CN111072715A

CN111072715A - Preparation method of bis (phenylcyclosiloxane)

Info

Publication number: CN111072715A
Application number: CN201911424074.7A
Authority: CN
Inventors: 熊永春; 邓道元
Original assignee: Shiantao Greenchem Industries Co ltd
Current assignee: Shiantao Greenchem Industries Co ltd
Priority date: 2019-12-31
Filing date: 2019-12-31
Publication date: 2020-04-28

Abstract

The invention relates to a method for preparing diphenyl cyclosiloxane. In a reaction kettle with a rectifying column, high-purity diphenyl dimethoxysilane without polychlorinated biphenyl and a small amount of water are used as raw materials, diether series such as ethylene glycol diethyl ether and diethylene glycol dimethyl ether with normal pressure boiling point higher than 100 ℃ are used as solvents, a small amount of organic alkali such as tetramethyl ammonium hydroxide is used as a catalyst, generated methanol is distilled off under the condition of maintaining slight boiling, and the commercialized diphenyl cyclosiloxane is obtained in one step. The generated powdery diphenyl cyclosiloxane is easy to separate from liquid, all solvents are completely recycled, the byproduct methanol can be applied by rectification and purification, and no wastewater is discharged in the whole process.

Description

Preparation method of bis (phenylcyclosiloxane)

Technical Field

The invention relates to a preparation method of an organic silicon intermediate, in particular to a preparation method of diphenyl cyclosiloxane with an environment-friendly process.

Background

Due to the structural characteristics of silicon and oxygen atoms, in general, when the organic cyclosiloxane is formed, silicon and oxygen elements are naturally interacted to form cyclotrisiloxane, cyclotetrasiloxane, cyclopentasiloxane, cyclohexasiloxane and complex isomeric states. In the case of a siloxane having two phenyl groups bonded to a silicon atom, this rule is also followed when a ring body is formed, that is, the constitution is composed of hexaphenylcyclotrisiloxane (hereinafter referred to as "P3"), octaphenylcyclotetrasiloxane (hereinafter referred to as "P4"), and decaphenylcyclopentasiloxane (hereinafter referred to as "P5"), and P4, P5 have two structures of "boat" and "chair", which are evident from a fine DSC analysis. Therefore, the siloxane ring body with the double phenyl structure is actually a polycyclic and multi-isomeric mixture, and all the siloxane ring bodies are effective components.

Since P4 is the major constituent of mixed siloxane rings of a bisphenyl structure, P4 will generally be used in the industry to express such bisphenyl cyclosiloxanes, but Pn will be used herein to represent the true constituent of the mixture, and the subscript n may have values of 3, 4, 5, representing P3, P4, P5, respectively.

High-quality Pn is a key monomer raw material for synthesizing the phenyl silicone rubber, and the copolymerization of Pn and methyl cyclosiloxane is the best technical route for synthesizing the phenyl silicone rubber. The Japanese Xinyue company, the French Rodiya company and the American Michigan company adopt the technical route.

The production method related to P4 known at home and abroad is summarized as follows:

1. various english patents such as US3842110, US4079070, US5739370, etc. fail and are effective.

2. Chinese patent publication nos. CN101362779A, CN106977538A, CN106967108A, granted patent No. CN101525347B, chinese expired patent No. CN1096467C, etc.

3. There have been many more early production methods using diphenylsilanediol or diphenyldichlorosilane as raw materials, which are summarized in Journal of the Chinese Chemical Society,1995,42,923-928, by Yangmuii et al, which is incorporated herein by reference.

The processes mentioned in the patents and documents above, in summary, have some of the following disadvantages:

1. when aromatic hydrocarbons (toluene and xylene are commonly used) are used as a solvent, viscous linear substances are wrapped on the surface layer of the produced crude particles, and the treatment in the production is difficult. In addition, since such aromatic hydrocarbon solvents are also very soluble to harmful impurities other than Pn, the product obtained by a single recrystallization tends to have a poor purity, requiring multiple recrystallizations, and thus the production operation steps are complicated.

Aromatic hydrocarbon solvents have a strong odor and are now key concerns for limiting VOCs in China and abroad.

