Anti-aging fluororubber sealing ring and preparation method thereof

Abstract

The invention relates to the technical field of fluororubber, in particular to an anti-aging fluororubber sealing ring and a preparation method thereof.The anti-aging fluororubber sealing ring is prepared from, by weight, 70-80 parts of raw fluororubber, 1-2 parts of vulcanizing agent, 2-4 parts of accelerant, 0.5-1.5 parts of zinc stearate, 3-5 parts of light magnesium oxide, 15-20 parts of modified carbon black and 2-4 parts of plasticizer. The anti-aging fluororubber sealing ring prepared by the invention has excellent anti-aging performance and mechanical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of fluororubber, and in particular to an aging-resistant fluororubber sealing ring and a preparation method thereof. Background Art

[0002] In industrial production, seals are core components that ensure the safe operation of equipment. Their primary function is to prevent fluid leakage and the intrusion of foreign matter. They are widely used in pressure vessels, automotive, aerospace, petrochemical, nuclear power, semiconductors, and other fields. Failure of seals, such as aging, cracking, and hardening, can directly lead to decreased equipment efficiency, increased energy consumption, and even significant risks such as explosions and pollution. Therefore, long-term stability is a core performance indicator for seals. Early seals were mostly made of ordinary rubbers such as nitrile rubber, silicone rubber, and chloroprene rubber. However, their aging resistance was significantly insufficient in complex environments. These materials could not meet the stringent requirements of modern industry for high temperature, high humidity, strong corrosion, and long life, driving the development of high-performance fluororubber seals. Fluororubber is a synthetic rubber containing fluorine atoms in the main chain or side chains. The strong electronegativity and small atomic radius of fluorine atoms give it unique resistance to high temperatures, chemical corrosion, and weathering. Due to these properties, fluororubber seals have gradually become the preferred choice in high-end industrial fields.

[0003] Patent CN116478492A discloses a modified fluororubber seal ring and its preparation method. The seal ring comprises raw materials fluororubber, aramid pulp, a resin composition, dicumyl peroxide, a reinforcing agent, and a stabilizer. The preparation method comprises: initially mixing the aramid pulp and reinforcing agent and then placing them together with the fluororubber in an internal mixer for mastication; placing the resin composition in the internal mixer, mixing, and then draining the mixture onto an open mixer for cooling; placing the cooled mixture back into an open mixer, adding dicumyl peroxide and a stabilizer, and then continuing to mix and cool; cutting the mixture obtained from the mixing process, placing it in a vulcanizer, and vulcanizing and shaping it. This application simplifies the selection of raw materials, maintains the excellent performance of traditional fluororubber seal rings, further improves mechanical strength and hardness, and reduces production costs. However, due to the significant difference in polarity between aramid and fluororubber, untreated pulp may cause debonding, resulting in a poor sealing effect.

[0004] Patent CN116836499A discloses a method for preparing a fluororubber sealing ring for semiconductors that is resistant to aging and cracking. The method uses fluororubber, high-temperature resistant perfluoroether rubber, high-temperature resistant EPDM rubber, carbon black N990, carbon black N330, metal oxides, and vulcanizing agents, and performs mixing, preforming, primary vulcanization, secondary vulcanization, trimming, polishing, clean cleaning, and dust-free packaging to prepare a fluororubber sealing ring for semiconductors that is resistant to aging and cracking. The fluororubber sealing ring for semiconductors that is resistant to aging and cracking prepared by the invention has good high-temperature resistance and aging-cracking resistance, but the compatibility between fluororubber and EPDM rubber is extremely poor, which easily leads to phase separation and a decrease in mechanical properties.

[0005] Therefore, there is an urgent need in the market for a fluororubber sealing ring with excellent aging resistance and mechanical properties. Summary of the Invention

[0006] In view of the problems existing in the prior art, the object of the present invention is to obtain a fluororubber sealing ring with excellent aging resistance and mechanical properties.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] On the one hand, the present invention provides an aging-resistant fluororubber sealing ring, which comprises the following raw materials, by weight: 70-80 parts of fluororubber raw rubber, 1-2 parts of a vulcanizing agent, 2-4 parts of an accelerator, 0.5-1.5 parts of zinc stearate, 3-5 parts of light magnesium oxide, 15-20 parts of modified carbon black, and 2-4 parts of a plasticizer.

