Starting method of extruding machine for producing polypropylene thin-wall injection molding product

Abstract

The starting method of the extruder for producing the polypropylene thin-wall injection molding product comprises the following steps: step 1, selecting a ZSK type double-screw extruder, and setting various initial working parameters of the extruder; step 2, starting an extruding machine, and carrying out material pulling on the template; 3, after template material pulling is completed, template seepage materials are cleaned, and after cleaning is completed, die assembly is conducted on the granulator; step 4, observing the shape of the granules at the sampling port, and if the granules are large and many, lifting the load of the extruding machine to adjust; according to the method, only the process parameters of the ZSK type double-screw extruder are adjusted, operation is easy, modification does not need to be added, and universality is good; meanwhile, by determining the optimal process parameters, the finally obtained polypropylene thin-wall injection molding product particles are regular in appearance, the operation power consumption of an extruder granulator is effectively reduced, and the wear of a cutter of the granulator is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of extrusion granulation of thin-wall injection molding products, and in particular relates to a method for starting an extruder for producing polypropylene thin-wall injection molding products. Background Art

[0002] Polypropylene resin is one of the five most common plastics and the most widely used plastic in life. It is widely used in disposable lunch boxes, cups, packaging bags, tube materials, non-woven fabrics, plastic toys, home appliances, household containers, medical containers, automotive components, etc.

[0003] However, due to the high melt index, good fluidity and difficult-to-control molding of polypropylene thin-walled injection molding products, once the extruder stops, it is very easy to have abnormal particle appearance when starting up. If it is not well controlled, it may even cause serious consequences such as knife entanglement. At present, the polypropylene industry often uses Coperion's ZSK twin-screw extruder to produce thin-walled injection molding products, but there is a lack of mature ZSK twin-screw extruder start-up methods when producing thin-walled injection molding products. The process parameter adjustments are all controlled according to their own experience, which has poor universality. In addition, when the thin-walled injection molding products have abnormal particle appearance after the extruder is started, there is no way to deal with it, resulting in irregular particle appearance. Summary of the invention

[0004] The purpose of the present invention is to provide an extruder start-up method for producing polypropylene thin-wall injection molding products, which solves the problem that there is a lack of mature ZSK type twin-screw extruder start-up method for producing thin-wall injection molding products in the prior art, and the method is controlled according to respective experience and has poor universality.

[0005] The technical solution adopted by the present invention is a method for starting an extruder for producing polypropylene thin-wall injection molding products, comprising the following steps: Step 1: Select a ZSK twin-screw extruder and set the initial working parameters of the extruder; Step 2, start the extruder and pull the material to the template; Step 3: After the template is pulled, clean the template for seepage, and close the pelletizer after cleaning; Step 4: Observe the shape of the pellets at the sampling port. If there are many large pellets, adjust the extruder load by raising or lowering it.

[0006] The present invention is also characterized in that The specific process of step 1 is as follows: Step 1.1, first modify the extruder barrel temperature alarm interlock value; The specific process of step 1.1 is as follows: The temperature alarm interlock value of the shearing section of the extruder barrel is modified to 160℃-180℃, and the temperature alarm interlock value of the homogenizing section of the extruder barrel is modified to 140℃-160℃.

[0007] Step 1.2, lowering the temperature of the extruder barrel to the operating temperature; The specific process of step 1.2 is as follows: The temperature of the shearing section of the extruder barrel is reduced to 200℃-220℃, the temperature of the homogenizing section is reduced to 180℃-200℃, and the temperature from the outlet of the extruder barrel to the template is reduced to 200℃-210℃.

[0008] Step 1.3, bypass the inlet and outlet pressure difference of the melt pump in the extruder, bypass the low torque of the main motor pelletizer, bypass the heating of the pelletizer and melt pump outlet section, and bypass the constant temperature time of the barrel section; Step 1.4, modify the PID parameters of the melt pump speed controller in the extruder, change the ratio to 2-3, and change the integral time to 25-40; Step 1.5, set the throttle valve opening of the extruder to 40-50 degrees, the pellet water temperature to 40-50°C, and the hot oil cooler temperature to 180-190°C; Step 1.6, the speed controller of the feed rotary valve of the extruder is put into manual control, and the speed of the feed rotary valve is manually changed to set to 3-10r / min.

