An extruder for producing a PET sheet

Abstract

The application provides an extruder for producing PET plate. The extruder screw assembly comprises a first screw and a second screw used in pairs, and the length direction of each columnar screw comprises a first screw end and a second screw end. The diameter of the first screw end of each screw is larger than the diameter of the second screw end, so that each screw forms a tapered structure. The two screws are matched from the first screw end to the second screw end, the central axis of the first screw and the central axis of the second screw form an included angle, and the included angle ranges from 10' to 1°20'. In the PET plate production process, the two screws rotate in opposite directions. In the application, the included angle between the two screws of the extruder screw assembly is greatly reduced compared with the included angle between the two screws of the tapered double extruder in the prior art, and the structure is close to that of the flat double extruder, but has a certain taper, thereby having the advantages of the flat double and the tapered double, and being capable of guaranteeing plasticizing effect and product processing efficiency, and being especially suitable for the production of PET plate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of processing machinery, in particular to an extruder for producing PET plate materials. BACKGROUND

[0002] Plate production needs to use an extruder, which is used for the preliminary plasticizing treatment of the blank and the extrusion of the blank as the front-end equipment of the plate production line.

[0003] In the prior art, the extruder includes a single-screw extruder and a double-screw extruder.

[0004] The single-screw extruder has one screw, and compared with the double-screw extruder, it has a simple structure and is convenient to operate and maintain. It has high production efficiency and low energy consumption, and is mainly suitable for the processing of various plastic materials such as polyethylene, polypropylene, and polyvinyl chloride, and can meet the demand for large-scale plastic processing.

[0005] The double-screw extruder is mainly used in the field of plate processing. The double-screw extruder has two screws, and according to the structure of the screws and the matching structure of the two screws, it can range from a parallel double extruder (parallel double-screw extruder) to a tapered double extruder (tapered double-screw extruder).

[0006] Among them, the two screws of the parallel double extruder are regular cylindrical, the diameters of the two screws are the same, the center distance is also the same, the kneading of the material is more uniform, and the energy consumption is higher than that of the tapered double extruder under the same capacity. However, due to the limitation of the small size of the center distance between the two screws, the pressure between the screws is small, resulting in small output torque and poor load capacity. The small end diameter of the tapered double extruder is different from the large end diameter, the two axes are at an angle, and the size of the center distance changes along the axis. The tapered double-screw extruder can be equipped with larger radial bearings and thrust bearings, and has large working torque and large load capacity.

[0007] Combining the characteristics of the double-screw extruder in the prior art, the pressure of the parallel double-screw extruder is small under the same screw size, the material is discharged quickly, and the efficiency is high. However, because the pressure is small, the plasticizing effect is poor, and it is necessary to increase the temperature to improve the plasticizing effect, but too high temperature can easily cause the material to denature, and in severe cases, the material may be over-burned, resulting in excessive plasticization. The plasticizing effect of the tapered double extruder is good, but the capacity is low.

[0008] According to different processing materials of the plate, the equipment of the plate production line can be improved. The polyester (PET) plate has the advantages of environmental protection and long service life. Different materials have different characteristics in the processing process. The PET material has high hardness and strength, which makes it brittle and rigid, and has a high glass transition temperature, which requires a high processing temperature, but has good environmental protection. The existing PET plate production line uses a same direction flat double screw for the extruder, and the screw needs to run at a high speed, but the production capacity is low, the power consumption is large, and the high production capacity of the PET plate cannot be realized, which limits the promotion and application of the PET plate. SUMMARY

[0009] The purpose of the present application is to solve the above technical problems, and provide an extruder for PET plate production, which has the advantages of good plasticizing of PET material and high processing efficiency.

