A system for polymerizing PVC materials

Abstract

The present invention belongs to the technical field of chemical equipment, and specifically relates to a system for PVC material polymerization. The system for PVC material polymerization includes a reactor for polymerization reaction, the reactor includes a reactor body, an upper cover with a feed pipe is installed on the reactor body, and a discharge pipe is installed at the lower end of the reactor body; a spiral stirring rod is rotatably installed on the upper cover, a motor is installed on the upper cover and drives the spiral stirring rod, and the spiral stirring rod is in a spiral shape; a rotary joint is installed at the upper end of the spiral stirring rod, and a liquid inlet pipe and a liquid outlet pipe are connected to the rotary joint, and a liquid inlet cavity and a liquid outlet cavity are opened in the spiral stirring rod, and the liquid inlet cavity and the liquid outlet cavity are connected to each other at the end of the spiral stirring rod away from the motor; the present invention has a simple structure, can effectively improve the heat exchange effect of the reactor, and avoid PVC accumulation and agglomeration, and is convenient for cleaning the reactor.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical equipment, and in particular relates to a system for polymerizing PVC materials. Background Art

[0002] Polyvinyl chloride (PVC) is a polymer formed by the polymerization of vinyl chloride monomer (VCM) in the presence of initiators such as peroxides and azo compounds, or under the action of light or heat according to the free radical polymerization mechanism. The polymerization principle of PVC is to use PVA as a dispersant, peroxide as an initiator, and VCM with a purity of 99.99% to polymerize into PVC resin that meets various standards in a deionized water dispersion system. The polymerization reaction of VCM is an exothermic reaction, and the process has the characteristics of hysteresis and nonlinearity. A large part of the operation in the production process is the regulation of temperature. Improving the heat exchange capacity of the polymerization kettle is an important step to improve the stable yield of the equipment.

[0003] There are usually two methods for cooling the PVC polymerization kettle in the prior art: one is to weld the outer coil half pipe to the polymerization kettle cylinder, and the other is to weld the inner half pipe to the polymerization kettle cylinder. The first method is designed according to the traditional structure of a large container with an outer coil. Since the outer coil is equivalent to applying external pressure to the cylinder, it is necessary to design a thicker cylinder wall thickness to prevent the cylinder from being unstable, deformed or even broken. The increase in wall thickness will not only increase material costs and manufacturing difficulty, but also reduce the heat removal efficiency. The second method uses an inner half pipe to avoid the defects of the outer coil. However, in the above two methods, welding is used between the tube body and the cylinder wall. The welding of a large number of inner half pipes to the polymerization kettle cylinder in a relatively small space is not only difficult to manufacture, but also prone to PVC accumulation in the gap between the coil and the kettle, agglomeration and difficult to clean, which is not conducive to future inspection and maintenance during operation; and due to the large amount of welding, a large welding residual stress will be generated, which will form a great safety hazard in actual production. Summary of the invention

[0004] In order to make up for the deficiencies of the prior art, improve the heat exchange capacity of the polymerization kettle and reduce the accumulation of PVC in corners and gaps, the present invention provides a system for polymerizing PVC materials.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a PVC material polymerization system of the present invention comprises a reaction kettle for polymerization reaction, and the reaction kettle comprises:

[0006] A kettle body, wherein the kettle body is installed on the ground through legs, an upper cover is installed on the kettle body, a feed pipe is provided on the upper cover, and a discharge pipe is installed at the lower end of the kettle body;

[0007] A spiral stirring rod, which is rotatably mounted on the upper cover, is located inside the kettle body, and a motor is mounted on the upper cover, which drives the spiral stirring rod to rotate, and the spiral stirring rod is in a spiral shape;

[0008] A rotary joint, wherein the rotary joint is installed at the upper end of the spiral stirring rod, and a liquid inlet pipe and a liquid outlet pipe are connected to the rotary joint. A liquid inlet chamber and a liquid outlet chamber are provided in the spiral stirring rod, and the liquid inlet chamber and the liquid outlet chamber are connected to each other at the end of the spiral stirring rod away from the motor, and the internal channel of the rotary joint is connected to the liquid inlet chamber and the liquid outlet chamber respectively.

