High-strength room temperature vulcanized fluorosilicone sealant, fluorosilicone crosslinker, and preparation and use thereof

Abstract

The present invention relates to a high-strength, room-temperature-vulcanized fluorosilicone sealant, a fluorosilicone crosslinker, and their preparation and use. The fluorosilicone crosslinker is an acyloxysilane oligomer containing a trifluoropropyl group. The fluorosilicone sealant comprises the following components in parts by weight: 100 parts of hydroxyfluorosilicone oil I; 20-30 parts of fumed silica; 10-20 parts of fumed titanium dioxide; 3-10 parts of hydroxyfluorosilicone oil II; 5-10 parts of methylfluorosilicone oil; 5-10 parts of fluorosilicone crosslinker; 1-3 parts of tackifier; and 0.01-0.5 parts of catalyst. The fluorosilicone crosslinker of the present invention is well compatible with the fluorosilicone system. By combining high- and low-viscosity hydroxyfluorosilicone oils, the crosslinked network system of the fluorosilicone sealant is significantly improved. Fluorosilicone materials of different structures cooperate and act synergistically with each other, maintaining good tolerance to various fuels and engine oils, and exhibiting significant oil resistance. The sealant can be used as an oil-resistant sealing material in a variety of fields.

Description

Technical Field

[0001] The present invention relates to the technical field of rubber materials, and in particular to a high-strength room temperature vulcanized fluorosilicone sealant, a fluorosilicone crosslinking agent, and a preparation method and application thereof. Background Art

[0002] Fluorosilicone sealant, also known as one-component room-temperature vulcanized fluorosilicone rubber, is made from a base rubber (α,ω-dihydroxypolytrifluoropropylmethylsiloxane) mixed with a crosslinker, catalyst, filler, and other additives in a moisture-proof environment. It is extruded from the packaging tube and crosslinked and cured upon exposure to moisture. It exhibits excellent water resistance and airtightness, is resistant to a variety of chemicals and oils, and adheres well to most substrates. It can be used for long-term operation within a temperature range of -60°C to 250°C. It is used for assembly and repair of components where welding is not possible, such as in narrow, irregular grooves, slots, and seams. It is also used as a form-in-place sealant for automobiles and various machinery, as an adhesive for electronic components, and is particularly useful for sealing, caulking, and potting aircraft engines and integral fuel tanks, meeting the operational requirements of aviation equipment.

[0003] In recent years, with the rapid development of the aviation industry and internal combustion engine technology, the sealing materials used are required to have not only good temperature resistance and oil resistance, but also high strength, high adhesion, and degradation resistance to meet the application requirements of fuel tanks, aircraft bodies, and places exposed to fuel and lubricating oil. Patent document CN102850807A discloses a one-component room temperature vulcanized fluorosilicone rubber and its preparation method. The invention comprises mixing a hydroxyl-terminated fluorinated polysiloxane, an inorganic filler, a crosslinking agent, a silane coupling agent, a titanate coupling agent, and a catalyst in a high-speed disperser. The crosslinking agent in the patent document uses a conventional silane coupling agent, such as methyltributylanoximesilane, methyltriacetoxysilane, and methyltrimethoxysilane. Such coupling agents have poor compatibility with fluorosilicone materials and are incompatible with the system. It is difficult to evenly disperse them into the rubber during the mixing process. Moreover, due to the differences in the system, it is difficult to react well with the base rubber. As a result, the effect of using the crosslinking agent is very poor, and a high-strength fluorosilicone sealant cannot be obtained. Patent document CN105086473A discloses a fluorosilicone sealant for fuel-solvent-resistant areas and its preparation method. The method involves first preparing a base material using hydroxyl-terminated fluorosilicone rubber, white carbon black, and activated nano-calcium carbonate by vacuum stirring for one hour. Then, an auxiliary agent is prepared by mixing ethyl orthosilicate, an accelerator, and a catalyst. Finally, a two-component potting compound is prepared by adding one part of the auxiliary agent to every ten parts of the base material. This method uses materials with low reactivity and a long dry-to-touch time, making it difficult to meet application requirements quickly. Furthermore, the two-component method increases construction difficulty. Furthermore, the material's low strength does not meet the high-strength requirements of modern industry, which limits its application to some extent.

[0004] Therefore, the development of a high-strength fluorosilicone sealant that can be vulcanized at room temperature has important practical significance. Summary of the Invention

[0005] In view of the above-mentioned state of the prior art, the inventors of the present invention have conducted in-depth and extensive research in the field of fluorosilicone sealants and found that the use of trifluoropropyl-containing acyloxysilane oligomers as cross-linking agents is well compatible with the fluorosilicone system, avoiding the problem of incompatibility between conventional coupling agents such as methyltriacetoxysilane and vinyltriacetoxysilane as cross-linking agents and the fluorosilicone system. In addition, the reactivity of the cross-linking agent is very high. During the room temperature vulcanization process, it can undergo an efficient condensation reaction with the terminal hydroxyl groups of the fluorosilicone rubber base, making the molecular chain segments more thoroughly cross-linked. In addition, the inventors also found that by compounding high and low viscosity hydroxyl fluorosilicone oils, the cross-linked network system of the fluorosilicone sealant can be significantly improved, the material is evenly dispersed in the system, easy to control, and can improve the mechanical properties of the fluorosilicone sealant. The present invention is completed based on the above-mentioned findings.