[0010] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0011] An extruder for producing PET plate, comprising a cylinder and a screw assembly arranged in the cylinder, a pair of first screw and second screw, the first screw and the second screw are both columnar, and each columnar screw comprises a first screw end and a second screw end along the length direction of each columnar screw, the diameter of the first screw end of each screw is larger than the diameter of the second screw end, so that each screw forms a tapered structure;

[0012] The outer peripheral wall of each screw is provided with a thread, and the two screws are matched from the first screw end to the second screw end, the first screw center axis and the second screw center axis form an included angle, and the range of the included angle is 10' to 1°20';

[0013] The first screw is connected with a driving gear reduction box output shaft one, the second screw is connected with a driving gear reduction box output shaft two, the driving rotation direction of the driving gear reduction box output shaft one and the driving gear reduction box output shaft two is opposite, and in the process of producing the PET plate, the first screw on the left side rotates counterclockwise and the second screw on the right side rotates clockwise from the second screw end side as a reference.

[0014] In some embodiments of the present application, along the length direction of each screw, from the first screw end to the second screw end, each screw comprises: a first screw section, a first mixing section, a second screw section, a second mixing section and a third screw section; the screw where each screw section is located has a helical thread, and the screw where each mixing section is located has a plurality of tooth-shaped threads, the tooth-shaped threads are arranged in a circle around the circumference of the screw, and each tooth-shaped thread comprises a plurality of tooth-shaped protrusions arranged at intervals in the circumferential direction.

[0015] In some embodiments of the present application, from the first screw end to the second screw end, the first screw section comprises a feeding section, a first temperature increasing section and a second temperature increasing section, the number of threads of the feeding section, the first temperature increasing section and the second temperature increasing section are equal, and the pitch and the size of the screw flanks in the axial direction of the screw are sequentially reduced.

[0016] In some embodiments of the present application, from the first screw end to the second screw end, the second screw section comprises a first exhaust section and a compression section; the first exhaust section is provided with an exhaust assembly at the corresponding position of the cylinder, which is used to exhaust the gas inside the cylinder to the outside of the cylinder.

[0017] In some embodiments of the present application, the number of threads of the first exhaust section and the compression section are equal, and the pitch and the size of the screw flanks in the axial direction of the screw are sequentially reduced.

[0018] In some embodiments of the present application, from the first screw end to the second screw end, the third screw section comprises a plasticizing section, a second exhaust section and a discharging section; the second exhaust section is provided with an exhaust assembly at the corresponding position of the cylinder, which is used to exhaust the gas inside the cylinder to the outside of the cylinder.

[0019] In some embodiments of the present application, the plasticizing section comprises a backflow section and a material blocking section, and at least part of the screw flanks in the backflow section are formed with backflow grooves.

[0020] In some embodiments of the present application, the lead of the material blocking section is smaller than the lead of the backflow section, the length of the backflow section is greater than the length of the material blocking section and less than twice the length of the material blocking section.

[0021] In some embodiments of the present application, along the length direction of each screw, the third screw section comprises a plasticizing section, a second exhaust section and a discharging section, along the length direction of each screw, the discharging section comprises a first discharging section and a second discharging section, the pitch of the first discharging section is greater than the pitch of the second discharging section, the number of threads of the first discharging section is less than the number of threads of the second discharging section, and at least part of the screw flanks of the first discharging section are formed with backflow grooves.

[0022] In some embodiments of the present application, the temperature of the extruder in the first screw section is 210-260℃, the temperature of the extruder from the first mixing section to the second screw section is 230-280℃, the temperature of the extruder in the second exhaust section and the discharging section is 190-250℃, and the temperature decreases from the second exhaust section to the discharging section.

[0023] Compared with the prior art, the technical advantages of the present application are that:

[0024] 1. The twin-screw structure in this invention is defined as a light conical flat twin-screw structure. The included angle between the twin screws in the screw assembly of this invention is significantly reduced compared to the included angle between the screws in a conical twin extruder in the prior art, achieving a structure similar to a flat twin extruder, but with a certain degree of taper, thus combining the advantages of both flat and conical twin extruders, ensuring plasticizing effect and product processing efficiency.

