Preparation method of alkyl-functionalized polysiloxanes

Abstract

This disclosure relates to a method for preparing alkyl-functionalized polysiloxanes, comprising the steps of: I) reacting a silane oligomer with a hydroxyl-terminated polysiloxane in the presence of catalyst 1, and II) reacting the reactant obtained in step (I) with a capping agent in the presence of catalyst 2, thereby obtaining the polysiloxane. This method allows for flexible adjustment of the degree of polymerization and viscosity of the desired polysiloxane by adjusting the feedstock, making it suitable for different applications; it can introduce multiple alkyl functional groups and further functional groups to obtain dual-modified polysiloxanes; using linear hydroxyl-terminated polysiloxanes as starting materials significantly reduces the proportion of undesirable cyclic siloxanes in the equilibrium product; and the reaction is mild, simple to operate, and environmentally friendly.

Description

Technical Field

[0001] This disclosure relates to a method for preparing an alkyl-functionalized polysiloxane. Background Technology

[0002] Long-chain alkyl functionalized siloxanes have attracted widespread attention due to their excellent lubricity, hydrophobicity, antifouling properties, wear resistance, defoaming properties, anti-adhesion, printability, and compatibility with organic materials.

[0003] Currently, there are three main methods for preparing long-chain alkyl functionalized siloxanes: one is to prepare them by co-hydrolysis and condensation of long-chain alkylalkoxysilanes or chlorosilanes with hydroxysilanes; the second is to prepare them by hydrosilylation of hydrogen-containing siloxanes with α-olefins; and the third is to prepare them by catalytic equilibrium of long-chain alkylalkoxysilanes or long-chain alkylsiloxane oligomers with small molecule cyclosiloxanes and end-capping agents.

[0004] Method 1 is well-suited for preparing long-chain alkyl-functionalized siloxanes with low polymerization degrees, and the reaction between alkoxysilanes or chlorosilanes and hydroxysilanes is highly sensitive to catalysts. Method 2 produces siloxanes whose molecular structure is limited by the starting hydrogen-containing siloxanes, making it impossible to flexibly adjust the degree of polymerization, viscosity, or further introduce functional groups as needed. Furthermore, the hydrosilylation reaction is highly exothermic, requiring high process safety, and the residual olefins are difficult to handle. Method 3 produces siloxanes that, even after vacuum distillation, still contain a significant proportion of cyclic siloxanes, affecting product performance. For example, the long-chain alkyl-functionalized vinyl siloxane prepared by catalytic equilibrium of tetramethyltetraalkylsiloxane, octamethylcyclotetrasiloxane, and tetramethyldivinyldisiloxane at 110-120°C, as disclosed in CN105838079A, suffers from this defect. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the method for preparing alkyl-functionalized polysiloxanes disclosed herein can achieve at least one or more of the following objectives:

[0006] i) The degree of polymerization and viscosity of the desired alkyl-functionalized polysiloxane can be flexibly adjusted by controlling the feeding of hydroxyl-terminated polysiloxane, silane oligomers and end-capping agents, making it suitable for different application fields.

[0007] ii) Multiple (≥3) alkyl functional groups can be introduced, and further functional groups can be easily introduced to obtain dual-modified polysiloxanes;

[0008] iii) Using linear hydroxyl-terminated polysiloxanes as starting materials greatly reduces the proportion of undesirable cyclosiloxanes in the equilibrium product;

[0009] iv) The reaction is mild, the operation is simple, and it is environmentally friendly.

[0010] This disclosure provides a method for preparing alkyl-functionalized polysiloxanes, comprising the steps of:

[0011] I) A silane oligomer (A) is reacted with a hydroxyl-terminated polysiloxane (B) in the presence of a catalyst 1, wherein the silane oligomer (A) comprises a cyclic oligomer (A1) as shown in Formula I.

