A class of bimetallic anionic ring-opening polymerization catalysts, their preparation methods, and their application in the preparation of controllable molecular weight fluorosilicone rubber.

Abstract

This invention provides a bimetallic anionic ring-opening polymerization catalyst, its preparation method, and its application in the preparation of controllable molecular weight fluorosilicone rubber, belonging to the field of catalysts for the preparation of fluorosilicone rubber. The catalyst consists of four components: an alkali metal compound, a cyclosiloxane, an alkyl metal compound, and an accelerator. The catalyst of this invention can efficiently catalyze the bulk self-polymerization of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane or its bulk copolymerization with vinyl- or phenyl-cyclosiloxane-containing compounds, thereby preparing high-temperature vulcanizable fluorosilicone rubber. Its advantages include a low reaction temperature, no need for neutralizing agents to quench the basic ends, and a simplified preparation process. Using the catalyst of this invention can effectively suppress the side reactions commonly caused by fluorinated substituents during anionic ring-opening polymerization, thereby significantly improving the mechanical properties of fluorosilicone rubber. The resulting high-molecular-weight vulcanized fluorosilicone rubber has excellent application prospects in aerospace, petrochemical, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of catalysts for the preparation of fluorosilicone rubber, and relates to a catalyst composition and preparation method suitable for the anionic ring-opening polymerization of cyclosiloxane monomers, as well as a stable and industrially applicable process for preparing raw fluorosilicone rubber with controllable molecular weight. In particular, it relates to a method for preparing a type of bimetallic anionic ring-opening polymerization catalyst and its application in the preparation of fluorosilicone rubber with controllable molecular weight. Technical Background

[0002] The main chain structure of fluorosilicone rubber is composed primarily of repeating -Si-O- units with high flexibility and high bond energy, which endows it with excellent high and low temperature resistance. The side chains consist of trifluoropropyl (-CH2-CH2-CF3) and methyl (-CH3) groups, with fluorinated substituents significantly enhancing the material's resistance to oils and solvents. Therefore, fluorosilicone rubber remains stable under extreme temperature conditions (-55℃ to 230℃) and in oily environments. Its applications cover defense, aerospace, deep-sea exploration, automotive, and petrochemical industries, making it one of the world's best-performing synthetic rubbers.

[0003] In the production of fluorosilicone rubber, molecular weight control is crucial, directly affecting the mechanical properties of the rubber and the quality of the final product. Commonly used catalysts in the preparation process, such as alkali metal hydroxides, quaternary ammonium hydroxides, and quaternary phosphorus hydroxides, are all strongly alkaline. The strong electron attraction of the fluorine side groups increases the electrophilicity of the ester bonds, which triggers intramolecular "biting back" and intermolecular chain transfer side reactions during polymerization, leading to a decrease in molecular weight and uneven distribution, thus generating a large amount of low molecular weight polymers. For example, when using potassium hydroxide for bulk ring-opening polymerization of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane (D3F), the average cyclic content at polymerization equilibrium can reach as high as 86.5% (Journal of Polymer Science Polymer Letter Edition, 1965, 3, 473-482).

[0004] To address these issues, two main strategies are currently employed. The first involves altering the catalytic system, such as using butyllithium with lower activity as the catalyst and dimethyl sulfoxide as a promoter, which effectively suppresses the "biting-back" reaction, thereby reducing the cyclic content at polymerization equilibrium (Journal of Polymer Science Part A, 1989, 27(4), 1241-1258). Although adjusting the additives and catalysts can reduce side reactions to some extent, it does not completely suppress them, potentially affecting the quality of fluorosilicone rubber. The second strategy involves controlling the polymerization time and terminating the reaction when the yield of the linear polymer is highest (CN 114381001 A). This requires greater control over the polymerization process and equipment, and may also lead to a decrease in batch stability of the product. Furthermore, the neutralization of the catalyst must be addressed at the end of polymerization. Residual catalyst may attack the silicone bonds in the polymer chain, causing chain breakage. Given the high viscosity and excellent oil and chemical resistance of high molecular weight fluorosilicone rubber, the addition and effective dispersion of neutralizing agents are particularly challenging. Therefore, special measures must be taken during the preparation process to ensure the high performance and safety of the product. Summary of the Invention

