Equipment and process for reducing B value in PBT (polybutylene terephthalate) product

Abstract

The invention discloses equipment and a process for reducing a B value in a PBT (Polybutylece Terephthalate) product, and relates to the technical field of polycondensation kettles for producing PBT. A main rotating shaft and a rotating frame are rotationally arranged in a kettle body, a hollow screw is arranged on the rotating frame, and a guide cylinder which can be driven by the main rotating shaft to lift is arranged at the bottom of the hollow screw; a stirring sleeve with a plurality of one-way sprayers on the outer wall is arranged at the bottom of the movable barrel, the main rotating shaft drives the two guide barrels on the opposite sides to do reverse reciprocating motion, a catalyst storage barrel is arranged at the top of the rotating frame, conveying pipelines are connected to the bottom of the catalyst storage barrel, and the conveying pipelines are rotationally connected to the tops of the hollow screws in a one-to-one correspondence mode. A one-way discharge valve is arranged on the conveying pipeline close to the catalyst storage barrel, a communicating pipe is connected between the conveying pipelines connected with the opposite hollow screws and below the one-way discharge valve, and a valve is arranged on the communicating pipe. The catalyst can be quickly and uniformly distributed, local overheating or reaction caused by non-uniform distribution of the catalyst is avoided, and the B value in the PBT product is effectively reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of PBT product processing equipment, and specifically relates to an apparatus and process for reducing the B value in PBT products, and particularly to a polycondensation reactor for producing PBT products. Background Art

[0002] PBT is an engineering plastic with high heat resistance, good chemical resistance and fatigue resistance, and is widely used in industrial fields such as electronics, automobiles, and aerospace. During the production process of PBT products, the B value is the yellowness index, which is an important indicator for measuring PBT products and also an important indicator affecting the final form of the products. The main process of the existing synthesis process of PBT is to carry out an esterification reaction of terephthalic acid and 1,4-butanediol at high temperature in the presence of a catalyst to generate dibutyl terephthalate, and then the dibutyl terephthalate generated by the esterification reaction needs to be further subjected to a polycondensation reaction to generate high-molecular-weight PBT. Finally, the PBT is subjected to subsequent treatment to obtain the required PBT product.

[0003] The main existing means for reducing the B value are: selecting monomer raw materials with high purity and good color to solve the problem of yellowing of the produced PBT from the source; or adding heat stabilizers and ultraviolet absorbers and other measures to reduce the generation of yellowing, thereby reducing the B value.

[0004] When the existing polycondensation reactor used for PBT production is feeding materials, generally, terephthalic acid and 1,4-butanediol are first added and stirred evenly, and then the catalyst is directly added from the feeding port. Through the stirring of the stirrer, the catalyst can be evenly diffused into the reaction solution. However, in this adding process, local accumulation of the catalyst will occur. Even if it is quickly stirred and dispersed, due to the fast reaction rate at the position with more catalyst and the slow reaction rate at the part with less catalyst, and the reaction is an exothermic reaction, it is easy to cause local overheating before the catalyst is stirred evenly, resulting in yellowing of the local overheated product. Furthermore, even if it is mixed evenly in the subsequent reaction, it cannot be compensated, resulting in too high a B value in the produced PBT product. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides an apparatus and process for reducing the B value in PBT products. The apparatus can gradually and dispersedly add the catalyst into the reaction solution, effectively avoiding local overheating caused by uneven distribution of the catalyst, effectively avoiding yellowing of the product caused by local overheating, and effectively reducing the B value in PBT products.

