A polysiloxane desulfurization system and desulfurization method

Abstract

The present invention provides a polysiloxane desulfurization system, comprising a first delivery pump, a first preheater, a first flash tank, a second delivery pump, a second preheater second flash tank, a product receiving tank, and a second delivery pump connected in sequence, wherein the first delivery pump is connected to a polymerization kettle, and the second delivery pump is connected to a large product tank; the low-molecular vapor outlet of the first flash tank is connected to a first condenser, the first condenser is connected to a first low-molecular vapor receiving tank, and the first low-molecular vapor receiving tank is connected to a first vacuum system; the second flash tank is provided with a built-in condenser, and the outlet of the built-in condenser is connected to a second low-molecular vapor receiving tank, the outlet of the uncondensed low-molecular vapor of the second flash tank is connected to the second low-molecular vapor receiving tank through a second condenser, and the second condenser is connected to a second vacuum system; the vacuum degree of the second vacuum system is higher than that of the first vacuum system. The system of the present invention is simple to operate, energy-saving, and efficient, and can remove volatiles to trace levels.

Description

Technical Field

[0001] The invention belongs to the field of polysiloxane production, and particularly relates to a polysiloxane deoxidation system and a deoxidation method. Background Art

[0002] The industrial production of polysiloxanes generally utilizes a mixed siloxane equilibrium method, using DMC (dimethylcyclosiloxane) or D4 (octamethylcyclotetrasiloxane) as raw materials, followed by dehydration and ring-opening polymerization. Unlike the preparation of other polymers, due to the chemical equilibrium involved in the polymerization reaction, some cyclosiloxane remains unconverted to polysiloxane, resulting in polymerization yields generally around 80-85%. Residual cyclosiloxanes (low-molecular weight) must be removed, recovered, and reused to reduce production costs. Furthermore, trace amounts of low-molecular weight substances in polysiloxanes can, to a certain extent, hinder their use in high-end applications such as electronics, optics, and cosmetics. For example, the EU Reach Regulation mandates that the individual contents of D4 and D5 in cosmetics must be less than 1000 ppm; in certain electronics applications, the content of D3-D10 is limited to approximately 100 ppm.

[0003] Therefore, in order to meet different needs, it is urgent to develop an ultra-low volatility, high-efficiency and energy-saving polysiloxane desulfurization system and method.

[0004] Currently, the polysiloxane desulfurization methods reported in patents include direct desulfurization in the kettle, single-stage membrane desulfurization or single-stage short-path distillation desulfurization, or membrane desulfurization and short-path distillation in series, or multi-stage membrane desulfurization. Since the optimal operating conditions, equipment and energy input of the equipment are not taken into consideration, an efficient and energy-saving desulfurization combination system has not been developed based on the state of the polymer in the desulfurization process and the desulfurization mechanism. As a result, the energy efficiency of the desulfurization process is low, the desulfurization effect is not ideal, and it is difficult to remove the volatile matter to the trace level (D3-D10 <100 ppm).

[0005] CN102206349 discloses a method for purifying α,ω-dihydroxypolysiloxane by connecting a scraper-type thin film desorption device and a short-path distillation device in series. Under two-stage absolute pressures of 50-90Pa and 20-50Pa, the low-molecular content of the two-stage separation system reaches 50-120ppm. However, the scraper-type thin film desorption device and the short-path distillation desorption device have dynamic seal leakage, and the high absolute pressure environment places very high demands on the vacuum system. In addition, this type of desorption device cannot solve the problem that the low-viscosity material has a short residence time and the scraper cannot update the interface.

[0006] In addition, there are patents reporting methods such as adsorption, extraction, and steam stripping to prepare ultra-low volatility polysiloxanes. However, these methods are difficult to commercialize.

[0007] CN104530432 discloses a method for preparing low-volatility polysiloxane by pressurized supercritical extraction. The minimum volatile content is 0.3%, and the equipment investment is relatively expensive, which greatly limits the application of this technology.

[0008] CN108102100 discloses a method for preparing volatile vinyl silicone oil by centrifugal extraction and thin film stripping. Acetic acid, methanol, ethanol, acetone, etc. are added to the silicone oil, and the volatile content of polysiloxane is reduced to <0.2% through centrifugal extraction and thin film stripping. However, it is difficult to avoid the introduction of solvent impurities, which limits its application.

[0009] CN105294954 discloses a method for purification by adsorption resin. Crude α,ω-dihydroxypolysiloxane is added to the top of an adsorption column. The effluent is purified polysiloxane, and the adsorption rate of low-molecular-weight products exceeds 80%. However, this method is limited by the viscosity of the polysiloxane, and impurities from the adsorption resin are inevitably introduced during the adsorption process.

[0010] In view of this, the present invention is proposed. Summary of the Invention

[0011] In view of the deficiencies of the prior art, the present invention provides a polysiloxane degassing system, which is simple to operate, energy-saving, highly efficient, and can degas volatiles to trace levels.

[0012] The basic concept of the technical solution adopted in the present invention is as follows:

[0013] A polysiloxane desulfurization system comprises a first delivery pump, a first preheater, a primary flash tank, a second delivery pump, a second preheater, a secondary flash tank, a product receiving tank and a second delivery pump connected in sequence through pipelines, wherein the first delivery pump is connected to a polymerization kettle and the second delivery pump is connected to a product tank;

[0014] The low molecular steam outlet of the first flash tank is connected to the first condenser, the first condenser is connected to the first low molecular receiving tank, and the first low molecular receiving tank is connected to the first vacuum system;

[0015] The secondary flash tank is provided with a built-in condenser and the outlet of the built-in condenser is connected to the second low-molecular-weight receiving tank. The outlet of the uncondensed low-molecular-weight steam of the secondary flash tank is connected to the second low-molecular-weight receiving tank through the second condenser, and the second condenser is connected to the secondary vacuum system.

[0016] Among them, the vacuum degree of the secondary vacuum system is higher than that of the primary vacuum system.

[0017] As an implementation example, the first-stage flash tank includes a vertical straight cylindrical structure in the upper part and a vertical cone structure in the lower part. A polysiloxane tangential feed port is provided on the upper outer side surface of the vertical straight cylindrical structure for tangential feeding of materials, and a polysiloxane discharge port is provided at the bottom of the vertical cone structure.

[0018] A spiral channel and a positioning tube are arranged inside the first-stage flash tank. The spiral channel is constructed by spiral spoiler blades. The positioning tube runs through the entire spiral spoiler blade. The outer edge of the spiral spoiler blade is fixed to the inner wall of the first-stage flash tank, and the inner edge is fixed to the positioning tube. The positioning tube is arranged at the axis of the cavity of the first-stage flash tank. The spiral spoiler blade and the positioning tube are coaxial and concentric with the inner cavity of the first-stage flash tank. An external heating companion pipe or jacket is provided on the outside of the first-stage flash tank to compensate for latent heat dissipation.

[0019] As an implementation case, a heating pipe is provided, which is coiled on the outside of the first-stage flash tank. The heating medium inlet of the heating pipe is located below the outside of the first-stage flash tank, and the heating medium outlet is located above the first-stage flash tank.

[0020] As an implementation example, the secondary flash tank is a vertical cylindrical structure with a distribution plate, a disc distributor and a built-in condenser, and a polysiloxane feed port is set on the top;

[0021] Several disc distributors are arranged around the cylinder wall of the secondary flash tank. The multiple disc distributors are supported by several vertical positioning rods fixedly connected to the cylinder wall, so that the polysiloxane forms a continuous liquid film flow on each group of disc distributors.

[0022] An external heating jacket or heating pipe is provided on the outside of the secondary flash tank.

[0023] As an implementation example, the distribution plate is a disc structure and has slits provided at intervals of 20-30° along a circumference concentric with the center of the disc structure. Preferably, the width of the slits is 0.1-2.5 mm.

[0024] As an implementation example, a disc distributor includes a disc structure and multiple layers are arranged in order from top to bottom. Overflow plates are provided on the outer and inner edges of the odd-numbered disc structures, and the height of the overflow plate on the outer edge is lower than that of the overflow plate on the inner edge. By controlling the height of the overflow plate on the outer edge, the thickness of the polysiloxane on the disc structure is adjusted.

