Continuous flow kettle type continuous synthesis process and equipment for polyphenylene sulfide

Abstract

The invention discloses a continuous flow kettle type continuous synthesis process and equipment for polyphenylene sulfide, and belongs to the technical field of polyphenylene sulfide preparation technologys.The continuous flow kettle type continuous synthesis process and equipment for polyphenylene sulfide comprise the following steps that 1, heating dehydration is conducted, specifically, an NMP solution, sodium hydroxide, Na2S. 5H2O and a catalyst are put into a reaction kettle, and heating dehydration is conducted; sampling and detecting that the moisture of the NMP eluate at the tower top should be about 2%, and stopping dehydration; through process improvement, a kettle type continuous reaction scheme is used for replacing a traditional kettle type intermittent process, and the method has the main advantages that continuous feeding instead of one-time feeding can be achieved, so that heat can be controlled to be continuously output within a certain time instead of being released within a short time, reaction conditions are controlled more easily, and the yield is increased. The polymerization reaction is carried out in different kettles, the temperature and the reaction rate are controlled more accurately, and the stable quality of the resin is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of polyphenylene sulfide preparation technology, and specifically relates to a polyphenylene sulfide continuous flow kettle type continuous synthesis process and equipment. Background Art

[0002] Polyphenylene sulfide (PPS) is a high-performance engineering plastic that is widely used in electronics, automobiles, aerospace, industrial machinery and other fields. In the market, the synthesis process of PPS mainly adopts a batch process.

[0003] Based on the research on the conventional polyphenylene sulfide synthesis process, the one currently industrialized in the market is a kettle intermittent process. It is found that the condensation reaction in this process is highly exothermic. In the large-scale production process, if too much material is added at one time, there will be a greater risk of loss of control, resulting in a certain volatility in the quality of the polyphenylene sulfide resin after polymerization, making the quality of the polyphenylene sulfide resin unstable. In view of this, a polyphenylene sulfide continuous flow kettle continuous synthesis process and equipment are provided. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the disadvantages of the prior art and provide a polyphenylene sulfide continuous flow kettle type continuous synthesis process and equipment.

[0005] The technical solution adopted to solve the above technical problems is:

[0006] A continuous flow kettle-type continuous synthesis process for polyphenylene sulfide comprises the following steps:

[0007] Step 1, heating dehydration process: 4.0-5.0w / w NMP solution, sodium hydroxide, Na2S·5H2O, and catalyst are added to the reactor. When the temperature in the reactor rises to 200-203°C, the total weight of water removed is about 0.57w / w p-DCB. When the weight of NMP removed by continuing to increase the temperature reaches 1.5w / w p-DCB, the water content of the NMP removed liquid at the top of the tower should be about 2% when sampling and testing, and the dehydration is stopped;

[0008] Step 2, solvent addition process: transfer the materials in the reaction kettle into the collection kettle, then inject the NMP solution containing p-DCB into the above reaction kettle, cool to below 100°C, add the NMP in the system to reach 3.9w / w p-DCB, and stir for 30-60 minutes until uniform;

[0009] Step 3, continuous flow reactor synthesis process: the material is injected into the first-stage polymerization kettle at a speed of 1-3.6L / h, the temperature in the first-stage polymerization kettle is maintained between 210 and 240°C, after the liquid level in the first-stage polymerization kettle reaches a certain level, it overflows into the second-stage polymerization kettle, the temperature in the second-stage polymerization kettle is maintained between 230 and 240°C, after the liquid level in the second-stage polymerization kettle reaches a certain position, it overflows into the third-stage polymerization kettle, the temperature in the third-stage polymerization kettle is maintained between 240 and 255°C, after the liquid level in the third-stage polymerization kettle reaches a certain level, it overflows into the fourth-stage polymerization kettle, the temperature in the fourth-stage polymerization kettle is maintained between 260 and 270°C;

[0010] Step 4, cooling and screening process: After the four-stage polymerization kettle reaches the liquid level, the overflow flows into the separation kettle, connected to cooling water to cool down to 80°C, and the PPS coarse particle product is screened and filtered out;

[0011] Step 5: Separate and dry to obtain the PPS finished product: wash the filter cake for 0.5 h, then centrifuge and filter, and repeat the washing 5-6 times until the content of inorganic salts in the product is reduced to within the qualified range, and then dry to obtain the product.

[0012] Furthermore, the capacity of the reaction kettle is 30L, the capacity of the collecting kettle is 30L, the capacity of the first-stage polymerization kettle is 5L, the capacity of the second-stage polymerization kettle is 5L, the capacity of the third-stage polymerization kettle is 10L, the capacity of the fourth-stage polymerization kettle is 10L, the capacity of the collecting kettle is 30, and the material of the reaction kettle, collecting kettle, polymerization kettle group and separation kettle group is 316L stainless steel.

[0013] Through the above technical scheme, the solvents in the reactor and the collecting reactor are equal, ensuring that the materials in the reactor can be emptied once after dehydration without affecting the subsequent entry of materials. The volume of the third-stage polymerization reactor and the fourth-stage polymerization reactor is increased in order to provide a larger volume for stirring and dispersing in the later stage of the polymerization reaction when the solids increase and the viscosity increases, thereby ensuring the thoroughness of the polymerization reaction of the materials and reducing the waste of raw materials.