[0025] 2. By improving the screw structure in the extruder according to the characteristics of PET material, suitable shear force can be provided for the plasticization of PET material, thereby improving the plasticization effect and efficiency, while reducing the energy consumption of the extrusion process. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the twin-screw assembly in an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram showing the distribution of the screw segments along the axial direction in an embodiment of this application;

[0029] Figure 3 for Figure 2 Cross-sectional view of the AA section;

[0030] Figure 4 for Figure 2 Cross-sectional view of the BB section;

[0031] Figure 5 This is a schematic diagram of the extruder in an embodiment of the present invention;

[0032] In the above figures:

[0033] 1-Barrel;

[0034] 2-First screw, 201-Feed section, 202-First heating section, 203-Second heating section, 204-First mixing section, 205-First exhaust section, 206-Compression section, 207-Second mixing section, 208-Toothed protrusion, 209-Reflux section, 2091-Reflux groove, 210-Baffle section, 211-Second exhaust section, 212-First discharge section, 213-Second discharge section, 214-Exhaust device, 215-First transition section, 216-Second transition section;

[0035] 3-Second screw. DETAILED DESCRIPTION

[0036] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application.

[0037] It should be noted that when an element is referred to as being "disposed on", "connected to", another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0038] It should be understood that the terms "upper", "lower", "bottom", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0039] The terms "first", "second" are only for descriptive purposes and do not imply relative importance.

[0040] In the prior art, each screw of the conical twin extruder is a conical screw. The structure size of the common conical twin extruder screw includes the following types:

[0041] In the prior art, each screw of the conical twin extruder is a conical screw, including a larger diameter end and a smaller diameter end. The structure size of the common conical twin extruder screw includes the following types. The larger diameter end is 100 mm in diameter, and the corresponding smaller diameter end is about 50 mm in diameter; the larger diameter end is 132 mm in diameter, and the corresponding smaller diameter end is about 65 mm in diameter; the larger diameter end is 188 mm in diameter, and the corresponding smaller diameter end is about 92 mm in diameter; the larger diameter end is 220 mm in diameter, and the corresponding smaller diameter end is about 110 mm in diameter. According to the design idea of the existing conical twin extruder screw, generally, the diameter of the larger diameter end is designed to be about 2 times the diameter of the smaller diameter end. The characteristic of this design structure is that the taper of the screw is large, and the shear force between the two screws is large, so the material is relatively easy to plasticize. However, the disadvantage is that it is easy to cause over-plasticization. Especially for some materials with high plasticization requirements, the use of the conical twin extruder in the prior art has the problem that the processing quality is difficult to control.

[0042] The material's journey also affects the time of plasticization, so in order to solve the problem of over-plasticization, the screw of the conical twin extruder is usually designed to be relatively short. The length-diameter ratio is generally below 22:1 of the medium diameter. However, the too short screw affects the output of the extruder.

[0043] Because the conical twin screw machine has a conical taper of nearly one-half, the space inside the screw is getting smaller and smaller during the forward movement of the material, so the pressure is getting larger and larger. Therefore, the pressure needs to be controlled during the production process of the main machine. If the pressure cannot be controlled, fluctuations will occur, resulting in poor stability. The above is the description of the advantages and disadvantages of the conical twin screw machine.

[0044] The present application provides an extruder for producing PET plate, comprising a barrel 1 and a screw assembly arranged in the barrel 1. In the present application, a double screw assembly is adopted in the extruder.

[0045] The structure of the screw assembly is as follows Figure 1 , comprising a pair of first screw 2 and second screw 3, the first screw 2 and the second screw 3 are both cylindrical, and each cylindrical screw comprises a first screw end and a second screw end along the length direction of each cylindrical screw, the diameter of the first screw end of each screw is larger than that of the second screw end, so that each screw forms a conical structure.

