A process for the preparation of a single-end, multi-alkoxy terminated linear polysiloxane

Abstract

The application discloses a preparation method of a single-end multi-alkoxy terminated linear polysiloxane, which comprises the following steps: mixing and reacting cyclosiloxane, an alkaline catalyst and a promoter, and then adding an acidic substance and an alkoxysilane to perform a termination reaction to obtain the single-end multi-alkoxy terminated linear polysiloxane. The raw material of the preparation method of the single-end multi-alkoxy terminated linear polysiloxane is cheap and easy to obtain, the production process is simple and easy to operate, the reaction condition is mild, no special requirement is needed for the equipment, and industrialization is easy to realize. The single-end multi-alkoxy terminated linear polysiloxane prepared by the method has high yield (more than 99%) and controllable viscosity, and industrialization is easy to realize.

Description

Technical Field

[0001] This invention belongs to the field of organosilicon materials, and in particular relates to a method for preparing a linear polysiloxane with single-terminated polyalkoxy groups. Background Technology

[0002] Silane coupling agents were initially developed as glass fiber treatment agents for glass fiber reinforced plastics. With the development of the polymer materials industry, silane coupling agents, due to their unique properties and significant modification effects, have seen their application fields continuously expand and their production volume increase dramatically, gradually becoming an important branch of the organosilicon industry. Silane coupling agents have become indispensable chemical additives in modern polymer industry and related high-tech fields. Currently, the three main application areas of silane coupling agents include: first, as crosslinking and curing agents, enabling room temperature and pressure curing of polymer systems; second, as material surface modifiers, imparting new functions to materials; and third, as tackifiers, used to improve the adhesion between two materials with different chemical properties.

[0003] The general formula for traditional silane coupling agents can be Q-R'-R. n SiX (3-n) In this formula, Q represents organic compound groups with special functions, such as chlorine, vinyl, amino, epoxy, mercapto, acryloyloxy, and isocyanate groups; R' = -(CH2). m - where m is 1 or ≥3; R is alkyl or vinyl; n = 0, 1, 2, usually 0.

[0004] With the rapid development of high-tech fields, the performance requirements for modified synthetic materials are gradually increasing, especially the high-temperature resistance of some materials. However, traditional carbon-chain silane coupling agents cannot meet these requirements. Therefore, there is an urgent need to develop a silane coupling agent that can perform surface treatment, thickening, and coupling functions while also improving the high-temperature resistance of modified materials. Alkoxy-terminated linear polysiloxanes are currently a research direction. By replacing the carbon chain structure in traditional silane coupling agents with linear polysiloxanes, the high-temperature resistance of modified materials can be effectively improved.

[0005] Patent document CN101298498A discloses an alkoxy-terminated linear polysiloxane coupling agent and its synthesis method. The method uses organocyclosiloxanes and trimethylchlorosilane, tetrachlorosilane, or thionyl chloride as raw materials. First, chlorine-terminated polysiloxanes are prepared, and then alkoxylation reactions are used to prepare alkoxy-terminated linear polysiloxanes. While this method can yield alkoxy-terminated linear polysiloxanes, the preparation process is complex and requires the use of highly corrosive chlorosilanes, thus placing high demands on equipment and the production environment, thereby increasing the production cost.

[0006] Patent document CN113024809A discloses a method for preparing a single-terminated (talkoxysiloxy)-terminated polysiloxane fluid. Using n-butyllithium as a catalyst and hexamethyltrisiloxane as the reactant, the method first prepares a lithium silanolate salt of dimethylbutylsiloxy-terminated polydimethylsiloxane, then adds a trialkoxychlorosilane for a capping reaction to prepare the single-terminated (talkoxysiloxy)-terminated polysiloxane. While this method can yield single-terminated (talkoxysiloxy)-terminated polysiloxanes, it requires the use of flammable and explosive n-butyllithium, and the capping agent, trialkoxychlorosilane, is not a readily available commodity and is expensive. Furthermore, the use of highly corrosive chlorosilanes in the preparation process places high demands on equipment and the production environment, thus increasing the production cost. Summary of the Invention

[0007] In order to improve the above-mentioned technical problems, the purpose of this invention is to provide a simple, safe and economical method for preparing linear polysiloxanes with low cost and single-ended polyalkoxy groups.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for preparing a linear polysiloxane with single-ended polyalkoxy groups includes the following steps:

[0010] After mixing and reacting cyclosiloxane, alkaline catalyst, and accelerator, acidic substances and alkoxysilane are added simultaneously for end-capping reaction to obtain the linear polysiloxane with single-terminated polyalkoxy groups.

