Loop line separation process of dimethyl polysiloxane

Abstract

The invention discloses a dimethyl polysiloxane loop line separation process. The process comprises the following steps: (1) two-stage heating: carrying out two-stage heating on dimethyl dichloropolysiloxane hydrolysate; (2) flash separation: introducing the heated dimethyl polysiloxane hydrolysate into a flash tank for flash separation, and enabling the ring body discharged from the top of the flash tank to sequentially enter a condenser, a reflux tank and a ring body storage tank; and (3) secondary separation: monitoring the purity of the line body separated by flash evaporation at the bottom of the flash evaporation tank in good time, directly discharging the line body at the bottom of the flash evaporation tank into a line body storage tank through an extraction pump when the purity of the line body is greater than or equal to 99%, and feeding the line body at the bottom of the flash evaporation tank into a loop line separation tower for secondary separation when the purity of the line body is less than 99%, the loop body discharged from the top of the loop separation tower enters a condenser, and the line body discharged from the bottom of the loop separation tower enters a line body storage tank. The process has the advantages of reasonable process route, high separation efficiency, high product purity and low operation cost.

Description

Technical Field

[0001] The invention belongs to the technical field of organosilicon production technology, and specifically relates to a dimethylpolysiloxane ring line separation process. Background Art

[0002] Methylchlorosilane is an important raw material for the preparation of silicone materials. The series of products derived from methylsiloxane made from methylchlorosilane monomers account for more than 90%wt of the total amount of silicone products. The methylchlorosilane monomer is mainly dimethyldichlorosilane with the chemical formula CH3Si CH3Cl2, accounting for more than 85%wt of methylchlorosilane monomers. The series of products derived from methylsiloxane is to transform dimethyldichlorosilane into hundreds of basic chemical products through hydrolysis and other technologies. They are widely used in aerospace, electronics and electrical, construction, transportation, textiles, food, light industry, medical and other industries. The dimethylpolysiloxane mixture formed in the hydrolysis process of dimethyldichlorosilane, according to the molecular structure of the compound, of which about 75-85% are linear products and 15-25% are cyclic products. Dimethyldichlorosilane is hydrolyzed to form dimethylpolysiloxane hydrolyzate, and its reaction equation is: In the above reaction equation, For the line body, For the ring body.

[0003] At present, dimethylpolysiloxane is used to make downstream products such as 110 glue, 107 glue, and dimethyl silicone oil. All the products are linear structures. At the same time, dimethylpolysiloxane is mainly produced by cracking process to obtain DMC, and then DMC is used to produce downstream products such as 110 glue. How to directly obtain high-quality linear bodies and ring bodies through ring-line separation and directly use them for downstream production is a technical problem that needs to be solved at present. With the continuous expansion of the application of ring bodies, the separation technology of ring bodies and linear bodies in China is not limited to the traditional cracking process, and there are also processes such as heating flash evaporation, negative pressure separation, phase separation, etc. Patent No. CN 104031084 B proposes a method for separating organic silicon hydrolysate in a loop. This process is to heat the organic silicon hydrolysate and directly send it into a loop separation tower to separate the ring body and the line body. This process uses a loop separation tower under vacuum to separate the ring body and the line body. All hydrolysates must pass through the loop separation tower. The loop separation tower requires a large amount of heat source for heating, and the operating cost is high. For example, patent CN 106083910 B proposes a method and device for separating organic silicon hydrolysate in a loop. The separation method adopted by the device is that the organic silicon initial hydrolysate is preheated by a primary and secondary preheater, and then the preheated organic silicon initial hydrolysate enters a flash tank for loop separation. The gaseous ring body obtained after separation is extracted from the top of the separation tank, and the linear hydrolysate is extracted from the bottom. The method uses a vacuum flash tank for separation after the hydrolysate is heated. Although the cost is saved, the ring body and the linear body are easily entrained with each other by only using the flash system, and it is difficult to achieve a thorough separation. The quality of the separated product is difficult to improve. The ring body needs to be further cracked before it can be used. The entrained ring body in the linear body will affect the subsequent production system. For example, patent CNCN115197425 proposes a process for separating siloxane linear bodies and ring bodies and its application. In the separation method of this process, the hydrolyzate of silane is heated to 180-240°C, and the heated hydrolyzate is fully contacted with saturated water vapor under a negative pressure of 30-90 kPa to form a gas at the top and a liquid at the bottom. The top gas is condensed and separated to obtain a ring body, and the bottom liquid is cooled to obtain a linear body. This process adopts a negative pressure flash evaporation method as a whole, and the ring body is subjected to phase separation technology. Although it can remove the water entrained in the ring body, it cannot essentially reduce the entrained linear body in the ring body. There is still a problem of unsatisfactory separation effect of the linear body and the ring body, which ultimately leads to low quality and purity of the separated product.

