Process for washing and dechlorinating organochlorosilane hydrolysate

Abstract

The invention discloses an organochlorosilane hydrolysate washing dechlorination process which comprises the following steps: continuously introducing an organochlorosilane raw material and process water into a hydrolysis dechlorination section to complete the production and preliminary dechlorination process of organochlorosilane hydrolysate siloxane; and sending the hydrolysate siloxane to a washing dechlorination section, and finally dechlorinating to obtain the product low-chlorine siloxane. According to the process, in the hydrolysis dechlorination section and the water washing dechlorination section, the dechlorination energy consumption is greatly reduced through a dual coalescence-sedimentation technology of coupling a coalescence phase separator and a high-voltage electrostatic device, the water consumption required by the water washing section can be greatly reduced on the basis that the total water washing dechlorination amount is reduced, and the energy consumption is reduced. And the water phase collected in the washing dechlorination section can be completely reused in the hydrolysis dechlorination section to replace a part of water replenishing amount required to be replenished in the hydrolysis reaction. The process has the advantages that the dechlorination efficiency of the organochlorosilane hydrolysate is improved, the energy consumption is reduced, the process is green and environment-friendly, no wastewater or waste alkali liquor is discharged, and high-quality siloxane can be continuously produced.

Description

Technical Field

[0001] The present invention relates to the field of organosilicon, and in particular to a new process for washing and dechlorinating organochlorosilane hydrolyzates. Background Art

[0002] Oligomeric siloxanes, intermediates with linear or cyclic structures, are generated through the hydrolysis and polycondensation of organochlorosilanes. They are important building blocks for the synthesis of silicone oils, silicone rubbers, and silicone resins. Typically, organochlorosilanes undergo hydrolysis under acidic conditions to produce hydrolyzed oligomeric siloxanes and a byproduct, HCl. However, HCl readily dissolves in the aqueous phase carried over by the hydrolyzate, resulting in high residual Cl ion concentrations in the hydrolyzed siloxanes, directly impacting their quality and subsequent application development.

[0003] (CH3)2SiCl2+2H2O→(CH3)Si(OH)2+2HCl

[0004]

[0005] Currently, methods for removing residual Cl ions from hydrolyzed siloxanes primarily involve implementing multi-stage water and alkali washing processes or designing specialized steam towers or distillation towers. Patent CN101817505A discloses a water-washing, alkali-neutralization, and water-washing method for removing chlorine, using a 5% to 30% soda ash solution or a 2% to 10% caustic soda solution as the alkali solution. While this process effectively removes free chlorine from the hydrolyzate, it also suffers from high water and alkali consumption, wastewater and waste salt generated during the water washing process, and high environmental treatment costs. Patents CN103214508A, CN102174200A, and CN1099435C employ multi-stage water and alkali washing for chlorine removal, but these also present significant wastewater and salt production, as well as high treatment costs. In order to overcome the above problems, patent CN101323666A uses a steam tower to dechlorinate the crude hydrolyzate. This process avoids the use of alkali solution and the generation of waste salt, but still has problems such as large steam consumption and high energy consumption. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a method for efficiently washing and dechlorinating organochlorosilane hydrolysates.

[0007] The technical solution adopted in the present invention is as follows:

[0008] The organic chlorosilane hydrolyzate washing and dechlorination process includes a hydrolysis dechlorination section and a water washing dechlorination section. The raw organic chlorosilane is subjected to the hydrolysis dechlorination section and the water washing dechlorination section to obtain a high-quality low-chlorine siloxane product.

[0009] (1) The hydrolysis dechlorination section includes a two-stage hydrolysis reactor, a hydrolysis phase separator and a hydrolysis electrostatic device; the raw material organic chlorosilane (dichlorodimethylsilane) and process water are continuously fed and transported to the two-stage hydrolysis reactor in turn for hydrolysis reaction, generating hydrolyzed siloxane and by-product HCl under acidic conditions, and the by-product HCl gas is extracted from the top of the hydrolysis reactor for subsequent treatment; the hydrolyzed siloxane and the acid-water mixture generated by the reaction in the hydrolysis reactor are transported to the hydrolysis phase separator for agglomeration, dehydration and dechlorination, and the oil phase hydrolyzate obtained at the upper outlet after dehydration and dechlorination of the hydrolysis phase separator is sent to the hydrolysis electrostatic device for further dehydration and dechlorination, and the oil phase hydrolyzate at the upper outlet after dehydration and dechlorination of the hydrolysis electrostatic device is transported to the water washing dechlorination section for further dechlorination treatment; the water phase extracted from the hydrolysis phase separator and the lower layer of the hydrolysis electrostatic device can be collected and reused in the hydrolysis reaction process in the two-stage hydrolysis reactor;

