GB777614A - Improvements in or relating to expanded bitumen - Google Patents

Abstract

A cellular material containing a major proportion of bitumen and a minor proportion of a synthetic thermoplastic resin is prepared by forming a dough comprising the bitumen and synthetic resin, a blowing agent, and a non-volatile plasticizer, heating the dough to gasify the blowing agent whilst applying external pressure to prevent full expansion of the dough, cooling the dough, releasing the pressure, and further expanding the mass by reheating. The bitumen may consist of a natural bitumen, or a derivative of coal tar, or a residue from a petroleum distillate. The non-volatile plasticizer may comprise dioctyl phthalate, polypropylene sebacate or adipate, or a butadieneacrylonitrile copolymer. As a blowing agent may be used ferrous oxalate, sodium bicarbonate, ammonium carbonate, a mixture of sodium nitrite and ammonium chloride, dinitrosopentamethylene tetramine, diazoaminobenzene, p, p1 oxy bis (benzene sulphonyl hydrazide), a, a-azo-bis-(iso-butyronitrile), 1, 1 azo-bis-(cyclohexane carbonitrile), benzene sulphonyl hydrazide, urea, or biuret. The synthetic resin is preferably an ethenoid resin, e.g. polyvinyl chloride or a copolymer thereof. To the non volatile plasticizer may be added a volatile solvent or a monomer polymerizable at the gassing and expansion temperatures as described in specification No. 716,366 [Group IV(a)]. In one example a dough is prepared comprising 31 parts by weight of a bituminous material sold under the trade name "Carbitum Pitch," 25 parts polyvinyl chloride, 4 parts lead stearate, 4 parts calcium stearate, 17 parts diazoaminobenzene, and 19 parts dioctyl phthalate. The mix is heated in a mould in a steam heated press for 25 minutes at 325 DEG F. under a pressure of 1 ton per square inch. The mould is cooled for 30 minutes, and the pressure then released. The partially expanded material is heated in an oven at 190 DEG F. for 2 hours. In two other examples the bituminous material is a product sold under the trade name "Catarex Pitch," and the plasticizer comprises a mixture of acetone and polypropylene adipate, and of styrene, acetone, and polypropylene adipate, respectively. In a further example the blowing agent consists of benzene sulphonyl hydrazide and the plasticizer is a butadiene acrylonitrile copolymer. Specification 716,495 also is referred to.