[0004] In summary, the above methods generally have the problems of high energy consumption, unsatisfactory separation effect and high operating cost. Therefore, it is an objective need to develop a dimethylpolysiloxane ring separation process with a reasonable process route, high separation efficiency, high product purity and low operating cost. Summary of the invention

[0005] In order to solve the technical problems of high process energy consumption and unsatisfactory separation effect existing in the background technology, the purpose of the present invention is to provide a dimethylpolysiloxane loop separation process with reasonable process route, high separation efficiency, high product purity and low operating cost.

[0006] The dimethylpolysiloxane loop separation process of the present invention comprises the following steps: 1. Two-stage heating: the dimethyldichloropolysiloxane hydrolyzate is heated in two stages using a preheater and a heater in sequence; ② Flash separation: The dimethylpolysiloxane hydrolyzate after heating in the step is passed into a flash tank for flash separation. The pressure of the flash tank is 1-10 kpaA and the temperature is 120-220°C. After flash separation, the ring body discharged from the top of the flash tank is condensed by the condenser and then enters the reflux tank. The ring body in the reflux tank is discharged into the ring body storage tank through a reflux pump; ③ Secondary separation: timely monitor the purity of the wire separated by flash evaporation at the bottom of the flash tank. When the wire purity is ≥99%, directly discharge the wire at the bottom of the flash tank into the wire storage tank through the extraction pump. When the wire purity is <99%, it is necessary to send the wire at the bottom of the flash tank into the loop separation tower for secondary separation. The bottom of the loop separation tower is heated by an evaporator, and a part of the ring body discharged by the reflux pump is introduced into the upper part of the loop separation tower as a washing liquid. After secondary separation, the ring body discharged from the top of the loop separation tower enters the condenser for condensation, and the wire body discharged from the bottom of the loop separation tower enters the wire storage tank.

[0007] Furthermore, in steps ① and ③, the preheater 1 uses the linear body discharged from the flash tank or the loop separation tower as a heat source to heat the dimethyldichloropolysiloxane hydrolyzate.

[0008] Furthermore, in step ①, the heater uses superheated steam as a heat source to heat the dimethyldichloropolysiloxane hydrolyzate, and the pressure of the superheated steam is 2.5-3.0 MpaG and the temperature is 120-220°C.

[0009] Furthermore, in step ③, the loop separation tower is a packed tower, a demister is provided on the top of the loop separation tower, the pressure of the loop separation tower is 1-10 kPaA, and the temperature is 120-220°C.

[0010] Furthermore, in step ③, the evaporator is a falling film evaporator, the superheated steam pressure in the evaporator is 2.5-3.0 MpaG, and the temperature is 120-220°C.

[0011] Furthermore, in steps ② and ③, the condenser uses cooling water to condense the ring body.

[0012] Furthermore, in step ②, a phase separator is used in the reflux tank, and a drain port is provided at the bottom of the reflux tank.

[0013] Furthermore, in step ③, the line body discharged from the bottom of the loop separation tower is introduced into the evaporator through a circulating pump, and then enters the line body storage tank after heat exchange with the superheated steam in the evaporator.

