Non-flocculant shearing demulsification method for perfluoroether elastomer emulsion and high-purity perfluoroether elastomer

Abstract

This invention belongs to the field of perfluoroether elastomer preparation technology, specifically relating to a flocculant-free shear demulsification and flocculation method for perfluoroether elastomer emulsions and a method for preparing high-purity perfluoroether elastomers. The preparation method involves: diluting the emulsion and adding it to a high-shear demulsifier for high-shear stirring and demulsification, collecting the floating flocs on the upper layer. The flocs are washed to obtain a solid-liquid mixture, which is then centrifuged, dehydrated, and vacuum-dried to obtain dried floc powder. The dried floc powder is then plasticized to obtain perfluoroether elastomers. Compounding agents are added, followed by mixing, molding, and secondary vulcanization to obtain the perfluoroether elastomer product. This invention achieves flocculant-free demulsification, flocculation, and washing of perfluoroether elastomer emulsions through the physical action of high shear force, solving the problems of high metal ion residue and low cleaning efficiency in traditional demulsification technologies. It is suitable for producing high-purity, high-cleanliness, and low-release perfluoroether elastomers and rubber products.

Description

Technical Field

[0001] This invention belongs to the field of perfluoroether elastomer preparation technology, specifically relating to a flocculant-free shear demulsification and flocculation method for perfluoroether elastomer emulsions and a method for preparing high-purity perfluoroether elastomers. Background Technology

[0002] Perfluoroether elastomers and their products are widely used in semiconductor manufacturing, aerospace, and other fields due to their excellent chemical inertness, high temperature resistance, and low surface energy. The preparation of perfluoroether elastomers involves processes such as emulsion polymerization, demulsification and flocculation, washing, drying, and plasticizing. Among these, the demulsification and flocculation of the perfluoroether elastomer emulsion is a critical step, affecting the quality of the perfluoroether elastomer, wastewater treatment, and resource recovery.

[0003] Traditional demulsification and flocculation methods for perfluoroether elastomer emulsions involve adding acid / salt flocculants. However, this approach generates large amounts of difficult-to-treat fluoride-containing wastewater during the washing process, leaving behind significant and difficult-to-remove metal ions. Consequently, the resulting perfluoroether rubber products fail to meet the cleanliness requirements of advanced semiconductor manufacturing processes. Furthermore, the production process generates substantial amounts of fluoride-containing organic wastewater, increasing wastewater treatment costs. Therefore, the development of novel demulsification and flocculation technologies is necessary. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned problems and provide a mechanical shear demulsification and flocculation method for perfluoroether elastomer emulsions and a method for preparing high-purity perfluoroether elastomers. This method achieves efficient demulsification of emulsions without the addition of flocculants, breaking through the technical bottlenecks of traditional demulsification technology, which relies on chemical agents, has high costs, and causes heavy secondary pollution. While ensuring recovery rate and product purity, it significantly reduces environmental impact and operating costs.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A flocculant-free shear demulsification and flocculation method for perfluoroether elastomer emulsions includes the following steps:

[0007] (1) After diluting the perfluoroether elastomer emulsion, add it to a high-shear demulsifier for high-shear stirring and demulsification;

[0008] (2) After stirring, collect the flocculent material floating on the upper layer;

[0009] (3) Wash the flocculants until the conductivity of the washing liquid meets the requirements, and then stop to obtain a solid-liquid mixture of flocculants;

[0010] (4) The obtained solid-liquid mixture is centrifuged and dehydrated, and then vacuum dried to obtain dried flocculent powder;

[0011] (5) The flocculant is dried and powdered to obtain perfluoroether elastomer, and then compounded with a compounding agent, mixed, molded and vulcanized to obtain perfluoroether elastomer product.

[0012] As a preferred embodiment of the present invention, in step (1), the density of the diluted perfluoroether elastomer emulsion is 1.02-1.08 g / cm³. 3 ;

[0013] The perfluoroether elastomer emulsion includes peroxide-based perfluoroether elastomer emulsion and triazine-based perfluoroether elastomer emulsion, with peroxide-based perfluoroether elastomer emulsion being preferred;

[0014] The volume of the perfluoroether elastomer emulsion added to the high-shear demulsifier is 1 / 2 to 2 / 3 of its effective volume.

