Improvements in or relating to intumescent fire seals and their method of manufacture

Abstract: A flexible intumescent seal capable of being applied directly to the surface of a flammable structure to provide for that structure a fire resistant barrier. The seal comprises a backing member of a fibrous material impregnated with a coating of a liquid intumescent material which when dried can flex with the seal without cracking. The intumescent material may comprise an intumescent paint known in the trade as Pyroplas C.

Description: This invention relates to intumescent fire seals and to methods of producing the same. More especially, but not exclusively, this invention concerns intumescent fire seals in the form of membranes or papers (hereinafter referred to simply as "membranes") capable of being applied directly to the surface of a flammable structure such as a wooden door, window frame or wall panel to provide for that structure a fire resistant barrier. The invention also concerns fire seals in the form of flexible sheets or strips which can be used, for example, as glazing strips. Sheet like intumescent fire seals are of course well known. However such fire seals cannot readily or effectively be applied directly to such structures as shaped doors or panels to be found in older buildings due to the relative inflexibility of the sheets. CA-A-1066180 discloses a method of applying fire retardant coating materials to a substrate comprising a backing sheet of glass fibres coated on at least one of its sides with an intumescent paint. This document does not, however, propose the use of a coating which enables flexible fire seals to be produced whose surfaces do not crack when they are flexed to conform to the shape and configuration of a doorway of the like which is to be sealed in the event of a fire. The present invention sets out to provide an intumescent fire seal which has sufficient flexibility to enable it to be applied directly to both plane and more intricate surfaces and which does not suffer from, or at least alleviates, disadvantages present in existing fire seals. According to the present invention in one aspect there is provided a flexible intumescent seal capable of being applied directly to the surface of a flammable structure to provide for that structure a fire resistant barrier, the seal comprising a flexible backing sheet containing glass or ceramic fibres impregnated with a coating of an intumescent paint and being characterised in that one or both sides of the backing sheet is coated with a layer of emulsion paint, the arrangement being such that when dry, the seal can flex without the incidence of surface cracking. The fibrous material may comprise a mixture of glass or ceramic fibres bulk clay. The material may include other fibres and binding materials. The intumescent material preferably comprises an intumescent paint which is known in the trade as Pyroplas C. One intumescent seal in accordance with the invention comprises a backing sheet of vermiculite and glass fibres which is coated on one or both sides with an intumescent paint or varnish as described above, the intumescent paint or varnish impregnating itself into the fibrous structure of the backing sheet to define a surface which expands in the presence of fire. The vermiculite/glass fibre backing sheet may be sprayed with a UPVC adhesive prior to coating with intumescent paint or varnish. One or both sides of the intumescent membrane may subsequently be coated with a layer of emulsion paint to enable adherents such as double sided tape or liquid adhesive to be applied thereto and to enable the membrane to be adhered directly to the surface of a structure to be protected. Wood veneer or plastics facing materials may be applied to the exposed surface of the membrane. Another fire seal in accordance with the present invention comprises a backing sheet produced from a mixture of a bulk clay and glass fibres coated on one or both surfaces with an intumescent paint or varnish. The fibrous structure of the backing sheet is impregnated with the intumescent paint or varnish to define a surface which expands on heating. One or both surfaces of the intumescent membrane may subsequently be coated with emulsion paint. A further seal in accordance with the invention comprises a backing sheet produced from ceramic fibres coated on one side with vermiculite granules. The backing sheet is then coated with an intumescent paint or varnish of the type referred to above, the intumescent material impregnating into the porous structure of the backing sheet. As mentioned previously fire seals in accordance with the invention can be applied directly to a surface to be protected by for example double sided adhesive tape. Alternatively the membrane may be attached to a surface by a liquid adhesive, tacks, pins or by any conventional means. The membrane can readily be shaped using a suitable cutting tool and its inherent flexibility allows it to follow the contour of even a relatively intricate moulded or curved surface. In another aspect the present invention provides a method of producing flexible intumescent fire seals in sheet form, the method being characterised by the step of impregnating a flexible fibrous sheet containing glass or ceramic fibres with a coating of intumescent paint which dries to form a surface which can flex with the membranes and which expands on heating to provide the required fire sealant characteristic, one or both sides of the backing sheet being coated with a layer of emulsion paint. The invention will now be described with reference to the following Examples of intumescent membranes in accordance with the invention and their methods of manufacture. Example 1 A backing sheet produced from a mixture of vermiculite and glass fibres is coated on one or both sides with intumescent paint known as Pyroplas C which on drying produces a surface which can flex with the membrane without cracking. The backing sheet may firstly be sprayed with a solution of UPVC adhesive to assist retention of the intumescent paint within the fibres of the backing sheet. The intumescent paint impregnates itself into the fibrous structure of the backing sheet to define a surface which expands on being exposed to fire to provide a seal thereto. This intumescent membrane is capable of fire proofing a structure to which it is applied for a period in excess of two hours. One or both surfaces of the intumescent membrane may subsequently be coated with an emulsion paint to enable an adhesive such as double sided tape to be applied to that surface thus enabling the membrane to be applied directly to the surface of a structure to be protected. Facings of, for example, wood veneer or plastics may be adhered to the free surface of the mebrane. Example 2 A backing sheet comprising a mixture of a bulk clay and glass fibres is produced (as, for example, that supplied under the trade name "Thermodene") and one or both surfaces coated with an intumescent paint such as described in accordance with Example 1 above. The intumescent paint impregnates itself into the fibrous structure of the backing sheet to form a surface which expands on being exposed to fire. As for the previous example, one or both surfaces of the intumescent membrane may subsequently be coated with emulsion paint to increase its ability to receive and retain adhesive. Typically the intumescent membranes described above in Examples 1 and 2 can be applied to the surface of ply panels and doors for fire proofing. Additionally membranes may be applied between raised and filled panel doors or laminated either over other materials or between materials to define a fire barrier. Example 3 A backing sheet of ceramic fibres coated on one side with vermiculite granules is coated on one or both sides with an intumescent paint of the type known as Pyroplas C. When a white finish to the product is required, the ceramic fibres surface of the backing sheet is firstly coated with white Pyroplas C intumescent paint. The vermiculite surface of the backing strip may be painted with an emulsion paint to provide an effective bond for an adhesive such as double sided tape. Example 4 The fire seal material of Examples 1 to 3 may be cut into strips for use as glazing strips or sealing strips for fire doors, screens etc. The inherent flexibility of the Pyroplas C intumescent paint enables a glazing strip or sealing strip so produced to be squeezed against glass or the encompassed structure to provide an effective seal thereto. As a sealing strip for fire doors, screens etc, the strip may be fixed to hard wood, soft wood or steel, the bead so formed being secured around the glass, door etc for retention purposes and for security in the event of a fire. Glazing and sealing strips can readily be cut from membrane produced in accordance with the invention, attached to suitable beads, and fixed in place with adhesive, pins or the like. For coloured glazing strips, the ceramic surface of the backing strip is firstly coated with a coloured emulsion paint and then coated with a clear Pyroplas C intumescent varnish which, as for the paint described above, is flexible when dry. A protective coating of a hyroscopic sealing material may then be applied to the intumescent coating to prevent or inhibit moisture absorbtion. Glazing strips in accordance with the invention may be applied to 10mm hardwood or 15mm soft wood beads for one hour fire proofing. The beads are coated with clear intumescent varnish as described and the galzing strips then applied to the beads. Once coated with hydroscopic material, the beads may be positioned in plastics sleeves for cutting to size and fixing using screws, pins or adhesive (e.g. double sided tape). Typically the thickness of a membrane in accordance with the invention is 0.75mm. As mentioned previously it can be attached to a surface to be fire proofed by means of double sided tape, a liquid adhesive, pins, tacks or indeed any conventional means. It can readily be shaped using a suitable cutting tool and because of its inherent flexibility it can closely follow the contour of even an intregot surface. Typically a membrane will provide up to two hours protection against fire damage. Upon a fire occurring, the intumescent content of the membrane is activated and expands to protect the structure to which it has been applied from flame damage for a period of up to two hours. It will be appreciated that the intumescent membranes described above are merely exemplary of fire seals in accordance with the invention and that modifications can be made thereto without departing from the true scope of the invention in accordance with the claims.

