Sulfur-free, zinc-free cure system for halobutyl and halogen containing polymers

1. A cured, sulfur free and ZnO free compound comprising a halogen containing polymer crosslinked with bis(2-diphenylphosphinophenyl)ether.

2. The compound according to claim 1 , wherein the halogen containing polymer is at least one halobutyl polymer selected from bromobutyl polymers, chlorobutyl polymers, and mixtures thereof.

3. The compound according to claim 1 , wherein the halogen containing polymer is at least one halogen containing polymer selected from bromine containing polymers, chlorine containing polymers, and mixtures thereof.

4. The compound according to claim 1 , wherein the halogen containing polymer is selected from the group consisting of brominated isobutylene para-methylstyrene, brominated isoprene isobutylene p-methylstyrene terpolymer, starbranch brominated butyl, and mixtures thereof.

5. The compound according to claim 1 , further comprising at least one filler and at least one process aid.

6. The compound according to claim 5 , wherein the filler is selected from the group consisting of carbon black, white fillers, and mixtures thereof.

7. A cured, sulfur free and ZnO free compound comprising:

a halogenated butyl rubber formed from isobutylene and less than 2.2 mol % isoprene;

and

a multifunctional phosphine crosslinking agent of the structure

 wherein n≥3.

8. The compound according to claim 7 , wherein the halogenated butyl polymer is a bromobutyl polymer or a chlorobutyl polymer.

9. The compound according to claim 7 , wherein the polymer is selected from the group consisting of brominated isobutyiene para-methylstyrene, brominated isoprene isobutylene p-methylstyrene terpolymer, and star branch brominated butyl.

10. The compound according to claim 7 , further comprising a filler and a process aid.

11. The compound according to claim 10 , wherein the filler is selected from the group consisting of carbon black, white filler, and mixtures thereof.

12. The compound according to claim 7 , wherein the multifunctional phosphine crosslinking agent is selected from the group consisting of 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, 1,5-bis(diphenylphosphino)pentane, 1,6-bis(diphenyl-phosphino)hexane, and 1,8-bis(diphenylphosphino)octane.

13. The compound according to claim 7 , wherein a molar ratio of allylic halide to multifunctional phosphine is 0.01:15 to 15:0.01.

14. The compound according to claim 7 , wherein a molar ratio of allylic halide to multifunctional phosphine ratio is 0.01 to 15.

15. The compound according to claim 7 , wherein a molar ratio of multifunctional phosphine to allylic halide is 0.01 to 15.

16. A process for preparing a cross-linked rubber compound, the process comprising contacting a halogenated butyl rubber formed from isobutylene and less than 2.2 mol % isoprene, with a multifunctional phosphine crosslinking agent of the structure

wherein n≥3.

17. The process according to claim 16 , wherein the halogenated butyl rubber is a bromobutyl rubber or a chlorobutyl rubber.

18. The process according to claim 16 , wherein:

the halogenated butyl rubber is a bromobutyl rubber; and

the contacting comprises reacting the polymer with the multifunctional phosphine crosslinking agent for about 10 to 90 minutes at a temperature of 140 to 200°C.