The production process of soft PVC and hard PVC is slightly different, because the most plasticizer is added to the soft product formula, so kneading plasticization is an important part of the production of soft PVC pipe. In the soft PVC kneading process, in order to make the resin swelling and perfect by the plasticizer and make the kneading material evenly dispersed, attention must be paid to the feeding sequence. When adding a certain amount of filler, such as CaCO3, the resin and plasticizer should be mixed first. If the resin and filler are mixed first, and then plasticizer is added; Because the particle structure of the filler is generally looser than the resin, when the two exist at the same time, the plasticizer first penetrates into the filler particles, and the resin cannot be fully swollen. Kneading generally uses "Z" type kneading machine, jacket heating, vapor pressure is about 0.24~0.39MPa. Knead 50~60min. After kneading, it should be turned frequently to prevent the resin from overheating locally and decomposing itself. After granulation, the kneading material is sent to the extruder to extrude the pipe. The extrusion temperature can be slightly lower than the temperature of the extruded PVC pipe.
