Meltable fluororesin end group fluorination treatment system and process

Abstract

The invention provides a meltable fluororesin end group fluorination treatment system and a meltable fluororesin end group fluorination treatment process. The system comprises at least two feeding tanks, a reaction tower and a cooling tank, the top ends of the feeding tanks are connected with an N2 gas pipeline and are provided with resin raw material inlets, and the N2 gas pipeline is provided with a valve; the top end of the reaction tower is connected with the bottom end of the feeding tank through a pipeline, a valve is arranged on the pipeline, the top end of the reaction tower is connected with a tail gas treatment pipeline, the bottom end of the reaction tower is connected with an N2 / F2 mixed gas pipeline and an N2 gas pipeline, and a valve is arranged on the pipeline; the top ends of the cooling tanks are connected with the bottom end of the reaction tower through pipelines, valves are arranged on the pipelines, the bottom ends of the cooling tanks are connected with a product output pipeline and an N2 gas pipeline, and valves are arranged on the pipelines. The system can ensure that the fluorination reaction of the end group of the meltable fluororesin is continuously carried out, the production efficiency of the fluorination reaction is remarkably improved, the system avoids the overflow of fluorine, and the safety of the working environment is improved.

Description

Technical Field

[0001] The invention relates to the technical field of fluorine materials, and in particular to a system and process for fluorination treatment of end groups of meltable fluorine resins. Background Art

[0002] Melt-processable fluorocarbon resin (melt-processable fluororesin) refers to a copolymer prepared from tetrafluoroethylene and perfluoroalkyl vinyl ether. Due to its special chemical composition, it has excellent comprehensive properties such as excellent chemical stability, extremely high high and low temperature resistance, aging resistance and radiation resistance. It has been widely used in various applications, such as materials for molded products such as pipes, joints, containers, wire insulation materials, coating materials, lining materials, etc.

[0003] For meltable fluororesins, due to their polymerization mechanism, more or less unstable groups will inevitably be formed at the polymer ends. In industry, polymerization initiators such as ammonium persulfate (APS) are widely used for emulsion polymerization or non-aqueous polymerization using organic peroxide initiators. Due to the effects of initiators, chain transfer agents, buffers, etc., unstable end groups will exist in the molecular chain segments of meltable fluororesins, such as ~COOH, ~COF, ~CF=CF2, ~CONH2, ~CF2OH, ~CF2H, ~CF2CH3, etc. Since these end groups are thermally unstable, they will produce volatile substances during the processing process, causing the finished product to contain bubbles, voids or HF, resulting in molding failure or molding machine mold corrosion, thereby limiting the further application of meltable fluororesin products in high-tech fields such as semiconductor silicon wafer processing, photoelectric copying hot roller anti-sticking and anti-corrosion thick film coating.

[0004] At present, some methods and technologies for stabilizing the thermally unstable end groups of meltable fluororesins have been extensively studied and proposed, such as wet heat treatment, methylation, oxidation treatment, and fluorination. Among them, fluorination is the most thorough and industrialized surface fluorination treatment method for treating end groups. A large number of companies have carried out industrial practical applications. The fluorination method can significantly improve the quality of meltable fluororesins and expand the application field of meltable fluororesins. However, the application of the fluorination method currently uses an intermittent reaction device, that is, raw materials are added into the reactor, and after the reaction is completed, the product is discharged, and the raw materials are added again for reaction, and then the product is discharged. On the one hand, the above-mentioned frequent feeding-reaction-discharge process significantly reduces the efficiency of the fluorination reaction. It has the disadvantages of long auxiliary time before and after the reaction and high labor intensity, and does not consider the efficiency and cost of actual industrial production; on the other hand, the raw material gas used in the fluorination reaction contains fluorine. Even if defluorination treatment is used after the reaction is completed, fluorine will inevitably remain in the reaction chamber. During the feeding and discharging process, fluorine will overflow, causing pollution to the construction environment, and the additional defluorination treatment process will inevitably reduce the production efficiency. Summary of the invention

[0005] The present invention aims to solve one of the technical problems in the prior art at least to a certain extent. To this end, one object of the present invention is to provide a system and process for fluorination treatment of end groups of meltable fluororesin.

