High-temperature-resistant silicone rubber and sealing ring

Abstract

The invention discloses high-temperature-resistant silicone rubber and a sealing ring. The high-temperature-resistant silicone rubber comprises the following raw materials in parts by weight: 80-120 parts of methyl vinyl silicone rubber; the methyl vinyl silicone rubber is a mixture of MVQ (Methyl Vinyl Quality) 110-0 and MVQ (Methyl Vinyl Quality) 110-2; 40 to 60 parts of modified fumed silica; 5 to 15 parts of fluorine micro powder; 5-15 parts of a high temperature resistant agent; the high-temperature-resistant agent is a mixture of iron oxide red and nano titanium dioxide; 3-6 parts of hydroxyl silicone oil; 1-3 parts of hydrogen-containing silicone oil; and 0.1-2 parts of a coupling agent. According to the high-temperature-resistant silicone rubber and the sealing ring, the design is reasonable, the high-temperature-resistant performance and the comprehensive performance of the silicone rubber are improved through the formula design of the high-temperature-resistant silicone rubber and optimization of the preparation method, and the application prospect is wide.

Description

Technical Field

[0001] The invention belongs to the technical field of rubber, and in particular relates to a high temperature resistant silicone rubber and a sealing ring. Background Art

[0002] Silicone rubber, with its unique performance advantages, occupies an important position in the production of sealing rings. Sealing rings made of silicone rubber are widely used in many industries. Silicone rubber is a polymer material with high elasticity, good flexibility and excellent insulation performance. The silicon-oxygen bond energy in its molecular structure is high, which makes silicone rubber have good thermal and chemical stability, and can maintain its performance under a variety of complex environmental conditions.

[0003] Silicone rubber seals play an indispensable role in sealing various industrial equipment, electronic products, automobile manufacturing, aerospace and other fields. For example, in electronic products, silicone rubber seals can effectively prevent dust, moisture and other impurities from entering the equipment, protecting precision electronic components from interference from external environmental factors; in the engine compartment of a car, facing harsh conditions such as high temperature, oil pollution and vibration, silicone rubber seals can ensure the sealing between the engine components and prevent problems such as oil leakage; in the aerospace field, for the extremely high requirements for the cabin sealing of aircraft and the sealing of aircraft engines, silicone rubber seals provide important guarantees for flight safety with their excellent performance.

[0004] In recent years, with the continuous development of modern industry, the demand for materials that can work stably in high temperature environments has been growing. In this context, the research on high temperature resistant silicone rubber sealing rings has received more and more attention, and related research work has also increased. In some special industrial application scenarios, such as high temperature furnaces, hot end components of aircraft engines, and certain chemical reactors, the temperature of the equipment during operation is extremely high. Traditional silicone rubber sealing rings may experience performance degradation due to high temperatures, such as increased hardness, reduced elasticity, and poor sealing effect.

[0005] In order to meet the sealing requirements in these high-temperature environments, it is necessary to develop new high-temperature resistant silicone rubber sealing rings. At present, research is being carried out from many aspects, such as modifying the molecular structure of silicone rubber, introducing special functional groups or additives to improve the high-temperature resistance of silicone rubber; optimizing the preparation process, optimizing the microstructure of silicone rubber sealing rings, so that they can maintain good physical and chemical properties at high temperatures; studying how to improve the comprehensive performance of high-temperature resistant silicone rubber sealing rings, while maintaining high temperature resistance, further improving their chemical corrosion resistance, wear resistance and anti-aging ability. The development of these research works is expected to provide technical support for the application of high-temperature resistant silicone rubber sealing rings in more high-temperature environments and promote the further development of related industries.

[0006] Therefore, the purpose of the present invention is to develop a high temperature resistant silicone rubber for use in sealing rings, and to improve its high temperature resistance through the formulation design of the high temperature resistant silicone rubber and the optimization of the preparation method. Summary of the invention

[0007] Purpose of the invention: In order to overcome the above shortcomings, the purpose of the present invention is to provide a high temperature resistant silicone rubber and a sealing ring. Through formula design and optimization of the preparation method, the high temperature resistance and comprehensive performance of the rubber are improved, and technical support is provided for the application of high temperature resistant silicone rubber sealing rings in more high temperature environments, and the application prospects are broad.

