Method for accurately synthesizing epoxy polysiloxane at low temperature

Abstract

The invention discloses a method for accurately synthesizing epoxy polysiloxane with controllable epoxy content by efficiently catalyzing ring-opening polymerization of cyclosiloxane monomers by adopting an organic phosphazene base catalyst. A siloxane copolymer with controllable epoxy siloxane group content can be accurately synthesized at 10-50 DEG C. The invention also discloses a preparation method of the epoxy polysiloxane with controllable epoxy content. The polymer preparation method has the obvious advantages that the polymerization process is simple, the polymerization efficiency is high, the reaction temperature is mild, polysiloxane containing methyl, ethyl, phenyl and vinyl side groups can be prepared, and the polymer preparation method has very high practical application value.

Description

Technical Field

[0001] This invention relates to a method for the precise low-temperature synthesis of epoxy-based polysiloxanes with controllable epoxy content. Specifically, it relates to a method for the ring-opening polymerization of tetraepoxy cyclotetrasiloxane monomers using organophosphoric nitrile bases to prepare linear polysiloxanes. Background Technology

[0002] Silicone rubber possesses excellent heat resistance, cold resistance, radiation resistance, oxidation resistance, weather resistance, and physiological inertness, making it widely used in defense, aerospace, electrical, electronics, instrumentation, automotive, and construction industries. However, silicone rubber generally suffers from weak adhesion.

[0003] To address these shortcomings, molecular modification is typically employed to introduce polar groups into silicone rubber, thereby enhancing its adhesive properties. Zhang Liqun's research group used a self-made alkaline adhesive as a catalyst to catalyze the ring-opening copolymerization of D4, P4, and V4 to prepare phenyl silicone rubber. They then successfully epoxidized the double bonds in the phenyl silicone rubber using m-chloroperoxybenzoic acid (MCPBA) as a modifier. Apart from this, other methods for epoxy-modified polysiloxanes involve introducing epoxy groups into the polymer through chemical methods such as polymer double bond epoxidation or hydrosilylation, or through physical blending with epoxy resin. These processes are complex and the epoxy content is difficult to control precisely.

[0004] Therefore, it is necessary to find a simple, efficient and precise method for synthesizing epoxy-based polysiloxanes by screening catalysts and optimizing catalytic conditions. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, one objective of this invention is to propose a method for the efficient preparation of silicone rubber with clearly defined negative epoxy groups through the ring-opening homopolymerization of cyclic siloxane monomers containing epoxy groups catalyzed by an organophosphorus nitrile catalyst and the ring-opening copolymerization with cyclic siloxane monomers containing different functional groups. The epoxy content can be precisely controlled within the range of 0.5~25 mol% according to the feed ratio. The polymer preparation method of this invention is simple, has high polymerization efficiency, short reaction time, and mild reaction temperature, and has extremely high practical application value.

[0006] This invention proposes a method for the precise low-temperature synthesis of epoxy-based polysiloxanes with controllable epoxy content. The epoxy content can be precisely controlled within the range of 0.5 ~ 25 mol% according to the feed ratio. The process is as follows:

[0007] (1) Bulk polymerization process: (a) Under a nitrogen atmosphere, tetracyclic tetrasiloxane and second and third cyclic siloxane monomers are mixed evenly; (b) Under a nitrogen atmosphere, initiator and phosphazene catalyst are added to the mixed monomers in (a), and polymerization is initiated at 10 ~ 50°C. After reacting for 0.5 ~ 48 h, end-capping agent is added and reacted for 30 minutes. Terminator is added to terminate the reaction. After sedimentation, the mixture is dried in a vacuum drying oven to obtain epoxy polysiloxane.

[0008] (2) Solution polymerization process: (c) Under a nitrogen atmosphere, anhydrous solvent, tetracyclic tetrasiloxane, and second and third cyclic siloxane monomers are mixed evenly; (d) Under a nitrogen atmosphere, initiator and phosphazene catalyst are mixed evenly and added to the system in (c). The mixture is placed at 10 ~ 50℃ to initiate polymerization. After reacting for 0.5 ~ 12 h, end-capping agent is added and reacted for 30 minutes. Terminator is added to terminate the reaction. After sedimentation, the mixture is dried in a vacuum drying oven to obtain epoxy polysiloxane.

[0009] According to embodiments of the present invention, the raw materials used in this method are readily available, low in cost, and the preparation method is simple, with high polymerization efficiency and low energy consumption.