[0005] This invention aims to address the shortcomings of existing anionic ring-opening polymerization catalysis technologies for fluorinated cyclosiloxanes by providing a method for preparing a bimetallic anionic ring-opening polymerization catalyst. By using the prepared bimetallic anionic ring-opening polymerization catalyst to perform bulk polymerization of fluorinated siloxanes, fluorosilicone rubbers with controllable molecular weight, narrow molecular weight distribution, and excellent stability can be produced. Compared with existing technologies, this method has advantages such as simple operation and strong controllability, making it very suitable for large-scale production.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing a class of bimetallic anionic ring-opening polymerization catalysts includes the following steps:

[0008] Step (1) Under the protection of an inert gas, an alkali metal compound and a cyclosiloxane are added to the preparation vessel in sequence, and aged at 60–210 degrees Celsius for 30–600 minutes to form a homogeneous transparent solution. In this step, the alkali metal compound and the cyclosiloxane react fully to reach a thermodynamic equilibrium state, generating an oxygen anion active center, and the counterion is the corresponding alkali metal positive ion used.

[0009] Step (2) Add the solution with the general formula MtR to the solution obtained in step (1). n The compound is aged at 0–60°C for 5–120 minutes to form a homogeneous, transparent solution; in this step, MtR nThe compound interacts with the oxygen anion terminal to form a bimetallic active center. Compared with the active center prepared in step (1), the active center has greater steric hindrance and weakened basicity, thereby suppressing the "biting back" side reaction of the active center to the polymer.

[0010] Step (3) Add an accelerator to the solution obtained in step (2) and mix thoroughly to prepare a bimetallic anionic ring-opening polymerization catalyst. In this step, the addition of different types and polarity accelerators can effectively regulate the alkalinity of the anionic active center, thereby adapting to the differences in polymerization activity caused by different cyclic siloxane structures and obtaining the target copolymerized fluorosilicone rubber.

[0011] In the bimetallic anionic ring-opening polymerization catalyst, alkali metal compounds, cyclosiloxanes, and MtR are present. n The molar ratio of the accelerator is 1:(2–10):(0.1–2):(2–1000), wherein the concentration of the alkali metal element is 0.05–1.6 mmol / g.

[0012] The structural formula of step (2) is MtR n In the compound, Mt is selected from magnesium, zinc or aluminum; R is selected from methyl, ethyl, isopropyl, n-butyl, isobutyl or n-octyl, phenyl; the value of n corresponds to the type of Mt. If Mt is magnesium or zinc, then n is 2; if Mt is aluminum, then n is 3.

[0013] The alkali metal compound is selected from lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium tert-butoxide, sodium tert-butoxide, potassium tert-butoxide, n-butyllithium, sec-butyllithium, and tert-butyllithium.

[0014] The cyclosiloxane is selected from hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane.

[0015] The accelerator is at least one selected from acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, pyridine, acetone, 1,4-dioxane, methylpyrrolidone, phosphazene base, tetrahydrofuran, methyl formate, ethyl acetate, toluene, diethylene glycol dimethyl ether, and ethylene glycol dimethyl ether.

[0016] A class of bimetallic anionic ring-opening polymerization catalysts were obtained using the above-described preparation method.

[0017] An application of a class of bimetallic anionic ring-opening polymerization catalysts for the preparation of fluorosilicone rubber with controllable molecular weight is described. The preparation method includes the following steps:

[0018] (1) 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane and cyclosiloxane monomers are added to a polymerization reactor, heated and vacuumed for dehydration; wherein the cyclosiloxane accounts for 0.5%–15% of the total monomers.

[0019] (2) Add the bimetallic anionic ring-opening polymerization catalyst to the polymerization reactor, wherein the molar ratio of the bimetallic anionic ring-opening polymerization catalyst to the monomer is 100–20000, heat to 60–120 degrees Celsius to start the polymerization reaction, and polymerize for 10–600 minutes to prepare fluorosilicone rubber.

[0020] The cyclosiloxane monomer is selected from one or more of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, and 2,4,6-triphenyl-2,4,6-trimethylcyclotrisiloxane.

[0021] The fluorosilicone rubber prepared by the above-described method also falls within the scope of protection of this invention;

[0022] The structure of the fluorosilicone rubber is shown in formula (I):

[0023]

[0024] Wherein, X is one or more of methyl, phenyl and vinyl, preferably methyl and vinyl;

[0025] The fluorosilicone rubber has a molecular weight of 0.2–2.5 million, with a molecular weight distribution of less than 1.25.