[0025] The outer edge of the disc structure of the even-numbered layers is fixed to the inner wall of the secondary flash tank, and an overflow plate is provided on the inner edge. The thickness of the polysiloxane on the disc structure is adjusted by controlling the height of the overflow plate on the inner edge; the outer diameter and inner diameter of the disc structure on the odd-numbered layers are both smaller than those of the disc structure on the even-numbered layers.

[0026] As an implementation example, the distance between the outer edge of the odd-numbered disc structure and the wall of the secondary flash tank is 1-5 mm, and the width can be adjusted according to the viscosity of the polysiloxane.

[0027] As an implementation case, a polysiloxane guide component is provided on the lower cylinder wall of the secondary flash tank at a position below the corresponding disc distributor. The silicone guide component is connected to the polysiloxane side discharge port or the uncondensed low-molecular vapor side outlet provided on the cylinder wall of the secondary flash tank. The polysiloxane side discharge port is provided above the polysiloxane guide component, and the uncondensed low-molecular vapor side outlet is provided below the polysiloxane guide component. The polysiloxane side discharge port is connected to the product receiving tank, and the uncondensed low-molecular vapor side outlet is connected to the second condenser.

[0028] As an implementation case, the polysiloxane flow guide component is arranged directly below the disc distributor. The outer edge of the polysiloxane flow guide component is fixed on the inner cylinder wall of the secondary flash tank, and the inner edge is provided with a flow guide baffle. The side close to the polysiloxane side discharge port is the lowest point of the polysiloxane flow guide component, and the side close to the uncondensed low molecular steam side outlet is the highest point of the polysiloxane flow guide component.

[0029] The present invention also provides a method for deoxidizing polysiloxanes, wherein the method uses the polysiloxane deoxidation system according to any one of the above items to process a polysiloxane semi-finished product to be deoxidized;

[0030] The semi-finished polysiloxane product is transported to the first preheater by the first delivery pump for preheating, and then enters the first flash tank for primary desulfurization in the first vacuum system. The polysiloxane after the primary desulfurization is again input into the second preheater for preheating, and then enters the second flash tank for secondary desulfurization in the second vacuum system. The polysiloxane after the secondary desulfurization is collected from the bottom of the second flash tank and input into the product receiving tank. The low molecular weight substances separated from the primary and secondary desulfurization are recovered through condensation.

[0031] As an implementation example, the molecular structure of the polysiloxane is X(MeRSiO) m (HRSiO) n X, wherein X is one of methyl, H, vinyl, hydroxyl, and alkoxy, R is one or two of methyl, phenyl, ethyl, and vinyl, m+n≥1300, m≥0, and n≥0;

[0032] As an implementation example, the low molecular weight content of the polysiloxane semi-finished product to be desulfurized is 1-15%, more preferably 3-10%, and most preferably 4-8%.

[0033] As an implementation case, the temperature of the primary degassing is 110-200°C, preferably 120-190°C, and more preferably 140-180°C; the absolute pressure of the primary vacuum system is 0.1-2.0KPa, preferably 0.3-1.3KPa, and more preferably 0.5-1.0KPa.

[0034] As an implementation case, the temperature of the secondary degassing is 130-250°C, preferably 140-240°C, and more preferably 150-230°C; the absolute pressure of the secondary vacuum system is 0.1-15Pa, preferably 1-7.5Pa, and more preferably 1.5-4Pa.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] 1. The present invention improves the degassing energy efficiency and product quality within the optimal operating range of the equipment through the design of the flash tank structure and the hierarchical control of the degassing conditions based on the characteristics of the material viscosity and volatile matter content during the degassing process.

[0037] 2. Furthermore, the present invention adopts a two-stage flash evaporation. The first-stage flash evaporation removes most of the low molecular weight, reducing the vacuum load of the entire desulfurization system and creating conditions for the second-stage flash evaporation to achieve ultra-high vacuum, thereby ensuring the quality of the polysiloxane product. The low molecular weight can reach the trace level (D3-D10 <100ppm).

[0038] 3. Furthermore, the flash tank designed in the present invention overcomes the dynamic seal leakage problem that cannot be solved by the current scraper film and scraper short-path distillation, and is easier to create an ultra-high vacuum. At the same time, it avoids the problem of introducing particulate impurities due to scraper wear, thereby improving the purity of polysiloxane.

[0039] 4. Furthermore, by setting up the fluid distribution structure in the flash tank, a polysiloxane flow film is fully formed, effectively solving the problems of poor material interface renewal effect and short residence time of polysiloxane materials in traditional flash tanks;

[0040] In addition, the built-in condensation structure allows the removed low-molecular-weight substances to be immediately condensed in the flash tank, which can create an ultra-high vacuum and further create favorable conditions for the removal of low-molecular-weight substances. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0042] Figure 1 It is a structural schematic diagram of a polysiloxane deoxidation system of the present invention.

[0043] Figure 2 yes Figure 1 Schematic diagram of the structure of the first-stage flash tank shown.

[0044] Figure 3 yes Figure 1 Schematic diagram of the structure of the secondary flash tank shown.

[0045] Figure 4 yes Figure 3 Schematic diagram of the structure of the distribution plate in the secondary flash tank shown.

[0046] Description of the marks in the figure:

[0047] 1. First delivery pump; 2. First preheater; 3. First flash tank; 4. Second delivery pump; 5. Second preheater, 6. Second flash tank; 7. Product receiving tank; 8. Third delivery pump; 9. First condenser; 10. First low-molecular-weight receiving tank; 11. Second condenser; 12. Second low-molecular-weight receiving tank; 3-1. Tangential feed port for polysiloxane; 3-2. Spiral channel; 3-3. Polysiloxane outlet; 3-4. Positioning pipe; 3-5. Low-molecular-weight steam outlet; 3-6. External heating companion pipe; 3-6-1. Heating medium outlet; 3-6-2. Heating medium inlet; 3-7. Material melt pool; 6-1. Polysiloxane feed port; 6-2. Storage silo; 6-3. Distribution plate; 6-4. (1-13) Disc distributor; 6-5. Positioning rod; 6-6. (1-2) Polysiloxane flow guide member; 6-6-3. Guide baffle; 6-7 Polysiloxane side discharge port; 6-8 Built-in condenser; 6-9 Low molecular weight discharge port; 6-10 Uncondensed low molecular weight steam side outlet; 6-11 External heating jacket; 6-11-1 Heating medium outlet; 6-11-2 Heating medium inlet; 6-12-1 Cooling medium inlet; 6-12-2 Cooling medium outlet; 6-3-1 Slit; 6-13-1 Inner edge overflow plate; 6-13-2 Outer edge overflow plate. DETAILED DESCRIPTION

[0048] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] Example 1 A polysiloxane removal system

[0050] Figure 1-4 The structure of a polysiloxane degassing system of the present invention is shown. In the figure, there are multiple structures. In order to facilitate the subsequent differentiation and introduction, each structure is numbered. For example, the polysiloxane flow guide component 6-6-(1-2) is Figure 3 The polysiloxane flow guide member 6-6-1 and the polysiloxane flow guide member 6-6-2. The disc distributor 6-4-(1-13) is Figure 3 There are 13 disc distributors in total at different levels, namely 6-4-1, 6-4-2, 6-4-3 to 6-4-13, which are specially explained here.

[0051] A polysiloxane removal system, such as Figure 1 As shown, it includes a first delivery pump 1, a first preheater 2, a first flash tank 3, a second delivery pump 4, a second preheater 5, a second flash tank 6, a product receiving tank 7 and a third delivery pump 8 which are connected in sequence through pipelines. The first delivery pump 1 is connected to the polymerization kettle, and the third delivery pump 8 is connected to the product large tank; the low molecular steam outlet 3-5 of the first flash tank 3 is connected to the first condenser 9, the first condenser 9 is connected to the first low molecular receiving tank 10, and the first low molecular receiving tank 10 is connected to the first vacuum system; the second flash tank 6 is provided with a built-in condenser 6-8 and the outlet of the built-in condenser 6-8 is connected to the second low molecular receiving tank 12, the outlet 6-10 of the uncondensed low molecular steam of the second flash tank 6 is connected to the second low molecular receiving tank 12 through the second condenser 11, and the second condenser 11 is connected to the second vacuum system; wherein, the vacuum degree of the secondary vacuum system is higher than that of the primary vacuum system.

