CA1162343A - Polymeric compositions - Google Patents

Abstract

ABSTRACT

The present invention concerns novel flame retarded polymeric compositions which comprise a vinyl ester copolymer at least some of the ester groupings of the copolymer containing at least 4 carbon atoms. The compositions exhibit low flammability whilst permitting a notable balance of physical properties.

Description

~16Z343 Im~rovements in or relatiny to Polymeric Compositions The present invention relates to flame retardant polymeric compositions.

In many commercial applications of polymers, non~flammability requirements are becoming increasingly more stringent particularly in relation to the electrical insulation field, e.g. wire and cable jackets and wire harnessins, and in tne construction industry, e.g. panelling and cladding materials and also in relation to dimensionally recovera~le, espec ally heat recoverable, articles. As a result, a large number of flame retardants have been developed for use in the polymeric materials normally employed in such industries. It is generally acknowledged, however, that even in the rare event that sufficient flame retar~ancy can be imparted to such polymeric materials, this is at the expense of other pro,erties.
For example, high levels of organo-halogen or organo-Dhosphorous flame retardants are often unacceptable in view of corrosive and/or toxic gas liberation under pyrolysis conditions. As regards inorganic flame retardants, many polymer materials cannot substain the high loadinys necessary for satisfac~ory flame retardancy without considerable detriment to the physica], properties thereo, e.g. tensile strength or elongation at break.
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- 2 - RK96 It has now been found that a certain class of polymers not employed hitherto in applications where flammability problems arise, permit an extraordinary level of flame retardancy when employed in association with flame retardants and enable the stringent flammability requirements to be met whilst exhibiting a satisfactory balance of physical properties. Such flame retardancy is indicated in standard flammability tests, e.g.
ASTMD-2863 even at temeratures as high as 300C or higher.

Accordingly, the present invention provides a flame retarded polymeric composition which comprises a non-cross-linked or cross-linked unsubstituted or substituted vinyl ester copolymer, at least some of the ester grouping of the polymer containing at least 4 carbon atoms, and incorporating an effective amount of flame retardant The term "copolymer" as employed herein is employed in a broard sense to mean any polymer containing at least two different monomeric species and including terpolymers and the like.

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11~i2343

- 3 - RK96 Many of the vinyl ester copolymers within the scope of the present invention are not commercially av~ilable.
They may be produced in manner known Per se e.g. from commercially available vinyl ester copolymers by ester interchange as described for example in US Patent 2,558,547 and 2,558,548.

The vinyl ester monomers of interest in the copolymers employed in the invention are those of formula I, R1 ~ R3 R ~ ~ O - C - R4 wherein R1, R2 and R3 are each, independentl~v, hydrogen or a C1 ~ C20 substituted or unsubstituted hydrocarbon e.g.
C1 ~ C6 alkyl, and R4 is a C3 - C20 substituted or unsubstituted hydrocarbon, especially where R1, R2 and R3 are each, independently, hydrogen or C1 ~ C6 alkyl, and one or more of R1, R2 and R3 may also signify phenl or benzyl, and R4 is a C3 - C20 alkyl, alkenyl, alkoxyalkyl or alkoxyalkenyl aryl or aralkyl, e.g. phenyl, naphthyl ~162343

- 4 - RK96 or benzyl, or C1 ~ C4 alkyl - or alkoxy-phenyl or benzyl, and particulary when R4 is C3 - C17, more preferably C6 ~ C15 alkyl, or phenyl or benzyl.

Examples of vinyl esters monomers of interest in the coplymers employed in the invention are vinyl hexanoate, vinyl versatate, vinyl stearate, vinyl laurate, vinyl methoxyacetate, vinyl trimethylacetate, vinyl isobutyrate, vinyl tert. pentoate, vinyl lactate, vinyl caprylate, vinyl pelargonate, vinyl myristate, vinyl oleate, vinyl linoleate, vinyl benzoa~e, vinyl (C1 ~ C4) alkoxy benzoate, vinyl octylphthalate vinyl ~-phenyl butyrate, vinyl ~-naphthoate, vinyl ethyl phthalàte and vinyl phenyl acetate. Other vinyl ester monomers of interest are described in UK Patent No. 1,539,664.
~, Vinyl ester copolymers of interest include mixed vinyl ester copolymers, e.g. copolymers of vinyl esters containing at least 4 ester carbon atoms with vinyl acetate or higher vinyl esters, as well as copolymers with comonomers other than vinyl esters. Other such comonomers include unsaturated hydro-carbons such as olefins, e.g. ethylene, propylene and C4 - C12 ~-unsaturated olefins, e.g. but-l-ene and oct-l-ene, styrene, unsubstituted or substituted esters other than vinyl esters, e.g. C4 - C12 (meth)acrylates, and other vinyl monomers, e.g. vinyl chloride.