[0012]

[0013] Among them, R 1 Each is an alkyl group from C6 to C18, such as hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, preferably C6 to C16 alkyl groups, especially C6 to C12 alkyl groups;

[0014] R 2 Each is independently a C1 to C5 alkyl group, such as methyl, ethyl, propyl, butyl, pentyl, preferably methyl;

[0015] m is any number between 3 and 20, for example, 3, 4, 5, 6, 8, 10, 15, 20; and

[0016] II) The reactants obtained in step (I) are reacted with the capping agent (C) under the action of catalyst 2 to obtain the final product.

[0017] Silane oligomers (A)

[0018] The content of the cyclic oligomer (A1) in the silane oligomer (A) is suitably greater than 20 wt%, for example greater than 50 wt%, preferably greater than 70 wt%. In one embodiment, the content of the cyclic oligomer (A1) in the silane oligomer (A) is 20-95 wt%, for example 50-95 wt%, preferably 70-95 wt%. To facilitate ring-opening of the cyclic oligomer in the equilibrium reaction, the cyclic trimer and tetramer shown in Formula I are preferred. In one embodiment, the silane oligomer (A) contains greater than 30 wt%, particularly greater than 60 wt%, of the cyclic trimer and tetramer shown in Formula I, the percentage being based on the total weight of the silane oligomer (A). In a more specific embodiment, the silane oligomer (A) contains greater than 30 wt%, particularly greater than 40 wt%, of the cyclic trimer shown in Formula I, the percentage being based on the total weight of the silane oligomer (A).

[0019] In this disclosure, the silane oligomer (A) may also contain a linear oligomer (A2) as shown in Formula II.

[0020]

[0021] Among them, R 3It is methyl, ethyl, or hydrogen, especially methyl or ethyl;

[0022] R 4 Compared with the previous R 1 The definitions are the same;

[0023] R 5 Compared with the previous R 2 The definitions are the same;

[0024] n is any number between 2 and 20, such as 2-8 or 9-20, for example, 5, 6, 8, 10, 15, 20.

[0025] The content of linear oligomer (A2) in the silane oligomer (A) can be, for example, less than 50 wt%, less than 30 wt%, less than 20 wt%, or less than 10 wt%, where the percentage is based on the total weight of the silane oligomer (A). While a higher content of linear oligomer in the silane oligomer (A) can also produce polyalkyl-functionalized polysiloxanes, it lacks flexibility in adjusting the degree of polymerization and viscosity of the polysiloxane because the higher content of alkoxy or hydroxyl groups in the linear oligomer is detrimental to the segment growth of the polysiloxane. The content of linear oligomer (A2) in the silane oligomer (A) is suitably greater than 5 wt%, where the percentage is based on the total weight of the silane oligomer (A). An appropriate amount of linear oligomer facilitates the introduction of alkoxy or hydroxyl groups onto the polysiloxane.

[0026] This disclosure surprisingly discovers that appropriate amounts of alkoxy and hydroxyl groups act on fillers, which to some extent helps to further reduce the viscosity of the composition and improve thermal conductivity while increasing the amount of thermally conductive filler in the polysiloxane composition; however, excessive alkoxy and hydroxyl content will affect the storage stability of the polysiloxane, and when applied to addition-cured thermally conductive siloxane compositions, it will easily generate bubbles and impair thermal conductivity.

[0027] The silane oligomer (A) can be prepared by the hydrolysis and condensation of silane, including the following steps:

[0028] i) The dialkoxysilane of Formula III is reacted with water in the presence of an organic solvent under the action of catalyst 3, wherein the molar ratio of water to dialkoxysilane is greater than 0.5:1, for example greater than 2:1, greater than 3:1, or greater than 5:1.

[0029] R 6 2R 7 R 8 Si III

[0030] Among them, R 6 It is methoxy or ethoxy.

[0031] R 7 Compared with the previous R 1The same definition

[0032] R 8 Compared with the previous R 2 The definitions are the same;

[0033] ii) Remove the reaction byproducts, water, catalyst 3 and organic solvent to obtain the final product.

