There are two types of pvc film process. One is direct extrusion blow molding using powder. The extruder used in this method has a large ratio of length to diameter to achieve good plasticization. The other method is to use an ordinary extrusion film blowing unit. . Blown film with pellets, although adding granulation process. However, the structure of the extruder is relatively simple, and most manufacturers of pvc transparent film adopt this method.
PVC blown film production process
(1) Ingredients In order to remove impurities in the material, the PV C 'resin needs to pass through a 4C mesh screen. The plasticizer passes through a 100 mesh copper wire mesh, and other additives are diluted with plasticizer and ground with a three-roll grinder. Degree below 80μm. Then, it is metered into the kneading machine according to the formula, and the kneading temperature is 100 ~ 120 ℃, and the material can be discharged after the material is loose and elastic. The kneaded materials are put into an extruding granulator for granulation. The granulation temperature should not be too high, generally controlled at 150 ~ 170 ℃. The granules of the extruder should be neat, with good plasticization and no blocking.
(2) PVC film extrusion blown film In order to ensure the quality of blown film, it is best to use thermal particles. On the one hand, the film is plasticized well, on the other hand, it can also reduce the energy consumption of blown film. In order to reduce the number of times the head is disassembled due to 'paste car', the head temperature should be lower than the body temperature. The specific process conditions are as follows: the rear temperature of the extruder is 150 ~ 160 ℃, the middle temperature is 170 ~ 180 ℃, the front temperature is 170 ~ 180 ℃, and the head temperature is about 170 ℃. The inflation ratio is usually 1.5 to 2.5. The blown film should be cooled well, otherwise the film will be sticky.