[0046] The improvement of the present application lies in improving the taper structure of the screw in the prior art, so that the double screw has the advantages of flat double extruder and conical double extruder after cooperation. It should be understood that the first screw 2 and the second screw 3 are the same structure. Hereinafter, the structure of one screw will be taken as an example to specifically illustrate the structure of the screw.

[0047] Each screw has a very small taper close to a flat screw (i.e. an equal-diameter cylindrical screw), and the taper is very small relative to the length of the screw. The outer peripheral wall of each screw is provided with a thread, and the two screws are cooperated from the first screw end to the second screw end, the first screw center axis and the second screw center axis form an included angle, the included angle α ranges from 10' to 1°20', and in the preferred embodiment, the included angle is 30' to 50'. In the prior art, in order to pursue the effect of extrusion shear, the included angle of the screw of the conical double extruder is usually designed to be relatively large. In the present application, the included angle between the double screws of the screw assembly is greatly reduced compared with the included angle between the screws of the conical double extruder in the prior art, which is close to the structure of the flat double extruder, but has a certain taper, so as to have the advantages of the flat double and the advantages of the conical double.

[0048] It should be understood that the double screw structure of the present application is a new type of screw structure between flat screw and conical screw, and the double screw structure in the present application is defined as a light conical flat double screw structure.

[0049] The taper of the existing conical screw is large, the diameter of the screw changes greatly from the feeding end to the discharging end, the shearing force generated on the material is large, but when used for processing PET material, over-plasticization or paste phenomenon may occur if not controlled properly; the outer diameter of the existing flat screw is equal, the shearing force on the material is relatively stable but the shearing force is limited, which may cause the plasticization process to be insufficient when used for processing PET material, and the PET material cannot reach a good plasticization state. By adopting the flat double screw structure in the present application, the taper is smaller and the length is longer than that of the existing conical screw, which can provide suitable shearing force for PET material plasticization, so that the PET material can be more fully plasticized, and at the same time, over-plasticization phenomenon will not occur.

[0050] Generally, the screw end with a smaller diameter of the conical double screw (corresponding to the second screw end in the present application) is the discharging end, and the screw end with a larger diameter (corresponding to the first screw end in the present application) is the feeding end.

[0051] Generally, the extruder screw is driven by a reduction gearbox. In some embodiments of the present application, the first screw is connected to the output shaft one of the drive gear reduction gearbox, the second screw is connected to the output shaft two of the drive gear reduction gearbox, and the driving rotation directions of the output shaft one and the output shaft two of the drive gear reduction gearbox are opposite. During the production of PET plates, the first screw on the left side rotates counterclockwise and the second screw on the right side rotates clockwise, with the second screw end side as the reference (i.e., the discharging end is observed).

[0052] In the prior art, the PET material extrusion molding process is subject to the structure of the screw, and both screws rotate in the same direction and must rotate at high speed during the extrusion process, which results in high energy consumption but low productivity. In the production of PET material, the present application adopts the opposite rotation scheme of the two screws, which has a lower rotation speed than the existing same direction scheme, for example, the rotation speed can be 10-40 r / min, which makes the energy consumption smaller but the productivity higher.

[0053] In some embodiments of the present application, the diameter of the first screw end of each screw ranges from 130 to 250 mm, and the diameter of the first screw end of the two screws is the same.

[0054] In some embodiments of the present application, the diameter of the second screw end of each screw ranges from 100 to 190 mm, and the diameter of the second screw end of the two screws is the same.

[0055] Generally, the productivity of the extruder is related to the length of the screw, therefore, in some embodiments of the present application, in order to ensure the productivity of the screw equipment, the length of the screw is 3-7 m.

[0056] In some embodiments of the present application, the length-diameter ratio of each screw is 30:1 to 35:1, the length-diameter ratio is the ratio of the length of the screw to the mean diameter of the screw, and the mean diameter of the screw is the average of the diameter of the first screw end and the diameter of the second screw end. For example, the diameter of the first end of the screw is 190 mm, the diameter of the second end is 150 mm, and the mean diameter of the screw is 170 mm. The length of each screw can be further selected according to the length-diameter ratio of the screw.