[0009] The specific process of step 2 is as follows: Step 2.1, drill all the holes of the template to ensure that all the holes of the template are unobstructed when the extruder is started, and add the nucleating agent normally to the small additive scale of the extruder and add the low melt index powder to the large additive scale; Step 2.2, start the extruder to pull the material, start the small additive scale and the large additive scale, add the nucleating agent at a normal ratio of 2000ppm, and feed the low melt index powder at 500-1000Kg / h; Step 2.3, set the melt pump inlet pressure to 2.8-3.0MPa, open the cylinder reversing valve to the template direction, and start pulling the material to the template; Step 2.4, increase the speed of the unloading rotary valve to 5r / min-8r / min; Step 2.5, observe the discharge of the die hole. If the die hole is blocked, open the cylinder reversing valve to the ground direction, reduce the speed of the unloading rotary valve to 3r / min, and after the discharge is stable, open the cylinder reversing valve to the mold plate direction again, and discharge the molten resin to the mold plate again; Step 2.6: Observe the resin melt temperature during the template drawing process. If the temperature exceeds 200°C, lower the hot oil temperature and then lower the extruder barrel temperature.

[0010] The specific process of step 3 is as follows: Step 3.1, after the template is pulled, open the cylinder reversing valve to the ground direction, restore the unloading load of the unloading rotary valve to 12t / h, repeatedly clean the template seepage, prepare for the pelletizer before closing the mold, and then prepare to close the pelletizer; Step 3.2, before the pelletizer is molded, set the pelletizer cutter speed to 500-600r / min, and the cutter advance and retreat pressure difference to 0.2-0.4MPa; Step 3.3, close the pelletizer mold, open the cylinder reversing valve to the template direction, increase the speed of the unloading rotary valve to 9-11r / min, and reduce the setting value of the melt pump inlet pressure from 2.8MPa to 2.0MPa.

[0011] The specific process of step 4 is as follows: Step 4.1, observe the shape of the pellets at the sampling port. If there are many large pellets in the pellets, start to adjust the extruder load by raising or lowering it; The specific process of step 4.1 is as follows: Specifically, reduce the load of the extruder to 30 t / h at a rate of 10-20 t / h in half an hour, and then increase the load of the extruder to 40-45 t / h at a rate of 10-20 t / h in half an hour. Continue to observe. If there are still many large particles in the pellets, repeat this operation.

[0012] Step 4.2: After the machine starts up normally, restore the related interlock bypass and modify the melt pump PID to the normal value.

[0013] The beneficial effects of the present invention are: The invention discloses an extruder start-up method for producing polypropylene thin-wall injection molding products. The method only adjusts the process parameters of a ZSK twin-screw extruder, is simple to operate, does not require additional modification, and has good universality. At the same time, by determining the optimal process parameters, the particles of the polypropylene thin-wall injection molding products finally obtained have a regular appearance, and effectively reduces the operating power consumption of the extruder pelletizer and the wear of the pelletizer cutter. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a process flow chart of the method for starting an extruder for producing polypropylene thin-wall injection molding products according to the present invention; Figure 2 The present invention is a schematic diagram of the positions of the shearing section and the homogenizing section in the method for starting up an extruder for producing polypropylene thin-wall injection molding products. DETAILED DESCRIPTION

[0015] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] The technical solution of the present invention is to provide a method for starting an extruder for producing polypropylene thin-wall injection molding products, such as Figure 1 As shown, the following steps are included: Step 1: Select a ZSK twin-screw extruder and set the initial working parameters of the extruder; Step 1.1, first modify the extruder barrel temperature alarm interlock value, such as Figure 2 As shown, the interior of the extruder barrel is a twin-screw, which is divided into a feeding section, a shearing section, a mixing section, a venting section, and a homogenizing section in the direction of raw material delivery. The temperature alarm interlocking value of the extruder barrel shearing section is modified to 160°C-180°C, and the temperature alarm interlocking value of the extruder barrel homogenizing section is modified to 140°C-160°C, which can prevent the barrel temperature from being too low and the phenomenon of chain parking when producing thin-walled injection molding products; Step 1.2, lowering the temperature of the extruder barrel to the operating temperature; Among them, the temperature of the shearing section of the extruder barrel is reduced to 200℃-220℃, the temperature of the homogenizing section is reduced to 180℃-200℃, and the temperature from the outlet of the extruder barrel to the template is reduced to 200℃-210℃. By lowering the temperature of the extruder barrel, it is beneficial to the molding and pelletizing of the molten resin.