[0009] The present application prepares an aging-resistant fluororubber sealing ring by mixing fluororubber raw rubber, a vulcanizing agent, an accelerator, zinc stearate, light magnesium oxide, modified carbon black, and a plasticizer. The aging-resistant fluororubber sealing ring has the characteristics of excellent aging resistance and excellent mechanical properties.

[0010] In some embodiments, the vulcanizing agent is bisphenol AF or bisphenol A.

[0011] In some embodiments, the accelerator is one or more of benzyltriphenylphosphonium chloride, benzyltriphenylphosphonium bromide, benzyltriethylammonium chloride, and tetrabutylammonium bromide.

[0012] Preferably, the accelerator is benzyltriphenylphosphonium chloride.

[0013] In some embodiments, the method for preparing the modified carbon black comprises the following steps:

[0014] A1. Place carbon black in a reaction vessel, add 7-9 mol / L nitric acid solution, stir and reflux at 70-80°C for 7-9 hours, wash, filter, and dry to constant weight to obtain activated carbon black;

[0015] A2. Add tridecafluorooctyltrimethoxysilane to an ethanol aqueous solution, stir at room temperature for 20-40 min, add the activated carbon black obtained in step A1, reflux at 50-60°C for 6-8 h, centrifuge, and wash the solid with ethanol 3-5 times, and dry to obtain modified carbon black.

[0016] This application increases the dispersibility of modified carbon black in fluororubber by using tridecafluorooctyltrimethoxysilane to modify activated carbon black, which is beneficial to improving the aging resistance and mechanical properties of fluororubber. After hydrolysis, the silane end group of tridecafluorooctyltrimethoxysilane forms a Si-OC covalent bond with the hydroxyl group on the surface of carbon black. At the same time, the long fluorine-containing chain at the other end has excellent compatibility with the fluororubber matrix, forming a strong chemical bridge of "carbon black-silane-fluororubber", which significantly enhances the interfacial bonding force. The fluorine-containing chain segments on the surface of the modified carbon black form a hydrophobic and oleophobic protective layer that can resist corrosion by strong acids and strong alkalis and penetration by organic solvents, further improving the sealing performance of the fluororubber sealing ring.

[0017] In some embodiments, the mass ratio of the activated carbon black to tridecafluorooctyltrimethoxysilane in step A2 is 1:(0.05-0.1).

[0018] In some embodiments, the carbon black is a mixture of N330 and N990.

[0019] Preferably, the mass ratio of N330 to N990 is 1:(1.5-2.5).

[0020] In some embodiments, the method for preparing the plasticizer comprises the following steps:

[0021] B1. Add rare earth metal oxide and KH-550 silane coupling agent to ethanol aqueous solution, ultrasonicate at 30-40° C. for 1-2 hours, and dry to obtain modified rare earth metal oxide;

[0022] B2. Add vinyl fluorosilicone oil, catalyst and modified rare earth oxide obtained in step B1 to toluene, react at 90-110° C. for 4-6 hours, wash, filter and dry to obtain a plasticizer.

[0023] The fluorine groups in the plasticizer prepared by this application are highly compatible with the fluorocarbon chains of fluororubber, forming a dense protective layer that can improve the aging resistance of fluororubber and hinder the penetration of solvents. It can also improve processing fluidity, making the various substances in fluororubber evenly dispersed, which is beneficial to improving the overall performance of fluororubber. This application further uses KH-550 silane coupling agent to modify rare earth metal oxides to obtain modified rare earth metal oxides containing amino groups, which are then reacted with vinyl fluorosilicone oil to obtain plasticizers loaded with rare earth metal oxides, wherein the rare earth metal oxides can limit the migration of vinyl fluorosilicone oil at high temperatures, making the performance of the plasticizer more stable and not easy to precipitate or degrade; and the siloxane chains in the plasticizer provide flexibility. The synergistic effect of the two improves the aging resistance and mechanical properties of fluororubber at the same time, and the rare earth metal oxides can catalyze the decomposition of peroxide radicals generated by fluororubber at high temperatures, delaying the breakage of the main chain, and further improving the aging resistance of fluororubber.

