Low-volatile alkoxy-terminated polydimethylsiloxane and preparation method thereof
By constructing a nanophase of modified cyclodextrin and fluorinated segments within siloxanes, the problem of controlling volatiles in alkoxy-terminated polydimethylsiloxanes was solved, achieving long-term volatile capture and fixation, and improving product stability and safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 广州盛泰诺新材料科技有限公司
- Filing Date
- 2026-03-17
- Publication Date
- 2026-05-15
AI Technical Summary
Existing technologies struggle to effectively control the volatile components of alkoxy-terminated polydimethylsiloxanes, especially D5 and some linear oligomers, leading to the release of small molecules during storage and use, which affects product performance.
A stable nanophase with both physical barrier and chemical adsorption functions was constructed in situ inside silicone oil using chemical methods. Modified cyclodextrin and fluorinated segments were chemically bonded to the siloxane prepolymer backbone to form a nanoscale physical barrier, and small molecules were captured through the host-guest interaction of the cyclodextrin cavity.
It significantly improves the product's ultra-low volatility and high stability, meeting the reliability requirements of silicone rubber materials in high-end electronics, electrical, and medical fields, and avoiding the risk of secondary volatilization during storage and use.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of polysiloxane technology, specifically relating to a low-volatile alkoxy-terminated polydimethylsiloxane and its preparation method. Background Technology
[0002] Alkoxy-terminated polydimethylsiloxane is a high-performance linear silicone oil whose molecular chains are capped at both ends with alkoxy groups (such as methoxy and ethoxy). Compared with traditional hydroxyl-terminated or methyl-terminated silicone oils, this structure endows it with excellent storage stability, hydrolysis resistance, and good compatibility with a variety of organic materials. Due to its low surface tension, wide viscosity range, and resistance to high and low temperatures, it has become an indispensable basic material in high-end fields. In the electronics and electrical fields, it is used as a plasticizer and leveling agent in semiconductor encapsulation adhesives and as a base oil for thermal greases, requiring low impurity ion content and volatile matter to prevent circuit corrosion and device failure. In the personal care and cosmetics fields, it is used as a film-forming agent, lubricant, and sensory modifier, coming into direct contact with the skin, and there are strict requirements for product purity and safety (low volatility and irritation). In the precision manufacturing field, it is used as a mold release agent and lubricant, and its stability directly affects mold life and product precision. Therefore, low volatility is an important indicator for polydimethylsiloxane, and its volatiles mainly come from linear oligomers (L3-L4) that have not been completely removed. 10 The residual small molecules (D3-D6) and cyclic siloxanes can slowly escape during subsequent storage, transportation or high-temperature use, leading to multiple adverse technical effects.
[0003] Existing technologies control the volatiles of alkoxy-terminated polydimethylsiloxanes through processes such as feedstock distillation and enhanced devolatilization, but fundamental defects remain. While continuous optimization of the devolatilization process, such as using molecular distillation and falling film evaporators, can effectively remove most low-boiling-point rings like D3 and D4, the separation efficiency significantly decreases for D5, which has a boiling point very close to the target product D4, and for some linear oligomers. Adding physical adsorbents (such as porous silica) to the product to capture small molecules is a simple physical blending method. The adsorbents have poor compatibility with the silicone oil matrix, easily settling and agglomerating, affecting product transparency and uniformity. Furthermore, their adsorption sites are easily saturated and ineffective, failing to provide long-term protection.
[0004] Therefore, based on the above-mentioned shortcomings, it is essential to propose a new low-volatile alkoxy-terminated polydimethylsiloxane and its preparation method. Summary of the Invention
[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a low-volatile alkoxy-terminated polydimethylsiloxane and its preparation method. By using chemical methods to construct a stable nanophase with both physical barrier and chemical adsorption functions in situ inside silicone oil, a deep and long-term control of volatile content can be achieved.
[0006] The first aspect of this invention is to provide a method for preparing a low-volatile alkoxy-terminated polydimethylsiloxane, comprising the following steps: S1: Mix and dehydrate octamethylcyclotetrasiloxane, methyltrifluoropropylcyclotrisiloxane and modified cyclodextrin; S2: Add catalyst I to the mixture of S1, stir and react. After the reaction is complete, add neutralizing agent and remove low-boiling substances to obtain cyclodextrin-modified fluorinated silicon prepolymer. S3: Under inert gas protection, the cyclodextrin-modified fluorinated silicon prepolymer and octamethylcyclotetrasiloxane are mixed and dehydrated, and catalyst II is added and stirred to react; S4: Add methyltrimethoxysilane to the S3 reaction system to carry out the reaction. After the reaction is completed, decompose the catalyst and volatilize to obtain low-volatile alkoxy-terminated polydimethylsiloxane.
