INTUMESCENT MATERIAL

Abstract: An intumescent material comprises expandible graphite in a polymeric binder. The binder may be a flexible or elastomeric binder or a formaldehyde resin. A suitable flexible binder is a polymer selected from vinyl acetate polymers, styrene polymers, vinyl chloride polymers, acrylic polymers, vinyl butyral polymers, melamine/urea/phenol formaldehyde resins, polyesters and phenolic resins. A suitable elastomeric binder is a rubber. A suitable formaldehyde resin is melamine formaldehyde resin, urea formaldehyde resin, phenol formaldehyde resin or resorcinol formaldehyde resin.

Description: INTUMESCENT MATERIAL The present invention relates to intumescent material comprising expandible graphite in a polymeric binder. In accordance with the present invention there is provided an intumescent material comprising expandable graphite in a polymeric binder. The intumescent material may further comprise at least one constituent selected from fillers and reinforcing agents. The intumescent material may be made by preparing a mixture of the expandible graphite, the polymeric binder and a liquid and causing or allowing the mixture to harden. Normally the intumescent material is non-foamed or non-cellular i.e. free of pores or cells. According to a first aspect of the invention, the binder is a flexible or elastomeric binder. In the first aspect of the invention, the graphite is preferably present in an amount of 15 to 60% by weight based on the combined weight of the binder and graphite. Preferably the graphite is present in an amount of at least 20% by weight based on the combined weight of the binder and graphite. Preferably also the graphite is present in an amount not exceeding 55% by weight based on the combined weight of the binder and graphite. Preferably, also in the first aspect of the invention, the binder and the graphite are present in a total amount of at least 70% by weight based on the weight of the intumescent material. The intumescent material according to the first aspect of the invention may comprise a plasticizer. The amount of the plasticiεer preferably does not exceed 15% by weight based on the weight of the intumescent material . A suitable plasticizer is dibutyl phthalate. The intumescent material according to -the first aspect of the invention may be made by preparing a mixture of the expandible graphite, the polymeric binder and water and causing or allowing the mixture to harden. Hardening may occur at least in part due to evaporation of water. The mixture may be liquid or formulated as a dough moulding compound. The flexible binder may be or comprise a polymer selected from vinyl acetate polymers, styrene polymers, vinyl chloride polymers , acrylic polymers, vinyl butyral polymers, πelamine/urea/phenol formaldehyde resins, polyesters and phenolic resins. Where the binder is an elastomeric binder, the intumescent material preferably ccrπprises 40 to 70% by weight of the binder and 25 to 60% by weight of the expandible graphite based on the combined weight of the binder and graphite. The intumescent material may be macie by preparing a mixture of the expandible graphite and a liquid emulsion o dispersion of the elastomeric binder and causing or allowing the mixture to cure by coagulation or cross-linking of the elastomeric binder. Suitable emulsions or dispersions of the elastcmeric binder may * comprise Neσprene latex 115 and Neoprene latex 671. These latices are marketed by Du Pent. Neoprene latex 115 is described as a chloroprene copolymer with carboxyl functionality of pH 7 . Neoprene latex 671 is described as polychloroprene in anionic colloidal system, pH 12.5. It may be advantageous to add one or more organic accelerators such as thiocarbanilide, diphenylguanidine or hexa ethylenediamine to the emulsion or dispersion of the elastomer. The elastomeric binder may be a rubber. The elastomeric binder is preferably fire- or flame-resistant 5 and/or self-extinguishing. According to a second aspect of the invention, the binder is a thermosetting formaldehyde resin. Such a resin is normally rigid (i.e. substantially non-flexible and non-_;lastαrτιeric) . ■ The thermosetting binder may be, for example, melamine formaldehyde 10 resin, urea formaldehyde resin, phenol formaldehyde resin, resorcinol formaldehyde resin or a mixture of two or more of these resins. Melamine formaldehyde resin is particularly preferred as the thermosetting binder because it provides an intumescent material which can intumesce smoothly and free of sputtering of 15 graphite particles. The thermosetting binder may incorporate a minor proportion of one or more of the flexible polymers referred to above in order to improve the flexural prc-perties and to reduce shrinkage of the binder. 