White polyolefin compositions having reduced die drool

Abstract

Filled polyolefin compositions suitable for use in extrusion/coextrusion processes which reduce die drool are provided. More particularly, the compositions are white or opaque compositions comprising a polyolefin, whitening or opacifying inorganic filler and a mercaptobenzimidazole compound.

1 . A polyolefin composition comprising: 
 (a) 40 to 98.5 weight percent, based on the weight of the composition, polyolefin resin selected from the group consisting of ethylene homopolymers, ethylene copolymers, propylene homopolymers and propylene copolymers, said polyolefin having a melt index from 0.5 to 50 g/10 min;    (b) 1.5 to 60 weight percent, based on the weight of the composition, whitening/opacifying inorganic filler; and    (c) 0.01 to 1 weight percent, based on the weight of the composition, mercaptobenzimidazole compound of the formula                          where A is hydrogen or zinc, R is a C 1-4  alkyl group, n is 0 to 4 and x is 1 or 2.    
     
     
         2 . The composition of  claim 1  wherein (b) is selected from the group consisting of titanium dioxide, calcium carbonate, barium sulfate, silica, silica dioxide, talc, mica and kaolin.  
     
     
         3 . The composition of  claim 1  wherein R is methyl and n is 0 or 1.  
     
     
         4 . The composition of  claim 1  comprising 45 to 97.5 weight percent (a), 2.5 to 55 weight percent (b) and 0.05 to 0.5 weight percent (c).  
     
     
         5 . The composition of  claim 4  wherein (b) is titanium dioxide and (c) is selected from the group consisting of 2-mercaptotolylimidazole, 2-mercaptobenzimidazole, zinc-2-mercaptobenzimidazole and zinc 2-mercaptotolylimidazole.  
     
     
         6 . The composition of  claim 5  wherein (a) is low density polyethylene or linear low density polyethylene having densities from 0.915 to 0.930 g/cm 3 .  
     
     
         7 . The composition of  claim 6  wherein the titanium dioxide has an average particle size from 0.1 to 10 microns.  
     
     
         8 . The composition of  claim 4  wherein (b) is calcium carbonate and (c) is selected from the group consisting of 2-mercaptotolylimidazole, 2-mercaptobenzimidazole, zinc-2-mercaptobenzimidazole and zinc 2-mercaptotolylimidazole.  
     
     
         9 . The composition of  claim 8  wherein (a) is low density polyethylene or linear low density polyethylene having densities from 0.915 to 0.930 g/cm 3 .  
     
     
         10 . The composition of  claim 9  wherein the calcium carbonate has an average particle size from 0.1 to 10 microns.  
     
     
         11 . The composition of  claim 1  which additionally contains 0.1 to 1 weight percent, based on the weight of the composition, processing aid.  
     
     
         12 . The composition of  claim 11  wherein the processing aid is a fatty acid metal soap.  
     
     
         13 . The composition of  claim 12  wherein the processing aid is aluminum stearate.  
     
     
         14 . The composition of  claim 1  which additionally contains 0.1 to 1 weight percent, based on the weight of the composition, hindered phenol stabilizer.  
     
     
         15 . The composition of  claim 14  wherein the hindered phenol stabilizer is selected from the groups consisting of 4,4′-methylenebis(2,6-di-t-butylphenol), tetrakis [methylene (3,5-di-t-butyl-4-hydroxyhydrocinnamate)methane,1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)-benzene, 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)-s-triazine 2,4,6(1H,3H,5H)trione, N,N′-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propanyl]-hydrazine and octadecyl 3,5-di-t-butyl-4-hydroxyhydrocinnamate.