Low-precipitate fluorine-containing resin

Abstract

The invention discloses a low-precipitate fluorine-containing resin, and belongs to the technical field of fluorine-containing polymers, the low-precipitate fluorine-containing resin is obtained from common fluorine-containing resin through a purification process, and the method comprises the following steps: S1, carrying out a fluorination treatment process on the fluorine-containing resin; s2, carrying out an acid treatment process on the fluorinated fluorine-containing resin; s3, the fluorine-containing resin subjected to acid treatment is subjected to a hot air treatment process; and S4, the fluorine-containing resin subjected to hot air treatment is subjected to a cooling treatment process. According to the low-precipitate fluorine-containing resin, the single metal precipitation amount is smaller than or equal to 1 ppb, the F-precipitation amount is smaller than or equal to 10 ppb, the Br-precipitation amount is smaller than or equal to 1 ppb, the SO4 < 2-> precipitation amount is smaller than or equal to 1 ppb, the NO3-precipitation amount is smaller than or equal to 1 ppb, the NO2-precipitation amount is smaller than or equal to 1 ppb, the PO4 < 3-> precipitation amount is smaller than or equal to 1 ppb, the number of unstable end groups is smaller than or equal to 5 per million carbon, and the TOC precipitation amount is smaller than or equal to 100 ppb.

Description

Technical Field

[0001] This invention belongs to the field of fluoropolymer technology, specifically relating to a low-exudate fluoropolymer resin. Background Technology

[0002] In the wet processing steps of semiconductor manufacturing, semiconductor wafers undergo various treatments, with temperatures approaching 200°C using solutions such as hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, ammonia, and hydrogen peroxide. Under such harsh conditions, corrosive metallic materials cannot be used; therefore, fluorinated resins with excellent heat and chemical resistance are preferred. Fluorinated resins possess the strongest chemical resistance and highest heat resistance, and can also be processed into complex shapes using common melt molding methods. Therefore, they are highly popular in semiconductor wafer manufacturing for use as lining materials for semiconductor wafer supports, chemical solution tubes, connectors, bottles, and tanks.

[0003] The main difference between fluoropolymers used in the semiconductor field and those commonly found on the market lies in the degree of precipitation of metal cations and anions, while their processing principles and other properties are essentially the same. Fluoropolymers are mainly obtained through emulsion polymerization or suspension polymerization. Freshly polymerized fluoropolymers contain unstable end groups, free fluorine, organic solvents, and volatile substances, which can lead to problems such as bubbling and discoloration during processing. The presence of free fluorine can corrode equipment during processing and increase the metal content in the finished product.

[0004] As semiconductor devices become more sophisticated, denser, and more integrated, and with an increase in the number of wiring layers, manufacturing processes become more complex. Consequently, the defect size in semiconductor devices is becoming smaller, and the metal content and total organic matter (TOC) deposition in raw materials have an increasingly significant impact on the yield and quality of semiconductor products.

[0005] Patent CN116367981A proposes using a fluorinated solvent to clean fluoropolymer particles to reduce low-molecular-weight substances within them. This method requires the fluorinated solvent itself to be of high purity, and the processing is complex. The patent describes its ability to remove large amounts of particulate matter and low-molecular-weight substances, but it does not mention its effectiveness in removing metal ions.

[0006] In patent US3085083A, DuPont describes a method for treating fluoropolymers containing unstable end groups with an alkali metal or alkaline earth metal base or basic salt in the presence of water vapor at 200–350°C. This method can convert -COF and -COOH into relatively stable -CF2H. The disadvantage of this method is that the alkali metal remains in the polymer, affecting the thermal stability of the fluoropolymer.

[0007] In patent CN119899399A, ultrapure water, ultrapure inorganic acid, and organic solvents are used to soak and wash fluoroplastic particles. While this can reduce surface metal to a low level, it cannot remove internal metals, anions, and TOC, thus failing to achieve truly low metal content. In the patent embodiments, a particle crushing process is added to remove internal metals. Although this removes the internal metals, it cannot prevent the introduction of metals during the re-granulation of the crushed powder and contact with high-temperature metals in extruders, making the operation complex. Furthermore, the persistent presence of anions and TOCs leads to corrosion of equipment during secondary high-temperature processing, failing to meet semiconductor requirements.

