Mixing process of peroxide vulcanization system fluororubber compound

Abstract

The invention discloses a mixing process of a peroxide vulcanization system fluororubber mixed rubber. The mixing process of the mixed rubber comprises the following steps: 1) preparing materials; 2) pretreatment; (3) preparing a premix; 4) mixing; and 5) remilling. The fluororubber disclosed by the invention can be applied to the fields of semiconductors, photovoltaics, food and medicine and the like which have content limitation requirements on fillers of rubber products, and meanwhile, a more efficient open milling mode is matched, so that the stability of the performance of the rubber material is ensured; according to the invention, the peroxide vulcanization system fluororubber is mixed in the open mill, so that the temperature of the rubber compound during mixing is effectively controlled, and the rubber compound is prevented from scorching during mixing; according to the invention, the mixing process of the peroxide vulcanized rubber with more excellent compression set performance is improved, so that acid acceptors such as metal oxides are not added, the purity of the formula is ensured, and the requirements of industries such as semiconductors, photovoltaics and food medicines on rubber products are met.

Description

Technical Field

[0001] The invention relates to the technical field of fluororubber, and in particular to a mixing process of a fluororubber compound rubber of a peroxide vulcanization system. Background Art

[0002] Fluororubber (fluororubber) refers to a synthetic polymer elastomer containing fluorine atoms on carbon atoms in the main chain or side chains. The introduction of fluorine atoms imparts excellent heat resistance, oxidation resistance, oil resistance, corrosion resistance, and atmospheric aging resistance to the rubber. It is widely used in aerospace, aviation, automotive, petroleum, and household appliances, and is an irreplaceable key material in the cutting-edge defense industry. Since 1943, various types of fluororubber have been developed, including polyolefin fluororubber, nitroso fluororubber, tetrapropylene fluororubber, phosphazene fluororubber, and perfluoroether rubber.

[0003] In the actual practice of peroxide-cured fluororubber, it has been found that liquid components added directly during open mixing, such as curing accelerators and curing agents, can sometimes suffer from various unintended losses, leading to insufficient crosslink density and substandard properties. This can also result in prolonged mixing times and reduced efficiency. While attempts to maintain compound properties by adding additional liquid components are limited, excessive additions can also have negative consequences, as the amount of liquid component loss varies from mixing to mixing. For example, experiments have shown that excessive amounts of curing accelerators (particularly TAIC), which have multiple vinyl functional groups, can precipitate on the rubber surface and self-polymerize into a solid under the high temperatures of curing. This can cause small, space-occupying cracks on the surface of the rubber product, significantly degrading its performance. While using internal mixing instead of open mixing theoretically avoids material losses, in practice, it has been found to be prone to scorching. Analysis reveals that this is because liquid curing agents have difficulty dispersing rapidly throughout the rubber compound, and the localized high temperatures generated by shear during internal mixing can lead to premature curing and scorching.

[0004] A proven solution is to reduce or eliminate the use of liquid components during mixing, such as replacing them with premixed solid peroxide curing agents. This improves workability and reduces unnecessary losses. However, solid curing agents contain inorganic fillers such as silica and calcium carbonate as carriers. These inorganic fillers are unnecessary for certain formulations and may even have adverse effects. For example, in some processes in the semiconductor industry, strict requirements are imposed on the quality loss of sealing materials under operating conditions, as this loss of quality indicates the release of contaminants. Extensive empirical evidence indicates that inorganic fillers and acid absorbers (commonly found in calcium oxide, magnesium oxide, and zinc oxide) in rubber materials are a major source of particulate contamination in sealing materials. In these applications, formulations containing inorganic fillers such as metal ions are limited.

