1. The process flow is: batching → plasticizing → T-type head extrusion casting → cooling → corona treatment → traction → coiling → aging treatment → slitting → finished product.
The screw rotation number was 60 rpm, the temperature was 180, 220, 240, 250 ° C, the traction speed was 80 m/min, the chill roll temperature was 30 ° C, and the film surface tension was 42 dynes/cm.
The heat sealing temperature depends on the application: ordinary grade, that is, non-cooking grade, homopolymer PP, high melting point, so the heat sealing temperature is 140-170 °C. The cooking grade PP is used, and the heat sealing temperature is 125-150 ° C.
2. Biaxially stretched PP film
The biaxially stretched PP film is abbreviated as BOPP or OPP, and its production process routes are roughly as follows:
(1) Flat film simultaneous biaxial stretching method: PP pellets are plasticized by an extruder, and a thick sheet is extruded from a T-type machine to a thickness of about 0.8-1 mm, and longitudinal and transverse stretching are simultaneously performed on a tenter. It is more difficult, and there are fewer methods.
(2) Flat film stepwise biaxial stretching method: after extruding the thick sheet, it is longitudinally stretched by a roller, then stretched laterally by a tenter, and stretched 40-50 times, and the film thickness is about 15-50 μm. . This method is more common.
(3) Two-way stretching method of the bubble tube method: a thick tube is first produced, and the thickness is 0.7-0.8 mm, and then inflated with compressed air, that is, transversely stretched, and longitudinally stretched by a drafting roller.
The film can be used for packaging materials and capacitor films.
For the food packaging industry, the gas permeability of the biaxially stretched PP film is required to be lower. To reduce the permeability, firstly, the permeability of the PP material itself can be reduced by filling modification, but the effect is not obvious. Second, the permeability is reduced by blocking the contact of the PP film with the gas, and it is easier to realize. The following two methods:
BOPP can be sprayed to block the gas. For example, a suspension of polyvinylidene chloride or vinyl hexahydrate is sprayed onto the surface of the membrane to a thickness of about 0.0075 mm.
Another method is vacuum aluminum plating with a thickness of about 0.0002 mm to block oxygen and the like.
3.PP needled omentum
The film is an upgraded product of the tear film, and can be used for sewing thread, carpet weaving, marine fishing and the like, in addition to being used as a tying rope.
The process flow is:
Feeding→Extrusion→Film cooling→cutting and dividing wire→three-rolling traction→heating→stretching→needle forming fiber→heat treatment→cooling setting→winding.
Body temperature: 220, 230, 260, 255 ° C, head temperature 250 ° C, die 250 ° C, PP material melt index 1.5-4 g / 10 minutes. The film was cooled, the water temperature was 38 ° C, the hot stretching temperature was 150-165 ° C, the stretching ratio was 5-6 times, the cooling roll speed was 2-5% lower than the heat treatment roll speed, and the drawing speed was 240 m/min.
4.PP isolation film
The PP separator can be used as a barrier between the conductor and the rubber insulation in wire and cable. It can prevent the adhesion of metal conductors and rubber sleeves.
The process flow is:
Ingredients → kneading → extrusion → inflation cooling → traction → cutting → winding → slitting → inspection of finished products.
The melt index of the PP material is below 3.5 g/10 min. The extruder temperature is 180, 190-200, 200-210 ° C, and the die temperature is 190-200 ° C.
5.PP tear film
Similar to the above film process, it will not be described here.