[0010] In some embodiments of the present invention, in process (1) and process (2), the tetraepoxycyclotetrasiloxane is a compound of formula I, which is a commercially available product that does not require special treatment and can be used directly;

[0011]

[0012] (І)

[0013] Epoxy groups can be introduced into polysiloxanes through anionic ring-opening polymerization of this monomer.

[0014] In some embodiments of the present invention, the molar ratio of the cyclosiloxane monomer to the phosphazene catalyst is (10~10000):1;

[0015] The second cyclosiloxane monomer is at least one of octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane, octaethylcyclotetrasiloxane, 2,4,6-trimethyl-2,4,6-triethylcyclotrisiloxane, octaphenylcyclotetrasiloxane, and 2,4,6,8-tetramethyl-2,4,6,8-tetraphenylcyclotetrasiloxane; and the third cyclosiloxane monomer is at least one of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisiloxane and 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane.

[0016] When the tetracyclooxytetrasiloxane is mixed with the second and third cyclosiloxane monomers, the molar ratio of the tetracyclooxytetrasiloxane is 0.5 mol% to 25 mol%, the molar ratio of the second cyclosiloxane monomer is 75 mol% to 99.5 mol%, and the molar ratio of the third cyclosiloxane monomer is 0 mol% to 10 mol%.

[0017] By adjusting the feeding ratio of tetracyclooxygenated tetrasiloxane monomer, epoxy-based polysiloxanes with controllable epoxy content can be precisely synthesized, and the content of epoxy units in the epoxy-based polysiloxane is consistent with the feeding ratio of tetracyclooxygenated tetrasiloxane monomer.

[0018] In some embodiments of the present invention, the phosphazene catalyst is at least one of the organophosphazene compounds represented by formula (II), formula (III), and formula (IV).

[0019]

[0020] (II)

[0021]

[0022] (III)

[0023]

[0024] (IV)

[0025] In Equation III,

[0026] R 1 Halogen, -NR2, or ,

[0027] R and R 2 C is an optional replacement 1-6 Alkyl, optionally substituted C 1-6 Cycloalkyl, optionally substituted aryl, optionally substituted benzyl, halogen, or R forming C with the attached N atom. 1-6 Heterocyclic alkyl groups

[0028] R 3 C is an optional replacement 1-6 Alkyl, optionally substituted C 1-6 Cycloalkyl, optionally substituted aryl, optionally substituted benzyl, or halogen,

[0029] m is an integer and m≥1;

[0030] In Equation IV,

[0031] X n- It can be a hydroxyl anion, an alkoxy anion, or a carboxyl anion.

[0032] n is an integer greater than or equal to 1, representing the number of phosphazene onion cations.

[0033] In some embodiments of the present invention, in processes (1) and (2), the polymerization temperature is low to prevent the epoxy group from opening the ring, while also satisfying the conditions for opening the silicon-oxygen macrocycle, which has energy-saving advantages. Moreover, the organophosphorus nitrile catalyst can only open the silicon-oxygen macrocycle and cannot open the epoxy microcycle.

[0034] In some embodiments of the present invention, the initiator is at least one of water, benzyl alcohol, ethylene glycol, 1,2-propanediol, 2,3-butanediol, cyclohexanediol, glycerol, trimethylolpropane, pentaerythritol, xylitol, inositol, glucose, lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium methoxide, sodium methoxide, potassium methoxide, lithium tert-butoxide, sodium tert-butoxide, potassium tert-butoxide, lithium methylsilanolate, sodium methylsilanolate, and potassium methylsilanolate.

[0035] The phosphazene catalyst and the initiator are reacted in a molar ratio of 1:(0.01~20).

[0036] In some embodiments of the present invention, the capping agent is at least one of tetramethyldivinyldisiloxane and hexamethyldisiloxane;

[0037] The terminating agent is at least one of formic acid, acetic acid, phosphoric acid, hydrochloric acid, sulfuric acid, benzoic acid, and acid gum.

[0038] In some embodiments of the present invention, in the solution polymerization process, the anhydrous solvent is at least one of tetrahydrofuran and toluene.

[0039] In some embodiments of the present invention, the epoxy-based polysiloxane is a compound represented by formula V.

[0040]

[0041] (V)

[0042] in,

[0043] R is an optionally substituted alkyl, optionally substituted aryl, or optionally substituted benzyl group.

[0044] R1 and R2 are methyl, ethyl, and phenyl, respectively or simultaneously.

[0045] R3 is at least one of SiMe3 and SiMe2Vi.

[0046] x is an integer, and 1 < x < 10.

[0047] m is an integer from 1 to 10000.