[0010] (2) The water-washing and dechlorination section includes a water-washing and stirring kettle, a water-washing phase separator, and a water-washing and electrostatic device. The oil phase hydrolyzate extracted from the upper outlet of the hydrolysis and electrostatic device of the hydrolysis section (1) is transported to the water-washing and stirring kettle of the water-washing and dechlorination section to be stirred, mixed, and washed with washing water. The hydrolyzate siloxane and washing water mixture after washing in the water-washing and stirring kettle is transported to the water-washing and phase separator for agglomeration, dehydration, and dechlorination. After dehydration and dechlorination in the water-washing and phase separator, the oil phase hydrolyzate overflowing from the upper outlet is transported to the water-washing and electrostatic device for further dehydration and dechlorination. Finally, high-quality low-chlorine siloxane products are extracted from the upper outlet of the water-washing and electrostatic device. The water phases extracted from the water-washing and phase separator and the lower outlet of the water-washing and electrostatic device can be reused in the hydrolysis reaction process in the two-stage hydrolysis reactor in the hydrolysis and dechlorination section (1).

[0011] The organochlorosilane hydrolyzate washing and dechlorination process is characterized in that the temperature in the primary hydrolysis reactor is controlled at 40°C to 60°C, the pressure is 0.1 to 0.3 MPa, the saturated hydrochloric acid concentration is controlled at 39% to 45%, and the residence time is 5 to 10 minutes; the temperature in the secondary hydrolysis reactor is controlled at 40°C to 60°C, the pressure is 0.1 MPa, the concentrated hydrochloric acid concentration is controlled at 12% to 25%, and the residence time is 5 to 10 minutes.

[0012] The process for washing and dechlorinating the organochlorosilane hydrolyzate is characterized in that the electric field strength in the hydrolysis electrostatic device or the water washing electrostatic device is 20-100 kV / m, the temperature is 40-90° C., and the power supply is a positive high-voltage DC power supply or a negative high-voltage DC power supply.

[0013] The process for washing and dechlorinating the organochlorosilane hydrolyzate is characterized in that the temperature of the hydrolysis phase separator is controlled at 40 to 90° C., and the residence time in the hydrolysis phase separator is 5 to 10 minutes.

[0014] The organic chlorosilane hydrolysate washing dechlorination process is characterized in that the temperature of the water washing phase separator is controlled at 40-90 DEG C, and the residence time in the water washing phase separator is 5-10 min.

[0015] The organic chlorosilane hydrolysate washing dechlorination process is characterized in that the temperature of the water washing phase separator is controlled at 40-90 DEG C, and the residence time in the water washing phase separator is 5-10 min.

[0016] The organic chlorosilane hydrolysate washing dechlorination process is characterized in that the temperature of the water washing phase separator is controlled at 40-90 DEG C, and the residence time in the water washing phase separator is 5-10 min.

[0017] Through the above process, compared with the existing process, the beneficial effects of the present application are as follows:

[0018] 1) The present process ingeniously couples the primary coalescence settling of the coalescence phase separator and the advanced coalescence settling of the high-voltage electrostatic device, and effectively reduces the acid water entrainment in the organic chlorosilane crude hydrolysate in the hydrolysis dechlorination section and the organic chlorosilane hydrolysate in the water washing dechlorination section through the double coalescence-settling technology, thereby greatly reducing the total water consumption of the process and avoiding the use of lye.

[0019] 2) The present process uses the water washing dechlorination section to replace the water washing and lye washing sections in the traditional process, avoids the use of lye, produces no waste liquid and waste salt, and is green and environmentally friendly in the production process.

[0020] 3) The present process can greatly reduce the water consumption of the water washing section on the basis of reducing the total amount of chlorine removed in the water washing section, and the water phase produced in the water washing section is correspondingly reduced, and the water phase collected in the water washing dechlorination section can be entirely used in the hydrolysis dechlorination section to replace part of the water supplement required by the hydrolysis reaction, so that no waste liquid is discharged in the water washing dechlorination section.

