What should be paid attention to in Extrusion molding of polypropylene blown film?
Global Plastics News:
what should be paid attention to in Extrusion molding of polypropylene blown film?
(1) The corona treatment process in the extrusion molding production process sequence of polypropylene blown film can be determined according to the purpose of the film.
(2) For the extrusion molding of polypropylene blown film, a filter screen and a perforated plate are generally added before the barrel of the extruder. The filter screen is 80 mesh/100 mesh/100 mesh/80 mesh. When extruding the microfilm, the mesh number of the intermediate filter screen is 120 mesh.
(3) The die gap should be controlled at 0 when polypropylene film is formed by down blowing. 8 ~ 1. Within the range of 2mm, pay attention to the Uniform circular clearance of the mouth die lip.
(4) The air pressure control of the blown film blank should be stable, and the blowing ratio of the blown film bubble of the film blank should not exceed 2:1; Drafting ratio ( The ratio of the speed of pulling the film Bubble and the extrusion speed of the film blank from the mold mouth)Control in (2 ~ 3)Between: 1.
(5) The flow control of cooling water in the membrane bubble cooling setting water ring should be balanced, and the water temperature control should be stable. Generally, the water temperature should be controlled at 15 ~ Within the range of 20 °c. High water temperature will affect the transparency of the film; The film with low water temperature is sticky.
(6) The selection of the coiling method of the finished film should pay attention to the influence of the dimensional shrinkage change of the product within 24h on the appearance quality of the product.
(7) Resin for polypropylene film for molded food packaging shall conform to GB 12670-1990 standard provisions. The sensory index requirements for resin are: normal color, no peculiar smell, odor and foreign matter.