20 The intumescent material may comprise 20 to 60% by weight of elarr-ine formaldehyde resin as the binder (calculated as uncross-linked resin) and 10 to 50%, more preferably 10 to 40%, by weight of the expandible graphite. Preferably the amount of the expandible graphite is in the range of 25 20 to 60% by weight based on the total weight of the binder and graphite. The intumescent material may be made by preparing a mixture of the expandible graphite and the binder and causing or allowing the mixture to harden by curing or cross-linking of the binder. The intumescent material according to the invention may expand, forming a solid foam or puff, to 8 to 25 times its original volume on heating to elevated temperature. The intumescent material according to the invention is fire resistant. Specifically, the solid form or puff formed on heating the material is fire-resistant. The intumescent material according to the invention is fire resistant. Specifically, the solid form or puff formed on heating the material is fire-resistant. As mentioned above, the intumescent material according to the invention may comprise one or more reinforcing agents and/or fillers. -- ■ Such reinforcing agents and fillers may be selected from glass fibre, cellulose-based fibre, chopped tissue, rcckwool, china clay, chalk, gypsum, silicas and mineral silicates e.g. calcium silicate. The intumescent material according to the invention may comprise, apart from the graphite, the polymeric binder, any plasticiser, any liquid (such as water or volatile organic liquid) derived from the manufacture of the material, any reinforcing agent, any filler and any catalyst, substantially no other component apart from any- incidental impurities which may be present. As mentioned above, the intumescent material of the invention may be made by a process comprising preparing a mixture of the expandible graphite, the polymeric binder and a liquid and causing or allowing the mixture to harden. The liquid may be water or an organic solvent. The graphite is dispersed (in particulate form) in the liquid and the polymeric binder is dispersed or dissolved in the liquid. Preferably the mixture is formulated as a viscous liquid mixture. The mixture may alternatively be formulated as a dough moulding compound for press moulding or extrusion. One or more reinforcing agents and/or 5 fillers such as described above may be included in the mixture. The mixture may be formulated to be almost self-levelling. The dough moulding compound may be easily extruded into almost iπrnediately handleable strips of the required dimensions, is unexpectedly tough after drying (e.g. carried in an oven at 60°C or by prolonged standing at room temperature), is resistant to creep on heating up to 200°C and does not need reinforcement to be incorporated. The mixture may be moulded into sheets of any convenient shape and cured to form the intumescent material or applied as a coating to a substrate and then cured to form the inturrescent material. Curing may be effected at ambient temperature particularly where the liquid mixture is in the form of a thin coating or layer. However, it may often be preferable to effect curing at elevated temperature, such as 50 to 60°C, such temperature obviously having to be kept below a temperature at which intumescence of the graphite or rapid dissolution of dissolved air (which would cause bubbles to form in the liquid mixture) would occur. In the first aspect of the invention, it is believed that curing is effected generally mainly by evaporation of water (or other liquid) . However, curing may occur additpenally or alternatively by cross-linking of the polymeric binder. Where the binder is a rubber, one or more compounds selected from oxides and salts of metals, such as zinc, may be used to accelerate hardening of the rubber. Zinc borate is a suitable zinc salt for this purpose. It has been found that the intumescent material according to the first aspect of the invention and made by the above-described method is flexible and is not adversely affected by carbon dioxide and moisture. In fact the material is virtually waterproof. In the second aspect of the invention hardening of the mixture may occur wholly or mainly by cross-linking or curing of the thermosetting resin. The mixture may be cured at, e.g. around 60°C, between platens in a heated press. The platens may have a covering of e.g. polyethylene