Plasma-resistant compression-deformation-resistant perfluoroether rubber seal ring and preparation process thereof

Abstract

The application relates to the technical field of high polymer materials, and discloses a nitrile group curing type perfluoroether rubber sealing ring resistant to plasma and compression deformation and a preparation process thereof, wherein the sealing ring is prepared through open mixing, mixing and gradient temperature vulcanization of nitrile group curing type perfluoroether rubber A, emulsion polytetrafluoroethylene premixed perfluoroether rubber B, polyperfluoroethylene propylene micro powder, fumed silica and a metal-free triazine vulcanization system; a double-network interpenetrating locking structure is established in a phase interface region by further introducing a bifunctional star-shaped compatibilizer, an end acyl fluoride group perfluoroether prepolymer and a three-arm perfluoroether amine crosslinking agent in an optimization scheme.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and more specifically, to a perfluoroether rubber sealing ring resistant to PLASMA compression deformation and its preparation process. Background Technology

[0002] In advanced semiconductor manufacturing equipment (such as plasma etching machines and chemical vapor deposition equipment), the sealing rings are subjected to the dual effects of high-energy plasma bombardment and high-temperature alternating compressive stress for a long time, which puts forward stringent requirements on the plasma resistance, resistance to permanent compression deformation and cleanliness of the sealing materials.

[0003] Currently, most sealing rings for semiconductor manufacturing equipment are made of perfluoroether rubber, which is vulcanized using a peroxide vulcanization system supplemented with metal oxide vulcanizing agents, and the rubber matrix is ​​reinforced with inorganic fillers.

[0004] However, the above-mentioned technical solutions have three mutually restrictive drawbacks: First, the single perfluoroether rubber matrix undergoes molecular chain creep and slippage under long-term high-temperature and high-pressure conditions, resulting in a high compression set value. After cooling, it cannot fully rebound to restore the sealing pressure, leading to vacuum leakage failure. Second, the metal oxide co-curing agent introduced by the peroxide curing system migrates and precipitates into the cavity during service, causing process contamination, and the residual carbon-hydrogen bonds in the curing products become the initiation sites for plasma chemical erosion. Third, the significant difference in the coefficient of thermal expansion between conventional inorganic fillers and the perfluoroether rubber matrix leads to microcracks and debonding defects at the interface under the alternating effects of high temperature and plasma, resulting in structural collapse failure. These three drawbacks are mutually restrictive and cannot be overcome simultaneously by a single technical approach, resulting in insufficient overall service reliability of existing perfluoroether rubber seals in advanced semiconductor processes. Summary of the Invention

[0005] This invention provides a PLASMA-resistant and compression-resistant perfluoroether rubber seal ring and its preparation process, solving the technical problems of insufficient resistance of perfluoroether rubber seal rings in plasma environment, large compression deformation, and high risk of metal ion contamination in related technologies.

[0006] This invention discloses a process for preparing a PLASMA-resistant and compression-resistant perfluoroether rubber sealing ring, comprising the following steps:

[0007] 55 to 70 parts by weight of nitrile-cured perfluoroether rubber A and 20 to 30 parts by weight of emulsion polytetrafluoroethylene premixed perfluoroether rubber B are mixed and blended on an open mill to form a homogeneous matrix.

[0008] 8 to 12 parts by weight of poly(perfluoroethylene propylene) micro powder and 1 to 3 parts by weight of fumed silica are added in batches to the homogeneous matrix and mixed and dispersed.

[0009] Add 2 to 5 parts by weight of metal-free triazine vulcanizing agent and 0.5 to 1.8 parts by weight of fluorinated organic base catalyst in sequence, mix evenly, and then extrude to obtain a compounded film.

[0010] After the compounded rubber sheet is pre-pressed, it is subjected to gradient temperature vulcanization, which includes a low temperature vulcanization section, a medium temperature vulcanization section, and a high temperature setting section.

[0011] Furthermore, the Mooney viscosity of the nitrile-cured perfluoroether rubber A is... The viscosity is 55 to 75, the nitrile content is 0.5 to 2.0 mol%, and the glass transition temperature is -10 to 5°C; the Mooney viscosity of the emulsion polytetrafluoroethylene premixed perfluoroether rubber B is... The concentration is 80 to 120, and the fluorine content is not less than 70 wt%.

[0012] Furthermore, the particle size D of the poly(fluoroethylene propylene) micropowder 50 The silica has a particle size of 1 to 5 μm and a melting point of not less than 305°C; the specific surface area of ​​the fumed silica is 150 to 200 m². 2 / g, with an average primary particle size of 12 to 20 nm; the polytetrafluoroethylene propylene micro powder and the fumed silica are dried at 100 to 120°C for 2 to 3 hours before being added.

[0013] Furthermore, when mixing the homogeneous matrix, the premixed polytetrafluoroethylene emulsion perfluoroether rubber B is first plasticized separately at a roller temperature of 60 to 70°C for 8 to 10 minutes, and then the nitrile-cured perfluoroether rubber A is added and mixed for 10 to 15 minutes; when adding filler, the roller gap is adjusted to 0.1 to 0.2 mm, the polytetrafluoroethylene propylene micro powder is added in 3 to 5 batches, and then the fumed silica is added in 2 to 3 batches.

[0014] Furthermore, the metal-free triazine vulcanizing agent is a melamine derivative with a total metal impurity content of no more than 10 μg / g, and is ground and sieved to an average particle size of no more than 50 μm before being added; the fluorinated organic base catalyst is a perfluorotributylamine quaternary ammonium salt type with a metal impurity content of no more than 5 μg / g; after being added to the vulcanization system, 0.1 to 0.3 parts by weight of a fluorinated internal release agent are also added.

[0015] Furthermore, the low-temperature vulcanization section is kept at a temperature range of 150 to 230°C in segments for a total holding time of 6 to 7 hours; the medium-temperature vulcanization section is kept at 230 to 250°C for 2 to 4 hours; and the high-temperature setting section is heated to 270 to 290°C at a heating rate of 1 to 2°C / min and kept at that temperature for 10 to 16 hours under continuous air circulation conditions.

[0016] Furthermore, after the high-temperature shaping section is completed, the furnace is cooled to below 60°C at a rate not exceeding 2°C / min before demolding. After demolding, the furnace is left to stand at room temperature for 24 to 48 hours for secondary shaping, and then the furnace is sequentially ultrasonically cleaned with ultrapure water, ultrasonically cleaned with semiconductor-grade isopropanol, and ultrasonically cleaned with ultrapure water before drying.

[0017] Furthermore, before mixing the homogeneous matrix, the emulsion polytetrafluoroethylene premixed perfluoroether rubber B is first mixed with 3 to 6 parts by weight of a bifunctional star-shaped compatibilizer to form a compatibilizing premix, and then the nitrile-cured perfluoroether rubber A is mixed and fused with the compatibilizing premix; the bifunctional star-shaped compatibilizer has a four-armed star structure, wherein nitrile functional groups are grafted at the ends of two arms, and acyl fluoride functional groups are grafted at the ends of the other two arms, with a number average molecular weight of 8,000 to 15,000.

[0018] Further, before adding the metal-free triazine vulcanizing agent, 5 to 10 parts by weight of the terminal acyl fluoride perfluoropolyether prepolymer and 1 to 3 parts by weight of the three-arm perfluoropolyether amine crosslinking agent are formulated into a second network precursor mixture and added to the rubber compound in batches for mixing and dispersion; the number average molecular weight of the terminal acyl fluoride perfluoropolyether prepolymer is 8,000 to 15,000, and the number average molecular weight of the three-arm perfluoropolyether amine crosslinking agent is 2,500 to 5,000, with each molecule containing 3 terminal primary amine groups.

[0019] This invention discloses a perfluoroether rubber sealing ring, which is prepared by the above-described preparation process.

[0020] The beneficial effects of this invention are as follows:

[0021] This invention addresses three key technical issues of traditional perfluoroether rubber seals: high compression set and insufficient cooling resilience; insufficient resistance to plasma erosion and cavity contamination due to metal ion precipitation and C-H bond introduction; and microcracks and debonding failure caused by thermal mismatch at the filler-rubber matrix interface. These issues are achieved through the synergistic combination of a nitrile-cured perfluoroether rubber A and a premixed perfluoroether rubber B from emulsion polytetrafluoroethylene; a synergistic filler system of polytetrafluoroethylene propylene micropowder and fumed silica; and microcracks and debonding failure due to thermal mismatch at the filler-rubber matrix interface. The invention reduces compression set, eliminates sources of metal ion precipitation, removes weak points in C-H bond chemical processes, and suppresses microcracks caused by thermal mismatch at the filler interface. In a further optimized design, a bifunctional star-shaped compatibilizer is used to establish a dual-network interpenetrating locking structure at the phase interface, effectively eliminating creep coupling failure pathways caused by low crosslinking density at the phase interface. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of the preparation process of the plasma-resistant and compression-resistant perfluoroether rubber sealing ring provided in the embodiments of the present invention;

[0023] Figure 2 This is a schematic diagram comparing the compression set and nitrile group conversion rate of various samples provided in the embodiments of the present invention;

[0024] Figure 3 This is a schematic diagram comparing the amount of metal ion deposition with the plasma mass loss rate provided in the embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of the SEM morphology of the cross-section of the perfluoroether rubber sealing ring provided in the embodiment of the present invention;

[0026] Figure 5 This is a schematic diagram of the FTIR spectrum of the perfluoroether rubber sealing ring provided in an embodiment of the present invention;

[0027] Figure 6 This is a schematic diagram of a cross-sectional TEM image of a dual-network perfluoroether rubber sealing ring provided in an embodiment of the present invention;

[0028] Figure 7 This is a TGA thermogravimetric analysis spectrum of a perfluoroether rubber sealing ring provided in an embodiment of the present invention. Detailed Implementation

[0029] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0030] Example 1

[0031] This invention discloses a preparation process for a PLASMA-resistant and compression-resistant perfluoroether rubber sealing ring, see [link to relevant documentation]. Figure 1 ,include:

[0032] Step 1: Drying the filler and refining the particle size of the vulcanizing agent.

[0033] Poly(fluoroethylene propylene) micro powder (particle size D) 50 8 to 12 parts by weight of fumed silica (1 to 5 μm, melting point not lower than 305℃) and fumed silica (specific surface area 150 to 200 m²) 21 to 3 parts by weight of the two fillers (with an average primary particle size of 12 to 20 nm) were placed in clean stainless steel trays and dried at 100 to 120°C for 2 to 3 hours. After drying, the two fillers were transferred to sealed drying containers and cooled at room temperature for no more than 24 hours. 2 to 4 parts by weight of the metal-free triazine sulfiding agent (melamine derivative, purity not less than 99.0%, total metal impurities not higher than 10 μg / g) were placed in a grinding device and ground. After grinding, the powder was sieved through a 200-mesh standard sieve to remove large agglomerates. The sieved fine powder with an average particle size not greater than 50 μm was collected and sealed for later use.

[0034] Furthermore, since fumed silica is a nano-scale lightweight powder, dust is easily generated during grinding and sieving operations. Operators must wear dust masks and goggles and conduct the operations on an operating table equipped with a local exhaust ventilation device to avoid inhaling nano-scale dust.

[0035] It should be noted that the drying temperature for the poly(perfluoroethylene propylene) micropowder and fumed silica is selected to be 100 to 120°C. This temperature is higher than the boiling point of water but much lower than the melting temperature of the poly(perfluoroethylene propylene) micropowder. This effectively removes adsorbed moisture from the material surface without altering the crystalline morphology of the poly(perfluoroethylene propylene) micropowder. Moisture removal prevents the formation of microbubble defects during subsequent high-temperature mixing and avoids competitive reactions between moisture and the fluorinated organic base catalyst, thus preventing interference with catalytic efficiency. The triazine vulcanizing agent is ground and sieved to an average particle size of no more than 50 μm, which helps to achieve uniform dispersion of the metal-free triazine vulcanizing agent in the rubber matrix during subsequent mixing and suppresses uneven crosslinking density caused by excessively high local concentrations of metal-free triazine vulcanizing agent.

[0036] Step 2: Plasticizing the matrix rubber and fusing the two phases.

[0037] Preheat the two-roll open mill to 60-70°C and adjust the roll gap to 1.5-2.0 mm. Premix the emulsion polytetrafluoroethylene with perfluoroether rubber B (Mooney viscosity). 20 to 30 parts by weight of a pre-dispersed ultrafine polytetrafluoroethylene (PTFE) microparticle (80 to 120 ppm, fluorine content not less than 70 wt%) are added to an open mill and separately plasticized at a roll temperature of 60 to 70°C for 8 to 10 minutes to fully soften the PTFE premixed perfluoroether rubber B. Then, a nitrile-cured perfluoroether rubber A (Mooney viscosity) is added. The content of acrylonitrile is 55 to 75%, the content of acrylonitrile is 0.5 to 2.0 mol%, and the glass transition temperature Tg is -10 to 5℃. 60 to 70 parts by weight are mixed and kneaded for 10 to 15 minutes. The two rubbers are fused into a homogeneous matrix under the action of roller shear force. The total plasticizing time is controlled at 18 to 25 minutes.

[0038] It should be noted that the operation sequence is as follows: first, refine the emulsion PTFE premixed perfluoroether rubber B, then add the nitrile-cured perfluoroether rubber A. After the emulsion PTFE premixed perfluoroether rubber B has been fully softened and plasticized under long-term shearing on the roller surface, the nitrile-cured perfluoroether rubber A can quickly penetrate and fuse with the softened emulsion PTFE premixed perfluoroether rubber B, avoiding stratification or uneven distribution due to excessive viscosity difference. The ratio of nitrile-cured perfluoroether rubber A to emulsion PTFE premixed perfluoroether rubber B is (60 to 70): (20 to 30) parts by weight. This ratio range allows the composite matrix to combine the low compression set characteristics of nitrile-cured perfluoroether rubber A with the high purity and plasma resistance of emulsion PTFE premixed perfluoroether rubber B.