[0024] In some embodiments, the rare earth metal oxide is one or more of lanthanum oxide, yttrium oxide, and cerium oxide.

[0025] Preferably, the rare earth metal oxide is cerium oxide.

[0026] In some embodiments, the mass ratio of the rare earth metal oxide and the KH-550 silane coupling agent is 1:(0.04-0.08).

[0027] In some embodiments, the mass ratio of the vinyl fluorosilicone oil and the modified rare earth metal oxide is 1:(0.07-0.11).

[0028] Another aspect of the present application provides a preparation method of an anti-aging fluororubber sealing ring, comprising the following steps:

[0029] S1, pass the fluororubber raw rubber on the open mill for 3-5 times, the roller temperature is 40-60℃, form a uniform package roller, add zinc stearate, light magnesium oxide, modified carbon black in turn, mix until there is no powder agglomeration, add plasticizer, mix and lay down for 20-24h, get the initial mixture;

[0030] S2, put the initial mixture into the open mill, the roller temperature is 40-50℃, add vulcanizing agent, accelerator, open mill for 4-6min, then cool; the material obtained by opening the mill is cut and molded by extrusion to obtain sealing ring blank;

[0031] S3, put the sealing ring blank into the vulcanizing machine for primary vulcanization, the condition is 170-180℃, 10-15MPa, vulcanize for 10-15min, then put it into the oven for secondary vulcanization, the condition is to raise the temperature from room temperature to 200℃ for 20-24h, then keep it for 4-5h.

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] (1) The anti-aging fluororubber sealing ring prepared by mixing the fluororubber raw rubber, vulcanizing agent, accelerator, zinc stearate, light magnesium oxide, modified carbon black and plasticizer has excellent anti-aging performance and mechanical properties.

[0034] (2) The fluorine group in the plasticizer prepared by the present application has good compatibility with the fluorocarbon chain of the fluororubber, forms a dense protective layer, can improve the anti-aging property of the fluororubber and hinder the penetration of the solvent, and can improve the processing fluidity, make the substances in the fluororubber disperse uniformly, and is beneficial to improve the overall performance of the fluororubber.

[0035] (3) The present invention uses rare earth metal oxides to modify vinyl fluorosilicone oil, which can decompose peroxide radicals generated by fluororubber at high temperatures, delaying the breakage of the main chain. Furthermore, the rare earth metal oxides can limit the migration of vinyl fluorosilicone oil at high temperatures, while the siloxane chains in the plasticizer provide flexibility. The rare earth metal oxides inhibit high-temperature degradation, thereby improving both the aging resistance and mechanical properties of the fluororubber. DETAILED DESCRIPTION

[0036] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following examples are illustrative of the present invention and are intended only to illustrate the present invention and are not intended to limit the present invention. Other combinations and various modifications within the scope of the present invention may be made without departing from the spirit or scope of the present invention.

[0037] In the following examples and comparative examples, except for the modified carbon black and plasticizer, the other compounds and related reagents used can be purchased from the market. Among them, the fluororubber raw rubber model is FKM 26, purchased from Dongguan Caihua Plastic Technology Co., Ltd.; the vinyl fluorosilicone oil has a CAS number of 68951-98-4; the average particle size of cerium oxide is 30 nm, purchased from Hubei Langbowan Biomedicine Co., Ltd.; and the CAS number of Custer catalyst is 68478-92-2.

[0038] Preparation Example 1

[0039] The preparation method of modified carbon black-1 comprises the following steps:

[0040] A1. Place 10 g of carbon black in a reaction vessel, add 80 g of 8 mol / L nitric acid aqueous solution, stir and reflux at 80° C. for 8 h, wash, filter, and dry to constant weight to obtain activated carbon black;

[0041] A2. Add 0.8 g of tridecafluorooctyltrimethoxysilane to 50 g of 80 wt% ethanol aqueous solution, stir at room temperature for 30 min, add 10 g of the activated carbon black obtained in step A1, reflux at 55° C. for 7 h, centrifuge, and wash the solid with anhydrous ethanol four times, and dry to obtain modified carbon black-1;

[0042] Among them, carbon black is a mixture of N330 and N990, and the mass ratio of the two is 1:2.

