Process for preparation of chlorinated and chlorosulfonated olefin polymers having low levels of residual monofluorobenzene reaction solvent and its chlorinated by-products

Abstract

Non-discolored chlorinated and chlorosulfonated olefin polymers having low levels of residual solvent are prepared in a process wherein monofluorobenzene is used as a reaction medium and isolation of the polymer is by means of a series of vented closed loop extruders. The process also results in suppression of the formation of monochloromonofluorobenzene as a by-product.

We claim: 
     
       1. A process for preparation of chlorinated olefin polymers having low residual solvent content which comprises (a) forming a solution or .suspension of an olefin polymer in a solvent consisting essentially of monofluorobenzene having a water content of less than 50 ppm, by bringing together the olefin polymer, a free radical catalyst, the monofluorobenzene, and a chlorinating agent selected from the group consisting of chlorine, sulfuryl chloride, a mixture of chlorine and sulfur dioxide, and mixtures thereof, the water content of the monofluorobenzene being reduced to less than 50 ppm i) prior to introduction to the reactor or ii) in situ, with the proviso that the chlorinating agent is introduced simultaneously with the addition of the free radical catalyst or following addition of the free radical catalyst;   (b) chlorinating the olefin polymer to a level of up to 70 percent chlorine by weight while maintaining a level of free radical catalyst sufficient to suppress chlorination of the monofluorobenzene; and   (c) separating the chlorinated olefin polymer and solvent, one from the other, substantially in the absence of oxygen, by means of a series of two or more vented closed-loop extruders, the first extruder having at least twice the cross sectional area of the second; thereby producing a non-discolored chlorinated olefin polymer having a total residual level of combined monofluorobenzene and chlorinated by-products of monofluorobenzene of less than 0.5 percent by weight.     
     
     
       2. The process of claim 1 wherein the chlorinating agent is a chlorosulfonating agent. 
     
     
       3. The process of claim 1 wherein the chlorinating agent is chlorine. 
     
     
       4. The process of claim 2 wherein the chlorosulfonating agent is sulfuryl chloride. 
     
     
       5. The process of claim 1 wherein the olefin polymer is selected from the group consisting of homopolymers of C 2  -C 3  alpha monoolefins, copolymers of ethylene and carbon monoxide, and copolymers of ethylene and at least one ethylenically unsaturated monomer selected from the group consisting of C 3  -C 10  alpha monoolefins, C 1  -C 12  alkyl esters of unsaturated C 3  -C 20  monocarboxylic acids, unsaturated C 3  -C 20  mono-or dicarboxylic acids, anhydrides of unsaturated C 4  -C 8  dicarboxylic acids, and vinyl esters of saturated C 2  -C 18  carboxylic acids. 
     
     
       6. The process of claim 5 wherein the olefin polymer is polyethylene. 
     
     
       7. The process of claim 5 wherein the olefin polymer is a copolymer of ethylene and octene. 
     
     
       8. The process of claim 1 wherein the olefin polymer is chlorinated to a level of 20-70 weight percent chlorine. 
     
     
       9. The process of claim 8 wherein the chlorinated olefin polymer has a sulfur level of up to 6 percent by weight. 
     
     
       10. The process of claim 9 wherein the chlorinated olefin polymer has a sulfur level of 1-3 percent by weight. 
     
     
       11. The process of claim 1 wherein the olefin polymer is chlorinated to a level of 50-70 weight percent chlorine. 
     
     
       12. The process of claim 1 wherein the free radical catalyst is added continuously throughout step (b). 
     
     
       13. The process of claim 1 wherein the series of extruders consists of two extruders. 
     
     
       14. The process of claim 1 wherein the screw speed of each subsequent extruder in the series is less than that of the preceding extruder in the series. 
     
     
       15. The process of claim 1 wherein at least one extruder is a non-intermeshing screw extruder. 
     
     
       16. The process of claim 1 wherein the material of construction of the extruder is a nickel chrome alloy. 
     
     
       17. The process of claim lwherein the total residual level of monofluorobenzene and monochloromonofluorobenzene is less than 0.3 weight percent.