[0052] The general working process of the above polysiloxane removal system is as follows:

[0053] The semi-finished polysiloxane product is delivered to a first preheater 2 via a first delivery pump 1 for preheating, then enters a first flash tank 3 for primary desulfurization in a first vacuum system. The polysiloxane, after the primary desulfurization, is again delivered to a second preheater 5 via a second delivery pump 4 for preheating, then enters a second flash tank 6 for secondary desulfurization in a second vacuum system. The secondary desulfurized polysiloxane is withdrawn from the bottom of the second flash tank 6 and delivered to a product receiving tank 7. The low-molecular weight fractions separated from the primary desulfurization are condensed and recovered in a first condenser 9 and a first low-molecular weight receiving tank 10. The low-molecular weight fractions separated from the secondary desulfurization are condensed and recovered in a second low-molecular weight receiving tank 12 via built-in condensers 6-8 or a second condenser 11.

[0054] As a specific example, Figure 2 As shown, the first-stage flash tank 3 comprises a vertical straight cylindrical structure in the upper half and a vertical cone structure in the lower half. A polysiloxane tangential feed port 3-1 is provided on the upper outer side of the vertical straight cylindrical structure for tangential feeding of materials, and a polysiloxane discharge port 3-3 is provided at the bottom of the vertical cone structure.

[0055] The first-stage flash tank 3 is internally provided with a spiral channel 3-2 and a positioning tube 3-4. The spiral channel 3-2 is constructed with spiral turbulent blades. The positioning tube 3-4 is a straight hollow tube that runs through the spiral turbulent blades. The outer edge of the spiral turbulent blades is fixed to the inner wall of the first-stage flash tank 3, and the inner edge is fixed to the positioning tube 3-4. The positioning tube 3-4 is arranged at the axial center of the cavity of the first-stage flash tank 3. The spiral turbulent blades and the positioning tube 3-4 are arranged coaxially and concentrically with the inner cavity of the first-stage flash tank 3.

[0056] The positioning pipe 3-4 can be connected to the melt pool at the bottom of the first-stage flash tank 3 to divert low-molecular steam.

[0057] In the above-mentioned first-stage flash tank 3, under the action of centrifugal force and inertial force, the polysiloxane material is thrown to the cylinder wall of the first-stage flash tank 3, and forms a flowing liquid film under the action of adhesion. It flows along the spiral channel 3-2 into the polysiloxane melt pool at the bottom of the tank, forming a material liquid seal at the bottom of the first-stage flash tank 3; a low-molecular vapor outlet 3-5 is provided at the top of the first-stage flash tank 3, and the low-molecular vapor outlet 3-5 is connected to an external first condenser 9. The low-molecular vapor is cooled by the first condenser 9, and the low-molecular vapor is recovered into the first low-molecular receiving tank 10.

[0058] As a specific example, the outer side of the first-stage flash tank 3 is provided with an external heating pipe 3-6 or a jacket for compensating for latent heat dissipation, preferably a heating pipe 3-6.

[0059] As a method, the heating pipe 3-6 is coiled on the outside of the first-stage flash tank 3, the heating medium inlet 3-6-2 of the heating pipe 3-6 is located below the outside of the first-stage flash tank 3, and the heating medium outlet 3-6-1 is located above the first-stage flash tank 3.

[0060] A heating medium is introduced into the heat tracing pipes 3-6, and the heating medium is saturated water vapor or heat transfer oil, preferably heat transfer oil.

[0061] The general working process in the above-mentioned first-level flash tank 3 is as follows:

[0062] Under the influence of centrifugal and inertial forces, the fluid of the polysiloxane semi-finished product is thrown onto the cylinder wall and spiral channel 3-2 of the first-stage flash tank 3. Adhesion forms a flowing liquid film, which is then guided by spiral channel 3-2 to the polysiloxane melt pool at the bottom of the first-stage flash tank 3. Low-molecular-weight vapor generated during the process rises one level along spiral channel 3-2 to low-molecular-weight vapor outlet 3-5 at the top of the flash tank 3. Steam generated from the polysiloxane melt pool is then transported directly to low-molecular-weight vapor outlet 3-5, which has risen to the top of the first-stage flash tank 3, through positioning pipe 3-4. Both streams of vapor flow through an external first condenser 9 and into the first low-molecular-weight receiving tank 10.

[0063] As a specific example, Figure 3As shown, the secondary flash tank 6 is a vertical cylindrical structure with multiple disc distributors 6-4 and built-in condenser pipes 6-8, and a polysiloxane feed port 6-1 is set on the top.

[0064] Several disc distributors 6-4-(1-13) are arranged around the cylinder wall of the secondary flash tank 6. The multiple disc distributors 6-4-(1-13) are supported by several vertical positioning rods 6-5 fixedly connected to the cylinder wall, so that the polysiloxane forms a continuous liquid film flow on each group of disc distributors 6-4-(1-13).

[0065] The number of the disc distributors 6-4-(1-13) is determined according to the stripping surface and the residence time, and as an example, 8-13 are preferred.

[0066] The positioning rod 6-5 directly passes through the disc distributor 6-4-(1-13) to play a fixing role. 2-4 positioning rods 6-5 can be provided.

[0067] Specifically, as an example, Figure 4 As shown, the distribution plate 6-3 is a disc structure and has slits 6-3-1 at intervals of 20-30° along a circumference concentric with the center of the disc structure. The width of the slits 6-3-1 is preferably 0.1-2.5 mm, and the width can be adjusted according to the viscosity of the polysiloxane. The length and number of the slits 6-3-1 can be adjusted according to the requirements of degassing production capacity.

[0068] Alternatively, a perforated plate having circular holes with a diameter of 1-10 mm may be provided on the edge of the distribution plate 6 - 3 .

[0069] The disc distributor 6 - 4 - ( 1 - 13 ) is arranged directly below the slit 6 - 3 - 1 of the distribution plate 6 - 3 at the top of the secondary flash tank 6 and is concentric with the secondary flash tank 6 .

[0070] The disc distributor 6-4-(1-13) is arranged in multiple layers in order from top to bottom. Overflow plates are set on the outer and inner edges of the disc structures of the 1st, 3rd, 5th, 7th, 9th, 11th and 13th odd-numbered layers, and the height of the overflow plate 6-13-2 at the outer edge is lower than the height of the overflow plate 6-13-1 at the inner edge. By controlling the height of the overflow plate 6-13-2 at the outer edge, the thickness of the polysiloxane on the disc structure is adjusted.

[0071] The outer edges of the disc structures of the 2nd, 4th, 6th, 8th, 10th and 12th even-numbered layers are fixed to the inner wall of the secondary flash tank 6, and an overflow plate is provided on the inner edge. The thickness of the polysiloxane on the disc structure is adjusted by controlling the height of the overflow plate 6-13-1 on the inner edge; the outer and inner diameters of the disc structures on the odd-numbered layers are smaller than those of the disc structures on the even-numbered layers.

[0072] As an example, the distance between the outer edge of the odd-numbered disc structure and the wall of the secondary flash tank 6 is 1-5 mm, and the width can be adjusted according to the viscosity of the polysiloxane.

[0073] The lower wall of the secondary flash tank 6 is provided with a polysiloxane flow guide member 6-6-(1-2) at a position below the corresponding disc distributor 6-4-(1-13). The polysiloxane flow guide member 6-6-(1-2) is connected to the polysiloxane side discharge port 6-7 or the uncondensed low molecular steam side outlet 6-10 provided on the wall of the secondary flash tank 6. The polysiloxane side discharge port 6-7 is above the polysiloxane flow guide member 6-6-(1-2), and the uncondensed low molecular steam side outlet 6-10 is above the polysiloxane flow guide member 6-6-(1-2). Below the silicone guide member 6-6-(1-2), polysiloxane finally flows out from the 13th layer's disc distributor 6-4-13 along the overflow plate 6-13-2 on the outer edge, through the polysiloxane guide member 6-6-(1-2) to the polysiloxane side discharge port 6-7, and the uncondensed low-molecular vapor is vacuumed out from the uncondensed low-molecular vapor side outlet 6-10. The polysiloxane side discharge port 6-7 is connected to the product receiving tank 7, and the uncondensed low-molecular vapor side outlet 6-10 is connected to the second condenser 11.