[0021] 4) The present process improves the dechlorination efficiency of the organic chlorosilane crude hydrolysate through the double coalescence-settling technology of coupling the coalescence phase separator and the high-voltage electrostatic device, greatly reduces the dechlorination energy consumption, can obtain a high-quality siloxane product with a residual chlorine ion content of less than 1 ppm, and is suitable for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 This is a process flow chart for producing oligosiloxane according to Example 1 of the present application;

[0023] Figure 2 This is a process flow chart of a new process for producing oligosiloxane according to Example 2 of the present application;

[0024] Figure 3 This is a process flow chart of producing oligosiloxane using a conventional process according to Example 2 of the present application;

[0025] Figure 4 The particle size distribution at the nine sampling points in Example 1. DETAILED DESCRIPTION

[0026] To further illustrate the present invention, the present invention is described in detail with reference to the following specific examples.

[0027] Example 1:

[0028] The process for preparing high-quality siloxane products in this embodiment includes a hydrolysis dechlorination section and a two-stage water washing dechlorination section, such as Figure 1 As shown, the process for preparing high-quality low-chlorine siloxane products includes the following steps:

[0029] 1) Hydrolysis dechlorination section:

[0030] The raw material dichlorodimethylsilane (purity exceeding 99%) and fresh process water are fed into two-stage series hydrolysis reactors at feed rates of 273 kg / h and 37.5 kg / h, respectively, for hydrolysis. (The primary hydrolysis reactor operates at a temperature of 50°C, a pressure of 0.3 MPa, a saturated hydrochloric acid solution concentration controlled at 41% to 42%, and a residence time of 10 minutes; the secondary hydrolysis reactor operates at a temperature of 60°C, a pressure of 0.1 MPa, a concentrated hydrochloric acid solution concentration controlled at 14% to 15%, and a residence time of 10 minutes.) During the two-stage hydrolysis reaction, the raw material dichlorodimethylsilane continuously releases HCl gas as a byproduct. The HCl gas is extracted from the top of the two-stage hydrolysis reactor for subsequent treatment. After the two-stage hydrolysis reaction, the conversion rate of dichlorodimethylsilane remains stable at over 99.5%.

[0031] The mixture of hydrolyzed siloxane and acid water generated by the two-stage hydrolysis reaction is sent to the hydrolysis phase separator for primary coalescence dehydration and dechlorination (the temperature in the hydrolysis phase separator is stable at 80°C, and the residence time is about 10 minutes). The acid water content of the upper outlet oil phase hydrolyzate is about 3.2% after detection; the upper outlet oil phase crude hydrolyzate (158-160 kg / h) after coalescence and dehydration in the hydrolysis phase separator is sent to the hydrolysis electrostatic device for advanced coalescence sedimentation dehydration (the hydrolysis electrostatic device is The operating temperature was 80°C, the power supply was a negative high-voltage DC power supply, the electric field strength was 60 kV / m, and the residence time was 10 minutes. Testing revealed that the water content of the oil phase hydrolyzate at the upper outlet had dropped to approximately 0.4%. The hydrolyzate, siloxane (154-155 kg / h), dehydrated by the hydrolysis electrostatic device, was then further sent to a primary water washing and dechlorination section for treatment. The aqueous phases extracted from the hydrolysis phase separator and the lower outlet of the hydrolysis electrostatic device were collected and reused in the hydrolysis reaction process in the two-stage hydrolysis reactor.

[0032] 2) Primary water washing and dechlorination section (primary water washing and dechlorination unit):