[0008] The objective of the present invention is achieved through the following technical solutions: A high temperature resistant silicone rubber, comprising the following raw materials in parts by weight: 80-120 parts of methyl vinyl silicone rubber; the methyl vinyl silicone rubber is a mixture of MVQ110-0 and MVQ110-2; 40-60 parts of modified fumed silica; 5-15 parts of fluorine micropowder; 5-15 parts of a high temperature resistant agent; the high temperature resistant agent is a mixture of red iron oxide and nano titanium dioxide; 3-6 parts of hydroxy silicone oil; 1-3 parts of hydrogen silicone oil; Coupling agent 0.1-2 parts.

[0009] Sealing components in high temperature environments require silicone rubber to have a certain degree of flexibility during installation to facilitate assembly, and also to maintain sealing performance during high temperature operation without deformation or damage. Therefore, the present invention uses low-methyl vinyl silicone rubber and high-methyl vinyl silicone rubber to blend to form a raw rubber system. Low-methyl vinyl silicone rubber has good flexibility, can maintain good elasticity, and is not easy to crack, while high-methyl vinyl silicone rubber has a higher cross-linking density and good heat resistance and mechanical properties. After the two are blended, the advantages of the two can be combined to make the silicone rubber have good flexibility at room temperature and maintain good mechanical properties in a high temperature environment.

[0010] The formula selects fumed silica as a reinforcing filler, which can form a bonding point with the main chain of methyl vinyl silicone rubber molecules to form a three-dimensional network structure, which can not only greatly improve the strength of silicone rubber itself, but also effectively prevent the random thermal motion of the molecular chain, thereby improving the high temperature resistance of silicone rubber. However, the surface of untreated fumed silica contains a large number of silanol groups, which have a large difference in polarity from the methyl vinyl silicone rubber molecular chain and are difficult to disperse in the silicone rubber matrix. At high temperatures, it may also cause the siloxane bond to break and trigger the main chain degradation reaction. Therefore, it is modified.

[0011] Silicone rubber is a non-polar rubber and has poor tolerance to non-polar oils. Fluorine micropowder has the wear resistance, strong polarity, and chemical resistance of fluororesin. By mixing fluorine micropowder and silicone rubber, silicone rubber can be made to have oil resistance, wear resistance, and high and low temperature resistance.

[0012] The formula selects red iron oxide and nano titanium dioxide as a high temperature resistant agent. Both red iron oxide and nano titanium dioxide have certain heat resistance. Red iron oxide can absorb and reflect part of the heat, reducing the transfer of heat to the inside of the silicone rubber. Nano titanium dioxide can form a stable oxide film at high temperature to prevent further thermal oxidation reaction of silicone rubber. After the two are compounded, the synergistic effect can more effectively improve the high temperature resistance of silicone rubber.

[0013] The formula also includes hydroxy silicone oil, hydrogen silicone oil, and coupling agent. The hydroxyl groups in hydroxy silicone oil can undergo condensation reaction with the silanol groups on the silicone rubber molecular chain, play a plasticizing role, and improve processing performance. Hydrogen silicone oil is a vulcanizing agent that reacts with the double bonds in the silicone rubber molecular chain and the hydroxyl groups in hydroxy silicone oil to form a cross-linked structure. This cross-linked structure can improve the hardness, strength, and heat resistance of silicone rubber. In addition, hydroxy silicone oil reacts with hydrogen silicone oil vulcanizing agent to form cross-links between silicone rubber molecular chains, which helps to increase the cross-linking density of the vulcanized rubber. The coupling agent is to improve the interfacial bonding between other raw materials and methyl vinyl silicone rubber, so that it can be better dispersed in the silicone rubber matrix.

[0014] Furthermore, in the above-mentioned high temperature resistant silicone rubber, in the methyl vinyl silicone rubber, the mass ratio of MVQ110-0 to MVQ110-2 is 60-90:10-40.

[0015] Furthermore, in the above-mentioned high temperature resistant silicone rubber, the modified fumed silica is modified by a treating agent, and the treating agent is one of HMDZ, PDMS, and DMDS.