[0026] Beneficial effects of this invention:

[0027] (1) In the preparation process of the bimetallic anion ring-opening catalyst of the present invention: The preparation process of the bimetallic anion ring-opening catalyst involves adding a metal compound with a MtRn structure to a traditional catalyst. By precisely controlling the volume of the R structure and the properties of the Mt metal in the compound, this method can effectively control the steric hindrance and basicity around the oxygen anion active center. This strategy not only suppresses the "biting back" side reaction commonly seen in siloxane polymerization, but also adapts to the copolymerization of different active cyclic siloxanes by finely controlling the basicity of the anion active center, thereby expanding the synthesis method of polymer chain structure of fluorosilicone rubber materials.

[0028] (2) Application of the bimetallic anionic ring-opening catalyst of this invention: The bimetallic anionic ring-opening catalyst used in this invention exhibits a beneficial ring-opening polymerization effect on 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane. Compared with existing catalysts, this catalytic system can effectively adjust the molecular weight of the resulting fluorosilicone rubber by controlling the amount of catalyst, ensuring a narrow molecular weight distribution and the absence of small molecule cyclic structures. Furthermore, using this catalytic system eliminates the need for additional neutralization processes, maintaining the good storage stability of the fluorosilicone rubber. This invention provides a reliable base adhesive for manufacturing high-strength fluorosilicone rubber products. Attached Figure Description

[0029] Figure 1 The 1H NMR spectra of the bimetallic anionic ring-opening polymerization catalysts prepared in Examples 13(A) and 16(B) of this invention;

[0030] Figure 2 The lithium NMR spectrum of the bimetallic anionic ring-opening polymerization catalyst prepared in Example 13 of this invention;

[0031] Figure 3 The 1H NMR spectrum of the fluorosilicone rubber prepared in Example 35 of this invention;

[0032] Figure 4 The fluorosilicone rubber gel permeation chromatography is shown for the samples prepared in Examples 31 (dashed line) and 32 (solid line) of this invention. Detailed Implementation

[0033] The technical solutions of the present invention will be further described below with reference to the embodiments.

[0034] Examples 1–28 describe the preparation methods of bimetallic anionic ring-opening polymerization catalysts.

[0035] Example 1

[0036] 0.51 g of lithium hydroxide (21.35 mmol) was added to a 500 mL reactor. 9.50 g of D3 (42.70 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 60 °C and maintained for 30 minutes. Next, 2.14 mL (2.14 mmol) of a triethylaluminum solution in hexane (1.0 mol / L) was added, and the reaction was carried out at 0 °C for 120 minutes. Finally, 1.75 g of acetonitrile (0.043 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 1.6156 mmol / g by titration.

[0037] Example 2

[0038] 0.08 g of lithium hydroxide (3.33 mmol) was added to a 500 mL reactor. 5.93 g of D4 (20.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 135 °C and maintained for 300 min. Next, 3.33 mL (3.33 mmol) of a triisobutylaluminum solution in hexane (1.0 mol / L) was added, and the reaction was carried out at 30 °C for 60 min. Finally, 130.22 g of dimethyl sulfoxide (1.667 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0241 mmol / g by titration.

[0039] Example 3

[0040] 0.05 g of lithium hydroxide (2.00 mmol) was added to a 500 mL reactor. 9.37 g of D3F (20.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 210 °C and maintained for 600 min. Next, 4.00 mL (4.00 mmol) of a hexane solution of di-n-butylmagnesium (1.0 mol / L) was added, and the reaction was carried out at 60 °C for 30 min. Finally, 146.18 g of N,N-dimethylformamide (2.000 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0126 mmol / g by titration.

[0041] Example 4

[0042] 2.67 g of sodium hydroxide (66.67 mmol) was added to a 500 mL reactor. 88.98 g of D3 (400.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 135 °C and maintained for 30 minutes. Next, 133.33 mL (133.33 mmol) of a hexane solution of diethylzinc (1.0 mol / L) was added, and the reaction was carried out at 60 °C for 0 minutes. Finally, 11.62 g of N,N-dimethylacetamide (0.133 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.3438 mmol / g by titration.

[0043] Example 5

[0044] 0.17 g of sodium hydroxide (4.27 mmol) was added to a 500 mL reactor. 12.67 g of D4 (42.70 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 210 °C and maintained for 300 minutes. Next, 0.43 mL (0.43 mmol) of a hexane solution of dioctylzinc (1.0 mol / L) was added, and the reaction was carried out at 0 °C for 60 minutes. Finally, 168.88 g of pyridine (2.135 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0235 mmol / g by titration.

