A chloro-terminated polydimethylsiloxane and a method for preparing the same

Abstract

The present application relates to the technical field of organic silicon material, and specifically provides a chloro-terminated polydimethylsiloxane and a preparation method thereof.The preparation method comprises the following steps: S100, mixing vinyl-terminated polydimethylsiloxane with chlorodimethylsilane under an inert atmosphere to obtain a mixture; S200, adding a platinum-based catalyst in the mixture to react, to obtain a crude product; and S300, removing the platinum-based catalyst from the crude product to obtain the chloro-terminated polydimethylsiloxane.The chloro-terminated polydimethylsiloxane prepared by the present application has high reactivity of the terminal Si-Cl functional group, can be quickly and controllably introduced with silanol, alkoxy or covalent Si-O-Si bond with a substrate surface through hydrolysis, alcohol exchange or condensation with a hydroxyl-containing surface under mild conditions, and expands the functionalization approach and application scenarios of polydimethylsiloxane.

Description

Technical Field

[0001] This invention relates to the field of siloxane polymer technology, and more specifically, this invention provides a chlorine-terminated polydimethylsiloxane and its preparation method. Background Technology

[0002] Polydimethylsiloxane (PDMS) is widely used in sealing, bonding, elastomers, coatings, lubrication, and microfluidics due to its low surface energy, good thermal stability, flexibility, and biocompatibility. Terminal functionalization of PDMS is key to achieving further chemical modification, coupling, and crosslinking. Chlorine-terminated PDMS, as an active terminal structure, can directly participate in nucleophilic or hydrolytic condensation reactions, offering unique advantages in silane coupling agent chemistry and surface immobilization.

[0003] Common end-functionalization methods in the prior art include: esterification / substitution of hydroxyl-terminated PDMS, hydrophobic treatment of allyl / vinyl ends, or direct introduction of end groups using chlorosilanes containing functional groups. However, these methods often suffer from problems such as difficulty in process control, numerous side reactions, difficulty in removing catalyst residues, and insufficient yield or end-saturation.

[0004] Therefore, a method for preparing chlorine-terminated polydimethylsiloxane with high selectivity, high end-conversion rate, easy purification, and industrial scalability is needed. Summary of the Invention

[0005] This invention provides a chlorine-terminated polydimethylsiloxane and its preparation method. Due to the high reactivity of its terminal Si-Cl functional groups, it can rapidly and controllably introduce silanols, alkoxy groups, or form covalent Si-O-Si bonds with the substrate surface under mild conditions through reactions such as hydrolysis, alcohol exchange, or condensation with hydroxyl-containing surfaces. This expands the functionalization pathways and application scenarios of polydimethylsiloxane. Covalent grafting with inorganic fillers or matrix surfaces can significantly improve the interfacial bonding strength, durability, and mechanical properties of composite materials. As a crosslinking / curing precursor, it can construct a dense silicon-oxygen network through condensation reactions to prepare adhesives, coatings, sealants, and other functional siloxane materials. The preparation method uses platinum-catalyzed addition, which has high end-group introduction efficiency, a mild process, and is easy to scale up industrially.

[0006] This invention provides a method for preparing chlorine-terminated polydimethylsiloxane, the method comprising the following steps: S100, mixing vinyl-terminated polydimethylsiloxane and chlorinated dimethylsilane under an inert atmosphere to obtain a mixture; S200, adding a platinum-based catalyst to the mixture to react and obtain a crude product; S300, removing the platinum-based catalyst from the crude product to obtain chlorine-terminated polydimethylsiloxane.

[0007] In any of the above technical solutions, in step S100, the molar ratio of terminal vinyl groups of chlorodimethylsilane to vinyl-terminated polydimethylsiloxane is 1:(1.01-1.30).

[0008] In any of the above technical solutions, in step S100, chlorodimethylsilane includes one or more of chlorodimethylsilane, methyldichlorosilane, and trichlorosilane.

