Production method and device of expandable polymethyl methacrylate resin

Abstract

The invention relates to the technical field of expandable polymethyl methacrylate, in particular to an expandable polymethyl methacrylate resin production method and device.The production device comprises a frame shell, a pair of side plates, a vertical rod and a plurality of screening nets, the frame shell is arranged above a supporting frame, and the section of the frame shell is in an inverted U shape; the two side plates are symmetrically installed on the two sides in the frame shell in a limiting mode, the end faces of the two sides are in sliding fit with the inner side surface of the frame shell, the frame shell and the side plates form a screening drying box, and the vertical rod is vertically arranged in the frame shell and located between the two side plates. The screening and drying processes are integrated through the screening drying box, the number of devices is reduced, the device cost and occupied space of a production line are reduced, meanwhile, materials are prevented from being transferred among multiple devices, the production period is shortened, hot air is conveyed from the bottom of the screening drying box through the hot air drying system, and heat flow upwards flows in the screening drying box; and the materials are fully contacted with the dynamically-rolled materials, so that the drying uniformity and efficiency are improved.

Description

Technical Field

[0001] This invention relates to the field of expandable polymethyl methacrylate (PMMA) preparation technology, specifically to a method and apparatus for producing expandable PMMA resin. Background Technology

[0002] Pattern making is one of the prerequisites for obtaining accurate castings in lost foam casting technology, and the selection of raw materials for foaming is particularly important for producing qualified lost foam castings. Currently, the main raw materials for lost foam casting patterns include expandable polystyrene, expandable polymethyl methacrylate (PMMA), and styrene-methyl methacrylate copolymer. Because expandable PMMA patterns can solve the defects such as bright carbon and surface carbonization that occur when expandable polystyrene patterns are used in ferrous metal lost foam casting, and because its decomposition products are mainly gases, resulting in clean, fluid, and reusable sand after pouring, expandable PMMA will become an important pattern material for ferrous metal lost foam casting.

[0003] Traditional methods for preparing expandable polymethyl methacrylate (PMMA) require a washing process followed by dehydration. While dehydration removes most of the water from the product, the surface moisture content remains high. Therefore, a subsequent drying process is necessary. The drying process involves pre-drying the product using a dryer, then sieving the dried product, and finally performing a second drying process according to the sieving specifications.

[0004] The above-mentioned drying, screening, and re-drying process requires multiple pieces of equipment, including a primary dryer, screening equipment, and secondary drying equipment. This results in a large number of devices, high costs, and a larger production line space. In addition, after the material is pre-dried, it needs to be transferred to the screening equipment, and after screening, it is transferred to the secondary drying equipment according to specifications. This process is lengthy and requires multiple material transfers, which increases the production cycle and reduces production efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for producing expandable polymethyl methacrylate resin, so as to solve the technical problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution.

[0007] A method for producing expandable polymethyl methacrylate resin specifically includes the following steps: S1. Pump pure water into the dissolving kettle, heat it to 90°C and start stirring. Add methyl cellulose ether and stir for more than 40 minutes. Then add sodium sulfate. Pump the pure water and the dissolved methyl cellulose ether and sodium sulfate into the reaction kettle and stir. Then cool it down to 25°C. S2. Methyl methacrylate, styrene, pentane and the initiator tert-butyl peroxide are gradually pumped into the mixing vessel, and then tetrabromomethane is added as an auxiliary agent and stirred for more than 40 minutes. S3. Stop stirring in the reactor, pump the mixed monomer from the mixing vessel into the reactor, purge with nitrogen at 0.25 MPa, stir for 1.5 hours, then heat at a constant rate to 72-75°C, hold for 6 hours, then heat to 90-94°C, hold for 2 hours, when the pressure reaches 0.8 MPa, then cool to room temperature and unload. S4. Press the reacted material into a water washing kettle for washing until it is clean, and then put it into a screening and drying box for screening and drying to obtain the finished product.

[0008] Preferably, an expandable polymethyl methacrylate resin production apparatus includes a frame shell, a pair of side plates, a vertical rod, and several screening screens. The frame shell is located above a support frame and has an inverted U-shaped cross-section. The two side plates are symmetrically positioned and installed on both sides inside the frame shell, and their end faces slide against the inner surface of the frame shell. The frame shell and the side plates constitute a screening and drying chamber. The vertical rod is vertically installed inside the frame shell and located between the two side plates. Several mounting strips are fixed on the vertical rod at intervals from top to bottom. Screening screens are hinged to both sides of the mounting strips. The other side of each screening screen is hinged to the inner surface of the side plate on the same side. A driving mechanism is provided on the outside of the frame shell to drive the vertical rod to lift and adjust. A hot air drying system is also provided outside the frame shell to deliver hot air from the bottom to the screening and drying chamber. A feeding mechanism is provided at the top of the frame shell to feed wet material into the screening and drying chamber from the top.

