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Mineral charge particles of silica or alumina are grafted with a hydrolysis product from a di- or trialkoxysilane whose functional group is compatible with an organic phase into which said grafted particles are ultimately incorporated. The grafted particles are separated from the aqueous hydrolysis

Mineral charge particles of silica or alumina are grafted with a hydrolysis product from a di- or trialkoxysilane whose functional group is compatible with an organic phase into which said grafted particles are ultimately incorporated. The grafted particles are separated from the aqueous hydrolysis medium by spray-drying. The organic phase comprising the grafted mineral particles is used to provide coatings with abrasion resistant properties.

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A process for producing a mineral charge of finely divided silica or alumina having organophilic substituents comprising: (a) hydrolyzing in a hydrolysis medium a di- or trialkoxysilane of formula (RO)3-nSiRIrn2 (I) in which R represents identical or different lower alkyls and R1 and R2 are identica

A process for producing a mineral charge of finely divided silica or alumina having organophilic substituents comprising: (a) hydrolyzing in a hydrolysis medium a di- or trialkoxysilane of formula (RO)3-nSiRIrn2 (I) in which R represents identical or different lower alkyls and R1 and R2 are identical or different and selected from the group consisting of alkyl, cycloalkyl, alkylated cycloalkyl, amino alkyl, alkyl amine, alkoxy, alkoxy alkyl, epoxy alkyl, epoxy cycloalkyl, alkenyl, glycidoxy, acryloxy alkyl, methacryloxy alkyl, gamma-ureidopropyl, gamma-chloropropyl, gamma-mercaptopropyl groups, n being 0 or 1, said hydrolysis providing a corresponding di- or trihydroxy silane of formula (HO)3-nSiR1Rn2 (II) in solution in the hydrolysis medium; (b) adding thereto a proportion of mineral particles of finely divided alumina or silica whereby compound II will react with said particles thus providing graft particles; (c) homogenizing the resultant mixture so as to provide a homogeneous dispersion of said graft particles in said medium; (d) spray-drying said homogeneous dispersion, thus forming a powdered substantially dry grafted mineral charge.