Single-terminated hydroxyl fluorosilicone oil, preparation method and application

Abstract

This application relates to the field of fluorosilicone rubber structure control agents, specifically disclosing a method for preparing a single-hydroxyl-terminated fluorosilicone oil, the single-hydroxyl-terminated fluorosilicone oil, and its applications. The single-hydroxyl-terminated fluorosilicone oil is prepared by reacting silazane and hydroxyl-terminated fluorosilicone oil as raw materials. In the process of using this single-hydroxyl-terminated fluorosilicone oil as a structure control agent, it can prevent the agglomeration of silica, reduce gel formation, and exhibit good anti-structural properties. It allows for long-term storage of fluorosilicone compounds without reducing plasticity, improves the tensile strength, resilience, and oil resistance of fluorosilicone rubber, and achieves a balance between the anti-agglomeration effect and the mechanical properties of fluorosilicone rubber systems.

Description

Technical Field

[0001] This application relates to the field of fluorosilicone rubber structure control agents, and in particular to a single-terminated hydroxyl fluorosilicone oil, its preparation method, and its application. Background Technology

[0002] Fluorosilicone rubber molecules have a helical structure, very flexible molecular chains, weak inter-chain interactions, and low intermolecular cohesive energy density, making crystallization difficult. This results in extremely poor mechanical strength for pure fluorosilicone rubber, with a tensile strength of only 0.3-0.5 MPa after vulcanization, rendering it impractical. Adding reinforcing filler silica to fluorosilicone rubber is the main method for adjusting its physical and mechanical properties. However, the rubber compound formed by mixing fluorosilicone raw rubber with highly hydrophilic silica gradually hardens during storage, reducing its plasticity and eventually losing its reprocessing and molding characteristics. This phenomenon is called "fluorosilicone rubber structuring." The reason for this structuring is that silica particles have a large specific surface area and contain a large number of Si-OH groups on their surface (the cohesive force between particles is quite strong, making them prone to agglomeration and difficult to disperse in silicone rubber raw rubber, which is not conducive to reinforcement). At room temperature, the active Si-OH groups and their adsorbed water undergo condensation reactions with the silanol groups and residual alkoxy groups at the ends of the raw rubber molecules. Some active hydroxyl groups can also form hydrogen-bonded chemical adsorption with the silicone rubber molecular chains, forming a three-dimensional network structure.

[0003] To control the molecular interactions between fluorosilicone raw rubber and fillers and extend the shelf life of the rubber compound, a structure control agent is typically added during the mixing process. This structure control agent prevents or delays the structural process; it consists of organosilicon compounds with active groups. Its anti-structural function is attributed to the condensation reaction between the active groups of the structure control agent and the active hydroxyl groups on the surface of silica, which passivate or shield these groups, thus achieving the anti-structural purpose.

[0004] Common structure control agents include diols, silazanes, and low-molecular-weight alkoxysilanes. These agents all suffer from limitations such as limited functionality, poor stability, and high dosage requirements. Therefore, the currently used structure control agent is primarily HO(CH3CH2CH2CF3Si). 2-10 OH, using hydroxyl fluorosilicone oil as a structure control agent has the advantages of good anti-structure properties and transparent mixed adhesive. However, hydroxyl fluorosilicone oil has some defects, which can cause the adhesive to become sticky, which is not conducive to vulcanization and demolding. In addition, the adhesive may exhibit gelation, which reduces the mechanical properties of the adhesive. Summary of the Invention

[0005] To address the problems of difficult demolding and reduced mechanical properties of fluorosilicone rubber caused by using hydroxyl fluorosilicone oil as a structuring control agent, this application provides a single-ended hydroxyl fluorosilicone oil, its preparation method, and its application.

[0006] In a first aspect, this application provides a single-ended hydroxyl fluorosilicone oil, which adopts the following technical solution:

[0007] A single-hydroxyl-terminated fluorosilicone oil, wherein the general structural formula of the single-hydroxyl-terminated fluorosilicone oil is:

[0008]

[0009] Where 2≤n≤10, and R is alkyl or alkenyl.