l~fi23~3 When copolymers with comonomers other than vinyl esters containing at least 4 ester carbon atoms 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 ~. Expressed in terms of weight %, at least 35 weight % of the vinyl ester monomer should be present.
Furthermore, the vinyl ester copolymer may be employed as a blend system containing other polymers. Blend polymers of interest are those which are preferably compatible either alone or in association with compatabilising agents, with the vinyl ester polymer and which do not render the compositions unsuitable for the purpose for which they are intended. Such polymers include thermopla~tic and ela~tomeric polymers, e~amples of which are polyesters including block copolymers of the type available from Dupont under the trade name Hytrel (Trade Mark) and described in Polymer Engineering and Science 14, volume 12, pages 849 - 852, 1974, "Segmented Polyether Ester copolymers - a new generation of high performance elastomers", polyolefins, e.g. branched low density polyethylene, linear low density polyethylene (e.g. as described in Canadian Patent 873,828 and UK Patent Application 7,911,916) and linear high density polyethylene, silicone resins and elastomers, ~meth)acrylate ~homo - or copolymers, e.g. terpolymers of ethylene, methyl acrylate) and a cure-site carboxyl-containing monomers such as the terpolymer commercially available from Dupont under the name "Vamac" (Trade Mark) and analogous polymers ~' -5 ~S.62:~3 described in UX Patent 1,54~,~32, ethylene/vinyl a^etate copolymers, ~PDM (a linear terpolymer based on ethylene propylene diene monomer), SBR (styrene/butadiene rubber) and block copolymers of styrene with butadiene or isoprene.

When blends are employed, then preferably the vinyl ester polymer is present in the blend in at least 20 wt %, e.g.
30 - 99 wt ~, more pre~erably at least 40 wt ~ e.g. 50 99 wt %.

It may be desirable that th~ compositiors of the invention include a coupling agent to improve the compatibility of the ~lame retardant dith ~he polyrner and there~y t:o improve the physlcal properties of the compositions, particularly when flame retardant inorganic fillers are employed. Preferred coupling agents include organo silicon and titanium der.vatives such as silanes and titanates although in some cases processing aids such as stearic acid and stearates, alurninium soaps such as alurninium diisopropoxy diversatate or polyoxo carboxy-lates such as polyoxo aluminium stearate may be particularly useful~

As exarnples of silanes may be mentioned dimethyl-dichlorosilane, methyl trichlorosilane, vinyl trichlorosil3ne, ~-methacryl-oxypropyl-trimet:hoxysilane, ~1, M-bis (~-hydroY.yethyl)-Y-~6~343 amino-propyl-triet.hoxy silane, y-methacryloxypropyl-trimethoxy s.ilane, y-mercaptopropyl-tri.methoxy silane, vinyl trimethoxy silane, y-glycidoxy propyl trimethoxysilane and vinyl trimethox~ethoxysilane. F~rther a~propriate silanes are exemplified in UK Patent No. 1,284,082.

As examples of titanates and other organo-titanium derivati.ves useful as coupling agents may be mentioned tetraisooctyl titanate, isopropyl diisostearyl methacryl titanate, isopropyl-triisostearoyl titanate, isopropyl-triacryl titanate and titanium di-(dioctyl pyrophosphate).

Additional suitabl~ titanium compounds are described in S.J.
Monte & G. Sugerman, J. Elastomers & Plastics 'lolume 8 (1976) pages 30-49, and in ~ulletins KR 0376-4 and 0278~7 "Ken-React Titanate Coupling Agents for Filled Polymers"
published by Xenrich Petrocnem Inc.

Exampl~s of aluminium soaps and polyoxo aluminium carboxylates are listed in UK Patent No. 825,878.

The weight ratio of coupling agent or processing aid, when employed, to flame retardant preferably lies in the range 0.005 1o O.l : l respectively, more preferably 0.01 to 0.05 : 1 respectivel.y.