[0007] It should be noted that the present invention uses octamethylcyclotetrasiloxane (D4) and methyltrifluoropropylcyclotrisiloxane (D3). ^ Using F) and modified cyclodextrin as raw materials, a functionalized prepolymer with fluorinated side chains and bonded cyclodextrin was first synthesized via ternary copolymerization. This prepolymer was then blended with D4 and subjected to ring-opening polymerization under the action of a catalyst. During polymerization, the molecular weight increase of PDMS induced in-situ phase separation of the prepolymer, forming a fluorinated nano-dispersed phase functionalized with cyclodextrin. Finally, methyltrimethoxysilane end-capping and deep devolatilization were performed to obtain a low-volatile alkoxy-terminated polydimethylsiloxane. The cyclodextrin cavities on the surface of the nanophase can adsorb and encapsulate residual cyclic siloxanes through host-guest interactions, thereby capturing volatile components.
[0008] In some embodiments, in S1, the mass ratio of octamethylcyclotetrasiloxane, methyltrifluoropropylcyclotrisiloxane, and modified cyclodextrin is 15-17:2-4:0.8-1.5; catalyst I is selected from at least one of tetramethylammonium hydroxide and tetraethylammonium hydroxide, and the mass amount of catalyst I is 0.8-1.2% of the mass of modified cyclodextrin; the neutralizing agent is glacial acetic acid, and the mass amount of the neutralizing agent is 0.3-0.5% of the mass of modified cyclodextrin.
[0009] In some embodiments, in S3, the mass ratio of the cyclodextrin-modified fluorinated silicon prepolymer to octamethylcyclotetrasiloxane is 0.8-1.2:98-100; catalyst II is selected from at least one of tetramethylammonium hydroxide and tetraethylammonium hydroxide, and the mass amount of catalyst II is 2-3% of the mass of the cyclodextrin-modified fluorinated silicon prepolymer; the mass amount of methyltrimethoxysilane is 46-50% of the mass of the cyclodextrin-modified fluorinated silicon prepolymer.
[0010] In some embodiments, in S1, the mixing and dehydration is carried out under nitrogen protection at 100-120°C and -0.04 to -0.08 MPa for 40-50 min; in S2, the stirring reaction is carried out at 70-80°C for 5-6 h, and the removal of low-boiling substances is carried out at 110-130°C and -0.07 to -0.09 MPa for 1-2 h.
[0011] In some embodiments, in S3, the mixing and dehydration is carried out at 100-120°C and -0.04 to -0.08 MPa for 25-35 min, and the stirring reaction is carried out at 75-85°C for 50-70 min; in S4, the reaction is carried out at 85-95°C for 1.5-2.5 h, the catalyst decomposition temperature is 125-135°C, and the devolatilization is carried out initially at 125-135°C and -0.093 to -0.095 MPa for 1-2 h, followed by deep devolatilization at 145-155°C and -0.098 to -0.1 MPa for 40-60 min.
[0012] In some embodiments, the modified cyclodextrin is prepared by the following steps: (1) Dissolve β-cyclodextrin in anhydrous pyridine, place it in an ice-water bath and add p-toluenesulfonyl chloride solution dropwise. After the addition is complete, carry out the reaction to obtain the reaction solution; (2) Pour the reaction solution into ice water, collect the precipitate, and wash to obtain the crude product; (3) The crude product was immersed in concentrated ammonia water and stirred to react. After concentration, it was added dropwise to acetone. The precipitate was collected, washed, and dried to obtain the aminocyclodextrin intermediate. (4) Under the protection of an inert gas, the aminocyclodextrin intermediate was dissolved in anhydrous DMF, triethylamine was added, and then 3-isocyanate propyltrimethoxysilane solution was added dropwise in an ice-water bath. After the addition was completed, the reaction was carried out. (5) Add the reaction liquid from step (4) dropwise into anhydrous diethyl ether, collect the precipitate, and obtain the modified cyclodextrin by washing and drying.
[0013] It should be noted that the present invention introduces a side chain containing a trimethoxysilyl group onto the β-cyclodextrin molecule. The trimethoxysilyl group enables it to form chemical bonds with the siloxane network, avoiding migration and failure that may be caused by physical blending. In addition, it can also ensure that each cyclodextrin adsorption site is fixed in a nanophase formed by fluorinated segments, which enhances the affinity for nonpolar siloxane small molecules and improves adsorption efficiency and stability.
[0014] In some embodiments, the ratio of β-cyclodextrin to anhydrous pyridine is 0.8-1.2 g: 3 mL; the p-toluenesulfonyl chloride solution is prepared by mixing p-toluenesulfonyl chloride and anhydrous pyridine in a ratio of 10-11 g: 28-32 mL, and the mass ratio of p-toluenesulfonyl chloride to β-cyclodextrin is 2-2.3: 8-12.
[0015] In some embodiments, the ratio of aminocyclodextrin intermediate to anhydrous DMF is 0.8-1.2 g: 8-12 mL; the volume of triethylamine is 0.8-1.2% of the volume of anhydrous DMF; the 3-isocyanate propyltrimethoxysilane solution is prepared by mixing 3-isocyanate propyltrimethoxysilane and anhydrous DMF in a volume ratio of 2-4:9-11, and the volume of the 3-isocyanate propyltrimethoxysilane solution is 12-14 times the volume of triethylamine.