[0006] Therefore, an object of the present invention is to provide a fluorosilicone crosslinking agent for fluorosilicone sealants and a preparation method thereof, wherein the crosslinking agent is well compatible with the fluorosilicone system and has high reactivity.

[0007] The second object of the present invention is to provide a high-strength room temperature vulcanized fluorosilicone sealant and a preparation method thereof. The fluorosilicone sealant can be vulcanized at room temperature, maintains good tolerance to various types of fuel, engine oil, etc., has significant oil resistance, and can be used as an oil-resistant sealing material in multiple fields.

[0008] The technical solution for achieving the above-mentioned invention object can be summarized as follows:

[0009] A fluorosilicone crosslinking agent is an acyloxysilane oligomer containing a trifluoropropyl group.

[0010] According to the present invention, preferably, the trifluoropropyl-containing acyloxysilane oligomer has a structure shown in formula (IV):

[0011]

[0012] In formula (IV), x represents the average degree of polymerization, and 1≤x≤3.

[0013] According to the present invention, the preparation method of the above-mentioned fluorosilicone crosslinking agent comprises the following steps:

[0014] Under the protection of inert gas, anhydrous sodium acetate and toluene are stirred and mixed, heated under reflux to remove moisture, and then trifluoropropyltrichlorosilane is added dropwise to the system to carry out acyl oxidation reaction. After the addition is completed, the reaction is continued by stirring, and then the temperature is lowered, filtered, and the solvent is recovered to obtain a fluorosilicone crosslinking agent with a structure of formula (IV).

[0015] According to the present invention, preferably, the molar ratio of trifluoropropyltrichlorosilane to anhydrous sodium acetate is 1:(3.1-3.3).

[0016] According to the present invention, preferably, the mass ratio of anhydrous sodium acetate to toluene is 1:(2.0-4.0).

[0017] According to the present invention, preferably, the time for removing moisture by heating and refluxing is 3 to 6 hours.

[0018] According to the present invention, preferably, the acyl oxidation reaction temperature is 50-60°C.

[0019] According to the present invention, preferably, the conditions for recovering the solvent are a temperature of 40 to 70° C. and a pressure of -0.04 MPa to -0.08 MPa.

[0020] According to the present invention, the trifluoropropyl-containing acyloxysilane oligomer of the structure represented by formula (IV) is used as a fluorosilicone crosslinking agent for the preparation of a room temperature vulcanized fluorosilicone sealant.

[0021] According to the present invention, a high-strength room temperature vulcanized fluorosilicone sealant comprises the above-mentioned fluorosilicone crosslinking agent and includes the following components in parts by weight:

[0022] Hydroxyfluorosilicone oil 1, 100 parts;

[0023] Fumed silica, 20-30 parts;

[0024] Fumed titanium dioxide, 10-20 parts;

[0025] Hydroxyfluorosilicone oil II, 3-10 parts;

[0026] Methyl fluorosilicone oil, 5-10 parts;

[0027] Fluorosilicone crosslinking agent, 5-10 parts;

[0028] Thickener, 1 to 3 parts;

[0029] Catalyst, 0.01-0.5 parts;

[0030] The hydroxy fluorosilicone oil I has a viscosity of 50,000 to 100,000 mPa.s and has a structure shown in formula (I):

[0031]

[0032] In formula (I), n represents the average degree of polymerization, 200≤n≤500;

[0033] The hydroxy fluorosilicone oil II has a viscosity of 100 to 150 mPa.s and has a structure shown in formula (II):

[0034]

[0035] In formula (II), m represents the average degree of polymerization, and 1≤m≤6.

[0036] According to the present invention, preferably, the methyl fluorosilicone oil has a viscosity of 100 to 300 mPa.s and has a structure shown in formula (III):

[0037]

[0038] In formula (III), p represents the average degree of polymerization, and 1≤p≤10.

[0039] According to the present invention, preferably, the BET specific surface area of ​​the fumed silica is 175 to 225 m 2 / g.

[0040] According to the present invention, preferably, the BET specific surface area of ​​the vapor phase titanium dioxide is 35 to 65 m 2 / g.

[0041] According to the present invention, preferably, the tackifier is a mixture of tert-butyl alcohol and vinyl triacetoxysilane in a molar ratio of 2:1, obtained by alcoholysis reaction and subsequent removal of low molecular weight treatment.

[0042] According to the present invention, preferably, the alcoholysis reaction temperature of the tackifier is 30-40° C., and the alcoholysis reaction time is 2-4 hours.

[0043] According to the present invention, preferably, the conditions for removing low molecular weight treatment of the tackifier are a temperature of 50 to 80° C. and a pressure of -0.09 MPa.

[0044] According to the present invention, preferably, the catalyst is at least one of dibutyltin dilaurate, dibutyltin diacetate, stannous octoate, and dioctyltin dilaurate.