~ ~ - RK96 Flame retardants such as organo-halo~en, organo phosphorus or boron compounds or flame retardant inorganic fillers may e employed. The preferred f]ame retardants are howevcr the halogen - and phosphorus-free compounds, particularly inorganic fillers such as metallic oxides, e.g. antimony trioxide, stannic oxide and molybdenum trioxide, and fillers that release water on heating. of specific interest are the inorganic fillers that release water on heating, particularly hydrated aluminium oxides such as Al203. 3H20, ammonium or sodium dawsonite, hydrated magnesia, hydrated calcium carbonate and hydrated calcium silicate, especially a-alumina trihydrates.

It may be a,dvantageous to ~mploy a flame retardant comprising a blend of different particle sizes, for example to r~duce the melt viscosity of the composition.

If desired the flame retardant may be chemically treated to improve its compatability with the polymeric material, for example by treatrnent with one of the above mentioned coupling agents or, in the case of hydrated inorganic flame retardants such as alurnina trihydrate, with a processing aid such as stearic acid or stearates e.g. calcium steaxate.

The flame retardant is precerably used in an amount by weight, o~ ~rom 10 to 400 parts per 100 parts vf polymers, ~lfi~343 most preferably from 50 to 200 parts per 100 parts of polymer. Notable results have been obtained using an amount of from 80 to 150 parts by weight of flame retardant per 100 parts of polymer.

Apart from the flame retardant, the compositions of the present invention may comprise additional additives, for example fillers, stabilisers such as ultra-violet stabilisers, antioxidants, acid acceptors and anti-hydrolysis stabilisers, foaming agents and colourants and processing aids such as plasticiz~rs.

It is pre~erred that the compositions contain less than 5 w~ight per sen~ halogen or phosphorus in the composition as a whole and more preferably less than 2 weight per cent halogen or phosphorus and particularly contain no halogen or phosphorus.

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 th~ 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 llnked composition is at least 10~

3~3 mor~ preferably at least 20% e.g. at leas-t 30~ more preferably at least 40%.

The compositions of the in~cntion are produced in conventional manner, for example by blending together the components 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 ~orm part of the present invention.

I'he polymeric cornponents of the composition may be cross-linked either by the incorporation of a cross-lin~ing asent or by exposure to high energy radiation. Suitable cross-linking agents are free radical initiators such as peroxiaes for example, dicumyl peroxide, 2,5-bis (t-butyl peroxy)-2,5-dimethylhexane, 2,5-bis(t-butylperoxy)-2,5-dimethylhexyne-3, and a, ~-bis, (t-butyl-peroxy)-di-isopropylbenzene. Other examples of appropriate cross-linking agents are disclosed ln C.S. Sheppard and V.R. K~nath, ~olymer ~ngineering and 5cience ~9, No. 9, 597 - 606, 1979, "The Selection and Use of Free Radical Initiators'!, the disclosure of which is incorporated herein by reference. In a typical chemically cross linkable composition there ~ill be about 0.5 to 5 weight per cent o cross-linking agent based on the weight ~2343 ~ 11 - RK96 of the pol~neric blel)d. The cross-linking agent may be employed alone or in associatlon with a co-curing agent ~uch as a poly-functional vlnyl or allyl compound, e.g.
triallyl cyanurate, triallyl isocyanurate or pentaerithritol tetra-methacrylate.

Radiation cross-linking may be effected by exposure to high energy irradiation such as an electron beam or y-rays.
Radiati,on dosages in the range 2 to 80 Mrads, preferably 2 to 50 Mrads, e.g. 2 to 20 Mrads and particularly 4 to 12 Mrads are in general appropriate.

For the purposes of promoting cro~s-linkinc~ during irradiation, preferably 0.2 to 5 wei,ght per cent of a prorad such as a poly-func,tional vinyl or allyl compound, for example, triallyl cyanurate, trially isocyanura~e or pentaerithritol tetramethacrylate are incorporated into the composition prior to irradiation.

The compositions of the invention in non cross-linked form incorporating an effective amount of a cross-linking agent or prorad also form part of the present invention. In such form, the compositions may also be employed as adhesives.

The composi,tions or' che invention are particlll,arly suitable for electrical insulation use where fl,a~unability requirements ~62343 - 12 - ~96 are stringent, for example in confined areas such as in aircraft, snips, mines or underground railways.

The production of electrical insulation material may be achieved by conventional techniques, for example by extrusion of the non-cross-linked composition, as an insulator onto an electri_al apparatus such as a copper conductor as a primary insulation or a bundle of primary insulated copper wires as a cable jacket and, pxeferably, simultaneously or subsequently cross-linking the a~plied insulation. Alternatively, the material may be extruded and cross-linked separately and then em~loye~ as n insulating filler in cable censtruction.

l~he compositions of the present invention are also suitable for use as cladding and par.elling materials, and as fire blocks, e.g. for cable feed-throughs, particularly in the passenger transit i~dustry e.g. in aircraft, trains and ships, for oil rigs and in the construction industry. For such use the materials may be employed in any desired shape produced for example by thermoforming.

