A process for the preparation of 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane

Abstract

The application belongs to the technical field of organic silicon chemical synthesis, and relates to a preparation method of 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane. The method uses alkoxysilane monomer and polysiloxane as raw materials, and under the action of a catalyst, is reacted at 60-80 DEG C for 1-3 h, then is subjected to rectification separation after temperature rising, after recovery of low-boiling-point raw materials, a stable distillate at 138-140 DEG C is received under a reflux ratio of 3-6:1, and the product is obtained; the alkoxysilane monomer comprises dimethyldimethoxysilane, the low-boiling-point raw material is dimethyldimethoxysilane, and the polysiloxane comprises oligomeric dimethylsiloxane. The method is a reaction rectification one-step method, the steps are simple, no solvent is needed, the raw materials are low in price, widely sourced, and do not need to use expensive noble metal catalysts, and the specific proton acid and Lewis acid are combined to catalyze the rearrangement reaction, the product is easy to separate, the yield is high, and the method is convenient for popularization and application.

Description

Technical Field

[0001] This invention belongs to the field of organosilicon chemical synthesis technology, and relates to a method for preparing 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane. Background Technology

[0002] 1,3-Dimethoxy-1,1,3,3-Tetramethyldisiloxane is an organosilicon intermediate and an important precursor of 1,3-dihydroxy-1,1,3,3-tetramethyldisiloxane, a raw material for the synthesis of various functional silicone oils and silicone rubbers.

[0003] There are few publicly available reports on the preparation of 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane in the prior art. Tanaka et al. reported a method for preparing 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane by reacting dimethylmethoxychlorosilane with sodium bicarbonate (see Tanaka T. Chemical Society Of Japan, 1955, 28(5)). (364-366), but the raw material dimethylmethoxychlorosilane in this method is not a commodity, and various linear and cyclic byproducts are generated in the product, making separation difficult, and the yield of the target product is only below 30%; Patent document US4395563A reports the preparation of 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane by partial hydrolysis of dimethyldimethoxysilane. Although dimethyldimethoxysilane is a commodity, various polymers containing Si-OH are generated in the product, making separation difficult, and the yield of the target product is also low; Patent document JP08325277A reports the preparation of 1,3-dichloro-1,1,3,3-tetramethyldisiloxane from the corresponding 1,3-dichloro-1,1,3,3-tetramethyldisiloxane through ammonolysis, hydrolysis, and methanol esterification. The route for 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane, while capable of suppressing the formation of polymers as byproducts and yielding high yields of 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane, is complex, and the starting material 1,3-dichloro-1,1,3,3-tetramethyldisiloxane is not a readily available commodity and is difficult to obtain. Patent document US8507709B2 reports a method for obtaining 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane by hydrogen evolution of 1,1,3,3-tetramethyldisiloxane with methanol under palladium / activated carbon catalysis. This method achieves a yield greater than 80%, but it uses a precious metal catalyst, resulting in higher costs. Summary of the Invention

[0004] Based on this, the purpose of this invention is to provide a method for preparing 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane. This method is a one-step reactive distillation method, which is simple, requires no solvent, uses inexpensive and widely available raw materials, and does not require expensive precious metal catalysts. It also uses a specific protic acid combined with a Lewis acid to catalyze a rearrangement reaction, resulting in easy product separation, high yield, and easy application.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane, comprising the following steps: S1, using alkoxysilane monomers and polysiloxanes as raw materials, reacts at 60~80℃ for 1~3h under the action of a catalyst; After the reactions in S2 and S1 are completed, the temperature is raised to perform distillation separation and recovery of low-boiling-point raw materials. After separating and recovering low-boiling-point raw materials in S3 and S2, the temperature is further increased, and the stable fraction at 138-140℃ is received at a reflux ratio of 3-6:1 to obtain the product.

[0006] Furthermore, the mass ratio of the alkoxysilane monomer to the polysiloxane in S1 is 3~12:1.

[0007] Furthermore, the mass ratio of the alkoxysilane monomer to the polysiloxane in S1 is 5~8:1.

[0008] Furthermore, the alkoxysilane monomer described in S1 includes dimethyldimethoxysilane.

