Preparation method of D3F

Abstract

The invention relates to a preparation method and application of trifluoropropyl methyl cyclotrisiloxane (D3F), and the method comprises the following steps: hydrolyzing trifluoropropyl methyl dichlorosilane to prepare a hydrolysate containing D3F, and then separating and purifying through distillation to obtain a high-purity D3F product. And the D3F yield is improved by optimizing hydrolysis conditions including reaction temperature, reaction time, reaction media, the feeding ratio of a substrate to the media and the like. According to the method, D3F is directionally prepared through one-step reaction, hydrochloric acid, an organic solvent and other catalysts do not need to be additionally added into a reaction system, further catalytic cracking is not needed, and the method has the advantages of being easy and convenient to operate, high in efficiency, green in reaction condition, high in product purity and the like.

Description

Technical Field

[0001] The invention belongs to the field of synthesis of organosilicon compounds, and specifically relates to 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane and a preparation method and application thereof. Background Art

[0002] Fluorosilicone rubber is a special synthetic material with a main chain of silicon oxygen structure and a side chain of methyl and trifluoropropyl structure. It is mainly obtained by ring-opening polymerization of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane (D3F). The special chemical structure of this material gives it many unique functions. The Si-O-Si structure of the main chain gives fluorosilicone rubber flexibility and thermal stability, while the side chain structure of trifluoropropyl gives fluorosilicone rubber good oil and solvent resistance. As an important raw material for fluorosilicone rubber, the output of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane has always been low and the price is relatively expensive. Therefore, a simpler method for synthesizing D3F is particularly important.

[0003] The existing data on the synthesis method of D3F is to drip trifluoropropylmethyldichlorosilane into a high concentration hydrochloric acid solution or a mixed solution of hydrochloric acid and xylene to first perform a hydrolysis reaction, and then add a catalyst such as sodium hydroxide to the hydrolyzate to perform a catalytic cracking reaction to prepare D3F. In this method, the concentration of the hydrochloric acid solution is above 20%, so a large amount of hydrochloric acid is required, or other organic solvents and auxiliary agents such as octadecyl alcohol are also required. Through multiple experiments, it has been verified that trifluoropropylmethyldichlorosilane is hydrolyzed in a high concentration hydrochloric acid solution to mainly generate trifluoropropylmethylcyclotetrasiloxane (D4F) and linear trifluoropropylmethylsiloxane. Even if a small amount of D3F is produced, it is unstable in a 20% hydrochloric acid aqueous solution and eventually converted into D4F and linear trifluoropropylmethylsiloxane. Therefore, D3F cannot be directly obtained by simple distillation, and D3F can only be synthesized by further catalytic cracking reactions, which undoubtedly increases the difficulty of preparing D3F and the production cost. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane (D3F) and a preparation method thereof. The present invention first hydrolyzes and condenses trifluoropropylmethyldichlorosilane in water at a certain temperature to cause intramolecular cyclization. Since the hydrolysis medium is water, even if a small amount of HCl is produced by hydrolysis, the concentration is low, so D3F can be stably generated. In addition, the present invention optimizes the reaction temperature, feed volume ratio, reaction time and other conditions to obtain a high content of D3F in the hydrolyzate. Then, D3F with a purity of >99.5% is obtained only by distillation purification.

[0005] This method is different from the traditional synthesis method. This method does not require the addition of high-concentration hydrochloric acid or other organic solvents for hydrolysis. In addition, this method directly obtains a large amount of D3F only through hydrolysis, and then obtains D3F with a purity of >99.5% through simple distillation.

[0006] The technical solution of the present invention is as follows: 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane has the following structure:

[0007]

[0008] According to the present invention, the preparation method of the above 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane comprises the following steps:

[0009] The hydrolysis medium is heated to a set temperature, and the raw material trifluoropropylmethyldichlorosilane is added dropwise to the hydrolysis medium, stirred, and a hydrolysis and cyclization reaction is performed; a hydrolyzate containing trifluoropropylmethylcyclotrisiloxane (D3F) is obtained, and D3F in the hydrolyzate is separated by distillation to obtain a high-purity D3F product.

