Patent ID: 8324286

Claim:
A method of producing heat-expandable microspheres, each comprising a shell of thermoplastic resin and a blowing agent encapsulated therein having a boiling point not higher than the softening point of the thermoplastic resin, the method comprising the steps of: dispersing an oily mixture, which contains a polymerizable component and the blowing agent, in an aqueous dispersing medium, which contains at least one water-soluble compound that is free from ascorbic acids; and polymerizing the polymerizable component contained in the oily mixture; wherein the water-soluble compound is selected from the group consisting of a water-soluble metal salt and/or its hydrate constituted with at least one metal selected from scandium, cerium, hafnium, vanadium, tantalum, molybdenum, tungsten, manganese, rhenium, ruthenium, osmium, cobalt, rhodium, nickel, silver, gold, zinc, cadmium, boron, aluminum, gallium, indium, thallium, lead, arsenic, antimony, and bismuth, a water-soluble polyphenol, a water-soluble vitamin B, and a water-soluble 1,1-substituted compound having a structure in which a hydrophilic functional group selected from the group consisting of a hydroxyl group, carboxylic acid (salt) group, and phosphonic acid (salt) group, and a hetero atom are bonded to the same carbon atom.