| abstract |
A process for treating clear hard water to reduce its scale-forming tendency comprises adding to it a water-soluble substantially linear synthetic polymer having a molecular weight of at least 1,000 in an amount not exceeding 20 per cent by weight of the hardness-imparting compounds present in the water. Examples of polymers are: the homo-polymers of the acids of the acrylic series; their amides; polyvinyl pyridinium alkyl halides; copolymers of acids of the acrylic series with polymerizable vinyl compounds; interpolymers of alpha-, beta-unsaturated dicarboxylic acids, of the amides or of the partial alkyl esters of these acids, or of the salts of the partial alkyl esters or of the substituted amides. The polycarboxylic acids may be reacted with salt-forming metal compounds. In the deposition from hard water of calcium carbonate by soda ash, the precipitate is rendered non-adherent to chemical equipment by the presence of a polymer according to the invention. It is stated to be known to add an alphahalogen-substituted polyacrylic acid to hard water so as to prevent the formation of calcium and magnesium precipitates. |