High-performance PFA resin and preparation method thereof

Abstract

The invention provides a high-performance PFA resin and a preparation method thereof. The preparation method of the high-performance PFA resin comprises the following steps: S1, mixing PAVE, TFE, a composite dispersant and water, and carrying out emulsion polymerization reaction in the presence of an initiator and a chain transfer agent to obtain a reaction emulsion; s2, performing demulsification, filtering, washing and drying on the reaction emulsion, and then performing heat treatment to obtain the high-performance PFA resin. The prepared high-performance PFA resin is more uniform and stable in molecular chain structure and more concentrated in molecular weight distribution, the product melting point fluctuation range is within + / -3 DEG C, the melt flow rate deviation is within + / -0.5 g / 10 min, the metal ion content is lower than 1 ppb, the number of unstable end groups is smaller than 10 / 10 < 6 > C atoms, the product performance consistency is good, the high-performance PFA resin can stably work in the complex and severe environment, and the service life of the high-performance PFA resin is prolonged. The service life of the product is prolonged, the production cycle of the product is shortened, and the production cost of the product is reduced.

Description

Technical Field

[0001] This invention relates to the field of fluoropolymer synthesis technology, and in particular to a high-performance PFA resin and its preparation method. Background Technology

[0002] Perfluoroalkoxy resins (PFAs), as high-performance fluoropolymers, possess excellent comprehensive properties and are widely used in numerous fields. In semiconductor manufacturing, due to their high purity, low metal ion content, and excellent chemical stability and electrical insulation, they are extensively used to manufacture critical components in semiconductor equipment, such as pipes, valves, and wafer carriers. This effectively prevents impurity contamination, ensuring high precision and high yield in the semiconductor manufacturing process. In the chemical industry, PFA's excellent corrosion resistance makes it suitable for manufacturing reactor linings, pipes, and pump bodies. It can withstand the erosion of various highly corrosive chemical media, ensuring the safe and stable operation of chemical production. In the medical field, PFA's biocompatibility and chemical stability make it an ideal material for medical devices, such as those used in the manufacture of medical catheters and dialysis equipment components. It does not cause adverse reactions in the human body and ensures stable performance of the equipment during use.

[0003] However, current PFA preparation technologies still have several shortcomings: 1) It is difficult to precisely control the molecular chain structure and monomer copolymerization ratio during polymerization, resulting in large fluctuations in key properties such as melting point and melt flow rate, which in turn affects the processing and performance of the product; 2) Existing preparation processes are prone to uneven monomer polymerization, resulting in PFA products with a wide distribution of molecular weight and molecular chain length, and poor mechanical properties (such as strength and toughness) and processing stability; 3) Products often contain a large number of impurities, metal ions, and unstable end groups. These impurities and unstable end groups decompose during high-temperature processing to produce small molecule compounds, which not only corrode processing equipment but also affect the color, mechanical properties, and electrical properties of the product, reducing its long-term temperature resistance and chemical stability, thus limiting the application of PFA in high-end fields; 4) Some preparation methods require the use of large amounts of organic solvents, which are costly and environmentally unfriendly, hindering large-scale industrial production.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a high-performance PFA resin and its preparation method. This high-performance PFA resin product has good performance consistency, high purity, and can work stably in complex and harsh environments, thus extending the product's service life.

[0006] This invention provides a method for preparing high-performance PFA resin, comprising the following steps:

[0007] S1: Perfluoroalkyl vinyl ether (PAVE), tetrafluoroethylene (TFE), composite dispersant, and water are mixed and emulsion polymerized in the presence of an initiator and a chain transfer agent to obtain a reactive emulsion.

[0008] S2: The reaction emulsion is broken down, filtered, washed, dried and then heat-treated to obtain high-performance PFA resin.

[0009] In this invention, the purity of tetrafluoroethylene (TFE) can be ≥99.95% to reduce the impact of impurities on the polymerization reaction; a suitable type of PAVE, such as perfluoropropyl vinyl ether (PPVE), with a purity of ≥99.9%, can be selected according to the performance of the target product. Furthermore, deionized water can be used.

[0010] In this invention, the molar ratio between TFE, PAVE, composite dispersant, initiator and chain transfer agent can be (150-180):(15-18):(1-2):(3-4):(0.5-0.6); in particular, the molar ratio of TFE to PAVE can be (8-12):1, for example 10:1.