[0016] In some embodiments, in step (1), the reaction is carried out at room temperature for 22-26 hours; in step (3), the stirring reaction is carried out at 35-45°C for 46-50 hours, and the solution is concentrated to 20-30% of the original volume; in step (4), the reaction is carried out at room temperature for 10-14 hours; in step (5), the drying is carried out at 40-45°C in the dark for 22-26 hours.
[0017] A second aspect of the present invention is to provide an alkoxy-terminated polydimethylsiloxane with low volatility.
[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention creatively grafts hydrophobic cavities of cyclodextrin and fluorinated segments onto the backbone of a siloxane prepolymer via chemical bonds. The fluorinated segments, due to their poor compatibility with the polydimethylsiloxane (PDMS) backbone, readily undergo microphase separation, thus forming a nanoscale physical barrier in situ. This barrier effectively blocks and prolongs the migration and diffusion paths of small molecule volatiles. Simultaneously, the cyclodextrin cavities chemically bonded to the barrier phase, through their hydrophobic interiors and inclusion interactions with small siloxane molecules (such as D4-D6), capture and immobilize residual volatiles. This nanophase, through the synergistic effect of physical barrier and chemical adsorption, can continuously and effectively lock small molecules within the product, significantly improving the product's ultra-low volatility and high stability.
[0019] 2. The alkoxy-terminated polydimethylsiloxane provided by this invention has a low volatile content, and its chemically anchored stable nanostructure can effectively avoid the risk of secondary volatilization during storage and use, meeting the stringent reliability requirements of silicone rubber materials in high-end electronic, electrical and medical fields. Detailed Implementation
[0020] The present invention will now be described in further detail with reference to specific embodiments.
[0021] Example 1 A low-volatility alkoxy-terminated polydimethylsiloxane is prepared by the following steps: S1: Mix octamethylcyclotetrasiloxane, methyltrifluoropropylcyclotrisiloxane and modified cyclodextrin in a mass ratio of 16:3:1, and dehydrate at 110℃ and -0.06MPa for 45 min under nitrogen protection. S2: Tetramethylammonium hydroxide was added to the mixture of S1, and the mixture was stirred at 75°C for 6 hours. After the reaction was completed, glacial acetic acid was added, and the mixture was subjected to a reaction at 120°C and -0.08 MPa for 1.5 hours to remove low-boiling-point substances, resulting in cyclodextrin-modified fluorosilicone prepolymer. The mass of tetramethylammonium hydroxide was 1% of the mass of the modified cyclodextrin, and the mass of glacial acetic acid was 0.4% of the mass of the modified cyclodextrin. S3: Under inert gas protection, cyclodextrin-modified fluorosilicone prepolymer and octamethylcyclotetrasiloxane were mixed at a mass ratio of 1:99, dehydrated at 110℃ and -0.06MPa for 30 min, and tetramethylammonium hydroxide was added and stirred at 80℃ for 60 min; wherein, the mass of tetramethylammonium hydroxide was 2.5% of the mass of the cyclodextrin-modified fluorosilicone prepolymer. S4: Methyltrimethoxysilane was added to the S3 reaction system and reacted at 90℃ for 2 hours. After the reaction was completed, the catalyst was decomposed at 130℃. Initial devaporization was carried out at 130℃ and -0.094MPa for 1.5 hours, followed by deep devaporization at 150℃ and -0.099MPa for 50 minutes. After devaporization, low-volatility alkoxy-terminated polydimethylsiloxane was obtained. The mass of methyltrimethoxysilane was 48% of the mass of the cyclodextrin-modified fluorinated silicon prepolymer.
[0022] The modified cyclodextrin is prepared by the following steps: (1) Dissolve β-cyclodextrin in anhydrous pyridine, place it in an ice-water bath and add p-toluenesulfonyl chloride solution dropwise. After the addition is complete, react at room temperature for 24 hours to obtain a reaction solution; wherein, the ratio of β-cyclodextrin to anhydrous pyridine is 1 g: 3 mL; the p-toluenesulfonyl chloride solution is prepared by mixing p-toluenesulfonyl chloride and anhydrous pyridine in a ratio of 1.5 g: 30 mL, and the mass ratio of p-toluenesulfonyl chloride to β-cyclodextrin is 2.1:10; (2) Pour the reaction solution into ice water, collect the precipitate, and wash to obtain the crude product; (3) Immerse the crude product in concentrated ammonia water and stir at 40°C for 48 hours. The concentrated ammonia water should cover the crude product. Then concentrate the solution to 25% of the original volume, add it dropwise to acetone, collect the precipitate, and obtain the aminocyclodextrin intermediate by washing and drying. (4) Under inert gas protection, the aminocyclodextrin intermediate was dissolved in anhydrous DMF, triethylamine was added, and then 3-isocyanate propyltrimethoxysilane solution was added dropwise in an ice-water bath. After the addition was completed, the mixture was transferred to room temperature and reacted for 12 hours. The ratio of aminocyclodextrin intermediate to anhydrous DMF was 1 g: 10 mL. The volume of triethylamine was 1% of the volume of anhydrous DMF. The 3-isocyanate propyltrimethoxysilane solution was prepared by mixing 3-isocyanate propyltrimethoxysilane and anhydrous DMF in a volume ratio of 3:10. The volume of the 3-isocyanate propyltrimethoxysilane solution was 13 times the volume of triethylamine. (5) Add the reaction liquid from step (4) dropwise into anhydrous diethyl ether, collect the precipitate, wash it, and dry it at 42°C in the dark for 24 hours to obtain modified cyclodextrin.
