| 摘要 |
A cation-active synthetic resin is prepared by heating a solution of a synthetic resinous condensate prepared from an aldehyde and an amino compound in presence of a bisulphite according to the process of Specification 595,366 in a solvent which is present during the reaction until a gel is formed, heating the gel at a temperature and for a time sufficient to form an infusible, porous mass and comminuting said mass. The preferred solvent is water. Alcohols, e.g. methanol, ketones, e.g. acetone or aqueous mixtures of these may be used. The heating may take place at 85-135 DEG C., e.g. 100 DEG C. for a few hours. If desired, the condensate may be spray-dried and the powder heated to cure it. The condensation products may be applied to supports such as cloth, asbestos or clay and cured thereon. The resins may be used intermittently or continuously for exchanging cations in solutions, e.g. by passing the solution through a bed of the resin or by stirring the resin in the solution. Regeneration of spent resin may be effected by treatment with aqueous solutions of salts, e.g. sodium or potassium chloride, followed by washing. Examples describe the preparation of resins from (1) melamine, aqueous formaldehyde and sodium sulphite, the initial condensate being heated at 105 DEG C. for 5 hours, comminuted and screened to yield particles of 0.3 to 0.4 mm. diameter with good cation-exchange properties; (2) urea, aqueous formaldehyde and sodium metabisulphite; (3) urea aqueous acetaldehyde and sodium metabisulphite; (4) melamine, urea, aqueous formaldehyde and sodium sulphite.ALSO:A synthetic resin prepared by heating a solution of a condensation product of an aldehyde, an amino compound and a bisulphite (see Group IV) in a solvent, preferably water, until a gel is formed, heating the gel to form an infusible porous mass and comminuting said mass, is used for absorbing cations such as magnesium, zinc, calcium, iron, manganese and lead from solutions. The ion exchange may be effected by passing the cation containing fluid through a bed of synthetic resin of suitable particle size or a batch of the synthetic resin may be stirred in the cation-containing liquid. Revivification of spent resin may be accomplished by treatment with a liquid containing desired cations, e.g. aqueous solutions of sodium or potassium chloride followed by washing with soft water. The resins may be used over a wide range of pH and do not impart colour to the treated liquids. |