[0011] In this invention, the composite dispersant is composed of ammonium perfluoro-2,5-dimethyl-3,6-dioxane (CAS: 510774-77-3) and ammonium perfluoro-2,5-dimethyl-3,6-dioxane (CAS: 510774-79-5). The molar ratio of ammonium perfluoro-2,5-dimethyl-3,6-dioxane to ammonium perfluoro-2,5-dimethyl-3,6-dioxane can be (2-4):1, for example, 3:1. The above-mentioned specific composite dispersant can ensure the stability of the emulsion polymerization system and reduce the influence of the dispersant on the product performance. It is beneficial to accurately control the molecular chain structure of PFA resin and the copolymerization ratio of monomers, thereby ensuring the stability of product performance.

[0012] In this invention, the initiator can be a redox initiation system; specifically, the initiator includes the oxidant potassium persulfate (K2S2O8) and the reducing agent sodium bisulfite (NaHSO3), and the molar ratio of potassium persulfate to sodium bisulfite can be (1-1.5):1. The above-mentioned initiator is beneficial to ensuring the smooth initiation and stable progress of the polymerization reaction.

[0013] In this invention, hydrogen (H2) can be used as the chain transfer agent, and its dosage can be precisely controlled according to the target molecular weight. Studies have shown that adding a small amount of hydrogen in the emulsion polymerization reaction is beneficial to effectively reduce the average molecular weight of the generated polymer, thereby avoiding problems such as product processing difficulties caused by excessively large molecular weight. In particular, in the emulsion polymerization reaction system of this invention, by precisely controlling the amount of hydrogen added, the molecular weight can be reduced while reducing the difference in polymer molecular chain length, making the molecular weight distribution of the generated polymer more concentrated, thereby improving the mechanical properties (such as strength, toughness, etc.) and processing stability of the product.

[0014] In this invention, the temperature of the emulsion polymerization reaction can be 40-45℃, the pressure can be 2-2.5MPa, and the time can be 7-8h; furthermore, the emulsion polymerization reaction is carried out under conditions where the oxygen content is less than 5ppm, so as to avoid the interference of oxygen on the polymerization reaction.

[0015] More specifically, step S1 includes:

[0016] Deionized water is added to the reactor, and nitrogen gas is introduced to replace the air in the reactor so that the oxygen content in the reactor is lower than 5 ppm. The temperature of the reactor is raised to 40-45℃, and a composite dispersant is added while stirring at a speed of 250-350 r / min. Then, a portion of PAVE, a portion of TFE, and a portion of initiator are added sequentially. Hydrogen gas is introduced as a chain transfer agent, and the pressure in the reactor is controlled at 2-2.5 MPa to start the emulsion polymerization reaction. Subsequently, the remaining PAVE and TFE are added to the reactor at a uniform rate over 5-7 hours, while the initiator solution made from the remaining initiator is added dropwise at a uniform rate. The mixture is kept at this temperature for another 0.5-1.5 hours to obtain the reaction emulsion. The PAVE added in the first step accounts for 5-15% of the total amount, the TFE added in the first step accounts for 5-15% of the total amount, and the initiator added in the first step accounts for 40-60% of the total amount.

[0017] Studies have shown that the above-mentioned specific processes are beneficial for precisely controlling the molecular chain structure and copolymerization ratio of PFA products, making the molecular chain structure more uniform and stable, which helps to ensure the stability of key properties such as melting point and melt flow rate, and improves the processing and performance of the products.

[0018] In step S2, demulsification may include: adding a 10-20% hydrochloric acid solution to the reaction emulsion to adjust the pH to 2-3; acidic conditions help deactivate the dispersant in the emulsion, thereby achieving polymer particle precipitation. After filtration, the emulsion can be washed repeatedly with deionized water 3-5 times to remove residual dispersant, initiator, and other impurities. The drying temperature can be 80-90℃, and the time can be 8-10 hours. The heat treatment temperature can be 280-300℃, and the time can be 2-3 hours; the above heat treatment can further remove unstable end groups (such as -COOH, -OH, etc.) in the PFA resin, thereby improving the thermal and chemical stability of the product. The heat-treated PFA resin can be further processed as needed, such as pulverizing and granulation.

