INTUMESCENT COMPOSITION

Abstract: The composition contains exfoliating graphite and a carrier which is preferably polyvinyl chloride. The composition can be produced by thermoforming or injection moulding of a suitable mixture. Composite products of which a first layer is formed by an intumescent composition as mentioned and a second is a plastics material are also described. Such composite products are made by thermoforming or injection moulding and may constitute electrical components such as conduits, conduit couplings, sockets, switches and light fittings.

Description: INTUMESCENT COMPOSITION This invention relates to intumescent materials which find application as fire-stop materials, for example fire penetration seals and cavity fire-stops, and otherwise. Known intumescent fire-stop or penetration-sealing products include: sealants and mastics which comprise exfoliating graphite in a suitable carrier material; intumescent pipe bands, collars and wraps; intumescent blocks, grills and strips; intumescent fire pillows; intumescent expansion joints; intumescent cavity and lap-jointing seals; intumescent paints; lightweight cavity barriers; and doorstrips which comprise intumescent material. All the intumescent products mentioned may contain exfoliating graphite . These products are incorporated into buildings, automobiles, aircraft, ships and boats at various stages and places in their construction or refitting and all have the property of intumescing when subjected to the heat of a fire and thereby closing a passageway through which the fire, flame and/or smoke would otherwise spread. The products thereby protect the elements of the building from structural collapse and may also allow a means of escape according to prescribed requirements in the relevant country or other geographical area. The products are however subject to disadvantages in that their incorporation into or onto the structure of a building, automobile, aircraft, ship or boat is a time-consuming operation or, in certain cases, the products themselves (e.g. cavity seals, lap joints, lightweight cavity barriers and doorstrips) are difficult to manufacture as they consist of assemblies of two or more component parts. According to the present invention a material comprising one or more of acrylonitrile butadiene styrene (ABS) , polyphthalamide (PPA) , crystalline polystyrene and polycarbonate is used as a carrier for exfoliating graphite in an intumescent composition. The invention also provides an intumescent composition which comprises the said carrier material and exfoliating graphite . The amount of carrier material in the composition is preferably from 30 to 65%, more preferably 30 to 55%, most preferably 30 to 45%, by weight of the composition. The amount of exfoliating graphite is preferably from 5 to 50% by weight, more preferably 15 to 45% by weight, most preferably 25 to 35% by weight of the composition. The invention further provides intumescent compositions produced by a process which comprises subjecting a mixture of a carrier material and exfoliating graphite to a thermoforming process or an injection moulding process. The thermoforming process is preferably a vacuum or pressure thermoforming process. The injection moulding process is preferably a one-shot injection moulding process, a two-shot injection moulding process or a gas-assisted injection moulding process. The carrier material is preferably a plastics material, more preferably comprising one or more of polyvinyl chloride, polyethylene, polypropylene, polyethylene-polypropylene copolymer, acrylic polymer or copolymer, metallocene polymer, polyphthalamide (PPA) , crystalline polystyrene, polycarbonate, acrylonitrile-butadiene-styrene (ABS) , silicone rubber or polymer and natural and synthetic polymer and rubber latexes (preferably comprising one or more of the foregoing) . The invention accordingly provides a mixture comprising the said carrier material and exfoliating graphite which is formable by a thermoforming process or mouldable by an injection moulding process; and a composition produced by subjecting a mixture of the said carrier material and exfoliating graphite to thermoforming or to injection moulding. The amount of carrier material in the composition or mixture is preferably from 30 to 65%, more preferably 30 to 55%, most preferably 30 to 45% by weight of the composition or mixture. In all aspects of the invention, the amount of exfoliating graphite is preferably from 5 to 50 % by weight, more preferably 15 to 45% by weight, most preferably 25 to 35% by weight of the composition or mixture. Compositions and mixtures of the invention preferably contain one or more plasticisers, at least one of which preferably has a fire-retardant effect. The or at least one of the plasticisers is preferably a phthalate plasticiser. The plasticiser (s) are suitably present in an amount of up to 35% by weight of the composition or mixture, preferably from 10 to 30% by weight, more preferably 20 to 30% by weight. The