Preparation method of polydimethylsiloxane with one end containing hydrogen and other end capped by methyl, and product and application thereof

Abstract

The invention belongs to the technical field of organic silicon materials, and relates to a preparation method of polydimethylsiloxane with one end containing hydrogen and the other end capped by methyl, and a product and application thereof. Aiming at the problems of harsh reaction conditions, tedious process, more byproducts, difficulty in separation and the like when the single-ended hydrogen-containing polysiloxane is prepared by the existing method, the invention discloses a method for preparing the single-ended hydrogen-containing polysiloxane by using a siloxane ring body, trimethylchlorosilane and reactive hydrogen-containing organochlorosilane as raw materials. The single-ended hydrogen-containing silicone oil is prepared by the steps of cation-catalyzed siloxane ring-opening polymerization reaction, hydrolysis reaction and replacement reaction, has the advantages of mild and easily-controlled reaction conditions, few side reactions, no need of further separation and purification and the like, and can be subjected to addition reaction with unsaturated bonds under the catalytic action of organic Pt to prepare the single-ended hydrogen-containing silicone oil. Therefore, various single-active-group-terminated polysiloxanes are prepared, and the method has a wide market application prospect.

Description

Technical Field

[0001] This application relates to the field of organosilicon materials technology, and in particular to a method for preparing a polydimethylsiloxane containing hydrogen at one end and methyl-terminated at the other end, as well as its products and applications. Technical Background

[0002] Hydrogen-containing silicone oils are a class of polysiloxane polymers containing Si-H bonds in their molecular chains. Under organic Pt catalysis, these Si-H bonds can undergo addition reactions with carbon-carbon unsaturated bonds in other materials (such as Si-CH=CH2, Si-C≡CH), making them highly valuable in surface treatment, organosilicon modification, and silicone rubber applications. Traditional hydrogen-containing silicone oils can be broadly classified into two categories based on the distribution of Si-H bonds: side-chain hydrogen-containing silicone oils are widely used as crosslinking agents for addition-type silicone rubbers due to their multi-point reaction characteristics, while double-terminated hydrogen-containing silicone oils are commonly used for polymer modification due to their linear structure.

[0003] From a molecular structure perspective, traditional hydrogen-containing silicone oils contain two or more Si-H bonds. When modifying the surface of materials, these bonds undergo addition reactions with two or more carbon-carbon unsaturated bonds, leading to increased polymer viscosity and even cross-linking, which seriously affects the preparation and use of polymer materials.

[0004] In this context, single-end hydrogen-containing polysiloxanes, which contain only silane-hydrogen bonds at one end of the organosilicon polymer molecular chain and no reactive functional groups at the other end, and whose polymer backbone also lacks active functional groups, exhibit unique advantages. They possess both reactivity and controllability; the single-end Si-H bond can serve as a directional reaction site, avoiding viscosity changes and excessive crosslinking issues that may arise during modification of double-end or side-chain hydrogen-containing structures. This results in greater applicability in areas such as surface modification, functional grafting, and silicone oil modification. For example, in the preparation of organic-inorganic hybrid materials, the single-end hydrogen-containing structure can bond to the target substrate surface through specific chemical reaction sites, forming a monolayer interface and significantly improving the compatibility of the composite material. In the field of cosmetic additives, single-end active design can optimize the compatibility of silicone oil and organic components, reducing system instability caused by multiple active sites.

[0005] However, compared with traditional hydrogen-containing silicone oils, the synthesis and purification of single-ended hydrogen-containing silicone oils are more difficult. Traditional equilibrium methods produce more byproducts, easily generating double-ended hydrogen-containing or incompletely capped byproducts, which have similar physical and chemical properties, making separation and purification difficult. Some methods use n-butyllithium as an initiator, but its chemical properties are too reactive, with extremely strong reducing properties, and it is easily flammable in contact with water or oxidants, requiring harsh operating conditions and increasing the cost of industrial production.