sheets, to prevent adhesion of the intumescent material to the platens. In the second aspect of the invention the liquid mixture may further comprise one or more of: water, a hardener or catalyst, a filler, dicyandiamide (or other polyamido compound), and another polymeric binder. The hardener or catalyst or dicyandiamide (or other polyamido compound) may act to cross-link or cure the thermosetting resin. The hardener or catalyst may be an acid catalyst or hardener. Suitable catalysts or hardeners include hydrochloric acid, sulphuric acid, phosphoric acid, organic acids such as formic acid, acetic acid, maleic acid, malic acid, tartaric acid and citric acid, ammonium phosphates and alkali metal phosphates. The invention further provides: a structure defining a gap and including an intumescent material according to the invention, the intjumescent material being arranged so that at elevated temperature as under fire conditions when the material intumesces it closes the gap; an intumescent seal comprising a coherent and self-supporting body of intumescent material according to the invention; the body preferably being shaped to form the seal; and an intumescent seal comprising a holder and intumescent material according to the invention, the intumescent material expanding from the holder at elevated temperature as under fire conditions. The intumescent material according to the first aspect of the 5 invention has the following advantages and features: 1. It is tough, flexible, non-friable and malleable and can be formed into strips with these properties. 2. It can be applied to substrates, such as door rebates, by inexpensive adhesive, e.g. pclyvinyl alcohol, or by self-adhesive strip or tacks. 3. The material can be manufactured to any required thickness and needs no added protection. . The material when cured is completely resistant to carbon dioxide, and water and can withstand prolonged exposure to water without its intumescent properties being affected. 5. The material exhibits considerable expansion force on heating. 6. The material can be bent to almost any radius without breaking or fracturing. With regard to Advantages 1 and 6 above, the intumescent material is unexpectedly flexible as compared with the thermoplastic polymer itself. This is perhaps because of an internal lubricating effect of the graphite. Preferred formulations of the liquid mixture according to the second aspect of the invention are in accordance with the table below: TABLE p.b.w. = parts by weight For each formulation parts by weight are preferably based on a total of 100 parts by weight of the components listed in the Table- The melamine formaldehyde referred to in the Table is substantially uncross-linked initially when incorporated into the liquid mixture. The second aspect of the invention as described herein and using a thermosetting resin as binder has the following advantages: 5 1. The liquid mixture will cure to form the intumescent material within 1 to 2 hours when pumped into a suitable holder of e.g. aluminium or polyvinyl * chloride (pvc). It is unnecessary to allow for evaporation of water to effect hardening. 2. The liquid mixture sets to a hard solid which can be machined 10 to a desired shape. 3. The hardened solid intumescent material is substantially completely resistant to carbon dioxide and water vapour and can withstand prolonged exposure to water without its intumescent properties being affected. 15 . The hardened intumescent material exerts a considerable expansion force on being heated to elevated temperature. 5. The intumescent material has an unexpectedly smooth, and hence aesthetically pleasing surface. 6. The intumescent material may be moulded, or otherwise shaped, 0 to form an intumescent seal, which may be elongate and of substantially uniform cross-section (or of any other shape), and does not require a holder since the material itself is sufficiently coherent, sufficiently strong and has a sufficient degree of rigidity to form the seal itself and itself provides a suitable, 5 aesthetically acceptable, surface for the seal. The seal may itself be shaped, e.g. by the provision of a re-entrant or undercut groove along its length, so that it may itself act as a holder for a smoke seal or other resilient sealing member. 7. The hardness of the intumescent material and the lack of need for a holder make it suitable for use in vandal-resistant seals. 