[0015] In step (1), heat exchange between walls or intermittent operation are used to control the temperature of the solution.

[0016] As a preferred technical solution of the present invention, in step (1), the high shear demulsifier adopts blade-type blades, with a stirring speed of 1000-3000 rpm, a time of 5-10 min, and a temperature of 20-50 ℃.

[0017] As a preferred technical solution of the present invention, in step (1), the lining material of the high-shear demulsifier is one of PFA, PTFE, ethylene-tetrafluoroethylene copolymer ETFE or alternating copolymer of trifluorochloroethylene and ethylene ECTFE.

[0018] As a preferred technical solution of the present invention, steps (1) and (2) involve repeated high-shear stirring demulsification and collection operations until no new flocculents are generated. The remaining bottom solution can be further flocculated by adding a flocculant, i.e., by adding a certain concentration of flocculant and performing demulsification and flocculation in the same manner as the mechanical shear demulsification and flocculation described above, to obtain the corresponding product. The flocculant includes inorganic salts, acids, organic solvents, or mixtures thereof, preferably one or a mixture of aluminum sulfate, magnesium chloride, ammonium acetate, ammonium nitrate, and magnesium sulfate.

[0019] As a preferred technical solution of the present invention, in step (3), the endpoint of washing is that the conductivity of the washing liquid is ≤2 μS / cm.

[0020] As a preferred technical solution of the present invention, in step (4), the vacuum drying temperature is 60-120 ℃, the vacuum degree is 0.01-0.1 bara, and the time is 2-8 h.

[0021] As a preferred technical solution of the present invention, in step (5), the compounding agent includes one or more of fillers, vulcanizing agents, and vulcanizing auxiliaries;

[0022] The filler includes PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) or PTFE (polytetrafluoroethylene); the vulcanizing agent includes peroxy-based perfluoroether elastomer vulcanizing agent and triazine-based perfluoroether elastomer vulcanizing agent. The peroxy-based perfluoroether elastomer vulcanizing agent includes 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (DBPH) or 1,3-bis(tert-butylperoxyisopropyl)benzene (BTPB); the triazine-based perfluoroether elastomer vulcanizing agent includes 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (BOAP) or crown ether, and the catalyst is tetraphenyltin; the vulcanization aid includes triallyl isocyanurate (TAIC) or fluorinated diene (CH2=CH-(CF2)n-CH=CH2) (n≧2).

[0023] This invention relates to the production of high-purity, low-emission perfluoroether elastomers and rubber products. The high-purity perfluoroether elastomer is prepared by the method described above. The high-purity perfluoroether elastomer is used to make O-rings, with a total metal ion content ≤900 ppb.

[0024] This invention is not only a specific improvement to the demulsification process, but also represents a fine chemical process design concept oriented towards sustainable development. It achieves green and efficient separation of complex emulsion systems through a combination of physical force field dominance, chemically assisted minimization, closed-loop parameter control, and product classification management. This invention realizes mechanical shear demulsification and flocculation of perfluoroether elastomer emulsions without the addition of chemical reagents, yielding high-purity perfluoroether elastomers, reducing the metal ion content, and significantly decreasing the amount of fluorinated organic wastewater.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. This invention uses high-shear physical action to replace the traditional chemical demulsification and flocculation technology, eliminating the need to add large amounts of acid / salt flocculants, effectively avoiding the problem of metal ion residue, significantly improving the purity of the product, and meeting the requirements of semiconductor-grade cleanliness.

[0027] 2. This invention achieves efficient flocculation and purification of perfluoroether elastomers through a phased gradient enhanced integrated process of demulsification-washing-drying, thereby improving the product yield and purity.

[0028] 3. This invention uses high-speed shear demulsification flocculation technology without flocculants, eliminating the need for chemical agents, thereby significantly reducing the discharge of fluoride-containing organic wastewater during the washing stage and greatly reducing wastewater treatment costs.

[0029] 4. This invention achieves thorough treatment of residual emulsion through closed-loop control of multiple cyclic shearing and density criteria, thereby improving the completeness of demulsification and the purity of the product.

