Synthesis of polycondensation ion exchange resin(III)
3、 Anion exchange resin
There are two main routes for the synthesis of polycondensation anion exchange resin, one is the polycondensation of aromatic amines or aromatic amines and fatty polyamines with formaldehyde; The other is polycondensation of polyamine and epichlorohydrin.
The hydrochloric acid solution of m-phenylenediamine and formaldehyde is dispersed and suspended in the mixed medium of diethyl phthalate, dioctyl phthalate and carbon tetrachloride, polymerized at 35 ℃ for 20 minutes, and then polymerized at 100 ℃ for 15~20 hours to obtain weakly basic resin.
Metaphenylenediamine and polyvinylamine can also be copolymerized with formaldehyde to obtain weak Zang resin, which is the earliest anion exchange resin Wofatit M with an exchange capacity of 1.2meq/ml.
The weakly basic resin can also be obtained by condensation polymerization of polyamines and formaldehyde with phenol instead of m-phenylenediamine. For example, phenol and tetraethylenepentamine are condensed with formaldehyde to slurry, and then suspended in o-dichlorobenzene to obtain spherical weakly basic resin with exchange capacity of 9.97meq/g and 2.39meq/ml.
The weakly basic resin made of melamine, guanidine and formaldehyde is 5.23 meq/g and 2.56 meq/ml. This resin can adsorb dyes from aqueous solution, form complexes with some nonferrous and precious metals (such as Cu2+Ni2+, etc.), and can also be used to purify sucrose. However, it is easy to hydrolyze in acid solution.
Chlorinated epoxy propane and its derivatives can be polycondensated with polyethylene polyamines to make anion exchange resins with primary amine, secondary amine, tertiary amine and quaternary amine. The synthesis method is 1mol tetraethylenepentamine and 3mol epichlorohydrin aqueous solution (add epichlorohydrin slowly at 28~30 ℃), heat at 50 ℃ for 1~1.5h to make slurry, and then disperse in the mixture of o-dichlorobenzene and xylene for suspension polymerization to obtain anion exchange resin with excellent performance. The total exchange capacity of the resin is 9.5 meq/g and 2.5 meq/ml, of which the strong base exchange capacity is close to 1 meq/g, and the compressive strength is close to 700 g. The resin has many applications in water treatment, extraction and separation of natural products, acid recovery, adsorption of copper and silver ions, etc.
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