[0011] It should be noted that, in this invention, "single-end" means that only one end of the polysiloxane is capped with a polyalkoxy group. "Polyalkoxy-capped" means that the capped end of the polysiloxane is capped with more than one (i.e., two or three) alkoxy groups.

[0012] According to an embodiment of the present invention, the cyclosiloxane is selected from one, two or more of the following: hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetraphenylcyclotetrasiloxane, and 1,3,5-trimethyl-1,3,5-tri(trifluoropropyl)cyclotrisiloxane.

[0013] According to an embodiment of the present invention, the alkaline catalyst is one or two of potassium trimethylsilanolate (Si(CH3)3OK), sodium trimethylsilanolate (Si(CH3)3ONa), and lithium trimethylsilanolate (Si(CH3)3OLi).

[0014] According to an embodiment of the present invention, the accelerator is selected from one, two or more of the following: butanone, methyl butanone, methyl isobutanone, dioxane, tetrahydrofuran, ethyl acetate, propyl acetate, butyl acetate, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, ethylene glycol diethyl ether, ethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

[0015] According to an embodiment of the present invention, the molar ratio of the siloxane chain segment to the alkaline catalyst in the cyclosiloxane is 10 to 150:1, for example 10 to 100:1, exemplarily 10:1, 20:1, 40:1, 60:1, 80:1, 100:1, 150:1, or any point within the range of the aforementioned pairs of values.

[0016] According to an embodiment of the present invention, the molar ratio of the alkaline catalyst to the promoter is 1:0.1 to 5, for example 1:0.2 to 4, and exemplary values ​​are 1:0.1, 1:0.2, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, or any point within the range of the aforementioned pairs of values.

[0017] According to an embodiment of the present invention, the reaction temperature of the cyclosiloxane, alkaline catalyst, and accelerator is 30 to 130°C, for example 50 to 120°C, such as 50°C, 60°C, 95°C, 100°C, 115°C, 120°C, 130°C, or any point within the range of the aforementioned values.

[0018] According to an embodiment of the present invention, the reaction time of the cyclosiloxane, alkaline catalyst, and accelerator is 1 to 6 hours, for example 2 to 5 hours, exemplarily 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, or any value within the range of the aforementioned pairs of values.

[0019] According to an embodiment of the present invention, the acidic substance is at least one selected from acetic acid, propionic acid, butyric acid, and [other substances].

[0020] According to an embodiment of the present invention, the molar ratio of the acidic substance to the alkaline catalyst is 1.03 to 1.18:1, for example 1.05 to 1.16:1, and exemplary values ​​are 1.03:1, 1.05:1, 1.06:1, 1.07:1, 1.10:1, 1.15:1, 1.18:1, or any value within the range of the aforementioned pairs of values.

[0021] According to an embodiment of the present invention, the alkoxysilane is at least one selected from tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltripropoxysilane.

[0022] According to an embodiment of the present invention, the molar ratio of the added alkoxysilane to the alkaline catalyst is 1 to 5:1, for example 1 to 4:1, exemplarily 1:1, 2:1, 2.5:1, 3:1, 4:1, 5:1, or any value within the range of the aforementioned pairs of values.

[0023] According to an embodiment of the present invention, the end-capping reaction time is 1 to 5 hours, for example 1 to 4 hours, with exemplary times being 1 hour, 2 hours, 3 hours, and 4 hours.

[0024] According to an embodiment of the present invention, the temperature of the end-capping reaction is 50–120°C, for example 60–100°C, with 60°C, 80°C, and 100°C being exemplary.

[0025] According to an embodiment of the present invention, the method for preparing the single-terminated polyalkoxy-terminated linear polysiloxane further includes a step of separating and purifying the reaction system after the end-capping reaction is completed. For example, the separation and purification can be carried out using methods known in the art, such as removing solid impurities by adsorption filtration and then removing excess alkoxysilane by vacuum to obtain the single-terminated polyalkoxy-terminated linear polysiloxane.

[0026] According to an embodiment of the present invention, the adsorbent used in the adsorption filtration is diatomaceous earth.

[0027] Preferably, the amount of diatomaceous earth used is 0.5% to 3% of the theoretical mass of the single-terminated polyalkoxy linear polysiloxane, for example, 0.8% to 2.5%, with exemplary values ​​of 0.5%, 0.8%, 1%, 1.2%, 1.7%, 2.0%, 2.5%, and 3.0%.

[0028] According to an embodiment of the present invention, the vacuuming time is 30 to 180 minutes, for example 40 to 160 minutes, and exemplary times are 30 minutes, 60 minutes, 100 minutes, 120 minutes, 130 minutes, 140 minutes, 150 minutes, 160 minutes, and 180 minutes.

