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AssigneeOji Paper Co., Ltd.
InventorsTetsuro Noguchi, Kozo Tajiri
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The present invention provides a dispersion of silica particle agglomerates having a sharp particle size distribution and capable of forming a porous coating film having a high transparency by drying. The present invention also provides a process for producing a colloidal dispersion of silica particle agglomerates having a specific surface area, as determined by nitrogen adsorption method, of 100 m2/g to 400 m2/g, an average secondary particle diameter of 20 nm to 300 nm and a pore volume of 0.5 ml/g to 2.0 ml/g, which comprises using a colloidal dispersion of silica particle agglomerates having a specific surface area, as determined by nitrogen adsorption method, of 300 m2/g to 1,000 m2/g and a pore volume of 0.4 ml/g to 2.0 ml/g as a seed dispersion, adding a feed solution comprising at least one of an aqueous active silicic acid solution and alkoxysilanes to the seed dispersion in small portions in the presence of an alkali to grow silica particle agglomerates.
A colloidal dispersion of silica particle agglomerates having a specific surface area, as determined by nitrogen adsorption method, of 100 m2/g to 400 m2/g and a pore volume of 0.5 ml/g to 2.0 ml/g, in which the main peak in the particle size distribution, calculated in terms of weight, is in the range of 10 nm to 70 nm as determined by dynamic light scattering method with a laser granulometer, the standard deviation thereof is not larger than 10 nm, and the cumulative weight of the main peak is at least 80% based on the cumulative total weight of all the peaks.
A colloidal dispersion of silica particle agglomerates having a specific surface area, as determined by nitrogen adsorption method, of 100 m2/g to 400 m2/g and a pore volume of 0.5 ml/g to 2.0 ml/g, which dispersion has an absorbance of not higher than 0.3 when the solid concentration is 1.0 wt. % and an absorbance of not higher than 0.3 when the solid concentration is 10.0 wt. % at a wave length of 560 nm.
A process for producing a colloidal dispersion of porous silica particle agglomerates, which comprises dropping an aqueous solution of active silicic acid in hot water to form a dispersion of agglomerates of silica particles, adding an alkali to the dispersion before the formation of precipitates in the dispersion or before the gelation of the dispersion to stabilize the agglomerates of the silica particles and adding an aqueous active silicic acid solution in small portions while the stable state is kept to grow the silica particle agglomerates.
A process for producing a colloidal dispersion of porous silica particle agglomerates, which comprises heating an aqueous solution of active silicic acid to form a dispersion of agglomerates of silica particles, adding an alkali to the dispersion before the formation of precipitates in the dispersion or before the gelation of the dispersion to stabilize the agglomerates of the silica particles and adding an aqueous active silicic acid solution in small portions while the stable state is kept to grow the silica particle agglomerates.
Dependencies are inferred from the claim text.