[0006] In a first aspect of the present invention, a system for treating end groups of a meltable fluororesin by fluorination is provided, the system comprising: A feeding tank, of which there are no less than 2, the top of which is connected to a N2 gas pipeline and is provided with a resin raw material inlet, and a valve is provided on the N2 gas pipeline; A reaction tower, wherein the top of the reaction tower is connected to the bottom of the feeding tank through a pipeline, and a valve is provided on the pipeline, the top of the reaction tower is connected to an exhaust gas treatment pipeline, and the bottom of the reaction tower is connected to an N2 / F2 mixed gas pipeline and an N2 gas pipeline, and a valve is provided on the pipeline; Cooling tank, there are no less than 2 cooling tanks, the top of the cooling tank is connected to the bottom of the reaction tower through a pipeline, and a valve is provided on the pipeline, and the bottom of the cooling tank is connected to the product output pipeline and the N2 gas pipeline, and a valve is provided on the pipeline.

[0007] The above-mentioned meltable fluororesin terminal group fluorination treatment system according to the present invention comprises a feed tank, a reaction tower and a cooling tank.

[0008] Among them, there are no less than 2 feeding tanks, the top of the feeding tank is connected to the N2 gas pipeline, and is provided with a resin raw material inlet. A valve is provided on the N2 gas pipeline. Resin raw materials are added to the feeding tank from the resin raw material inlet. After the feeding tank is filled with resin raw materials, the resin raw material inlet can be closed, and the valve on the N2 gas pipeline can be opened to pass N2 gas into the feeding tank and discharge the air in the feeding tank.

[0009] The top of the reaction tower is connected to the bottom of the feeding tank through a pipeline, and a valve is provided on the pipeline. When the valve is opened, the resin raw material in the feeding tank is transported to the reaction tower. The bottom of the reaction tower is connected to an N2 / F2 mixed gas pipeline and an N2 gas pipeline. The N2 / F2 mixed gas pipeline allows the N2 / F2 mixed gas and the resin raw material to contact in countercurrent flow in the reaction tower for fluorination reaction. Before the fluorination reaction, the N2 gas pipeline transports N2 gas into the reaction tower to exhaust the air in the reaction tower. The top of the reaction tower is connected to an exhaust gas treatment pipeline. The fluorination reaction will produce some waste gas, which can be discharged from the reaction tower through the exhaust gas treatment pipeline for centralized treatment.

[0010] There are no less than 2 cooling tanks. The top of the cooling tank is connected to the bottom of the reaction tower through a pipe, and a valve is provided on the pipe. When the fluorination reaction in the reaction tower is completed, the valve is opened and the fluorination product is transported to the cooling tank through the pipe. The bottom of the cooling tank is connected to the product output pipe and the N2 gas pipe. On the one hand, the N2 gas pipe can transport N2 gas to discharge the air in the cooling tank before feeding. On the other hand, because the product obtained by fluorination contains fluorine, the N2 gas pipe transports N2 gas from the bottom into the cooling tank to remove residual fluorine. The obtained mixed gas of N2 and fluorine can be sent to the reaction tower for further fluorination reaction. Finally, the product is discharged from the system through the product output pipe and enters subsequent processing.