[0009] Preferably, the wall thickness of the end of the liquid inlet chamber close to the motor is greater than the wall thickness of the end of the liquid inlet chamber away from the motor, and the wall thickness of the end of the liquid outlet chamber close to the motor is greater than the wall thickness of the end of the liquid outlet chamber away from the motor.

[0010] Preferably, the spiral stirring rod comprises an upper tube and a lower tube, the spiral directions of the upper tube and the lower tube are opposite, and the upper tube and the lower tube are connected by a connecting tube.

[0011] Preferably, the upper tube includes an inlet pipe and an outlet pipe, and the inlet pipe and the outlet pipe are connected to each other at the end of the spiral stirring rod away from the motor. The cross-sectional outer contours of the inlet pipe and the outlet pipe are semicircular, and the combination of the two obtains an upper tube with a circular cross-sectional outer contour. An insulation layer is arranged between the inlet pipe and the outlet pipe, and the internal structures of the upper tube, the lower tube, and the connecting tube are the same and correspond one to one.

[0012] Preferably, there is a gap between the liquid inlet pipe and the liquid outlet pipe, the gap is enclosed into a closed cavity, the interior of the cavity is evacuated, and the cavity serves as a heat insulation layer.

[0013] Preferably, the spiral stirring rod is provided with fins, and the fins are symmetrically arranged on the outer walls of the liquid inlet pipe and the liquid outlet pipe on both sides of the thermal insulation layer.

[0014] Preferably, the thermal conductivity of the fins on the liquid inlet pipe is smaller than the thermal conductivity of the fins on the liquid outlet pipe.

[0015] Preferably, reinforcing ribs are evenly arranged on the inner wall of the cavity.

[0016] Preferably, a guide rail is fixedly installed on the inner wall of the kettle body, a scraper is slidably installed on the guide rail, an adsorption block is installed on the end of the scraper away from the guide rail, the adsorption block is adsorbed on the inner wall of the kettle body by magnetic force, a passive block is installed in the middle part of the scraper, and an active block is installed on the outer wall of the connecting pipe, and the active block and the passive block are connected and matched with each other through magnetic attraction.

[0017] Preferably, an inclined surface is provided on the side wall of the guide rail for mounting the scraper, and a through hole is provided on the inclined surface, and the through hole connects the inside of the guide rail with the inside of the kettle body.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. The system for polymerization of PVC materials described in the present invention is provided with a spiral stirring rod and a coolant flows in the spiral stirring rod, so that the raw materials in the reactor are cooled by the spiral stirring rod to control the reaction temperature. At the same time, through the action of the spiral stirring rod, there is no gap between the coil and the reactor in the reactor, which can avoid PVC accumulation, reduce the difficulty of cleaning, and improve product quality.

[0020] 2. The system for polymerization of PVC materials described in the present invention is provided with a liquid inlet pipe, a liquid outlet pipe and a cavity, so that the coolant is relatively isolated in the process of entering and flowing out of the reactor, and heat exchange between the coolant entering the reactor and the coolant discharged from the reactor will not occur, which affects the heat exchange of heat in the reactor, thereby affecting the temperature control effect in the reactor and resulting in poor product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below in conjunction with the accompanying drawings.

[0022] Figure 1 It is a front view of the reaction kettle in the present invention;

[0023] Figure 2 It is a schematic diagram of the structure of the reactor in the present invention;

[0024] Figure 3 It is a structural schematic diagram of the cross section of the spiral stirring rod in the present invention;

[0025] Figure 4 yes Figure 2 A magnified view of middle;

[0026] Figure 5 It is a three-dimensional schematic diagram of a connecting pipe and a fixing cylinder according to an embodiment.