compositions and mixtures of the invention preferably also contain one or more stabilisers, preferably of low toxicity, suitably in a total amount of up 1% by weight of the composition or mixture, preferably 0.015 to 0.025% by weight. Compositions and mixtures of the invention may contain an inert filler, preferably in an amount of 4 to 6% by weight of the composition or mixture. Suitable exfoliating graphite materials are those sold under the names "Callotek 50", "Callotek 100", "Callotek 200", "Callotek 500" and "Callotek 600" and available from P.F.C. Surechem Limited of Davis Road, Chessington, Surrey, KT9 1TV, United Kingdom. A typical single-shot injection-moulding process is one in which the composition or mixture to be moulded is injected into a mould or tool under pressure and solidifies to form a finished product. A typical two-shot injection moulding process is one in which the composition or mixture to be moulded is injected into a mould or tool by a first injection unit and the mould or tool is then rotated and a second composition or mixture is injected by a second injection unit to provide a second body of material moulded over the first, for example when aesthetic considerations are important. A typical gas-assisted injection moulding process is one in which the composition or mixture to be moulded is injected into a mould or tool and a gas under high pressure is also shot into the mould or tool to hollow-out certain parts of the finished product which would otherwise be thicker. A typical vacuum thermoforming process is one in which an article, produced for example by extrusion, is simultaneously heated and pushed or drawn into a mould or tool, so that, upon cooling, the article conforms to the shape of the mould or tool . In a typical pressure thermoforming process, a superatmosphere pressure is created around the mould or tool and the article is deformed accordingly. This tends to produce surface definition in the final product which is better than in vacuum thermoforming. In another aspect, the present invention provides a composite product formed by a thermoforming or injection moulding process, the composite product comprising first and second portions or layers of respective different materials, the first material being an intumescent composition comprising exfoliating graphite and a carrier material. The second material is preferably a plastics material, more preferably polyvinyl chloride . The thermoforming process is preferably a vacuum or pressure thermoforming process. The injection moulding process is preferably a one-shot injection moulding process, a two-shot injection moulding process or a gas-assisted injection moulding process. The carrier material is preferably a plastics material, more preferably comprising one or more of polyvinyl chloride, polyethylene, polypropylene, polyethylene-polypropylene copolymer, acrylic polymer or copolymer, metallocene polymer, polyphthalamide (PPA) , crystalline polystyrene, polycarbonate, acrylonitrile-butadiene-styrene (ABS) , silicone rubber or polymer and natural and synthetic polymer and rubber latexes (preferably comprising one or more of the foregoing) . The first material preferably contains from 5 to 50% by weight of exfoliating graphite, more preferably 15 to 45% by weight, most preferably 25 to 35% by weight, based on the weight of the first material. The amount of carrier material in the first material is preferably from 30 to 65%, more preferably 30 to 55%, most preferably 30 to 45% by weight of the first material. The first material may contain one or more plasticisers and/or one or more stabilisers and/or an inert filler, of the types and in amounts based on the first material as stated above for the first-mentioned compositions and mixtures of the invention. The intumescent composition produced according to the invention by thermoforming or injection moulding preferably forms all or part of an electrical component, for example a conduit or conduit coupling, a socket box, or a switch box. Composite products according to the invention preferably also form all or part of an electrical component. Such components are preferably components in which the second material has a reflective surface, for example in a lighting component, or has an aesthetic function to cover, at least partially, the first material. The terms •■ polyvinyl chloride" and "PVC" are each used throughout this specification and its claims to cover plasticised and unplasticised polyvinyl chloride and also derivatives of both those materials. Similarly the terms "polyethylene" and "polypropylene" used to cover both these materials themselves and also derivatives thereof. The invention will be described further by way of the following examples 1 to 3. Embodiments of the invention will now be described by way of example with reference to the drawings, in which: Figure 1 is a side view of a cable conduit coupling having a single-walled construction; Figure 2 is a section on the line II -II of Figure 