The compositiGns of the present invention are also particularly suitable in cross-linked ~orm for the production of dimensionally recoverable articles, that is to say, articles, the dimensional configuration o~ wnich may be made substantially to change when subjected to an appropriate treatment. Of particular intere.st are heat recoverable articies, the dimensional configuration of whicn may be made substantially to change , 1~62343 when subjec.ed to heat treatment. Heat-recoverable articles ma~ be produced by deforming a dimensionally heat-stable configuration to a heat-unstable configuration, in which case the article t~nds to ass~me the original heat-stable configuration on the application of heat alone. As is made clear in US Patent No. 2,027,962, however, the original dimensionally heat-stable configuration may be a transient form in a continuous process in which, fox example, an extruded tu.be is expanded, whilst hot, to a dimensionally heat-unstable form. Alternatively a preformed dimensionaily heat-stable article may be deformed to a dimensionally heat-unstable form in a separate stage. In the production or d~mensionally recovera~le articles, the composition may be cxoss-linked at any stage in the production process that will accomplish the desired dimensional recoverability, subsequent to the shaping of the dimensionally unstable configuratiGn. One manner of producins a heat-re~overable article comprises shaping the pre-cross-linked composition into the desired heat stable form, subsequently cross-linking the composition, heating the 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 deformed shape 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 originâl hea~ stable shape. Such dimensionally ~ .~

Z3~3 recoverable articles may be employed for covering and/or sealing 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 and heating ducts and conduits or pipes carrying domestic or industrial effluent. Such articles may be in tape, sheet, sleeve or moulded form. In addition and under certain circumstances, it may be desirable to coat at least a part of the surface of the heat-recoverable article with a sealant or adhesive, e.g. a hot-melt, heat-activatable, pressure senstive or contact adhesive or a mastic, particularly with a hot-melt adhesive such as disclosed in W. German Offenlegungschrift, 2,723,116.

For heat-recoverable applications it is preferable that the composition comprises a blend of the vinyl ester copolymer with at least one thermoplastic polymer. The weight ratio of vinyl es~er copolymer to thermoplastic polymer may for example be in the range 1 : 0.2 to 4 e.g. 1 : 0.2 to 1.5, particularly 1 : 0.2 to 0.55.
Preferred blend thermoplastic polymers for heat-recoverable applications are thermoplastic alkene homo and copolymers. Polyalkene homo polymers are preferably derived from a C2-C6 alkene, particularly in ~-unsaturated alkene such as ethylene, 1-propylene and 1-butene and partic~larly ethylene. Polyalkene copolymers are ': ,,: t ~fi2343 _ 15 _ RK96 preferably C2-C6 al~ene/C2-C12 alkene copolymers, particularly ethylene copolymers with C3-C12 alkenes, especially ~-unsaturated C3-C12 alkenes such as n-propyl-l-ene, n-but-l-ene, n-pent-l-ene and n-hex-l-ene and alkene vinyl ester e.g. ethylene/vinyl acetate copolymers. Particularly preferred ethylene copolymers contain greater than ~0 weight per cent, for example greater than 60 weight per cent, more preferably greater than 70 weight per cent, for example greater than 85 weight per cent, ethylene. Of particular interest are the so-called linear low density ethylene copolymers havng a density in the range 0.910 to 0.940 gm/cm3 at 25C described in UK Patent Application No.
7,911,916 and Canadian Patent No. 873,828~

The invention is illustrated by the accompanying examples wherein unless otherwise indicated parts and percentages are by weight and temperatures are expressed in C.

Examples 1 - 9 The relevant compositions set out in the examples below were compounded on a 2 roll laboratory mill heated to a temperature of 120 - 140C, moulded at 190C into test plaques ~nd irradiated on a ;.8 MeV electron beam to a total dose of 6 Mrads. Flammability (Limiting Oxygen Index - LOI) was measured following the ASTM-D-2863 method; in addition 11~i;~343 Limiting Oxygen Indices and Critical Temperature Indices were obtained following the method of A.F. Routley (ERA
Symposium "Flammability and ~moke Testing Materials", London 1974) and described in detail by J. P. Redfern (Technical Information Sheet No. 24 "Critical Oxygen Index in Temperature Studies" available from Stanton Redcroft, a Division of L.
Oerting Ltd).