[0005] Patent CN106589709A discloses a fluororubber motor seal ring for nuclear power plants and its preparation method. The seal ring comprises the following raw materials by weight: 85-90 parts fluororubber, 5-8 parts acid absorber, 2-5 parts composite vulcanizing agent, 8-10 parts reinforcing agent, and 1-2 parts additive. This fluororubber motor seal ring exhibits high mechanical strength and excellent oil resistance at high temperatures, making it suitable for use in nuclear-powered ship motors. The patent discloses uniformly mixing the acid absorber, composite vulcanizing agent, reinforcing agent, and additives to form a premix; the reinforcing agent is carbon black, which is slowly added to the premix during mixing.

[0006] However, this patent uses a different vulcanization system (bisphenol AF system), and the vulcanizers (bisphenol AF, No. 3 vulcanizer, and No. 5 vulcanizer) are all solid at room temperature, and the formula does not involve any liquid components. In addition, due to the different vulcanization mechanisms, this vulcanization system will produce toxic and harmful acidic gas HF, which must be absorbed by adding calcium oxide, magnesium oxide, etc. as acid absorbers. Obviously, these metal oxides have poor tolerance to acid and water vapor. Moreover, the patent uses an internal mixer to mix the rubber, which may cause the rubber to vulcanize and burn prematurely. Summary of the Invention

[0007] The present invention aims to provide a mixing process for a peroxide-cured fluororubber compound using a liquid component, which can effectively reduce the loss of liquid components and the accompanying quality instability problem, while significantly shortening the mixing time and improving the mixing efficiency.

[0008] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows: A mixing process for a peroxide-cured fluororubber compound, the compound comprising the following components in parts by weight: Fluororubber raw rubber: 100 parts; Carbon black: 5-40 parts; Vulcanization accelerator: 0.5~3 parts; Vulcanizing agent: 0.5~3 parts; Modifier: 0.1~5 parts; Accelerator: 0.1~5 parts; The vulcanizing agent is dicumyl peroxide, di-tert-butyl peroxide isopropyl benzene or 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; The vulcanization auxiliary agent is triallyl isocyanurate or triallyl tricyanurate; The mixing process of the rubber compound comprises the following steps: 1) Prepare materials: weigh the ingredients of each group according to the weight ratio; 2) Pretreatment: Add the weighed carbon black, accelerator and modifier to the pretreatment solvent, ultrasonicate at room temperature for 5-10 minutes, heat under reflux and stir for 4 hours, then filter and remove the solvent by vacuum rotary evaporation to obtain the pretreated filler carbon black; 3) Preparation of premix: Heat the vulcanizing agent and vulcanizing accelerator until melted, then place them together with the carbon black pretreated in step 2) into a blender and stir at 150-300 rpm for 5-20 seconds until the powder is free of lumps and oil stains. This is to prepare the premix. 4) Mixing: The fluororubber raw rubber weighed in step 1) is plasticized uniformly on an open mill. Then, the premix prepared in step 3) is slowly added to the rubber material until the premix is ​​completely mixed into the rubber material. The rubber material is then thinly passed through 12 times to ensure uniform dispersion of the filler. Finally, the rubber material is cooled to room temperature. During the mixing process, the rubber material temperature should be controlled below 65°C. 5) Re-mixing: The rubber compound prepared in step 4) is allowed to stand for 8-12 hours, and is thinned on an open mixing mill at least 8 times to obtain a sheet of mixed rubber. During the re-mixing process, the temperature of the rubber compound is controlled below 65°C.

[0009] The fluororubber raw rubber is one or a combination of two or more of binary fluororubber (commonly known as F-26 rubber), three or more of fluororubber (commonly known as F-246 rubber) or perfluoroether rubber (FFKM for short).

[0010] The carbon black is selected from one or a combination of brands N990, N330, and N220.

[0011] The vulcanization accelerators are common vulcanization accelerators, including but not limited to triallyl isocyanurate (TAIC) or triallyl tricyanurate (TAC). TAC has a melting point of approximately 27°C. While it may become more viscous or even crystallize at room temperature (25°C), it will melt into a liquid upon heating during the mixing process.