[0009] In any of the above technical solutions, step S200 specifically includes: S201, adding a first part of platinum-based catalyst, accounting for 10-30% of the total amount of platinum-based catalyst, to the mixture at 40-50℃ and stirring the reaction; S202, after the reaction in step S201 has stabilized, adding the remaining platinum-based catalyst and raising the reaction temperature to 70-90℃ until the reaction is complete and the crude product is obtained.

[0010] In any of the above technical solutions, the platinum-based catalyst is supported on a support; the support includes one or more of silica, alumina, activated carbon, carbon nanotubes, and polymer microspheres.

[0011] In any of the above technical solutions, after the reaction in step S200 is completed and before step S300 begins, the method further includes adding a terminator, which includes one or more of nitrogen-containing compounds, organophosphorus compounds, and ene-yne ​​compounds.

[0012] In any of the above technical solutions, the platinum-based catalyst is removed in step S300 using a composite adsorption method, which includes primary adsorption and secondary adsorption; primary adsorption uses diatomaceous earth or activated carbon; and secondary adsorption uses amine compounds.

[0013] In any of the above technical solutions, the amine compound includes one or more of polyamine resin, triethylamine, and ethanolamine.

[0014] In any of the above technical solutions, the inert atmosphere includes either nitrogen or argon.

[0015] The present invention also provides a chlorine-terminated polydimethylsiloxane, which is prepared by any of the preparation methods described above. Therefore, it includes the beneficial effects of any of the above-described technical solutions, which will not be elaborated further here.

[0016] The technical effects that can be achieved by adopting the technical solution of the present invention are as follows: 1. By using a slightly excess ratio of chlorosilane to vinyl-PDMS in step S100 and implementing platinum-catalyzed Chalk-Harrod addition in steps S200, a high conversion rate of vinyl to chloro-terminated PDMS can be achieved under mild conditions, while significantly suppressing crosslinking and side reactions. This results in chloro-terminated PDMS with high end-group saturation and linear structure, reducing unreacted vinyl groups and byproducts, and improving product consistency and downstream functionalization efficiency. 2. The purification route adopts a supported platinum catalyst combined with composite adsorption, and is supplemented by a terminator passivation strategy. This makes the catalyst both highly efficient in catalysis and easy for solid-liquid separation and adsorption removal, which can meet the metal limits of sensitive applications such as electronics, optics and medical. The process is simple to operate, facilitates catalyst recovery and waste treatment, and is easy for industrial scale-up and quality control. 3. The obtained chlorine-terminated PDMS retains highly reactive Si-Cl end groups, which can rapidly and controllably introduce Si-OH, Si-OR, or form Si-O-Si bonds through hydrolysis, alcohol exchange, or condensation with hydroxyl-containing substrates. This enables surface grafting, crosslinking regulation, or integration into block / graft copolymer systems, significantly expanding the applicability of PDMS in interface modification, composite materials, adhesives, sealants, coatings, and functional elastomers. Detailed Implementation

[0017] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0018] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0019] To make the above-mentioned objectives, features and advantages of this aspect more apparent and understandable, specific embodiments of this aspect are described in detail below.

[0020] PDMS, due to its unique low-temperature flexibility, high permeability, excellent weather resistance, electrical insulation, and biocompatibility, has been widely used in sealants, adhesives, coatings, medical devices, and soft materials. Its performance largely depends on the functional groups at the ends of its molecular chains, which determine its reactivity and ability to interact with other materials. Traditional PDMS end-functionalization methods mainly involve end-capping with hydroxyl, alkoxy, or vinyl groups. Chlorine-terminated polydimethylsiloxane, as a highly reactive functional silicone oil, possesses highly electrophilic Si-Cl bonds at its ends. Under mild conditions, it can undergo rapid and controlled hydrolysis, alcoholysis, or aminolysis reactions with compounds containing active hydrogen, such as water, alcohols, and amines, readily transforming into silanol end groups, alkoxy end groups, or forming strong Si-O-Si covalent bonds with other hydroxylated surfaces. This characteristic makes it highly promising for interface modification, composite material reinforcement, and as a precursor for constructing functional siloxane materials.