[0074] A built-in condenser pipe 6-8 is located at the center axis of the secondary flash tank 6. This pipe is fixed to the bottom of the tank, and a low-molecular-weight discharge port 6-9 is located at the bottom of the tank, communicating with this pipe. After the steam condenses, the low-molecular-weight steam is discharged from the bottom low-molecular-weight discharge port 6-9. A small amount of uncondensed steam is withdrawn from the uncondensed low-molecular-weight steam side outlet 6-10, cooled again in the second condenser 11, and discharged to the second low-molecular-weight receiving tank 12.

[0075] Specifically, the built-in condensing pipes 6-8 are serpentine pipes or inline pipes, preferably inline pipes. The built-in condensing pipes 6-8 can pass circulating water, 5°C water or chilled brine, preferably 5°C water.

[0076] As an example, an external heating jacket 6-11 is provided on the outside of the secondary flash tank 6 to compensate for latent heat dissipation, and the heating medium is saturated water vapor or heat transfer oil, preferably heat transfer oil.

[0077] Alternatively, a heat tracing pipe may be used. The polysiloxane flow guide member 6-6-(1-2) is positioned directly below the multi-layered disc distributor 6-4-(1-13). The outer edge of the polysiloxane flow guide member 6-6-(1-2) is fixed to the inner wall of the secondary flash tank 6, and the inner edge is provided with a flow guide baffle 6-6-3. The lowest point of the polysiloxane flow guide member 6-6-1 is located near the polysiloxane side discharge port 6-7, and the highest point of the polysiloxane flow guide member 6-6-2 is located near the uncondensed low-molecular vapor side outlet 6-10.

[0078] The definition of the “inner edge” and “outer edge” mentioned above is that the one close to the central axis of the secondary flash tank 6 is the “inner edge”, and the one away from the central axis is the “outer edge”.

[0079] The general working process in the above-mentioned secondary flash tank 6 is as follows:

[0080] The fluid of the polysiloxane semi-finished product passes through the slit 6-3-1 on the disc distributor 6-4-(1-13) and forms a liquid film, which is evenly distributed on the disc distributor 6-4-1 of the first layer. It overflows through the overflow plate 6-13-2 on its outer edge and forms a liquid film. It flows along the inner wall of the cylinder of the secondary flash tank 6 to the disc distributor 6-4-2 of the second layer. Then, it overflows through the overflow plate 6-13-1 on its inner edge and forms a liquid film. It flows to the disc distributor 6-4-3 of the third layer. It overflows through the overflow plate 6-13-2 on its outer edge and forms a liquid film. It flows along the inner wall of the secondary flash tank 6 to the disc distributor 6-4-4 of the fourth layer. This process alternates and overflows to the disc distributor 6-4-13 of the last layer. Finally, it overflows to the polysiloxane guide component 6-6-(1-2) of the secondary flash tank 6 and is collected into the product receiving tank 7.

[0081] The low-molecular-weight vapor generated during this process condenses on the surface of the internal condenser pipe 6-8 and flows along its surface to the bottom of the secondary flash tank 6, flows out through the low-molecular-weight discharge port 6-9 at the bottom, and flows into the second low-molecular-weight receiving tank 12. A small amount of uncondensed low-molecular-weight vapor is condensed by the external second condenser 11, and finally the low-molecular-weight vapor is combined with the second low-molecular-weight receiving tank 12.

[0082] Several examples of application methods of the polysiloxane removal system according to Example 1 are provided below.

[0083] The test method for polysiloxane volatile matter is:

[0084] Using a balance accurate to 0.001g, weigh about 2g of polysiloxane in a glass culture dish with a diameter of 75mm. Place the dish in a forced air oven at 105℃, 150℃ or 200℃ and bake it for 3h or 4h. Then weigh the mass and calculate the ratio of mass loss to initial mass.

[0085] The test method for the low molecular weight ring content of polysiloxane is as follows: 0.5 g of polysiloxane is dissolved in 10 ml of acetone, extracted at room temperature for 24 hours, and the supernatant is taken for GC analysis.

[0086] The conditions for GC analysis were:

[0087] FID detector

[0088] Injection volume 1 μL, no splitting

[0089] Inlet temperature: 250°C

[0090] Detector temperature: 300°C

[0091] Chromatographic column: HP-5MS 30m×320μm×0.25μm

[0092] Column temperature: 50°C for 3 min, then increase to 250°C at 10°C / min and maintain for 8 min

[0093] Flow rate: 1.5ml / min

[0094] H2 flow rate: 40 ml / min

[0095] Air flow: 300 ml / min

[0096] Make-up flow rate: 15 ml / min

[0097] Among them, D4-D6 quantitative analysis, D7-D 10 Semiquantitative analysis.

[0098] Example 2: Methyl silicone oil removal

[0099] Semi-finished methyl silicone oil after pre-degradation in the polymerization kettle, molecular structure: Me(Me2SiO) 70-100 Me, with an initial volatile content of 5% (150°C, 3h), is delivered to the first preheater 2 by the first delivery pump 1 and preheated to 180°C. It then enters the first flash tank 3 through the polysiloxane tangential feed port 3-1. 210°C thermal oil is fed into the heating medium inlet 3-6-2 for thermal compensation. The first (low) vacuum system is controlled at ~1.3 kPa.

[0100] The material is thrown onto the cylinder wall and spiral channel 3-2 of the first-stage flash tank 3 by centrifugal and inertial forces, and forms a flowing liquid film under the action of adhesion. Under the guidance of the spiral channel 3-2, it flows to the material melt pool 3-7 of the first-stage flash tank 3; the low-molecular annular steam generated in the process rises along the spiral channel 3-2 to the low-molecular steam outlet 3-5 at the top of the flash tank, and the low-molecular annular steam generated in the material melt pool 3-7 is guided by the positioning pipe 3-4 and directly rises to the low-molecular steam outlet 3-5 at the top of the first-stage flash tank 3. The two steam streams are condensed by the external first condenser 9 and flow into the first low-molecular receiving tank 10.

[0101] After the first-stage flash evaporation, the methyl silicone oil is fed into the second preheater 5 through the second delivery pump 4 and preheated to 220°C. It then enters the second-stage flash tank 6 through the polysiloxane feed port 6-1. 250°C heat transfer oil is fed into the heating medium inlet 6-11-2, and 5°C cooling water is fed into the cooling medium inlet 6-12-1. The secondary vacuum system is controlled at ~3.5Pa. The material in the storage bin 6-2 of the second-stage flash tank 6 passes through the slit 6-3-1 of the distribution plate 6-3, with a slit width of 0.3mm, and is evenly distributed into a liquid film. It then flows evenly to the disc distributor 6-4-1 on the first layer and flows through the overflow plate 6-13-1 at its outer edge. 2 overflows in the form of a liquid film, flows along the inner wall of the cylinder of the secondary flash tank 6 to the disc distributor 6-4-2 of the second layer, then overflows in the form of a liquid film through the overflow plate 6-13-1 at its inner edge, flows to the disc distributor 6-4-3 of the third layer, overflows in the form of a liquid film through the overflow plate 6-13-2 at its outer edge, flows along the inner wall of the secondary flash tank 6 to the disc distributor 6-4-4 of the fourth layer, and so on alternately, overflows to the disc distributor 6-4-13 of the last layer, and finally overflows to the polysiloxane guide component 6-6-(1-2) of the secondary flash tank 6, is collected to the product receiving tank 7, and finally is pumped to the product large tank by the transfer pump 8.