[0023] Example 2 A low-volatility alkoxy-terminated polydimethylsiloxane is prepared by the following steps: S1: Mix octamethylcyclotetrasiloxane, methyltrifluoropropylcyclotrisiloxane and modified cyclodextrin in a mass ratio of 17:4:1.5, and dehydrate at 120℃ and -0.08MPa for 50 min under nitrogen protection. S2: Tetraethylammonium hydroxide was added to the mixture of S1, and the mixture was stirred at 80℃ for 5 hours. After the reaction was completed, glacial acetic acid was added, and the mixture was subjected to desorption at 130℃ and -0.09 MPa for 1 hour. After desorption of low-boiling substances, cyclodextrin-modified fluorosilicone prepolymer was obtained. The mass of tetraethylammonium hydroxide was 1.2% of the mass of the modified cyclodextrin, and the mass of glacial acetic acid was 0.5% of the mass of the modified cyclodextrin. S3: Under inert gas protection, cyclodextrin-modified fluorosilicone prepolymer and octamethylcyclotetrasiloxane were mixed at a mass ratio of 1.2:98.8 and dehydrated at 120℃ and -0.08MPa for 25 min. Tetraethylammonium hydroxide was then added and the mixture was stirred at 85℃ for 50 min. The mass of tetraethylammonium hydroxide was 3% of the mass of the cyclodextrin-modified fluorosilicone prepolymer. S4: Add methyltrimethoxysilane to the S3 reaction system and react at 95℃ for 1.5h. After the reaction is completed, decompose the catalyst at 135℃, perform preliminary devaporization at 135℃ and -0.095MPa for 1h, and then perform deep devaporization at 155℃ and -0.1MPa for 40min. After devaporization, low-volatile alkoxy-terminated polydimethylsiloxane is obtained. The mass of methyltrimethoxysilane is 50% of the mass of the cyclodextrin-modified fluorinated silicon prepolymer.
[0024] The modified cyclodextrin is prepared by the following steps: (1) Dissolve β-cyclodextrin in anhydrous pyridine, place it in an ice-water bath and add p-toluenesulfonyl chloride solution dropwise. After the addition is complete, react at room temperature for 26 h to obtain a reaction solution; wherein, the ratio of β-cyclodextrin to anhydrous pyridine is 1.2 g: 3 mL; the p-toluenesulfonyl chloride solution is a mixture of p-toluenesulfonyl chloride and anhydrous pyridine in a ratio of 11 g: 32 mL, and the mass ratio of p-toluenesulfonyl chloride to β-cyclodextrin is 2.3: 12; (2) Pour the reaction solution into ice water, collect the precipitate, and wash to obtain the crude product; (3) Immerse the crude product in concentrated ammonia water and stir at 45°C for 46 hours. The concentrated ammonia water should cover the crude product. Then concentrate the solution to 30% of the original volume, add it dropwise to acetone, collect the precipitate, and obtain the aminocyclodextrin intermediate by washing and drying. (4) Under inert gas protection, the aminocyclodextrin intermediate was dissolved in anhydrous DMF, triethylamine was added, and then 3-isocyanate propyltrimethoxysilane solution was added dropwise in an ice-water bath. After the addition was completed, the mixture was transferred to room temperature and reacted for 14 h. The ratio of aminocyclodextrin intermediate to anhydrous DMF was 1.2 g: 12 mL. The volume of triethylamine was 1.2% of the volume of anhydrous DMF. The 3-isocyanate propyltrimethoxysilane solution was prepared by mixing 3-isocyanate propyltrimethoxysilane and anhydrous DMF in a volume ratio of 4:11. The volume of the 3-isocyanate propyltrimethoxysilane solution was 14 times the volume of triethylamine. (5) Add the reaction liquid from step (4) dropwise into anhydrous diethyl ether, collect the precipitate, wash it, and dry it at 45°C in the dark for 26 hours to obtain modified cyclodextrin.
