Rubber solution two-stage devolatilization system based on dynamic mixing reinforcement and application

Abstract

The invention discloses a rubber solution two-stage devolatilization system based on dynamic mixing reinforcement and application. The rubber solution two-stage devolatilization system comprises a rubber solution feeding device, a horizontal double-shaft devolatilization device, a dynamic mixer, a steam stripping agent adding device, a screw extruder and an exhaust chamber assembly, the rubber solution feeding device is arranged above a feeding hole of the horizontal double-shaft devolatilization device, a discharging hole of the horizontal double-shaft devolatilization device is connected with a feeding hole of the dynamic mixer, and a discharging hole of the dynamic mixer is connected with a feeding hole of the screw extruder; the steam stripping agent adding device is arranged on the side of a feeding hole of the dynamic mixer; and exhaust chamber assemblies are arranged above the horizontal double-shaft devolatilization device and the screw extruder. According to the present invention, with the method of the close combination of the dynamic mixing enhanced stripping agent dispersion and the two-stage devolatilization process, the volatile components in the rubber solution can be efficiently removed, and the addition amount of the stripping agent in the high-viscosity rubber solution can be accurately controlled so as to significantly improve the stability of the low-VOC rubber production and prepare the low-VOC rubber.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rubber preparation, in particular to a two-stage devolatilization system for rubber solution based on dynamic mixing enhancement and application of the system in preparation of low-VOC rubber. BACKGROUND

[0002] In the synthesis of butadiene-styrene rubber, butadiene rubber, isoprene rubber and other rubbers, unreacted monomers (such as styrene, butadiene, isoprene, etc.) and small molecular volatile substances (such as solvents, initiator residues, etc.) often remain in the rubber, which not only reduces the mechanical properties and thermal stability of the rubber product, but also has a negative impact on its environmental friendliness. Removing these residual volatile substances through devolatilization can significantly improve the physical properties of the rubber product, while optimizing its appearance quality and dimensional accuracy, providing a strong guarantee for the production of high-quality rubber products.

[0003] Currently, vacuum devolatilization technology is mainly used for rubber devolatilization. For example, patent CN110053179A discloses a system and method for removing volatile substances from methyl vinyl silicone rubber. In this method, the synthesized methyl vinyl silicone rubber is first subjected to a first vacuum devolatilization in a falling thread devolatilizer, and then enters a devolatilization-type screw extruder for a second vacuum-enhanced devolatilization. Through secondary heating in the screw extruder, the heat loss in the falling thread devolatilizer can be compensated for, and the devolatilization effect can be further enhanced, ultimately reducing the volatile content to below 0.75wt%.

[0004] However, the traditional vacuum devolatilization technology has limited devolatilization efficiency for high-viscosity rubber systems. To improve the devolatilization effect, researchers have introduced devolatilization aids (such as stripping agents, supercritical fluids, etc.) to assist the devolatilization process. For example, patent CN113999332A proposes a supercritical carbon dioxide-assisted periodic devolatilization process that utilizes the permeability of supercritical carbon dioxide and the "bubble-breaking effect" generated by periodic pressure changes to significantly improve the devolatilization efficiency of heat-sensitive polymers.

[0005] In addition, CN119746441A discloses a steam counter-current contact stripping devolatilization system that achieves efficient solvent removal and reduces product odor through counter-current contact between saturated steam and the material. However, due to the heterogeneous, heterogeneous, and heterogeneous characteristics of devolatilization aids and rubber, the existing method of directly injecting devolatilization aids often leads to excessive local concentration or insufficient mixing, thereby affecting the stability of the devolatilization efficiency. SUMMARY

[0006] In order to overcome the technical problems of mixing difficulty in the existing rubber stripping devolatilization process, the application provides a two-stage devolatilization system for rubber solution based on dynamic mixing enhancement, which can realize accurate measurement and high-efficiency dispersion of stripping agent, effectively improve the devolatilization efficiency of rubber, and ensure the stability of low-VOC rubber production.

