Abstract: A method for producing a silica sol containing a small amount of metal impurities and in which colloidal silica having an elongated particle shape dispersed in a solvent, includes: preparing a raw material liquid by adding a compound as an anion source selected from inorganic acids, organic acids, and their ammonium salts, and ammonia to a colloidal aqueous solution of activated silica having an SiO2 concentration of 1 to 6% by mass and a pH of 2 to 5 so that the mass ratio of the compound to SiO2 is 3.0 to 7.0%; and heating the raw material liquid at 80 to 200° C. for 0.5 to 20 hours. The elongated colloidal silica particles exhibit a DL/DB ratio of 2.5 or more. DL is an average particle diameter as measured by the dynamic light scattering method. DB is a primary particle diameter as measured by the nitrogen gas adsorption method.

Abstract: A method for producing a silica sol containing a small amount of metal impurities and wherein colloidal silica having an elongated particle shape is dispersed in a solvent, by addition of a compound as an anion source and ammonia as an alkali source and heating of the resultant mixture at a predetermined temperature, includes the following steps: (a) preparing a raw material liquid by adding at least one compound as an anion source selected from the group of inorganic acids, organic acids, and ammonium salts of these acids, and ammonia to a silica sol as a raw material having SiO2 of 1% by mass to 30% by mass and a pH of 2 to 5 so the mass ratio of the compound to SiO2 is 0.5% to 1.9%; and (b) heating the raw material liquid prepared in step (a) at 80° C. to 200° C. for 0.5 hours to 20 hours.

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: A silica-blended resin varnish contains a silica sol with a high dispersibility that is dispersed in a ketone organic solvent, in a nitrogen atom-containing polymer. The particles have an average size of 5 to 100 nm and have a carbon-carbon unsaturated bond-containing organic group and an alkoxy group bonded to surfaces thereof. The carbon-carbon unsaturated bond-containing organic group is bonded at 0.5 to 2.0 groups per unit area (nm2) of the particle surfaces. The alkoxy group is bonded at 0.1 to 2.0 groups per unit area (nm2) of the particle surfaces. The molar ratio of {(the carbon-carbon unsaturated bond-containing organic group)/(the alkoxy group)} is 0.5 to 5.0. The carbon-carbon unsaturated bond-containing organic group may be a phenyl group-containing organic group or a (meth)acryloyl group-containing organic group.

Abstract: A silica-blended resin varnish contains a silica sol with a high dispersibility that is dispersed in a ketone organic solvent, in a nitrogen atom-containing polymer. The particles have an average size of 5 to 100 nm and have a carbon-carbon unsaturated bond-containing organic group and an alkoxy group bonded to surfaces thereof. The carbon-carbon unsaturated bond-containing organic group is bonded at 0.5 to 2.0 groups per unit area (nm2) of the particle surfaces. The alkoxy group is bonded at 0.1 to 2.0 groups per unit area (nm2) of the particle surfaces. The molar ratio of {(the carbon-carbon unsaturated bond-containing organic group)/(the alkoxy group)} is 0.5 to 5.0. The carbon-carbon unsaturated bond-containing organic group may be a phenyl group-containing organic group or a (meth)acryloyl group-containing organic group.

Abstract: A method for producing a silica sol containing a small amount of metal impurities and in which colloidal silica having an elongated particle shape dispersed in a solvent, includes: preparing a raw material liquid by adding a compound as an anion source selected from inorganic acids, organic acids, and their ammonium salts, and ammonia to a colloidal aqueous solution of activated silica having an SiO2 concentration of 1 to 6% by mass and a pH of 2 to 5 so that the mass ratio of the compound to SiO2 is 3.0 to 7.0%; and heating the raw material liquid at 80 to 200° C. for 0.5 to 20 hours. The elongated colloidal silica particles exhibit a DL/DB ratio of 2.5 or more. DL is an average particle diameter as measured by the dynamic light scattering method. DB is a primary particle diameter as measured by the nitrogen gas adsorption method.

Abstract: A method for producing a silica sol containing a small amount of metal impurities and wherein colloidal silica having an elongated particle shape is dispersed in a solvent, by addition of a compound as an anion source and ammonia as an alkali source and heating of the resultant mixture at a predetermined temperature, includes the following steps: (a) preparing a raw material liquid by adding at least one compound as an anion source selected from the group of inorganic acids, organic acids, and ammonium salts of these acids, and ammonia to a silica sol as a raw material having SiO2 of 1% by mass to 30% by mass and a pH of 2 to 5 so the mass ratio of the compound to SiO2 is 0.5% to 1.9%; and (b) heating the raw material liquid prepared in step (a) at 80° C. to 200° C. for 0.5 hours to 20 hours.

Abstract: A free cutting graphitic steel comprising:Si: from more than 1.5 to 2.3%Mn: 0.1 to 0.7%S: not more than 0.015%One or both Al and Ti: 0.015 to 0.1% in totalRare earth: 0.01 to 0.2% andSpheroidized graphite: 0.20 to 0.90% with the balance being iron and unavoidable impurities,Said spheroidized graphite being distributed at a ratio of more than particles 50/mm.sup.2.