A thermoplastic polyester resin is fed into a twin extruder, wherein a resin is heated for melting, thereby removing moisture in the resin by evacuating and sucking from a vent port thereof, injecting a foaming agent into the resin to which is pushed out as a foaming sheet and, after that, forming the foaming sheet which is divided into a forming body and a trimming loss, whereby the trimming loss is crushed to obtain crushed materials which are provided so as to put the materials into the twin extruder as collection materials and recycle them.
This application is a divisional application filed under 37 CFR .sctn.1.53(b) of parent application Ser. No. 08/579,271 filed Dec. 27, 1995 now U.S. Pat. No. 5,958,164.
Priority Data
Dec 27, 1994 [JP] 6-339666 Feb 28, 1995 [JP] 7-66977 Aug 24, 1995 [JP] 7-240572