[0009] Preferably, a fixing plate is fixed on both sides of the top of the frame shell, and several sliding rods are fixed on both fixing plates. The sliding rods are arranged at intervals along the width direction of the screening and drying box. Several sliding holes are evenly distributed on both side plates, and each sliding rod slides through the sliding hole on both side plates in a corresponding manner.

[0010] Preferably, each slide bar has a hollow cavity extending along its length, and each hollow cavity is fitted with an electric heating rod extending along the length of the slide bar.

[0011] Preferably, the hot air drying system includes a U-shaped shell and baffles. The U-shaped shell is fixed to the outside of the frame shell and forms a U-shaped flow channel between it and the outer surface of the frame shell. The support frame is fixed to the bottom of the U-shaped shell. Baffles are fixed on both sides of the U-shaped shell near the top. An air collecting chamber is formed between the baffles and the top of the U-shaped shell. Inlet pipes communicating with the air collecting chamber are provided on both sides of the U-shaped shell. Several vertically penetrating diversion holes are evenly distributed on the two baffles. The ends of the two inlet pipes are connected to the air outlet of the hot air generator.

[0012] Preferably, the drive mechanism includes a mounting base, a threaded rod, a drive motor, a nut seat, and an L-shaped connecting arm. The mounting base is vertically fixed on the outer surface of the U-shaped housing. The threaded rod is rotatably mounted on the mounting base. The drive motor is fixed at the top of the mounting base, and its output shaft is fixedly connected to the top of the threaded rod. A guide rod is fixed on the mounting base. The nut seat is slidably fitted on the guide rod and threadedly fitted on the threaded rod. The bottom end of the vertical rod extends through to the bottom of the U-shaped housing. One end of the L-shaped connecting arm is fixed to the nut seat, and the other end extends to the bottom of the U-shaped housing and is fixed to the vertical rod.

[0013] Preferably, the L-shaped connecting arm is provided with a striking vibration structure, which includes a rotating shaft, a circular seat, and striking rods. The rotating shaft is rotatably mounted on the L-shaped connecting arm and extends vertically. The top end of the rotating shaft is fixedly connected to the bottom end of the threaded rod. The bottom end of the rotating shaft is fixed with a circular seat. An annular groove is provided on the outer edge of the circular seat. Several striking rods are installed in an annular array in the annular groove. A vibration plate is installed at the bottom end of the vertical rod at the same height as the striking rods. During the rotation of the circular seat, it can drive each striking rod to strike the vibration plate in sequence to achieve striking vibration.

[0014] Preferably, a number of shafts are rotatably mounted in an annular array within the annular groove, and the two ends of the shafts are elastically connected to the inner wall of the annular groove through spiral springs. One end of each striking rod is fixedly fitted onto the corresponding shaft, and the vibrating plate has two symmetrical arc-shaped surfaces at the end facing the round seat.

[0015] Preferably, a partitioned discharge mechanism is provided on the side of the two side plates that are far apart from each other. The partitioned discharge mechanism is used to discharge the screened material in sections. The partitioned discharge mechanism includes a baffle plate and a cylinder A. The baffle plate is vertically slidably installed on the outer surface of the side plate. Several outwardly inclined discharge ports are evenly distributed on the baffle plate from top to bottom. The side plate is provided with discharge ports at the corresponding positions of each layer of screening mesh, and the spacing and number of discharge ports correspond to the discharge ports. A bracket A is fixed at the bottom of the outer surface of the two side plates. The cylinder A is vertically fixed on the bracket A. The telescopic end of the cylinder A is fixedly connected to the baffle plate on the same side through a connector. When there is a connected and overlapping area between the discharge port and the discharge port, a discharge channel is formed.

[0016] Preferably, the feeding mechanism includes a collection box, a cylinder B, and a horizontal plate. The collection box is fixed to the top of the frame shell and has a feeding hopper at the top. The bottom is connected to the screening and drying box. The collection box has a horizontally extending sliding opening near its bottom end. The horizontal plate is slidably installed in the sliding opening. The horizontal plate has several material discharge ports evenly distributed. A bracket B is fixed to the outer surface of the collection box. The cylinder B is horizontally fixed to the side of the bracket B, and the telescopic end of the cylinder B is fixedly connected to the side end of the horizontal plate through a connecting block. The cylinder B is used to drive the horizontal plate to slide and adjust along the length direction of the screening and drying box.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0018] By integrating the screening and drying processes into a screening and drying chamber, the number of equipment is reduced, equipment costs and production line space are lowered, and the transfer of materials between multiple devices is avoided, shortening the production cycle. The hot air drying system delivers hot air from the bottom of the screening and drying chamber, and the heat flows upward inside the chamber, making full contact with the dynamically tumbling materials. At the same time, electric heating rods preheat the materials through the heat conduction of the sliding rods, reducing the surface moisture of the materials, reducing adhesion, improving drying uniformity and efficiency, and solving the problems of insufficient drying and low efficiency in traditional drying methods.

