| 摘要 |
Synthetic resins are powdered by forming foams thereof which are then comminuted to a particle size of 40-325 mesh (U.S.S.). The expansion may be effected mechanically, e.g. by beating gases into or bubbling gases through the molten resin or chemically by the use of volatile liquid or decomposable solid blowing agents (e.g. azobisisobutyronitrile). With the latter type of blowing agent extrusion processes may be used. If the product is required to be non-cellular as for fusion-coating processes, care is taken to ensure that the cell size is larger than the final particle size, for example by varying the amount of blowing agent added. During grinding, the resin may be cooled by liquid nitrogen, water or by the atmosphere. In Example 1 the resin is a PVC composition containing dioctylphthalate plasticizer, epoxidized soya oil, TiO2, CaSO4, Ba and Cd laurates, dibasic Pb phosphate and azodicarbonamide. In Example 2 the resin is nylon 11, and in Example 3 a chlorinated polyether resin. The products are said to be useful in a number of fusion coating processes such as flame spraying, electrostatic spraying, knife coating, sublimation and fluidized bed processes. |