[0010] By adopting the above technical solution, the single-hydroxyl-terminated fluorosilicone oil obtained in this application can avoid the agglomeration of silica during the process of using it as a structure control agent, reduce gel formation, and has good anti-structural properties. It can allow fluorosilicone compound to be stored for a long time without reducing plasticity, improve the mechanical properties and oil resistance of fluorosilicone rubber, and achieve a balance between the anti-agglomeration effect of the fluorosilicone rubber system and the mechanical properties of fluorosilicone rubber. In addition, it can also improve the problems of stickiness on the surface of the rubber compound, sticking to rollers and sticking to the mold during vulcanization, and ensure that fluorosilicone rubber can be easily demolded during the production process.

[0011] Preferably, R is methyl or vinyl, and the general structural formula of the single-terminated hydroxyl fluorosilicone oil is:

[0012]

[0013] Secondly, this application provides a method for preparing a single-hydroxyl-terminated fluorosilicone oil, employing the following technical solution: a method for preparing a single-hydroxyl-terminated fluorosilicone oil, wherein the single-hydroxyl-terminated fluorosilicone oil is obtained by reacting silazane and hydroxyl fluorosilicone oil; the molecular structural formula of the hydroxyl fluorosilicone oil is:

[0014] Where 2≤n≤10;

[0015] The molecular structural formula of the silazane is:

[0016] Wherein, R is an alkyl or alkenyl group;

[0017] The reaction mechanism of the silazane with hydroxy fluorosilicone oil is as follows:

[0018]

[0019] Preferably, R is methyl or vinyl.

[0020] Preferably, the molar ratio of the hydroxyl fluorosilicone oil to the silazane is 2:1.

[0021] Preferably, the preparation method of the single-hydroxyl-terminated fluorosilicone oil includes the following steps:

[0022] Hydroxyfluorosilicone oil was subjected to vacuum dehydration treatment at 50°C and a vacuum degree not exceeding 100 kPa.

[0023] After dehydration by vacuum, connect the ammonia absorption device and control the vacuum degree of the ammonia absorption device to not exceed 0.01 MPa. Add silazane dropwise to the hydroxy fluorosilicone oil at 30-60℃, and control the dropwise addition time to 1-2 hours.

[0024] After the addition is complete, continue the reaction at 30–60°C until the reaction is complete, while maintaining ammonia absorption during the reaction.

[0025] After the reaction is complete, the low-boiling point is removed under conditions of 160℃ and a vacuum degree not exceeding 100KPa.

[0026] After the low-boiling point is removed, the temperature is lowered to below 50°C, and the material is discharged to obtain single-ended hydroxyl fluorosilicone oil.

[0027] By adopting the above technical solution, the hydroxyl fluorosilicone oil is first subjected to dehydration treatment under reduced pressure. Silazane has high activity, and water in the system easily leads to the hydrolysis of silazane. Then, silazane is added dropwise to react with the hydroxyl fluorosilicone oil. Next, the system is subjected to de-boiling treatment to remove low-molecular-weight impurities and residual alkane substances. Finally, the material is cooled and discharged to obtain single-end hydroxyl fluorosilicone oil.

[0028] Since ammonia is alkaline, it can affect the activity of hydroxyl groups. Therefore, ammonia needs to be continuously absorbed during the reaction. However, excessive pressure can lead to the removal of silazane. Therefore, controlling the vacuum level to no more than 0.01 MPa can both continuously remove ammonia and ensure the stability of the system reaction.

[0029] Thirdly, this application provides the application of a single-terminated hydroxyl fluorosilicone oil as a structure control agent in fluorosilicone rubber.

[0030] In summary, this application includes at least one of the following beneficial technical effects:

[0031] 1. The single-hydroxyl-terminated fluorosilicone oil of this application can prevent the agglomeration of silica during the process of using it as a structure control agent, reduce gel formation, and has good anti-structural properties. It can allow fluorosilicone compound to be stored for a long time with small changes in plasticity, improve the mechanical properties and oil resistance of fluorosilicone rubber, and take into account both the anti-agglomeration effect of fluorosilicone rubber system and the mechanical properties of fluorosilicone rubber. In addition, it also improves the problems of stickiness on the surface of the rubber compound, sticking to rollers and sticking to the mold during vulcanization, so that fluorosilicone rubber can be easily demolded during the production process and is easy to produce.