[0045] Example 6

[0046] 0.06 g of sodium hydroxide (1.50 mmol) was added to a 500 mL reactor. 1.41 g of D3F (3.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 60 °C and maintained for 600 minutes. Next, 1.50 mL of a hexane solution of diphenylmagnesium (1.0 mol / L) was added, and the reaction was carried out at 30 °C for 5 minutes. Finally, 132.17 g of 1,4-dioxane (1.500 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0111 mmol / g by titration.

[0047] Example 7

[0048] 2.24 g of potassium hydroxide (40.00 mmol) was added to a 500 mL reactor. 88.98 g of D3 (400.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 210 °C and maintained for 600 minutes. Next, 80.00 mL (80.00 mmol) of a triethylaluminum solution in hexane (1.0 mol / L) was added, and the reaction was carried out at 30 °C for 60 minutes. Finally, 7.93 g of methylpyrrolidone (0.080 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.2605 mmol / g by titration.

[0049] Example 8

[0050] 0.04 g of potassium hydroxide (0.75 mmol) was added to a 500 mL reactor. 0.44 g of D4 (1.50 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 60°C and maintained for 30 minutes. Next, 0.08 mL (0.08 mmol) of a triisobutylaluminum solution in hexane (1.0 mol / L) was added, and the reaction was carried out at 60°C for 5 minutes. Finally, 180.23 g of phosphazene base (0.375 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0041 mmol / g by titration.

[0051] Example 9

[0052] 0.14 g of potassium hydroxide (2.50 mmol) was added to a 500 mL reactor. 7.03 g of D3F (15.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 135 °C and maintained for 300 minutes. Next, 2.50 mL of a hexane solution of di-n-butylmagnesium (1.0 mol / L) was added, and the reaction was carried out at 0 °C for 120 minutes. Finally, 180.28 g of tetrahydrofuran (2.500 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0132 mmol / g by titration.

[0053] Example 10

[0054] 0.44 g of lithium tert-butoxide (5.50 mmol) was added to a 500 mL reactor. 2.45 g of D3 (11.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 60 °C and maintained for 300 min. Next, 11.00 mL (11.00 mmol) of a hexane solution of diethylzinc (1.0 mol / L) was added, and the reaction was carried out at 30 °C for 120 min. Finally, 165.14 g of methyl formate (2.750 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0313 mmol / g by titration.

[0055] Example 11

[0056] 0.17 g of lithium tert-butoxide (2.17 mmol) was added to a 500 mL reactor. 3.86 g of D4 (13.00 mmol) was added at room temperature, and the mixture was stirred thoroughly. The temperature was then gradually increased to 135 °C and maintained for 600 min. Next, 0.22 mL (0.22 mmol) of a hexane solution of dioctylzinc (1.0 mol / L) was added, and the reaction was carried out at 60 °C for 5 min. Finally, 190.91 g of ethyl acetate (2.167 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0111 mmol / g by titration.

[0057] Example 12

[0058] 2.40 g of lithium tert-butoxide (30.00 mmol) was added to a 500 mL reactor. 140.56 g of D3F (300.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 210 °C and maintained for 30 minutes. Next, 30.00 mL (30.00 mmol) of a hexane solution of diphenylmagnesium (1.0 mol / L) was added, and the reaction was carried out at 0 °C for 60 minutes. Finally, 8.05 g of dimethyl sulfoxide (0.060 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.1750 mmol / g by titration.

[0059] Example 13

[0060] 2.00 g of lithium tert-butoxide (25.00 mmol) was added to a 500 mL reactor. 46.85 g of D3F (100.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 210 °C and maintained for 600 min. Next, 12.50 mL (12.50 mmol) of a triethylaluminum solution in hexane (1.0 mol / L) was added, and the reaction was carried out at 30 °C for 30 min. Finally, 97.66 g of dimethyl sulfoxide (1.250 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.1613 mmol / g by titration.

[0061] Example 14

[0062] 0.40 g of sodium tert-butoxide (4.17 mmol) was added to a 500 mL reactor. 5.56 g of D3 (25.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 210 °C and maintained for 300 min. Next, 0.42 mL (0.42 mmol) of a triethylaluminum solution in hexane (1.0 mol / L) was added, and the reaction was carried out at 60 °C for 60 min. Finally, 187.75 g of diethylene glycol dimethyl ether (2.083 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0215 mmol / g by titration.