[0025] Example 3 A low-volatility alkoxy-terminated polydimethylsiloxane is prepared by the following steps: S1: Mix octamethylcyclotetrasiloxane, methyltrifluoropropylcyclotrisiloxane and modified cyclodextrin in a mass ratio of 15:2:0.8, and dehydrate at 100℃ and -0.04MPa for 40 min under nitrogen protection. S2: Tetramethylammonium hydroxide was added to the mixture of S1, and the mixture was stirred at 70°C for 6 hours. After the reaction was completed, glacial acetic acid was added, and the mixture was subjected to desorption at 110°C and -0.07 MPa for 2 hours. After desorption of low-boiling-point substances, cyclodextrin-modified fluorosilicone prepolymer was obtained. The mass of tetramethylammonium hydroxide was 0.8% of the mass of the modified cyclodextrin, and the mass of glacial acetic acid was 0.3% of the mass of the modified cyclodextrin. S3: Under inert gas protection, cyclodextrin-modified fluorosilicone prepolymer and octamethylcyclotetrasiloxane were mixed at a mass ratio of 0.8:99.2 and dehydrated at 100℃ and -0.04MPa for 35 min. Tetramethylammonium hydroxide was then added and the mixture was stirred at 75℃ for 70 min. The mass of tetramethylammonium hydroxide was 2% of the mass of the cyclodextrin-modified fluorosilicone prepolymer. S4: Methyltrimethoxysilane was added to the S3 reaction system and reacted at 85℃ for 2.5h. After the reaction was completed, the catalyst was decomposed at 125℃, and then initially devastated at 125℃ and -0.093MPa for 2h, followed by deep devastating at 145℃ and -0.098MPa for 60min. After devastating, low-volatility alkoxy-terminated polydimethylsiloxane was obtained. The mass of methyltrimethoxysilane used was 50% of the mass of the cyclodextrin-modified fluorinated silicon prepolymer.
[0026] The modified cyclodextrin is prepared by the following steps: (1) Dissolve β-cyclodextrin in anhydrous pyridine, place it in an ice-water bath and add p-toluenesulfonyl chloride solution dropwise. After the addition is complete, react at room temperature for 26 h to obtain a reaction solution; wherein, the ratio of β-cyclodextrin to anhydrous pyridine is 0.8 g: 3 mL; the p-toluenesulfonyl chloride solution is a mixture of p-toluenesulfonyl chloride and anhydrous pyridine in a ratio of 10 g: 28 mL, and the mass ratio of p-toluenesulfonyl chloride to β-cyclodextrin is 2:8; (2) Pour the reaction solution into ice water, collect the precipitate, and wash to obtain the crude product; (3) Immerse the crude product in concentrated ammonia water and stir at 35°C for 50 hours. The concentrated ammonia water should cover the crude product. Then concentrate the solution to 20% of the original volume, add it dropwise to acetone, collect the precipitate, and obtain the aminocyclodextrin intermediate by washing and drying. (4) Under inert gas protection, the aminocyclodextrin intermediate was dissolved in anhydrous DMF, triethylamine was added, and then 3-isocyanate propyltrimethoxysilane solution was added dropwise in an ice-water bath. After the addition was completed, the mixture was transferred to room temperature and reacted for 14 h. The ratio of aminocyclodextrin intermediate to anhydrous DMF was 0.8 g: 8 mL. The volume of triethylamine was 0.8% of the volume of anhydrous DMF. The 3-isocyanate propyltrimethoxysilane solution was prepared by mixing 3-isocyanate propyltrimethoxysilane and anhydrous DMF in a volume ratio of 2:9. The volume of the 3-isocyanate propyltrimethoxysilane solution was 12 times the volume of triethylamine. (5) Add the reaction liquid from step (4) dropwise into anhydrous diethyl ether, collect the precipitate, wash it, and dry it at 40°C in the dark for 26 hours to obtain modified cyclodextrin.
[0027] Example 4 A low-volatility alkoxy-terminated polydimethylsiloxane is prepared by the following steps: S1: Mix octamethylcyclotetrasiloxane, methyltrifluoropropylcyclotrisiloxane and modified cyclodextrin in a mass ratio of 15:4:1.2 and dehydrate at 115℃ and -0.05MPa for 50 min under nitrogen protection. S2: Tetraethylammonium hydroxide was added to the mixture of S1, and the mixture was stirred at 75°C for 6 hours. After the reaction was completed, glacial acetic acid was added, and the mixture was subjected to desorption at 115°C and -0.07 MPa for 2 hours. After desorption of low-boiling substances, cyclodextrin-modified fluorosilicone prepolymer was obtained. The mass of tetraethylammonium hydroxide was 0.9% of the mass of the modified cyclodextrin, and the mass of glacial acetic acid was 0.4% of the mass of the modified cyclodextrin. S3: Under inert gas protection, cyclodextrin-modified fluorosilicone prepolymer and octamethylcyclotetrasiloxane were mixed at a mass ratio of 1.1:98.9 and dehydrated at 105℃ and -0.05MPa for 30 min. Tetraethylammonium hydroxide was then added and the mixture was stirred at 80℃ for 55 min. The mass of tetraethylammonium hydroxide was 2.5% of the mass of the cyclodextrin-modified fluorosilicone prepolymer. S4: Methyltrimethoxysilane was added to the S3 reaction system and reacted at 90℃ for 2 hours. After the reaction was completed, the catalyst was decomposed at 135℃, and then initially devastated at 130℃ and -0.094MPa for 2 hours. Then, it was deeply devastated at 155℃ and -0.1MPa for 55 minutes. After devastating, low-volatility alkoxy-terminated polydimethylsiloxane was obtained. The mass of methyltrimethoxysilane was 49% of the mass of the cyclodextrin-modified fluorinated silicon prepolymer.