[0006] Therefore, it is of great significance to explore a mild and easy method for preparing single-ended hydrogen-containing silicone oil to obtain high-purity products. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a method for preparing polydimethylsiloxane with hydrogen at one end and methyl at the other end. The reaction conditions are mild, the reaction process is easy to control, there are few reaction byproducts, the purity is high, and no further separation and purification is required.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for preparing a polydimethylsiloxane containing hydrogen at one end and methyl at the other end, comprising the following steps: (1) Using siloxane cyclic compounds and trimethylchlorosilane as raw materials, a ring-opening polymerization reaction is carried out under the action of a cationic catalyst to generate a single-terminal chlorinated polysiloxane; (2) Hydrolyze a single-terminal chlorinated polysiloxane to obtain a single-terminal hydroxyl-containing polysiloxane; (3) Prepare single-ended hydrogen-containing polysiloxanes by substitution reaction of organochlorosilanes containing active hydrogen with single-ended hydroxyl-containing polysiloxanes.

[0009] Preferably, the single-ended hydrogen-containing polysiloxane has the chemical structural formula shown in (I), where n≥5; .

[0010] Preferably, in step (1), the siloxane cyclic body is selected from at least one of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecylcyclohexasiloxane, or a mixture of dimethylcyclosiloxanes (DMC), wherein the DMC is a mixture of dimethylcyclosiloxanes composed of cyclic siloxanes such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and decamethylcyclopentasiloxane and linear siloxanes with low degree of polymerization. More preferably, the siloxane cyclic body is selected from octamethylcyclotetrasiloxane.

[0011] Preferably, in step (1), the amount of trimethylchlorosilane used is 5%-20% of the mass of the cyclosiloxane, and more preferably, the amount of trimethylchlorosilane used is 10%-15% of the mass of the cyclosiloxane.

[0012] Preferably, in step (1), the cationic catalyst is selected from at least one of FeCl3, AlCl3, ZnCl2 or their corresponding hydrates; more preferably, the cationic catalyst is FeCl3 or its hydrate. Preferably, the amount of the cationic catalyst is 0.1% to 1% of the mass of the siloxane cyclic compound; more preferably, the amount of the cationic catalyst is 0.3% to 0.7% of the mass of octamethylcyclotetrasiloxane. Preferably, the cationic catalyst participates in the reaction in a corresponding aqueous solution. More preferably, the mass concentration of the cationic catalyst aqueous solution is 10%-80%, and more preferably, the concentration is 50%-70%. By employing a cationic catalyst and combining it with appropriate conditions and reaction conditions, this invention effectively improves the reaction yield and product purity in step 1 compared to existing related technologies, further enhancing reaction efficiency and production capacity, resulting in higher economic value. Simultaneously, it lays a solid foundation for subsequent reactions.

[0013] Preferably, in step (1), the reaction conditions are to keep warm at 30℃-60℃ for 5-12 hours.

[0014] Preferably, in step (1), after the reaction is completed, post-treatment is performed, specifically, after the reaction is completed, activated carbon is added for decolorization, filtration, heating and depressurization to remove small molecules, and after treatment, a single-terminal chlorine-capped polysiloxane is obtained. Preferably, the amount of activated carbon used is 1% to 10% of the mass of the siloxane cyclic compound; more preferably, the amount of activated carbon used is 3% to 7% of the mass of octamethylcyclotetrasiloxane. Preferably, the temperature range for removing small molecules is 90-180℃, and more preferably, the temperature range for removing small molecules is 120-160℃.

[0015] Preferably, the reaction in step (1) is carried out under an inert atmosphere.

[0016] Preferably, in step (2), the hydrolysis reaction is carried out using a saturated sodium bicarbonate aqueous solution; more preferably, the single-terminal chlorinated polysiloxane is dissolved in a solvent, and a saturated sodium bicarbonate aqueous solution is added under stirring to carry out the hydrolysis reaction. Preferably, the solvent is at least one of toluene and cyclohexane, more preferably toluene, and even more preferably, the amount of solvent used is 30%-200% of the mass of the single-terminal chlorinated polysiloxane, and even more preferably, the amount of toluene solution used is 50%-150% of the mass of the single-terminal chlorinated polysiloxane. Preferably, the stirring speed is 100-400 rpm; Preferably, the amount of the saturated sodium bicarbonate aqueous solution is 20%-150% of the mass of the single-terminated chlorinated polysiloxane; more preferably, the amount of the saturated sodium bicarbonate aqueous solution is 40%-120% of the mass of the single-terminated chlorinated polysiloxane. Preferably, a saturated sodium bicarbonate aqueous solution is slowly added dropwise to the system; more preferably, the temperature of the reaction system is maintained at 15°C-20°C during the dropwise addition process.