[0027] In the figure: kettle body 1, upper cover 11, feed pipe 12, discharge pipe 13, motor 14, spiral stirring rod 2, upper pipe 21, connecting pipe 22, lower pipe 23, liquid inlet pipe 24, liquid inlet cavity 241, liquid outlet pipe 25, liquid outlet cavity 251, cavity 26, reinforcing rib 27, rotary joint 3, liquid inlet pipe 31, liquid outlet pipe 32, fin 4, guide rail 5, scraper 51, inclined surface 52, through hole 53, adsorption block 54, passive block 55, active block 56. DETAILED DESCRIPTION

[0028] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0029] like Figures 1 to 4 As shown, the system for PVC material polymerization of the present invention comprises a reactor for polymerization reaction, and the reactor comprises:

[0030] A kettle body 1, wherein the kettle body 1 is installed on the ground through legs, an upper cover 11 is installed on the kettle body 1, a feed pipe 12 is opened on the upper cover 11, and a discharge pipe 13 is installed at the lower end of the kettle body 1;

[0031] A spiral stirring rod 2, which is rotatably mounted on the upper cover 11, and is located inside the kettle body 1. A motor 14 is mounted on the upper cover 11, and the motor 14 drives the spiral stirring rod 2 to rotate, and the spiral stirring rod 2 is in a spiral shape;

[0032] A rotary joint 3, the rotary joint 3 is installed at the upper end of the spiral stirring rod 2, the rotary joint 3 is connected with a liquid inlet pipe 31 and a liquid outlet pipe 32, the spiral stirring rod 2 is provided with a liquid inlet chamber 241 and a liquid outlet chamber 251, the liquid inlet chamber 241 and the liquid outlet chamber 251 are connected to each other at the end of the spiral stirring rod 2 away from the motor 14, and the internal channel of the rotary joint 3 is connected with the liquid inlet chamber 241 and the liquid outlet chamber 251 respectively;

[0033] After the raw materials are added into the reactor, the PVC polymerization process begins. A large amount of heat will be generated during the reaction process, so it is necessary to reduce the temperature in the reactor in time to ensure the normal progress of the PVC polymerization reaction and improve the quality of the product. At the same time, the motor 14 drives the spiral stirring rod 2 to rotate, and stirs the raw materials in the reactor to a certain extent, so that the raw materials are fully in contact with each other, thereby improving the polymerization reaction effect. At the same time, during the operation of the reactor, external coolant is introduced into the liquid inlet pipe 31 on the rotary joint 3, and then the coolant enters the liquid inlet chamber 241 and the liquid outlet chamber 251 in the spiral stirring rod 2, and is finally discharged from the liquid outlet pipe 32 on the rotary joint 3, so that under the action of the external circulation device, the circulation of the coolant is realized, and the heat inside the reactor is effectively taken out through the circulation of the coolant, and the temperature in the reactor is controlled to always be at a preset temperature suitable for the polymerization reaction. In addition, since the coolant flows in the spiral stirring rod 2 and the spiral stirring rod 2 rotates continuously during the polymerization reaction, the degree of contact between the coolant and the raw materials in the reactor can be effectively improved, and the effect of transferring the heat generated in the reactor to the outside world can be improved, thereby avoiding that as the polymerization reaction proceeds, the raw materials inside the reactor are gradually converted into PVC, making the liquid viscous and difficult to transfer heat, causing local heat accumulation in the reactor and overheating, affecting product quality and creating safety hazards. At the same time, since the reactor is cooled by the coolant flowing in the spiral stirring rod 2, there is no need to set a cooling coil on the inner wall of the reactor, thereby avoiding the formation of an angle between the cooling coil and the inner wall of the reactor, or the existence of an angle in the structure of the coil itself, resulting in the accumulation of the raw materials in the reactor or the PVC generated by the polymerization reaction in the gap at the angle, which is difficult to clean and affects the quality of subsequent PVC products.