[0032] 2. This application uses silazane and hydroxyl fluorosilicone oil to react and generate single-hydroxyl fluorosilicone oil. The preparation process is simple, and the obtained single-hydroxyl fluorosilicone oil can enable the fluorosilicone compound to be stored for a long time without reducing its plasticity. It is easy to demold during the production process, and the obtained fluorosilicone rubber has excellent tensile strength, resilience and oil resistance. Attached Figure Description

[0033] Figure 1 This is a product image of the single-ended hydroxyl fluorosilicone oil prepared in Example 1 of this application;

[0034] Figure 2 This is a product image of the single-hydroxyl-terminated fluorosilicone oil prepared in Example 4 of this application;

[0035] Figure 3 This is the infrared spectrum of the single-hydroxyl-terminated fluorosilicone oil prepared in Example 1 of this application;

[0036] Figure 4 This is the infrared spectrum of the single-hydroxyl-terminated fluorosilicone oil prepared in Example 4 of this application;

[0037] Figure 5 This is a magnified view of the infrared spectrum of the single-ended hydroxyl fluorosilicone oil obtained in Example 4 of this application. Detailed Implementation

[0038] To facilitate a better understanding of the technical solutions of this application, the following detailed description of this application is provided in conjunction with tables and embodiments, but this is not intended to limit the scope of protection of this application.

[0039] Example

[0040] Example 1

[0041] Weigh 2 mol of hydroxyl fluorosilicone oil and add it to a four-necked flask equipped with a thermometer and a stir bar. Dehydrate the hydroxyl fluorosilicone oil under reduced pressure at 50°C and a vacuum of 100 kPa for 1 hour.

[0042] After dehydration under reduced pressure, connect the four-necked flask to the ammonia absorption bottle, control the vacuum of the water pump to 0.01 MPa, and add 1 mol of silazane to the hydroxyl fluorosilicone oil at 30°C for 1 hour.

[0043] After the addition is complete, continue the reaction at 60°C until the reaction is complete. The reaction is considered complete when the characteristic peak of silazane in the gas chromatograph completely disappears. Ammonia absorption is maintained during the reaction.

[0044] After the reaction is complete, maintain the vacuum of the water pump at 0.1 MPa and continue adsorption for 30 minutes to remove all ammonia.

[0045] After ammonia removal, switch the oil pump and perform de-boiling treatment at 160℃ and 100KPa vacuum. The endpoint of de-boiling is when there is no obvious bubbling on the liquid surface of the system and the gauge pressure fluctuates within 0.02KPa.

[0046] After the low-boiling point is removed, the temperature is allowed to drop naturally to below 50°C, and the material is discharged to obtain single-hydroxyl-terminated fluorosilicone oil, such as... Figure 1 As shown.

[0047] The molecular structural formula of hydroxyl fluorosilicone oil is as follows:

[0048] In this context, 2≤n≤10 indicates that in actual industrial production, the hydroxyl fluorosilicone oil system contains molecules with various chain lengths, and there is no pure substance with a single molecular chain length. However, the higher the degree of polymerization of the hydroxyl fluorosilicone oil, the lower the hydroxyl content, and the worse the effect of treating silica. Through experiments, controlling 2≤n≤10 can better meet industrial needs. The viscosity range corresponding to this chain length of hydroxyl fluorosilicone oil is 120~140 / mPa·s. The hydroxyl fluorosilicone oil used in the embodiments of this application is produced by the applicant's own company (Shenzhen Guanheng New Material Technology Co., Ltd.), batch number 22-FY-25, with a viscosity of 130 / mPa·s and a refractive index of 1.3765.

[0049] The molecular structural formula of silazane is:

[0050] That is, hexamethyldisilazane.

[0051] The molecular structural formula of the obtained single-hydroxyl-terminated fluorosilicone oil is as follows:

[0052] Where 2≤n≤10.

