Fire-retardant moulded components and their manufacture

Abstract: A fire-retardant moulded component is prepared from a dough moulding compound comprising (i) a resin, (ii) one or more frits capable of melting when heated in a fire situation and (iii) glass or ceramic fibres or ceramic powder. The dough moulding compound preferably contains two or more frits melting progressively when heated in a fire situation.

Description: The invention concerns fire-retardant moulded components and their manufacture with particular reference to glazing beads and other products to conform with B.S. Fire Test 476. The present application is a divisional of our European Application No. 88301024.1 (EP-A-0 278 711). Glazing beads that hold glass in apertures of fire doors are conventionally made from hard wood. These, when subjected to test, usually burn away within thirty minutes, leaving the bead fixing screws to hold the glass in place. Thus, flames and fumes can penetrate the gaps left between the glass and the surrounding material. The use of alternative materials to wood is also not satisfactory as, for example, steel buckles, aluminum melts and buckles, and mica based products shatter when struck or put under pressure by screws. In GB-A-2,171,136 there is described a fire-resistant glazing strip comprising a hollow casing (of plastics material, e.g. polyvinyl chloride) having a filling formed from a settable mixture comprising intumescent material (preferably hydrated sodium silicate) with glass fibres as reinforcement. The intumescent material is in laminate form, the layers being so disposed that on intumescence expansion occurs in such direction that the intumescent material exudes to provide an insulating border for a pane of glass retained by the strip. In co-pending European Application No. 88311509.9 (published as EP-A-0 322 135) there are described inter alia certain moulding compositions comprising a phenolic resin, a foamed filler and two or more frits capable of melting progressively when heated in a fire situation. According to this invention there is provided a fire retardant composition comprising (i) a resin, (ii) glass or ceramic fibres, or ceramic powder characterised in that the composition is a dough moulding compound and comprises two or more frits capable of melting progressively when heated in a fire situation, said compound being other than a compound comprising a phenolic resin, a foamed filler, and chopped glass strand. The invention also provides a method of making a fire-retardant moulded component comprising moulding a composition as defined in the preceding paragraph under heat and pressure to form a component having an outer skin integral with a filling of the said compound. A suitable catalyst may be included in the resin to aid the setting process. Suitable resins include phenolic resins and, with the addition of additives, such as antimony oxide or alumina trihydrate, polyesters, epoxies and urethane methacrylates. When heated, such as in a fire situation, the progressive melting of the frits and the insulating qualities of the ceramic (when present) protects glass components and allows say glazing beads to survive over a long period under intense heat and flame. In a preferred embodiment of the invention a dough moulding compound is prepared from a mixture of preferably low smoke and low toxic fume resin, such as phenolic resin or polyester resin, optionally alumina trihydrate, the frits and glass reinforcement, such as of chopped glass strand. The compound is then moulded under heat and pressure and the moulding operation causes a majority of the resin to form a skin leaving the remaining ingredients as a generally homogeneous filling. Preferably the moulding compound comprises a low melting frit, typically melting at 300-450 degrees C and a devitrifying frit that melts at 700 to 800 degrees C. An advantage of the devitrifying frit is that after melting it sets and remains stable to over 1000 degrees C. The preferred materials used in the components of the invention are chosen for low smoke emission, low toxic fume, and high stability under heat up to 1100 degrees C. A decorative finish may be applied to the components of the invention, such as of P.V.C. sheet which is available in a variety of colours and finishes such as metallic and wood grain before or after moulding. On other occasions a paint such as mentioned in UK patent applications nos. 8608075 or 8615006 may be used as an outer finish. The invention further provides a component of the invention in the form of a glazing bead. Whilst particular reference has been made to the production of glazing beads, it will be appreciated that other items may be produced by the same techniques, such as slabs to provide such items as a rigid barrier in a fire panel construction, or on its own as a three-dimensional work surface top, or a wall board as a flat sheet or with cast-in three dimensional forms. Components of the invention may be able to stand the temperatures needed to apply a vitreous enamel finish on outer faces. This invention will now be further described, by way of example only, with reference to the accompanying drawing, which is a section through a form of moulded component. The accompanying drawing is a section through a moulded component 70 whose outer skin 72 is formed during the moulding process integrally with a filling 74. The component 70 is produced by moulding in a heated mould a mixture of 30 parts by weight low smoke/low toxic fume powdered polyester resin (an alternative would be phenolic resin), 30 parts by weight alumina trihydrate, 12 parts by weight of a low melting frit (300-450 degrees C), 18 parts by weight of higher melting devitrifying frit (700-800 degrees C) and 20 parts by weight of chopped glass strand that has been formed into a sheet or lump for moulding. Moulding is carried out at a temperature of 120 to 140 degrees C and at a pressure of 140 to 150 psi. During the moulding process resin flows to form a skin 72 conforming to the inside surface of the mould. Remaining resin and the other ingredients consolidate within the skin to form the filling 74.

Claims: A fire retardant composition comprising (i) a resin, (ii) glass or ceramic fibres, or ceramic powder, characterised in that the composition is a dough moulding compound and comprises two or more types of frit capable of melting at different temperatures when heated in a fire situation, said compound being other than a compound comprising a phenolic resin, a foamed filler, and chopped glass strand. A compound according to Claim 1 comprising:- (i) a first type of frit having a relatively low melting point and, (ii) at least one other type of frit which is a devitrifying frit having a relatively high melting point. A composition according to Claim 2 wherein the first type of frit melts in the range from 300 to 450 degrees C. A composition according to Claim 2 or Claim 3 wherein the devitrifying type of frit melts in the range from 700 to 800 degrees C. A composition according to any of the preceding claims wherein the resin is a phenolic or polyester resin. A composition according to any of the preceding claims and further containing alumina trihydrate. A composition according to any of the preceding claims containing glass fibre in the form of chopped glass strand. A fire-retardant moulded component comprising an outer skin formed integrally with a filling comprising a composition as claimed in any one of the preceding claims. A component according the Claim 8 in the form of a glazing bead. A method of producing a fire-retardant moulded component wherein a composition as claimed in any one of Claims 1 to 7 is moulded under heat and pressure to form a component having an outer skin integral with a filling of the said composition.

Inventors: CROMPTON GEOFFREY, CROMPTON, GEOFFREY
Applicants: BRUNNER MOND & CO LTD, BRUNNER MOND & COMPANY LIMITED
Application year: 1988
Main classification: C04B26
IPC codes: C04B14, C04B26, E06B5