2. Due to the difference of the times, in these patents or articles mentioned above, there is no mention at all of the permanent harmfulness of polychlorinated biphenyls (hereinafter referred to as "PCBs") introduced from various raw materials, but the world is extremely restricted in the continuous harmful pollutants represented by PCBs today (the RoHS recommendation of the European Union is increasing). At present, diphenyl dichlorosilane (direct synthesis process catalyzed by copper powder) produced in China, or diphenyl dimethoxysilane (hereinafter, referred to as "DDS") obtained by alcoholysis of diphenyl dichlorosilane, and PCBs (polychlorinated biphenyl) mainly comprising dichlorobiphenyl in commercially available diphenyl silanediol generally exceed international standards. The organosilicon publication, the seventeenth proceedings of the society of organosilicon science of China, pp 86-89 methods for producing phenylsilane monomers and polychlorinated biphenyls (PCBs), provides relevant data. Although the general concept of PCBs is to say chlorinated biphenyls above trichlorobiphenyls, some countries such as Japan have put restrictions on monochlorobiphenyl and dichlorobiphenyl. With the improvement of environmental protection, the two substances should be limited in China. Domestic Pn producers should actively assume social responsibility to prevent PCBs in products from being carried into downstream customers and thus spreading to various environments.

The subtractive processing of PCBs in the raw material is an essential prospective step.

3. Satisfactory diphenyl silanediol is high in cost, and the synthesized Pn product has half of linear cold polymer and is difficult to purify through recrystallization, so that the yield of Pn is too low. The product made by the method of the granted patent No. CN101525347B is not easy to satisfy the application of polymer grade in quality, in particular the synthesis of high-temperature vulcanized silicone rubber.

4. The heavy use of water and wastewater discharge are very common phenomena in the existing Pn production process. This is due to the addition of large amounts of inorganic bases such as sodium hydroxide, potassium hydroxide, and salts produced by neutralization to almost all production processes, which can only be separated from the product produced by washing. Otherwise Pn is not available for aggregation applications.

5. It is to be particularly emphasized here that the method mentioned in chinese expired patent CN1096467C has disadvantages that are difficult to overcome: firstly, because the invention uses the material with the generally low boiling point as the solvent, the obvious amplification effect appears in the production process with a large batch size, and the violent heat release phenomenon is concentrated, so that the solvent is boiled, and great hidden trouble is brought to the production safety. Secondly, because the solvent used has solubility to both Pn and the by-product thereof and has low selectivity to the target product, the purity of the obtained product is not high, the crystal is coated in a viscous linear substance, even the purity of the crystal is only 80 percent, and the yield of Pn actually obtained by recrystallization is not higher than 50 percent. Thirdly, because the diphenyl dihalogen silane is used as the initial raw material, hydrochloric acid treatment during alcoholysis, solvent recovery, waste water discharge, PCBs and the like are carried out, so that the method has multiple steps and great difficulty in production operation.

With the requirement of domestic industry upgrading, the Pn produced by the traditional process has more or less quality problems, or treatment steps are complicated, or a large amount of by-products exist, or the emission exceeds the standard, so that the environmental protection pressure is brought. There is an urgent need for an environmentally friendly method for producing Pn with high yield in China.

Disclosure of Invention

The present invention has been made to solve the above problems occurring in the prior art, and an object of the present invention is to provide a method for preparing a bis-phenylcyclosiloxane.

In order to achieve the purpose, the invention provides the following technical scheme: a bis-phenyl cyclosiloxane is characterized by the following chemical reaction formula:

the reaction solvent adopted in the formula is a diether series solvent with the normal pressure boiling point higher than 100 ℃.

The preparation method of the bis-phenyl cyclosiloxane comprises the following steps:

A. adding metal sodium into diphenyl dimethoxysilane containing polychlorinated biphenyl (PCBs), wherein the addition amount of the metal sodium is 1% of the weight of the diphenyl dimethoxysilane, stirring for 2 hours at 115-125 ℃ in an oil bath, cooling to room temperature, adding methanol with the weight of 2% of the diphenyl dimethoxysilane, stirring for 2 hours at room temperature to inactivate the metal sodium, and quickly evaporating the diphenyl dimethoxysilane under the condition of high pressure and reduced pressure to obtain the diphenyl dimethoxysilane with the total amount of PCBs being less than 0.5 ppm;

B. in a 500ml reaction kettle with a filler and a temperature-controlled rectifying column, a diether series solvent, distilled water and tetramethylammonium hydroxide (TMAOH, the same below) are added in proportion;

C. heating the reaction solution to a reflux state at the temperature of nearly 100 ℃, and controlling the heating temperature to keep refluxing;

D. heating the rectifying column to 60 ℃, dropwise adding diphenyldimethoxysilane with the total amount of PCBs less than 0.5ppm into the reaction kettle, controlling the liquid temperature to keep 100-105 ℃ and reacting for 1-1.5 hours under the condition of appropriate reflux;

E. continuously dripping the diphenyldimethoxysilane, continuously generating solids in the kettle, then discharging methanol from the column top, wherein the methanol can be used in the production flow of other products in a factory;

F. after the dropwise addition of the diphenyl dimethoxysilane is finished, continuously maintaining the working condition in the kettle for at least 2 hours, and then cooling the kettle liquid to a room temperature state;

G. uniformly stirring the cooled kettle liquid, and carrying out closed filtration to obtain a filtrate, wherein the obtained filtrate is white powder Pn, and the filtrate is a solvent mixture in which a small amount of linear impurities are dissolved;

H. and (4) carrying out rotary drying on the Pn powder to obtain a finished product.

Preferably, the filtrate filtered out in the step 8 is transferred to another distillation kettle, a matched freezing condenser is opened, and all solvents are evaporated out under reduced pressure; the solvent is directly used in the next batch of production, and the residue is a micro-color organosilicon high-boiling residue used for producing high-temperature resistant resin products.