[0012] The curing agent is a common peroxide curing agent, including but not limited to the following peroxides: dicumyl peroxide (DCP), di-tert-butyl peroxyisopropylbenzene (BIPB), and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (DBPH or BIBP). DCP and BIBP are solid at room temperature (25°C), but due to their relatively low melting points (around 40°C and 46°C, respectively), they quickly melt into an oily liquid during the mixing process.

[0013] The modifier is a fluorine-containing room temperature ionic liquid, including but not limited to 1,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-propyl-2, 3-Dimethylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide, N-butylpyridinium bis(trifluoromethanesulfonyl)imide, tri-n-butylmethylammonium bis(trifluoromethanesulfonyl)imide, tributylphosphine bis(trifluoromethanesulfonyl)imide, 1-propyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-propyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium hexafluorophosphate salt, 1-octyl-3-methylimidazolium tetrafluoroborate, 1-octyl-3-methylimidazolium hexafluorophosphate, 1-decyl-3-methylimidazolium tetrafluoroborate, 1-decyl-3-methylimidazolium hexafluorophosphate, 1-dodecyl-3-methylimidazolium tetrafluoroborate, 1-tetradecyl-3-methylimidazolium tetrafluoroborate, 1-hexadecyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-propyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide salt or 1-butyl-2,3-dimethylimidazolium hexafluorophosphate, or a combination of more thereof.

[0014] The accelerator is a fluoroether oil, preferably a commercial fluoroether oil, preferably with a molecular weight of 500-8000, which can be selected from the Krytox series of Dupont; the Fomblin series, Galden series, and Fluorolink series of Solvay; the Demnum series of Daikin; the fluoroether oil series of Sinopec Great Wall Lubricant Company; the Fluocon series of Sichuan Chenguang Boda New Materials Company, etc.

[0015] The pretreatment solvent is anhydrous ethanol or isopropanol.

[0016] Beneficial effects of the present invention: 1. The fluororubber produced by the present invention can be used in fields such as semiconductors, photovoltaics, and food and medicine, which have filler content restrictions on rubber products. At the same time, it is matched with a more efficient open mixing method, which can avoid the unexpected loss of various liquid components and ensure the stability of the rubber performance. In the present invention, the peroxide-cured system fluororubber is mixed in an open mixing mill, which avoids scorching caused by excessive local temperature of the rubber during internal mixing.

[0017] 2. In the present invention, the curing accelerators triallyl isocyanurate (TAIC) and triallyl cyanurate (TAC) are both colorless solids at room temperature with a melting point of 26-28°C, and the curing agent dicumyl peroxide (DCP) is a white crystalline powder at room temperature with a melting point of 41-42°C. ℃; di-tert-butyl peroxide isopropyl benzene (abbreviated as BIPB) is a white crystalline powder at room temperature with a melting point of 44~48℃; 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (abbreviated as DBPH or bis(25)) has an appearance of light yellow liquid, paste or milky white powder; the melting points of the vulcanizing agent and the vulcanizing accelerator are not high, and they will quickly melt into oily liquids due to heat during the mixing process. In the present invention, the vulcanizing agent and the vulcanizing accelerator are melted by preheating and then stirred with carbon black to prepare a premix. The melted vulcanizing agent and the vulcanizing accelerator are fully mixed with the carbon black during the stirring process, and are adsorbed on the surface of the carbon black when cooled to room temperature and condensed into a solid, and are fully mixed with the carbon black. Since the vulcanizing accelerator and the vulcanizing accelerator are adsorbed on the surface of the carbon black, during the feeding process, the vulcanizing agent and the vulcanizing accelerator are more easily dispersed into the mixed rubber along with the dispersion of the carbon black, the vulcanizing agent and the vulcanizing accelerator are dispersed faster and are less likely to burn.