[0010] According to the present invention, preferably, the hydrolysis medium is water, and the hydrolysis temperature is 30-70°C; according to the present invention, preferably, the feed volume ratio of methyldichlorosilane to the hydrolysis medium is 1:(2-3); preferably, the hydrolysis reaction time is 0.1-2h;

[0011] According to the present invention, after the reaction is completed, the reaction system is allowed to stand and separate, the organic layer is taken out and washed with water until it is neutral; under reduced pressure, the organic layer is distilled to obtain purified 1,3,5-trimethyl-1,3,5-tri(3,3,3-trifluoropropyl)cyclotrisiloxane; preferably, the water washing temperature is 40-50°C, and the water washing time is 0.5-1h; preferably, the distillation conditions are pressure 1-3kPa and temperature 100-180°C; the fraction of 125-130°C / 2kPa is intercepted during the distillation process, which is the product 1,3,5-trimethyl-1,3,5-tri(3,3,3-trifluoropropyl)cyclotrisiloxane; further, the reflux ratio is controlled in the distillation process (6-10): 1;

[0012] According to the method for preparing 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane of the present invention, a preferred embodiment comprises the following steps:

[0013] (1) Heat the hydrolysis medium to 30-70°C, drop the raw material trifluoropropylmethyldichlorosilane into the hydrolysis medium for hydrolysis and cyclization reaction, and stir the reaction for 0.1-2h;

[0014] (2) Let stand, separate into layers, take the organic phase and wash with water until it becomes neutral;

[0015] (3) Under reduced pressure, the organic layer is distilled to obtain 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane.

[0016] According to the present invention, the purity of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane obtained by rectification is greater than 99.5%. 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane is used for preparing fluorosilicone rubber by ring-opening copolymerization with other fluorosilanes, especially preparing fluorosilicone rubber or fluorosilicone silicone oil by ring-opening polymerization of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane monomer.

[0017] The equation of the present invention is:

[0018]

[0019] Anything not described in detail in the present invention is based on conventional techniques in the art.

[0020] Compared with the prior art, the technical features and beneficial effects of the present invention are as follows:

[0021] 1. The present invention utilizes trifluoropropylmethyldichlorosilane to directly hydrolyze and cyclize in one step under relatively mild conditions to prepare 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane, and the product is stable and has good reproducibility.

[0022] 2. The hydrolysis solvent of the present invention only requires water, and no high-concentration hydrochloric acid and other solvents and catalysts need to be added, so the reaction conditions are green and environmentally friendly.

[0023] 3. The preparation method of the present invention has simple process, easy operation, and the hydrolysis medium can be recycled, which reduces the production cost and is easy to realize industrial production.

[0024] 4. The 3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane of the present invention has high ring-opening activity, good ring-opening polymerization effect as a monomer or with other siloxanes, and the obtained fluorosilicone rubber and fluorosilicone oil have excellent performance.

[0025] This method prepares D3F in a targeted manner through a one-step reaction, does not require the addition of hydrochloric acid, organic solvents and other catalysts to the reaction system, and does not require further catalytic cracking. It has the advantages of simple operation, high efficiency, green reaction conditions and high product purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1This is the 1H-NMR spectrum of the product obtained by reactive distillation in Example 1 of the present invention.

[0027] Figure 2 It is the H NMR spectrum of the product of Example 1. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with the following examples, which are not intended to limit the present invention. The raw materials described in the examples are all conventional raw materials, which can be purchased on the market or prepared according to the prior art.

[0029] Example 1

[0030] The preparation method of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane (D3F) comprises the following steps:

[0031] (1) Add 2.3 L of water (the volume ratio of trifluoropropylmethyldichlorosilane to water is 1:3) as a hydrolysis medium into a 10 L glass three-necked flask, heat to 60 ° C, add 1000 g of the raw material trifluoropropylmethyldichlorosilane into the water using a dropping funnel, stir magnetically to carry out hydrolysis and cyclization reaction, and stir for 0.5 h;

[0032] (2) After the reaction is completed, the reaction solution is allowed to stand and separate into layers, and the organic phase is taken out and washed with 50°C water for 5 times until the system (eluent) becomes neutral to obtain an organic layer, i.e., a crude hydrolyzate;

[0033] (3) Collect the organic layer, distill it under reduced pressure, and then purify it by distillation at a reflux ratio of 10:1 by volume, and cut the fraction at 125-130°C / 2kPa, which is the product 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane, with a purity of 99.6% and a yield of 46.8%.

