Synthesis method of high-purity methylsiloxane

Abstract

The invention relates to the technical field of organic silicon materials, in particular to a synthesis method of high-purity methylsiloxane. Comprising the following steps: mixing a methyl chlorosilane monomer with deionized water according to a molar ratio of 1: (3-5), adding a metal oxide catalyst, and carrying out a hydrolysis reaction under the protection of inert gas; controlling the temperature by stages after the hydrolysis reaction: stirring and reacting for 1-2 hours at 60-80 DEG C in the first stage, heating to 90-110 DEG C and reducing the pressure to 0.05-0.1 MPa in the second stage, and continuously reacting for 0.5-1 hour; and after the reaction is finished, purifying through reduced pressure distillation, molecular sieve adsorption and membrane filtration in sequence to obtain the methylsiloxane with the purity of more than or equal to 99.8%. The invention provides a synthetic method with high-efficiency catalysis, precise temperature control and deep purification, so that the bottleneck of the prior art is broken through, and the purity of methylsiloxane is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of silicone materials, and particularly relates to a method for synthesizing high-purity methylsiloxane. Background Art

[0002] Methylsiloxane is a kind of important silicone compound, which is widely used in fields such as electronic packaging materials, pharmaceutical intermediates, high-temperature lubricants and high-performance coatings. Its purity directly affects the performance of end products. For example, high-purity methylsiloxane can significantly improve the heat resistance and dielectric properties of semiconductor packaging materials. Therefore, developing an efficient and high-purity synthesis process has important industrial value.

[0003] Traditional methods for synthesizing methylsiloxane usually use methylchlorosilane (such as methyltrichlorosilane, dimethyldichlorosilane) as raw materials and prepare through hydrolysis and condensation reactions. However, the following problems exist in the prior art: (1) Insufficient catalyst efficiency: Conventional metal oxide catalysts (such as single platinum or cerium-supported catalysts) have problems of uneven distribution of active sites and low selectivity, resulting in an increase in side reactions (such as excessive condensation of silanol groups) and a relatively high content of cyclic siloxane impurities in the product. (2) Coarse reaction conditions: The hydrolysis reaction mostly uses a single temperature or a simple heating mode, making it difficult to accurately control the condensation process. Low-boiling impurities (such as unreacted chlorosilane, HCl, etc.) remain in the later stage of the reaction, and multiple distillations are required for purification, resulting in high energy consumption and easy thermal decomposition of the product. (3) Limitations in the purification process: Existing technologies mostly use a single purification method (such as distillation or adsorption), making it difficult to completely remove small-molecule impurities (such as trace chloride ions) and high-molecular-weight by-products (such as hexamethylcyclotrisiloxane), and the product purity is usually lower than 99.5%, which is difficult to meet the requirements of high-end applications. Summary of the Invention

[0004] The present invention proposes a synthesis method with high-efficiency catalysis, precise temperature control and deep purification to break through the bottleneck of the prior art and achieve a significant improvement in the purity of methylsiloxane.

[0005] The technical solution adopted by the present invention is as follows: A method for synthesizing high-purity methylsiloxane, comprising the following steps:

[0006] S1: Mix methylchlorosilane monomers and deionized water in a molar ratio of 1:3 - 5, add a metal oxide catalyst, and carry out a hydrolysis reaction under the protection of an inert gas;

[0007] S2: Control the temperature in stages after the hydrolysis reaction: In the first stage, stir and react at 60 - 80°C for 1 - 2 hours, and in the second stage, raise the temperature to 90 - 110°C and reduce the pressure to 0.05 - 0.1 MPa, and continue to react for 0.5 - 1 hour;

[0008] S3: After the reaction is completed, purification is carried out by vacuum distillation, molecular sieve adsorption and membrane filtration in sequence to obtain methylsiloxane with a purity ≥ 99.8%.

[0009] As a further improvement of the present invention, the methylchlorosilane monomer is selected from at least one of methyltrichlorosilane and dimethyldichlorosilane.

[0010] As a further improvement of the present invention, the metal oxide catalyst is a platinum-cerium composite catalyst supported on alumina, wherein the molar ratio of platinum to cerium is 1:0.5 - 2, and the loading amount is 1 - 3% of the mass of the alumina support.

[0011] As a further improvement of the present invention, the preparation method of the catalyst includes: impregnating the alumina support in a mixed solution containing a platinum salt and a cerium salt, and after ultrasonic treatment and drying, calcining at 400 - 500 °C for 2 - 4 hours.

[0012] As a further improvement of the present invention, the inert gas is one of nitrogen and argon, and the gas flow rate is 10 - 20 mL / min.