Example 1 The composition prepared from equal weights of a copolymer of vinyl versatate* ~25%) and vinyl acetate (75%) (hereinafter referred to as W /VA, and alumina trihydrate (ALTH) exhibited the following oxygen index values for the given test temperature The alumina trihydrate is known as Hydral 705 (Trade Mark -available from Alcoa Corporation) and was silane coated with 1.5~ vinyl trimethoxyethoxysilane.
Temperature C LOI

23 58.5 300 25.0 340 19.5 370 16.0 (*Vinyl versatate is the vinyl ester of versatic acid, a mixture of Cg, C11 acids available from Shell Ltd).

~l~iZ343 By extropolation of these results the critical temPerature index (CTI) (the temperature at which LOI equals 20.8%) was found to be 335C.

Example 2 A composition analogous to that of example 1 was prepared except that the percentage of W /VA in this example was 40~.
The following flammability was obtained.

Temperature C LOI

23 90.5 300 29.5 340 23.5 370 20.0 CTI = 360 Example 3 A composition containing W /VA, silane coated alumina trihydrate and Hytrel 4056 (Trade Mark - a polyester resin available from Dupont) was prepared. The weight ratio of the components was 36, 60 and 4% respectively. It exhibited a limiting oxygen index of 78.0 at 23C.

~16;Z3~3 Example 4 A composition similar to that in example 3 was prepared.
The weight ratio of the components was W /VA - 32~, Hytrel 4056 - 8~ and Silane treated ALTH - 60%. It exhibited a limiting oxygen index of 73.0 at 23C.

Example 5 A composition similar to that of example 4 was prepared with the following components; W /VA - 28%, Hytrel 4056 - 12~ and Silane treated ALTH - 60%. It exhibited a limiting oxygen index Gf 70.0 at 23C.

Example 5 A composition containing 50% W /VA and 50% hydrated magnesia was prepared in analagous manner to example 1. It exhibited a limiting oxygen index of 31.5 at 23C.

Example 7 A composition containing 50% W /VA 25% hydrated magnesia and 25% ~Ll~H was prepared in analagous manner to example 1. It exh:Lhited a limiting oxygen ir.dex oi 38.5 at 23C.

~ fi2343 - 19 - ~K96 Exam~le 8 A composition containing 50% W /VA, 33% ALTH and 17% Firebrake (Trade Name - zinc borate available from U.S. Borax Corp.) was prepared. It exhibited a limiting oxygen index of 41.0 at 23C.

Example 9 As a comparison, a sample of W JVA alone was prepared and tested. It exhibited a limiting oxygen index of 20.5 at 23C.

Ex les 10 to 53 amp In analogous manner to that described above the compositions set out in the accompanying Tables I, II and III were prepared and subjected to limiting oxygen index testing. In the tables, the following abbreviations are employed ..

- 20 - _K96 VV/VA~ ..... a 25% vinyl versatate (vide supra) 75~ vinyl acetate copolymer .

W /VA2 ..... a 78% vinyl versatate/22% vinyl acetate copol~ner VL/VA ..... a 50% vinyl laurate/50% vinyl acetate copolymer LLDPE ..... a linear low density polyethylene available from Dupont under the trade name Sclair ll-D-l BLDPEl ..... a branched low density polyethylere commercially available from Union Carbide Corporation under the trade name DYNH-3 Silicone ..... a commercially available polydimethyl-Elastomer siloxane rubber containing 25 reinforcing silica filler Silicone ..... a thermoplastic mono-organo poly-Resin siloxane produced in accordance with the process described in Example 3 of French Patent Application No.
7,822,138 by hydrolysing 166.4 moles of phenyltrichlorosiloxane and 93.7 moles of methyltrichlorosilane and end capping with 9.2 moles of trime-~ thylchlorosilane. The resulting ; :^esin has a T.~ softening point of EP~M ..... a linear terpolymer based on ethylene propylene diene monomer commercially available from Exxon Corp. undcr the trade name Vi.stalon 3704 ~1~23'~3 A1203- 3H20 alumina trihydrate coated with 1.5%
silane coated thereof of trimethoxyethoxysilane VA/W/E ..... an 85% vinyl acetate/10% vinyl versatate

