Continuous synthesis device and process for polymethyl methacrylate with adjustable technical route

Abstract

The invention relates to the technical field of polymer synthesis, in particular to a polymethyl methacrylate continuous synthesis device and process with an adjustable technical route. A material outlet end of a complete mixing type reactor I of the device is connected with a material inlet end of a complete mixing type reactor II through a pipeline with a valve; the material outlet ends of the complete mixing type reactor I and the complete mixing type reactor II are respectively connected with the system inlet of the piston flow type reactor, the inlet of the devolatilization device and the inlet of the double-screw devolatilization extruder II through pipelines with valves; an outlet of the piston flow type reactor system is connected with an inlet of the double-screw devolatilization extruder I through a pipeline with a valve, and an outlet of the devolatilization device is respectively connected with the inlet of the double-screw devolatilization extruder I and an inlet of the double-screw devolatilization extruder II through pipelines with valves. According to the invention, continuous and stable batch production of PMMA molding compound products is realized, and adaptability and flexibility to a raw material system and a process route are high.

Description

Technical field:

[0001] The invention relates to the technical field of polymer synthesis, and in particular to a polymethyl methacrylate continuous synthesis device and process with adjustable technical routes. Background technology:

[0002] Polymethyl methacrylate (PMMA) is an engineering material with excellent optical properties. Its light transmittance exceeds 90%, comparable to glass, and is widely used in all aspects of daily life. PMMA products can be divided into molding compound (granular material) products and sheet products according to their morphological specifications. At present, for the purpose of technical economy, safety and environmental protection, the continuous synthesis process of PMMA molding compound products usually adopts the technical route of bulk polymerization and solution polymerization.

[0003] The raw material system of PMMA bulk polymerization mainly includes monomers, initiators, other monomers or additives. Since the polymerization of the monomer methyl methacrylate (MMA) belongs to the free radical mechanism, the gel effect will occur due to automatic acceleration during the synthesis process, and the polymerization system will release heat violently. It is necessary to accurately control the temperature, pressure and other process conditions of the synthesis process to avoid excessive viscosity and local overheating. Solution polymerization can be understood as adding a solvent with a mass fraction of more than 40% to the raw material system of bulk polymerization. The solvent can not only reduce the viscosity of the polymerization system, but also affect the chain transfer effect of free radical polymerization.

[0004] Despite the differences in the raw material systems, the process flow of solution polymerization and bulk polymerization is basically the same, that is, it is divided into two key parts: polymerization and devolatilization: MMA and comonomers are polymerized by free radical initiators, and then the polymer is obtained by devolatilization, and the PMMA molding compound product is obtained by granulation and drying. The difference between these two technical routes lies in the key equipment selected.

[0005] The polymerization process can be divided into primary polymerization and multi-stage polymerization. The document "Overview of Research on Polymethyl Methacrylate (PMMA) Production Process and Equipment" provides optional types and comparisons of polymerization reactors for PMMA, such as single complete mixing (CSTR) reactor, two reactors (CSTR) in series, reactor-tube series, and loop-straight tube series. The devolatilization process is based on the polymer concentration (solid mass fraction) and the residual volatiles of the product. It can select single-stage or multi-stage devolatilizers in series, devolatilizers and devolatilizer screws, devolatilizer screws, etc. Mitsubishi Rayon Co., Ltd. of Japan proposed a complete mixing reactor and a tubular reactor in series in CN 200410069172 and CN 104011084 B, using the technical route of bulk polymerization to achieve continuous or intermittent stable production of methyl methacrylate polymers. Its tubular reactors selected commercially available equipment from NORITAKE and Sumitomo Heavy Industries.

[0006] Bulk polymerization has significant advantages in terms of technological advancement, economy, and product quality. It can produce PMMA molding products with rich brands and advanced performance, but its system viscosity is high, and the mass transfer and heat transfer control in the synthesis process are difficult, and the requirements for equipment and operation are strict. Compared with bulk polymerization, solution polymerization is less difficult to control mass transfer and heat transfer, but during the devolatilization process, it is necessary to remove the unreacted monomer and solvent at the same time. To achieve the recycling of raw materials, distillation and purification are also required, which increases energy consumption and material consumption, and high production costs.

