| abstract |
Non-flying plastic microballoons are produced by bringing unexpanded, expandable plastic microballoons, which have been heated to a temperature lower than an expansion starting temperature thereof, and a mixture of a wetting agent and gas, the mixture having been heated to a temperature at least equal to the expansion starting temperature of the expandable plastic microballoons, into contact with each other to cause expansion of the expandable plastic balloons, and then cooling the resulting expanded plastic balloons. |