An initiator for cationic polymerization comprises a salt of a protic acid as well as a protic add. The molar ratio of protic acid to salt is in the range from 1:0.01 to 1:2000. The initiator is used for example for cationic homo- or copolymerization of trioxane, and permits stable and flexible operation of the polymerization.
1. A polyacetal polymer formed by polymerizing an initiator comprising at least one protic acid and at least one salt of a protic acid, wherein said at least one protic acid is sulfuric acid, tetrafluoroboric acid, perchloric acid, fluorinated alkyl sulfonic acid, chlorinated alkyl sulfonic acid or aryl sulfonic acid, and wherein said salt of protic acid is an alkali metal or alkaline earth metal salt of protic acid and/or a substituted ammonium salt of protic acid, the cations of the ammonium salt having the general formula (I)
where R 1 -R 4 are independently hydrogen, an alkyl group or an aryl group; and
at least one monomer comprising trioxane.
2. A polymer according to claim 1 , wherein the protic acid is trifluoromethanesulfonic acid, pentafluoroethanesulfonic acid, heptafluoropropanesulfonic acid, nonafluorobutanesulfonic acid, perfluoropentanesulfonic acid, perfluorohexanesulfonic acid or perfluoroheptanesulfonic acid.
3. A polymer according to claim 1 , wherein where R 1 -R 4 are independently hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or 4-methoxyphenyl.
4. A polymer according to claim 1 , wherein the protic acid comprises fluorinated alkyl sulfonic acid, chlorinated alkyl sulfonic acid or aryl sulfonic acid.
5. A polymer according to cairn 1 , wherein the protic acid comprises trifluoromethanesulfonic acid, pentalluoroethanesulfonic acid, heptafluoropropanesulfonic acid, nonaflucrobutanesulfonic acid, perfluoropentanesulfonic acid, perfluorohexanesulfonic acid or perfluoroheptanesulfonic acid.
6. A polymer according to claim 1 , wherein the protic acid is present in relation to the salt in the initiator at a molar ratio of from 1:1 to 1:4 during the polymerization.
7. A polymer according to claim 1 , wherein, during the polymerization, the initiator is present in an amount of 10 −6 % to 1% by weight, based on the total weight of the monomers.
8. A polymer according to claim 1 , wherein, the protic acid comprises trifluoromethanesulfonic acid and the salt comprises triethylammonium triflate.
9. A polymer according to claim 1 , wherein the protic acid is present in relation to the salt in the initiator at a molar ratio of from 1:0,5 to 1:10 during the polymerization.
10. A polymer according to claim 1 , wherein the polymer comprises a copolymer.
11. A polymer according to claim 1 , wherein the at least one monomer comprises trioxane and a comonomer.
12. A polymer according to claim 11 , wherein the comonomer comprises a cyclic ether.
13. A polymer according to claim 11 , wherein the comonomer comprises dioxolane.
14. A polymer according to claim 1 , wherein the polymer is formed in the presence of methylal.
15. A polymer according to claim 11 , wherein the polymer is formed in the presence of methylal.
16. A polymer according to claim 11 , wherein the comonomer is present in the range of 0.5% to 10% by weight, based on the weight of the total mixture of monomers.