[0007] In order to achieve the above-mentioned purpose, the technical scheme adopted by the application is:

[0008] A two-stage devolatilization system for rubber solution based on dynamic mixing enhancement, comprising a rubber solution feeding device, a horizontal double-shaft devolatilizer, a dynamic mixer, a stripping agent adding device, a screw extruder and an exhaust chamber assembly.

[0009] The rubber solution feeding device is arranged above the feeding port of the horizontal double-shaft devolatilizer, the discharging port of the horizontal double-shaft devolatilizer is connected to the feeding port of the dynamic mixer, and the discharging port of the dynamic mixer is connected to the feeding port of the screw extruder; the stripping agent adding device is arranged on the side of the feeding port of the dynamic mixer.

[0010] The horizontal double-shaft devolatilizer and the screw extruder are both provided with the exhaust chamber assembly above.

[0011] The rubber solution feeding device comprises a rubber solution container and a feeding metering pump; preferably, the metering pump is a gear pump or a double-plunger pump; further preferably, the metering pump can be connected to a controller to realize accurate adjustment.

[0012] The stripping agent adding device comprises a stripping agent and a metering pump; preferably, the stripping agent feeding metering pump is a plunger pump, and is adjusted by a controller.

[0013] The horizontal double-shaft devolatilizer connected to the feeding port of the dynamic mixer is provided with a metering pump.

[0014] As a preferred, the metering pumps for the rubber solution feeding, the horizontal double-shaft devolatilizer, the dynamic mixer, the screw extruder and the stripping agent adding device are all equipped with frequency converters, which can realize stepless speed regulation according to the yield and ratio requirements.

[0015] The horizontal double-shaft devolatilizer mainly adopts a self-cleaning design, and the core structure is a non-symmetrical meshing tooth-shaped double screw rotating in opposite directions, which produces mutual scraping effect in the rotating process, can effectively prevent the accumulation of volatile components and rubber on the inner wall of the equipment, and ensure the stability of the devolatilization efficiency in the continuous production process.

[0016] The exhaust chamber assembly comprises an exhaust chamber and a vacuum pump; the exhaust chamber is connected to 1-3 exhaust ports.

[0017] The feed inlet of the dynamic mixer connected with the horizontal double-shaft devolatilizer and the feed inlet connected with the stripping agent adding device are staggered with each other. Preferably, the stripping agent feed inlet has a smaller diameter to prevent the rubber solution from flowing into the stripping agent feed channel; further preferably, the stripping agent feed inlet is arranged at the mixing section where the stator and the rotor are staggered, especially at the position of the rotor tip. After entering the dynamic mixer, the stripping agent can be rapidly dispersed in the rubber solution under the high shear action of the rotor.

[0018] Preferably, the mixing elements of the dynamic mixer adopt a modular design and have a star-shaped structure, including a stator and a sub-rotor which are staggered. This structure can adjust the assembly level according to the specific mixing requirements.

[0019] The stator and rotor teeth of the dynamic mixer are in the form of one or more combinations of straight teeth, asymmetric arc-shaped teeth, helical teeth and rod-shaped teeth.

[0020] The dynamic mixer is externally provided with a heat-conducting oil circulating jacket. The heat-conducting oil flows out of the heat-conducting oil circulating jacket, enters the dynamic mixer from below, heats the mixer, and then flows out from above to return to the heat-conducting oil circulating jacket to realize circulation.

[0021] Preferably, an advanced high-temperature dynamic temperature control system is used to ensure stable temperature control. Further preferably, the stirring shaft of the dynamic mixer is designed as a hollow structure, and heat-conducting oil heat medium is introduced into the inside to achieve more uniform heating effect.

[0022] The application also provides a method for preparing low-VOC rubber by using the two-stage devolatilization system based on dynamic mixing enhancement of the rubber solution.

[0023] The rubber solution enters the horizontal double-shaft devolatilizer through the rubber solution feeding device, is subjected to one-stage devolatilization through kneading and vacuumizing of the exhaust chamber assembly, and is discharged from the discharge outlet; the material is discharged from the horizontal double-shaft devolatilizer into the dynamic mixer, and stripping agent is added to the other feed inlet of the dynamic mixer through the stripping agent adding device; the material and the stripping agent are mixed and then enter the double-screw extruder, are subjected to two-stage devolatilization through mixing and vacuumizing of the exhaust chamber assembly, and low-VOC rubber is obtained.