[0019] The drive mechanism drives the vertical rod to rise and fall, causing the screening screen to dynamically change into a V-shape or an inverted V-shape, so that the material continuously rolls on the screening screen, avoiding local accumulation and blockage. Combined with the design of the screening screen with progressively decreasing screen aperture, it can achieve efficient screening of materials of various specifications, solving the problems of easy material blockage and incomplete screening in traditional screening.

[0020] The threaded rod drives the rotating shaft seat to rotate, causing the striking rods to strike the vibrating plate in sequence. The vibration is transmitted to the screening screen through the vertical rod mounting strip, which enhances the screening screen's shaking effect on the material, avoids excessive local accumulation of material, ensures unobstructed screening channels and smooth heat flow, and further improves the screening and drying effect.

[0021] In the partitioned discharge mechanism, cylinder A drives the baffle plate to rise and fall, forming a discharge channel between the discharge port and the outlet. Materials of different specifications are discharged through the corresponding channels in partitioned areas, eliminating the need for further screening, thus shortening the production process and improving production efficiency. Attached Figure Description

[0022] Figure 1 A flowchart of the production method steps provided by the present invention; Figure 2 A three-dimensional schematic diagram of the overall structure of the production device provided by the present invention; Figure 3 This is a partial structural diagram of the frame shell in this invention; Figure 4 for Figure 3 The diagram shows a cross-sectional view of the structure. Figure 5 for Figure 4 Enlarged schematic diagram of the structure at point A in the middle; Figure 6 This is a schematic diagram of the partitioned material feeding mechanism in this invention; Figure 7 for Figure 1 The structure shown omits the schematic diagram of the support frame and feeding mechanism; Figure 8 This is a schematic diagram of the hot air drying system in this invention; Figure 9 This is a schematic diagram showing the flow direction of hot air within the U-shaped channel. Figure 10 This is a schematic diagram of the drive mechanism structure in this invention; Figure 11 This is a schematic diagram of a hammering and vibration structure. Figure 12 for Figure 11 Enlarged schematic diagram of the structure at point B; Figure 13 This is a schematic diagram of the feeding mechanism in this invention; Figure 14 for Figure 13 A cross-sectional schematic diagram of the structure shown.

[0023] In the diagram: 01. Vibrating plate; 02. Rotating shaft; 03. Round seat; 031. Annular groove; 04. Striking rod; 041. Shaft; 042. Scroll spring; 1. Support frame; 2. Frame shell; 201. Screening and drying box; 3. Side plate; 301. Sliding hole; 31. Discharge port; 4. Vertical rod; 41. Mounting strip; 42. Screening screen; 5. Drive mechanism; 51. Mounting seat; 52. Threaded rod; 53. Drive motor; 54. Guide rod; 55. Nut seat; 56. L-shaped connecting arm; 6. Sliding rod; 61. Fixing plate; 6 2. Electric heating rod; 7. Zoned discharge mechanism; 71. Baffle plate; 711. Discharge port; 72. Support A; 73. Cylinder A; 74. Connecting parts; 8. Hot air drying system; 81. U-shaped shell; 82. Inlet pipe; 83. U-shaped flow channel; 84. Baffle plate; 841. Diverting hole; 842. Air collection chamber; 85. Grating plate; 9. Feeding mechanism; 91. Collection box; 911. Feeding hopper; 912. Sliding port; 92. Support B; 93. Cylinder B; 94. Connecting block; 95. Horizontal plate; 951. Discharge port. Detailed Implementation

[0024] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0025] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection" and "installation" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. Furthermore, "connection" can be a direct connection or an indirect connection through an intermediate medium. "Fixed" means that the devices are connected to each other and their relative positional relationship remains unchanged after the connection. The directional terms mentioned in the embodiments of the present invention, such as "inner," "outer," "top," and "bottom," are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of the present invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention.

[0026] In this embodiment of the invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0027] In this embodiment of the invention, "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0028] References to "one embodiment" or "some embodiments" as used in this specification mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in one or more embodiments of the invention. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including, but not limited to," unless otherwise specifically emphasized. Example 1

[0029] Please see Figure 1 This invention provides a method for producing expandable polymethyl methacrylate resin, specifically including the following steps: S1. Pump pure water into the dissolving kettle, heat it to 90°C and start stirring. Add methyl cellulose ether and stir for more than 40 minutes. Then add sodium sulfate. Pump the pure water and the dissolved methyl cellulose ether and sodium sulfate into the reaction kettle and stir. Then cool it down to 25°C. S2. Methyl methacrylate, styrene, pentane and the initiator tert-butyl peroxide are gradually pumped into the mixing vessel, and then tetrabromomethane is added as an auxiliary agent and stirred for more than 40 minutes. S3. Stop stirring in the reactor, pump the mixed monomer from the mixing vessel into the reactor, purge with nitrogen at 0.25 MPa, stir for 1.5 hours, then heat at a constant rate to 72-75°C, hold for 6 hours, then heat to 90-94°C, hold for 2 hours, when the pressure reaches 0.8 MPa, then cool to room temperature and unload. S4. Press the reacted material into the washing kettle for washing until it is clean, and then put it into the screening and drying box 201 for screening and drying to obtain the finished product.