[0102] The low-molecular-weight vapor generated during this process condenses on the surface of the internal condenser tube 6-8, flows along its surface to the bottom of the secondary flash tank 6, exits through the low-molecular-weight outlet 6-9 at the bottom, and flows into the second low-molecular-weight receiving tank 12. A small amount of uncondensed low-molecular-weight vapor is condensed in the external second condenser 11, and finally the low-molecular-weight vapor is combined with the second low-molecular-weight receiving tank 12. A small amount of uncondensed low-molecular-weight vapor enters the external second condenser 11 through the uncondensed low-molecular-weight vapor side outlet 6-10, is condensed by the external condenser 11, and finally the low-molecular-weight vapor is combined with the low-molecular-weight receiving tank 12.

[0103] The product was purified by two-stage flash distillation. After testing, the volatile matter content was 0.03% (200℃, 4h) and the D3-D10 ring content was 10ppm.

[0104] Example 3: Desaturation of hydrogenated silicone oil

[0105] The semi-finished product of hydrogenated silicone oil after pre-degradation in the polymerization kettle, molecular structure: H(Me2SiO) 20-50 (MeHSiO) 40-50 H, with an initial volatile content of 6% (105°C, 3h), is delivered to the first preheater 2 by the first delivery pump 1 and preheated to 140°C. It then enters the first flash tank 3 through the polysiloxane tangential feed port 3-1. 150°C thermal oil is fed into the heating medium inlet 3-6-2 for thermal compensation. The first (low) vacuum system is controlled at ~0.6KPa;

[0106] The material is thrown onto the cylinder wall and spiral channel 3-2 of the first-stage flash tank 3 by centrifugal and inertial forces, and forms a flowing liquid film under the action of adhesion. Under the guidance of the spiral channel 3-2, it flows to the material melt pool 3-7 of the first-stage flash tank 3; the low-molecular annular steam generated in the process rises along the spiral channel 3-2 to the low-molecular steam outlet 3-5 at the top of the flash tank, and the low-molecular annular steam generated in the material melt pool 3-7 is guided by the positioning pipe 3-4 and directly rises to the low-molecular steam outlet 3-5 at the top of the first-stage flash tank 3. The two steam streams are condensed by the external first condenser 9 and flow into the first low-molecular receiving tank 10.

[0107] After the first-stage flash evaporation, the hydrogenated silicone oil is again fed into the second preheater 5 through the second delivery pump 4 and preheated to 150°C. It then enters the second-stage flash tank 6 through the polysiloxane feed port 6-1. 160°C heat transfer oil is fed into the heating medium inlet 6-11-2, and 5°C cooling water is fed into the cooling medium inlet 6-12-1. The secondary vacuum system is controlled at ~2.5Pa. The material in the storage bin 6-2 of the second-stage flash tank 6 passes through the slit 6-3-1 of the distribution plate 6-3, with a slit width of 0.3mm, and is uniformly distributed into a liquid film. It then flows evenly to the first-layer disc distributor 6-4-1 and flows through the overflow plate 6-13-1 at its outer edge. 2 overflows in the form of a liquid film, flows along the inner wall of the cylinder of the secondary flash tank 6 to the disc distributor 6-4-2 of the second layer, then overflows in the form of a liquid film through the overflow plate 6-13-1 at its inner edge, flows to the disc distributor 6-4-3 of the third layer, overflows in the form of a liquid film through the overflow plate 6-13-2 at its outer edge, flows along the inner wall of the secondary flash tank 6 to the disc distributor 6-4-4 of the fourth layer, and so on alternately, overflows to the disc distributor 6-4-13 of the last layer, and finally overflows to the polysiloxane guide component 6-6-(1-2) of the secondary flash tank 6, is collected to the product receiving tank 7, and finally is pumped to the product large tank by the transfer pump 8.

[0108] The low-molecular-weight vapor generated during this process condenses on the surface of the internal condenser tube 6-8, flows along its surface to the bottom of the secondary flash tank 6, exits through the low-molecular-weight outlet 6-9 at the bottom, and flows into the second low-molecular-weight receiving tank 12. A small amount of uncondensed low-molecular-weight vapor is condensed in the external second condenser 11, and finally the low-molecular-weight vapor is combined with the second low-molecular-weight receiving tank 12. A small amount of uncondensed low-molecular-weight vapor enters the external second condenser 11 through the uncondensed low-molecular-weight vapor side outlet 6-10, is condensed by the external condenser 11, and finally the low-molecular-weight vapor is combined with the low-molecular-weight receiving tank 12.

[0109] The product was purified by two-stage flash distillation. After testing, the volatile matter content was 0.05% (105℃, 3h) and the D3-D10 ring content was 1360ppm.

[0110] Example 4: Ethylene silicone oil removal

[0111] Semi-finished vinyl silicone oil after pre-degradation in the polymerization kettle, molecular structure: C2H3(Me2SiO) 160-200 C2H3, with an initial volatile content of 6% (150°C, 3h), is delivered to the first preheater 2 by the first delivery pump 1 and preheated to 180°C. It then enters the first flash tank 3 through the polysiloxane tangential feed port 3-1. 210°C thermal oil is fed into the heating medium inlet 3-6-2 for thermal compensation. The first (low) vacuum system is controlled at ~1.0 kPa.

[0112] The material is thrown onto the cylinder wall and spiral channel 3-2 of the first-stage flash tank 3 by centrifugal and inertial forces, and forms a flowing liquid film under the action of adhesion. Under the guidance of the spiral channel 3-2, it flows to the material melt pool 3-7 of the first-stage flash tank 3; the low-molecular annular steam generated in the process rises along the spiral channel 3-2 to the low-molecular steam outlet 3-5 at the top of the flash tank, and the low-molecular annular steam generated in the material melt pool 3-7 is guided by the positioning pipe 3-4 and directly rises to the low-molecular steam outlet 3-5 at the top of the first-stage flash tank 3. The two steam streams are condensed by the external first condenser 9 and flow into the first low-molecular receiving tank 10.

[0113] After the first-stage flash evaporation, the vinyl silicone oil is again fed into the second preheater 5 through the second delivery pump 4 and preheated to 200°C. It then enters the second-stage flash tank 6 through the polysiloxane feed port 6-1. 230°C heat transfer oil is fed into the heating medium inlet 6-11-2, and 5°C cooling water is fed into the cooling medium inlet 6-12-1. The secondary vacuum system is controlled at ~3.0Pa. The material in the second-stage flash tank silo 6-2 passes through the slit 6-3-1 of the distribution plate 6-3, with a slit width of 0.3mm, and is evenly distributed into a liquid film. It then flows evenly to the first-layer disc distributor 6-4-1 and flows through the overflow plate 6-1 at its outer edge. 3-2 overflows in the form of a liquid film, flows along the inner wall of the cylinder of the secondary flash tank 6 to the disc distributor 6-4-2 of the second layer, then overflows in the form of a liquid film through the overflow plate 6-13-1 at its inner edge, flows to the disc distributor 6-4-3 of the third layer, overflows in the form of a liquid film through the overflow plate 6-13-2 at its outer edge, flows along the inner wall of the secondary flash tank 6 to the disc distributor 6-4-4 of the fourth layer, and so on alternately, overflows to the disc distributor 6-4-13 of the last layer, and finally overflows to the polysiloxane guide component 6-6 of the secondary flash tank 6, is collected to the product receiving tank 7, and finally is pumped to the product large tank by the transfer pump 8.

[0114] The low-molecular-weight annular vapor generated during the process condenses on the surface of the internal condenser 6-8, flows along its surface to the bottom of the secondary flash tank 6, exits through the low-molecular-weight outlet 6-9 at the bottom, and flows into the second low-molecular-weight receiving tank 12. A small amount of uncondensed low-molecular-weight vapor is condensed in the external second condenser 11, and finally the low-molecular-weight vapor is combined with the second low-molecular-weight receiving tank 12. A small amount of uncondensed low-molecular-weight vapor enters the external second condenser 11 through the uncondensed low-molecular-weight vapor side outlet 6-10, is condensed by the external condenser 11, and finally the low-molecular-weight vapor is combined with the low-molecular-weight receiving tank 12.

[0115] The product was purified by two-stage flash distillation. After testing, the volatile matter content was 0.04% (200℃, 4h) and the D3-D10 ring content was 26ppm.