[0021] However, existing methods for preparing chlorine-terminated polydimethylsiloxanes have significant limitations. Classical methods typically involve polymerization and end-capping with monomers such as highly reactive, water- and air-sensitive dichlorodimethylsilane, or chlorination of hydroxyl-terminated PDMS using highly toxic and corrosive reagents such as chlorine. However, these methods often suffer from difficulties in process control, numerous side reactions, difficulty in removing catalyst residues, and insufficient yield or end-cap saturation.

[0022] Therefore, a method for preparing chlorine-terminated polydimethylsiloxanes with high selectivity, high end-group conversion rate, easy purification, and industrial scalability is needed. This embodiment provides a method for preparing chlorine-terminated polydimethylsiloxanes. Due to the high reactivity of its terminal Si-Cl functional groups, silanols, alkoxy groups, or covalent Si-O-Si bonds with the substrate surface can be rapidly and controllably introduced under mild conditions through reactions such as hydrolysis, alcohol exchange, or condensation with hydroxyl-containing surfaces. This expands the functionalization pathways and application scenarios of polydimethylsiloxanes. Covalent grafting with inorganic fillers or matrix surfaces can significantly improve the interfacial bonding strength, durability, and mechanical properties of composite materials. As a crosslinking / curing precursor, it can construct a dense silicon-oxygen network through condensation reactions to prepare adhesives, coatings, sealants, and other functional siloxane materials. The method employs platinum-catalyzed addition, which features high end-group introduction efficiency, a mild process, and ease of industrial scale-up.

[0023] Specifically, this embodiment provides a method for preparing chlorine-terminated polydimethylsiloxane, including the following steps: S100. Under an inert atmosphere, vinyl-terminated polydimethylsiloxane and chlorodimethylsilane are mixed to obtain a mixture. S200, a platinum-based catalyst is added to the mixture to carry out the reaction, and the crude product is obtained; S300: After removing the platinum-based catalyst from the crude product, chlorine-terminated polydimethylsiloxane is obtained.

[0024] Preferably, in step S100, vinyl-terminated polydimethylsiloxane and chlorodimethylsilane are mixed under an inert atmosphere to lay the foundation for the subsequent platinum-catalyzed addition reaction, thereby achieving the controllable introduction of terminal functional groups. The chlorosilane used for the addition must contain Si-H bonds. Under platinum catalysis, Si-H adds to C=C according to the Chalk–Harrod mechanism. The platinum catalyst is first activated with Si-H, and the vinyl group inserts into the Pt-H or Pt-Si bond. Subsequently, reductive elimination occurs to generate new Si-C bonds and attach the chlorinated silicon group to the polymer end, completing the conversion from vinyl to chlorinated end-capped.

[0025] Furthermore, the molar ratio of terminal vinyl groups of dichlorosilane to vinyl-terminated polydimethylsiloxane is 1:(1.01-1.30). Using a slight excess of dichlorosilane to vinyl groups can drive the addition reaction toward complete end-group closure, thereby improving the conversion rate of end-substitution. The lower limit ensures close stoichiometry to prevent excessive reagent from burdening subsequent purification; the upper limit restricts excessive excess to avoid crosslinking / branching of silanes containing polychlorinated sites under conditions of moisture or side reactions. Excessive dichlorosilane increases wastewater treatment costs and the risk of residual volatile reagents.

