Hydrophobic particulate inorganic oxides and polymeric compositions containing same
Described are hydrophobic particulate inorganic oxides useful for reinforcing polymeric composition, e.g., rubber. The materials are characterized by: (a) the substantial absence of functional groups capable of chemical reaction with rubber; (b) a BET surface area of in the range of from 40 to 350 m 2 /g; (c) a hydroxyl content in the range of 2 to 15 OH/nm 2 ; (d) a carbon content in the range of from 0.1 to 6 percent by weight that is substantially non-extractable; (e) a pH in the range of from 3 to 10; (f) an M1 Standard White Area less than 0.4 percent and (g) a methanol wettability of from 15 to 45 percent. Compositions such as polymers, cured organic rubber articles, master batches and slurries containing the hydrophobic fillers are also described.
1. A cured organic rubber article having dispersed therein from 10 to 150 parts per 100 parts of rubber of a hydrophobic particulate inorganic oxide selected from the group consisting of amorphous precipitated silica, alumina and mixtures of such inorganic oxides, said hydrophobic inorganic oxide being characterized by
(a) a substantial absence of functional groups capable of chemically reacting with rubber,
(b) a hydroxyl content of from 4–12 OH/nm 2 ,
(c) a carbon content of from 0.3 to 3 weight percent that is substantially non-extractable,
(d) a methanol wettability of from 25 to 35 percent,
(e) an M1 Standard White Area of less than 0.2 percent, and
(f) a BET surface area of from 40 to 350 m 2 /g.
2. The cured organic rubber article of claim 1 wherein the organic rubber comprises styrene-butadiene rubber, polybutadiene or mixtures thereof.
3. The cured organic rubber article of claim 2 wherein the article is a tire.