[0018] 3. The introduction of ionic liquids into rubber can inherently reduce friction and entanglement between rubber molecules, acting as a plasticizer. Using them as a modifier for carbon black can improve its dispersibility and bonding with the base rubber, thereby enhancing the mechanical properties of the rubber after vulcanization. Furthermore, the carbon black acts as a carrier for the vulcanizer, vulcanizing accelerator, ionic liquid, and fluoroether oil as a dispersant. Compared to the existing method of directly adding liquid components, this method solves the problems of contamination and unstable fluororubber performance caused by liquid loss during addition and mixing, such as splashing and sticking to equipment. Furthermore, it eliminates the need for multiple cycles of "adding, dispersing, and re-adding."

[0019] 4. In the present invention, the possibility of excessive cross-linking agent precipitation and self-aggregation on the surface of the product during the vulcanization process is avoided, so the surface of the product is smooth and complete, defects such as small cracks are reduced, and the performance of the product is improved.

[0020] 5. The present invention uses carbon black as a carrier to attach liquid components, ionic liquids and fluoroether oils as dispersing aids. Compared with the solid finished vulcanizing agents used in the prior art, this patent avoids the introduction of unnecessary components, ensuring the purity of the formula. It can be applied to fields that require purity, such as food, medicine, and semiconductor manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is an appearance diagram of the rubber compound prepared in parallel with Example 1 of the present invention.

[0022] Figure 2This is the appearance of the rubber mix after vulcanization prepared in parallel with Example 1 of the present invention.

[0023] Figure 3 This is a diagram showing the scorching condition of the mixed sample of Comparative Example 1 of the present invention.

[0024] Figure 4 This is a diagram of a cylindrical specimen used to measure the compression set rate in Group 2 of Comparative Example 4 of the present invention.

[0025] Figure 5 This is a diagram of cylindrical specimens in Group 3 of Comparative Example 4 of the present invention.

[0026] Figure 6 This is a picture of the product after tensile-related mechanical properties testing of Group 1 of Comparative Example 4 of the present invention.

[0027] Figure 7 This is a picture of the product after tensile-related mechanical properties testing of Group 2 of Comparative Example 4 of the present invention.

[0028] Figure 8 This is a picture of the product after tensile-related mechanical properties testing of Group 3 of Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0029] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. It is obvious that the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] The present disclosure, including the relevant parameters or data in the examples, were obtained according to the following test methods: 1. Tensile strength and elongation at break: Tests were conducted using a microcomputer-controlled electronic universal testing machine in accordance with GB / T 528-2009. Fluororubber sheets measuring 100 mm × 100 mm × 2 mm were cut into Type I dumbbell shapes for tensile testing. The specimen length was 25 mm ± 0.5 mm.

[0031] 2. Hardness: Shore A hardness is tested according to GB / T531.1-2008 test method.

[0032] 3. Compression set: Tested according to GB / T 1683-2018 (70°C x 24h, 20% compression). The specimen is cylindrical with a diameter of (10±0.2) mm and a height of (10±0.2) mm.

[0033] Example 1 This embodiment provides a mixing process for a peroxide-cured fluororubber compound. The types and amounts of raw materials used in this embodiment are as shown in Table 1 below: Table 1 Types and amounts of raw materials used in Example 1 In this embodiment, the rubber compound is prepared by the following process steps: 1) Prepare materials: weigh the ingredients of each group according to the weight ratio; 2) Pretreatment: The weighed carbon black, accelerator, and modifier were added to anhydrous ethanol, ultrasonicated at room temperature for 5-10 minutes, then heated under reflux with stirring for 4 hours, then filtered and vacuum evaporated to obtain the pretreated filler carbon black; 3) Preparation of premix: Heat the vulcanizing agent and vulcanizing accelerator until melted, and place them together with the carbon black pretreated in step 2) in a blender and stir at 150-300 rpm for 5-20 seconds until the powder is free of lumps and oil stains, thereby preparing a premix; 4) Mixing: The fluororubber raw rubber weighed in step 1) is plasticized uniformly on an open mill. Then, the premix prepared in step 3) is slowly added to the rubber material until the premix is ​​completely mixed into the rubber material. The rubber material is then thinly passed through 12 times to ensure uniform dispersion of the filler. Finally, the rubber material is cooled to room temperature. During the mixing process, the rubber material temperature should be controlled below 65°C. 5) Re-mixing: The rubber compound prepared in step 4) is allowed to stand for 8 hours, and then thinned on an open mill 8 times to obtain a sheet of mixed rubber. During the re-mixing process, the temperature of the rubber compound is controlled below 65°C. To verify repeatability, three samples were mixed in parallel using the same procedure, and the mixing time and mass loss of the rubber compound were recorded for each mix. Subsequently, vulcanization and mechanical property testing were performed, with the results shown in Table 2. Vulcanization conditions were: a first stage at 175°C for 15 minutes, and a second stage at 230°C for 4 hours. The vulcanization conditions were identical.