[0034] As an embodiment of the present invention, the wall thickness of the end of the liquid inlet chamber 241 close to the motor 14 is greater than the wall thickness of the end of the liquid inlet chamber 241 away from the motor 14, and the wall thickness of the end of the liquid outlet chamber 251 close to the motor 14 is greater than the wall thickness of the end of the liquid outlet chamber 251 away from the motor 14;

[0035] Since the coolant is still discharged from the rotary joint 3 at the upper end of the spiral stirring rod 2 after flowing from the liquid inlet chamber 241 to the liquid outlet chamber 251 in the spiral stirring rod 2, the temperature of the coolant is relatively low when the coolant flows downward in the spiral stirring rod 2, and the coolant has absorbed the heat in the reactor when the coolant flows upward in the spiral stirring rod 2, making the temperature of the coolant relatively high. Therefore, the closer the raw material is to the upper end of the spiral stirring rod 2 in the reactor, the greater the temperature difference between the coolant and the raw material, so that the raw material near the upper end of the spiral stirring rod 2 can more easily transfer heat to the coolant in the spiral stirring rod 2, and finally the temperature of the upper layer of the raw material in the reactor is lower than that of the lower layer. The temperature of the raw materials causes uneven temperature distribution in the reactor, which affects the quality of the PVC products. At the same time, by making the wall thickness of the upper end of the liquid inlet chamber 241 in the spiral stirring rod 2 greater than the wall thickness of the lower end, the heat exchange between the upper raw material in the reactor and the coolant in the spiral stirring rod 2 is hindered, and the heat exchange between the lower raw material and the coolant in the spiral stirring rod 2 is promoted, so that the temperature of the lower raw material in the reactor is made the same as that of the upper raw material, thereby ensuring the quality of the PVC products. At the same time, based on the same principle, by making the wall thickness of the upper end of the liquid outlet pipe 25 smaller than that of the lower end, the temperature of the lower raw material in the reactor is made the same as that of the upper raw material, thereby improving the quality of the PVC products.

[0036] As an embodiment of the present invention, the spiral stirring rod 2 includes an upper tube 21 and a lower tube 23, the spiral directions of the upper tube 21 and the lower tube 23 are opposite, and the upper tube 21 and the lower tube 23 are connected by a connecting tube 22;

[0037] Since the spiral directions of the upper tube 21 and the lower tube 23 are opposite, when the spiral stirring rod 2 rotates, the raw materials in the reactor are promoted to the connection between the upper tube 21 and the lower tube 23 on the spiral stirring rod 2, further allowing the raw materials to be fully mixed and improving the effect of the polymerization reaction.

[0038] As an embodiment of the present invention, the upper tube 21 includes a liquid inlet pipe 24 and a liquid outlet pipe 25, the liquid inlet pipe 24 and the liquid outlet pipe 25 are connected to each other at one end of the spiral stirring rod 2 away from the motor 14, the cross-sectional outer contours of the liquid inlet pipe 24 and the liquid outlet pipe 25 are semicircular, and the combination of the two obtains the upper tube 21 with a circular cross-sectional outer contour, and a heat insulation layer is provided between the liquid inlet pipe 24 and the liquid outlet pipe 25, and the internal structures of the upper tube 21, the lower tube 22, and the connecting tube 23 are the same and correspond one to one;

[0039] Since the internal structures of the upper tube 21, the lower tube 22, and the connecting tube 23 are the same and correspond one to one, the internal structure of the upper tube 21 can represent the internal structure of the spiral stirring rod 2, that is, the interior of the spiral stirring rod 2 is divided into a liquid inlet pipe 24 and a liquid outlet pipe 25, so that the coolant enters from the liquid inlet pipe 24 and is then discharged from the liquid outlet pipe 25. Since an insulating layer is provided between the liquid inlet pipe 24 and the liquid outlet pipe 25, the heat exchange between the coolant with a relatively low temperature entering from the liquid inlet pipe 24 and the coolant with a relatively high temperature discharged from the liquid outlet pipe 25 can be reduced, which affects the process of the coolant absorbing heat from the raw materials in the reactor, resulting in the inability to quickly reduce the temperature in the reactor, affecting the quality of the product and creating safety hazards.

