e.g. triallyl cyanurate, triallyl isocyanurate or pentaerythritol tetra methacrylate.
Radiation cross-linking may be effected by exposure to high energy irradiation such as an electron beam or ~-rays.
Radiation dosages in the range 2 to 80 Mrads, preferably 2 to 50 Mrads, e.g. 2 to 20 Mrads and particularly 4 to 15 Mrads are in general appropriate.

- 1B - 123~6~9 RK102/128 .
For the purposes of promoting cross~linking during irradia-tion preferably from ~.2 to 5 weight per cent of a prorad such as a poly-functional vinyl or allyl compound, for example, triallyl cyanurate, triallyl isocyanurate or pentaerythritol tetramethacrylate are incorporated into the composition prior to irradiation.

The compositions of the invention are particularly suitable for electrical insulation use, e.g. where flammability requirements are stringent or high voltage anti-tracking properties are desired and water absorption highly undesir-able, for example wire and cable applications in confined areas such as aircraft, ships, mines or railways including metro systems, or terminatlon and splicing of high voltage cables or as insulation in non-tracking high voltage appli-cations, e.g. insulators, bushings and bus bar systems.

The production of electrical insulation ma~erial may be achieved by conventional techniques, for example by extru-sion of the non-cross-linked composition, as an insulator, onto the electrical equipment such as a copper conductor as a primary insulation, or a bundle of primary insulated copper wires as a cable jacket and preferably, simultan-eously or subsequently cross-linking the applied insulation.

, As aforedescribed, the compositions of the present invention are also particularly suitable in cross-linked form for the - 1 9 - lZ3~6~9 RK102/128 production of dimensionally recoverable articles, that is to say, articles, the dimensional configuration of which may be made substantially to change when su~jected to an appro-priate treatment. Of particular interest are heat-recover-able articles, the dimensional configuration of which may be made substantially to change when subjected to hea~ tre~atment.
Heat-recoverable articles may be produced by deforming a dimensionally heat-stable configuration of the article to a dimensionally heat-unstable configuration, the article assuming or tending to assume the heat-stable configuration thereof on the application of heat alone. As is made clear in US Patent No. 2,027,962, however, the original dimen-sionally heat-stable configuration may~be a transient form in a continuous process in whichr for example, an extruded tube is expanded, whilse hotr to a dimen~ionally heat-unstable form.

AlternatiYely a preformed dimensionally heat-stable article may be deformed to a dimensionally heat-unstable form in a separate stage. In the production of dimensionally recover-able articles, the composition may be cross-linked at any stage in the production process that will acomplish the desired dimensional recoverability. One manner of producing heat-recoverable article comprises shaping the pre-cross-linked composition into the desired heat-stable form, subsequently cross-linking the composition, heating the - 20 - ~23~9 RK102/128 article to a temperature above the crystalline melting point or, for amorphous materials the softening point, as the case may be, of the polymer, deforming the article and cooling the article whilst in the deformed state so that the de-formed state of the article is retained~ In use, since the deformed state of the article is heat-unstable, application of heat will cause the article to assume its original heat-stable shape~ Such dimensionally recoverable articles may be employed as flame retarded and/or anti-tracking sleeves for covering and/or sealins splices and terminations in electrical conductors, for environmentally sealing damaged regions or joints in utility supply systems, e.g.
gas or water- pipes, district heating systems, ventilation ancl heating ducts and conduits or pipes carrying domestic or industrial effluent.

Adhesives and sealants in accordance with the fourth aspect of the invention are particularly those whic~ find use in electrical applications for example in harnessing systems, and especially in high voltage applications wherein anti-tracking fillers such as hydrated alumina are employed.

Preferred sealants include elastomer/tackifier formulations such as butyl rubber/polyisobutylene or epichlorohydrin rubber/polyketone resin compositions. Preferred adhesives include epoxy, especially cyclo aliphatic epoxy and silicone based adhesives.

L6~3 Panelling and cladding materials in accordance with the fifth aspect of the invention include materials such as those disclosed and claimed in UK Patent Applications Nos.
2035333A and 2044777A, as well as epoxy moulding compositions and unsaturated polyesters particularly when glass-fibre reinforced. Such materials may be processed into final shape by thermoforming, e.g. hy vacuum forming, moulding or laying-up techniques.
The invention is illustrated by the accompanying examples wherein parts and percentages are by weight and temperatures are expressed in C.

