With the innovation of domestic plate production line, the introduction of foreign capital and imported equipment, and the application of new raw and auxiliary materials, thermoforming industry is booming. The processing technology of thermoformed sheet is also different due to different equipment, materials and uses. The increasingly mature sheet metal processing technology has gradually broken the old conventional theory. Now, even on the same plate production line, qualified plates with different uses, specifications and materials can be produced by different processes; Plates of the same specification can also be processed by different equipment and processes. "No mode" has brought great convenience to production.
PP thermoformed sheets can be produced by calendering, calendering and salivation (with or without air knives).
In this paper, some technologies of producing various polypropylene thermoformed sheets by "calendering" are discussed. For reference only, please criticize and correct me if there is anything wrong.
This paper is based on the simplest equipment configuration of "extruder -T-head-vertical three-roll calender-traction-coiling". High-grade plate production lines generally adopt "precision extrusion" technology, including PLC highly automatic programmable computer control system, melt pump, static mixer, etc. Most of the three rollers are horizontal, driven independently by servo motors, equipped with independent circulating water control system, and generally produced by "calendering method". In general, in order to prevent the deformation of rollers and racks and affect the processing accuracy of plates, the "calendering method" is not recommended in the production line of high-grade plates in principle. Therefore, some high-grade plate production lines have automatic protection function. When the sheet is produced by calendering, if the three-roller drive motor is overloaded, the whole production line will automatically stop. )
The biggest difference between "calendering" and other methods is that there is obviously smooth and uniform residual rubber rotation between the first and second rollers that the head enters, and the third roller generally does not need to press the intermediate roller.
Because there is some residual glue between rollers, it plays a great role in stable production, and ordinary electromechanical configuration can meet it. That is, there is no need for melt pump, static mixer, PLC highly automatic programmable computer control system and so on. Investment cost and production cost can be reduced. Only the roller and the frame have higher strength than the "calendering method" and "salivation method" because the roller bears greater separation force. When the "calendering method" is used for production, the operation is convenient, the workers can easily master the technical essentials, and the equipment maintenance is simple. At present, almost 100% of domestic equipment can meet the requirements. Therefore, it is more economical to use domestic equipment than imported equipment when producing PP thermoformed sheets by "calendering" process.
Selection of common PP raw materials for thermoforming: PP pellets usually choose extrusion plate grade, sheet grade, drawing grade, narrow band grade or thermoforming grade.
1. thick PP "positive pressure thermoformed sheet" (0.50——2.50 mm) is calendered, and the PP material has strong adaptability to equipment and relatively loose technological requirements.
Take the vertical three-roll feeding as an example: when the "calendering method" is used for production, there is glue between the upper roll and the intermediate roll, which is as thin as a pencil. When producing 0.50 mm-2.5 mm or even thicker positive pressure thermoformed PP sheets, the equipment has a wide range of applications and the process adjustment is easy. In addition, there are the following advantages:
(1) When PP positive pressure thermoformed sheet is produced by calendering process, PP material has strong adaptability to screw and barrel;
Whether it is a special, abrupt and separated single screw with L/D = 22-25 recommended in theory, or other new single screws with gradual change, general use, exhaust type, L/D = 2O-35, barrier type and split type, there are successful production examples in actual production.
This is because in actual production, the strength of each factory is different, and it is impossible to have special equipment or configuration. In addition, it is impossible to replace materials with special barrels and screws every time. Therefore, in actual production, a sheet production line can be used to produce HIPS, CPS and ABS sheets, and can also arrange to produce PP and PE sheets, and can also process PP degradation materials and PP and PE sheets containing filler masterbatch.
Enterprises specializing in producing sheet production line equipment are generally suitable for processing PP materials. Such as: Tianjin Hengrui, Wei, Jinhu, Shantou Dacheng, etc.
(2) When using calendering technology to produce PP positive pressure thermoformed sheet, PP material has strong adaptability to die structure, speed regulation mode, transmission mode, temperature control mode, lip opening and feeding mode (upper feeding and lower feeding).
The processing range of PP material is wide, so the temperature setting is also wide. Because the melting point of PP material is 164- 170℃, in actual production, the processing temperature can be set between 170℃ and 270℃, which varies according to the origin of the material, different equipment and different processing places.