[0030] Similar to existing technologies, the product is a polymer polymerization reaction, which is a synthesis reaction of styrene with methyl methacrylate, pentane, tetrabromomethane, etc., forming spherical particles of 0.2-1.0 mm. Pentane does not participate in the reaction, but it is already present in each chamber of the sphere during the initial stirring. The inner cavity of the sphere is honeycomb-like, and pentane is present in it. When the customer uses it, it is expanded by heating and adding steam.

[0031] Subsequently, the project's waste liquid enters the sewage treatment plant for treatment, using a combination of physicochemical treatment and biochemical processes. The solid waste is stored in the hazardous waste warehouse, and the waste gas is incinerated in the waste gas incinerator after being washed with alkaline water. The exhaust gas treatment system and sewage treatment plant mentioned above are all existing technologies, so this application will not elaborate on them. Example 2

[0032] Please see Figures 2-14 This invention provides a production apparatus for expandable polymethyl methacrylate resin, specifically applied to step four of Example 1. The production apparatus includes a frame shell 2, a pair of side plates 3, a vertical rod 4, and several screening screens 42. The frame shell 2 is located above the support frame 1 and has an inverted U-shaped cross-section. The two side plates 3 are symmetrically positioned and installed on both sides inside the frame shell 2, and their end faces slide against the inner surface of the frame shell 2, which allows the two side plates 3 to slide left and right inside the frame shell 2. The frame shell 2 and the two side plates 3 constitute a screening and drying box 201, which is used to hold materials for screening and drying.

[0033] The vertical rod 4 is set vertically inside the frame 2 and located between the two side plates 3. The vertical rod 4 is centrally arranged inside the screening and drying box 201, and several mounting strips 41 are fixed on the vertical rod 4 at intervals from top to bottom. The spacing between two adjacent mounting strips 41 is basically the same.

[0034] Each mounting strip 41 is hinged to both sides with a screening screen 42, and the other side of each screening screen 42 is hinged to the inner surface of the side plate 3 on the same side. The specific hinge method adopts the existing technology, which will not be described in detail in this application. Both sides of each screening screen 42 are slidably attached to the inner surfaces of both sides of the frame shell 2 to avoid excessive gaps between them and the inner surfaces of the frame shell 2, which could lead to material leakage.

[0035] Two screening screens 42 on the same side form a screening structure. The diameter of the screen holes on each layer of screening screen 42 decreases downwards, thereby realizing multi-stage screening of materials. The screening screen 42 in this application is set with five layers according to production requirements, so that the materials can be screened into five specifications. It is worth noting that the screen hole diameter on the bottom layer of screening screen 42 is smaller than the minimum particle size of the material, which can prevent the material from falling out from the bottom. At the same time, it also facilitates the hot flow for drying to enter from the bottom of the screening and drying box 201 and flow upwards.

[0036] In addition, a drive mechanism 5 is provided on the outside of the frame shell 2. The drive mechanism 5 is used to drive the vertical rod 4 to lift and adjust. A hot air drying system 8 is also provided on the outside of the frame shell 2 to deliver hot air from the bottom to the screening and drying box 201. A feeding mechanism 9 is provided on the top of the frame shell 2 to feed wet material from the top into the screening and drying box 201.

[0037] The material is fed into the screening and drying box 201 by the feeding mechanism 9. Under the action of gravity, the material falls and is screened into different specifications by the layered screening mesh 42. At the same time, the hot air drying system 8 works to send hot air into the screening and drying box 201 from the bottom. The hot air flows upward on the screening and drying box 201. While screening, the wet material can be dried. Thus, the screening and drying of multiple specifications of material can be completed at the same time, reducing the complexity of the process, improving production efficiency and reducing production costs. Example 3

[0038] Please see Figure 5 The difference between this embodiment and Embodiment 2 is that: Both sides of the top of the frame shell 2 are fixed with fixing plates 61. Several sliding rods 6 are fixed on the two fixing plates 61. The sliding rods 6 are arranged at intervals along the width direction of the screening and drying box 201. Several sliding holes 301 are evenly distributed on the side plates 3. Each sliding rod 6 slides through the sliding hole 301 on the side plates 3. The sliding cooperation between the sliding rod 6 and the sliding hole 301 provides a guiding and limiting function for the side plates 3, ensuring that the movement of the side plates 3 is limited to the length direction of the screening and drying box 201.