8. The intumescent material unexpectedly has the property of delayed intumescence. I.e. it does not start to intumesce immediately on being raised to a high temperature. This is of particular advantage in certain circumstances. Intumescent material according to the invention may be used as sealing strips for doers and windows, in pipe closures as a pressure and gap filling sealant, as coatings on ventilator grilles or as material from which ventilator grilles are moulded, in penetration seals, in glazing panels and other panels, in hinges, locks and in other situations where conflagration needs holding back. The intumescent material according to the invention may have a very low toxicity. The invention is illustrated by the following examples. Exaπples 1, 4, 5 and 6 relate to the first aspect of the invention. Examples 2 and 3 relates to the second aspect of the invention. The expandible graphite used in the examples is particulate. It was obtained from Foseco Technik Limited and was in the form of free-flowing platelets. EXAMPLE 1 35 parts by weight of expandible graphite 61 parts of weight of Vinamul 9340 and 4 parts by weight dibutyl phthalate were mixed together to form a viscous liquid mixture. The liquid mixture was cured at 50 - 60°C. The cured product was a tough flexible malleable intumescent material. Vinamul 9340 is an aqueous emulsion or dispersion of vinylacetate/ethylene copolymer manufactured by Vinamul Limited of Carshalton, Surrey, England. Vinamul 9340 comprises 60% by weight of polyvinylacetate and 5% by weight dibutyl phthalate as plasticiser. The viscous liquid mixture comprised: 35 parts by weight expandible graphite 36.6 parts by weight vinylacetate/ethylene copolymer 21.35 parts by weight water 7.05 parts by weight plasticiser Total 100 parts by weight The following test was carried out to measure the expansion force of the material. A strip of material prepared in accordance with this example and having a cross section of 2ιrm x 10mm was heated. A force of approximately 1000 Newtons per metre length of the strip was generated. This compares well with Palusol, a proprietary sodium silicate based intumescent product, up to about 320°C and much more favourably at higher temperatures. EXAMFLE 2 A mixture of the following ingredients was prepared. Aerolite 308 46 p.b.w. Expandible graphite 28 p.b.w. Water 20 p.b.w. Aqueous formic acid (50% w/w) 6 p.b.w. Aerolite 308 is a substantially uncross-linked melamine formaldehyde resin supplied by Ciba-Geigy. The mixture was a viscous but virtually self-levelling liquid which, at 20 degrees C, sets to a fairly hard mass within 2 hours. It was found that the rate of hardening could be accelerated by increasing the temperature. EXAMPLE 3 A mixture of the following ingredients was prepared. Melamine formaldehyde resin 37 p.b.w. MonoaπTronium phosphate 7 p.b.w. Expandible graphite 30 p.b.w. Vinamul 9340 7 p.b.w. Water 19 p.b.w. This formulation is more shrink resistant than the mixture of Example 2, but is also virtually self levelling, setting to a hard mass within 2 hours at 20°C. EXAMPLE 4 A mixture of the following ingredients was prepared. Neoprene latex 115 65.5 p.b.w. (approx. 50% solids) Expandible graphite 27 Zinc Oxide 1.5 " Zinc borate 3 Water 3 The mixture was then cured. The curing is accelerated by increasing the temperature to 60°C. Alternatively, the mixture can be thickened with suitable fillers and cured by a two stage pressing process at 60°C, the excess water being allcrwed to evaporate after the first pressing, the partially cured sheet being then layered into small pieces and again pressed. The resulting sheet is tough and elastic. EXA_ PLE 5 A mixture of the following ingredients was prepared. MR Revultex latex 55 p.b.w. (approx. 60% solids) Expandible graphite 43 p.b.w. Zinc 2 p.b.w. This mixture was a material of dough-like consistency. The material was cured by initially pressing at 60°C for 5 minutes to form a sheet, allowing the sheet to "breathe" for a further 5 minutes to aliow the excess water to evaporate and then reforming the sheet under pressure for a further 5 minutes and allcrwing the sheet to dry. MR Revultex latex is a pre-vulcanised natural rubber latex marketed by Rever ex Limited of Ha low, England. It is envisaged that a heat-sensitive coagulant such as polyvinyl methyl ether (e.g. as marketed under the trade name "Lutonal") could be included in the above-mentioned mixture. EXAMPLE 6 A mixture of the following ingredients were prepared Vinapol 1080 powder 25 p.b.w. Dibutyl phthalate 2 p.b.w. Water 5 p.b.w Expandible graphite 36 p.b.w. Vinamul 9340 32 p.b.w. This mixture was of dough like consistency and could be moulded by extrusion or press moulding. After drying the material was tough and flexible.