The lip opening is generally not too strict, but the lip opening should be at least greater than the thickness of the plate. In fact, there are many specifications of plates, and it is troublesome to adjust the lip. Even the lip of the thickest plate can always be produced. Some use lip (thickness) openings ≈ plate thickness x (1+10-30%); In some cases, when the thickness of the sheet is less than 0.8mm, the lip opening is 1.0mm, and when the thickness of the sheet is more than 0.8mm and less than 1.5mm, the lip opening is 2.0mm (because the thickness of thermoformed sheets rarely exceeds 2.0 mm).
The temperature of three-roller common circulating water is controlled at 30℃-80℃. There are several ways of three-roller circulating waterway, such as series connection, parallel connection and independent control, which can meet the production requirements.
For example: a. Sheet production line made in Taiwan Province Province: screw Ф150 mm x34, single screw, no exhaust in the barrel; Coat hanger head, 100mm wide, with shock absorbing strips; Drum Ф 490mmx110mm, chain drive, hydraulic cylinder to control the lifting of the upper and lower drums; Independent circulating water tank automatically controls the temperature of three rollers at constant temperature; Vertical feeding; DC variable frequency motor with power of 300 HP; ; The waste materials are randomly crushed and then squeezed into a hopper for later use; Vacuum feeding.
When the "calendering method" is used to produce (thickness) 1.70 mm X (width) 7 10 mm CPP, the normal production process is recorded as follows:
The ingredients of (1) are: 50k g of granular material PT 103 (Taiwan Province province is rich in polymen), 60Kg of broken material (50 kg of coarse material and 50 kg of fine material 10Kg), and 0.2Kg of powdery transparent agent (made in Hong Kong).
(2) fuselage temperature control: 233-237-235-236-239-239-245-250-243 (unit:℃)
(3) Head temperature control: 235-235-235-235 (unit:℃)
(4) Three-roller water temperature control: (lower-middle-upper) 28.4-28.6-23.5 (unit:℃)
(5) Screw speed: 57.7 rpm.
(6) Three-roller linear speed: 9.3m/min; Traction: 30.8kN.
(7) Main motor speed: 938 (rpm); Host current: 390A
(8) State of upper and lower rollers: Both the upper and lower rollers are under pressure.
(9) Residual glue state: as thin as a ballpoint pen core, evenly distributed, in a straight line, above the extruded blank. Only exists between the middle roller and the lower roller.
(10) filter: 80 mesh X2+ 100 mesh; The net pressure is 230Kg/cm?
(1 1) Lip opening: 2.3mm.
(12) Distance from the head to the center lines of the three rollers:100 mm.
(13) Plate quality: good surface, good transparency and good thermoformability.
Note: (a) During the test: both the upper and lower rollers are pressed; The residual glue is as thin as a ballpoint pen core and evenly distributed in a straight line, above the extrusion blank and only between the middle roller and the lower roller; The temperature setting is optional.
(b) The temperature of the fuselage and nose can be increased by 10-20℃ due to the large current of the main engine and the low screw speed.
(c) Through the test, when the upper and lower rollers are pressed, the residual glue exists not only between the upper and middle rollers, but also between the middle and lower rollers. The residual glue is as thin as a ballpoint pen core, evenly distributed and straight, and the sheet can also be produced and used normally.
(d) Through the test, when the upper roller does not press, only the lower roller presses, and the residual glue is as fine as a ballpoint pen core, evenly distributed and flat, and only exists above the extruded blank between the middle roller and the lower roller, the sheet can also be produced and used normally.
(e) After testing, the forward temperature setting (235-260℃), the reverse temperature setting (260-235℃) or the fuselage setting (245℃) are the same, and the plate can be used in normal production.
Description: (1) This production line is mainly used for calendering PP, HIPS, CPS and other sheets.
(2) I just want to prove that it is feasible for this production line to produce PP thermoformed sheets by calendering, and there are many forms.