[0017] Step 1.3, bypass the inlet and outlet pressure difference of the melt pump in the extruder, bypass the low torque of the main motor pelletizer, bypass the heating of the pelletizer and melt pump outlet section, and bypass the constant temperature time of the barrel section; Step 1.4, modify the PID parameters of the melt pump speed controller in the extruder, change the ratio to 2-3, and change the integral time to 25-40, to prevent the melt pump from stopping due to excessive pressure difference of the resin inlet and outlet of the melt pump when the extruder is started, and also to ensure that the melt pump speed can be increased as soon as possible when the extruder is started, and the die pressure can be established as soon as possible; Step 1.5, set the throttle valve opening of the extruder to 40-50 degrees, the pellet water temperature to 40-50℃, and the hot oil cooler temperature to 180-190℃, to ensure that when the extruder is started, the die pressure is increased and the water temperature is reduced, which is conducive to the rapid molding of the molten resin after it exits the die; Step 1.6, the speed controller of the material discharge rotary valve of the extruder is put into manual control, and the speed of the material discharge rotary valve is manually changed to 3-10r / min to ensure that when the extruder is started to pull the material to the template, the load can be established as soon as possible, and the die head pressure can be established as soon as possible; Step 2, start the extruder and pull the material to the template; Step 2.1, drill all holes in the template to ensure that all holes of the template are unobstructed when the extruder is started, and add nucleating agent normally to the small additive scale of the extruder, and add low melt index powder to the large additive scale; when the extruder is started, add nucleating agent normally and low melt index powder to prevent excessive oxidation and decomposition of the resin and prevent the melt index from being too high; Step 2.2, start the extruder to pull the material, start the small additive scale and the large additive scale, add the nucleating agent at a normal ratio of 2000ppm, and feed the low melt index powder at 500-1000Kg / h. When the extruder is started, add the nucleating agent normally and the low melt index powder to prevent excessive oxidation and decomposition of the resin and prevent the melt index from being too high; Step 2.3, set the melt pump inlet pressure to 2.8-3.0MPa, open the barrel reversing valve to the template direction, start pulling the material to the template, increase the overall pressure of the molten resin in the extruder barrel, and flush the template holes when pulling the material to the template; Step 2.4, increase the speed of the upstream discharge valve to 5-8r / min; Step 2.5, observe the discharge of the die hole. If the die hole is blocked, open the cylinder reversing valve to the ground direction, reduce the speed of the unloading rotary valve to 3r / min, and after the discharge is stable, open the cylinder reversing valve to the template direction again, and discharge the molten resin to the template again; Step 2.6: Observe the temperature of the resin melt during the template drawing process. If the temperature exceeds 200°C, reduce the temperature of the hot oil, and then reduce the temperature of the extruder barrel to increase the amount of molten resin passing through and flush the template holes; Step 3: After the template is pulled, clean the template for seepage, and close the pelletizer after cleaning; Step 3.1, after the template is pulled, open the direction of the cylinder reversing valve to the ground, restore the unloading load of the unloading rotary valve to 12t / h, repeatedly clean the template seepage, prepare for the pelletizer before closing the mold, and then prepare to close the pelletizer; Step 3.2, before the pelletizer is molded, set the pelletizer cutter speed to 500-600r / min, and the cutter advance and retreat pressure difference to 0.2-0.4MPa, to ensure that after the pelletizer is molded, the cutter fits tightly to the template, and to ensure that the cutter is in a high-speed rotation state when the molten resin exits the template to avoid entanglement of the cutter; Step 3.3, close the pelletizer mold, open the cylinder reversing valve to the template direction, increase the speed of the unloading rotary valve to 9-11r / min, and reduce the melt pump inlet pressure setting value from 2.8MPa to 2.0MPa to ensure that after the pelletizer mold is closed, the granulation load is established as soon as possible, and the template mold hole filling rate is increased as soon as possible to avoid mold hole blockage.

[0018] Step 4: Observe the shape of the pellets at the sampling port. If there are many large pellets, adjust the extruder load by raising or lowering it.

