Silica gel sealing ring and preparation method thereof

Abstract

The invention relates to a silica gel sealing ring and a preparation method thereof, and belongs to the technical field of polymer sealing materials. The material is prepared from the following raw materials in parts by weight: 90 parts of fluorinated modified methyl vinyl phenyl silicone rubber raw rubber, 10 to 30 parts of tetrafluoroethylene-propylene rubber, 0.1 to 1 part of inorganic pigment, 5 to 20 parts of filler, 10 to 30 parts of fumed silica and 0.5 to 2 parts of vulcanizing agent. The silica gel sealing ring provided by the invention can keep excellent mechanical properties in a wide temperature range, and the reliability and the service life of the sealing ring under extreme conditions are ensured.

Description

Technical Field

[0001] The present invention relates to the field of polymer sealing materials. Specifically, it relates to a silicone rubber seal ring and a preparation method thereof. Background Art

[0002] Due to its good elasticity, chemical stability and excellent weather resistance, silicone rubber seal rings are widely used in many industrial applications. Most traditional silicone rubber seal rings are prepared from methyl vinyl silicone rubber, and this silicone material exhibits good mechanical properties at room temperature. However, when in extremely high or low temperature environments, the performance of traditional silicone materials significantly deteriorates, affecting their use effect and service life in these harsh environments.

[0003] To improve the performance of silicone rubber seal rings in low temperature environments, researchers have introduced phenyl silicone rubber. The introduction of phenyl groups effectively enhances the low temperature resistance of silicone rubber. Through phenyl silicone rubber, the tensile strength and elongation at break of silicone rubber seal rings in low temperature environments have also been significantly improved, thus maintaining good elasticity and mechanical properties. However, although phenyl silicone rubber performs well in terms of temperature resistance, its performance in extremely low temperature environments is still not ideal. A high content of phenyl groups will cause the glass transition temperature of silicone rubber to increase, making it prone to losing ductility under extremely low temperature conditions, resulting in crack and brittle fracture phenomena. Especially in cold environments such as chemical low temperature production, refrigeration facilities, low temperature transportation and polar exploration equipment, traditional silicone rubber seal rings are prone to brittle fracture and failure, unable to meet the stable low temperature working requirements, and affecting the normal use and sealing reliability of equipment.

[0004] Aiming at the deficiencies of existing phenyl silicone rubber in low temperature resistance, the present invention proposes a method for preparing a seal ring using fluorinated modified methyl vinyl phenyl silicone rubber. By introducing long-chain fluorinated groups into the molecular chain of this fluorinated modified silicone rubber material, the glass transition temperature of the silicone rubber material can be further reduced, thereby improving the low temperature resistance. At the same time, the excellent high temperature resistance of phenyl silicone rubber can be retained, thus effectively solving the problem that traditional phenyl silicone rubber is prone to brittle fracture in low temperature environments, enhancing its stability and reliability in a wide temperature range, and thus meeting the requirements of different industrial fields. Summary of the Invention

[0005] The present invention aims to solve the problem of insufficient applicability of existing silicone rubber seal rings in a wide temperature range, especially the decline in their mechanical properties in high temperature and low temperature environments, and the difficulty in simultaneously meeting durability. The present invention provides a silicone rubber seal ring and a preparation method thereof. The silicone rubber seal ring provided by the present invention can retain its good mechanical properties after being treated under high temperature and low temperature conditions, thus having the advantage of durability in a wide temperature range.

[0006] The present invention provides a silicone rubber sealing ring, which is made of the following raw materials in parts by weight: 90 parts of fluorinated modified methyl vinyl phenyl silicone rubber raw rubber, 10-30 parts of tetrapropyl fluororubber, 0.1-1 part of inorganic pigment, 5-20 parts of filler, 10-30 parts of fumed silica, 0.5-2 parts of vulcanizing agent, wherein: The filler is made of the following raw materials in parts by weight: 20 parts of polypropylene resin, 60-100 parts of hexagonal boron nitride, 40-60 parts of silica sol; The fluorinated modified methyl vinyl phenyl silicone rubber raw rubber is prepared by the following preparation method: (1), React octamethylcyclotetrasiloxane and tetramethyltetravinylcyclotetrasiloxane to obtain a catalyst base rubber; (2), Mix octamethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, catalyst base rubber, decamethyltetrasiloxane and octaphenylcyclotetrasiloxane and carry out a polymerization reaction to obtain a main chain polymer; (3), Mix the main chain polymer, 13-fluorooctane-1-thiol and a photoinitiator and carry out a fluorination grafting reaction to obtain fluorinated modified methyl vinyl phenyl silicone rubber; (4), React the fluorinated modified methyl vinyl phenyl silicone rubber with a radical initiator to obtain the fluorinated modified methyl vinyl phenyl silicone rubber raw rubber.