[0028] The modified cyclodextrin is prepared by the following steps: (1) Dissolve β-cyclodextrin in anhydrous pyridine, place it in an ice-water bath and add p-toluenesulfonyl chloride solution dropwise. After the addition is complete, react at room temperature for 25 h to obtain a reaction solution; wherein, the ratio of β-cyclodextrin to anhydrous pyridine is 1.1 g: 3 mL; the p-toluenesulfonyl chloride solution is prepared by mixing p-toluenesulfonyl chloride and anhydrous pyridine in a ratio of 10.8 g: 29 mL, and the mass ratio of p-toluenesulfonyl chloride to β-cyclodextrin is 2.1: 11; (2) Pour the reaction solution into ice water, collect the precipitate, and wash to obtain the crude product; (3) Immerse the crude product in concentrated ammonia water and stir at 40°C for 49 hours. The concentrated ammonia water should cover the crude product. Then concentrate the solution to 28% of the original volume, add it dropwise to acetone, collect the precipitate, and obtain the aminocyclodextrin intermediate by washing and drying. (4) Under inert gas protection, the aminocyclodextrin intermediate was dissolved in anhydrous DMF, triethylamine was added, and then 3-isocyanate propyltrimethoxysilane solution was added dropwise in an ice-water bath. After the addition was completed, the mixture was transferred to room temperature and reacted for 13 h. The ratio of aminocyclodextrin intermediate to anhydrous DMF was 0.9 g: 9 mL. The volume of triethylamine was 0.9% of the volume of anhydrous DMF. The 3-isocyanate propyltrimethoxysilane solution was prepared by mixing 3-isocyanate propyltrimethoxysilane and anhydrous DMF in a volume ratio of 3:11. The volume of the 3-isocyanate propyltrimethoxysilane solution was 14 times the volume of triethylamine. (5) Add the reaction liquid from step (4) dropwise into anhydrous diethyl ether, collect the precipitate, wash it, and dry it at 43°C in the dark for 24 hours to obtain modified cyclodextrin.
[0029] Example 5 A low-volatility alkoxy-terminated polydimethylsiloxane is prepared by the following steps: S1: Octamethylcyclotetrasiloxane, methyltrifluoropropylcyclotrisiloxane and modified cyclodextrin were mixed in a mass ratio of 16:2:1.3 and dehydrated at 115℃ and -0.07MPa for 45 min under nitrogen protection. S2: Tetramethylammonium hydroxide was added to the mixture of S1, and the mixture was stirred at 78°C for 5.5 h. After the reaction was completed, glacial acetic acid was added, and the mixture was subjected to removal at 125°C and -0.08 MPa for 1.5 h. After removing low-boiling substances, cyclodextrin-modified fluorosilicone prepolymer was obtained. The mass of tetramethylammonium hydroxide was 1.1% of the mass of the modified cyclodextrin, and the mass of glacial acetic acid was 0.5% of the mass of the modified cyclodextrin. S3: Under inert gas protection, cyclodextrin-modified fluorosilicone prepolymer and octamethylcyclotetrasiloxane were mixed at a mass ratio of 0.9:99.1 and dehydrated at 115℃ and -0.07MPa for 30 min. Tetraethylammonium hydroxide was then added and the mixture was stirred at 80℃ for 65 min. The mass of tetraethylammonium hydroxide was 2.8% of the mass of the cyclodextrin-modified fluorosilicone prepolymer. S4: Methyltrimethoxysilane was added to the S3 reaction system and reacted at 90℃ for 2 hours. After the reaction was completed, the catalyst was decomposed at 135℃, and then initially devastated at 125℃ and -0.095MPa for 1.5 hours. Then, it was deeply devastated at 150℃ and -0.098MPa for 45 minutes. After devastating, low-volatility alkoxy-terminated polydimethylsiloxane was obtained. The mass of methyltrimethoxysilane was 47% of the mass of the cyclodextrin-modified fluorinated silicon prepolymer.
[0030] The modified cyclodextrin is prepared by the following steps: (1) Dissolve β-cyclodextrin in anhydrous pyridine, place it in an ice-water bath and add p-toluenesulfonyl chloride solution dropwise. After the addition is complete, react at room temperature for 23 h to obtain a reaction solution; wherein, the ratio of β-cyclodextrin to anhydrous pyridine is 0.9 g: 3 mL; the p-toluenesulfonyl chloride solution is prepared by mixing p-toluenesulfonyl chloride and anhydrous pyridine in a ratio of 10.2 g: 31 mL, and the mass ratio of p-toluenesulfonyl chloride to β-cyclodextrin is 2.2: 9; (2) Pour the reaction solution into ice water, collect the precipitate, and wash to obtain the crude product; (3) Immerse the crude product in concentrated ammonia water and stir at 45°C for 47 hours. The concentrated ammonia water should cover the crude product. Then concentrate the solution to 22% of the original volume, add it dropwise to acetone, collect the precipitate, and obtain the aminocyclodextrin intermediate by washing and drying. (4) Under inert gas protection, the aminocyclodextrin intermediate was dissolved in anhydrous DMF, triethylamine was added, and then 3-isocyanate propyltrimethoxysilane solution was added dropwise in an ice-water bath. After the addition was completed, the mixture was transferred to room temperature and reacted for 11 h. The ratio of aminocyclodextrin intermediate to anhydrous DMF was 1.1 g: 10 mL. The volume of triethylamine was 1.1% of the volume of anhydrous DMF. The 3-isocyanate propyltrimethoxysilane solution was prepared by mixing 3-isocyanate propyltrimethoxysilane and anhydrous DMF in a volume ratio of 4:9. The volume of the 3-isocyanate propyltrimethoxysilane solution was 12 times the volume of triethylamine. (5) Add the reaction liquid from step (4) dropwise into anhydrous diethyl ether, collect the precipitate, wash it, and dry it at 40°C in the dark for 22 hours to obtain modified cyclodextrin.
