| 主权项 |
1. A method for producing a purified alkali silicate aqueous solution fulfilling the following condition:
an existing amount of plate-like fine particles having a length of one side of 0.2 to 4.0 μm and a thickness of 1 to 100 nm is determined to be 0 to 30% in accordance with a measurement method A, the method for producing a purified alkali silicate aqueous solution comprising the steps of: adjusting a silica concentration of an alkali silicate aqueous solution to 0.5 to 10.0% by mass; and filtering the alkali silicate aqueous solution through a filter having a removal rate of particles with a primary particle size of 1.0 μm of 50% or more, wherein: the measurement method A is a method in which 30 mL of an alkali silicate aqueous solution at 25° C. adjusted to have a silica concentration of 4% by mass is passed through a membrane type filter (filtration area: 4.90 cm2) having an absolute pore size of 0.4 μm, then the membrane type filter is observed by a scanning electron microscope at a magnification of 5,000 times, presence of one or more of plate-like fine particles in one visual field of a 15-by-20 μm rectangle is regarded as one count, presence or absence of the count in each of 100 visual fields that are not overlapped with each other is determined, and the total number of the obtained counts is regarded as an existing amount (%) of the plate-like fine particles, and the filter is at least one selected from the group consisting of a pleats type filter, a depth type filter, and a diatomaceous earth-containing type filter. |