[0011] The above-mentioned meltable fluorine resin end group fluorination treatment system of the present invention is filled with raw material resin in no less than 2 feed tanks and the reaction tower. Before starting the reaction, nitrogen is transported to the feed tank, the reaction tower and the cooling tank through the N2 gas pipeline, and the air in the system is discharged. The reaction tower starts to heat up. After reaching the reaction temperature, the valve is opened, and the raw material resin is transported from the feed tank to the reaction tower. At the same time, the N2 / F2 mixed gas pipeline continuously passes N2 / F2 mixed gas and raw material resin into the reaction tower from the bottom of the reaction tower to undergo fluorination reaction. After the reaction is completed, the product is transported from the pipeline to the cooling tank. When the system is started and debugged stably, the valve of the feed tank connecting the pipeline with the reaction tower and the valve of the pipeline connecting the reaction tower with the cooling tank are always in an open state, that is, the feed tank continuously supplies resin raw materials to the reaction tower, the reaction is always in the reaction tower, and the reaction product is continuously transported to the cooling tank, thereby ensuring the continuity of the fluorination reaction. Compared with the existing intermittent reaction, the fluorination reaction efficiency can be significantly improved, cost is saved, labor is reduced, and it is suitable for industrial production.

[0012] Specifically, because the present invention uses no less than two feeding tanks, and both are filled with raw resin, the air has been removed in the early stage. When the raw resin in one feeding tank is added, it can be immediately switched to the next feeding tank to continuously transport the resin raw material to the reaction tower, which ensures the continuity of the reaction and improves the efficiency of the fluorination reaction. It is not necessary to open the feeding tank frequently to add materials, and the fluorine overflowing from the feeding tank (the fluorine in the feeding tank comes from the fluorine in the reaction tower that inevitably overflows into the feeding tank) is avoided from being discharged to the external environment, ensuring the safety of the working environment. The feeding tank is connected to the N2 gas pipeline, and N2 gas can be introduced to send the overflowed fluorine back to the reaction tower as much as possible, reducing the residual fluorine content in the feeding tank, and further ensuring the safety of the operation.

[0013] Similarly, no less than two cooling tanks ensure that the reaction products in the reaction tower can be continuously discharged. If the product of one cooling tank is full, it can be immediately switched to another cooling tank, thereby improving the efficiency of the fluorination reaction. And because the product obtained by fluorination contains fluorine (fluorine overflowing from the reaction tower), the N2 gas pipeline transports N2 gas from the bottom to the cooling tank, which can remove the residual fluorine. The obtained N2 and fluorine mixed gas can be sent back to the reaction tower for fluorination reaction, which significantly reduces the risk of fluorine leakage in the cooling tank.

[0014] Therefore, the system can ensure the continuous fluorination reaction of the end group of the meltable fluororesin, significantly improve the production efficiency of the fluorination reaction, reduce auxiliary labor, and reduce product costs. It is suitable for large-scale industrial production. The system avoids fluorine overflow, improves the safety of the working environment, and ensures the health of operators.

[0015] According to the above-mentioned meltable fluororesin end group fluorination treatment system of the present invention, three-stage heating devices are provided on the side wall of the reaction tower to heat the upper, middle and lower parts of the reaction tower respectively.

[0016] According to the above-mentioned meltable fluororesin end group fluorination treatment system of the present invention, a stirring device is provided in the reaction tower.

[0017] According to the above-mentioned meltable fluororesin terminal group fluorination treatment system of the present invention, the resin raw material inlet is connected to the raw material supply device through a pipeline, and a valve is provided on the pipeline.

[0018] According to the above-mentioned meltable fluororesin end group fluorination treatment system of the present invention, the tail gas treatment pipeline is connected to the tail gas treatment device, and a valve is provided on the pipeline.

[0019] According to the above-mentioned meltable fluororesin end group fluorination treatment system of the present invention, on the cooling tank, the N2 gas pipeline is connected to the product output pipeline, and the valve on the product output pipeline is arranged at one end away from the N2 gas pipeline and the cooling tank.

[0020] According to the above-mentioned meltable fluororesin end group fluorination treatment system of the present invention, the N2 / F2 mixed gas pipeline is connected to the pipeline between the reaction tower and the cooling tank.

[0021] According to the above-mentioned meltable fluororesin end group fluorination treatment system of the present invention, the bottom end of the cooling tank is connected to the air pipeline, and the top end of the cooling tank is connected to the tail gas treatment pipeline.

