A method for reducing dissolved oxygen in MMA raw material liquid, the MMA raw material liquid and its application

Abstract

The present invention relates to a method for reducing dissolved oxygen in an MMA raw material liquid, an MMA raw material liquid, and an application thereof. The method comprises the following steps: (1) mixing the MMA raw material liquid with nitrogen and performing a gas replacement treatment to obtain a mixed MMA raw material liquid; (2) decompressing and degassing the mixed MMA raw material liquid obtained in step (1) to obtain a mixed gas and an MMA raw material liquid with low dissolved oxygen; and (3) sequentially pressurizing, condensing, and separating the mixed gas obtained in step (2) to achieve separation of nitrogen, oxygen, and the MMA raw material liquid. The present invention can remove dissolved oxygen from the MMA raw material liquid to below 0.1 ppm, and complete a polymerization reaction using a conventional polymerization process to obtain a PMMA material with excellent performance.

Description

Technical Field

[0001] The invention relates to the technical field of PMMA synthesis, and in particular to a method for reducing dissolved oxygen in an MMA raw material liquid, the MMA raw material liquid and applications thereof. Background Art

[0002] The chemical name of PMMA is polymethyl methacrylate, commonly known as acrylic or plexiglass. It has the characteristics of high surface hardness, good dimensional stability and good electrical insulation. It is currently widely used in automobiles, displays, electronic appliances, lighting, billboards and other fields.

[0003] PMMA polymerization methods primarily include solution polymerization and bulk polymerization. Both methods require MMA monomer as the starting material for polymerization. Oxygen is required as an inhibitor before polymerization to prevent the formation of oligomers from entering the polymerization stage and affecting the molecular weight distribution of the overall polymerization reaction. Therefore, dissolved oxygen is present in the MMA raw material solution. Excessive dissolved oxygen in the raw material solution can reduce the viscosity of the polymer product, thereby affecting the thermal stability, weather resistance, transparency, and other application properties of the resulting polymer product.

[0004] Existing processes use inert gas to strip dissolved oxygen from the MMA feed solution in a vertical tower or container, typically reducing the oxygen content to 5-10 ppm. However, CN1303397A states that "if the dissolved oxygen content exceeds 2 ppm, not only will the polymerization reaction become unstable, but also colored components may be easily formed during the polymerization step when the reactor mixture is maintained at high temperatures for a long time." Therefore, the oxygen content of the MMA feed solution obtained using existing processes remains high.

[0005] CN104492125A discloses a method for removing dissolved oxygen from a viscous liquid, comprising the following steps: placing a sample bottle filled with the viscous liquid in a vacuum desiccator, wherein the higher the viscosity of the liquid, the longer it takes to evacuate; after evacuating, connecting the vacuum desiccator to high-purity nitrogen, opening the valve connecting the high-purity nitrogen bottle and the vacuum desiccator, and raising the negative pressure in the vacuum desiccator to atmospheric pressure; then placing the sample bottle containing the viscous liquid in an anaerobic glove box for secondary deoxygenation; finally, sealing the sample bottle with a rubber stopper and an aluminum cap to complete the deoxygenation process. This method uses an anaerobic glove box to remove dissolved oxygen from a polymer solution, but due to the high viscosity of the polymer solution, it is difficult for the glove box to extract the dissolved oxygen therein, and glove boxes are not commonly used, and the operation is also relatively cumbersome. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide a method for reducing dissolved oxygen in an MMA raw material liquid, an MMA raw material liquid and its application, which can remove the dissolved oxygen in the MMA raw material liquid to below 0.1 ppm, and use a conventional polymerization process to complete the polymerization reaction to obtain a PMMA material with excellent performance.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for reducing dissolved oxygen in an MMA raw material solution, the method comprising the steps of:

[0009] (1) Mixing the MMA raw material liquid with nitrogen and performing gas replacement treatment to obtain a mixed MMA raw material liquid;

[0010] (2) degassing the mixed MMA raw material liquid obtained in step (1) to obtain a mixed gas and an MMA raw material liquid with low dissolved oxygen;

[0011] (3) The mixed gas obtained in step (2) is pressurized, condensed and separated in sequence to achieve separation of nitrogen, oxygen and MMA raw material liquid.