[0006] To solve the above technical problems, the present invention is solved by the following technical solutions: A device for reducing the B value in PBT products, including a kettle body, a main rotating shaft is rotatably arranged in the kettle body, a rotating frame is rotatably arranged in the kettle body, the rotating frame is driven by a first motor fixed on the kettle body, the main rotating shaft passes through the rotating frame, and the main rotating shaft is driven by a second motor fixed on the rotating frame. At least one group of hollow screws are rotatably arranged on opposite sides of the rotating frame. An activity cylinder is in threaded cooperation with the outer side of the bottom of the hollow screw. A stirring sleeve with a plurality of one-way nozzles on the outer wall is arranged at the bottom of the activity cylinder. A guide rod in the same direction as the activity cylinder is arranged on the side of the stirring sleeve. A guide cylinder is arranged on the rotating frame, and the guide rod is movably inserted into the guide cylinder. A first transmission mechanism is arranged between the main rotating shaft and the hollow screw. The main rotating shaft drives the two opposite guide cylinders to reciprocate in opposite directions. A catalyst storage barrel is arranged at the top of the rotating frame. The bottom of the catalyst storage barrel is connected with a feeding pipeline. The feeding pipelines are rotatably connected to the tops of the hollow screws one by one. A one-way discharging valve is arranged on the feeding pipeline near the catalyst storage barrel. A communicating pipe is connected between the feeding pipelines connecting the opposite hollow screws below the one-way discharging valve. A valve is arranged on the communicating pipe. When this device for reducing the B value in PBT products processes PBT products, a catalyst is pre-added into the catalyst storage barrel, and then terephthalic acid and 1,4-butanediol are added into the kettle body. After closing the valve, the first motor and the second motor are started to drive the rotating frame and the main rotating shaft to rotate forward and backward. There is a speed difference between the rotating frame and the main rotating shaft. When the main rotating shaft rotates, the hollow screw is driven to rotate through the first transmission mechanism. The rotation of the hollow screw drives the two opposite guide cylinders to reciprocate in opposite directions. A structure similar to a piston is formed between the guide cylinder and the hollow screw. When the guide cylinder descends, the volume of the cavity between the guide cylinder and the hollow screw expands, sucking out the catalyst from the catalyst storage barrel. When the guide cylinder ascends, the volume of the cavity between the guide cylinder and the hollow screw decreases, and the catalyst is sprayed out from the one-way nozzles. Since the guide cylinder continuously ascends and revolves around the main rotating shaft, the catalyst is sprayed to various positions in the kettle body and continuously stirred and dispersed. The catalyst can be gradually and dispersedly added to the reaction solution, effectively avoiding local overheating caused by uneven catalyst distribution, effectively avoiding product yellowing caused by local overheating, and effectively reducing the B value in PBT products. To prevent external air from entering, the catalyst storage barrel is sealed after loading the catalyst. At the end of the step of adding the catalyst, by opening the valve, the communicating pipe between the feeding pipelines can be connected. When continuing to stir, one guide cylinder ascends and the other guide cylinder descends, so that the material in the channel between the two guide cylinders can flow reciprocally, without affecting the continuous progress of stirring. And because the catalyst storage barrel is in a negative pressure state after sucking out the catalyst, the catalyst will not continuously enter the feeding pipeline.

[0007] In the above technical solution, preferably, the first transmission mechanism includes a first bevel gear fixedly arranged on the main rotating shaft, a first rotating shaft rotatably arranged on the rotating frame, second bevel gears and third bevel gears fixedly arranged at both ends of the first rotating shaft, and a fourth bevel gear fixedly arranged at the top of the hollow screw. The first bevel gear meshes with the second bevel gear, the third bevel gear meshes with the fourth bevel gear, and the thread directions of the hollow screws on the opposite sides are opposite. By adopting this first transmission mechanism, the rotation of the hollow screw can be stably controlled, and the reciprocating movement of the movable cylinders on the opposite sides in the opposite direction can be ensured.

[0008] In the above technical solution, preferably, the guide cylinder is rotatably connected to the rotating frame, the guide cylinder and the main rotating shaft are driven by a second transmission mechanism, the inner channel of the guide cylinder is a non-circular cross-section, the cross-section of the guide rod matches the cross-section of the inner channel of the guide cylinder, the stirring sleeve is rotatably arranged at the bottom of the movable cylinder, and the stirring sleeve and the guide rod are driven by a third transmission mechanism. By adopting this structure, the rotation of the main rotating shaft can drive the guide cylinder to rotate through the second transmission mechanism, and then the guide rod can drive the stirring sleeve to rotate through the third transmission mechanism. The stirring sleeve not only revolves around the main rotating shaft but also rotates on its own axis, making the distribution of the catalyst more uniform and further improving the stirring effect.