[0014] Furthermore, the filter cake is washed for the first time using the secondary washing water of the previous batch, and the washing water of the filter cake is applied step by step for repeated washing.

[0015] Through the above technical scheme, the secondary washing water of the previous batch is reused in the current batch, and the washing water of the current batch can be applied step by step. Under the premise of ensuring the washing needs, the washing water can be fully utilized, effectively reducing energy consumption and saving water resources.

[0016] Furthermore, when sampling and detecting the water content of the NMP effluent from the top of the tower, at least one of the KF method and the volumetric method can be used.

[0017] Through the above technical solution, the KF method is a titration method used to determine the water content in a sample, and the volumetric method is a method for determining the concentration of a substance through a chemical reaction. The two methods are used simultaneously or separately to reduce errors and avoid large errors between the measurement results of the dehydration amount and the actual value.

[0018] Furthermore, the molar ratio of the sodium hydroxide to Na2S·5H2O is 1:0.035, and the pH value of the Na2S·5H2O is acidic.

[0019] Through the above technical scheme, Na2S·5H2O can participate in the polymerization reaction as a catalyst to form an intermediate or an active intermediate, thereby accelerating the polymerization reaction. Na2S·5H2O can also be used to adjust the pH value of the reaction system, which is conducive to the polymerization reaction being carried out in a suitable pH environment.

[0020] Furthermore, in step 2, the temperature inside the collecting kettle can be lowered by adding p-DCB solution, and the molar number of the p-DCB solution is 1.0 eq.

[0021] Through the above technical solution, by adding low-temperature p-DCB solution, the material inside the collection kettle can be assisted in cooling, the cooling rate can be increased, and the cooling time can be shortened.

[0022] Furthermore, the mother liquor after filtration is recovered by distillation, and the residual liquid is then added with coarse particles of primary water to dissolve the salt, and then filtered and washed to obtain oligomeric fine powder. The fine powder is then washed 6 times and dried to obtain the finished product. The mother liquor after filtration is decolorized to recover the catalyst, and then dehydrated to recover NMP. The waste salt is filtered and dried, and then dissolved and filtered to recover sodium chloride.

[0023] Through the above technical scheme, by recycling catalysts, solvents and sodium chloride, etc., the generation of waste is reduced, environmental pollution is reduced, and by recycling and reusing catalysts, solvents and sodium chloride, etc., the production cost is reduced.

[0024] A polyphenylene sulfide continuous flow kettle continuous synthesis equipment comprises a reactor, wherein the outlet end of the reactor is connected to a collecting kettle, wherein the collecting kettle is connected to a polymerization kettle group via a delivery pump, wherein the polymerization kettle group comprises a first-stage polymerization kettle, a second-stage polymerization kettle, a third-stage polymerization kettle and a fourth-stage polymerization kettle connected end to end, wherein the outlet end of the fourth-stage polymerization kettle is connected to a separation kettle group, wherein the separation kettle group comprises at least one separation kettle one and one separation kettle two installed in parallel.

[0025] Furthermore, the inlet positions of the separation kettle one and the separation kettle two are connected by a three-way pipe, and a reversing valve is connected in series on the three-way pipe. The reversing valve is a three-way valve, and the inlet of the reversing valve is connected to the outlet end of the four-stage polymerization kettle via the three-way pipe.

[0026] Through the above technical scheme, the material in the four-stage polymerization kettle first overflows into the separation kettle one for cooling and filtration. After the separation kettle one is full, the reversing valve is actuated to connect the four-stage polymerization kettle with the separation kettle two, thereby realizing seamless switching between the separation kettle one and the separation kettle two, ensuring the continuity and efficiency of the polyphenylene sulfide synthesis process. The parallel combination can increase the required number of collection kettles, and has strong adaptability.

[0027] Furthermore, the outer wall of the collecting kettle is provided with a jacket, the side wall of the jacket is installed with a drainage flange and a water inlet flange arranged up and down, a water spray ring is provided above the outer side of the jacket, and the water spray ring and the water inlet flange are connected to an external water supply pump via a water distribution pipe.

[0028] Through the above technical scheme, cold water takes away the heat in the collecting kettle from bottom to top through the jacket, and part of the cold water is sprayed from top to bottom onto the upper outer wall of the jacket through the water spray ring, thereby alleviating the insufficient cooling of the upper layer of the collecting kettle caused by the continuous heat absorption and temperature rise of the cold water in the jacket. The cold water absorbs heat and vaporizes upward to generate a circulating airflow, which allows the heat to quickly dissipate into the atmosphere for efficient supplementary cooling, thereby improving the heat exchange efficiency and shortening the stirring time.