[0012] The method for reducing dissolved oxygen in an MMA raw material liquid provided by the present invention comprises the following steps: firstly, the MMA raw material liquid is subjected to a gas replacement treatment, during which nitrogen is fully mixed into the MMA raw material liquid, thereby facilitating the removal of dissolved oxygen; and then the treated MMA raw material liquid is subjected to a decompression degassing treatment, during which the solubility of the gas is reduced, and dissolved oxygen escapes from the MMA raw material liquid along with the nitrogen, thereby further removing the dissolved oxygen remaining in the MMA raw material liquid to obtain an MMA raw material liquid with low dissolved oxygen. During a subsequent polymerization reaction, oxygen-induced MMA polymerization products can be reduced, and the obtained PMMA material has the characteristics of strong thermal stability, good weather resistance, high transparency, and the like, and can be expanded to applications in higher-standard situations.

[0013] It should be noted that the "gas replacement treatment" and "degassing treatment under reduced pressure" in the present invention refer to the process of replacing dissolved oxygen from the MMA raw material liquid with nitrogen and removing the dissolved oxygen under reduced pressure.

[0014] Preferably, the temperature of the gas replacement treatment in step (1) is between -10°C and 45°C, and the pressure is greater than 2.5 MPaG.

[0015] The temperature of the gas replacement treatment is -10°C to 45°C, for example, it can be -10°C, 10°C, 20°C, 25°C, 30°C, 35°C, 40°C or 45°C, but is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0016] The pressure of the gas replacement treatment is greater than 2.5 MPaG, for example, it can be 2.8 MPaG, 3 MPaG, 3.5 MPaG, 4 MPaG, 4.5 MPaG or 5 MPaG, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably 3-4.5 MPaG.

[0017] Preferably, the pressure of the reduced pressure degassing treatment in step (2) is 0.102-0.105 MPaG, for example, it can be 0.102 MPaG, 0.103 MPaG, 0.104 MPaG or 0.105 MPaG, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0018] As pressure increases, the solubility of a gas increases; as pressure decreases, the solubility of a gas decreases. Based on the conditions of a temperature of -10°C and a pressure of 2.5 MPaG, the amount of nitrogen dissolved is approximately 1 wt%. Studies have shown that when the nitrogen dissolved in the solution exceeds 1 wt%, and the gaseous nitrogen and liquid phases are evenly mixed, the dissolved oxygen removal rate is high. However, considering energy consumption and equipment investment costs, the pressure should not exceed 5 MPaG. Therefore, the present invention performs gas replacement and reduced pressure degassing on the MMA raw material liquid in a medium-pressure environment.

[0019] Preferably, the pressure of the supercharged mixed gas in step (3) is greater than 2.6 MPaG, for example, it can be 2.8 MPaG, 3.1 MPaG, 3.5 MPaG, 4.6 MPaG or 5 MPaG, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably 3.1-4.6 MPaG.

[0020] Preferably, the condensation temperature in step (3) is -10°C to 40°C, for example, -10°C, 0°C, 10°C, 20°C, 25°C, 30°C or 40°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0021] The MMA raw material liquid produced after the condensation in step (3) is recycled and used in the gas replacement process.

[0022] Preferably, the separation in step (3) comprises membrane separation, and the membrane used for membrane separation is a membrane with an oxygen permeation rate greater than the nitrogen and MMA permeation rates.

[0023] The material of the membrane used for membrane separation includes polyimide or polysulfone.

[0024] After the membrane separation, oxygen-rich gas and nitrogen-rich gas are obtained, and the nitrogen-rich gas is recycled and used in the gas replacement process.