[0039] In addition, each slide rod 6 has a hollow cavity extending along its length, and each hollow cavity is fitted with an electric heating rod 62 extending along the length of the slide rod 6. Furthermore, each slide rod 6 is made of aluminum, which has good thermal conductivity.

[0040] On the one hand, the slide bars 6 are arranged at intervals along the width of the screening and drying box 201, which can divide and guide the material falling into the screening and drying box 201, ensuring that the material can fall evenly on the uppermost screening screen 42, thus improving the screening effect. On the other hand, the electric heating rod 62 is powered on and generates heat, which is transferred to the slide bars 6 and then to the surrounding area, which can preheat and dry the material in the path, initially reducing the moisture on the outer surface of the material, reducing the adhesion between the materials, and further facilitating subsequent screening. Example 4

[0041] Please see Figure 7 and Figure 8 The difference between this embodiment and Embodiment 3 is as follows: The hot air drying system 8 includes a U-shaped shell 81 and baffles 84. The U-shaped shell 81 is fixed to the outside of the frame shell 2, and a U-shaped flow channel 83 is formed between the U-shaped shell 81 and the outer surface of the frame shell 2. The support frame 1 is fixed to the bottom of the U-shaped shell 81. Baffles 84 are fixed on both sides of the U-shaped shell 81 near the top. An air collecting chamber 842 is formed between the baffles 84 and the top of the U-shaped shell 81. Inlet pipes 82 communicating with the air collecting chamber 842 are provided on both sides of the U-shaped shell 81. Several vertically penetrating diversion holes 841 are evenly distributed on the two baffles 84. The ends of the two inlet pipes 82 are connected to the air outlet of the hot air generator. The hot air generator is an external device and adopts existing technology. Its specific structure and working principle will not be described in detail.

[0042] The hot air generator produces a hot air flow, which is supplied into the air collection chamber 842 through the inlet pipe 82. The hot air then flows into the U-shaped flow channel 83 through the diversion hole 841, and finally flows into the screening and drying chamber 201 through the bottom. The hot air flow forms an upward flow in the screening and drying chamber 201 to provide a drying effect while screening.

[0043] In addition, several grid plates 85 are slidably installed at intervals at the bottom of the frame shell 2, and an airflow channel is formed between two adjacent grid plates 85 so that the heat flow entering the screening and drying chamber 201 is evenly distributed and the drying uniformity is improved. The adjacent grid plates 85 are elastically connected by springs. When the two side plates 3 approach each other, they can push each grid plate 85 to move synchronously, so as to avoid the fixed installation of the grid plates 85 from obstructing the movement of the two side plates 3. In addition, when the two side plates 3 move away from each other, the elastic force of the springs can push each grid plate 85 to slide back to its original position. The specific installation method of the grid plates 85 adopts the existing technology, so it is not shown in the attached drawings. Example 5

[0044] Please see Figure 7 and Figure 10 The difference between this embodiment and embodiment 4 is that: The drive mechanism 5 includes a mounting base 51, a threaded rod 52, a drive motor 53, a nut seat 55, and an L-shaped connecting arm 56. The mounting base 51 is vertically fixed on the outer surface of the U-shaped housing 81. The threaded rod 52 is rotatably mounted on the mounting base 51. The drive motor 53 is fixed at the top of the mounting base 51, and its output shaft is fixedly connected to the top of the threaded rod 52. A guide rod 54 is fixed on the mounting base 51. The nut seat 55 is slidably fitted on the guide rod 54 and threadedly fitted on the threaded rod 52. The bottom end of the vertical rod 4 extends through to the bottom of the U-shaped housing 81. One end of the L-shaped connecting arm 56 is fixed to the nut seat 55, and the other end extends to the bottom of the U-shaped housing 81 and is fixed to the vertical rod 4.

[0045] The drive motor 53 can drive the threaded rod 52 to rotate in the forward or reverse direction. The rotating threaded rod 52 can drive the nut seat 55 to slide up and down along the guide rod 54. Under the connection of the L-shaped connecting arm 56, it drives the vertical rod 4 to rise and fall synchronously, providing a stable drive for the rise and fall of the vertical rod 4.

[0046] When the vertical rod 4 rises, it simultaneously drives the mounting strip 41 to move upward. Under the action of the two ends of the screening mesh 42 interacting with the mounting strip 41 and the inner surface of the side plate 3 respectively, it can drive the two side plates 3 to move closer to each other. At this time, the two screening meshes 42 of each layer are arranged in an inverted V-shape in the screening and drying box 201. Similarly, when the vertical rod 4 descends, it can pull the two screening meshes 42 of each layer to be arranged in a V-shape in the screening and drying box 201. The vertical rod 4 is driven to move up and down repeatedly by the drive mechanism 5, so that the structure formed by the two screening meshes 42 of each layer in the screening and drying box 201 is constantly changing dynamically, and the angle of the screening mesh 42 is also constantly changing dynamically. This causes the material to roll continuously during the screening and drying process, reducing local accumulation. On the one hand, it avoids the blockage caused by local accumulation of material, which affects screening. On the other hand, it avoids the blockage of the flow of hot air. At the same time, it makes the material roll continuously, avoiding mutual shading and affecting drying, effectively improving the drying efficiency of wet material.