[0013] As a further improvement of the present invention, the stirring speed of the hydrolysis reaction is 300 - 500 rpm, and a phase transfer catalyst of 0.1 - 0.5 wt% is added to the reaction system.

[0014] As a further improvement of the present invention, the phase transfer catalyst is one of tetrabutylammonium bromide and polyethylene glycol - 600.

[0015] As a further improvement of the present invention, the reaction temperature in the first stage is 65 - 75 °C, the reaction temperature in the second stage is 95 - 105 °C, and the pressure is 0.06 - 0.08 MPa.

[0016] As a further improvement of the present invention, the molecular sieve adsorption uses a molecular sieve with a pore size of , the adsorption time is 2 - 4 hours, and the molecular sieve is pretreated: activated at 200 - 250 °C for 1 - 2 hours and then cooled to room temperature.

[0017] As a further improvement of the present invention, the membrane filtration uses a ceramic nanofiltration membrane with a molecular weight cut-off of 500 - 1000 Da, the operating pressure is 1.5 - 2.5 MPa, and the temperature is 25 - 40 °C.

[0018] Advantages of the present invention: (1) By using a platinum-cerium composite catalyst supported on alumina (molar ratio of platinum to cerium is 1:0.5 - 2), the synergistic effect of the high catalytic activity of platinum and the oxygen vacancies of cerium is utilized to significantly improve the selectivity of the hydrolysis and condensation reaction, effectively inhibit side reactions such as excessive condensation of silanol groups. Combining the preparation process of ultrasonic impregnation and high-temperature calcination, the active sites of the catalyst are evenly distributed and have strong stability, reducing the content of by-products such as cyclic siloxanes to less than 0.1%, and at the same time increasing the reaction yield to more than 95%.

[0019] (2) Through the coordinated control of mild condensation in the first stage (60 - 80 °C) and enhanced reaction under reduced pressure in the second stage (90 - 110 °C), the growth rate of the siloxane chain is precisely regulated, avoiding the problem of molecular chain breakage caused by local overheating. The reduced pressure operation (0.05 - 0.1 MPa) simultaneously promotes the efficient removal of low-boiling impurities (such as HCl and unreacted chlorosilanes), reducing the subsequent purification burden, and the overall energy consumption is reduced by more than 30% compared with the traditional process. Detailed implementation manners

[0020] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0021] The present invention provides a method for synthesizing high-purity methylsiloxane, comprising the following steps:

[0022] S1: Mix methylchlorosilane monomers and deionized water in a molar ratio of 1:3 - 5, add a metal oxide catalyst, and carry out a hydrolysis reaction under the protection of an inert gas;

[0023] S2: Control the temperature in stages after the hydrolysis reaction: Stir and react in the first stage at 60 - 80 °C for 1 - 2 hours, and in the second stage, raise the temperature to 90 - 110 °C and reduce the pressure to 0.05 - 0.1 MPa, and continue to react for 0.5 - 1 hour;

[0024] S3: After the reaction is completed, carry out purification by vacuum distillation, molecular sieve adsorption and membrane filtration in sequence to obtain methylsiloxane with a purity ≥ 99.8%.

[0025] The methylchlorosilane monomers in the present invention are selected from at least one of methyltrichlorosilane and dimethyldichlorosilane.

[0026] The metal oxide catalyst in the present invention is a platinum-cerium composite catalyst supported on alumina, wherein the molar ratio of platinum to cerium is 1:0.5 - 2, and the loading amount is 1 - 3% of the mass of the alumina support.

[0027] The preparation method of the catalyst in the present invention includes: impregnating an alumina support in a mixed solution containing a platinum salt and a cerium salt, followed by ultrasonic treatment and drying, and then calcining at 400 - 500 °C for 2 - 4 hours.

[0028] The inert gas in the present invention is one of nitrogen and argon, and the gas flow rate is 10 - 20 mL / min.

[0029] The stirring speed of the hydrolysis reaction in the present invention is 300 - 500 rpm, and a phase transfer catalyst of 0.1 - 0.5 wt% is added to the reaction system.

[0030] The phase transfer catalyst in the present invention is one of tetrabutylammonium bromide and polyethylene glycol - 600.

[0031] The reaction temperature in the first stage in the present invention is 65 - 75 °C, the reaction temperature in the second stage is 95 - 105 °C, and the pressure is 0.06 - 0.08 MPa.

[0032] The molecular sieve adsorption in the present invention uses a molecular sieve with a pore size of and the adsorption time is 2 - 4 hours. The molecular sieve is pretreated: activated at 200 - 250 °C for 1 - 2 hours and then cooled to room temperature.