[0014] Compared with the traditional loop separation process, the advantages of the invention are: first, after the process performs two-stage heating on dimethylpolysiloxane, the dimethylpolysiloxane is flash-separated by pressurized flash evaporation, which can quickly separate the ring body and the line body, and improve the separation effect of the line body and the ring body. At the same time, after the flash separation treatment, the line body can be separated again according to the purity of the line body, and the line body separated by flash evaporation can be separated for the second time by using a loop separation tower, so that the ring body and the line body can be completely separated, and the phenomenon of the ring body being mixed in the line body can be avoided. After the secondary separation, the separation efficiency of the line body and the ring body can be improved. Improve the purity of the line body and the ring body after separation, and ensure the quality of the line body and the ring body products after separation; secondly, the preheater uses the waste heat of the line body separated by the flash tower and the ring separation tower as the heating medium, which not only realizes the recycling of waste heat and improves the energy utilization rate, but also in the entire separation process, only the evaporator and the heater use superheated steam to heat the ring separation, and the steam usage is small, the energy consumption is low, and the operating cost can be further reduced. This process has the advantages of reasonable process route, high separation efficiency, high product purity and low operating cost, can produce good economic benefits, and is easy to promote and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the present invention; In the figure: 1-preheater, 2-heater, 3-flash tank, 4-condenser, 5-reflux tank, 6-reflux pump, 7-annular storage tank, 8-production pump, 9-line storage tank, 10-annular separation tower, 11-evaporator, 12-circulation pump. DETAILED DESCRIPTION

[0016] The present invention is further described below in conjunction with the embodiments and accompanying drawings, but the present invention is not limited in any way. Any changes or substitutions made based on the teachings of the present invention belong to the protection scope of the present invention. Example

[0017] The dimethylpolysiloxane ring separation process described in this embodiment 1 includes the following steps: ① Two-stage heating: The dimethyldichloropolysiloxane hydrolyzate is heated in two stages by using a preheater 1 and a heater 2 in sequence. The preheater 1 uses the linear body discharged from the flash tank 3 or the loop separation tower 10 as a heat source to heat the dimethyldichloropolysiloxane hydrolyzate. The preheater 1 uses the separated linear body waste heat as a heating medium, which not only realizes the recycling of waste heat and improves the energy utilization rate, but also reduces the production load and further reduces the operating cost. The heater 2 uses superheated steam as a heat source to heat the dimethyldichloropolysiloxane hydrolyzate. The pressure of the superheated steam is 2.5MpaG and the temperature is 120°C. ② Flash separation: The dimethylpolysiloxane hydrolyzate heated in step ① is passed into the flash tank 3 for flash separation. The pressure of the flash tank 3 is 1 kpaA and the temperature is 120°C. After flash separation, the ring body discharged from the top of the flash tank 3 is condensed by the condenser 4 and enters the reflux tank 5. The condenser 4 uses cooling water to condense the ring body, and after condensation, it enters the reflux tank 5. The ring body in the reflux tank 5 is discharged into the ring body storage tank 7 through the reflux pump 6. The reflux tank 5 uses a phase separator. The bottom of the reflux tank 5 is provided with a drain port. The separated water can be discharged from the bottom of the reflux tank 5 through the drain port, thereby improving the product purity of the ring body. The flash separation treatment of dimethylpolysiloxane by pressurized flash evaporation can allow the ring body and the linear body to be quickly separated, thereby improving the separation effect of the linear body and the ring body; ③ Secondary separation: timely monitor the purity of the wire separated by flash evaporation at the bottom of the flash tank 3. When the purity of the wire is ≥99%, the wire at the bottom of the flash tank 3 is directly discharged into the wire storage tank 9 through the extraction pump 8. When the purity of the wire is <99%, the wire at the bottom of the flash tank 3 needs to be sent to the ring separation tower 10 for secondary separation. The bottom of the ring separation tower 10 is heated by an evaporator 11, and a part of the ring discharged by the reflux pump 6 is introduced into the upper part of the ring separation tower 10 as a washing liquid. The ring separation tower 10 adopts a packed tower, and a demister is provided at the top of the ring separation tower 10. The pressure of the ring separation tower 10 is 1kpaA and the temperature is 120°C. After secondary separation, the ring discharged from the top of the ring separation tower 10 is mixed with the ring discharged from the top of the flash tank 3 and enters the condenser 4. The condenser 4 uses cooling water to condense the ring body, and the line body discharged from the bottom of the ring line separation tower 10 is introduced into the evaporator 11 through the circulating pump 12, and then enters the line body storage tank 9 after heat exchange with the superheated steam in the evaporator 11. The evaporator 11 uses a falling film evaporator, and the superheated steam pressure in the evaporator 11 is 2.5MpaG and the temperature is 120°C. The evaporator 11 uses the separated line body waste heat as the heating medium, which not only realizes the recycling of waste heat and improves the energy utilization rate, but also reduces the production load and further reduces the operating cost. After flash separation treatment, it can be separated again according to the purity of the line body. The ring line separation tower 10 is used to perform secondary separation on the line body separated by flash evaporation, which can realize the complete separation of the ring body and the line body, and avoid the phenomenon of the ring body being mixed in the line body. After secondary separation, the separation efficiency of the line body and the ring body can be improved, the purity of the line body and the ring body after separation can be improved, and the quality of the line body and the ring body products after separation can be guaranteed.