[0030] 5. This invention employs a multi-stage cleaning process based on graded washing and conductivity criteria, which effectively removes impurity ions and residual emulsifiers from the product, ensuring the purity and stability of the final product. Attached Figure Description

[0031] Figure 1 This is the design process for the high-shear demulsification system of perfluoroether elastomers of the present invention.

[0032] Figure 2 This is a flow chart of the perfluoroether elastomer flocculation process of the present invention.

[0033] Figure 3 The curves showing the change in conductivity over time during the washing and soaking process of the diene high-temperature peroxy-based perfluoroether elastomer emulsion under different flocculation processes are shown in Example 1.

[0034] Figure 4 The following is a curve showing the change in conductivity over time during the washing and soaking process of a general-purpose perfluoroether emulsion with oxygen-based fluoroethers in Example 2, under different flocculation processes. Detailed Implementation

[0035] The present invention will now be described in detail with reference to specific embodiments, but these are by no means limitations on the present invention.

[0036] The preparation process of the perfluoroether elastomer of this invention is divided into flocculation, washing, centrifugation, drying, mixing, molding, and secondary vulcanization. This is a graded method for demulsifying and flocculating perfluoroether elastomer emulsions. The detailed process flow is as follows: Figure 1 and Figure 2 The specific details are as follows.

[0037] Stage 1: High-shear demulsification and flocculation without flocculants

[0038] 1) Emulsion pretreatment and initial shear treatment

[0039] The original perfluoroether elastomer emulsion was diluted with deionized water to the target density range of 1.02-1.08 g / cm³. 3 To adjust the system viscosity and interfacial tension, the rheological properties and interfacial tension of the system were optimized within the target density range, enabling the emulsion to fully absorb and transfer mechanical energy during subsequent high-shear processes, thereby improving demulsification efficiency and avoiding energy waste and incomplete demulsification due to unsuitable rheological properties.

[0040] Inject the diluted emulsion into a high-shear demulsifier, controlling the solution volume to approximately 1 / 2 to 2 / 3 of the equipment's effective volume. Initiate the first shearing operation: control the rotation speed at 1000-3000 rpm, the time at 5-10 min, and the temperature at 20-50 ℃.

[0041] The high-shear demulsifier uses blade-type blades, and the shearing equipment is lined with PFA / PTFE / F40 / F30, etc., which effectively isolates the emulsion from contact with the metal equipment and avoids the metal ion shedding and contamination problems that may occur in traditional stainless steel equipment during high-speed shearing.

[0042] By utilizing the intense turbulence, cavitation effects, and interfacial tearing generated by high-speed rotation, the stable structure of the emulsion is disrupted, promoting its aggregation into larger elastomer clusters, thus achieving physical flocculation. In the mechanical shear demulsification and flocculation stage, the centrifugal force of the blade-type impeller indirectly affects the fluid shear rate; the shear strength ψ obtained by the solution is proportional to the centrifugal force Ψ = a(ω) under equivalent gravity. 2 (r / g), where ω is the angular velocity of the rotating reference frame, i.e., the angular velocity of the blade as it rotates with the reference frame, in radians per second (rad / s=2π×rpm / 60), r is the radius from the blade to the axis of rotation, in meters (m), and a is the proportionality coefficient, which comprehensively reflects factors such as solution viscosity, blade geometry, and flow field distribution.

[0043] This invention constructs a strong turbulent flow field, cavitation field, and interfacial tearing field within the equipment by controlling the rotation speed, time, and temperature. This effectively disrupts the stability of the emulsion interfacial film, promoting the aggregation of emulsion droplets into clusters, achieving highly efficient demulsification without the addition of any chemical flocculants. The rotation speed determines the energy input intensity and shear rate of the system. Controlling the rotation speed between 1000-3000 rpm ensures sufficient energy input to disrupt the emulsion interfacial film while avoiding excessive shearing that could cause molecular chain breakage, thus achieving a gentle and efficient demulsification effect. The operating time is controlled within 5-10 minutes to ensure a complete transition from the induction phase to the growth phase, achieving a large flocculant yield in a single operation, while avoiding the hardening of colloidal particles due to excessive stirring time, which could impair subsequent processing performance. The operating temperature is controlled between 20-50 °C, maintaining good emulsion fluidity and a moderately fragile interfacial film, while avoiding the risks of thermal agglomeration and thermal degradation, providing an optimal thermodynamic environment for efficient demulsification.