[0026] Furthermore, the chlorodimethylsilane includes one or more of dichlorodimethylsilane, methyldichlorosilane, and trichlorosilane, and the number average molecular weight of the vinyl-terminated polydimethylsiloxane is between 500 and 50,000 g·mol⁻¹. -1 Within this range, the chain concentration and molar number of end groups per unit mass are sufficient to ensure a high end-group conversion rate in platinum-catalyzed addition reactions, facilitating the efficient introduction of chlorine end groups under mild conditions. Simultaneously, this upper molecular weight limit avoids excessive system viscosity leading to difficulties in mixing, mass transfer, and catalyst dispersion, thus simplifying stirring, heating, and subsequent catalyst removal processes. The lower limit prevents volatilization losses and low-boiling impurities caused by excessively low molecular weights. Chlorodimethylsilanes are monofunctional Si-H chlorosilanes with good stereoshikation. When participating in hydrophobic addition, they tend to undergo single-stage end-capping, making secondary cross-linking less likely. This facilitates the highly selective generation of chlorine-capped PDMS and simplifies purification. Dichloro or trichloro types exhibit stronger electron attraction than monochloro compounds, with more positively charged Si atoms, resulting in higher hydrophobic addition activity.

[0027] In addition, an inert atmosphere, including nitrogen or argon, can prevent chlorosilanes from hydrolyzing with water to produce HCl and silanols, thus preventing uncontrolled condensation and polymerization.

[0028] Preferably, step S200 specifically includes: S201. At 40-50℃, add 10-30% of the first part of the platinum-based catalyst to the mixture and stir to react; S202. After the reaction in step S201 has stabilized, add the remaining platinum-based catalyst and raise the reaction temperature to 70-90℃ until the reaction is complete and the crude product is obtained.

[0029] Preferably, in step S200, a platinum-based catalyst is introduced and catalytically added in two stages at different temperatures and times. The core function is to selectively add Si-H to the C=C terminal of the vinyl group using platinum-catalyzed Chalk-Harrod addition, forming a new Si-C terminal and introducing a chlorine-capped end group. Adding the first portion of the platinum catalyst at a lower temperature and stirring allows for mild activation of the Si-H catalyst and pre-activation of the reaction system, enabling the reaction to begin at a controlled rate. The low temperature helps suppress unnecessary side reactions, reduce exothermic reactions, and promotes system stability. After the system stabilizes, the remaining catalyst is added and the temperature is raised to 70-90°C to accelerate the reaction and improve conversion and efficiency. Furthermore, the staged addition allows for better reaction rate control, reduces catalyst poisoning or deposition, and minimizes undesirable interactions between alkyl / silane groups, thereby improving end-capping selectivity and facilitating the acquisition of a linear, low-impurity crude product.

[0030] Furthermore, supported platinum catalysts are employed. The support effectively disperses platinum particles through its high specific surface area and porous structure, enhancing the surface activity and selectivity per unit platinum and reducing catalyst dosage. Simultaneously, the catalyst exists in solid-phase microparticle form, facilitating removal via solid-liquid separation and subsequent adsorption after the reaction, significantly reducing Pt residue and simplifying the S300 purification process. The differences in supports can also be used for process optimization. For example, silica / alumina often possesses good thermal stability and mechanical strength, activated carbon / carbon nanotubes have strong adsorption capacity for organic matter, which is beneficial for capturing organic byproducts, and polymer microspheres can have their hydrophilicity / hydrophobicity and dispersibility regulated through surface functionalization.

[0031] In addition, a terminator is added at the end of S200 and before S300. The terminator includes one or more of nitrogen-containing compounds, organophosphorus compounds, and alkenyne compounds. On the one hand, the chemical passivation of the platinum surface rapidly terminates the catalytic activity, preventing uncontrollable reactions from continuing to occur during subsequent heating or operation. On the other hand, some terminators can also neutralize or capture trace amounts of acidic byproducts generated in the reaction, reducing corrosion to the products and equipment, thereby facilitating subsequent solid-liquid separation and composite adsorption removal steps.