[0045] According to the present invention, the preparation method of the above-mentioned high-strength room temperature vulcanized fluorosilicone sealant comprises the following steps:

[0046] (1) Add hydroxy fluorosilicone oil I and part of fumed silica and fumed titanium dioxide into a vacuum kneader for kneading and mixing, then add hydroxy fluorosilicone oil II and the remaining fumed silica and fumed titanium dioxide in batches, and mix at room temperature for 2 to 4 hours;

[0047] (2) After mixing is complete, heat the rubber material to 150-180°C for heat treatment for 2-6 hours;

[0048] (3) Cool the rubber compound to room temperature and use a three-roll mill to grind it 3 to 5 times until the rubber compound is uniform and fine without agglomerated particles;

[0049] (4) According to the formula ratio, the dispersed rubber and methyl fluorosilicone oil are stirred and mixed and the water is removed under vacuum. Then the fluorosilicone crosslinker, catalyst and tackifier are added and the vacuum is maintained and the stirring is continued for 2 to 4 hours;

[0050] (5) Cooling the material to room temperature to obtain a high-strength room-temperature vulcanized fluorosilicone sealant.

[0051] According to the present invention, preferably, the kneading treatment interval of each batch of materials in step (1) is 0.5 to 1 hour.

[0052] According to the present invention, preferably, the system pressure is maintained at -0.098 MPa during the heat treatment in step (2).

[0053] According to the present invention, preferably, the dehydration time in step (4) is 2 to 4 hours, and the dehydration pressure is -0.05 MPa to -0.09 MPa.

[0054] According to the present invention, the above-mentioned high-strength room temperature vulcanized fluorosilicone sealant is used in oil-resistant sealing materials.

[0055] Compared with the prior art, the technical features and beneficial effects of the present invention are as follows:

[0056] 1. The fluorosilicone crosslinker of this invention is an acyloxysilane oligomer containing a trifluoropropyl group. Its molecular structure is highly compatible with fluorosilicone sealant systems, eliminating the incompatibility issues with conventional coupling agents such as methyltriacetoxysilane and vinyltriacetoxysilane. During mixing, it can be evenly dispersed within the rubber compound. Furthermore, the crosslinker is highly reactive, undergoing a highly efficient condensation reaction with the terminal hydroxyl groups of the base rubber during room temperature vulcanization, resulting in more thorough crosslinking of the molecular segments and significantly improving the mechanical properties of the fluorosilicone sealant, particularly its tensile strength.

[0057] 2. The present invention significantly improves the cross-linked network system of the fluorosilicone sealant by compounding high- and low-viscosity hydroxyl fluorosilicone oils. Combined with a tackifier and methyl fluorosilicone oil, the synergistic effect of multiple materials allows the formed vulcanization system to intertwine with each other and form a stable dispersion state with the reinforcing filler, which can not only ensure the good mechanical properties of the fluorosilicone sealant, but also greatly reduce the viscosity of the rubber.

[0058] 3. The low-viscosity hydroxyl fluorosilicone oil in the present invention has a short molecular chain, which can not only be used as a building material for the rubber system, but also can well treat the silanol groups on the surface of the powder, playing the role of a structuring control agent. In addition, due to the presence of trifluoropropyl, the powder material and the fluorosilicone oil have good compatibility and can form a homogeneous system, avoiding the thickening phenomenon of the sealant during storage and increasing the storage stability of the product.

[0059] 4. The fluorosilicone sealant of the present invention preferably combines fluorosilicone materials of various structures to provide it with excellent oil resistance and adhesion properties, and maintains good tolerance to various fuels, engine oils, etc. The oil resistance effect is very significant, and it can be used as an oil-resistant sealing material in multiple fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is the infrared spectrum of the fluorosilicone crosslinking agent prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0061] The present invention provides a high-strength room temperature vulcanized fluorosilicone sealant, a fluorosilicone crosslinker, and their preparation and use. The fluorosilicone crosslinker of the present invention is an acyloxysilane oligomer containing trifluoropropyl and is well compatible with the fluorosilicone system.

[0062] In one or more preferred embodiments, the trifluoropropyl-containing acyloxysilane oligomer has a structure shown in formula (IV):

[0063]

[0064] In formula (IV), x represents the average degree of polymerization, and 1≤x≤3.

[0065] According to the present invention, the trifluoropropyl acyloxysilane oligomer of the structure shown in formula (IV) contains multiple acyloxy groups in its molecular structure and has high reactivity. During the room temperature vulcanization process, it can undergo an efficient condensation reaction with the terminal hydroxyl groups of hydroxy fluorosilicone oil, making the molecular chain segments more thoroughly cross-linked. When used in the formulation of fluorosilicone sealants, it can greatly improve the mechanical properties of the fluorosilicone sealants.

[0066] According to the present invention, the preparation method of the above-mentioned fluorosilicone crosslinking agent comprises the following steps:

[0067] Under the protection of inert gas, anhydrous sodium acetate and toluene are stirred and mixed, heated under reflux to remove moisture, and then trifluoropropyltrichlorosilane is added dropwise to the system to carry out acyl oxidation reaction. After the addition is completed, the reaction is continued by stirring, and then the temperature is lowered, filtered, and the solvent is recovered to obtain a fluorosilicone crosslinking agent with a structure of formula (IV).

