Polyethylene sheet (sheet) extrusion molding
DATE：2022/10/14 8:43:33 / READ： / SOURCE：This station
Polyethylene sheet (sheet) extrusion molding
(1) Raw materials for extrusion forming of polyethylene sheet (sheet) shall be special resin for sheet forming. For example, 5000H high-density polyethylene produced by Sinopec Beijing Yanshan Petrochemical Co., Ltd. and DGDS-6097 (MFR=0.4g/10min, density 0.948g/cm) PE resin produced by Sinopec Guangzhou Petrochemical Company. LDPE resin is selected, MFR=0.4~0.6g/10min; HDPE resin, MFR=0.1~0.4g/10min, can also be used for extruding board (sheet) materials.(2) ) Single screw universal extruder for production, screw diameter can be selected according to experience in Table 7-2. The pole structure mostly adopts the uniform gradual change universal screw, the length diameter ratio L/D>25:1, and the compression ratio is (3~4): 1
Unit: mm
Table 7-2 Relation between Screw Diameter and Width of Plate Products
Plate width Screw diameter 65400~80090700~12001000~14001201200~2500150 (3) Forming process
① Extrusion PE material process temperature control, temperature of each section of the barrel: when the raw material is LDPE, the feeding section is 150~160 ℃, the plasticizing section is 160~170 ℃, and the homogenizing section is 170~180 ℃; When the raw material is HDPE, the feeding section is 120~140 ℃, the plasticizing section is 140~160 ℃, and the homogenizing section is 160~180 ℃.
Molding mold temperature: when LDPE material is used, the middle section of the mold is 160~170 ℃, and the two ends of the mold are 180~190 ℃; For HDPE material, the middle section of the mold is 155~165 ℃, and the two ends of the mold are 175~180 ℃.
Three roll temperature (if slab roll inlet position is as shown in Fig. 6-3): upper roll temperature 60~70 ℃, intermediate roll temperature 80~90 ℃, lower roll temperature 70~80 ℃. The slab shall be cooled gradually when three rolls pass, to prevent the products from producing large internal stress and warping deformation.
② The distance between the three rolls and the die mouth shall be controlled within 50~100mm to prevent objects from
The slab extruded from the die mouth sags.
③ The speed of drawing products can be close to or slightly faster than the speed of extruding products from the die mouth
The speed of product extrusion die mouth shall not be too fast, and too fast traction speed will cause
The width shrinks greatly. (4) Quality requirements The quality requirements of polyethylene (plate) shall conform to the standard QB/T group
2490-2000. The specification and limit deviation of PE sheet (plate) shall comply with the provisions in Table 7-3.
The appearance quality requirements of polyethylene sheet are: the surface of sheet (plate) shall be smooth and flat, without bubbles, cracks, obvious impurities, dents and color marks. The mechanical property indexes of polyethylene sheet shall comply with Table 7-4.
Table 7-4 Mechanical Properties of Polyethylene Sheet
The hygiene index of polyethylene sheet used for food containers and tableware shall comply with GB9687.
The extrusion process of high-density polyethylene calcium plastic corrugated board is as follows.
High density polyethylene calcium plastic corrugated board is a product formed by three layers of calcium plastic board with thermal bonding method. The top and bottom of the calcium plastic corrugated board are flat calcium plastic sheets, and the middle layer is corrugated calcium plastic sheets. The high-density polyethylene calcium plastic corrugated board has high strength, good vibration resistance and fall resistance, and a certain stiffness. It is waterproof and moth resistant, and its price is relatively low. The calcium plastic corrugated board can be made into packaging containers (boxes) of various shapes for various
(Packaging of type 1 high-density materials.
Polyethylene and light calcium carbonate, and then add a certain proportion of lubricant (to improve the fluidity of molten materials) and antioxidant (to improve the oxidation energy of P grease) additives
① Refer to formula 1: high-density polyethylene (HDE 60 parts, calcium carbonate to form calcium plastic sheet.
(CaCO) 40 shares, antioxidant 113 tribune (A) 0.75 shares, dilaryl dipropionate (DLTP) 0.075 shares, barium stearate (ZnSt) 0.45 shares, barium stearate (BaSt) 0.35 shares (CaCO3) 50 shares, antioxidant B octadecyl propionate (1076) 0.13 shares.
(2) The calcium workers and equipment can be molded by extrusion or calendering. Two different methods of producing calcium plastic sheets are described below.