[0025] In the method provided by the present invention, the mixed gas is pressurized and condensed, and the MMA raw material liquid in the gas can be condensed and then transported to the gas replacement treatment, so as to reduce the loss of the MMA raw material liquid by recycling. The mixed gas enters the membrane separation. On the one hand, a membrane with an oxygen permeability greater than that of nitrogen and MMA is selected to effectively separate oxygen from the mixed gas. On the other hand, due to the fast permeability of oxygen, oxygen preferentially passes through the membrane and enters the downstream side of the membrane to become oxygen-rich gas. The nitrogen has a slow permeability and is retained on the upstream side of the membrane to become nitrogen-rich gas. This not only separates the nitrogen for recycling, thereby reducing the loss of nitrogen, but also increases the oxygen concentration, which is beneficial to reducing the energy consumption of downstream gas processing equipment.

[0026] Preferably, the method is carried out in a device system for reducing dissolved oxygen in an MMA raw material liquid, wherein the device system comprises a booster pump, a mixing device, a pressure reducing valve and a degassing device connected in sequence along the material flow direction, the top of the degassing device is connected in sequence to a compressor, a condenser and a membrane separation device, and the bottom of the degassing device discharges the MMA raw material liquid with low dissolved oxygen; a nitrogen inlet pipeline is connected between the booster pump and the mixing device.

[0027] The MMA raw material liquid discharged from the condenser is recycled and used in the mixing device.

[0028] The nitrogen-rich gas discharged from the membrane separation device is recycled and used in the mixing device.

[0029] It should be noted that internal components can be provided in the degassing device, which are suitable for MMA raw material liquid containing different polymerization inhibitors, and can remove other impurities such as free acid, polymerization inhibitor, free metal ions, etc., which may affect the quality of PMMA while removing dissolved oxygen; the internal components can preferably be ion exchange resins, but are not limited thereto.

[0030] As a preferred technical solution of the method of the present invention, the method comprises the following steps:

[0031] (1) The MMA raw material liquid is pumped into a mixing device with a pressure greater than 2.5 MPaG through a booster pump, and nitrogen is introduced through a nitrogen inlet pipe. The mixture is mixed and gas replacement is performed at a temperature of -10°C to 45°C to obtain a mixed MMA raw material liquid;

[0032] (2) The mixed MMA raw material liquid obtained in step (1) is decompressed to 0.102-0.105 MPaG through a pressure reducing valve and then sent to a degassing device for decompression and degassing to obtain a mixed gas and an MMA raw material liquid with low dissolved oxygen;

[0033] (3) The mixed gas obtained in step (2) is pressurized to greater than 2.6 MPaG by a compressor and condensed by a condenser at -10°C to 40°C. The generated MMA raw liquid is recycled back to the mixing device for gas replacement treatment; then, the mixed gas is separated into oxygen-rich gas and nitrogen-rich gas by a membrane separation device. The obtained nitrogen-rich gas is recycled back to the mixing device for gas replacement treatment, thereby achieving separation of nitrogen, oxygen and MMA raw liquid.

[0034] In a second aspect, the present invention provides a low-dissolved-oxygen MMA raw material solution, which is obtained by processing the method described in the first aspect.

[0035] Preferably, the oxygen content of the MMA raw material solution is ≤0.1 ppm, for example, it can be 0.1 ppm, 0.08 ppm, 0.05 ppm, 0.03 ppm or 0.01 ppm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0036] The MMA raw material liquid provided by the present invention has the characteristic of low dissolved oxygen. During the subsequent polymerization reaction, oxygen-induced MMA polymerization products can be reduced, thereby obtaining a PMMA material with strong thermal stability, good weather resistance and high transparency.

[0037] In a third aspect, the present invention provides an application of the low dissolved oxygen MMA raw material solution as described in the second aspect, wherein the PMMA material obtained by polymerization of the MMA raw material solution is used in electronic equipment, aerospace, and medical fields.