[0029] The beneficial effects of the present invention are as follows:

[0030] (1) The present invention uses a kettle continuous reaction scheme to replace the traditional kettle intermittent process through process improvement. The main advantage is that it can continuously feed materials instead of feeding materials all at once. In this way, the heat can be controlled to be continuously output within a certain period of time instead of being released in a short period of time, thereby making it easier to control the reaction conditions. The polymerization reaction is dispersed in different kettles, and the temperature and reaction rate control is more accurate, ensuring the stability of the resin quality.

[0031] (2) The present invention optimizes the process flow and utilizes a continuous polymerization kettle to independently react materials at different polymerization stages at the same time. The temperature change of a single kettle body is small, which reduces the energy consumption required for repeated heating and cooling. The heating and dehydration and cooling and feeding are carried out separately in different kettles, thereby avoiding the pause and energy waste caused by the entire process of heating, cooling, mixing and dispersing a reactor at different times during the polymerization process, thereby improving production efficiency.

[0032] (3) The present invention improves the equipment, utilizes kettles of different capacities in series, conducts kettle-type continuous reaction, optimizes the cooling structure of the collecting kettle, conducts water bath heat exchange and gasification heat dissipation, and compensates for the weak positions of the water bath through gasification heat dissipation, generates circulating airflow and utilizes the surrounding air for auxiliary heat dissipation, improves the heat dissipation efficiency, improves the path of the separation kettle group, filters and disperses the slower coarse material, and ensures that the polymerization kettle can work continuously. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1It is a process flow chart of the present invention;

[0034] Figure 2 It is the overall structural diagram of the present invention;

[0035] Figure 3 It is a top view of the four-stage polymerization kettle, the separation kettle 1, the separation kettle 2 and the reversing valve of the present invention;

[0036] Figure 4 It is a schematic structural diagram of the collecting kettle of the present invention when it is equipped with a jacket.

[0037] Figure numerals: 3, reaction kettle; 4, collecting kettle; 5, conveying pump; 6, first-stage polymerization kettle; 7, second-stage polymerization kettle; 8, third-stage polymerization kettle; 9, fourth-stage polymerization kettle; 10, separation kettle one; 11, separation kettle two; 12, three-way pipe; 13, jacket; 14, water spray ring; 15, drain flange; 16, water inlet flange; 17, water distribution pipe; 18, reversing valve. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0039] like Figure 1 As shown, this embodiment provides a continuous flow kettle-type continuous synthesis process of polyphenylene sulfide, comprising the following steps:

[0040] Step 1: Heating and dehydration process:

[0041] First, NMP solvent with a concentration range of 4.0 to 5.0 w / w, sodium hydroxide, Na2S·5H2O and a catalyst dissolved with polyphenylene sulfide polymerization raw materials p-MB and p-DCB are added into the reaction kettle 3 to provide a suitable environment for the reaction;

[0042] Next, sodium hydroxide (0.035 eq) and Na2S·5H2O (1.0 eq) are added to the reactor 3. Sodium hydroxide, as an alkaline catalyst, can promote the reaction, while Na2S·5H2O can participate in the polymerization reaction as a catalyst to form an intermediate or an active intermediate, thereby accelerating the polymerization reaction. It should be noted that the molar ratio of sodium hydroxide to Na2S·5H2O is 1:0.035. Na2S·5H2O can also be used to adjust the pH value of the reaction system, which is conducive to the polymerization reaction in a suitable pH environment;

[0043] The reactor 3 is heated to 200-203° C. to activate the catalyst and reactants and promote the chemical reaction. At high temperature, the NMP solvent in the reactor 3 reacts chemically with the sodium hydroxide, Na2S·5H2O and the catalyst to remove water with a total weight of about 0.57w / w p-DCB. In this process, the removal of water helps to improve the purity of the reactants and the reaction efficiency;

[0044] After the dehydration process is completed, the temperature is continued to rise until the weight of the NMP removed reaches 1.5w / w p-DCB. This step helps to further remove unwanted impurities and improve the purity of the final product;

[0045] Take samples to test the water content of the NMP effluent at the top of the tower to ensure that it is around 2% (KF method, volumetric method). If the water content meets the requirements, stop the dehydration process.

[0046] Among them, NMP solvent is used as a solvent. NMP can effectively dissolve sodium hydroxide, Na2S·5H2O and the catalyst, providing a uniform reaction environment for the reaction. At the same time, NMP reacts chemically with sodium hydroxide, Na2S·5H2O and the catalyst at a high temperature, and the total weight of water removed is about 0.57w / w p-DCB, which helps to improve the purity of the reactants and the reaction efficiency.

[0047] At the same time, sodium hydroxide, as an alkaline catalyst, can promote the reaction, while Na2S·5H2O may act as an auxiliary catalyst or reactant to participate in the chemical reaction. The catalyst can accelerate the chemical reaction and improve the reaction efficiency.

[0048] Through the above steps, moisture and impurities can be effectively removed, the purity of the reactants and the reaction efficiency can be improved, and thus a high-quality final product can be obtained.