[0063] Example 15

[0064] 0.19 g of sodium tert-butoxide (2.00 mmol) was added to a 500 mL reactor. 5.93 g of D4 (20.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 60 °C and maintained for 600 min. Next, 4.00 mL (4.00 mmol) of a triisobutylaluminum solution in hexane (1.0 mol / L) was added, and the reaction was carried out at 0 °C for 120 min. Finally, 180.24 g of ethylene glycol dimethyl ether (2.000 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0106 mmol / g by titration.

[0065] Example 16

[0066] 10.09 g of sodium tert-butoxide (105.00 mmol) was added to a 500 mL reactor. 98.39 g of D3F (210.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 135 °C and maintained for 30 minutes. Next, 105.00 mL (105.00 mmol) of a hexane solution of di-n-butylmagnesium (1.0 mol / L) was added, and the reaction was carried out at 30 °C for 5 minutes. Finally, 8.62 g of acetonitrile (0.210 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.5570 mmol / g by titration.

[0067] Example 17

[0068] 0.48 g of potassium tert-butoxide (4.27 mmol) was added to a 500 mL reactor. 9.50 g of D3 (42.70 mmol) was added at room temperature and the mixture was stirred thoroughly. The temperature was then gradually increased to 135 °C and maintained for 600 min. Next, 0.43 mL (0.43 mmol) of a hexane solution of diethylzinc (1.0 mol / L) was added, and the reaction was carried out at 30 °C for 120 min. Finally, 166.81 g of dimethyl sulfoxide (2.135 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0241 mmol / g by titration.

[0069] Example 18

[0070] 0.28 g of potassium tert-butoxide (2.50 mmol) was added to a 500 mL reactor. 4.45 g of D4 (15.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 210 °C and maintained for 30 minutes. Next, 2.50 mL of a hexane solution of dioctylzinc (1.0 mol / L) was added, and the reaction was carried out at 60 °C for 5 minutes. Finally, 182.73 g of N,N-dimethylformamide (2.500 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0132 mmol / g by titration.

[0071] Example 19

[0072] 8.42 g of potassium tert-butoxide (75.00 mmol) was added to a 500 mL reactor. 70.28 g of D3F (150.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 60 °C and maintained for 300 minutes. Next, 150.00 mL (150.00 mmol) of a hexane solution of diphenylmagnesium (1.0 mol / L) was added, and the reaction was carried out at 0 °C for 60 minutes. Finally, 13.07 g of N,N-dimethylacetamide (0.150 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.3871 mmol / g by titration.

[0073] Example 20

[0074] 46.88 mL of n-butyllithium (75.00 mmol) was added to a 500 mL reactor. 100.11 g of D3 (450.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 60°C and maintained for 300 minutes. Next, 75.00 mL of a triethylaluminum solution in hexane (1.0 mol / L) was added, and the reaction was carried out at 60°C for 5 minutes. Finally, 11.87 g of pyridine (0.150 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.3849 mmol / g by titration.

[0075] Example 21

[0076] 2.50 mL of n-butyllithium (4.00 mmol) was added to a 500 mL reactor. 11.86 g of D4 (40.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 135 °C and maintained for 600 min. Next, 8.00 mL of a hexane solution of triisobutylaluminum (1.0 mol / L) was added, and the reaction was carried out at 0 °C for 60 min. Finally, 176.22 g of 1,4-dioxane (2.000 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0205 mmol / g by titration.

[0077] Example 22

[0078] 1.19 mL of n-butyllithium (1.90 mmol) was added to a 500 mL reactor. 1.78 g of D3F (3.80 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 210 °C and maintained for 30 minutes. Next, 0.19 mL of a hexane solution of di-n-butylmagnesium (1.0 mol / L) was added, and the reaction was carried out at 30 °C for 120 minutes. Finally, 188.35 g of methylpyrrolidone (1.900 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0099 mmol / g by titration.

[0079] Example 23

[0080] 0.22 mL of sec-butyllithium (0.28 mmol) was added to a 500 mL reactor. 0.38 g of D3 (1.70 mmol) was added at room temperature and the mixture was stirred thoroughly. The temperature was then gradually increased to 60°C and maintained for 600 minutes. Next, 0.28 mL of a hexane solution of diethylzinc (1.0 mol / L) was added, and the reaction was carried out at 30°C for 60 minutes. Finally, 136.17 g of phosphazene base (0.283 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0021 mmol / g by titration.

