Abstract: A process for preparing composite particles having a coating of an organic compound on their surfaces, comprising the steps of (a) dissolving an organic compound in supercritical carbon dioxide to give an organic compound solution; (b) contacting particles which do not dissolve in the supercritical carbon dioxide with the organic compound solution in a vessel; and (c) reducing the internal pressure of the vessel at an internal temperature of not less than the critical temperature of carbon dioxide. The composite particles have controlled properties such as water repellency, oil repellency, optical properties, ultraviolet shielding ability, texture, safety, activity, color tone, stability of dispersion and weatherproof, which can be suitably used for paints, ink-jet ink and cosmetics, and the composite particles obtained.

Abstract: A process for preparing composite particles comprising particles and an organic compound in a vessel, comprising the steps of (a) contacting particles with an organic compound in the presence of supercritical carbon dioxide or liquefied carbon dioxide in the vessel; and (b) reducing the internal pressure of the vessel. The composite particles have controlled properties such as water repellency, oil repellency, optical properties, ultraviolet shielding ability, texture, safety, activity, color tone, stability of dispersion and weatherproof, which can be suitably used for paints, ink-jet ink and cosmetics, and the composite particles obtained.

Abstract: To provide a method for purification of the ionic polymer compound comprising efficiently removing low-molecular impurities, for example, ionic remaining monomers, which are charged identically to the ionic polymer compound from the ionic polymer compound in a shorter period of time. A method for purification of an ionic polymer compound, characterized by removing low-molecular impurities, such as ionic remaining monomers, by the use of an ultrafiltration membrane and/or a reverse osmosis membrane from an aqueous solution containing the ionic polymer compound and low-molecular impurities which are charged identically to the ionic polymer compound, under conditions that a concentration of the ionic polymer compound is from 7 to 20% by weight, and that an amount of charges of the ionic polymer compound in the aqueous solution is 0.30 gram-equivalent/liter or more.