[0022] According to the above-mentioned meltable fluororesin terminal group fluorination treatment system of the present invention, the air pipe is connected to the product output pipe.

[0023] In a second aspect of the present invention, the present invention provides a process for fluorinating the thermally unstable end groups of a meltable fluororesin using the above system, which comprises: N2 gas is transported through the N2 gas pipeline to exhaust the air in the feed tank, reaction tower and cooling tank, and the feed tank is filled with resin raw materials; The feeding tank delivers the meltable fluororesin to the reaction tower through a pipeline, the N2 / F2 mixed gas pipeline continuously delivers the N2 / F2 mixed gas to the reaction tower for reaction, the feeding tank and the cooling tank continuously introduce N2 gas, and when the resin raw material in one feeding tank is used up, the next feeding tank is immediately switched to deliver the resin raw material to the reaction tower; The reaction product obtained in the reaction tower is transported to a cooling tank through a pipeline for degassing. When one cooling tank is full, the next cooling tank is immediately switched.

[0024] Therefore, the fluorination reaction can be carried out continuously by adopting this process, which significantly improves the production efficiency of the fluorination reaction, while avoiding the overflow of fluorine and improving the safety of the working environment.

[0025] According to the process for fluorinating thermally unstable terminal groups of a meltable fluororesin of the present invention, the heating temperature of the upper and lower parts of the reaction tower is higher than the temperature of the middle part of the reaction tower.

[0026] According to the above-mentioned process for fluorinating thermally unstable end groups of meltable fluororesin of the present invention, the flow rate of the N2 gas is smaller than the flow rate of the N2 / F2 mixed gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 This is a schematic diagram of the structure of a meltable fluororesin end group fluorination treatment system according to an embodiment of the present invention; Figure 2 It is a schematic structural diagram of a meltable fluororesin end group fluorination treatment system according to another embodiment of the present invention; Figure 3 It is a schematic structural diagram of a meltable fluororesin end group fluorination treatment system according to another embodiment of the present invention. DETAILED DESCRIPTION

[0029] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0030] In the first aspect of the present invention, the present invention provides a meltable fluorine resin end group fluorination treatment system, referring to Figure 1-Figure 3 The system comprises: A feeding tank 100, wherein the number of the feeding tanks 100 is no less than 2, the top of the feeding tank 100 is connected to a N2 gas pipeline 110, and is provided with a resin raw material inlet 120, and the N2 gas pipeline 110 is provided with a valve 10; A reaction tower 200, wherein the top of the reaction tower 200 is connected to the bottom of the feed tank 100 through a pipeline, and a valve 10 is provided on the pipeline, the top of the reaction tower 200 is connected to a tail gas treatment pipeline 210, and the bottom of the reaction tower 200 is connected to a N2 / F2 mixed gas pipeline 220 and a N2 gas pipeline 110, and a valve 10 is provided on the pipeline; The cooling tank 300 includes at least two cooling tanks 300, the top of each cooling tank 300 is connected to the bottom of the reaction tower 200 via a pipeline, and a valve 10 is provided on the pipeline, and the bottom of each cooling tank 300 is connected to a product output pipeline 310 and a N2 gas pipeline 110, and a valve 10 is provided on the pipeline.

[0031] The terminal fluorination treatment system of the meltable fluororesin according to the present invention comprises a feeding tank 100 , a reaction tower 200 and a cooling tank 300 .

[0032] Among them, there are no less than 2 feeding tanks 100, the top of the feeding tank 100 is connected to the N2 gas pipeline 110, and is provided with a resin raw material inlet 120. The N2 gas pipeline 110 is provided with a valve 10, and the resin raw material is added to the feeding tank 100 from the resin raw material inlet 120. After the feeding tank 100 is filled with the resin raw material, the resin raw material inlet 120 can be closed, and the valve 10 on the N2 gas pipeline 110 can be opened to pass N2 gas into the feeding tank 100 and discharge the air in the feeding tank 100.