B jp-750p extrusion sheet unit of Shantou Dacheng packaging machinery factory: screw Ф105mm x35, single exhaust screw and barrel; Commutator speed regulating motor, power100 kw; ; Coat hanger type machine head with damping strip; Three-roller specifications Ф 316mm x 800mm, chain drive; Manual worm gear reducer controls the upper roller to rise and fall, while the lower roller cannot rise and fall; Vertical feeding; The constant temperature circulating water tank controls the temperature of the three rollers.
When the "calendering method" is used to produce biodegradable positive pressure thermoformed sheets with a thickness of 1.50mmX and a width of 580mmWPP, the normal production process is recorded as follows:
(1) Ingredients: PP bio-starch degradation granular material (Xi Anwanjie) 100kg+ degradation crushed material 120Kg.
(2) airframe temperature:180-185-190-195-195 (unit:℃).
(3) Head temperature:195-190-195 (unit:℃)
(4) filter screen: 60 mesh X2+80 mesh X2
(5) Residual glue state: the index finger is thick, evenly distributed, well rotated and smooth.
(6) Upper roller temperature: 40℃; The middle roller is 45℃ and the lower roller is 30℃.
(7) Lip opening: 2.5mm.
(8) When the residual rubber is kept at an appropriate level, the main engine speed and the three-roller speed can be accelerated or decelerated at the same time.
(9) Sheet quality: good surface, good thermoformability (tested in a positive pressure cup thermoforming machine) and even stretching.
Description: (a) This production line is mainly used to produce HIPS, CPS, environmentally-friendly degradable materials, highly filled PP and PE sheets. It is also suitable for producing general filler-free polypropylene thermoformed sheets.
(b) "Calendering" can also be used to produce thinner PP negative pressure (vacuum) thermoformed biodegradable sheets (see the following three types. (2))
(c) Because it contains a lot of starch, the temperature of the machine body should not be too high, and the filter screen should not be too dense or too dense, otherwise the paper will be prone to yellowing, and even scorch lines will appear in the longitudinal direction.
(d) When the production line is used to process PP filled sheets (filled with more than 50% master batch), the temperature of the three rollers and the machine body should be properly increased to facilitate uniform plasticization and prevent the extruder from overloading and damaging the equipment.
C. JP-90-700 Extrusion Sheet Unit of Shantou Dacheng Packaging Machinery Factory:
Single screw Ф 90x28, split type; 37KW electromagnetic speed regulating motor; ; , straight pipe head, no damping strip; Three-roller specifications Ф Ф 256x700 mm, worm gear transmission, pneumatic control of lifting roller, the upper roller can not be lifted; Vertical feeding; Parallel or series circulating waterways.
Description: (a) This production line is an early production line dedicated to the production of PP and PE filled and unfilled sheets by calendering, which is convenient to adjust and cheap.
(2) The production process is relatively simple, so I won't go into details here. Please refer to a and d. ..
D. Zhejiang Honghua extruded board production line: two-stage progressive single screw Ф100 mm x30, with no exhaust hole in the barrel; 45KW electromagnetic speed regulating motor; ; Three-roll specifications Ф Ф 260 mmx 800 mm, gear transmission, manual lead screw to control the upper roll lifting, the lower roll can not be lifted; Coat hanger type machine head with damping strip; Vertical feeding; Parallel circulating waterway; Artificial feeding; Scrap sheets are crushed separately.
When a 0.55mmX580 CPP positive pressure thermoformed sheet is produced by "calendering", the normal production process is recorded as follows:
(1) Ingredients: 25Kg of T30S granular material (Puyang) and 70Kg of broken materials (including 60Kg thick broken materials).
Powder transparent agent (made in China) 0.03Kg
(2) fuselage temperature: 200-220-230-240-240 (unit:℃)
(3) Head temperature: 225—220—225 (unit:℃)
(4) Host (table display): 1450 rpm; Three rollers (as shown in the table): 525 rpm.
(5) Three-roller temperature (measured by thermometer): 48℃ for the upper roller, 45℃ for the middle roller and 35℃ for the lower roller.
(6) Residual glue state: thin as a pencil, evenly distributed and well rotated.
(7) Lip opening:1.20mm.
(8) Distance from head to intermediate roller: 250 mm.
