Stabilizer compositions for halogen containing polymers

Abstract

The instant invention relates to a composition and process for the stabilization of halogen containing polymer slurries, in particular polyvinylchloride (PVC). The composition comprises a halogen containing polymer in the form of an aqueous suspension or emulsion, a partially hindered phenolic antioxidant and selected sulfur containing antioxidants, which are both solid at 20° C. A further aspect of the invention is the use of specific antioxidant mixtures for the stabilization of halogen containing polymer suspensions or emulsions, in particular PVC.

1 . A composition comprising
 a) a halogen containing polymer or copolymer in the form of an aqueous suspension or emulsion;   b) a sterically hindered phenolic antioxidant with a melting point of more than 20° C. containing a compound of formula (Ia) or (Ib)   
     
       
         
         
             
             
         
       
       wherein
 n is 2 or 3 
 R 1  is tert-butyl, secondary bound C 3 -C 18 alkyl or C 5 -C 6 cycloalkyl; 
 R′ 1  is tert-butyl, primary or secondary bound C 1 -C 18 alkyl, phenyl, C 7 -C 9 phenylalkyl or 
 C 5 -C 6 cycloalkyl; 
 R 3  is C 1 -C 18  alkyl, C 1 -C 18 alkoxy, C 5 -C 6 cycloalkyl or —CH 2 —CH 2 —CO—O—(C 1 -C 18 )alkyl; 
 R′ 2  is a divalent or trivalent bridging group; 
 R 4  is a group 
 
     
     
       
         
         
             
             
         
       
       
         R 2  is hydrogen, methyl or a group 
       
     
     
       
         
         
             
             
         
       
       
          wherein m is a number from 1 to 10; and 
       
       c) a thioether or thioether-ester with a melting point of more than 20° C. of formula (IIa), (IIb) or (IIc) 
     
     
       
         
         
             
             
         
       
       
         wherein 
         R 11  and R 12  are independently C 1 -C 18 alkyl 
         k is 2-4; and 
         X is 2-methyl-1,2,3-propane-triyl- or 1,2,3,4-methane-tetryl- and 
         where zinc compounds are not present. 
       
     
   
   
       2 . A composition according to  claim 1  wherein the sterically hindered phenolic antioxidant containing a structural element of formula (Ia) or (Ib) is of formulae (IIIa), (IIIb) or (IIIc) 
     
       
         
         
             
             
         
       
       wherein 
       n is 2 or 3 
       R 1  is tert-butyl, secondary bound C 3 -C 18 alkyl or C 5 -C 6 cycloalkyl; 
       R 11  is tert-butyl, primary or secondary bound C 1 -C 18 alkyl, phenyl, C 7 -C 9 phenylalkyl or 
       C 5 -C 6 cycloalkyl; 
       R 3  is C 1 -C 18  alkyl, C 1 -C 18 alkoxy, C 5 -C 6 cycloalkyl or a group 
       —CH 2 —CH 2 —CO—O—(C 1 -C 18 )alkyl; 
       R 12  is C 1 -C 12 alkylene, —S—, trimethylene-isocyanurate, or a group 
       —CH 2 —CH 2 —CO—(OCH 2 CH 2 ) p —O—CO—CH 2 CH 2 — wherein p is a number from 1 to 3; 
       R 2  is hydrogen, methyl or a group 
     
     
       
         
         
             
             
         
       
        wherein m is a number from 1 to 10. 
     
   
   
       3 . A composition according to  claim 1  wherein the halogen containing polymer is PVC. 
   
   
       4 . A composition according to  claim 1  wherein in component c) both R 11  are C 12 alkyl or C 1-8 alkyl and the R 12  are C 12 alkyl. 
   