[0081] Example 24

[0082] 28.46 mL of sec-butyllithium (37.00 mmol) was added to a 500 mL reactor. 109.75 g of D4 (370.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 135°C and maintained for 30 minutes. Next, 74.00 mL (74.00 mmol) of a hexane solution of dioctylzinc (1.0 mol / L) was added, and the reaction was carried out at 60°C for 120 minutes. Finally, 5.34 g of tetrahydrofuran (0.074 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.2003 mmol / g by titration.

[0083] Example 25

[0084] 3.85 mL of sec-butyllithium (5.00 mmol) was added to a 500 mL reactor. 4.69 g of D3F (10.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 210 °C and maintained for 300 minutes. Next, 0.50 mL of a hexane solution of diphenylmagnesium (1.0 mol / L) was added, and the reaction was carried out at 0 °C for 5 minutes. Finally, 150.13 g of methyl formate (2.500 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0317 mmol / g by titration.

[0085] Example 26

[0086] 50.00 mL of tert-butyllithium (50.00 mmol) was added to a 500 mL reactor. 111.23 g of D3 (500.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 210 °C and maintained for 30 minutes. Next, 50.00 mL of a hexane solution of triethylaluminum (1.0 mol / L) was added, and the reaction was carried out at 0 °C for 120 minutes. Finally, 8.81 g of ethyl acetate (0.100 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.2659 mmol / g by titration.

[0087] Example 27

[0088] 2.85 mL of tert-butyllithium (2.85 mmol) was added to a 500 mL reactor. 1.69 g of D4 (5.70 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 60°C and maintained for 300 minutes. Next, 5.70 mL of a hexane solution of triisobutylaluminum (1.0 mol / L) was added, and the reaction was carried out at 30°C for 5 minutes. Finally, 191.19 g of dimethyl sulfoxide (1.425 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0143 mmol / g by titration.

[0089] Example 28

[0090] 1.83 mL of tert-butyllithium (1.83 mmol) was added to a 500 mL reactor. 5.15 g of D3F (11.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 135 °C and maintained for 600 min. Next, 0.18 mL of a hexane solution of di-n-butylmagnesium (1.0 mol / L) was added, and the reaction was carried out at 60 °C for 60 min. Finally, 165.22 g of diethylene glycol dimethyl ether (1.833 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0107 mmol / g by titration.

[0091] Example 29 (Comparative Example)

[0092] 2.00 g of lithium tert-butoxide (25.00 mmol) was added to a 500 mL reactor. 46.85 g of D3F (100.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 210 °C and maintained for 600 minutes. Finally, 97.66 g of dimethyl sulfoxide (1.250 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.1706 mmol / g by titration.

[0093] Example 30 (Comparative Example)

[0094] 0.40 g of sodium tert-butoxide (4.17 mmol) was added to a 500 mL reactor. 5.56 g of D3 (25.00 mmol) was added at room temperature and stirred thoroughly. The mixture was then gradually heated to 210 °C and maintained for 300 minutes. Finally, 187.75 g of diethylene glycol dimethyl ether (2.083 mol) was added, stirred thoroughly, and stored in a desiccator for later use. The alkali metal concentration in the catalyst was determined to be 0.0215 mmol / g by titration.

[0095] Examples 31–40 illustrate the use of the above catalyst in the preparation of fluorosilicone rubber.

[0096] Add the cyclosiloxane monomers corresponding to those in Table 1 to a 250 mL reactor and preheat to the specified polymerization temperature. Add the specified catalyst all at once and maintain polymerization for 1 hour. Remove the reactor and determine the molecular weight and its distribution using gel permeation chromatography. The corresponding results are listed in Table 1.

[0097]

[0098]

[0099] Note: a The catalyst corresponds to the catalyst prepared in the numbered examples; b D3F, D3, D4, D3 Vi D3 Ph These correspond to 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, and 2,4,6-triphenyl-2,4,6-trimethylcyclotrisiloxane, respectively.

[0100] Examples 31–34, 35–36, 3

[0101] The structures of the fluorosilicone rubber of formula (1) prepared in Examples 31–40, wherein the repeating unit without the X substituent in Examples 31–34 is a homopolymer of fluorosiloxane, the X substituent in Examples 34–37 is vinyl, the X substituent in Example 38 is phenyl, and the X substituent in Examples 39–40 is methyl.