[0040] As an embodiment of the present invention, there is a gap between the liquid inlet pipe 24 and the liquid outlet pipe 25, and the gap is surrounded by a closed cavity 26. The interior of the cavity 26 is vacuumed, and the cavity 26 acts as a heat insulation layer;

[0041] By evacuating the cavity 26, the heat transfer between the liquid inlet pipe 24 and the liquid outlet pipe 25 is hindered, the heat exchange between the liquid inlet pipe 24 and the liquid outlet pipe 25 is reduced, the cooling liquid's absorption effect on the heat in the reactor is improved, and the speed and control effect of reducing the temperature in the reactor are improved.

[0042] As an embodiment of the present invention, the spiral stirring rod 2 is provided with fins 4, and the fins 4 are symmetrically arranged on the outer walls of the liquid inlet pipe 24 and the liquid outlet pipe 25 on both sides of the thermal insulation layer;

[0043] By means of the fins 4, when the spiral stirring rod 2 rotates, the raw materials in the reactor are further stirred, thereby promoting sufficient mixing between the raw materials, ensuring the normal progress of the polymerization reaction, and producing high-quality PVC products. At the same time, by means of the fins 4, the problem of insufficient stirring of the raw materials when the spiral stirring rod 2 with a circular cross-section outer contour is used alone during rotation can be avoided.

[0044] As an embodiment of the present invention, the thermal conductivity of the fins 4 on the liquid inlet pipe 24 is smaller than the thermal conductivity of the fins 4 on the liquid outlet pipe 25;

[0045] Since the temperature of the coolant in the liquid inlet pipe 24 is relatively lower than the temperature of the coolant in the liquid outlet pipe 25, the fins 4 are made of a material with low thermal conductivity on the liquid inlet pipe 24, and the fins 4 are made of a material with high thermal conductivity on the liquid outlet pipe 25, thereby ensuring that the thermal conductivity of the fins 4 on the liquid inlet pipe 24 is smaller than that of the fins 4 on the liquid outlet pipe 25, so that the heat absorbed by the fins 4 on the liquid inlet pipe 24 is smaller than the heat absorbed by the fins 4 on the liquid outlet pipe 25, thereby avoiding uneven temperature in the reactor and affecting the quality of the product.

[0046] As an embodiment of the present invention, reinforcing ribs 27 are evenly arranged on the inner wall of the cavity 26;

[0047] By providing the reinforcing ribs 27, the strength of the spiral stirring rod 2 can be improved, and the possibility of deformation of the spiral stirring rod 2 during rotation can be reduced, thereby ensuring that the spiral stirring rod 2 can be used normally, so as to prevent the spiral stirring rod 2 from being subjected to excessive resistance from the raw materials during rotation, causing the spiral stirring rod 2 to deform or break, thereby affecting the normal use of the reactor.

[0048] As an embodiment of the present invention, a guide rail 5 is fixedly installed on the inner wall of the kettle body, and a scraper 51 is slidably installed on the guide rail 5. The scraper 51 extends from top to bottom. An adsorption block 54 is installed at the end of the scraper 51 away from the guide rail 5. The adsorption block 54 is adsorbed on the inner wall of the kettle body by magnetic force. A passive block 55 is installed in the middle part of the scraper 51. An active block 56 is installed on the outer wall of the connecting pipe. The active block 56 and the passive block 55 are connected and matched with each other by magnetic attraction, such as attracting each other; for example, an annular groove is concavely provided on the circumference of the lower part of the inner wall of the kettle body, and a guide block (not shown) is provided at the lower end of the scraper 51. The guide block is located on the side away from the adsorption block 54 and is slidably arranged in the annular groove, so that the lower end of the scraper 51 can be guided by the guide block. The active block 56 is located in the middle of the scraper 51.