[0038] The MMA raw material liquid enters the downstream section to complete polymerization and extrusion granulation to obtain PMMA material, which can be used in electronic equipment, aerospace and medical fields.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) The method for reducing dissolved oxygen in MMA raw material liquid provided by the present invention first performs gas replacement treatment on the MMA raw material liquid. During this process, nitrogen is fully mixed into the MMA raw material liquid, which helps to remove the dissolved oxygen. The treated MMA raw material liquid is subjected to decompression degassing treatment. During the decompression process, the solubility of the gas is reduced, and the dissolved oxygen escapes from the MMA raw material liquid together with the nitrogen, further removing the dissolved oxygen remaining in the MMA raw material liquid, thereby obtaining a low-dissolved-oxygen MMA raw material liquid. In the subsequent polymerization reaction, oxygen-induced MMA polymerization products can be reduced. The obtained PMMA material has the characteristics of strong thermal stability, good weather resistance, high transparency, etc., and can be expanded to applications in higher-standard occasions.

[0041] (2) The method for reducing dissolved oxygen in the MMA raw material liquid provided by the present invention can separate the MMA raw material liquid and nitrogen in the gas for recycling, thereby reducing material loss and being beneficial to energy saving and efficiency improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 1 is a schematic structural diagram of a device system for reducing dissolved oxygen in an MMA raw material solution provided in Example 1 of the present invention;

[0043] Figure 2 Schematic diagram of the structure of the device system for reducing dissolved oxygen in the MMA raw material solution provided in Comparative Example 1 of the present invention;

[0044] Figure 3 Schematic diagram of the structure of the mixing device system provided in Comparative Example 2 of the present invention.

[0045] Among them: 1, booster pump; 2, mixing device; 3, pressure reducing valve; 4, degassing device; 5, compressor; 6, condenser; 7, membrane separation device; 8, degassing tower; 9, cooler; 10, oxygen analyzer. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0047] Example 1

[0048] This embodiment provides a method for reducing dissolved oxygen in MMA raw material liquid. The method is carried out in a device system for reducing dissolved oxygen in MMA raw material liquid. The structural diagram is shown in FIG. Figure 1 As shown, the method includes the following steps:

[0049] (1) The MMA raw material liquid is pumped into the mixing device 2 at a pressure of 3 MPaG by the booster pump 1, and nitrogen is introduced through the nitrogen inlet pipe at the same time. The mixture is mixed and gas-exchanged at 30°C to obtain a mixed MMA raw material liquid;

[0050] (2) The mixed MMA raw material liquid obtained in step (1) is decompressed to 0.103 MPaG through a pressure reducing valve 3 and then sent to a degassing device 4 for decompression and degassing to obtain a mixed gas and an MMA raw material liquid with low dissolved oxygen;

[0051] (3) The mixed gas obtained in step (2) is pressurized to 3.5 MPaG by a compressor 5 and condensed by a condenser 6 at 10°C. The generated MMA raw liquid is circulated back to the mixing device 2 for gas replacement treatment; then, it is separated by a membrane separation device 7 to obtain oxygen-rich gas, nitrogen-rich gas and waste gas. The waste gas is discharged for treatment, and the nitrogen-rich gas is circulated back to the mixing device 2 for gas replacement treatment, thereby achieving separation of nitrogen, oxygen and MMA raw liquid.

[0052] The MMA raw material liquid with low dissolved oxygen obtained in step (2) enters the downstream process section after being tested by the oxygen analyzer 10 and passing the test, and the PMMA material is obtained through polymerization reaction and extrusion granulation.

[0053] Example 2

[0054] This embodiment provides a method for reducing dissolved oxygen in an MMA raw material solution. The difference from Example 1 is that the pressure of the decompression in step (2) is adjusted to 0.102 MPaG, the pressure of the pressurization in step (3) is adjusted to 3.1 MPaG, and the process side temperature of the condenser 6 is adjusted to -10°C. The rest is the same as in Example 1.

[0055] Example 3

[0056] This embodiment provides a method for reducing dissolved oxygen in an MMA raw material solution. The difference from Example 1 is that the pressure of the decompression in step (2) is adjusted to 0.105 MPaG, the pressure of the pressurization in step (3) is adjusted to 4.6 MPaG, and the temperature on the process side of the condenser 6 is adjusted to 25°C. The rest is the same as in Example 1.