[0102] The only difference between Example 31 and Comparative Example 32 is that triethylaluminum was added during the catalyst preparation process in Example 31, while it was not in Comparative Example 32. Both used the same molar equivalent ratio D3F / Li = 200 for catalytic polymerization. The molecular weight and distribution of the resulting fluorosilicone rubber material were determined by gel permeation chromatography. The data showed that... Figure 4The results showed that the fluorosilicone rubber material prepared in Example 31 could completely suppress the formation of low molecular weight cyclic structures; while Comparative Example 32 did not contain triethylaluminum. This indicates that the addition of triethylaluminum can change the activity of the active center, causing the active center to attack only the silanol bonds in the cyclosiloxane monomer and not the silanol bonds in the polymer chain, thereby completely suppressing the side reactions in the polymerization process and obtaining a high-purity linear high molecular weight fluorosilicone rubber.

[0103] The above-described embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A method for preparing a class of bimetallic anionic ring-opening polymerization catalysts, characterized in that, Includes the following steps: Step (1): Under the protection of an inert gas, alkali metal compounds and cyclosiloxanes are aged at 60–210 degrees Celsius for 30–600 minutes to form a homogeneous transparent solution; Step (2): Add the solution with the general formula MtR to the solution obtained in step (1). n The compound, when aged at 0–60 degrees Celsius for 5–120 minutes, forms a homogeneous, transparent solution; Step (3): Add the accelerator to the solution obtained in step (2), mix thoroughly, and then prepare the bimetallic anionic ring-opening polymerization catalyst; In the bimetallic anionic ring-opening polymerization catalyst, alkali metal compounds, cyclosiloxanes, and MtR are present. n The molar ratio of the accelerator is 1:(2–10):(0.1–2):(2–1000), wherein the concentration of the alkali metal element is 0.05–1.6 mmol / g; The structural formula of step (2) is MtR n In the compound, Mt is selected from magnesium, zinc or aluminum; R is selected from methyl, ethyl, isopropyl, n-butyl, isobutyl or n-octyl, phenyl; the value of n corresponds to the type of Mt. If Mt is magnesium or zinc, then n is 2; if Mt is aluminum, then n is 3. The alkali metal compound is selected from lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium tert-butoxide, sodium tert-butoxide, potassium tert-butoxide, n-butyllithium, sec-butyllithium, and tert-butyllithium. The cyclosiloxane is selected from hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane.

2. The method for preparing a bimetallic anionic ring-opening polymerization catalyst according to claim 1, characterized in that: The accelerator is at least one selected from acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, pyridine, acetone, 1,4-dioxane, methylpyrrolidone, phosphazene base, tetrahydrofuran, methyl formate, ethyl acetate, toluene, diethylene glycol dimethyl ether, and ethylene glycol dimethyl ether.

3. A class of bimetallic anionic ring-opening polymerization catalysts, characterized in that, It is obtained by using the preparation method described in any one of claims 1-2.

4. The application of the bimetallic anionic ring-opening polymerization catalyst as described in claim 3, characterized in that, The aforementioned bimetallic anionic ring-opening polymerization catalyst is used to prepare fluorosilicone rubber with controllable molecular weight.

5. The application of the bimetallic anionic ring-opening polymerization catalyst according to claim 4, characterized in that, The method for preparing fluorosilicone rubber includes the following steps: Step (1): 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane and cyclosiloxane monomer are added to a polymerization reactor, heated and vacuumed for dehydration; Step (2): Add the bimetallic anionic ring-opening polymerization catalyst to the polymerization reactor, heat to 60–120 degrees Celsius to start the polymerization reaction, and polymerize for 10–600 minutes to prepare fluorosilicone rubber.

6. The application of the bimetallic anionic ring-opening polymerization catalyst according to claim 5, characterized in that: In step (1), the cyclosiloxane monomer is selected from one or more of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, and 2,4,6-triphenyl-2,4,6-trimethylcyclotrisiloxane.

7. The application of the bimetallic anionic ring-opening polymerization catalyst according to claim 5, characterized in that, The molecular weight of the fluorosilicone rubber is 0.2–2.5 million, with a molecular weight distribution of less than 1.

25. The structure of the fluorosilicone rubber is shown below: Wherein, X is one or more of methyl, phenyl, and vinyl.

8. The application of the bimetallic anionic ring-opening polymerization catalyst according to claim 7, characterized in that, X is methyl and vinyl.

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