[0039] Step 3: Add and mix the filler in stages.

[0040] The homogeneous matrix obtained in step 2 is retained on the open mill. The roller gap is adjusted to 0.1 to 0.2 mm, and the roller temperature is maintained at 60 to 70°C. 8 to 12 parts by weight of the pretreated poly(fluoroethylene propylene) micropowder from step 1 are added to the rubber compound on the roller surface in 3 to 5 batches. After each batch is added, the powder is allowed to largely penetrate the compound before adding the next batch. After all the poly(fluoroethylene propylene) micropowder has been added, mixing continues for 5 minutes. Subsequently, 1 to 3 parts by weight of fumed silica are added in 2 to 3 batches. After all the silica has been added, mixing continues at a constant temperature for 10 to 15 minutes. The total filling mixing time is controlled at 15 to 20 minutes. During the mixing process, a cutting and folding operation is performed every 3 minutes, alternately folding the rubber sheet left and right and then pressing it back into the roller gap to promote uniform dispersion of the filler in three dimensions.

[0041] It should be noted that adjusting the roller gap to a narrow range of 0.1 to 0.2 mm aims to increase the shear stress intensity experienced by the rubber compound as it passes through the roller gap. This forces the micro-powder filler to disperse and break up agglomerates in a high shear field, achieving full contact between the filler particles and the rubber matrix. The perfluoroethylene propylene (PFEP) micro-powder is added before the fumed silica because its larger particle size and higher density make it easier to disperse under narrow roller gap shear. The fumed silica, being a nano-scale lightweight powder, is added later; the PFEP micro-powder already dispersed in the matrix acts as anchoring points, reducing secondary agglomeration of the fumed silica.

[0042] Step 4: Adding the vulcanization system and final refining to produce sheets.

[0043] After the filler is mixed, maintain the rolling mill temperature at 60 to 70°C. Add 2 to 4 parts by weight of the metal-free triazine vulcanizing agent treated in step 1 to the rubber compound and mix for 5 minutes. Then add 0.5 to 1.5 parts by weight of the fluorinated organic base catalyst (perfluorotributylamine quaternary ammonium salt type, purity not less than 98%, metal impurities not higher than 5 μg / g) and mix for 5 minutes. Finally, add the fluorinated internal release agent (perfluoropolyether wax type, kinematic viscosity V... 25℃ 50 to 150 mm 2 / s, where V 25℃ Add 0.1 to 0.3 parts by weight of the kinematic viscosity at 25°C and continue mixing for 2 to 5 minutes. The total mixing time of the three components should be controlled at 12 to 15 minutes, and the roller temperature should be strictly controlled not to exceed 75°C.

[0044] In step 4, the order of adding the components of the vulcanization system is as follows: first, add the metal-free triazine vulcanizing agent to the rubber compound and mix it evenly; then add the fluorinated organic base catalyst; and finally, add the fluorinated internal release agent. The metal-free triazine vulcanizing agent must first form a uniform dispersion in the rubber matrix. Only when the fluorinated organic base catalyst is added later can the nitrile trimerization reaction be uniformly activated throughout the matrix. If the fluorinated organic base catalyst is added before the metal-free triazine vulcanizing agent, premature crosslinking may occur in localized areas. The fluorinated internal release agent is added last to avoid interfering with the dispersion of the metal-free triazine vulcanizing agent.

[0045] After the vulcanization system is added, adjust the roller gap to 0.4 to 0.5 mm, reduce the roller temperature to 50 to 60°C, and perform a thin-pass operation at a roller surface linear speed of 5 to 8 m / min. After folding, perform the thin-pass operation 2 to 3 times, and control the sheet thickness to 3 to 5 mm. Lay the film flat on a PTFE liner, cover it with a release film, and let it stand for 12 to 24 hours in a clean environment at room temperature (23±2°C) and relative humidity not exceeding 50% for curing. The cured compounded film must be processed within 72 hours.

[0046] It should be noted that controlling the roller temperature to no more than 75℃ is to prevent the triazine cyclization reaction from starting prematurely during the mixing stage, which could lead to scorching. The static curing after final sheeting allows the internal stress accumulated during the mixing process to be eliminated through the slow relaxation of molecular chain segments, ensuring the uniformity of subsequent vulcanization molding.

[0047] All components are expressed in parts by weight. The complete formulation of Example 1 is as follows: 60 to 70 parts by weight of nitrile-cured perfluoroether rubber A, 20 to 30 parts by weight of emulsion polytetrafluoroethylene premixed perfluoroether rubber B, 8 to 12 parts by weight of polytetrafluoroethylene propylene micropowder, 1 to 3 parts by weight of fumed silica, 2 to 4 parts by weight of metal-free triazine vulcanizing agent, 0.5 to 1.5 parts by weight of fluorinated organic base catalyst, and 0.1 to 0.3 parts by weight of fluorinated internal release agent. The weight parts of the filler, vulcanizing agent, catalyst, and release agent are calculated based on the amounts of nitrile-cured perfluoroether rubber A and emulsion polytetrafluoroethylene premixed perfluoroether rubber B.

[0048] Step 5: Pre-compression molding.

[0049] Based on the sealing ring specifications and mold cavity volume, cut the compounded rubber sheet obtained in step 4 according to a filling coefficient k of 1.05 to 1.10, where k is defined as the ratio of the billet volume to the mold cavity volume. Place the billet into the cleaned metal mold cavity, close the mold, and place it between the hot plates of a flat vulcanizing machine. Hold the pressure for 3 to 5 minutes at a pre-compression temperature of 170 to 190°C and a pre-compression pressure of 12 to 18 MPa. Perform an venting operation within 30 to 60 seconds after pressurization: reduce the pressure to approximately 0.5 MPa, hold for 5 seconds, and then raise it back to the set pressure. Repeat the venting cycle 2 to 3 times. After pre-compression is complete, slowly release the pressure to atmospheric pressure, open the mold, remove the preform, and inspect for defects such as missing material or bubbles before proceeding to the next step.

[0050] Furthermore, the pre-compression molding operation involves a hot plate at a high temperature of 170 to 190°C and a high pressure of 12 to 18 MPa. Operators must wear high-temperature resistant protective gloves, and protective baffles must be set up around the equipment. When opening the mold and removing the part, it must be confirmed that the pressure has been completely released before operation to prevent the high-temperature rubber from splashing or the high-pressure mold from popping open and causing burns.

[0051] It should be noted that the pre-compression temperature of 170 to 190°C is below the main reaction temperature range of the triazine cyclization reaction. At this temperature, the rubber compound obtains sufficient fluidity to fully fill the cavity, but will not yet trigger large-scale cross-linking and hardening. The venting operation removes the trace amounts of residual air in the blank from the cavity before the rubber compound has cross-linked and cured, preventing the formation of internal bubble defects due to gas thermal expansion during the subsequent high-temperature vulcanization stage.

[0052] Step 6: Gradient temperature vulcanization.

[0053] Place the preform obtained in step 5 on a clean polytetrafluoroethylene tray and send it into a programmable blast-drying oven. Perform vulcanization according to the following three-stage gradient heating program, with a heating rate of 2 to 3 °C / min for each stage.

[0054] Low-temperature vulcanization stage: Temperatures are sequentially maintained at 150-160℃ for 2 hours, 170-190℃ for 2 hours, and 220-230℃ for 2 hours, for a total of 6 hours. The triazine cyclization reaction proceeds from initiation to near completion, with the cross-linked network gradually forming. Stepwise, slow heating prevents surface cross-linking from completing before the internal cross-linking, which could lead to internal bubbles or cracking defects.

[0055] Medium-temperature vulcanization stage: Heat to 230-250℃ and hold for 2 hours. Residual nitrile groups undergo further cyclization, increasing crosslinking density. The surface of the perfluoroethylene propylene micropowder softens slightly at temperatures below its melting point (not lower than 305℃), further enhancing its interfacial bonding with the rubber matrix.

[0056] High-temperature setting stage: The temperature is increased to 270-290℃ at a rate of 1-2℃ / min and held for 10 hours. Residual nitrile groups almost completely participate in the triazine cyclization reaction, and the cross-linked network reaches its final density. Simultaneously, low-molecular-weight residues (including decomposition products of fluorinated organic base catalysts, unreacted residues of metal-free triazine vulcanizing agents, and volatile components of fluorinated internal release agents) are fully volatilized and released under continuous forced-air circulation.

[0057] Furthermore, the gas discharged from the blower circulation during the gradient temperature vulcanization process contains fluorinated organic waste gas, such as thermal decomposition products of fluorinated organic base catalysts and volatile components of fluorinated internal release agents. This waste gas must be treated by activated carbon adsorption devices or alkaline scrubbing towers before it can be discharged and must not be directly discharged into the atmosphere.

[0058] It should be noted that the temperature and time parameters of the three-stage gradient heating program are matched with the rheological properties and triazine vulcanization reaction kinetics of the compound system of nitrile-cured perfluoroether rubber A and premixed polytetrafluoroethylene (PTFE) perfluoroether rubber B. The three sub-temperature ranges of the low-temperature stage correspond to the initiation, acceleration, and near-completion stages of the triazine cyclization reaction, respectively. The medium-temperature stage allows the residual nitrile groups to react further under higher thermal energy, while the slight softening of the surface of the PTFE micropowder facilitates a tighter physical bond between it and the surrounding rubber matrix. The high-temperature setting stage, with a holding time of 270 to 290°C for 10 hours, allows the very small amount of residual nitrile groups to complete the final cyclization and achieve cross-linking network densification. On the other hand, the continuous high temperature and forced-air circulation effectively remove all low-molecular-weight residues that can migrate out, meeting the cleanliness requirements of the sealing material in semiconductor manufacturing processes.

[0059] In step 6, the nitrile conversion rate was characterized by Fourier transform infrared spectroscopy (FTIR) at 2230 to 2240 cm⁻¹. -1 The change in the area of ​​the characteristic absorption peak of the nitrile group relative to the area of ​​the same characteristic peak in the pre-cured compounded rubber sheet is used to calculate the nitrile group conversion rate η, which is defined as:

[0060]

[0061] in This represents the area of ​​the characteristic absorption peak of the acrylonitrile group in the pre-cured compounded rubber sheet. This represents the area of ​​the characteristic absorption peak of the nitrile group in the vulcanized product. This refers to the nitrile group conversion rate. The nitrile group conversion rate of the product after the high-temperature setting stage should not be less than 95%.

[0062] Step 7: Cooling, shaping, and post-processing.

[0063] After the high-temperature setting stage is completed, the oven continues to circulate air, cooling the product along with the furnace at a rate not exceeding 2℃ / min. Once the oven temperature drops below 60℃, the initial sealing ring is removed using a non-metallic tool made of polytetrafluoroethylene (PTFE). The initial sealing ring is then placed flat on a support frame in an ISO Class 6 cleanroom and left to stand for 24 hours at room temperature (23±2℃) and relative humidity not exceeding 50% for secondary setting. This allows the molecular chains to relax to a thermodynamic equilibrium state, eliminating residual thermal stress from the vulcanization process and stabilizing the dimensions.

[0064] After the secondary shaping is completed, trimming and cleaning are performed sequentially. Trimming is done using a PTFE or ceramic trimming knife under 10x magnification to remove burrs, ensuring a smooth, burr-free surface. Cleaning is conducted in an ISO Class 5 cleanroom, involving sequential ultrasonic cleaning in ultrapure water (resistivity not less than 18.2 MΩ·cm) for 10 minutes, ultrasonic cleaning in semiconductor-grade isopropanol for 10 minutes, and then ultrasonic cleaning in ultrapure water for another 10 minutes. Following this, the product is dried in a 60℃ cleanroom oven for 2 hours. After all indicators pass inspection, the finished product is heat-sealed in double-layer clean polyethylene bags and stored at 15-25℃, relative humidity not exceeding 60%, and in the dark.

[0065] Furthermore, the semiconductor-grade isopropanol used in the cleaning process is a flammable organic solvent. Ultrasonic cleaning operations must be carried out in a fume hood or a clean bench with local exhaust ventilation, and the operating area must be kept away from open flames and heat sources. The isopropanol-containing waste liquid generated during cleaning must be collected separately in a sealed container and disposed of by a professional waste liquid treatment company; it must not be poured into ordinary sewers.

[0066] It should be noted that the cooling rate is controlled to no more than 2℃ / min to avoid excessive internal stress caused by the difference in thermal expansion coefficients between the rubber matrix and the filler due to rapid cooling, which could lead to microcracks. The 24-hour settling period after secondary shaping is the minimum time required for the molecular chain segments to fully relax to equilibrium at room temperature, ensuring that the finished product dimensions do not change over time during use. The three-step ultrasonic cleaning process involves ultrapure water, isopropanol, and then ultrapure water again. Ultrapure water removes water-soluble inorganic residues from the surface, isopropanol dissolves and removes organic residues, and finally, ultrapure water replaces any remaining isopropanol.

[0067] In step 7, the ultrasonic frequency for each step of the ultrasonic cleaning process is controlled between 40 and 80 kHz, and the ultrasonic power density is between 0.3 and 0.8 W / cm². 2 The ultrasonic power density is defined as the ratio of the effective radiation power of the ultrasonic transducer to the bottom area of ​​the cleaning tank. The above parameter range ensures effective removal of surface residues while avoiding micro-damage to the sealing ring surface due to excessive ultrasonic cavitation.