[0034] The gas chromatogram of the hydrolyzate is shown in Figure 1 As shown, after comparison with the commercially available D3F bulk drug and homemade D4F, the peak at 1.2 min is the solvent peak, the peak at 4.8 min is the internal standard n-decane peak, the peak at 7.6 min is the product D3F peak, the peak at 9.2 min is the D4F peak, and the peak at 10.4 min is the D5F peak.

[0035] The NMR hydrogen spectrum of the product is as follows Figure 2As shown, 7.26ppm is the deuterated chloroform solvent peak, of which 2.01-2.12ppm is the chemical shift of the methylene H close to -CF3 in Si-CH2CH2CF3, with an integrated area of ​​2, 0.82-0.86ppm is the chemical shift of the methylene H close to Si in Si-CH2CH2CF3, with an integrated area of ​​2; 0.17-0.23ppm is the chemical shift of H in Si-CH3, with an integrated area of ​​3; the integrated area ratio of H in the two groups is 2:2:3, and it can be determined that the product is 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane, and the purity of the product can be calculated to be 99.6% by adding internal standard to measure NMR.

[0036] Example 2

[0037] The preparation method of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane comprises the following steps:

[0038] (1) Add 2.3 L of water (the volume ratio of trifluoropropylmethyldichlorosilane to water is 1:3) as a hydrolysis medium to a 10 L glass three-necked flask, heat to 50 °C, and use a dropping funnel to drop 1 kg of the raw material trifluoropropylmethyldichlorosilane into the water. Stir magnetically to carry out hydrolysis and cyclization reaction, and stir for 0.5 h.

[0039] (2) After the reaction is completed, the reaction solution is allowed to stand and separate into layers, and the organic phase is taken out and washed with 50°C water for 5 times until the system becomes neutral, thereby obtaining an organic layer, i.e., a crude hydrolyzate;

[0040] (3) Collect the organic layer, distill it under reduced pressure, and then purify it by distillation with a reflux ratio of 9:1 by volume, and cut the fraction of 125-130°C / 2kPa, which is the product 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane, with a purity of 99.6% and a yield of 45.9%.

[0041] Example 3

[0042] The preparation method of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane comprises the following steps:

[0043] (1) Add 230 mL of water (the volume ratio of trifluoropropylmethyldichlorosilane to water is 1:3) as a hydrolysis medium into a 500 mL glass three-necked flask, heat to 70°C, and use a dropping funnel to drop 103 g of the raw material trifluoropropylmethyldichlorosilane into the water. Stir magnetically to carry out hydrolysis and cyclization reaction, and stir for 0.5 h.

[0044] (2) After the reaction is completed, the reaction solution is allowed to stand and separate into layers, and the organic phase is taken out and washed with 50°C water four times until the system becomes neutral, thereby obtaining an organic layer, i.e., a crude hydrolyzate;

[0045] (3) Collect the organic layer, distill it under reduced pressure, and then purify it by distillation at a reflux ratio of 10:1 by volume, and cut the fraction at 125-130°C / 2kPa, which is the product 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane, with a purity of 99.6% and a yield of 43.6%.

[0046] Comparative Example 1

[0047] 100 g of the remaining material in the container (flask) after the distillation (rectification and purification) of D3F in Example 1 was taken, and distilled again under reduced pressure, and then distilled and purified with a reflux ratio of 10:3, and the fraction at 133-135°C / 400Pa was intercepted, which was the by-product trifluoropropylmethylcyclotetrasiloxane (D4F). The purity of D4F was 99.6% as determined by NMR, and was used as a by-product D4F reference substance.