[0018] The process of Example 1 can not only improve the separation efficiency of the wire body and the ring body, but also allow the wire body and the ring body to be completely separated, thereby obtaining wire body and ring body products with higher purity, with the wire body purity being greater than 99.90%, and the ring body purity being greater than 99.92%, thereby ensuring the quality of the wire body and ring body products after separation, but also realizing the recycling of waste heat, reducing production load, effectively reducing operating costs, and being able to produce better economic benefits. Example

[0019] The dimethylpolysiloxane ring separation process described in Example 2 includes the following steps: ① Two-stage heating: The dimethyldichloropolysiloxane hydrolyzate is heated in two stages in turn by using a preheater 1 and a heater 2. The preheater 1 uses the linear body discharged from the flash tank 3 or the loop separation tower 10 as a heat source to heat the dimethyldichloropolysiloxane hydrolyzate. The preheater 1 uses the separated linear body waste heat as a heating medium, which not only realizes the recycling of waste heat and improves the energy utilization rate, but also reduces the production load and further reduces the operating cost. The heater 2 uses superheated steam as a heat source to heat the dimethyldichloropolysiloxane hydrolyzate. The pressure of the superheated steam is 2.8MpaG and the temperature is 180°C. ② flash separation: the dimethylpolysiloxane hydrolyzate after heating in step ① is passed into the flash tank 3 for flash separation. The pressure of the flash tank 3 is 5kpaA and the temperature is 180°C. After flash separation, the ring body discharged from the top of the flash tank 3 enters the reflux tank 5 after condensation by the condenser 4. The condenser 4 uses cooling water to condense the ring body, and after condensation, it enters the reflux tank 5. The ring body in the reflux tank 5 is discharged into the ring body storage tank 7 through the reflux pump 6. The reflux tank 5 uses a phase separator, and a drain port is provided at the bottom of the reflux tank 5. The separated water can be discharged from the bottom of the reflux tank 5 through the drain port, thereby improving the product purity of the ring body. The flash separation treatment of dimethylpolysiloxane by pressurized flash evaporation can allow the rapid separation of the ring body and the line body, and improve the separation effect of the line body and the ring body; ③ Secondary separation: timely monitor the purity of the wire separated by flash evaporation at the bottom of the flash tank 3. When the purity of the wire is ≥99%, the wire at the bottom of the flash tank 3 is directly discharged into the wire storage tank 9 through the extraction pump 8. When the purity of the wire is <99%, the wire at the bottom of the flash tank 3 needs to be sent to the ring separation tower 10 for secondary separation. The bottom of the ring separation tower 10 is heated by an evaporator 11, and a part of the ring discharged by the reflux pump 6 is introduced into the upper part of the ring separation tower 10 as a washing liquid. The ring separation tower 10 adopts a packed tower, and a demister is provided at the top of the ring separation tower 10. The pressure of the ring separation tower 10 is 5kpaA and the temperature is 180°C. After secondary separation, the ring discharged from the top of the ring separation tower 10 is mixed with the ring discharged from the top of the flash tank 3 and enters the condenser 4. The condenser 4 uses cooling water to condense the ring body, and the line body discharged from the bottom of the ring line separation tower 10 is introduced into the evaporator 11 through the circulating pump 12, and enters the line body storage tank 9 after heat exchange with the superheated steam in the evaporator 11. The evaporator 11 uses a falling film evaporator, and the superheated steam pressure in the evaporator 11 is 2.8MpaG and the temperature is 180°C. The evaporator 11 uses the separated line body waste heat as the heating medium, which not only realizes the recycling of waste heat and improves the energy utilization rate, but also reduces the production load and further reduces the operating cost. After flash separation treatment, it can be separated again according to the purity of the line body. The ring line separation tower 10 is used to perform secondary separation on the line body separated by flash evaporation, which can realize the complete separation of the ring body and the line body, and avoid the phenomenon of the ring body being mixed in the line body. After secondary separation, the separation efficiency of the line body and the ring body can be improved, the purity of the line body and the ring body after separation can be improved, and the quality of the line body and the ring body products after separation can be guaranteed.

