GELS This invention relates to gel compositions comprising a block copolymer having an elastomeric mid-block between relatively hard end blocks and at least 200 (preferably at least 300) parts by weight, per 100 parts by weight of the said copolymer, of an extender liquid which extends and softens the said mid-block. The relatively hard end blocks of the copolymer are selected to undergo phase separation within the copolymer mass, thus acting as pseudo-cross-links in the gel at temperatures below the end-block softening temperature, while the gel remains fully thermoplastic at higher temperatures, as known per se. Such gels made from block copolymers having styrene (which term includes alpha-methyl styrene) end blocks are described in WO-A-8800603 (RK308), WO-A- 9005166 (RK403), WO-A-9305113 (RK451), WO-A-9323472 (RK469), and WO-A- 9418273 (RK472), the disclosures of all of which are incorporated herein by reference.

Other such gels, made from block copolymers having alkyl methacrylate end blocks of potentially higher temperature performance, are described in WO-A-9700292 (RK509), the disclosure of which is incorporated herein by reference.

Although the block copolymers may be largely composed of combustible hydrocarbon, and a majority by weight of the gels may be combustible extender liquid, preferably paraffin/naphthene oil, it has been found according to the present invention that the gels may be flame-retarded to a commercially significant degree using surprisingly low levels of various flame-retardant additives.

The invention accordingly provides a flame-retardant gel composition comprising a block copolymer having an elastomeric mid-block between relatively hard end blocks, at least 200 (preferably at least 300) parts by weight, per 100 parts by weight of the said copolymer, of an extender liquid (preferably a hydrocarbon oil) which extends and softens the elastomeric mid-block (preferably substantially only the mid-block) of the said copolymer, and flame-retardant additive in an amount of not more than 40% by weight based on the combined weight of the said copolymer, extender liquid and additive, the amount of the said additive being sufficient to reduce the burning rate of a sample of the composition by at least 25 %, preferably at least 45 %, more preferably at least 65 %, when tested in accordance with the UL-94 Horizontal Burn Test (19 April 1995 version).

The relatively hard, phase-separating end blocks of the copolymer may for example be polystyrene or poly(alpha-methyl styrene), as in the styrene-ethylene/butylene-styrene (SEBS) and styrene-ethylene/propylene-styrene (SEPS) triblock copolymers described in the first five references mentioned above, or the end blocks may be alkyl (preferably methyl) methacrylate as in the sixth reference above. The copolymers are not necessarily restricted to triblocks, and more than one kind of end block may be present, for example as in the methacrylate-styrene-alkylene-styrene-methacrylate penta-block copolymers also described in the sixth reference. The extendable mid-block will preferably be a polyalkylene, more preferably a hydrogenated polyalkylene, of relatively high molecular weight, preferably having a number average molecular weight Mn of at least 38000, preferably within the range from 38000 to 150000, more preferably 50000 to 140000, especially 60000 to 130000. The harder end blocks preferably have lower Mn, for example in the range from 30000 to 40000.

Depending on the specific gel composition and the specific flame-retardant additive selected, it has been found possible to produce gel compositions according to the present invention wherein the amount of the said additive is sufficient (a) to achieve self-extinction of the said sample when tested as aforesaid and/or (b) to avoid ignition of cotton wool positioned 30 cm below the said sample when so tested. Furthermore, the flame-retarding performance according to the present invention may be achieved in preferred cases when the amount of the flame-retardant additive is not more than 35 %, preferably not more than 30%, by weight of the composition. It is usually preferable that the amount of the flame- retardant additive is at least 5 %, preferably at least 10%, more preferably at least 15 %, by weight of the composition. It has very surprisingly been found that the desired levels of flame-retardancy tend to be achieved more easily as the proportion of combustible extender oil in the gel increases, contrary to the natural expectation that more oil would render the gel more combustible. Thus, the present invention may be especially useful in gels wherein the weight ratio of the extender liquid to the said polymer is within the range from 3:1 to 30:1, preferably 4:1 to 15:1, especially 4:1 to 10:1.

Suitable flame-retardant additives may be selected from known flame-retardant materials. One class of such materials, for example, comprises halogenated organic compounds, preferably in combination with a synergist such as antimony oxide.

Preferably, the flame-retardant additive comprises a char-forming or intumescent material.

Especially-preferred flame-retardant additives comprise phosphorus or a phosphorus compound.

In one preferred form of the gel compositions according to the present invention, the flame-retardant additive comprises inorganic phosphate, preferably ammonium polyphosphate, preferably together with a nitrogen-containing synergist therefor.

Preferred synergists include organic amine phosphates, preferably melamine phosphate.

