Provided is a hollow particle, including silica, having a D.sub.SL of primary particles that satisfies the following expression (1), and having a breaking strength of 10 MPa or more: 1≤D.sub.SL≤1.5 . . . (1) where D.sub.SL=D.sub.75L/D.sub.25L, and D.sub.25L and D.sub.75L represent a 25th value and a 75th value, respectively, when long diameters of 100 randomly selected primary particles are measured in observation with a scanning electron microscope and sorted in order of increasing size.

Provided is a hollow particle, including silica, having a D.sub.SL of primary particles that satisfies the following expression (1), and having a breaking strength of 10 MPa or more: 1≤D.sub.SL≤1.5 . . . (1) where D.sub.SL=D.sub.75L/D.sub.25L, and D.sub.25L and D.sub.75L represent a 25th value and a 75th value, respectively, when long diameters of 100 randomly selected primary particles are measured in observation with a scanning electron microscope and sorted in order of increasing size.

Modified silanized colloidal silica particles are reaction products of silanized colloidal silica particles having epoxy moieties with a nitrogen of an amino group of an amino acid to form stable modified silanized colloidal silica particles. The modified silanized colloidal silica particles can be used as an abrasive in chemical mechanical polishing of various substrates.

Modified silanized colloidal silica particles are reaction products of silanized colloidal silica particles having epoxy moieties with a nitrogen of an amino group of an amino acid to form stable modified silanized colloidal silica particles. The modified silanized colloidal silica particles can be used as an abrasive in chemical mechanical polishing of various substrates.

Embodiments of the invention include silica fiber compositions useful for treatment of animal wounds and tissue, as well as for other applications in industry. The fiber compositions may be formed via electrospinning of a sol gel produced with a silicon alkoxide reagent, such as tetraethyl ortho silicate, alcohol solvent, and an acid catalyst.

Embodiments of the invention include silica fiber compositions useful for treatment of animal wounds and tissue, as well as for other applications in industry. The fiber compositions may be formed via electrospinning of a sol gel produced with a silicon alkoxide reagent, such as tetraethyl ortho silicate, alcohol solvent, and an acid catalyst.

The present invention relates to a silica sol having a pH above about 10, molar ratio of SiO2:M2O, in which M is alkali metal, of from about 6:1 to about 16:1, concentration of soluble silica above about 3000 mg SiO2/l, and S-value of from about 18 to about 40%. The invention further relates to a process for producing a silica sol which comprises acidifying an aqueous alkali metal silicate solution to a pH of from 1 to 4 to form an acid sol, alkalizing the acid sol by addition of aqueous alkali metal silicate solution to obtain an intermediate sol and interrupt the addition of aqueous alkali metal silicate solution when the intermediate sol has reached a pH of from about 5 to about 8, stirring the intermediate sol for a time period of from about 10 to about 6000 seconds without addition of aqueous alkali metal silicate solution, alkalizing the intermediate sol by addition of aqueous alkali metal silicate solution to obtain a silica sol having a pH above about 10 and molar ratio of SiO2:M2O, in which M is alkali metal, of from about 6:1 to about 16:1, and optionally adding an aluminum compound to the acid sol, intermediate sol or silica sol. The invention further relates to a silica sol obtainable by the process of the invention. The invention further relates to the use of the silica sol as a flocculating agent, in water purification and in producing paper and board. The invention further relates to a process for producing paper and board which comprises: (i) providing an aqueous suspension comprising cellulosic fibers; (ii) adding to the suspension one or more drainage and retention aids comprising the silica sol; and (iii) dewatering the obtained suspension to provide a sheet or web of paper or board.

The present invention relates to a silica sol having a pH above about 10, molar ratio of SiO2:M2O, in which M is alkali metal, of from about 6:1 to about 16:1, concentration of soluble silica above about 3000 mg SiO2/l, and S-value of from about 18 to about 40%. The invention further relates to a process for producing a silica sol which comprises acidifying an aqueous alkali metal silicate solution to a pH of from 1 to 4 to form an acid sol, alkalizing the acid sol by addition of aqueous alkali metal silicate solution to obtain an intermediate sol and interrupt the addition of aqueous alkali metal silicate solution when the intermediate sol has reached a pH of from about 5 to about 8, stirring the intermediate sol for a time period of from about 10 to about 6000 seconds without addition of aqueous alkali metal silicate solution, alkalizing the intermediate sol by addition of aqueous alkali metal silicate solution to obtain a silica sol having a pH above about 10 and molar ratio of SiO2:M2O, in which M is alkali metal, of from about 6:1 to about 16:1, and optionally adding an aluminum compound to the acid sol, intermediate sol or silica sol. The invention further relates to a silica sol obtainable by the process of the invention. The invention further relates to the use of the silica sol as a flocculating agent, in water purification and in producing paper and board. The invention further relates to a process for producing paper and board which comprises: (i) providing an aqueous suspension comprising cellulosic fibers; (ii) adding to the suspension one or more drainage and retention aids comprising the silica sol; and (iii) dewatering the obtained suspension to provide a sheet or web of paper or board.

Embodiments of the invention include silica fiber compositions useful for treatment of animal wounds and tissue, as well as for other applications in industry. The fiber compositions may be formed via electrospinning of a sol gel produced with a silicon alkoxide reagent, such as tetraethyl ortho silicate, alcohol solvent, and an acid catalyst.

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 SiO.sub.2 of 1% by mass to 30% by mass and a pH of 2 to 5 so the mass ratio of the compound to SiO.sub.2 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.