[0049] Step 2: Solvent addition process:

[0050] The material in the reactor 3 is transferred to the collecting reactor 4 (30L, 316L), and the temperature of the material in the collecting reactor 4 is cooled to below 100°C, while the reactor 3 which has been preheated does not need to be cooled down, saving energy consumption, directly introducing new reactants, and performing continuous dehydration work to optimize the process flow;

[0051] Inject an NMP solution containing p-DCB (1.0 eq) into the collecting kettle 4. The newly introduced NMP solution can assist in cooling the material in the collecting kettle 4 and replace a portion of the NMP in the collecting kettle 4. The NMP is replenished until the NMP in the system reaches 3.9 w / w p-DCB, ensuring that the concentrations of the solvent and solute in the reaction mixture meet the requirements of subsequent reactions.

[0052] Stirring for 30-60 minutes to ensure that the new solvent and the original reactants are fully mixed, providing a uniform reaction environment for subsequent reactions. The reaction kettle 3 and the collection kettle 4 work simultaneously to reduce the dehydration preparation time of the materials and provide a continuous material supply for the subsequent continuous flow kettle continuous synthesis process;

[0053] Among them, by adding the NMP solution containing p-DCB, a part of the NMP in the collection kettle 4 can be replaced, and the concentration of the solvent can be adjusted or the reaction environment can be changed;

[0054] Through the above steps, the solvent concentration can be effectively replaced and adjusted to ensure that the concentrations of the solvent and solute in the reaction mixture meet the requirements of the subsequent reaction, thereby preparing for the subsequent chemical reaction or treatment steps.

[0055] Step 3: Continuous flow reactor synthesis process:

[0056] Primary polymerization kettle 6: The material in the collecting kettle 4 is pumped into the primary polymerization kettle 6 at a rate of 1-3.6 L / h. The temperature in the kettle is maintained at 210-240°C. At this stage, the reaction conditions are conducive to the initial polymerization of the material to form shorter polyphenylene sulfide chains.

[0057] In a further embodiment, the material entry rate is 1-3.6 L / h. It can be understood that the material entry rate can be, for example, 1 L / h, 1.1 L / h, 2 L / h, 2.1 L / h, 3 L / h, 3.1 L / h, 3.2 L / h, 3.3 L / h, 3.4 L / h, 3.5 L / h, 3.6 L / h, and the material entry rate can also be other values ​​within the range.

[0058] Secondary polymerization kettle 7: After the liquid level in the first polymerization kettle 6 reaches a certain position, it overflows into the secondary polymerization kettle 7, and the temperature in the kettle is maintained at 230-240°C. In the secondary polymerization kettle 7, the reaction conditions are conducive to further growth of the polyphenylene sulfide chain to form a longer molecular chain;

[0059] Three-stage polymerization kettle 8: After the liquid level in the second-stage polymerization kettle 7 reaches a certain position, it overflows into the three-stage polymerization kettle 8, and the temperature in the kettle is maintained at 240-255°C. In the three-stage polymerization kettle 8, the reaction conditions are conducive to further improving the degree of polymerization and forming high molecular weight polyphenylene sulfide;

[0060] Four-stage polymerization kettle 9: After the liquid level in the three-stage polymerization kettle 8 reaches a certain position, it overflows into the four-stage polymerization kettle 9. The temperature in the kettle is maintained at 260-270°C. In the four-stage polymerization kettle 9, the reaction conditions are conducive to the final completion of the polymerization reaction to form fully polymerized polyphenylene sulfide.

[0061] In a further embodiment, the temperature inside the first-stage polymerization kettle 6 is maintained at 210-240°C, the temperature inside the second-stage polymerization kettle 7 is maintained at 230-240°C, the temperature inside the tertiary polymerization kettle 8 is maintained at 240-255°C, and the temperature inside the quaternary polymerization kettle 9 is maintained at 260-270°C. It can be seen that the temperatures of the first-stage polymerization kettle 6, the second-stage polymerization kettle 7, the tertiary polymerization kettle 8 and the quaternary polymerization kettle 9 can be any temperature or temperature range within the corresponding range.

[0062] In the continuous flow reactor continuous synthesis process of polyphenylene sulfide, the materials are polymerized in multiple polymerization reactors in sequence. The temperature and reaction conditions of each polymerization reactor are different to promote the polymerization reaction and control the quality of the product. In this way, the materials gradually increase the degree of polymerization in multiple polymerization reactors, and finally form high-quality polyphenylene sulfide products.

[0063] It should be emphasized that the continuous flow tank process has the following advantages over the batch process:

[0064] Continuous production: Continuous flow autoclave process can achieve continuous production, reduce downtime and improve production efficiency;

[0065] Quality control: By gradually increasing the degree of polymerization in multiple polymerization reactors, product quality can be better controlled and batch-to-batch variability can be reduced;

[0066] Temperature control: Each polymerization reactor can independently control the temperature, which is conducive to optimizing reaction conditions and improving reaction efficiency;

[0067] Energy saving and emission reduction: The continuous flow kettle process reduces the material transfer time between kettles, reducing energy consumption and emissions;

[0068] Easy to operate: The continuous flow autoclave process is relatively simple to operate, reducing the need for manual intervention;

[0069] High degree of automation: The continuous flow autoclave process can achieve high degree of automation, which improves the stability of the production process;

[0070] Strong adaptability: The continuous flow tank process can adapt to different types of polymerization reactions and is suitable for the synthesis of a variety of polymers;

[0071] In general, the continuous flow autoclave process has obvious advantages in improving production efficiency, quality control, energy conservation and emission reduction, and is an important development direction in the field of polymer synthesis.