[0009] Furthermore, the polysiloxane mentioned in S1 includes oligomeric dimethylsiloxane, which includes low-viscosity hydroxyl silicone oil, wherein the viscosity (at 25°C) of the low-viscosity hydroxyl silicone oil is 15~100 mm. 2 / s.

[0010] Furthermore, the viscosity (25°C) of the low-viscosity hydroxyl silicone oil described in S1 is 15~40 mm. 2 / s.

[0011] Furthermore, the low-boiling-point raw material in S2 is an alkoxysilane monomer, which can be recovered and used as a reaction raw material in S1.

[0012] Furthermore, the catalyst in S3 includes a protic acid and a Lewis acid, wherein the amount of protic acid added is 0.05% to 0.2% of the total mass of the reaction raw materials, and the amount of Lewis acid added is 20% to 200% of the mass of the protic acid.

[0013] Furthermore, the protic acid includes any one or more of trifluoromethanesulfonic acid, sulfuric acid, hydrochloric acid, and phosphoric acid; preferably trifluoromethanesulfonic acid.

[0014] Furthermore, the Lewis acid includes any one or more of zinc chloride, aluminum chloride, ferric chloride, and boron fluoride; preferably zinc chloride.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention provides a method for preparing 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane. The preparation method is a one-step reactive distillation method, which is simple, requires no solvent, uses inexpensive and widely available raw materials, and does not require expensive precious metal catalysts. It also uses a specific protic acid combined with a Lewis acid to catalyze a rearrangement reaction, resulting in easy product separation, high yield, and easy application.

[0016] 2. This invention provides a method for preparing 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane. In this method, the unreacted raw material dimethyldimethoxysilane can be directly recovered during the preparation and separation process and reused in the next batch of feed. The residue after distillation is α,ω-dimethoxy oligomeric dimethylsiloxane, which can be used as a structure control agent for compounded silicone rubber after simple treatment. No waste is generated and the raw material utilization rate is high. Attached Figure Description

[0017] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Appendix Figure 1 The 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane obtained in Example 1 of this invention 1 HNMR spectrum; Appendix Figure 2 The 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane obtained in Example 1 of this invention 29 SiNMR spectrum. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. All mentioned embodiments are implemented based on the technical solutions of the present invention, and detailed implementation processes are given. However, it should be stated that the scope of protection of the present invention is not limited to the following embodiments.

[0020] The following embodiments provide detailed implementation procedures for the technical solutions of the present invention. Unless otherwise specified, the experimental methods used in the following experimental examples are conventional methods; unless otherwise specified, the materials and reagents used are commercially available.

[0021] Example 1

[0022] Add 1200g of dimethyldimethoxysilane and low-viscosity hydroxyl silicone oil (viscosity 20mm) to a 2L three-necked flask equipped with a reactive distillation apparatus. 2 165g of trifluoromethanesulfonic acid, 1.4g of zinc chloride, and 1.4g of sodium chloride were reacted with stirring at 80℃ for 2 hours. The mixture was then heated for distillation separation. After recovering 897g of the low-boiling-point feedstock dimethyldimethoxysilane, the temperature was further increased, and 295g of the stable fraction at 139℃ was collected at a reflux ratio of 6:1. Analysis showed that this was 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane with a GC content of 99.3%, yielding 68.2%. The yield calculation formula is as follows: In the formula, 74 is the molecular weight of the dimethylsiloxane repeating unit, and 194 is the molecular weight of 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane.

[0023] The 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane prepared in this embodiment was characterized, and its structural information is as follows: Figure 1 and Figure 2 As shown, specifically: 1 H NMR (CDCl3, 400MHz) Figure 1 ), δ (ppm): 0.05~0.08 (12H, Si-C H 3), 3.43~3.46 (6H, Si-OC) H 3); 29 Si NMR (CDCl3, 99MHz) Figure 2 ), δ (ppm): -10.6 ( Figure 2 ).

[0024] Example 2

[0025] Add 1200g of dimethyldimethoxysilane (including 897g of dimethyldimethoxysilane recovered in Example 1) and hydroxyl silicone oil (viscosity 20mm) to a 2L three-necked flask equipped with a reactive distillation apparatus. 2165g of dimethyldimethoxysilane, 2.7g of trifluoromethanesulfonic acid, and 0.6g of zinc chloride were reacted with stirring at 80°C for 2 hours, followed by distillation to separate the components. After recovering 875g of dimethyldimethoxysilane, the temperature was further increased, and 288g of the stable fraction at 139°C was collected at a reflux ratio of 5:1. Analysis revealed that this was 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane with a GC content of 99.0%, yielding 66.6%, calculated using the same method as in Example 1.

