Performance index of PP diaphragm
DATE：2022/10/17 9:13:12 / READ： / SOURCE：This station
Performance index of PP diaphragm
Note: The change rate of longitudinal dimension is not considered for the sheet with thickness less than 0.5mm.⑤ The filter screen has three layers of 40/80/40 mesh. The 80 mesh filter screen should be placed in the middle of the filter screen with small mesh to increase its strength.
⑥ The working surface of the three calender rolls shall be plated with hard chromium, and the surface roughness R shall not be greater than
zero point one μ m. The surface shall be smooth and clean without air holes.
⑦ The distance between the three roll calender and the die lip shall be controlled within the range of 50~150mm, and the distance shall be adjusted according to the shrinking size of the width during production.
⑧ The working surface temperature of calender roller is adjustable, and the temperature of each position on the roller surface is consistent, and the temperature is controlled within ± 0.5 ℃.
⑨ The rotational speed of the roller matches the speed of the film extruded from the die lip. Generally, the rotational speed of the roller is 10%~20% faster than the flow rate of the film extruded from the die lip.
⑩ The finished diaphragm can be rolled or cut according to the user's requirements.
7.3 PVC sheet (sheet) extrusion molding
(1) Polyvinyl chloride (PVC) molding materials are selected: SG4 or SG5 PVC resin for rigid suspension is the main raw material; The suspension method SG2 or SG3 PVC resin is used as the main raw material for soft materials, and stabilizer, plasticizer, filler and other auxiliary materials are properly added according to the requirements of the application conditions of the product to form the raw material formula. The food packaging is made of hard sheet and sanitary PVC resin. See Table 4-8 for the formula of extrusion materials for different plates (sheets). Extrusion formula of soft tablets (mass fraction): polyvinyl chloride (PVC SG2) 100, tribasic lead sulfate (3PbO) 3, dibasic lead phosphite (2PbO) 1, dioctyl phthalate (DOP) 30, dibutyl phthalate (DBP) 25,
Appropriate amount of colorant.
(2) For equipment type B), the screw diameter is also selected according to the data in Table 7-2. The screw structure is an equidistant gradual change type, with a length diameter ratio of L/D ≥ 20:1 and a compression ratio of 3. Generally, branch pipe type or screw distributed T-shaped mold is adopted for the selection of mold structure.
(3) Forming process
① See Chapter 4 for mixing process parameters and requirements of raw materials. ② Extrusion plasticizing raw material barrel temperature.
a. The feeding section of hard board (sheet) is 120~130 ℃, the plasticizing section is 130~150 ℃, and the homogenizing section is 160~180 ℃.
b. The material section of soft plate (sheet) is 100~120 ℃, the plasticizing section is 130~140 ℃, and the homogenizing section is 150~160 ℃.
③ Forming mold temperature
a. The middle part of the hard board (sheet) is 155~165 ℃, and the two ends are 170~
180℃。
b. The middle part of the soft plate (sheet) is 145~155 ℃, and the two ends are 160~170 ℃.
④ Three roller calender roller temperature
a. 70~80 ℃ above, 80~90 ℃ in the middle and 60~70 ℃ below the hard board (sheet). b. 60~70 ℃ on soft board (sheet), 70~80 ℃ in middle, lower 50~60℃。 (4) Quality requirements The quality requirements of PVC sheets (sheets) shall comply with the provisions of GB/T4454-1996. See Table 7-8 for the dimensions of plates (sheets). See Table 7-9 for the appearance quality requirements of plates (sheets).
Table 7-8 Dimensions of PVC sheets (sheets) (excerpted from GB/T4454-1996)
Nominal size of the project/mm Limit deviation/% Limit deviation/mm
(5) Key points of process operation
① The temperature of each section on the barrel increases gradually from the feeding section to the connection between the barrel and the forming die- 460 - Table 7-9 Appearance Quality Requirements for PVC Panels (Sheets)
② The mold temperature is slightly higher than the barrel temperature. The higher temperature shall be controlled at 5~10 ℃. The temperature at both ends of the mold is slightly higher than the temperature in the middle of the mold, and the higher temperature is controlled at 5~10 ℃. ③ As shown in Figure 6-3, the upper roll surface of the intermediate roll of the three rolls should be on the same horizontal plane with the lower plane of the die lip; The lip end face is parallel to the center line of the intermediate roll, with a distance of 50~100mm.