[0034] In step (i), considering that the hydrolysis and condensation of silane is an exothermic reaction, the reaction is preferably carried out at a lower temperature, such as below 30°C, like room temperature or even below 10°C; considering the large exothermic reaction, water is preferably added dropwise to the dialkoxysilane represented by Formula III. The reaction time is suitably 1-8 hours, for example 3-6 hours.

[0035] In step (i), the organic solvent acts to inhibit the reaction rate; it can be, for example, ethanol or acetonitrile. The amount of organic solvent used is not particularly limited, as long as it ensures the reaction proceeds at a moderate pace. Catalyst 3 is preferably an acidic catalyst, such as hydrochloric acid or concentrated sulfuric acid, to promote the hydrolysis and condensation of the dialkoxysilane. To further increase the degree of polymerization of the silane oligomer, the acidic catalyst can be removed in the later stages of the reaction, and a basic catalyst such as potassium hydroxide can be added, followed by a further reaction period.

[0036] In step (i), the molar ratio of water to dialkoxysilane is crucial to the composition and structure of the resulting silane oligomer. A lower molar ratio is unfavorable for the condensation of dialkoxysilane, or the resulting oligomer may have a higher content of alkoxy and hydroxyl groups.

[0037] In step (ii), the reaction byproducts, mainly small molecule alcohols, are usually removed by distillation; catalyst 3 can be removed by neutralization with alkali; and organic solvents can be removed by washing with water or distillation.

[0038] In a preferred embodiment, the silane oligomer (A) is prepared by a method comprising the following steps: i) adding water dropwise to a diekoxysilane of Formula III in the presence of ethanol and hydrochloric acid, reacting the mixture, wherein the molar ratio of water to diekoxysilane is greater than 2:1; ii) removing the reaction byproducts, water, hydrochloric acid and ethanol, thereby obtaining the product.

[0039] Hydroxyl-terminated polysiloxane (B)

[0040] The structural formula of the terminal hydroxyl polysiloxane (B) is typically shown in Formula IV:

[0041]

[0042] Among them, R a Each is independently a C1 to C5 alkyl group, such as methyl, ethyl, propyl, butyl, pentyl or phenyl, preferably methyl;

[0043] p is suitably any number between 3 and 150, for example, any number between 10 and 100, particularly between 10 and 60, such as 15, 20, 25, 30, 35, 40, 45, 50, 55. In one embodiment, p is any number between 15 and 55, particularly between 20 and 50.

[0044] Capping agent (C)

[0045] The structural formula of the capping agent (C) is typically shown in Formula V:

[0046]

[0047] Among them, R b It can be methyl, vinyl, hydrogen, aminopropyl, aminoethylaminopropyl, or glycidylpropyl.

[0048] R c Each is independently a C1 to C5 alkyl group, such as methyl, ethyl, propyl, butyl, pentyl, preferably methyl;

[0049] q is any number between 0 and 20, such as 0, 3, 6, 9, 12, 15, 18.

[0050] In one embodiment, the capping agent has the structural formula shown in Formula V, where R c For methyl groups, q = 0.

[0051] Catalysts 1 and 2 can be alkaline catalysts, such as alkali metal hydroxides like potassium hydroxide, quaternary ammonium hydroxides like tetramethylammonium hydroxide, and their hydrates; or acidic catalysts, such as phosphazene chloride, trifluoromethanesulfonic acid, and acidic ion exchange resins. The amounts of catalysts 1 and 2 need only be sufficient to ensure they serve as effective catalysts for polycondensation and / or equilibration reactions. Catalysts 1 and 2 can be the same or different. To avoid introducing more catalyst impurities and increasing the difficulty of subsequent catalyst removal, catalyst 2 is preferably the same as catalyst 1. In this case, for the sake of simplifying the feeding operation, catalyst 2 in step (II) can be added together in step (I).

[0052] Generally, the preparation of the alkyl-functionalized polysiloxanes disclosed herein can be achieved using either a basic catalyst or an acidic catalyst, but the specific method may vary depending on the type of end-capping agent used. In one embodiment, the end-capping agent shown in Formula V is used, wherein R... b The catalyst is methyl, vinyl, aminopropyl, aminoethylaminopropyl, or glycidylpropyl, and catalysts 1 and 2 are basic catalysts. In another embodiment, the end-capping agent shown in formula V is used, wherein R b The catalyst is hydrogen, and catalysts 1 and 2 are acidic catalysts.

