Heat-resistant and wear-resistant O-shaped sealing ring and preparation method thereof

Abstract

The invention relates to the technical field of sealing ring products, and discloses a heat-resistant and wear-resistant O-shaped sealing ring and a preparation method thereof.The heat-resistant and wear-resistant O-shaped sealing ring is prepared from methyl vinyl dichlorosilane, 2-hydroxy-6-naphthoic acid, gamma-glycidyl ether oxypropyl trimethoxy silane and the like, a naphthyl vinyl siloxane coupling agent is synthesized, montmorillonite is modified, and the heat-resistant and wear-resistant O-shaped sealing ring is obtained. And finally, mixing and vulcanizing to obtain the heat-resistant and wear-resistant O-shaped sealing ring. Due to the addition of the coupling agent, the dispersion condition of the montmorillonite in a rubber matrix is improved, so that an inorganic phase and an organic phase which are not compatible originally can be well dispersed mutually through the bridge action of the coupling agent, and a rubber macromolecular chain can enter the interlamellae of the montmorillonite to achieve nano-scale dispersion; the modified montmorillonite is very similar to the natural rubber and the silicone rubber matrix in structure and relatively high in compatibility, and the modified montmorillonite, the natural rubber and the silicone rubber matrix have a synergistic effect to form a unique interpenetrating network structure, so that the wear resistance, the heat resistance and the barrier property of the sealing ring can be well improved.

Description

Technical Field

[0001] The invention relates to the technical field of sealing ring products, in particular to a heat-resistant and wear-resistant O-type sealing ring and a preparation method thereof. Background Art

[0002] Rubber sealing products are widely used in various mechanical equipment. O-rings are a type of rubber sealing ring with a circular cross-section. They are mainly used for static sealing and reciprocating motion sealing in hydraulic and pneumatic transmission systems and are widely used in various fields. With the development of precision instruments, the disassembly of instruments has become more difficult. In addition, when operating in an environment with high temperature, high pressure and a large number of wear particles, O-rings often fail to seal due to performance degradation, causing the contact stress between the sealing product and the mechanical equipment to be released, affecting production safety. Therefore, O-rings must have higher requirements on heat resistance, wear resistance and other properties, but the existing O-rings do not meet the requirements.

[0003] Currently, commonly used materials for O-rings include nitrile rubber, acrylic rubber, fluororubber, etc. Although nitrile rubber has the advantages of high wear resistance and stable chemical properties, its hardness may decrease and its elasticity weakened under high temperature conditions, thus affecting its heat resistance; although high temperature resistant materials such as acrylic rubber and fluororubber can improve heat resistance, they are expensive and difficult to process; natural rubber (NR) has high strength, high elasticity, tear resistance and other properties and excellent processing properties, but it contains a large number of unsaturated double bonds and is very prone to chemical reactions; silicone rubber sealing rings have the characteristics of large compression and good weather resistance, but their wear resistance needs to be further improved.

[0004] Patent No. CN109867886A discloses a novel pressure-resistant and wear-resistant O-type sealing ring, which mixes a variety of rubber materials such as fluororubber, nitrile rubber, EPDM rubber and methyl vinyl silicone rubber together, so that the prepared O-type sealing ring can be applied to different working environments, but the added components are more, the cost is higher, and the heat resistance of the sealing ring is not significantly improved, and the wear resistance is also limited. In the prior art, the wear resistance of rubber is generally improved by adding montmorillonite. Relevant studies have shown that adding montmorillonite (MMT) with a layered structure to NR can effectively improve the physical properties and barrier properties of vulcanized rubber, but the compatibility of natural rubber and montmorillonite is poor, and phase separation is prone to occur after mixing; therefore, the present invention aims to synthesize a modifier, which can not only embed montmorillonite into the rubber matrix, but also have good compatibility with natural rubber and silicone rubber, thereby improving the wear and heat resistance of the sealing ring and broadening its application range. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a heat-resistant and wear-resistant O-type sealing ring and a preparation method thereof, so as to solve the problem of poor heat resistance and wear resistance of the sealing ring in the prior art.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A method for preparing a heat-resistant and wear-resistant O-type sealing ring is carried out according to the following steps:

[0008] Step (1), under nitrogen atmosphere, sodium montmorillonite and deionized water were added to a reaction flask, stirred at high speed for 1-3 hours, allowed to stand overnight, and hexadecyltrimethylammonium bromide and a solution of the structural formula The naphthyl vinyl siloxane coupling agent was added and stirred for reaction. After the reaction was completed, the mixture was washed with deionized water until no precipitation was detected by silver nitrate, and then filtered and dried to obtain modified montmorillonite.