[0008] In patent CN119285829A, PVDF is first dissolved in a solvent to form a solution, and then the solution is acid-washed. This method can effectively remove metal residues inside and outside the PVDF product. However, this method is only applicable to fluoroplastics that can be dissolved in organic solvents. It cannot be used to process commonly used semiconductor fluororesins such as PFA, PTFE, and FEP.

[0009] In patent CN119591753A, the resin is also pulverized in order to remove the internal metal. However, the pulverized particles are still granular. In the state where the molecular chains are not open, the removal effect of internal metal ions is poor, and can only reach the ppb level. In addition, it requires fluorinated solvents and freezing treatment, which is complicated and difficult to industrialize.

[0010] In patent CN117736355A, metal treatment is performed in the emulsion and wet powder stages, which can only reduce metal precipitation to the ppb level. However, anions and TOC are still present. Furthermore, the dry powder will corrode the screw during high-temperature processing in the extruder, leading to an increase in the metal content in the particles. This does not solve the fundamental problem.

[0011] The above technologies only target the purification of metal ions, but they are complex to operate and difficult to industrialize. Furthermore, semiconductor fluoropolymers not only have high requirements for metal ions, but also for anions and TOC. Therefore, a production process that is simple to operate and can remove metal cations, anions and TOC from fluoropolymers at the same time is needed. Summary of the Invention

[0012] To address the shortcomings of existing technologies, this invention provides a low-exudate fluorinated resin that can simultaneously remove metal cations, anions, and TOC from fluorinated polymers.

[0013] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A low-leaching fluorinated resin with a single metal leaching amount ≤1 ppb, F - Precipitation amount ≤10ppb, Br - Precipitation amount ≤1ppb, SO42- Precipitation amount ≤1ppb, NO3 - Precipitation amount ≤1ppb, NO2 - ≤1 ppb of PO4 3- Precipitation amount ≤1ppb, unstable end groups ≤5 per million carbons, TOC precipitation amount ≤100ppb; The precipitation test method is to take 100g of the fluoropolymer particles to be tested, add 100g of ultrapure water, soak them at 85℃ for 168h, and test the metal, anion content and TOC in the extract. The purification process for obtaining low-precipitate fluorinated resins involves the following steps: S1 fluorinated resin undergoes a fluorination process. The fluorinated resin after S2 fluorination treatment undergoes an acid treatment process. The fluorinated resin after S3 acid treatment is then subjected to a hot air treatment process. The fluorinated resin after S4 hot air treatment undergoes a cooling process.

[0014] Preferably, in step S1, the fluorinated resin is heated to 150-220°C in the reactor, and an F2 / N2 mixed gas is introduced to maintain the temperature and perform fluorination treatment for 12-36 hours.

[0015] Preferably, in step S2, after venting the F2 / N2 mixed gas from the reactor, an aqueous solution of acid is added for circulating acid washing.

[0016] Preferably, the temperature of the acid treatment process is 5-85℃, and the temperature of the hot air treatment process is 80-220℃.

[0017] Preferably, the acid treatment process takes 4-36 hours, and the hot air treatment process takes 20-30 hours.

[0018] Preferably, the acid used in the acid treatment process is one or a mixture of at least two of HCl, HNO3, and HF, and the acid concentration is 1-30 wt%.

[0019] Preferably, the fluorinated resin is obtained by homopolymerization or copolymerization of tetrafluoroethylene, hexafluoropropylene and perfluoroalkyl vinyl ether, with a melting point of 250-327°C, and the perfluoroalkyl vinyl ether is one or more of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether or perfluoropropyl vinyl ether.

[0020] Preferably, the metals include Fe, Cr, Ni, K, Na, Ca, Al, Zn, Cu, Mg, and Ti.

[0021] This invention involves a fluorination process, an acid treatment process, a hot air treatment process, and a cooling treatment process to simultaneously remove metal cations, anions, and TOC from ordinary fluorinated resins, ultimately yielding a fluorinated resin with low precipitates.