[0047] Secondly, combining Figure 11 and Figure 12 The L-shaped connecting arm 56 is equipped with a striking vibration structure, which includes a rotating shaft 02, a circular seat 03, and striking rods 04. The rotating shaft 02 is rotatably mounted on the L-shaped connecting arm 56 and extends vertically. The top end of the rotating shaft 02 is fixedly connected to the bottom end of the threaded rod 52. The circular seat 03 is fixed to the bottom end of the rotating shaft 02. The outer edge of the circular seat 03 is provided with an annular groove 031. Several striking rods 04 are installed in an annular array in the annular groove 031. A vibrating plate 01 is installed at the bottom end of the vertical rod 4 at the same height as the striking rods 04. During the rotation of the circular seat 03, it can drive each striking rod 04 to strike the vibrating plate 01 in sequence to achieve striking vibration.

[0048] When the threaded rod 52 rotates, it can drive the rotating shaft 02 and the round seat 03 to rotate synchronously, and drive the striking rod 04 to swing. Each striking rod 04 can strike the vibrating plate 01 in sequence to achieve the striking effect. The vibration generated is transmitted to the vertical rod 4 through the vibrating plate 01, and then to each layer of screening screen 42 through each mounting strip 41. This allows the screening screen 42 to move in the screening and drying box 201 while improving the vibration and shaking effect, and further reducing the local accumulation of materials.

[0049] The annular groove 031 contains a number of shafts 041 arranged in an annular array for rotation. The two ends of the shafts 041 are elastically connected to the inner wall of the annular groove 031 through a spiral spring 042. One end of each striking rod 04 is fixedly mounted on the corresponding shaft 041. The vibrating plate 01 has two arc-shaped surfaces symmetrically facing the round seat 03.

[0050] By utilizing the installation method of shaft 041 and spiral spring 042, the striking rod 04 and the round seat 03 are elastically connected. After the striking rod 04 contacts the vibrating plate 01, as the rotating shaft 02 continues to rotate, the striking rod 04 can swing, avoiding obstruction and interference with the vibrating plate 01. After the striking rod 04 separates from the vibrating plate 01, the striking rod 04 elastically returns to its original position, thereby ensuring the smoothness of the rotation of the rotating shaft 02. Example 6

[0051] Please see Figure 6 The difference between this embodiment and embodiment 5 is as follows: On the side of each side plate 3 that is far apart from each other, there is a partitioned discharge mechanism 7. The partitioned discharge mechanism 7 is used to discharge the screened material in sections. The partitioned discharge mechanism 7 includes a baffle plate 71 and a cylinder A73. The baffle plate 71 is vertically slidably installed on the outer surface of the side plate 3. Several outwardly inclined discharge ports 711 are evenly distributed on the baffle plate 71 from top to bottom. The side plate 3 is provided with discharge ports 31 at the corresponding positions of each layer of screening mesh 42. The spacing and number of discharge ports 31 correspond to the discharge ports 711. A bracket A72 is fixed at the bottom of the outer surface of each side plate 3. The cylinder A73 is vertically fixed on the bracket A72. The telescopic end of the cylinder A73 is fixedly connected to the baffle plate 71 on the same side through a connector 74. When there is a connecting and overlapping area between the discharge port 711 and the discharge port 31, a discharge channel is formed.

[0052] After the material is dried, the vertical rod 4 is driven upward by the drive mechanism 5, so that each layer of screening screen 42 is in an inverted V-shaped structure in the screening and drying box 201. The slope on both sides guides the material to the side plates 3. At the same time, the cylinder A73 pushes the baffle plate 71 upward, so that each discharge port 711 corresponds to the discharge port 31. The material rolling down along the screening screen 42 is finally discharged at an angle through the corresponding discharge port 711. By connecting the corresponding receiving pipe to each discharge port 711, the zonal collection of materials of different specifications can be realized.

[0053] Secondly, as the vertical rod 4 moves upward and pulls the two screening screens 42 in the same layer, the included angle gradually decreases, which can link the knocking and vibration structure to work synchronously to produce the effect of vibrating material, further improving the material discharge effect.

