Abstract: A silica sol dispersed in a nitrogen-containing solvent and a silica-containing resin composition containing a nitrogen atom-containing polymer. A silica sol including silica particles containing aluminum atoms and having an average primary particle diameter of 5 to 100 nm, the silica particles being dispersed in a nitrogen-containing solvent, wherein the aluminum atoms are bonded to the surfaces of the silica particles in an amount in terms of Al2O3 of 800 to 10,000 ppm/SiO2. The silica particles are bonded to a silane compound or a hydrolysate of the silane compound. The nitrogen-containing solvent is an amide solvent. The nitrogen-containing solvent is dimethylacetamide, dimethylformamide, N-methylpyrrolidone, or N-ethylpyrrolidone. The insulating resin composition includes the silica sol and a nitrogen-containing polymer. The nitrogen-containing polymer is polyimide, polyamide, polyamic acid, polyamideimide, polyetherimide, or polyesterimide.

Abstract: A silica sol dispersed in a nitrogen-containing solvent and a silica-containing resin composition containing a nitrogen atom-containing polymer. A silica sol including silica particles containing aluminum atoms and having an average primary particle diameter of 5 to 100 nm, the silica particles being dispersed in a nitrogen-containing solvent, wherein the aluminum atoms are bonded to the surfaces of the silica particles in an amount in terms of Al2O3 of 800 to 10,000 ppm/SiO2. The silica particles are bonded to a silane compound or a hydrolysate of the silane compound. The nitrogen-containing solvent is an amide solvent. The nitrogen-containing solvent is dimethylacetamide, dimethylformamide, N-methylpyrrolidone, or N-ethylpyrrolidone. The insulating resin composition includes the silica sol and a nitrogen-containing polymer. The nitrogen-containing polymer is polyimide, polyamide, polyamic acid, polyamideimide, polyetherimide, or polyesterimide.

Abstract: In a machine tool comprising a column (2) mounted for a horizontal sliding movement, a drive unit (4) mounted on the column for a vertical sliding movement, and a magazine (7) located above the drive unit and mounted on the column for a rotational movement and for a horizontal sliding movement, the magazine is particularly adapted to store a plurality of gang heads (8) and individual tools (9) which may be equipped selectively to the drive unit one by one. The drive unit includes a first clamping device (16) disposed within a spindle (14) thereof and further plural second clamping devices (18) which contributes to clamp each of the heads firmly to the unit so that large-scaled gang heads may be employed.Gang heads and tools may be exchanged quickly between the drive unit and magazine. Portions of workpieces unworkable by large-scaled gang heads may be worked by the individual tools.