[0019] The present invention also provides a high-performance PFA resin, which is prepared according to the above preparation method.

[0020] The implementation of this invention has at least the following advantages:

[0021] 1) Controllable molecular chain structure: The preparation method of this invention can effectively control the copolymerization ratio and sequence distribution of TFE and PAVE in the PFA molecular chain, making the molecular chain structure more uniform and stable. While effectively reducing the average molecular weight of the polymer, it also reduces the difference in polymer molecular chain length, making the molecular weight distribution more concentrated and narrowing. According to the test, the PFA product prepared by the method of this invention has a melting point fluctuation range controlled within ±3℃ and a melt flow rate deviation within ±0.5g / 10min. The product has good performance consistency and can meet the strict requirements of different application fields for PFA performance.

[0022] 2) High product purity: The preparation method of this invention can effectively reduce the content of impurities and unstable end groups in the product. The metal ion content of the prepared PFA product is less than 1 ppb, and the number of unstable end groups is less than 10 / 10. 6 Carbon atoms result in a product with a pure white color and excellent mechanical and electrical properties, making it particularly suitable for applications in fields such as semiconductors and medical devices where material purity is extremely important.

[0023] 3) Stable performance: The preparation method of the present invention can significantly improve the thermal and chemical stability of PFA products; the mechanical properties of PFA products are maintained at more than 90% after long-term use at a high temperature of 260℃, and the mass change rate is less than 1% after immersion in a highly corrosive chemical medium for 100 hours. It can work stably in complex and harsh environments, thus extending the service life of the products.

[0024] 4) Reduced cost and environmentally friendly: The preparation method of the present invention reduces the use of organic solvents, thereby reducing production costs and environmental pollution; at the same time, the optimized emulsion polymerization process and post-processing flow improve production efficiency and shorten the production cycle, which is conducive to large-scale industrial production; compared with the traditional preparation method, the production cost of the preparation method of the present invention is reduced by 15-20%, and the production efficiency is increased by 20-30%. Detailed Implementation

[0025] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] 1. Emulsion polymerization reaction

[0030] 600L of deionized water was added to a 1200L stainless steel polymerization reactor, and nitrogen gas was purged five times to purge the air, reducing the oxygen content inside the reactor to below 3ppm. The temperature was raised to 42℃, and stirring was started at 300 rpm. A composite dispersant consisting of 1.2 mol of perfluoro-2,5-dimethyl-3,6-dioxane ammonium salt and 0.4 mol of perfluoro-2,5-dimethyl-3,6-dioxane ammonium salt was added and stirred until homogeneous. Subsequently, 1.5 mol of perfluoropropyl vinyl ether (PPVE, purity ≥99.9%), 15 mol of tetrafluoroethylene (TFE, purity ≥99.95%), 0.9 mol of potassium persulfate (K2S2O8), and 0.75 mol of sodium bisulfite (NaHSO3) were added, and 0.5 mol of hydrogen gas was introduced as a chain transfer agent. The pressure inside the reactor was controlled to reach 2.1 MPa to initiate the emulsion polymerization reaction.

[0031] Subsequently, the monomer feed pump was started, and the remaining mixture of 13.5 mol PPVE and 135 mol TFE was added to the reactor at a uniform rate. At the same time, the remaining 0.9 mol potassium persulfate and 0.75 mol sodium bisulfite were dissolved in 200 L of deionized water and added dropwise to the reactor at a uniform rate. The pressure fluctuation inside the reactor was controlled to be ±0.01 MPa and the temperature fluctuation to be ±2℃. The remaining materials were added after 6 hours, and the mixture was kept at this temperature for another 1 hour to obtain the reaction emulsion.

[0032] 2. Post-processing

[0033] The reacted emulsion was transferred to a demulsifier, and a suitable amount of 10% hydrochloric acid solution was added to adjust the pH to 2.5, thus demulsifying the emulsion. The precipitate was filtered and washed four times with deionized water. The filter cake was placed in a vacuum drying oven and dried at 85°C for 9 hours. The preliminarily dried PFA resin was then subjected to high-temperature heat treatment at 290°C for 2.5 hours, followed by pulverization and granulation to obtain the PFA product.