[0032] Preferably, in step S300, a composite adsorption method is used to remove the platinum-based catalyst. Through a triple mechanism of physical retention, adsorption / complexation purification, and neutralization / capture, solid catalyst particles, organic impurities, and soluble platinum species in the reaction system are rapidly and efficiently removed, resulting in low-metal-residue, high-purity chlorine-terminated PDMS. Primary adsorption mainly relies on physical retention and pore adsorption. Diatomaceous earth, as a filter aid, can retain suspended carrier particles and improve filterability. Activated carbon, in addition to retention, can also physically adsorb reaction residues, organic byproducts, and other pollutants through its large specific surface area and microporous structure. Partially organically liganded platinum particles significantly reduce the turbidity and organic impurity content of the system; secondary adsorption removes residual soluble platinum species and trace acidic byproducts through a dual action of chemical adsorption / coordination complexation and acid-base neutralization. Amine groups can coordinate or exchange with the dissolved state of platinum, thereby fixing dissolved metals that are difficult to remove by simple filtration onto the solid-phase adsorbent; small molecule amines can also neutralize trace amounts of HCl generated in the reaction, reducing corrosion to products and equipment; polyamine resins provide recyclable and highly selective solid-phase complexation sites, facilitating the elution and recovery of platinum or regeneration of the adsorbent.

[0033] Furthermore, combining the composite adsorption in step S300 with the segmented addition of the platinum catalyst supported on a carrier in step S200 produces synergistic advantages and further enhances the purification effect. The solid-phase morphology of the carrier-supported catalyst ensures that most of the platinum exists in the form of solid particles. Segmented addition helps reduce the instantaneous peak activity of the catalyst and side reactions, thereby reducing catalyst dissolution or agglomeration. As a result, the platinum entering S300 mainly exists in a solid phase form that can be retained by primary adsorption, reducing the difficulty of subsequent treatment. For the small amount of platinum ions / coordinated platinum species dissolved due to reaction conditions or carrier characteristics, secondary amine adsorption can efficiently capture and passivate them, ensuring that the Pt residue in the final product is reduced to the low ppm level required by sensitive fields such as industry, electronics, optics, and medical. In addition, this combined process facilitates catalyst recovery, simplifies waste treatment processes, and improves product storage stability and consistency of subsequent functionalization by reducing the presence of organic impurities and acidic byproducts. Example 1

[0034] This embodiment provides a chlorine-terminated polydimethylsiloxane and its preparation method, including the following steps: S100. Under a nitrogen atmosphere, vinyl-terminated polydimethylsiloxane and dichlorosilane are mixed at a terminal vinyl molar ratio of 1:1.15 to obtain a mixture. S201. At 45°C, a first portion of platinum-based catalyst, accounting for 20% of the total amount of platinum-based catalyst, is added to the mixture and stirred to react; wherein, the platinum-based catalyst is supported on silica. S202. After the reaction in step S201 has stabilized, add the remaining platinum-based catalyst and raise the reaction temperature to 80°C. React for 2 hours until the vinyl groups are basically eliminated to obtain the crude product. After the crude product is cooled to 45°C, add ethanolamine and stir for 15 minutes. S300. After removing the platinum-based catalyst from the crude product containing ethanolamine using a composite adsorption method, diatomaceous earth is used for the first adsorption and triethylamine is used for the second adsorption to obtain chlorine-terminated polydimethylsiloxane. Example 2

[0035] This embodiment provides a chlorine-terminated polydimethylsiloxane and its preparation method, including the following steps: S100. Under an argon atmosphere, vinyl-terminated polydimethylsiloxane and dichlorosilane are mixed at a terminal vinyl molar ratio of 1:1.01 to obtain a mixture. S201. At 40°C, a first portion of platinum-based catalyst, accounting for 10% of the total amount of platinum-based catalyst, is added to the mixture and stirred to react; wherein, the platinum-based catalyst is supported on alumina; S202. After the reaction in step S201 has stabilized, add the remaining platinum-based catalyst and raise the reaction temperature to 70°C. React for 1.5 hours until the vinyl groups are basically gone to obtain the crude product. After the crude product is cooled to 40°C, add 1-ethynylcyclohexanol and stir for 10 minutes. S300: After removing the platinum-based catalyst from the crude product containing 1-ethynylcyclohexanol using a composite adsorption method, activated carbon is used for the first adsorption and ethanolamine is used for the second adsorption to obtain chlorine-terminated polydimethylsiloxane. Example 3