[0068] The finished sealing ring obtained in step 7 was characterized and evaluated using the following methods: Elastic recovery performance was characterized by compression set test (according to GB / T 7759 standard, 200℃, 72 hours, 25% compression); thermal stability was assessed by thermogravimetric analysis (TGA) at the onset temperature of thermogravimetric analysis in air; the metal element content in the finished product was detected by X-ray fluorescence spectrometry (XRF) to confirm that the total amount of metal impurities met the semiconductor process specifications; and the amount of ultra-trace metal ion deposition on the surface of the finished product was detected by glow discharge mass spectrometry (GDMS).

[0069] To further improve the overall performance of the sealing ring under high compression conditions with a large cross-section, the following optimization scheme (Example 2) is also included based on steps 1 to 7. Example 2, based on the perfluoroether rubber matrix formulation and metal-free triazine vulcanization system of Example 1, introduces a bifunctional star-shaped compatibilizer, a terminal acyl fluoride perfluoroether prepolymer, and a three-arm perfluoroether amine crosslinking agent to establish a chemical interconnection bridge in the phase interface region. This eliminates the problem in the two-phase blend system where the interface region between the nitrile-cured perfluoroether rubber A phase and the emulsion polytetrafluoroethylene premixed perfluoroether rubber B phase becomes a weak link in the coupling failure of plasma erosion and compression creep due to disordered chain segment stacking and low crosslinking density.

[0070] Example 2

[0071] The difference between this embodiment and Embodiment 1 is that:

[0072] Step S1: Synthesis of bifunctional star-shaped compatibilizer.

[0073] Eight to twelve parts by weight of perfluoropentaerythritol (purity not less than 98%, number average molecular weight Mn = 420) and 30 to 50 parts by weight of perfluorobutyltetrahydrofuran (purity not less than 99%, number average molecular weight Mn = 254) were added to a glass-lined reactor. Perfluorotributylamine was used as the solvent, and the amount of solvent was 1.5 to 2.5 times the total mass of the reactants (mass ratio). The ring-opening polymerization reaction was carried out at 160 to 180 °C for eight to twelve hours to obtain a four-armed star-shaped perfluorocyclic ether intermediate.

[0074] Take 100 parts by weight of the above-mentioned four-armed star-shaped perfluorocyclic ether intermediate, and react the ends of two arms with 3 to 5 parts by weight of perfluoroglutaronitrile (purity not less than 97%) at 140 to 160°C for 4 to 6 hours to complete nitrile grafting; react the ends of the other two arms with 2 to 4 parts by weight of perfluoroadipoxyfluoride (purity not less than 97%) at 100 to 120°C for 2 to 4 hours to complete acyl fluoride grafting. Purify by vacuum distillation (vacuum degree not higher than 100 Pa, distillation temperature 120 to 150°C) to remove unreacted monomers and low molecular weight byproducts. The residue in the reactor is the purified bifunctional star-shaped compatibilizer, with a number average molecular weight Mn controlled in the range of 8000 to 15000. Store in a sealed container protected from light for later use.

[0075] Furthermore, both perfluoroglutaronitrile and perfluoroadipoxyfluoride are irritating fluorine-containing compounds, and the grafting reaction must be carried out in a fume hood, with operators wearing chemical-resistant gloves and protective masks. Although the solvent for perfluorotributylamine is chemically inert, it still has a certain vapor pressure; the perfluorotributylamine-containing fraction distilled during vacuum distillation must be condensed and recovered, and must not be directly discharged.

[0076] It should be noted that in the four-arm structure of the bifunctional star compatibilizer, nitrile functional groups are grafted onto the ends of two arms, enabling them to participate in the nitrile trimerization reaction of the first network (triazine crosslinking network) and anchor to the crosslinking nodes of the first network. Acyl fluoride functional groups are grafted onto the ends of the other two arms, allowing them to undergo a condensation reaction with the primary amine groups of the three-arm perfluoropolyetheramine crosslinker in the second network and connect to the second network backbone. The bifunctional star compatibilizer simultaneously forms covalent bonds with both the first and second networks in the interphase interface region, establishing a chemical bridge across the phase interface. The mass ratio of perfluoropentaerythritol to perfluorobutyltetrahydrofuran is controlled at (8 to 12):(30 to 50). This ratio range ensures that the four-armed star intermediate has sufficient arm length (Mn of a single arm is approximately 2000 to 3500), allowing the star configuration to occupy a large volume in the interphase region and effectively penetrate into the respective phase domains of both phases.

[0077] The amount of solvent used for perfluorotributylamine is 1.5 to 2.5 times (by mass) of the total mass of the reactants, preferably 2.0 times. If the amount of solvent is less than 1.5 times, the viscosity of the system is too high, which is not conducive to mass transfer; if it is more than 2.5 times, the concentration of reactants is too low, and the ring-opening polymerization efficiency decreases.

[0078] In step S1, the ring-opening polymerization reaction is carried out in a glass-lined reactor under an inert atmosphere of nitrogen or argon. The pressure inside the reactor is maintained at 0.1 to 0.3 MPa (gauge pressure), and the heating rate is controlled at 2 to 5 °C / min. The inert atmosphere protection can prevent side reactions between the perfluoroether intermediate and trace amounts of moisture or oxygen under high-temperature conditions, which could affect the uniformity of the arm length of the star-shaped intermediate.

[0079] In step S1, both the nitrile grafting reaction and the acyl fluoride grafting reaction were carried out under an inert nitrogen atmosphere. The pressure inside the reaction vessel was maintained at atmospheric pressure, the heating rate was controlled at 2 to 5 °C / min, and the mixture was stirred with a magnetic stirrer at a speed of 100 to 200 rpm. The inert atmosphere protection prevents the nitrile and acyl fluoride functional groups from undergoing oxidation side reactions at high temperatures, ensuring the grafting functionality.

[0080] After the bifunctional star compatibilizer obtained in step S1 is purified by vacuum distillation, the distillate consists of unreacted monomers and low molecular weight byproducts, which are discarded; the residue in the reactor is the purified bifunctional star compatibilizer.

[0081] Furthermore, the distillate waste contains unreacted perfluoroglutaronitrile, perfluoroadipoxyfluoride, and low molecular weight byproducts, which are classified as fluorine-containing organic waste. It must be collected in a special sealed waste container, labeled "fluorine-containing organic waste," and disposed of by a professional hazardous waste treatment agency.

[0082] In step S1, the number-average molecular weight (Mn) of the bifunctional star-shaped compatibilizer was determined by gel permeation chromatography (GPC), using perfluoropolyether standards as a reference, perfluorotributylamine as the detection solvent, a column temperature of 40℃, a flow rate of 1.0 mL / min, and a differential refractive index detector. The nitrile and acyl fluoride content of the grafted functional groups were determined by fluorine-19 nuclear magnetic resonance spectroscopy (NMR spectroscopy). 19 Quantitative characterization was performed using perfluorobenzene as an internal standard and measured on a 400 MHz nuclear magnetic resonance spectrometer (F-NMR).

[0083] Step S2: Preparation of terminal acyl fluoride perfluoropolyether prepolymer.

[0084] Perfluoropolyether glycols with a number average molecular weight Mn of 2000 to 4000 (terminated hydroxyl groups, each molecule containing 2) 100 parts by weight of the end-group perfluoropolyether glycol and 12 to 18 parts by weight of the perfluoroadipoxy fluoride are added to a polycondensation reactor and polycondensed at 80 to 100°C for 4 to 6 hours. The terminal hydroxyl groups of the perfluoropolyether glycol and the acyl fluoride groups of the perfluoroadipoxy fluoride undergo a condensation reaction to form ester bonds, resulting in chain elongation and yielding a perfluoropolyether prepolymer with terminal acyl fluoride groups and a number average molecular weight (Mn) of 8000 to 15000. After polycondensation, the solvent is removed under vacuum at a vacuum degree not exceeding 200 Pa and a temperature of 60 to 80°C, and the prepolymer is sealed for later use.

[0085] Furthermore, the byproduct of the condensation reaction is hydrogen fluoride gas, which is highly corrosive and extremely toxic. The exhaust port of the reactor must be connected to an alkaline solution (such as sodium hydroxide solution) washing bottle or a tail gas absorption device to fully absorb and neutralize the escaping hydrogen fluoride. Operators must wear protective gloves and face shields resistant to hydrogen fluoride corrosion. Hydrogen fluoride gas extracted during the vacuum desolventizing process must also be absorbed by alkaline solution before being released. The fluoride-containing waste liquid generated after alkaline absorption must be neutralized to neutral and then disposed of by a professional waste liquid treatment facility.

[0086] It should be noted that the molar ratio of perfluoropolyether glycol to perfluoroadipoxyfluoride is calculated to ensure that the final product is terminally acyl fluoride groups. The molar amount of perfluoroadipoxyfluoride must be slightly in excess of the perfluoropolyether glycol. When the perfluoropolyether glycol Mn is 2000, the molar ratio of perfluoropolyether glycol to perfluoroadipoxyfluoride is approximately 1:1.05 to 1:1.15; when Mn is 4000, the molar ratio is approximately 1:1.02 to 1:1.08. This excess ratio ensures that both ends of the terminally acyl fluoride perfluoropolyether prepolymer are acyl fluoride active groups, so that it can undergo a condensation reaction with the primary amine groups of the three-arm perfluoropolyether amine crosslinker in subsequent steps to form a second network.

[0087] In step S2, the polycondensation reaction is carried out under an inert nitrogen atmosphere to prevent oxidation side reactions of the terminal hydroxyl groups and acyl fluoride groups at high temperatures. The stirring speed is controlled at 100 to 200 rpm, with the stirring speed measured by the speed of the anchor-type stirrer. Moderate stirring ensures uniform contact of the reactants and avoids excessive shear that could cause the chain segments of the already formed terminal acyl fluoride perfluoropolyether prepolymer to break.

[0088] After the polycondensation reaction in step S2 is completed, the reaction system is subjected to vacuum desolventizing treatment at a vacuum degree not exceeding 200 Pa and a temperature of 60 to 80°C to remove the polycondensation byproduct hydrogen fluoride and unreacted excess perfluoroadipyl fluoride molecules. The resulting terminal acyl fluoride-terminated perfluoropolyether prepolymer is sealed in a clean container and stored at an environment not exceeding 5°C for no more than 30 days to prevent hydrolytic deactivation of the terminal acyl fluoride groups.

[0089] The number-average molecular weight (Mn) of the terminal acyl fluoride-terminated perfluoropolyether prepolymer obtained in step S2 was determined by gel permeation chromatography (GPC), using the same method as in step S1. The content of terminal acyl fluoride groups was determined by fluorine-19 nuclear magnetic resonance spectroscopy (NMR spectroscopy). 19 Quantitative characterization by F-NMR was used to confirm that the terminal acyl fluoride perfluoropolyether prepolymer carries acyl fluoride active groups at both ends, and the terminal group functionality is not less than 1.8 (based on the average number of acyl fluoride groups per molecule).

[0090] Step S3: Preparation of three-arm perfluoropolyetheramine crosslinking agent.

[0091] Perfluorinated melamine (triaminotriazine perfluorinated compound, purity not less than 97%, molecular weight M) W= 285) 5 to 8 parts by weight of a perfluoropropylene oxide oligomer (terminal epoxy groups) with a number average molecular weight Mn of 500 to 1000 is added to a reaction vessel. The reaction is carried out at 100 to 120°C for 3 to 5 hours, where the three primary amine groups of the perfluoromelamine undergo ring-opening addition reactions with the epoxy groups of the perfluoropropylene oxide oligomer, generating a three-arm structure linked by secondary amine bonds. After the reaction, unreacted monomers are removed under vacuum at a temperature not exceeding 100 Pa and 80 to 100°C, yielding a three-arm perfluoropolyetheramine crosslinking agent with a number average molecular weight Mn of 2500 to 5000, containing 3 terminal primary amine groups per molecule, which is then sealed for later use.

[0092] It should be noted that the mass ratio of perfluoromelamine to perfluoropropylene oxide oligomer is controlled at (5 to 8):(15 to 25), corresponding to approximately three perfluoropolyether arms per molecule of perfluoromelamine. The three-arm structure ensures that the three-arm perfluoropolyetheramine crosslinker forms a three-dimensional network topology in the second network rather than extending nonlinear chains, giving the second network independent three-dimensional elastic recovery capability.

[0093] The preferred mass ratio of perfluoromelamine to perfluoropropylene oxide oligomer is (6 to 7): (18 to 22). Within this range, the arm length uniformity of the three-arm structure is good, and the crosslinking density distribution of the second network is relatively uniform.

[0094] The ring-opening addition reaction in step S3 was carried out under an inert nitrogen atmosphere, with the pressure inside the reaction vessel maintained at atmospheric pressure and the heating rate controlled at 2 to 5 °C / min. The reaction was stirred with a magnetic stirrer at a speed of 150 to 300 rpm. The inert atmosphere prevented the primary amine groups from being oxidized at high temperatures, which would affect the functionality of the three-arm perfluoropolyetheramine crosslinking agent.

[0095] After the reaction in step S3 is completed, when removing unreacted monomers under vacuum, the volatile components removed by vacuum should be condensed, collected, and disposed of centrally. They must not be directly discharged to avoid environmental pollution caused by perfluoropropylene oxide oligomer vapors.

[0096] Furthermore, perfluoropropylene oxide oligomers contain epoxy functional groups, which are irritating to the skin and mucous membranes. Feeding and reaction operations must be carried out in a fume hood, and operators must wear chemical-resistant gloves and safety goggles. The condensed waste liquid containing perfluoropropylene oxide oligomers must be collected in a sealed container, labeled "Fluorine-containing organic waste liquid," and handed over to a professional waste liquid treatment facility for disposal.

[0097] The number-average molecular weight (Mn) of the three-arm perfluoropolyetheramine crosslinker obtained in step S3 was determined by gel permeation chromatography (GPC), using the same method as in step S1. The content of terminal primary amine groups was determined by fluorine-19 nuclear magnetic resonance spectroscopy (NMR spectroscopy). 19Characterization was performed by a combination of F-NMR and amine titration, with the number of terminal primary amine groups (functionality) per molecule not less than 2.7.