[0053] Example 2

[0054] The difference from Example 1 is that silazane was added dropwise to hydroxy fluorosilicone oil at 40°C, and after the addition was complete, the reaction was continued at 40°C until the reaction was complete.

[0055] Example 3

[0056] The difference from Example 1 is that silazane was added dropwise to hydroxy fluorosilicone oil at 30°C, and after the addition was complete, the reaction was continued at 60°C until the reaction was complete.

[0057] Example 4

[0058] Weigh 2 mol of hydroxyl fluorosilicone oil and add it to a four-necked flask equipped with a thermometer and a stir bar. Dehydrate the hydroxyl fluorosilicone oil under reduced pressure at 50°C and a vacuum of 100 kPa for 1 hour.

[0059] After dehydration under reduced pressure, connect the four-necked flask to the ammonia absorption bottle, control the vacuum of the water pump to 0.01 MPa, and add 1 mol of silazane to the hydroxyl fluorosilicone oil at 30°C over a period of 2 hours.

[0060] After the addition is complete, continue the reaction at 60°C for 2 hours until the reaction is complete. The reaction is considered complete when the characteristic peak of silazane in the gas chromatograph completely disappears.

[0061] After the reaction is complete, adjust the vacuum of the water pump to 0.1 MPa and continue adsorption for 30 minutes to remove the ammonia gas.

[0062] After ammonia removal, switch the oil pump and perform de-boiling treatment at 160℃ and 100KPa vacuum. The endpoint of de-boiling is when there is no obvious bubbling on the liquid surface of the system and the gauge pressure fluctuates within 0.02KPa.

[0063] After the low-boiling point is removed, the temperature is allowed to drop naturally to below 50°C, and the material is discharged to obtain single-hydroxyl-terminated fluorosilicone oil, such as... Figure 2 As shown.

[0064] The molecular structural formula of hydroxyl fluorosilicone oil is as follows:

[0065] The hydroxy fluorosilicone oil used in Example 4 was from the same batch as that used in Example 1.

[0066] The molecular structural formula of silazane is:

[0067] That is, tetramethyldivinyldisilazane.

[0068] The molecular structural formula of the obtained single-hydroxyl-terminated fluorosilicone oil is as follows:

[0069] Where 2≤n≤10.

[0070] Example 5

[0071] The difference from Example 4 is that silazane was added dropwise to hydroxy fluorosilicone oil at 40°C, and after the addition was complete, the reaction was continued at 40°C until the reaction was complete.

[0072] Example 6

[0073] The difference from Example 4 is that silazane was added dropwise to hydroxy fluorosilicone oil at 30°C, and after the addition was complete, the reaction was continued at 60°C until the reaction was complete.

[0074] The refractive index, viscosity and yield of the single-hydroxyl-terminated fluorosilicone oils prepared in Examples 1 to 6 were tested, and the test results are shown in Table 1.

[0075] Refractive index: The test method refers to the rotation method in GB / T 10247-1988.

[0076] Viscosity: The test method is in accordance with GB / T 6408-2008.

[0077] Yield: M1 is the weight of the four-necked flask, M2 is the weight of the hydroxyl fluorosilicone oil, M3 is the weight of the silazane, and M4 is the total weight of the remaining reaction products and the four-necked flask after the system has undergone de-boiling treatment.

[0078] Table 1: Physical properties of the single-hydroxyl-terminated fluorosilicone oils prepared in Examples 1-6

[0079] refractive index Viscosity / mPa·s Yield / % Example 1 1.3796 45 83.6 Example 2 1.3796 42 83.8 Example 3 1.3795 40 84.9 Example 4 1.3809 47 85.6 Example 5 1.3810 45 86.6 Example 6 1.3809 47 87.6

[0080] The experiment found that silazane and hydroxyfluorosilicone oil can both undergo alcoholysis at 30-60℃, and the higher the reaction temperature, the faster the reaction rate (judged by the disappearance time of the characteristic peak of silazane in gas chromatography).