[0007] In the present invention, the vulcanizing agent is 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0008] In the present invention, in step (3), the structural formula of the fluorinated modified methyl vinyl phenyl silicone rubber is: , wherein the molar ratio of x:y:z:w is (40-80):(5-20):(5-20):(10-30).

[0009] In the present invention, in step (3), optionally, the photoinitiator is benzoin dimethyl ether.

[0010] In the present invention, in step (4), optionally, the radical initiator is m-chloroperbenzoic acid.

[0011] In the present invention, the preparation method of the filler is: Weigh polypropylene resin, hexagonal boron nitride and silica sol respectively according to parts by weight, put these materials into a planetary ball mill for ball milling; after ball milling is completed, put the mixture into an oven for drying to obtain a dry material; then screen the dry material through a sieve to obtain the filler.

[0012] In the present invention, in the preparation method of the filler, during the ball milling treatment, the ball milling time is 0.5 to 1.5 hours, the drying temperature is 40 to 80 °C, and the mesh number of the sieve is 100 to 200 meshes.

[0013] The present invention also provides a preparation method of a silica gel sealing ring, which comprises the following steps: (1) Put the fluorinated modified methyl vinyl phenyl silicone rubber raw rubber, tetrapropyl fluororubber, inorganic pigment, fumed silica and filler into a mixer and mix them thoroughly to obtain a mixed material; (2) Transfer the mixed material to a two-roll rubber mill for further treatment. Add a vulcanizing agent during the rubber mixing process. After mixing evenly, transfer it to a mold, and put the mold into a flat plate hot pressing and vulcanizing machine for vulcanization; after the reaction is completed, cool it to obtain the silica gel sealing ring; Among them, the fluorinated modified methyl vinyl phenyl silicone rubber raw rubber and the filler are as defined above.

[0014] In the present invention, the vulcanizing agent is 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0015] In the present invention, in step (1), according to the weight ratio: 90 parts of fluorinated modified methyl vinyl phenyl silicone rubber raw rubber, 10 to 30 parts of tetrapropyl fluororubber, 0.1 to 1 part of inorganic pigment, 5 to 20 parts of filler, 10 to 30 parts of fumed silica, 0.5 to 2 parts of vulcanizing agent.

[0016] In the present invention, in step (1), according to the weight ratio: 90 parts of fluorinated modified methyl vinyl phenyl silicone rubber raw rubber, 20 parts of tetrapropyl fluororubber, 0.5 part of inorganic pigment, 10 parts of filler, 17 parts of fumed silica, 1 part of vulcanizing agent.

[0017] The present invention also provides a polymer sealing material, which has the following structural formula: , wherein, the molar ratio of x:y:z:w is (40 to 80):(5 to 20):(5 to 20):(10 to 30).

[0018] On the basis of conforming to the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0019] The reagents and raw materials used in the present invention are all commercially available.

[0020] The positive and progressive effect of the present invention is that: the present invention obtains a silica gel sealing ring that is durable in a wide temperature range. Description of the Drawings

[0021] Figure 1 It is the GPC test result of the fluorinated modified methyl vinyl phenyl silicone rubber in Example 1. Detailed implementation mode

[0022] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions indicated in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0023] Example 1: In a three-necked flask, 30 g of octamethylcyclotetrasiloxane and 1 g of tetramethylammonium hydroxide pentahydrate were added. It was slowly heated to 50 °C under reduced pressure while maintaining the temperature in the system stable. Nitrogen was bubbled into the reaction flask for 30 minutes to remove oxygen. Subsequently, the reaction temperature was gradually increased to 80 °C and maintained at this temperature. At this time, the water in the reaction system was continuously evaporated, and the viscosity of the reaction solution gradually increased. To ensure the effective removal of water, the reaction solution should remain transparent and viscous until no obvious water volatilization occurred. When the reaction solution reached the required viscosity and transparency, heating was stopped and it was naturally cooled to room temperature to obtain a tetramethylsilicon hydroxide alkoxide catalyst (catalyst base gel).