[0034] Table 2 Performance test results of each parallel case of Example 1 As can be seen from Tables 1 and 2, the main mass loss during the open mixing process comes from the falling of small fragments of fluororubber raw rubber and the accumulated errors during multiple weighing processes; the mass loss basically accounts for about 0.2% of the raw rubber mass; compared with the performance of the rubber compound, there is no obvious deviation in the three mixings, and the product is relatively stable. Figure 1 Shown is the appearance of the rubber mix prepared in parallel with Example 1; Figure 2 The figure shows the appearance of the rubber mix prepared in parallel with Example 1 after vulcanization.

[0035] Example 2 This embodiment provides a mixing process for a peroxide-cured fluororubber compound, according to the types and amounts of raw materials shown in Table 3 below: Table 3 Types and amounts of raw materials used in Example 2 In this example, a rubber mix was prepared using the same process steps as in Example 1. To verify repeatability, three samples were mixed in parallel, and the mixing time and mass loss of the rubber were recorded for each mixing. Vulcanization and mechanical property testing were then performed. The specific time consumption, mass loss, and mechanical property records are shown in Table 4: Table 4 Performance test results of each parallel case of Example 2 In this embodiment, the mass loss is about 0.2%. The properties of the rubber compound do not show obvious deviation during the three mixings, and the product is relatively stable.

[0036] Example 3 This embodiment provides a mixing process for a fluororubber compound of a peroxide curing system. Compared with Example 1, the difference is that in this embodiment, the types and amounts of raw materials are as shown in Table 5, wherein the room temperature ionic liquid is EMI-TFSI, the fluoroether oil is Z60 from Solvay, and the pretreatment solvent is isopropyl alcohol. The compound is prepared in this embodiment according to the same process steps as in Example 1.

[0037] Table 5 Types and amounts of raw materials used in Example 3 The specific time consumption, mass loss and mechanical properties of this example are shown in Table 6: Table 6 Performance test results of Example 3 Example 4 This embodiment provides a mixing process for a fluororubber compound of a peroxide curing system. Compared with Example 1, the difference is that the types and amounts of raw materials in this embodiment are different, as shown in Table 7. The compound is prepared in this embodiment using the same process steps as in Example 1.

[0038] Table 7 Types and amounts of raw materials used in Example 4 The specific time consumption, mass loss and mechanical properties of this example are shown in Table 8: Table 8 Performance test results of Example 4 This embodiment changes the vulcanizing agent and the modifier, and can still stably obtain a rubber compound with performance that meets the standards in a relatively short period of time.