[0068] In one or more preferred embodiments, the molar ratio of trifluoropropyltrichlorosilane to anhydrous sodium acetate is 1:(3.1-3.3).

[0069] In one or more preferred embodiments, the mass ratio of anhydrous sodium acetate to toluene is 1:(2.0-4.0).

[0070] In one or more preferred embodiments, the time for removing moisture by heating under reflux is 3 to 6 hours.

[0071] In one or more preferred embodiments, the acyl oxidation reaction temperature is 50-60°C.

[0072] In one or more preferred embodiments, the conditions for recovering the solvent are a temperature of 40 to 70° C. and a pressure of -0.04 MPa to -0.08 MPa.

[0073] According to the present invention, the trifluoropropyl-containing acyloxysilane oligomer of the structure represented by formula (IV) is used as a fluorosilicone crosslinking agent for the preparation of a room temperature vulcanized fluorosilicone sealant.

[0074] The high-strength room-temperature vulcanized fluorosilicone sealant provided by the present invention significantly improves the cross-linked network system of the fluorosilicone sealant by compounding high- and low-viscosity hydroxyl fluorosilicone oils. Furthermore, by combining a tackifier and methyl fluorosilicone oil, the synergistic effect of multiple materials results in a fluorosilicone sealant with high strength, good tolerance to various fuels, engine oils, etc., and significant oil resistance. Therefore, the sealant can be used as an oil-resistant sealing material in multiple fields.

[0075] According to the present invention, a high-strength room temperature vulcanized fluorosilicone sealant comprises the above-mentioned fluorosilicone crosslinking agent and includes the following components in parts by weight:

[0076] Hydroxyfluorosilicone oil 1, 100 parts;

[0077] Fumed silica, 20-30 parts;

[0078] Fumed titanium dioxide, 10-20 parts;

[0079] Hydroxyfluorosilicone oil II, 3-10 parts;

[0080] Methyl fluorosilicone oil, 5-10 parts;

[0081] Fluorosilicone crosslinking agent, 5-10 parts;

[0082] Thickener, 1 to 3 parts;

[0083] Catalyst, 0.01-0.5 parts;

[0084] The hydroxy fluorosilicone oil I has a viscosity of 50,000 to 100,000 mPa.s and has a structure shown in formula (I):

[0085]

[0086] In formula (I), n represents the average degree of polymerization, 200≤n≤500;

[0087] The hydroxy fluorosilicone oil II has a viscosity of 100 to 150 mPa.s and has a structure shown in formula (II):

[0088]

[0089] In formula (II), m represents the average degree of polymerization, and 1≤m≤6.

[0090] In one or more preferred embodiments, the methyl fluorosilicone oil has a viscosity of 100 to 300 mPa.s and has a structure shown in formula (III):

[0091]

[0092] In formula (III), p represents the average degree of polymerization, and 1≤p≤10.

[0093] In one or more preferred embodiments, the tackifier is a mixture of tert-butyl alcohol and vinyl triacetoxysilane in a molar ratio of 2:1, obtained by alcoholysis and subsequent desulfurization.

[0094] In one or more preferred embodiments, the alcoholysis reaction temperature of the tackifier is 30-40°C.

[0095] In one or more preferred embodiments, the stirring reaction temperature of the tackifier is 30-40° C., and the stirring time is 2-4 hours.

[0096] In one or more preferred embodiments, the conditions for the desulfurization treatment of the tackifier are a temperature of 50 to 80° C. and a pressure of -0.09 MPa.

[0097] In one or more preferred embodiments, the tackifier is prepared as follows:

[0098] When vinyl triacetoxysilane is stirred and heated to 30-40°C, tert-butanol is added dropwise thereto for alcoholysis reaction. After the addition is completed, the temperature is maintained at 30-40°C and the stirring reaction is continued. After the reaction is completed, the low molecular weight treatment is carried out while maintaining the temperature at 50-80°C / -0.09MPa to obtain a thickener.

[0099] In one or more preferred embodiments, the catalyst is at least one of dibutyltin dilaurate, dibutyltin diacetate, stannous octoate, and dioctyltin dilaurate.

[0100] According to the present invention, the preparation method of the above-mentioned high-strength room temperature vulcanized fluorosilicone sealant comprises the following steps:

[0101] (1) Add hydroxy fluorosilicone oil I and part of fumed silica and fumed titanium dioxide into a vacuum kneader for kneading and mixing, then add hydroxy fluorosilicone oil II and the remaining fumed silica and fumed titanium dioxide in batches, and mix at room temperature for 2 to 4 hours;

[0102] (2) After mixing is complete, heat the rubber material to 150-180°C for heat treatment for 2-6 hours;

[0103] (3) Cool the rubber compound to room temperature and use a three-roll mill to grind it 3 to 5 times until the rubber compound is uniform and fine without agglomerated particles;

[0104] (4) Add the dispersed rubber and methyl fluorosilicone oil into a planetary mixer according to the formula ratio, stir and mix, and remove moisture in a vacuum. Then add the fluorosilicone crosslinker, catalyst, and tackifier, and continue stirring for 2 to 4 hours while maintaining the vacuum;

[0105] (5) Cooling the material to room temperature and sealing the package to obtain the high-strength room temperature vulcanized fluorosilicone sealant.