[0020] The process of Example 2 can not only improve the separation efficiency of the wire body and the ring body, but also allow the wire body and the ring body to be completely separated, thereby obtaining wire body and ring body products with higher purity, with the wire body purity being greater than 99.94%, and the ring body purity being greater than 99.96%, thereby ensuring the quality of the wire body and ring body products after separation, but also realizing the recycling of waste heat, reducing production load, effectively reducing operating costs, and being able to produce better economic benefits. Example

[0021] The dimethylpolysiloxane ring separation process described in this embodiment 3 includes the following steps: ① Two-stage heating: The dimethyldichloropolysiloxane hydrolyzate is heated in two stages by using a preheater 1 and a heater 2 in sequence. The preheater 1 uses the linear body discharged from the flash tank 3 or the loop separation tower 10 as a heat source to heat the dimethyldichloropolysiloxane hydrolyzate. The preheater 1 uses the separated linear body waste heat as a heating medium, which not only realizes the recycling of waste heat and improves the energy utilization rate, but also reduces the production load and further reduces the operating cost. The heater 2 uses superheated steam as a heat source to heat the dimethyldichloropolysiloxane hydrolyzate. The pressure of the superheated steam is 3.0MpaG and the temperature is 220°C. ② Flash separation: The dimethylpolysiloxane hydrolyzate heated in step ① is passed into the flash tank 3 for flash separation. The pressure of the flash tank 3 is 10kpaA and the temperature is 220°C. After separation, the ring body discharged from the top of the flash tank 3 enters the condenser 4. The condenser 4 uses cooling water to condense the ring body. After condensation, it enters the reflux tank 5. The ring body in the reflux tank 5 is discharged into the ring body storage tank 7 through the reflux pump 6. The reflux tank 5 uses a phase separator. The bottom of the reflux tank 5 is provided with a drain port. The separated water can be discharged from the bottom of the reflux tank 5 through the drain port, thereby improving the product purity of the ring body. The flash separation treatment of dimethylpolysiloxane by pressurized flash evaporation can allow the rapid separation of the ring body and the line body, thereby improving the separation effect of the line body and the ring body; ③ Secondary separation: According to the purity of the filaments in the liquid at the bottom of the flash tank 3, when the purity of the filaments is ≥99%, the liquid at the bottom of the flash tank 3 is directly discharged into the filament storage tank 9 through the extraction pump 8. When the purity of the filaments is <99%, the liquid discharged from the bottom of the flash tank 3 needs to be sent to the loop separation tower 10 for secondary separation. The bottom of the loop separation tower 10 is heated by an evaporator 11, and a part of the ring body discharged by the reflux pump 6 is introduced into the upper part of the loop separation tower 10 as a washing liquid. The loop separation tower 10 adopts a packed tower, and a demister is arranged at the top of the loop separation tower 10. The pressure of the loop separation tower 10 is 1-10kpaA and the temperature is 220°C. After secondary separation, the ring body discharged from the top of the loop separation tower 10 is mixed with the ring body discharged from the top of the flash tank 3 and then enters the condenser 4. The condenser 4 uses cooling water to condense the ring body, and the line body discharged from the bottom of the ring line separation tower 10 is introduced into the evaporator 11 through the circulating pump 12, and then enters the line body storage tank 9 after heat exchange with the superheated steam in the evaporator 11. The evaporator 11 uses a falling film evaporator, and the superheated steam pressure in the evaporator 11 is 3.0MpaG and the temperature is 220°C. The evaporator 11 uses the separated line body waste heat as the heating medium, which not only realizes the recycling of waste heat and improves the energy utilization rate, but also reduces the production load and further reduces the operating cost. After flash separation treatment, it can be separated again according to the purity of the line body. The ring line separation tower 10 is used to perform secondary separation on the line body separated by flash evaporation, which can realize the complete separation of the ring body and the line body, and avoid the phenomenon of the ring body being mixed in the line body. After secondary separation, the separation efficiency of the line body and the ring body can be improved, the purity of the line body and the ring body after separation can be improved, and the quality of the line body and the ring body products after separation can be guaranteed.