[0033] The top of the reaction tower 200 is connected to the bottom of the feed tank 100 through a pipeline, and a valve 10 is provided on the pipeline. When the valve 10 is opened, the resin raw material in the feed tank 100 is transported to the reaction tower 200. The bottom of the reaction tower 200 is connected to the N2 / F2 mixed gas pipeline 220 and the N2 gas pipeline 110. The N2 / F2 mixed gas pipeline 220 countercurrently contacts the N2 / F2 mixed gas and the resin raw material in the reaction tower 200 to perform a fluorination reaction. Before the fluorination reaction, the N2 gas pipeline 110 transports N2 gas into the reaction tower to discharge the air in the reaction tower 200. The top of the reaction tower 200 is connected to the tail gas treatment pipeline 210. The fluorination reaction will produce some waste gas, which can be discharged from the reaction tower 200 through the tail gas treatment pipeline 210 for centralized treatment. It should be noted that when N2 gas is introduced into the system, the exhaust air can also be discharged from the system from the tail gas treatment pipeline 210.

[0034] There are no less than two cooling tanks 300. The top of the cooling tank 300 is connected to the bottom of the reaction tower 200 through a pipeline, and a valve 10 is provided on the pipeline. When the fluorination reaction in the reaction tower 300 is completed, the valve 10 is opened, and the fluorination product is transported to the cooling tank 300 through the pipeline. The bottom end of the cooling tank 300 is connected to the product output pipeline 310 and the N2 gas pipeline 110. On the one hand, the N2 gas pipeline 110 can transport N2 gas to discharge the air in the cooling tank 300 before feeding. On the other hand, because the product obtained by fluorination contains fluorine, the N2 gas pipeline 110 transports N2 gas from the bottom to enter the cooling tank 300, which can remove residual fluorine. The obtained mixed gas of N2 and fluorine can be sent to the reaction tower 200 for further fluorination reaction. Finally, the product obtained is discharged from the system through the product output pipeline 310 and enters subsequent processing.

[0035] In the above-mentioned meltable fluororesin end group fluorination treatment system of the present invention, at least two feeding tanks 100 and a reaction tower 200 are filled with raw material resin. Before starting the reaction, nitrogen is transported to the feeding tank 100, the reaction tower 200 and the cooling tank 300 through the N2 gas pipeline 110 to exhaust the air in the system. The reaction tower starts to be heated. After reaching the reaction temperature, the valve 10 is opened, and the raw material resin is transported from the feeding tank 100 to the reaction tower 200. At the same time, the N2 / F2 mixed gas pipeline 220 continuously introduces the N2 / F2 mixed gas into the reaction tower 200 from the bottom end of the reaction tower 200 to react with the raw material resin for fluorination. When the reaction is completed, the product is transported from the pipeline to the cooling tank 300. When the system is started and debugged stably, the valve 10 of the pipe connecting the feeding tank 100 and the reaction tower 200 and the valve 10 of the pipe connecting the reaction tower 200 and the cooling tank 300 are always in an open state, that is, the feeding tank 100 continuously supplies resin raw materials to the reaction tower 200, the reaction is always going on in the reaction tower 200, and the reaction product is continuously transported to the cooling tank 300, thereby ensuring the continuity of the fluorination reaction. Compared with the existing intermittent reaction, the fluorination reaction efficiency can be significantly improved, the cost can be saved, the labor can be reduced, and it is suitable for industrial production.

[0036] Specifically, because the present invention uses no less than two feeding tanks 100, and both are filled with raw resin, the air has been removed in the early stage. When the raw resin in one feeding tank 100 is added, it can be immediately switched to the next feeding tank 100 to continuously transport the resin raw material to the reaction tower 200, which ensures the continuity of the reaction and improves the efficiency of the fluorination reaction. It is not necessary to open the feeding frequently, and the fluorine overflowed from the feeding tank 100 (the fluorine in the feeding tank 100 comes from the fluorine in the reaction tower 200 that inevitably overflows into the feeding tank 100) is avoided from being discharged to the external environment, ensuring the safety of the working environment. In addition, the feeding tank 100 is connected to the N2 gas pipeline 110, and N2 gas can be introduced to send the overflowed fluorine back to the reaction tower 200 as much as possible, reducing the residual fluorine content in the feeding tank 100, and further ensuring the safety of the operation.