[0054] In addition, when not discharging material, the cylinder A73 drives the baffle plate 71 downward, causing the discharge port 711 to be misaligned with the corresponding outlet 31. The remaining part of the baffle plate 71 blocks the outlet 31, which can prevent material leakage. Example 7

[0055] Please see Figure 13 and Figure 14 The difference between this embodiment and embodiment 6 is that: The feeding mechanism 9 includes a collection box 91, a cylinder B93, and a horizontal plate 95. The collection box 91 is fixed to the top of the frame shell 2 and has a feeding hopper 911 at the top. The bottom is connected to the screening and drying box 201. The collection box 91 has a horizontally extending sliding opening 912 near its bottom end. The horizontal plate 95 is slidably installed in the sliding opening 912. The horizontal plate 95 has several material discharge ports 951 evenly distributed. A bracket B92 is fixed on the outer surface of the collection box 91. The cylinder B93 is horizontally fixed to the side of the bracket B92, and the telescopic end of the cylinder B93 is fixedly connected to the side end of the horizontal plate 95 through a connecting block 94. The cylinder B93 is used to drive the horizontal plate 95 to slide and adjust along the length direction of the screening and drying box 201.

[0056] Wet material is fed from the feeding hopper 911 into the collection box 91 and falls onto the horizontal plate 95. Finally, it falls into the screening and drying box 201 through the discharge port 951. The horizontal plate 95 is moved back and forth by the extension and retraction of the cylinder B93, so that the discharge port 951 on the horizontal plate 95 changes position from left to right, so that the material can be evenly fed into the screening and drying box 201.

[0057] The control method of the present invention is automatic control through a controller. The control circuit of the controller can be implemented by simple programming by those skilled in the art. The power supply is also common knowledge in the art. Therefore, the present invention will not explain the control method and circuit connection in detail.

[0058] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

Claims

1. A method for producing expandable polymethyl methacrylate resin, characterized in that, Specifically, the following steps are included: S1. Pump pure water into the dissolving kettle, heat it to 90°C and start stirring. Add methyl cellulose ether and stir for more than 40 minutes. Then add sodium sulfate. Pump the pure water and the dissolved methyl cellulose ether and sodium sulfate into the reaction kettle and stir. Then cool it down to 25°C. S2. Methyl methacrylate, styrene, pentane and the initiator tert-butyl peroxide are gradually pumped into the mixing vessel, and then tetrabromomethane is added as an auxiliary agent and stirred for more than 40 minutes. S3. Stop stirring in the reactor, pump the mixed monomer from the mixing vessel into the reactor, purge with nitrogen at 0.25 MPa, stir for 1.5 hours, then heat at a constant rate to 72-75°C, hold for 6 hours, then heat to 90-94°C, hold for 2 hours, when the pressure reaches 0.8 MPa, then cool to room temperature and unload. S4. Press the reacted material into the washing kettle for washing until it is clean, and then put it into the sieving and drying box (201) for sieving and drying to obtain the finished product.

2. An apparatus for producing expandable polymethyl methacrylate resin, used in step four of the method for producing expandable polymethyl methacrylate resin according to claim 1, characterized in that: It includes a frame (2), a pair of side plates (3), vertical rods (4) and several screening screens (42); The frame (2) is located above the support frame (1) and has an inverted U-shaped cross section; The two side plates (3) are symmetrically positioned and installed on both sides inside the frame (2), and the end faces of both sides slide against the inner surface of the frame (2). The frame (2) and the side plates (3) constitute a screening and drying oven (201). The vertical rod (4) is vertically set inside the frame (2) and located between the two side plates (3). Several mounting strips (41) are fixed on the vertical rod (4) from top to bottom at intervals. The screening mesh (42) is hinged on both sides of the mounting strip (41), and the other side of each screening mesh (42) is hinged to the inner surface of the side plate (3) on the same side. The outer side of the frame (2) is provided with a drive mechanism (5), which is used to drive the vertical rod (4) to adjust its height. The frame (2) is also provided with a hot air drying system (8) for conveying hot air from the bottom to the screening and drying box (201); The top of the frame (2) is provided with a feeding mechanism (9) for feeding wet material from the top into the screening and drying box (201).

3. The apparatus for producing expandable polymethyl methacrylate resin according to claim 2, characterized in that: The top two sides of the frame shell (2) are fixed with fixing plates (61), and several sliding rods (6) are fixed on the two fixing plates (61). The slide bars (6) are arranged at intervals along the width direction of the sieving and drying box (201); Several sliding holes (301) are evenly distributed on the two side plates (3), and each sliding rod (6) slides through the sliding holes (301) on the two side plates (3) in a corresponding manner.

4. The apparatus for producing expandable polymethyl methacrylate resin according to claim 3, characterized in that: Each of the slide rods (6) has a hollow cavity extending along its length, and each hollow cavity is fitted with an electric heating rod (62) extending along the length of the slide rod (6).

