Nissan Chemical Industries Limited

Mikio Ando

Yoshitane Watanabe

Isao Yogo

Takanobu Kikawa

Kenji Tanimoto

Hiromi Suzuki

Eiji Okumura

Makoto Kawashima

Tsutomu Kagamimiya

A stable aqueous sol of amorphous alumina containing Al.sub.2 O.sub.3 up to 15% by weight and 0.1 to 0.5 gram equivalent of an anion of acid to 1 mol of aluminum in the sol, in which the colloidal particles of amorphous alumina have a controlled thickness in a range of 20 to 100 millimicrons and a uniform length in a range of 200 to 500 millimicrons is produced by a process comprising feeding an aqueous solution of an acid into an aqueous slurry containing 1 to 7% by weight of metallic aluminum, 10 to 200 ppm by weight as SiO.sub.2 of a water-soluble silicate and 0 to 20 ppm by weight of a water-soluble sulfate as SO.sub.4 to the water in the slurry while maintaining the slurry at a temperature of 80.degree. C. to boiling point under normal pressure, said acid being in an amount of 0.1 to 0.5 gram equivalent to 1 mol of the metallic aluminum in said slurry, at a rate of 0.001 to 0.03 gram equivalent of the acid to 1,000 g of the water in the slurry per minute, and continuing heating the slurry after completion of the feeding of the acid at a temperature of 80.degree. C. to boiling point of the slurry until a sol of amorphous alumina having a uniform length of 200 to 500 millimicrons is formed.

Stable aqueous alumina sol and method for preparing the same

A stable aqueous sol of amorphous alumina containing Al.sub.2 O.sub.3 up to 15% by weight and 0.1 to 0.5 gram equivalent of an anion of acid to 1 mol of aluminum in the sol, in which the colloidal particles of amorphous alumina have a controlled thickness in a range of 20 to 100 millimicrons and a uniform length in a range of 200 to 500 millimicrons is produced by a process comprising feeding an aqueous solution of an acid into an aqueous slurry containing 1 to 7% by weight of metallic aluminum, 10 to 200 ppm by weight as Si0.sub.2 of a water-soluble silicate and 0 to 20 ppm by weight of a water-soluble sulfate as S0.sub.4 to the water in the slurry while maintaining the slurry at a temperature of 80.degree. C. to boiling point under normal pressure, said acid being in an amount of 0.1 to 0.5 gram equivalent to 1 mol of the metallic aluminum in said slurry, at a rate of 0.001 to 0.03 gram equivalent of the acid to 1,000 g of the water in the slurry per minute, and continuing heating the slurry after completion of the feeding of the acid at a temperature of 80.degree. C. to boiling point of the slurry until a sol of amorphous alumina having a uniform length of 200 to 500 millimicrons is formed.

A method for preparing a stable silica sol having an SiO.sub.2 concentration of 40% or less, the colloidal particles of said silica having a particle size of 40 to 500 nm, as measured by dynamic light-scattering and having an elongated shape having a thickness of 5 to 40 nm and an elongation of 5 to 30 times the thickness in only one plane, the method comprising the steps (a), (b) and (c): (a) mixing an aqueous solution of Ca or Mg salt with an aqueous solution of active silicic acid having an SiO.sub.2 concentration of 1 to 6% and a pH value of 2 to 5, or with an aqueous acidic silica sol having a particle size of 3 to 30 nm, an SiO.sub.2 concentration of 0.5 to 25% and a pH value of 1 to 5 in a weight ratio of 1500 to 10000 ppm of (CaO or MgO)/SiO.sub.2 ; (b) mixing an alkali metal hydroxide with the solution obtained by step (a) in a molar ratio of 20 to 300 as SiO.sub.2 /M.sub.2 O, wherein M represents an alkali metal atom; and (c) heating the mixture obtained by step (b) at 60.degree. to 300.degree. C. for 0.5 to 40 hours.

Elongated-shaped silica sol and method for preparing the same

A high-purity stable aqueous silica sol is prepared which has an SiO.sub.2 concentration of from 30 to 50% by weight and which is substantially free from any other polyvalent metal oxides than silica and in which the colloidal silica has a mean particle size falling within the range of from 10 to 30 millimicrons. The silica sol obtained by the method of the present invention has an extremely low content of oxides of polyvalent metals such as iron or aluminum and may therefore be employed for uses which require the absence of such metals in the silica sol, for example, as an abrasive for semiconductors.

Method of preparing high-purity aqueous silica sol

A chemical grout for ground injection which is prepared by incorporating from 0.1 to 4.5 parts by weight of sulfamic acid and from 0.2 to 10.0 parts by weight of a water soluble magnesium salt into 100 parts by weight of an aqueous sol having a pH of 8 to 10.5 and containing from 5 to 25% by weight of colloidal silica (as SiO.sub.2) having a particle size of 3 to 7 m.mu., and from 0.05 to 1.5% by weight of Na.sub.2 O. This injecting grout has a gelation time not longer than 300 minutes. Soft ground can be consolidated by using the grout.

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Funabashi, Japan

Mikio Ando