[0098] Step S4: Preparation of the second network precursor mixture.

[0099] Five to ten parts by weight of the terminal acyl fluoride-terminated perfluoropolyether prepolymer obtained in step S2 and one to three parts by weight of the three-arm perfluoropolyetheramine crosslinking agent obtained in step S3 were placed in a clean polytetrafluoroethylene container and stirred with a magnetic stirrer for 15 to 20 minutes at room temperature (23±2℃) until homogeneous, to obtain the second network precursor mixture. The mass ratio of the terminal acyl fluoride-terminated perfluoropolyether prepolymer to the three-arm perfluoropolyetheramine crosslinking agent was (5 to 10):(1 to 3), calculated based on a molar ratio of acyl fluoride groups to primary amine groups of approximately 1:0.8 to 1:1.2 (where the molar number of acyl fluoride groups was calculated based on the Mn of the terminal acyl fluoride-terminated perfluoropolyether prepolymer and the functionality of the terminal groups, and the molar number of primary amine groups was calculated based on the Mn of the three-arm perfluoropolyetheramine crosslinking agent and the trifunctionality). This ratio range ensures that the second network can form an effective three-dimensional crosslinked structure during the subsequent vulcanization process. The second network precursor mixture was prepared immediately before use and stored for no more than 4 hours.

[0100] It should be noted that the storage time is limited to within 4 hours because although the reaction rate between the acyl fluoride group and the primary amine group is extremely low at room temperature, slow condensation may still occur if left for a long time, which will increase the viscosity of the second network precursor mixture and reduce the subsequent dispersion effect.

[0101] Step S4, preparing the second network precursor mixture, is carried out in a dry environment with a relative humidity of no more than 40% to prevent the terminal acyl fluoride groups from hydrolyzing upon contact with moisture in the environment to generate carboxylic acid groups, which would lead to a decrease in activity and functionality.

[0102] Step S5: Filler pretreatment and vulcanizing agent refinement.

[0103] The drying operations of polytetrafluoroethylene propylene micro powder and fumed silica, as well as the grinding and sieving operations of the metal-free triazine vulcanizing agent, are the same as in step 1. The dosage range of each component is also the same as in step 1, namely, 8 to 12 parts by weight of polytetrafluoroethylene propylene micro powder, 1 to 3 parts by weight of fumed silica, and 3 to 5 parts by weight of metal-free triazine vulcanizing agent.

[0104] Step S6: Preparation of compatibilized premix.

[0105] Preheat the two-roll mill to 60-70°C and adjust the roll gap to 1.5-2.0 mm. Add 20-30 parts by weight of the premixed polytetrafluoroethylene perfluoroether rubber B to the two-roll mill and separately plasticize it for 8-10 minutes at a roll temperature of 60-70°C to fully soften it. Then, add 3-6 parts by weight of the bifunctional star-shaped compatibilizer obtained in step S1 to the rubber compound on the roll surface in 2-3 portions and continue mixing for 12-18 minutes to allow the star-shaped multi-arm structure of the bifunctional star-shaped compatibilizer to penetrate and diffuse into the polytetrafluoroethylene particles and the interior of the phase domains, thus obtaining the compatibilized premix for later use.

[0106] It should be noted that the bifunctional star-shaped compatibilizer must be added after the premixed PTFE emulsion perfluoroether rubber B has been separately plasticized and softened. This allows sufficient time for its star-shaped configuration to diffuse and penetrate into the phase domains surrounding the PTFE particles, provided that the PTFE premixed perfluoroether rubber B matrix already possesses sufficient molecular chain mobility. The bifunctional star-shaped compatibilizer is used at a ratio of 3 to 6 parts by weight relative to 20 to 30 parts by weight of the premixed PTFE emulsion perfluoroether rubber B, with a mass ratio of (3 to 6):(20 to 30). This dosage range ensures sufficient bridging molecular density in the interfacial region.

[0107] Step S7: Fusion of the two-phase matrix and mixing of filler.

[0108] 55 to 65 parts by weight of nitrile-cured perfluoroether rubber A are separately plasticized at a roller temperature of 60 to 70°C for 5 to 8 minutes. Then, the compatibilizer premix obtained in step S6 is added, and mixing continues for 15 to 20 minutes until the two phases are uniformly fused. The roller gap is then adjusted to 0.1 to 0.2 mm, and 8 to 12 parts by weight of the pretreated poly(fluoroethylene propylene) micropowder from step S5 are added in 3 to 5 batches. After each batch is added, the powder is allowed to penetrate sufficiently before adding the next batch. After all the poly(fluoroethylene propylene) micropowder has been added, mixing continues for 5 minutes. Then, 1 to 3 parts by weight of fumed silica are added in 2 to 3 batches. After all the silica has been added, mixing continues at a constant temperature for 10 to 15 minutes. The total filler mixing time is controlled at 15 to 20 minutes. During the mixing process, a cutting and folding operation is performed every 3 minutes.

[0109] It should be noted that the operational sequence of the nitrile-cured perfluoroether rubber A and the premixed perfluoroether rubber B of the emulsion PTFE differs from that in step 2. In this embodiment, the premixed perfluoroether rubber B of the emulsion PTFE is first prepared into a compatibilizer premix with a bifunctional star-shaped compatibilizer before being fused with the nitrile-cured perfluoroether rubber A. The purpose is to ensure that the bifunctional star-shaped compatibilizer is pre-anchored on one side of the premixed perfluoroether rubber B phase before the phase interface is formed between the nitrile-cured perfluoroether rubber A phase and the premixed perfluoroether rubber B phase, so that the bifunctional star-shaped compatibilizer can fully exert its bridging function in the interface region during subsequent fusion to form the phase interface. The batch addition method of the filler and the cutting blade folding operation are the same as in step 3.

[0110] Step S8: The second network precursor dispersion and sulfidation system is added.

[0111] Adjust the rolling mill temperature to 55-65℃. Add the second network precursor mixture obtained in step S4 to the rubber compound obtained in step S7 in 4-5 portions, mixing for 3-5 minutes after each addition to ensure the second network precursor mixture is fully dispersed and penetrates into the rubber compound and the phase interface region. After all the second network precursor mixture has been added, add 3-5 parts by weight of the metal-free triazine vulcanizing agent treated in step S5 to the rubber compound and mix for 5-8 minutes. Then add 0.8-1.8 parts by weight of the fluorinated organic base catalyst (perfluorotributylamine quaternary ammonium salt type, purity not less than 98%, metal impurities not higher than 5 μg / g) and mix for 5-8 minutes. The total mixing time for the two components should be controlled to 10-16 minutes. Finally, add the fluorinated internal release agent (perfluoropolyether wax type, kinematic viscosity V... 25℃ 50 to 150 mm 2 / s, where V 25℃ Add 0.1 to 0.3 parts by weight (kinematic viscosity at 25°C) and mix for 2 to 3 minutes. Strictly control the roller temperature throughout the process to not exceed 70°C.

[0112] In step S8, the second network precursor mixture must be fully dispersed before the addition of the metal-free triazine vulcanizing agent and the fluorinated organic base catalyst. The metal-free triazine vulcanizing agent and the fluorinated organic base catalyst can only be added sequentially after the second network precursor mixture has been added, with the fluorinated internal release agent added last. If the metal-free triazine vulcanizing agent and the fluorinated organic base catalyst are added before the second network precursor mixture, a nitrile trimerization reaction may occur in localized areas, forming preliminary gel points. This hinders the penetration of the second network precursor mixture into these areas, resulting in uneven spatial distribution of the second network. The roller temperature is controlled at 55 to 65°C, lower than the upper limit of the 60 to 70°C roller temperature range in step 4. This aims to suppress premature condensation reactions between the acyl fluoride groups and amine groups in the second network precursor mixture during the mixing stage, ensuring sufficient reaction within the specific temperature window of the subsequent gradient vulcanization.

[0113] After the vulcanization system is added, adjust the roller gap to 0.4 to 0.5 mm, reduce the roller temperature to 50 to 60°C, and perform thin-folding operations 2 to 3 times at a roller surface linear speed of 5 to 8 m / min, controlling the sheet thickness to 3 to 5 mm. Lay the film flat on a PTFE liner, cover it with a release film, and let it stand for 16 to 24 hours in a clean environment at room temperature (23±2°C) and relative humidity not exceeding 50% for curing. The cured compounded film must be processed within 72 hours.

[0114] All components are expressed in parts by weight. The complete formulation of Example 2 is as follows: 55 to 65 parts by weight of nitrile-cured perfluoroether rubber A, 20 to 30 parts by weight of emulsion polytetrafluoroethylene premixed perfluoroether rubber B, 3 to 6 parts by weight of bifunctional star-shaped compatibilizer, 8 to 12 parts by weight of polytetrafluoroethylene propylene micropowder, 1 to 3 parts by weight of fumed silica, 5 to 10 parts by weight of terminal acyl fluoride perfluoroether prepolymer, 1 to 3 parts by weight of three-arm perfluoroether amine crosslinking agent, 3 to 5 parts by weight of metal-free triazine vulcanizing agent, 0.8 to 1.8 parts by weight of fluorinated organic base catalyst, and 0.1 to 0.3 parts by weight of fluorinated internal release agent. The weight parts of the filler, vulcanizing agent, catalyst, compatibilizer, second network component, and release agent are calculated based on the amounts of nitrile-cured perfluoroether rubber A and emulsion polytetrafluoroethylene premixed perfluoroether rubber B.

[0115] Step S9: Pre-compression molding.

[0116] Based on the sealing ring cross-sectional diameter specifications of 8 to 12 mm (corresponding to large cross-section, high compression sealing conditions), cut the mixed rubber sheet obtained in step S8 according to a filling coefficient k of 1.05 to 1.10, where k is defined as the ratio of the billet volume to the mold cavity volume. Place the billet into the cleaned metal mold cavity, close the mold, and place it between the hot plates of a flat vulcanizing machine. Adjust the pre-compression temperature to 180 to 195℃, the pre-compression pressure to 16 to 20 MPa, and the holding time to 6 to 10 minutes. Perform an venting operation within 30 to 60 seconds after pressurization: release the pressure to about 0.5 MPa, hold for 5 seconds, and then raise it back to the set pressure. Repeat the venting cycle 3 to 4 times. After pre-compression is completed, slowly release the pressure to atmospheric pressure, open the mold, and check the appearance of the preform for defects such as missing parts and bubbles before proceeding to the next step.

[0117] Furthermore, the pre-compression temperature in this step is 180 to 195°C and the pressure is 16 to 20 MPa, which is higher than the temperature and pressure in step 5. Operators must wear high-temperature resistant protective gloves and ensure that the pressure is completely released before opening the mold to prevent burns caused by the high-temperature rubber material or the mold popping open.

[0118] It should be noted that, compared to step 5, this step increases the pre-compression temperature to 180-195℃, the pressure to 16-20 MPa, and the holding time to 6-10 minutes, while increasing the exhaust circulation to 3-4 times. The large cross-section sealing ring blank has a larger volume, resulting in a longer flow path for the adhesive within the cavity, requiring higher temperatures and pressures to provide sufficient flow driving force; the longer holding time and more exhaust circulation ensure that residual gas inside the large-volume blank is fully discharged.

[0119] Step S10: Gradient temperature vulcanization.

[0120] Place the preform obtained in step S9 on a clean polytetrafluoroethylene tray and send it into a programmable blast-drying oven. Control the heating rate of each section at 1.5 to 2.5 °C / min and carry out vulcanization according to the following procedure.

[0121] Low-temperature vulcanization section: Holding at 150-160℃ for 3 hours initiates the triazine cyclization reaction. The acyl fluoride groups of the terminal acyl fluoride perfluoropolyether prepolymer in the second network precursor mixture begin a condensation reaction with the primary amine groups of the three-arm perfluoropolyetheramine crosslinking agent at this temperature range. Subsequently, the temperature is raised to 180-195℃ and held for 4 hours. The triazine cyclization and second network condensation reactions proceed simultaneously. The nitrile arms of the bifunctional star-shaped compatibilizer participate in the first network triazine cyclization reaction, anchoring at the crosslinking nodes at the phase interface. The acyl fluoride arms undergo a condensation reaction with the primary amine groups of the three-arm perfluoropolyetheramine crosslinking agent in the second network, establishing a chemical interconnection bridge between the first and second networks in the phase interface region.

[0122] Medium-temperature vulcanization stage: Temperature is increased to 230-245℃ and held for 4 hours. Residual nitrile groups undergo further cyclization, increasing the crosslinking density of the first network. The three-dimensional elastomer structure of the second network becomes more complete, and the interpenetrating topological locking structure of the two networks is basically formed. The polytetrafluoroethylene propylene micropowder undergoes slight softening at temperatures below its melting point, further enhancing its interfacial bonding with the rubber matrix.

[0123] High-temperature setting stage: The temperature is increased to 275-290°C at a rate of 1-2°C / min and held for 14-16 hours. Residual nitrile groups almost completely participate in the triazine cyclization reaction, and both the first and second networks reach their final crosslinking density. The bifunctional star-shaped compatibilizer is completely cured by chemical anchoring at the phase interface. Under continuous air circulation, low molecular weight residues are fully volatilized and released, including decomposition products of the fluorinated organic base catalyst, unreacted residues of the metal-free triazine vulcanizing agent, volatile components of the fluorinated internal release agent, and unreacted small molecules remaining from the second network synthesis step.

[0124] Furthermore, the exhaust gas composition during the gradient temperature vulcanization process in this step is the same as that in step 6, but it additionally contains byproducts of the second network condensation reaction (including trace amounts of hydrogen fluoride) and unreacted small molecule volatiles. These must be fully absorbed and neutralized in an alkaline scrubbing tower before being discharged. The high-temperature setting section requires a holding time of 14 to 16 hours, and the alkaline solution in the oven exhaust gas treatment device must be regularly checked and replaced promptly to ensure absorption efficiency. The fluoride-containing waste liquid generated after alkaline absorption must be neutralized to neutral and then disposed of by a professional waste liquid treatment facility.

