Luperox® for Polymerization of Vinyl Chloride
A Range of Solutions
The wide range of Luperox® organic peroxides is well adapted to suspension process for polymerizations of vinyl chloride. The reaction is generally performed between 40 and 80°C over 3 to 10 hours. The molecular weight and density of the polymer can be regulated by temperature in the reactor. Temperature is constant during polymerization for a given grade, for example, K-67 is typically manufactured at 57°C.
Process
Suspension polymerization represents 80% worldwide production. The main characteristics of this process are:
- Batch technology
- Reaction in water, liquid vinyl chloride in droplets of lower than 50 µm
- Autoclave reactor: 8-12 bars, 50 - 70°C
- Polymerization conducted up to 75% conversion
- Reaction finished or stopped at about 90% conversion
Peroxide Selection
The best productivity in vinyl chloride polymerization is achieved when the thermal energy generated by peroxide decomposition is as constant as possible. For this reason, a selection of several peroxides is recommended:
- A high activity, short half-life peroxide to quickly start the reaction
- A medium half-life peroxide to continue the reaction
- A long half-life peroxide to achieve good monomer conversion
| Half-Life (°C) | Peroxide Recommended | K Value | Reaction Temperature (°C) | Application |
| 54-58 |
|
≥ 70 | < 54 | Flexibles |
| 64-66 |
|
≥ 67 | 57 | Pipe/Profile |
| 72-81 |
|
≥ 62 | > 60 | Rigid Film/Sheet |
Peroxide Emulsions
Emulsions of peroxide in water offer unique advantages:
- Water in the formulation acts as a heat-sink, reducing risk of ignition
- Fish-eyes in the resins can be reduced
- Faster dispersion in the reactor
- Improvements in waste water treatment
Arkema is offering a range of emulsions to the PVC industry.