[0049] When the spiral stirring rod 2 rotates, the connecting pipe 22 in the middle of the spiral stirring rod 2 starts to rotate synchronously. Since the active block 56 installed on the outer wall of the connecting pipe 22 and the passive block 55 installed in the middle of the scraper 51 are attracted and connected to each other through magnetic attraction, the spiral stirring rod 2 will drive the scraper 51 to rotate synchronously.

[0050] At the same time, since the scraper 51 is close to the inner wall of the kettle body, when the scraper 51 rotates, the raw materials attached to the inner wall of the kettle body 1 will be removed to avoid excessive attachment of raw materials to the inner wall of the kettle body 1, which will affect the quality of the final PVC material. At the same time, during the rotation of the scraper 51, the raw materials near the inner wall of the kettle body are stirred to avoid the raw materials near the inner wall of the kettle body 1 not being fully mixed and heated, resulting in the raw materials not being able to fully react, which will affect the quality of the final PVC.

[0051] At the same time, by installing an adsorption block 54 at the lower end of the scraper 51 away from the guide rail 5, the magnetism of the adsorption block 54 allows the lower end of the scraper 51 to be close to the inner wall of the kettle body, thereby preventing the scraper 51 from being blocked by the raw materials in the kettle body 1 during rotation, causing the lower end of the scraper 51 to deviate from the inner wall of the kettle body 1, thereby causing the inner wall of the lower half of the kettle body 1 to be unable to contact the scraper 51, and the attached raw materials cannot be cleaned by the scraper 51, affecting the normal use of the reactor and the quality of the final product.

[0052] As an embodiment of the present invention, the side wall of the guide rail 5 for mounting the scraper 51 is provided with an inclined surface 52, and a through hole 53 is opened on the inclined surface 52, and the through hole 53 connects the inside of the guide rail 5 with the inside of the kettle body;

[0053] Since the raw materials in the kettle body 1 are stirred by the spiral stirring rod 2 and the scraper 51, there is a possibility that the raw materials will splash onto the guide rail 5 during use. When the raw materials splash onto the guide rail 5, since the side wall of the guide rail 5 for installing the scraper 51 is provided with an inclined surface 52, the raw materials will slide down along the inclined surface 52 until they fall back into the raw materials in the kettle body 1 from the opening on the guide rail 5, thereby preventing the guide rail 5 from accumulating too much raw materials and affecting the normal use of the guide rail 5, and making the scraper 51 unable to slide.

[0054] At the same time, by opening a through hole 53 connecting the inside of the guide rail 5 and the inside of the kettle body 1 on the inclined surface 52, the raw materials splashed up from the inside of the guide rail 5, when they have not slid into the inside of the kettle body 1 in time and have already contacted the scraper 51, the raw materials splashed into the guide rail 5 are scraped by the scraper 51, so that the raw materials are scraped and then fall into the inside of the kettle body 1 from the through hole 53, thereby avoiding the raw materials splashed into the guide rail 5 not having time to fall, but being repeatedly squeezed and ground by the scraper 51, causing the raw materials to accumulate between the guide rail 5 and the scraper 51, affecting the normal movement of the scraper 51.