[0007] The existing technology restricts the composition of the raw material system and the selection of the process route, and has poor adaptability, adjustability and flexibility. For example, when the raw material system does not contain solvent, the solution polymerization equipment cannot meet the process technology requirements; if the solvent content is high, it is difficult to ensure the continuous and stable operation of the bulk polymerization synthesis process. In actual production, since MMA is very easy to spontaneously polymerize, the device needs to be regularly inspected and repaired, which reduces production efficiency. Summary of the invention:

[0008] The technical problem to be solved by the present invention is to provide a polymethyl methacrylate continuous synthesis device and process with adjustable technical route, which realizes continuous and stable batch production of PMMA molding compound products and has high adaptability and flexibility to raw material systems and process routes.

[0009] The technical scheme adopted by the present invention is: a polymethyl methacrylate continuous synthesis device with adjustable technical route, comprising a completely mixed reactor I and a completely mixed reactor II, wherein the material outlet end of the completely mixed reactor I is connected to the material inlet end of the completely mixed reactor II through a pipeline with a valve, the material outlet ends of the completely mixed reactor I and the completely mixed reactor II are respectively connected to the inlet of a piston flow reactor system, the inlet of a devolatilizer, and the inlet of a twin-screw devolatilizer extruder II through pipelines with valves, the outlet of the piston flow reactor system is connected to the inlet of the twin-screw devolatilizer extruder I through a pipeline with a valve, and the outlet of the devolatilizer is respectively connected to the inlet of the twin-screw devolatilizer extruder I and the inlet of the twin-screw devolatilizer extruder II through pipelines with valves.

[0010] Furthermore, the completely mixed reactor I and the completely mixed reactor II can adopt a combined stirring structure of a spiral ribbon and a paddle, or a combined stirring structure of a paddle and an anchor.

[0011] Furthermore, the plug flow reactor system includes one plug flow reactor or a plurality of plug flow reactors connected in series.

[0012] Furthermore, the plug flow reactor system can adopt one or more of a static mixer, a tubular reactor, a loop tube and a straight tube series reactor, a reaction type screw extruder, and a plug flow horizontal reactor.

[0013] Furthermore, the twin-screw devolatilizer extruder I and the twin-screw devolatilizer extruder II are provided with 4 or more vacuum exhaust chambers.

[0014] Furthermore, the vacuum exhaust chamber of the twin-screw devolatilizer extruder I and the twin-screw devolatilizer extruder II is divided into two parts, and the two parts of the vacuum exhaust chamber are respectively connected to two sets of independent storage tanks, and the two sets of independent storage tanks are used to receive and store the recovered raw materials separated by devolatilization; the storage tanks are connected to the vacuum unit, and the storage tanks are connected to the raw material supply ports of the completely mixed reactor I and the completely mixed reactor II, and are used to supply them with recovered raw materials that may include solvents.

[0015] A continuous synthesis process of polymethyl methacrylate using a continuous synthesis device of polymethyl methacrylate with adjustable technical route, the process comprising the following steps:

[0016] Process 1: Polymerization reaction of MMA to PMMA; Process 1 has the following 3 process logistics routes:

[0017] a. Feed the PMMA synthetic raw material to the completely mixed reactor I continuously, polymerize it and complete the reaction with a conversion rate of 30% to 55%, and continuously feed it from its outlet to the completely mixed reactor II to complete the polymerization reaction with a final conversion rate of 55% to 80%, and feed it to step II;

[0018] b. Feeding the PMMA synthetic raw materials continuously to the completely mixed reactor I or the completely mixed reactor II, completing 45% to 80% of the polymerization reaction therein, and feeding to step II;

[0019] c. Feeding the PMMA synthetic raw material to the completely mixed reactor I or the completely mixed reactor II continuously, polymerizing and completing the reaction with a conversion rate of 40% to 55% therein, and continuously feeding from the outlet of the completely mixed reactor I or the completely mixed reactor II to the plug flow reactor system to complete the polymerization reaction with a final conversion rate of 40% to 80%, and supplying to step II;

[0020] According to the PMMA synthetic raw materials, solution polymerization or bulk polymerization is carried out. For solution polymerization, you can choose process logistics routes a and b, and for bulk polymerization, you can choose process material routes b and c;

[0021] Step 2: Devolatilization of unreacted monomers and solvents in the polymerization system: twin-screw devolatilizer extruder I and twin-screw devolatilizer extruder II are used to flash and separate the unreacted monomers and solvents in the process one logistics from the polymerization system under high temperature and vacuum conditions to achieve removal; wherein, the components removed by twin-screw devolatilizer extruder I are only unreacted monomers; the components removed by twin-screw devolatilizer extruder II include unreacted monomers and solvents, or only unreacted monomers.

[0022] Furthermore, in the PMMA synthesis raw material suitable for solution polymerization in step 1, the mass fraction of the solvent does not exceed 20%.

