Synthesis process of 3H-heptamethyltrisiloxane

Abstract

The present invention belongs to the technical field of siloxane synthesis, and specifically relates to a synthesis process for 3H-heptamethyltrisiloxane. The method comprises the following steps: putting monomethyldichlorosilane, hexamethyldisiloxane and metal chloride into a reactor, controlling the temperature to react, and obtaining a product through separation. The present invention uses metal chloride as a catalyst, and through the "activation-silicon increase" reaction of monomethyldichlorosilane and hexamethyldisiloxane, realizes the controllable embedding of Si-H bonds and the reuse of catalysts. The present invention avoids the safety hazards such as the release of acid water or hydrogen in traditional processes, and improves production efficiency and safety factor. The Si-Cl bond of monomethyldichlorosilane in the raw material of the present invention is transferred to generate trimethylchlorosilane, which is used as a synthetic raw material for organosilicon products such as hexamethyldisiloxane and MQ silicone resin, prolongs the service life of Si-Cl bonds in the organosilicon industry, and optimizes production costs.

Description

Technical Field

[0001] The invention belongs to the technical field of siloxane synthesis, and specifically relates to a synthesis process of 3H-heptamethyltrisiloxane. Background Art

[0002] 3H-heptamethyltrisiloxane (MD H MD is an important organosilicon intermediate. With the active silicon-hydrogen bond (Si-H) in its molecule, it is widely used in modified silicone oil, silicone rubber crosslinking agent, LED packaging material and surface hydrophobic treatment agent. With the continuous deepening of organosilicon industry research, MD H The requirements for M synthesis process, purification method, safety and environmental protection are increasing day by day, and the development of efficient and highly selective catalytic technology is particularly important.

[0003] Currently, MD H The synthesis methods of M are mainly divided into acid decomposition and telomerization methods and chlorosilane hydrolysis methods. The telomerization method is to decompose the high hydrogen content siloxane polymer (high hydrogen content silicone oil) into activated hydrogen content siloxane fragments under the action of acidic catalysts such as concentrated sulfuric acid or solid super acid, and then use hexamethyldisiloxane (MM) as a terminator to achieve the reduction of silicon atoms in the high hydrogen content silicone oil ("silicon reduction") through the cleavage / termination reaction of Si-O-Si bonds, thereby synthesizing small molecule MD. H M; The chlorosilane hydrolysis condensation method is to hydrolyze the Si-Cl or Si-N bond in small molecules of methyldichlorosilane (MeSiHCl2), trimethylchlorosilane (Me3SiCl) or hexamethyldisilazane to generate activated Me3Si-OH and intermediate [MeSiH(OH)2], respectively, and then realize MD through the random condensation of the above two Si-OH H Synthesis of M.

[0004] Patent CN116462698A discloses a method for preparing a porous carbon material catalyst (ZrO2 / SO4) with high hydrogen content silicone oil as raw material and a capping agent MM and a loaded active component. 2- ) was used to prepare MD by telomerization at 40-95 °C. H The M route. The catalyst used in this process is highly efficient and active, but the catalyst must be synthesized at high temperatures, making the process cumbersome and costly. Furthermore, the main raw material used is high-hydrogen silicone oil, which is produced by the hydrolysis and condensation of MeSiHCl2. The direct hydrolysis of the Si-Cl bond increases the raw material cost, reduces the economic benefits, and releases a large amount of acid water.

[0005] Patent CN105503931A discloses a catalytic telomerization reaction using low-cost 98% concentrated sulfuric acid as a catalyst, high-hydrogen silicone oil, and MM as raw materials. However, to dispose of the residual concentrated sulfuric acid after the reaction, alkaline deacidification washing is required, which leads to the release of wastewater and the dehydrogenation of silicon-hydrogen bonds under alkaline conditions, among other safety concerns.

[0006] Patent CN101020691A discloses a hydrolysis method for preparing MD H M process. This method first hydrolyzes trimethylsilane with the general formula Me3SiX with an inorganic weak base solution, then slowly drops methylhydrogensilane with the general formula MeSiHX2 into the hydrolysis system, and conducts hydrolysis and condensation reaction under stirring. However, MD H The yield of M is low.