[0053] In this disclosure, the amounts of silane oligomer (A), hydroxyl-terminated polysiloxane (B), and end-capping agent (C) can be selected according to the number of M and D structural units of the alkyl-functionalized polysiloxane to be synthesized.

[0054] In step (I), the reaction comprises a condensation polymerization reaction and an equilibration reaction, which typically occur simultaneously. The reaction temperature is suitably 80-110°C, particularly 90-105°C. The reaction time is suitably 15 min to 4 h. Advantageously, a reduced pressure operation is employed during step (I) to remove the small molecule alcohols and water produced in the reaction. This reduced pressure can be lowered to below 100 mbar, for example, below 80 mbar.

[0055] In step (II), the reaction is typically an equilibrium reaction. The reaction temperature is preferably 100-140°C, particularly 110-130°C. The reaction time is preferably 3-8 hours. Generally, the longer the equilibrium reaction time, the more uniform the reaction becomes, but the above-mentioned reaction time is preferred considering cost factors.

[0056] To adjust the proportion of hydroxyl, alkoxy, and other end groups in the target alkyl-functionalized polysiloxane, a small amount of hydroxyl-terminated polysiloxane (B) can be added to the equilibration reaction in step (II).

[0057] The preparation method disclosed herein may further include a catalyst removal step (III) to minimize the impact of catalyst impurities on product performance. For alkali metal hydroxide catalysts, neutralization with an acidic substance is generally employed; for quaternary ammonium hydroxide catalysts, high-temperature decomposition is generally employed; and for acidic catalysts, neutralization with an alkaline substance is generally employed.

[0058] The preparation method disclosed herein further includes a step (IV) of removing low-boiling substances, which include small molecule cyclosiloxanes, small molecule alcohols, water, etc. The removal of low-boiling substances is preferably carried out by vacuum distillation, with the pressure suitable to be below 100 mbar, such as below 60 mbar, and the temperature suitable to be between 140-190°C, such as 160-180°C.

[0059] In this disclosure, steps (I), (II), and (III) are advantageously performed under an inert atmosphere. The inert atmosphere typically refers to a nitrogen atmosphere or an argon atmosphere.

[0060] In this disclosure, unless otherwise specified, room temperature refers to 23±2℃. Detailed Implementation

[0061] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0062] Molecular weight distribution characterization

[0063] Silane hydrolysis oligomers with different degrees of polymerization were separated by PSS SECcurity gel permeation chromatography, and their molecular weights were determined by comparison with reference compounds. Tetrahydrofuran was used as the solvent, and Agilent PLgel 5um guard and PLgel 5um 100A columns were used. The column temperature was 45℃, the injection rate was 1 ml / min, and the injection volume was 20 μl.

[0064] Molecular structure characterization

[0065] 1 H NMR measurements

[0066] Test solvent: Deuterated chloroform (TMS-free)

[0067] Spectrometer: Bruker Avance III HD 400

[0068] Sampling head: 5mm BBO sampling head

[0069] Measurement parameters:

[0070] Pulse sequence (Pulprog) = zg30

[0071] TD = 65536

[0072] NS=64

[0073] SW = 18ppm

[0074] AQ = 4.54s

[0075] D1 = 5s

[0076] Depending on the type of spectrometer used, some measurement parameters may need to be adjusted appropriately.

[0077] 29 Si NMR Measurement

[0078] Test solvent: deuterated benzene (containing the relaxant chromium acetylacetone, without internal standard)

[0079] Spectrometer: Bruker Avance III HD 400

[0080] Sampling head: 5mm BBO sampling head

[0081] Measurement parameters:

[0082] Pulse sequence = zgig60

[0083] TD = 65536

[0084] NS=2048

[0085] SW = 200ppm

[0086] AQ = 2.04s

[0087] D1 = 5s

[0088] Depending on the type of spectrometer used, some measurement parameters may need to be adjusted appropriately.