5. The apparatus for producing expandable polymethyl methacrylate resin according to claim 2, characterized in that: The hot air drying system (8) includes a U-shaped shell (81) and a baffle (84). The U-shaped shell (81) is fixed to the outside of the frame shell (2) and forms a U-shaped flow channel (83) between it and the outer surface of the frame shell (2). The support frame (1) is fixed to the bottom of the U-shaped shell (81). A baffle plate (84) is fixed on both sides of the U-shaped shell (81) and near the top, and an air collection cavity (842) is formed between the baffle plate (84) and the top of the U-shaped shell (81). The U-shaped shell (81) is provided with inlet pipes (82) on both sides that are connected to the gas collection chamber (842), and the two baffles (84) are provided with a number of vertically penetrating diversion holes (841). The ends of the two inlet pipes (82) are connected to the air outlet of the hot air generator.

6. The apparatus for producing expandable polymethyl methacrylate resin according to claim 5, characterized in that: The drive mechanism (5) includes a mounting base (51), a threaded rod (52), a drive motor (53), a nut seat (55), and an L-shaped connecting arm (56). The mounting base (51) is vertically fixed on the outer surface of the U-shaped housing (81), the threaded rod (52) is rotatably mounted on the mounting base (51), the drive motor (53) is fixed at the top of the mounting base (51), and the output shaft is fixedly connected to the top of the threaded rod (52). A guide rod (54) is fixed on the mounting base (51), and the nut seat (55) is slidably fitted on the guide rod (54), while the threaded matching is fitted on the threaded rod (52); The bottom end of the vertical rod (4) extends through to the bottom of the U-shaped shell (81); One end of the L-shaped connecting arm (56) is fixed to the nut seat (55), and the other end extends to the bottom of the U-shaped housing (81) and is fixed to the vertical rod (4).

7. The apparatus for producing expandable polymethyl methacrylate resin according to claim 6, characterized in that: The L-shaped connecting arm (56) is provided with a striking vibration structure, which includes a rotating shaft (02), a round seat (03) and a striking rod (04). The rotating shaft (02) is rotatably mounted on the L-shaped connecting arm (56) and extends vertically; The top end of the rotating shaft (02) is fixedly connected to the bottom end of the threaded rod (52), and the bottom end of the rotating shaft (02) is fixed with the round seat (03). The outer edge of the round base (03) is provided with an annular groove (031), and a plurality of the striking rods (04) are installed in an annular array inside the annular groove (031). A vibrating plate (01) is installed at the bottom of the vertical rod (4) at the same height as the striking rod (04). During the rotation of the round seat (03), it can drive each striking rod (04) to strike the vibrating plate (01) in sequence to achieve striking vibration.

8. The apparatus for producing expandable polymethyl methacrylate resin according to claim 7, characterized in that: Several shafts (041) are rotatably mounted in an annular array inside the annular groove (031), and the two ends of the shafts (041) are elastically connected to the inner wall of the annular groove (031) through spiral springs (042). One end of each of the striking rods (04) is fixedly fitted onto the corresponding shaft (041); The vibrating plate (01) has two arc-shaped surfaces symmetrically facing the round seat (03).

9. The apparatus for producing expandable polymethyl methacrylate resin according to claim 2, characterized in that: The two side plates (3) are respectively provided with a partitioned discharge mechanism (7) on the side that is far apart from each other. The partitioned discharge mechanism (7) is used to discharge the screened material in partitions. The partitioned material discharge mechanism (7) includes a baffle plate (71) and a cylinder A (73); The baffle plate (71) is vertically slidably installed on the outer surface of the side plate (3), and the baffle plate (71) has a number of outwardly inclined discharge ports (711) evenly distributed from top to bottom. The side plate (3) is provided with discharge ports (31) at the corresponding positions of the screening mesh (42) in each layer, and the spacing and number of discharge ports (31) correspond to the discharge ports (711); A bracket A (72) is fixed at the bottom of the outer surface of the two side plates (3). The cylinder A (73) is vertically fixed on the bracket A (72). The telescopic end of the cylinder A (73) is fixedly connected to the baffle plate (71) on the same side through a connector (74). When there is a common and overlapping area between the discharge port (711) and the outlet (31), a discharge channel is formed.

10. The apparatus for producing expandable polymethyl methacrylate resin according to claim 2, characterized in that: The feeding mechanism (9) includes a collection box (91), a cylinder B (93), and a horizontal plate (95); The collection box (91) is fixed to the top of the frame shell (2), and has a feeding hopper (911) at the top and is connected to the screening and drying box (201) at the bottom; The material collection box (91) has a horizontally extending sliding opening (912) near its bottom end. A horizontal plate (95) is slidably installed in the sliding opening (912), and the horizontal plate (95) has a number of material drop openings (951) evenly distributed. A bracket B (92) is fixed on the outer surface of the collection box (91), and the cylinder B (93) is horizontally fixed on the side of the bracket B (92). The telescopic end of the cylinder B (93) is fixedly connected to the side of the horizontal plate (95) through the connecting block (94). The cylinder B (93) is used to drive the horizontal plate (95) to slide and adjust along the length of the screening and drying box (201).

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