Copolymers, devoid of rubber, with low residual monomer content and a method and device for producing the same
View Patent ↗Rubber-free copolymers of unsaturated monomers selected from the group comprising styrenes and vinyl cyanides are disclosed. The copolymers that contain 65 to 80 wt. %, of styrene and 20 to 35 wt. % of acrylonitrile are characterized in their low content of residual monomers and improved physical properties. Also disclosed are a process and a device for the preparation of these copolymers.
1. A process for the preparation of rubber-free copolymers of ethylenically unsaturated monomers selected from the group consisting of styrenes and vinyl cyanides containing 65 wt. % to 80 wt. % styrene and 20 wt. % to 35 wt. % vinyl cyanide with a low residual monomer content, wherein concentration takes place in two steps, characterized in that solutions of the rubber-free copolymers are brought to concentrations of greater than or equal to 99.8% in a first step of concentration by introducing energy with simultaneous evaporation in tubes in a tube evaporator and, in a second step without intermediate heating, further removal of the monomers is carried out in a strand evaporator.
2. A process according to claim 1 , characterized in that the heating in the first step results in an outlet temperature of 165° C. to 240° C.
3. A process according to claim 1 , characterized in that the tube evaporator in the first step is working at a pressure from 50 mbar to 100 mbar.
4. A process according to claim 1 , characterized in that a throughput through the tubes in the first step is 1 to 10 kg/h.
5. A process according to claim 1 , characterized in that the strand evaporator in the second step is working at a pressure from 0.5 mbar to 10 mbar.
6. A process according to claim 1 , characterized in that the tubes are heated.
7. The process of claim 1 , wherein said vinyl cyanide is acrylonitrile.
8. A device of carrying out a process according to claim 1 , characterized by a tube evaporator having tubes in the first step, a strand evaporator in the second step and equipment for conveying the product solutions.
9. A device according to claim 8 , characterized in that the length of the tubes in the first step is 1 m to 2.5 m and the internal diameter is 8 mm to 23 mm.
10. A device according to claim 8 , characterized in that static mixing components are provided in the tubes.
11. A device according to claim 8 , characterized in that the product in the strand evaporator is introduced by way of a tube manifold to tubes with bores with a diameter from 1 mm to 4 mm and the tubes are situated in a vertically arranged apparatus with a height from 2 m to 10 m.
12. A device according to claim 8 , characterized in that that tubes include conically shaped bores.
13. A device according to claim 8 , characterized in that the tube evaporator includes a tube manifold having orifices wherein a throughput per orifice is 100 g/h to 200 g/h.