[0026] Example 3

[0027] Add 1200g of dimethyldimethoxysilane (including 875g of dimethyldimethoxysilane recovered in Example 2) and hydroxyl silicone oil (viscosity 20 mm) to a 2L three-necked flask equipped with a reactive distillation apparatus. 2 165g of dimethyldimethoxysilane, 0.7g of trifluoromethanesulfonic acid, and 1.4g of zinc chloride were reacted with stirring at 80°C for 2 hours, followed by distillation to separate the components. After recovering 903g of dimethyldimethoxysilane, the temperature was further increased, and 292g of the stable fraction at 139°C was collected at a reflux ratio of 6:1. Analysis revealed that this was 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane with a GC content of 99.2%, yielding 67.5%, calculated using the same method as in Example 1.

[0028] Example 4

[0029] Add 1200g of dimethyldimethoxysilane (containing 903g of dimethyldimethoxysilane recovered in Example 3) and hydroxyl silicone oil (viscosity 40mm) to a 2L three-necked flask equipped with a reactive distillation apparatus. 2 165g of dimethyldimethoxysilane, 1.4g of trifluoromethanesulfonic acid, and 1.4g of zinc chloride were reacted with stirring at 60°C for 2 hours, followed by distillation to separate the components. After recovering 860g of dimethyldimethoxysilane, the temperature was further increased, and 280g of the stable fraction at 139°C was collected at a reflux ratio of 3:1. Analysis revealed that this was 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane with a GC content of 98.3%, yielding 64.7%, calculated using the same method as in Example 1.

[0030] Example 5

[0031] Add 1200g of dimethyldimethoxysilane (including 860g of dimethyldimethoxysilane recovered in Example 4) and hydroxyl silicone oil (viscosity 20mm) to a 2L three-necked flask equipped with a reactive distillation apparatus. 2240g of dimethyldimethoxysilane, 1.4g of trifluoromethanesulfonic acid, and 1.4g of zinc chloride were reacted with stirring at 60°C for 2 hours, followed by distillation to separate the components. After recovering 845g of dimethyldimethoxysilane, the temperature was further increased, and 413g of the stable fraction at 139°C was collected at a reflux ratio of 3:1. Analysis revealed that this was 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane with a GC content of 98.5%, yielding 65.6%, calculated using the same method as in Example 1.

[0032] Example 6

[0033] Add 1200g of dimethyldimethoxysilane (including 845g of dimethyldimethoxysilane recovered in Example 5) and hydroxyl silicone oil (viscosity 40 mm) to a 2L three-necked flask equipped with a reactive distillation apparatus. 2 400g of dimethyldimethoxysilane, 1.4g of trifluoromethanesulfonic acid, and 1.4g of zinc chloride were reacted with stirring at 60°C for 2 hours, followed by distillation to separate the components. After recovering 642g of dimethyldimethoxysilane, the temperature was further increased, and 585g of the stable fraction at 139°C was collected at a reflux ratio of 3:1. Analysis revealed that this was 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane with a GC content of 98.2%, yielding 55.8%, calculated using the same method as in Example 1.

[0034] Example 7

[0035] Add 1200g of dimethyldimethoxysilane (containing 642g of dimethyldimethoxysilane recovered in Example 6) and hydroxyl silicone oil (viscosity 100mm) to a 2L three-necked flask equipped with a reactive distillation apparatus. 2 165g of dimethyldimethoxysilane, 1.4g of trifluoromethanesulfonic acid, and 1.4g of zinc chloride were reacted with stirring at 60°C for 2 hours, followed by distillation to separate the components. After recovering 768g of dimethyldimethoxysilane, the temperature was further increased, and 252g of the stable fraction at 139°C was collected at a reflux ratio of 5:1. Analysis revealed that this was 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane with a GC content of 99.0%, yielding 58.3%, calculated using the same method as in Example 1.