[0022] Compared with the prior art, the present invention has the following beneficial effects: Without fluorination treatment, fluoride ions, total organic carbon (TOC), and unstable end groups in fluorinated resins cannot be reduced to very low levels. This is because unstable end groups continue to decompose, leading to the continuous release of fluoride ions and the generation of a large number of short-chain low-molecular-weight molecules, resulting in TOC contamination. Therefore, unstable end groups require effective treatment using an F2 / N2 mixed gas at high temperatures. This is a prerequisite for ensuring the subsequent processing of fluorinated resins and for their use in the semiconductor field.

[0023] Fluoropolymers that have not undergone acid treatment exhibit metal leaching levels far exceeding normal limits. Acid washing primarily removes surface contaminants. During fluoropolymer production, particles come into close contact with metal materials, potentially leaving a large number of metal particles on the fluoropolymer surface. These particles differ from the metal elements within the resin; they are abundant and mostly granular, requiring acid dissolution for removal. In contrast, the metals within the resin are mostly introduced during the polymerization stage, existing in an ionic state attached to the polymer molecular chains, and can be carried away by high-temperature, pure gas purging. Anions and TOCs, being mostly ionic and lightweight, can also be carried away by high-temperature, pure gas purging. Therefore, a combination of acid treatment and hot air treatment is necessary to ensure low leaching levels in fluoropolymers.

[0024] Furthermore, in the method of obtaining low-precipitate fluorinated resin by purifying fluorinated resin according to the present invention, the fluorination process, acid treatment process, hot air treatment process and cooling process are carried out continuously in the same reaction vessel, which is relatively simple to operate and can be continuously industrialized.

[0025] The specific technical solution of the present invention and its beneficial effects will be described in detail in the following specific embodiments in conjunction with the accompanying drawings. Attached Figure Description

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments: Figure 1 This is a flowchart of a method for preparing a low-exudate fluorinated resin according to the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] This invention provides a method for preparing a low-precipitation fluorinated resin, which yields a low-precipitation fluorinated resin with a single metal precipitation amount ≤1 ppb and F. - Precipitation amount ≤10ppb, Br - Precipitation amount ≤1ppb, SO4 2- Precipitation amount ≤1ppb, NO3 - Precipitation amount ≤1ppb, NO2 - ≤1 ppb of PO4 3- The amount of precipitation is ≤1 ppb, the number of unstable end groups is ≤5 per million carbons, and the amount of TOC precipitation is ≤100 ppb.

[0029] The low-exudate fluorinated resins prepared in the embodiments of the present invention are mainly fluorinated resin products obtained by homopolymerization or copolymerization of tetrafluoroethylene, hexafluoropropylene, and perfluoroalkyl vinyl ethers, with melting points between 250-327°C. The perfluoroalkyl vinyl ether is one or more of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, or perfluoropropyl vinyl ether, preferably perfluoropropyl vinyl ether.

[0030] Ordinary fluorinated resins are purified to obtain low-precipitate fluorinated resins.

[0031] like Figure 1 As shown, the processing steps are as follows: S1 fluorinated resin undergoes a fluorination process. The fluorinated resin after S2 fluorination treatment undergoes an acid treatment process. The fluorinated resin after S3 acid treatment is then subjected to a hot air treatment process. The fluorinated resin after S4 hot air treatment undergoes a cooling process.

[0032] In step S1, the fluorinated resin is heated to 150-220℃ in the reactor, and an F2 / N2 mixed gas is introduced while maintaining the temperature. Fluorination treatment lasts for 12-36 hours. In step S2, after venting the F2 / N2 mixed gas from the reactor, an aqueous acid solution is added for circulating acid washing. In step S3, after venting the acid solution from the reactor, a high-temperature pure gas at 80-200℃ is continuously introduced for purging for 12-36 hours. It is understood that the temperature of the high-temperature pure gas is determined by the type of fluorinated resin, maintaining the fluorinated resin particles in a softened but non-melting state with open molecular chains. The acid treatment process lasts for 4-36 hours. The acid used in the acid treatment process is one or a mixture of at least two of HCl, HNO3, and HF, with an acid concentration of 1-30 wt%.

[0033] The purification process in this embodiment of the invention uses fluorinated resin A, as shown in Table 1.