[0019] Step 4.1, observe the shape of the pellets at the sampling port. If there are many large pellets in the pellets, start to adjust the extruder load by lifting and lowering. Specifically, reduce the extruder load to 30t / h at a rate of 10-20t per half an hour, and then increase the extruder load to 40-45t / h at a rate of 10-20t per half an hour. Continue to observe. If there are still many large pellets in the pellets, continue to repeat this operation. In the case that the die hole is blocked after the pelletizer is closed, the blocked die hole can be cleared as soon as possible at an appropriate load lifting speed. Step 4.2, after the machine is started normally, the relevant interlock bypass is restored, and the melt pump PID is modified to a normal value. The present invention provides an extruder start-up method for producing polypropylene thin-wall injection molding products. The method only adjusts the process parameters of the ZSK twin-screw extruder, is simple to operate, does not require additional modification, and has good universality. At the same time, by determining the optimal process parameters, the final polypropylene thin-wall injection molding product particles have a regular appearance, and effectively reduce the operating power consumption of the extruder pelletizer and reduce the wear of the pelletizer cutter.

[0020] The present invention is used for the extruder start-up method of producing polypropylene thin-wall injection molding products, and the specific embodiments are as follows: Example 1 The method for starting up an extruder for producing polypropylene thin-wall injection molding products comprises the following steps: Step 1: Select a ZSK twin-screw extruder and set the initial working parameters of the extruder; Step 2, start the extruder and pull the material to the template; Step 3: After the template is pulled, clean the template and close the pelletizer after cleaning; Step 4: Observe the shape of the pellets at the sampling port. If there are many large pellets, adjust the extruder load by raising or lowering it.

[0021] Example 2 The method for starting up an extruder for producing polypropylene thin-wall injection molding products comprises the following steps: Step 1: Select a ZSK twin-screw extruder and set the initial working parameters of the extruder; The specific process of step 1 is as follows: Step 1.1, first modify the extruder barrel temperature alarm interlock value; The specific process of step 1.1 is as follows: The temperature alarm interlocking value of the extruder barrel shearing section is changed to 160℃-180℃, and the temperature alarm interlocking value of the extruder barrel homogenizing section is changed to 140℃-160℃; Step 1.2, lowering the temperature of the extruder barrel to the operating temperature; The specific process of step 1.2 is as follows: The temperature of the shearing section of the extruder barrel is reduced to 200℃-220℃, the temperature of the homogenizing section is reduced to 180℃-200℃, and the temperature from the outlet of the extruder barrel to the die plate is reduced to 200℃-210℃; Step 1.3, bypass the inlet and outlet pressure difference of the melt pump in the extruder, bypass the low torque of the main motor pelletizer, bypass the heating of the pelletizer and melt pump outlet section, and bypass the constant temperature time of the barrel section; Step 1.4, modify the PID parameters of the melt pump speed controller in the extruder, change the ratio to 2-3, and change the integral time to 25-40; Step 1.5, set the throttle valve opening of the extruder to 40-50 degrees, the pellet water temperature to 40-50°C, and the hot oil cooler temperature to 180-190°C; Step 2, start the extruder and pull the material to the template; Step 3: After the template is pulled, clean the template and close the pelletizer after cleaning; Step 4: Observe the shape of the pellets at the sampling port. If there are many large pellets, adjust the extruder load by raising or lowering it.

[0022] Example 3 The method for starting up an extruder for producing polypropylene thin-wall injection molding products comprises the following steps: Step 1: Select a ZSK twin-screw extruder and set the initial working parameters of the extruder; The specific process of step 1 is as follows: Step 1.1, first modify the extruder barrel temperature alarm interlock value; The specific process of step 1.1 is as follows: The temperature alarm interlocking value of the extruder barrel shearing section is changed to 160℃-180℃, and the temperature alarm interlocking value of the extruder barrel homogenizing section is changed to 140℃-160℃; Step 1.2, lowering the temperature of the extruder barrel to the operating temperature; The specific process of step 1.2 is as follows: The temperature of the shearing section of the extruder barrel is reduced to 200℃-220℃, the temperature of the homogenizing section is reduced to 180℃-200℃, and the temperature from the outlet of the extruder barrel to the die plate is reduced to 200℃-210℃; Step 1.3, bypass the inlet and outlet pressure difference of the melt pump in the extruder, bypass the low torque of the main motor pelletizer, bypass the heating of the pelletizer and melt pump outlet section, and bypass the constant temperature time of the barrel section; Step 1.4, modify the PID parameters of the melt pump speed controller in the extruder, change the ratio to 2-3, and change the integral time to 25-40; Step 1.5, set the throttle valve opening of the extruder to 40-50 degrees, the pellet water temperature to 40-50°C, and the hot oil cooler temperature to 180-190°C; Step 2, start the extruder and pull the material to the template; The specific process of step 2 is as follows: Step 2.1, drill all the holes of the template to ensure that all the holes of the template are unobstructed when the extruder is started, and add the nucleating agent normally to the small additive scale of the extruder and add the low melt index powder to the large additive scale; Step 2.2, start the extruder to pull the material, start the small additive scale and the large additive scale, add the nucleating agent at a normal ratio of 2000ppm, and feed the low melt index powder at 500-1000Kg / h; Step 2.3, set the melt pump inlet pressure to 2.8-3.0MPa, open the cylinder reversing valve to the template direction, and start pulling the material to the template; Step 2.4, increase the speed of the unloading rotary valve to 5r / min-8r / min; Step 2.5, observe the discharge of the die hole. If the die hole is blocked, open the cylinder reversing valve to the ground direction, reduce the speed of the unloading rotary valve to 3r / min, and after the discharge is stable, open the cylinder reversing valve to the mold plate direction again, and discharge the molten resin to the mold plate again; Step 2.6: Observe the resin melt temperature during the template drawing process. If the temperature exceeds 200°C, lower the hot oil temperature and then lower the extruder barrel temperature.