[0089] Viscosity determination of polysiloxanes

[0090] The dynamic viscosity of polysiloxane was measured using a Brookfield viscometer with rotor No. 3 at 25°C and 300 rpm for 30 seconds.

[0091] Viscosity determination of the composition

[0092] The viscosity of a composition is measured in liquid form or as a determination of the viscosity of an emulsion or dispersion polymer and resin using a rotational viscometer at a specified shear rate, in accordance with standard DIN EN ISO 3219 (ISO 3219:1993).

[0093] Raw material information in the following examples:

[0094] Hydroxyl-terminated polydimethylsiloxane, FINISH WS 62M, with a dynamic viscosity of 50-110 mPa·s at 25°C according to DIN 51562, is supplied by Wacker Chemie.

[0095] Phosphazene chloride, PNCL 2 / 100PERCENT, supplied by Wacker Chemie;

[0096] 1,1,3,3-Tetramethyldisiloxane, supplied by Silicon Science New Materials;

[0097] Tetramethyldivinyldisiloxane, supplied by THIAI;

[0098] Alumina A, spherical alumina powder with an average particle size of 40 μm;

[0099] Alumina B, spherical alumina powder with an average particle size of 5 μm;

[0100] Zinc oxide, non-spherical zinc oxide powder with an average particle size of 5 μm;

[0101] Hydrogen-terminated polydimethylsiloxane C1, with a dynamic viscosity of 85 mPa·s at 25°C, is provided by Wacker Chemie and is referred to as H Polymer C1 below.

[0102] Hydrogen-terminated polydimethylsiloxane C2, with a dynamic viscosity of 1,040 mPa·s at 25°C, is supplied by Wacker Chemie and is referred to as H Polymer C2 below.

[0103] Vinyl-terminated polydimethylsiloxane C2, VINYLPOLYMER 120, with a dynamic viscosity of 120 mPa·s at 25°C, is supplied by Wacker Chemie and will be referred to as V Polymer C2 below.

[0104] All other raw materials are commercially available.

[0105] Synthesis Example 1

[0106] At room temperature, 68.5 g of dodecyl diethoxymethylsilane, 110 g of ethanol, and 1.22 g of 5% hydrochloric acid aqueous solution were added to a flask. Then, 25 g of water was added dropwise with stirring. The reaction was carried out at room temperature for 4 h, followed by a reaction at 65 °C for 1 h, yielding a white solid precipitate. The precipitate was then transferred to a distillation flask and rotary distilled at 85 °C and 100 mbar for 1 h to synthesize a hydrolyzed oligomer of dodecyl diethoxymethylsilane. NMR analysis showed that this oligomer contained 53.60 wt% of the cyclic trimer D3. C12H25 18.17 wt% of cyclic tetramer D4 C12H25 6.83 wt% CH3(OR)(C 12 H 25 SiO 1 / 2 Unit (where R is -C2H5 or H, mainly -C2H5) and 21.40 wt% CH3 (C 12 H 25 SiO 2 / 2 The oligomer contains cyclic pentamers, cyclic hexamers, and higher-order cyclic oligomers. GPC analysis revealed that the oligomer contains 52.17 wt% trimers, 18.75 wt% tetramers, 6.36 wt% pentamers, and 22.73 wt% hexamers and higher-order oligomers.

[0107] Synthesis Example 2

[0108] At room temperature, 68.5 g of dodecyl diethoxymethylsilane, 20.87 g of ethanol, and 0.14 g of 5% hydrochloric acid aqueous solution were added to a flask. Then, 4.08 g of water was added dropwise with stirring. The reaction was carried out at room temperature for 4 h, followed by a reaction at 65 °C for 1 h, yielding a white solid precipitate. The precipitate was then neutralized with sodium carbonate and transferred to a distillation flask. Rotary distillation was performed at 85 °C and 100 mbar for 1 h to remove ethanol, waste acid, and water, synthesizing a hydrolyzed oligomer of dodecyl diethoxymethylsilane. NMR analysis showed that this oligomer contained 19.38 wt% of the cyclic trimer D3. C12H25 2.76 wt% of cyclic tetramer D4 C12H25 65.00 wt% CH3(OR)(C 12 H 25 SiO 1 / 2 Unit (where R is -C2H5 or H, mainly -C2H5) and 11.63 wt% CH3 (C 12 H 25 SiO 2 / 2 Units and cyclic pentamers, cyclic hexamers and higher-order cyclic oligomers.