[0033] The oil phase hydrolyzed siloxane from the hydrolysis dechlorination section in step 1) flows into the water washing stirring tank of the primary water washing dechlorination section together with the water phase collected by the secondary water washing unit for stirring, mixing and washing (the temperature in the stirring tank is 80°C, the stirring speed is 150r / min, and the residence time is 10min). The washed siloxane and water mixture is sent to the primary water washing phase separator for coalescence, sedimentation and dehydration (temperature is 80°C, and the residence time is 10min). After phase separation, the water content of the oil phase hydrolyzed siloxane is about 2.9%; the upper layer outlet oil phase hydrolyzed siloxane (15 The first-level electrostatic water washing device is used to transport the hydrolyzed siloxane (154-155 kg / h) to a primary water washing electrostatic device for advanced coalescence sedimentation dehydration treatment (the operating temperature in the primary water washing electrostatic device is 80°C, the power supply is a negative high-voltage DC power supply, the electric field strength is 60 kV / m, and the residence time is 10 minutes). After testing, the water content of the hydrolyzed siloxane in the upper layer outlet is reduced to about 0.2%. The hydrolyzed siloxane (154-155 kg / h) after dehydration in the primary water washing electrostatic device is further transported to the subsequent secondary water washing and dechlorination section for treatment. The aqueous phases extracted from the primary water washing phase separator and the lower layer outlet of the primary water washing electrostatic device are collected in a storage tank for future use.

[0034] 3) Secondary water washing and dechlorination section (secondary water washing unit):

[0035] The hydrolyzed siloxane from the primary water washing and dechlorination section of step 2) is fed together with process water (34 kg / h) into a secondary water washing stirred tank for washing and dechlorination (temperature in the stirred tank is 80°C, stirring speed is 150 r / min, and residence time is 10 min). The mixture of the oil phase hydrolyzed siloxane and washing water after the secondary washing is fed into a secondary water washing phase separator for coalescence and sedimentation dehydration (temperature is 80°C, and residence time is 10 min). After phase separation, the water content of the oil phase hydrolyzed siloxane is approximately 3.1%. The upper layer outlet oil phase hydrolyzed siloxane after coalescence and dehydration in the secondary water washing phase separator ( The oil phase is transported to a secondary water-wash electrostatic device at a rate of 158 to 160 kg / h for advanced coalescence and sedimentation dehydration treatment (the operating temperature in the secondary water-wash electrostatic device is 80° C., the power supply is a negative high-voltage DC power supply, the electric field strength is 70 kV / m, and the residence time is 10 minutes). After testing, the water content of the siloxane in the oil phase hydrolyzate at the upper outlet is reduced to approximately 0.2%, and the final low-chlorine siloxane product is produced (154 to 155 kg / h) with a chloride ion content of less than 1 ppm. The aqueous phases produced from the secondary water-wash phase separator and the lower outlet of the secondary water-wash electrostatic device are collected and transported back to the primary water-wash stirred tank.

[0036] The device was operated stably for 24 hours continuously, and the hydrolysis conversion rate of dichlorodimethylsilane was stable at above 99.5%. The experimental results are shown in Table 1.

[0037] Table 1 Continuous dechlorination process unit continuous operation 24h organochlorosilane crude hydrolyzate dechlorination results

[0038]

[0039] After the device was continuously operated for 24 hours, samples were taken from nine locations, including the hydrolysis phase separator inlet, the upper outlet of the hydrolysis phase separator, and the upper outlet of the hydrolysis electrostatic device in the hydrolysis dechlorination section; the first-level water washing phase separator inlet, the upper outlet of the first-level water washing phase separator, the upper outlet of the first-level water washing electrostatic device in the first-level water washing unit in the water washing dechlorination section; the second-level water washing phase separator inlet, the upper outlet of the second-level phase separator, and the upper outlet of the second-level water washing electrostatic device in the second-level water washing unit. The samples were placed under a microscope to photograph the particle size of the aqueous phase droplets in the oil phase sample, and the droplet size distribution was statistically analyzed. The results are as follows: Figure 4 and as shown in Table 2.

[0040] Table 2 Summary of the average particle size changes at different sampling locations during continuous operation of the new continuous dechlorination process for 24 hours

[0041]

[0042] From the results of Example 1 above, it can be seen that within each work section unit, the phase separator and the electrostatic device both have a coalescence-sedimentation effect; through the dual coalescence-sedimentation system composed of the phase separator and the electrostatic device, the water content of the oil phase hydrolyzate siloxane is significantly reduced within a limited time, thereby reducing the residual chloride ion concentration in the oil phase hydrolyzate siloxane, thereby achieving the purpose of efficient chlorine removal from the dichlorodimethylsilane hydrolyzate.