~1 `

6~1 EXAMPLE l The compositions set out in Table 1 below were compounded on a 2 roll laboratory mill heated to a temperature of 120 - 140~, and moulded at 170 into test plaques of 2mm thickness. Each composition incorporated commercial'fire retardant grade A1203. 3H20 which had been pre-coated with the coupling agents disclosed in Table 1 and the indicated amount of commercial grade Sb205. H20, The test plaques were then irradiated wi.th a 508 MeV electron beam to a total dosage of 12 Mrads.

The composition of each formulation employed is set out in Table 1 below which shows the number of parts of each constituent.

~ 23~

_ COMPOSITION POLYMER FILLER COATING Sb20s. ~2 . (Wt % of filler) ~Wt %~of filler) A VAMAC N-123 (Trade Name - 5% silane 5%
elastomeric copolymer of (commercially ethylene and methyl acrylate available under TM
containing monoalkyl ester A172 from Union cure sites commercially C~arbide) available from DuPont B ,. 5% silane (A172) 10%

C HYTREL 40~6 (Trade Name - 5% titanate - 5%
Thermoplastic copolyestér (available under TM
commercially available from TTS from Kenrich - DuPont) Petrochem) D ~ 5% titanate (TTS) lOX

~L23~

The samples so produced were subjected to the following test methods TEST METHODS

(i) Water U~take ^- 3 test discs 2.5 cm in diameter were employed to determine water uptake by immersion in water at 90 (compositions C to G) or 50 (remaining compositions) for various periods. At the end of each period, the discs were removed, excess water wiped off the discs weight and the percentage weight in-crease computed. `-.
(ii) Permittivity after immersion in water at 50 - ,~

In accordance with BS2782, Method 206B.

(iii) Tensile strength and elongation .

In accordance with IS037 employing a strain rate of 1 a cm/minute and type 2 dumbells.

(iv) Flammability In accordance with the limiting Oxygen Index (LOI3 method of ASTM-D-2863.

~L23~
- 25 - RK102/12~

The results are set out in Table II below. For comparison purposes, the results for control samples incorporating no Sb205. H20 and 60~ uncoated Al203. 3H20 ~re given.

3L23~

.
TABLE II

% WATER UPTAKE PERMITTIVITY TENSILE ELONGATION LOI @ 23C
COMPOSITION STRENGTH @ 23 (%) @ 23 ( 24168 336 0 24 336 ` (MPa) hourshours hours hourshourshours A 1.31 3.06 3.645.038.048.20 10.91 82 42.7 B l.oo 1.89 2.094.696.287.29 11.88 108 33.9 CONTROL2.86 6.94 8.033.3811.14 lS.99 9.37 313 43.0 C 1.07 1.01 1.124.166.847.23 19.94 26 35.4 D 0.81 0.61 0.584.555.346.68 .11.96 21 30.2 CONTROL2.70 1.47 1.474.3423.26 32.34 16.89 21 43.5 ~23~

.

The compositions set out in Table III belQw (which shows the number of parts of each constituent) were compounded on a 2 roll laboratory mill heated to a temperature of 120 -140, and moulded at 190 into test plaques of 2mm-thick-ness. The test plaques were then irradiated on a 5.8 MeV
electron beam to a total dosage of 12 Mrads. 3 test discs 2.5cm in diameter were cut out of each plaque and the discs were employed to determine water pick-up by immersion in water at 90 for various period. At the end of each period, the discs were removed, excess water wiped off and the discs weighed. The results are listed in Table IV below each result reported being the average result for three identical discsO ~ ;`r TABLE III

CONSTITUENTS FORMULATIONS

AB C ~ D E F G H I J K

60X vinyl acetate/
ethylene copolymer 40 40 40 40 40 40 - - 40 - -25~ vinyl acetate/
ethylene copolymer - - - - - - 40 - - 40 ethylene/ethyl acrylate (18X) copolymer - - - - - - - 40 - - 40 Al203 3H20 - 60 60 60 57 57 57 Al203.3H20 coated with 1.5% vinyl trimethoxy-ethoxysilane 60 60 60 60 60 Sb205.H20 ~ . ~ 3 12 - - - - - 3 3 3 Sb203 _ _ _ 3 12 The water immersion results are set out in Table VI below - 29 - RKlD2/128 , : TABLE IV

