To obtain a synthetic resin compsn. excellent in heat absorption properties by dispersing a fine particulate substance having specified heat absorption properties, light-wavelength conversion characteristics, and adsorption characteristics into a synthetic resin selected from among PE, PP, PVC, PS, a polyurethane. etc.

A fine particulate substance having a particle size of 5μm or lower, a specific gravity of about 0.9-1.2, and a water absorption of about 10-3% is obtd. e.g. by extracting coal with pyridine, etc., by pulverizing coal followed by density separation, or by thermally reacting coal with an aq. NaOH soln. and removing inorganics. The substance maintains the structure of an arom. high-molecular compd. of coal and functional groups of the high-molecular compd. and hence has characteristics inherent in the high-molecular compd., such as heat absorption properties, light-wavelength conversion characteristics, and capability for absorbing an odorous gas or heavy metal ions. A synthetic resin compsn. excellent in heat absorption properties is obtd. by mixing and dispersing the substance into a synthetic resin selected from among PE, PP, PVC, PS, a polyurethane, a urea resin, a phenol resin, a polyester resin, an epoxy resin, polyvinyl acetate, and a nylon resin.