[0057] Example 4

[0058] This embodiment provides a method for reducing dissolved oxygen in an MMA raw material solution. The difference from Example 1 is that the pressure of the mixing device 2 in step (1) is adjusted to 3.5 MPaG. The rest is the same as Example 1.

[0059] Example 5

[0060] This embodiment provides a method for reducing dissolved oxygen in an MMA raw material solution. The difference from Example 1 is that the pressure of the mixing device 2 in step (1) is adjusted to 4.5 MPaG. The rest is the same as Example 1.

[0061] Example 6

[0062] This embodiment provides a method for reducing dissolved oxygen in an MMA raw material solution. The difference from Example 1 is that the pressure of the mixing device 2 in step (1) is adjusted to 5 MPaG. The rest is the same as Example 1.

[0063] Example 7

[0064] This embodiment provides a method for reducing dissolved oxygen in an MMA raw material solution. The difference from Example 1 is that the pressure of the mixing device 2 in step (1) is adjusted to 2.5 MPaG. The rest is the same as Example 1.

[0065] Example 8

[0066] This embodiment provides a method for reducing dissolved oxygen in an MMA raw material solution. The difference from Example 4 is that the temperature of the gas replacement treatment in step (1) is adjusted to 20° C., and the rest is the same as Example 4.

[0067] Example 9

[0068] This embodiment provides a method for reducing dissolved oxygen in an MMA raw material solution. The difference from Example 4 is that the temperature of the gas replacement treatment in step (1) is adjusted to 25°C. The rest is the same as Example 4.

[0069] Example 10

[0070] This embodiment provides a method for reducing dissolved oxygen in an MMA raw material solution. The difference from Example 4 is that the temperature of the gas replacement treatment in step (1) is adjusted to 35°C. The rest is the same as Example 4.

[0071] Example 11

[0072] This embodiment provides a method for reducing dissolved oxygen in an MMA raw material solution. The difference from Example 4 is that the temperature of the gas replacement treatment in step (1) is adjusted to 40° C., and the rest is the same as Example 4.

[0073] Example 12

[0074] This embodiment provides a method for reducing dissolved oxygen in an MMA raw material solution. The difference from Example 4 is that the temperature of the gas replacement treatment in step (1) is adjusted to -10°C. The rest is the same as Example 4.

[0075] Example 13

[0076] This embodiment provides a method for reducing dissolved oxygen in an MMA raw material solution. The difference from Example 4 is that the temperature of the gas replacement treatment in step (1) is adjusted to 45°C. The rest is the same as Example 4.

[0077] Example 14

[0078] This embodiment provides a method for reducing dissolved oxygen in an MMA raw material solution. The difference from Example 1 is that the pressure of the pressurization in step (3) is adjusted to 2.6 MPaG. The rest is the same as Example 1.

[0079] Comparative Example 1

[0080] This comparative example provides a method for reducing dissolved oxygen in MMA raw material liquid. The method uses inert gas to strip the dissolved oxygen in the MMA raw material liquid in a vertical tower or container. The structural diagram of the device system is shown in FIG. Figure 2 As shown, the specific steps include:

[0081] (1) The MMA raw material liquid at 15°C and 0.3MPaG is passed into the degassing tower 8, and nitrogen at 25°C and 0.1MPaG is passed into the degassing tower 8 at the same time. The operating conditions of the degassing tower 8 are 15°C and ATM. After the stripping and degassing treatment, the oxygen content of the MMA raw material liquid can reach 5-10ppm.

[0082] (2) The gas at the top of the degassing tower 8 is cooled by the cooler 9 and then discharged into the exhaust system;

[0083] (3) The MMA raw material liquid obtained after treatment is tested by an oxygen analyzer 10 and enters the downstream process section, where the polymerization reaction is completed using a conventional polymerization process, and PMMA material is obtained by extrusion granulation.