[0033] The membrane filtration in the present invention uses a ceramic nanofiltration membrane with a molecular weight cut - off of 500 - 1000 Da, the operating pressure is 1.5 - 2.5 MPa, and the temperature is 25 - 40 °C.

[0034] Example 1:

[0035] Step S1: Hydrolysis reaction

[0036] (1) Weigh 100 g of methyltrichlorosilane (CH3Cl3Si) and 360 g of deionized water (molar ratio 1:4) and add them to the reaction kettle;

[0037] (2) Add a platinum - cerium composite catalyst supported on alumina (platinum:cerium = 1:1, loading amount 2%), and the catalyst dosage is 1.5% of the total mass of the reactants;

[0038] (3) Introduce nitrogen for protection (flow rate 15 mL / min), start stirring (400 rpm), and add 0.3 wt% of tetrabutylammonium bromide as a phase transfer catalyst;

[0039] (4) Maintain the system temperature at 70 °C and react for 1.5 hours.

[0040] Step S2: Temperature - controlled reaction in stages

[0041] (1) First stage: Heat up to 70 °C and stir - react for 1.5 hours;

[0042] (2) Second stage: Heat up to 100 °C, reduce the pressure to 0.07 MPa, and continue the reaction for 0.8 hours.

[0043] Step S3: Purification

[0044] (1) Vacuum distillation: Distill off low-boiling substances (including HCl and unreacted monomers) at 0.08 MPa and 120 °C;

[0045] (2) Molecular sieve adsorption: Pass the crude product through a molecular sieve with a pore size (pretreatment: Activate at 220 °C for 1.5 hours), and adsorb for 3 hours;

[0046] (3) Membrane filtration: Use a ceramic nanofiltration membrane with a molecular weight cut-off of 800 Da, filter at 2.0 MPa and 30 °C, and collect the filtrate.

[0047] Test results: The product is a colorless transparent liquid. After gas chromatography (GC) analysis, the purity of methylsiloxane is 99.82%, the content of cyclic siloxane impurities is 0.09%, the chloride ion content is 8 ppm, and the yield is 96.3%.

[0048] Example 2:

[0049] Step S1: Hydrolysis reaction

[0050] (1) Mix dimethyldichlorosilane (C2H6Cl2Si) with deionized water (molar ratio 1:3.5);

[0051] (2) The catalyst is platinum: cerium = 1:0.5, the loading amount is 3%, and the dosage is 2% of the total mass of the reactants;

[0052] (3) Protect with argon (flow rate 20 mL / min), stir at a speed of 500 rpm, and add 0.5 wt% polyethylene glycol-600.

[0053] Step S2: Temperature-controlled reaction in stages

[0054] (1) First stage: React at 65 °C for 2 hours;

[0055] (2) Second stage: 95 °C, reduce the pressure to 0.06 MPa, and react for 1 hour.

[0056] Step S3: Purification

[0057] (1) Vacuum distillation (0.06 MPa, 110 °C);

[0058] (2) Molecular sieve ( Pretreatment: Activate at 250 °C for 1 hour) adsorb for 4 hours;

[0059] (3) Filtration through a ceramic nanofiltration membrane (molecular weight cut-off 500 Da, 2.5 MPa, 25 °C).

[0060] Test results: purity 99.79%, cyclic impurities 0.11%, chloride ions 9 ppm, yield 94.8%.

[0061] Example 3:

[0062] Step S1: Hydrolysis reaction

[0063] (1) Mix methyltrichlorosilane and dimethyldichlorosilane (mass ratio 1:1), molar ratio 1:5;

[0064] (2) Catalyst platinum:cerium = 1:2, loading 1%, dosage 1%;

[0065] (3) Nitrogen protection (10 mL / min), stirring at 300 rpm, phase transfer catalyst 0.1 wt% tetrabutylammonium bromide.

[0066] Step S2: Temperature-controlled reaction in stages

[0067] (1) First stage: React at 80 °C for 1 hour;

[0068] (2) Second stage: At 110 °C, reduce the pressure to 0.1 MPa, react for 0.5 hour.

[0069] Step S3: Purification

[0070] (1) Vacuum distillation (0.1 MPa, 130 °C);

[0071] (2) Molecular sieve ( Activated at 200 °C for 2 hours) adsorption for 2 hours;

[0072] (3) Filtration through a ceramic nanofiltration membrane (1000 Da, 1.5 MPa, 40 °C).

[0073] Test results: purity 99.81%, cyclic impurities 0.08%, chloride ions 7 ppm, yield 95.6%.

[0074] Comparative example (traditional process):

[0075] (1) Use a single alumina-supported platinum catalyst (loading 2%), without cerium component;

[0076] (2) The hydrolysis reaction is carried out at 80 °C and atmospheric pressure for 3 hours throughout the process;

[0077] (3) Purification only uses vacuum distillation twice.