[0125] It should be noted that, compared to step 6, the low-temperature section of this step is divided into two sub-sections: 150 to 160°C and 180 to 195°C, each with its own holding temperature. This is to accommodate the respective reaction temperature windows of the amide condensation reaction (preferably starting temperature of approximately 150 to 160°C) in the second network precursor mixture and the triazine cyclization reaction (accelerated propagation temperature of approximately 180 to 195°C) in the first network. The holding time in the high-temperature setting section is extended to 14 to 16 hours to ensure that the residual active groups in the dual-network system react completely and to provide sufficient time for chain segment diffusion and chemical reaction of the higher molecular weight components in the second network precursor mixture.

[0126] In step S10, the nitrile group conversion rate was characterized by Fourier transform infrared spectroscopy (FTIR), using the same method as in step 6. After the high-temperature setting stage, the nitrile group conversion rate of the product was not less than 97%. The condensation conversion rate of the second network acyl fluoride was determined by fluorine-19 nuclear magnetic resonance spectroscopy (FMR). 19 Quantitative characterization was performed using F-NMR, and the change in the area of ​​the characteristic peak of the acyl fluoride group was calculated according to the following formula:

[0127]

[0128] in This represents the peak area of ​​the characteristic acyl fluoride group in the rubber compound before vulcanization. This represents the peak area of ​​the acyl fluoride group characteristic in the product after the high-temperature setting stage. This represents the condensation conversion rate of amide fluoride. The condensation conversion rate of the product after the high-temperature setting stage should not be less than 90%.

[0129] Step S11: Cooling, shaping, and post-processing.

[0130] After the high-temperature setting stage is completed, continue to run the forced-air circulation, cooling the product with the oven at a rate not exceeding 1.5℃ / min. Once the oven temperature drops below 50℃, use a non-metallic tool made of polytetrafluoroethylene to demold and remove the initial sealing ring.

[0131] The initial sealing ring is placed flat on a support frame in an ISO Class 6 clean room and left to stand for 36 to 48 hours at room temperature (23±2℃) and relative humidity not exceeding 50% for secondary shaping, so as to fully eliminate the residual thermal stress caused by the difference in relaxation rate between the two networks in the dual-network system.

[0132] After the secondary shaping is completed, the trimming operation is the same as in step 7. Cleaning is performed in an ISO Class 5 cleanroom, sequentially ultrasonically cleaned in ultrapure water (resistivity not less than 18.2 MΩ·cm) for 15 minutes, ultrasonically cleaned in semiconductor-grade isopropanol for 10 minutes, and then ultrasonically cleaned in ultrapure water for 15 minutes, followed by drying in a 60℃ clean oven for 3 hours. The time parameters for each cleaning step are extended compared to step 7 to fully remove trace amounts of low molecular weight residues introduced in the double-network synthesis step. After all indicators pass the test, the finished product sealing ring is placed in a double-layer clean polyethylene bag and heat-sealed for storage at a temperature of 15 to 25℃, relative humidity not exceeding 60%, and in the absence of light.

[0133] Furthermore, the semiconductor-grade isopropanol used in this cleaning step is a flammable organic solvent, and the operating precautions and waste liquid treatment methods are the same as in step 7.

[0134] In step S11, the ultrasonic frequency of each step of the ultrasonic cleaning process is controlled between 40 and 80 kHz, and the ultrasonic power density is between 0.3 and 0.8 W / cm². 2 The ultrasonic power density is defined as the ratio of the effective radiation power of the ultrasonic transducer to the bottom area of ​​the cleaning tank. The above parameter range ensures that trace amounts of low-molecular-weight residues introduced by the dual-network system are fully removed without damaging the surface of the sealing ring.

[0135] The finished sealing ring obtained in step S11 was characterized and identified by the following methods: the elastic recovery performance was characterized by compression set test (according to GB / T 7759 standard, 200℃, 72 hours, compression amount 25%); the thermogravimetric analysis (TGA) was used to determine the thermogravimetric initiation temperature; the metal element content in the finished product was detected by X-ray fluorescence spectrometry (XRF); the amount of ultra-trace metal ion precipitation on the surface of the finished product was detected by glow discharge mass spectrometry (GDMS); and the storage modulus and loss factor of the dual-network system were characterized by dynamic thermomechanical analysis (DMA) to confirm the formation of the dual-network interpenetrating topology.

[0136] This invention addresses three technical problems in existing technologies through synergistic optimization of four dimensions: matrix formulation, filler system, vulcanization system, and preparation process. These problems include excessively high compression set and insufficient resilience, insufficient plasma resistance due to metal ion migration and carbon-hydrogen bond introduction, and microcracks and debonding failure caused by thermal mismatch at the filler-matrix interface.

[0137] At the base rubber level, nitrile-cured perfluoroether rubber A ( (55 to 75, acrylonitrile content 0.5 to 2.0 mol%) and premixed perfluoroether rubber B with emulsion polytetrafluoroethylene. It is used in a compounding ratio of (60 to 70): (20 to 30) by weight of 80 to 120. The nitrile sites of the nitrile-cured perfluoroether rubber A form high-bond-energy triazine ring crosslinking nodes under the action of a metal-free triazine vulcanization system, endowing the co-crosslinked network with elastic recovery ability; the pre-dispersed ultrafine polytetrafluoroethylene particles in the emulsion polytetrafluoroethylene premixed perfluoroether rubber B are embedded in the crosslinked network to form physical reinforcement nodes, improving the resistance to stress relaxation. After the two are compounded, the co-crosslinked network has a better ability to resist molecular chain creep and slippage under long-term high-temperature and high-pressure conditions than either matrix alone, thereby reducing the compression set value and improving the resilience after cooling, thus solving technical problem one.

[0138] At the filler system level, perfluoroethylene propylene micro powder (D 50 (1 to 5 μm) and fumed silica (specific surface area 150 to 200 m²) 2 The perfluoroethylene propylene (PFEP) micropowder and the rubber matrix both belong to fluoropolymers and have similar coefficients of thermal expansion, fundamentally avoiding the interfacial debonding and microcrack problems caused by the difference in thermal expansion coefficients of traditional inorganic fillers, thus addressing technical problem three. PFEP micropowder itself is chemically inert to plasma; the PFEP particles uniformly dispersed on the surface of the sealing ring can form a chemically inert interface, mitigating the direct etching of the matrix by high-energy plasma. The nanoscale reinforcement of fumed silica further densifies the cross-linked structure and reduces the size of network defects. The amount of fumed silica is strictly controlled between 1 and 3 parts by weight to avoid affecting cleanliness due to excessive introduction of silanol release sources.

[0139] At the vulcanization system level, the metal-free triazine vulcanization system generates symmetrical six-membered triazine ring crosslinking nodes in situ through nitrile trimerization, without introducing any metal catalysts or metal oxide additives throughout the process, thus eliminating the source of metal ion precipitation. In the triazine crosslinking network, both the crosslinking nodes and the molecular chain backbone are in a chemical environment rich in carbon-fluorine bonds (C–F bonds) and contain no carbon-hydrogen bonds (C–H bonds), thereby eliminating the chemical initiation sites for main chain degradation caused by plasma-active particles through hydrogen abstraction reactions. The high-temperature setting stage, under continuous air circulation, fully volatilizes and removes low-molecular-weight residues, ensuring that the amount of metal ion precipitation and volatile organic compound release in the product meets the cleanliness requirements of sealing materials in semiconductor processes, thus addressing technical problem two.

[0140] At the manufacturing process level, the segmented open mixing process (first mixing premixed PTFE emulsion perfluoroether rubber B, then mixing nitrile-based cured perfluoroether rubber A, with fillers added in batches and a final low-speed thin pass) helps to achieve uniform dispersion of fillers and suppress scorching in high-viscosity perfluoroether rubber compounds. The gradient temperature vulcanization process (three-stage gradual temperature increase from low to high temperature) ensures that the crosslinking reaction proceeds uniformly from the outside to the inside, eliminating the defect of excessive surface crosslinking and insufficient internal crosslinking in one-step isothermal vulcanization, while also alleviating the interfacial micro-stress caused by the difference in thermal expansion between the filler and the matrix.

[0141] In the further enhanced scheme of Example 2, a bifunctional star-shaped compatibilizer (Mn of 8000 to 15000) simultaneously participates in the triazine cyclization reaction of the first network and the condensation reaction of the second network through the nitrile arm in the phase interface region, establishing a covalent chemical bridge across the phase interface. The three-arm perfluoropolyetheramine crosslinking agent enables the second network to form a three-dimensional network elastomer topology, forming an interpenetrating locked structure with the first network. This allows the interface region to simultaneously possess the creep resistance brought by high crosslinking density and the independent elastic recovery capability brought by the three-dimensional elastomer, eliminating the limitation in Example 1 where the interface region became a preferential channel for plasma erosion and creep coupling failure due to the relatively low crosslinking density. The chemical properties of the crosslinking nodes of both networks are mainly carbon-fluorine bonds (C–F bonds), maintaining a chemical resistance to erosion and a cleanliness level comparable to Example 1 under high-energy plasma environment.

[0142] Furthermore, the fluorinated compounds involved in the overall preparation process of this invention, such as perfluorotributylamine, perfluoroglutaronitrile, perfluoroadipoxyfluoride, and perfluoropropylene oxide oligomers, are all substances with high global warming potential. The fluorinated organic waste gases emitted during distillation, vacuum removal, and forced-air discharge in each step must undergo tail gas absorption treatment before being released. The fluorinated organic waste liquids and solid wastes generated in each step must be collected separately and disposed of by a professional hazardous waste treatment agency to meet environmental protection requirements. This invention uses a metal-free triazine sulfidation system to replace the traditional metal oxide peroxide sulfidation system, eliminating the generation of metal ion pollutants at the source and embodying the green chemistry principle of pollution reduction at the source.

[0143] In summary, this invention addresses three key technical issues in advanced semiconductor manufacturing processes of traditional perfluoroether rubber seals: high compression set and insufficient cooling resilience; plasma erosion and cavity contamination caused by metal ion precipitation and carbon-hydrogen bond introduction; and microcracks and debonding failure caused by interfacial thermal mismatch of fluorinated fillers. These issues are addressed through a four-pronged synergistic effect: reducing molecular chain creep and slippage tendency through matrix compounding; synergistic reinforcement by fluorinated fillers to eliminate interfacial thermal mismatch; metal ion precipitation and carbon-hydrogen bond introduction; and interfacial thermal mismatch of fluorinated fillers.

[0144] Implementation Example 1

[0145] Following the process in Example 1, each parameter is taken as its minimum endpoint value. The poly(fluoroethylene propylene) micro powder (D... 50 = 1 μm) 8 parts by weight of fumed silica (specific surface area 150 m²) 2 One part by weight of the triazine sulfide agent (average primary particle size 12 nm) was placed in a clean stainless steel dish and dried at 100°C for 2 hours. After cooling, it was sealed and stored for later use. Two parts by weight of the metal-free triazine sulfide agent were ground through a 200-mesh sieve and sealed for later use.

[0146] Preheat the two-roll open mill to 60°C and adjust the roll spacing to 1.5 mm. Add the emulsion polytetrafluoroethylene premixed perfluoroether rubber B (Mooney viscosity). = 80) 20 parts by weight, separately masticated for 8 minutes; then nitrile-based curing perfluoroether rubber A (Mounney viscosity) was added. = 55, acrylonitrile content 0.5 mol%, Tg = -10℃) 60 parts by weight, continue mixing for 10 minutes, total plasticizing time 18 minutes.

[0147] Adjust the roller gap to 0.1 mm and maintain the roller temperature at 60℃. Add the polytetrafluoroethylene propylene micro powder in three batches, and continue mixing for 5 minutes after all the powder has been added. Then add the fumed silica in two batches, and mix at a constant temperature for 10 minutes after all the silica has been added. The total filling mixing time is 15 minutes, and the cutting blade is folded every 3 minutes.

[0148] Add 2 parts by weight of metal-free triazine vulcanizing agent and mix for 5 minutes; then add 0.5 parts by weight of fluorinated organic base catalyst and mix for 5 minutes; finally add fluorinated internal release agent (V 25℃ = 50 mm 2 Mix 0.1 parts by weight (per s) for 2 minutes, for a total mixing time of 12 minutes for all three components, with the roller temperature strictly not exceeding 75°C. Adjust the roller gap to 0.4 mm, reduce the roller temperature to 50°C, and pass through the sheet twice at a linear speed of 5 m / min, producing a sheet thickness of 3 mm. Lay the film flat on a PTFE backing and allow it to cure for 12 hours in a clean environment at room temperature (23±2°C) and relative humidity not exceeding 50%.

[0149] The blanks were cut according to the filling coefficient k = 1.05, the pre-compression temperature was 170℃, the pre-compression pressure was 12 MPa, the pressure was held for 3 minutes, and the exhaust circulation was repeated twice.

[0150] Vulcanization was carried out according to the following gradient heating procedure, with a heating rate of 2℃ / min for each stage: Low-temperature stage: held at 150℃ for 2 hours, 170℃ for 2 hours, and 220℃ for 2 hours sequentially; Medium-temperature stage: held at 230℃ for 2 hours; High-temperature setting stage: heated to 270℃ at 1℃ / min and held for 10 hours. The furnace cooling rate should not exceed 1℃ / min, and the product should be removed when cooled to below 60℃. After a second setting in an ISO Class 6 cleanroom for 24 hours, the product was trimmed and then ultrasonically cleaned sequentially (10 minutes with ultrapure water → 10 minutes with semiconductor-grade isopropanol → 10 minutes with ultrapure water, ultrasonic frequency 40 kHz, ultrasonic power density 0.3 W / cm³). 2 Dry at 60℃ for 2 hours, heat-seal packaging, and store at 15℃.