[0009] Step (2), thinning natural rubber and methyl vinyl silicone rubber on an open mill for 5-10 times, adding modified montmorillonite, zinc oxide, stearic acid, accelerator CZ, accelerator DM, sulfur and antioxidant in sequence, mixing evenly and thinning for 3-6 times to sheet, leaving the mixed rubber overnight, placing it in a mold for slicing, placing it in a flat vulcanizer for vulcanization and sheeting, and obtaining a heat-resistant and wear-resistant O-ring.

[0010] Furthermore, in step (1), the ratio of sodium montmorillonite, hexadecyltrimethylammonium bromide and naphthyl vinylsiloxane coupling agent is 100 g:(18-25) g:(3-15) g.

[0011] Furthermore, in step (1), the reaction temperature is 75-90° C. and the reaction time is 5-12 h.

[0012] Furthermore, in step (2), the ratio of natural rubber, methyl vinyl silicone rubber and modified montmorillonite is 100 g:(35-50) g:(2-10) g.

[0013] Furthermore, in step (2), the vulcanization temperature is 135-145° C., the pressure is 1.5-2 MPa, and the vulcanization time is 5-10 min.

[0014] Furthermore, the preparation method of the naphthyl vinyl siloxane coupling agent in step (1) is carried out according to the following steps:

[0015] Step S1. Under a nitrogen atmosphere, add methylvinyldichlorosilane and toluene to a reaction flask, stir evenly, then add 2-hydroxy-6-naphthoic acid and sodium hydride, stir to react, filter after the reaction, wash the organic layer with saturated brine, separate by column chromatography (silica gel, 8-15% n-heptane in ethyl acetate), and dry to obtain naphthylvinylsiloxane diacid.

[0016] Step S2, under a nitrogen atmosphere, add naphthyl vinyl siloxane diacid and tetrahydrofuran to a reaction flask, stir evenly, add γ-glycidyloxypropyltrimethoxysilane and tetrabutylammonium bromide, react at 50-65°C for 12-24h, concentrate under reduced pressure, purify by column chromatography (silica gel, 5-10% methanol in dichloromethane), and obtain a naphthyl vinyl siloxane coupling agent after drying.

[0017] Furthermore, in step S1, the ratio of methylvinyldichlorosilane, 2-hydroxy-6-naphthoic acid, and sodium hydride is 1 mol: (2.05-2.2) mol: (2.3-2.5) mol.

[0018] Furthermore, in step S1, the reaction temperature is 95-110° C., and the reaction time is 3-8 h.

[0019] Furthermore, in step S2, the ratio of naphthyl vinyl siloxane diacid, γ-glycidyloxypropyl trimethoxysilane, and tetrabutylammonium bromide is 1 mol: (2.4-3.2) mol: (0.05-0.1) mol.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The invention firstly uses methylvinyldichlorosilane, 2-hydroxy-6-naphthoic acid, γ-glycidyloxypropyltrimethoxysilane and the like as raw materials to synthesize a naphthylvinylsiloxane coupling agent, then modifies montmorillonite, and finally performs mixing and vulcanization to obtain a heat-resistant and wear-resistant O-type sealing ring; the addition of the coupling agent improves the dispersion of the montmorillonite in the rubber matrix, so that the originally incompatible inorganic phase and organic phase can be well dispersed with each other through the bridge effect of the coupling agent, and the rubber macromolecular chain can enter between the montmorillonite sheets to achieve nanometer-scale dispersion.