[0109] Synthesis Example 3

[0110] Under a nitrogen atmosphere, 200 g of hydroxyl-terminated polydimethylsiloxane, 30.8 g of the hydrolyzed oligomer of dodecyl diethoxymethylsilane from Example 1, and 0.0592 g of phosphazene chloride were added to a flask. The mixture was stirred and reacted at 95 °C and 50 mbar for 0.5 h. Then, 6 g of 1,1,3,3-tetramethyldisiloxane was added to the flask, and the temperature was raised to 120 °C, and the reaction was carried out for 5 h. After the reaction was completed, sodium carbonate solid was added, and the mixture was treated at 50 °C for 1.5 h and filtered. The reactants were transferred to a distillation flask and distilled at 170 °C and 30 mbar for 1.5 h to remove low-boiling substances. After cooling to room temperature, alkyl-functionalized hydrogen-containing polydimethylsiloxane H Polymer 1 with the following structural formula and a dynamic viscosity of 95 mPa·s at 25 °C was obtained.

[0111] (H(CH3)2SiO) 1.88 ((CH3)2SiO) 60.95 ((CH3)(C 12 H 25 )SiO) 3.02 (Si(CH3)2(OH)) 0.09 (Si(CH3)2(OC2H5)) 0.03

[0112] Synthesis Example 4

[0113] Under a nitrogen atmosphere, 220 g of hydroxyl-terminated polydimethylsiloxane, 7.7 g of the hydrolyzed oligomer of dodecyl diethoxymethylsilane from Example 1, and 0.0573 g of phosphazene chloride were added to a flask. The mixture was stirred and reacted at 95 °C and 50 mbar for 0.5 h. Then, 1.5 g of 1,1,3,3-tetramethyldisiloxane was added to the flask, and the temperature was raised to 120 °C, and the reaction was carried out for 5 h. After the reaction was completed, sodium carbonate solid was added, and the mixture was treated at 50 °C for 1.5 h and filtered. The reactants were transferred to a distillation flask and distilled at 170 °C and 30 mbar for 1.5 h to remove low-boiling substances. After cooling to room temperature, alkyl-functionalized hydrogen-containing polydimethylsiloxane H Polymer 2 with the following structural formula and a dynamic viscosity of 1,155 mPa·s at 25 °C was obtained.

[0114] (H(CH3)2SiO) 1.63 ((CH3)2SiO) 241.14 ((CH3)(C 12 H 25 )SiO) 3.78 (Si(CH3)2(OH)) 0.35 (Si(CH3)2(OC2H5)) 0.02

[0115] Synthesis Example 5

[0116] Under a nitrogen atmosphere, 200 g of hydroxyl-terminated polydimethylsiloxane, 41 g of the hydrolyzed oligomer of dodecyl diethoxymethylsilane from Synthesis Example 1, and 0.52 g of a 25% aqueous solution of tetramethylammonium hydroxide were added to a flask. The mixture was stirred and reacted at 95 °C and 40 mbar for 40 min. Then, 8.35 g of tetramethyldivinyldisiloxane was added to the flask, the temperature was raised to 120 °C, and the reaction was carried out for 2 h. After that, 2.4 g of hydroxyl-terminated polydimethylsiloxane was added, and the reaction was carried out at 120 °C for 2 h. After the reaction was completed, the temperature was raised to 175 °C to decompose the catalyst for 1.5 h. The above reactants were transferred to a distillation flask and distilled at 175 °C and 30 mbar for 1.5 h to remove low-boiling substances. After cooling to room temperature, alkyl-functionalized vinyl polydimethylsiloxane V Polymer 1 with the following structural formula and a dynamic viscosity of 102 mPa·s at 25 °C was obtained.