These flame-retardant additives may further include polyols, preferably pentaerythritol.

In other preferred forms of the invention, the flame-redardant additive comprises organic phosphates other than the above synergists, possibly, but not necessarily, in the absence of inorganic phosphates. Preferred organic phosphates for this form of the invention include phosphate oils, for example one or more selected from tris(2- chloroethyl)phosphate (TCEP), tris (2-chloropropyl)phosphate (TCPP), trixylyl phosphate, and tributoxyethyl phosphate.

In a further preferred form of the invention the flame-retardant additive comprises red phosphorus, the additive preferably being supplied in the form of a mixture of the phosphorus with organic polymer (preferably a phenol-formaldehyde resin), the amount of the red phosphorus preferably being up to 70%, more preferably up to 60%, by weight of the additive mixture.

Mixtures of the various additives hereinbefore described may be used. The additive materials and quantities will preferably be selected to retain physical properties of the gels within typical "gel-like" ranges, for example substantially elastic recovery after elongation up to 100%, preferably up to 200%; tensile strength less than 1 MPa; and dynamic storage modulus G' less than 0.05MPa, as described in the aforementioned WO-A-9005166.

Some classes of additive, notably the phosphate oils, when used in higher percentages may tend to reduce the elongation of the gel material below desirable levels. Lower levels of the phosphate oils together with additional amounts of one or more solid flame-retardant additives may be advantageous.

The invention includes the use of the gel compositions as a sealant between adjacent solid surfaces, many such uses of un-flame-retarded gels being known per se.

The invention also includes sealant gaskets or profiles comprising a carrier member carrying coatings of the gel composition. The invention is especially relevant to gels for use in commercial or domestic environments, for example in appliances, instrumentation, communications equipment, where UL94 performance is increasingly required.

Specific embodiments of the present invention will now be described by way of example.

The weight percentages of flame retardants (based on the whole composition) indicated in the following table were stirred together with the extender oil, the copolymer and a small amount of antioxidant. After five or ten minutes, the mixtures were converted into gels using known methods and conditions by mixing for 1 hour at 220"C in a 1 litre Baker Perkins Z-blade mixer. The resulting gels with the indicated oil/copolymer weight ratio (O/R) were made for these examples either from SEPS triblock copolymer available under the Trade Mark "Septon 2006" (from Kuraray) and a paraffin/naphthene oil available under the Trade Mark "Vestan A360B" from Fina Chemicals, or from SEBS triblock copolymer available under the Trade Mark "Kraton G1654" from Shell and a paraffin/naphthene oil available under the Trade Mark "Witco 380" from Witco. In all cases, 0.5% of antioxidant (Irganox 1010 Trade Mark) was included, based on the total composition weight. The gels were pressed into 125 mm x 50 mm x 6 mm plaques. Bar samples 125 mm long, 13 mm wide, and 6 mm thick were cut from these plaques using a hot knife and were tested in accordance with the UL 94 Horizontal Burning Test (April 19, 1995) to give the indicated burning rates in mm per minute ("SE"=Self extinguished).

