Continuous dosing of extremely fast initiators during polymerization reactions

Abstract

The invention pertains to a process wherein initiators having a half-life from 0.0001 hour to 0.05 hour at the polymerization temperature are dosed to a polymerization mixture. The dosing of such initiator allows improved control of the polymerization rate and faster polymerization rates, and the process will render a polymer with very low residual initiator levels.

1 . Process to polymerize vinyl chloride monomer and optional further monomers using one or more initiators, with at least part of said initiators being dosed to the polymerizing reaction mixture, characterized in that at least one organic initiator with a half-life of from 0.0001 hour to 0.050 hour at the polymerization temperature is dosed to the polymerizing reaction mixture at said polymerization temperature.  
     
     
         2 . A process according to  claim 1  comprising a step wherein at least part of the dosing of one or more of the initiators is controlled such that the desired cooling capacity of the reactor is used, preferably while keeping the temperature of the polymerization mixture constant.  
     
     
         3 . A process according to  claim 1  wherein at least part of the initiator(s) is dosed after at least 40% w/w, preferably at least 60% w/w, of all monomer has been polymerized.  
     
     
         4 . A process according to  claim 1  wherein the initiator(s), or part of the initiator(s), is (are) dosed, intermittently and/or continuously, during a period wherein at least 20% of all monomer used in the polymerization is polymerized.  
     
     
         5 . A process according to  claim 1  wherein the initiator(s), or part of the initiator(s), is (are) dosed, intermittently and/or continuously, and wherein during the dosing period at least 2% of all monomer used in the process is polymerized.  
     
     
         6 . A process according to  claim 1  wherein essentially all of the initiator(s) is (are) selected from the group consisting of organic peroxides.  
     
     
         7 . The process of  claim 6  wherein essentially all initiator(s) has (have) a half-life of from 0.0001 hour to 0.050 hour at the polymerization temperature.  
     
     
         8 . Vinyl chloride based (co)polymer obtainable by any one of the processes of  claim 1 , having less than 50 parts by weight of residual initiator, based on one million parts by weight of the (co)polymer, when measured immediately after polymerization and drying of the (co)polymer for 1 hour at 60° C.  
     
     
         9 . Use of a vinyl chloride (co)polymer according to  claim 7  in a shaping process involving the heating of the co(polymer) to above its melting temperature.