[0048] n is an integer from 1 to 2500.

[0049] o is an integer from 0 to 1000. Attached Figure Description

[0050] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0051] Appendix Figure 1 This is the GPC curve of the epoxy-containing polysiloxane in Example 1 of the present invention.

[0052] Appendix Figure 2 This is the GPC curve of the epoxy-containing polysiloxane in Example 2 of the present invention.

[0053] Appendix Figure 3 This is the GPC curve of the epoxy-containing polysiloxane in Example 3 of the present invention. Detailed Implementation

[0054] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0055] Example 1

[0056] Under nitrogen protection, 0.0125 mmol phosphazene catalyst and 0.0125 mmol benzyl alcohol were uniformly mixed in 92 μL tetrahydrofuran and added to 158 μL tetraepoxycyclotetrasiloxane monomer. The polymerization reaction was initiated by stirring at 45 °C. After 4 h of reaction, hexamethyldisiloxane was added and reacted for 30 minutes. The reaction was terminated by adding acetic acid to obtain a homopolymer of epoxy-negative polysiloxane with a monomer conversion rate of 99% and Mn = 3.7 kg / mol.

[0057] Example 2

[0058] Under nitrogen protection, 0.0125 mmol phosphazene catalyst and 0.0125 mmol benzyl alcohol were uniformly mixed in 183 μL tetrahydrofuran and added to 316 μL tetraepoxycyclotetrasiloxane monomer. The polymerization reaction was initiated by stirring at 45 °C. After 4 h of reaction, hexamethyldisiloxane was added and reacted for 30 minutes. The reaction was terminated by adding sulfuric acid to obtain a homopolymer of epoxy-negative polysiloxane with a monomer conversion rate of 99% and Mn = 4.4 kg / mol.

[0059] Example 3

[0060] Under nitrogen protection, 0.0125 mmol of phosphazene catalyst and 0.0125 mmol of benzyl alcohol were uniformly mixed in 183 μL of tetrahydrofuran and added to 0.922 g of tetramethyltetracyclohexylethylcyclotetrasiloxane monomer. The polymerization reaction was initiated by stirring at 45 °C. After 1 h of reaction, hexamethyldisiloxane was added and reacted for 30 minutes. The reaction was terminated by adding hydrochloric acid to obtain a homopolymer of epoxy-negative polysiloxane with a monomer conversion rate of 99% and Mn = 4.1 kg / mol.

[0061] Example 4

[0062] Under nitrogen protection, 0.0125 mmol phosphazene catalyst and 0.0125 mmol benzyl alcohol were uniformly mixed in 400 μL tetrahydrofuran and added to a dilute tetrahydrofuran solution of 3.495 mL tetramethylcyclotetrasiloxane and 795 μL tetraepoxycyclotetrasiloxane (monomer concentration 1.5 M). The mixture was stirred at 50 °C to initiate the polymerization reaction. After 4 h of reaction, hexamethyldisiloxane was added and reacted for 30 minutes. Phosphoric acid was added to terminate the reaction, yielding an epoxy-negative polysiloxane copolymer with an epoxy content of 8.8 mol% and Mn = 6.2 kg / mol.

[0063] Example 5

[0064] Under nitrogen protection, 0.0125 mmol of phosphazene catalyst and 0.0125 mmol of benzyl alcohol were uniformly mixed in 400 μL of toluene and added to a dilute toluene solution of 3.49 mL of tetramethylcyclotetrasiloxane and 0.922 g of tetramethyltetracyclooxycyclohexylethylcyclotetrasiloxane (monomer concentration 1.5 M). The mixture was stirred at 50 °C to initiate the polymerization reaction. After 4 h of reaction, tetramethyldivinyldisiloxane was added and reacted for 30 minutes. The reaction was terminated by adding acid glue to obtain an epoxy-negative polysiloxane copolymer with an epoxy content of 7.1 mol% and Mn = 5.9 kg / mol.