[0022] The naphthalene ring in the naphthyl vinyl siloxane coupling agent has a stable aromatic ring structure and is not easy to rotate. Its rigid structure can withstand high temperatures without being easily deformed or decomposed, thereby showing excellent heat resistance. The modified montmorillonite is dispersed in the natural rubber matrix in nanometer size, which effectively restricts the movement of the rubber macromolecular chain. Its unsaturated double bonds are chemically bonded with the unsaturated double bonds of natural rubber, and the trimethoxysilane group is coupled with the active group on the surface of the montmorillonite, thereby increasing the cross-linking density of the vulcanized rubber and making the whole system tightly combined. At the same time, the organic siloxane in its structure has structural similarities with silicone rubber, which improves the interface compatibility and forms a network structure that is interpenetrating and closely interwoven among the three, effectively improving the mechanical properties and heat resistance of the sealing ring.

[0023] After modification, the interlamellar spacing of montmorillonite increases, and it is evenly dispersed in the rubber matrix at the nanometer scale. This intercalation or exfoliation nanocomposite structure enables the rubber matrix to more effectively utilize the nanometer effect of montmorillonite when subjected to external forces, reducing the possibility of stress concentration and crack propagation, thereby improving the wear resistance of the material. The uniform dispersion of montmorillonite flakes in the polymer matrix can also reduce the possibility of stress concentration and crack propagation. In addition, the structure of the modified montmorillonite is very similar to that of the natural rubber and silicone rubber matrix, and the compatibility is relatively strong. The three work together to form a unique interpenetrating network structure, which can greatly improve the wear resistance of the sealing ring material.

[0024] The layered distribution of montmorillonite effectively blocks the intrusion of oxygen and nitrogen. The active groups of the bifunctional naphthyl vinyl siloxane coupling agent have binding points between the montmorillonite flakes, natural rubber and silicone rubber. First, the montmorillonite flakes can be better dispersed or intercalated into the rubber matrix. Second, the rubber macromolecule chain can be tightly combined with the montmorillonite. Its molecular movement is restricted between the montmorillonite flakes, so that the entire composite system forms a tightly interwoven network structure. When the gas passes through the composite material, it must go through an extended distance to penetrate, which reduces the air permeability of the composite material, thereby improving the barrier performance of the O-ring. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Methylvinyldichlorosilane, CAS number is 124-70-9.

[0027] 2-Hydroxy-6-naphthoic acid, CAS number is 16712-64-4.

[0028] γ-Glycidyloxypropyltrimethoxysilane (KH560), CAS No. 2530-83-8.

[0029] Example 1

[0030] (1) Under nitrogen atmosphere, 45 mmol of methylvinyldichlorosilane and 360 mL of toluene were added to a reaction flask, and after stirring, 97.2 mmol of 2-hydroxy-6-naphthoic acid and 108 mmol of sodium hydride were added, and the mixture was reacted at 105° C. for 5 h, filtered, and the organic layer was washed with saturated brine, separated by column chromatography (silica gel, 8-15% n-heptane in ethyl acetate), and dried to obtain naphthylvinylsiloxane diacid. The preparation reaction formula is as follows:

[0031]

[0032] (2) Under nitrogen atmosphere, 40 mmol of naphthyl vinyl siloxane diacid and 600 mL of tetrahydrofuran were added to the reaction flask, and after stirring, 114 mmol of γ-glycidyloxypropyl trimethoxysilane and 2.5 mmol of tetrabutylammonium bromide were added, and the mixture was reacted at 55° C. for 16 h, and then concentrated under reduced pressure, purified by column chromatography (silica gel, 5-10% methanol in dichloromethane), and dried to obtain a naphthyl vinyl siloxane coupling agent. The preparation reaction formula is as follows:

[0033]

[0034] (3) Under nitrogen atmosphere, 10 g of sodium montmorillonite and 200 mL of deionized water were added to a reaction flask, stirred at high speed for 2 h, allowed to stand overnight, 2.2 g of hexadecyltrimethylammonium bromide and 0.3 g of naphthyl vinylsiloxane coupling agent were added, reacted at 85 °C for 8 h, washed with deionized water until no precipitate was detected by silver nitrate, filtered and dried to obtain modified montmorillonite.