[0024] By the method of combining dynamic mixing enhancement of stripping agent dispersion with two-stage devolatilization process, the application can efficiently remove volatile components in the rubber solution, accurately control the addition amount of the stripping agent in the high-viscosity rubber solution, and realize efficient dispersion of the stripping agent in the dynamic mixer, thereby significantly improving the stability of low-VOC rubber production.

[0025] Preferably, the mass flow ratio of the stripping agent and the rubber solution entering the dynamic mixer is 1:99 to 30:70; preferably, 5:95 to 20:80.

[0026] Preferably, the horizontal double-shaft devolatilizer is controlled at a temperature of 120-280℃; preferably 140-160℃; and a rotation speed of 10-100rpm, preferably 20-50rpm.

[0027] Preferably, the dynamic mixer is controlled at a temperature of 120-280℃; preferably 140-160℃; and a rotation speed of 100-1500rpm, preferably 600-1000rpm.

[0028] Preferably, the screw extruder is controlled at a temperature of 120-280℃, preferably 140-160℃; and a rotation speed of 50-300rpm, preferably 100-200rpm.

[0029] Preferably, the rubber solution is a solution of one or more of POE (polyolefin elastomer), BR (butadiene rubber), IR (isoprene rubber), EPDM (ethylene propylene diene rubber), SBR (styrene butadiene rubber), or NBR (nitrile rubber) synthesized by solution polymerization.

[0030] The stripping agent refers to a liquid substance that can effectively remove VOCs in the rubber solution. These stripping agents are mixed with the rubber solution in the dynamic mixer and carry out the VOCs out of the system in the subsequent devolatilization process, thereby realizing the low VOCs of the rubber melt. The stripping agent in the present method can be water, supercritical carbon dioxide, organic solvents (such as acetone, toluene, etc.). The preferred stripping agent is water and supercritical carbon dioxide.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] (1) Through the two-stage devolatilization system of rubber solution based on dynamic mixing enhancement, efficient continuous processing of rubber devolatilization is realized. The online addition system supports real-time adjustment of the stripping agent formula, the gradient mixing path is coupled with the continuous devolatilization device, which ensures efficient mixing and continuous removal of liquid stripping agents in high-viscosity rubber. The synergistic effect of dynamic mixing and devolatilization process significantly improves the devolatilization efficiency.

[0033] (2) The present application adopts a multi-stage star-shaped fixed-rotor mixing element, which applies multi-directional shearing and stretching action to high-viscosity materials during rotation through the precise staggered arrangement of the rotor and the stator. This modular design has the following core advantages: micro-mixing enhancement, the gradient mixing path can quickly disperse the stripping agent at the nanoscale; the central shaft heating and jacket heating system maintains the flow state of the rubber, effectively preventing equipment blockage; the modular internal elements support on-demand assembly, which can adapt to different material processing needs.

[0034] (3) The low VOC rubber preparation method of the present application is simple and flexible in process, can realize continuous operation, is efficient and stable in production process, and obtains a low VOC rubber product. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a schematic diagram of a two-stage devolatilization system for rubber solution based on dynamic mixing enhancement in Example 1.

[0036] Figure 2 is a schematic diagram of a two-stage continuous devolatilization integrated system in Example 3.

[0037] Figure 3 is a schematic diagram of a two-stage continuous devolatilization integrated system in Example 5.

[0038] In the figure: 1 rubber solution container, 2 rubber solution feed metering pump, 3 horizontal double-shaft devolatilizer, 4 first exhaust chamber, 5 first vacuum system, 6 metering pump, 7 dynamic mixer, 8 stripping agent container, 9 stripping agent feed metering pump, 10 high-temperature thermostat, 11 heat conduction oil inlet, 12 heat conduction oil loop, 13 screw extruder, 14 second exhaust chamber, 15 second vacuum system. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below in combination with examples. It should be understood that the specific examples described herein are only used to explain the present application and are not used to limit the present application. Those skilled in the art can modify or replace equivalently on the basis of understanding the technical scheme of the present application without departing from the spirit and scope of the present application, and all should be covered within the protection scope of the present application.

