Foam manufacture using two catalysts and a vaporizable auxiliary blowing agent

A method of manufacturing foam polyurethane material comprising the steps of:

• mixing in a mixing head foam-forming components comprising:
• a polyol, an isocyanate, water, first and second catalysts respectively for catalysing polymer formation by intersecting on the polyol and the isocyanate and for catalysing blowing by intereaction of the isocyanate and the water, and methylene chloride as an auxiliary blowing agent;
• feeding said mixed components as a liquid from the mixing head to an open-topped reaction vessel wherein said components are maintained for a dwell time of 20 to 45 seconds during which exothermic reaction occurs and the liquid froths;
• and
• discharging said frothing liquid from the reaction vessel to a surface on which it is allowed to expand and form the foam material;
• the proportion of said methylene chloride being in excess of 12% of the weight of the polyol, and the proportion of said first catalyst being reduced below the level required to achieve satisfactory foam formation without said dwell time.