Process for preparing polymers from monomers comprising laurolactam
Polymers can be prepared from monomers comprising laurolactam, by a process including a. Beckmann rearrangement of cyclododecanone oxime to give laurolactam in the presence of a Beckmann rearrangement catalyst, b. removal of impurities from the laurolactam to obtain purified laurolactam, and c. polymerization of monomers comprising purified laurolactam. For avoidance of discolouration or yellowing under ageing conditions, prior to the polymerization, polycyclic substances containing 24 carbon atoms and at least one heteroatom selected from oxygen and nitrogen and having a molar mass between 300 and 380 g/mol are limited to 500 ppm, based on laurolactam.
1 . A process for preparing a polymer from at east one monomer comprising laurolactam, the process comprising:
a. performing Beckmann rearrangement of cyclododecanone oxime to give laurolactam in the presence of a Beckmann rearrangement catalyst,
b. removal of at least one impurity from the laurolactam to obtain purified laurolactam, and
c. polymerizing the at least one monomer comprising said purified laurolactam,
wherein the impurity is selected from the group consisting of polycyclic substances containing 24 carbon atoms and at least one heteroatom;
wherein the heteroatom is selected from nitrogen and oxygen;
wherein the polycyclic substances have a molar mass between 300 and 380 g/mol,
wherein the impurities are limited in step b. to 500 ppm, based on laurolactam.
2 . The process according to claim 1 , wherein the at least one impurity is removed by crystallization or distillation.
3 . The process according to claim 2 , wherein the distillation is undertaken with at least five theoretical plates.
4 . The process according to claim 1 , wherein the cyclododecanone oxime is pretreated prior to the Beckmann rearrangement, the pretreatment being selected from the group consisting of scrubbing with water, scrubbing with alkali, scrubbing with acid, hydrogenation, crystallization and combinations thereof.
5 . The process according to claim 1 , wherein the polymerization is conducted continuously.
6 . The process according to claim 1 , wherein the Beckmann rearrangement catalyst is selected from an acid with pKA≤0, cyanuric chloride, phosphorus trichloride, thionyl chloride and mixtures thereof.
7 . The process according to claim 1 , wherein polymerization is conducted at a temperature between 250° C. and 350° C., in the presence of 2% to 51% by weight of water, based on the total weight of monomers and water.
8 . The process according to claim 1 , wherein the impurities are limited in step b. to 100 ppm, based on laurolactam.
9 . The process according to claim 1 , wherein the polymer contains at least 20% by weight of laurolactam, based on the total weight of the polymer.
10 . A polymer containing laurolactam, prepared according to the process of claim 1 .
11 . The process according to claim 1 , wherein the Beckmann rearrangement catalyst is sulfuric acid.