[0023] Furthermore, in the PMMA synthesis raw material suitable for solution polymerization in the step 1, in addition to the mass fraction of the solvent, the composition of the raw material system includes a copolymer of MMA with a mass fraction of not less than 80% and an acrylic acid ester monomer or other suitable monomers with a mass fraction of not more than 20%.

[0024] Furthermore, in the step 1, the polymerization temperature of the completely mixed reactor I and the completely mixed reactor II is 140°C to 170°C, and the reaction conversion rate can reach 30% to 80%; the polymerization temperature of the plug flow reactor system is 140°C to 200°C, and the final conversion rate of the polymerization reaction at its outlet can reach more than 80%.

[0025] Furthermore, in the step 2, the devolatilization temperature of the twin-screw devolatilization extruder I and the twin-screw devolatilization extruder II is 210° C. to 240° C., and the vacuum condition is 10 Pa to 600 Pa.

[0026] Furthermore, the outlets of the twin-screw devolatilizer extruder I and the twin-screw devolatilizer extruder II in the step 2 can be connected to an underwater hot melt pelletizer or a water-cooled strand pelletizing unit to achieve subsequent pelletizing and drying of PMMA molding compound products.

[0027] The beneficial effect of the present invention is that: in combination with the difference in the composition of the raw material system, the PMMA synthesis process of two different technical routes, solution polymerization and bulk polymerization, can be realized, ensuring the adjustability and flexibility of continuous and stable operation. At the same time, in actual production, when a certain technical route needs to be stopped for maintenance, the synthesis process can still be continuously and batch produced by adjusting and switching the technical route, ensuring that the shutdown and maintenance of the device is carried out synchronously with the production operation without interfering with each other, and significantly improving the production efficiency. Description of the drawings:

[0028] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Figure 1 The schematic diagram is a structural diagram of a continuous synthesis device for polymethyl methacrylate with adjustable technical routes. Specific implementation method:

[0030] Example 1

[0031] according to Figure 1 The schematic diagram of the device shown adopts route b, using a completely mixed reactor Ⅰ1 for bulk polymerization and a completely mixed reactor Ⅱ2 for solution polymerization.

[0032] MMA, comonomer and initiator are prepared in a certain ratio, stored at low temperature after preparation, and continuously fed to the complete mixing reactor Ⅰ1, and bulk polymerization is carried out at 155° C. In this embodiment, the polymerization residence time in the complete mixing reactor Ⅰ1 is 30 minutes, the reaction conversion rate is 45%, and the polymerization system that meets the above process conditions is fed to the devolatilizer 4 through a gear pump, and then enters the twin-screw devolatilization extruder Ⅰ5, and after devolatilization treatment, granulation and drying are obtained to obtain the product.

[0033] MMA, comonomer, initiator and solvent are prepared in a certain proportion, and continuously fed into the complete mixing reactor II2 at a low temperature to carry out solution polymerization at 165° C. In this embodiment, the polymerization residence time in the complete mixing reactor II2 is 60 minutes, the reaction conversion rate is 72%, and the mixture is transported to the twin-screw devolatilizing extruder II6 by a gear pump, and the product is obtained by devolatilization, extrusion, granulation and drying.

[0034] After devolatilization treatment, the raw materials recovered by the twin-screw devolatilizer extruder Ⅰ5, the twin-screw devolatilizer extruder Ⅱ6, and the devolatilizer 4 are analyzed by gas chromatography for the mass fraction of MMA and the solvent, and are recycled as raw materials for solution polymerization in the completely mixed reactor Ⅱ2.

[0035] In actual production, in addition to the synchronous operation method for mass production of synthesized PMMA described in this embodiment, when production operation and shutdown for maintenance need to be switched, or when the technical route of the synthesis process is adjusted, the completely mixed reactor I1 and the completely mixed reactor II2 are used to achieve the above-mentioned different purposes.

[0036] Example 2

[0037] according to Figure 1 The schematic diagram of the device shown adopts a combination of route b and route c, connecting the completely mixed reactor Ⅰ1 and the plug flow reactor system 3 in series to carry out bulk polymerization, and using the completely mixed reactor Ⅱ2 for solution polymerization.