[0117] ((H2C=CH)(CH3)2SiO) 1.70 ((CH3)2SiO) 52.33 ((CH3)(C 12 H 25 )SiO) 3.81 (Si(CH3)2(OH)) 0.07 (Si(CH3)2(OC2H5))0.23

[0118] Synthetic Comparative Example 6

[0119] Under a nitrogen atmosphere, 632 g of hydroxyl-terminated polydimethylsiloxane, 25.9 g of dodecyl diethoxymethylsilane, and 0.51 g of a 25% aqueous solution of tetramethylammonium hydroxide were added to a flask. The mixture was stirred and reacted at 95 °C and 30 mbar for 30 min. Then, 14.9 g of tetramethyldivinyldisiloxane was added to the flask, the temperature was raised to 120 °C, and the reaction was carried out for 2 h. Next, 11.8 g of hydroxyl-terminated polydimethylsiloxane was added, and the reaction was carried out at 120 °C for 2 h. After the reaction was complete, the temperature was raised to 175 °C to decompose the catalyst for 1.5 h. The reactants were transferred to a distillation flask and distilled at 175 °C and 30 mbar for 1.5 h to remove low-boiling substances. After cooling to room temperature, alkyl-functionalized vinyl polydimethylsiloxane V Polymer C1 with the following structural formula and a dynamic viscosity of 110 mPa·s at 25 °C was obtained. The number of dodecyl groups introduced onto the polysiloxane using this synthetic method is limited.

[0120] ((H2C=CH)(CH3)2SiO) 1.12 ((CH3)2SiO) 63.14 ((CH3)(C 12 H 25 )SiO) 0.68 (Si(CH3)2(OH)) 0.08 (Si(CH3)2(OC2H5)) 0.80

[0121] Synthesis Example 7

[0122] Under a nitrogen atmosphere, 170.7 g of hydroxyl-terminated polydimethylsiloxane, 35 g of the hydrolyzed oligomer of dodecyl diethoxymethylsilane from Synthesis Example 2, and 0.12 g of a 25% aqueous solution of tetramethylammonium hydroxide were added to a flask. The mixture was stirred and reacted at 95 °C and 100 mbar for 1 h. Then, 2.95 g of tetramethyldivinyldisiloxane was added to the flask, and the temperature was raised to 120 °C, and the reaction was carried out for 3 h. After the reaction was completed, the temperature was raised to 175 °C to decompose the catalyst for 1.5 h. The reactants were transferred to a distillation flask and distilled at 175 °C and 30 mbar for 1.5 h to remove low-boiling substances. After cooling to room temperature, alkyl-functionalized vinyl polydimethylsiloxane V Polymer 2 with the following structural formula and a dynamic viscosity of 125 mPa·s at 25 °C was obtained.

[0123] ((H2C=CH)(CH3)2SiO) 0.28 ((CH3)2SiO) 50.26 ((CH3)(C12 H 25 )SiO) 3.60 (Si(CH3)2(OH)) 0.05 (Si(CH3)2(OC2H5)) 1.66

[0124] According to Table 1, H Polymer 1-2, V Polymer 1, H Polymer C1-C2, and V Polymer C1-C2 were mixed with thermally conductive fillers respectively, and the compositions were tested in 1 second. -1 and 10s -1 Viscosity at shear rate.

[0125] Table 1

[0126]

[0127] As shown in Table 1, H Polymer 1-2 significantly reduces the viscosity of the composition compared to H Polymer C1-C2 with similar viscosities, thereby improving the thermal conductivity of the composition. V Polymer 1 has a very significant advantage in reducing the viscosity of the composition compared to V Polymer C2, and it also performs better in reducing the viscosity of the composition than alkyl-functionalized V Polymer C1 synthesized by methods other than those described in this invention. This is closely related to the number of long-chain alkyl groups introduced.