[0036] This embodiment provides a chlorine-terminated polydimethylsiloxane and its preparation method, including the following steps: S100. Under an argon atmosphere, vinyl-terminated polydimethylsiloxane and dichlorosilane are mixed at a terminal vinyl molar ratio of 1:1.30 to obtain a mixture. S201. At 50°C, a first portion of platinum-based catalyst, accounting for 30% of the total amount of platinum-based catalyst, is added to the mixture and stirred to react; wherein, the platinum-based catalyst is supported on alumina; S202. After the reaction in step S201 has stabilized, add the remaining platinum-based catalyst and raise the reaction temperature to 90°C. React for 3 hours until the vinyl groups are basically gone to obtain the crude product. After the crude product is cooled to 50°C, add triphenylphosphine for 20 minutes. S300. After removing the platinum-based catalyst from the crude product containing triphenylphosphine using a composite adsorption method, activated carbon is used for the first adsorption and polyamine resin is used for the second adsorption to obtain chlorine-terminated polydimethylsiloxane.

[0037] Comparative Example 1 This comparative example provides a chlorine-terminated polydimethylsiloxane, which is purchased externally.

[0038] Test data The following performance tests were performed on Examples 1-3 and Comparative Example 1:

[0039] (1) Determination of terminal chlorine content: Acid-base titration method was used; approximately 1.0 g of sample (denoted as m, accurate to 0.0001 g) was accurately weighed into a 250 mL Erlenmeyer flask, and 50 mL of anhydrous ethanol was added to dissolve it. A few drops of phenolphthalein indicator were added, and titration was performed with 0.1 mol / L sodium hydroxide-ethanol standard solution until a faint red color appeared, and the volume consumed was recorded as V1. Subsequently, 10 mL of distilled water was added, and the mixture was shaken to fully hydrolyze the terminal Si-Cl bonds to generate HCl. Titration was then performed with 0.1 mol / L sodium hydroxide standard aqueous solution until a stable faint red color reappeared in the solution, and the volume consumed was recorded as V2.

[0040] Calculation: Terminal chlorine content (mmol / g) = (C NaOH ×V2) / m Among them, C NaOH This represents the accurate concentration (mol / L) of the sodium hydroxide standard solution.

[0041] (2) Vinyl conversion determination: Fourier transform infrared spectroscopy was used. Infrared scanning was performed on the vinyl-terminated PDMS raw material before the reaction and on each sample after the reaction.

[0042] Calculation: Conversion rate (%) = [1 - (A)] sample / A reference )]×100% Among them, A sample A represents the area of ​​the characteristic peak of vinyl groups in the sample. reference This represents the area of ​​the corresponding vinyl characteristic peak in the raw material.

[0043] (3) Determination of Platinum (Pt) Residual Content: Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used. Approximately 0.5 g of sample (accurate to 0.0001 g) was accurately weighed, and 5 mL of concentrated nitric acid and 2 mL of hydrogen peroxide were added. The sample was then completely digested using a microwave digester. After cooling, the sample was transferred to a volumetric flask and diluted to 50 mL with ultrapure water. A reagent blank was prepared simultaneously. The Pt content in the solution was determined using ICP-MS.

[0044] Calculation: Pt residual amount (ppm) = (C measured ×V dilution ) / m Among them, C measured The concentration of Pt (μg / L) measured by ICP-MS, V dilution is the constant volume (L), and m is the sample mass (g).

[0045] (4) Thermal stability analysis: Thermogravimetric analysis was used; 5-10 mg of sample was placed in an alumina crucible and heated from 50°C to 800°C at a rate of 10°C / min under a nitrogen atmosphere. The weight change curve of the sample with temperature was recorded. The temperature at which 5% weight loss occurred (T0) was recorded. d5% ( ) is used as an indicator for evaluating thermal stability.