[0106] In one or more preferred embodiments, the kneading treatment interval of each batch of materials in step (1) is 0.5 to 1 hour.

[0107] In one or more preferred embodiments, the system pressure is maintained at -0.098 MPa during the heat treatment in step (2).

[0108] In one or more preferred embodiments, the dehydration time in step (4) is 2 to 4 hours, and the dehydration pressure is -0.05 MPa to -0.09 MPa.

[0109] According to the present invention, the above-mentioned high-strength room temperature vulcanized fluorosilicone sealant is used in oil-resistant sealing materials.

[0110] Anything not described in detail in the present invention is based on conventional techniques in the art.

[0111] The viscosities described in the examples are all viscosities at 25°C, and the room temperature is 25±5°C.

[0112] The present invention will be further described below with reference to specific embodiments, which are not intended to limit the present invention.

[0113] The raw materials described in the examples are all conventional raw materials and can be purchased from the market or prepared according to existing technologies.

[0114] The hydroxy fluorosilicone oil I used in the examples has the structure shown in formula (I):

[0115]

[0116] In formula (I), n represents the average degree of polymerization, and 200≤n≤500.

[0117] The hydroxy fluorosilicone oil II used has the structure shown in formula (II):

[0118]

[0119] In formula (II), m represents the average degree of polymerization, and 1≤m≤6.

[0120] The methyl fluorosilicone oil used has the structure shown in formula (III):

[0121]

[0122] In formula (III), p represents the average degree of polymerization, and 1≤p≤10.

[0123] The viscosity of the hydroxyfluorosilicone oil I is 50,000 to 100,000 mPa.s, the viscosity of the hydroxyfluorosilicone oil II is 100 to 150 mPa.s, and the viscosity of the methylfluorosilicone oil is 100 to 300 mPa.s.

[0124] The tackifier used in the examples was prepared as follows:

[0125] To a reactor equipped with a mechanical stirrer, a thermometer, a reflux tube, and a dropping funnel, 464 g of vinyl triacetoxysilane was added, stirring was started, and the temperature was raised to 30-40 ° C. 296 g of tert-butanol was slowly added dropwise to the reactor for alcoholysis reaction. The reaction was exothermic during the addition process, and the temperature was cooled by condensing brine. After the addition was completed, the temperature was maintained at 30-40 ° C and stirring was continued for 2 h, and then the temperature was maintained at 50-80 ° C / -0.09 MPa for desulfurization to obtain 387 g of thickener.

[0126] Example 1

[0127] Fluorosilicone crosslinking agent having the structure shown in formula (IV):

[0128]

[0129] In formula (IV), x represents the average degree of polymerization, and 1≤x≤3.

[0130] The preparation method of fluorosilicone crosslinking agent is as follows:

[0131] Under nitrogen protection, 1312g of anhydrous sodium acetate and 3936g of toluene were added to a reactor equipped with a mechanical stirrer, a thermometer, a reflux tube, and a dropping funnel, and stirred to form a suspension. The temperature was raised to 110°C and maintained at reflux for 3h, and then the kettle temperature was lowered to 50°C. 1157.5g of trifluoropropyltrichlorosilane was added dropwise to the kettle for acyl oxidation reaction. The reaction was exothermic during the addition, and the kettle temperature was cooled by the jacket so that the temperature did not exceed 60°C. After the addition was completed, stirring was continued at 50-60°C for 3h. After the reaction was complete, the system was cooled to room temperature, the sodium chloride and excess sodium acetate generated by the reaction were filtered out, and the filtrate was collected. The solvent was evaporated and recovered at a temperature of 40-70°C and a pressure of -0.04MPa to -0.08MPa to obtain 1377g of fluorosilicone crosslinker with a viscosity of 13mPa.s and a yield of 91.2%.

[0132] The infrared spectrum of the fluorosilicone crosslinking agent prepared above is as follows: Figure 1 As shown, 1739cm -1 The strong peak at 1201 cm is the typical characteristic absorption peak of Si-OCOCH3. -1 The peak at 1371 cm is the characteristic absorption peak of the CF bond in Si-CH2CH2CF3. -1 The peak at 1257 cm is the bending vibration absorption peak of Si-C bond. -1 The peak at 1319 cm is the deformation vibration absorption peak of Si-C bond. -1 The peak at 900 cm is the absorption peak of CC bond in -CH2-CH2-. -1 The peak at is the absorption peak of the CC bond in -CH2-CF3. The data represented by this spectrum can indicate the structure of the product.

[0133] Example 2

[0134] The preparation of a high-strength room temperature vulcanized fluorosilicone sealant, including the use of the fluorosilicone crosslinking agent described in Example 1, comprises the following steps:

[0135] (1) Add 1000 g of hydroxy fluorosilicone oil I (viscosity 64000 mPa.s), 50 g of fumed silica (specific surface area 200 m 2 / g), 25g fumed titanium dioxide (specific surface area 50m 2 / g) and kneaded and mixed for 0.5 h, and then the remaining 150 g of fumed silica, 75 g of fumed titanium dioxide and 80 g of hydroxy fluorosilicone oil II (viscosity 140 mPa.s) were added to the kneader in three batches, with a kneading interval of 0.5 h between each batch. After all the materials were added, kneading and mixing were continued at room temperature for 2 h;

[0136] (2) After mixing is complete, turn on the heating and heat the rubber compound to 180°C for 3 hours. During the heat treatment, the system pressure is maintained at -0.098 MPa.