[0017] Preferably, in step (2), the hydrolysis reaction temperature is 15℃-20℃ and the hydrolysis reaction time is 1-5h.

[0018] Preferably, in step (3), the organochlorosilane containing active hydrogen is dimethylchlorosilane. More preferably, the mass ratio of the single-ended hydroxyl-containing polysiloxane to the organochlorosilane is 1:0.05 to 0.1. More preferably, the mass ratio of the single-ended hydroxyl-containing polysiloxane to the dimethylchlorosilane is 1:0.06 to 0.08.

[0019] Preferably, in step (3), the solution after the hydrolysis reaction in step (2) is slowly added dropwise to the organochlorosilane containing active hydrogen; more preferably, the temperature of the reaction system is maintained at 5℃-15℃ during the dropwise addition process.

[0020] Preferably, in step (3), the reaction temperature is 5℃-15℃ and the reaction time is 8-12h.

[0021] Preferably, in step (3), after the reaction is completed, a post-processing is performed, specifically, the small molecules are removed by reducing the pressure and heating under an inert atmosphere, and after cooling, a polydimethylsiloxane with hydrogen at one end and methyl at the other end is obtained; more preferably, the temperature range for removing the small molecules is 90-180℃, and even more preferably, the temperature range for removing the small molecules is 120-160℃.

[0022] Preferably, the polydimethylsiloxane with one end containing hydrogen and the other end capped with methyl is prepared by a three-step method: (1) Add the siloxane cyclic compound, the aqueous solution of the cationic catalyst and trimethylchlorosilane to the reactor, and raise the temperature to 30-60℃ and keep it for 5-12 hours under stirring. After the reaction is completed, add a certain amount of activated carbon for decolorization, filtration, and removal of small molecules by raising the temperature and reducing the pressure. After treatment, a single-terminal chlorine-capped polysiloxane is obtained. The reaction is carried out in an inert atmosphere. (2) Dissolve the above-mentioned single-terminal chlorine-capped polysiloxane in a certain amount of toluene solution, and slowly add saturated sodium bicarbonate aqueous solution while stirring. During the addition process, maintain the reaction temperature at 15-20℃. After the addition is completed, react for 1-5 hours in this temperature range. After separation and filtration, a single-terminal hydroxyl-capped polysiloxane toluene solution is obtained. (3) The above-mentioned polysiloxane toluene solution with single-hydroxyl end capping is slowly added dropwise to dimethylchlorosilane, and the temperature is maintained at 5-15℃ throughout the process. After the addition is completed, the mixture is stirred for 8-12 hours in this temperature range. Then, the small molecules are removed by reducing the temperature to 90-180℃ under the protection of an inert atmosphere. After cooling, polydimethylsiloxane with hydrogen at one end and methyl at the other end is obtained.

[0023] Preferably, the inert atmosphere of the present invention is selected from at least one of nitrogen, helium, and argon.

[0024] The present invention also provides a polydimethylsiloxane with one end containing hydrogen and the other end capped with methyl by any of the above preparation methods.

[0025] The present invention also provides the application of polydimethylsiloxanes prepared by any of the above preparation methods, which are hydrogen-containing at one end and methyl-terminated at the other end, in the field of hydrogen-containing silicone oil applications.

[0026] Preferably, the application includes the addition reaction of a polydimethylsiloxane with hydrogen at one end and methyl at the other end to an unsaturated bond under the catalysis of organic Pt, to prepare various polysiloxanes with single active group-terminated ends.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses cyclic siloxanes such as octamethylcyclotetrasiloxane, trimethylchlorosilane, and organochlorosilanes such as dimethylchlorosilane as raw materials to prepare single-ended hydrogen-containing polysiloxanes through cationic-catalyzed ring-opening polymerization of octamethylcyclotetrasiloxane, hydrolysis, and displacement reactions. It produces few byproducts, eliminates the need for further separation and purification, and yields high-purity single-ended hydrogen-containing polysiloxanes. The reaction conditions are mild, the process is simple, and the raw materials are readily available, making it suitable for industrial production and possessing broad market application prospects. Attached Figure Description