[0035] (4) 100 g of natural rubber and 45 g of silicone rubber were thinned 8 times on an open mill, and 2 g of modified montmorillonite, 5 g of zinc oxide, 2 g of stearic acid, 1.5 g of accelerator CZ, 0.5 g of accelerator DM, 1.5 g of sulfur and 2 g of antioxidant 4010NA were added in sequence. After mixing evenly, the mixed rubber was thinned 5 times and sliced. After the mixed rubber was left overnight, it was placed in a mold for slicing and was put into a flat vulcanizer for vulcanization and tableting. The vulcanization temperature was 140°C, the pressure was 1.8 MPa, and the vulcanization time was 6 min. The mixed rubber was placed in a mold for compression molding to obtain a heat-resistant and wear-resistant O-ring.

[0036] Example 2

[0037] (1) Under nitrogen atmosphere, 150 mmol of methylvinyldichlorosilane and 750 mL of toluene were added to a reaction flask, and after stirring, 307.5 mmol of 2-hydroxy-6-naphthoic acid and 345 mmol of sodium hydride were added, and the mixture was reacted at 110° C. for 3 h. The mixture was filtered, and the organic layer was washed with saturated brine. The mixture was separated by column chromatography (silica gel, 8-15% n-heptane in ethyl acetate), and the naphthylvinylsiloxane diacid was obtained after drying.

[0038] (2) Under nitrogen atmosphere, 135 mmol of naphthyl vinyl siloxane diacid and 1620 mL of tetrahydrofuran were added to a reaction flask, and after stirring, 324 mmol of γ-glycidyloxypropyl trimethoxysilane and 6.75 mmol of tetrabutylammonium bromide were added, and the mixture was reacted at 65° C. for 12 h, concentrated under reduced pressure, purified by column chromatography (silica gel, 5-10% methanol in dichloromethane), and dried to obtain a naphthyl vinyl siloxane coupling agent.

[0039] (3) Under nitrogen atmosphere, 10 g of sodium montmorillonite and 200 mL of deionized water were added to a reaction flask, stirred at high speed for 1 h, allowed to stand overnight, 1.8 g of hexadecyltrimethylammonium bromide and 0.6 g of naphthyl vinylsiloxane coupling agent were added, reacted at 90 °C for 5 h, washed with deionized water until no precipitate was detected by silver nitrate, filtered and dried to obtain modified montmorillonite.

[0040] (4) 100 g of natural rubber and 35 g of silicone rubber were thinned on an open mill for 5 times, and 4 g of modified montmorillonite, 5 g of zinc oxide, 2 g of stearic acid, 1.5 g of accelerator CZ, 0.5 g of accelerator DM, 1.5 g of sulfur and 2 g of antioxidant 4010NA were added in sequence. After mixing evenly, the mixed rubber was thinned for 3 times and sheeted. After the mixed rubber was left overnight, it was placed in a mold for slicing and forming. The mixed rubber was placed in a flat vulcanizer for vulcanization and sheeting. The vulcanization temperature was 145 ° C, the pressure was 2 MPa, and the vulcanization time was 5 min. The mixed rubber was placed in a mold for compression molding to obtain a heat-resistant and wear-resistant O-ring.

[0041] Example 3

[0042] (1) Under nitrogen atmosphere, 80 mmol of methylvinyldichlorosilane and 800 mL of toluene were added to a reaction flask, and after stirring, 176 mmol of 2-hydroxy-6-naphthoic acid and 200 mmol of sodium hydride were added, and the mixture was reacted at 95° C. for 8 h. The mixture was filtered, and the organic layer was washed with saturated brine. The mixture was separated by column chromatography (silica gel, 8-15% n-heptane in ethyl acetate), and the naphthylvinylsiloxane diacid was obtained after drying.

[0043] (2) Under nitrogen atmosphere, 70 mmol of naphthyl vinyl siloxane diacid and 1400 mL of tetrahydrofuran were added to a reaction flask, and after stirring, 224 mmol of γ-glycidyloxypropyltrimethoxysilane and 7 mmol of tetrabutylammonium bromide were added, and the mixture was reacted at 50° C. for 24 h, concentrated under reduced pressure, purified by column chromatography (silica gel, 5-10% methanol in dichloromethane), and dried to obtain a naphthyl vinyl siloxane coupling agent.

