| 摘要 |
The present invention relates to a method in association with production of plastic pieces, particularly plastic pieces containing interior shapes, such as cavity spaces, counterdrafts and equivalent, essentially without any connecting joints. In the method, pieces to be made from a plastic material are produced upon a core, whereby the core is made from granular forming material and from a binding agent binding the forming material grains together, said core being removed after completing the piece. For the binding agent, water-soluble inorganic salt is used, said salt, being in the form of a binding agent solution dissolved in water, is mixed with a granular forming material and the chemical properties whereof being maintained unchanged in the forming incident and during the production process of the plastic piece. The combination of the binding agent and the forming material is so selected that the main minerals of the binding agent and the forming material are chemically unreacting with each other at the forming temperature and during the production process of the plastic pieces. In the forming incident the binding agent is crystallized by heating the core to be produced from the aqueous solution thereof for producing from the binding agent a fixed bridge binding the forming material grains together between the forming material grains. After the production process of the plastic pieces, the binding agent can be dissolved in water or in a non-saturated aqueous solution of the binding agent for breaking up the core and for removing it away from inside the finished piece. |