[0024] Octamethylcyclotetrasiloxane (237 g, 800 mmol) and tetramethyltetravinylcyclotetrasiloxane (41 g, 120 mmol) were added to the reaction flask, the temperature was controlled at 45 °C, and it was evacuated for 1 hour under high vacuum conditions for water treatment. Then, under nitrogen protection, a tetramethylsilicon hydroxide alkoxide catalyst (80 mg, 0.24 mmol) was added to the reaction system, and decamethyltetrasiloxane (93 mg, 0.3 mmol) was added. Subsequently, octaphenylcyclotetrasiloxane (3.6 g, 45 mmol) was added as a crosslinking agent, and it was evacuated for 1 hour at 45 °C to ensure that the water in the reaction system was completely removed, and the vacuum degree was maintained at 0.01 MPa. Then, under normal pressure and nitrogen protection, the reaction temperature was raised to 100 °C and reacted for 2 hours, and reacted at 160 °C for 30 minutes to destroy the catalyst and remove the unreacted catalyst residue. Then, the temperature was raised to 170 °C, and the reaction was continued for 1.5 hours under vacuum conditions, and the vacuum degree was maintained at 0.01 MPa. The obtained product was added to 500 mL of tetrahydrofuran and stirred to dissolve.

[0025] Then, (5.7 g, 15 mmol) 1H,1H,2H,2H-perfluorooctan-1-thiol was added and stirred for 30 minutes, then benzoin dimethyl ether (0.5 g, 2 mmol) was added, and the reaction system was irradiated with a 365 nm wavelength ultraviolet light source in a closed chamber for 2 hours to carry out a fluorination grafting reaction.

[0026] After the reaction was completed, the solution was poured into 1 L of absolute ethanol, and after thorough mixing, flocculation was carried out. The precipitate was filtered and washed with absolute ethanol 2-3 times to remove unreacted impurities. Then, it was placed in a vacuum oven and dried at 50 °C for 12 hours to remove the solvent, obtaining fluorinated modified methyl vinyl phenyl silicone rubber; the GPC test results are as Figure 1 shown.

[0027] In a round-bottom flask, 2 L of chloroform and 110 g of fluorinated modified methyl vinyl phenyl silicone rubber were added.

[0028] After stirring and dissolving, m-chloroperbenzoic acid (50 g, 30 mmol) was added as an initiator, and the free radical initiation reaction was started. The reaction was carried out at room temperature for 96 hours. After the reaction was completed, the reaction solution was precipitated with absolute ethanol, and the filtered solid was washed with absolute ethanol 2-3 times. The washed product was placed in a vacuum oven and vacuum dried at 55 °C to constant weight to ensure complete removal of the solvent, obtaining the final fluorinated modified methyl vinyl phenyl silicone rubber raw rubber.

[0029] Example 2: Weigh 20 g of polypropylene resin, 80 g of hexagonal boron nitride, and 50 g of silica sol, and put these materials into a planetary ball mill for ball milling for 1 hour; after ball milling, the mixture was placed in an oven at 50 °C to dry, removing moisture and impurities; the dried material was sieved through a 150-mesh sieve to obtain filler powder.

[0030] Next, weigh 90 g of fluorinated modified methyl vinyl phenyl silicone rubber raw rubber, 20 g of tetrapropyl fluororubber, 0.5 g of iron oxide red, 17 g of fumed silica, and 10 g of the above filler powder, and put these raw materials into a mixer for thorough mixing.

[0031] Heat to 130 °C and maintain this temperature for 90 minutes. Transfer the mixed material to a two-roll rubber mill for further processing. During the rubber milling process, 1 g of vulcanizing agent 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane was added. After mixing evenly, the material was transferred to a mold, and the mold was placed in a flat plate hot press molding vulcanizer for vulcanization. The vulcanization temperature was set at 175 °C, the pressure was set at 5 Mpa, and the vulcanization time was 10 minutes. After vulcanization, take out and cool to obtain the finished silicone rubber sealing ring.

