| 摘要 |
<p>Fire-fighting foam effective against burning hydrophilic or polar liquids like lower alcohols, ketones, etc. is made from concentrate containing thixotropic thickener dissolved in large amount, yet has a tolerable viscosity so that it can be poured or pumped. Heteropolysaccharide-7 or chain-shortened modifications of it are particularly suitable for this purpose. The concentrate can also be made suitable for fighting fires on hydrophobic liquids by adding surfactants that cause aqueous film formation over such liquids. Solution of polysaccharide thickeners is speeded and higher concentrations made practical by including in the concentrate urea, thiourea, ammonium cyanate or ammonium thiocyanate. Slurrying the polysaccharide in liquid amides such as N-methyl-pyrollidone-2 or dimethylformamide and then pouring the slurry in water also conveniently dissolves the polysaccharides in high concentrations. The liquid amide can be diluted with up to 3 times its weight of a glycol, polyglycol, or a monoalkyl ether of such glycol or polyglycol, the diluent having not over 10 carbons in its molecule. Magnesium salts can be dissolved in concentrate to improve fire extinguishing action when diluted with fresh water. </p> |