[0057] For example, the ratio of the length of each screw to the mean diameter can be 31:1, 32:1, 33:1, 34:1, etc., and the length can be 4 m, 4.5 m, 5 m, 5.5 m, etc. According to the length of the screw and the ratio of the length to the mean diameter, the outer diameter value (the maximum value of the outer diameter) of the feeding end 201 of the screw and the outer diameter value (the minimum value of the outer diameter) of the discharging end can be determined, thereby determining the outer dimensions of the screw.

[0058] The light taper parallel double screw machine type proposed in the present application can lengthen the screw of the taper double extruder and reduce the taper, thereby solving the problem of over-plasticization of the taper double. It should be understood that the size ratio of the two screw heads of the double screw is improved, and the size ratio of the two screw heads is no longer close to 2, but is reduced, for example, the first screw end is 200 mm, and the second screw end is 150 mm, thereby controlling the taper. By reducing and retaining the appropriate taper of the taper double screw, the appropriate pressure is retained, and the advantage of easy plasticization of the taper double screw is controlled within a proper range. Since the screw taper is small, the degree of plasticization is reduced, and the present application achieves the plasticization requirement by increasing the appropriate length.

[0059] Based on the above screw length configuration structure, the screw is rotated in opposite directions to manufacture the PET plate, which can ensure the plasticization effect, processing quality and processing efficiency of the PET plate. In addition, the taper and length of the screw are limited in the present application, the screw has a longer length and a smaller taper than the existing taper screw, so that the combination of the shear force provided by the screw and the action time of the PET material is optimized, the plasticization process of the PET material is more sufficient, the plasticization effect is improved, and the required processing state is obtained.

[0060] The present application further designs the structure of each thread segment of the extruder screw. Taking the design of the thread segment on the first screw 2 as an example to illustrate the structure of the thread segment. The structure of the thread segment on the second screw 3 is the same as that of the first screw 2, which will not be described again.

[0061] The functions of each section of the screw are realized by the design of the screw flight on the screw (including pitch, lead, and number of flights), the design of the length of the screw, and the temperature control of the barrel 1. It can be understood that the application focuses on adjusting the distribution of each functional section on the screw after the improvement of the screw structure, rather than on how to realize the functions of each section. Those skilled in the art can realize the scheme for realizing the corresponding functions of each section with reference to the prior art. Matters not described in the application should not be considered as insufficient disclosure.

[0062] In some embodiments of the application, along the length direction of the first screw 2, from the first screw end to the second screw end, the first screw 2 comprises a first screw section, a first mixing section 204, a second screw section, a second mixing section 207, and a third screw section. Among them, the first mixing section 204 and the second mixing section 207 are used for mixing and finely processing the material.

[0063] The initial state of the material when added to the extruder 2 is solid or granular or powdery, and the barrel 1 of the extruder is provided with a heating ring corresponding to each section of the screw to control the temperature inside the barrel 1 of each section. In this embodiment, based on the improvement of the screw structure, the functions of each section of the screw from the material inlet end to the material outlet end are rearranged, two mixing sections and two exhaust sections are provided, so that the mixing of PET material before entering the plasticizing section is more sufficient, and the exhaust is also more thorough.

[0064] Each screw section has a helical thread, and each mixing section has a plurality of toothed threads on the screw. The toothed threads are arranged in a circle around the circumference of the screw, and each toothed thread includes a plurality of toothed protrusions 208 arranged at intervals in the circumferential direction.

[0065] When applied to an extruder, the first screw section is located near the material inlet end of the extruder and is used for preheating the material. The length of the first screw section accounts for 30% to 40% of the total length of the first screw 2, and the pitch of the first screw section is 50 to 65 mm. From the first screw end to the second screw end, the first screw section includes a material inlet section 201, a first temperature rising section 202, and a second temperature rising section 203.