[0034] The PFA product prepared in this embodiment was tested, and the results are as follows:

[0035] - Molecular weight (gel permeation chromatography): 820,000;

[0036] - Melting point (differential scanning calorimetry): 305℃;

[0037] - Melt flow rate (297℃, 5kg load): 15g / 10min;

[0038] -Metal ion content (inductively coupled plasma mass spectrometry): less than 0.5 ppb;

[0039] - Number of unstable end groups (Fourier transform infrared spectroscopy): 7.2 / 10 6 C atom;

[0040] - High temperature stability: After long-term use at 260℃, the mechanical properties (in terms of tensile strength) are retained at 92%;

[0041] - Corrosion resistance: After immersion in a highly corrosive chemical medium (concentrated hydrochloric acid, mass content 37%) for 100 hours, the mass change rate is 0.8%.

[0042] In addition, 10 batches of PFA products were prepared using the above method. The melting point fluctuation range of the 10 batches of PFA products was within ±3℃, and the deviation of the melt flow rate was within ±0.5g / 10min, indicating good product performance consistency.

[0043] Example 2

[0044] 1. Emulsion polymerization reaction

[0045] 700L of deionized water was added to a 1200L stainless steel polymerization reactor. Nitrogen gas was purged four times to replace the air, reducing the oxygen content inside the reactor to below 4ppm. The temperature was raised to 43℃, and stirring was started at 320 rpm. A composite dispersant consisting of 1.5 mol of perfluoro-2,5-dimethyl-3,6-dioxane ammonium salt and 0.5 mol of perfluoro-2,5-dimethyl-3,6-dioxane ammonium salt was added and stirred until homogeneous. Subsequently, 1.8 mol of perfluoropropyl vinyl ether (PPVE, purity ≥99.9%), 18 mol of tetrafluoroethylene (TFE, purity ≥99.95%), 0.84 mol of potassium persulfate (K₂S₂O₈), and 0.7 mol of sodium bisulfite (NaHSO₃) were added, and 0.6 mol of hydrogen gas was introduced as a chain transfer agent. The pressure inside the reactor was controlled to reach 2.2 MPa to initiate the emulsion polymerization reaction.

[0046] Subsequently, the monomer feed pump was started, and the remaining mixture of 16.2 mol PPVE and 162 mol TFE was added to the reactor at a uniform rate. At the same time, the remaining 1.26 mol potassium persulfate and 1.05 mol sodium bisulfite were dissolved in 300 L of deionized water and added dropwise to the reactor at a uniform rate. The pressure fluctuation inside the reactor was controlled to be ±0.01 MPa and the temperature fluctuation to be ±2 °C. The remaining materials were added after 6 hours, and the mixture was kept at this temperature for another 1 hour to obtain the reaction emulsion.

[0047] 2. Post-processing

[0048] The reacted emulsion was transferred to a demulsifier, and an appropriate amount of 15% hydrochloric acid solution was added to adjust the pH to 2.5, thus demulsifying the emulsion. The precipitate was filtered and washed four times with deionized water. The filter cake was placed in a vacuum drying oven and dried at 85°C for 9 hours. The preliminarily dried PFA resin was then subjected to high-temperature heat treatment at 295°C for 2.8 hours, followed by pulverization and granulation to obtain the PFA product.

[0049] The method described in Example 1 was used for testing. The results showed that the PFA prepared in this example had a melting point of 307℃, a melt flow rate of 13 g / 10 min, a metal ion content of less than 0.6 ppb, and fewer than 7 unstable end groups per 10 min. 6 Carbon atoms retain 93% of their mechanical properties after long-term use at 260℃, and their mass change rate is only 0.7% after immersion in a highly corrosive chemical medium for 100 hours.

[0050] Compare with Example 1

[0051] This comparative example is identical to Example 1, except that 1.6 mol of a single perfluoro-2,5-dimethyl-3,6-dioxane ammonium salt is used instead of the composite dispersant composed of 1.2 mol of perfluoro-2,5-dimethyl-3,6-dioxane ammonium salt and 0.4 mol of perfluoro-2,5-dimethyl-3,6-dioxane ammonium salt in Example 1.