Also recorded was ignition (Y) or non-ignition (N) of cotton wool placed 30 cm below the test sample as a modification of this test, which does not call for the cotton wool. Ex. No. Flame Retardant Additive Additive Gel O/R Burn Time to Ignite (Trade Mark unless stated not) % mm/min SE (sec) cotton S2006 Control nil 6:1 29.5 - Y 1 Am ard MPC1000 29.5 6:1 SE N 2 TCEP (not Trade Mark) 29.5 6:1 SE 1 N 3 Novomasse 29.5 6:1 SE 5 N 4 Hostaflam AP745 29.5 6:1 SE 41 N 5 Hostaflam AP750 29.5 6:1 SE 59 N 6 Melapur X69 29.5 6:1 SE 101 N 7 Saytex 8010/Fireshield (2:1) 29.5 6:1 SE N 8 Melapur P46 29.5 6:1 6.57 N 9 S Spinflam (Z-blade mixer) 29.5 6:1 3.9 Y 10 Spinflam (Brabender mixer) 29.5 6:1 9.1 Y 11 Pyrochek/Sb2O3 (2:1) 29.5 6:1 5.3 Y 12 Melamine cyanurate 29.5 6:1 9.6 Y 13 Bentone 38 29.5 6:1 9.4 Y 14 Firebrake 290 29.5 6:1 12.0 Y 15 Firebrake 290/Fireshield (2:1) 29.5 6:1 15.6 Y 16 Magnifin fin H5 29.5 6:1 13.8 Y 17 MelapurP46/Saytex 8010 (1:1) 29.5 6:1 8.9 Y 18 MelapurP46/Saytex 8010 (2:1) 29.5 6:1 7.9 Y 19 MelapurP46/Saytex8010/ 29.5 6:1 10.1 Y Fireshield (4:2:1) 20 Bentone 38/Magnifin H5 (1:1) 29.5 6:1 7.6 Y 21 Spinflam 35.0 6:1 10.4 Y 22 Phosflex 179A 30.0 6:1 SE 1 N 23 Phosflex T-BEP 30.0 6:1 SE 1.3 N 24 Phosflex 179A 20.0 6:1 SE instant N 25 Phosflex T-BEP 20.0 6:1 SE 6 N 26 Melapur P46 35.0 6:1 SE 166 N 27 Amgard MC 35.0 6:1 17.7 Y 28 Bromoklor 70/Sb203 (2: 1) 20.0 6:1 11.6 Y 29 Novomasse 15.0 6:1 21 Y 30 Saytex 8010/Fireshield (2:1) 15 6:1 23 Y 31 Am Amgard MPC1000 15 6:1 17.1 Y 32 Phosflex 179A 10 6:1 4.8 Y 33 Phosflex T-BEP 10 6:1 18.8 Y 52006 Control nil 4:1 24.6 Y 34 Spinflam 30.0 4:1 SE 5.8 N 35 Novomasse 30.0 4:1 SE 10 N 36 Am Amgard MPC1000 30.0 4:1 SE 20 N 37 Saytex 8010/Fireshield (2:1) 30.0 4:1 8.2 Y S2006 Control nil 9:1 24.3 Y 38 TCEP (not Trade Mark) 10 8:1 SE 2 N S2006 Control nil 19:1 SE 2 N 39 Amgard MPC1000 30.0 19:1 SE 2 Y In another set of Examples using Kraton G1654 SEBS triblock copolymer, the following results were similarly obtained. Ex. No. Formulation Additive gEL O/R Burn Time to Ignite % mm/min SE (sec) Control 10% Kraton G1654 nil 8.3:1 Y 2% Irganox B225 A/Oxidant 88% Witco 380 Oil Control 6% Kraton G1654 nil 15.3:1 Y 2% Irganox B225 92% Witco 380 40 10% Kraton G1654 10 7.8:1 Y 2% Irganox B225 78% Witco 380 10% Bromklor 50 41 10% Kraton G1654 15 7.3:1 2/5 Y 2% Irganox B225 73% Witco 380 10% Bromklor 50 42 6% Kraton G1654 13 13:1 N 2% Irganox B225 79% Witco 380 10% Bromklor 50 3% Antimony trioxide Flame retardant additives in the above gel formulations Trade Name @ Chemical Amgard MC ammonium polyphosphate (APP) Melapur P46 APP + melamine phosphate + pentaerthyritol (3:1:1) Melapur X69 Similar to above but contains a higher mol wt polyol Amgard MPC 1000 @ Formulated intumescent 5 stem similar to Melapur P46 llostaflamAP745 APP+melaminecanurate+ Decomp temp 230°C. Hostaflam AP750 Like AP745, but less moisture sensitive. Decomp > 250°C. Spinflam MF82/PE APP + with nitrogen-containing synergist TCEP Tris (2-chloroethyl) phosphate Phosflex 179 A Trixylyl Phosphate (aromatic) Phosflex T-BEP Tri-butoxyethyl phosphate (aliphatic) Novomasse Phenol-formaldehyde resin cont. 60 wt%red phosphorus Firebrake 290 Zinc borate Magnifin H5 Magnesium hydroxide Saytex 8010 Decabromo diphenylethane Fireshield antimony trioxide Pyrochek 68PB \ brominated polystyrene Bentone 38 organclay (thixotrope) Bromoklor 70 Halo-aliphatic oil:35%Br, 35%Cl, SG 1.65-1.67 Bromoklor 50 Halo-aliphatic oil:33%Br, 19%Cl, SG 1.36-1.38 Examples 22 to 25, 32 and 33 illustrate the aforementioned point that some additives may detract from desirable gel properties to some extent. The Phosflex additives used at 30% levels in Examples 22 and 23 produced good flame-retarding performance, but reduced the elongation to break from the desirable 100+ % to less clearly "gel-like" levels of 67% and 49% respectively, while tensile strength and dynamic storage modulus remained within the desirable gel-like ranges. When the same additives were used at 10% level as in Examples 32 and 33, the elongations were over 200% and over 100% respectively, but with less flame retardancy. The 20% additive levels of Examples 24 and 25 produced good flame retardancy with expected borderline gel elongations. Thus, mixtures of the Phosflex oils with other solid flame-retardant additives may advantageously provide good flame retardancy with better gel properties, possibly with less total additive.