% WEIGHT INCREASE AFTER IMME~SION AT 90 IN WATER
FORMULATION24 HR~ 48 HRS 168 HRS 336 HRS 672 HRS

A 5.2 5.7 - - 9.3 B 3.3 3.5 _ _ 1 9 C 1.0 1.0 - - 0.65 D 4.7 5.5 - - 8.2 E 4.9 5.7 - - 8.3 F 20.3 20.6 14.2 14.1 - --G 9.0 -12.9 24.8 28 H 7.t 10.3 19.5 31 I 7.1 5.8 3.4 3.3 a - ~.3 7.5 6.3 5.1 K 5.9 7.8 10.6 11.0

3~
- 30 - RK102~128 The results clearly demonstrate a substantial reduction in the tendency of alumina trihydrate filled vinyl acetate/
ethylene copolymer (formulations A,F and G) and ethylene/
ethyl acrylate systems (formulation H) to absorb water by the incorporation of Sb2O5.H2O (formulations B, C, I, J and K) and the lack of such effect by the incorporation-of ~b2O3 (formulations D and E).

In analogous manner to that described in Example 2, composi-tions comprising 25 parts of a 50% vinyl acetate/vinyl laurate copolymer, 5 parts of a linear low density polyethy-lene (Sclair~ 1D1 - Trade Name - Ex DuPont) and 70 parts of alumina trihydrate coated with 1.5% vinyl trimethoxyethoxy-silane wer~ compounded with varying amounts of Sb2O5.H2O~
The percentage of Sb205.X20 in the formulations were as set out in Table V below.

TABLE V

Formulation % Sb25 H2 ;B 0.17 C 0.5 D 1.0 E 3.0 F 5.0 -~ ~'r~e v~,~J k~

_ 31 ~ ~L23~ RK102/128 The water absorption of samples of such materials was deter-mined in accordance wi~h the procedure described in Example 3.
Oil uptake employing identical samples as employed for water absorption was determined in accordance with ASTM-D-570-77 carried out at 100 employing mineral oil (ASTM No. 2) and synthetic lubricating oil (British Spec. D. Eng. R D. 2487 "OX-38'~) and limiting oxygen index at 23, determined in accordance with ASTM-D-2863, and at 250C in accordance with British Ministry of Defence method NES 715.

The results are set out below in Table VI and indicate that a substantial decrease in water absorption by the incor-poration of small amounts of Sb205.H20 is not accompanied by a significant change in oil uptake ât 100C. The results also show that at low levels Sb205.H20 giv~s no significant improvement in flame retardance at 23C.

TABLE VI

Formulation ~ water u~take % oil uptake Oxygen Index at 90 at 100 24 hrs 48 hrsASTM 2 OX 38 at 23 at 250 A 5.2 6.7 7.5 22.9 49.5 35.5 B 5.0 6.1 g.3 24.5 42.5 C 4.5 5.4 9.3 2~.7 43.5 D 2.8 3.~ 807 22.1 46.0 37.5 E 1.8 1.8 908 23.6 5i.5 F 0.9 0.9 8.8 22.6 48.5 39.5 L6~t , Compositions exposed to an extended prffcessing time on a 2 roll laboratory mill have also been prepared. Test plaques were made up in analogous manner to that described in Example 1, except the normal compounding times on the mill were extended by (i) 10 minutes, (ii) 30 minutes and (iii) 60 minutes. The composition comprised 40 parts by weight of a 60% vinyl acetate/40% ethylene copolymer, 54 parts by weight untreated alumina trihydra~e and 6 parts by weight antimony pentoxide monohydrate.

The samples so produced were subjected to water uptake and permittivity tests as detailed in the test methods of Example 1. The results are shown in Table YII below.

. . ~ !

.

.
TABLE VII

Weight increase after Permittiv;ty after immersion immersion in H20 @ 90C in H20; @ 50C

24h 48h 168h Oh 24h 168h 1. Norma.l milling 7.4 6.2 3.1 4.06 22 .32 2. 1 ~ 10 minutes 1.30 1.27 1.215.41 9.80 12 3. 1 + 30 minutes 1.24 1.60 1.04~.35 11.20 15

4. 1 + 60 minutes 1.33 1.82 1.014.99 8.51 13 ~ ' ~

3~6~

From table VII it can be clearly seen that an extended, milling time can be of substantial benefit, especiaIly with espect to water uptake. In commercial production this benefit can be achieved by optimising residence times in processing equipment such as extruders or banbury mixers.