[0031] Comparative Example 1 It is basically the same as Example 1, except that no modified cyclodextrin is added.
[0032] Comparative Example 2 It is basically the same as Example 1, except that methyltrifluoropropylcyclotrisiloxane is not added.
[0033] Comparative Example 3 It is basically the same as Example 1, except that the modified cyclodextrin is replaced with the same amount of unmodified cyclodextrin, that is, the preparation step of modified cyclodextrin is omitted.
[0034] Comparative Example 4 It is basically the same as Example 1, except that a one-step process is used, that is, steps S1 and S2 are omitted, and the same amount of cyclodextrin-modified fluorinated silicon prepolymer as in Example 1 is added in step S3.
[0035] The performance of the alkoxy-terminated polydimethylsiloxanes prepared in Examples 1-5 and Comparative Examples 1-4 was tested, and the test results are shown in Table 1.
[0036] Referring to GB / T 28112-2011 "Determination of Volatile Methylcyclosiloxanes in Silicone Rubber", headspace gas chromatography-mass spectrometry (GC-MS) was used: approximately 0.2 g (accurate to 0.1 mg) of sample debris was placed in a 20 mL headspace vial, 50 μL of D4 internal standard solution (2000 μg / mL) was added, the vial was sealed, and the sample was equilibrated at 120℃ for 60 minutes. 1.0 mL of headspace sample was then injected, and the contents of D3, D4, D5, and D6 were detected by GC-MS. Simultaneously, a 150℃ control experiment was set up to verify the completeness of inclusion dissociation for the cyclodextrin inclusion samples (Examples 1-5, Comparative Example 3).
[0037] Table 1 As can be seen from Table 1, the total amount of D4-D6 in all embodiments is less than 150 μg / g, indicating that the alkoxy-terminated polydimethylsiloxanes prepared in each embodiment of the present invention have low volatile content.
[0038] As can be seen from Comparative Examples 1-4, Comparative Example 1, lacking modified cyclodextrin, only has the physical barrier formed by the fluorinated phase, lacking the adsorption function of cyclodextrin. Low-molecular-weight siloxanes cannot be effectively captured after formation, resulting in a large amount escaping. Comparative Example 2 lacks the fluorinated monomer D3. ^In Comparative Example F, only chemically anchored cyclodextrin serves as an adsorption site. Although it can adsorb small molecules, it lacks a barrier constructed by fluorinated segments. The adsorbed small molecules are easily desorbed from the cyclodextrin cavity and re-diffuse under thermal motion. Comparative Example 3 uses unmodified cyclodextrin, which has poor compatibility with PDMS and easily forms particle agglomerates. The agglomerates have numerous pores at the PDMS interface, accelerating the volatilization of small molecules. Furthermore, the accessibility of the agglomerated cyclodextrin cavity is low, significantly reducing its adsorption capacity. Comparative Example 4 uses a one-step process, resulting in random copolymerization of all monomers. The reaction sites on the modified cyclodextrin are similar to those on D4 and D3. ^ Due to competition from fluorinated groups, the cyclodextrin-fluorinated segment structure cannot be formed. In the final product, the two functional groups are randomly distributed on the polymer chain, and an effective nano-functional phase cannot be formed, resulting in a high volatile content in the product.
[0039] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.
Claims
1. A method for preparing a low-volatile alkoxy-terminated polydimethylsiloxane, characterized in that, Includes the following steps: S1: Mix and dehydrate octamethylcyclotetrasiloxane, methyltrifluoropropylcyclotrisiloxane and modified cyclodextrin; S2: Add catalyst I to the mixture of S1, stir and react. After the reaction is complete, add neutralizing agent and remove low-boiling substances to obtain cyclodextrin-modified fluorinated silicon prepolymer. S3: Under inert gas protection, the cyclodextrin-modified fluorinated silicon prepolymer and octamethylcyclotetrasiloxane are mixed and dehydrated, and catalyst II is added and stirred to react; S4: Add methyltrimethoxysilane to the S3 reaction system to carry out the reaction. After the reaction is completed, decompose the catalyst and obtain the low-volatility alkoxy-terminated polydimethylsiloxane after devolatation.