[0043] Example 2:

[0044] This example compares the dechlorination effect of the process of the present invention and the traditional process on organochlorosilane hydrolyzate. The specific process is as follows:

[0045] The process of preparing high-quality low-chlorine siloxane products by the present invention includes a hydrolysis dechlorination section and a two-stage water washing dechlorination section, such as Figure 2 As shown, based on Example 1, the water phase collected in the water washing and dechlorination section is completely recycled to the hydrolysis reactor in the hydrolysis dechlorination section. The process for preparing high-quality low-chlorine siloxane products includes the following steps:

[0046] 1) Hydrolysis dechlorination section:

[0047] The raw material, dichlorodimethylsilane (purity exceeding 99%), and fresh process water are fed into two-stage series hydrolysis reactors at feed rates of 273 kg / h and 3.5 kg / h, respectively, for hydrolysis. (The primary hydrolysis reactor operates at a temperature of 50°C, a pressure of 0.3 MPa, a saturated hydrochloric acid solution concentration controlled at 41% to 42%, and a residence time of 10 minutes; the secondary hydrolysis reactor operates at a temperature of 60°C, a pressure of 0.1 MPa, a concentrated hydrochloric acid solution concentration controlled at 14% to 15%, and a residence time of 10 minutes.) During the two-stage hydrolysis reaction, the raw material, dichlorodimethylsilane, continuously releases HCl gas as a byproduct. The HCl gas is extracted from the top of the two-stage hydrolysis reactor for subsequent treatment. After the two-stage hydrolysis reaction, the conversion rate of dichlorodimethylsilane remains stable at over 99.5%.

[0048] The mixture of hydrolyzed siloxane and acid water generated by the two-stage hydrolysis reaction is sent to the hydrolysis phase separator for primary coalescence dehydration and dechlorination (the temperature in the hydrolysis phase separator is stable at 80°C, and the residence time is about 10 minutes). The water content of the upper oil phase hydrolyzed product is about 3.4% after detection; the upper oil phase hydrolyzed siloxane (158-160 kg / h) after coalescence and dehydration in the hydrolysis phase separator is sent to the hydrolysis electrostatic device for advanced coalescence sedimentation dehydration (the hydrolysis electrostatic device is operated at 100 °C). The operating temperature was 80°C, the power supply was a negative high-voltage DC power supply, the electric field strength was 60 kV / m, and the residence time was 10 minutes. After testing, the water content of the oil phase hydrolyzate at the upper outlet was reduced to approximately 0.4%. Then, the siloxane in the oil phase hydrolyzate (154-155 kg / h) after dehydration by the hydrolysis electrostatic device was further sent to the primary water washing and dechlorination section for treatment. The aqueous phases extracted from the hydrolysis phase separator and the lower outlet of the hydrolysis electrostatic device were collected and reused in the hydrolysis reaction process in the two-stage hydrolysis reactor.

[0049] 2) Primary water washing and dechlorination section (primary water washing and dechlorination unit):

[0050] The oil phase hydrolyzed siloxane from the hydrolysis dechlorination section in step 1) and the water phase collected from the secondary water washing unit are flowed together into the water washing stirring tank of the primary water washing dechlorination section for stirring, mixing and washing (temperature in the stirring tank is 80°C, stirring speed is 150 r / min, and residence time is 10 min). The washed hydrolyzed product and water mixture are sent to the primary water washing phase separator for coalescence, sedimentation and dehydration (temperature is 80°C, residence time is 10 min). After phase separation, the water content of the oil phase hydrolyzed siloxane is approximately 3.0%; the upper layer outlet oil phase hydrolyzed siloxane (158-160 kg / min) after coalescence, sedimentation and dehydration in the primary water washing phase separator is h) transported to a primary water-wash electrostatic device for advanced coalescence and sedimentation dehydration treatment (the operating temperature in the primary water-wash electrostatic device is 80° C., the power supply is a negative high-voltage DC power supply, the electric field strength is 60 kV / m, and the residence time is 10 minutes). Testing shows that the water content of the siloxane in the upper oil phase hydrolyzate is reduced to approximately 0.2%; the siloxane in the oil phase hydrolyzate (154-155 kg / h) after dehydration in the primary water-wash electrostatic device is further transported to the subsequent secondary water-wash dechlorination section for treatment; the aqueous phase (34 kg / h) extracted from the primary water-wash phase separator and the lower layer of the primary water-wash electrostatic device is collected and transported to a two-stage hydrolysis reactor in the hydrolysis dechlorination section.