5% ethylene terpolymer VA/E ..... a 60% vinyl acetate/40~ ethylene copolymer Hytrel ..... trade name for a thermoplastic elastomeric polyester derived from dimethyl terephth~late, a polyglycol and a short chain diol, commercially available from Dupont - Grade 4056 VA/VPA/El ..... ....a 19 mole ~ vinyl acetate/14 mo]e ~ vinyl phenyl acetate/67 mGle ~ ethylene terpolymer VA/VPA/E2 ..... ,. a 4 mole % vinyl acetate/7.3 mole % vinyi phenyl acetate/88.7 mole % ethylene terpolvmer VA/VP/E ..... a 25 mole % vinyl acetate/8 mole % vinyl palmitate/67 mole % ethylene terpolymer VA/VS/El ..... a 3 mole % vinyl acetate/15 mole % vinyl stearateJ82 mole % ethylene terpolymer VA/VS/E2 ..... a 2.7 mole ~ vinyl acetate/8.6 mole ~ vinyl stearate/88.7 mole % ethylene terpolymer VA/VB/E ~...... a 2.7 mole ~ vinyl ac~tate/8.6 mole ~ vinyl b~nzoaJce/88.7 mole ~ ethylene terpolymer i;162343 VA/VH/~i .,,,, a 4.7 mole % vinyl acetate/6.6 mole % vinyl hexanoa~e/88.7 mole % ethylene terpolymer VA/VI./E . . . ~ . a 1.9 mole % vinyl acetate/9.4 mole % vinyl laurate/88.7 mole % ethylene terpolymer VPA/E ..... an 18 mole % vinyl phenyl acetate/82 mole . ethylene copolymer ,~
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In the preceeding Examples ~here LOI values in the range 25 to 35 are obtained, these are accompanied by a notable balance oi physical properties as rneasured for example by tensile strength (MPa) and elongation at break (%) at 23C
(per BS903 part A2). Such properties r~nder such materials suitable for hea~-recoverable applications or for proces~ing by thermoforming techniques into, e.~. cladding and panneling. ln the preceeding Examples where hi~her LOI
values are obtained, e.g. greater than 35, and depending on the particular application it is desired to al~er the balance of physical properties, this may be achieved by changing the filler le-lel and/or by blending with an appropriate polymer whilst still permitting high LOI values to be achieved.

xamples 54 to 57 In analogous manner to that described above, the compositions set out in Table lV were prepared and subjected 'co limiting oxygen index and physical property testing. In the tables, the following abbreviatiol1s are employed. Other abbreviations are as previously defined in Examples 10 to 53.

VA/VH/E2 ........... a 28 mole % vinyl acetate/5 mole % vinyl hexanoate/67 rnole ~ ethylene terpolymer VA/VS/E3 ........... a 27 mole ~ vir~y:l acetate/6 mole % vi~yl stearale/67 mole O ethylene terpolYmer ~16~3 - 27 - RIt96 VA/VH ..... a 7 8 mole g~ vinyl hexanoa te/2 2 mole ~6 vinyl acetate copolymer.

i~

TABLE IV

CONSTITUENTS ~ _____________ _ __ 54 55 56 57 __ _ .

~_ ___ _. __ _ ~ ~ ~ __ _ _~ ______ ___ __ ~___ __.
Al203 3H20 68 60 60 60 ~__ . --_ Silicone Elastomer 16 _. ___ . . , ., , __ Electron Beam Dosage (Mrads) 12 12 12 12 ____ ..__ _ __. ___ LOI @ 23C 54.5 38.0 36.2 60.2 _ __ ~ ~ . .r Tens~le Strength (MPa) @ 23 C (per BS703 part A2) 11.1 . _ 6.36 __ % Elonqation at break @ 23 (per BS703 ~r~ A~) 63 _ 86 _ ~1'162343 - ~Y - RK96 Example 58 Example 1 is repeated employing each of the followin~
copolymers instead of W /VA viz.

(a) Vinyl laurate (40%)/Vinyl acetate ~60%) (b) Vinyl stearate (40%)/Vinyl acetate (60%) S (c) Vinyl versatate (40~)/Vinyl acetat (d) Vinyl benzoate (40%)/Vinyl acetate (60~) (e) Vinyl versatate (40%)/Vinyl acetate (60%) - (f) Vinyl stearate (40%)/Vinyl acetate (60%) (g) Vinyl benzoate (40%)/Vinyl acetate (60%) (h) Ethylene (59%)/Vinyl acetate (7%)/Vinyl phenyl acetate ~34%) (i) Ethylene (56~)/Vinyl acetate (11%)/Vinyl laurate ' (33~

In each case, substantial flame retardancy is observed.