[0022] The process of Example 3 can not only improve the separation efficiency of the wire body and the ring body, but also allow the wire body and the ring body to be completely separated, thereby obtaining wire body and ring body products with higher purity, with the wire body purity being greater than 99.85%, and the ring body purity being greater than 99.0%, thereby ensuring the quality of the wire body and ring body products after separation, but also realizing the recycling of waste heat, reducing production load, effectively reducing operating costs, and being able to produce better economic benefits.

Claims

1. A dimethylpolysiloxane loop separation process, characterized in that: The following steps are involved: ① Two-stage heating: the dimethyldichloropolysiloxane hydrolyzate is heated in two stages using a preheater (1) and a heater (2) in sequence; ② Flash separation: the dimethyl polysiloxane hydrolyzate heated in step ① is passed into a flash tank (3) for flash separation. The pressure of the flash tank (3) is 1 to 10 kPaA and the temperature is 120 to 220° C. After flash separation, the ring bodies discharged from the top of the flash tank (3) are condensed by the condenser (4) and then enter the reflux tank (5). The ring bodies in the reflux tank (5) are discharged into the ring body storage tank (7) through the reflux pump (6); ③ Secondary separation: timely monitor the purity of the wire separated by flash evaporation at the bottom of the flash tank (3). When the wire purity is ≥99%, the wire at the bottom of the flash tank (3) is directly discharged into the wire storage tank (9) through the extraction pump (8). When the wire purity is <99%, the wire at the bottom of the flash tank (3) needs to be sent to the loop separation tower (10) for secondary separation. The bottom of the loop separation tower (10) is heated by an evaporator (11), and a part of the ring body discharged by the reflux pump (6) is introduced into the upper part of the loop separation tower (10) as a washing liquid. After the secondary separation, the ring body discharged from the top of the loop separation tower (10) enters the condenser (4) for condensation, and the wire body discharged from the bottom of the loop separation tower (10) enters the wire storage tank (9).

2. A dimethylpolysiloxane loop separation process according to claim 1, characterized in that: In steps ① and ③, the preheater 1 uses the linear body discharged from the flash tank (3) or the loop separation tower (10) as a heat source to heat the dimethyldichloropolysiloxane hydrolyzate.

3. A dimethylpolysiloxane loop separation process according to claim 1, characterized in that: In step ①, the heater (2) uses superheated steam as a heat source to heat the dimethyldichloropolysiloxane hydrolyzate, the pressure of the superheated steam is 2.5-3.0 MpaG, and the temperature is 120-220°C.

4. A dimethylpolysiloxane loop separation process according to claim 1, characterized in that: In step ③, the loop separation tower (10) is a packed tower, a demister is provided at the top of the loop separation tower (10), the pressure of the loop separation tower (10) is 1-10 kPaA, and the temperature is 120-220°C.

5. A dimethylpolysiloxane loop separation process according to claim 1, characterized in that: In step ③, the evaporator (11) is a falling film evaporator, and the superheated steam pressure in the evaporator (11) is 2.5 to 3.0 MPaG, and the temperature is 120 to 220°C.

6. A dimethylpolysiloxane loop separation process according to claim 1, characterized in that: In steps ② and ③, the condenser (4) uses cooling water to condense the ring body.

7. A dimethylpolysiloxane loop separation process according to claim 1, characterized in that: In step ②, a phase separator is used in the reflux tank (5), and a drain outlet is provided at the bottom of the reflux tank (5).

8. A dimethylpolysiloxane loop separation process according to claim 1, characterized in that: In step ③, the linear body discharged from the bottom of the loop separation tower (10) is introduced into the evaporator (11) through the circulation pump (12), and then enters the linear body storage tank (9) after heat exchange with the superheated steam in the evaporator (11).

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