[0038] MMA, comonomer and initiator are prepared in a certain proportion, and the mixture is continuously fed to the complete mixing reactor Ⅰ1 at a low temperature, and the polymerization is carried out at 160°C. The polymerization system logistics is continuously conveyed to the piston flow reactor system 3 by a gear pump, and the polymerization is continued at 175°C. In the embodiment, the polymerization residence time in the complete mixing reactor Ⅰ1 is about 25 minutes, and the polymerization residence time in the piston flow reactor system 3 is about 20 minutes. The material at the outlet of the piston flow reactor system 3 is conveyed to the twin-screw devolatilization extruder Ⅰ5 by a gear pump, and the product is obtained by devolatilization, extrusion, granulation and drying.

[0039] MMA, comonomer, initiator and solvent are prepared in a certain proportion, and continuously fed into the complete mixing reactor II2 at a low temperature to carry out solution polymerization at 165° C. In this embodiment, the polymerization residence time in the complete mixing reactor II2 is 60 minutes, the reaction conversion rate is 72%, and the mixture is transported to the twin-screw devolatilizing extruder II6 by a gear pump, and the product is obtained by devolatilization, extrusion, granulation and drying.

[0040] This embodiment does not need to use the devolatilizer 4. The raw materials recovered by the twin-screw devolatilizer extruder Ⅰ5 and the twin-screw devolatilizer extruder Ⅱ6 are analyzed by gas chromatography for the mass fraction of MMA and solvent, and are recycled as raw materials for solution polymerization in the complete mixing reactor Ⅱ2.

[0041] Route b: MMA or MMA prepared in a certain proportion, comonomer, initiator, and auxiliary agent (which may include solvent) are continuously fed to the completely mixed reactor Ⅰ1 or completely mixed reactor Ⅱ2, and 45% to 80% of the polymerization reaction is completed therein, and then the material is fed to step 2. That is, the completely mixed reactor Ⅰ1 and the completely mixed reactor Ⅱ2 are operated in parallel.

[0042] Route c: MMA or MMA prepared in a certain proportion, comonomers, initiators and additives are continuously fed into a completely mixed reactor Ⅰ1 or a completely mixed reactor Ⅱ2, where they are polymerized and a reaction with a conversion rate of 40% to 55% is completed. From the outlet of the completely mixed reactor Ⅰ1 or the completely mixed reactor Ⅱ2, they are continuously fed into the plug flow reactor system 3 to complete a polymerization reaction with a final conversion rate of 40% to 80%, and then the materials are supplied to step 2.

[0043] It can be understood that the above specific description of the present invention is only used to illustrate the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced by equivalents to achieve the same technical effects; as long as the use requirements are met, they are within the protection scope of the present invention.

Claims

1. A polymethyl methacrylate continuous synthesis device with adjustable technical route, characterized in that: The invention comprises a completely mixed reactor I (1) and a completely mixed reactor II (2). The material outlet of the completely mixed reactor I (1) is connected to the material inlet of the completely mixed reactor II (2) through a pipeline with a valve. The material outlets of the completely mixed reactor I (1) and the completely mixed reactor II (2) are respectively connected to the inlet of a piston flow reactor system (3), the inlet of a devolatilizer (4), and the inlet of a twin-screw devolatilizer extruder II (6) through pipelines with valves. The outlet of the piston flow reactor system (3) is connected to the inlet of a twin-screw devolatilizer extruder I (5) through a pipeline with a valve. The outlet of the devolatilizer (4) is respectively connected to the inlet of the twin-screw devolatilizer extruder I (5) and the inlet of the twin-screw devolatilizer extruder II (6) through pipelines with valves.

2. The polymethyl methacrylate continuous synthesis device with adjustable technical route according to claim 1, characterized in that: The complete mixing reactor I (1) and the complete mixing reactor II (2) can adopt a combined stirring structure of a spiral ribbon and a paddle, or a combined stirring structure of a paddle and an anchor.

3. The polymethyl methacrylate continuous synthesis device with adjustable technical route according to claim 1, characterized in that: The plug flow reactor system (3) comprises one plug flow reactor or a plurality of plug flow reactors connected in series.

4. The polymethyl methacrylate continuous synthesis device with adjustable technical route according to claim 1, characterized in that: The plug flow reactor system (3) can adopt one or more of a static mixer, a tubular reactor, a loop and straight tube series reactor, a reaction screw extruder, and a plug flow horizontal reactor.

5. The polymethyl methacrylate continuous synthesis device with adjustable technical route according to claim 1, characterized in that: The twin-screw devolatilizing extruder I (5) and the twin-screw devolatilizing extruder II (6) are provided with 4 or more vacuum exhaust chambers.