[0009] In the above technical solution, preferably, the second transmission mechanism includes a fifth bevel gear fixedly arranged on the main rotating shaft, a second rotating shaft rotatably arranged on the rotating frame, sixth bevel gears and seventh bevel gears fixedly arranged at both ends of the second rotating shaft, and an eighth bevel gear fixedly arranged at the top of the guide cylinder. The fifth bevel gear meshes with the sixth bevel gear, and the seventh bevel gear meshes with the eighth bevel gear. By adopting this second transmission mechanism, the rotation of the guide cylinder can be stably controlled, thereby driving the stirring sleeve to rotate.

[0010] In the above technical solution, preferably, the third transmission mechanism includes a first gear fixed to the outside of the stirring sleeve and a second gear fixed to the outside of the guide rod, and the first gear meshes with the second gear. By adopting this structure, the rotation of the stirring sleeve can be stably driven by the guide rod.

[0011] In the above technical solution, preferably, a first sealed housing is arranged at the bottom of the movable cylinder, and the third transmission mechanism is located inside the first sealed housing. By adopting this structure, the influence of external reaction materials on the third transmission mechanism can be avoided, and the problem of difficult cleaning can also be avoided. The cleanliness of the equipment also has an important impact on the B value of the subsequent PBT processing.

[0012] In the above technical solution, preferably, a number of first stirring bars are arranged outside the stirring sleeve, and a number of second stirring bars are arranged outside the main rotating shaft. By adopting this structure, the stirring range can be increased, making the stirring effect better.

[0013] In the above technical solution, preferably, an annular groove is provided on the inner wall of the top of the movable cylinder, and an annular seal is provided in the annular groove. Adopting this structure can increase the sealing performance between the movable cylinder and the hollow screw, and improve the efficiency of sucking the catalyst.

[0014] In the above technical solution, preferably, a second closed housing is provided on the rotating frame, and the first transmission mechanism and the second transmission mechanism are both arranged in the second closed housing. Adopting this structure can prevent the external reaction materials from affecting the first transmission mechanism and the second transmission mechanism, and also avoid the problem of difficult cleaning. The cleanliness of the equipment also has an important impact on the B value of the subsequent PBT processing.

[0015] The process for processing PBT products by the above equipment for reducing the B value of PBT products includes the following steps: 1) Pre-add a catalyst in the catalyst storage tank, and add terephthalic acid and 1,4-butanediol into the kettle body; 2) Close the valve, start the first motor and the second motor to drive the rotating frame and the main shaft to rotate forward and backward. There is a speed difference between the rotating frame and the main shaft. Stir and mix terephthalic acid and 1,4-butanediol continuously, and at the same time, the main shaft drives the hollow screw to rotate, and the movable cylinder reciprocates up and down outside the hollow screw to extract the catalyst in the catalyst storage tank and spray it from the one-way nozzle at different heights; 3) Heat the terephthalic acid and 1,4-butanediol in the kettle body to a preset temperature; 4) When the catalyst is added to the set amount, open the valve, and the first motor and the second motor continuously drive the rotating frame and the main shaft to rotate, and the movable cylinders on the opposite sides reciprocate in the opposite direction to stir the materials; 5) After the esterification reaction is completed, evacuate to extract part of the water, and carry out polycondensation reaction under low pressure conditions until the polycondensation reaction is completed. By using the above equipment and process for reducing the B value of PBT products, the catalyst can be more evenly distributed and quickly stirred and dispersed, effectively avoiding local overheating caused by uneven catalyst distribution, effectively avoiding product yellowing caused by local overheating, and effectively reducing the B value of PBT products.

