| 摘要 |
In making anion-exchange resins, an irreversible gel is formed by the reaction of guanidine, biguanide or guanyl urea (in the form of free bases or their salts) with formaldehyde or paraformaldehyde and a ketone that contains at least two reactive hydrogen atoms and that reacts with formaldehyde to form methylol compounds, the reaction being carried out with or without preliminary condensation of the ketone with some of the aldehyde before any reaction with the guanidine &c. takes place and the reaction mixture being maintained alkaline throughout the reaction. Thus the reaction may be effected either by mixing all the ingredients and heating the mixture until a gel forms or by preliminary condensation of the ketone with some of the formaldehyde and thereafter effecting further condensation by adding the guanidine &c. with the remainder of the formaldehyde. Ketones specified are: acetone, methyl-ethyl ketone, methyl n-propyl ketone and cyclohexanone. When acetone is used, the upper limit of the guanidine &c. is 1.5 mols. per mol of acetone, and the amount of formaldehyde is from 3 to 6 mols. per mol. of acetone. The reaction is maintained alkaline by an alkali such as caustic soda preferably in amount between 0.1 and 0.5 mol. per mol. of ketone, which is added preferably in two portions, one before and one after the preliminary condensation. The gels produced are dried, e.g. between 70 DEG and 160 DEG C. and then granulated, preparation for use or regeneration consisting in treatment with caustic alkali or alkali metal carbonate. Examples are given. Specification 572,836 is referred to.ALSO:An anion-exchange resin, formed as an irreversible gel by reacting guanidine, biguanide or guanyl urea with formaldehyde or paraformaldehyde and a ketone (see Group IVa), is used in the treatment of water or other liquid. In examples, the resin, when prepared for use or regenerated by treatment with caustic alkali, remove (1 and 4) mineral acid and silica; (2) phenol; (3) carbon dioxide; and (5) hydrogen sulphide from impure liquids. Specification 572,836 is referred to. |