(9) Filter screen: 60 mesh X3+80 mesh X2
(10) sheet quality: good surface, good tensile property (tested on a pressure thermoforming machine), no damage to the plastic cup, no whitening at the bottom, and good transparency.
Description: (a) Through the test, when the temperature of the upper, middle and lower rollers is 30-35℃ and the main machine is 1200r/min, the residual glue remains unchanged, the tensile property of the thermoformed sheet is still good, and the transparency is improved.
(b) The fuselage temperature can also be reduced by 10-20℃.
(c) The transparent agent is granular and powdery. When using powdery transparent agent, a small amount of white oil, turpentine and alcohol can be added to the formula to make the powdery transparent agent evenly dispersed and improve the transparency.
(d) The filter screen overlaps with the standard mesh (25+50+ 100+50 mesh); With scissors (100x2+80x2, 100+80x2+60, 100+80+60x2, 100+80+60+40, 80x2+60x20. Punching holes with a punching machine; There are also single-layer or double-layer screens with an inlet thickness of 60- 100 mesh.
(e) Because the plate is narrow and the head is wide and not blocked, in order to reduce the trimming width, the head is far away from the three rollers.
2. When the thin PP "positive pressure thermoformed sheet" (0.30—0.40 mm) is calendered, the adaptability of PP material to equipment is relatively weak, and the technological requirements are also harsh.
Take Zhejiang Honghua extrusion sheet production line as an example: (See I. D for specific configuration)
When 0.36mmX620 CPP is produced by "calendering", the normal production process is recorded as follows:
(1) Ingredients: T30S powder (Puyang) 25Kg, transparent crumbs 105Kg (including 90Kg thick crumbs) and transparent agent 0.03Kg.
(2) fuselage temperature: 190—225—240—240—245—245 (unit:℃)
(3) Head temperature: 225—222—225 (unit:℃)
(4) Main engine (see table): 1500 rpm; Three rolls (as shown in the table): 725 rpm.
(5) Three-roller temperature (measured by thermometer): 47℃ for upper roller, 47℃ for middle roller and 35℃ for lower roller.
(6) Residual glue state: as thick as a pencil, evenly distributed and well rotated.
(7) Lip opening:1.20mm.
(8) Distance from head to intermediate roller: 170 mm.
(9) Filter screen: 60 mesh X3+80 mesh X2
(10) sheet quality: good surface, good tensile property (tested on a pressure thermoforming machine), no damage to the plastic cup, no whitening at the bottom, and good transparency.
Note: (a) The fuselage temperature can also be reduced by 10-20℃.
(b) This formula is used when there are a lot of recycled materials and the color requirements of thermoformed products are not too high.
(c) Through the test, when the temperature of the upper and middle rollers is lower than 45℃ and the main machine is at 1300 rpm, the residual glue remains unchanged, and the surface quality of the thermoformed sheet is good. However, when testing the formability of "small plum blossom cup" on the positive pressure thermoforming machine, it was found that the tensile properties of the plate became worse, the tensile fracture of the plastic cup increased, and there were many waste products, which could not be produced normally. Even if the parameters of the positive pressure thermoforming machine are changed, there is no improvement. Even if the opening of the nose is reduced to 0.60 mm, it has no effect. Therefore, it is judged that the thermoformability of thin PP "positive pressure thermoforming sheet" (0.30—0.40 mm) produced by calendering method has a great relationship with the speed of the main machine.
(d) When the rotational speed of the main engine is 65,438+500 r/min and the roll temperature drops below 35℃, the thermoformability of the plate becomes poor and the plastic cup is difficult to form. However, when the roll temperature rises to 75℃, the thermoformability of the sheet is better, but the transparency of the plastic cup becomes worse and the surface is blurred.
Therefore, it is judged that the thermoformability of thin PP "positive pressure thermoforming sheet" (0.30—0.40 mm) produced by calendering method and the transparency of thermoformed products have a great relationship with the three-roll temperature.
3. If the negative pressure (vacuum suction) PP thermoformed sheet is produced by "calendering method", a proper amount of PE can be added to the ingredients of positive pressure thermoformed sheet, or the PP extrusion grade modified by PE-* * * PP can be directly selected.