[0044] 2) Settling and stratification and collection of upper powder

[0045] After stopping stirring, let it stand for 10-15 minutes to allow it to naturally separate into layers due to density differences. The upper layer is a white or milky white perfluoroether elastomer flocculent (powder), which should be collected using a scraper or an automatic skimming device; the lower layer solution may be recycled or used in the next stage, depending on the situation.

[0046] 3) Repeatedly shear until no flocculant remains and flocculation is complete.

[0047] Continue processing the remaining emulsion phase, repeating the shear-settle-collect process described above. Typically, 3-5 cycles are required to extract the mechanically flocculated polymer phase. When no more significant new powder is generated in the upper layer, the first stage is considered complete, and the residual solution is transferred to the second stage for processing.

[0048] Phase 2: Flocculant-assisted demulsification

[0049] 1) Introduce flocculants for secondary shearing treatment

[0050] Add 0.1%-0.5% flocculant (by mass) to the residual emulsion that has not been mechanically demulsified to enhance its destabilizing ability. Run the high-shear equipment again under the same shear parameters (1000-3000 rpm, 5-10 min, 20-50 ℃) to promote the bridging and aggregation of fine particles. After stopping stirring, allow the mixture to stand and separate, and observe the precipitation of the upper powder layer.

[0051] 2) Density criterion-driven closed-loop iterative control

[0052] After stratification, the density of the lower liquid layer is measured as a key indicator of the thoroughness of demulsification.

[0053] If density ≤ 1.01 g / cm³ 3 It was determined that the emulsion phase had been largely flocculated, and flocculation was terminated.

[0054] If the density is greater than 1.01 g / cm³ 3 This indicates that a significant amount of emulsion still needs flocculation, requiring the addition of 0.05% flocculant for re-shearing and flocculation. The "dosage-shearing-setting-testing" process is repeated until the solution density meets the standard.

[0055] Phase 3: Graded washing and soaking to remove impurities

[0056] 1) Sort and clean powders from different sources

[0057] The non-flocculating powder obtained in stage 1 and the flocculant-containing powder obtained in stage 2 are stored and cleaned separately to ensure that the purity of the final product is controllable.

[0058] During washing, place the powder into a high-shear demulsifier and add deionized water to approximately 1 / 2 to 2 / 3 of the volume. Run the shear washing program: 1000-3000 rpm for 5-10 minutes.

[0059] Washing also includes a soaking process. The shearing and soaking actions are to fully disperse and dissolve water-soluble impurities such as salts, residual emulsifiers, and metal ions trapped inside and on the surface of the powder into the water.

[0060] 2) Conductivity as the endpoint control criterion

[0061] After washing, the liquid is drained from the bottom, and the conductivity of the drained water is monitored in real time.

[0062] If the conductivity of the effluent is greater than 2 μS / cm, there is soluble electrolyte contamination, and it needs to be washed or soaked again with water; if the conductivity of the effluent is ≤2 μS / cm, the washing standard is met, and the washing is complete.

[0063] The specific number of washing cycles depends on the initial cleanliness level, and usually 5-15 repeated operations are required to reach the conductivity endpoint criterion.

[0064] Phase 4: Centrifugal dehydration and vacuum drying

[0065] 1) High-speed centrifugation to remove free water

[0066] Transfer the washed wet powder to an industrial centrifuge. Set the speed to 1000-3000 rpm and the time to 5-10 minutes. The powerful centrifugal force removes most of the free water in the gaps between the powder particles, forming a loose filter cake with a moisture content of about 10-15%.

[0067] 2) Vacuum drying

[0068] Spread the filter cake evenly in a tray and place it in a vacuum oven. Dry at 60-120 ℃ (low temperature to protect the polymer structure) for 2-8 hours. The final product is a white powder with a moisture content of <0.1%, meeting storage and usage requirements.