[0028] Figure 1 This is a schematic diagram showing the reaction results of a single-ended hydrogen-containing polydimethylsiloxane sample with polyvinyl silicone oil in Example 1. Figure 2 This is a schematic diagram showing the reaction results of the double-ended hydrogen-containing silicone oil sample of Comparative Example 1 with polyvinyl silicone oil. Detailed Implementation

[0029] To better clarify and understand the objectives, process solutions, and advantages of this invention, the technical solutions and implementation methods of this invention will be further described clearly, completely, and in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the embodiments described in this invention are implemented under the premise of the technical solutions of this invention, providing detailed implementation methods and specific operating procedures, but are only some embodiments of this invention, not all embodiments. The specific implementation methods described are limited to illustrating and explaining this invention and do not limit this invention. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0030] Unless otherwise specified, the experimental methods and conditions used in the embodiments of this invention are conventional methods and conditions. The materials, reagents, instruments, and equipment used in the embodiments, unless otherwise specified, are all conventional substances or equipment known to those skilled in the art and can be obtained commercially or prepared by conventional methods. The reaction conditions described in the invention's content can all achieve the stated reactions and obtain the desired products. Due to space limitations, some embodiments are listed below to further illustrate the advantages of the technical solution of this invention. Example 1

[0031] (1) Preparation of single-terminated chlorinated polysiloxane: 300 g of octamethylcyclotetrasiloxane, 30 g of trimethylchlorosilane and 1 g of ferric chloride aqueous solution were added to a 500 ml four-necked reaction flask. The reaction was stopped by stirring at 50 °C for 7 h under a nitrogen atmosphere. Then, 20 g of activated carbon was added and stirred at room temperature for 2 h for decolorization. The liquid was filtered under reduced pressure to obtain a colorless and transparent liquid. Small molecules were removed under vacuum at 140 °C to obtain 243.3 g of single-terminated chlorinated polysiloxane, with a yield of 73.7%.

[0032] (2) Preparation of polysiloxane with one hydroxyl end and one methyl end: Add 150g of the previously prepared single-chloro-terminated polysiloxane to a 500ml four-necked reaction flask and add 150g of toluene to dissolve it. Slowly add 120g of saturated sodium bicarbonate aqueous solution, control the dropping rate, and ensure that the internal temperature is within the range of 15-20℃. After the addition is completed, continue stirring at 18℃ for 2h. Then transfer the mixed solution to a separatory funnel and let it stand. Separate the upper layer to obtain a toluene solution with one hydroxyl end.

[0033] (3) Preparation of polydimethylsiloxane with hydrogen at one end and methyl at the other: 8g of dimethylchlorosilane was added to a 500ml reaction flask, the temperature was lowered to 10℃, and 200g of the previously prepared single-hydroxyl-terminated toluene solution was slowly added dropwise. After the addition was complete, the mixture was stirred at 10℃ for 10h, and then the temperature was gradually increased to 140℃ to remove small molecules. After cooling, polydimethylsiloxane with hydrogen at one end and methyl at the other was obtained, with a final yield of 71.1% and a hydrogen content of 0.05%. The hydrogen content was determined by the exhaust method, where the active hydrogen at the end was converted into hydrogen gas, the volume of hydrogen gas was measured, and the hydrogen content was calculated.

[0034] The polydimethylsiloxane sample prepared in Example 1, with one end containing hydrogen and the other end methyl-terminated, was mixed with polyvinyl silicone oil at a mass ratio of 10:1. 10 ppm Pt catalyst was added, and the mixture was stirred and heated to 80°C to carry out a hydrosilylation reaction. After 2 hours of reaction, the viscosity of the product increased, but no cross-linking occurred. Figure 1 As shown, the prepared sample contains virtually no double-ended hydrogen-capped polysiloxanes. Example 2

[0035] (1) Preparation of polysiloxane with one end containing chlorine and the other end methyl: In a 500ml four-necked reaction flask, 300g of octamethylcyclotetrasiloxane, 30g of trimethylchlorosilane and 1g of aluminum trichloride aqueous solution were added. The reaction was stopped by stirring at 50℃ for 7h under nitrogen atmosphere. Then, 20g of activated carbon was added and stirred at room temperature for 2h for decolorization. The liquid was filtered under reduced pressure to obtain a colorless and transparent liquid. Small molecules were removed under vacuum at 140℃ to obtain 233.8g of polysiloxane with one end chlorine and the yield was 70.8%.