[0072] Step 4: Cooling and screening process:

[0073] After the four-stage polymerization kettle 9 reaches the liquid level, the overflow flows into the separation kettle 1 10 (30L, 316L) and the separation kettle 2 11 (30L, 316L). Both separation kettles are equipped with a stirring device, a cooling system, a feed port and a discharge port. The four-stage polymerization kettle 9 is connected to the two separation kettles through a three-way pipe 12. A reversing valve 18 is provided at the intersection of the three-way pipe 12 to ensure that the materials can flow from the four-stage polymerization kettle 9 into different separation kettles respectively;

[0074] When the liquid level in the four-stage polymerization kettle 9 reaches the set value, the reversing valve 18 is opened to communicate with the separation kettle 10, and the material begins to overflow into the separation kettle 10. The material in the separation kettle 10 is cooled to 80°C under the control of the stirring and cooling system;

[0075] While the separation kettle 10 starts to be filled with materials, the separation kettle 2 11 is ready, and the stirring device and cooling system of the separation kettle 2 11 are pre-set to receive and process the materials in the fourth-stage polymerization kettle 9;

[0076] When the liquid level of the separation kettle 10 reaches the set value, the feed port of the separation kettle 10 is closed, the stirring and heating / cooling system is stopped, and at the same time, the feed port of the separation kettle 2 11 is opened, the reversing valve 18 is switched to communicate with the separation kettle 2 11, the stirring and cooling system is started, and the material in the fourth-stage polymerization kettle 9 is transferred to the separation kettle 2 11. During the transfer process, the stirring and cooling system of the separation kettle 2 11 is kept running to ensure that the material maintains a stable temperature and state during the transfer process;

[0077] When the separation kettle 11 is collecting materials, the materials in the separation kettle 10 are discharged through the discharge port at the bottom and are screened and filtered to separate the coarse particle product of PPS. After the internal materials are gradually emptied, the discharge port is closed and a discharge port closing signal is emitted to prompt the separation kettle 10 to enter the state of preparing to receive materials. When the liquid level in the separation kettle 11 reaches the set value, the four-stage polymerization kettle 9 is disconnected from the separation kettle 11 through the reversing valve 18, and the materials are input into the separation kettle 10 again through the reversing valve 18 for alternating material collection.

[0078] Step 5: Separate and dry to obtain PPS finished product:

[0079] The separated cake-like PPS coarse particle product is placed in a washing device and washed with the secondary washing water of the previous batch for 0.5 hours to ensure that the inorganic salts and other impurities in the filter cake are fully removed. After washing, the filter cake is separated by a centrifugal filter;

[0080] After the filter cake is centrifuged and filtered, the washing process is repeated again, usually 5-6 times. The washing water can be reused step by step, that is, the washing water can be used again to wash the next batch of filter cakes. The recycling of washing water helps to reduce water consumption and reduce costs;

[0081] Use drying equipment, such as an oven or drying tower, to dry the washed PPS filter cake. The drying equipment should have good temperature control and thermal efficiency to ensure that the quality and performance of PPS are not affected during the drying process. The drying temperature should be controlled within a suitable range, usually between 80-120°C. The drying progress needs to be monitored regularly to avoid over-drying.

[0082] It should be emphasized that the washing equipment should have sufficient capacity and efficiency to handle large amounts of filter cake. The washing equipment can be a stirring tank or a spray washer. The appropriate design should be selected according to actual needs. The centrifugal filter should have sufficient centrifugal force to quickly and effectively separate the filter cake and washing water. The equipment should have automatic feeding and discharging functions to improve operating efficiency.

[0083] In addition, the drying equipment should have a good heat exchange system to provide uniform drying conditions, and the equipment should have automatic control and monitoring functions to ensure the stability of the drying process and product quality;

[0084] In a further embodiment, the operating temperature of the oven or drying tower is between 80-120°C, that is, it can be 80°C, 90°C, 100°C, 110°C and 120°C, or it can be 81°C, 82°C, 83°C, 84°C85°C, 86°C, 87°C, 88°C, 89°C. It can be selected according to actual equipment and production scenarios to ensure that the inorganic salt content in the PPS finished product is reduced to within the qualified range, thereby obtaining high-quality products.

[0085] Running data statistics:

[0086]

[0087]

[0088] The above 0-180h trial operation data mainly records the changes in four data items: P-DCB residue, moisture, sodium chloride and melt index, among which:

[0089] P-DCB residue: P-DCB (paradichlorobenzene) is one of the raw materials in the synthesis of polyphenylene sulfide. Its residue should decrease as the reaction proceeds. If the residue remains unchanged or increases, it may indicate problems with the reaction conditions or process control.