[0137] (3) Cool the rubber compound to room temperature and continue to grind it through a three-roll mill for 3 to 5 times until the rubber compound is uniform and fine with no visible agglomerated particles.

[0138] (4) The thinned rubber material was added to a planetary mixer, and then 50 g of methyl fluorosilicone oil (viscosity 150 mPa.s) was added and stirred for 2 h while removing moisture under vacuum. Then, 80 g of a fluorosilicone crosslinker of formula (IV), 10 g of a tackifier, and 1 g of dibutyltin dilaurate were added to the kettle, and the vacuum condition was maintained and stirring was continued for 3 h.

[0139] (5) The material is cooled to room temperature and sealed in a plastic barrel to obtain the high-strength room temperature vulcanized fluorosilicone sealant.

[0140] The obtained fluorosilicone sealant was cured at 23° C. and 50% relative humidity for 7 days to prepare a 2 mm standard test piece. The test piece was tested for mechanical properties, and the results are shown in Table 1. The test piece was tested for oil resistance, and the results are shown in Table 2.

[0141] Example 3

[0142] The preparation of a high-strength room temperature vulcanized fluorosilicone sealant, including the use of the fluorosilicone crosslinking agent described in Example 1, comprises the following steps:

[0143] (1) Add 1000 g of hydroxy fluorosilicone oil I (viscosity 64000 mPa.s), 50 g of fumed silica (specific surface area 200 m 2 / g), 25g fumed titanium dioxide (specific surface area 50m 2 / g) and kneaded and mixed for 0.5 h, and then the remaining 150 g of fumed silica, 75 g of fumed titanium dioxide and 100 g of hydroxy fluorosilicone oil II (viscosity 140 mPa.s) were added to the kneader in three batches, with a kneading interval of 0.5 h for each batch. After all the materials were added, kneading and mixing were continued at room temperature for 2 h;

[0144] (2) After mixing is complete, turn on the heating and heat the rubber compound to 180°C for 3 hours. During the heat treatment, the system pressure is maintained at -0.098 MPa.

[0145] (3) Cool the rubber compound to room temperature and continue to grind it through a three-roll mill for 3 to 5 times until the rubber compound is uniform and fine with no visible agglomerated particles.

[0146] (4) The thinned rubber material was added to a planetary mixer, and then 60 g of methyl fluorosilicone oil (viscosity 150 mPa.s) was added and stirred for 2 h while removing moisture under vacuum. Then, 90 g of a fluorosilicone crosslinker of formula (IV), 15 g of a tackifier, and 1.2 g of dibutyltin dilaurate were added to the kettle, and the vacuum condition was maintained and stirring was continued for 3 h.

[0147] (5) The material is cooled to room temperature and sealed in a plastic barrel to obtain the high-strength room temperature vulcanized fluorosilicone sealant.

[0148] The obtained fluorosilicone sealant was cured at 23° C. and 50% relative humidity for 7 days to prepare a 2 mm standard test piece. The test piece was tested for mechanical properties, and the results are shown in Table 1. The test piece was tested for oil resistance, and the results are shown in Table 2.

[0149] Example 4

[0150] The preparation of a high-strength room temperature vulcanized fluorosilicone sealant, including the use of the fluorosilicone crosslinking agent described in Example 1, comprises the following steps:

[0151] (1) Add 1000 g of hydroxy fluorosilicone oil I (viscosity 64000 mPa.s), 55 g of fumed silica (specific surface area 200 m 2 / g), 30g fumed titanium dioxide (specific surface area 50m 2 / g) and kneaded and mixed for 0.5 h, and then the remaining 165 g of fumed silica, 100 g of fumed titanium dioxide and 100 g of hydroxy fluorosilicone oil II (viscosity 140 mPa.s) were added to the kneader in three batches, with a kneading interval of 0.5 h for each batch. After all the materials were added, kneading and mixing were continued at room temperature for 2 h;

[0152] (2) After mixing is complete, turn on the heating and heat the rubber compound to 180°C for 3 hours. During the heat treatment, the system pressure is maintained at -0.098 MPa.

[0153] (3) Cool the rubber compound to room temperature and continue to grind it through a three-roll mill for 3 to 5 times until the rubber compound is uniform and fine with no visible agglomerated particles.

[0154] (4) The thinned rubber material was added to a planetary mixer, and then 50 g of methyl fluorosilicone oil (viscosity 150 mPa.s) was added and stirred for 2 h while removing moisture under vacuum. Then, 90 g of a fluorosilicone crosslinker of formula (IV), 15 g of a tackifier, and 1.2 g of dibutyltin dilaurate were added to the kettle, and the vacuum condition was maintained and stirring was continued for 3 h.