700 gms. of high surface area (13m2/g~ alumina trihydrate were dispersed in ~ litres of:-(i) Triply distilled water.

(ii) Triply distilled water to which 35 grams ofzinc uranyl acetate had been added.

and vigorously agitated for 3 hours at 80 - 85 C. The washed ALTH was recovered by filtration and washed dried under vacuum and ball milled. This yielded material with physical properties (e.g. T.G.A. curve, surface area etc) similar to those of the starting material. The recovered ALTH was (à) compounded with 40% by weight -of a 60% vinyl acetate /40% ethylene copolymer as described in Example ~23~

1 (b) coated only with 10% antimony pentoxide before compoun-ding with 40% by weight of a 60% vinyl acetate/40% ethylene copolymer. Ta~le VIII shows that the benefits of the invention are observed even when using ALTH which has been treated to remove soluble sodium impurity.

- - ~ w r~
c~ ~ v - - v v ~ ~:
- I g C tD - g C ~D I_ OV n -5 OV n ~D V D :~--~ D
O ~ O tD I
S Cl. ~
~_ _. ~ _, _.
, ~ P~ ~
O O

N I N
N . r ~, _, ~ ~U :
O o ~ ~ ~
~O ~o r ~ 2 o I_ I
Q ~nI _ O
~ C~ :
~.

V
V
~n ~ ~ ~ lo ~
- ~

co o w~a~ I ~ C
c.n --.P- rrl Cn ~n ~ ~ - ~ 3 O
rr1 N
o U~ ~ tnCO ~ :1 a~ ~ ~ ~
~s O

o , . .

`` `` ~L2~

Benefits in reduced water uptake and maintained low permit-tivity can also be obtained with alumina monohydrate (ALMH).
Samples based on a 25% vinyl acetate/75~ ethylene copolymer ;--, 7~

and aluminium oxyhydroxide (Boehmite AlO.OH) were. prepared in an identical manner to that described in Example 1. The - weight ratio of ALMH to the 25~ vinyl acetate/75~ ethylene copolymer was 3:2, and the coating level of the antimony pentoxide monohydrate was 10% wt on the ALMH. The results are shown in Table IX below and illustrate the improvement in water uptake and permi~tivity that is achieved by coating ALMH by antimony pentoxide monohydrate.

TABLE IX

Weight uptake after Permittivity afteOr immersion in H20 at 90C immersion H20 @ 50 C
24h 4 168h Oh 24h 168h_ _ Uncoated sample 1.24 1.61 2.43 4.23 8.23 10.37 Sb2O5H20 coated sample 0.58 0.79 0.93 3.49 7.63 6.B7 ~ t~ e~s The following formulation was compounded and extruded as a primary wire insulation and as a cable jacket YiZ, 60% vinyl acetate/40% ethylene copolymer 16.50 Masterbatch (see below) 16~00 Dibasic lead fumarate 0.50 Agerite Re~in D 0.60 Carbon Black 0.50 Al2O3.3HzO coated with 1.5% thereof 54.90 of A-172 silane 2 5-H2O 11.00 ej~ ~ ~ . .

The composition of the aforementioned masterbatch was as follows:

.
Hytrel 4056 (TM-segmented polyester available 85.16 from DuPont~

Hytrel 10 MS (TM-segmented polyester 9.46 available from DuPont) HTR 3139 (TM-stabiliser available from DuPont) 4.26 Anchor DNPD (TM-stabiliser ~vailable from 1.11 Anchor Chemicals) The cable jacket was. extruded over a 19 component braided cable to yièld a wall thickness of lrnm employing a 3 inch extruder, an L/D ratio of 24:1, the extruder having a 5 zone temperature control with zone temperatures, from feed to die of 110-130-140-140-140C, a die body temperature of 140 and die tip temperature of 150.

The primary insulation was extruded onto a 16 AWG tinned copper conductor to yield a wall thickness of 1mm employing ~3~

a 1 inc`h exteuder, an L/D ratio of 24:1, the extruder having a 4 zone temperature control with zone temperatures from feed to die of 140-180-185-190,.a die-body temperature of 190 and a die tip temperature of 190.