[0044] (3) Under nitrogen atmosphere, 10 g of sodium montmorillonite and 200 mL of deionized water were added to a reaction flask, stirred at high speed for 3 h, allowed to stand overnight, 2.5 g of hexadecyltrimethylammonium bromide and 0.9 g of naphthyl vinylsiloxane coupling agent were added, reacted at 75 °C for 12 h, washed with deionized water until no precipitate was detected by silver nitrate, filtered and dried to obtain modified montmorillonite.

[0045] (4) 100 g of natural rubber and 50 g of silicone rubber were thinned 10 times on an open mixing mill, and 6 g of modified montmorillonite, 5 g of zinc oxide, 2 g of stearic acid, 1.5 g of accelerator CZ, 0.5 g of accelerator DM, 1.5 g of sulfur and 2 g of antioxidant 4010NA were added in sequence. After mixing evenly, the mixed rubber was thinned 6 times and sliced. After the mixed rubber was left overnight, it was placed in a mold for slicing and was put into a flat vulcanizer for vulcanization and sheeting. The vulcanization temperature was 135 ° C, the pressure was 1.5 MPa, and the vulcanization time was 10 min. The mixed rubber was placed in a mold for compression molding to obtain a heat-resistant and wear-resistant O-ring.

[0046] Example 4

[0047] (1) Under nitrogen atmosphere, 25 mmol of methylvinyldichlorosilane and 210 mL of toluene were added to a reaction flask, and after stirring, 53.5 mmol of 2-hydroxy-6-naphthoic acid and 59 mmol of sodium hydride were added, and the mixture was reacted at 100° C. for 7 h. The mixture was filtered, and the organic layer was washed with saturated brine. The mixture was separated by column chromatography (silica gel, 8-15% n-heptane in ethyl acetate), and the naphthylvinylsiloxane diacid was obtained after drying.

[0048] (2) Under nitrogen atmosphere, 22 mmol of naphthyl vinyl siloxane diacid and 365 mL of tetrahydrofuran were added to a reaction flask, and after stirring, 80 mmol of γ-glycidyloxypropyl trimethoxysilane and 1.75 mmol of tetrabutylammonium bromide were added, and the mixture was reacted at 60° C. for 18 h, concentrated under reduced pressure, purified by column chromatography (silica gel, 5-10% methanol in dichloromethane), and dried to obtain a naphthyl vinyl siloxane coupling agent.

[0049] (3) Under nitrogen atmosphere, 10 g of sodium montmorillonite and 200 mL of deionized water were added to a reaction flask, stirred at high speed for 2 h, allowed to stand overnight, 2.2 g of hexadecyltrimethylammonium bromide and 1.2 g of naphthylvinylsiloxane coupling agent were added, reacted at 80 °C for 10 h, washed with deionized water until no precipitate was detected by silver nitrate, filtered and dried to obtain modified montmorillonite.

[0050] (4) 100 g of natural rubber and 45 g of silicone rubber were thinned 9 times on an open mill, and 8 g of modified montmorillonite, 5 g of zinc oxide, 2 g of stearic acid, 1.5 g of accelerator CZ, 0.5 g of accelerator DM, 1.5 g of sulfur and 2 g of antioxidant 4010NA were added in sequence. After mixing evenly, the mixed rubber was thinned 4 times and sheeted. After the mixed rubber was left overnight, it was placed in a mold for slicing and forming. It was then put into a flat vulcanizer for vulcanization and sheeting. The vulcanization temperature was 140°C, the pressure was 1.6 MPa, and the vulcanization time was 9 min. The mixed rubber was placed in a mold for compression molding to obtain a heat-resistant and wear-resistant O-ring.

[0051] Example 5

[0052] (1) Under nitrogen atmosphere, 60 mmol of methylvinyldichlorosilane and 520 mL of toluene were added to a reaction flask, and after stirring, 130 mmol of 2-hydroxy-6-naphthoic acid and 146 mmol of sodium hydride were added, and the mixture was reacted at 105° C. for 8 h. The mixture was filtered, and the organic layer was washed with saturated brine. The mixture was separated by column chromatography (silica gel, 8-15% n-heptane in ethyl acetate), and the naphthylvinylsiloxane diacid was obtained after drying.