,~ ~ "
,.. ..

Example _ To exempl7.fy the abili~y of the po]ymer systems of the invention to accept high loadings of inorganic fillers, a VA/VL copolymer (vide s~ ) was loaded with 80~ of silane coated alumina trihydrate (vide supra) and cross-linked in analogous manner to that described in Example 1. The resul~ing material exhibited the following LOI values at different temperatures whilst possessing an acceptable balance o.
physical properties.

__ __ TEMPERATURE LOI
__ ~

~_ ~62343 Examples 60 - 65 Heat-shrinka~le tapes were produced from the formulations set out in Table V. In -the table tne following abbreviations are employed. Other ahbreviations are as defined in the preceeding Examples.

BLDPE2 ..... a branched low density polyethylene avai].able under the trade name PN220 from BXL Limited.

EVA ..... an ethylene/vinyl acetate copol~mer 18~ vinyl acetat~

Al203. 3~2 alumina trihydrate available under the stearic acid trade name Hydral 705 from Alcoa Corp.
and coated with 2~ stearic acid The constituents of ~ach formulation were compounded on a twin roll mill at 120 to 140C, cooled and pelletised. The pellets so produced were fed to a conventional extruded filler with a tape die, maintained at 140C and extruded into a tape 6mm wide and 2mm thick. The resulting tape was subsequently irradiat~d w:ith hi.gh energy electrons to a total dosage o~ 8 Mrads. After irradiatlon, the tape was heated to 1~0C, eY.pand~d lenyth wise ~o double i~s ~4~
- 32 - RX9~

original ].engtll and allowed to cool in this expanded condition.
ThereaEter the tape was coated with a thin layer (O.~mm) of ~ hot-melt adhesive of composition in accordance with W.
German Ofrerllegungschrift 2,723,116, Ex~nple 3, formulation "O". The physical properties and LOI of the resulting tapes are set out in Table V.

The heat-shrinkable adhesive coated tapes so produced were employed to seal the joints of 150mm diameter metal air conditioning ducts by preheating the duct in the region of the joint, wrapping each tape around the duct over the joint ~egion so that sequential turns of each tape partially overlap and heating each tape with a conventional propane gas torch to a temperature of 145C, so causing the adhesive to melt and each tape to shrink tightly around the joint and form a strong adhesive band between each tape and duct.

~62343 ~ 33 - RK96 TAeLE V
-,_ ~
_ EXhMPLE NO. .
CONSTITUFNTS _ _ ~._ ,_. ___ VL/VA 20 ~ 30 60 90 __ __ _ __ __ ~
BLDPE2 10 10 . 30 _____ ____ ~
VAE 20 ¦ 10 60 30 ___ _~_ _ __ _. _ __ ______ __ _ _ . _.___ Steari c Aci d 50 50 160 160 160 160 Coated ___ __ _____ ~ Elonga2t30c at 320 340 400 400 ¦ 518 366 __ __.__ ,___ _~
@ 150~ 400 400 400 7400 400 350 __ __.____ Tensile stOength 3.2 2.3 6.4 4.1 8.3 5.8 _ _ ~ _ _ _ @ 150C 0.9 0.6 0.9 0.8 1.7 1.5 _. __ ._ ____ ';00% Tangent Modulus @150~C 0.4 0.2 0.50 0.35 0.85 0.8 D~ _ ~_. ~ ~ _ LOI 29.5 29.5 30.5 31.5 26.0 27.0 _ _ _ 11~43 J~XAMPLE 6 6 ___ ~
CONST:~TUE~TS Pl~TS BY WE:[GI-IT
~_ .~

Al 2 O 3 . 3H 2 Si ane Coated 150 ___ _._ The a~ove formulation was compounded in an internal mixer of the Ban~ury t~lpe, at a temperature of about 1~5 C. After compoundin~, the material was processed into a strip on a twin roll mill, cooled diced into pell~ts, and lightly talced to prevent blocking of the pellets. The material was then extruded as a cable jacket onto a m~lti-conductor cable of O.D. 22.5r~m to provide a jacket having a wall thickness of 1.2mm, using a 3~ inch extruder, 25.1 L/D ratio screw, at barrel temperatures of 60, 80, 110, 120 and 130C and an extruded die temperature temperature profile of 150, 140 ~nd 120C. The jacketed ca~le was then irracliated with high energy electrons to a total dose of 8 Mrads. The jacketed material was ~ound to have the following properties.