[0043] Preparation Example 2

[0044] The preparation method of modified carbon black-2 is the same as that of Preparation Example 1, except that the amount of tridecafluorooctyltrimethoxysilane added is 1.5 g.

[0045] Preparation Example 3

[0046] The preparation method of plasticizer-1 comprises the following steps:

[0047] B1. Add 1 g of cerium oxide and 0.06 g of KH-550 silane coupling agent to 50 g of 80 wt% ethanol aqueous solution, ultrasonicate at 35° C. for 1.5 h, and dry to obtain a modified rare earth metal oxide;

[0048] B2. Add 10 g of vinyl fluorosilicone oil, 0.1 g of Custer catalyst and 0.9 g of modified rare earth oxide to 50 g of toluene, react at 100° C. for 5 h, wash, filter and dry to obtain plasticizer-1.

[0049] Preparation Example 4

[0050] The preparation method of plasticizer-2 is the same as that of Preparation Example 3, except that the addition amount of KH-550 silane coupling agent is 0.02 g.

[0051] Preparation Example 5

[0052] The preparation method of Plasticizer-3 is the same as that of Preparation Example 3, except that the added amount of the modified rare earth metal oxide is 1.3 g.

[0053] Example 1

[0054] An aging-resistant fluororubber sealing ring comprises the following raw materials, measured by weight: 75 parts of fluororubber raw rubber, 1.5 parts of bisphenol AF, 3 parts of benzyltriphenylphosphonium chloride, 1 part of zinc stearate, 4 parts of light magnesium oxide, 117 parts of modified carbon black, and 13 parts of plasticizer.

[0055] The method for preparing the aging-resistant fluororubber sealing ring of this embodiment comprises the following steps:

[0056] S1. Roll the fluororubber raw rubber on an open mill 4 times with a roller temperature of 50°C to form a uniform roll. Then, zinc stearate, light magnesium oxide, and modified carbon black-1 are added in sequence and mixed until there is no powder agglomeration. Then, plasticizer-1 is added, mixed, and the mixture is left to stand for 22 hours to obtain a primary mixture.

[0057] S2. Add the primary mixed material into an open mill, set the roller temperature at 45° C., add bisphenol AF and benzyl triphenyl phosphonium chloride, and continue milling for 5 minutes, then cool. Extrude, cut, and mold the material obtained from the mill to obtain a sealing ring blank.

[0058] S3. Place the sealing ring blank into a vulcanizer for primary vulcanization at 175°C and 12 MPa for 12 minutes, then place it into an oven for secondary vulcanization at a temperature raised from room temperature to 200°C for 22 hours and then kept warm for 4.5 hours.

[0059] Example 2

[0060] An aging-resistant fluororubber sealing ring comprises the following raw materials, measured by weight: 70 parts of fluororubber raw rubber, 1 part of bisphenol AF, 2 parts of benzyltriphenylphosphonium chloride, 0.5 parts of zinc stearate, 3 parts of light magnesium oxide, 115 parts of modified carbon black, and 12 parts of plasticizer.

[0061] The method for preparing the aging-resistant fluororubber sealing ring of this embodiment comprises the following steps:

[0062] S1. Roll the fluororubber raw rubber on an open mill three times at a roller temperature of 40°C to form a uniform roll, then add zinc stearate, light magnesium oxide, and modified carbon black-1 in sequence and mix until there is no powder agglomeration. Then add plasticizer-1, mix thoroughly, and let stand for 20 hours to obtain a primary mix.

[0063] S2. The primary mixed material is put into an open mill, the roller temperature is 40° C., bisphenol AF and benzyl triphenyl phosphonium chloride are added, and the mill is continued for 6 minutes, followed by cooling; the material obtained from the open mill is extruded, cut, and molded to obtain a sealing ring blank;

[0064] S3. Place the sealing ring blank into a vulcanizer for primary vulcanization at 170°C and 10 MPa for 15 minutes, then place it into an oven for secondary vulcanization at a temperature raised from room temperature to 200°C for 20 hours and then kept warm for 4 hours.