1; Figure 3 is a side view of a cable conduit coupling having a twin-walled construction; Figure 4 is a section on the line IV-IV of Figure 3; Figure 5 is a side view of a pipe coupling having a single-walled construction; Figure 6 is a section on the line VI -VI of Figure 5; Figure 7 is a side view of a pipe coupling having a twin- walled construction; Figure 8 is a section on the line VIII-VIII of Figure 7; Figure 9 is a plan view of an electrical socket box having a single-walled construction; Figure 10 is a plan view of an electrical socket back box having a twin-walled construction; and Figure 11 is a transverse sectional view of an electrical downlighte . The cable conduit coupling 11 shown in figures 1 and 2 of the drawings was produced by a single-shot injection moulding process using a composition according to example 1. The injection moulding machine used was a DGP Windsor SPH machine fitted with a suitable tool . Other couplings were made on the same machine from compositions according to examples 2 and 3. Similar couplings using compositions according to examples 1, 2 and 3 were made using a DGP Windsor FRC injection moulding machine. The cable conduit coupling shown in figures 3 and 4 of the drawings has an inner layer 21 of a material according to the invention and an outer layer 22 of polyvinyl chloride which is coloured for aesthetic reasons. The coupling was made by a two-shot injection moulding process using a DGP Windsor SPH machine fitted with a suitable tool. The first material to be introduced was in accordance with example 1; the second material was polyvinyl chloride. Other couplings were made on the same machine replacing the composition according to example 1 by compositions according to examples 2 and 3, respectively. Similar couplings using compositions according to examples 1, 2 and 3 were made using a DGP Windsor FRC injection moulding machine. The pipe coupling 31 shown in figures 5 and 6 of the drawings was produced by a single-shot injection moulding process using a composition according to example 2. The injection moulding machine used was a DGP Windsor SPH machine fitted with a suitable tool. Another coupling were made on the same machine from a composition according to example 3. Similar couplings using compositions according to examples 2 and 3 were made using a DGP Windsor FRC injection moulding machine . The pipe coupling shown in figures 7 and 8 of the drawings has an inner layer 41 of a material according to the invention and an outer layer 42 of polyvinyl chloride which is coloured for aesthetic reasons. The coupling was made by a two-shot injection moulding process using a DGP Windsor SPH machine fitted with a suitable tool. The first material to be introduced was in accordance with example 2; the second material was polyvinyl chloride. Another coupling was made on the same machine replacing the composition according to example 2 by a composition according to example 3. Similar couplings using compositions according to examples 2 and 3 were made using a DGP Windsor FRC injection moulding machine. The electrical socket back box 51 shown in figure 9 of the drawings was produced by a single-shot injection moulding process using a composition according to example 2. The injection moulding machine used was a Sumitomo SHM machine fitted with a suitable tool . Another socket box was made on the same machine from a composition according to example 3. Electrical lighting switch back boxes can be made by similar moulding processes . The electrical socket back box shown in figure 10 of the drawings has an inner layer 61 of a material according to the invention and an outer layer 62 of polyvinyl chloride which is coloured for aesthetic reasons. The box was made by a two- shot injection moulding process using a Sumitomo SHM machine fitted with a suitable tool. The first material to be introduced was in accordance with example 2 ; the second material was polyvinyl chloride . Another socket box was made on the same machine replacing the composition according to example 2 by a composition according to example 3. Electrical lighting switch back boxes can be made by similar moulding processes. The electrical downlighter shown in figure 11 of the drawings has a twin-walled construction having outer and inner layers 71, 72. The outer layer 71 was formed by thermoforming an extruded sheet of a composition according to example 2 by use of a Sumitomo SHC thermoforming machine. The inner layer 72 was formed from a reflective metal or metal alloy, the outer layer 72 being thermoformed to fit the outer dimensions of the inner, reflector layer 71. A further downlighter was made in a similar manner but using a composition according to example 3. The products according to the invention described above were tested for compliance with fire safety requirements by heating in a furnace at a temperature and for a time specified by the relevant test requirements. All products were found to exhibit good intumescent firestop characteristics.