[0016] Compared with the prior art, the present invention has the following beneficial effects: When processing PBT products with this device for reducing the B value in PBT products, a catalyst is pre-added into the catalyst storage barrel, and then terephthalic acid and 1,4-butanediol are added into the kettle body. After closing the valve, the first motor and the second motor are started to drive the rotating frame and the main shaft to rotate forward and backward. There is a speed difference between the rotating frame and the main shaft. When the main shaft rotates, it drives the hollow screw to rotate through the first transmission mechanism. The rotation of the hollow screw drives the two guide cylinders on the opposite side to reciprocate in the opposite direction. A structure similar to a piston is formed between the guide cylinder and the hollow screw. When the guide cylinder descends, the volume of the cavity between the guide cylinder and the hollow screw expands, sucking out the catalyst from the catalyst storage barrel. When the guide cylinder ascends, the volume of the cavity between the guide cylinder and the hollow screw decreases, and the catalyst is sprayed out from the one-way nozzle. Since the guide cylinder continuously ascends and revolves around the main shaft, the catalyst is sprayed to various positions in the kettle body and continuously stirred and dispersed. The catalyst can be gradually and dispersedly added to the reaction solution, effectively avoiding local overheating caused by uneven distribution of the catalyst, effectively avoiding the yellowing of the product caused by local overheating, and effectively reducing the B value in PBT products; to prevent external air from entering, the catalyst storage barrel is sealed after loading the catalyst. At the end of the step of adding the catalyst, by opening the valve, the connecting pipe between the feeding pipelines can be connected. When continuing to stir, one guide cylinder ascends and the other guide cylinder descends, so that the material in the channel between the two guide cylinders can flow reciprocally, without affecting the continuous progress of stirring; and because the catalyst storage barrel is in a negative pressure state after sucking out the catalyst, the catalyst will not continuously enter the feeding pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention.

[0018] Figure 2 It is a schematic diagram of the internal structure of an embodiment of the present invention.

[0019] Figure 3 It is a schematic cross-sectional structure diagram of an embodiment of the present invention.

[0020] Figure 4 It is a partial enlarged view of A in FIG. 3.

[0021] Figure 5 It is a partial enlarged view of B in FIG. 3.

[0022] Figure 6 It is a partial enlarged view of C in FIG. 3.

[0023] Figure 7 It is a partial enlarged view of D in FIG. 3.

[0024] Figure 8 It is a partial enlarged view of E in FIG. 3.

[0025] Figure 9 This is a schematic structural view of the installation locations of the first motor and the second motor in the embodiments of the present invention. Detailed implementation manners

[0026] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners: Refer to Figures 1 to 9 , a device for reducing the B value in PBT products, comprising a kettle body 1. A conventional feeding port and a vacuum pumping port are provided at the top of the kettle body 1, and a conventional discharging port is provided at the bottom. A main rotating shaft 2 is rotatably arranged in the kettle body 1, and the top of the main rotating shaft 2 extends out of the kettle body 1. A rotating frame 3 is rotatably arranged in the kettle body 1, and the top of the rotating frame 3 also extends out of the kettle body 1. Refer to Figure 9 , a first motor 4 is fixed on the kettle body 1. The first motor 4 and the top of the rotating frame 3 are driven by a synchronous belt. A second motor 5 is fixed to the top of the rotating frame 3. The main rotating shaft 2 passes through the rotating frame 3, and the main rotating shaft 2 is located at the center of the rotating frame 3. The second motor 5 and the main rotating shaft 2 rotate through gears.