[0155] (5) The material is cooled to room temperature and sealed in a plastic barrel to obtain the high-strength room temperature vulcanized fluorosilicone sealant.

[0156] The obtained fluorosilicone sealant was cured at 23° C. and 50% relative humidity for 7 days to prepare a 2 mm standard test piece. The test piece was tested for mechanical properties, and the results are shown in Table 1. The test piece was tested for oil resistance, and the results are shown in Table 2.

[0157] Example 5

[0158] The preparation of a high-strength room temperature vulcanized fluorosilicone sealant, including the use of the fluorosilicone crosslinking agent described in Example 1, comprises the following steps:

[0159] (1) Add 1000 g of hydroxy fluorosilicone oil I (viscosity 64000 mPa.s), 55 g of fumed silica (specific surface area 200 m 2 / g), 30g fumed titanium dioxide (specific surface area 50m 2 / g) and kneaded and mixed for 0.5 h, and then the remaining 165 g of fumed silica, 100 g of fumed titanium dioxide and 80 g of hydroxy fluorosilicone oil II (viscosity 140 mPa.s) were added to the kneader in three batches, with a kneading interval of 0.5 h for each batch. After all the materials were added, kneading and mixing were continued at room temperature for 2 h;

[0160] (2) After mixing is complete, turn on the heating and heat the rubber compound to 180°C for 3 hours. During the heat treatment, the system pressure is maintained at -0.098 MPa.

[0161] (3) Cool the rubber compound to room temperature and continue to grind it through a three-roll mill for 3 to 5 times until the rubber compound is uniform and fine with no visible agglomerated particles.

[0162] (4) The thinned rubber material was added to a planetary mixer, and then 70 g of methyl fluorosilicone oil (viscosity 150 mPa.s) was added and stirred for 2 h while removing moisture under vacuum. Then, 70 g of a fluorosilicone crosslinker of formula (IV), 10 g of a tackifier, and 1 g of dibutyltin dilaurate were added to the kettle, and the vacuum condition was maintained and stirring was continued for 3 h.

[0163] (5) The material is cooled to room temperature and sealed in a plastic barrel to obtain the high-strength room temperature vulcanized fluorosilicone sealant.

[0164] The obtained fluorosilicone sealant was cured at 23° C. and 50% relative humidity for 7 days to prepare a 2 mm standard test piece. The test piece was tested for mechanical properties, and the results are shown in Table 1. The test piece was tested for oil resistance, and the results are shown in Table 2.

[0165] Comparative Example 1

[0166] The preparation method of Example 2 of the present invention was repeated, except that the fluorosilicone crosslinking agent of formula (IV) was replaced by methyltriacetoxysilane, and the amounts of other materials and the operating steps remained unchanged.

[0167] The obtained fluorosilicone sealant was cured at 23° C. and 50% relative humidity for 7 days to prepare a 2 mm standard test piece. The test piece was subjected to mechanical property testing. The results are shown in Table 1.

[0168] Comparative Example 2

[0169] The preparation method of Example 2 of the present invention was repeated, except that the fluorosilicone crosslinking agent of formula (IV) was replaced by vinyltriacetoxysilane, and the amounts of other materials and the operating steps remained unchanged.

[0170] The obtained fluorosilicone sealant was cured at 23° C. and 50% relative humidity for 7 days to prepare a 2 mm standard test piece. The test piece was subjected to mechanical property testing. The results are shown in Table 1.

[0171] Comparative Example 3

[0172] The preparation method of Example 2 of the present invention was repeated, except that the hydroxyfluorosilicone oil II was removed, and the amounts of other materials and the operating steps remained unchanged.

[0173] When kneading and mixing the materials in a kneader, it was found that the viscosity of the rubber compound in Comparative Example 3 was significantly increased compared to Example 2. The powder was difficult to evenly disperse in the system, and the rubber compound was viscous, stiff, and non-thixotropic. During the subsequent formulation preparation process, crosslinkers, tackifiers, catalysts, and other ingredients were also difficult to mix in the system, and even increasing the speed of the planetary mixer did not produce satisfactory results. Furthermore, the rubber compound gradually thickened during storage, gradually losing its workability, making it unsuitable for use in preparing fluorosilicone sealants.

[0174] Test example

[0175] The mechanical properties and oil resistance of the fluorosilicone sealants prepared in Examples 2 to 5 and Comparative Examples 1 to 2 were tested, and the test results are shown in Tables 1 and 2. The density was tested in accordance with ASTM D792; the hardness was tested in accordance with ASTM D2240; the tensile strength and elongation at break were tested in accordance with ASTM D412; the tear strength was tested in accordance with ASTM D624B; the peel strength was tested in accordance with GB / T 15254; the open-drying time was tested in accordance with GB / T 13477.5; and the oil resistance was tested in accordance with ASTM D471. The viscosity was tested using a German HAAKE VTiQ intelligent rheometer using the following test methods: 20 mm flat rotor, shear rate 10 s -1 , tested at 25℃ for 50 seconds.