[0023] Step 3: After the template is pulled, clean the template and close the pelletizer after cleaning; Step 4: Observe the shape of the pellets at the sampling port. If there are many large pellets, adjust the extruder load by raising or lowering it.

[0024] Example 4 The method for starting up an extruder for producing polypropylene thin-wall injection molding products comprises the following steps: Step 1: Select a ZSK twin-screw extruder and set the initial working parameters of the extruder; The specific process of step 1 is as follows: Step 1.1, first modify the extruder barrel temperature alarm interlock value; The specific process of step 1.1 is as follows: The temperature alarm interlocking value of the extruder barrel shearing section is changed to 160℃-180℃, and the temperature alarm interlocking value of the extruder barrel homogenizing section is changed to 140℃-160℃; Step 1.2, lowering the temperature of the extruder barrel to the operating temperature; The specific process of step 1.2 is as follows: The temperature of the shearing section of the extruder barrel is reduced to 200℃-220℃, the temperature of the homogenizing section is reduced to 180℃-200℃, and the temperature from the outlet of the extruder barrel to the die plate is reduced to 200℃-210℃; Step 1.3, bypass the inlet and outlet pressure difference of the melt pump in the extruder, bypass the low torque of the main motor pelletizer, bypass the heating of the pelletizer and melt pump outlet section, and bypass the constant temperature time of the barrel section; Step 1.4, modify the PID parameters of the melt pump speed controller in the extruder, change the ratio to 2-3, and change the integral time to 25-40; Step 1.5, set the throttle valve opening of the extruder to 40-50 degrees, the pellet water temperature to 40-50°C, and the hot oil cooler temperature to 180-190°C; Step 2, start the extruder and pull the material to the template; The specific process of step 2 is as follows: Step 2.1, drill all the holes of the template to ensure that all the holes of the template are unobstructed when the extruder is started, and add the nucleating agent normally to the small additive scale of the extruder and add the low melt index powder to the large additive scale; Step 2.2, start the extruder to pull the material, start the small additive scale and the large additive scale, add the nucleating agent at a normal ratio of 2000ppm, and feed the low melt index powder at 500-1000Kg / h; Step 2.3, set the melt pump inlet pressure to 2.8-3.0MPa, open the cylinder reversing valve to the template direction, and start pulling the material to the template; Step 2.4, increase the speed of the unloading rotary valve to 5r / min-8r / min; Step 2.5, observe the discharge of the die hole. If the die hole is blocked, open the cylinder reversing valve to the ground direction, reduce the speed of the unloading rotary valve to 3r / min, and after the discharge is stable, open the cylinder reversing valve to the mold plate direction again, and discharge the molten resin to the mold plate again; Step 2.6: Observe the resin melt temperature during the template drawing process. If the temperature exceeds 200°C, lower the hot oil temperature and then lower the extruder barrel temperature.

[0025] Step 3: After the template is pulled, clean the template and close the pelletizer after cleaning; The specific process of step 3 is as follows: Step 3.1, after the template is pulled, open the cylinder reversing valve to the ground direction, restore the unloading load of the unloading rotary valve to 12t / h, repeatedly clean the template seepage, prepare for the pelletizer before closing the mold, and then prepare to close the pelletizer; Step 3.2, before the pelletizer is closed, set the pelletizer cutter speed to 500-600r / min and the cutter advance and retreat pressure difference to 0.2-0.4MPa; Step 3.3, close the pelletizer mold, open the cylinder reversing valve to the template direction, increase the speed of the unloading rotary valve to 9-11r / min, and reduce the setting value of the melt pump inlet pressure from 2.8MPa to 2.0MPa.

