Monomers recovered from polymerization
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I would like to ask the experts: what are the potential hazards if monomers recovered through polymerization are directly used in the reactor for further polymerization, and does it affect the quality of the resin? What if it is mixed with newly produced monomers and fed into the polymerization reactor?
It contains water, as well as a significant amount of waste. It is recovered and sent to the gas holder for re-compression and distillation
It contains water, oligomers, and other organic impurities; if these are not distilled off, the presence of water and compounds with high and low boiling points can lead to an increase in defects such as fish eyes and black spots in PVC, which has a significant impact on its quality. Removing it through distillation and then polymerizing it together with fresh monomer in a certain ratio generally does not have a significant impact on the quality.
After the recovered VCM is fed into the gas holder, it undergoes alkaline washing, condensation, and distillation to remove high-boiling substances; thereafter, fresh VCM is added: recovered VCM : fresh VCM = 9:1
After recovery, compression, condensation, and water removal, it is mixed with new monomer and fed into the polymerization reactor for reaction, posing no hazard
After direct drainage, as well as when fresh monomer was added at a ratio of 1:2, there were no abnormalities; the fish eyes met the standards for premium quality, and of course, even smaller ratios resulted in no issues at all
There will be a small amount of terminator in the recycled monomer; the ratio to fresh monomer should not be too high, and it’s best if it has been treated
After compression and condensation, it is stored in the recycled monomer tank; after allowing the liquid to settle and drain, new material is added at a ratio of 5:1 – no issues
The ratio of fresh monomer to recycled monomer is determined by the quantity and quality of the recycled monomer; if there is a large amount of it with low moisture content, the ratio can be higher, otherwise it should be lower
Personally, I feel that recycled VCM still differs from fresh VCM even after processing; it might be advisable to use them separately in the production of PVC. By using only fresh VCM or only recycled material for PVC production, it is possible to ensure stability in the quality of the product in most cases.
What would be the result if everything were produced from recycled monomers?