[0090] Moisture: The moisture content should be as low as possible, as the presence of moisture may affect the performance and stability of the product. If the moisture content increases, it may be necessary to check whether the dehydration process is effective;

[0091] Sodium chloride: Sodium chloride usually exists as an impurity and its content should be as low as possible. If the sodium chloride content increases, it may be necessary to check the purity of the raw materials or whether there is leakage in the reaction process;

[0092] Melt index: Melt index is an indicator to measure the melt fluidity of polymer. Its value should be within a certain range, and the change of melt index should match the reaction progress. If the melt index fluctuates greatly, it may be necessary to check whether the reaction conditions or raw materials have changed.

[0093] Based on the data obtained from the trial run, we can see that:

[0094] 1. The overall P-DCB residue is on a downward trend, which is reasonable;

[0095] 2. The content of water and sodium chloride is generally stable and does not change much, which is reasonable;

[0096] 3. The change of melt index is within a reasonable range, but the differences between some data points are large, but there are no abnormal changes such as sharp increase or decrease, which may require further investigation and improvement;

[0097] In general, these data seem reasonable, but in order to ensure the stability of the production process and product quality, the following operations can be performed:

[0098] Regularly check reaction conditions and raw materials to ensure they meet specifications;

[0099] Take samples regularly for analysis to monitor changes in P-DCB residue, moisture, sodium chloride and melt index;

[0100] If data anomalies are found, immediate steps should be taken to investigate the causes and take appropriate corrective measures.

[0101] In a further embodiment, the filtered mother liquor contains recoverable solvent and other valuable components, which can be separated from the mother liquor through the distillation process, thereby reducing waste and reducing costs. The evaporator is used to heat the mother liquor during the distillation process to evaporate it, separate the solvent and other components in the mother liquor using the distillation tower, and cool the vapor in conjunction with the condenser to condense it back into a liquid state;

[0102] In the recovery of the residual liquid from the kettle, the primary water generated during the washing of the coarse particles is added to dissolve the salt therein, and the solid particles are separated by filtering through a filter press. The solid particles are washed by a spray washing device to remove the solid particles and impurities to obtain oligomeric fine powder. The fine powder is washed 6 times to further remove inorganic salts and other impurities. Finally, the washed fine powder is dried to remove excess water to obtain a finished product.

[0103] During the process, the distillation recovery and washing processes improve resource utilization and reduce waste generation. Through the distillation recovery and washing processes, the emission of harmful substances is reduced and environmental pollution is reduced. The continuous washing and drying processes improve production efficiency and reduce the production cycle. Through multiple washing and drying, the product quality is improved and the performance of the final product is ensured.

[0104] In actual operation, it is necessary to select appropriate equipment according to specific process requirements and ensure the compatibility and coordination between equipment. In addition, the operability, maintainability and safety of the equipment need to be considered to ensure the smooth progress of the production process.

[0105] In a further embodiment, in the synthesis process of polyphenylene sulfide (PPS), the filtered mother liquor undergoes a series of treatment steps to achieve environmentally friendly and economical production goals, wherein the filtered mother liquor needs to be decolorized because the filtered mother liquor may contain unreacted substances, by-products or catalyst residues, which may affect the color and quality of the product. Through the decolorization process, adsorbents or ion exchange resins are used to remove or reduce these substances so that the color of the mother liquor meets the standard requirements. During the process, a decolorization tower or decolorization column is used to load the adsorbent or ion exchange resin, and a water pump is also used to circulate the mother liquor and regenerate the adsorbent or ion exchange resin.

[0106] In addition, the mother liquor after decolorization may contain catalysts, which are valuable resources for the production process. The catalysts are separated from the mother liquor by centrifugation or filtration and regenerated or recovered. At this time, a centrifuge or filter is used to separate the catalyst, and different regeneration devices are used for different catalysts to regenerate or recover the catalyst.

[0107] The mother liquor after decolorization and catalyst recovery may contain a large amount of solvent NMP. NMP can be separated from the mother liquor by distillation or evaporation to achieve solvent recovery and reuse. A distillation tower or evaporator can be used to separate NMP, and a cooler is used to cool the vapor and condense it back into a liquid state.

[0108] The dehydrated waste salt contains sodium chloride and other inorganic salts. The water in the waste salt is removed through the drying process to obtain dry waste salt. The dry waste salt is dissolved in water to form a sodium chloride solution. The solid particles in the solution are removed through the filtering process to obtain a sodium chloride solution. During this process, drying equipment such as an oven or a dryer is used to remove water from the waste salt. The dry waste salt is dissolved in a dissolving tank. A filter is used to separate the solid particles in the sodium chloride solution.

[0109] In summary, by recycling catalysts, solvents, sodium chloride, etc., the generation of waste is reduced and environmental pollution is reduced. By recycling and reusing catalysts, solvents, sodium chloride, etc., the production cost is reduced and the economic benefit is improved. Through the above steps, the environmental protection and economy of the polyphenylene sulfide synthesis process can be achieved. In actual operation, it is necessary to select appropriate equipment according to specific process requirements and ensure the compatibility and coordination between equipment.