[0048] Comparative Example 2

[0049] Add 230ml of 20%wt hydrochloric acid aqueous solution (the volume ratio of trifluoropropylmethyldichlorosilane to water is 1:3) as the hydrolysis medium to a 1L glass three-necked flask, heat to 60°C, and use a dropping funnel to drop 101.2g of the raw material trifluoropropylmethyldichlorosilane into the water, stir magnetically, and perform a hydrolysis and cyclization reaction. Stir the reaction for 0.5h. After the reaction is completed, let the reaction liquid stand and separate, take out the organic phase and wash it with 50°C water for 5 times until the system becomes neutral, and obtain the organic layer, i.e., the crude hydrolyzate. The hydrolyzate is sampled and measured by GC. The internal standard method calculates that the yield of D3F is 7.4%, which is relatively low. The product is mainly composed of by-product D4F and linear trifluoropropylmethylsiloxane.

[0050] Comparative Example 3

[0051] Add 85 ml of water (the volume ratio of trifluoropropylmethyldichlorosilane to water is 1:1) as the hydrolysis medium to a 1L glass three-necked flask, heat to 60°C, and use a dropping funnel to drop 103.6 g of the raw material trifluoropropylmethyldichlorosilane into the water, stir magnetically, and perform a hydrolysis and cyclization reaction. Stir the reaction for 0.5 h. After the reaction is completed, let the reaction liquid stand and separate, take out the organic phase and wash it with 50°C water for 5 times until the system becomes neutral, and obtain the organic layer, i.e., the crude hydrolyzate. The hydrolyzate is sampled and measured by GC, and the D3F yield calculated by the internal standard method is 23.4%, which is relatively low.

[0052] Comparative Example 4

[0053] Add 245ml of water (the volume ratio of trifluoropropylmethyldichlorosilane to water is 1:3) as the hydrolysis medium to a 1L glass three-necked flask, control the reaction temperature at 5-10°C in an ice bath, and use a dropping funnel to drop 103.1g of the raw material trifluoropropylmethyldichlorosilane into the water, stir magnetically, and perform a hydrolysis and cyclization reaction. Stir the reaction for 0.5h. After the reaction is completed, let the reaction liquid stand and separate, take out the organic phase and wash it with 50°C water for 5 times until the system becomes neutral, and obtain the organic layer, i.e., the crude hydrolyzate. The hydrolyzate is sampled and measured by GC, and the D3F yield calculated by the internal standard method is 15.3%, which is a low yield.

[0054] Comparative Example 5

[0055] Add 245ml of water as a hydrolysis medium (the volume ratio of trifluoropropylmethyldichlorosilane to water is 1:3) to a 1L glass three-necked flask, heat to 80°C, and use a dropping funnel to drop 100g of the raw material trifluoropropylmethyldichlorosilane into the water, stir magnetically, and perform a hydrolysis and cyclization reaction. Stir the reaction for 0.5h. After the reaction is completed, let the reaction liquid stand and separate, take out the organic phase and wash it with 50°C water for 5 times until the system becomes neutral, and obtain the organic layer, i.e., the crude hydrolyzate. The hydrolyzate is sampled and measured by GC, and the D3F yield calculated by the internal standard method is 21.6%, which is a low yield.

[0056] Comparative Example 6

[0057] Add 245ml of water as a hydrolysis medium (the volume ratio of trifluoropropylmethyldichlorosilane to water is 1:3) to a 1L glass three-necked flask, heat to 60°C, and use a dropping funnel to drop 100g of the raw material trifluoropropylmethyldichlorosilane into the water, stir magnetically, and perform a hydrolysis and cyclization reaction. Stir the reaction for 0.5h. After the reaction is completed, let the reaction liquid stand and separate, take out the organic phase and wash it with 25°C water 5 times until the system becomes neutral, and obtain the organic layer, i.e., the crude hydrolyzate. The hydrolyzate is sampled and measured by GC, and the D3F yield calculated by the internal standard method is 32.1%, which is a low yield.