[0151] Implementation Example 2

[0152] Following the process described in Example 1, each parameter was taken at its maximum endpoint value. The poly(fluoroethylene propylene) micro powder (D... 50 = 5 μm) 12 parts by weight of fumed silica (specific surface area 200 m²) 2 Three parts by weight (g, average primary particle size 20 nm) were dried at 120℃ for 3 hours, cooled, and sealed for later use. Four parts by weight of the metal-free triazine sulfiding agent were ground through a 200-mesh sieve and sealed for later use.

[0153] Preheat the two-roll open mill to 70°C and adjust the roll gap to 2.0 mm. Add the emulsion polytetrafluoroethylene premixed perfluoroether rubber B (Mooney viscosity). = 120) 30 parts by weight, separately masticated for 10 minutes; then nitrile-based curing perfluoroether rubber A (Mounney viscosity) was added. = 75, acrylonitrile content 2.0 mol%, Tg = 5℃) 70 parts by weight, continue mixing for 15 minutes, total plasticizing time 25 minutes.

[0154] Adjust the roller gap to 0.2 mm and maintain the roller temperature at 70℃. Add the polytetrafluoroethylene propylene micro powder in 5 batches, and continue mixing for 5 minutes after all the powder has been added. Then add the fumed silica in 3 batches, and mix at a constant temperature for 15 minutes after all the silica has been added. The total mixing time for the fillers is 20 minutes, and a cutting and folding operation is performed every 3 minutes.

[0155] Add 4 parts by weight of metal-free triazine vulcanizing agent and mix for 5 minutes; then add 1.5 parts by weight of fluorinated organic base catalyst and mix for 5 minutes; finally add fluorinated internal release agent (V 25℃ = 150 mm 2Mix 0.3 parts by weight of the three components for 5 minutes, with a total mixing time of 15 minutes. The roller temperature must not exceed 75°C. Adjust the roller gap to 0.5 mm, reduce the roller temperature to 60°C, and pass through the sheet 3 times at a linear speed of 8 m / min to produce a sheet thickness of 5 mm. Lay the film flat on a PTFE backing and allow it to cure for 24 hours in a clean environment at room temperature (23±2°C) and relative humidity not exceeding 50%.

[0156] Cut the billet according to the filling coefficient k = 1.10, pre-press temperature 190℃, pre-press pressure 18 MPa, hold pressure for 5 minutes, and vent and circulate 3 times.

[0157] Vulcanization was carried out according to the following gradient heating program, with a heating rate of 3℃ / min for each stage: Low-temperature stage: 160℃ for 2 hours, 190℃ for 2 hours, and 230℃ for 2 hours sequentially; Medium-temperature stage: 250℃ for 2 hours; High-temperature setting stage: heating at 2℃ / min to 290℃ and holding for 10 hours. The furnace cooling rate should not exceed 2℃ / min, and the product should be removed when cooled to below 60℃. After a second setting in an ISO Class 6 cleanroom for 24 hours, the product was trimmed and then ultrasonically cleaned (10 minutes with ultrapure water → 10 minutes with semiconductor-grade isopropanol → 10 minutes with ultrapure water, ultrasonic frequency 80 kHz, power density 0.8 W / cm³). 2 Each step is the same as in Example 1. Dry at 60°C for 2 hours, heat-seal packaging, and store at 25°C.

[0158] Implementation Example 3

[0159] Following the process in Example 1, intermediate values ​​(including preferred values) were taken for each parameter. The poly(fluoroethylene propylene) micro powder (D... 50 = 3 μm) 10 parts by weight of fumed silica (specific surface area 175 m²) 2 Two parts by weight of the triazine sulfide agent (with an average primary particle size of 16 nm) were dried at 110°C for 2.5 hours, cooled, and sealed for later use. Three parts by weight of the metal-free triazine sulfide agent were ground through a 200-mesh sieve and sealed for later use.

[0160] Preheat the two-roll open mill to 65°C and adjust the roll gap to 1.8 mm. Add the emulsion polytetrafluoroethylene premixed perfluoroether rubber B (Mooney viscosity). = 100) 25 parts by weight, separately masticated for 9 minutes; then nitrile-based curing perfluoroether rubber A (Mounney viscosity) was added. = 65, acrylonitrile content 1.0 mol%, Tg = -3℃) 65 parts by weight, continue mixing for 12 minutes, total plasticizing time 21 minutes.

[0161] Adjust the roller gap to 0.15 mm and maintain the roller temperature at 65℃. Add the polytetrafluoroethylene propylene micro powder in four batches, and continue mixing for 5 minutes after all the powder has been added. Then add the fumed silica in two batches, and mix at a constant temperature for 12 minutes after all the silica has been added. The total mixing time for the filler is 17 minutes, and the cutter is folded every 3 minutes.

[0162] Add 3 parts by weight of metal-free triazine vulcanizing agent sequentially and mix for 5 minutes; then add 1.0 part by weight of fluorinated organic base catalyst and mix for 5 minutes; finally add fluorinated internal release agent (V 25℃ = 100 mm 2 Mix 0.2 parts by weight of the film (per s) for 3 minutes, for a total mixing time of 13 minutes, with the roller temperature strictly not exceeding 75°C. Adjust the roller gap to 0.45 mm, reduce the roller temperature to 55°C, and pass through the film twice at a linear speed of 6.5 m / min, producing a sheet thickness of 4 mm. Lay the film flat on a PTFE backing and allow it to cure for 18 hours in a clean environment at room temperature (23±2°C) and relative humidity not exceeding 50%.

[0163] The blanks are cut according to the filling coefficient k = 1.08, the pre-compression temperature is 180℃, the pre-compression pressure is 15 MPa, the pressure is held for 4 minutes, and the exhaust circulation is repeated twice.

[0164] Vulcanization was carried out according to the following gradient heating program, with a heating rate of 2.5℃ / min for each stage: Low-temperature stage: 155℃ for 2 hours, 180℃ for 2 hours, and 225℃ for 2 hours sequentially; Medium-temperature stage: 240℃ for 2 hours; High-temperature setting stage: heating to 280℃ at 1.5℃ / min and holding for 10 hours. The furnace cooling rate should not exceed 1℃ / min, and the product should be removed when cooled to below 60℃. After a second setting in an ISO Class 6 cleanroom for 24 hours, the product was trimmed and then ultrasonically cleaned (10 minutes with ultrapure water → 10 minutes with semiconductor-grade isopropanol → 10 minutes with ultrapure water, ultrasonic frequency 60 kHz, power density 0.5 W / cm³). 2 Each step is the same as in Example 1. Dry at 60°C for 2 hours, heat-seal packaging, and store at 20°C.

[0165] Implementation Example 4

[0166] According to the process of Example 2, the minimum endpoint value is taken for each parameter.

[0167] Step S1: 8 parts by weight of perfluoropentaerythritol and 30 parts by weight of perfluorobutyltetrahydrofuran were added to a glass-lined reactor. Perfluorotributylamine was used as the solvent (1.5 times the total mass of the reactants). Under argon protection, with a reactor gauge pressure of 0.1 MPa and a heating rate of 2 °C / min, the temperature was raised to 160 °C for 8 hours for ring-opening polymerization to obtain a four-armed star-shaped perfluorocyclic ether intermediate. 100 parts by weight of the intermediate were taken, and the ends of two arms were reacted with 3 parts by weight of perfluoroglutaronitrile at 140 °C for 4 hours under nitrogen protection and a stirring speed of 100 rpm to complete nitrile grafting. The other two arms were reacted with 2 parts by weight of perfluoroadipoxyfluoride at 100 °C for 2 hours to complete acyl fluoride grafting. The mixture was purified by vacuum distillation (vacuum degree not exceeding 100 Pa, distillation temperature 120 °C) to obtain a bifunctional star-shaped compatibilizer with Mn = 8000.

[0168] Step S2: 100 parts by weight of perfluoropolyether diol (Mn = 2000) and 12 parts by weight of perfluoroadipoxy fluoride (molar ratio of perfluoropolyether diol to perfluoroadipoxy fluoride 1:1.05) were polycondensed at 80°C for 4 hours under nitrogen protection and stirring speed of 100 rpm. Then, the solvent was removed under vacuum at 60°C with a vacuum degree not exceeding 200 Pa to obtain a terminal acyl fluoride perfluoropolyether prepolymer with Mn = 8000, which was sealed and stored in an environment not exceeding 5°C.

[0169] Step S3: 5 parts by weight of perfluoromelamine and 15 parts by weight of perfluoropropylene oxide oligomer (terminated epoxy group, Mn = 500) were subjected to a ring-opening addition reaction at 100°C for 3 hours under nitrogen protection and stirring speed of 150 rpm. Unreacted monomers were then removed under vacuum at 80°C with a vacuum degree not exceeding 100 Pa to obtain a three-arm perfluoropolyetheramine crosslinking agent with Mn = 2500.

[0170] Step S4: Mix 5 parts by weight of terminal acyl fluoride perfluoropolyether prepolymer and 1 part by weight of three-arm perfluoropolyether amine crosslinker (acyl fluoride to primary amine molar ratio of approximately 1:0.8) with magnetic stirring for 15 minutes at room temperature (23±2℃) and relative humidity not exceeding 40% to obtain a second network precursor mixture. Prepare immediately before use and store for no more than 4 hours.

[0171] Step S5: The filler pretreatment and vulcanizing agent refining operations are the same as in Example 1, using polytetrafluoroethylene propylene micro powder (D... 50 = 1μm) 8 parts by weight, fumed silica (specific surface area 150 m²) 2 / g, average primary particle size 12 nm) 1 part by weight, all dried at 100℃ for 2 hours; 3 parts by weight of metal-free triazine sulfide agent were ground through a 200-mesh sieve and sealed for later use.

[0172] Step S6: Preheat the two-roll open mill to 60°C, adjust the roll gap to 1.5 mm, and add the premixed polytetrafluoroethylene emulsion perfluoroether rubber B (Mooney viscosity). = 80) 20 parts by weight, separately plasticize for 8 minutes until fully softened; then add 3 parts by weight of bifunctional star-shaped compatibilizer to the roller surface compound in 2 portions, and continue to mix for 12 minutes to obtain the compatibilized premix.

[0173] Step S7: Apply nitrile-based cured perfluoroether rubber A (Mooney viscosity) = 55, acrylonitrile content 0.5 mol%, Tg = -10℃) 55 parts by weight were separately plasticized at a roller temperature of 60℃ for 5 minutes, then the compatibilizer premix obtained in step S6 was added, and mixing was continued for 15 minutes until the two phase matrices were uniformly fused. The roller gap was adjusted to 0.1 mm, and the polytetrafluoroethylene propylene micro powder was added in 3 batches. After all the powder was added, mixing was continued for 5 minutes. Then the fumed silica was added in 2 batches. After all the powder was added, mixing was carried out at a constant temperature for 10 minutes. The total filling mixing time was 15 minutes, and the cutter was folded once every 3 minutes.

[0174] Step S8: Adjust the rolling mill temperature to 55°C. Add the second network precursor mixture to the rubber compound from Step S7 in four batches, mixing for 3 minutes after each addition. Then add 3 parts by weight of the metal-free triazine vulcanizing agent and mix for 5 minutes. Next, add 0.8 parts by weight of the fluorinated organic base catalyst and mix for 5 minutes. The total mixing time for the two components is 10 minutes. Finally, add the fluorinated internal release agent (V... 25℃ = 50 mm 2 Mix 0.1 parts by weight of film for 2 minutes, ensuring the roller temperature does not exceed 70℃ throughout the process. Adjust the roller gap to 0.4mm, reduce the roller temperature to 50℃, and pass through the film twice at a linear speed of 5 m / min, producing a sheet thickness of 3 mm. Allow the film to cure for 16 hours in a clean environment at room temperature (23±2℃) and relative humidity not exceeding 50%.

[0175] Step S9: Cut the blank according to the sealing ring specification of 8 mm cross-section diameter (k = 1.05), pre-press temperature 180℃, pre-press pressure 16 MPa, hold pressure for 6 minutes, and vent and circulate 3 times.

[0176] Step S10: The heating rate for each section is 1.5℃ / min; the low-temperature section is held at 150℃ for 3 hours, followed by a holding at 180℃ for 4 hours; the medium-temperature section is held at 230℃ for 4 hours; the high-temperature setting section is heated to 275℃ at a rate of 1℃ / min and held for 14 hours. The furnace cooling rate is no higher than 1℃ / min, and the furnace is removed when the temperature drops below 50℃.

[0177] Step S11: Place the item flat in an ISO Class 6 cleanroom and allow it to set for 36 hours. After trimming, perform ultrasonic cleaning sequentially (15 minutes with ultrapure water → 10 minutes with semiconductor-grade isopropanol → 15 minutes with ultrapure water; ultrasonic frequency 40 kHz, ultrasonic power density 0.3 W / cm³). 2 Dry at 60℃ for 3 hours, heat-seal packaging, and store at 15℃.

[0178] Implementation Example 5

[0179] According to the process of Example 2, the maximum endpoint value of each parameter is taken.

[0180] Step S1: 12 parts by weight of perfluoropentaerythritol and 50 parts by weight of perfluorobutyltetrahydrofuran were added to a glass-lined reactor. Perfluorotributylamine was used as the solvent (2.5 times the total mass of the reactants). Under argon protection, with a reactor gauge pressure of 0.3 MPa and a heating rate of 5 °C / min, the temperature was raised to 180 °C for 12 hours to complete the ring-opening polymerization reaction, yielding a four-armed star-shaped perfluorocyclic ether intermediate. 100 parts by weight of the intermediate were taken, and two arms were reacted with 5 parts by weight of perfluoroglutaronitrile at 160 °C for 6 hours under nitrogen protection and a stirring speed of 200 rpm to complete nitrile grafting. The other two arms were reacted with 4 parts by weight of perfluoroadipoxyfluoride at 120 °C for 4 hours to complete acyl fluoride grafting. The mixture was purified by vacuum distillation (vacuum degree not exceeding 100 Pa, distillation temperature 150 °C) to obtain a bifunctional star-shaped compatibilizer with Mn = 15000.