[0046] Table 1 As shown in Table 1, the terminal chlorine content of the chlorinated PDMS prepared in the three examples is higher than that of the commercial product in Comparative Example 1, and the vinyl conversion rate is higher than 98.5%, which is significantly better than that of the comparative example. This proves that the stepwise catalytic addition method and the optimized material ratio described in this invention can efficiently and almost completely convert the terminal vinyls into the target chlorinated end, achieving high terminal saturation and functionalization efficiency.

[0047] Through a combined adsorption method and the use of a terminator, the residual platinum catalyst in the example samples was effectively controlled to an extremely low level, meeting the stringent requirements of high-end applications for metal impurity content. Comparative Example 1 showed no detectable Pt, indicating that the product may use a non-Pt catalytic system or a different purification process. The initial decomposition temperatures of the products in Examples 1-3 were all higher than 375°C, and significantly higher than those in Comparative Example 1. This indicates that the chlorine-terminated PDMS prepared in this invention has better thermal stability, which is closely related to its linear molecular structure, high terminal conversion rate, and effective purification.

[0048] In summary, the preparation method provided by this invention successfully overcomes the problems of numerous side reactions, insufficient conversion rate, high catalyst residue, and poor product thermal stability that may exist in existing technologies. Through precise control of process parameters and efficient purification strategies, the preparation of chlorine-terminated PDMS with high selectivity, high conversion rate, and high purity is achieved.

[0049] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0050] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for preparing chlorine-terminated polydimethylsiloxane, characterized in that, The preparation method includes the following steps: S100. Under an inert atmosphere, vinyl-terminated polydimethylsiloxane and chlorodimethylsilane are mixed to obtain a mixture. S200, A platinum-based catalyst is added to the mixture to carry out the reaction, and a crude product is obtained; S300. After removing the platinum-based catalyst from the crude product, the chlorine-terminated polydimethylsiloxane is obtained.

2. The preparation method according to claim 1, characterized in that, In step S100, the molar ratio of the terminal vinyl groups of the chlorodimethylsilane to the vinyl-terminated polydimethylsiloxane is 1:(1.01-1.30).

3. The preparation method according to claim 1, characterized in that, In step S100, the chlorodimethylsilane includes one or more of dichlorodimethylsilane, methyldichlorosilane, and trichlorosilane.

4. The preparation method according to claim 1, characterized in that, Step S200 specifically includes: S201. At 40-50°C, add 10-30% of the first portion of platinum-based catalyst, which accounts for 10-30% of the total amount of platinum-based catalyst, to the mixture and stir to react. S202. After the reaction in step S201 has stabilized, add the remaining platinum-based catalyst and raise the reaction temperature to 70-90°C until the reaction is complete and the crude product is obtained.

5. The preparation method according to claim 1, characterized in that, The platinum-based catalyst is supported on a carrier; The carrier includes one or more of the following: silica, alumina, activated carbon, carbon nanotubes, and polymer microspheres.

6. The preparation method according to claim 1, characterized in that, After the reaction in step S200 is completed and before step S300 begins, the process also includes: A terminator is added, wherein the terminator comprises one or more of nitrogen-containing compounds, organophosphorus compounds, and enyne compounds.

7. The preparation method according to claim 1, characterized in that, In step S300, the platinum-based catalyst is removed using a composite adsorption method, which includes primary adsorption and secondary adsorption. The primary adsorption uses diatomaceous earth or activated carbon; the secondary adsorption uses amine compounds.

8. The preparation method according to claim 7, characterized in that, The amine compounds include one or more of polyamine resins, triethylamine, and ethanolamine.

9. The preparation method according to claim 1, characterized in that, The inert atmosphere includes either nitrogen or argon.

10. A chlorine-terminated polydimethylsiloxane, characterized in that, The chlorine-terminated polydimethylsiloxane is prepared by the preparation method described in any one of claims 1-9.

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