Co-metering of organic initiators and protective colloids during polymerization reactions
View Patent ↗The invention pertains to a process wherein initiators and protective colloids are both metered to a polymerization mixture. This manner of metering allows for improved control of the polymerization rate and an improved reactor space-time yield, and the process will render a polymer with a relatively high porosity.
1. A process of polymerizing a polymerization mixture comprising at least one monomer wherein at least an organic initiator and 0.01–1 wt.% of a protective colloid, based on the weight of the monomers to be polymerized, are metered to the polymerization mixture at a polymerization temperature by (a) adding portions of the initiator and the protective colloid separately in an alternating way or sequentially in random order of at least 2 moments, (b) by metering at least part of the initiator and at least part of the protective colloid intermittently and/or continuously, over a period of time during which at least 20% of all monomer used in the process is polymerized, or (c) by metering the initiator and the protective colloid continuously and/or intermittently after at least 1% of the monomer(s) has already been polymerized, with at least 10% of all monomer used in the process being polymerized during the metering period.
2. The process according to claim 1 wherein at least one of the monomers is vinyl chloride.
3. The process according to claim 1 wherein the protective colloid is a polyvinyl alcohol.
4. The process according to claim 1 wherein the organic initiator has a half-life of from 0.0001 hour to 1 hour at the polymerization temperature.
5. The process according to any one of claims 1 – 4 wherein the initiator and the protective colloid are at least partially metered simultaneously.
6. The process according to any one of claims 1 – 4 wherein the metering of the initiator and the protective colloid is controlled such that the maximum cooling capacity of the reactor is used.
7. The process according to any one of claims 1 – 4 wherein the polymerization time of a batch process or the residence time of a continuous process is shorter than 4 hours.
8. A process according to claim 3 wherein the polyvinyl alcohol is a saponified polyvinyl alcohol with a degree of hydrolysis of between 40 and 90%.
9. A process according to claim 4 wherein the half life of the initiator is from 0.0001 hour to 0.5 hour.
10. A process according to claim 1 wherein at least part of the initiator and the protective colloid is metered, intermittently and/or continuously, after at least 10% of the monomer(s) has already been polymerized and wherein during the metering period at least 30% of all monomer used in the process is polymerized.