2. The method for preparing low-volatile alkoxy-terminated polydimethylsiloxane according to claim 1, characterized in that, In S1, the mass ratio of octamethylcyclotetrasiloxane, methyltrifluoropropylcyclotrisiloxane, and modified cyclodextrin is 15-17:2-4:0.8-1.5; the catalyst I is selected from at least one of tetramethylammonium hydroxide and tetraethylammonium hydroxide, and the mass amount of the catalyst I is 0.8-1.2% of the mass of the modified cyclodextrin; the neutralizing agent is glacial acetic acid, and the mass amount of the neutralizing agent is 0.3-0.5% of the mass of the modified cyclodextrin.
3. The method for preparing low-volatile alkoxy-terminated polydimethylsiloxane according to claim 1, characterized in that, In step S3, the mass ratio of the cyclodextrin-modified fluorinated silicon prepolymer to octamethylcyclotetrasiloxane is 0.8-1.2:98-100; the catalyst II is selected from at least one of tetramethylammonium hydroxide and tetraethylammonium hydroxide, and the mass amount of the catalyst II is 2-3% of the mass of the cyclodextrin-modified fluorinated silicon prepolymer; the mass amount of the methyltrimethoxysilane is 46-50% of the mass of the cyclodextrin-modified fluorinated silicon prepolymer.
4. The method for preparing low-volatile alkoxy-terminated polydimethylsiloxane according to claim 1, characterized in that, In step S1, the mixed dehydration is carried out under nitrogen protection at 100-120℃ and -0.04 to -0.08 MPa for 40-50 minutes; in step S2, the stirring reaction is carried out at 70-80℃ for 5-6 hours, and the removal of low-boiling substances is carried out at 110-130℃ and -0.07 to -0.09 MPa for 1-2 hours.
5. The method for preparing low-volatile alkoxy-terminated polydimethylsiloxane according to claim 1, characterized in that, In step S3, the mixing and dehydration is carried out at 100-120℃ and -0.04 to -0.08 MPa for 25-35 min, and the stirring reaction is carried out at 75-85℃ for 50-70 min. In step S4, the reaction is carried out at 85-95℃ for 1.5-2.5 h, the catalyst decomposition temperature is 125-135℃, and the devolatilization is carried out at 125-135℃ and -0.093 to -0.095 MPa for 1-2 h, followed by deep devolatilization at 145-155℃ and -0.098 to -0.1 MPa for 40-60 min.
6. The method for preparing low-volatile alkoxy-terminated polydimethylsiloxane according to claim 1, characterized in that, The modified cyclodextrin was prepared by the following steps: (1) Dissolve β-cyclodextrin in anhydrous pyridine, place it in an ice-water bath and add p-toluenesulfonyl chloride solution dropwise. After the addition is complete, carry out the reaction to obtain the reaction solution; (2) Pour the reaction solution into ice water, collect the precipitate, and wash to obtain the crude product; (3) The crude product is immersed in concentrated ammonia water and stirred to react. After concentration, it is added dropwise to acetone, the precipitate is collected, and after washing and drying, aminocyclodextrin intermediate is obtained. (4) Under the protection of an inert gas, the aminocyclodextrin intermediate was dissolved in anhydrous DMF, triethylamine was added, and then 3-isocyanate propyltrimethoxysilane solution was added dropwise in an ice-water bath. After the addition was completed, the reaction was carried out. (5) Add the reaction liquid from step (4) dropwise into anhydrous diethyl ether, collect the precipitate, and obtain the modified cyclodextrin by washing and drying.
7. The method for preparing low-volatile alkoxy-terminated polydimethylsiloxane according to claim 6, characterized in that, The ratio of β-cyclodextrin to anhydrous pyridine is 0.8-1.2 g: 3 mL; the p-toluenesulfonyl chloride solution is prepared by mixing p-toluenesulfonyl chloride and anhydrous pyridine in a ratio of 10-11 g: 28-32 mL, and the mass ratio of p-toluenesulfonyl chloride to β-cyclodextrin is 2-2.3: 8-12.
8. The method for preparing low-volatile alkoxy-terminated polydimethylsiloxane according to claim 6, characterized in that, The ratio of the aminocyclodextrin intermediate to anhydrous DMF is 0.8-1.2 g: 8-12 mL; the volume of triethylamine is 0.8-1.2% of the volume of anhydrous DMF; the 3-isocyanate propyltrimethoxysilane solution is prepared by mixing 3-isocyanate propyltrimethoxysilane and anhydrous DMF in a volume ratio of 2-4:9-11, and the volume of the 3-isocyanate propyltrimethoxysilane solution is 12-14 times the volume of triethylamine.
9. The method for preparing low-volatile alkoxy-terminated polydimethylsiloxane according to claim 6, characterized in that, In step (1), the reaction is carried out at room temperature for 22-26 hours; in step (3), the stirring reaction is carried out at 35-45°C for 46-50 hours, and the solution is concentrated to 20-30% of the original volume; in step (4), the reaction is carried out at room temperature for 10-14 hours; in step (5), the drying is carried out at 40-45°C in the dark for 22-26 hours.
10. A method for preparing a low-volatile alkoxy-terminated polydimethylsiloxane according to any one of claims 1-9.