[0016] After the fumed silica is modified by the treating agent, most of the silanol groups on the surface are replaced by siloxane, the interaction force between the silica particles is weakened, and the appearance is fluffy. Compared with the untreated silica, the volume density is lower, the compatibility with silicone oil is good, and it is easy to disperse evenly in silicone rubber.

[0017] Furthermore, in the above-mentioned high temperature resistant silicone rubber, the fluorine micropowder is one or a combination of PTFE micropowder, PFA micropowder, and FEP micropowder, and the particle size is 1-20 μm.

[0018] Preferably, the fluorine micropowder is PFA micropowder.

[0019] PFA fluorine powder itself has excellent heat resistance. Silicone rubber with PFA fluorine powder added can maintain its physical properties at higher temperatures. PFA fluorine powder can also reduce the surface energy of silicone rubber, making silicone rubber have certain self-lubricating and anti-stick properties. For example, in silicone rubber seals that need to contact with sticky substances, low surface energy can prevent the adhesion of sticky substances and improve the cleanliness and service life of silicone rubber seals.

[0020] Furthermore, in the above-mentioned high temperature resistant silicone rubber, in the high temperature resistant agent, the mass ratio of red iron oxide to nano titanium dioxide is 50-80:20-50.

[0021] The side chains of silicone rubber are usually methyl, ethyl or vinyl. Under high temperature conditions, these side groups will be oxidized, and the main chain of silicone rubber may be degraded, resulting in rearrangement of the rubber molecular chain. The present invention uses red iron oxide and titanium dioxide as high temperature resistant additives. The synergistic effect of the two can maximize the high temperature resistance of silicone rubber.

[0022] Furthermore, in the above-mentioned high temperature resistant silicone rubber, the coupling agent is one or a combination of multiple of A-171, A-172, A-151, KH550, and KH792.

[0023] The present invention also relates to a preparation method of the high-temperature resistant silicone rubber, comprising the following contents: during the preparation, a kneading machine is first used to prepare a masterbatch, the initial temperature of the kneading machine is 60-90°C, methyl vinyl silicone rubber, modified fumed silica and hydroxy silicone oil are sequentially placed in the kneading machine, and after kneading for 1-3 hours, the temperature is raised to 140-160°C and vacuumed, and the kneading is continued for 1-3 hours to obtain a masterbatch; then an open mill is used to prepare a mixed rubber, the masterbatch is placed in the open mill, and then a high-temperature resistant agent, hydrogen-containing silicone oil, fluorine micropowder, and a coupling agent are added in sequence, the left and right cutters are used 3 times each, and finally the rubber is rolled 5-10 times. After uniform mixing, the sheet is removed and parked for 24 hours to obtain a mixed rubber; finally, a vulcanizer is used to prepare the high-temperature resistant silicone rubber, and a two-stage vulcanization process is used.

[0024] Furthermore, in the above-mentioned preparation method of high temperature resistant silicone rubber, the two-stage vulcanization process is specifically as follows: the first-stage vulcanization condition is (60-90)°C×(5-20)min×(10-20)MPa, and the second-stage vulcanization condition is vulcanization in an oven at (200-220)°C for (1-3)h.

[0025] The present invention also relates to a sealing ring, which is made of the above-mentioned high temperature resistant silicone rubber.