Claims: A flexible intumescent seal capable of being applied directly to the surface of a flammable structure to provide for that structure a fire resistant barrier, the seal comprising a flexible backing sheet containing glass or ceramic fibres impregnated with a coating of an intumescent paint and being characterised in that one or both sides of the backing sheet is coated with a layer of emulsion paint, the arrangment being such that when dry, the seal can flex without the incidence of surface cracking. A seal as claimed in Claim 1 characterised in that the backing member comprises a mixture of glass or ceramic fibres and bulk clay. A seal as claimed in Claim 1 or Claim 2 characterised in that the backing sheet is sprayed with a UPVC adhesive prior to coating with intumescent paint. A method of producing flexible intumescent fire seals in sheet form, the method being characterised by the step of impregnating a flexible fibrous sheet containing glass or ceramic fibres with a coating of intumescent paint which dries to form a surface which can flex with the membrane and which expands on heating to provide the required fire sealant characteristic, one or both sides of the backing sheet being coated with a layer of emulsion paint.

Inventors: WARD DEREK ALFRED, WARD, DEREK ALFRED
Applicants: ENVIRONMENTAL SEALS LTD, ENVIRONMENTAL SEALS LIMITED
Application year: 1990
Main classification: E06B5
IPC codes: A62C8, E04B1, E06B7, E06B5