[0027] Refer to Figure 2 and Figure 3, a set of hollow screws 6 are rotatably arranged on both sides of the rotating frame 3 in a relative manner. An outer side of a bottom of the hollow screw 6 is in threaded fit with a movable cylinder 7. A stirring sleeve 9 with a plurality of one-way nozzles 8 on an outer wall is arranged at a bottom of the movable cylinder 7. The one-way nozzles 8 are located on an outer periphery and a bottom of the stirring sleeve 9. The shape of the stirring sleeve 9 is not limited. A guide rod 10 in the same direction as the movable cylinder 7 is arranged on a side surface of the stirring sleeve 9. A guide cylinder 11 is arranged on the rotating frame 3. The guide rod 10 is movably inserted into the guide cylinder 11. A first transmission mechanism is arranged between the main rotating shaft 2 and the hollow screw 6. The main rotating shaft 2 drives the two guide cylinders 11 on the opposite side to reciprocate in opposite directions. A catalyst storage barrel 12 is arranged at a top of the rotating frame 3. A feeding pipeline 13 is connected to a bottom of the catalyst storage barrel 12. The feeding pipelines 13 are rotatably connected to tops of the hollow screws 6 in a one-to-one correspondence. A one-way discharging valve 14 is arranged on the feeding pipeline 13 near the catalyst storage barrel 12. A communicating pipe 15 is connected between the feeding pipelines 13 connecting the opposite hollow screws 6 below the one-way discharging valve 14. A valve 16 is arranged on the communicating pipe 15. For convenient control, the valve 16 is preferably an electromagnetic valve.When this device for reducing the B value in PBT products processes PBT products, a catalyst is pre-added into the catalyst storage barrel 12. Then, terephthalic acid and 1,4-butanediol are added into the kettle body 1. After closing the valve 16, the first motor 4 and the second motor 5 are started to drive the rotating frame 3 and the main rotating shaft 2 to rotate forward and backward. There is a speed difference between the rotating frame 3 and the main rotating shaft 2. When the main rotating shaft 2 rotates, it drives the hollow screw 6 to rotate through the first transmission mechanism. The rotation of the hollow screw 6 drives the two guide cylinders 11 on the opposite side to reciprocate in the opposite direction. A structure similar to a piston is formed between the guide cylinder 11 and the hollow screw 6. When the guide cylinder 11 descends, the volume of the cavity between the guide cylinder 11 and the hollow screw 6 expands, sucking out the catalyst from the catalyst storage barrel 12. When the guide cylinder 11 ascends, the volume of the cavity between the guide cylinder 11 and the hollow screw 6 decreases, and the catalyst is sprayed out from the one-way nozzle 8. Since the guide cylinder 11 continuously ascends and revolves around the main rotating shaft 2, the catalyst is sprayed to various positions in the kettle body 1 and is continuously stirred and dispersed, enabling the catalyst to be gradually and dispersedly added to the reaction solution, effectively avoiding local overheating caused by uneven catalyst distribution, effectively avoiding product yellowing caused by local overheating, and effectively reducing the B value in PBT products; to prevent external air from entering, the catalyst storage barrel 12 is sealed after loading the catalyst. At the end of the step of adding the catalyst, by opening the valve 16, the connecting pipe 15 between the feeding pipes 13 can be connected. When continuing to stir, one guide cylinder 11 ascends and the other guide cylinder 11 descends, so that the material in the channel between the two guide cylinders 11 can flow reciprocally, without affecting the continuous stirring; and because the catalyst storage barrel 12 is in a negative pressure state after sucking out the catalyst, the catalyst will not continuously enter the feeding pipe 13. Of course, in order to further prevent the catalyst from continuing to flow out of the catalyst storage barrel 12 after the catalyst addition amount is sufficient, a control valve can also be provided at the connection with the one-way discharge valve 14. This control valve is preferably an electromagnetic valve for convenient control and is closed after the catalyst is sufficient.

[0028] In this embodiment, the first transmission mechanism includes a first bevel gear 17 fixedly arranged on the main rotating shaft 2, a first rotating shaft 18 rotatably arranged on the rotating frame 3, second bevel gears 19 and third bevel gears 20 fixedly arranged at both ends of the first rotating shaft 18, and a fourth bevel gear 21 fixedly arranged at the top of the hollow screw 6. The first bevel gear 17 meshes with the second bevel gear 19, and the third bevel gear 20 meshes with the fourth bevel gear 21. The thread directions of the hollow screws 6 on the opposite sides are opposite. Using this first transmission mechanism can stably control the rotation of the hollow screw 6 and ensure the reciprocating movement of the movable cylinders 7 on the opposite sides in the opposite direction.

[0029] In other embodiments, the first transmission mechanism can also be in the form of driving by fixing pulleys on the main rotating shaft 2 and the hollow screw 6 and setting a belt between the pulleys; or in the form of chain drive.