[0084] Comparative Example 2

[0085] This comparative example provides a method for reducing dissolved oxygen in MMA raw material liquid. The method is carried out using a mixing device system. The structural diagram is shown in FIG. Figure 3 As shown, the difference from Example 4 is that there is no step (2) and step (3), and the rest is the same as Example 4.

[0086] The oxygen content and nitrogen content of the MMA raw material solutions provided in Examples 1-14 and Comparative Examples 1 and 2, as well as the MMA raw material solution with low dissolved oxygen, were tested using an oxygen content tester and a nitrogen detector. The results are shown in Table 1.

[0087] Table 1

[0088]

[0089] According to the data in Table 1, we can see that:

[0090] (1) At the same operating temperature, the effect of pressure change on the oxygen content in MMA is small. Comparing Example 1 with Examples 4-6, when the operating temperature is 30°C, the oxygen content in the MMA solution obtained after treatment is close to 0.1ppm by changing the operating pressure. This shows that the method of the present invention is applicable to a variety of pressure conditions and can reduce the difficulty of equipment selection. However, considering energy consumption and equipment investment costs, the pressure condition should not be greater than 5MPaG. Comparing Example 1 with Example 7, it is shown that the pressure should not be too low, which will lead to a decrease in gas solubility and a decrease in the dissolved oxygen removal rate. Comparing Example 1 with Example 14, it is shown that in the separation stage, if the boost pressure is too low, it will also lead to a decrease in oxygen permeability. Oxygen continues to circulate with the circulating nitrogen, increasing the load of downstream equipment and increasing the dissolved oxygen content.

[0091] (2) Comparing Example 1 with Examples 8-13, under the same operating pressure, the higher the temperature, the better the deoxygenation effect, and the oxygen content in the MMA solution is below 0.1 ppm; on the other hand, it should be considered that too high a temperature can easily induce a polymerization reaction in the MMA solution. Therefore, performing gas replacement treatment within a reasonable temperature range can not only prevent the polymerization reaction of the MMA solution, but also reduce the oxygen content in the MMA solution to below 0.1 ppm, which greatly improves the performance of the PMMA material obtained after treatment.

[0092] (3) Comparative Example 1 shows that the oxygen content of the MMA solution after deoxygenation treatment by the method of the present invention is much lower than that after treatment by the existing process.

[0093] Selecting examples with the same operating pressure and different operating temperatures, the PMMA materials obtained in Examples 4, 8, and 11 and Comparative Examples 1 and 2 were tested for yellowing index using a yellowness tester. The results are shown in Table 2, and the yellowing index table is shown in Table 3. According to the data in Tables 2 and 3, it can be seen that:

[0094] The lower the oxygen content of the MMA raw material liquid during the polymerization reaction, the lower the yellowing index of the PMMA material obtained, which means that the transparency of the PMMA material is better.

[0095] By comparing the data of Examples 4, 8, and 11 with Comparative Examples 1 and 2, it can be seen that the yellowing index of the PMMA material obtained by polymerization of the MMA raw material solution provided by the present invention is lower than the yellowing index of the PMMA material obtained by polymerization of the MMA raw material solution of Comparative Examples 1 and 2; by comparing the PMMA yellowing index of Examples 4, 8, and 11, it can be seen that when the oxygen content in the MMA raw material solution changes slightly, the yellowing index of PMMA also fluctuates significantly, and the lower the oxygen content, the lower the yellowing index of the PMMA material obtained.

[0096] The lower the oxygen content during the polymerization reaction, the more conducive it is to improving the performance of the PMMA material, but it is not limited to transparency. The present invention uses transparency as an example to illustrate that the performance of the PMMA material obtained is improved.