[0055] For example, and especially importantly, see Figure 5In one embodiment, the upper tube 21 and the lower tube 23 are fixedly connected by a plurality of fixing rods (not shown), and the connecting tube 22 is an elastic tube for connecting the upper tube 21 and the lower tube 23. A fixed sleeve 101 is fixedly provided on the outer periphery of the middle part of the connecting tube 22, and the active block 56 is fixed on the fixed sleeve 101. For example, springs 103 are provided at both the upper and lower ends of the fixed sleeve 101, the upper end of the spring 103 at the upper end of the fixed sleeve 101 is connected to the lower end of the upper tube 21, and the lower end of the spring 103 at the lower end of the fixed sleeve 101 is connected to the upper end of the lower tube 23. Both springs 103 are wrapped around the periphery of the connecting tube 22 to prevent the connecting tube 22 from blocking the flow channel therein due to bending. When the spiral stirring rod 2 is stirred at a speed lower than the first speed. The active block 56 drives the passive block 55 to rotate, and forces the fixed tube 101 of the connecting tube 22 to drive the upper and lower springs 103 to undergo elastic deformation. Due to the setting of the fixed tube 101 and the protection of the two springs 103, the elastic tube 22 will not be greatly twisted, such as folded, so that the coolant can flow smoothly, and the scraper 5 is continuously driven to rotate. For example, the fixed tube 101 is a curved tube, such as a V-shaped zigzag tube.

[0056] When the spiral stirring rod 2 stirs at a speed higher than the first speed, the active block 56 can gradually move away from the magnetic attraction range of the passive block 55 and thus detach from the scraper 51 (i.e., the passive block 55 cannot keep up with the speed of the active block 56), and then the connecting pipe 22 returns to its original position under the action of the two springs 103. In this process, the return action of the connecting pipe 55 can keep the coolant inside it unobstructed. Even if the flow is slow locally due to the blockage of impurities, the coolant can be shaken off to keep it unobstructed again. After that, the scraper 51 decelerates and scrapes the inner wall of the kettle body 1 under the action of inertia. When the active block 56 passes the passive block 55 again, the active block 56 drives the connecting pipe 55 to deform again, and drives the scraper 51 to accelerate and scrape the inner wall of the kettle body 1 again through the magnetic attraction until the active block 56 detaches from the passive block 55 again.

[0057] Through the rotation of the spiral stirring rod 2, the connecting pipe 55 can be repeatedly deformed and reset, so that the internal coolant can be kept unobstructed, and the circulation can be restored even if it is occasionally blocked. The scraper 51 is repeatedly accelerated and decelerated, so that the inside of the kettle body 1 can be scraped at a variable speed, and the scraping efficiency can be improved by accelerated scraping. However, it cannot be accelerated to a maximum value all the time. Therefore, after reaching a certain speed, the active block 56 is separated from the magnetic attraction range of the passive block 55, and the scraper 51 is decelerated, so that a large amount of hard matter in the raw material caused by excessive speed is accumulated in front of the moving direction of the scraper 51 and can be dissipated, thereby preventing impurities from passing between the scraper 51 and the inner wall of the kettle body 1 and reducing the scraping efficiency. The present invention can avoid this problem through the deceleration process.