[0051] 3) Secondary water washing and dechlorination section (secondary water washing unit):

[0052] The oily phase hydrolyzed siloxane from the primary water washing and dechlorination section in step 2) was fed together with process water (34 kg / h) into a secondary water washing stirred tank for stirring, mixing, and washing (temperature in the stirred tank: 80° C., stirring speed: 150 r / min, residence time: 10 min). The mixture of the oily phase hydrolyzed siloxane and washing water after the secondary washing was fed into a secondary water washing phase separator for coalescence, sedimentation, and dehydration (temperature: 80° C., residence time: 10 min). After phase separation, the water content of the oily phase hydrolyzed siloxane was found to be approximately 2.8%. The upper layer of the siloxane after coalescence and dehydration in the secondary water washing phase separator was discharged. The oil phase hydrolyzed siloxane was transported to a secondary water washing electrostatic device for advanced coagulation sedimentation dehydration treatment (the operating temperature in the secondary water washing electrostatic device was 80°C, the power supply was a negative high-voltage DC power supply, the electric field strength was 70 kV / m, and the residence time was 10 minutes). After testing, the water content of the oil phase low-chlorosiloxane at the upper outlet was reduced to approximately 0.2%. The final low-chlorosiloxane product was produced (154-155 kg / h) with a chloride ion content of less than 1 ppm. The aqueous phases produced from the secondary water washing phase separator and the lower outlet of the secondary water washing electrostatic device were collected and transported back to the primary water washing stirred tank.

[0053] The device was operated stably for 24 hours continuously, and the hydrolysis conversion rate of dichlorodimethylsilane was stable at above 99.5%. The experimental results are shown in Table 3.

[0054] Comparative Example 1, Traditional Technology: The traditional process of producing low-chlorine siloxane is as follows Figure 3 The specific steps are as follows:

[0055] 1) Hydrolysis section: The raw material dichlorodimethylsilane (purity above 99%) and fresh process water are fed into a two-stage hydrolysis reactor at feed rates of 273 kg / h and 3.5 kg / h, respectively, for hydrolysis reaction (the operating conditions in the first hydrolysis reactor are temperature of 50° C., pressure of 0.3 MPa, concentration of saturated hydrochloric acid solution controlled at 41-42%, and residence time of 10 min; the operating conditions in the second hydrolysis reactor are temperature of 60° C., pressure of 0.1 MPa, concentration of concentrated hydrochloric acid solution controlled at 14%-15%, and residence time of 10 min). The raw material dichlorodimethylsilane undergoes a two-stage hydrolysis reaction to generate hydrolyzed siloxane and a by-product, HCl. The HCl gas is extracted from the top of the two-stage hydrolysis reactor for subsequent treatment. The conversion rate of dichlorodimethylsilane is stabilized at above 99.5%. A mixture of the hydrolyzed siloxane and acid water is fed into a hydrolysis phase separator for stratification. The temperature in the hydrolysis phase separator is stabilized at T=80°C, and the mixture resides for 10 minutes. The oil phase hydrolyzed siloxane (160-161 kg / h) at the upper outlet of the hydrolysis phase separator is fed to a subsequent water washing and alkali washing section, and the water phase at the lower outlet is fed back to the two-stage hydrolysis reactor to participate in the hydrolysis reaction.

[0056] 2) Water and Alkali Washing Section: The water and alkali washing section consists of three water washing units and a primary alkali washing unit. Each water washing unit includes a water washing agitator and a water washing phase separator. The primary alkali washing unit includes an alkali washing agitator and an alkali washing phase separator. The oil phase hydrolyzed siloxane is sequentially dechlorinated in the primary water washing unit, the primary alkali washing unit, the secondary water washing unit, and the tertiary water washing unit to obtain the final low-chlorine siloxane product. The specific operation process is as follows:

[0057] S1: The oil phase hydrolyzate siloxane obtained in step 1) is introduced into a water washing stirring tank of a primary water washing unit, and mixed and stirred for washing with the secondary water washing aqueous phase collected from the secondary water washing unit, with the stirring tank temperature T=80°C, the stirring speed 150r / min, and the residence time 10min; the stirred water washing mixture is sent to a primary water washing phase separator for stratification, with the temperature in the primary water washing phase separator T=80°C, the residence time 10min, and the primary water washed siloxane (oil phase) flows out from the upper end outlet of the primary water washing phase separator and is sent to the primary alkali washing unit, and about 40% of the primary water washing aqueous phase collected in the phase separator in the primary water washing unit is recycled for the hydrolysis reaction process in the two-stage hydrolysis reactor, and the remaining about 60% of the water washing aqueous phase is discharged as waste liquid.

