Patent ID: 8455425

Claim:
Alkali agent-containing particles comprising: (a) particles containing an alkali agent and having an average particle size of from 150 to 1000 μm, and a layer of (b) clay mineral particles exhibiting a water impregnation capacity of 400% by mass or more as calculated according to the following method and having an average particle size of from 10 to 100 μm, wherein the layer of (b) clay mineral particles is formed on a surface of the respective particles (a); Method for calculation of water impregnation capacity: a dispersion of the clay mineral particles (b) obtained after measuring a swelling power of the particles (b) according to a volumetric method of a Standard Testing Method of Japan Bentonite Manufactures Association “Swelling Test Method for Bentonite (Powder)” prescribed JBAS104-77 is subjected to suction filtration under 0.5 MPa for 2 h filter paper: “Type No. 4A” having a diameter of 90 mm available from Advantec Toyo Kaisha, Ltd. using a Buchner funnel to measure a mass (A) of a residue of the clay mineral particles (b) on the filter paper; the clay mineral particles (b) are dried according to a drying method of a sample prescribed in HS K0068 “Method for Measuring Water Content of Chemical Products; 7: Loss-on-Drying Method” to measure a mass (B) of the dried clay mineral particles (b); and a water impregnation capacity of the clay mineral particles (b) is calculated from the thus measured mass (A) and mass (B) according to the following formula: water impregnation capacity (%)=[( A−B )/ B]× 100; further comprising a layer of (c) metal oxide particles exhibiting a water impregnation capacity of 150% by mass or less and having an average particle size of from 0.1 to 20 μm which layer is formed on an outer surface of the layer of the clay mineral particles (b).