6. The polymethyl methacrylate continuous synthesis device with adjustable technical route according to claim 1, characterized in that: The vacuum exhaust chamber of the twin-screw devolatilizer extruder I (5) and the twin-screw devolatilizer extruder II (6) is divided into two parts, and the two parts of the vacuum exhaust chamber are respectively connected to two sets of independent storage tanks, and the two sets of independent storage tanks are used to receive and store the recovered raw materials separated by devolatilization; the storage tanks are connected to the vacuum unit, and the storage tanks are connected to the raw material supply ports of the complete mixing reactor I (1) and the complete mixing reactor II (2) for supplying the recovered raw materials that may include solvents thereto.

7. A continuous synthesis process of polymethyl methacrylate using the polymethyl methacrylate continuous synthesis device with adjustable technical route according to claim 1, characterized in that: The process includes the following steps: Process 1: Polymerization reaction of MMA to PMMA; Process 1 has the following 3 process logistics routes: a. Feeding the PMMA synthetic raw material to the completely mixed reactor I (1) continuously, polymerizing and completing the reaction with a conversion rate of 30% to 55%, and continuously feeding from the outlet to the completely mixed reactor II (2) to complete the polymerization reaction with a final conversion rate of 55% to 80%, and supplying to step II; b. Feeding the PMMA synthesis raw material continuously to the completely mixed reactor I (1) or the completely mixed reactor II (2), completing 45% to 80% of the polymerization reaction therein, and supplying the material to step 2; c. Feeding the PMMA synthetic raw material to the completely mixed reactor I (1) or the completely mixed reactor II (2) continuously, polymerizing and completing the reaction with a conversion rate of 40% to 55% therein, and continuously feeding from the outlet of the completely mixed reactor I (1) or the completely mixed reactor II (2) to the plug flow reactor system (3) to complete the polymerization reaction with a final conversion rate of 40% to 80%, and supplying the material to step 2; According to the PMMA synthetic raw materials, solution polymerization or bulk polymerization is carried out. For solution polymerization, you can choose process logistics routes a and b, and for bulk polymerization, you can choose process material routes b and c; Step 2: Devolatilization of unreacted monomers and solvents in the polymerization system: Using twin-screw devolatilizer extruder I (5) and twin-screw devolatilizer extruder II (6) under high temperature and vacuum conditions, the unreacted monomers and solvents in the process one logistics are flash evaporated and separated from the polymerization system to achieve removal; wherein the components removed by the twin-screw devolatilizer extruder I (5) are only unreacted monomers; the components removed by the twin-screw devolatilizer extruder II (6) include unreacted monomers and solvents, or only unreacted monomers.

8. The continuous synthesis process of polymethyl methacrylate using the continuous synthesis device of polymethyl methacrylate with adjustable technical route according to claim 7, characterized in that: In the PMMA synthesis raw material suitable for solution polymerization in the step 1, the mass fraction of the solvent does not exceed 20%.

9. The continuous synthesis process of polymethyl methacrylate using the continuous synthesis device of polymethyl methacrylate with adjustable technical route according to claim 7, characterized in that: In the PMMA synthesis raw material suitable for solution polymerization in the step 1, in addition to the mass fraction of the solvent, the raw material system comprises a copolymer of MMA with a mass fraction of not less than 80% and an acrylic acid ester monomer or other suitable monomers with a mass fraction of not more than 20%.

10. The continuous synthesis process of polymethyl methacrylate using the continuous synthesis device of polymethyl methacrylate with adjustable technical route according to claim 7, characterized in that: In the process 1, the polymerization temperature of the completely mixed reactor I (1) and the completely mixed reactor II (2) is 140°C to 170°C, and the reaction conversion rate can reach 30% to 80%; the polymerization temperature of the plug flow reactor system (3) is 140°C to 200°C, and the final conversion rate of the polymerization reaction at its outlet can reach up to more than 80%.

11. The continuous synthesis process of polymethyl methacrylate using the continuous synthesis device of polymethyl methacrylate with adjustable technical route according to claim 7, characterized in that: In the step 2, the devolatilization temperature of the twin-screw devolatilization extruder I (5) and the twin-screw devolatilization extruder II (6) is 210°C to 240°C, and the vacuum condition is 10Pa to 600Pa.

12. The continuous synthesis process of polymethyl methacrylate using the continuous synthesis device of polymethyl methacrylate with adjustable technical route according to claim 7, characterized in that: The outlets of the twin-screw devolatilizing extruder I (5) and the twin-screw devolatilizing extruder II (6) in the second step can be connected to an underwater hot melt pelletizer or a water-cooled strand pelletizing unit to achieve subsequent pelletizing and drying of PMMA molding compound products.

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