[0058] S2: The oil phase hydrolyzed siloxane in the primary alkali washing unit is fed together with 5% NaOH alkali liquor (26 kg / h) into an alkali washing stirring kettle for mixing, stirring and washing. The temperature in the stirring kettle is 80° C., the stirring speed is 150 r / min, and the residence time is 10 min. The alkali washing mixture is passed into an alkali washing phase separator for separation. The temperature in the primary alkali washing phase separator is T=80° C. and the residence time is 10 min. The oil phase hydrolyzed siloxane (159-160 kg / h) at the upper layer outlet of the alkali washing phase separator is fed to a secondary water washing unit, and the aqueous alkali liquor collected at the lower layer outlet is discharged as waste alkali liquor.

[0059] S3: The oily phase hydrolyzate siloxane is washed and dechlorinated in a secondary water washing unit and a tertiary water washing unit in sequence. The operating conditions in the water washing agitator and the water washing phase separator in the secondary and tertiary water washing units are the same as those in the primary water washing unit. Fresh process water (80 kg / h) is introduced from the water washing agitator in the tertiary water washing unit and sent to the tertiary water washing phase separator together with the oily phase hydrolyzate siloxane for stratification. The water phase at the lower outlet is extracted and countercurrently returned to the water washing agitator in the secondary water washing unit. Similarly, the secondary water washing water phase is recycled to the water washing agitator in the primary water washing unit. Finally, after dechlorination in the tertiary water washing unit and the primary alkali washing unit, a low-chlorine siloxane product with a stable chloride ion concentration of 2 to 4 ppm is obtained.

[0060] Table 3 shows the comparison of the results of preparing low-chlorine siloxane products using the technology of the present invention and the traditional technology.

[0061] Table 3 Comparison of the results of dechlorination of organochlorosilane hydrolyzate by the new process of the present invention and the traditional process

[0062]

[0063] As can be seen in the above Example 2, in the new process of the present invention, the reuse of the water phase collected in the water washing and dechlorination section into the hydrolysis reactor of the hydrolysis dechlorination section has little effect on the dechlorination effect of the organochlorosilane hydrolyzate. At the same time, the reuse of the water phase collected in the water washing and dechlorination section can effectively replace part of the fresh process water consumed in the hydrolysis reaction, effectively reducing the total water consumption of the new process, and no excess wastewater is discharged from the water washing and dechlorination section.

[0064] At the same time, by comparing the dechlorination effect of the new process of the present invention with that of the traditional process on the organochlorosilane hydrolyzate, it can be seen that the new process of the present invention significantly improves the dechlorination efficiency of the organochlorosilane hydrolyzate by coupling the dual agglomeration-sedimentation technology of the agglomeration phase separator and the high-voltage electrostatic device; the process water consumption in the washing and dechlorination process of the organochlorosilane hydrolyzate is reduced by 55% compared with the traditional technology; the new process of the present invention replaces the alkali washing and dechlorination section in the traditional process with a multi-stage water washing and dechlorination section, avoiding the use of alkali solution, and thus no waste alkali solution is discharged; the water phase collected in the water washing and dechlorination section of the new process of the present invention can be fully reused in the hydrolysis section, and there is no excess wastewater discharge compared with the traditional process. In summary, the new process of the present invention has obvious advantages over the traditional technology for preparing low-chlorine siloxane products.

[0065] The above description is not intended to limit the present invention, and the present invention is not limited to the above examples. Any changes, modifications, additions or substitutions made by persons of ordinary skill in the art within the spirit and scope of the present invention shall also fall within the scope of protection of the present invention.

