| 摘要 |
PROBLEM TO BE SOLVED: To make small-diameter and flat holes, heighten the hole density of the surface and obtain good thickness accuracy by making the apparent specific gravity of hollow polyester sheet under a specified value, and forming a cavity taking noncompatible thermoplastic resin not compatible with polyester as a nucleus. SOLUTION: The apparent specific gravity of a hollow polyester sheet is set under about 1.25 and a cavity is formed taking noncompatible thermoplastic resin not compatible with polyester as a nucleus. When the apparent specific gravity is not less than about 1.25, the cavity rate is under about 10%, so it is not practical. The noncompatible thermoplastic resin is used as thermoplastic resin not compatible with polyester so as to obtain a hollow polyester sheet layer which has small-diameter and flat holes and has high hole density of the surface. |