[0110] A continuous flow kettle type continuous synthesis equipment for polyphenylene sulfide, referring to Figure 2 , including a reactor 3, the outlet end of the reactor 3 is connected to a collecting reactor 4, the collecting reactor 4 is connected to a polymerization reactor group via a delivery pump 5, the polymerization reactor group includes a first-stage polymerization reactor 6, a second-stage polymerization reactor 7, a third-stage polymerization reactor 8 and a fourth-stage polymerization reactor 9 connected end to end, the outlet end of the fourth-stage polymerization reactor 9 is connected to a separation reactor group, the separation reactor group includes at least one separation reactor 10 and one separation reactor 2 11 installed in parallel.

[0111] In a further embodiment, referring to Figure 3 The inlet positions of the separation kettle 10 and the separation kettle 2 11 are connected through a three-way pipe 12, and a reversing valve 18 is connected in series on the three-way pipe 12. The reversing valve 18 is a three-way valve. The inlet of the reversing valve 18 is connected to the outlet end of the four-stage polymerization kettle 9 through the three-way pipe 12. The material in the four-stage polymerization kettle 9 first overflows into the separation kettle 10 for cooling and filtering. After the separation kettle 10 is full, the reversing valve 18 is actuated to connect the four-stage polymerization kettle 9 with the separation kettle 2 11. At this time, the separation kettle 10 continues to filter and separate the PPS coarse material. After the second kettle 11 is full, the reversing valve 18 is activated again to connect with the separation kettle 10, so as to realize seamless switching between the separation kettle 10 and the separation kettle 2 11, thereby ensuring the continuity and efficiency of the polyphenylene sulfide synthesis process. In actual operation, if the liquid level in the separation kettle 2 11 reaches the set value and the separation kettle 10 cannot be emptied in time, a new set of separation kettles 10 and separation kettles 2 11 can be added, and the new reversing valve 18 and pipelines can be used to add channels, which may need to be adjusted and optimized according to the specific process requirements.

[0112] In a further embodiment, referring to Figure 4The stirring time of the collecting kettle 4 is related to the cooling rate. By improving the equipment, the stirring time can be shortened. The present embodiment provides a configuration. The outer wall of the collecting kettle 4 is provided with a jacket 13. The side wall of the jacket 13 is provided with a drainage flange 15 and a water inlet flange 16 arranged up and down. A water spray ring 14 is provided above the outer side of the jacket 13. The water spray ring 14 and the water inlet flange 16 are connected to an external water supply pump via a water distribution pipe 17. Two water outlets are designed at the outlet end of the water supply pump using the water distribution pipe 17. One of the water outlets of the water distribution pipe 17 inputs cold water from the water inlet flange 16 to the bottom of the jacket 13, and overflows from the drainage flange 15 at the top of the jacket 13 to take away the heat in the collecting kettle 4. The other water outlet of the water distribution pipe 17 inputs cold water from the water inlet flange 16 to the bottom of the jacket 13. The water is sent into the spray ring 14 and sprayed from top to bottom in a ring shape onto the outer wall of the jacket 13, thereby cooling the upper half of the jacket 13 and alleviating the insufficient cooling of the upper layer of the collecting kettle 4 caused by the continuous heat absorption and temperature rise of the cold water in the jacket 13. In addition, the sprayed water carries the external air to contact the collecting kettle 4 and the jacket 13, wherein the air absorbs heat and moves upward, and the cold water absorbs heat and vaporizes and also moves upward. At this time, the cold air below and around will be supplemented to the jacket 13, and the continuous circulating airflow generated will prevent the heat dissipated into the atmosphere from being retained around the collecting kettle 4 and the outer wall of the jacket 13. The low temperature of the surrounding air can be used to efficiently supplement and cool the collecting kettle 4 and the jacket 13, thereby ensuring that the temperature inside the collecting kettle 4 is uniform, improving the heat exchange efficiency, and shortening the stirring time.

[0113] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention.

Claims

1. A continuous flow kettle-type continuous synthesis process for polyphenylene sulfide, characterized in that: The steps include: Step 1: Heating and dehydration process: 4.0-5.0w / w NMP solution, sodium hydroxide, Na2S·5H2O and a catalyst are added to the reaction kettle (3). When the temperature in the reaction kettle (3) rises to 200-203°C, the total weight of water removed is about 0.57w / w p-DCB. When the weight of NMP removed by continuing to increase the temperature reaches 1.5w / w p-DCB, the water content of the NMP removed liquid at the top of the tower is sampled and tested. The water content should be about 2%, and the dehydration is stopped. Step 2: Solvent addition process: The material in the reaction kettle (3) is transferred to the collection kettle (4), and then the NMP solution containing p-DCB is injected into the above reaction kettle (3), cooled to below 100°C, and added until the NMP in the system reaches 3.9w / w p-DCB, and stirred for 30-60 minutes until it is uniform; Step 3: Continuous flow reactor synthesis process: The material is pumped into a first-stage polymerization kettle (6) at a speed of 1-3.6 L / h, the temperature in the first-stage polymerization kettle (6) is maintained between 210 and 240° C., after the liquid level in the first-stage polymerization kettle (6) reaches a certain level, the material overflows into a second-stage polymerization kettle (7), the temperature in the second-stage polymerization kettle (7) is maintained between 230 and 240° C., after the liquid level in the second-stage polymerization kettle (7) reaches a certain level, the material overflows into a third-stage polymerization kettle (8), the temperature in the third-stage polymerization kettle (8) is maintained between 240 and 255° C., after the liquid level in the third-stage polymerization kettle (8) reaches a certain level, the material overflows into a fourth-stage polymerization kettle (9), the temperature in the fourth-stage polymerization kettle (9) is maintained between 260 and 270° C.; Step 4: Cooling and screening process: After the fourth-stage polymerization kettle (9) reaches the liquid level, the overflow flows into the separation kettle group, is connected to cooling water to cool down to 80°C, and the PPS coarse particle product is sieved and filtered out; Step 5: Separate and dry to obtain PPS finished product: The filter cake was washed for 0.5 h and then centrifuged and filtered. The filter cake was washed again 5-6 times until the content of inorganic salts in the product was reduced to within the qualified range, and then dried to obtain the product.

