<；P>；PROBLEM TO BE SOLVED: To provide a method for producing a heat insulating agent having a coating comprising dense silica on the surface of a hydrotalcite particle, exhibiting excellent heat insulation, transparency, dispersibility and acid resistance. <；P>；SOLUTION: The method for producing the heat insulating agent is carried out by the followings: after adding a water-soluble silicate to slurry of the hydrotalcite particle at a temperature in the range of 60-100°；C, an acid is added thereto, forming a coating comprising hydrous silica on the surface of the hydrotalcite particle； aging the slurry at a temperature in the range of 60-100°；C； and heating the obtained cake at a temperature in the range of 130-300°；C, obtaining the hydrotalcite particle having the coating comprising silica in an amount of 1-50 wt.% on the surface thereof. <；P>；COPYRIGHT: (C)2011,JPO&INPIT