[0007] Patent CN 117466932A produces MDHM in high yield by adding hexamethyldisilazane, water, and an organic amine to a reactor for hydrolysis, then adding methylhydrodichlorosilane dropwise to the hydrolysis system and separating the aqueous layer. The two aforementioned approaches, respectively, use inorganic bases and organic amines to adsorb the hydrogen chloride produced by Si-Cl bond hydrolysis, alleviating the Si-H instability issue associated with Si-Cl hydrolysis to some extent. However, both approaches produce large amounts of acidic brine wastewater.

[0008] Patent CN119060080A discloses a MD H The method for synthesizing M. The method first mixes Me3SiCl and MeSiHCl2 to obtain a mixed solution, drops the mixed solution into a mixed solvent at 10-20°C, and reacts at 0-40°C for 1-3 hours. After the reaction is completed, the upper layer is taken, adjusted to neutrality, and a catalyst is added to perform a rearrangement reaction to prepare MD. H This process requires the use of a mixed solvent of organic solvent and water in a specific ratio, which increases the cost of waste liquid treatment. In addition, the use of a solid acid catalyst requires subsequent neutralization and washing, and the waste liquid generated pollutes the environment.

[0009] In summary, the following problems are unavoidable in the existing synthesis process. Whether it is the hydrolysis process using chlorosilane as raw material or the "silicon reduction" polymerization process using high hydrogen content silicone oil as raw material, both are based on the loss of Si-Cl bonds in the upstream of the organosilicon industry; at the same time, the strong acid environment triggers the breakage of Si-H bonds to produce hydrogen, the catalyst cannot be recovered, and the wastewater / waste residue treatment caused by deacidification is a major problem for MD. H M's industrial production brings hidden dangers in safety and environmental protection. Summary of the Invention

[0010] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a synthesis process for 3H-heptamethyltrisiloxane. The raw materials used in this process are upstream products of organic silicon. During the reaction, Si-Cl bonds are only transferred without loss, and no wastewater or waste gas is generated. The process has high economic benefits, the catalyst is safe and recyclable, and is suitable for industrial production.

[0011] The structure of 3H-heptamethyltrisiloxane is shown in Formula I:

[0012]

[0013] Formula I.

[0014] The synthesis process of 3H-heptamethyltrisiloxane of the present invention comprises the following steps: adding monomethylhydrogendichlorosilane, hexamethyldisiloxane and metal chloride into a reaction kettle, reacting under controlled temperature, and separating by normal pressure and reduced pressure distillation to obtain the product.

[0015] Preferably, the metal chloride is one or more of aluminum trichloride, ferric trichloride, and gallium trichloride.

[0016] More preferably, the metal chloride is ferric chloride, the amount of ferric chloride used is 0.5% of the amount of hexamethyldisiloxane, and the reaction time using ferric chloride as a catalyst is 2 to 5 hours.

[0017] The principle of the present invention is to activate the Si-O-Si bond in hexamethyldisiloxane by ferric chloride (FeCl3), and the transition state formed is shown in Formula II:

[0018]

[0019] Formula II.

[0020] Since the Si-Cl bond in MeHSiCl2 is more reactive than O┈FeCl2, the transition state [Si-O-FeCl2] is broken and FeCl3 is regenerated. At the same time, the [MeHSi] unit is embedded in the transition state structure to form a new [Si-O-SiH] compound; and the Cl in MeHSiCl2 is transferred to the newly generated trimethylchlorosilane (Me3SiCl). Similarly, with the formation of trimethylchlorosilane (Me3SiCl), the transition from disiloxane (MM) to trisiloxane (MD) is achieved. H Finally, the product containing the metal chloride substrate after distillation can be further fed to produce 3H-heptamethyltrisiloxane.

[0021] The molar ratio of monomethyldichlorosilane to hexamethyldisiloxane is 1:(2.0-3.0).

[0022] The reaction temperature of the temperature-controlled reaction is 20°C to 50°C, more preferably 50°C.

