SEALANT COMPOSITION

1279644 Bituminous composition SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ NV 23 Sept 1969 [25 Sept 1968] 46744/69 Headings C3N and C3P A composition comprises: (a) 20-65% by weight of an oxidized asphalt, (b) 15-30% by weight of either (1) a block copolymer having the general configuration A-B-(-B-A) n wherein each A is a thermoplastic polymer block of a mono-vinyl substituted aromatic hydrocarbon or a 1-alkene, B is an elastomeric polymer block of a conjugated diene or more than one 1-alkene, and n is an integer of between 1 and 5, or (2) a hydrogenated derivative of said block copolymer, (c) 10-40% by weight of a petroleum oil having a content of aromatic constituents of less than 50% by weight based on clay-gel analysis, and (d) 10-30% by weight of a coumarone-indene resin, a terpenephenolic resin or a mixture of these resins. The unoxidized asphalt has a viscosity of 150-350 poises at 60‹ C. and a penetration of 190-350 dmm. at 25‹ C., whilst the petroleum oil has a viscosity of 40-300 SSU at 99‹ C. Suitable block copolymers are polystyrene-polyisoprenepolystyrene, polystyrene-polybutadiene-polystyrene, polyethylene - (ethylene - propylene copolymer) - polyethylene, polypropylene- (ethylene-propylene copolymer)-polypropylene of which polystyrene-polybutadiene-polystyrene in which each polystyrene block has an average molecular weight between 10,000 and 50,000 and each polybutadiene block has an average molecular weight of between 35,000 and 150,000, the polystyrene blocks comprising 20-50% by weight of the weight of the block copolymer, is preferred. The thermoplastic blocks A may have average molecular weights of 7500-100,000 and the elastomeric block B may have an average molecular weight of 25,000-1,000,000. The proportion of the thermoplastic blocks A suitably is 10-70% by weight of the weight of the block copolymer. α-Methyl styrene may be employed as A whilst 1-alkenes used for A and B are ethylene, propylene, butene-1, hexene-1, and octene-1.