[0116] Example 5: Hydroxyl silicone oil removal

[0117] The semi-finished product of hydroxy silicone oil after pre-degradation in the polymerization kettle, molecular structure: OH(Me2SiO) 350-480 H, with an initial volatile content of 7% (150°C, 3h), is delivered to the first preheater 2 by the first delivery pump 1 and preheated to 180°C. It then enters the first flash tank 3 through the polysiloxane tangential feed port 3-1. 210°C thermal oil is fed into the heating medium inlet 3-6-2 for thermal compensation. The first (low) vacuum system is controlled at ~1.0KPa;

[0118] The material is thrown onto the cylinder wall and spiral channel 3-2 of the first-stage flash tank 3 by centrifugal and inertial forces, and forms a flowing liquid film under the action of adhesion. Under the guidance of the spiral channel 3-2, it flows to the material melt pool 3-7 of the first-stage flash tank 3; the low-molecular annular steam generated in the process rises along the spiral channel 3-2 to the low-molecular steam outlet 3-5 at the top of the flash tank, and the low-molecular annular steam generated in the material melt pool 3-7 is guided by the positioning pipe 3-4 and directly rises to the low-molecular steam outlet 3-5 at the top of the first-stage flash tank 3. The two steam streams are condensed by the external first condenser 9 and flow into the first low-molecular receiving tank 10.

[0119] The hydroxy silicone oil after the first-stage flash evaporation is again fed into the second preheater 5 through the second delivery pump 4 and preheated to 220°C. It then enters the second-stage flash tank 6 through the polysiloxane feed port 6-1. 250°C heat transfer oil is fed into the heating medium inlet 6-11-2, and 5°C cooling water is fed into the cooling medium inlet 6-12-1. The secondary vacuum system is controlled at ~4.0Pa. The material in the second-stage flash tank silo 6-2 passes through the slit 6-3-1 of the distribution plate 6-3. The slit width is 0.5mm and is uniformly distributed into a liquid film. It then flows evenly to the first-layer disc distributor 6-4-1 and flows through the overflow plate 6-13-2 at its outer edge. The overflow forms a liquid film, flows along the inner wall of the cylinder of the secondary flash tank 6 to the disc distributor 6-4-2 of the second layer, then overflows into a liquid film through the overflow plate 6-13-1 at its inner edge, flows to the disc distributor 6-4-3 of the third layer, overflows into a liquid film through the overflow plate 6-13-2 at its outer edge, flows along the inner wall of the secondary flash tank 6 to the disc distributor 6-4-4 of the fourth layer, and so on alternately, overflows to the disc distributor 6-4-13 of the last layer, and finally overflows to the polysiloxane guide component 6-6 of the secondary flash tank 6, is collected to the product receiving tank 7, and finally is pumped to the product large tank by the transfer pump 8.

[0120] The low-molecular-weight annular vapor generated during the process condenses on the surface of the internal condenser 6-8, flows along its surface to the bottom of the secondary flash tank 6, exits through the low-molecular-weight outlet 6-9 at the bottom, and flows into the second low-molecular-weight receiving tank 12. A small amount of uncondensed low-molecular-weight vapor is condensed in the external second condenser 11, and finally the low-molecular-weight vapor is combined with the second low-molecular-weight receiving tank 12. A small amount of uncondensed low-molecular-weight vapor enters the external second condenser 11 through the uncondensed low-molecular-weight vapor side outlet 6-10, is condensed by the external condenser 11, and finally the low-molecular-weight vapor is combined with the low-molecular-weight receiving tank 12.

[0121] The product was purified by two-stage flash evaporation. After testing, the volatile matter content was 0.06% (200℃, 4h) and the D3-D10 ring content was 47ppm.

[0122] Example 6: Alkoxy silicone oil desaturation

[0123] Alkoxy silicone oil semi-finished product after pre-degradation in the polymerization kettle, molecular structure: (CH3O)2MeSiO(Me2SiO) 480-660 OSiMe(CH3O)2, with an initial volatile content of 6% (150°C, 3h), is delivered to the first preheater 2 by the first delivery pump 1 and preheated to 160°C. It then enters the first flash tank 3 through the polysiloxane tangential feed port 3-1. 175°C thermal oil is fed to the heating medium inlet 3-6-2 for thermal compensation. The first (low) vacuum system is controlled at ~0.8 kPa.

[0124] The material is thrown onto the cylinder wall and spiral channel 3-2 of the first-stage flash tank 3 by centrifugal and inertial forces, and forms a flowing liquid film under the action of adhesion. Under the guidance of the spiral channel 3-2, it flows to the material melt pool 3-7 of the first-stage flash tank 3; the low-molecular annular steam generated in the process rises along the spiral channel 3-2 to the low-molecular steam outlet 3-5 at the top of the flash tank, and the low-molecular annular steam generated in the material melt pool 3-7 is guided by the positioning pipe 3-4 and directly rises to the low-molecular steam outlet 3-5 at the top of the first-stage flash tank 3. The two steam streams are condensed by the external first condenser 9 and flow into the first low-molecular receiving tank 10.

[0125] The alkoxy silicone oil after the first-stage flash evaporation is again fed into the second preheater 5 through the second delivery pump 4 and preheated to 170°C. It then enters the second-stage flash tank 6 through the polysiloxane feed port 6-1. 185°C heat transfer oil is fed into the heating medium inlet 6-11-2, and 5°C cooling water is fed into the cooling medium inlet 6-12-1. The secondary vacuum system is controlled at ~2.5Pa. The material in the storage bin 6-2 of the second-stage flash tank 6 passes through the slit 6-3-1 of the distribution plate 6-3, with a slit width of 0.5mm, and is evenly distributed into a liquid film. It then flows evenly to the first-layer disc distributor 6-4-1 and flows through the overflow plate 6-1 at its outer edge. 3-2 overflows in the form of a liquid film, flows along the inner wall of the cylinder of the secondary flash tank 6 to the disc distributor 6-4-2 of the second layer, then overflows in the form of a liquid film through the overflow plate 6-13-1 at its inner edge, flows to the disc distributor 6-4-3 of the third layer, overflows in the form of a liquid film through the overflow plate 6-13-2 at its outer edge, flows along the inner wall of the secondary flash tank 6 to the disc distributor 6-4-4 of the fourth layer, and so on alternately, overflows to the disc distributor 6-4-13 of the last layer, and finally overflows to the polysiloxane guide component 6-6 of the secondary flash tank 6, is collected to the product receiving tank 7, and finally is pumped to the product large tank by the transfer pump 8.

[0126] The low-molecular-weight annular vapor generated during the process condenses on the surface of the internal condenser tube 6-8, flows along its surface to the bottom of the secondary flash tank 6, exits through the low-molecular-weight outlet 6-9 at the bottom, and flows into the second low-molecular-weight receiving tank 12. A small amount of uncondensed low-molecular-weight vapor is condensed in the external second condenser 11, and finally the low-molecular-weight vapor is combined with the second low-molecular-weight receiving tank 12. A small amount of uncondensed low-molecular-weight vapor enters the external second condenser 11 through the uncondensed low-molecular-weight vapor side outlet 6-10, is condensed by the external condenser 11, and finally the low-molecular-weight vapor is combined with the low-molecular-weight receiving tank 12.

[0127] The product was purified by two-stage flash distillation. After testing, the volatile matter content was 0.05% (150℃, 3h) and the D3-D10 ring content was 162ppm.

[0128] Example 7: Phenyl silicone oil desulfurization

[0129] The semi-finished product of phenyl silicone oil after pre-degradation in the polymerization kettle, molecular structure: Me(Me2SiO) 60-80 (MePhSiO) 10- 20 Me, with an initial volatile content of 5% (150°C, 3h), is delivered to the first preheater 2 by the first delivery pump 1 and preheated to 180°C. It then enters the first flash tank 3 through the polysiloxane tangential feed port 3-1. 210°C thermal oil is fed into the heating medium inlet 3-6-2 for thermal compensation. The first (low) vacuum system is controlled at ~1.0KPa;

[0130] The material is thrown onto the cylinder wall and spiral channel 3-2 of the first-stage flash tank 3 by centrifugal and inertial forces, and forms a flowing liquid film under the action of adhesion. Under the guidance of the spiral channel 3-2, it flows to the material melt pool 3-7 of the first-stage flash tank 3; the low-molecular annular steam generated in the process rises along the spiral channel 3-2 to the low-molecular steam outlet 3-5 at the top of the flash tank, and the low-molecular annular steam generated in the material melt pool 3-7 is guided by the positioning pipe 3-4 and directly rises to the low-molecular steam outlet 3-5 at the top of the first-stage flash tank 3. The two steam streams are condensed by the external first condenser 9 and flow into the first low-molecular receiving tank 10.