[0053] (2) Under nitrogen atmosphere, 50 mmol of naphthyl vinyl siloxane diacid and 810 mL of tetrahydrofuran were added to a reaction flask, and after stirring, 140 mmol of γ-glycidyloxypropyl trimethoxysilane and 4.5 mmol of tetrabutylammonium bromide were added, and the mixture was reacted at 65° C. for 24 h, concentrated under reduced pressure, purified by column chromatography (silica gel, 5-10% methanol in dichloromethane), and dried to obtain a naphthyl vinyl siloxane coupling agent.

[0054] (3) Under nitrogen atmosphere, 10 g of sodium montmorillonite and 200 mL of deionized water were added to a reaction flask, stirred at high speed for 3 h, allowed to stand overnight, 2.4 g of hexadecyltrimethylammonium bromide and 1.5 g of naphthylvinylsiloxane coupling agent were added, reacted at 90 °C for 12 h, washed with deionized water until no precipitate was detected by silver nitrate, filtered and dried to obtain modified montmorillonite.

[0055] (4) 100 g of natural rubber and 40 g of silicone rubber were thinned 9 times on an open mill, and 10 g of modified montmorillonite, 5 g of zinc oxide, 2 g of stearic acid, 1.5 g of accelerator CZ, 0.5 g of accelerator DM, 1.5 g of sulfur and 2 g of antioxidant 4010NA were added in sequence. After mixing evenly, the mixed rubber was thinned 5 times and sliced. After the mixed rubber was left overnight, it was placed in a mold for slicing and was put into a flat vulcanizer for vulcanization and tableting. The vulcanization temperature was 145 ° C, the pressure was 1.6 MPa, and the vulcanization time was 6 min. The mixed rubber was placed in a mold for compression molding to obtain a heat-resistant and wear-resistant O-ring.

[0056] Comparative Example 1

[0057] (1) Under nitrogen atmosphere, 10 g of sodium montmorillonite and 200 mL of deionized water were added to a reaction flask, stirred at high speed for 2 h, allowed to stand overnight, and 2.2 g of hexadecyltrimethylammonium bromide and 0.3 g of glycidyl methacrylate (structural formula: The CAS number is 106-91-2), reacted at 85°C for 8h, washed with deionized water until no precipitation was detected by silver nitrate, filtered and dried to obtain modified montmorillonite.

[0058] (2) 100 g of natural rubber and 45 g of silicone rubber were thinned 8 times on an open mill, and 2 g of modified montmorillonite, 5 g of zinc oxide, 2 g of stearic acid, 1.5 g of accelerator CZ, 0.5 g of accelerator DM, 1.5 g of sulfur and 2 g of antioxidant 4010NA were added in sequence. After mixing evenly, the mixed rubber was thinned 5 times and sliced. After the mixed rubber was left overnight, it was placed in a mold for slicing and was put into a flat vulcanizer for vulcanization and tableting. The vulcanization temperature was 140°C, the pressure was 1.8 MPa, and the vulcanization time was 6 min. The mixed rubber was placed in a mold for compression molding to obtain an O-ring.

[0059] Comparative Example 2

[0060] 100g natural rubber and 45g silicone rubber are thinned 8 times on an open mixing mill, and 2g sodium montmorillonite, 5g zinc oxide, 2g stearic acid, 1.5g accelerator CZ, 0.5g accelerator DM, 1.5g sulfur and 2g antioxidant 4010NA are added in sequence. After mixing evenly, the mixture is thinned 5 times and sliced. After the mixed rubber is left overnight, it is placed in a mold for slicing and is put into a flat vulcanizer for vulcanization and tableting. The vulcanization temperature is 140°C, the pressure is 1.8MPa, and the vulcanization time is 6min. It is placed in a mold for compression molding to obtain a heat-resistant and wear-resistant O-ring.

[0061] Tensile performance test: According to GB / T 528-1998 standard, the test was carried out using an electronic tensile testing machine with a tensile rate of 500 mm / min.

[0062] Tear strength test: According to GB / T 529-1999 standard, the test was carried out using an electronic tensile testing machine with a tensile rate of 500 mm / min.