[0026] Compared with the prior art, the present invention has the following beneficial effects: (1) The high temperature resistant silicone rubber disclosed in the present invention has a reasonable formula design. Low-methyl vinyl silicone rubber and high-methyl vinyl silicone rubber are blended to form a raw rubber system. After the two are blended, the advantages of the two can be combined to make the silicone rubber have good flexibility at room temperature and maintain good mechanical properties under high temperature environment; modified fumed silica is used as a reinforcing filler, which is easy to disperse evenly in the silicone rubber, which can not only greatly improve the strength of the silicone rubber itself, but also effectively prevent the random thermal motion of the molecular chain, thereby improving the high temperature resistance of the silicone rubber; by mixing fluorine micropowder and silicone rubber, the silicone rubber can have oil resistance, wear resistance and high and low temperature resistance; iron oxide red and nano titanium dioxide are compounded as a high temperature resistant agent. After the two are compounded, the synergistic effect can more effectively improve the high temperature resistance of the silicone rubber; (2) The preparation method of high temperature resistant silicone rubber disclosed in the present invention is reasonably designed. First, the components are mixed in a kneading machine under relatively mild conditions to avoid premature vulcanization of silicone rubber or uneven reaction between components due to excessively high temperature. Then, the temperature is increased and vacuum is drawn to continue kneading. Heating to a temperature that helps to further promote the reaction between the components and make the silicone rubber and the filler more tightly bonded. The vacuum operation can remove bubbles generated during the kneading process and improve the quality of the masterbatch. Under high temperature and vacuum conditions, the structure of the masterbatch can be made denser. After the masterbatch is placed in the open mill, a high temperature resistant agent, hydrogenated silicone oil, fluorine powder, and a coupling agent are added in sequence. Adding the high temperature resistant agent and other additives first can make them more The left and right cutting knives and the rolling make the components evenly dispersed in the masterbatch, and the uniformity of the mixed rubber is improved. After the mixing is even, the sheet is parked. The parking process can further stabilize the components in the mixed rubber, reduce the internal stress, and improve the quality of the mixed rubber. Finally, a two-stage vulcanization process is adopted. The lower temperature and shorter time of the first stage vulcanization can avoid the vulcanization process being too intense, so that the silicone rubber is initially vulcanized and a certain cross-linking structure is formed. The two-stage vulcanization can further increase the cross-linking density of the silicone rubber and make the structure of the silicone rubber more stable. The two-stage vulcanization at high temperature can make the silicone rubber have better performance in high temperature resistance, and also help to improve the aging resistance of the silicone rubber. DETAILED DESCRIPTION

[0027] The following embodiment 1 is combined with specific experimental data to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0028] The following embodiment 1 provides a high temperature resistant silicone rubber.

[0029] The main raw materials of Example 1: MVQ110-0, with a vinyl content of 0.04%, a product of Ho Sheng Silicon Co., Ltd.; MVQ110-2, with a vinyl content of 0.22%, a product of Ho Sheng Silicon Co., Ltd.; untreated fumed silica, with a brand name A200, a product of Ho Sheng Silicon Co., Ltd.; red iron oxide, with a brand name S130, a product of Shanghai Shenhong Pigment Co., Ltd.; nano titanium dioxide, with a brand name JWN-A1, a product of Ningbo Jiwei Nano New Material Technology Co., Ltd.; the others are all commercially available products.

[0030] The high temperature resistant silicone rubber of Example 1 comprises the following raw materials in parts by weight: 75 parts of MVQ110-0, 25 parts of MVQ110-2, 50 parts of modified fumed silica (treated with HMDZ), 10 parts of PFA fluorine powder (particle size of 6 μm), 6 parts of red iron oxide, 4 parts of nano titanium dioxide, 5 parts of hydroxy silicone oil, 1 part of hydrogen-containing silicone oil, and 1.5 parts of silane coupling agent KH550.

[0031] The preparation method of the high temperature resistant silicone rubber of Example 1 comprises the following contents: During the preparation, a kneading machine is first used to prepare a masterbatch, the initial temperature of the kneading machine is 70°C, methyl vinyl silicone rubber, modified fumed silica and hydroxy silicone oil are put into the kneading machine in turn, and after kneading for 3 hours, the temperature is raised to 155°C and vacuumed, and the kneading is continued for 2 hours to obtain a masterbatch; then an open mill is used to prepare a mixed rubber, the masterbatch is put into the open mill, and then a high temperature resistant agent, hydrogen-containing silicone oil, fluorine powder, and a coupling agent are added in turn, the left and right kneading knives are used 3 times each, and finally rolled 8 times. After mixing evenly, the sheet is removed and parked for 24 hours to obtain a mixed rubber; finally, a vulcanizer is used to prepare a high temperature resistant silicone rubber using a two-stage vulcanization process, the first stage vulcanization conditions are 75°C×12min×10MPa, and the second stage vulcanization conditions are: vulcanization in an oven at 210°C for 2.5 hours.

[0032] Performance tests of the high temperature resistant silicone rubber of Example 1: tensile strength and elongation at break were tested according to GB / T528-2009, hardness was tested according to GB / T531-2008, and hot air accelerated aging was tested according to GB / T 3512-2001.