[0052] The method of Example 1 was used for testing. The results showed that the melting point fluctuation range of the 10 batches of PFA products prepared in this control example was as high as ±8℃, the melt flow rate deviation was as high as ±2g / 10min, and the product performance consistency was poor.

[0053] Compare with Example 2

[0054] This comparative example is identical to Example 1, except that 1.6 mol of a single perfluoro-2,5-dimethyl-3,6-dioxanoic acid ammonium salt is used instead of the composite dispersant composed of 1.2 mol of perfluoro-2,5-dimethyl-3,6-dioxanoic acid ammonium salt and 0.4 mol of perfluoro-2,5-dimethyl-3,6-dioxanoic acid ammonium salt in Example 1.

[0055] The method of Example 1 was used for testing. The results showed that the melting point fluctuation range of the 10 batches of PFA products prepared in this control example was ±10℃, the melt flow rate deviation was ±3g / 10min, and the product performance consistency was poor.

[0056] Compare with Example 3

[0057] This comparative example is the same as Example 1, except that 0.5 mol of hydrogen gas is not introduced as a chain transfer agent in the emulsion polymerization reaction.

[0058] The method of Example 1 was used for testing. The results showed that the melting point fluctuation range of the 10 batches of PFA products prepared in this control example was ±15℃, the melt flow rate deviation was ±5g / 10min, and the product performance consistency was poor.

[0059] Compare with Example 4

[0060] This comparative example is the same as Example 1 except that 0.5 mol of propane is introduced as a chain transfer agent.

[0061] The method of Example 1 was used for testing. The results showed that the melting point fluctuation range of the 10 batches of PFA products prepared in this control example was ±7℃, the melt flow rate deviation was ±2g / 10min, and the product performance consistency was poor.

[0062] Compare with Example 5

[0063] This comparative example is the same as Example 1 except that the high-temperature heat treatment is not performed in the post-processing steps.

[0064] The method described in Example 1 was used for detection. The results showed that the metal ion content of the PFA product prepared in this control example was 3 ppb, and the number of unstable end groups was 25 / 10. 6 Carbon atoms retain 75% of their mechanical properties after long-term use at 260℃, and their mass change rate is 5% after immersion in a highly corrosive chemical medium for 100 hours.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing a high performance PFA resin, characterized by, The method comprises the following steps: S1: mixing PAVE, TFE, composite dispersant and water, and performing emulsion polymerization in the presence of initiator and chain transfer agent to obtain a reaction emulsion; S2: performing thermal treatment on the reaction emulsion after demulsification, filtration, washing and drying to obtain high-performance PFA resin.

2. The production method according to claim 1, characterized by, The molar ratio of TFE, PAVE, composite dispersant, initiator and chain transfer agent is (150-180):(15-18):(1-2):(3-4):(0.5-0.6).

3. The preparation method according to claim 1, characterized in that, The composite dispersant is composed of perfluoro-2,5-dimethyl-3,6-dioxahexanoic acid ammonium salt and perfluoro-2,5-dimethyl-3,6-dioxaoctanoic acid ammonium salt, and the molar ratio of perfluoro-2,5-dimethyl-3,6-dioxahexanoic acid ammonium salt to perfluoro-2,5-dimethyl-3,6-dioxaoctanoic acid ammonium salt is (2-4):

1.

4. The production method according to claim 1, characterized by, The initiator comprises potassium persulfate and sodium bisulfite, and the molar ratio of potassium persulfate to sodium bisulfite is (1-1.5):

1.

5. The preparation method according to claim 1, characterized in that, Hydrogen is used as the chain transfer agent.

6. The method of claim 1, wherein, The temperature of the emulsion polymerization is 40-45℃, the pressure is 2-2.5MPa, and the time is 7-8h.

7. The preparation method according to claim 1, characterized in that, The demulsification comprises: Hydrochloric acid solution with a mass concentration of 10-20% is added to the reaction emulsion to adjust the pH value to 2-3.

8. The method of claim 1, wherein, The temperature of the drying is 80-90℃, and the time is 8-10h.

9. The method of claim 1, wherein, The temperature of the thermal treatment is 280-300℃, and the time is 2-3h.

10. A high performance PFA resin characterized in that, The method is prepared according to any one of claims 1-9.