[0066] The feeding section 201, the first temperature increasing section 202 and the second temperature increasing section 203 have equal number of threads, and the pitch and the size of the thread in the axial direction of the screw gradually decrease. The length of the feeding section 201 is greater than the length of the first temperature increasing section 202, and the length of the first temperature increasing section 202 is greater than the length of the second temperature increasing section 203. The feeding section 201, the first temperature increasing section 202 and the second temperature increasing section 203 have equal number of threads, and the pitch and the size of the thread in the axial direction of the first screw gradually decrease. In the embodiment, the first screw section has a relatively long length, so that the material can be sufficiently heated before being mixed, and the pitch and the size of the thread of the first screw section gradually decrease, so that the material can be heated more sufficiently and better transition to the first mixing section 204.

[0067] In the preferred embodiment, the number of threads of the feeding section 201, the first temperature increasing section 202 and the second temperature increasing section 203 is 3, the lead is 140-190mm, and the pitch is 45-70mm.

[0068] In some embodiments of the present application, from the direction of the first screw end to the second screw end, the second screw section includes a first exhaust section 205 and a compression section 206. The first exhaust section 205 is provided with an exhaust assembly corresponding to the position of the cylinder 1, which is used to exhaust the gas inside the cylinder 1 to the outside of the cylinder 1. The compression section 206 is used to apply pressure to the material to compress the material.

[0069] In some embodiments of the present application, the number of threads of the first exhaust section 205 and the compression section 206 is equal, and the pitch and the size of the thread in the axial direction of the screw gradually decrease. The pitch of the compression section 206 is smaller than the pitch of the first exhaust section 205 and greater than the interval of the stirring assembly of the first mixing section 204 and the second mixing section 207. The size of the thread of the compression section 206 in the axial direction of the first screw 2 is smaller than the length of the tooth-shaped protruding part 208 of the first mixing section 204 and the second mixing section 207 in the axial direction of the first screw 2. The small pitch and the small size of the thread of the compression section 206 can enhance the extrusion of the material, so that the material is compressed more tightly.

[0070] In some embodiments of the present application, along the length direction of each screw, the third screw section includes a plasticizing section, a second exhaust section and a discharge section. The plasticizing section is used to provide shear force to make the material compressed by the compression section 206 in a molten state. The discharge section is used to output the material in the molten state from the extruder into the mold. Along the length direction of each screw, the discharge section includes a first discharge section 212 and a second discharge section 213. The pitch of the first discharge section 212 is greater than the pitch of the second discharge section, and the number of threads of the first discharge section 212 is less than the number of threads of the second discharge section 213. At least part of the thread of the first discharge section 212 is formed with a backflow groove.

[0071] In some embodiments of the present application, the plasticizing section further comprises a backflow section 209 and a material blocking section 210 in the direction from the first screw end to the second screw end. At least part of the screw flight in the backflow section 209 is provided with a backflow groove 2091. The lead of the material blocking section 210 is smaller than the lead of the backflow section 209. The length of the backflow section 209 is greater than the length of the material blocking section 210 and less than twice the length of the material blocking section 210. The backflow section 209 can cause part of the material to form a backflow in the first screw 2. During the backflow process, the material of different levels and time entering the first screw 2 can be fully mixed, the residence time of the material in the plasticizing section is increased, heat transfer is promoted, the plasticizing of the material is further promoted, and the material can reach a good plasticizing state. The lead of the backflow section 209 can be 80-100 mm (for example, 90 mm), the lead of the material blocking section 210 is smaller, which can be 40-55 mm (for example, 50 mm), the axial advancing speed of the material in the material blocking section 210 is relatively slow, the pressure can be adjusted, the material is prevented from excessive backflow, the material flowing out of the backflow section 209 can be orderly and stably advanced in the material blocking section 210 according to the predetermined direction, and the plasticizing process is more stable. In addition, the design of the lengths of the backflow section 209 and the material blocking section 210 can find a balance point between the plasticizing efficiency and the plasticizing effect, so that the material can be fully processed and the extrusion process can be efficiently completed.