Claims

1. A method for the precise low-temperature synthesis of epoxy-based polysiloxanes, characterized in that, include: (1) Bulk polymerization process: (a) Under a nitrogen atmosphere, tetracyclic tetrasiloxane and second and third cyclic siloxane monomers are mixed evenly; (b) Under a nitrogen atmosphere, initiator and phosphazene catalyst are added to the mixed monomers in (a), and polymerization is initiated at 10 ~ 50°C. After reacting for 0.5 ~ 48 h, end-capping agent is added and reacted for 30 minutes. Terminator is added to terminate the reaction. After sedimentation, the mixture is dried in a vacuum drying oven to obtain epoxy polysiloxane. (2) Solution polymerization process: (c) Under a nitrogen atmosphere, anhydrous solvent, tetracyclic tetrasiloxane, and second and third cyclic siloxane monomers are mixed evenly; (d) Under a nitrogen atmosphere, initiator and phosphazene catalyst are mixed evenly and added to the system in (c). The mixture is placed at 10 ~ 50℃ to initiate polymerization. After reacting for 0.5 ~ 12 h, end-capping agent is added and reacted for 30 minutes. Terminator is added to terminate the reaction. After sedimentation, the mixture is dried in a vacuum drying oven to obtain epoxy polysiloxane.

2. The method according to claim 1, characterized in that, The tetracyclic siloxane is a compound of formula I, which is a commercially available product that requires no special processing and can be used directly. Epoxy groups can be introduced into polysiloxanes through anionic ring-opening polymerization of this monomer.

3. The method according to claim 1, characterized in that, The molar ratio of the cyclosiloxane monomer to the phosphazene catalyst is (10~10000):1; The second cyclosiloxane monomer is at least one of octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane, octaethylcyclotetrasiloxane, 2,4,6-trimethyl-2,4,6-triethylcyclotrisiloxane, octaphenylcyclotetrasiloxane, and 2,4,6,8-tetramethyl-2,4,6,8-tetraphenylcyclotetrasiloxane; and the third cyclosiloxane monomer is at least one of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisiloxane and 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane. When the tetracyclooxytetrasiloxane is mixed with the second and third cyclosiloxane monomers, the molar ratio of the tetracyclooxytetrasiloxane is 0.5 mol% to 25 mol%, the molar ratio of the second cyclosiloxane monomer is 75 mol% to 99.5 mol%, and the molar ratio of the third cyclosiloxane monomer is 0 mol% to 10 mol%. By adjusting the feeding ratio of tetracyclooxygenated tetrasiloxane monomer, epoxy-based polysiloxanes with controllable epoxy content can be precisely synthesized, and the content of epoxy units in the epoxy-based polysiloxane is consistent with the feeding ratio of tetracyclooxygenated tetrasiloxane monomer.

4. The method according to claim 1, characterized in that, The phosphazene catalyst is at least one of the organophosphazene compounds shown in formula (II), formula (III), and formula (IV). In Equation III, R 1 Halogen, -NR2, or , R and R 2 C is an optional replacement 1-6 Alkyl, optionally substituted C 1-6 Cycloalkyl, optionally substituted aryl, optionally substituted benzyl, halogen, or R forming C with the attached N atom. 1-6 Heterocyclic alkyl groups R 3 C is an optional replacement 1-6 Alkyl, optionally substituted C 1-6 Cycloalkyl, optionally substituted aryl, optionally substituted benzyl, or halogen, m is an integer and m≥1; In Equation IV, X n- It can be a hydroxyl anion, an alkoxy anion, or a carboxyl anion. n is an integer greater than or equal to 1, representing the number of phosphazene onion cations.

5. The method according to claim 1, characterized in that, The initiator is at least one of water, benzyl alcohol, ethylene glycol, 1,2-propanediol, 2,3-butanediol, cyclohexanediol, glycerol, trimethylolpropane, pentaerythritol, xylitol, inositol, glucose, lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium methoxide, sodium methoxide, potassium methoxide, lithium tert-butoxide, sodium tert-butoxide, potassium tert-butoxide, lithium methylsilanolate, sodium methylsilanolate, and potassium methylsilanolate. The phosphazene catalyst and the initiator are reacted in a molar ratio of 1:(0.01~20).

6. The method according to claim 1, characterized in that, The end-capping agent is at least one of tetramethyldivinyldisiloxane and hexamethyldisiloxane; The terminating agent is at least one of formic acid, acetic acid, phosphoric acid, hydrochloric acid, sulfuric acid, benzoic acid, and acid gum.

7. The method according to claim 1, characterized in that, In the solution polymerization process, the anhydrous solvent is at least one of tetrahydrofuran and toluene.

8. The method according to claim 1, characterized in that, The epoxy-based polysiloxane is a compound represented by formula V. in, R is an optionally substituted alkyl, optionally substituted aryl, or optionally substituted benzyl group. R1 and R2 are methyl, ethyl, and phenyl, respectively or simultaneously. R3 is at least one of SiMe3 and SiMe2Vi. x is an integer, and 1 < x < 10. m is an integer from 1 to 10000. n is an integer from 1 to 2500. o is an integer from 0 to 1000.

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