[0029] According to an embodiment of the present invention, the vacuum degree of the vacuum pumping is -0.05 to -0.1 MPa, and exemplary values ​​are -0.06 MPa, -0.08 MPa, -0.09 MPa, and -0.10 MPa.

[0030] According to an embodiment of the present invention, the vacuuming temperature is 80-160°C, for example 90-150°C, and exemplary values ​​are 110°C, 120°C, 130°C, 140°C, and 150°C.

[0031] In this invention, by controlling the ratio of catalyst and promoter as well as the reaction temperature, the activity of the catalytic system can be effectively controlled, thereby controlling the ring-opening reaction of cyclosiloxanes to reduce or avoid the occurrence of equilibrium reaction during the reaction process (i.e., reduce the content of cyclic compounds in the reaction products, mainly linear polysiloxanes), and thus prepare linear polysiloxane products with single-ended polyalkoxy groups.

[0032] In summary, the preparation method of this invention can yield linear polysiloxanes with single-terminated polyalkoxy groups, and the reaction equation is as follows:

[0033]

[0034] in:

[0035] R 1 R 2 They can be the same or different, and can be methyl, vinyl, phenyl, or trifluoropropyl, independently of each other;

[0036] X is selected from methoxy, ethoxy, and propoxy;

[0037] M = Na, K, Li (metallic elements);

[0038] R is selected from ethyl, propyl, and butyl;

[0039] R 3 Selected from methyl and vinyl;

[0040] n = 3, 4, 5;

[0041] The value of a is a positive integer from 10 to 300, preferably a positive integer from 20 to 100;

[0042] m = 0 or 1.

[0043] The present invention also provides linear polysiloxanes with single-ended polyalkoxy groups prepared by the above preparation method.

[0044] According to an embodiment of the present invention, the single-ended polyalkoxy-terminated linear polysiloxane has the structure shown in Formula I:

[0045]

[0046] in:

[0047] R 1 R 2They can be the same or different, and can be methyl, vinyl, phenyl, or trifluoropropyl, independently of each other;

[0048] R 3 Selected from methyl and vinyl;

[0049] X is selected from methoxy, ethoxy, and propoxy;

[0050] The value of a is a positive integer from 10 to 300, preferably a positive integer from 20 to 100, for example 10, 20, 28, 30, 40, 50, 60, 80, 100, 200, 300;

[0051] m = 0 or 1.

[0052] The present invention also provides the application of the above preparation method in the preparation of α,ω-polyalkoxy-terminated polysiloxanes, preferably in the preparation of polyalkoxy-terminated linear polysiloxanes, and more preferably in the preparation of single-terminated polyalkoxy-terminated linear polysiloxanes.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] The method for preparing single-terminated polyalkoxy-capped linear polysiloxanes of the present invention uses inexpensive and readily available raw materials, and the production process is simple and easy to operate. Furthermore, the reaction conditions are mild, and there are no special requirements for equipment, making it easy to industrialize. The single-terminated polyalkoxy-capped linear polysiloxanes prepared by this method have high yields (greater than 99%) and controllable viscosity, making them easy to industrialize. Attached Figure Description

[0055] Figure 1 The structure obtained in Example 1 is (CH3)3Si[OSi(CH3)2]. 20 Silicon spectrum of OSi(OCH3)3 polysiloxane. Detailed Implementation

[0056] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0057] Unless otherwise stated, the raw materials and reagents used in the following examples are all commercially available products.

[0058] In the following embodiments of the present invention, the method for testing the alkoxy end-capping rate is based on NMR (nuclear magnetic resonance)... 29The ratio of the area corresponding to silane oxygen groups to the sum of the areas corresponding to silane oxygen groups and silanol groups in the (Si) spectrum; and the viscosity of linear polysiloxanes with single-ended polyalkoxy groups is determined according to the viscosity measurement method of GB / T 10247.

[0059] Example 1

[0060] In a 100L mechanical reactor, 60 kg of octamethylcyclotetrasiloxane, 5.24 kg of potassium trimethylsilanolate (Si(CH3)3OK), and 2.71 kg of diethylene glycol dimethyl ether were added sequentially. After stirring until homogeneous, the reactor temperature was raised to 80℃. After reacting for 5 hours, 2.55 kg of acetic acid and 12.34 kg of tetramethoxysilane were added. The temperature was kept constant, and the reaction was continued with stirring for 1 hour. After adding 480 g of diatomaceous earth and stirring until homogeneous, the mixture was filtered under pressure. The filtrate was transferred to a distillation vessel, heated to 120℃, and the vacuum degree was controlled at -0.06 MPa. After vacuuming for 60 minutes, a colorless and transparent polydimethylsiloxane with single-terminated trimethoxy groups was obtained, with the structural formula: (CH3)3Si[OSi(CH3)2]. 20 The performance data of OSi(OCH3)3 is shown in Table 1.