[0037] Similarly, no less than two cooling tanks 300 ensure that the reaction products in the reaction tower 200 can be continuously discharged. If the product of one cooling tank 300 is full, it can be immediately switched to another cooling tank 300, thereby improving the efficiency of the fluorination reaction. And because the product obtained by fluorination contains fluorine (fluorine overflowing from the reaction tower), the N2 gas pipeline 110 delivers N2 gas from the bottom to the cooling tank 300, which can remove the residual fluorine. The obtained N2 and fluorine mixed gas can be sent back to the reaction tower 200 for fluorination reaction, which significantly reduces the risk of fluorine leakage in the cooling tank 300.

[0038] Therefore, the system can ensure the continuous fluorination reaction of the end group of the meltable fluororesin, significantly improve the production efficiency of the fluorination reaction, reduce auxiliary labor, and reduce product costs. It is suitable for large-scale industrial production. The system avoids fluorine overflow, improves the safety of the working environment, and ensures the health of operators.

[0039] According to an embodiment of the present invention, a three-stage heating device 230 is provided on the side wall of the reaction tower 200 to heat the upper, middle and lower parts of the reaction tower 200. By providing the three-stage heating device 230, the temperature of the upper, middle and lower parts of the reaction tower 200 can be adjusted respectively to improve the reaction efficiency.

[0040] According to an embodiment of the present invention, a stirring device 240 is provided in the reaction tower. By providing the stirring device 240, the surface of the pellets is renewed, and the end group stabilization efficiency is improved.

[0041] According to an embodiment of the present invention, the resin raw material inlet 120 is connected to a raw material supply device through a pipeline, and a valve is provided on the pipeline.

[0042] According to an embodiment of the present invention, the tail gas treatment pipeline 210 is connected to the tail gas treatment device 250, and a valve 10 is provided on the pipeline.

[0043] According to an embodiment of the present invention, on the cooling tank 300, the N2 gas pipeline 110 is connected to the product output pipeline 310, and the valve 10 on the product output pipeline 310 is arranged at one end away from the N2 gas pipeline 110 and the cooling tank 300. When N2 gas is transported from the bottom of the cooling tank 300 through the N2 gas pipeline 110 to perform preliminary degassing on the product, the residual fluorine in the pipeline can be removed as much as possible, thereby reducing the residual fluorine.

[0044] According to an embodiment of the present invention, the N2 / F2 mixed gas pipeline 220 is connected to the pipeline between the reaction tower 200 and the cooling tank 300.

[0045] According to an embodiment of the present invention, the bottom end of the cooling tank 300 is connected to the air pipe 320, and the top end of the cooling tank 300 is connected to the tail gas treatment pipe 210. After the cooling tank 300 collects the fluorinated pellets to the specified pellets, the feed valve is closed to stop the collection, and then compressed air is introduced from the air pipe 320 for secondary degassing, and the pellets are cooled to room temperature, that is, after the product in the cooling tank 300 is initially degassed, it is degassed for the second time by compressed air, and the residual fluorine in the pellets is further removed. The waste gas generated by the secondary degassing enters the downstream tail gas treatment device 250 from the tail gas treatment pipe 210, and the high-quality fluorine product is packaged after passing the inspection.

[0046] According to an embodiment of the present invention, the air duct 320 is connected to the product output duct 310 .