[0065] Example 3

[0066] An aging-resistant fluororubber sealing ring comprises the following raw materials, measured by weight: 80 parts of fluororubber raw rubber, 2 parts of bisphenol AF, 4 parts of benzyltriphenylphosphonium chloride, 1.5 parts of zinc stearate, 5 parts of light magnesium oxide, 20 parts of modified carbon black-1, and 14 parts of plasticizer.

[0067] The method for preparing the aging-resistant fluororubber sealing ring of this embodiment comprises the following steps:

[0068] S1. Roll the fluororubber raw rubber on an open mill for 5 times at a roller temperature of 60°C to form a uniform roll. Then, zinc stearate, light magnesium oxide, and modified carbon black-1 are added in sequence and mixed until no powder agglomerates. Then, plasticizer-1 is added, mixed, and the mixture is allowed to stand for 24 hours to obtain a primary mixture.

[0069] S2. The primary mixed material is put into an open mill, the roller temperature is 50° C., bisphenol AF and benzyl triphenyl phosphonium chloride are added, and the mill is continued for 4 minutes, followed by cooling; the material obtained from the open mill is extruded, cut, and molded to obtain a sealing ring blank;

[0070] S3. Place the sealing ring blank into a vulcanizer for primary vulcanization at 180°C and 15MPa for 10 minutes, then place it into an oven for secondary vulcanization at a temperature raised from room temperature to 200°C for 24 hours and then kept warm for 5 hours.

[0071] Example 4

[0072] An aging-resistant fluororubber sealing ring and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified carbon black-1 is replaced by modified carbon black-2.

[0073] Example 5

[0074] An aging-resistant fluororubber sealing ring and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of plasticizer-1 is replaced by plasticizer-2.

[0075] Example 6

[0076] An aging-resistant fluororubber sealing ring and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of plasticizer-1 is replaced by plasticizer-3.

[0077] Example 7

[0078] An aging-resistant fluororubber sealing ring and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of plasticizer-1 is replaced by vinyl fluorosilicone oil.

[0079] Comparative Example 1

[0080] An aging-resistant fluororubber sealing ring and a preparation method thereof, the specific implementation method is the same as that of Example 1, except that an equal amount of modified carbon black-1 is replaced by carbon black, wherein the carbon black is a mixture of N330 and N990, and the mass ratio of the two is 1:2.

[0081] Performance Testing

[0082] The following performance tests were performed on the aging-resistant fluororubber sealing rings obtained in the above embodiments and comparative examples:

[0083] The tensile properties are tested according to GB / T528-2009.

[0084] The compression set performance is tested according to GB / T 7759.1-2015.

[0085] The test results are shown in Table 1:

[0086] Table 1

[0087]

[0088]

[0089] It can be seen from the data in Table 1 that the fluororubber sealing rings in Examples 1-3 of the present invention have good mechanical properties and aging resistance. From the comparison between Example 4 and Example 1, it can be seen that changing the ratio of activated carbon black and tridecafluorooctyltrimethoxysilane will increase the silane segments, resulting in a weakening of the rubber molecular chain force, and the residual silane segments are easily decomposed, thereby reducing the mechanical properties and aging resistance of the fluororubber sealing ring; from the comparison between Example 5 and Example 1, it can be seen that changing the ratio of rare earth metal oxide and KH-550 silane coupling agent will reduce the amino groups on the modified rare earth metal oxide, affecting its reaction with vinyl fluorosilicone oil, thereby reducing the mechanical properties and aging resistance of the fluororubber sealing ring. The mechanical properties and aging resistance of the ring are reduced; from the comparison of Example 6 and Example 1, it can be seen that when the ratio of vinyl fluorosilicone oil and modified rare earth metal oxide is changed, excessive rare earth metal may catalyze the degradation of the fluororubber main chain, causing its mechanical properties and compression permanent deformation to deteriorate; from the comparison of Example 7 and Example 1, it can be seen that directly using vinyl fluorosilicone oil as a plasticizer will make the plasticizer easily precipitated at high temperature, resulting in the compression permanent deformation of the rubber being affected, and the rigid inorganic phase in the fluororubber is reduced, resulting in the reduction of the mechanical properties of the fluororubber; from the comparison of Comparative Example 1 and Example 1, it can be seen that when unmodified carbon black is used, the mechanical properties and aging resistance of the fluororubber sealing ring are poor.

