A method of imparting hydrophilicity to a polyester-polyurethane foam by introducing therein sulphonate and/or sulphonic acid groups comprises treating a foamed polyester-polyurethane mass with an aqueous solution of an alkali metal sulphite or bisulphite at a temperature from room temperature to 100 DEG C., said foamed mass being formed by the reaction, in the presence of water or a compound that releases water, of (a) one or more polyisocyanates and (b) one or more polyester resins each obtained from a mixture comprising a polyol component and a dicarboxylic acid component, at least 10 mole per cent of the dicarboxylate groups in the polyester resin or mixture of resins being derived from one or more alphabeta ethylenically unsaturated aliphatic dicarboxylic acids, anhydrides or esters. The polyester may be derived from such unsaturated acids as maleic, citraconic, mesaconic, fumaric and itaconic, and it may be mixed with a polyester obtained from saturated reactants. Alternatively, a combination polyester form mixed saturated and unsaturated acids can be used. The polyol may be a diol, such as ethylene, diethylene, propylene, dipropylene or trimethylene glycols, or 1, 3- or 1, 4-butane-diol or 1, 5-pentanediol. Higher polyols include glycerol, sorbitol, pentaerythritol, inositol, tetramethylcyclohexanol, di- and poly-pentaerythritol and trimethylolpropane. The polyol and dicarboxylic acids are reacted in the molar ratio 1,2 to 1,8 : 1. Sulphuri or toluene sulphonic acids, zinc chloride and phosphorous pentoxide are suitable esterification catalysts. The polyester may be modified with a fatty acid having 8-30 carbon atoms, such as lauric, stearic, oleic, linoleic, linolenic, palmitic or ricinoleic acids, by reaction directly or as its glycerol ester with the polyol or hydroxypolyester. Preferably the modifier is reacted with the polyol before the reaction with the dicarboxylic acid. Hydrophilic fillers such as cotton and regenerated cellulose rayon fibres and filaments may be incorporated in the products. The treatment of the polyurethane foam with the alkali metal sulphite or bisulphite is preferably effected at a pH of 5,5-13. A metabisulphite may be used if caustic soda or potash is added to convert it to a simple bisulphite. The solution may be entirely aqueous or may contain, for example, isopropanol, ethanol, butanol, acetone, methyl ethyl ketone, dimethylformamide or glycol. Wetting agents may also be present. In Examples (1) a polyester prepared from adipic, maleic and capric acids and glycerol is reacted with N-alkylmorpholine, water silicone fluid and 2, 4- and 2, 6-toluene diisocyanates to give a polyurethane foam. This is treated with saturated sodium bisulphite solution at 60 DEG C.; (2) a polyester from adipic acid, maleic anhydride, diethylene glycol and trimethylolmethane is reacted similarly; (3) in a process similar to (2) the bisulphite treatment is preceded by immersion of the foam in isopropanol to cause swelling; (4) a mixture of water, sodium metabisulphite, sodium hydroxide and isopropanol is used in the final treatment; (5) the final step is effected at 100 DEG C.ALSO:A method of imparting hydrophilicity to a polyester-polyurethane foam by introducing therein sulphonate and/or sulphonic acid groups comprises treating a foamed polyester-polyurethane mass with an aqueous solution of an alkali metal sulphite or bisulphite at a temperature from room temperature to 100 DEG C., said foamed mass being formed by the reaction, in the presence of water or a compound that releases water, of (a) one or more polyisocyanates and (b) one or more polyester resins each obtained from a mixture comprising a polyol component and a dicarboxylic acid component, at least 10 mole per cent. of the dicarboxylate groups in the polyester resin or mixture of resins being derived from one or more alphabeta ethylenically unsaturated aliphatic dicarboxylic acids, anhydrides or esters. The polyester may be derived from such unsaturated acids as maleic, citraconic, mesaconic, fumaric and itaconic, and it may be mixed with a polyester obtained from saturated reactants. Alternatively, a combination polyester form mixed saturated and unsaturated acids can be used. The polyol may be a diol, such as ethylene, diethylene, propylene, dipropylene or trimethylene glycols, or 1, 3- or 1, 4-butane-diol or 1, 5-pentanediol. Higher polyols include glycerol, sorbitol, pentaerythritol, inositol, tetramethylcyclohexanol, di- and poly-pentaerythritol and trimethylolpropane. The polyol and dicarboxylic acids are reacted in the molar ratio 1,2 to 1,8 : 1. Sulphuric or toluene sulphonic acids, zinc chloride and phosphorus pentoxide are suitable esterification catalysts. The polyester may be modified with a fatty acid having 8 to 30 carbon atoms, such as lauric, sterric, oleic, linoloic, linolenic, palmitic or ricinoleic acids, by reaction directly or as its glycerol ester with the polyol or hydroxy-polyester. Preferably the modifier is reacted with the polypol before the reaction with the dicarboxylic acid. Hydrophilic fillers such as cotton and regenerated cellulose rayon fibres and filaments may be incorporated in the products. The treatment of the polyurethane foam with the alkali metal sulphite or bisulphite is preferably effected at a pH of 5,5 to 13. A metabisulphite may be used if caustic soda or potash is added to convert it to a simple bisulphite. The solution may be entirely aqueous or may contain, for example, isopropanol, ethanol, butanol, acetone, methyl ethyl ketone, dimethylformamide or glycol. Wetting agents may also be present. In Examples (1) a polyester prepared from adipic, maleic and capric acids and glycorol is reacted with N-alkylmorpholine, water silicone fluid and 2, 4- and 2, 6- toluene diisocyanates to give a polyurethane foam. This is treated with saturated sodium bisulphite solution at 60 DEG C.; (2) a polyester from adipic acid, maleic anhydride, diethylene glycol and trimethylolmethane is reacted similarly; (3) in a process similar to (2) the bisulphite treatment is preceded by immersion of the foam in isopropanol to cause swelling; (4) a mixture of water, sodium metabisulphite, sodium hydroxide and isopropanol is used in the final treatment; (5) the final step is effected at 100 DEG C.