[0069] Phase 5: Mixing, Compression Molding, and Secondary Vulcanization

[0070] The first-stage flocculant dried micro powder 1 and the second-stage flocculant dried micro powder 2 obtained after drying are respectively plasticized to obtain perfluoroether elastomer 1 without flocculant flocculation and perfluoroether elastomer 2 with flocculant flocculation. After plasticizing, fillers, vulcanizing aids and vulcanizing agents are added and mixed in a thin pass, molded and formed, and then vulcanized a second time to obtain the corresponding perfluoroether elastomer rubber products.

[0071] The following detailed examples illustrate this further. Examples and comparative examples refer to the results of mechanical flocculation without flocculant in the same set of experiments, which are examples, and the results of flocculation with flocculant are comparative examples.

[0072] Example 1 / Comparative Example 1

[0073] The processing steps for a diene high-temperature resistant peroxy-based perfluoroether elastomer emulsion are as follows:

[0074] Step 1: The diene-containing high-temperature resistant perfluoroether emulsion (solid content about 30%, average particle size about 100nm) is subjected to flocculant-free high-speed shear demulsification.

[0075] The original perfluoroether elastomer emulsion was diluted with deionized water to a density of 1.05 g / cm³. 3 To adjust the viscosity and interfacial tension of the system;

[0076] The diluted emulsion was loaded into a high-shear demulsifier, model HR-1500 (Chengdu Xingkaixing Technology Co., Ltd.), and the solution volume was controlled to be 2 / 3 of the effective volume of the equipment.

[0077] Start the shearing operation, set the rotation speed to 2800 rpm, the time to 8 min, and the temperature to 35 ℃;

[0078] After shearing, the solution was allowed to stand for 10 minutes to separate into layers naturally due to density differences. The upper layer of perfluoroether elastomer flocculent material was collected using a scraper, and the lower layer solution was sheared again.

[0079] When no more obvious new powder is generated in the upper layer, the first stage is considered complete. The first stage of mechanical flocculation flocculates about 73% of the raw rubber, and the remaining solution is transferred to the second stage of treatment.

[0080] Step 2: Perform flocculant-assisted mechanical demulsification on the residual emulsion.

[0081] Add 0.5% aluminum sulfate by mass to the remaining emulsion as a flocculant, and run the high-shear equipment again under the same shear parameters as in step 1. After stopping the machine, let it stand for 10 minutes to separate into layers. The upper layer is a white or milky white peroxy-based perfluoroether elastomer flocculent (powder), which is collected by scraper or automatic powder skimming device.

[0082] Take a sample to test the density of the lower liquid layer. If the density is ≤1.01 g / cm³... 3 If the density is greater than 1.01 g / cm³, it is considered that the emulsion phase has basically broken down and flocculated, and flocculation is terminated; 3 If the result is negative, it indicates that there is still a lot of emulsion that needs to be flocculated, and 0.2% aluminum sulfate flocculant needs to be added to re-shear and flocculate.

[0083] Repeat the "dosing-shearing-standing-detection" process until the solution density is ≤1.01 g / cm³. 3 .

[0084] Step 3: Wash the obtained powders separately.

[0085] The flocculant-free powder obtained in step 1 and the flocculant-containing powder obtained in step 2 were stored and washed separately. The washing process involved placing the powder into a high-shear demulsifier, injecting deionized water to about 2 / 3 of the volume, running a shear wash at 2000 rpm for 6 minutes at 30 ℃, and draining the liquid from the bottom after washing.

[0086] The conductivity of the discharged water is monitored in real time. If the conductivity is greater than 2 μS / cm, water is added again for washing and soaking. If the conductivity is ≤2 μS / cm, the washing meets the required standard.

[0087] Step 4: Centrifuge and dehydrate the washed powder separately, and then vacuum dry it.

[0088] The washed wet powder was transferred to an industrial centrifuge (Ding's centrifuge: PSBQF450), and the centrifugation speed was set to 2000 rpm for 8 min. After removing most of the free water in the gaps between the powder particles by relying on the strong centrifugal force, the filter cake was evenly spread on a tray and placed in a vacuum oven. The vacuum drying temperature was 100 ℃ for 6 h to obtain a loose, free-flowing white powder.