[0081] Combining the data from Examples 1-6 and Table 1, it can be seen that the physical properties of the final products obtained at different reaction temperatures are not significantly different. The viscosity of the products is significantly lower than that of hydroxyl fluorosilicone oil. This is partly because the hydroxyl content in the products is lower than that in hydroxyl fluorosilicone oil, which reduces the hydrogen bonding between hydroxyl groups and thus lowers the viscosity. On the other hand, the trifluoropropyl content in the products is lower than that in hydroxyl fluorosilicone oil, which weakens the polymerization inhibition effect of the groups and causes a decrease in viscosity.

[0082] The refractive index of hydroxyl-terminated fluorosilicone oil is approximately 1.3765, while the refractive indices of the prepared single-terminated hydroxyl-terminated fluorosilicone oils are all greater than 1.3765. (Combined...) Figure 3 Infrared spectral analysis, including the 3400 cm⁻¹ -1 The peak is the hydroxyl stretching vibration peak, 2960 cm⁻¹. -1 and 2910cm -1 The peaks for the CH stretching vibrations of CH3 and CH2 are at 1440 cm⁻¹. -1 1368cm -1 1260cm -1 800cm -1 The peak is the stretching vibration peak of Si(CH)3, at 1310 cm⁻¹. -1 CH2-CH2, 1210cm -1 900cm -1 The peak value is the stretching vibration peak of CF3, 1000-1100 cm⁻¹. -1 The peaks are Si-O-Si stretching vibrations, indicating that the fluorine content in the single-ended hydroxyl fluorosilicone oil of this application is lower than that in the double-sealed hydroxyl fluorosilicone oil, and that methyl groups in silazane have been successfully introduced.

[0083] Combination Figure 4 and Figure 5 Infrared spectral analysis, including the 3400 cm⁻¹ -1 This is the peak of the hydroxyl stretching vibration, at 1410 cm⁻¹. -1 and 960cm -1 The peak is the stretching vibration peak of CH=CH, at 1440 cm⁻¹.-1 1368cm -1 1260cm -1 800cm -1 The peak represents the stretching vibration of Si(CH)3, at 1210 cm⁻¹. -1 900cm -1 The peak value is the stretching vibration peak of CF3, 1000-1100 cm⁻¹. -1 The presence of the Si-O-Si stretching vibration peak indicates that the fluorine content in the single-ended hydroxyl fluorosilicone oil of this application is lower than that in the double-ended hydroxyl fluorosilicone oil, and that the vinyl group in the silazane has been successfully introduced. Furthermore, when the introduced group is vinyl, the refractive index of the product is greater than that of the product obtained when the introduced group is methyl.

[0084] Application Examples: The single-hydroxyl-terminated fluorosilicone oils prepared in Examples 1-6 were used as structure control agents in fluorosilicone rubber experiments. The formulation of the fluorosilicone rubber by weight is as follows:

[0085] Fluorosilicone raw rubber: 100 parts;

[0086] Silica: 35-45 parts;

[0087] Structure control agent: 10-15 parts;

[0088] Vulcanizing agent: 0.5–1.2 parts;

[0089] Heat resistant agent: 0.5–5 parts;

[0090] The fluorosilicone raw rubber has a molecular weight of 500,000 to 1,000,000 and a vinyl content of 0.05% to 1.2%. The vulcanizing agent is selected from one or a combination of several of the following: benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl peroxide, di-tert-butyl peroxide, and 2,5-dimethyl-2,5-di-tert-butylperoxide. The heat resistant agent is selected from one or a combination of several of the following: iron oxide, iron hydroxide, ferric octanoate, titanium dioxide, and cerium dioxide.

[0091] In the application examples of this application, the molecular weight of the fluorosilicone raw rubber used is 800,000 to 1,000,000, the vinyl content is 0.3%, the vulcanizing agent is 2,5-dimethyl-2,5-di-tert-butylperoxyhexane, the heat resistant agent is cerium oxide, and 80g of each part by weight of material is used for testing.