The resulting cable jacket and primary wire insulation were subjected to electron beam irradiation under a 1.5 MeV
electron accelerator to a total dosage of 6 Mrads.

The resulting jacket and. primary wire insulatian material exhibited an LOI at 23C of 48 and a capacitance change after immersion in water at 50C of 8% (1 to 14 days) and 6.2~ (7 to 14 days) (per BS2782 method 206B).

Claims (27)

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

1. A water stabilised polymeric composition incorporating a hydrated alum-ina filler, which is characterised by the presence of an effective amount of an antimony V compound and comprises less than 15 weight percent based on the compo-sition of halogen atoms.

2. A composition according to claim 1, in which the hydrated alumina is alumina trihydrate Al2O3.3H2O.

3. A composition according to claim 1, in which the hydrated alumina has a surface area of from 2 to 40m2/g as measured by the B.E.T. method.

4. A composition according to claim 1, in which the hydrated alumina is present in an amount of from 20 to 70% based on the weight of the composition.

5. A composition according to claim 1, in which the antimony V compound is a hydrated antimony V oxide or a precursor thereof.

6. A composition according to claim 1, in which the antimony V compound is present in an amount of from 0.1 to 10 weight percent, based on the weight of the composition.

7. A composition according to claim 1, in which the antimony V compound is present in an amount of from 10 to 25 weight percent, based on the weight of the composition.

8. A composition according to claim 1, in which the hydrated alumina has been treated with a silane or titanate coupling agent.

9. A composition according to claim 1, in which the hydrated alumina has been pre-treated to reduce the level of sodium impurity therein.

10. A composition according to claim 9, in which the hydrated alumina has been pre-treated by washing with water or an aqueous medium to reduce the total sodium level therein to less than 1000 ppm measured as Na2O, based on the weight of the hydrated alumina.

11. A composition according to claim 9, in which the hydrated alumina has been pre-treated with a sodium complexing or chelating agent and washed to remove water soluble compounds thus formed.

12. A composition according to claim 11, in which the sodium complexing or chelating agent is zinc uranyl acetate.

13. A composition according to claim 1, which comprises a vinyl ester homo - or copolymer or a (meth)acrylate homo - or copolymer.

14. A composition according to claim 1, which comprises a polymer blend comprising a vinyl ester homo - or copolymer, a (meth)acrylate homo - or copoly-mer, a polyalkene or alkene copolymer, a segmented polyether ester copolymer, a silicone resin or elastomer, or an acrylic elastomer.

15. A composition according to claim 14, which comprises a vinyl ester homo - or copolymer or (meth)acrylate homo - or copolymer, and wherein the vinyl ester homo - or copolymer or (meth)acrylate homo - or copolymer is present in an amount of from 30 to 99 weight percent based on the total weight of polymers present.

16. Water stabilised hydrated alumina characterised in that it includes an effective amount of an antimony V compound.

17. Water stabilised hydrated alumina according to claim 16, in which the hydrated alumina is treated with a silane or titanate coupling agent.

18. Water stabilised hydrated alumina according to claim 16, in which the hydrated alumina has been pre-treated to reduce the total sodium level therein to less than 1000 ppm, measured as Na2O, based on the weight of the hydrated alumina.

19. A process for producing a water stabilised hydrated alumina character-ised in that the hydrated alumina is treated with an effective amount of an anti-mony V compound.

20. A process according to claim 19, in which the hydrated alumina is trea-ted with an effective amount of a silane or titanate coupling agent in addition to the antimony V compound.

21. A process according to claim 20, in which the hydrated alumina is pre-treated to reduce the level of sodium impurity therein.

22. A process according to claim 21, in which the hydrated alumina has been pre-treated by washing with water or an aqueous medium to reduce the total sodium level therein to less than 1000 ppm measured as Na2O, based on the weight of the hydrated alumina.

23. A process according to claim 21, in which the hydrated alumina has been pre-treated with a sodium complexing or chelating agent and washed to remove water soluble compounds thus formed.

24. A process according to claim 23, in which the sodium complexing or che-lating agent is zinc uranyl acetate.

25. A polymeric composition incorporating a water stabilised hydrated alum-ina according to claim 16.

26. A water stabilised dimensionally recoverable article comprising a poly-meric composition according to claim 1.

27. Electrical equipment incorporating as electrical insulation a polymeric composition according to claim 1.