[0072] In some embodiments of the present application, the lead of the material blocking section 210 is smaller than the lead of the backflow section 209, and the length of the backflow section 209 is greater than the length of the material blocking section 210 and less than twice the length of the material blocking section 210.

[0073] In some embodiments, the screw pitch and screw flight of the first venting section 205 and the second venting section 211 are the same, and the screw pitch and screw flight of the first venting section 205 and the second venting section 211 in the axial direction of the screw are greater than the screw pitch and screw flight of other sections of the screw in the axial direction of the screw. The length of the second venting section 211 is greater than the length of the first venting section 205 and less than twice the length of the first venting section 205. The large screw pitch and large size screw flight of the venting section can increase the residence time of the material in the venting section and reduce the pressure, which is helpful for the gas in the material to be discharged out of the barrel 21. In addition, two venting sections are designed respectively at the rear end of the first mixing section 204 and the rear end of the plasticizing section, which is helpful for improving the plasticizing effect of the PET material, and the second venting section 211 has a relatively long length, which is helpful for the gas in the material after plasticizing to be fully discharged, further reducing defects such as bubbles in the product.

[0074] In some embodiments, three venting devices are provided, one of which is provided at the first venting section 205, and the other two are provided side by side at the second venting section 211 in the processing direction.

[0075] In some embodiments, a first transition section 215 is arranged between the first mixing section 204 and the first exhaust section 205, and a second transition section 216 is arranged between the second mixing section 207 and the plasticizing section; the pitch of the first transition section 215 is greater than the interval of the stirring assembly of the first mixing section 204 and less than the pitch of the first exhaust section 205; the pitch of the second transition section 215 is greater than the interval of the stirring assembly of the second mixing section 207 and greater than the pitch of the plasticizing section.

[0076] In some embodiments, the discharge section comprises a first discharge section 212 and a second discharge section 213 arranged behind the second exhaust section 211 along the processing direction; the pitch of the first discharge section 212 is greater than the pitch of the second discharge section 213, and the number of flights of the first discharge section 212 is less than the number of flights of the second discharge section 213; the length of the first discharge section 212 is greater than twice the length of the second discharge section 213. The design of the first discharge section 212 and the second discharge section 213 in the discharge section can efficiently transport the material and establish stable pressure, so that the material is smoothly transported forward, and the quality problem of the product caused by pressure fluctuation is avoided.

[0077] In some embodiments of the present application, the temperature of the extruder at the first screw section is 210-260℃, the temperature from the first mixing section to the second screw section is 230-280℃, the temperature of the second exhaust section and the discharge section is 190-250℃, and the temperature decreases from the second exhaust section to the discharge section. This temperature configuration can better adapt to the production of PET material plates.

[0078] The process of using the present application for PET plate production is as follows.

[0079] The mixture of PET material and auxiliary materials is mixed with calcium powder in a ratio of 1:2-1:5;

[0080] The mixed material is fed into the extruder for extrusion molding, and the rotation directions of the two screws of the extruder are opposite, and the rotation speed is 10-40 r / min;

[0081] The material plasticized by the extruder enters the mold for shaping, and the temperature of the mold is 220-260℃;

[0082] The plate blank after the mold forming process enters the calender for calendering treatment, and the temperature of the calender roll is 180-250℃;

[0083] The plate blank output by the calender is cut to form a PET plate.

[0084] The present application can improve the plasticizing process of PET material, such as the PET material extruded by using the existing extruder, the plasticizing process is not easy to control, the problem of insufficient plasticizing or over plasticizing is easy to occur, the current fluctuation is large, the product quality is unstable and the production capacity is low. The production quality of the PET plate is improved.