[0040] In the present application, unless specified, all equipment and raw materials can be purchased from the market or commonly used in the industry, and the methods in the following examples are all conventional methods in the art, unless otherwise specified.

[0041] Example 1

[0042] A two-stage devolatilization system for rubber solution based on dynamic mixing enhancement, comprising a rubber solution feeding device, a horizontal double-shaft devolatilizer 3, a dynamic mixer 7, a stripping agent adding device, a screw extruder 13 and an exhaust chamber assembly.

[0043] The rubber solution feeding system comprises a rubber solution container 1 and a feeding metering pump 2 connected in sequence. The rubber solution feeding system is connected to the feeding port of the horizontal double-shaft devolatilizer 3, the exhaust port of the horizontal double-shaft devolatilizer 3 is connected to a first exhaust chamber assembly, which comprises a first exhaust chamber 4 and a first vacuum system 5. The rubber solution enters the horizontal double-shaft devolatilizer 3 for primary devolatilization. The horizontal double-shaft devolatilizer 3 adopts double screws rotating in opposite directions, and the screws are designed as asymmetric meshing tooth profiles, which can effectively prevent volatile components and rubber from accumulating on the inner wall of the equipment during rotation, and the outer side is additionally provided with heating (such as an electric heating jacket), and the temperature is controlled by a temperature control system.

[0044] The rubber solution after primary devolatilization is transported to one feeding port of the dynamic mixer 7 through a metering pump 6. The stripping agent adding device comprises a stripping agent container 8 and a metering pump 9. The stripping agent adding device is connected to another feeding port of the dynamic mixer 7. The stripping agent feeding port is staggered with the rubber solution feeding port, has a smaller diameter, and is located at the mixed section of the stator and rotor, close to the position of the rotor tip. After entering the dynamic mixer, the stripping agent can be rapidly dispersed into the rubber solution under the high shear action of the rotor.

[0045] The dynamic mixer 7 is externally provided with a heat-conducting oil circulating jacket, which is controlled by a high-temperature thermostat 10. The heat-conducting oil enters from the lower measuring jacket inlet 11 of the mixer, is heated by the jacket, and flows out from the upper jacket outlet 12 of the dynamic mixer to return to the high-temperature thermostat 10 to realize circulation.

[0046] The exhaust port of the screw extruder 13 is connected to a second exhaust chamber assembly, which comprises a second exhaust chamber 14 and a second vacuum system 15. The pipelines through which the rubber solution flows are all provided with heat preservation measures, such as fixed rock wool outside the horizontal double-shaft devolatilizer, the screw extruder, the dynamic mixer and the pipelines connecting them. The rubber solution metering pump and the stripping agent feeding metering pump are connected to a flow controller to realize precise flow adjustment.

[0047] Example 2

[0048] A method for preparing low-VOC rubber based on the device of Example 1, comprising the following steps:

[0049] The POE / n-hexane solution is added to the preheated horizontal double-shaft devolatilizer 3 at 150°C through the rubber solution feeding metering pump 2, the screw rotation speed is set to 20 rpm, and the devolatilization is performed for 1 hour. The vacuum degree of the first vacuum system 5 reaches 5000 Pa or below, and the n-hexane content in the POE / n-hexane solution can be reduced to 5% or below.

[0050] The POE / n-hexane solution after primary devolatilization is delivered by metering pump 6 to one feed port of dynamic mixer 7; the stripping agent is water, which is delivered by stripping agent feed metering pump 9 to another feed port of dynamic mixer 7; the mass flow ratio of water to POE / n-hexane solution is 5:95-10:90; the dynamic mixer has 10 sets of stator and rotor, each rotor has 8 teeth, and the rotor rotation speed is 100 rpm, 200 rpm, 300 rpm, 400 rpm, 600 rpm, 800 rpm, 1000 rpm, and the temperature of the heat conducting oil is set to 150℃; the water and POE / n-hexane solution enter the heated dynamic mixer and are mixed and dispersed by the multiple stator-rotor to obtain POE / n-hexane / water mixed solution at the outlet, which enters screw extruder 13; the temperature of the extruder is set to 150℃, the rotation speed is 100 rpm, and the vacuum degree of the second vacuum system 15 is below 100 Pa, and the outlet obtains POE sample; a proper amount of sample is taken for headspace-gas chromatography test, and when the rotation speed of the dynamic mixer is more than 300 rpm, the n-hexane content in the POE is less than 200 ppm.

