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 SiO.sub.2 concentration of 1 to 6% by mass and a pH of 2 to 5 so that the mass ratio of the compound to SiO.sub.2 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 D.sub.L/D.sub.B ratio of 2.5 or more. D.sub.L is an average particle diameter as measured by the dynamic light scattering method. D.sub.B is a primary particle diameter as measured by the nitrogen gas adsorption method.

A silica-based particle dispersion including a silica-based particle group and a high polishing rate and high surface precision is achieved to a silica-based substrate or a NiP-plated substrate to be polished or the like. A silica-based particle dispersion containing a group including irregularly-shaped and non-irregularly-shaped silica-based particles, wherein the irregularly-shaped silica-based particles each have a plurality of small holes thereinside and a covering silica layer which covers the core, and the silica-based particle group satisfies [1]-[3]. [1] Having an average particle size (D.sub.1) of 100-600 nm, and a particle size (D.sub.2) of 30-300 nm in terms of specific surface area. [2] An irregular-shape degree D (D=D.sub.1/D.sub.3) represented by the average particle size (D.sub.1) and a projected area-equivalent particle size (D.sub.3) being in the range of 1.1-5.0. [3] When waveform separation is performed on a volume-reference particle size distribution, a multi-peak distribution in which three or more peaks are detected.

An insulating composition containing silica particles, a resin, and a curing agent, wherein: when an aqueous solution of the silica particles having an SiO.sub.2 concentration of 3.8% by mass is heated at 121? C. for 20 hours, the amount of Na ions eluted from the silica particles is 40 ppm/SiO.sub.2 or less, especially, wherein the amount of Na ions eluted from the silica particles after the heating may be 5-38 ppm/SiO.sub.2, and, the silica particles may contain a polyvalent metal oxide so the ratio by mole of a polyvalent metal M to Si is 0.001-0.02; the mass ratio of Na.sub.2O/SiO.sub.2 in the silica particles may be 700-1,300 ppm; and the silica particles may have, on the surfaces thereof, a layer having a thickness of 0.1-1.5 nm and an Na.sub.2O/SiO.sub.2 mass ratio of 10-400 ppm, and may have an average particle diameter of 5-40 nm.

The present invention relates to a hydrophilic silica aerogel blanket for ultra-high temperature insulation, a production method thereof, and a construction method thereof. More specifically, the present invention provides a production method a hydrophilic silica aerogel blanket, the method capable of strengthening the structure of a silica gel by adding a basic catalyst in an aging step, reducing processing time and cost by omitting a surface modification step, thereby reducing manufacturing cost, and suppressing the generation of a bad odor during construction by fundamentally blocking a volatile organic compound (VOC), a hydrophilic silica aerogel blanket produced thereby, and a construction method of a hydrophilic silica aerogel blanket, the method capable of suppressing the generation of a bad odor when constructing the hydrophilic aerogel blanket on an ultra-high temperature piping equipment, and at the same time, preventing the loss of heat insulation performance due to moisture in the air.

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.

A method for producing an active silicic acid solution in which the existing amount of foreign matters as plate-like fine particles is reduced and a method for producing a silica sol in which such foreign matters are reduced. The method fulfills the following condition: the existing amount of plate-like fine particles having a length of one side of 0.2 to 4.0 m and a thickness of 1 to 100 nm is measured to be 0% to 30% in accordance with measuring method A, the method including the steps of: preparing an active silicic acid solution by subjecting an alkali silicate aqueous solution having a silica concentration of 0.5% by mass to 10.0% by mass to cation-exchange to remove alkaline components; and filtering the active silicic acid solution through a filter whose removal rate of particles having a primary particle size of 1.0 m is 50% or more.

A preparation method for a silica aerogel, comprising the following steps: A) raw material containing a solid silicon source and an alkaline solution is used to produce an aerogel precursor after mixing; and B) the aerogel precursor is dried to obtain a silica aerogel. An improved silica aerogel preparation method, comprising the following steps: A) a cation exchange resin and a silicate solution are used as raw materials and mixed; B) the mixed material is allowed to stand to obtain an aerogel precursor; and C) the aerogel precursor is dried to obtain a silica aerogel.

An exemplary embodiment of the present disclosure provides a method for manufacturing an aerogel. The method may include mixing a silicate salt with a solution to obtain a sol-gel. The method may include conditioning the sol-gel with one or more abradants to obtain an aerogel product.

A method of preparing a particulate material comprising the steps of adding silicic acid solution, optionally doped with aluminum, optionally added to a slurry of pre-existing nanoparticles at a neutral to slightly acidic pH of no more than seven, and at a temperature of about 20 to 30 C. This yields a polysilicate particulate dispersion. Then, the pH of the dispersion is raised to greater than seven, to stabilize/reinforce particles of the particulate dispersion. Optionally, the particles may be dried, and have increased porosity and surface area.