[0089] Step 5: Mixing, molding, and secondary vulcanization

[0090] The first-stage flocculant dried micro powder 1 (Example 1) and the second-stage flocculant dried micro powder 2 (Comparative Example 1) obtained after drying were respectively plasticized to obtain perfluoroether elastomer 1 without flocculant flocculation and perfluoroether elastomer 2 with flocculant flocculation. 1.0 wt% of the vulcanizing aid fluorinated diene (CH2=CH-(CF2)6-CH=CH2) and 0.9 wt% of the vulcanizing agent bis(2,5-diphenyl) were added respectively. After thin-pass mixing, compression molding (conditions: 170 ℃, 9 min, 10 MPa), and secondary vulcanization (conditions: 250 ℃, 6 h), the corresponding diene high-temperature peroxy-resistant perfluoroether elastomer rubber products were obtained.

[0091] Emulsions have complex compositions, mainly consisting of the target product, a fluorinated elastomer obtained from monomer polymerization, as well as emulsifiers, initiators, pH adjusters, chain transfer agents, low molecular weight polymers, and water. Some of these components must be removed during flocculation, washing, and drying processes, but the flocs still contain impurities, especially metal ions, when flocculants are added. Figure 3 The conductivity of diene high-temperature peroxy-based perfluoroether elastomer emulsion changes with time during washing and soaking under different flocculation processes.

[0092] Example 2 / Comparative Example 2

[0093] The following are the steps for treating a common perfluoroether emulsion:

[0094] Step 1: The peroxide-based perfluoroether emulsion (solid content approximately 30%, average particle size 100 nm) is subjected to flocculant-free high-speed shear demulsification.

[0095] The original perfluoroether elastomer emulsion was diluted with deionized water to a density of 1.06 g / cm³. 3To adjust the system viscosity and interfacial tension, the diluted emulsion was loaded into a high-shear demulsifier (model HR-1000, Chengdu Xingkaixing Technology Co., Ltd.), with the solution volume controlled at 2 / 3 of the equipment's effective volume.

[0096] The first shearing operation was initiated at a speed of 2800 rpm for 8 minutes and a temperature of 35 ℃. After shearing, the solution was allowed to stand for 10 minutes to separate into layers naturally due to density differences. The upper layer of perfluoroether elastomer flocculent material was collected using an automatic skimming device, and the lower layer of solution was sheared again.

[0097] When no more obvious new powder is generated in the upper layer, the first stage is considered complete. The first stage of mechanical flocculation produces about 65% of the raw rubber; the remaining solution is transferred to the second stage of treatment.

[0098] Step 2: Use flocculants to enhance demulsification of the residual emulsion.

[0099] Add 0.5% aluminum sulfate (by mass) to the remaining emulsion as a flocculant, and run the high-shear equipment again under the same shear parameters as in step 1. After shutdown, allow the mixture to settle and separate into layers. The upper layer is a white or milky white peroxy-based perfluoroether elastomer flocculent (powder), which is collected using a scraper or an automatic skimming device.

[0100] Take a sample to test the density of the lower liquid layer. If the density is ≤1.01 g / cm³... 3 If the density is greater than 1.01 g / cm³, it is considered that the emulsion phase has basically broken down and flocculated, and flocculation is terminated; 3 If the result is negative, it indicates that there is still a lot of emulsion that needs to be flocculated, and 0.2% aluminum sulfate flocculant needs to be added to re-shear and flocculate.

[0101] Repeat the "dosing-shearing-standing-detection" process until the solution density is ≤1.01 g / cm³. 3 .

[0102] Step 3: Grading and washing the obtained powder.

[0103] The flocculant-free powder obtained in step 1 (Example 2) and the flocculant-containing powder obtained in step 2 (Comparative Example 2) were stored and washed separately. The washing process involved placing the powder into a high-shear demulsifier, injecting deionized water to about 2 / 3 of the volume, running a shear wash at 2000 rpm for 6 minutes at a temperature of 30 °C, and draining the liquid from the bottom after washing.

