Production of non-woven fiber webs stable to water

Claim 1

IN THE PROCESS FOR THE PRODUCTION OF NON-WOVEN SHEET MATERIAL IN WHICH A LOOSE FIBER FLEECE IS IMPREGNATED WITH A BINDING AGENT AND THEREAFTER THE BINDING AGENT SET, BONDING THE FIBERS TOGETHER AT THEIR CROSSING POINTS THE IMPROVEMEMT FOR IMPARTING STABILITY TO WATER HYDROPHOBIC PROPERTIES TO TH RESULTING SHEET MATERIAL, WHICH COMPRISES IMPREGNATING THE FLEECE WITH AN AQUEOUS SOLUTION OF A BONDING AGENT CONTAINING BOTH HYDROXYL AND CARBOXYL GROUPS IN THE MOLECULE SELECTED FROM THE GROUP CONSISTING OF WATER-SOLUBLE DERIVATIVES OF CARBOXY ALKYL CELLULOSE AND ALGINIC ACID, THEREAFTER IMPREGNATING THE RESULTING FLEECE WITH AN AQUEOUS SOLUTION OF (1) A WATER-SOLUBLE SYNTHETIC RESIN CAPABLE OF REACTING AT INCREASED TEMPERATURE AND IN THE PRESENCE OF AN ACID CATALYST WITH THE HYDROXYL GROUPS OF THE BONDING AGENT IN COMBINATION WITH (2) A WATER-SOLUBLE METAL SALT CAPABLE OF REACTING WITH THE CARBOXYL GROUPS OF THE BONDING AGENT WITH COAGULATION OF SAID BONDING AGENT, AND (3) AN ACID CATALYST AND HEATING TO A TEMPERATURE FROM 120 TO 160*C., SAID SYNTHETIC RESIN BEING A MEMBER SELECTED FROM THE GROUP CONSISTING OF TETRAMETHYLACETYLENEDIUREA, DIMETHYLOLDIHYDROXYETHYLENEUREA, AND DIMETHYLOLETHYLENEUREA.