[0058] Application Example 1

[0059] Referring to patent US4125551, 30g of octamethylcyclotetrasiloxane and 2.1g of hexamethyldisiloxane were added to a reactor, and after preheating at 150°C for 30 minutes, 4.3g of phosphoric acid aqueous solution was added dropwise within 0.5 hours. The temperature was then raised to 180°C, and the reaction was continued for 10 hours to fully evaporate the water. Finally, the prepared silicon-based phosphate was placed in a dryer for standby use.

[0060] 16 mg (0.10 mmol) of sodium hydroxide was added to a glass reactor with mechanical stirring, and then 230 g of dry D3F (490 mmol) prepared in Example 1 was added, and the reactor was heated to 50° C. When the temperature reached 50° C., it was maintained for 10 minutes, and then 0.7 g of dry tetrahydrofuran (9.7 mmol) was added. The viscosity of the solution in the reactor gradually increased. When the viscosity reached the maximum value (that is, the current of mechanical stirring reached the peak value), 2.3 g of silyl phosphate with a mass% of D3F monomer was added, and the fluorosilicone rubber was obtained after sufficient stirring.

[0061] Product appearance: clear and transparent, yield 97.6%, molecular weight: 400.0 kDa, molecular weight distribution: 1.30, volatile matter: 2.5% (150°C×4h).

[0062] Application Example 2

[0063] 80 mg (0.10 mmol) of lithium tert-butoxide was added to a glass reactor with mechanical stirring, and then 230 g of dry D3F (490 mmol) prepared in Example 2 was added, and the reactor was heated to 50° C. When the temperature reached 50° C., it was maintained for 10 minutes, and then 0.4 g of dry ethyl acetate (4.5 mmol) was added. The viscosity of the solution in the reactor gradually increased. When the viscosity reached the maximum value (i.e., the current of mechanical stirring reached the peak value), 2.3 g of silyl phosphate with a mass% of D3F monomer was added, and the fluorosilicone rubber was obtained after sufficient stirring.

[0064] Product appearance: clear and transparent, yield 96.8%, molecular weight: 980.0 kDa, molecular weight distribution: 1.26, volatile matter: 1.0% (150°C×4h).

[0065] Finally, the method of the present invention is only a preferred implementation scheme and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing D3F, characterized in that: The method comprises the following steps: heating water to 30-70 DEG C, dropping trifluoropropylmethyldichlorosilane into the water, stirring, and carrying out a hydrolysis and cyclization reaction, wherein the amount of water added is more than twice the volume of the trifluoropropylmethyldichlorosilane; after the reaction is completed, standing and separating the layers, separating and obtaining an organic layer hydrolyzate, washing the organic layer hydrolyzate with water, and separating D3F (1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane) in the hydrolyzate by distillation to obtain a high-purity D3F product.

2. The preparation method according to claim 1, characterized in that: Preferably, the amount of water added is 2-6, more preferably 2-3 times the volume of trifluoropropylmethyldichlorosilane.

3. The preparation method according to claim 1, characterized in that: The temperature of the hydrolysis and cyclization reaction should not be too high or too low; the reaction temperature is 30 to 70°C, more preferably 50 to 60°C; the reaction time is 0.1 to 2h, preferably 0.3 to 1.5h, more preferably 0.5 to 1h.

4. The preparation method according to claim 1, characterized in that: After the hydrolysis and cyclization reaction is completed, the system is allowed to stand and separate into layers, and the organic layer is taken and washed with water until it is neutral to remove HCl produced by the hydrolysis, thereby obtaining a hydrolyzate; the hydrolyzate is distilled under reduced pressure to obtain purified 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane.

5. The preparation method according to claim 1 or 4, characterized in that: The water washing temperature is 30 to 60°C, preferably 40 to 60°C, more preferably 40 to 50°C.

6. The preparation method according to claim 1 or 4, characterized in that: The hydrolyzate is subjected to vacuum distillation to obtain purified 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane; the distillation conditions are pressure 1-3 KPa, more preferably 1-2 KPa; temperature 100-180°C, preferably 120-150°C, more preferably 125-130°C; the volume reflux ratio during the distillation process is controlled to be (6-10):1, preferably (7-10):1, more preferably (8-10):1.

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