[0023] The reaction time of the temperature-controlled reaction is 0.5h~5h.

[0024] The products obtained by the separation are specifically: trimethylchlorosilane generated by the reaction is separated by distillation at 65°C under normal pressure, unreacted hexamethyldisiloxane is separated by distillation at 110°C under normal pressure, 3H-heptamethyltrisiloxane is fractionated under reduced pressure at -0.025MPa and 138°C, and 3H,5H-octamethyltetrasiloxane is fractionated under reduced pressure at -0.025MPa and 160°C.

[0025] After the product is obtained by separation, the metal chloride at the bottom of the kettle is recycled.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention uses metal chloride as a catalyst and realizes the controllable embedding of Si-H bonds and the reuse of catalysts through the "activation-siliconization" reaction of monomethylhydrodichlorosilane and hexamethyldisiloxane (both raw materials are upstream products of organic silicon and have low costs).

[0028] (2) The present invention avoids the safety hazards such as the release of HCl acid water caused by the hydrolysis of monomethylhydrodichlorosilane in the traditional hydrolysis process, and the release of hydrogen from the Si-H bond during the polymerization production and post-treatment process, thereby improving production efficiency and safety factor.

[0029] (3) The Si-Cl bond of monomethylhydrodichlorosilane in the raw material of the present invention is transferred to generate trimethylchlorosilane. Trimethylchlorosilane is used as a raw material for the synthesis of organosilicon products such as hexamethyldisiloxane and MQ silicone resin, which prolongs the service life of the Si-Cl bond in the organosilicon industry and optimizes production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the gas phase spectrum of the crude product obtained in Example 1;

[0031] Figure 2 is the gas chromatography-mass spectrometry of trimethylchlorosilane prepared in Example 1;

[0032] Figure 3 is the gas chromatography-mass spectrometry of 3H-heptamethyltrisiloxane prepared in Example 1;

[0033] Figure 4 This is the NMR spectrum of 3H-heptamethyltrisiloxane prepared in Example 1. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the examples.

[0035] Unless otherwise specified, all raw materials used in the examples are commercially available.

[0036] Example 1

[0037] The synthesis process of 3H-heptamethyltrisiloxane comprises the following steps:

[0038] Hexamethyldisiloxane, monomethyldichlorosilane and ferric chloride were added to the reaction kettle at a molar ratio of 30:10:0.15, stirring was started, and the reaction temperature was controlled at 50°C. After reacting for 2 hours, a hydrogenated siloxane mixture was obtained. Figure 1 As shown in the gas phase spectrum data of the crude product, the components of the crude product after the reaction are mainly trimethylchlorosilane, hexamethyldisiloxane, 3H-heptamethyltrisiloxane and 3H,5H-octamethyltetrasiloxane. The temperature was raised to 65°C under normal pressure to separate trimethylchlorosilane, and then the temperature was raised to 110°C to separate hexamethyldisiloxane. Subsequently, the pressure was reduced to -0.025MPa, and 3H-heptamethyltrisiloxane and 3H,5H-octamethyltetrasiloxane were separated at 138°C and 160°C, respectively. GC-MS analysis of each product showed clear characteristic peaks, and the purity of the target components reached 99%. Figure 2 As shown in the gas chromatography-mass spectrometry of trimethylchlorosilane, the recovery rate of trimethylchlorosilane is 95.6%. Figure 3 The gas chromatography-mass spectra of 3H-heptamethyltrisiloxane are shown in Figure 2. The yield of 3H-heptamethyltrisiloxane obtained after distillation is 50.3%. Figure 4 shown.

[0039] After the distillation is completed, the catalyst in the reactor does not need any treatment. The same amount of feed as in the first experiment is added and the same treatment steps as in the first experiment are repeated. This process is repeated for four batches, as shown in Table 1:

[0040] Table 1 Product yields of Example 1 after 5-times catalyst recycling

[0041]

[0042] Remark:

[0043] Yield of 3H-heptamethyltrisiloxane = product mass / theoretical mass × 100%;

[0044] Theoretical mass = amount of methylhydrogendichlorosilane × molecular weight of 3H-heptamethyltrisiloxane.

