The present invention provides a method for producing an aerogel, comprising a sol generating step of generating, by hydrolyzing a silane oligomer, a sol containing a hydrolysis product of the silane oligomer; a wet gel generating step of obtaining a wet gel by gelation of the sol; and a drying step of drying the wet gel to obtain an aerogel, wherein a proportion of silicon atoms each bonded to three oxygen atoms in a total number of silicon atoms contained in the silane oligomer is 50% or more.

The present invention provides a method for producing an aerogel, comprising a sol generating step of generating, by hydrolyzing a silane oligomer, a sol containing a hydrolysis product of the silane oligomer; a wet gel generating step of obtaining a wet gel by gelation of the sol; and a drying step of drying the wet gel to obtain an aerogel, wherein a proportion of silicon atoms each bonded to three oxygen atoms in a total number of silicon atoms contained in the silane oligomer is 50% or more.

A method for producing a liquid dispersion containing irregular-shaped silica particles in which two or more primary particles are linked together, by simultaneously adding a liquid A containing silane alkoxide and a liquid B containing an alkali catalyst and water to a liquid I consisting substantially of an organic solvent to cause hydrolysis and polycondensation of the silane alkoxide, wherein the period from the start of the addition until the silica concentration of the reaction system at the end of the addition reaches 70% is 20% or less of the full reaction time period.

A method for producing a liquid dispersion containing irregular-shaped silica particles in which two or more primary particles are linked together, by simultaneously adding a liquid A containing silane alkoxide and a liquid B containing an alkali catalyst and water to a liquid I consisting substantially of an organic solvent to cause hydrolysis and polycondensation of the silane alkoxide, wherein the period from the start of the addition until the silica concentration of the reaction system at the end of the addition reaches 70% is 20% or less of the full reaction time period.

A silica-containing resin composition, characterized by containing a resin and silica particles in an amount of 5 to 300 parts by mass, with respect to 100 parts by mass of the resin, wherein the silica particles satisfy the following requirements (a) to (c): (a) the silica particles have a specific surface area, as determined through a nitrogen absorption method, of 20 to 500 m.sup.2/g; (b) the silica particles have a percent moisture absorption of 5.0 mass % or less at a relative humidity of 50%; and (c) the silica particles contain substantially no metallic impurity or halogen.

A silica-containing resin composition, characterized by containing a resin and silica particles in an amount of 5 to 300 parts by mass, with respect to 100 parts by mass of the resin, wherein the silica particles satisfy the following requirements (a) to (c): (a) the silica particles have a specific surface area, as determined through a nitrogen absorption method, of 20 to 500 m.sup.2/g; (b) the silica particles have a percent moisture absorption of 5.0 mass % or less at a relative humidity of 50%; and (c) the silica particles contain substantially no metallic impurity or halogen.

There is provided a method of producing silica capsules, the method comprising: adding a silica precursor to emulsified droplets in the presence of salt and alcohol to enhance silica growth around the emulsified droplets by an ion association effect, thereby forming silica capsules. Also provided are silica capsules producible by such a method.

An optical member includes a base material and a film on the base material, the film includes hollow particles that have prickle-like protrusions on their surface, the heights of the protrusions are 3 nm or more and 20 nm or less, the proportion of the prickle-like protrusions is 3% or more and 30% or less of the particle surface, and the film includes 50 percent by volume or more and 68 percent by volume or less of hollow particles. Consequently, an antireflection film having a low refractive index and a low level of scattering in combination is provided.

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.