| abstract |
The present invention provides heat-expanded microspheres having high packing efficiency, and a production method thereof. The heat-expanded microspheres are produced by expanding heat-expandable microspheres, which comprise shell of thermoplastic resin and a blowing agent encapsulated therein having a boiling point not higher than the softening point of the thermoplastic resin and have an average particle size from 1 to 100 micrometer, at a temperature not lower than their expansion initiating temperature, and the heat-expanded microspheres result in a void fraction not higher than 0.70. |