[0026] Step 4: Observe the shape of the pellets at the sampling port. If there are many large pellets, adjust the extruder load by raising or lowering it.

[0027] Example 5 The method for starting up an extruder for producing polypropylene thin-wall injection molding products comprises the following steps: Step 1: Select a ZSK twin-screw extruder and set the initial working parameters of the extruder; The specific process of step 1 is as follows: Step 1.1, first modify the extruder barrel temperature alarm interlock value; The specific process of step 1.1 is as follows: The temperature alarm interlocking value of the extruder barrel shearing section is modified to 160℃-180℃, and the temperature alarm interlocking value of the extruder barrel homogenizing section is modified to 140℃-160℃; Step 1.2, lowering the temperature of the extruder barrel to the operating temperature; The specific process of step 1.2 is as follows: The temperature of the shearing section of the extruder barrel is reduced to 200℃-220℃, the temperature of the homogenizing section is reduced to 180℃-200℃, and the temperature from the outlet of the extruder barrel to the die plate is reduced to 200℃-210℃; Step 1.3, bypass the inlet and outlet pressure difference of the melt pump in the extruder, bypass the low torque of the main motor pelletizer, bypass the heating of the pelletizer and melt pump outlet section, and bypass the constant temperature time of the barrel section; Step 1.4, modify the PID parameters of the melt pump speed controller in the extruder, change the ratio to 2-3, and change the integral time to 25-40; Step 1.5, set the throttle valve opening of the extruder to 40-50 degrees, the pellet water temperature to 40-50°C, and the hot oil cooler temperature to 180-190°C; Step 2, start the extruder and pull the material to the template; The specific process of step 2 is as follows: Step 2.1, drill all the holes of the template to ensure that all the holes of the template are unobstructed when the extruder is started, and add the nucleating agent normally to the small additive scale of the extruder and add the low melt index powder to the large additive scale; Step 2.2, start the extruder to pull the material, start the small additive scale and the large additive scale, add the nucleating agent at a normal ratio of 2000ppm, and feed the low melt index powder at 500-1000Kg / h; Step 2.3, set the melt pump inlet pressure to 2.8-3.0MPa, open the cylinder reversing valve to the template direction, and start pulling the material to the template; Step 2.4, increase the speed of the unloading rotary valve to 5r / min-8r / min; Step 2.5, observe the discharge of the die hole. If the die hole is blocked, open the cylinder reversing valve to the ground direction, reduce the speed of the unloading rotary valve to 3r / min, and after the discharge is stable, open the cylinder reversing valve to the mold plate direction again, and discharge the molten resin to the mold plate again; Step 2.6: Observe the resin melt temperature during the template drawing process. If the temperature exceeds 200°C, lower the hot oil temperature and then lower the extruder barrel temperature.

[0028] Step 3: After the template is pulled, clean the template for seepage, and close the pelletizer after cleaning; The specific process of step 3 is as follows: Step 3.1, after the template is pulled, open the cylinder reversing valve to the ground direction, restore the unloading load of the unloading rotary valve to 12t / h, repeatedly clean the template seepage, prepare for the pelletizer before closing the mold, and then prepare to close the pelletizer; Step 3.2, before the pelletizer is closed, set the pelletizer cutter speed to 500-600r / min and the cutter advance and retreat pressure difference to 0.2-0.4MPa; Step 3.3, close the pelletizer mold, open the cylinder reversing valve to the template direction, increase the speed of the unloading rotary valve to 9-11r / min, and reduce the setting value of the melt pump inlet pressure from 2.8MPa to 2.0MPa.

[0029] Step 4: Observe the shape of the pellets at the sampling port. If there are many large pellets, adjust the extruder load by raising or lowering it.

[0030] The specific process of step 4 is as follows: Step 4.1, observe the shape of the pellets at the sampling port. If there are many large pellets in the pellets, start to adjust the extruder load by raising or lowering it; Step 4.2: After normal startup, restore the related interlock bypass and modify the melt pump PID to the normal value.