[0036] (2) Preparation of polysiloxane with one hydroxyl end and one methyl end: Add 150g of the previously prepared single-chloro-terminated polysiloxane to a 500ml four-necked reaction flask and add 150g of toluene to dissolve it. Slowly add 120g of saturated sodium bicarbonate aqueous solution, control the dropping rate, and ensure that the internal temperature is within the range of 15-20℃. After the addition is completed, continue stirring at 18℃ for 2h. Then transfer the mixed solution to a separatory funnel and let it stand. Separate the upper layer to obtain a toluene solution with one hydroxyl end.

[0037] (3) Preparation of polydimethylsiloxane with hydrogen at one end and methyl at the other end: 8g of dimethylchlorosilane was added to a 500ml reaction flask, the temperature was lowered to 10℃, and 200g of the previously prepared toluene solution with hydroxyl end capping was slowly added dropwise. After the addition was completed, the mixture was stirred at 10℃ for 10h, and then the temperature was gradually raised to 140℃ to remove small molecules. After cooling, polydimethylsiloxane with hydrogen at one end and methyl at the other end was obtained. The final yield was 68.6%, and the hydrogen content was 0.05%.

[0038] The polydimethylsiloxane sample with hydrogen at one end and methyl at the other end prepared in Example 2 was mixed with polyvinyl silicone oil at a mass ratio of 10:1. 10 ppm Pt catalyst was added, and the mixture was stirred and heated to 80°C to carry out a hydrosilylation reaction. After 2 hours of reaction, the viscosity of the product increased, but no cross-linking phenomenon was observed, indicating that the prepared sample basically did not contain double-ended hydrogen-capped polysiloxane. Example 3

[0039] (1) Preparation of polysiloxane with one end containing chlorine and the other end containing methyl: In a 500ml four-necked reaction flask, 300g of octamethylcyclotetrasiloxane, 20g of trimethylchlorosilane and 1g of ferric chloride aqueous solution were added. The reaction was stopped by stirring at 50℃ for 7h under a nitrogen atmosphere. Then, 20g of activated carbon was added and stirred at room temperature for 2h for decolorization. The liquid was filtered under reduced pressure to obtain a colorless and transparent liquid. Small molecules were removed under vacuum at 140℃ to obtain 249.1g of polysiloxane with one end containing chlorine and the other end containing methyl, with a yield of 77.8%.

[0040] (2) Preparation of polysiloxane with one hydroxyl end and one methyl end: Add 150g of the previously prepared single-chloro-terminated polysiloxane to a 500ml four-necked reaction flask and add 150g of toluene to dissolve it. Slowly add 120g of saturated sodium bicarbonate aqueous solution, control the dropping rate, and ensure that the internal temperature is within the range of 15-20℃. After the addition is completed, continue stirring at 18℃ for 2h. Then transfer the mixed solution to a separatory funnel and let it stand. Separate the upper layer to obtain a toluene solution with one hydroxyl end.

[0041] (3) Preparation of polydimethylsiloxane with hydrogen at one end and methyl at the other end: 7g of dimethylchlorosilane was added to a 500ml reaction flask, the temperature was lowered to 10℃, and 200g of the previously prepared toluene solution with hydroxyl end capping was slowly added dropwise. After the addition was completed, the mixture was stirred at 10℃ for 10h, and then the temperature was gradually raised to 140℃ to remove small molecules. After cooling, polydimethylsiloxane with hydrogen at one end and methyl at the other end was obtained. The final yield was 73.1%, and the hydrogen content was 0.04%.

[0042] The polydimethylsiloxane sample with hydrogen at one end and methyl at the other end prepared in Example 3 was mixed with polyvinyl silicone oil at a mass ratio of 10:1, 10 ppm Pt catalyst was added, and the mixture was stirred and heated to 80°C to carry out a hydrosilylation reaction. After 2 hours of reaction, the viscosity of the product increased, but no cross-linking phenomenon was observed, indicating that the prepared sample basically did not contain double-end hydrogen-capped polysiloxane. Example 4

[0043] (1) Preparation of polysiloxane with one end containing chlorine and the other end containing methyl: In a 500ml four-necked reaction flask, 350g of decamethylcyclopentasiloxane, 20g of trimethylchlorosilane and 1g of ferric chloride aqueous solution were added. The reaction was stopped by stirring at 30℃ for 12h under nitrogen atmosphere. Then, 20g of activated carbon was added and stirred at room temperature for 2h for decolorization. The liquid was filtered under reduced pressure to obtain a colorless and transparent liquid. Small molecules were removed under vacuum at 140℃ to obtain 260.1g of polysiloxane with one end containing chlorine and the other end containing methyl, with a yield of 70.3%.