[0045] Recovery rate of trimethylchlorosilane = product mass / theoretical mass × 100%;

[0046] Theoretical mass = amount of methylhydrogendichlorosilane × 2 × molecular weight of trimethylchlorosilane.

[0047] The present invention can achieve an average recovery rate of trimethylchlorosilane of about 94.2% and an average yield of 3H-heptamethyltrisiloxane of about 49.02%, verifying the reusability of the catalyst.

[0048] Example 2

[0049] Hexamethyldisiloxane, monomethylhydrodichlorosilane, and ferric chloride were added to a reactor at a molar ratio of 28:10:0.14, respectively. Stirring was initiated and the reaction temperature was maintained at 40°C. After 3 hours of reaction, a hydrogenated siloxane mixture was obtained. Trimethylchlorosilane (94% recovery), hexamethyldisiloxane, 3H-heptamethyltrisiloxane (48.1% yield), and 3H,5H-octamethyltetrasiloxane were subsequently separated (separation procedures were the same as in Example 1).

[0050] Example 3

[0051] The synthesis process of 3H-heptamethyltrisiloxane comprises the following steps:

[0052] Hexamethyldisiloxane, monomethyldichlorosilane, and ferric chloride were added to a reactor at a molar ratio of 25:10:0.125, respectively. Stirring was initiated and the reaction temperature was controlled at 40°C. After 3 hours of reaction, a hydrogenated siloxane mixture was obtained. Trimethylchlorosilane (95.1% recovery), hexamethyldisiloxane, 3H-heptamethyltrisiloxane (46.3% yield), and 3H,5H-octamethyltetrasiloxane were separated in sequence (separation procedures were the same as in Example 1).

[0053] Example 4

[0054] The synthesis process of 3H-heptamethyltrisiloxane comprises the following steps:

[0055] Hexamethyldisiloxane, monomethyldichlorosilane, and ferric chloride were added to a reactor at a molar ratio of 22:10:0.11, respectively. Stirring was initiated and the reaction temperature was maintained at 30°C. After 3.5 hours of reaction, a hydrogenated siloxane mixture was obtained. Trimethylchlorosilane (94.5% recovery), hexamethyldisiloxane, 3H-heptamethyltrisiloxane (46.2% yield), and 3H,5H-octamethyltetrasiloxane were subsequently separated (separation procedures were the same as in Example 1).

[0056] Example 5

[0057] The synthesis process of 3H-heptamethyltrisiloxane comprises the following steps:

[0058] Hexamethyldisiloxane, monomethylhydrodichlorosilane, and ferric chloride were added to a reactor at a molar ratio of 20:10:0.1, stirred, and the reaction temperature was controlled at 20°C. After 5 hours of reaction, trimethylchlorosilane and unreacted hexamethyldisiloxane were distilled off under atmospheric pressure to obtain a hydrogenated siloxane mixture. Trimethylchlorosilane (95% recovery), hexamethyldisiloxane, 3H-heptamethyltrisiloxane (45.0% yield), and 3H,5H-octamethyltetrasiloxane were separated in sequence (separation procedures were the same as in Example 1).

[0059] Example 6

[0060] Hexamethyldisiloxane, monomethylhydrodichlorosilane, and gallium trichloride were added to a reactor at a molar ratio of 30:10:0.15, respectively. Stirring was initiated and the reaction temperature maintained at 50°C. After 30 minutes of reaction, a hydrogenated siloxane mixture was obtained. The crude product contained trimethylchlorosilane, hexamethyldisiloxane, 3H-heptamethyltrisiloxane, and 3H,5H-octamethyltetrasiloxane. The reaction was heated to 65°C under atmospheric pressure to separate trimethylchlorosilane, followed by heating to 110°C to separate hexamethyldisiloxane. The reaction was then decompressed to -0.025 MPa, and 3H-heptamethyltrisiloxane and 3H,5H-octamethyltetrasiloxane were separated at 138°C and 160°C, respectively. The recovery rate of trimethylchlorosilane was 95%, with a purity of 99%. The yield of 3H-heptamethyltrisiloxane was 51%, with a purity of 99%.