[0030] In other embodiments, what can be easily improved by those skilled in the art is that the first transmission mechanism can reverse the rotation of the hollow screws 6 on both sides through existing transmission structures. At this time, the thread directions of the two opposite hollow screws 6 are the same. Based on this, the reverse reciprocating movement of the guide cylinder 11 can still be ensured.

[0031] In this embodiment, the guide cylinder 11 is rotatably connected to the rotating frame 3. The guide cylinder 11 and the main rotating shaft 2 are driven by a second transmission mechanism. The inner channel of the guide cylinder 11 is a non-circular cross-section, and the cross-section of the guide rod 10 matches the cross-section of the inner channel of the guide cylinder 11. The stirring sleeve 9 is rotatably arranged at the bottom of the movable cylinder 7. The stirring sleeve 9 and the guide rod 10 are driven by a third transmission mechanism. With this structure, the rotation of the main rotating shaft 2 can drive the rotation of the guide cylinder 11 through the second transmission mechanism, and then the guide rod 10 can drive the rotation of the stirring sleeve 9 through the third transmission mechanism. The stirring sleeve 9 not only revolves around the main rotating shaft 2 but also rotates on its own axis, making the distribution of the catalyst more uniform and further improving the stirring effect.

[0032] In this embodiment, the second transmission mechanism includes a fifth bevel gear 22 fixedly arranged on the main rotating shaft 2, a second rotating shaft 23 rotatably arranged on the rotating frame 3, a sixth bevel gear 24 and a seventh bevel gear 25 fixedly arranged at both ends of the second rotating shaft 23, and an eighth bevel gear 26 fixedly arranged on the top of the guide cylinder 11. The fifth bevel gear 22 meshes with the sixth bevel gear 24, and the seventh bevel gear 25 meshes with the eighth bevel gear 26. Using this second transmission mechanism can stably control the rotation of the guide cylinder 11, thereby driving the rotation of the stirring sleeve 9.

[0033] In other embodiments, the second transmission mechanism can also use existing transmission mechanisms, such as belt drive or chain drive, to drive the rotation of the guide cylinder 11 by the main rotating shaft 2.

[0034] In this embodiment, the third transmission mechanism includes a first gear 27 fixed to the outside of the stirring sleeve 9 and a second gear 28 fixed to the outside of the guide rod 10. The first gear 27 meshes with the second gear 28. Using this structure can stably drive the rotation of the stirring sleeve 9 by the guide rod 10.

[0035] In other embodiments, the third transmission mechanism can also use existing transmission mechanisms, such as belt drive or chain drive, to drive the rotation of the stirring sleeve 9 by the guide rod 10.

[0036] In this embodiment, a first sealed housing 29 is arranged at the bottom of the movable cylinder 7, and the third transmission mechanism is located inside the first sealed housing 29. Using this structure can avoid the influence of external reaction materials on the third transmission mechanism and also avoid the problem of difficult cleaning. The cleanliness of the equipment also has an important impact on the B value of the subsequent PBT processing.

[0037] In this embodiment, a number of first stirring bars 30 are arranged outside the stirring sleeve 9, and a number of second stirring bars 31 are arranged outside the main rotating shaft 2. This structure is adopted to increase the stirring range and make the stirring effect better.

[0038] In this embodiment, an annular groove 32 is arranged on the inner wall of the top of the movable cylinder 7, and an annular seal 33 is arranged in the annular groove 32. This structure can increase the sealing performance between the movable cylinder 7 and the hollow screw 6 and improve the efficiency of sucking the catalyst.

[0039] In this embodiment, a second closed housing 34 is arranged on the rotating frame 3, and the first transmission mechanism and the second transmission mechanism are both arranged in the second closed housing 34. This structure can prevent the external reaction materials from affecting the first transmission mechanism and the second transmission mechanism, and also avoid the problem of difficult cleaning. The cleanliness of the equipment also has an important impact on the B value of the subsequent PBT processing.