[0131] The phenyl silicone oil after the first-stage flash evaporation is again fed into the second preheater 5 through the second delivery pump 4 and preheated to 230°C. It then enters the secondary flash tank 6 through the polysiloxane feed port 6-1. 260°C heat transfer oil is fed into the heating medium inlet 6-11-2, and 5°C cooling water is fed into the cooling medium inlet 6-12-1. The secondary vacuum system is controlled at ~3.5Pa. The material in the storage bin 6-2 of the secondary flash tank 6 passes through the slit 6-3-1 of the distribution plate 6-3, with a slit width of 0.3mm, and is evenly distributed into a liquid film. It then flows evenly to the first-layer disc distributor 6-4-1 and flows through the overflow plate 6-1 at its outer edge. 3-2 overflows in the form of a liquid film, flows along the inner wall of the cylinder of the secondary flash tank 6 to the disc distributor 6-4-2 of the second layer, then overflows in the form of a liquid film through the overflow plate 6-13-1 at its inner edge, flows to the disc distributor 6-4-3 of the third layer, overflows in the form of a liquid film through the overflow plate 6-13-2 at its outer edge, flows along the inner wall of the secondary flash tank 6 to the disc distributor 6-4-4 of the fourth layer, and so on alternately, overflows to the disc distributor 6-4-13 of the last layer, and finally overflows to the polysiloxane guide component 6-6 of the secondary flash tank 6, is collected to the product receiving tank 7, and finally is pumped to the product large tank by the transfer pump 8.

[0132] The low-molecular-weight annular vapor generated during the process condenses on the surface of the internal condenser tube 6-8, flows along its surface to the bottom of the secondary flash tank 6, exits through the low-molecular-weight outlet 6-9 at the bottom, and flows into the second low-molecular-weight receiving tank 12. A small amount of uncondensed low-molecular-weight vapor is condensed in the external second condenser 11, and finally the low-molecular-weight vapor is combined with the second low-molecular-weight receiving tank 12. A small amount of uncondensed low-molecular-weight vapor enters the external second condenser 11 through the uncondensed low-molecular-weight vapor side outlet 6-10, is condensed by the external condenser 11, and finally the low-molecular-weight vapor is combined with the low-molecular-weight receiving tank 12.

[0133] The product was purified by two-stage flash distillation. After testing, the volatile matter content was 0.03% (200℃, 4h) and the D3-D10 ring content was 16ppm.

[0134] Comparative Example 1: Vinyl silicone oil removal

[0135] The two-stage flash evaporator was used for desulfurization. The process flow, process conditions and equipment structure conditions were the same as those in Example 4. The vinyl silicone oil after pre-desulfurization in the polymerization kettle was: C2H3(Me2SiO 160-200 C2H3, volatile matter 15% (150℃, 3h), is delivered to the first preheater 2 by the first delivery pump 1 and preheated to 180℃. It then enters the first flash tank 3 through the polysiloxane tangential feed port 3-1. 210℃ heat transfer oil is input into the heating medium inlet 3-6-2 for thermal compensation. The first (low) vacuum system is controlled at ~1.4KPa.

[0136] The vinyl silicone oil after the first-stage flash desulfurization is fed into the second preheater 5 again through the second delivery pump 4 and preheated to 200°C. It then enters the secondary flash tank 6 through the polysiloxane feed port 6-1. 230°C heat transfer oil is fed into the heating medium inlet 6-11-2, and 5°C cooling water is fed into the cooling medium inlet 6-12-1. The secondary vacuum system is controlled at ~4.0Pa. The product purified by two flash desulfurizations has a volatile matter content of 0.17% (200°C, 4h) and a D3-D10 ring content of 175ppm.

[0137] Comparative Example 2: Vinyl silicone oil removal

[0138] Only the first-stage flash evaporator is used for degassing. The first-stage flash evaporation process and equipment structure conditions are the same as those in Example 4.

[0139] Vinyl silicone oil pre-degraded in the polymerization kettle, molecular structure: C2H3(Me2SiO) 160-200C2H3, volatile matter 6% (150℃, 3h), is delivered to the first preheater 2 by the first delivery pump 1 and preheated to 180℃. It then enters the first flash tank 3 through the polysiloxane tangential feed port 3-1. 210℃ heat transfer oil is input to the heating medium inlet 3-6-2 for thermal compensation. The first (low) vacuum system is controlled at ~1.0KPa.

[0140] The product was purified by primary flash distillation. After testing, the volatile matter content was 0.6% (150℃, 3h) and the D3-D10 ring content was 2400ppm.

[0141] Comparative Example 3: Vinyl silicone oil removal

[0142] Only the second stage flash evaporator is used for desulfurization. The second stage flash evaporation process and equipment structure conditions are the same as those in Example 4. The vinyl silicone oil after pre-desulfurization in the polymerization kettle has the molecular structure formula: C2H3(Me2SiO 160-200 C2H3, volatile matter 6% (150℃, 3h), is fed into the second preheater 5 through the second delivery pump 4 and preheated to 200℃, and enters the secondary flash tank 6 through the polysiloxane feed port 6-1. 230℃ heat transfer oil is fed into the heating medium inlet 6-11-2, and 5℃ cooling water is fed into the cooling medium inlet 6-12-1. The secondary vacuum system is controlled at ~15Pa.

[0143] The product was purified by secondary flash evaporation and tested to have a volatile matter content of 0.36% (200°C, 4h) and a D3-D10 ring content of 900ppm.

[0144] Comparative Example 4: Vinyl silicone oil removal

[0145] This embodiment uses a two-stage flash evaporator to remove the low-carbon oil. The process flow and equipment structure conditions are the same as those in Example 4. The vinyl silicone oil pre-desulfurized in the polymerization kettle has the molecular structure: C2H3(Me2SiO 160-200 C2H3, with an initial volatile content of 7% (150°C, 3h), is transported to the first preheater 2 by the first delivery pump 1 and preheated to 160°C. It then enters the first flash tank 3 through the polysiloxane tangential feed port 3-1, and 190°C heat transfer oil is input into the heating medium inlet 3-6-2 for thermal compensation. The first (low) vacuum system is controlled at ~2.0KPa.

[0146] The vinyl silicone oil after the first-stage flash evaporation is again fed into the second preheater 5 through the second delivery pump 4 and preheated to 180°C. It then enters the secondary flash tank 6 through the polysiloxane feed port 6-1. 210°C heat transfer oil is fed into the heating medium inlet 6-11-2, and 5°C cooling water is fed into the cooling medium inlet 6-12-1. The secondary vacuum system is controlled at ~7.5Pa.

[0147] The product was purified by two-stage flash distillation. After testing, the volatile matter content was 0.31% (200℃, 4h) and the D3-D10 ring content was 420ppm.