[0032] Example 3: The preparation method of Example 3 is basically the same as that of Example 2, except that 60 g of fluorinated modified methyl vinyl phenyl silicone rubber and 30 g of commercially purchased methyl vinyl phenyl silicone rubber (IOTA 120) are used instead of 90 g of fluorinated modified methyl vinyl phenyl silicone rubber, and finally the finished silicone rubber sealing ring is prepared.

[0033] Example 4: The preparation method of Example 4 is basically the same as that of Example 2, except that 30 g of fluorinated modified methyl vinyl phenyl silicone rubber and 60 g of commercially purchased methyl vinyl phenyl silicone rubber (IOTA 120) are used instead of 90 g of fluorinated modified methyl vinyl phenyl silicone rubber, and finally a finished silicone rubber sealing ring is prepared.

[0034] Example 5: The preparation method of Example 5 is basically the same as that of Example 2, except that 90 g of commercially purchased methyl vinyl phenyl silicone rubber (IOTA 120) is used instead of 90 g of fluorinated modified methyl vinyl phenyl silicone rubber, and finally a finished silicone rubber sealing ring is prepared.

[0035] Example 6: Tear strength and tensile strength are detected Silicone rubber sealing ring samples are prepared by the preparation methods of Examples 2 - 5. Further, according to the preparation method of Type B standard ring specimens in the Chinese standard GB / T531.1 - 2008 "Determination Method for Tensile Stress - Strain Properties of Vulcanized Rubber or Thermoplastic Rubber", sealing ring test samples with an outer diameter × wire diameter of 11 × 1.5 mm are prepared. Then, according to this standard, the tensile strength (TS, unit: MPa), breaking tensile strength (TS b , unit: MPa) and elongation at break (E b , %) are respectively detected.

[0036] The calculation formula for tensile strength is: TS = F m / (2×W t ) The calculation formula for breaking tensile strength is: TS b = F b / (2×W t ) The calculation formula for elongation at break is: E b = [100(πd + 2L b - C i )] / C i Where F m is the maximum force recorded, unit: N; F b is the force recorded at break, unit: N; d is the diameter of the pulley, unit: mm; L b is the center distance between the two pulleys when the specimen breaks, unit: mm; C i is the initial inner circumference of the ring specimen, unit: mm. The test results are shown in Table 1.

[0037] Example 7: High and low temperature resistance performance test Prepare the sealing ring test samples with an outer diameter × wire diameter of 11 × 1.5 mm according to Example 6 for Examples 2 - 5. Keep them at a high temperature (e.g., 150 °C) for 72 hours respectively, and then keep them at a low temperature (e.g., -100 °C) for 72 hours. After the treated samples are restored to room temperature, conduct tests on tensile strength, breaking tensile strength, and elongation at break according to the test method of Example 6. Evaluate the changes in mechanical properties after high and low temperature treatments. Through these tests, the performance of the silicone sealing ring under different environmental conditions can be comprehensively understood. The test results of the sealing ring test samples obtained in the above examples are shown in Table 1.

[0038]

[0039] The data in the table reflect the mechanical properties of the silicone sealing ring under different treatment conditions, including tensile strength, breaking tensile strength, and elongation at break. It provides strong support for the tolerance and performance changes of the silicone sealing ring in high and low temperature environments. The specific analysis is as follows: The silicone sealing ring samples have excellent mechanical properties at room temperature. The tensile strength is in the range of 8.4 to 8.9 MPa, the breaking tensile strength is between 8.1 and 8.7 MPa, and the elongation at break is 225% to 260%, showing good ductility. After high temperature treatment, the performance decreases slightly but still remains good. For example, the tensile strength and breaking tensile strength are basically in the range of 8.1 to 8.6 MPa, and the elongation at break is within 215% to 255%, indicating that the material has good tolerance in high temperature environments. However, for the sealing ring samples prepared by reducing the amount of the fluorinated modified methyl vinyl phenyl silicone rubber of the present invention, the low temperature treatment has a significant impact on their mechanical properties. For example, in Examples 4 and 5, after low temperature treatment, the tensile strength and breaking tensile strength drop to 6.5 MPa and 6.2 MPa respectively, and the elongation at break drops to 120%, reflecting a significant reduction in the ductility and fracture resistance of the material in low temperature environments and an increase in brittleness.

[0040] Generally speaking, the sealing ring samples prepared in Example 2 can maintain relatively excellent performance under room temperature, high temperature, and low temperature environments, especially showing significant advantages in mechanical strength and ductility. This makes it widely applicable in application scenarios with a wide temperature range and provides a stable sealing effect.