Claims: CLAIMS 1. An intumescent material comprising expandible graphite in a polymeric binder. 2. An intumescent material according to claim 1, further comprising at least one constituent selected from fillers and reinforcing agents. 3. An intumescent material according to either preceding claim, made by preparing a mixture of the expandible graphite, the polymeric binder and a liquid and causing or allowing the mixture to harden. 4. An intumescent material according to any preceding claim, being substantially non-foamed i.e. free ©f pores. 5. An intumescent material according to any preceding claim, wherein the binder is a flexible or elastomeric binder. 6. An intumescent material according to claim 5, wherein the graphite is present in an amount of 15 to 60% by weight based on the combined weight of the binder and graphite. 7. An intumescent material according to claim 6, wherein the graphite is present in an amount of at least 20% by weight based on the combined weight of the binder and graphite. 8. An intumescent material according to claim 5 or 6, wherein the graphite is present in an amount not exceeding 55% by weight based on the combined weight of the binder and graphite. 9. An intumescent material according to any of claims 2 to 5, wherein the binder and the graphite are present in a total amount of at least 70% by weight based on the weight of the intumescent material . 10. An intumescent material according to any of claims 5 to 9, further comprising plasticizer. 11. An intumescent material according to claim 10, wherein the 5 amount of plasticizer does not exceed 15% by weight based on the weight of the intumescent material. 12. An intumescent material according to any of claims 5 to 11, made by preparing a mixture of the expandible graphite the polymeric binder and water and causing or allowing the mixture to 10 harden. 13. An intumescent material according to any of claims 12, wherein hardening occurs at least in part due to evaporation of the water. 14. An intumescent material according to any of claims 5 to 13, 15 wherein the mixture is liquid. 15. An intumescent material according to any of claims 5 to 13, wherein the mixture is formulated as a dough moulding compound. 16. An intumescent material according to any of claims 5 to 15, wherein the flexible binder comprises a polymer selected from vinyl 20 acetate polymers, styrene polymers, vinyl chloride polymers, acrylic polymers, vinyl butyral polymers, melamine/urea/phenol formaldehyde resins, polyesters and phenolic resins. 17. An intumescent material according to any of claims 5 to 15, and 12 comprising 40 to 70% by weight of the elastomeric binder and 2525 to 60% by weight of the expandable graphite based on the combined weight of the binder and graphite. 18. An intumescent material according to any of claims 5 to 13 and 17, made by preparing a mixture of the expandible graphite and a liquid emulsion or dispersion of the elastomeric binder and causing or allowing the mixture to cure by coagulation or cross-linking of the elastomeric binder. 5 19. An intumescent material according to any of claims 5 to 15, 17 and 18, wherein the elastomeric binder is a rubber. 20. An intumescent material according to any of claims 5 to 15, wherein the elastomeric binder is fire- or flame-resistant and/or self-extinguishing. 10 21. An intumescent material according to any of claims 1 to 4, wherein the binder is at least one formaldehyde resin. 22. An intumescent material according to claim 21, wherein the binder is at least one resin selected from melamine formaldehyde resin, urea formaldehyde resin, phenol formaldehyde resin and 15 resorcinol formaldehyde resin. 23. An intumescent material according to claim 21 or 22, comprising 20 to 60% by weight of formaldehyde resin as the binder (calculated as uncross-linked resin) and 10 to 50% by weight of the expandible graphite based on the weight of the intumescent 0 material. 24. An intumescent material according to any of claims 21 to 23, wherein the amount of graphite is in the range of 20 to 60% by weight based on the total weight of graphite and binder. 25. An intumescent material according to any of claims 21 to 24, 5 made by preparing a mixture of the expandible graphite and the binder and causing or allowing the mixture to harden by curing or cross-linking of the binder. 26. An intumescent material according to claim 25, wherein the mixture comprises a polyamido compound and/or ιτ noamrronιum phoshate as a cross-linking agent for the binder. 27. A structure defining a gap and including an intumescent material according to any preceding claim, the intumescent material being arranged to intumesce and close the gap at elevated temperature as under fire conditions. 28. An intumescent seal comprising a holder and intumescent material according to any of claims 1 to 25, the intumescent material expanding frcm the holder at elevated temperature as under fire conditions. 29. An intumescent seal comprising a coherent and self-supporting body of intumescent material according to any of claims 1 to 26. 30. An intumescent seal according to claim 29, wherein the body of intumescent material is shaped to form the seal.

Inventors: MALCOLM-BROWN TESSA, MILNER BRUCE ALAN, SOUTHERN ERIC, MALCOLM-BROWN, TESSA, MILNER, BRUCE, ALAN, SOUTHERN, ERIC
Applicants: DIXON INTERNATIONAL LTD, DIXON INTERNATIONAL LIMITED
Application year: 1987
Main classification: C09K21
IPC codes: C09D5, C09K21