[0034] Table 1: ; Example 1: Fluorine-containing resin A was processed using the following steps: a. Place the fluorinated resin A into a fluorinated tank, heat it to 200°C, introduce F2 / N2 mixed gas, and maintain the temperature for fluorination treatment for 24 hours; b. Exhaust the F2 / N2 mixed gas, add 10% HF aqueous solution for acid washing for 12 hours, exhaust the HF aqueous solution; then wash with 10% HCl aqueous solution for 12 hours; c. Purge the 10% HCl aqueous solution and introduce high-temperature pure gas at 200℃ for 24 hours continuously. d. Stop the high-temperature pure gas purging and introduce room-temperature pure gas to cool the fluorinated resin; e. After the particles are cooled to room temperature, fluorinated resin A1 is obtained.

[0035] Example 2: Compared with Example 1, the temperature of the high-temperature pure gas in step c is 100°C, and the other steps are the same, to obtain fluorinated resin A2.

[0036] The low-exudate fluorinated resins A1 and A2 obtained in Examples 1 and 2 are shown in Table 2.

[0037] Table 2: ; The levels of metals, anions, and TOC in fluorinated resin A2 are significantly lower than those in fluorinated resin A, but still much higher than those in fluorinated resin A1. This is mainly because the metal and anion contamination in fluorinated resins exists on both the surface and internal parts. Acid washing can remove a large amount of surface contamination, but due to the strong acid and alkali resistance of fluorinated resins, not all internal metals can be dissolved and removed by the acid solution. However, at 200℃, the resin softens, and the molecular chains are in an open state. At this temperature, the high-temperature gas will carry out the metal ions, anions, and TOC from inside the resin. When the temperature is only 100℃, the resin molecular chains are tightly packed, and the internal metal ions, anions, and TOC cannot be carried out, resulting in unacceptable data.

[0038] In some embodiments, a fluorinated resin with a melting point of 262°C can also be used for the process of this invention. Experiments have shown that the temperature cannot exceed 180°C, otherwise the resin will stick together, which is detrimental to production. When the temperature is controlled between 150-180°C, a single metal precipitation amount ≤1 ppb can be obtained. - Precipitation amount ≤10ppb, Br - Precipitation amount ≤1ppb, SO4 2- Precipitation amount ≤1ppb, NO3 - Precipitation amount ≤1ppb, NO2 - ≤1 ppb of PO4 3- The low-exudate fluoropolymer with ≤1ppb precipitation, ≤5 unstable end groups per million carbons, and ≤100ppb TOC precipitation indicates that temperature is the key to controlling whether the polymer molecular chains can be in a softened and open state.

[0039] Example 3: Compared with Example 1, in step b, the resin was first washed with a 10% HF aqueous solution for 12 hours, and then washed with a 10% HNO3 aqueous solution for 12 hours. The remaining steps were the same, and fluorinated resin A3 was obtained.

[0040] Example 4: Compared with Example 1, step b was washed with an aqueous solution of 10% HF and HNO3 for 24 hours, and the remaining steps were the same to obtain fluorinated resin A4.

[0041] Example 5: a. Fluorine-containing resin A is placed in a fluoropolymer-lined tank, heated to 200°C, F2 / N2 mixed gas is introduced, and the temperature is kept constant for fluorination treatment for 24 hours; b. Purge the F2 / N2 mixture and introduce high-temperature pure gas at 200℃ for 24 hours continuously; c. Stop the high-temperature pure gas purging and introduce room-temperature pure gas to cool the fluorinated resin; d. After the particles are cooled to room temperature, fluorinated resin A5 is obtained.

[0042] The low-exudate fluorinated resins A3, A4, and A5 obtained in Examples 3, 4, and 5 are shown in Table 3.

[0043] Table 3: ; Although different acids were used for pickling in the processing of fluoropolymers A3 and A4, the process of this invention resulted in very low levels of precipitates. Fluoropolymer A5, however, was not acid-treated, and its metal precipitates were far higher than normal. This is because pickling primarily removes surface contaminants. During the production of fluoropolymers, particles come into close contact with metal materials, potentially leaving a large number of metal particles on the surface of the fluoropolymer. These particles differ from the metal elements within the resin; they are abundant and mostly granular, requiring acid dissolution for removal. The metals within the resin are mostly introduced during the polymerization stage and are primarily ionic, attached to the polymer molecular chains. High-temperature, pure gas purging can remove them. Anions and TOCs, on the other hand, are mostly ionic and lightweight, easily carried away by high-temperature pure gas purging. Therefore, a combination of acid treatment and hot air treatment is necessary to ensure low precipitate levels in fluoropolymers.

