Method of making thermally regenerable salt sorbent resins
View Patent ↗A heterogenous hybrid thermally regenerable salt sorbent resin is formed from a hybrid precursor resin. The hybrid precursor resin is formed by intimately mixing a dry, solid crosslinked macroporous copolymer with a solution containing a polyunsaturated monomer, a monoethylenically unsaturated monomer containing a haloalkyl group and a polymerization initiator, followed by heating to cause polymerization. The hybrid precursor resin is then treated with a weak base, then subjected to hydrolysis conditions to form, respectively, weak base groups and weak acid groups to produce the hybrid thermally regenerable salt sorbent resin.
1. The method forming a precursor for a heterogenous thermally regenerable salt sorbent having two relatively independent phases by polymerizing in the presence of a host macroporous copolymer a first polyunsaturated monomer and a monoethylenically unsaturated monomer containing a haloalkyl group to form a guest crosslinked copolymer, wherein said host macroporous copolymer is formed from a second polyunsaturated monomer and a monoethylenically unsaturated monomer containing a functionality convertible to a weak acid, comprising the steps of
(a) intimately mixing at a temperature less than about 40° C. a nonaqucous solution of said first polyunsaturated monomer, said monoethylenically unsaturated monomer containing a haloalkcyl group and a polymerization initiation reagent with said macroporous copolymer as a solid to imbibe said solution into said solid macroporous copolymer; and
(b) heating the mixture formed in step (a) within the temperature range of about 70° C. to 100° C. for a period of time sufficient to polymerize said monomers to thereby form said precursor.
2. The method according to claim 1 wherein said haloalkyl group comprises a chloroalkyl group.
3. The method according to claim 2 wherein said chloroalkyl group comprises a chloromethyl group.
4. The method according to claim 1 wherein said monoethylenically unsaturated monomer containing a functionality convertible to a weak acid comprises an acrylic ester.
5. The method according to claim 1 wherein said first and second polyunsaturated monomers comprise divinylbenzene.
6. The method according to claim 1 wherein said monoethylenically unsaturated monomer containing haloalkyl group comprises vinylbenzyl chloride.
7. A method according to claim 1 wherein said step (a) comprises (1) forming a solution of said polyunsaturated monomer and polymerization initiation reagent; (2) adding said unsaturated monomer containing a haloalkyl group to said solution from step (1); and (3) intimately mixing said solution from step (2) with said macroporous copolymer as a solid to imbibe said solution into said macroporous copolymer.
8. A method according to claim 1 wherein the mixing of step (a) is conducted for a period of at least 30 minutes.
9. The method according to claim 8 wherein said period of mixing is in the range of about 2 to 12 hours.
10. A method according to claim 1 wherein said polymerization agent comprises an organic acid peroxide.
11. A method according to claim 10 wherein said peroxide comprises benzoyl peroxide.
12. A method according to claim 1 wherein the temperature range in said step (b) is about 80° C. to 90° C.