[0078] Test results: product purity 98.7%, cyclic siloxane content 1.2%, chloride ions 35 ppm, yield 88.4%.

[0079] Example Analysis

[0080] Purity and Yield: The purity of the products in Examples 1 - 3 of the present invention is all ≥99.7%, significantly higher than that of the comparative example (98.7%), verifying the effectiveness of platinum-cerium synergistic catalysis and multi-stage purification;

[0081] Energy Consumption Comparison: Through staged temperature control and pressure reduction operations, the reaction time of the present invention is shortened to 2 - 2.5 hours (the traditional process requires more than 3 hours), and the number of distillations is reduced, with the comprehensive energy consumption reduced by about 32%;

[0082] Impurity Control: The chloride ion content is ≤10 ppm (≥35 ppm for the traditional process), meeting the stringent requirements of semiconductor materials for trace ions.

[0083] In summary, the synthesis method of a high-purity methylsiloxane of the present invention not only significantly improves the purity of the product, but also reduces energy consumption and effectively controls the impurity content, demonstrating excellent technical advantages and application potential. Compared with the traditional process, the synthesis method of the present invention not only greatly improves the purity of methylsiloxane, but also realizes an energy-efficient production process through fine-tuning of reaction conditions and optimization of purification steps. This innovative synthesis strategy provides new ideas and technical paths for the preparation of high-end silicone materials, and is expected to play an important role in fields such as electronic packaging, pharmaceutical intermediates, and high-performance coatings, promoting the upgrading and development of related industries.

[0084] The above examples are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing examples, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for synthesizing high-purity methylsiloxane, characterized in that, It includes the following steps: S1: Mix methylchlorosilane monomer and deionized water in a molar ratio of 1:3 - 5, add a metal oxide catalyst, and carry out a hydrolysis reaction under the protection of an inert gas; S2: Control the temperature in stages after the hydrolysis reaction: In the first stage, stir and react at 60 - 80 °C for 1 - 2 hours, and in the second stage, raise the temperature to 90 - 110 °C and reduce the pressure to 0.05 - 0.1 MPa, and continue the reaction for 0.5 - 1 hour; S3: After the reaction is completed, carry out purification by vacuum distillation, molecular sieve adsorption and membrane filtration in sequence to obtain methylsiloxane with a purity ≥ 99.8%.

2. The synthesis method of a high-purity methylsiloxane according to claim 1, wherein, The metal oxide catalyst is a platinum - cerium composite catalyst supported on alumina, where the molar ratio of platinum to cerium is 1:0.5 - 2, and the loading amount is 1 - 3% of the mass of the alumina support.

3. The synthesis method of a high-purity methylsiloxane according to claim 2, characterized in that, The preparation method of the catalyst includes: impregnating the alumina support in a mixed solution containing platinum salt and cerium salt, after ultrasonic treatment and drying, calcining at 400 - 500 °C for 2 - 4 hours.

4. The synthesis method of a high-purity methylsiloxane according to claim 1, characterized in that, The reaction temperature in the first stage is 65 - 75 °C, the reaction temperature in the second stage is 95 - 105 °C, and the pressure is 0.06 - 0.08 MPa.

5. A method for synthesizing a high-purity methylsiloxane according to claim 1, characterized in that, The molecular sieve adsorption uses a molecular sieve with a pore size of , the adsorption time is 2-4 hours, and the molecular sieve is pretreated: activated at 200-250 °C for 1-2 hours and then cooled to room temperature.

6. The synthesis method of a high-purity methylsiloxane according to claim 1, wherein, The membrane filtration uses a ceramic nanofiltration membrane with a molecular weight cut - off of 500 - 1000 Da, the operating pressure is 1.5 - 2.5 MPa, and the temperature is 25 - 40 °C.

7. A method for synthesizing high-purity methylsiloxane according to claim 1, characterized in that, The methylchlorosilane monomer is selected from at least one of methyltrichlorosilane and dimethyldichlorosilane.

8. The synthesis method of a high-purity methyl siloxane according to claim 1, characterized in that, The inert gas is one of nitrogen and argon, and the gas flow rate is 10 - 20 mL / min.

9. A method for synthesizing high-purity methylsiloxane according to claim 1, characterized in that, The stirring speed of the hydrolysis reaction is 300 - 500 rpm, and a phase - transfer catalyst of 0.1 - 0.5 wt% is added to the reaction system.

10. The synthesis method of a high-purity methyl siloxane according to claim 1, characterized in that, The phase - transfer catalyst is one of tetrabutylammonium bromide and polyethylene glycol - 600.