[0090] The above embodiments are only for illustrating the technical concept and features of the present invention. Its purpose is to enable people familiar with this technology to understand the content of the present invention and implement it. It cannot be used to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. An aging-resistant fluororubber sealing ring, characterized in that: The raw materials are as follows: 70-80 parts of fluororubber raw rubber, 1-2 parts of vulcanizing agent, 2-4 parts of accelerator, 0.5-1.5 parts of zinc stearate, 3-5 parts of light magnesium oxide, 15-20 parts of modified carbon black, and 2-4 parts of plasticizer.

2. The aging-resistant fluororubber sealing ring according to claim 1, characterized in that: The vulcanizing agent is bisphenol AF or bisphenol A.

3. The aging-resistant fluororubber sealing ring according to claim 1, characterized in that: The preparation method of the modified carbon black comprises the following steps: A1. Place carbon black in a reaction vessel, add 7-9 mol / L nitric acid solution, stir and reflux at 70-80°C for 7-9 hours, wash, filter, and dry to constant weight to obtain activated carbon black; A2. Add tridecafluorooctyltrimethoxysilane to an ethanol aqueous solution, stir at room temperature for 20-40 min, add the activated carbon black obtained in step A1, reflux at 50-60°C for 6-8 h, centrifuge, and wash the solid with ethanol 3-5 times, and dry to obtain modified carbon black.

4. The aging-resistant fluororubber sealing ring according to claim 3, characterized in that: The mass ratio of the activated carbon black to tridecafluorooctyltrimethoxysilane in step A2 is 1:(0.05-0.1).

5. The aging-resistant fluororubber sealing ring according to claim 3, characterized in that: The carbon black is a mixture of N330 and N990.

6. The aging-resistant fluororubber sealing ring according to claim 1, characterized in that: The preparation method of the plasticizer comprises the following steps: B1. Add rare earth metal oxide and KH-550 silane coupling agent to ethanol aqueous solution, ultrasonicate at 30-40° C. for 1-2 hours, and dry to obtain modified rare earth metal oxide; B2. Add vinyl fluorosilicone oil, catalyst and modified rare earth oxide obtained in step B1 to toluene, react at 90-110° C. for 4-6 hours, wash, filter and dry to obtain a plasticizer.

7. The aging-resistant fluororubber sealing ring according to claim 6, characterized in that: The rare earth metal oxide is one or more of lanthanum oxide, yttrium oxide and cerium oxide.

8. The aging-resistant fluororubber sealing ring according to claim 6, characterized in that: The mass ratio of the rare earth metal oxide to the KH-550 silane coupling agent is 1:(0.04-0.08).

9. The aging-resistant fluororubber sealing ring according to claim 6, characterized in that: The mass ratio of the vinyl fluorosilicone oil to the modified rare earth metal oxide is 1:(0.07-0.11).

10. A method for preparing the aging-resistant fluororubber sealing ring according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Roll the fluororubber raw rubber on an open mill for 3-5 times at a roller temperature of 40-60°C to form a uniform roll, then add zinc stearate, light magnesium oxide, and modified carbon black in sequence and mix until there is no powder agglomeration, add plasticizer, mix thoroughly, and let stand for 20-24 hours to obtain a primary mix; S2. Add the primary mixed material into an open mill, set the roller temperature at 40-50°C, add the vulcanizing agent and accelerator, and mill for 4-6 minutes before cooling; extrude, cut, and mold the material obtained from the mill to obtain a sealing ring blank; S3. Place the sealing ring blank into a vulcanizer for primary vulcanization at 170-180°C, 10-15MPa, and vulcanize for 10-15 minutes. Then place the blank into an oven for secondary vulcanization at a temperature of 20-24 hours from room temperature to 200°C, and then keep warm for 4-5 hours.

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