Preferably, the weight ratio is as follows: bis-ether series solvents: distilled water: tetramethylammonium hydroxide (1) (0.06 to 0.2) (0.001 to 0.002)

Preferably, the ratio of the parts by weight of the diether series solvent to the parts by weight of the diphenyl dimethoxysilane is as follows: 1: (0.8 to 1.2).

To summarize the principles of the invention, the reaction equation is expressed as follows:

the invention provides a synthesis method for synthesizing Pn by taking a DDS subjected to refining treatment as a raw material in one step in consideration of the current situation of domestic raw materials. The method has the characteristics of environmental friendliness, high yield and full utilization. Can avoid the defects in the traditional production method, solves the difficulty in Pn production, and has the following characteristics:

1. residual PCBs are eliminated from the raw materials, and products and kettle residues are avoided.

2. Because the boiling point of the reaction solvent is high (the normal pressure boiling point is higher than the diether solvent of 100 ℃), and the boiling point difference between the reaction solvent and the by-product methanol is large, the input solvent and the by-product methanol can be directly recovered in high yield, and the discharge of excessive VOCs in the production process can be avoided.

3. The amplification heat effect of the production process is small, the reaction can be very stable by controlling the speed of dripping the raw materials, and the total energy consumption is not high.

4. No waste water is discharged at all. Because the solvent and the water are in an azeotropic relationship, the distilled recovered solvent is allowed to contain water, and the recycling is not influenced. The water consumption in the reaction formula is not large, and most of water reacts with methoxyl on DDS molecules to generate methanol.

5. The low-concentration alkaline catalyst TMAOH used in the process belongs to a temporary catalyst, is widely applied in the organic silicon industry, can be thoroughly decomposed by heating during solvent recycling and Pn drying, and has no residue.

6. The kettle residue can be fully and effectively utilized.

7. High yield of target product and one-time finished product. The solvent selected is insoluble to Pn and soluble to linear substances, so that Pn can be self-crystallized and precipitated from the reaction solution with high selectivity, and the product purity is high.

Drawings

FIG. 1 is a chart of a synthesized product Pn silicon spectrum analysis;

FIG. 2 shows, by rough DSC analysis, that Pn is mainly composed of P4 and is composed of P3, P4 and P5 in admixture;

fig. 3 two melting peaks after adjustment of the DSC heating rate demonstrate that P4 consists of two isomers.

Detailed Description

A500 ml four-mouth glass bottle is additionally provided with a glass rectifying column with heating and heat preservation and a glass spring filler, and the rectifying device is formed by a column top reflux regulator, a condensing tube and a receiving bottle. The bottle is also provided with a liquid temperature thermometer, a dropping funnel and a sealed tetrafluoro stirring paddle and is heated by an oil bath pan.

Adding metal sodium into diphenyl dimethoxysilane containing polychlorinated biphenyl (PCBs), wherein the addition amount of the metal sodium is 1% of the weight of the diphenyl dimethoxysilane, stirring for 2 hours at 115-125 ℃ in an oil bath, cooling to room temperature, adding methanol with the weight of 2% of the diphenyl dimethoxysilane, stirring for 2 hours at room temperature to inactivate the metal sodium, and then quickly evaporating the diphenyl dimethoxysilane under the condition of high pressure and reduced pressure to obtain the diphenyl dimethoxysilane with the total amount of PCBs being less than 0.5ppm, wherein the total amount of phenyltrimethoxysilane in the diphenyl dimethoxysilane is less than 0.5 ppm.

Example 1:

adding 120g of diethylene glycol dimethyl ether, 14g of water and 2g of a tetramethylammonium hydroxide (TMAOH) aqueous solution into a bottle, wherein the concentration of the tetramethylammonium hydroxide aqueous solution is 1mol/L, preheating the kettle liquid to 95-100 ℃, and ensuring that the wall of the bottle has a slightly-returning flow state. The glass rectification column was heated to 60 ℃ and held. Slowly dripping 120g of diphenyl dimethoxysilane with the total amount of the treated PCBs being less than 0.5ppm and the total amount of the phenyl trimethoxy silane being less than 0.5ppm into the bottle, adjusting and heating according to the temperature of the kettle liquid, and keeping the temperature of the kettle liquid at 95-100 ℃. The kettle begins to be turbid after about 1 hour from the beginning of dripping, the methanol distilled from the top of the column is collected from a receiving bottle after 2 hours, and the methanol only contains partial moisture and can be used in the production flow of other products in factories.