Claims

1. A silicone sealing ring, characterized in that: The invention is made of the following raw materials in parts by weight: 90 parts of fluorinated modified methyl vinyl phenyl silicone rubber, 10-30 parts of tetrafluoroethylene rubber, 0.1-1 parts of inorganic pigment, 5-20 parts of filler, 10-30 parts of fumed silica, and 0.5-2 parts of vulcanizing agent, wherein; The filler comprises the following raw materials in parts by weight: 20 parts of polypropylene resin, 60-100 parts of hexagonal boron nitride, and 40-60 parts of silica molten glue; The fluorinated modified methyl vinyl phenyl silicone rubber raw rubber is prepared by the following preparation method: (1) reacting octamethylcyclotetrasiloxane and tetramethyltetravinylcyclotetrasiloxane to obtain a catalyst alkali gel; (2) octamethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, catalyst alkali rubber, decamethyltetrasiloxane and octaphenylcyclotetrasiloxane are mixed and polymerized to obtain a main chain polymer; (3) mixing the main chain polymer, tridecafluorooctane-1-thiol and a photoinitiator to carry out a fluorination grafting reaction to obtain a fluorinated modified methyl vinyl phenyl silicone rubber; (4) reacting the fluorinated modified methyl vinyl phenyl silicone rubber with a free radical initiator to obtain the fluorinated modified methyl vinyl phenyl silicone rubber raw rubber.

2. The silicone seal ring according to claim 1, characterized in that: The vulcanizing agent is 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

3. The silicone seal ring according to claim 1, characterized in that: In step (3), the structural formula of the fluorinated modified methyl vinyl phenyl silicone rubber is: , wherein the molar ratio of x:y:z:w is (40-80):(5-20):(5-20):(10-30).

4. The silicone seal ring according to claim 1, characterized in that: In step (3), the photoinitiator is dimethyl benzoate.

5. The silicone seal ring according to claim 1, characterized in that: In step (4), the free radical initiator is m-chloroperbenzoic acid.

6. The silicone seal ring according to claim 1, characterized in that: The preparation method of the filler is as follows: polypropylene resin, hexagonal boron nitride and silica molten rubber are weighed respectively by weight, and these materials are put into a planetary ball mill for ball milling; after the ball milling is completed, the mixture is put into an oven for drying to obtain a dry material; and then the dry material is sieved through a sieve to obtain the filler.

7. The silicone seal ring according to claim 1, characterized in that: In the preparation method of the filler, in the ball milling treatment, the ball milling time is 0.5 to 1.5 hours, the drying temperature is 40 to 80° C., and the mesh number of the sieve is 100 to 200 meshes.

8. A method for preparing a silicone sealing ring, characterized in that: It includes the following steps: (1) placing fluorinated modified methyl vinyl phenyl silicone rubber raw rubber, tetrafluoroethylene rubber, inorganic pigment, fumed silica and filler in an internal mixer and mixing them thoroughly to obtain a mixed material; (2) transferring the mixed material to a double-roll rubber mixer for further processing, adding a vulcanizing agent during the mixing process, transferring the mixed material to a mold after uniform mixing, and placing the mold into a flat-plate hot pressing vulcanizer for vulcanization; cooling after the reaction is completed to obtain the silicone sealing ring; the vulcanizing agent is 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; Wherein, the fluorinated modified methyl vinyl phenyl silicone rubber and the filler are as defined in claim 1.

9. The method for preparing a silicone seal ring according to claim 8, characterized in that: In step (1), the following are added in proportion by weight: 90 parts of fluorinated modified methyl vinyl phenyl silicone rubber, 10 to 30 parts of tetrafluoroethylene rubber, 0.1 to 1 part of inorganic pigment, 5 to 20 parts of filler, 10 to 30 parts of fumed silica, and 0.5 to 2 parts of vulcanizing agent.

10. The method for preparing a silicone seal ring according to claim 8, characterized in that: In step (1), the following proportions are used in parts by weight: 90 parts of fluorinated modified methyl vinyl phenyl silicone rubber, 20 parts of tetrapropylene fluororubber, 0.5 parts of inorganic pigment, 10 parts of filler, 17 parts of fumed silica, and 1 part of vulcanizing agent.

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