Cation exchange resins

摘要

A cation-exchange resin is made by condensing at an elevated temperature and in an acid medium (1) one or more aromatic compounds which individually or between them possess different cation-exchange groups and at least one of which contains an etherified phenolic hydroxyl group with (2) one or more aldehydes or aldehyde yielding substances, continuing the condensation to form a gel and drying the gel at an elevated temperature. Specified starting materials to be condensed with an aldehyde are (a) the condensation product of 1 mol. of an aromatic aldehyde containing at least one carboxylic acid group with 2 mols. of an aromatic sulphonic acid containing at least one etherified phenolic hydroxyl group; (b) the triphenyl methane derivative of formula obtained by condensing 2 mols. phenoxy acetic acid with 1 mol. of benzaldehyde-2,4-disulphonic acid; (c) a mixture of phenoxyacetic acid and the sulphonic acid of a polycyclic hydrocarbon (e.g. naphthalene or acenaphthene) or aromatic ether (e.g. diphenyl ether, anisole, diphenylene oxide or diphenylene dioxide). When two aromatic substances are used they may be separately condensed with the aldehyde, the two condensates mixed and the mixture heated to form a gel; alternatively the lesser reactive aromatic compound may be precondensed with the aldehyde before adding the more reactive compound. In examples: (1) the sodium salt of benzaldehyde-2,4-disulphonic acid and phenoxy acetic acid are introduced into 70 per cent sulphuric acid and later further phenoxy acetic acid is added. When the condensation is complete the whole is condensed with formaldehyde to form a gel; (2) a mixture of sulphonated naphthalene, phenoxyacetic acid and formalin is condensed to form a gel; (3) a mixture of sulphonated acenaphthene, phenoxyacetic acid and formalin is condensed. Paraformaldehyde is then added, whereupon a gel soon forms.ALSO:A triphenylmethane derivative of formula is made by condensing 2 mols. of phenoxy acetic acid with 1 mol. of benzaldehyde-2,4-disulphonic acid. It is condensed with an aldehyde to yield an ion-exchange resin (see Group IV (a)).