① Extrusion process for production of molded calcium plastic sheet a. Production process flow sequence
Measure all kinds of raw materials according to the formula of calcium plastic sheet → high-speed mixing → extruding granulation → extruding plasticizing raw materials → die forming sheet → three roll calendering, cooling and shaping → trimming → traction → coiling
b. Mixer, the original extruder for granulation after uniform mixing, the extruder for plasticizing and melting raw materials, the die for forming sheet and the auxiliary machine for three roll calendering, trimming, traction and coiling, etc.
c. Extrusion molding process of calcium plastic sheet
For the mixing of raw materials, add light calcium carbonate (CaCO3) into the mixing room of the high-speed mixer, stir and heat up to 110~120 ℃, add coupling agent intermittently, and then add lubricant: after full mixing, add high-density polyethylene resin and antioxidant to mix the raw materials evenly.
Pelletizing can be made by mixing plasticized raw materials with a single screw or twin screw extruder. The raw material temperature shall be controlled within the range of 180~205 ℃.
The equipment for extruding calcium plastic sheet is the same as that for plastic PE sheet (plate), and the temperature range for raw material extrusion is 170~270 ℃. Temperature control of forming die: 210 ℃ for middle section and 250~260 ℃ for both ends. The roller temperature of the three roll calender is about 100 ℃ for the middle roll and 70 ℃ for the upper and lower rolls.
② Calendering process for production of molded calcium plastic sheet a. Production process flow sequence
Measure various raw materials according to the material formula for forming calcium plastic sheet → mix them at high speed (add calcium carbonate first, then add coupling agent and lubricant), mix them evenly, and then add HDPE and antioxidant → mix them in an internal mixer → mix them in a two roller open mill → mix them in a second two roller open mill → calender them in a three roller or four roller calender → calender → calender → cool → trim → draw → roll
b. The production equipment includes high-speed mixer, internal mixer, open mill, calender and auxiliary machines such as giant light, cooling, trimming, traction and coiling.
c. Calendering process of calcium plastic sheet Blending method and process conditions of raw materials and extrusion 54 - Chapter 7 Extrusion molding of plastic sheet (sheet)
The mixing method and process conditions of raw materials in the plastic forming process are the same. The plasticizing and calendering process temperature of raw materials can also refer to the material temperature requirements in the extrusion process.
(3) Compound forming of calcium plastic corrugated board The compound forming production process sequence of three layers of calcium plastic sheets in calcium plastic corrugated board is shown in Figure 7-1. It can be seen from the figure that the production process sequence of thermal bonding of three-layer calcium plastic sheet is:
Three layers of calcium plastic sheets shall be bundled and placed at the same time → three layers of calcium plastic sheets shall be preheated respectively (the middle calcium plastic sheet shall be pressed into a corrugated triangle after preheating) → three layers of calcium plastic sheets shall be hot laminated into one and cold cut
Figure 7-1 Production process of three layers of calcium plastic corrugated board
1 - Calcium plastic sheet for upper surface; 2 - upper surface calcium plastic sheet heating roller; 3 - Calcium plastic sheet for corrugated sheet;
4 - Corrugated sheet heating roller; 5 - Corrugating forming press roll; 6 Calcium plastic sheet is used for the lower surface;
7 Lower surface calcium plastic sheet heating roller; 8, 9-calcium plastic sheet thermal bonding roller; 10 - Cooling roll group; 11 All side devices; 12 One piece cutting device
The composite molding production process of three layers of calcium plastic sheets, first of all, heat the three layers of calcium plastic sheets on a 140~160 ℃ preheating roller (the preheating temperature of the middle corrugated sheet is 160~170 ℃, and then use the corrugated roller to press the sheets into an equilateral triangular corrugated shape), and then enter the thermal composite roller. The three layers of calcium plastic corrugated sheets are bonded to form calcium plastic corrugated sheets under the heating pressure of the composite roller, and then cut off after trimming and embossing to form products.
(4) The quality requirements of polyethylene glycol plastic corrugated board shall comply with QB/T 1651-92.
① Specification and dimension requirements of calcium plastic board. The length shall be greater than or equal to 50mm, the width shall be greater than or equal to 2000mm, and the limit deviation of the two dimensions shall be ± 1%. The thickness of the plate is 2~6mm, and the limit deviation is ± 10%.
② The number of bars in the middle layer of corrugated board. When the plate thickness is 2~3.9 mm, the number of vertical bars is greater than or equal to 24/10 cm; When the plate thickness is 4~6mm, the number of vertical bars shall be greater than or equal to 15 pieces/10cm. The mass deviation of the two in unit area is ± 5%.