[0061] Figure 1 The structure obtained in Example 1 is (CH3)3Si[OSi(CH3)2]. 20 The silicon spectrum of the polysiloxane OSi(OCH3)3 is shown. The chemical shifts are approximately 7.5 ppm (CH3)3Si-, -22 ppm (Si(CH3)2O-), and -84 ppm (Si(OCH3)3). This indicates that the present invention successfully prepared the polysiloxane with the structural formula (CH3)3Si[OSi(CH3)2]. 20 A linear polysiloxane with single-ended polyalkoxy groups of OSi(OCH3)3.

[0062] Example 2

[0063] In a 100L mechanical reactor, 60kg of octamethylcyclotetrasiloxane, 3.28kg of sodium trimethylsilanolate (Si(CH3)3ONa), and 2.61kg of ethylene glycol dimethyl ether were added sequentially. After stirring until homogeneous, the reactor temperature was raised to 100℃ and reacted for 4 hours. Then, 2.29kg of propionic acid and 9.86kg of methyltrimethoxysilane were added, and the temperature was kept constant while stirring for another 2 hours. After adding 600g of diatomaceous earth and stirring until homogeneous, the mixture was filtered under pressure. The filtrate was transferred to a distillation vessel, heated to 110℃, and the vacuum degree was controlled at -0.08MPa. After evacuating for 100 minutes, a colorless and transparent polydimethylsiloxane with single-terminated dimethoxymethyl groups was obtained, with the structural formula: (CH3)3Si[OSi(CH3)2]. 28The performance data of OSiCH3(OCH3)2 are shown in Table 1.

[0064] Example 3

[0065] In a 100L mechanical reactor, 10 kg of 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, 50 kg of octamethylcyclotetrasiloxane, 2.56 kg of potassium trimethylsilanolate (Si(CH3)3OK), and 1.45 kg of N,N-dimethylformamide were added sequentially. After stirring until homogeneous, the reactor temperature was raised to 75℃. After reacting for 3 hours, 1.32 kg of acetic acid and 7.34 kg of vinyltrimethoxysilane were added. The temperature was maintained, and the reaction was continued for another 4 hours with stirring. 600 g of diatomaceous earth was added and stirred until homogeneous. The mixture was then filtered under pressure. The filtrate was transferred to a distillation vessel, heated to 120℃, and the vacuum degree was controlled at -0.08 MPa. After vacuuming for 120 minutes, a colorless and transparent polymethylvinylsiloxane with single-terminated dimethoxyvinyl end-capped structure was obtained, with the structural formula: (CH3)3Si[OSi(CH3)2]. 34 The performance data of [OSi(CH3)(CH=CH2)]6OSi(CH=CH2)(OCH3)2 are shown in Table 1.

[0066] Example 4

[0067] In a 100L mechanical reactor, 60kg of 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane, 628g of sodium trimethylsilanolate (Si(CH3)3ONa), and 866g of dimethyl sulfoxide were added sequentially. After stirring until homogeneous, the reactor temperature was raised to 60℃ and reacted for 2 hours. Then, 380g of acetic acid and 3.46kg of tetraethoxysilane were added, and the temperature was raised to 80℃ for end-capping reaction for 3 hours. After adding 720g of diatomaceous earth and stirring until homogeneous, the mixture was filtered under pressure. The filtrate was transferred to a distillation vessel, heated to 140℃, and the vacuum degree was controlled at -0.09MPa. After evacuating for 140 minutes, a colorless and transparent triethoxy-terminated polymethylphenylsiloxane was obtained, with the structural formula: (CH3)3Si[OSi(CH3)(C6H5)]. 80 The performance data of OSi(OCH2CH3)3 are shown in Table 1.

[0068] Example 5

[0069] In a 100L mechanical reactor, 60 kg of 1,3,5-trimethyl-1,3,5-tris(trifluoropropyl)cyclotrisiloxane, 1.23 kg of lithium trimethylsilanolate (Si(CH3)3OLi), and 3.38 kg of dioxane were added sequentially. After stirring until homogeneous, the reactor temperature was raised to 50℃ and reacted for 3 hours. Then, 1.35 kg of butyric acid and 6.85 kg of methyltriethoxysilane were added, and the temperature was raised to 100℃ for end-capping reaction for 4 hours. After adding 1000 g of diatomaceous earth and stirring until homogeneous, the mixture was filtered under pressure. The filtrate was transferred to a distillation vessel, heated to 150℃, and the vacuum degree was controlled at -0.10 MPa. After vacuuming for 150 minutes, colorless and transparent diethoxymethyl-terminated polymethyltrifluoropropylsiloxane was obtained, with the structural formula: (CH3)3Si[OSi(CH3)(CH2CH2CF3)]. 30 The performance data of OSiCH3(OCH2CH3)2 are shown in Table 1.