[0040] The process of processing PBT products by the above equipment for reducing the B value in PBT products includes the following steps: 1) Pre-add a catalyst in the catalyst storage tank 12. The catalyst is a titanium-based catalyst, such as tetramethyl titanate, tetrabutyl titanate, tetraisopropyl titanate, etc. Add terephthalic acid and 1,4-butanediol into the kettle body 1; 2) Close the valve 16, start the first motor 4 and the second motor 5 to drive the rotating frame 3 and the main rotating shaft 2 to rotate forward and backward. There is a speed difference between the rotating frame 3 and the main rotating shaft 2. Stir and mix the terephthalic acid and 1,4-butanediol continuously. At the same time, the main rotating shaft 2 drives the hollow screw 6 to rotate, and the movable cylinder 7 reciprocates up and down outside the hollow screw 6 to extract the catalyst in the catalyst storage tank 12 and spray it from the one-way nozzle 8 at different heights; 3) Heat the terephthalic acid and 1,4-butanediol in the kettle body 1 to a preset temperature, and control the temperature of the esterification reaction at 150-200 °C; 4) Open the valve 16 when the catalyst is added to the set amount, and stop adding the catalyst when the addition amount of the catalyst is 0.01%-0.05% of the mass of terephthalic acid. The first motor 4 and the second motor 5 continuously drive the rotating frame 3 and the main rotating shaft 2 to rotate, and the movable cylinders 7 on the opposite sides reciprocate in the opposite direction to stir the materials; 5) After the esterification reaction is completed, evacuate to extract part of the water, and at the same time adjust the reaction temperature to be controlled at 250-260 °C, and carry out the polycondensation reaction under a low pressure condition of 0.05-0.1 kPa until the polycondensation reaction is completed.

[0041] The equipment and process for reducing the B value in PBT products mainly improve the equipment. The catalyst is sucked by the lifting of the movable cylinder 7 and sprayed from the one-way nozzle 8, so that the catalyst that was originally prone to local accumulation can be more evenly distributed and quickly stirred and dispersed, effectively avoiding local overheating caused by uneven catalyst distribution, effectively preventing the product from turning yellow due to local overheating, and effectively reducing the B value in PBT products.

[0042] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A device for reducing the B value in a PBT product, comprising a kettle (1), wherein a main rotating shaft (2) is rotatably arranged in the kettle (1), characterized in that: A rotating frame (3) is rotatably arranged in the kettle body (1), and the rotating frame (3) is driven by a first motor (4) fixed to the kettle body (1). The main rotating shaft (2) is inserted into the rotating frame (3), and the main rotating shaft (2) is driven by a second motor (5) fixed to the rotating frame (3). At least one group of hollow screws (6) are rotatably arranged on both sides of the rotating frame (3). The outer threads of the bottom of the hollow screws (6) are matched with a movable cylinder (7). The bottom of the movable cylinder (7) is provided with a stirring sleeve (9) with a plurality of one-way nozzles (8) on the outer wall. The side of the stirring sleeve (9) is provided with a guide rod (10) in the same direction as the movable cylinder (7). The rotating frame (3) is provided with a guide cylinder (11), and the guide rod (10) is movably inserted into the guide cylinder (11). In the guide cylinder (11), the main rotating shaft (2) and the hollow screw (6) are driven by a first transmission mechanism, the main rotating shaft (2) drives the two guide cylinders (11) on the opposite side to reciprocate in the opposite direction, a catalyst storage barrel (12) is arranged on the top of the rotating frame (3), the bottom of the catalyst storage barrel (12) is connected to a feed pipe (13), the feed pipe (13) is rotationally connected to the top of the hollow screw (6) in a one-to-one correspondence, a one-way discharge valve (14) is arranged on the feed pipe (13) near the catalyst storage barrel (12), a connecting pipe (15) is connected between the feed pipes (13) connecting the opposite hollow screws (6) and located below the one-way discharge valve (14), and a valve (16) is arranged on the connecting pipe (15).