Generally, extrusion grade HDPE, LLDPE and LDPE are added, and the addition amount is 10-50%, or the extrusion grade of PE modified PP is directly selected to improve the tensile properties of the sheet and increase the yield.
For example: (1) A factory produces PP China white tablets with a size of 0.40mm× 700mm for plastic absorption.
The ingredients are as follows: PP(F40 1, Yangzi Petrochemical) 100 Kg, PE(5000S, Beiyan) 100 Kg, and 80 Kg of white foam waste.
Degradable masterbatch 100 Kg, china white masterbatch (Shandong) 5 Kg.
Equipment used: Ф 90x28, separated single screw; 37KW electromagnetic speed regulating motor; ; Hanger head, without shock absorber; Three-roller specifications Ф Ф 256x700 mm, chain drive; Manual worm controls the upper roller to rise and fall, while the lower roller cannot rise and fall; Vertical feeding; Parallel circulating waterway.
Process parameters: fuselage temperature: 225-237-245-248-255-260 (unit:℃).
Head temperature: 240——232——240 (unit:℃)
Three-roller temperature (hand mold): about 50-60℃ for the upper and middle rollers.
Filter: 80 mesh+120 mesh X2+ 150 mesh X2.
Lip:1.5mm.
Residual glue: pencil thickness, uniform distribution and good rotation.
Sheet quality: good surface, good water absorption (tested on a water absorber), no cracking and uneven stretching.
Description: (a) The formula of PP thermoformed sheet for plastic suction varies with the processing difficulty, application and quality requirements of the product.
(b) PP sheets for plastic suction can also be produced by "salivation method", which will be introduced in detail in another chapter.
(c) When producing flakes by calendering, in order to prevent hard impurities (gravel, metal) from damaging the head, melt pump and roller, it is necessary to pay attention to placing the magnetic frame and replacing the screen in time. Generally, the filter screen used for producing thin sheets is denser and stronger than that used for thick sheets. A special network stack is usually used.
(2) Take JP-750P Extrusion Sheet Unit of Shantou Dacheng Packaging Machinery Factory as an example (see I for specific configuration). b)
When the "calendering method" is used to produce a biodegradable negative pressure (blister) thermoformed sheet with a thickness of 0.50mmX and a width of 6 10mmWPP, the normal production process is recorded as follows:
(1) Ingredients: PP bio-starch degradation granular material (Xi 'an Wanjie) 100Kg+ degradation crushed material 100kg.
(2) airframe temperature:180-185-190-195-195 (unit:℃).
(3) Head temperature:195-190-195 (unit:℃)
(4) filter screen: 60 mesh X2+80 mesh X2
(5) Residual glue state: thin as a pencil, evenly distributed, well rotated and smooth.
(6) Upper roller temperature: 45℃; The middle roller is 48℃ and the lower roller is 35℃.
(7) Lip opening:1.5mm.
(8) When the residual rubber is kept at an appropriate level, the main engine speed and the three-roller speed can be accelerated or decelerated at the same time.
(9) Sheet quality: good surface, good thermoformability (tried in plastic thermoforming machine) and uniform stretching.
Description: (a) The temperature of the fuselage, the nose, the three rollers and the rotating speed of the main engine have great influence on the uniform distribution and good rotation of the residual rubber.
(b) The formula of degradable particles plays a key role in the processing difficulty and thermoformability of the sheet.
(c) Accelerating the extrusion speed and increasing the roll temperature are beneficial to improve the thermoformability of the sheet.
Conclusion: (1) From the above real test records from the production line, it can be seen that the "calendering method" can produce PP thermoformed sheets with various formulations on various equipments with different configurations. Although the production of thin PP thermoformed sheet by calendering method has strict requirements on process parameters such as formula, roll temperature and speed, it is still easy to operate after finding out the law.
(2) The key of "calendering method" is to control the residual rubber so that it is always in a bubble-free, stable, uniform and smooth state.
(3) The temperature of the roller is directly proportional to the speed of the extruder, which has a great influence on the thermoformability of the thermoformed sheet.
Note: WPP- white PP- white PP
Transparent polypropylene
Cps- transparent PS- transparent PS