[0061] Example 7

[0062] Hexamethyldisiloxane, monomethylhydrodichlorosilane, and aluminum trichloride were added to a reactor at a molar ratio of 30:10:0.15, respectively. Stirring was initiated and the reaction temperature maintained at 50°C. After 2 hours of reaction, a hydrogenated siloxane mixture was obtained. The crude product contained trimethylchlorosilane, hexamethyldisiloxane, 3H-heptamethyltrisiloxane, and 3H,5H-octamethyltetrasiloxane. The reaction mixture was heated to 65°C under atmospheric pressure to separate trimethylchlorosilane, followed by heating to 110°C to separate hexamethyldisiloxane. The reaction mixture was then decompressed to -0.025 MPa, and 3H-heptamethyltrisiloxane and 3H,5H-octamethyltetrasiloxane were separated at 138°C and 160°C, respectively. The recovery rate of trimethylchlorosilane was 90% with a purity of 99%, while the yield of 3H-heptamethyltrisiloxane was 36% with a purity of 99%.

[0063] Comparative Example 1

[0064] In the reactor, 202 type methyl hydrogen silicone oil and hexamethyldisiloxane were added in a mass ratio of 1:2, and then 98% mass concentration of concentrated sulfuric acid was added according to 0.5% of the total mass of 202 type methyl hydrogen silicone oil and hexamethyldisiloxane. The reaction was stirred at room temperature for 4 hours, and the reaction was allowed to settle. The upper reaction liquid was neutralized with 5% mass concentration of sodium bicarbonate solution. When the pH was equal to 7, the upper clear liquid was taken and distilled in a distillation tower to obtain more than 99% MD H M yield 20%.

[0065] Comparative Example 2

[0066] 150 parts by mass of Me3SiCl2 were added to a jacketed reactor connected to a low-temperature thermostat, stirring was started, 70 parts by mass of NaHCO3 saturated solution were gradually added to the reactor, the reaction temperature was controlled not to exceed 10°C, and then 60 parts by mass of MeSiHCl2 were added dropwise, the reaction temperature was 10°C, the addition time was controlled within 2.5h, and the reaction was stopped immediately after the addition was completed. The oil phase was washed with water until neutral, dried with anhydrous CaCl2, and MD was distilled. H The yield of M was 23.3%.

Claims

1. A synthesis process for 3H-heptamethyltrisiloxane, characterized in that: The following steps are involved: Putting monomethyldichlorosilane, hexamethyldisiloxane and metal chloride into a reactor, controlling the temperature for reaction, and obtaining the product through separation; The structure of 3H-heptamethyltrisiloxane is shown in Formula I: Formula I; The metal chloride is one of aluminum trichloride, ferric trichloride and gallium trichloride; The molar ratio of monomethyldichlorosilane to hexamethyldisiloxane is 1:(2.0-3.0); The reaction temperature of the temperature-controlled reaction is 20°C to 50°C.

2. The synthesis process of 3H-heptamethyltrisiloxane according to claim 1, wherein The metal chloride is ferric chloride.

3. The synthesis process of 3H-heptamethyltrisiloxane according to claim 2, characterized in that: The amount of ferric chloride used is 0.5% of the amount of hexamethyldisiloxane.

4. The synthesis process of 3H-heptamethyltrisiloxane according to claim 1, characterized in that: The reaction time of the temperature-controlled reaction is 0.5h~5h.

5. The synthesis process of 3H-heptamethyltrisiloxane according to claim 1, characterized in that: The separation to obtain the product is specifically as follows: heating in sequence and distilling out the trimethylchlorosilane generated by the reaction, unreacted hexamethyldisiloxane, 3H-heptamethyltrisiloxane, and 3H,5H-octamethyltetrasiloxane respectively.

6. The synthesis process of 3H-heptamethyltrisiloxane according to claim 1, characterized in that: After the product is obtained by separation, the metal chloride at the bottom of the kettle is recycled.

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