Treatment of resins to lower levels of CPD-producing species and improve gelation stability
View Patent ↗A process for treating a composition containing a polyamine-epihalohydrin resin that has a low level of CPD-producing species and good gelation stability is disclosed. A polyamine-epihalohydrin resin is prepared with a ratio of epihalohydrin:amine of less than about 1.1:1.0; The resin is then subjected to a base treatment followed by an acid treatment resulting in a resin that has good gelation storage stability and produces low levels of CPD.
1. A process for producing a composition comprising a polyamine-epihalohydrin resin that has a low level of CPD-producing species and good gelation stability, comprising the steps: (A) preparing the resin with a ratio of epihalohydrin:amine of less than about 1.1:1.0; (B) treating a composition comprising a polyamine-epihalohydrin resin which includes CPD forming species with at least one basic agent, under conditions to at least one of reduce and remove the CPD-forming species; (C) subsequent to the base treatment, treating the composition comprising a polyamine-epihalohydrin resin at a temperature at least about 35° C. for a time about 20 minutes to 5 hours with at least one acidic agent, under conditions to obtain a gelation storage stable composition; and wherein the resulting reduced CPD-forming, gelation storage stable resin composition produces less than about 250 ppm dry basis of CPD, when stored at pH 1 for 24 hours at 50° C. and measured at 24 hours.
2. The process of claim 1 wherein the epihalohydrin:amine ratio is less than about 1.05:1.0.
3. The process of claim 1 wherein the epihalohydrin:amine ratio is less than about 1.0:1.0.
4. The process of claim 1 wherein the polyamine-epihalohydrin resin is a polyaminopolyamide-epihalohydrin resin.
5. The process of claim 1 wherein the epihalohydrin is epichlorohydrin.
6. The process of claim 1 wherein the azetidinium content of the resin is greater than 40 mole %.
7. The process of claim 1 wherein the resin composition has an active solids content of greater than 13%.
8. The process of claim 1 wherein the resin composition has an active solids content of greater than 15%.
9. The process of claim 1 wherein the temperature of step (B) is about 35° C. to about 55° C.
10. The process of claim 1 wherein the pH of step (B) is between 10.5 to about 12.5.
11. The process of claim 1 wherein the time for step (B) is about 10 minutes to about 2 hours.
12. The process of claim 1 wherein the basic agent is selected from sodium hydroxide, potassium hydroxide and combinations thereof.
13. The process of claim 1 wherein the pH of step (C) is between 1.0 and 4.0.
14. The process of claim 13 wherein the pH of step (C) is between 1.8 and 3.5.
15. The process of claim 1 wherein the pH value for step (C) is maintained at or near the starting acidic pH during acid treatment by periodic or continuous addition of the acidic agent.
16. The process of claim 1 wherein the acidic agent is a non-halogen containing acid.
17. The process of claim 1 wherein the acidic agent is sulfuric acid.
18. The process of claim 1 further comprising treatment of the resin either prior to or subsequent to steps (B) and (C) wherein the further treatment is by ionic exchange, membrane separation, biodehalogenation or carbon absorption.
19. The process of claim 1 wherein the resulting resin has an AOX content of less than 75% of the initial value of the AOX content in the untreated resin on an equal actives basis.
20. The process of claim 1 wherein the time of step (C) is about 30 minutes to 4 hours.
21. The process of claim 20 wherein the time of step (C) is about 40 minutes to 3 hours.
22. The process of claim 21 wherein the time of step (C) is about 50 minutes to 2.5 hours.