Claims: CLAIMS : 1. An intumescent composition comprising exfoliating graphite and a carrier material selected from acrylonitrile butadiene styrene, polyphthalamide, crystalline polystyrene, polycarbonate and mixtures of any of the foregoing. 2. A thermoformable or injection mouldable mixture comprising exfoliating graphite and a carrier material selected from acrylonitrile butadiene styrene, polyphthalamide, crystalline polystyrene, polycarbonate and mixtures of any of the foregoing. 3. An intumescent composition produced by thermoforming or injection moulding of a mixture according to claim 2. 4. An intumescent composition produced a process which comprises subjecting a mixture of a carrier material and exfoliating graphite to a thermoforming or injection moulding process . 5. An intumescent composition according to claim 4, in which the carrier material comprises a plastics material . 6. An intumescent composition according to claim 5, in which the plastics material comprises one or more of polyvinyl chloride, polyethylene, polypropylene, polyethylene- polypropylene copolymer, acrylic polymer or copolymer, metallocene polymer, polyphthalamide (PPA) , crystalline polystyrene, polycarbonate, acrylonitrile-butadiene-styrene (ABS) , silicone rubber or polymer and natural and synthetic polymer and rubber latexes . 7. A thermoformable or injection mouldable mixture comprising exfoliating graphite and a carrier material comprising one or more of polyvinyl chloride, polyethylene, polypropylene, polyethylene-polypropylene copolymer, acrylic polymer or copolymer, metallocene polymer, polyphthalamide (PPA) , crystalline polystyrene, polycarbonate, acrylonitrile- butadiene-styrene (ABS) , silicone rubber or polymer and natural and synthetic polymer and rubber latexes. 8. An intumescent composition produced by a process which comprises subjecting a mixture comprising exfoliating graphite and a carrier material comprising one or more of polyvinyl chloride, polyethylene, polypropylene, polyethylene- polypropylene copolymer, acrylic polymer or copolymer, metallocene polymer, polyphthalamide (PPA) , crystalline polystyrene, polycarbonate, acrylonitrile-butadiene-styrene (ABS) , silicone rubber or polymer and natural and synthetic polymer and rubber latexes to a thermoforming or injection moulding process . 9. An intumescent composition according to any of claims 3 to 6 and 8, produced by vacuum thermoforming or pressure thermoforming. 10. An intumescent composition according to any of claims 3 to 6 and 8, produced by a one-shot injection moulding process, a two-shot injection moulding process or a gas- assisted injection moulding process. 11. A composition or mixture according to any preceding claim, in which the amount of carrier material is from 30 to 65% by weight of the composition or mixture. 12. A composition or mixture according to any preceding claim, in which the amount of exfoliating graphite is from 5 to 50% by weight of the composition or mixture. 13. A composition or mixture according to claim 12, in which the amount of exfoliating graphite is from 15 to 45 % by weight of the composition or mixture. 14. A composition or mixture according to claim 13, in which the amount of exfoliating graphite is from 25 to 35% by weight of the composition or mixture. 15. A composition or mixture according to any preceding claim, containing at least one plasticiser, the total amount of plasticiser (s) being no more than 35% by weight of the composition or mixture. 16. A composition or mixture according to claim 15, in which the total amount of plasticiser (s) is from 10 to 30% by weight of the composition or mixture. 17. A composition or mixture according to any preceding claim, containing at least one stabiliser, the total amount of stabiliser (s) being no more than 1% by weight of the composition or mixture. 18. A composition or mixture according to claim 17, in which the total amount of stabiliser (s) is from 0.015 to 0.025% by weight of the composition or mixture. 19. A composition or mixture according to any preceding claim, containing at least one inert filler, the total amount of filler (s) being from 4 to 6% by weight of the composition or mixture . 