[0031] Example 6 The method for starting up an extruder for producing polypropylene thin-wall injection molding products comprises the following steps: Step 1: Select a ZSK twin-screw extruder and set the initial working parameters of the extruder; The specific process of step 1 is as follows: Step 1.1, first modify the extruder barrel temperature alarm interlock value; The specific process of step 1.1 is as follows: The temperature alarm interlocking value of the extruder barrel shearing section is changed to 160℃-180℃, and the temperature alarm interlocking value of the extruder barrel homogenizing section is changed to 140℃-160℃; Step 1.2, lowering the temperature of the extruder barrel to the operating temperature; The specific process of step 1.2 is as follows: The temperature of the shearing section of the extruder barrel is reduced to 200℃-220℃, the temperature of the homogenizing section is reduced to 180℃-200℃, and the temperature from the outlet of the extruder barrel to the die plate is reduced to 200℃-210℃; Step 1.3, bypass the inlet and outlet pressure difference of the melt pump in the extruder, bypass the low torque of the main motor pelletizer, bypass the heating of the pelletizer and melt pump outlet section, and bypass the constant temperature time of the barrel section; Step 1.4, modify the PID parameters of the melt pump speed controller in the extruder, change the ratio to 2-3, and change the integral time to 25-40; Step 1.5, set the throttle valve opening of the extruder to 40-50 degrees, the pellet water temperature to 40-50°C, and the hot oil cooler temperature to 180-190°C; Step 2, start the extruder and pull the material to the template; The specific process of step 2 is as follows: Step 2.1, drill all the holes of the template to ensure that all the holes of the template are unobstructed when the extruder is started, and add the nucleating agent normally to the small additive scale of the extruder and add the low melt index powder to the large additive scale; Step 2.2, start the extruder to pull the material, start the small additive scale and the large additive scale, add the nucleating agent at a normal ratio of 2000ppm, and feed the low melt index powder at 500-1000Kg / h; Step 2.3, set the melt pump inlet pressure to 2.8-3.0MPa, open the cylinder reversing valve to the template direction, and start pulling the material to the template; Step 2.4, increase the speed of the unloading rotary valve to 5r / min-8r / min; Step 2.5, observe the discharge of the die hole. If the die hole is blocked, open the cylinder reversing valve to the ground direction, reduce the speed of the unloading rotary valve to 3r / min, and after the discharge is stable, open the cylinder reversing valve to the mold plate direction again, and discharge the molten resin to the mold plate again; Step 2.6: Observe the resin melt temperature during the template drawing process. If the temperature exceeds 200°C, lower the hot oil temperature and then lower the extruder barrel temperature.

[0032] Step 3: After the template is pulled, clean the template and close the pelletizer after cleaning; The specific process of step 3 is as follows: Step 3.1, after the template is pulled, open the cylinder reversing valve to the ground direction, restore the unloading load of the unloading rotary valve to 12t / h, repeatedly clean the template seepage, prepare for the pelletizer before closing the mold, and then prepare to close the pelletizer; Step 3.2, before the pelletizer is molded, set the pelletizer cutter speed to 500-600r / min, and the cutter advance and retreat pressure difference to 0.2-0.4MPa; Step 3.3, close the pelletizer mold, open the cylinder reversing valve to the template direction, increase the speed of the unloading rotary valve to 9-11r / min, and reduce the setting value of the melt pump inlet pressure from 2.8MPa to 2.0MPa.

[0033] Step 4: Observe the shape of the pellets at the sampling port. If there are many large pellets, adjust the extruder load by raising or lowering it.

[0034] The specific process of step 4 is as follows: Step 4.1, observe the shape of the pellets at the sampling port. If there are many large pellets in the pellets, start to adjust the extruder load by raising or lowering it; The specific process of step 4.1 is as follows: Specifically, reduce the load of the extruder to 30 t / h at a rate of 10-20 t / h in half an hour, and then increase the load of the extruder to 40-45 t / h at a rate of 10-20 t / h in half an hour. Continue to observe. If there are still many large particles in the pellets, repeat this operation.

[0035] Step 4.2: After the machine starts up normally, restore the related interlock bypass and modify the melt pump PID to the normal value.

Claims

1. A method for starting an extruder for producing polypropylene thin-wall injection molding products, characterized in that: The following steps are involved: Step 1: Select a ZSK twin-screw extruder and set the initial working parameters of the extruder; Step 2, start the extruder and pull the material to the template; Step 3: After the template is pulled, clean the template for seepage, and close the pelletizer after cleaning; Step 4: Observe the shape of the pellets at the sampling port. If there are many large pellets, adjust the extruder load by raising or lowering it.