[0085] The above merely describes the preferred embodiments of the present application, and is not used to limit the present application, any modification, equivalent replacement and improvement within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. An extruder for producing a PET sheet material, characterized in that, The extruder comprises a barrel and a screw assembly arranged in the barrel, a first screw and a second screw used in pairs, each of the first screw and the second screw being columnar and comprising a first screw end and a second screw end along the length direction of each columnar screw, the diameter of the first screw end of each screw being larger than the diameter of the second screw end, so that each screw forms a tapered structure; Each screw is provided with a thread on the outer peripheral wall, and the two screws are matched from the first screw end to the second screw end, the central axis of the first screw and the central axis of the second screw form an included angle, the range of the included angle is 10' to 1°20'; The first screw is connected with a driving gear reduction box output shaft one, the second screw is connected with a driving gear reduction box output shaft two, the driving rotation directions of the driving gear reduction box output shaft one and the driving gear reduction box output shaft two are opposite, and in the process of producing the PET plate, the first screw on the left side rotates counterclockwise and the second screw on the right side rotates clockwise with the second screw end as a reference. Along the length direction of each screw, from the first screw end to the second screw end, each screw comprises a first screw section, a first mixing section, a second screw section, a second mixing section and a third screw section. From the first screw end to the second screw end, the second screw section comprises a first exhaust section and a compression section, and the third screw section comprises a plasticizing section, a second exhaust section and a discharge section. The pitch and the size of the screw flight of the first exhaust section and the second exhaust section are the same, the pitch and the size of the screw flight of the first exhaust section and the second exhaust section in the axial direction of the screw are larger than the pitch and the size of the screw flight of each of the other sections of the screw in the axial direction of the screw, and the length of the second exhaust section is greater than the length of the first exhaust section and less than twice the length of the first exhaust section. The plasticizing section comprises a backflow section and a material blocking section, at least part of the screw flights in the backflow section are provided with backflow grooves, the lead of the material blocking section is smaller than the lead of the backflow section, and the length of the backflow section is greater than the length of the material blocking section and less than twice the length of the material blocking section.

2. The extruder for producing a PET sheet according to claim 1, wherein, Each screw section has a helical thread, and each mixing section has a plurality of toothed threads, the toothed threads are arranged in a circle around the circumference of the screw, and each toothed thread comprises a plurality of toothed protrusions arranged at intervals in the circumferential direction.

3. The extruder for producing a PET sheet according to claim 2, wherein From the first screw end to the second screw end, the first screw section comprises a feeding section, a first temperature rising section and a second temperature rising section, the number of threads of the feeding section, the first temperature rising section and the second temperature rising section is equal, and the pitch and the size of the screw flight in the axial direction of the screw decrease in turn.

4. The extruder for producing a PET sheet according to claim 2, wherein An exhaust assembly is arranged at the position corresponding to the first exhaust section of the barrel, for exhausting the gas in the barrel to the outside of the barrel.

5. The extruder for producing a PET sheet according to claim 2, wherein An exhaust assembly is arranged at the position corresponding to the second exhaust section of the barrel, for exhausting the gas in the barrel to the outside of the barrel.

6. The extruder for producing a PET sheet according to claim 2, wherein Along the length direction of each screw rod, the third screw rod section comprises a plasticizing section, a second degassing section and a discharge section, along the length direction of each screw rod, the discharge section comprises a first discharge section and a second discharge section, the screw pitch of the first discharge section is greater than that of the second discharge section and the number of flights of the first discharge section is less than that of the second discharge section, and backflow grooves are formed on at least part of the flights of the first discharge section.

7. The extruder for producing a PET sheet according to claim 6, wherein The temperature of the extruder at the first screw rod section is 210-260 ℃, the temperature from the first plasticizing section to the second screw rod section is 230-280 ℃, the temperature of the second degassing section and the discharge section is 190-250 ℃, and the temperature decreases from the second degassing section to the discharge section.

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