[0033] The performance changes of the high temperature resistant silicone rubber of Example 1 before and after hot air accelerated aging are shown in Table 1.

[0034] Table 1 Performance changes of high temperature resistant silicone rubber of Example 1 before and after hot air accelerated aging According to the formula: Aging coefficient = (tensile strength after aging × elongation at break) / (tensile strength before aging × elongation at break).

[0035] It can be concluded that the aging coefficient of the high temperature resistant silicone rubber of Example 1 after accelerated aging in hot air at 200°C × 24 h is 0.97, and the aging coefficient after accelerated aging in hot air at 300°C × 2 h is 0.88.

[0036] Therefore, Example 1 prepared by the high temperature resistant rubber formula and preparation method of the present invention has excellent high temperature resistance and is not prone to thermal oxidation aging.

[0037] The present invention has many specific application paths, and the above is only a preferred embodiment of the present invention. It should be pointed out that the above embodiments are only used to illustrate the present invention, and are not used to limit the protection scope of the present invention. For those of ordinary skill in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. A high temperature resistant silicone rubber, characterized in that: The high temperature resistant silicone rubber comprises the following raw materials in parts by weight: 80-120 parts of methyl vinyl silicone rubber; the methyl vinyl silicone rubber is a mixture of MVQ110-0 and MVQ110-2; 40-60 parts of modified fumed silica; 5-15 parts of fluorine micropowder; 5-15 parts of a high temperature resistant agent; the high temperature resistant agent is a mixture of red iron oxide and nano titanium dioxide; 3-6 parts of hydroxy silicone oil; 1-3 parts of hydrogen silicone oil; Coupling agent 0.1-2 parts.

2. The high temperature resistant silicone rubber according to claim 1, characterized in that: In the methyl vinyl silicone rubber, the mass ratio of MVQ110-0 to MVQ110-2 is 60-90:10-40.

3. The high temperature resistant silicone rubber according to claim 1, characterized in that: The modified fumed silica is modified by a treating agent, and the treating agent is one of HMDZ, PDMS and DMDS.

4. The high temperature resistant silicone rubber according to claim 1, characterized in that: The fluorine micropowder is one or a combination of PTFE micropowder, PFA micropowder and FEP micropowder, and the particle size is 1-20 μm.

5. The high temperature resistant silicone rubber according to claim 1, characterized in that: In the high temperature resistant agent, the mass ratio of red iron oxide to nano titanium dioxide is 50-80:20-50.

6. The high temperature resistant silicone rubber according to claim 1, characterized in that: The coupling agent is one of A-171, A-172, A-151, KH550, and KH792, or a combination of more thereof.

7. A method for preparing high temperature resistant silicone rubber according to any one of claims 1 to 6, characterized in that: The invention comprises the following contents: during preparation, a kneading machine is first used to prepare a masterbatch, the initial temperature of the kneading machine is 60-90°C, methyl vinyl silicone rubber, modified fumed silica and hydroxy silicone oil are sequentially put into the kneading machine, after kneading for 1-3 hours, the temperature is raised to 140-160°C and vacuum is drawn, and the kneading is continued for 1-3 hours to obtain a masterbatch; then an open mill is used to prepare a mixed rubber, the masterbatch is put into the open mill, and then a high temperature resistant agent, hydrogen-containing silicone oil, fluorine micropowder and coupling agent are sequentially added, the left and right kneading knives are used for 3 times each, and finally the rubber is rolled for 5-10 times. After the mixing is even, the sheet is removed and left to rest for 24 hours to obtain a mixed rubber; finally, a vulcanizer is used to prepare a high temperature resistant silicone rubber, and a two-stage vulcanization process is adopted.

8. The method for preparing high temperature resistant silicone rubber according to claim 7, characterized in that: The two-stage vulcanization process is specifically as follows: the first-stage vulcanization condition is (60-90)°C×(5-20)min×(10-20)MPa, and the second-stage vulcanization condition is vulcanization in an oven at (200-220)°C for (1-3)h.

9. A sealing ring, characterized in that: The method is prepared by using the high temperature resistant silicone rubber as described in any one of claims 1 to 6.

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