[0063] Heat resistance test: The prepared O-ring was placed in a heat aging box at 100°C for 48 hours, and then its tensile strength and tear strength were tested according to the above method to determine its heat resistance.

[0064] Table 1 Heat resistance test

[0065]

[0066] From the test results in the above table, it can be seen that with the increase of the content of modified montmorillonite, the heat resistance of the O-ring is gradually enhanced. After being placed at 100°C for 48 hours, its tensile strength and tear strength do not change much. This is because, on the one hand, the naphthalene ring in the naphthyl vinyl siloxane coupling agent has a stable aromatic ring structure and is not easy to rotate. Its rigid structure can withstand high temperatures without deformation or decomposition, thus showing excellent heat resistance; on the other hand, the modified montmorillonite is dispersed in the natural rubber matrix in nanometer size, which better restricts the movement of the rubber macromolecular chain. Its unsaturated double bonds are chemically bonded with the unsaturated double bonds of natural rubber, and the trimethoxysilane group is coupled with the active group on the surface of montmorillonite, thereby increasing the cross-linking density of the vulcanized rubber and making the whole system tightly combined. At the same time, the organic siloxane in its structure has structural similarities with silicone rubber, which improves the interface compatibility and forms a network structure that is interpenetrating and closely interwoven among the three, effectively improving the mechanical properties and heat resistance of the sealing ring. Comparative Example 1 does not contain naphthalene rings and organosiloxane, has poor compatibility with silicone rubber, and its heat resistance and mechanical properties are inferior to those of the embodiment; Comparative Example 2 does not contain montmorillonite, has poor interface compatibility, and has poor mechanical properties and heat resistance.

[0067] Wear resistance test: refer to GB 9867-2008 and use DIN abrasion testing machine to test. Under the test conditions of friction distance of 40m and load of 10N, the prepared O-ring is subjected to friction between the transversely moving sample and the gauze on the drum. The wear resistance of the sample is expressed by the wear volume.

[0068] Table 2 Wear resistance test

[0069] <![CDATA[Wear volume (mm 3 )]]> Example 1 225.26 Example 2 170.85 Example 3 126.72 Example 4 80.64 Example 5 65.30 Comparative Example 1 284.35 Comparative Example 2 335.62

[0070] From the test results in the above table, it can be seen that with the increase of the modified montmorillonite content, the wear resistance of the O-ring is gradually enhanced, and the wear volume of Example 5 is as low as 65.30 mm 3 This is because the interlamellar spacing of the modified montmorillonite increases, and it is evenly dispersed in the rubber matrix at the nanoscale. This intercalation or exfoliation type nanocomposite structure enables the rubber matrix to more effectively utilize the nano effect of montmorillonite when subjected to external forces, reducing the possibility of stress concentration and crack propagation, thereby improving the wear resistance of the material. The uniform dispersion of montmorillonite flakes in the polymer matrix can also reduce the possibility of stress concentration and crack propagation. In addition, the structure of the modified montmorillonite is very similar to that of the natural rubber and silicone rubber matrix, and the compatibility is relatively strong. The three work together to form a unique interpenetrating network structure, which can greatly improve the wear resistance of the sealing ring material.

[0071] Gas barrier performance test: The test was conducted in accordance with GB / T 7755-2003 standard, with oxygen and nitrogen as the test gases and a gas pressure of 0.5 MPa.

[0072] Table 3 Barrier performance test

[0073]

[0074] From the test results in the above table, it can be seen that with the increase of the content of modified montmorillonite, the barrier performance of the O-ring is gradually enhanced. This is because the layered montmorillonite effectively blocks the intrusion of oxygen and nitrogen. The active groups of the bifunctional naphthyl vinyl siloxane coupling agent have binding points between the montmorillonite flakes, natural rubber and silicone rubber. First, the montmorillonite flakes can be better dispersed or intercalated into the rubber matrix. Second, the rubber macromolecular chain can be tightly combined with the montmorillonite. Its molecular movement is restricted between the montmorillonite flakes, so that the entire composite system forms a tightly interwoven network structure; when the gas passes through the composite material, it must go through an extended distance to penetrate, which reduces the air permeability of the composite material, thereby improving the barrier performance of the O-ring.

