Abstract: The present invention relates to a process for continuously recycling water soluble resin whereby a resin solution including about 6-12 percent by weight of resin is sprayed onto a core made of the resin. The resin used for the solution and core is selected from polyacrylic acid, copolymers of acrylic acid and acrylamide, copolymers of acrylic acid salt and ethyl acrylate, copolymers of acrylamide and acrylic acid, polymethacrylic acid, and copolymers of vinyl alcohol and vinyl acetate. The spraying of the resin solution dissolves the core to form a polymer suspension from which resin is recovered for reuse.

Abstract: A method for manufacturing a plastic hollow product with complicated geometry using water soluble resin. The method includes the steps of making a half shell of the core out of the water soluble resin, joining the half shells together into a piece by solvent welding, ultrasonic welding, vibration welding, or the like, overmolding the core with water resistant resin, and dissolving the core away from the overmolded product by spraying hot water thereto. The injection conditions such as injection time, injection speed, and injection pressure are varied in the respective zone which is divided into several divisions by same distance in the injection cylinder. Therefore, injection procedure is performed in a stepwise manner to make a hollow product.