[0044] Example 6: a. Place fluorinated resin A into a fluorinated tank, add 10% HF aqueous solution for acid washing for 12 hours, drain the HF aqueous solution; then wash with 10% HCl aqueous solution for 12 hours. b. Purge the 10% HCl aqueous solution and introduce high-temperature pure gas at 200℃ for 24 hours continuously. c. Stop the high-temperature pure gas purging and introduce room-temperature pure gas to cool the fluorinated resin; d. After the particles are cooled to room temperature, fluorinated resin A6 is obtained.

[0045] The low-exudate fluorinated resin A6 obtained in Example 6 is shown in Table 4.

[0046] Table 4: ; Fluorinated resin A6, without fluorination treatment, only meets the acceptable data for metal precipitation compared to fluorinated resins. However, its fluoride ion, TOC, and unstable end groups cannot be reduced to very low levels. This is because unstable end groups continuously decompose, leading to continuous fluoride ion precipitation and the generation of large amounts of short-chain low-molecular-weight compounds, resulting in TOC contamination. Therefore, unstable end groups require effective treatment using an F2 / N2 mixed gas at high temperatures. This is a prerequisite for ensuring the subsequent processing of fluorinated resins and for their use in the semiconductor field.

[0047] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes, but is not limited to, the content described in the above specific embodiments. Any modifications that do not depart from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. A low-exudate fluorinated resin, characterized in that, Its single metal precipitation is ≤1 ppb, F - Precipitation amount ≤10ppb, Br - Precipitation amount ≤1ppb, SO4 2- Precipitation amount ≤1ppb, NO3 - Precipitation amount ≤1ppb, NO2 - ≤1 ppb PO4 3- Precipitation amount ≤1ppb, unstable end groups ≤5 per million carbons, TOC precipitation amount ≤100ppb; The precipitation test method is to take 100g of the fluoropolymer particles to be tested, add 100g of ultrapure water, soak them at 85℃ for 168h, and test the metal, anion content and TOC in the extract. The purification process for obtaining low-precipitate fluorinated resins involves the following steps: S1 fluorinated resin undergoes a fluorination process. The fluorinated resin after S2 fluorination treatment undergoes an acid treatment process. The fluorinated resin after S3 acid treatment is then subjected to a hot air treatment process. The fluorinated resin after S4 hot air treatment undergoes a cooling process.

2. The low-exudate fluorinated resin according to claim 1, characterized in that, In step S1, the fluorinated resin is heated to 150-220°C in a reactor, and an F2 / N2 mixed gas is introduced while maintaining the temperature. The fluorination process lasts for 12-36 hours.

3. The low-exudate fluorinated resin according to claim 2, characterized in that, In step S2, after venting the F2 / N2 mixed gas from the reactor, an aqueous solution of acid is added for circulating acid washing.

4. The low-exudate fluorinated resin according to claim 1, characterized in that, The temperature of the acid treatment process is 5-85℃, and the temperature of the hot air treatment process is 80-220℃.

5. The low-exudate fluorinated resin according to claim 1, characterized in that, The acid treatment process takes 4-36 hours, and the hot air treatment process takes 20-30 hours.

6. The low-exudate fluorinated resin according to claim 1, characterized in that, The acid used in the acid treatment process is one or a mixture of at least two of HCl, HNO3, and HF, and the acid concentration is 1-30 wt%.

7. The low-exudate fluorinated resin according to claim 2, characterized in that, The fluorinated resin is obtained by homopolymerization or copolymerization of tetrafluoroethylene, hexafluoropropylene and perfluoroalkyl vinyl ether, with a melting point of 250-327°C. The perfluoroalkyl vinyl ether is one or more of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether or perfluoropropyl vinyl ether.

8. The low-exudate fluorinated resin according to claim 1, characterized in that, The metals include Fe, Cr, Ni, K, Na, Ca, Al, Zn, Cu, Mg, and Ti.

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