~162~43 - 35 ~ RK96 ~ ~'loncJation @ 23C ..... 100 'I~c,lsile Stength (l~l~a) @ 23C ..... 8 LO:X @ 23C ..... 31. 5 CTI ..... ~ 50C

Claims (28)

Claims

1. A melt-fabricated flame-retarded polymeric composition which comprises a non-cross-linked or cross-linked vinyl ester copolymer with at least 35 weight % of vinyl ester monomer(s) according to formula I, I

wherein R1, R2 and R3 are each independently hydrogen or a substituted or unsubstituted hydrocarbon and R4 is a substituted or unsubstituted hydrocarbon containing at least 3 carbon atoms, and incorporating an effective amount of a flame retardant.

2. A composition according to Claim 1 wherein R1, R2 and R3 of formula I are each independently hydrogen or a C1 - C20 substituted or unsubstituted hydrocarbon, and R4 is a C3 - C20 substituted or unsubstituted hydrocarbon.

3. A composition according to Claim 1 wherein R1, R2, R3 of formula I are each, independently, hydrogen or C1 - C6 alkyl.

4. A composition according to Claim 3 wherein R1, R2 and R3 of formula I are each hydrogen.

5. A composition according to Claim 1 wherein R4 of formula I is C3 - C20 alkyl, alkenyl, alkoxyalkyl or alkoxyalkenyl, aryl, aralkyl, or aryl or aralkyl substituted by C1 - C4 alkyl or alkoxy.

6. A composition according to Claim 5 wherein R4 of formula I is C3 - C20 alkyl, alkenyl, alkoxyalkyl or alkoxy-alkenyl, phenyl, naphthyl, benzyl, or phenyl, naphthyl or benzyl substituted by C1 - C4 alkyl or alkoxy.

7. A composition according to Claim 6 wherein R4 of formula I is C3 - C17 alkyl, phenyl or benzyl.

8. A composition according to Claim 1 wherein the vinyl ester polymer is a copolymer of a vinyl ester as defined with a different ester and/or an unsaturated hydrocarbon.

9. A composition according to Claim 8 wherein the vinyl ester polymer is a copolymer of a vinyl ester as defined with a different vinyl ester, the ester grouping of which contains at least 2 carbon atoms, a C4 - C12 olefin and/or a C4 - C12 (meth)acrylate.

10. A composition according to Claim 9 wherein the vinyl ester polymer is a copolymer of a vinyl ester polymer as defined with vinyl acetate and/or ethylene.

11. A composition according to Claim 1 wherein the vinyl ester copolymer contains at least 5 mole % of a vinyl ester monomer containing at least 4 ester carbon atoms.

12. A composition according to Claim 11 wherein the vinyl ester copolymer contains 10 to 95 mole % of a vinyl ester monomer containing at least 4 ester carbon atoms.

13. A composition according to Claim 1 wherein the composition comprises a blend of the vinyl ester copolymer with at least one other polymer.

14. A composition according to Claim 13 wherein the blend polymer comprises a polyethylene, polyester, a silicone resin or elastomer, a (meth)acrylate homo - or copolymer, an ethylene/viny acetate copolymer, an EPDM or an SBR.

15. A composition according to either of Claims 13 or 14 containing at least 20 weight % vinyl ester copolymer in the blend.

16. A composition according to Claim 1 in substantially cross linked form.

17. A composition according to Claim 16 having a gel content in accordance with ANSI/ASTM D2765-68 of at least 10%.

18. A composition according to Claim 1 wherein the flame retardant is an inorganic flame retardant.

19. A composition according to Claim 18 wherein the inorganic flame retardant is hydrated.

20. A composition according to Claim 19 wherein the hydrated inorganic flame retardant comprises alumina trihydrate.

21. A composition according to Claim 1 incor-porating 10 to 400 parts of flame retardant per 100 parts of polymer(s).

22. A composition according to Claim 1 incor-porating less than 5 weight per cent halogen or phosphorus.

23. Flame retarded electrical insulation comprising a composition as defined in Claim 1.

24. A wire or cable provided with electrical insulation according to Claim 23.

25. A flame retarded heat-recoverable article comprising a composition as defined in Claim 1 in a cross-linked and heat-recoverable form.

26. An article according to Claim 25 in the form of an extruded tape, sheet or sleeve or a hollow moulded part.

27. An article according to either of Claims 25 or 26 incorporating a thermoplastic polymer.

28. An article according to either of Claims 25 or 26 incorporating a thermoplastic ethylene homo -or copolymer.