[0176] Table 1

[0177]

[0178] Table 2

[0179] Oil resistance Example 2 Example 3 Example 4 Example 5 IRM903, ΔV / % (150℃×168h) 1.5 1.1 1.4 1.2 RP-3 aviation kerosene, ΔV / % (60°C×168h) 3.9 3.9 4.2 4.0 0# diesel, ΔV / % (60℃×168h) 2.3 2.0 2.4 2.5 Fuel C, ΔV / % (60℃×168h) 19.7 19.6 19.4 19.1 FAM B, ΔV / % (60℃×168h) 28.0 29.0 27.7 28.2

[0180] As shown in Tables 1 and 2, the high-strength fluorosilicone sealants prepared according to the methods described in Examples 2-5 of the present invention exhibit excellent mechanical properties, particularly tensile strength exceeding 4 MPa. The rubber compound exhibits low viscosity, good thixotropy, strong adhesion, and high reactivity at room temperature. Furthermore, the fluorosilicone sealants exhibit excellent oil resistance, maintaining good tolerance to various test oils. The oil resistance is highly significant, making them suitable for use as oil-resistant sealing materials in a variety of applications.

[0181] Comparative Example 1 used methyltriacetoxysilane as a crosslinker. Due to its high melting point (approximately 40°C), it needed to be melted before use. The resulting rubber compound was subject to the risk of crystallization during storage, affecting product quality and storage stability. Furthermore, due to its incompatibility with fluorosilicone systems, the resulting fluorosilicone sealant exhibited poor performance and could not be used as a high-strength sealing material.

[0182] Comparative Example 2 uses vinyl triacetoxysilane as a crosslinking agent. Also due to system compatibility issues, the product strength is very low, and the viscosity of the rubber is high, the operation time is short, the construction is difficult, and it has no use value.

[0183] The technical contents and features of the present invention are as shown above, but the protection scope of the present invention should not be limited to the contents described in the embodiments, but should include various replacements and modifications that do not deviate from the present invention and are covered by the claims of the present invention.

Claims

1. A high-strength room temperature vulcanized fluorosilicone sealant, characterized in that: Calculated by weight, it includes the following components: Hydroxyfluorosilicone oil 1, 100 parts; Fumed silica, 20-30 parts; Fumed titanium dioxide, 10-20 parts; Hydroxyfluorosilicone oil II, 3-10 parts; Methyl fluorosilicone oil, 5-10 parts; Fluorosilicone crosslinking agent, 5-10 parts; Thickener, 1-3 parts; Catalyst, 0.01~0.5 parts; The hydroxy fluorosilicone oil I has a viscosity of 50,000 to 100,000 mPa.s and has a structure shown in formula (I): ； In formula (I), n represents the average degree of polymerization, 200≤n≤500; The hydroxy fluorosilicone oil II has a viscosity of 100-150 mPa.s and has a structure shown in formula (II): ； In formula (II), m represents the average degree of polymerization, 1≤m≤6; The fluorosilicone crosslinking agent has a structure shown in formula (IV): ； In formula (IV), x represents the average degree of polymerization, and x=1.

2. The high-strength room temperature vulcanized fluorosilicone sealant according to claim 1, characterized in that: The methyl fluorosilicone oil has a viscosity of 100-300 mPa.s and has a structure shown in formula (III): ； In formula (III), p represents the average degree of polymerization, 1≤p≤10; The BET specific surface area of ​​the fumed silica is 175~225m 2 / g; The BET specific surface area of ​​the vapor phase titanium dioxide is 35~65m 2 / g; The tackifier is a mixture of tert-butyl alcohol and vinyl triacetoxysilane in a molar ratio of 2:1, which is subjected to alcoholysis reaction and then to low molecular weight removal treatment; The catalyst is at least one of dibutyltin dilaurate, dibutyltin diacetate, stannous octoate and dioctyltin dilaurate.

3. A method for preparing the high-strength room temperature vulcanized fluorosilicone sealant according to claim 1 or 2, comprising the following steps: (1) Add hydroxy fluorosilicone oil I and part of fumed silica and fumed titanium dioxide into a vacuum kneader for kneading and mixing, then add hydroxy fluorosilicone oil II and the remaining fumed silica and fumed titanium dioxide in batches and mix at room temperature for 2 to 4 hours; (2) After mixing is complete, heat the rubber material to 150-180°C for heat treatment for 2-6 hours; (3) Cool the rubber compound to room temperature and use a three-roll mill to grind it 3 to 5 times until the rubber compound is uniform and fine without agglomerated particles. (4) According to the formula ratio, mix the dispersed rubber and methyl fluorosilicone oil and remove the moisture in a vacuum. Then add the fluorosilicone crosslinker, catalyst and tackifier, and continue stirring for 2 to 4 hours while maintaining the vacuum; (5) Cool the material to room temperature to obtain a high-strength room-temperature vulcanized fluorosilicone sealant.

4. The method for preparing the high-strength room temperature vulcanized fluorosilicone sealant according to claim 3, characterized in that: The kneading treatment interval of each batch of materials in step (1) is 0.5~1h, the system pressure is maintained at -0.098MPa during the heat treatment in step (2), and the dehydration time in step (4) is 2~4h, and the dehydration pressure is -0.05MPa to -0.09MPa.

5. Use of the high-strength room temperature vulcanized fluorosilicone sealant according to claim 1 or 2 in oil-resistant sealing materials.

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