White polyolefin compositions having reduced die drool
View Patent ↗Extrudable white-filled polyolefin compositions which exhibit reduced 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. Extrudable white-filled polyolefin concentrate compositions consisting essentially of:
(a) 20 to 60 weight percent, based on the total weight of the composition, low density polyethylene or linear low density polyethylene having a melt index from 0.5 to 50 g/10 mm and density from 0.915 to 0.930 g/cm 3 ;
(b) 40 to 80 weight percent, based on the total weight of the composition, titanium dioxide or calcium carbonate; and
(c) 0.01 to 1 weight percent, based on the total 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 R is methyl and n is 0 or 1.
3. The composition of claim 2 wherein (b) is titanium dioxide and (c) is selected from the group consisting of 2-mercaptotolylimidazole, 2-mercaptobenzimidazole, zinc-2-mercaptobenzimidazole and zinc 2-mercaptotolyimidazole.
4. The composition of claim 3 wherein the titanium dioxide has an average particle size from 0.1 to 10 microns.
5. The composition of claim 1 which additionally contains 0.1 to 1 weight percent, based on the weight of the composition, processing aid.
6. The composition of claim 5 wherein the processing aid is a fatty acid metal soap.
7. The composition of claim 6 wherein the processing aid is aluminum stearate.
8. The composition of claim 1 which additionally contains 0.1 to 1 weight percent, based on the weight of the composition, hindered phenol stabilizer.
9. The composition of claim 8 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.
10. The composition of claim 1 containing 0.05 to 0.5 weight percent (c).
11. The composition of claim 10 wherein (a) is low density polyethylene and (b) is titanium dioxide.
12. The composition of claim 11 containing 30 to 55 weight percent (a) and 45 to 70 weight percent (b).