[0047] In a second aspect of the present invention, the present invention provides a process for fluorinating the thermally unstable end groups of a meltable fluororesin using the above system, which comprises: N2 gas is transported through the N2 gas pipeline to exhaust the air in the feed tank, reaction tower and cooling tank, and the feed tank is filled with resin raw materials; The feeding tank delivers the meltable fluororesin to the reaction tower through a pipeline, the N2 / F2 mixed gas pipeline continuously delivers the N2 / F2 mixed gas to the reaction tower for reaction, the feeding tank and the cooling tank continuously introduce N2 gas, and when the resin raw material in one feeding tank is used up, the next feeding tank is immediately switched to deliver the resin raw material to the reaction tower; The reaction product obtained in the reaction tower is transported to a cooling tank through a pipeline for degassing. When one cooling tank is full, the next cooling tank is immediately switched.

[0048] Therefore, the fluorination reaction can be carried out continuously by adopting this process, which significantly improves the production efficiency of the fluorination reaction, while avoiding the overflow of fluorine and improving the safety of the working environment.

[0049] According to an embodiment of the present invention, the heating temperature of the upper and lower parts of the reaction tower is higher than the temperature of the middle part of the reaction tower. By making the heating temperature of the upper and lower parts of the reaction tower higher than the temperature of the middle part of the reaction tower, the resin raw material and the fluorine-nitrogen mixed gas continuously entering the reaction tower can be quickly preheated and heated to the fluorination reaction temperature, thereby improving the fluorination reaction efficiency. For example, the temperature of the top of the reaction tower is adjusted to 230°C, the temperature of the middle part is adjusted to 220°C, and the temperature of the bottom is adjusted to 230°C.

[0050] According to an embodiment of the present invention, the flow rate of the N2 gas is less than the flow rate of the N2 / F2 mixed gas. By continuously introducing N2 gas into the feeding tank and the cooling tank, and the flow rate of the N2 gas is less than the flow rate of the N2 / F2 mixed gas, the fluorine-nitrogen mixed gas is prevented from entering the feeding tank and the cooling tank as much as possible. For example, the flow rate of the N2 gas is 0.05 L / min, and the flow rate of the N2 / F2 mixed gas is 1 L / min.

[0051] The present invention is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0052] Example 1 A 100 L (inner diameter 0.15×6 m) fluorination reaction tower was filled with fluororesin PFA pellets (about 120 kg), and the air in the process system was replaced by N2 purge. At the same time, the electric heating was started to heat the reaction tower to the reaction temperature. The top, middle and bottom of the tower were heated to 230°C, 220°C and 230°C, respectively. Then the N2 flow rate was adjusted. The N2 flow rates of the feeding tank and the cooling tank were both 0.05 L / min. The N2 flow rates entered the feeding tank and the cooling tank, respectively, and then were discharged to the downstream through the reaction tower and the cooling tank, respectively.

[0053] At the bottom of the reaction tower, a fluorine-nitrogen mixed gas (fluorine concentration: 22 mol%) is introduced at a flow rate of 1 L / min to contact and react with the fluororesin pellets in the tower, and each flow rate is adjusted to ensure a constant value; the gas discharge valve of the cooling tank is closed, and the discharge valve at the bottom of the reaction tower is opened. The pellets are slowly released to the cooling tank for collection. The residence time of the fluororesin pellets in the reaction tower is controlled to be 12 h. The pellets at the top of the tower are continuously added, and the N2 in the cooling tank flows upstream along the pellet collection pipe to preliminarily degas the fluorinated pellets. When the cooling tank collects a certain amount of pellets, it is switched to another cooling tank to continue collecting. Compressed air is introduced into the previous cooling tank to degas and cool the pellets for the second time, and the first start-up material is obtained for reuse; similarly, the fluorinated pellets quantitatively collected in another cooling tank are degassed and cooled to obtain fluorinated pellets in stable working conditions. Samples are taken to detect the number of end groups in the fluororesin PFA before and after treatment by infrared spectroscopy.

[0054] Example 2 The difference between Example 2 and Example 1 is: Except that the fluororesin PFA pellets were kept in the reaction tower for 24 h, the other process parameters and operation methods remained unchanged.