[0044] (2) Preparation of polysiloxane with one hydroxyl end and one methyl end: Add 150g of the previously prepared single-chloro-terminated polysiloxane to a 500ml four-necked reaction flask and add 150g of toluene to dissolve it. Slowly add 120g of saturated sodium bicarbonate aqueous solution, control the dropping rate, and ensure that the internal temperature is within the range of 15-20℃. After the addition is completed, continue stirring at 18℃ for 2h. Then transfer the mixed solution to a separatory funnel and let it stand. Separate the upper layer to obtain a toluene solution with one hydroxyl end.

[0045] (3) Preparation of polydimethylsiloxane with hydrogen at one end and methyl at the other end: 7g of dimethylchlorosilane was added to a 500ml reaction flask, the temperature was lowered to 10℃, and 200g of the previously prepared toluene solution with hydroxyl end capping was slowly added dropwise. After the addition was completed, the mixture was stirred at 5℃ for 12h, and then the temperature was gradually raised to 140℃ to remove small molecules. After cooling, polydimethylsiloxane with hydrogen at one end and methyl at the other end was obtained. The final yield was 66.3%, and the hydrogen content was 0.03%.

[0046] The polydimethylsiloxane sample with hydrogen at one end and methyl at the other end prepared in this embodiment was mixed with polyvinyl silicone oil at a mass ratio of 10:1, 10 ppm Pt catalyst was added, and the mixture was stirred and heated to 80°C to carry out a hydrosilylation reaction. After 2 hours of reaction, the viscosity of the product increased, but no cross-linking phenomenon was observed, indicating that the prepared sample basically did not contain double-end hydrogen-capped polysiloxane. Comparative Example 1

[0047] A commercially available hydrogen-containing dual-end silicone oil (Zhejiang Runhe Organosilicon, a dual-end silicone oil) with a hydrogen content of 0.04% was mixed with polyvinyl silicone oil at a mass ratio of 10:1. 10 ppm Pt catalyst was added, and the mixture was stirred and heated to 80°C to carry out a hydrosilylation reaction. After 30 minutes of reaction, the viscosity of the product gradually increased and cross-linking phenomena appeared. Figure 2 As shown. Comparative Example 2

[0048] Based on Example 1, the aqueous solution of ferric chloride was replaced with solid ferric chloride, while everything else remained the same as in Example 1. The hydrogen content of the product was measured to be 0.04%, and the final yield was 22.1%. The sample obtained in this example was subjected to a hydrosilylation reaction with polyvinyl silicone oil. After 2 hours of reaction, the viscosity of the product gradually increased, but no cross-linking phenomenon was observed. Comparative Example 3

[0049] Based on Example 1, trimethylchlorosilane was replaced with dimethyldichlorosilane, while everything else remained the same as in Example 1. The hydrogen content of the product was measured to be 0.08%, and the final yield was 70.1%. The sample obtained in this example was subjected to a hydrosilylation reaction with polyvinyl silicone oil. After 30 minutes of reaction, the viscosity of the product gradually increased and cross-linking occurred. Comparative Example 4

[0050] In the second step of Example 1, the single-terminated chlorinated polysiloxane was not dissolved in toluene but reacted directly with a saturated aqueous solution of sodium bicarbonate, with all other conditions remaining the same. The hydrogen content of the product was found to be 0%. The sample obtained in this example was subjected to a hydrosilylation reaction with polyvinyl silicone oil, and the viscosity of the product did not change after 2 hours of reaction.

[0051] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

Claims

1. A method for preparing a polydimethylsiloxane capped with hydrogen at one end and methyl at the other end, comprising the following steps: (1) ring-opening polymerization of a siloxane ring and trimethylchlorosilane as raw materials in the presence of a cationic catalyst to produce a monochloro-terminated polysiloxane; (2) hydrolysis of the monochloro-terminated polysiloxane to obtain a monohydroxyl-terminated polysiloxane; (3) substitution reaction of the monohydroxyl-terminated polysiloxane with an organic chlorosilane containing active hydrogen to produce a monohydrogen-terminated polysiloxane.