[0181] Step S2: 100 parts by weight of perfluoropolyether diol (Mn = 4000) and 18 parts by weight of perfluoroadipyl fluoride (molar ratio of perfluoropolyether diol to perfluoroadipyl fluoride 1:1.08) were polycondensed at 100°C for 6 hours under nitrogen protection and stirring speed of 200 rpm. Then, the solvent was removed under vacuum at 80°C and a vacuum degree not exceeding 200 Pa to obtain a terminal acyl fluoride perfluoropolyether prepolymer with Mn = 15000, which was sealed and stored in an environment not exceeding 5°C.

[0182] Step S3: 8 parts by weight of perfluoromelamine and 25 parts by weight of perfluoropropylene oxide oligomer (terminated epoxy group, Mn = 1000) were subjected to a ring-opening addition reaction at 120°C for 5 hours under nitrogen protection and stirring speed of 300 rpm. Unreacted monomers were then removed under vacuum at 100°C and a vacuum degree not exceeding 100 Pa to obtain a three-arm perfluoropolyetheramine crosslinking agent with Mn = 5000.

[0183] Step S4: Mix 10 parts by weight of terminal acyl fluoride perfluoropolyether prepolymer and 3 parts by weight of three-arm perfluoropolyether amine crosslinker (acyl fluoride to primary amine molar ratio of approximately 1:1.2) at room temperature (23±2℃) and relative humidity not exceeding 40% for 20 minutes to obtain a second network precursor mixture. Prepare immediately before use and store for no more than 4 hours.

[0184] Step S5: The filler pretreatment and vulcanizing agent refining operations are the same as in Example 2, using polytetrafluoroethylene propylene micro powder (D... 50 = 5μm) 12 parts by weight, fumed silica (specific surface area 200 m²) 2 / g, average primary particle size 20 nm) 3 parts by weight, all dried at 120℃ for 3 hours; 5 parts by weight of metal-free triazine sulfide agent were ground through a 200-mesh sieve and sealed for later use.

[0185] Step S6: Preheat the two-roll mill to 70°C, adjust the roll gap to 2.0 mm, and add the premixed polytetrafluoroethylene emulsion perfluoroether rubber B (Mooney viscosity). = 120) 30 parts by weight, separately plasticized for 10 minutes; then add 6 parts by weight of bifunctional star-shaped compatibilizer in 3 portions, and continue to mix for 18 minutes to obtain compatibilized premix.

[0186] Step S7: Apply nitrile-based cured perfluoroether rubber A (Mooney viscosity) = 75, acrylonitrile content 2.0 mol%, Tg = 5℃) 65 parts by weight were individually plasticized at a roller temperature of 70℃ for 8 minutes, then the compatibilizer premix was added, and mixing was continued for 20 minutes until uniformly blended. The roller gap was adjusted to 0.2 mm, and the polytetrafluoroethylene propylene micro powder was added in 5 batches. After all the powder was added, mixing was continued for 5 minutes. Then the fumed silica was added in 3 batches. After all the powder was added, mixing was carried out at a constant temperature for 15 minutes. The total filling mixing time was 20 minutes, and the cutter was folded once every 3 minutes.

[0187] Step S8: Adjust the rolling mill temperature to 65°C. Add the second network precursor mixture to the rubber compound from Step S7 in 5 portions, mixing for 5 minutes after each addition. Then add 5 parts by weight of the metal-free triazine vulcanizing agent and mix for 8 minutes. Next, add 1.8 parts by weight of the fluorinated organic base catalyst and mix for 8 minutes. The total mixing time for the two components is 16 minutes. Finally, add the fluorinated internal release agent (V... 25℃ = 150 mm 2 Mix 0.3 parts by weight of the film for 3 minutes, ensuring the roller temperature does not exceed 70°C throughout the process. Adjust the roller gap to 0.5 mm, reduce the roller temperature to 60°C, and pass through the film 3 times at a linear speed of 8 m / min, producing a sheet thickness of 5 mm. Allow the film to cure for 24 hours in a clean environment at room temperature (23±2°C) and relative humidity not exceeding 50%.

[0188] Step S9: Cut the blank according to the sealing ring specification of 12 mm cross-section diameter (k = 1.10), pre-press temperature 195℃, pre-press pressure 20 MPa, hold pressure for 10 minutes, and venting cycle 4 times.

[0189] Step S10: The heating rate for each section is 2.5℃ / min; the low-temperature section is held at 160℃ for 3 hours, followed by a holding at 195℃ for 4 hours; the medium-temperature section is held at 245℃ for 4 hours; the high-temperature setting section is heated to 290℃ at a rate of 2℃ / min and held for 16 hours. The furnace cooling rate is no higher than 1.5℃ / min, and the furnace is removed when the temperature drops below 50℃.

[0190] Step S11: Place the item flat in an ISO Class 6 cleanroom and allow it to set for 48 hours for a second shaping process. After trimming, perform ultrasonic cleaning (15 minutes with ultrapure water → 10 minutes with semiconductor-grade isopropanol → 15 minutes with ultrapure water, ultrasonic frequency 80 kHz, ultrasonic power density 0.8 W / cm³). 2 Dry at 60℃ for 3 hours, heat-seal packaging, and store at 25℃.

[0191] Implementation Example 6

[0192] According to the process of Example 2, the intermediate values ​​(including preferred values) of each parameter are taken.

[0193] Step S1: 10 parts by weight of perfluoropentaerythritol and 40 parts by weight of perfluorobutyltetrahydrofuran were added to a glass-lined reactor. Perfluorotributylamine was used as the solvent (2.0 times the total mass of the reactants). Under argon protection, with a reactor gauge pressure of 0.2 MPa and a heating rate of 3 °C / min, the temperature was raised to 170 °C for 10 hours to complete the ring-opening polymerization reaction, yielding a four-armed star-shaped perfluorocyclic ether intermediate. 100 parts by weight of the intermediate were taken, and two arms were reacted with 4 parts by weight of perfluoroglutaronitrile at 150 °C for 5 hours under nitrogen protection and a stirring speed of 150 rpm to complete nitrile grafting. The other two arms were reacted with 3 parts by weight of perfluoroadipoxyfluoride at 110 °C for 3 hours to complete acyl fluoride grafting. The mixture was purified by vacuum distillation (vacuum degree not exceeding 100 Pa, distillation temperature 135 °C) to obtain a bifunctional star-shaped compatibilizer with Mn = 11500.

[0194] Step S2: 100 parts by weight of perfluoropolyether diol (Mn = 3000) and 15 parts by weight of perfluoroadipyl fluoride (molar ratio of perfluoropolyether diol to perfluoroadipyl fluoride 1:1.10) were polycondensed at 90°C for 5 hours under nitrogen protection and stirring speed of 150 rpm. Then, the solvent was removed under vacuum at 70°C and a vacuum degree not exceeding 200 Pa to obtain a terminal acyl fluoride perfluoropolyether prepolymer with Mn = 11500, which was sealed and stored in an environment not exceeding 5°C.

[0195] Step S3: 6.5 parts by weight of perfluoromelamine and 20 parts by weight of perfluoropropylene oxide oligomer (terminated epoxy group, Mn = 750) were subjected to a ring-opening addition reaction at 110°C for 4 hours under nitrogen protection and stirring speed of 225 rpm. Unreacted monomers were then removed under vacuum at 90°C with a vacuum degree not exceeding 100 Pa to obtain a three-arm perfluoropolyetheramine crosslinking agent with Mn = 3750.

[0196] Step S4: Mix 7.5 parts by weight of terminal acyl fluoride perfluoropolyether prepolymer and 2 parts by weight of three-arm perfluoropolyether amine crosslinker (acyl fluoride to primary amine molar ratio of approximately 1:1.0) at room temperature (23±2℃) and relative humidity not exceeding 40% for 17 minutes to obtain a second network precursor mixture. Prepare immediately before use and store for no more than 4 hours.

[0197] Step S5: The filler pretreatment and vulcanizing agent refining operations are the same as in Example 3, using polytetrafluoroethylene propylene micro powder (D 50 = 3μm) 10 parts by weight, fumed silica (specific surface area 175 m²) 2 / g, average primary particle size 16 nm) 2 parts by weight, both dried at 110℃ for 2.5 hours; 4 parts by weight of metal-free triazine sulfide agent were ground through a 200-mesh sieve and sealed for later use.

[0198] Step S6: Preheat the two-roll mill to 65°C, adjust the roll gap to 1.8 mm, and add the premixed polytetrafluoroethylene emulsion perfluoroether rubber B (Mooney viscosity). = 100) 25 parts by weight, separately plasticized for 9 minutes; then add 4.5 parts by weight of bifunctional star-shaped compatibilizer in 2 portions, and continue to mix for 15 minutes to obtain compatibilized premix.

[0199] Step S7: Apply nitrile-based cured perfluoroether rubber A (Mooney viscosity) = 65, acrylonitrile content 1.0 mol%, Tg = -3℃) 60 parts by weight were individually plasticized at a roller temperature of 65℃ for 6.5 minutes, then the compatibilizer premix was added, and mixing was continued for 17 minutes until uniformly blended. The roller gap was adjusted to 0.15 mm, and the polytetrafluoroethylene propylene micro powder was added in 4 batches. After all the powder was added, mixing was continued for 5 minutes. Then the fumed silica was added in 2 batches. After all the powder was added, mixing was carried out at a constant temperature for 12 minutes. The total filling mixing time was 17 minutes, and the cutter was folded once every 3 minutes.

[0200] Step S8: Adjust the rolling mill temperature to 60℃, add the second network precursor mixture to the rubber compound from Step S7 in four batches, mixing for 4 minutes after each addition; then add 4 parts by weight of the metal-free triazine vulcanizing agent and mix for 6.5 minutes, followed by 1.3 parts by weight of the fluorinated organic base catalyst and mix for 6.5 minutes. The total mixing time for the two components is 13 minutes. Finally, add the fluorinated internal release agent (V... 25℃ = 100 mm 2Mix 0.2 parts by weight of the film for 2.5 minutes, ensuring the roller temperature does not exceed 70°C throughout the process. Adjust the roller gap to 0.45 mm, reduce the roller temperature to 55°C, and pass through the film twice at a linear speed of 6.5 m / min, producing a sheet thickness of 4 mm. Allow the film to cure for 20 hours in a clean environment at room temperature (23±2°C) and relative humidity not exceeding 50%.

[0201] Step S9: Cut the blank according to the sealing ring specification of 10 mm cross-section diameter (k = 1.08), pre-press temperature 187℃, pre-press pressure 18 MPa, hold pressure for 8 minutes, and exhaust circulation 3 times.

[0202] Step S10: The heating rate for each section is 2.0℃ / min; the low-temperature section is held at 155℃ for 3 hours, followed by a holding at 187℃ for 4 hours; the medium-temperature section is held at 237℃ for 4 hours; the high-temperature setting section is heated to 282℃ at a rate of 1.5℃ / min and held for 15 hours. The furnace cooling rate is no higher than 1℃ / min, and the furnace is removed when the temperature drops below 50℃.

[0203] Step S11: Place the item flat in an ISO Class 6 cleanroom and allow it to set for 42 hours for a second shaping process. After trimming, perform ultrasonic cleaning (15 minutes with ultrapure water → 10 minutes with semiconductor-grade isopropanol → 15 minutes with ultrapure water, ultrasonic frequency 60 kHz, ultrasonic power density 0.5 W / cm³). 2 Dry at 60℃ for 3 hours, heat-seal packaging, and store at 20℃.

[0204] Comparative Example 1

[0205] The process of Example 1 is followed (parameters are the same as the intermediate value group of Example 3), but the metal-free triazine vulcanizing agent and the fluorinated organic base catalyst are replaced with a conventional peroxide vulcanization system: in the step of adding vulcanizing components, 2 parts by weight of dicumyl peroxide replace 3 parts by weight of the metal-free triazine vulcanizing agent, and 3 parts by weight of zinc oxide replace 1.0 part by weight of the fluorinated organic base catalyst. The base rubber, filler system, mixing process, sheeting parameters, and gradient temperature vulcanization procedure are all completely consistent with Example 3.

[0206] Comparative Example 2

[0207] The process of Example 1 (the base rubber, filler system, vulcanization system, and mixing parameters are completely consistent with Example 3) is followed, but the gradient temperature vulcanization program is changed to a single constant temperature vulcanization at 240℃ for 6 hours, with a heating rate of 2.5℃ / min to 240℃. The step-by-step holding process for low-temperature, medium-temperature, and high-temperature setting stages is omitted. The total vulcanization time is similar to the cumulative holding time of the gradient temperature vulcanization in Example 3 (approximately 6 hours). All other post-processing parameters remain consistent with Example 3.

[0208] Experimental test:

[0209] The technical effects of the plasma-resistant and compression-deformation-resistant perfluoroether rubber sealing ring of the present invention are verified in the following three aspects: First, by replacing the traditional peroxide vulcanization system with a metal-free triazine vulcanization system, metal ion precipitation contamination is eliminated and plasma erosion resistance is improved; Second, the cross-linked network is homogenized through a three-stage gradient temperature vulcanization process, reducing the compression set value and improving elastic recovery performance; Third, by introducing a bifunctional star-shaped compatibilizer and a second network precursor system in Example 2, weak links at the phase interface are further eliminated, further reducing the compression set value under high compression conditions with large cross-sections. The control experiments of Examples 1 to 6 and Comparative Examples 1 and 2 correspond to the above three technical effects, respectively.