[0128] According to Table 2, H Polymer 1-2 and H Polymer C1-C2 were mixed with thermally conductive fillers respectively, and the compositions were tested in 1 second. -1 and 10s -1 Viscosity at shear rate.

[0129] Table 2

[0130]

[0131] As shown in Table 2, H Polymer 1-2, compared to H Polymer C1-C2 with similar viscosity, can significantly reduce the viscosity of compositions with the same filling amount in different thermally conductive filler systems, thereby improving the thermal conductivity of the compositions.

[0132] Table 3 lists the viscosity changes of H Polymer 1-2 after being stored at room temperature for 10 months. The viscosity changes are within ±5%, indicating that it has good storage stability.

[0133] Table 3

[0134]

Claims

1. A method for preparing alkyl-functionalized polysiloxanes, characterized in that, Including the following steps: I) A silane oligomer (A) is reacted with a hydroxyl-terminated polysiloxane (B) in the presence of a catalyst 1, wherein the silane oligomer (A) comprises a cyclic oligomer (A1) as shown in Formula I, and wherein the silane oligomer (A) comprises more than 30 wt% of cyclic trimers and tetramers as shown in Formula I, the percentages being based on the total weight of the silane oligomer (A). Among them, R 1 Each is an alkyl group that is C6 to C18. R 2 Each is an alkyl group, from C1 to C5. m is any number between 3 and 20; The structural formula of the hydroxyl-terminated polysiloxane (B) is shown in Formula IV: Among them, R a Each is independently a C1 to C5 alkyl or phenyl group. p is any number between 3 and 150, and II) The reactants obtained in step (I) are reacted with the capping agent (C) under the action of catalyst 2 to obtain the final product.

2. The method as described in claim 1, characterized in that, The silane oligomer (A) contains more than 30 wt% of the cyclic trimer represented by Formula I, the percentage being calculated based on the total weight of the silane oligomer (A).

3. The method according to any one of claims 1-2, characterized in that, The silane oligomer (A) further comprises a linear oligomer (A2) as shown in Formula II. Among them, R 3 It can be methyl, ethyl, or hydrogen. R 4 Each is an alkyl group, ranging from C6 to C18. R 5 Each is an alkyl group, from C1 to C5. n is any number between 2 and 20.

4. The method as described in claim 3, characterized in that, The structural formula of the hydroxyl-terminated polysiloxane (B) is shown in Formula IV: Among them, R a Each is independently a C1 to C5 alkyl or phenyl group. p is any number between 10 and 100.

5. The method according to any one of claims 1-2, characterized in that, The structural formula of the capping agent (C) is shown in Formula V: Among them, R b It can be methyl, vinyl, hydrogen, aminopropyl, aminoethylaminopropyl, or glycidylpropyl. R c Each is an alkyl group, from C1 to C5. q is any number between 0 and 20.

6. The method according to any one of claims 1-2, characterized in that, The reaction temperature in step (I) is 80-110℃.

7. The method according to any one of claims 1-2, characterized in that, The reaction temperature for step (II) is 100-140℃.

8. The method according to any one of claims 1-2, characterized in that, The silane oligomer (A) is prepared by a method comprising the following steps: i) The dialkoxysilane of Formula III is reacted with water in the presence of an organic solvent under the action of catalyst 3, and the molar ratio of water to dialkoxysilane is greater than 0.5:

1. R 6 2R 7 R 8 SiIII Among them, R 6 It is methoxy or ethoxy. R 7 Alkyl groups from C6 to C18 R 8 It is an alkyl group from C1 to C5; ii) Remove the reaction byproducts, water, catalyst 3 and organic solvent to obtain the final product.

9. The method as described in claim 8, characterized in that, The molar ratio of water to dialkoxysilane is greater than 2:

1.

10. The method as described in claim 8, characterized in that, Catalyst 3 is an acidic catalyst.

11. The method as described in claim 8, characterized in that, The organic solvent is ethanol or acetonitrile.

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