[0036] Comparative Example 1 Add 1200g of dimethyldimethoxysilane and hydroxyl silicone oil (viscosity 10000 mm) to a 2L three-necked flask equipped with a reactive distillation apparatus. 2 165g of dimethyldimethoxysilane, 1.4g of trifluoromethanesulfonic acid, and 1.4g of zinc chloride were reacted with stirring at 80°C for 2 hours, followed by distillation to separate the components. After recovering 362g of dimethyldimethoxysilane, the temperature was further increased, and 115g of the stable fraction at 139°C was collected at a reflux ratio of 6:1. Analysis revealed that this was 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane with a GC content of 99.1%, yielding 26.6%, calculated using the same method as in Example 1.

[0037] Comparative Example 2 Add 1200g of dimethyldimethoxysilane and hydroxyl silicone oil (viscosity 20mm) to a 2L three-necked flask equipped with a reactive distillation apparatus. 2 1200g of dimethyldimethoxysilane, 2.4g of trifluoromethanesulfonic acid, and 2.4g of zinc chloride were reacted with stirring at 80°C for 2 hours, followed by distillation to separate the components. After recovering 128g of dimethyldimethoxysilane, the temperature was further increased, and 587g of the stable fraction at 139°C was collected at a reflux ratio of 6:1. Analysis revealed that this was 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane with a GC content of 99.3%, yielding 18.6%, calculated using the same method as in Example 1.

[0038] Comparative Example 3 Add 1200g of dimethyldimethoxysilane and hydroxyl silicone oil (viscosity 20mm) to a 2L three-necked flask equipped with a reactive distillation apparatus. 2 165g of dimethyldimethoxysilane and 1.4g of trifluoromethanesulfonic acid were reacted with stirring at 80°C for 2 hours, followed by distillation to separate the distillate. After recovering 708g of dimethyldimethoxysilane, the temperature was further increased, and 184g of the stable fraction at 139°C was collected at a reflux ratio of 6:1. Analysis showed that it was 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane with a GC content of 99.1%, yielding 42.5%, calculated in the same manner as in Example 1.

[0039] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane, characterized in that, Includes the following steps: S1, using alkoxysilane monomers and polysiloxanes as raw materials, reacts at 60~80℃ for 1~3h under the action of a catalyst; After the reactions in S2 and S1 are completed, the temperature is raised to perform distillation separation and recovery of low-boiling-point raw materials. After separating and recovering low-boiling-point raw materials in S3 and S2, the temperature is further increased, and the stable fraction at 138-140℃ is received at a reflux ratio of 3-6:1 to obtain the product.

2. The method for preparing 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane according to claim 1, characterized in that, The mass ratio of the alkoxysilane monomer to the polysiloxane in S1 is 3~12:

1.

3. The method for preparing 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane according to claim 1, characterized in that, The mass ratio of the alkoxysilane monomer to the polysiloxane in S1 is 5~8:

1.

4. The method for preparing 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane according to claim 1, characterized in that, The alkoxysilane monomers described in S1 include dimethyldimethoxysilane.

5. The method for preparing 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane according to claim 1, characterized in that, The polysiloxane mentioned in S1 includes oligomeric dimethylsiloxane, which includes low-viscosity hydroxyl silicone oil, wherein the viscosity of the low-viscosity hydroxyl silicone oil is 15~100 mm. 2 / s.

6. The method for preparing 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane according to claim 5, characterized in that, The viscosity of the low-viscosity hydroxyl silicone oil described in S1 is 15~40 mm. 2 / s.

7. The method for preparing 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane according to claim 1, characterized in that, The low-boiling-point raw material in S2 is an alkoxysilane monomer, which can be recovered and used as a reaction raw material in S1.

8. The method for preparing 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane according to claim 1, characterized in that, The catalyst in S3 includes a protic acid and a Lewis acid. The amount of protic acid added is 0.05% to 0.2% of the total mass of the reaction raw materials, and the amount of Lewis acid added is 20% to 200% of the mass of the protic acid.

9. The method for preparing 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane according to claim 8, characterized in that, The protic acid includes any one or more of trifluoromethanesulfonic acid, sulfuric acid, hydrochloric acid, and phosphoric acid.

10. The method for preparing 1,3-dimethoxy-1,1,3,3-tetramethyldisiloxane according to claim 8, characterized in that, The Lewis acid includes any one or more of zinc chloride, aluminum chloride, ferric chloride, and boron fluoride.

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