[0210] Experimental sample preparation:

[0211] Finished sealing ring samples were prepared according to the formulations and processes of Examples 1 to 6 and Comparative Examples 1 and 2, respectively. The sample numbers were Sample 1 to Sample 6, Control Sample 1, and Control Sample 2, respectively. The sealing ring cross-sectional diameter used in Examples 1 to 3 and Comparative Examples 1 and 2 was 5 mm (standard cross-sectional condition); the sealing ring cross-sectional diameters used in Examples 4 to 6 were 8 mm, 12 mm, and 10 mm, respectively (large cross-sectional high compression condition). Five samples were prepared for each group for performance testing, and the average value was taken as the final result.

[0212] Experimental conditions:

[0213] Compression set test: Press The standard test temperature is 200℃, the compression time is 72 hours, the compression amount is 25%, and the test medium is air.

[0214] Characterization of nitrile conversion: Fourier transform infrared spectroscopy (FTIR) was used, with wavelengths ranging from 2230 to 2240 cm⁻¹. -1 The change in the area of ​​the characteristic absorption peak of the nitrile group is calculated using the following formula to determine the nitrile group conversion rate η:

[0215]

[0216] in This represents the area of ​​the characteristic absorption peak of the acrylonitrile group in the pre-cured compounded rubber sheet. This represents the area of ​​the characteristic absorption peak of the nitrile group in the vulcanized product.

[0217] Characterization of condensation conversion of amide fluoride (Examples 4 to 6 only): using 19 Quantitative characterization by F-NMR, and calculation of the condensation conversion rate ηAF of acylfluoride using the following formula:

[0218]

[0219] in This represents the peak area of ​​the characteristic acyl fluoride group in the rubber compound before vulcanization. This represents the area of ​​the characteristic peak of the acyl fluoride group in the product after the high-temperature setting stage.

[0220] Metal ion deposition detection: Glow discharge mass spectrometry (GDMS) was used to detect trace metal ion deposition on the surface of the finished product, expressed in ng / cm³. 2 count.

[0221] Plasma erosion mass loss rate: The sealing ring sample was placed in a simulated plasma etching chamber environment (RF power 400 W, working gas is...). The mass loss rate (in wt%) was calculated as the ratio of the mass difference before and after exposure to the mass before exposure (4:1 volume ratio, 15 Pa chamber pressure, 2 hours exposure time).

[0222] Cross-sectional microcrack observation: After vulcanization, cross-sectional samples were taken and observed under a 100x optical microscope for the presence of microcracks and bubble defects, measured per centimeter. 2 Count of microcracks within the cross-sectional area.

[0223] Experimental steps:

[0224] The sealing rings were prepared according to the formulations and processes of each implementation example and comparative example. After cleaning, drying, and packaging, they were equilibrated in a clean room at a temperature of (23±2℃) for 24 hours before being used for testing.

[0225] according to The standard procedure involves a compression set test. The diameter d of the sample cross-section before compression is recorded. o , thickness d of the compression tool c After removing and cooling for 30 minutes, the cross-sectional diameter d r Calculate the compressive permanent deformation rate CS using the following formula:

[0226]

[0227] For each sample, a longitudinal section specimen was taken, and the nitrile group conversion η was determined by FTIR; for the samples of Examples 4 to 6, the condensation conversion ηAF of acyl fluoride was determined simultaneously.

[0228] According to the plasma erosion mass loss rate test conditions, plasma exposure experiments were carried out on all samples, the mass before and after exposure was accurately weighed, and the mass loss rate was calculated.

[0229] All samples were analyzed by GDMS for ultra-trace metal ion precipitation, with a detection area of ​​1 cm² for each sample. 2 Take the average of the three points.

[0230] Cross-sectional samples were cut and analyzed under a 100x optical microscope, with each cm section counted.2 Number of microcracks in the cross section.

[0231] Summarize all test data and calculate the performance improvement ratio of each implementation example relative to the control group (Comparative Example 1 or Comparative Example 2).

[0232] See experimental or test results Figures 2-7 And as shown in the table below:

[0233] Table 1 Summary of formulation parameters for Implementation Examples 1 to 3 and Comparative Examples 1 and 2

[0234]

[0235] As shown in Table 1, Comparative Example 1 and Example 3 are completely identical in vulcanization method, temperature program, and filler system, differing only in the vulcanization system; Comparative Example 2 and Example 3 are completely identical in formulation and vulcanization system, differing only in the vulcanization program, which is changed to a single isothermal process. This comparative design ensures that each of the two control experiments changes only a single technical variable, providing rigorous control experimental conditions.

[0236] Table 2 Performance test results of Implementation Examples 1 to 6 and Comparative Examples 1 and 2

[0237]

[0238] The results in Table 2 show that:

[0239] Regarding metal ion contamination and plasma resistance, the zinc oxide introduced by the peroxide sulfidation system in control sample 1 (Comparative Example 1) resulted in a metal ion deposition rate as high as 38.6 ng / cm³. 2 The plasma exposure mass loss rate was 1.47 wt%. After using a metal-free triazine sulfidation system, the metal ion deposition rate of Sample 3 (Example 3) decreased to 0.08 ng / cm³. 2 Compared to control sample 1, the plasma exposure mass loss rate was reduced by approximately 99.8%; the plasma exposure mass loss rate was reduced to 0.25 wt%, a decrease of approximately 83.0% compared to control sample 1. These results indicate that the metal-free triazine sulfidation system eliminates the source of metal ion precipitation at its origin, while the triazine ring crosslinking nodes are predominantly carbon-fluorine bonds throughout the process, effectively inhibiting the chemical erosion of the substrate by high-energy plasma.

[0240] Regarding the effect of gradient temperature vulcanization process on crosslinking uniformity, control sample 2 (comparative example 2) underwent single isothermal vulcanization at 240℃ for 6 hours, resulting in a nitrile group conversion rate of only 82.4%, insufficient crosslinking, and a cross-sectional microcrack count of 7 lines / cm. 2 The compression set was as high as 28.3%. Sample 3 (Example 3) underwent three-stage gradient temperature vulcanization, resulting in a nitrile conversion rate of 96.8% and a reduction in the number of microcracks per cm section to 0.2 The compression set was reduced to 14.5%, a decrease of approximately 48.8% compared to control sample 2. This indicates that the three-stage gradient heating process allows the triazine cyclization reaction to proceed uniformly from the surface to the interior, effectively eliminating internal defects and significantly improving elastic recovery.

[0241] Regarding the further enhancement effect of the dual-network system in Example 2, compared with Sample 3 (Example 3), Sample 6 (Example 6) showed a further decrease in compressive permanent deformation rate from 14.5% to 10.9%, a reduction of approximately 24.8%; plasma exposure mass loss rate decreased from 0.25 wt% to 0.18 wt%, a reduction of approximately 28.0%; and metal ion deposition decreased from 0.08 ng / cm³. 2 Reduced to 0.05 ng / cm 2 The reduction was approximately 37.5%. The condensation conversion rate ηAF of the amide condensation reached 93.1%, indicating that the second network had formed an effective three-dimensional cross-linked structure in the phase interface region. The above results confirm that the chemical interconnection bridge established between the bifunctional star-shaped compatibilizer and the second network precursor system in the phase interface region eliminates the weak link of relatively low cross-linking density in the phase interface region of the single network system, further improving the overall resistance to compressive deformation and plasma erosion performance under large cross-section and high compression conditions.

[0242] In summary, the comparative experimental data from Examples 1 to 3 and Comparative Examples 1 and 2 respectively confirmed the following three improvement effects: the metal-free triazine sulfidation system reduced the amount of metal ion precipitation by approximately 99.8% and the plasma exposure mass loss rate by approximately 83.0%; the three-stage gradient temperature sulfidation process reduced the compression set by approximately 48.8% and eliminated cross-sectional microcrack defects; the dual-network system in Example 2 further reduced the compression set by approximately 24.8% compared to Example 1. These three improvement effects are independent of each other and are all quantitatively supported by experimental data.

[0243] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A process for preparing a PLASMA-resistant and compression-resistant perfluoroether rubber sealing ring, characterized in that, Includes the following steps: 55 to 70 parts by weight of nitrile-cured perfluoroether rubber A and 20 to 30 parts by weight of premixed perfluoroether rubber B with emulsion polytetrafluoroethylene are mixed and blended on an open mill to form a homogeneous matrix. 8 to 12 parts by weight of poly(perfluoroethylene propylene) micro powder and 1 to 3 parts by weight of fumed silica are added in batches to the homogeneous matrix and mixed and dispersed. Add 2 to 5 parts by weight of metal-free triazine vulcanizing agent and 0.5 to 1.8 parts by weight of fluorinated organic base catalyst in sequence, mix evenly, and then extrude to obtain a compounded film. After the compounded rubber sheet is pre-pressed, it is subjected to gradient temperature vulcanization, which includes a low temperature vulcanization section, a medium temperature vulcanization section, and a high temperature setting section.

2. The preparation process of the PLASMA-resistant and compression-resistant perfluoroether rubber sealing ring according to claim 1, characterized in that, The Mooney viscosity of the nitrile-cured perfluoroether rubber A The viscosity is 55 to 75, the nitrile content is 0.5 to 2.0 mol%, and the glass transition temperature is -10 to 5°C; the Mooney viscosity of the emulsion polytetrafluoroethylene premixed perfluoroether rubber B is... The concentration is 80 to 120, and the fluorine content is not less than 70 wt%.

3. The preparation process of the PLASMA-resistant and compression-resistant perfluoroether rubber sealing ring according to claim 1, characterized in that, The particle size D of the poly(fluoroethylene propylene) micro powder 50 The silica has a particle size of 1 to 5 μm and a melting point of not less than 305°C; the specific surface area of ​​the fumed silica is 150 to 200 m². 2 / g, with an average primary particle size of 12 to 20 nm; the polytetrafluoroethylene propylene micro powder and the fumed silica are dried at 100 to 120°C for 2 to 3 hours before being added.

4. The preparation process of the PLASMA-resistant and compression-resistant perfluoroether rubber sealing ring according to claim 1, characterized in that, When mixing the homogeneous matrix, the premixed polytetrafluoroethylene emulsion perfluoroether rubber B is first plasticized separately at a roller temperature of 60 to 70°C for 8 to 10 minutes, and then the nitrile-cured perfluoroether rubber A is added and mixed for 10 to 15 minutes. When adding filler, the roller gap is adjusted to 0.1 to 0.2 mm. The polytetrafluoroethylene propylene micro powder is added in 3 to 5 batches, and then the fumed silica is added in 2 to 3 batches.

5. The preparation process of the PLASMA-resistant and compression-resistant perfluoroether rubber sealing ring according to claim 1, characterized in that, The metal-free triazine vulcanizing agent is a melamine derivative with a total metal impurity content of no more than 10 μg / g, and is ground and sieved to an average particle size of no more than 50 μm before being added; the fluorinated organic base catalyst is a perfluorotributylamine quaternary ammonium salt type with a metal impurity content of no more than 5 μg / g; after being added to the vulcanization system, 0.1 to 0.3 parts by weight of a fluorinated internal release agent are also added.

6. The preparation process of the PLASMA-resistant and compression-resistant perfluoroether rubber sealing ring according to claim 1, characterized in that, The low-temperature vulcanization section is held at temperatures ranging from 150 to 230°C in segments for a total holding time of 6 to 7 hours; the medium-temperature vulcanization section is held at 230 to 250°C for 2 to 4 hours; and the high-temperature setting section is heated to 270 to 290°C at a heating rate of 1 to 2°C / min and held for 10 to 16 hours under continuous air circulation conditions.

7. The preparation process of the PLASMA-resistant and compression-resistant perfluoroether rubber sealing ring according to claim 1, characterized in that, After the high-temperature shaping section is completed, the temperature is cooled to below 60°C with the furnace at a rate not exceeding 2°C / min before demolding. After demolding, the mold is left to stand at room temperature for 24 to 48 hours for secondary shaping, and then subjected to ultrasonic cleaning with ultrapure water, ultrasonic cleaning with semiconductor-grade isopropanol, and ultrasonic cleaning with ultrapure water in sequence before drying.

8. The preparation process of the PLASMA-resistant and compression-resistant perfluoroether rubber sealing ring according to claim 1, characterized in that, Before mixing the homogeneous matrix, the emulsion polytetrafluoroethylene premixed perfluoroether rubber B is first mixed with 3 to 6 parts by weight of a bifunctional star-shaped compatibilizer to form a compatibilizing premix. Then, the nitrile-cured perfluoroether rubber A is mixed and fused with the compatibilizing premix. The bifunctional star-shaped compatibilizer has a four-armed star structure, wherein nitrile functional groups are grafted at the ends of two arms, and acyl fluoride functional groups are grafted at the ends of the other two arms, with a number average molecular weight of 8,000 to 15,000.

9. The preparation process of the PLASMA-resistant and compression-resistant perfluoroether rubber sealing ring according to claim 8, characterized in that, Before adding the metal-free triazine vulcanizing agent, 5 to 10 parts by weight of the terminal acyl fluoride perfluoropolyether prepolymer and 1 to 3 parts by weight of the three-arm perfluoropolyether amine crosslinking agent are formulated into a second network precursor mixture and added to the rubber compound in batches for mixing and dispersion; the number average molecular weight of the terminal acyl fluoride perfluoropolyether prepolymer is 8,000 to 15,000, and the number average molecular weight of the three-arm perfluoropolyether amine crosslinking agent is 2,500 to 5,000, with each molecule containing 3 terminal primary amine groups.

10. A perfluoroether rubber seal ring prepared by the preparation process of the PLASMA-resistant and compression-resistant perfluoroether rubber seal ring according to any one of claims 1 to 9.

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