[0051] The present application can realize high-efficiency devolatilization of rubber solution by high-efficiency mixing of stripping agent and rubber solution by dynamic mixer and coupling with secondary devolatilization, and effectively improve the production stability of low-VOC rubber.

[0052] Example 3

[0053] As shown in Figure 2 , a secondary continuous devolatilization system:

[0054] This system removes dynamic mixer 7 and stripping agent adding system based on example 1. The rubber solution enters horizontal double-shaft devolatilizer 3 for primary devolatilization by metering pump 2. The exhaust port of horizontal double-shaft devolatilizer 3 is connected with the first exhaust chamber assembly, including first exhaust chamber 4 and first vacuum system 5. The rubber solution after primary devolatilization is delivered by metering pump 6 to screw extruder 13 for secondary devolatilization. The exhaust port of screw extruder 13 is connected with the second exhaust chamber assembly, including second exhaust chamber 14 and second vacuum system 15. The outlet of screw extruder obtains the devolatilized rubber product.

[0055] Example 4

[0056] A rubber preparation method based on the system of example 3:

[0057] The POE / n-hexane solution is fed into a horizontal biaxial devolatilizer 3 via a rubber solution feed metering pump 2. The biaxial devolatilizer is heated to 150°C, the screw speed is set to 20 rpm, and devolatilization is performed for 1 hour. The vacuum level in the first vacuum chamber reaches below 5000 Pa, and the n-hexane content in the POE / n-hexane solution can be reduced to 5% or less. The POE / n-hexane solution after the first-stage devolatilization is then conveyed to a screw extruder 13 via a metering pump 6. The extruder temperature is set to 150°C, the speed is 100 rpm, and the vacuum level in the second vacuum system is below 100 Pa. A POE sample is obtained at the outlet. A suitable amount of sample is subjected to headspace-gas chromatography testing. When the dynamic mixer speed exceeds 300 rpm, the n-hexane content in the POE is consistently around 1000 ppm.

[0058] Example 5

[0059] like Figure 3 As shown, a stripping-assisted two-stage continuous extrusion devolatilization system:

[0060] This system, based on Example 1, eliminates the dynamic mixer 7 and its corresponding heat transfer oil circulation jacket. The rubber solution enters the horizontal biaxial devolatilizer 3 via the rubber solution feed metering pump 2 for primary devolatilization. The exhaust port of the horizontal biaxial devolatilizer 3 is connected to the first exhaust chamber assembly, including the first exhaust chamber 4 and the first vacuum system 5. After primary devolatilization, the rubber solution is conveyed to one inlet of the screw extruder 13 via the metering pump 6. Simultaneously, stripping agent is added to the other inlet of the screw extruder 13 via the metering pump 9, mixing with the rubber solution in the front section of the screw extruder. The exhaust port at the rear end of the screw extruder 13 is connected to the second exhaust chamber assembly, including the second exhaust chamber 14 and the second vacuum system 15. After stripping and devolatilization in the rear section of the screw extruder, the devolatilized rubber product is obtained at the outlet.

[0061] Example 6

[0062] A method for preparing rubber based on the system of Example 5:

[0063] The POE / n-hexane solution is pushed by melt metering pump 3 into horizontal double-shaft devolatilizer 3, which is heated to 150℃, with screw rotation speed set at 20 rpm, devolatilized for 1 hour, with the first vacuum chamber vacuum degree reaching within 5000 Pa, and the n-hexane content in the POE / n-hexane solution reduced to 5% or below. The POE / n-hexane solution after the first devolatilization is delivered to screw extruder 13 by metering pump 6. The stripping agent is water, which is fed into another feeding port of screw extruder 13 by metering pump 9; the mass flow ratio of water and POE / n-hexane solution is 5:95-10:90. The extruder temperature is set at 150℃, the rotation speed is 100 rpm, the vacuum degree of the second vacuum system is 100 Pa or below, and the POE sample is obtained at the outlet. A proper amount of sample is taken for headspace-gas chromatography test, and the n-hexane content in the POE is about 1000 ppm when the dynamic mixer rotation speed exceeds 300 rpm.