[0039] Comparative Example 1 Compared with Example 1, the types and amounts of raw materials used in this comparative example 1 are the same as those in Example 1, except that the rubber compound is prepared according to the following process steps: 1) Prepare materials: weigh the ingredients of each group according to the weight ratio; 2) Pretreatment: The weighed carbon black, accelerator, and modifier were added to anhydrous ethanol, ultrasonicated at room temperature for 5-10 minutes, then heated under reflux with stirring for 4 hours, then filtered and vacuum evaporated to obtain the pretreated filler carbon black; 3) Preparation of premix: Heat the vulcanizing agent and vulcanizing accelerator until melted, and place them together with the carbon black pretreated in step 2) in a blender and stir at 150-300 rpm for 5-20 seconds until the powder is free of lumps and oil stains, thereby preparing a premix; 4) Mixing: Set the internal mixer temperature to the desired value and mix the fluororubber raw rubber weighed in step 1) in the internal mixer until uniform. Then, add the premix prepared in step 3) to the rubber all at once and begin mixing. Record the mixing time and the mixing consistency of the rubber. Repeat the mixing three times with the same formula at different set temperatures.

[0040] Inspection: The mixed rubber after internal mixing is thinly passed on an open mixing mill to form a sheet. Observe and record whether the rubber material contains agglomerated particles formed after scorch. The mixing effect is shown in Table 9.

[0041] Table 9 Mixing effect of comparative example 1 When using an internal mixer for mixing, the time consumed is inversely proportional to the set temperature. At a set temperature of 50°C, obvious white rubber clumps can still be seen in the rubber compound after 30 minutes of internal mixing, indicating that the raw rubber has not yet been completely dispersed with components such as fillers. After the rubber compound is passed through an open mixer to mix the rubber compound and fillers, it is observed that a small amount of agglomerated debris particles have appeared in the rubber compound. Repeated thinning cannot completely restore the uniformity and smoothness of the rubber compound, indicating that the rubber compound has been scorched. When the temperature setting is gradually increased to 110°C, the internal mixing efficiency is significantly improved, but correspondingly, the number of agglomerated particles caused by scorch increases significantly. Compared with open mixing, the shear force of the internal mixer screw is greater, and the rubber compound heats up more significantly. However, the local heat in the enclosed space cannot be quickly conducted and dispersed, resulting in localized excessive temperature of the rubber compound and scorch.

[0042] Because the rubber compound is scorched after mixing, it can no longer be used normally and the performance test is meaningless; Figure 3 The figure shows the scorching condition of the mixed sample of parallel 1 of this comparative example. After thin-passing, a large number of agglomerated particles can be seen, and the scorching is obvious.

[0043] Comparative Example 2 Compared with Example 1, the types and amounts of raw materials used in this comparative example are the same as those in Example 1, except that the rubber compound is prepared according to the following process steps: 1) Prepare materials: weigh the ingredients of each group according to the weight ratio; 2) Mixing: Thinly plasticize the raw fluororubber on an open mill and then roll it; first add carbon black and disperse it thinly; then add modifier and accelerator in sequence and disperse them thinly; then slowly add vulcanizing agent dropwise, and after thin dispersion, slowly add vulcanizing agent dropwise and mix; 3) After all components are mixed into the rubber compound, pass it through the mixer 12 times to fully disperse all the materials. During the whole mixing process, pay attention to control the temperature of the rubber compound not higher than 65℃; 4) After mixing, cool and let stand in a dryer at room temperature for 12 hours, then return to the mixer and thin it 8 times; the temperature of the rubber compound is controlled below 65℃, and the mixed rubber is sheeted.

[0044] Three parallel samples were mixed in the same way, and the test phenomena and mass loss were recorded. Then, vulcanization and mechanical property tests were performed. The specific time consumption, mass loss and mechanical property records are shown in Table 10: Table 10 Performance test results of each parallel example of Comparative Example 2 The main difference between this comparative example and Example 1 lies in the mixing process, which employs batch addition of the components. Table 10 shows that the sequential, multiple-addition method of open mixing consumes significantly more time than the all-at-once addition in Example 1. Furthermore, liquid splashing was observed during the mixing of the three parallel samples in the comparative example, ultimately resulting in more pronounced mass loss of varying degrees. This also led to fluctuations in mechanical properties, primarily manifested by significant deviations in compression set, particularly pronounced in parallel group 3.

