SEALANTS

Abstract: A fire retarding sealant comprises a silicone resin, a filler, a ceramic fire retardant such as zinc borate, a smoke suppressant such as stearate coated calcium hydroxide, and either aluminium hydroxide or magnesium hydroxide, preferably the former. The sealant is intumescent, and non-setting, and is intended for placement around pipes, cables and service penetrations in walls, floors and ceilings. At the temperatures encountered in fires, the aluminium hydroxide decomposes to form aluminium oxide and steam, the latter causing the sealant to intumesce while being relatively harmless to people (no halogen gases are evolved). The aluminium oxide and zinc borate form a crust on the intumesced sealant, providing a further fire retardant property.

Description: TITLE Sealants DESCRIPTION The invention relates to a sealant which is silicone based and has non-setting and fire-retarding and intumescing properties. It is known that fire retarding sealants may be placed around pipes, cables and service penetrations in walls, floors and ceilings. However, such sealants may prevent access for servicing purposes. The invention provides a sealant comprising a silicone resin, a filler, a ceramic fire retardant, a smoke suppressant, and either aluminium hydroxide or magnesium hydroxide. The sealant according to the invention has intumescer. properties derived from the aluminium or magnesium hydroxide. Its fire retarding properties are enhanced b the inclusion of the ceramic fire retardant, which is preferably zinc borate. The preferred hydroxide is aluminium hydroxide. At a temperature of about 200°C, this compound decomposes to form aluminium oxide and steam, the latter causing the sealant to intumesce while being relatively harmless to people. The aluminium oxide and zinc borate form a crust on the intumesced seala r providing a further fire retardant property. At the temperatures encountered in fires, the magnesium hydroxide behaves in a corresponding manner. The sealant according to the invention, being placed m the service penetration, will thus intumesce upon exposure to heat in a fire, effectively sealing ar.y spaces in the penetration which would allow fire and smoke to pass into another contained area. Since the • ? _ sealant is non-setting, nowever , it can oe removed after installation for servicing purposes. Furtnernore the sealant is solvent free and halogen free and will not evolve halogen gases upon intumescence. The sealant according to the invention preferably contains a minimum of 30% by weight of tne heat-curing silicone resin, and 10 to 20% by weight of filler. The silicone resin used is commercially availaole as silicone gum. The silicone gum may have a molecular weight of about 250000 to 550000 and a penetration test value of about 600 to 900. Other silicone resins may be used in tne compounding of the sealant. Although many fillers could be used, dolomite is preferred on tne grounds of whiteness and economy. The aluminium hydroxide preferably constitutes up to 40% by weight of the sealant. The amount of intumescence increases with the amount of aluminium hydroxide. The sealant according to the invention may further contain any additives customarily included in such compositions. These may include surfactants, plasticisers , preservatives, pigments, toolability (shaping and forming) improvers and rheology modifiers. So called "high pressure" intumescent products, such as activated graphite and sodium silicate, may also be added. It is especially preferred to add a luminous pigment suchas copper-activated zinc sulphide. This pigment luminesces in the absence of light, and may act as a visual identification of the grade of sealant to building inspectors and fire prevention officers, both on initial and subsequent inspections. The invention is illustrated bv tne followinσ Exa oies: A f re retardant intumescent non-setting seal ant was prepared by compounding the following substances in a Narben mixer : % bv weiσht al na, omega - άivinylpolydimethylsiloxane, or alpha, omega - dimethylpolydimethylsiioxane 30.175 Aluminium hydroxide 31.225 Stearate coated calcium carbonate 3.772 Dolomite 17.544 Zinc borate 12.281 100.000 In th s composition, the stearate coated carbonate is a smc<e suppressant and rheoioσy modifier to prevent slump of the product. The zinc borate is fire retarding ennancmα the fire retardant properties of the compound. The composition is a non-setting, hand malleable paste capable of extrusion into rope form or custom profiled forms. It had a Smoke Index of 23 as determined according to Naval Engineering Standard 711, Isse 2 and a Tox city Index of 0.19 as determined by Naval Engineering Standard 713, Issue 3. The following results have been obtained by testing according to the stated British Standards: BS 476 Part 6 (1989) Class 'C BS 476 Part 7 (1987) Class ' 2 ' BS 476 Part 20 (1987) 4 nours ΞΞ 68Ξ3 .1987) Appendix A - Clause A.9 < 350°C ΞΞ 6853 (1987) Aooendix B - Clause B.5.1 Ao O.029 S 5853 (198 > Appendix B - Clause B.5.Ξ Ao(ON)3.20; Ao(OFF) 3.55 Example 2 A fire retardant intumescent luminous non-setting sealant was prepared as described in Example 1, but to the following composition: % by weiσht alpha, omega - divinylpolydimethyl≤iloxane, zr alpha, omega - dimethylpolvdimethvlsiloxane 30.175 Aluminium hydroxide 31.228 Stearate coated calcium carbonate 8.772 Iclomite 15.544 l ne berate 12.281 Ccpper activated zinc sulphide 2.000 100.000 The copper activated zinc sulphide pigment provides luminosity to the composition. The inclusion of the copper activated zinc sulphide does not affect the properties or performance as detailed in Example 1.

Claims: CLAIMS sealant comprising a silicone resin, . --- -. ceramic fire retardant, a smoke suppressant, and an intumescent compound which is either aluminium r.ydrcxide or magnesium hydroxide. 2. A sealant according to claim 1 in wr.ich the intumescent compound is aluminium hydroxide. 3. A sealant according to claim 2 containing up to 40% of aluminium hydroxide. 4. A sealant according to any preceding cla rr. in which the ceramic fire retardant is zinc borate. 5. A sealant according to any preceding claim containing at least 30% by weight of the silicone resm. 5. A sealant according to any preceding claim containing from 10% to 20% by weight of the filler. 7. A sealant according to any preceding claim m r.icn the smoke suppressant is stearate coated calcium carbonate. 3. A sealant according to any preceding claim further comprising one or more of a surfactant, a plastici≤er, a preservative, a pigment, a toolability improver and a rheology modifier. 9. A sealant according to any preceding clai: furtner comprising activated graphite or sodium silicate as a nigh pressure intumescent additive. 10. A sealant according to any preceding claim furtner comprising copper activated zinc sulphide as a luminous oiσ ent.

Inventors: HLUCHAN WOLODYMYR IWAN, TRAHEARN GUYDO REES, HLUCHAN, WOLODYMYR, IWAN, TRAHEARN, GUYDO, REES
Applicants: HLUCHAN WOLODYMYR IWAN, TRAHEARN GUYDO REES, VISPAK LTD, HLUCHAN, WOLODYMYR, IWAN, TRAHEARN, GUYDO, REES, VISPAK LIMITED
Application year: 1993
Main classification: C09K3
IPC codes: C08K3, C09K3, C09K21