③ Appearance quality of plate
a. The four sides should be straight and the four corners should be at right angles.
b. The products with the same color have uniform color without obvious color difference.
c. The surface shall be smooth and flat without cracks, holes, obvious impurities, bubbles and other defects that affect the use.
④ The mechanical properties of the plate shall comply with the provisions in Table 7-5 and Table 7-6.
(5) ) ① The longitudinal thickness size error of the plate is large
The temperature control of the barrel is unstable, which makes the molten material flow rate unstable. b. The rotational speed of the screw is unstable, which makes the extrusion amount of the molten material uneven. C. The roller speed in the three roller calender is not stable. d. The traction speed is uneven, fast and slow. ② The lateral thickness size error of the plate is large ()
a. The temperature control of each part of the molding die body is unreasonable.
b. The design (or processing) of the specific melting cavity of the die is unreasonable, resulting in uneven distribution of the melting material flow. C. The die lip clearance is adjusted unreasonably, and the clearance is uneven. The middle clearance should be slightly less than the clearance on both sides. d. The adjustment error of the three roll gap is large.
e. If the selection or processing of the middle height of the three rolls is unreasonable, the middle height of the roll surface should be appropriately changed. ③ There are transverse lines on the board surface
a. The screw speed is unstable, and the amount of molten material extruded is uneven. b. The barrel temperature control is unstable, and the molten material flow rate changes. c. The rotation speed of the three rolls is not stable or the roll surface is scratched.
d. The traction speed is not stable or the tension of the traction roller is insufficient, and the products run unevenly. ④ There are longitudinal lines on the plate surface. a. The filter screen is cracked.
b. There are scratches on the die lip.
c. There are foreign matters or decomposed materials in the mold body. ⑤ The board surface is rough and lusterless
a. The three roll working surface is rough or sticky. b. The working temperature of the three rollers is low. c. The die lip is not smooth. d. The filter screen is broken.
7.2 Extrusion molding of polypropylene plate (sheet)
(1) The resin can be EP2S34F and D60P from Shun Petrochemical Company and EPS30R from Sinopec Qilu Petrochemical Co., Ltd. PP (MFR=0.5~2.5gl10min) and HDPE (MFR-0.1~2g/10min) mixtures can also be used, and the mixing ratio is between (8:2) and (6:4) (the mixing ratio should be determined according to the molecular weight of HDPE, and the mixing amount should be smaller if the molecular weight is large, otherwise the mixing amount should be larger). Note: The resin with the melt flow rate (MFR) values of the two admixtures as close as possible shall be selected.
(2) The equipment conditions are the same as those for PE () production molding. Twin screw extruder is recommended.
(3) Forming process
① Raw materials in the barrel of the extruder The temperature of each section of the plasticizing barrel is 1 section (feed inlet) (150 ± 5) ℃, 2 sections (160 ± 5) ℃, 3 sections (170 ± 5) ℃, 4 sections (180+5) ℃, 5 sections (190+5) ℃, and 6 sections (outlet) (200 ± 5) ℃.
② The temperature of the forming die is 200~210 ℃ (the temperature at both ends of the die is taken as the high value, and the temperature in the middle is taken as the low value).
③ The roller temperature of the three roll calender (according to the sheet feeding operation mode in Figure 6-3) is 70 ℃ for the intermediate roll, 60 ℃ for the lower roll and 50 ℃ for the upper roll.
(4) Key points of process operation
① When PP resin extrusion sheet is used for food blister packaging, special resin shall be selected. If the resin contains too much water, it shall be dried in an oven at 90~100 ℃ for 2h.
② PP sheet for food packaging shall meet the hygienic indicators specified in GB9688.
③ The diaphragm quality shall comply with QB/T 2471-2000 standard.
a. The diaphragm thickness is within 0.20~1.00mm, and the limit deviation is ± 10%. The width deviation is determined according to the user's requirements, and can be controlled within ± 1% of the deviation according to the width.
b. One broken head is allowed in each roll of diaphragm length, and the length shall not be less than 20m. c. The appearance shall be smooth and flat without bubbles, perforations and impurities affecting the use.
d. The performance index of the diaphragm shall comply with Table 7-7.
④ The clearance of the forming die lip is adjustable, and the surface roughness R should not be greater than 0.3 μ m。 - 458-
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