Claims

1. A two-stage devolatilization system for rubber solution based on dynamic hybrid intensification, characterized in that, The rubber solution feeding device, the horizontal double-shaft devolatilizer, the dynamic mixer, the stripping agent adding device, the screw extruder and the exhaust chamber assembly are included. The rubber solution feeding device is arranged above the feeding port of the horizontal double-shaft devolatilizer, the discharging port of the horizontal double-shaft devolatilizer is connected to the feeding port of the dynamic mixer, and the discharging port of the dynamic mixer is connected to the feeding port of the screw extruder. The exhaust chamber assembly is arranged above the horizontal double-shaft devolatilizer and the screw extruder.

2. The dynamic hybrid-intensified two-stage devolatilization system for rubber solution according to claim 1, wherein, The rubber solution feeding device includes a rubber solution container and a feeding metering pump. Preferably, the metering pump is a gear pump or a double-plunger pump.

3. The dynamic hybrid-intensified two-stage devolatilization system for rubber solution of claim 1, wherein, The stripping agent adding device includes a stripping agent and a metering pump. The feeding port of the dynamic mixer connected to the horizontal double-shaft devolatilizer is provided with a metering pump.

4. The dynamic hybrid-intensified two-stage devolatilization system for rubber solution of claim 1, wherein, The exhaust chamber assembly includes an exhaust chamber and a vacuum pump, and the exhaust chamber is connected to 1-3 exhaust ports.

5. The dynamic hybrid-intensified two-stage devolatilization system for rubber solution of claim 1, wherein, The feeding ports of the dynamic mixer connected to the horizontal double-shaft devolatilizer and the stripping agent adding device are staggered.

6. The dynamic hybrid-intensified two-stage devolatilization system for rubber solution of claim 1, wherein, The dynamic mixer is externally provided with a heat-conducting oil circulating jacket, and the heat-conducting oil flows out of the heat-conducting oil circulating jacket, enters the dynamic mixer from below, heats the mixer, and then flows out from above to return to the heat-conducting oil circulating jacket to realize circulation.

7. A process for the production of low VOC rubber using the two-stage devolatilization system based on dynamic mixing intensification according to any one of claims 1 to 6, characterized in that, The method includes the following steps: The rubber solution is fed into the horizontal double-shaft devolatilizer through the rubber solution feeding device, and is subjected to primary devolatilization through kneading and vacuumizing by the exhaust chamber assembly, and the rubber solution material is discharged from the discharging port. The material is discharged from the horizontal double-shaft devolatilizer into the dynamic mixer, the stripping agent is added to the other feeding port of the dynamic mixer through the stripping agent adding device, the material and the stripping agent are mixed and then fed into the double-screw extruder, and secondary devolatilization is performed through mixing and vacuumizing by the exhaust chamber assembly to obtain low-VOC rubber.

8. The method of claim 7, wherein the low VOC rubber is prepared by the dynamic mixed enhanced rubber solution two-stage devolatilization system, characterized in that, The mass flow ratio of the stripping agent to the rubber solution entering the dynamic mixer is 1:99-30:

70.

9. The method of claim 7, wherein the low VOC rubber is prepared by the dynamic mixed enhanced rubber solution two-stage devolatilization system, characterized in that, The temperature of the horizontal double-shaft devolatilizer is controlled at 120-280℃, the temperature of the dynamic mixer is controlled at 120-280℃, and the temperature of the screw extruder is controlled at 120-280℃.

10. The method of claim 7, wherein the low VOC rubber is prepared by a two-stage devolatilization system based on dynamic mixed intensification, characterized in that, The rubber solution is a rubber solution synthesized by a solution polymerization method, and includes a solution of one or more of POE, BR, IR, EPDM, SBR or NBR.

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