Process for mixing polymer melts with additives
View Patent ↗A continuous process for mixing polymer melts with additives, in particular polycarbonate melts with additives in liquid form, in solution or in dispersion is described. The additives are added to a main stream of polymer melt and are then mixed, preferably directly, with the main stream in a static mixer.
1. Continuous process for mixing highly viscous polymer melts as main stream in a flow tube with additives from a liquid side stream, characterized in that the additives ( 11 ) are premixed with part of the polymer melt ( 12 ) in the side stream, that the additive-containing side stream ( 13 ) is fed through a feed line ( 14 ) arranged in particular centrally in the flow tube, into the main stream ( 8 ), the combined streams are intensively mixed in a first static mixer ( 10 directly connected downstream, and this premixture is finely divided in a mixing tube ( 15 ) of enlarged cross-section and in a second static mixer ( 16 ) of finer structure (mesh width).
2. Process according to claim 1 , characterised in that the cross-section of the mixing tube of the second static mixer is by a factor of at least 1.2 larger than the cross-section of the mixing tube of the first static mixer.
3. Process according to claim 1 characterised in that the cross-section of the mixing tube of the second static mixer is by a factor of at least 2 larger than the cross-section of the mixing tube of the first static mixer.
4. Process according to claim 1 characterised in that the number of the product throughput openings (per unit surface area) in the second static mixer is at least 1.5 times the number of throughput openings (per unit surface area) in the first static mixer.
5. Process according to claim 1 characterised in that the highly viscous polymer melt is polycarbonate.
6. The mixture of thermoplastic polycarbonate and at least one additive prepared by the process of claim 1 .
7. The process of claim 1 wherein the side stream is formed from recycled polycarbonate.
8. The process according to claim 1 wherein the weight ratio of the side stream to the main stream is 1:4 to 1:30.