2. The device for reducing the B value in PBT products according to claim 1, characterized in that: The first transmission mechanism comprises a first bevel gear (17) fixedly arranged on the main rotating shaft (2), a first rotating shaft (18) rotatably arranged on the rotating frame (3), a second bevel gear (19) and a third bevel gear (20) fixedly arranged at both ends of the first rotating shaft (18), and a fourth bevel gear (21) fixedly arranged on the top of the hollow screw (6), the first bevel gear (17) meshing with the second bevel gear (19), the third bevel gear (20) meshing with the fourth bevel gear (21), and the screw threads of the hollow screw (6) on opposite sides have opposite directions.

3. The device for reducing the B value in PBT products according to claim 1, characterized in that: The guide cylinder (11) is rotatably connected to the rotating frame (3); the guide cylinder (11) and the main rotating shaft (2) are driven by a second transmission mechanism; the inner channel of the guide cylinder (11) has a non-circular cross section; the cross section of the guide rod (10) matches the cross section of the inner channel of the guide cylinder (11); the stirring sleeve (9) is rotatably arranged at the bottom of the movable cylinder (7); the stirring sleeve (9) and the guide rod (10) are driven by a third transmission mechanism.

4. The device for reducing the B value in PBT products according to claim 3, characterized in that: The second transmission mechanism comprises a fifth bevel gear (22) fixedly arranged on the main rotating shaft (2), a second rotating shaft (23) rotatably arranged on the rotating frame (3), a sixth bevel gear (24) and a seventh bevel gear (25) fixedly arranged at both ends of the second rotating shaft (23), and an eighth bevel gear (26) fixedly arranged on the top of the guide cylinder (11), the fifth bevel gear (22) meshing with the sixth bevel gear (24), and the seventh bevel gear (25) meshing with the eighth bevel gear (26).

5. The device for reducing the B value in PBT products according to claim 3, characterized in that: The third transmission mechanism comprises a first gear (27) fixed to the outside of the stirring sleeve (9) and a second gear (28) fixed to the outside of the guide rod (10), the first gear (27) being meshed with the second gear (28).

6. The device for reducing the B value in PBT products according to claim 3, characterized in that: A first sealed shell (29) is provided at the bottom of the movable cylinder (7), and the third transmission mechanism is located inside the first sealed shell (29).

7. The device for reducing the B value in PBT products according to claim 3, characterized in that: A plurality of first stirring bars (30) are arranged outside the stirring sleeve (9), and a plurality of second stirring bars (31) are arranged outside the main rotating shaft (2).

8. The device for reducing the B value in PBT products according to claim 1, characterized in that: An annular groove (32) is provided on the inner wall of the top of the movable cylinder (7), and an annular sealing member (33) is provided in the annular groove (32).

9. The device for reducing the B value in PBT products according to claim 3, characterized in that: A second sealed shell (34) is provided on the rotating frame (3), and the first transmission mechanism and the second transmission mechanism are both provided in the second sealed shell (34).

10. A process for processing PBT products using the device for reducing the B value in PBT products as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: 1) Adding a catalyst into a catalyst storage barrel (12) in advance, and adding terephthalic acid and 1,4-butanediol into a kettle (1); 2) closing the valve (16), starting the first motor (4) and the second motor (5) to drive the rotating frame (3) and the main rotating shaft (2) to rotate forward and reverse, with a speed difference between the rotating frame (3) and the main rotating shaft (2), so that the terephthalic acid and 1,4-butanediol are stirred and mixed continuously, and at the same time, the main rotating shaft (2) drives the hollow screw (6) to rotate, and the movable cylinder (7) reciprocates and rises and falls outside the hollow screw (6), so that the catalyst in the catalyst storage barrel (12) is extracted from the one-way nozzle (8) spraying from different heights; 3) heating the terephthalic acid and 1,4-butanediol in the kettle (1) to a preset temperature; 4) opening the valve (16) when the catalyst is added to a preset amount, the first motor (4) and the second motor (5) continuously drive the rotating frame (3) and the main rotating shaft (2) to rotate, and the movable cylinders (7) on both sides move back and forth in the opposite direction to stir the materials; 5) after the esterification reaction is completed, vacuuming is performed to extract part of the water, and polycondensation reaction is performed under low pressure conditions until the polycondensation reaction is completed.

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