[0104] The conductivity of the discharged water is monitored in real time. If the conductivity is greater than 2 μS / cm, water is added again for washing and soaking; if the conductivity is ≤2 μS / cm, the required washing standard is met.

[0105] Step 4: Centrifuge and vacuum dry the washed powder.

[0106] Transfer the washed wet powder to an industrial centrifuge (Ding's centrifuge: PSBQF450); set the centrifugation parameters to 2000 rpm and 8 min.

[0107] Most of the free moisture in the gaps between the powder particles is removed by strong centrifugal force; the filter cake is evenly spread on a tray and placed in a vacuum oven; the drying temperature is set to 100 °C for 6 h; a loose, free-flowing white powder is obtained.

[0108] Step 5: Mixing, molding, and secondary vulcanization

[0109] The dried flocculant powder 1 and the dried flocculant powder 2 obtained after drying were respectively plasticized to obtain perfluoroether elastomer 1 without flocculant flocculation and perfluoroether elastomer 2 with flocculant flocculation. 1.8 wt% of vulcanizing aid TAIC and 0.9 wt% of vulcanizing agent bis(2,5-dimethyl)propane were added to each, and the mixture was thin-pass mixed, molded (conditions: 170℃, 9 min, 10 MPa), and then vulcanized a second time (conditions: 220℃, 6 h) to obtain the corresponding peroxy-based perfluoroether elastomer rubber products. The corresponding parameters were measured. Figure 4 The curves show the change in conductivity over time during the washing and soaking process of ordinary perfluoroether emulsions with different flocculation processes.

[0110] [Sample Performance Testing]

[0111] The rubber products obtained in Example 1 / Comparative Example 1 and Example 2 / Comparative Example 2 were tested according to the performance parameters in Table 1. Among them, tensile strength, 100% tensile stress, and elongation at break were tested. The products were made into sample AS568-214 type O-rings.

[0112] Plasma radiation mass loss rate was tested according to Senhuan Enterprise Standard Q / SMS001-2024 "Test Method for Plasma Etching Resistance of Perfluoroether Rubber Seals";

[0113] ICP-MS testing for metal content involves leaching raw rubber after ashing, measuring the metal ion content in the leachate, and then converting this to the metal ion content in the raw rubber. The testing method is as follows:

[0114] The sample was weighed and placed in a platinum crucible, and ashed in a microwave muffle furnace at 500 °C for 1 h. After ashing, it was soaked in 3% dilute nitric acid solution overnight. The diluted solution was tested by ICP-MS, and the test results were converted.

[0115] For detailed test results, please refer to Tables 1 and 2.

[0116] Table 1 Mechanical properties and metal ion content of the products from the examples and comparative examples

[0117]

[0118] Table 2. Metal ion residues (ppb) as determined by ICP-MS

[0119]

[0120] Test Result Analysis

[0121] A systematic and comprehensive analysis of Example 1 and Comparative Example 1, and Example 2 and Comparative Example 2, was conducted, providing an in-depth interpretation from multiple dimensions, including mechanical properties, residual metal ions, process influences, and material purity. Through a comprehensive evaluation of experimental data and process descriptions, the key differences between flocculant-free mechanical flocculation (Example) and flocculant-assisted demulsification (Comparative Example) in the preparation of perfluoroether elastomers and their impact on the final product performance were revealed. The results are listed in Table 3.

[0122] Table 3 Process Description and Analysis

[0123]

[0124] The test results show that:

[0125] 1. The product prepared by the method of this invention has low metal ion residue, which is a core indicator determining the "cleanliness" of materials. ICP-MS test results show that whether or not a flocculant is used directly determines the type and concentration distribution of metal ions in the final powder, especially in terms of Al element residue: In Example 1, Al was 23.28 ppb, while in Comparative Example 1 it was as high as 146.52 ppb; in Example 2, Al was 17.92 ppb, while in Comparative Example 2 it was as high as 150.22 ppb. This is because aluminum sulfate, as a flocculant, forms an Al(OH)3 colloidal network during shearing, capturing emulsion droplets while also embedding itself within the flocculent, making it difficult to completely remove through subsequent washing and soaking. Even after multiple washes and soaks, Al still exists in a complexed or adsorbed state in the polymer microporous structure, becoming a long-term release source and affecting the stability of the product.

