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Can be heat sealing of BOPET film processing

by:LINYANG     2020-03-16
Can be heat sealing B0PET film and processing method of ordinary BOPET film basic same, through melting extrusion system, stretch film casting slice, longitudinal extension and transverse stretching, traction winding, made by cutting and etc. Can be heat sealing B0PET film processing, whether single extrusion tensile or three-layer extrusion tensile, its key technology is to grasp the characteristics of the copolymerization of polyester: it is the amorphous structure and high glass transition temperature and melting point and low softening point. Now with three layers co-extrusion ( A/B/C) Structure as an example, will the membrane process briefly described as follows. (1) mixing. C layer for heat sealing layer, in order to make its can open sex, prevent winding when adhesion, to a certain proportion in copolymer polyester blending of containing silicon slice, and mixed evenly, the purpose is to make made of thin film surface has a certain degree of thick seam, reduce the friction coefficient. (2) dry processing. Because of PET resin molecules containing ester base, even at high temperatures is the presence of trace moisture, also susceptible to hydrolysis, make PET molecular weight drops, quality become worse. At the same time, because of the existence of water, in the process of processing will produce a large number of bubbles. So before the membrane processing must be dry processing. Dry processing temperature control at about 70 ℃, the drying time awake 6 h ( Vacuum drum drying) , moisture content control in 50 parts per million. (3) melt extrusion. A/B/C of the structure of the three-layer co-extrusion, need three extruder, A main extruder used as core layer ( B) Material extrusion, two extruder were used as two surface ( A and C) Out of the material. If the surface material using exhaust type double screw extruder, the drying device. Because the exhaust type twin-screw extruder with two exhaust outlet, they are connected to the vacuum pump through a pipeline, under the high vacuum degree, All - 0. 08MPa) , the moisture of PET and the processing can be produced in the process of low molecular material to remove, also achieve the purpose of drying. Copolymerization PET resin extrusion temperature control at 230 ~ 270 ℃. Metering pump, filter, and the temperature of the melt pipe - in 270 280℃。 (4) die casting. For A/B/C three-layer coextrusion heat sealing PET film, had better choose three flow channel of the die. The reason is that three layers of cavity die design can make the ends of the cast piece does not contain can heat sealing components, aim is to avoid during the transverse tensile chain tongs. Die head temperature about 270 ℃, the cooling drum temperature 30 ℃. (5) the longitudinal tensile. In order to prevent heat sealing layer adhesive tensile steel roller, longitudinal tensile last few preheat roll and stretch roll only appropriate USES ceramic roller or spray Teflon anti-sticking layer. Longitudinal tensile temperature is 75 - 80 ℃, draw ratio of 3 to 3. 5 times. Added the infrared heater heating temperature should be lower, and on the other side of the heat sealing layer. 6 transverse stretching. Process conditions and common BOPET transverse tensile basic similar. If it is single layer can be heat sealing PET stretch, transverse tensile temperature control in the 90 - 100 ℃, draw ratio of 3 to 3. 5 times. Chain tongs must strengthen cooling to prevent copolymer polyester adhesive prod-ucts. All landowners traction winding. Corona treatment is chosen athermal cover, can heat cover without corona treatment has the very good printing performance.
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