[0092] Application Example 1

[0093] First, 100 parts by weight of fluorosilicone raw rubber is passed through a two-roll mill to mix the raw rubber evenly. Then, 40 parts by weight of silica and 15 parts by weight of structural control agent are added. The mixture is then passed through the two-roll mill eight more times to mix the materials evenly. The distance between the two rolls of the two-roll mill is then adjusted so that the rubber compound is sheeted at about 2.5 mm. Finally, the rubber compound is placed in an oven and heat-treated at 190°C for 1.5 hours.

[0094] After heat treatment, the rubber compound is cooled to below 50°C, and 2 parts by weight of heat resistant agent and 0.8 parts by weight of vulcanizing agent are added. The mixture is then passed through a two-roll mill eight times to ensure uniform mixing. The rubber compound is then sheeted, rolled, and left to stand for 12 hours. It is then passed through a two-roll mill eight times for re-mixing. After re-mixing, it is vulcanized at 175°C for 15 minutes using a flat vulcanizing machine to obtain fluorosilicone rubber.

[0095] The structuring control agent used is the single-ended hydroxyl fluorosilicone oil from Example 1.

[0096] Application Example 2

[0097] The difference from Application Example 1 is that the structuring control agent used is the single-ended hydroxyl fluorosilicone oil from Example 4.

[0098] Application Comparative Example 1

[0099] The difference from Application Example 1 is that the structuring control agent used is hydroxyl fluorosilicone oil, while the hydroxyl fluorosilicone oil used in Comparative Example 1 is the same as that used in Example 1.

[0100] Application Comparative Example 2

[0101] The difference from Application Example 1 is that the structuring control agent is a compound of single-terminated hydroxyl fluorosilicone oil and double-terminated hydroxyl fluorosilicone in Example 1 at a weight ratio of 1:1, and the hydroxyl fluorosilicone oil used in Comparative Example 2 is the same as the hydroxyl fluorosilicone oil used in Example 1.

[0102] Application Comparative Example 3

[0103] The difference from Application Example 2 is that the structuring control agent is a compound of single-terminated hydroxyl fluorosilicone oil and double-terminated hydroxyl fluorosilicone in Example 4 in a 1:1 weight ratio, and the hydroxyl fluorosilicone oil used in Comparative Example 3 is the same as the hydroxyl fluorosilicone oil used in Example 4.

[0104] The following performance tests were conducted on the fluorosilicone rubbers prepared in Application Examples 1-2 and Comparative Examples 1-3. The test results are shown in Tables 2-4.

[0105] Hardness: The test method refers to the Shore A type hardness test method in GB / T 531.1-2008 Shore hardness tester method.

[0106] Tensile strength: The test method refers to the dumbbell-shaped specimen test method in GB / T 528-2009.

[0107] Elongation: The test method is in accordance with GB / T 528-2009.

[0108] Tear strength: The test method refers to Method C, Crescent-shaped specimen method in GB / T 529-2008.

[0109] Resilience: The test method refers to ASTM D2632, the test method for vertical elasticity of rubber.

[0110] Thermal aging: The test method is in accordance with GB / T 3512-2014.

[0111] Oil resistance: The test method refers to the standard simulated liquid C test method in GB / T 1690-2010.

[0112] Table 2: Mechanical property data of fluorosilicone rubbers prepared in Application Examples 1-2 and Comparative Examples 1-3

[0113]

[0114] Table 3: Test data on the aging resistance of fluorosilicone rubbers prepared in Application Examples 1-2 and Comparative Examples 1-3

[0115] Hardness (HA) Tensile strength (MPa) Elongation (%) Application Example 1 54 10.5 324 Application Comparative Example 1 55 9.1 299 Application Comparative Example 2 54 10.0 313 Application Example 2 70 11.9 183 Application Comparative Example 3 66 10.8 229

[0116] Table 4: Oil resistance test data of fluorosilicone rubbers prepared in Application Examples 1-2 and Comparative Examples 1-3

[0117]

[0118] As can be seen from the data in Tables 2-4, the fluorosilicone rubber prepared by using the single-hydroxyl-terminated fluorosilicone oil of this application as a structure control agent has excellent mechanical properties and oil resistance. This indicates that the single-hydroxyl-terminated fluorosilicone oil of this application has excellent anti-structural properties when used as a structure control agent for fluorosilicone rubber, which is beneficial to improving the mechanical properties, aging resistance and oil resistance of fluorosilicone rubber.