[0097] Table 2

[0098]

[0099] Table 3

[0100]

[0101] In summary, the method for reducing dissolved oxygen in an MMA raw material liquid provided by the present invention first performs a gas replacement treatment on the MMA raw material liquid. During this process, nitrogen is fully mixed into the MMA raw material liquid, which helps to remove the dissolved oxygen. The treated MMA raw material liquid is subjected to a decompression degassing treatment. During the decompression process, the solubility of the gas decreases, and the dissolved oxygen escapes from the MMA raw material liquid along with the nitrogen, further removing the dissolved oxygen remaining in the MMA raw material liquid, thereby obtaining an MMA raw material liquid with low dissolved oxygen. In the subsequent polymerization reaction, oxygen-induced MMA polymerization reaction products can be reduced, and the obtained PMMA material has the characteristics of strong thermal stability, good weather resistance, high transparency, etc., and can be expanded to applications in higher standard occasions.

[0102] The method for reducing dissolved oxygen in an MMA raw material liquid provided by the present invention can separate the MMA raw material liquid and nitrogen in the gas for recycling, thereby reducing material loss and facilitating energy conservation and efficiency improvement.

[0103] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for reducing dissolved oxygen in an MMA raw material solution, characterized in that: The method comprises the following steps: (1) Mixing the MMA raw material liquid with nitrogen and performing a gas replacement treatment to obtain a mixed MMA raw material liquid; the temperature of the gas replacement treatment is -10°C to 45°C, and the pressure is greater than 2.5 MPaG and less than or equal to 5 MPaG; (2) degassing the mixed MMA raw material liquid obtained in step (1) to obtain a mixed gas and an MMA raw material liquid with low dissolved oxygen; (3) The mixed gas obtained in step (2) is pressurized to a pressure greater than 2.6 MPaG, condensed, and membrane separated in sequence. The membrane used for membrane separation is a membrane with an oxygen permeability greater than the permeability of nitrogen and MMA, thereby obtaining oxygen-rich gas and nitrogen-rich gas. The nitrogen-rich gas is recycled and used in the gas replacement process to achieve separation of nitrogen, oxygen, and MMA raw material liquid.

2. The method according to claim 1, characterized in that The pressure of the reduced pressure degassing treatment in step (2) is 0.102-0.105 MPaG.

3. The method according to claim 1, characterized in that The condensation temperature in step (3) is -10°C to 40°C; The MMA raw material liquid produced after the condensation in step (3) is recycled and used in the gas replacement process.

4. The method according to claim 1, wherein The material of the membrane used for membrane separation includes polyimide or polysulfone.

5. The method according to claim 1, wherein The method is carried out in a device system for reducing dissolved oxygen in an MMA raw material liquid. The device system includes a booster pump, a mixing device, a pressure reducing valve, and a degassing device connected in sequence along the material flow direction. The top of the degassing device is connected in sequence to a compressor, a condenser, and a membrane separation device, and the bottom of the degassing device discharges the MMA raw material liquid with low dissolved oxygen; a nitrogen inlet pipeline is connected between the booster pump and the mixing device; The MMA raw material liquid discharged from the condenser is recycled and used in the mixing device; The nitrogen-rich gas discharged from the membrane separation device is recycled and used in the mixing device.

6. The method according to claim 1, characterized in that The method comprises the following steps: (1) The MMA raw material liquid is pumped into a mixing device with a pressure greater than 2.5 MPaG and less than or equal to 5 MPaG through a booster pump, and nitrogen is introduced through a nitrogen inlet pipe. The mixture is mixed and gas-exchanged at -10°C to 45°C to obtain a mixed MMA raw material liquid; (2) The mixed MMA raw material liquid obtained in step (1) is decompressed to 0.102-0.105 MPaG through a pressure reducing valve and then sent to a degassing device for decompression and degassing to obtain a mixed gas and an MMA raw material liquid with low dissolved oxygen; (3) The mixed gas obtained in step (2) is pressurized to greater than 2.6 MPaG by a compressor and condensed by a condenser at -10°C to 40°C. The generated MMA raw liquid is recycled back to the mixing device for gas replacement treatment; then, the mixed gas is separated into oxygen-rich gas and nitrogen-rich gas by a membrane separation device. The obtained nitrogen-rich gas is recycled back to the mixing device for gas replacement treatment, thereby achieving separation of nitrogen, oxygen and MMA raw liquid.

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