METHOD FOR INJECTION MOULDING OF LARGE-SIZED POLYMERIC ARTICLES Russian patent published in 2002 - IPC

FIELD: injection moulding of large-sized polymeric articles, for example, baths, pools and other reservoirs of various standard sizes and configurations used for any media, corrosive ones inclusive. SUBSTANCE: method consists in feeding of fused polymer to the mould through the gates, filling of it in the preset conditions and sealing at the instant of appearance of the polymer melt in the ventilation ducts with a subsequent cooling of polymer. Filling of the mould preliminarily heated to the temperature of the polymer melt is accomplished by two or several pulsating flows in the cyclic condition, varying the pressure in the flow gate from 0.5 to 1 MPa to 1.5 to 2 MPa. Then, the pressure is released to the initial one. The time of mould filling with the melt at 0.5 to 1.0 MPa makes up 15 to 20 minutes, and at 1.5 to 2 MPa - 5 to 10 minutes. Such a condition remains up to the complete filling of the mould and its sealing. After that the melt is fed to the mould at a pressure of 3.0 to 4.0 MPa at a simultaneous reduction of the mould temperature. As soon as the temperature becomes lower than the polymer melt temperature by 15 to 20 C, the pressure is released, and then it is uniformly cooled down to the ambient temperature. The mould is heated to a temperature exceeding the polymer melt temperature by 20 to 30 C. The time of mould filling is set depending on the article size, configuration and specific consumption of materials. EFFECT: produced large-sized homogeneous polymeric articles of high-quality and resistance to corrosive media at a high rate of production. 3 cl