2. The process for preparing a polydimethylsiloxane terminated with hydrogen at one end and with methyl at the other end according to claim 1, characterized in that, The siloxane ring in step (1) is at least one of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, or a mixture of dimethylcyclosiloxanes; and / or, the amount of trimethylchlorosilane used in step (1) is 5-20% of the mass of the siloxane ring; and / or, the cationic catalyst used in step (1) is at least one of FeCl3, AlCl3, ZnCl2, or their corresponding hydrates; the amount of cationic catalyst used is 0.1-1% of the mass of the siloxane ring; and / or, the reaction conditions in step (1) are incubation at a temperature of 30-60°C for 5-12 h.

3. The process for producing a polydimethylsiloxane terminated with hydrogen at one end and with a methyl group at the other end according to claim 1, characterized by, The hydrolysis reaction in step (2) is carried out using saturated aqueous sodium bicarbonate; the hydrolysis reaction temperature is 15-20°C, and the hydrolysis reaction time is 1-5 h.

4. The process for producing a polydimethylsiloxane terminated with hydrogen at one end and with methyl at the other end according to claim 3, characterized in that, The hydrolysis reaction is carried out by dissolving the monochloro-terminated polysiloxane in a solvent, adding saturated aqueous sodium bicarbonate under stirring, and then carrying out the hydrolysis reaction; the solvent is at least one of toluene and cyclohexane, and the amount of solvent used is 30-200% of the mass of the monochloro-terminated polysiloxane; the amount of saturated aqueous sodium bicarbonate used is 20-150% of the mass of the monochloro-terminated polysiloxane.

5. The method of preparing a polydimethylsiloxane capped at one end with hydrogen and at the other end with a methyl group according to claim 1, characterized in that, The organic chlorosilane containing active hydrogen in step (3) is dimethylchlorosilane; the mass ratio of monohydroxyl-terminated polysiloxane to organic chlorosilane is 1:0.05-0.

1.

6. The method of preparing a polydimethylsiloxane capped at one end with hydrogen and at the other end with a methyl group according to claim 1, characterized in that, The reaction temperature in step (3) is 5-15°C, and the reaction time is 8-12 h.

7. The process for producing a polydimethylsiloxane capped with hydrogen at one end and with a methyl group at the other end according to claim 1, characterized by, The method comprises the following steps: (1) adding a siloxane ring, an aqueous solution of a cationic catalyst, and trimethylchlorosilane to a reactor, stirring to raise the temperature to 30-60°C, and incubating for 5-12 h; after the reaction is completed, adding activated carbon for decolorization, filtering, and removing small molecules under elevated temperature and reduced pressure to obtain a monochloro-terminated polysiloxane; the whole reaction process is carried out in an inert atmosphere; (2) dissolving the monochloro-terminated polysiloxane in a certain amount of toluene solution, slowly adding saturated aqueous sodium bicarbonate under stirring, maintaining the reaction temperature at 15-20°C during the addition process, and continuing to react at this temperature interval for 1-5 h after the addition is completed; after separation and filtration, a monohydroxyl-terminated polysiloxane toluene solution is obtained; (3) slowly adding the monohydroxyl-terminated polysiloxane toluene solution to dimethylchlorosilane, maintaining the temperature at 5-15°C throughout the process, continuing to stir at this temperature interval for 8-12 h after the addition is completed, and then removing small molecules under reduced pressure and elevated temperature in an inert atmosphere to obtain a polydimethylsiloxane capped with hydrogen at one end and methyl at the other end.

8. Process for the preparation of a polydimethylsiloxane terminated at one end with hydrogen and at the other end with a methyl group according to any one of claims 1 to 7, characterized in that, The polydimethylsiloxane capped with hydrogen at one end and methyl at the other end has a chemical structural formula as shown in (I), wherein n≥5. 。 9. The polydimethylsiloxane capped with hydrogen at one end and methyl at the other end prepared by the preparation method according to any one of claims 1-8.

10. The polydimethylsiloxane capped with hydrogen at one end and methyl at the other end prepared by the preparation method according to any one of claims 1-8, and application thereof in the field of hydrogen-containing silicone oil.

Images