Claims

1. A polysiloxane desulfurization system, comprising a first delivery pump (1), a first preheater (2), a primary flash tank (3), a second delivery pump (4), a second preheater (5), a secondary flash tank (6), a product receiving tank (7) and a third delivery pump (8) connected in sequence through pipelines, wherein the first delivery pump (1) is connected to a polymerization kettle, and the third delivery pump (8) is connected to a product tank; The low molecular steam outlet (3-5) of the first flash tank (3) is connected to the first condenser (9), the first condenser (9) is connected to the first low molecular receiving tank (10), and the first low molecular receiving tank (10) is connected to the first vacuum system; The secondary flash tank (6) is provided with a built-in condenser (6-8), and the outlet of the built-in condenser (6-8) is connected to the second low-molecular-weight receiving tank (12). The outlet (6-10) of the uncondensed low-molecular-weight steam of the secondary flash tank (6) is connected to the second low-molecular-weight receiving tank (12) through the second condenser (11). The second condenser (11) is connected to the secondary vacuum system. in, The vacuum degree of the secondary vacuum system is higher than that of the primary vacuum system; The secondary flash tank (6) is a vertical cylindrical structure equipped with a distribution plate (6-3), a disc distributor (6-4-(1-13)) and a built-in condenser (6-8), and a polysiloxane feed port (6-1) is arranged on the top; a plurality of disc distributors (6-4-(1-13)) are arranged on the upper and lower sides of the cylinder wall of the secondary flash tank (6), and the plurality of disc distributors (6-4-(1-13)) are supported by a plurality of vertical positioning rods (6-5) fixedly connected to the cylinder wall, so that the polysiloxane forms a continuous liquid film flow on each group of disc distributors (6-4-(1-13)); The disc distributor (6-4-(1-13)) includes a disc structure and is sequentially arranged in multiple layers from top to bottom; A polysiloxane flow guide component (6-6-(1-2)) is provided on the lower wall of the secondary flash tank (6) at a position below the corresponding disc distributor (6-4-(1-13)). The polysiloxane flow guide component (6-6-(1-2)) is connected to a polysiloxane side discharge port (6-7) or an uncondensed low-molecular vapor side outlet (6-10) provided on the wall of the secondary flash tank (6). The polysiloxane side discharge port (6-7) is provided above the polysiloxane flow guide component (6-6-(1-2)). The uncondensed low-molecular vapor side outlet (6-10) is provided below the polysiloxane flow guide component (6-6-(1-2)). The polysiloxane side discharge port (6-7) is connected to a product receiving tank (7), and the uncondensed low-molecular vapor side outlet (6-10) is connected to a second condenser (11).

2. A polysiloxane removal system according to claim 1, characterized in that: The first-stage flash tank (3) comprises a vertical straight cylindrical structure in the upper half and a vertical cone structure in the lower half. A polysiloxane tangential feed port (3-1) is provided on the upper outer side surface of the vertical straight cylindrical structure for tangential feeding of materials, and a polysiloxane discharge port (3-3) is provided at the bottom of the vertical cone structure. A spiral channel (3-2) and a positioning tube (3-4) are arranged inside the first-stage flash tank (3), wherein the spiral channel (3-2) is constructed by a spiral flow-turbulating blade, and the positioning tube (3-4) runs through the entire spiral flow-turbulating blade, wherein the outer edge of the spiral flow-turbulating blade is fixed on the inner wall of the first-stage flash tank (3), and the inner edge is fixed on the positioning tube (3-4); the positioning tube (3-4) is arranged at the axis of the cavity of the first-stage flash tank (3), and the spiral flow-turbulating blade and the positioning tube (3-4) are coaxially and concentrically arranged with the inner cavity of the first-stage flash tank (3); and an external heating companion pipe (3-6) or a jacket is arranged on the outer side of the first-stage flash tank (3) to compensate for latent heat dissipation.

3. A polysiloxane removal system according to claim 2, characterized in that: A heating pipe (3-6) is provided, and the heating pipe (3-6) is coiled and arranged outside the first-stage flash tank (3). A heating medium inlet (3-6-2) of the heating pipe (3-6) is located below the outside of the first-stage flash tank (3), and a heating medium outlet (3-6-1) is located above the first-stage flash tank (3).

4. A polysiloxane removal system according to claim 1, characterized in that: An external heating jacket (6-11) or a heating pipe is provided on the outside of the secondary flash tank (6).

5. A polysiloxane removal system according to claim 4, characterized in that: The distribution plate (6-3) is a disc structure and has slits (6-3-1) provided at intervals of 20-30° along a circumference concentric with the center of the disc structure.

6. A polysiloxane removal system according to claim 5, characterized in that: The width of the slit (6-3-1) is 0.1-2.5 mm.

7. A polysiloxane removal system according to claim 4, characterized in that: Overflow plates are provided on both the outer and inner edges of the odd-numbered disc structures, and the height of the overflow plates (6-13-2) on the outer edges is lower than the height of the overflow plates (6-13-1) on the inner edges. By controlling the height of the overflow plates (6-13-2) on the outer edges, the thickness of the polysiloxane on the disc structure is adjusted. The outer edge of the disc structure of the even-numbered layers is fixed to the inner wall of the secondary flash tank (6), and an overflow plate is provided on the inner edge. The thickness of the polysiloxane on the disc structure is adjusted by controlling the height of the overflow plate (6-13-1) on the inner edge. The outer diameter and inner diameter of the disc structure on the odd-numbered layers are both smaller than those of the disc structure on the even-numbered layers.

8. A polysiloxane removal system according to claim 7, characterized in that: The distance between the outer edge of the odd-numbered disc structure and the wall of the secondary flash tank (6) is 1-5 mm, and the width can be adjusted according to the viscosity of the polysiloxane.

9. A polysiloxane removal system according to claim 4, characterized in that: The polysiloxane flow guide component (6-6-(1-2)) is arranged directly below the disc distributor (6-4-(1-13)). The outer edge of the polysiloxane flow guide component (6-6-(1-2)) is fixed on the inner wall of the secondary flash tank (6), and a flow guide baffle (6-6-3) is provided on the inner edge.

10. A method for deoxidizing polysiloxane, characterized in that: The method uses the polysiloxane deoxidation system according to any one of claims 1 to 9 to process the polysiloxane semi-finished product to be deoxidized; The polysiloxane semi-finished product is transported to a first preheater (2) for preheating by a first delivery pump (1), and then enters a first flash tank (3) for primary desulfurization in a first vacuum system; the polysiloxane after the primary desulfurization is again input into a second preheater (5) for preheating, and then enters a second flash tank (6) for secondary desulfurization in a second vacuum system; the polysiloxane after the secondary desulfurization is collected from the bottom of the second flash tank (6) and input into a product receiving tank (7), and low molecular weight substances separated from the primary desulfurization and the secondary desulfurization are recovered through condensation.

11. A method for deoxidizing polysiloxane according to claim 10, characterized in that: The molecular structure of the polysiloxane is X(MeRSiO) m (HRSiO) n X, wherein X is one of methyl, H, vinyl, hydroxyl, and alkoxy, R is one or two of methyl, phenyl, ethyl, and vinyl, m+n≥1300, m≥0, and n≥0.

12. A method for deoxidizing polysiloxane according to claim 11, characterized in that: The low molecular weight content of the polysiloxane semi-finished product to be desulfurized is 1-15%.

13. A method for deoxidizing polysiloxane according to claim 12, characterized in that: The low molecular weight content of the polysiloxane semi-finished product to be desulfurized is 3-10%.

14. A method for deoxidizing polysiloxane according to claim 13, characterized in that: The low molecular weight content of the polysiloxane semi-finished product to be desulfurized is 4-8%.

15. The method for deoxidizing polysiloxane according to claim 10, wherein: The temperature of the primary degassing is 110-200° C., and the absolute pressure of the primary vacuum system is 0.1-2.0 KPa.

16. A method for deoxidizing polysiloxane according to claim 15, characterized in that: The temperature of the primary degassing is 120-190° C., and the absolute pressure of the primary vacuum system is 0.3-1.3 KPa.

17. A method for deoxidizing polysiloxane according to claim 16, characterized in that: The temperature of the primary degassing is 140-180°C, and the absolute pressure of the primary vacuum system is 0.5-1.0KPa.

18. The method for deoxidizing polysiloxane according to claim 10, wherein: The temperature of the secondary degassing is 130-250° C., and the absolute pressure of the secondary vacuum system is 0.1-15 Pa.

19. A method for deoxidizing polysiloxane according to claim 18, characterized in that: The temperature of the secondary degassing is 140-240°C, and the absolute pressure of the secondary vacuum system is 1-7.5Pa.

20. The method for deoxidizing polysiloxane according to claim 19, wherein: The temperature of the secondary degassing is 150-230° C., and the absolute pressure of the secondary vacuum system is 1.5-4 Pa.

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