[0045] Comparative Example 3 The difference between this comparative example and Example 1 is that the modifier and accelerator are deleted from the raw materials of this comparative example, and the remaining components are the same as those of Example 1. The rubber compound is prepared by the following process steps in this example: 1) Prepare materials: weigh the ingredients of each group according to the weight ratio; 2) Preparation of premix: Heat the vulcanizing agent and vulcanizing accelerator until melted, then place them together with carbon black into a blender and stir at a speed of 150-300 r / min for 5-20 seconds until the powder is free of lumps and oil stains on the surface, thereby preparing a premix; 3) Mixing: The fluororubber raw rubber weighed in step 1) is plasticized evenly on an open mill. Then, the premix prepared in step 3) is slowly added to the rubber material until the premix is ​​completely mixed into the rubber material. The rubber material is then thinly passed through 12 times to evenly disperse the filler. Finally, the rubber material is cooled to room temperature. During the mixing process, the rubber material temperature should be controlled below 65°C. 4) Re-mixing: The rubber compound prepared in step 4) is allowed to stand for 8 hours, and is thinned 8 times on an open mixing mill to obtain a sheet of mixed rubber. During the re-mixing process, the temperature of the rubber compound is controlled below 65°C.

[0046] In this comparative example, three parallel samples were mixed in the same manner, and the test phenomena and mass loss were recorded. Then, vulcanization and mechanical property tests were performed. The specific time consumption, mass loss and mechanical property records are shown in Table 11: Table 11 Performance test results of each parallel example of comparative example 3 It can be seen from Table 11 that the dispersion of filler decreases after the modifier and accelerator are removed. Moreover, the carbon black is not modified after the modifier and accelerator are removed. The dispersion of carbon black and the bonding ability of carbon black with base rubber are reduced, thereby reducing the mechanical properties of the rubber after vulcanization. The thin-pass process cannot completely disperse it well, and the compression permanent set rate of the rubber after vulcanization increases slightly.

[0047] Comparative Example 4 This comparative example differs from Example 1 in the amount of TAIC used as a vulcanization accelerator: the first group used less TAIC than in Example 1, while the remaining two groups used significantly more. Detailed raw material types and amounts are shown in Table 12. A rubber compound was prepared using the same process steps as Example 1. Test results and mass loss were recorded. Vulcanization and mechanical property testing were also performed. Specific time consumption, mass loss, and mechanical property records are shown in Table 13. Table 12 Types and amounts of raw materials for comparative example 4 Table 13 Performance test results of each parallel example of Comparative Example 4 In Group 1, due to insufficient addition of vulcanizing accelerators, the crosslinking density of the rubber after vulcanization is insufficient, its tensile strength is low, and the compression set rate is high.

[0048] After vulcanization, crystals precipitated and cracks appeared on the surface of the parts of Groups 2 and 3. The mechanical properties test data are no longer of reference value. Only hardness was measured. Figure 4 The cylindrical specimen used to measure the compression set rate in Group 2 of this comparative example is shown, in which obvious crystal precipitates and cracks can be seen; Figure 5This is an abnormal cylindrical specimen in Group 3, with more obvious white crystalline precipitates and arc-shaped cracks; Figure 6 The figure shows the effective parts after the tensile-related mechanical properties test of the rubber mix obtained in Group 1. The fracture is located at the narrow part of the dumbbell-shaped part; Figure 7 and 8 These are some parts from Groups 2 and 3 after tensile testing of mechanical properties. According to Section 13.1 of GB / T 1683-2018, all of these specimens are considered abnormal and invalid. The tensile fracture did not occur in the narrow area of ​​the part, but rather in other locations. This indicates that small cracks on the surface of the part caused unexpected cracking.

[0049] It will be understood that the present invention is described by way of some embodiments, and it will be appreciated by those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by the present invention.