20. A composite product formed by a thermoforming or injection moulding process, the composite product comprising first and second materials, the first material being an intumescent composition comprising exfoliating graphite and a carrier material . 21. A composite product according to claim 20, produced by vacuum thermoforming or pressure thermoforming. 22. A composite product according to claim 20, produced by a one-shot injection moulding process, a two-shot injection moulding process or a gas-assisted injection moulding process. 23. A composite product according to any of claims 20 to 22, in which the carrier material comprises a plastics material . 24. A composite product according to claim 23, in which the plastics material comprises one or more of polyvinyl chloride, polyethylene, polypropylene, polyethylene- polypropylene copolymer, acrylic polymer or copolymer, metallocene polymer, polyphthalamide (PPA) , crystalline polystyrene, polycarbonate, acrylonitrile-butadiene-styrene (ABS) , silicone rubber or polymer and natural and synthetic polymer and rubber latexes. 25. A composite product according to any of claims 20 to 24, in which the amount of carrier material is from 30 to 65% by weight of the first material. 26. A composite product according to any of claims 20 to 25, in which the amount of exfoliating graphite is from 5 to 50% by weight of the first material. 27. A composite product according to claim 26, in which the amount of exfoliating graphite is from 15 to 45% by weight of the first material. 28. A composite product according to claim 27, in which the amount of exfoliating graphite is from 25 to 35% by weight of the first material. 29. A composition product according to any of claims 20 to 28, in which the first material contains at least one plasticiser, the total amount of plasticiser (s) being no more than 35% by weight of the first material. 30. A composite product according to claim 29, in which the total amount of plasticiser (s) is from 10 to 30% by weight of the first material . 31. A composite product according to any of claims 20 to 30, in which the first material contains at least one stabiliser, the total amount of stabiliser (s) being no more than 1% by weight of the first material. 32. A composite product according to claim 31, in which the total amount of stabilise (s) is from 0.015 to 0.025% by weight of the first material . 33. A composite product according to any of claims 20 to 32, in which the first material contains at least one inert filler, the total amount of filler (s) being from 4 to 6% by weight of the composition or mixture. 34. An electrical component of which at least a part is formed by thermoforming or injection-moulding a composition or mixture according to any of claims 1 to 19. 35. An electrical component of which at least a part is constituted by a composite product according to any of claims 20 to 33. 36. An electrical product according to claim 34 or 35 which is a conduit, a conduit coupling, a socket box or a switch box. 37. An electrical product according to claim 35, in which the second material of the composite product has a reflective surface. 38. An electrical product according to claim 35, in which the second material of the composite product has an aesthetic function to cover, at least partially, the first material . 39. An electrical product according to claim 35, which is a light fitting. 40. An intumescent composition substantially as hereinbefore described with reference to any of examples 1 to 3 hereof . 41. An electrical product substantially as hereinbefore described with reference to figures 1 and 2, figures 3 and 4, figures 5 and 6, figures 7 and 8, figure 9, figure 10 or figure 11 of the drawings.

Inventors: ASHLING GEOFFREY EDWARD, COULTER ROBERT GLYN, SMITH WAYNE, ASHLING, GEOFFREY, EDWARD, COULTER, ROBERT, GLYN, SMITH, WAYNE
Applicants: ASHLING GEOFFREY EDWARD, COULTER ROBERT GLYN, P F C SURECHEM LTD, SMITH WAYNE, ASHLING, GEOFFREY, EDWARD, COULTER, ROBERT, GLYN, P.F.C. SURECHEM LIMITED, SMITH, WAYNE
Application year: 2000
Main classification: C09K21
IPC codes: C08K3, C09K21