Process for producing solid dispersion of finely particulate functional compound

A process for producing a solid dispersion in which a functional compound is dispersed as fine particles in a resin, comprising the following steps:

• (1) kneading the functional compound with solely deionized water and no organic solvent while gradually adding the deionized water;
• (2) adding a polymerized resin which is insoluble in water and solid at room temperature, and optionally an additive to the kneaded product, and kneading the resultant mixture while heating it under the conditions in which the resin softens at a temperature equal to or less than a boiling point of the deionized water, whereby the functional compound is dispersed into the softened resin with no dispersing agent being present;
• and
• (3) kneading further the obtained kneaded dispersion while heating under atmospheric pressure or reduced pressure to distill off moisture contained in the kneaded dispersion,
• wherein said process includes no ion-exchange step, and
• wherein said functional compound is selected from the group consisting of a fluorescent coloring matter, electrochromic coloring matter, photochromic coloring matter, dichromatic coloring matter for polarizing films, thermochromic coloring matter, and piezochromic coloring matter;
• or is selected from the group consisting of a pigment, a near infrared ray absorbing compound, ultraviolet ray absorbing compound, a magnetic compound, and a flame-retardant compound.