[0058] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A system for polymerization of PVC materials, comprising a reactor for polymerization reaction, characterized in that: The reaction kettle comprises a kettle body, a spiral stirring rod and a rotary joint. The kettle body is installed on the ground through supporting feet. An upper cover is installed on the kettle body. A feed pipe is provided on the upper cover, and a discharge pipe is provided at the lower end of the kettle body. The spiral stirring rod is rotatably installed on the upper cover. The spiral stirring rod is located inside the kettle body. A motor is installed on the upper cover. The motor drives the spiral stirring rod to rotate. The spiral stirring rod is in a spiral shape. The rotary joint is installed at the upper end of the spiral stirring rod. A liquid inlet pipe and a liquid outlet pipe are connected to the rotary joint. A liquid inlet cavity and a liquid outlet cavity are provided in the spiral stirring rod. The liquid inlet cavity and the liquid outlet cavity are connected to each other at the end of the spiral stirring rod away from the motor. The internal channel of the rotary joint is respectively connected to the liquid inlet cavity and the liquid outlet cavity. The wall thickness of the end of the liquid inlet chamber close to the motor is greater than the wall thickness of the end of the liquid inlet chamber away from the motor, the wall thickness of the end of the liquid outlet chamber close to the motor is greater than the wall thickness of the end of the liquid outlet chamber away from the motor, the spiral stirring rod includes an upper tube and a lower tube, the spiral directions of the upper tube and the lower tube are opposite, and the upper tube and the lower tube are connected by a connecting tube; a guide rail is fixedly installed on the inner wall of the kettle body, a scraper is slidably installed on the guide rail, an adsorption block is installed at the end of the scraper away from the guide rail, the adsorption block is adsorbed on the inner wall of the kettle body by magnetic force, a passive block is installed in the middle part of the scraper, an active block is installed on the outer wall of the connecting tube, and the active block and the passive block are connected and matched with each other by magnetic attraction; The connecting tube is an elastic tube used to connect the upper tube and the lower tube. A fixed sleeve is provided on the outer periphery of the middle part of the connecting tube. The active block is fixed on the fixed sleeve. Springs are provided at both the upper and lower ends of the fixed sleeve. The upper end of the spring at the upper end of the fixed sleeve is connected to the lower end of the upper tube, and the lower end of the spring at the lower end of the fixed sleeve is connected to the upper end of the lower tube. Both springs are wrapped around the periphery of the connecting tube to prevent the connecting tube from blocking the flow channel therein due to bending. When the spiral stirring rod stirs at a speed lower than the first speed, the active block drives the passive block to rotate, and forces the fixed sleeve of the connecting tube to drive the upper and lower springs to undergo elastic deformation. The fixed tube is changed into a V-shaped zigzag tube; when the spiral stirring rod stirs at a speed higher than the first speed, the active block can gradually move away from the magnetic attraction range of the passive block and thus separate from the scraper, so that the connecting tube returns to its original position under the action of the two springs. In this process, the returning action of the connecting tube can keep the coolant inside it unobstructed; thereafter, the scraper decelerates and scrapes the inner wall of the kettle body under the action of inertia. When the active block passes the passive block again, the active block drives the connecting tube to deform again, and drives the scraper to accelerate and scrape the inner wall of the kettle body again through the magnetic attraction force, until the active block separates from the passive block again.

2. The system for polymerizing PVC materials according to claim 1, characterized in that: The upper tube includes an inlet tube and an outlet tube, which are connected to each other at the end of the spiral stirring rod away from the motor. The cross-sectional outer contours of the inlet tube and the outlet tube are semicircular, and the combination of the two obtains an upper tube with a circular cross-sectional outer contour. A heat insulation layer is arranged between the inlet tube and the outlet tube, and the internal structures of the upper tube, the lower tube and the connecting tube are the same and correspond one to one.

3. The system for polymerizing PVC materials according to claim 2, characterized in that: There is a gap between the liquid inlet pipe and the liquid outlet pipe, and the gap is surrounded to form a closed cavity. The interior of the cavity is vacuumed and the cavity acts as a heat insulation layer.

4. The system for polymerizing PVC materials according to claim 3, characterized in that: The spiral stirring rod is provided with fins, and the fins are symmetrically arranged on the outer walls of the liquid inlet pipe and the liquid outlet pipe on both sides of the heat insulation layer.

5. The system for polymerizing PVC materials according to claim 4, characterized in that: The thermal conductivity of the fins on the liquid inlet pipe is smaller than the thermal conductivity of the fins on the liquid outlet pipe.

6. The system for polymerizing PVC materials according to claim 5, characterized in that: Reinforcing ribs are evenly arranged on the inner wall of the cavity.

7. The system for polymerizing PVC materials according to claim 6, characterized in that: An inclined surface is arranged on the side wall of the guide rail for installing the scraper, and a through hole is opened on the inclined surface, and the through hole communicates the inside of the guide rail with the inside of the kettle body.

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