[0070] Comparative Example 1

[0071] In a 100L mechanical reactor, 60kg of octamethylcyclotetrasiloxane, 5.24kg of potassium trimethylsilanolate (Si(CH3)3OK), and 2.71kg of diethylene glycol dimethyl ether were added sequentially. After stirring evenly, the reactor temperature was raised to 80℃. After reacting for 5 hours, 2.46kg of acetic acid and 12.34kg of tetramethoxysilane were added. The temperature was kept constant, and the reaction was continued for 1 hour. After adding 480g of diatomaceous earth and stirring evenly, the mixture was filtered under pressure. The filtrate was transferred to a distillation vessel, heated to 120℃, and the vacuum degree was controlled at -0.06MPa. After vacuuming for 60 minutes, a colorless and transparent liquid was obtained. Nuclear magnetic resonance analysis showed that no single-terminated trimethoxy polydimethylsiloxane was obtained.

[0072] The alkoxy end-capping rate and viscosity (mPa.s) of the products prepared in Examples 1 to 5 and Comparative Example 1 of this invention are shown in Table 1 below.

[0073] Table 1

[0074]

[0075]

[0076] Note: "-" in the table indicates that no linear polysiloxanes with single-ended polyalkoxy groups were detected.

[0077] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a linear polysiloxane with single-terminated polyalkoxy groups, characterized in that, Includes the following steps: After mixing and reacting cyclosiloxane, alkaline catalyst, and accelerator, acidic substances and alkoxysilane are added simultaneously to carry out end-capping reaction to obtain the linear polysiloxane with single-terminal polyalkoxy end-capping. The alkaline catalyst is one or two of potassium trimethylsilanolate (Si(CH3)3OK), sodium trimethylsilanolate (Si(CH3)3ONa), and lithium trimethylsilanolate (Si(CH3)3OLi); The alkoxysilane is selected from at least one of tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltripropoxysilane. The acidic substance is selected from at least one of acetic acid, propionic acid, and butyric acid; The molar ratio of the acidic substance to the alkaline catalyst is 1.03 to 1.18:1; The molar ratio of the alkoxysilane added to the alkaline catalyst is 1 to 5:

1.

2. The preparation method according to claim 1, characterized in that, The cyclosiloxane is selected from one, two or more of the following: hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetraphenylcyclotetrasiloxane, and 1,3,5-trimethyl-1,3,5-tri(trifluoropropyl)cyclotrisiloxane.

3. The preparation method according to claim 1, characterized in that, The accelerator is selected from one, two or more of the following: butanone, methyl butanone, methyl isobutanone, dioxane, tetrahydrofuran, ethyl acetate, propyl acetate, butyl acetate, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, ethylene glycol diethyl ether, ethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

4. The preparation method according to any one of claims 1-3, characterized in that, The molar ratio of siloxane repeating units to alkaline catalyst in the cyclosiloxane is 10–150:

1.

5. The preparation method according to any one of claims 1-3, characterized in that, The molar ratio of the alkaline catalyst to the promoter is 1:0.1 to 5.

6. The preparation method according to any one of claims 1-3, characterized in that, The reaction of the cyclosiloxane, alkaline catalyst, and accelerator takes place at a temperature of 30–130°C and for a time of 1–6 hours.

7. The preparation method according to any one of claims 1-3, characterized in that, The end-capping reaction takes 1 to 5 hours and is carried out at a temperature of 50 to 120°C.

8. The preparation method according to any one of claims 1-3, characterized in that, The method for preparing the linear polysiloxane with single-ended polyalkoxy groups further includes a step of separating and purifying the reaction system after the end-capping reaction is completed.

9. The preparation method according to claim 8, characterized in that, Solid impurities are removed by adsorption filtration, and then excess alkoxysilane is removed by vacuum to obtain the linear polysiloxane with single-ended polyalkoxy groups.

10. The preparation method according to claim 9, characterized in that, The adsorbent used in the adsorption filtration is diatomaceous earth.

11. The preparation method according to claim 10, characterized in that, The amount of diatomaceous earth used is 0.5% to 3% of the theoretical mass of the single-terminated polyalkoxy-terminated linear polysiloxane.

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