PVC hose is made by adding a large amount of plasticizer and stabilizer and other additives, by extrusion molding, PVC hose has excellent chemical stability, electrical insulation properties and good flexibility, colorability. This kind of pipe is commonly used instead of rubber pipe to transport liquid and corrosive media, and is also used as cable bushing and wire insulation.
The production process of PVC soft and PVC hard is slightly different, because a large number of plasticizers are added to the soft product formula, so kneading plasticization is an important part of the production of soft PVC pipes. In the soft PVC kneading process, in order to make the resin swelling and perfect by the plasticizer, the kneading material is evenly dispersed, and the feeding order is paid attention to. When adding a 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.
The extruder chooses SJ65-B, the machine head chooses the straight-through type, and the compression of the machine head is larger to 2.5:1; The aspect ratio is: L/D value is 25:1; The screw groove of the screw is equally spaced and unequal in depth.
Soft PVC melt viscosity is low, fluidity is very good, so that the compression ratio of the head is controlled at 10~20, the length of the straight part of the mouth film is about 10~20 times the wall thickness of the hose, and the size of the core film can be expanded by 10%~20% compared with the inner and outer diameter of the tube. After extruding the PVC hose, it needs to be stretched to reach the required pipe diameter size, and the cooling method adopts spray cooling water cooling, and the spray position is 20~40mm away from the machine head.
Temperature control range of each section of the extruder when extruding PVC hose:
Feeding section: 100°C-120°C; Compression section: 120°C-140°C; Homogenization measurement section: 140°C-160°C; Shunt: 140°C-160°C; Mouth film: 160°C-180°C.
Screw speed selection:
Because the melting fluidity of soft PVC is good and easy to plasticize, the screw speed is faster than that of hard PVC material, and the screw speed of the extruder with a general screw diameter of 65mm is (30±10)r/min. Because the ventilation hole is connected to the outside air, no compressed air is required during processing, and there is no adhesion and unrounded pipe diameter.
Control of traction speed
PVC hose in the production, no need to pass compressed air into the pipe, no need to cool and shape, so that the traction force is correspondingly reduced, to strictly control the traction speed to ensure the wall thickness of the pipe and the outer diameter size of the PVC hose.