④ The clearance between die lips shall be slightly less than or equal to the thickness of plate products, and the clearance between die lips shall be slightly less than the clearance between end die lips on both sides.
⑤ Note that the roughness R of the three roll working surface shall not be greater than 0.2 μ m。 When cleaning the roll surface, it is not allowed to scratch the roll surface with a hard steel knife. Instead, a copper knife should be used to clean the residue on the roll surface.
⑥ The roll surface shall have some middle height; The clearance between the three rolls shall be equal to or slightly greater than the thickness of the plate.
⑦ The temperature control of the forming die shall be stable. When the temperature is high, the molten material flows faster in the mold; When the temperature is low, the molten material flows slowly in the mold. Unstable melt flow rate will cause large longitudinal thickness error of plate (sheet) products.
⑧ Pay attention to controlling the working surface temperature of the three rollers. The temperature of the sheet feeding roller should be slightly higher and the temperature of the sheet discharging roller should be slightly lower. The roller surface temperature is too high, the slab is not easy to roll off, and the product surface is easy to produce transverse lines; The temperature is low, and the surface of the product is dull. According to this phenomenon, the roller surface temperature control should be adjusted in time.
⑨ The running speed of the three rollers is slightly higher than the extrusion speed of the slab from the die mouth, and the speed difference generally does not exceed 10%. The working speed of the three rollers should be controlled stably. Too fast or too slow running speed has a great impact on the thickness error of the plate.
The forming of PVC corrugated plate is very simple. During production, just heat and soften the PVC hard plate, roll it with a group of arc shaped convex and concave steel rollers to form corrugated plate, and then cool it to shape and cut it to form corrugated plate products. Process flow diagram is shown in Figure 7-2
The thickness of PVC corrugated plate is generally 2-4mm. Its application performance is the same as that of ordinary PVC board, with corrosion resistance, good temperature resistance, aging resistance and other characteristics. As its production cost is lower than that shown in Figure 7-2, the corrugated plate production process flow and price are low, so it is suitable
1-PVC plate is introduced into the oven;
2-2 - Resistance heater; Temporary simple shed covers
3 - Formed corrugated steel roll;
4-4 - Traction device (wave construction barrier material, which can prevent rain and
Cooling and setting of corrugated plate);
5 One plate preheating conveyor belt for wind protection.
Forming process: the preheating temperature of the plate is 125~135 ℃, and the heating time is determined by the thickness of the plate, which can be controlled within the range of 2~10min (the large value for thick plate and the small value for thin plate); The temperature of the arc forming surface of the convex and concave steel rollers of the die should be controlled within the range of 40~50 ℃; The high temperature plate of pressed corrugated plate shall be cut off after cooling, shaping and curing for at least 10min.
7.4 ABS plate extrusion molding
ABS is the abbreviation of acrylonitrile butadiene styrene copolymer resin. ABS board is a kind of product extruded from ABS resin. It is tough, hard and rigid; It has the characteristics of heat resistance and smooth surface, and is easy to conduct the second processing. Therefore, household appliances, electronics, packaging and other industries have been widely used. For example, making (molding) refrigerators, clothing machine linings, housing of household appliances and instruments, dashboard, various file boxes and travel
(1) The raw materials are selected from the special resin for ABS plate extrusion molding. For example, H-08, E-7 and E-3 resins of Sinopec; Extrusion Molding of PetroChina Daqing Petrochemical Company Board (Sheet)
(2) 767, HFA-451, ABS770, etc. of the Department of Equipment Conditions: ABS sheet extrusion molding equipment and polyethylene sheet extrusion molding
Wet treatment, therefore, a dryer is required. The equipment used is basically the same. But extruded ABS is dried
(3) Forming process
① Before production, the resin shall be treated for 2~4h in a drying oven at 80~85 ℃. The resin after drying and dehumidification shall be put into production immediately, and shall not be stored in the air for a long time to prevent absorption of moisture in the air.
② Extrusion and plasticizing temperature of raw materials (from barrel feeding section to homogenizing section): 150~170 ℃, 160~180 ℃, 170~190 ℃.
③ Temperature of T-shaped mold: 180~190 ℃ in the middle, 195~210 ℃ at both ends.
④ The temperature of the three rolls (according to the feeding method in Figure 6-3): about 100 ℃ for the lower roll, about 80 ℃ for the middle roll, and about 70 ℃ for the upper roll.
⑤ The quality requirements of plates are basically the same as those of other plastic plates.
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