Claims

1. A mixing process for a peroxide-cured fluororubber compound, characterized by: The rubber mix comprises the following components in parts by weight: Fluororubber raw rubber: 100 parts; Carbon black: 5-40 parts; Vulcanization accelerator: 0.5~3 parts; Vulcanizing agent: 0.5~3 parts; Modifier: 0.1~5 parts; Accelerator: 0.1~5 parts; The vulcanizing agent is dicumyl peroxide, di-tert-butyl peroxide isopropyl benzene or 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; The vulcanization auxiliary agent is triallyl isocyanurate or triallyl tricyanurate; The mixing process of the rubber compound comprises the following steps: 1) Prepare materials: weigh the ingredients of each group according to the weight ratio; 2) Pretreatment: Add the weighed carbon black, accelerator and modifier to the pretreatment solvent, ultrasonicate at room temperature for 5-10 minutes, heat under reflux and stir for 4 hours, then filter and remove the solvent by vacuum rotary evaporation to obtain the pretreated filler carbon black; 3) Preparation of premix: Heat the vulcanizing agent and vulcanizing accelerator until melted, and place them together with the carbon black pretreated in step 2) in a blender and stir at 150-300 rpm for 5-20 seconds until the powder is free of lumps and oil stains, thereby preparing a premix; 4) Mixing: The fluororubber raw rubber weighed in step 1) is plasticized uniformly on an open mill. Then, the premix prepared in step 3) is slowly added to the rubber material until the premix is ​​completely mixed into the rubber material. The rubber material is then thinly passed through 12 times to ensure uniform dispersion of the filler. Finally, the rubber material is cooled to room temperature. During the mixing process, the rubber material temperature should be controlled below 65°C. 5) Re-mixing: The rubber compound prepared in step 4) is allowed to stand for 8-12 hours, and is thinned on an open mixing mill at least 8 times to obtain a sheet of mixed rubber. During the re-mixing process, the temperature of the rubber compound is controlled below 65°C.

2. The mixing process of the peroxide-cured fluororubber compound according to claim 1, characterized in that: The fluororubber raw rubber is one of binary fluororubber, ternary fluororubber or perfluoroether rubber or a combination of several thereof.

3. The mixing process of the peroxide-cured fluororubber compound according to claim 1, characterized in that: The carbon black is selected from one or a combination of brands N990, N330, and N220.

4. The mixing process of the peroxide-cured fluororubber compound according to claim 1, characterized in that: The modifier is a fluorine-containing room temperature ionic liquid.

5. The mixing process of the peroxide-cured fluororubber compound according to claim 4, characterized in that: The fluorine-containing room temperature ionic liquid is 1,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-propyl-2, 3-Dimethylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide, N-butylpyridinium bis(trifluoromethanesulfonyl)imide, tri-n-butylmethylammonium bis(trifluoromethanesulfonyl)imide, tributylphosphine bis(trifluoromethanesulfonyl)imide, 1-propyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-propyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium hexafluorophosphate salt, 1-octyl-3-methylimidazolium tetrafluoroborate, 1-octyl-3-methylimidazolium hexafluorophosphate, 1-decyl-3-methylimidazolium tetrafluoroborate, 1-decyl-3-methylimidazolium hexafluorophosphate, 1-dodecyl-3-methylimidazolium tetrafluoroborate, 1-tetradecyl-3-methylimidazolium tetrafluoroborate, 1-hexadecyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-propyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide salt or 1-butyl-2,3-dimethylimidazolium hexafluorophosphate, or a combination of more thereof.

6. The mixing process of the peroxide-cured fluororubber compound according to claim 1, characterized in that: The accelerator is fluoroether oil, and the molecular weight of the fluoroether oil is 500-8000.

7. The mixing process of the peroxide-cured fluororubber compound according to claim 1, characterized in that: The pretreatment solvent in step 2) is anhydrous ethanol or isopropanol.

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