[0119] As can be seen from the data in Table 2, compared with the single-hydroxyl-terminated fluorosilicone oil prepared by hexamethyldisilazane, the single-hydroxyl-terminated fluorosilicone oil prepared by tetramethyldivinyldisilazane as a structure control agent will increase the hardness of fluorosilicone rubber. This is because the system contains vinyl groups, which have high activity and will also undergo cross-linking reaction during the vulcanization process of fluorosilicone rubber, resulting in a higher cross-linking density of the fluorosilicone rubber system, which in turn causes the hardness of fluorosilicone rubber to increase. As the hardness increases, the elongation will decrease.

[0120] As can be seen from the data in Tables 3 and 4, when the single-terminated hydroxyl fluorosilicone oil of this application is used as a structural control agent for fluorosilicone rubber, it exhibits excellent aging resistance and oil resistance. After the aging resistance test, the fluorosilicone rubber can still maintain good hardness, tensile strength and elongation. After the oil resistance test, it also has good hardness, excellent tensile strength change rate and volume change rate, with tensile strength reduction not exceeding 50% and volume change rate not exceeding 20%.

[0121] The single-hydroxyl-terminated fluorosilicone oil obtained in this application contains active hydroxyl groups in its molecular structure, which can preferentially react with the hydroxyl groups on the surface of silica, thereby achieving an anti-structural effect. In contrast, when conventional double-terminated hydroxyl-terminated silicone oil is used as a structural control agent, the reaction between the double-terminated hydroxyl-terminated silicone oil and silica during the processing of fluorosilicone rubber easily forms small-scale agglomerates, resulting in uneven dispersion of the filler and thus affecting the mechanical properties and oil resistance of fluorosilicone rubber. The single-hydroxyl-terminated fluorosilicone oil obtained in this application reduces the gelation phenomenon during rubber processing, which is more conducive to the dispersion of silica filler, thereby improving the mechanical properties and oil resistance of fluorosilicone rubber.

[0122] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a single-hydroxyl-terminated fluorosilicone oil, characterized in that, The general structural formula of the single-terminated hydroxyl fluorosilicone oil is: Where 2≤n≤10, and R is alkyl or alkenyl; The single-ended hydroxyl fluorosilicone oil is prepared by reacting silazane and hydroxyl fluorosilicone oil. The molecular structural formula of the hydroxyl fluorosilicone oil is: Where 2≤n≤10; The molecular structural formula of the silazane is: Wherein, R is an alkyl or alkenyl group; The preparation method includes the following steps: Hydroxyfluorosilicone oil was subjected to vacuum dehydration treatment at 50°C and a vacuum degree not exceeding 100 kPa. After dehydration by vacuum, connect the ammonia absorption device and control the vacuum degree of the ammonia absorption device to not exceed 0.01 MPa. Add silazane dropwise to the hydroxy fluorosilicone oil at 30-60℃, and control the dropwise addition time to 1-2 hours. After the addition is complete, continue the reaction at 30–60°C until the reaction is complete, while maintaining ammonia absorption during the reaction. After the reaction is complete, the low-boiling point is removed under conditions of 160℃ and a vacuum degree not exceeding 100KPa. After the low-boiling point is removed, the temperature is lowered to below 50°C, and the material is discharged to obtain single-ended hydroxyl fluorosilicone oil.

2. The method for preparing single-hydroxyl-terminated fluorosilicone oil according to claim 1, characterized in that: R is methyl or vinyl.

3. The method for preparing single-hydroxyl-terminated fluorosilicone oil according to claim 1, characterized in that: The molar ratio of the hydroxyl fluorosilicone oil to the silazane is 2:

1.

4. A single-hydroxyl-terminated fluorosilicone oil, characterized in that, It is prepared by any of the preparation methods described in claims 1-3.

5. The application of the single-terminated hydroxyl fluorosilicone oil of claim 4 as a structuring control agent for fluorosilicone rubber.

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