[0055] Example 3 The difference between Example 3 and Example 1 is: Except that the fluororesin PFA pellets were kept in the reaction tower for 48 h, the other process parameters and operation methods remained unchanged.

[0056] The results of the detection of the number of end groups in the fluororesin PFA prepared in Examples 1-3 are shown in Table 1.

[0057] Table 1

[0058] It can be seen from the data in Table 1 that the unstable end group continuous fluorination treatment system and process used in the present application can effectively stabilize the unstable end groups in the meltable fluororesin PFA, improve the quality of the product, and at the same time greatly improve production efficiency, reduce labor intensity, ensure production safety, and reduce product costs.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A meltable fluororesin end group fluorination treatment system, characterized in that: include: A feeding tank, the number of which is no less than 2, the top of which is connected to a N2 gas pipeline, and a resin raw material inlet is provided at the top of the feeding tank, and a valve is provided on the N2 gas pipeline; A reaction tower, wherein the top of the reaction tower is connected to the bottom of the feeding tank through a pipeline, and a valve is provided on the pipeline, the top of the reaction tower is connected to an exhaust gas treatment pipeline, and the bottom of the reaction tower is connected to an N2 / F2 mixed gas pipeline and an N2 gas pipeline, and a valve is provided on the pipeline; Cooling tank, there are no less than 2 cooling tanks, the top of the cooling tank is connected to the bottom of the reaction tower through a pipeline, and a valve is provided on the pipeline, and the bottom of the cooling tank is connected to the product output pipeline and the N2 gas pipeline, and a valve is provided on the pipeline.

2. The system according to claim 1, characterized in that: The side wall of the reaction tower is provided with three sections of heating devices for heating the upper, middle and lower parts of the reaction tower respectively.

3. The system according to claim 1 or 2, characterized in that: A stirring device is arranged in the reaction tower.

4. The system according to claim 1 or 2, characterized in that: The resin raw material inlet is connected to the raw material supply device through a pipeline, and a valve is provided on the pipeline; And / or, the tail gas treatment pipeline is connected to the tail gas treatment device, and a valve is provided on the pipeline.

5. The system according to claim 1 or 2, characterized in that: On the cooling tank, the N2 gas pipeline is connected to the product output pipeline, and the valve on the product output pipeline is arranged at one end away from the N2 gas pipeline and the cooling tank.

6. The system according to claim 1 or 2, characterized in that: The N2 / F2 mixed gas pipeline is connected to the pipeline between the reaction tower and the cooling tank.

7. The system according to claim 1 or 2, characterized in that: The bottom end of the cooling tank is connected to an air pipeline, and the top end of the cooling tank is connected to an exhaust gas treatment pipeline; Preferably, the air duct is connected to the product output duct.

8. A process for fluorinating thermally unstable end groups of meltable fluororesins using the system described in any one of claims 1 to 7, characterized in that: include: N2 gas is delivered through an N2 gas pipeline to exhaust the air in the feed tank, the reaction tower and the cooling tank, and the feed tank is filled with resin raw materials; The feeding tank delivers the meltable fluororesin to the reaction tower through a pipeline, and the N2 / F2 mixed gas pipeline continuously delivers the N2 / F2 mixed gas to the reaction tower for reaction. At the same time, the feeding tank and the cooling tank continuously introduce N2 gas. When the resin raw material in one feeding tank is used up, the next feeding tank is immediately switched to deliver the resin raw material to the reaction tower; The reaction product obtained in the reaction tower is transported to a cooling tank through a pipeline for degassing. When one cooling tank is full, the next cooling tank is immediately switched.

9. The process according to claim 8, characterized in that: The heating temperatures of the upper and lower parts of the reaction tower are higher than the temperature of the middle part of the reaction tower.

10. The process according to claim 8 or 9, characterized in that: The flow rate of the N2 gas is smaller than the flow rate of the N2 / F2 mixed gas.

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