2. The method for starting up an extruder for producing polypropylene thin-wall injection molding products according to claim 1, characterized in that: The specific process of step 1 is as follows: Step 1.1, first modify the extruder barrel temperature alarm interlock value; Step 1.2, lowering the temperature of the extruder barrel to the operating temperature; Step 1.3, bypass the inlet and outlet pressure difference of the melt pump in the extruder, bypass the low torque of the main motor pelletizer, bypass the heating of the pelletizer and melt pump outlet section, and bypass the constant temperature time of the barrel section; Step 1.4, modify the PID parameters of the melt pump speed controller in the extruder, change the ratio to 2-3, and change the integral time to 25-40; Step 1.5, set the throttle valve opening of the extruder to 40-50 degrees, the pellet water temperature to 40-50°C, and the hot oil cooler temperature to 180-190°C; Step 1.6, the speed controller of the feed rotary valve of the extruder is put into manual control, and the speed of the feed rotary valve is manually changed to set to 3-10r / min.

3. The method for starting up an extruder for producing polypropylene thin-wall injection molded products according to claim 2, characterized in that: The specific process of step 1.1 is as follows: The temperature alarm interlock value of the shearing section of the extruder barrel is modified to 160℃-180℃, and the temperature alarm interlock value of the homogenizing section of the extruder barrel is modified to 140℃-160℃.

4. The method for starting up an extruder for producing polypropylene thin-wall injection molding products according to claim 2, characterized in that: The specific process of step 1.2 is as follows: The temperature of the shearing section of the extruder barrel is reduced to 200℃-220℃, the temperature of the homogenizing section is reduced to 180℃-200℃, and the temperature from the outlet of the extruder barrel to the template is reduced to 200℃-210℃.

5. The method for starting up an extruder for producing polypropylene thin-wall injection molding products according to claim 1, characterized in that: The specific process of step 2 is as follows: Step 2.1, drill all the holes of the template to ensure that all the holes of the template are unobstructed when the extruder is started, and add the nucleating agent normally to the small additive scale of the extruder and add the low melt index powder to the large additive scale; Step 2.2, start the extruder to pull the material, start the small additive scale and the large additive scale, add the nucleating agent at a normal ratio of 2000ppm, and feed the low melt index powder at 500-1000Kg / h; Step 2.3, set the melt pump inlet pressure to 2.8-3.0MPa, open the cylinder reversing valve to the template direction, and start pulling the material to the template; Step 2.4, increase the speed of the unloading rotary valve to 5r / min-8r / min; Step 2.5, observe the discharge of the die hole. If the die hole is blocked, open the cylinder reversing valve to the ground direction, reduce the speed of the unloading rotary valve to 3r / min, and after the discharge is stable, open the cylinder reversing valve to the mold plate direction again, and discharge the molten resin to the mold plate again; Step 2.6: Observe the resin melt temperature during the template drawing process. If the temperature exceeds 200°C, lower the hot oil temperature and then lower the extruder barrel temperature.

6. The method for starting up an extruder for producing polypropylene thin-wall injection molding products according to claim 1, characterized in that: The specific process of step 3 is as follows: Step 3.1, after the template is pulled, open the cylinder reversing valve to the ground direction, restore the unloading load of the unloading rotary valve to 12t / h, repeatedly clean the template seepage, prepare for the pelletizer before closing the mold, and then prepare to close the pelletizer; Step 3.2, before the pelletizer is closed, set the pelletizer cutter speed to 500-600r / min and the cutter advance and retreat pressure difference to 0.2-0.4MPa; Step 3.3, close the pelletizer mold, open the cylinder reversing valve to the template direction, increase the speed of the unloading rotary valve to 9-11r / min, and reduce the setting value of the melt pump inlet pressure from 2.8MPa to 2.0MPa.

7. The method for starting up an extruder for producing polypropylene thin-wall injection molding products according to claim 1, characterized in that: The specific process of step 4 is as follows: Step 4.1, observe the shape of the pellets at the sampling port. If there are many large pellets in the pellets, start to adjust the extruder load by raising or lowering it; Step 4.2: After the machine starts up normally, restore the related interlock bypass and modify the melt pump PID to the normal value.

8. The method for starting up an extruder for producing polypropylene thin-wall injection molded products according to claim 7, characterized in that: The specific process of step 4.1 is as follows: Specifically, reduce the load of the extruder to 30 t / h at a rate of 10-20 t / h in half an hour, and then increase the load of the extruder to 40-45 t / h at a rate of 10-20 t / h in half an hour. Continue to observe. If there are still many large particles in the pellets, repeat this operation.

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