Surface-modified metal oxide fine particles and process for producing the same

Surface-modified metal oxide fine particles obtained by treating metal oxide fine particles having a specific surface area of 5 to 500 m.sup.2 /g with a silane coupling agent and then treating the metal oxide fine particles with an organopolysiloxane having a reactive group at each terminus thereof, wherein the organopolysiloxane having a reactive group at each terminus thereof has a viscosity at 25.degree. C. of 20 to 2,000 cs and is represented by the following formula (I):

• ##STR3## wherein each substituent represented by R is, independently, selected from the group consisting of a methyl group and an ethyl group, with the proviso that part of each said substituent may be a vinyl group, a phenyl group, or an alkyl group;
• each X represents, independently, a halogen atom, a hydroxy group or an alkoxy group;
• and p represents a degree of polymerization and is an integer of 15 to 500;
• and wherein the silane coupling agent is represented by the following formula (II) or (III):
• Y.sub.4-m SiR'm (II)
• R'.sub.3 SiNHSiR'.sub.3 (III)
• wherein Y is selected from the group consisting of a hydroxy group, an alkoxy group and a halogen atom;
• each R' represents, independently, an alkyl group having 1 to 18 carbon atoms;
• and m represents an integer of 0 to 3.