2. The polyphenylene sulfide continuous flow kettle continuous synthesis process according to claim 1, characterized in that: In step 1, the molar ratio of the sodium hydroxide to Na2S·5H2O is 1:0.035, and the pH value of the Na2S·5H2O is acidic.

3. The continuous flow kettle-type continuous synthesis process of polyphenylene sulfide according to claim 1, characterized in that: In step 2, the internal temperature of the collecting kettle (4) can be lowered by adding p-DCB solution, and the molar number of the p-DCB solution is 1.0 eq.

4. The continuous flow kettle-type continuous synthesis process of polyphenylene sulfide according to claim 1, characterized in that: In step 2, when sampling and detecting the water content of the NMP effluent from the top of the tower, at least one of the KF method and the volumetric method is used.

5. The continuous flow kettle-type continuous synthesis process of polyphenylene sulfide according to claim 1, characterized in that: In step 5, the filter cake is washed for the first time using the secondary washing water of the previous batch, and the washing water of the filter cake is applied step by step for repeated washing.

6. The polyphenylene sulfide continuous flow kettle continuous synthesis process according to claim 1, characterized in that: The capacity of the reaction kettle (3) is 30L, the capacity of the collecting kettle (4) is 30L, the capacity of the first-stage polymerization kettle (6) is 5L, the capacity of the second-stage polymerization kettle (7) is 5L, the capacity of the third-stage polymerization kettle (8) is 10L, the capacity of the fourth-stage polymerization kettle (9) is 10L, the capacity of the collecting kettle (4) is 30, and the material of the reaction kettle (3), the collecting kettle (4), the polymerization kettle group and the separation kettle group is 316L stainless steel.

7. The continuous flow kettle-type continuous synthesis process of polyphenylene sulfide according to claim 1, characterized in that: In step five, the filtered mother liquor is recovered by distillation, and the residual liquid is then added with coarse particles of primary water to dissolve the salt, and then filtered by pressure to obtain oligomeric fine powder. The fine powder is then washed 6 times and dried to obtain the finished product. The filtered mother liquor is decolorized to recover the catalyst, and then dehydrated to recover NMP. The filtered waste salt is dried and then dissolved and filtered to recover sodium chloride.

8. A polyphenylene sulfide continuous flow kettle continuous synthesis equipment, used to implement the polyphenylene sulfide continuous flow kettle continuous synthesis process according to any one of claims 1 to 7, characterized in that: The invention comprises a reaction kettle (3), wherein the outlet end of the reaction kettle (3) is connected to a collecting kettle (4), wherein the collecting kettle (4) is connected to a polymerization kettle group via a delivery pump (5), wherein the polymerization kettle group comprises a first-stage polymerization kettle (6), a second-stage polymerization kettle (7), a third-stage polymerization kettle (8) and a fourth-stage polymerization kettle (9) connected end to end, wherein the outlet end of the fourth-stage polymerization kettle (9) is connected to a separation kettle group, wherein the separation kettle group comprises at least one separation kettle one (10) and one separation kettle two (11) installed in parallel.

9. The polyphenylene sulfide continuous flow kettle continuous synthesis equipment according to claim 8, characterized in that: The inlet positions of the separation kettle 1 (10) and the separation kettle 2 (11) are connected via a three-way pipe (12), a reversing valve (18) is connected in series to the three-way pipe (12), and the reversing valve (18) is a three-way valve. The inlet of the reversing valve (18) is connected to the outlet end of the four-stage polymerization kettle (9) via the three-way pipe (12).

10. The polyphenylene sulfide continuous flow kettle continuous synthesis equipment according to claim 8, characterized in that: The outer wall of the collecting kettle (4) is provided with a jacket (13), and the side wall of the jacket (13) is provided with a drainage flange (15) and a water inlet flange (16) arranged up and down. A water spray ring (14) is provided above the outer side of the jacket (13), and the water spray ring (14) sprays water toward the jacket (13) to generate an ascending airflow.

Images