Claims

1. A washing and dechlorination process for organochlorosilane hydrolyzate, characterized in that The raw material organochlorosilane is dechlorinated by hydrolysis and then washed with water to obtain high-quality low-chlorine siloxane products. The following processes are included: (1) The hydrolysis dechlorination section includes a hydrolysis reactor, a hydrolysis phase separator and a hydrolysis electrostatic device; The raw material organochlorosilane and process water are continuously fed into the hydrolysis reactor respectively, and the hydrolysis reaction is carried out under acidic conditions. The byproduct HCl gas released during the reaction is extracted for subsequent treatment. The hydrolyzed siloxane and acid-water mixture generated by the reaction are transported to the hydrolysis phase separator for agglomeration, dehydration and chlorination, and then enter the hydrolysis electrostatic device for further dehydration and chlorination. After that, it is transported to the water washing and dechlorination section for further dechlorination treatment. The aqueous phases extracted from the lower layers of the hydrolysis phase separator and the hydrolysis electrostatic device are collected and reused in the hydrolysis reaction process in the hydrolysis reactor. (2) The water washing and dechlorination section comprises at least one stage, and each stage of the water washing and dechlorination section comprises a water washing stirring kettle, a water washing phase separator and a water washing electrostatic device. The oil phase hydrolyzate siloxane output from the hydrolysis dechlorination section in step (1) enters the water washing stirring kettle of the water washing and dechlorination section and is stirred and mixed with washing water for washing. The washing mixture is transported to the water washing phase separator for agglomeration, dehydration and dechlorination, and then enters the water washing electrostatic device for further dehydration and dechlorination, and finally a high-quality low-chlorine siloxane product is produced; the water phases produced from the lower layers of the water washing phase separator and the water washing electrostatic device can be collected and reused in the hydrolysis reaction process in the hydrolysis dechlorination section in step (1).

2. The process for washing and dechlorinating the organochlorosilane hydrolyzate according to claim 1, characterized in that The hydrolysis reactor is a two-stage series reactor. The temperature in the first hydrolysis reactor is controlled at 40°C to 60°C, the pressure is 0.1 MPa to 0.3 MPa, the concentration of saturated hydrochloric acid is controlled at 39% to 45%, and the residence time is 5 to 10 minutes. The temperature in the second hydrolysis reactor is controlled at 40°C to 60°C, the pressure is 0.1 MPa, the concentration of concentrated hydrochloric acid is controlled at 12% to 25%, and the residence time is 5 to 10 minutes.

3. The process for washing and dechlorinating the organochlorosilane hydrolyzate according to claim 1, wherein The electric field strength in the hydrolysis electrostatic device or the water washing electrostatic device is 20~100kV / m, the temperature is 40~90℃, and the power supply is a positive high-voltage DC power supply or a negative high-voltage DC power supply.

4. The process for washing and dechlorinating the organochlorosilane hydrolyzate according to claim 1, wherein The temperature of the hydrolysis phase separator is controlled at 40-90° C., and the residence time in the hydrolysis phase separator is 5-10 minutes.

5. The process for washing and dechlorinating the organochlorosilane hydrolyzate according to claim 1, wherein The temperature of the water-wash phase separator is controlled at 40-90° C., and the residence time in the water-wash phase separator is 5-10 minutes.

6. The process for washing and dechlorinating the organochlorosilane hydrolyzate according to claim 1, wherein The temperature of the water washing stirring kettle in the water washing and dechlorination section is 40~90℃, the stirring speed is 50~150 r / min, and the residence time is 5-10min.

7. The process for washing and dechlorinating the organochlorosilane hydrolyzate according to claim 1, wherein In step (2), the water washing and dechlorination section is a two-stage or three-stage series connection. The oil phase output from the hydrolysis dechlorination section in step (1) flows from the first-stage water washing and dechlorination section to the last-stage water washing and dechlorination section. Fresh process water is first introduced into the water washing and stirring kettle of the last-stage water washing and dechlorination section. The water phases extracted from the lower layers of the water washing phase separator and the water washing electrostatic device of the last-stage water washing and dechlorination section are refluxed to the water washing and stirring kettle of the adjacent previous water washing and dechlorination section. Similarly, the water phases extracted from the lower layers of the water washing phase separator and the water washing electrostatic device of the first-stage water washing and dechlorination section are refluxed to the hydrolysis reaction process in the hydrolysis dechlorination section in step (1).

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