   
       5 . A composition according to  claim 1  wherein in component b) the sterically hindered phenolic antioxidant is
 2-tert-butyl-4,6-dimethylphenol;   2,4-dimethyl-6-(1′-methylundec-1′-yl)phenol, 2,4-dimethyl-6-(1′-methylheptadec-1′-yl)phenol,   2,4-dimethyl-6-(1′-methyltridec-1′-yl)phenol, 2,4-dimethyl-6-(1′-methyltetradec-1′-yl)phenol or mixtures thereof;   2,2′-methylenebis(6-tert-butyl-4-methylphenol), 2,2′-methylenebis(6-tert-butyl-4-ethylphenol),   2,2′-methylenebis(4,6-di-tert-butylphenol), 2,2′-ethylidenebis(4,6-di-tert-butylphenol),   2,2′-ethylidenebis(6-tert-butyl-4-isobutylphenol)   
     or
 (ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate]. 
 
   
   
       6 . A composition according to  claim 1  wherein in component b) the sterically hindered phenolic antioxidant is
 2-tert-butyl-4,6-dimethylphenol or 2,4-dimethyl-6-(1′-methyltetradec-1′-yl)phenol or a mixture thereof   
     and component c) is 
     di-lauryl-thio-di-propionate or di-stearyl-thio-di-propionate or a mixture thereof. 
   
   
       7 . A composition according to  claim 1  wherein in component b) the sterically hindered phenolic antioxidant is
 2,4-dimethyl-6-(1′-methyltetradec-1′-yl)phenol   
     and component c) is 
     di-lauryl-thio-di-propionate. 
   
   
       8 . A composition according to  claim 1  wherein the sterically hindered phenolic antioxidant, component b) is present in an amount from 50 ppm to 2000 ppm based on the weight of the halogen containing monomer. 
   
   
       9 . A composition according to  claim 1  wherein component c) is present in an amount from 50 ppm to 2000 ppm based on the weight of the halogen containing monomer. 
   
   
       10 . A composition according to  claim 1  wherein the ratio of component b) to component c) is from 1:10 to 10:1. 
   
   
       11 . A composition according to  claim 1 , which additionally contains a sterically hindered phenolic antioxidant different from that of component b), a phosphorous containing stabilizer, a 2-benzofuranone stabilizer, a sterically hindered amine light stabilizer or a UV-absorber. 
   
   
       12 . A process for the stabilization of halogen containing polymers against thermal degradation, which process comprises
 adding to the halogen containing polymer, which is in an aqueous suspension or emulsion during or after the polymerization process
 b) a sterically hindered phenolic antioxidant with a melting point of more than 20° C. containing a compound of formula (Ia) or (Ib) 
   
     
       
         
         
             
             
         
       
       
         
           wherein 
           n is 2 or 3 
           R 1  is tert-butyl, secondary bound C 3 -C 18 alkyl or C 5 -C 6 cycloalkyl; 
           R′ 1  is tert-butyl, primary or secondary bound C 1 -C 18 alkyl, phenyl, C 7 -C 9 phenylalkyl or C 5 -C 6 cycloalkyl; 
           R 3  is C 1 -C 18  alkyl, C 1 -C 18 alkoxy, C 5 -C 6 cycloalkyl or —CH 2 —CH 2 —CO—O—(C 1 -C 18 )alkyl; 
           R′ 2  is a divalent or trivalent bridging group; 
           R 4  is a group 
         
       
     
     
       
         
         
             
             
         
       
     
     or hydrogen;
 R 2  is hydrogen, methyl or a group 
 
     
       
         
         
             
             
         
       
        wherein m is a number from 1 to 10; and
 c) a thioether or thioether-ester with a melting point of more than 20° C. of formula (IIa), (IIb) or (IIc) 
 
     
     
       
         
         
             
             
         
       
       
         
           wherein 
           R 11  and R 12  are independently C 1 -C 18 alkyl 
           k is 2-4; and 
           X is 2-methyl-1,2,3-propane-triyl- or 1,2,3,4-methane-tetryl- and 
         
       
     
     where zinc compounds are not added during the process. 
   
   
       13 . A process according to  claim 12  wherein the components b) and c) are added towards the end of the polymerization reaction. 
   
   
       14 . A process according to  claim 12  wherein the polymerization is a suspension polymerization and the components b) and c) are added as an emulsion to the slurry towards the end of the polymerization reaction.