[0075] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a heat-resistant and wear-resistant O-type sealing ring, characterized in that: The preparation method is carried out according to the following steps: Step (1), under nitrogen atmosphere, sodium montmorillonite and deionized water were added to a reaction flask, stirred at high speed for 1-3 hours, allowed to stand overnight, and hexadecyltrimethylammonium bromide and a solution of the structural formula The naphthyl vinyl siloxane coupling agent is added and stirred for reaction. After the reaction is completed, the mixture is washed with deionized water until no precipitation is detected by silver nitrate, and then filtered and dried to obtain modified montmorillonite. Step (2), thinning natural rubber and methyl vinyl silicone rubber on an open mill for 5-10 times, adding modified montmorillonite, zinc oxide, stearic acid, accelerator CZ, accelerator DM, sulfur and antioxidant in sequence, mixing evenly and thinning for 3-6 times to sheet, leaving the mixed rubber overnight, placing it in a mold for slicing, placing it in a flat vulcanizer for vulcanization and sheeting, and obtaining a heat-resistant and wear-resistant O-ring.

2. The method for preparing a heat-resistant and wear-resistant O-ring according to claim 1, characterized in that: In the step (1), the ratio of sodium montmorillonite, hexadecyltrimethylammonium bromide and naphthyl vinylsiloxane coupling agent is 100 g:(18-25) g:(3-15) g.

3. The method for preparing a heat-resistant and wear-resistant O-ring according to claim 1, characterized in that: In the step (1), the reaction temperature is 75-90° C. and the reaction time is 5-12 h.

4. The method for preparing a heat-resistant and wear-resistant O-type sealing ring according to claim 1, characterized in that: In the step (2), the ratio of natural rubber, methyl vinyl silicone rubber and modified montmorillonite is 100 g: (35-50) g: (2-10) g.

5. The method for preparing a heat-resistant and wear-resistant O-type sealing ring according to claim 1, characterized in that: In the step (2), the vulcanization temperature is 135-145° C., the pressure is 1.5-2 MPa, and the vulcanization time is 5-10 min.

6. The method for preparing a heat-resistant and wear-resistant O-type sealing ring according to claim 1, characterized in that: The preparation method of the naphthyl vinyl siloxane coupling agent in step (1) is carried out according to the following steps: Step S1, under a nitrogen atmosphere, add methylvinyldichlorosilane and toluene to a reaction flask, stir evenly, add 2-hydroxy-6-naphthoic acid and sodium hydride, stir to react, filter after the reaction is completed, wash the organic layer with saturated brine, separate by column chromatography, and dry to obtain naphthylvinylsiloxane diacid; Step S2, under a nitrogen atmosphere, add naphthyl vinyl siloxane diacid and tetrahydrofuran to a reaction flask, stir evenly, add γ-glycidyloxypropyl trimethoxysilane and tetrabutylammonium bromide, react at 50-65° C. for 12-24 h, concentrate under reduced pressure, purify by column chromatography, and dry to obtain a naphthyl vinyl siloxane coupling agent.

7. The method for preparing a heat-resistant and wear-resistant O-type sealing ring according to claim 6, characterized in that: In the step S1, the ratio of methylvinyldichlorosilane, 2-hydroxy-6-naphthoic acid and sodium hydride is 1 mol: (2.05-2.2) mol: (2.3-2.5) mol.

8. The method for preparing a heat-resistant and wear-resistant O-type sealing ring according to claim 6, characterized in that: In step S1, the reaction temperature is 95-110° C. and the reaction time is 3-8 hours.

9. The method for preparing a heat-resistant and wear-resistant O-type sealing ring according to claim 6, characterized in that: In the step S2, the ratio of naphthyl vinyl siloxane diacid, γ-glycidyloxypropyl trimethoxysilane, and tetrabutylammonium bromide is 1 mol: (2.4-3.2) mol: (0.05-0.1) mol.

10. A heat-resistant and wear-resistant O-type sealing ring, characterized in that: Obtained by the preparation method according to any one of claims 1 to 9.

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