After completion of the dropwise addition, the temperature of the pot liquid was maintained for about 2 hours. When the discharge amount of the methanol at the top of the column begins to decrease, the heating amount is slowly increased, when the temperature of distillate at the top of the column is higher than 65 ℃ and begins to rise, the heating is stopped, and the natural cooling of the kettle liquid under stirring is maintained.

When the kettle liquid is cooled to room temperature, supernatant can be clarified, and most of the kettle is white powder. And filtering the materials to respectively obtain organic phase filtrate and powder.

The powder was dried under reduced pressure by rotation to obtain 95.3g of finished product. The collected condensed solvent is mixed with the organic phase filtrate. The mixture of the diethylene glycol dimethyl ether and the water evaporated from the organic phase filtrate is repeatedly used for synthesis and reuse. A small amount of kettle residue with high boiling point is hydroxyl-terminated polyphenyl organosiloxane which is used as a raw material for producing high-temperature resistant organic silicon resin.

Example 2: 1 (0.06 to 0.2) (0.001 to 0.002)

120g of diethylene glycol diethyl ether, 8g of water and 1.2g of an aqueous tetramethylammonium hydroxide (TMAOH) solution having a concentration of 1mol/L were added to a flask, and the pot solution was preheated to 98 ℃ with a slight reflux state on the wall of the flask. Also, the glass rectification column was heated to 60 ℃ and maintained. Slowly dripping 130g of diphenyl dimethoxysilane with the total amount of the treated PCBs being less than 0.5ppm and the total amount of the phenyl trimethoxy silane being less than 0.5ppm into the bottle, adjusting and heating according to the temperature of the kettle liquid, and keeping the temperature of the kettle liquid at 95-100 ℃. From the start of the dropwise addition, the resulting reaction solution became turbid within about 1 hour and was added dropwise over a total of 2 hours.

The remaining processing steps were the same as in example 1, and the final powder was dried under reduced pressure by rotation to obtain 95.5g of finished product.

Example 3:

120g of ethylene glycol diethyl ether, 20g of water and 2.3g of a tetramethylammonium hydroxide (TMAOH) aqueous solution are added into a bottle, wherein the concentration of the tetramethylammonium hydroxide aqueous solution is 1mol/L, the kettle liquid is preheated to 99 ℃, and the wall of the bottle has a micro-reflux state. Also, the glass rectification column was heated to 60 ℃ and maintained. Slowly dripping 115g of diphenyl dimethoxysilane with the total amount of the treated PCBs being less than 0.5ppm and the total amount of the phenyl trimethoxy silane being less than 0.5ppm into the bottle, adjusting and heating according to the temperature of the kettle liquid, and keeping the temperature of the kettle liquid at 95-100 ℃. From the start of the dropwise addition, the resulting reaction solution became turbid within about 1 hour and was added dropwise over a total of 2 hours.

The remaining processing steps were the same as in example 1, and the final powder was dried under reduced pressure by rotation to obtain 95.3g of finished product.

In the above case, three kinds of diethers such as diethylene glycol dimethyl ether are used as the solvents, and actually, diether series solvents such as ethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol dibutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol methyl propyl ether, tetraethylene glycol dimethyl ether and the like can be used. Solvents with boiling points above 150 c and below 200 c are preferred for reasons of energy consumption cost only, as well as the need to decompose the temporary catalyst TMAOH. But may be applied to the synthesis of Pn as long as the diether solvent meets the spirit of the present patent.

Claims

1. A bis-phenyl cyclosiloxane is characterized by the following chemical reaction formula:

the reaction solvent adopted in the chemical reaction is a diether series solvent with normal pressure boiling point higher than 100 ℃.

2. The preparation method of the bis-phenyl cyclosiloxane comprises the following steps:

3. The method for preparing diphenylcyclosiloxane as claimed in claim 2, wherein said filtrate from step G is transferred to another distillation still, and said refrigeration condenser is opened, and all solvent is distilled off under reduced pressure; the solvent is directly used in the next batch of production, and the residue is a micro-color organosilicon high-boiling residue used for producing high-temperature resistant resin products.

4. The method for preparing bis-phenylcyclosiloxane as claimed in claim 2, wherein the weight ratio is: bis-ether series solvents: distilled water: tetramethylammonium hydroxide (1) (0.06-0.2) and (0.001-0.002).

5. The method of claim 2, wherein the ratio of the parts by weight of the solvent in the diether series to the parts by weight of the diphenyldimethoxysilane is: 1: (0.8 to 1.2).