Process for the compounding of polymers
A compounding process is disclosed. The process includes (i) melt blending in an extruder at least two polymeric resins to produce a mixture that includes at least one resin that dissociates to yield monomers and/or oligomers upon heating, said mixture containing less than 1 percent of volatile components, (ii) introducing into said extruder an inert entraining agent, and (iii) removing said entraining agent together with said volatile components from said extruder. The extruder includes at least one melting zone, at least two degassing zones and at least one mixing zone. The end product has a particularly low content of residual solvent and at the same time a low content of monomers or oligomers.
1. A compounding process comprising
(i) melt blending in an extruder at least two polymeric resins comprising acrylonitrile-butadiene-styrene graft copolymer and polycarbonate to produce a mixture that includes at least one resin that dissociates to yield monomers and/or oligomers upon heating, said mixture containing initially less than 1 percent of volatile components,
(ii) introducing into said mixture an inert entraining agent
(iii) removing said entraining agent together with said volatile components from said mixture, wherein the degassing efficiency of the process, calculated according to the formula
∑
residual
contents
input
-
∑
residual
contents
output
∑
residual
contents
input
·
100
%
=
degassing
efficiency
is at least 68%, the entraining agent is introduced at an amount of 0.1 to 0.5% based on the total weight of said polymeric resins, and
wherein the extruder includes at least one melting zone, at least two degassing zones and at least one mixing zone.
2. The process of claim 1 wherein the removing is carried out by applying reduced pressure of less than 500 mbar.
3. The process of claim 1 wherein said resin that dissociates upon heating is acrylonitrile-butadiene-styrene graft copolymer.
4. The process of claim 1 wherein said mixture contains at least two polymers that dissociate.
5. The process of claim 1 wherein the at least one resin that dissociates is present in the mixture in an amount of 10 to 66% relative to the weight of the mixture.
6. The process of claim 1 where at least one of (ii) and (iii) takes place in more than one stage.
7. The process of claim 1 wherein the extruder is a twin screw extruder.
8. The process of claim 7 wherein the twin-shaft screw extruder includes co-rotation of the shafts.
9. The process of claim 1 wherein the extruder has a ratio of length to diameter of the screw shaft is 32-44.
10. The process of claim 1 wherein said extruder further includes a metering zone.
11. The process of claim 1 wherein said extruder includes two mixing zones and a metering zone.
12. The process of claim 1 , wherein the resulting blend has less than 0.1 percent by weight of volatile components, said percent relative to the weight of said resins.
13. The process of claim 1 wherein the entraining agent is selected from the group consisting of nitrogen, noble gas, and carbon dioxide.
14. The process of claim 1 wherein the residual content of 1,3-butadiene in the resulting blend is less than 0.6 ppm relative to the weight of said resins.
15. A compounding process comprising
(i) melt blending in an extruder at least two polymeric resins comprising acrylonitrile-butadiene-styrene graft copolymer and polycarbonate to produce a mixture that includes at least one resin that dissociates to yield monomers and/or oligomers upon heating, said mixture containing initially less than 1 percent of volatile components,
(ii) introducing into said mixture an inert entraining agent selected from the group consisting of nitrogen, noble gas and carbon dioxide, and
(iii) removing said entraining agent together with said volatile components from said mixture, wherein the resulting blend has less than 0.1 percent by weight of volatile components, and
wherein the extruder includes at least one melting zone, at least two degassing zones and at least one mixing zone, said percent relative to the weight of said resins, and wherein said resin that dissociates upon heating is an acrylonitrile-butadiene-styrene graft copolymer,
and wherein
the degassing efficiency of the process, calculated according to the formula
∑
residual
contents
input
-
∑
residual
contents
output
∑
residual
contents
input
·
100
%
=
degassing
efficiency
is at least 68%, the entraining agent is introduced at an amount of 0.1 to 0.5% based on the total weight of said polymeric resins.