GB803771A - Production of cellular synthetic rubbers - Google Patents

Abstract

Polyurethane foams are prepared by dispersing an inert gas under pressure into a liquid intermediate reaction product of a polyisocyanate and a polyester, polyether or polyesteramide, the intermediate containing free isocyanate groups, releasing the pressure to cause the intermediate to expand and curing the expanded material. Expansion may be enhanced by the presence of water, carboxylic acids, hydrogen peroxide, organic peroxides and hydroperoxides, if necessary with additional polyisocyanate, volatile liquids or liquefied gases. The composition may include accelerators, plasticizers, thickeners, surface active agents and cross-linking agents (polyhydric alcohols, water, polyamines, amino-alcohols) which may have been reacted with the intermediate product. Pressures up to 1000 p.s.i. are referred to, the intermediate with any additions and containing the dispersed gas being passed through a continuous pressure reactor, which may be a scraped surface heat exchanger, leaving the reactor by a pressure reducing valve and being discharged into moulds or on to a conveyer belt. In an example 15 per cent by weight of aluminium naphthenate was mixed with a polyglycol adipate and then successively 4 per cent of a mixture of tertiary amines, 2 per cent of triethylamine and 12 per cent of mixed toluene diisocyanates were mixed in and the whole fed to a scraped surface reactor at 2 DEG C. together with sufficient carbon dioxide from a cylinder of liquid carbon dioxide to give a final product of density 0.05 grams/cc. The pressure in the reactor was 350 p.s.i. The emerging foam was directed into moulds, left for 20 minutes to set at room temperature and matured at 50 DEG C. in a hot air oven. The foam was mangled, trimmed and sliced.