Soft PVC and hard PVC production process is slightly different, because the soft products formula in addition to the most plasticizer, so kneading plasticizing is a soft PVC tube production of an important link. In the soft PVC kneading process, in order to make the resin to be plasticizer swelling perfect, so that the kneading material dispersed evenly, must pay attention 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 first mixed, and then add a person plasticizer, because the filler particle structure is generally more lax than the resin, when both exist, the plasticizer first infiltration filler particles, but not the full swelling of the resin. Kneading general use of "z" type kneading machine, jacket heating, vapor pressure of about 0.24~0.39mpa. Kneading 50~60min. After kneading to often flip, to prevent the resin local overheating and decomposition. The kneading material is extruded after granulation and then sent out to extrude the pipe. The extrusion temperature can be slightly lower than the extrusion PVC pipe temperature.