[0126] 2. In terms of mechanical properties, the tensile strength and elongation at break are similar, indicating that the main structure is not damaged. Although the treatment methods are different, the tensile properties of the four groups of samples are basically similar: tensile strength is 11.18-11.37 MPa; elongation at break is 361.8-372.5%; 100% constant elongation stress is 1.97-2.07 MPa; the compression set data are similar. Both demulsification methods can effectively preserve the integrity of the polymer main chain and do not cause obvious degradation or cross-linking damage.

[0127] 3. Under the commonly used O2, O2 / CF4, and O2 / NF3 plasma conditions in semiconductor processes, all samples exhibited low mass loss rates (0.79-1.48%). The plasma etching mass loss rate reflects the surface stability and radiation resistance of the material, indicating that this type of perfluoroether elastomer possesses excellent resistance to plasma erosion.

[0128] In summary, the present invention has the following advantages: (1) The product has high purity: the flocculant-free high-speed shear demulsification technology significantly reduces metal ion residues, especially key pollutants such as aluminum and calcium, providing higher purity assurance for high-end application scenarios (such as semiconductors and aerospace); (2) The product has good performance retention: in terms of compression set and mechanical properties, the tensile strength and elongation at break of the examples tend to be consistent, indicating that the main structure is not damaged. Although the treatment methods are different, the tensile properties of the four groups of samples are basically similar; (3) It is environmentally friendly: from the perspective of green manufacturing and sustainable development, the physical demulsification process without chemical additives is more environmentally friendly and economically sustainable, which is in line with the trend of modern fine chemical industry to transform towards "zero emissions and low toxicity", and has significant technological progress.

[0129] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method of perfluoroether elastomer emulsion coagulation without flocculants and shearing demulsification, characterized by, Includes the following steps: (1) After diluting the perfluoroether elastomer emulsion, add it to a high-shear demulsifier for high-shear stirring and demulsification; (2) After stirring, collect the flocculent material floating on the upper layer; (3) Wash the flocculants until the conductivity of the washing liquid meets the requirements, and then stop to obtain a solid-liquid mixture of flocculants; (4) The obtained solid-liquid mixture is centrifuged and dehydrated, and then vacuum dried to obtain dried flocculent powder; (5) The flocculant is dried and powdered to obtain perfluoroether elastomer, and then compounded with a compounding agent, mixed, molded and vulcanized to obtain perfluoroether elastomer product.

2. The method according to claim 1, characterized in that, In step (1), the perfluoroether elastomer emulsion has a density of 1.02 to 1.08 g / cm3 after dilution 3 ; The volume of the perfluoroether elastomer emulsion added to the high-shear demulsifier is 1 / 2 to 2 / 3 of its effective volume.

3. The method according to claim 1, characterized in that, In step (1), the high-shear demulsifier uses blade-type blades, with a stirring speed of 1000-3000 rpm, a time of 5-10 min, and a temperature of 20-50 ℃.

4. The method according to claim 1, characterized in that, In step (1), the lining material of the high-shear demulsifier is one of PFA, PTFE, ethylene-tetrafluoroethylene copolymer ETFE or alternating copolymer of trifluorochloroethylene and ethylene ECTFE.

5. The method according to claim 1, characterized in that, Steps (1) and (2) are repeated multiple times with high-shear stirring demulsification and collection until no new flocs are generated.

6. The method according to claim 1, characterized in that, In step (3), the washing endpoint is when the conductivity of the washing liquid is ≤2 μS / cm.

7. The method according to claim 1, characterized in that, In step (4), the vacuum drying temperature is 60-120 ℃, the vacuum degree is 0.01-0.1 bara, and the time is 2-8 h.

8. The method according to claim 1, characterized in that, In step (5), the compounding agent includes one or more of fillers, vulcanizing agents, and vulcanizing aids.

9. A high-purity perfluoroether elastomer, characterized in that, Prepared by the method described in any one of claims 1 to 7.

10. The high-purity perfluoroether elastomer according to claim 9, characterized in that, The perfluoroether elastomer is used to make O-rings with a total metal ion content ≤900 ppb.

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